A Study of the Physical Structure of Coke and the Influence Thereof on Blast Furnace Practice

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A Study of the Physical Structure of Coke and the Influence Thereof on Blast Furnace Practice

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THESIS.

A STUDY OP THE PHYSICAL STRUCTURE OP COKE and th e in f lu e n c e th e r e o f on b l a s t fu rn a c e p r a c t ic e

S ubm itted to th e U n iv e r s ity o f Glasgow hy James Duncan G i l c h r i s t f o r th e Degree of D ocotor o f P h ilo so p h y

v 5-k Ju n e, 1 9 5 0 .

ProQuest Number: 13838117

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is d e p e n d e n t upon the quality of the copy subm itted. In the unlikely e v e n t that the a u thor did not send a c o m p le te m anuscript and there are missing pages, these will be noted. Also, if m aterial had to be rem oved, a n o te will ind ica te the deletion.

uest ProQuest 13838117 Published by ProQuest LLC(2019). C opyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C o d e M icroform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 - 1346

COITETO

P art One# BJTBOlXJCTXOEr 1# Coke in th e B la s t Furnace# ............................. #. • ! 2# The Sampling’ o f Coke##

..................................

.10

P art Two# TEE POROSITY OF COKE 3# The O rigin o f Pores in C

o

k

4% The Apparent D en sity o f Coke#

e

# ..........

#

*16 .10

5# The B eal D en sity o f C oke##.................... • • • • • • • • • • • • • • • • # • 2 6 6

# In term ed iate D e n s itie s by "Diakon" Displacement# . # • • • *28

7# A bsolute P o r o s i t y . . . . # . # .....................

#33

P art Three PORE SIZE DISTRIBUTION ( EXPERIMENTAL } # In tro d u ctio n to Experim ental Work#............................................... . 38 .

8

9# Dye S o rp tio n i Mercury P e n e tr a tio n , and A ir Perm eation Experiments# • • . • • #41 10# In term ed iate D e n s itie s by th e "Counting" Method##• .# .4 7 lie

In te rm e d ia te D e n s itie s b y B ulk D en sity Measurement# . . . . . . . 6 9

P art Four CONCLUSIONS

Page

12* Shape Factors* . . * . . . . ................................• • • . # •

«..*•*.

77

13* Pore S iz e D is tr ib u tio n s in C o k e i * ...............

84

14* Pore Surface Areas** • • • • • ........... * . • « . . * • ......................

97

15* The Average C e ll W all T hickness*................... • » * *# « • • • • • • « • 103 16* General C onclu sion s*•

.......... • • * • • • • « 109

APPENDICES A*

An I n v e s tig a tio n in to Methods o f D eterm ining The Heal D en sity o f Coke**

B*

The Mechanics o f S ie v in g * ..............• • • • ..........................................1^° Acknowledgements*

. . . • . • . . • • • • • * • *38

D eferences* • • • • * # « • * • • ......................................................................

■' . . .

..

f

i -'i i : > - • •

a,l in i' p in n ia c i

' 'r;;X\J; I d

11

p a r t Qne*

c?,y

y a i.p

p r o p e r - ty

c i

till

SECTION I*

COKE IN THE BLAST FURNACE, i n th e F irs tly ,

I r o n b l a s t f u r n a c e c o k e s e r v e s t h r e e m a in p u r p o s e s *

it

is

th e f u e l o f th e f u r n a c e , p ro v id in g th e h e a t

n e c e s s a r y f o r th e

c h e m ic a l and p h y s i c a l r e a c t i o n s o f th e s m e lt­

in g p r o c e s s . S e c o n d ly i t

s u p p lie s

t h e r e d u c i n g a g e n t b y r e a c t i o n w i t h w h ic h

t h e o x i d e s o f i r o n a r e m ade t o y i e l d

t h e m e ta l*

T h ird ly

to b e v e ry im p o rta n t i n

coke i s g e n e r a lly

c o n s id e re d

m a in ta in in g h ig h p e r m e a b il ity o f th e b u rd e n to g a s e s , th e o n ly m a t e r i a l dow n to

th e

c h a rg e d w h ic h m a i n t a i n s i t s

tu y e re s *

i t b e in g

sh a p e and s i z e

I t m ust a ls o p la y an im p o rta n t p a r t i n

m a in ta in in g c o n d itio n s o f h ig h p e rm e a b ility

to s la g i n

t h e b o sh *

T he b e h a v i o u r o f c o k e a s a r e d u c i n g a g e n t n e e d h a r d l y b e d i s ­ c u s s e d . A la r g e p a r t o f th e r e d u c tio n o f o re s ta k e s p la c e th e

a g e n c y o f c a r b o n m o n o x id e .

D i r e c t r e a c t i o n s b e tw e e n co k e

c a r b o n and o x id e o f i r o n w i l l o c c u r i n f u r n a c e w h e re th e

t h e lo w e r r e a c h e s o f th e

o x id e i s p r e s e n t a s a c o n s t i t u e n t o f a s l a g

v e ry h ig h te m p e ra tu re . ra th e r

th ro u g h

at

T h ese r e a c t i o n s w i l l p ro b a b ly d ep en d

on th e n a tu r e and c o m p o s itio n o f th e l i q u i d m e lt and on

th e te m p e ra tu re

th a n on any p r o p e r ty

o f th e

coke. R e a c tio n r a t e s

w i l l p r o b a b l y b e v e r y h ig h *

Work done by p e r r o t and Kinney (1) in U*S.A. ab o u t 1923 showed t h a t com bustion o cc u rred in a zone ex ten d in g to about lj.0 in c h e s round th e nose o f e a c h tu y e r e .

T he s i z e o f t h e z o n e se e m e d t o h e i n d e p e n d e n t o f t h e o p e r a t i n g c o n d i t i o n s o f b l a s t p r e s s u r e a n d ( a b o v e a m in im u m s i z e ) f u r n a c e d ia m e te r.

i n g e n e ra l th e p a t t e r n i s th e same a s t h a t found by H ile s and Mott (2) in t h e i r s tu d ie s o f th e com bustion o f coke in f u e l beds.

The com bustion zone may b e co n sid ered to b e i n two p a r t s

d is tin g u is h e d by gas co m p o sitio n and by th e r e a c tio n s ta k in g p la c e .

I n th e f i r s t or " o x id iz in g zone" th e re i s f r e e oxygen

over 1 f0, n itr o g e n , carbon d io x id e and a sm all p ro p o rtio n o f CO. In th e second or " re d u c tio n zone" th e 02h as been alm o st a l l com­ b in e d , CO2 i s r e a c t i n g w ith carbon, and th e gas co m p o sitio n changes r a p id ly u n t i l i t i s alm o st e n t i r e l y F2 ancL CO. The d e t a i l s o f th e mechanism o f th e o x id a tio n of carbon a r e r a t h e r o b sc u re .

E arly work has been review ed by H ile s and

M ott (2) who showed how th e c o n c lu sio n s reac h ed u s u a lly depended on th e e x p e rim e n ta l c o n d itio n s o p e r a tin g , th e stu d y o f com bustion in beds a p p e a rin g to be a p a r t i c u l a r l y u n s a t i s f a c t o r y approach to th e fundam ental mechanism o f th e r e a c t i o n s . p e rh a p s th e most s a t i s f a c t o r y c o n tr ib u tio n has been by S tricld L an d -C o n stab le (3) who a d m itte d oxygen a t v e ry low p r e s s u r e to an evacuated b u lb c o n ta in in g a h o t carbon f ila m e n t. The low p r e s s u r e red u ce d th e p r o b a b ili ty o f secondary r e a c tio n s i n th e gas w hich could b e co n sid e re d a t low te m p e ra tu re .

The gas was

a n a ly se d when tim e had been allow ed f o r about t h r e e - q u a r te r s o f th e oxygen to b e u sed u p .

A ccuracy o f a n a ly s is was r a t h e r low

b u t i t was e s ta b lis h e d t h a t th e r e a c t i o n was p ro b a b ly of th e f i r s t o rd e r.

He deduced t h a t GO was th e p ro d u c t o f th e p rim ary

r e a c tio n *

T his has r e c e n tly been confirm ed by Loon and sm eets

(i^.) who burned sp h e re s o f carbon in f a s t stream s o f oxygen, t h a t i s , under more "norm al” c o n d itio n s*

CO2 m ust, th e n , be formed

by o x id a tio n o f th e CO in th e gas p h a se , though p o s s ib ly v ery c lo s e indeed to th e carbon s u r fa c e and Loon and sm eets su g g e st a " d if f u s io n la y e r " en v elo p in g th e carbon in w hich oxygen must p a s s th ro u g h newly formed CO to r e a c h th e carbon s u r f a c e . The n e t e f f e c t s of th e p rim ary and subseq u en t r e a c tio n s i s o bserved as th e two zones o f com bustion d e s c rib e d above* The work o f H ile s and Mott c o v e rs th e e f f e c t s o f d i f f e r e n t f u e l s and c o n d itio n s on th e e x te n t and d e f i n i t i o n o f th e two zones o f com bustion and on th e te m p e ra tu re s developed*

B roadly

sp e ak in g " c o n d itio n s o f low r e a c t i v i t y " — l a r g e siz e d or un­ r e a c t i v e f u e l l i k e b ee h iv e coke, and low gas v e l o c i t i e s — p r o ­ duced a lo n g w e ll d e fin e d o x id a tio n zone c h a ra c te ris e d by a v ery h ig h maximum te m p e ra tu re a t i t s boundary*

On th e o th e r hand

" c o n d itio n s o f h ig h r e a c t i v i t y " caused by sm all or h ig h ly r e ­ a c t i v e f u e l su ch a s c h a rc o a l, o r h ig h gas v e l o c i t i e s p ro d u cin g v e ry tu r b u le n t flow c o n d itio n s , gave a s h o r te r o x id a tio n zone m erging in to th e r e d u c tio n zone, a much low er maximum te m p e ra tu re b e in g d ev elo p ed . The ty p e o f com bustion zone formed must depend upon th e r e l a t i v e r a t e s a t w hich th e fo llo w in g r e a c tio n s can p ro c e e d . (1 ) 2 c + 0 2 ~ 2 CO —

p rim ary r e a c t i o n a t C s u r f a c e .

(2) 2 C0 + 0 2 = 2 CO2 — Secondary r e a c t i o n i n gas p h a s e , and

(3) G + G 0 2 ~ 2 CO

— Secondary r e a c t i o n a t c s u r fa c e .

At com bustion te m p e ra tu re s and in th e p re se n c e o f f r e e oxygen, b o th (1) and (2) p ro c e e d r a p id ly to th e r i g h t .

R e a c tio n (3)

would b e ex p ected to be i n e f f e c t i v e u n t i l th e oxygen was used up, f o r th e CO formed by i t would im m ediately e n te r in to r e a c t i o n (2 ). Under H ile s and Motts c o n d itio n s of ’’h ig h r e a c t i v i t y ”, however i t would appear t h a t (3 ) m ust p ro cee d s u f f i c i e n t l y f a s t t h a t CO and O2 can e x i s t to g e th e r in th e re g io n w here o x id a tio n and r e d u c tio n zones merge o r o v e rla p .

The in d ep en d en t v a r ia b le c o n tr o llin g

th e r e l a t i v e r a t e s o f th e s e r e a c tio n s seems to be th e ”r e a c t i v i t y ” o f th e carbon to 02 and CO2 .

T his r e a c t i v i t y may depend on one

or b o th o f two f a c t o r s — f i r s t l y th e chem ical p r o p e r tie s o f th e s u rfa c e as th e y a f f e c t th e r e a c t i o n s , and seco n d ly th e e x te n t o f th e a v a ila b le carbon s u rfa c e and i t s s p a t i a l d i s t r i b u t i o n . It

is not

R e a c tiv ity itio n s

c l e a r t h a t c h e m ic a l p r o p e r t i e s a r e r e a l l y

can b e enhanced i n

co k e f o r d o m e s tic p u rp o s e s b y a d d ­

o f s o d a a s h w h ic h p r o b a b l y h a s som e c a t a l y t i c

w h e th e r t h e r e

is

im p o rta n t

an y p r a c t i c a l d i f f e r e n c e b e tw e e n t h e

a c tio n b u t c h e m ic a l

p r o p e r tie s o f th e s u rfa c e s o f m e ta llu r g ic a l co k es o f d i f f e r e n t o r i g i n by th e

tim e th e y r e a c h th e t u y e r e z o n e o f a b l a s t f u r n a c e

seem s d o u b t f u l .

T he e x t e n t o f t h e

s u r f a c e a t w h ic h th e c a rb o n

m ay b e b u r n e d d e p e n d s u p o n t h e p o r o s i t y , d is trib u tio n

in

s e a r c h to f in d a firs t

s te p

th e u t i l i t y

th e

coke.

It

is

and on th e p o re s i z e

t h e m a in p u r p o s e o f t h i s r e ­

a m e th o d o f d e t e r m i n i n g p o r e s i z e d i s t r i b u t i o n

to w a r d d e c i d i n g i t s o f eoke.

as

im p o rta n c e a s a f a c t o r a f f e c t i n g

The e f f e c t o f th e se c o n s id e r a tio n s on b l a s t fu rn a c e o p e ra tio n i s d i f f i c u l t to asse ss#

consensus o f o p in io n i s t h a t f u e l s o f low

r e a c t i v i t y a r e most d e s ir a b le b ecau se th e y s u f f e r l e s s s o lu tio n by CO2 in th e s ta c k , and develop h ig h e r maximum te m p e ra tu re s a t th e tu y e r e s .

High s o lu tio n l o s s o f carbon in th e s ta c k i s o f

co u rse u n d e s ir a b le from th e p o in t o f view o f th e rm a l e ffic ie n c y # High te m p e ra tu re s in th e tu y e re zone may have an im p o rta n t e f f e c t on th e l a s t s ta g e s i n th e r e d u c tio n o f th e o x id es o f ir o n and th e m e ta llo id s and on th e c o n d itio n s in th e h e a rth a f f e c t i n g s la g m e tal r e a c t i o n s .

On th e o th e r hand th e t o t a l volume o f th e v ery

h o t zone i s sm all and th e p o s s i b i l i t i e s of h e a t t r a n s f e r down to th e h e a r th by r a d i a t i o n lim ite d , so t h a t th e im p o rtan ce of t h i s f a c t o r may have b een e x a g g e ra te d .

B eehive coke o f low r e ­

a c t i v i t y has f r e q u e n tly been u se d in th e p a s t a s a ’'m e d ic in e ” f o r " s i c k ” b l a s t fu rn a c e s b u t i t s v a lu e may l i e in i t s s iz e and s t r e n g t h r a t h e r th a n in i t s r e a c t i v i t y .

R e c e n tly i t has been

r e p o r te d ( 5) t h a t th e u se of v e ry low p o r o s ity coke ( o f , presum­ ab ly v e ry low r e a c t i v i t y ) le d to u n fa v o u ra b le te m p e ra tu re g r a d ie n ts i n th e b o sh w hich u p s e t th e w orking of th e fu rn a c e a s p r e s e n tly d e s ig n e d .

i t w i l l be obvious t h a t th e t r u e in f lu e n c e

o f f u e l r e a c t i v i t y on b l a s t fu rn a c e o p e r a tio n i s n o t y e t p r o p e r ly u n d e rs to o d . Supposing however t h a t h ig h ly u n r e a c tiv e f u e l I s d e s ir a b le , w hat does t h i s mean i n term s o f th e p r o p e r tie s o f th e coke? Chemical r e a c t i v i t y , may be ex p ected to d im in is h a s th e coking te m p e ra tu re i s r a i s e d .

The a v a ila b le s u rfa c e w i l l depend upon

th e s iz e o f th e coke a t th e tu y e re s and th e s iz e d i s t r i b u t i o n

( f o r s m a lle r p ie c e s o b v io u sly p r e s e n t a g r e a t e r a re a to g a s e s ) ; i t depends to a minor e x te n t on p a r t i c l e sh ap e; and i t depends on p o ro s ity # For a g iv e n shape and s iz e o f coke th e " v is ib le " s u r f a c e de­ pends d i r e c t l y upon p o r o s i t y .

I f th e p o r o s ity i s 50$ th e s u r fa c e

i s 1 . 5 tim e s t h a t o f a s im ila r p a r t i c l e hav in g no p o r o s i t y .

If

th e p o r o s ity i s kOfo o r 60f£, th e f a c t o r i s 1 . 1+ or 1 .6 r e s p e c t i v e l y . As th e s e a r e extrem e v a lu e s i t can be s a id t h a t " v i s i b l e ” s u rfa c e i s i t s e l f o f l i t t l e im p o rta n ce. Mott and W heeler ( 6) have shown however t h a t com bustion a f f ­ e c ts th e o u te r § t h in c h la y e r o f th e coke p ie c e so t h a t th e su r­ f a c e s o f p o re s w ith in t h a t zone i s a ls o in v o lv e d .

The e f f e c t i v e

a r e a o f i n t e r n a l s u rfa c e depends n o t only on t o t a l p o r o s ity b u t on p o re s i z e o r more g e n e r a lly on s iz e d i s t r i b u t i o n , and on th e a c c e s s i b i l i t y o f th e s u r f a c e s o f th e s e p o re s to th e r e a c t i n g g a s e s. Mott and W heeler ( 6) have a s s e r te d t h a t th e p e r m e a b ility o f coke i s n e g l i g i b l e b u t i t i s n o t z e ro and may w e ll be one o f th e more im p o rta n t v a r ia b le s d i f f e r e n t i a t i n g cokes o f "good" and "bad" q u a lity . D is c u s s in g th e e f f e c t o f p o r o s ity p e r se M ott and W heeler have r e p o r te d t h a t h ig h e s t te m p e ra tu re s were o b ta in e d from cokes o f h ig h e s t p o r o s ity — b u t t h a t a c e r t a i n coke o f only i+0 fo p o r ­ o s it y a ls o gave v e ry h ig h te m p e ra tu re s .

R ecent work a lre a d y

m entioned however ( 5 ) su g g e sts t h a t i n th e b l a s t fu rn a c e a t any r a t e , low p o r o s ity g iv e s low r e a c t i v i t y and h ig h te m p e ra tu re s , and though th e t r u t h o f th e m a tte r i s o b v io u sly i n some d o u b t, t h a t i s th e assu m p tio n t h a t w i l l be made h e re .

7. p o re s i z e s , fo llo w in g th e above assu m p tio n , should be l a r g e i n o rd e r t h a t t h e i r c o n tr ib u tio n to s u rfa c e a r e a be s m a ll.

P o re s

should be u n -co n n ected and p e r m e a b ility low . The assu m p tio n made must o f course be t e s te d by experim ent, and i t i s th e p u rp o se o f th e p r e s e n t work to c o n tr ib u te to th e s o lu t io n o f th e many problem s in v lo v e d .

t

I t i s g e n e ra lly c o n s id e r­

ed t h a t p o r o s ity should be h ig h . The re a s o n f o r t h i s i s n o t c le a r b u t may be concerned w ith th e m a in ta in a n c e of h ig h eoke volume i n th e charge w ith a view to h ig h p e r m e a b ility o f th e burden to g a s e s . Ho s u c c e s s fu l l a r g e s c a le c o r r e la tio n o f p o r o s ity a g a in s t b l a s t f u rn a c e perfo rm an ce has been c a r r ie d o u t.

T his ta s k would be v ery

d i f f i c u l t i n view o f th e com plexity o f f a c t o r s from w hich t h i s one would have to be d is tin g u is h e d . The r a t e a t w hich carbon i s consumed a t th e tu y e re s c o n tr o ls th e o u tp u t o f th e fu rn a c e and i s li m i t e d by o th e r f a c t o r s th a n th o se c o n s id e re d , depending im m ediately upon th e r a t e a t w hich oxygen can be s u p p lie d th ro u g h th e tu y e r e s .

T his i n tu r n i s

l i m i t e d by th e p e r m e a b ility o f th e s to c k th ro u g h w hich th e p ro ­ d u c ts o f th e com bustion must escape from th e tu y e re zone.

P e r­

m e a b ility depends on s iz e and s iz e d i s t r i b u t i o n o f " th e m a te r ia l s charged and on th e way th ey s e g re g a te when th ey come o f f th e b e l l . As coke com prises betw een 50fo and 70 $ o f th e burden volum e, and a s coke a lo n e m a in ta in s i t s s iz e and shape down to th e tu y e re l e v e l , i t i s c le a r t h a t f a c t o r s a f f e c t i n g th e p e rm e a b ility o f coke beds, namely coke s i z e and s iz e d i s t r i b u t i o n and t h e i r s t a b i l i t y a r e o f g r e a t im p o rta n c e .

L arge s iz e and c lo s e g ra d in g a r e th e r e f o r e con­

s id e re d a fte r

to b e d e s ir a b le .

th e y m e lt i n th e b o s h th e

p e rm e a b le b o t h to

s iz e s

o re s to o , b u t

coke a lo n e m u st b e s u f f i c i e n t l y

s u c h s m a ll coke te n d s to a c c u m u la te

th e h e a r th and c r e a te s u n fa v o u ra b le c o n d itio n s .

p o s s ib ly

to

th e p a ssa g e o f l iq u id s to

scree n i t

Its

th e h e a r th ,

S iz e and s iz e s t a b i l i t y coke i s

f o r c e s to w h ic h i t fu rn a c e .

is

e ffe c t and

fro m t h e h e a t i n t h e t u y e r e z o n e t o o .

n o t c l e a r w!$r s u c h s m a l l m a t e r i a l i s n o t r a p i d l y

s u r in g t h a t th e

it

im p o rta n t t h a t th e p r o p o r tio n o f b re e z e

(u n d e r § in c h ) b e lo w .

m ay b e t o r e s t r i c t

is

e q u a lly to

a s c e n d in g g a s e s and to d e s c e n d in g l i q u i d s ,

seem s to b e p a r t i c u l a r l y

in

T h is a p p l i e s

can b e m a in ta in e d

It

consum ed.

h ig h o n ly by en­

ws t r o n g 11 e n o u g h t o r e s i s t

th e m e c h a n ic a l

s u b je c te d d u r in g t r a n s p o r t and w ith in th e

T he f a c t o r s i n f l u e n c i n g t h e n a t u r a l s i z e d i s t r i b u t i o n s

fo u n d i n b ro k e n co ke a r e n o t u n d e r s to o d , b u t c lo s e g r a d in g i s u s u a lly

im p o s e d b y s c r e e n i n g o u t f i n e s .

p lq y s ic a l p r o p e r t i e s a f f e c t i n g and fre e d o m fro m f i s s u r i n g .

s i z e and s t r e n g t h a r e

"h ard n ess*

To som e e x t e n t t h e s e a r e m u t u a l l y

in c o m p a ta b le , f o r h ig h h a rd n e s s

c a n b e a c h i e v e d b y e m p lo y m e n t o f

h i g h c o k i n g t e m p e r a t u r e s w h ic h u s u a l l y p r o d u c e a s m a l l h i g h l y fis s u re d

coke.

s t r u c t u r e o f th e

A n o t h e r p r o p e r t y w h i c h m ay b e i m p o r t a n t i s c e lls

and th e th ic k n e s s o f t h e i r w a l l s .

a r e f u n c tio n s o f p o r o s i t y and i t s b ility

s iz e d is trib u tio n .

o f a c t u a l l y m e a s u rin g h a r d n e s s ,

th e T hese

The p o s s i ­

te n s ile s tre n g th or

e l a s t i c m o d u li o f c o k e - c a rb o n seem s v e r y r e m o te .

T he f o l l o w i n g sum m ary h a s b e e n m ade o f t h e p r o p e r t i e s p r o b a b l y d e s i r a b l e i n a good m e t a l l u r g i c a l c o k e .

9.

PHYSICAL PROPERTIES. S iz e s

L a rg e w ith in l i m i t s and g r a d in g

c lo s e .

S tre n g th s

H ig h b o t h to w a r d s h a t t e r a n d a b r a s i o n t o k e e p s i z e up and f i n e s dow n.

R e a l D e n s i t y ’s

H ig h -

if

t h i s m eans h a r d e r o r l e s s r e a c t i v e f u e l .

p o ro s ity s

Low, w i t h a v ie w t o lo w r e a c t i v i t y ,

( T h i s v ie w

i s n o t g e n e r a lly a c c e p te d ) B u lk D e n s ity s

Low, b u t i n v i r t u e o f c l o s e g r a d i n g , n o t h i g h p o ro s ity .

p o re p e r m e a b i l i t y s Low - i f p o s s i b l e C e l l W a ll s s

p ro b a b ly d e s ir e d

to

c o n tro l i t .

th ic k .

CHEMICAL PROPERTIES. M o is tu re , S u l p h u r , A sh s A l l lo w ,

and s te a d y .

The e f f e c t s o f t h e s e on

m e ta llu r g ic a l lo a d a re la r g e ly V o la tile s s

Low -

c a lc u la b le .

c o rre sp o n d in g to h ig h d e n s it y .

B ffe c t in

fu r n a c e o f v o l a t i l e s p e r s e i s p ro b a b ly s m a ll. Reac t i v i ty s

Low .

The e x t e n t t o w h ic h t h e s e p r o p e r t i e s a r e is

la rg e ly

a m a tte r o f c o n je c tu re ,

y e t even b e en m e asu re d . on p o r o s ity and i t s a c tiv ity

fu rn a c e p e rfo rm a n c e , end.

a n d som e o f th e m h a v e n o t

The p r e s e n t r e s e a r c h w i l l c o n c e n t r a t e

s iz e d is tr ib u tio n

and s tr e n g th .

s e p a r a te ly im p o rta n t

a s t h e y may a f f e e t r e ­

I t w i l l n o t p ro c e e d to

b u t w ill,

it

c o r r e la tio n w ith

i s h o p e d a d v a n c e to w a r d t h a t

S e c tio n 2 . THE SAMPLING- OP COKE. The aim o f th e p r e s e n t work i s to c o n tr ib u te toward th e th e b e t t e r u n d e rs ta n d in g o f th e p r o p e r tie s d e s ir a b le i n b l a s t fu rn a c e coke by a tte m p tin g to m easure p o re s iz e d i s t r i b u t i o n and to d e c id e w hether i t i s r e a l l y an im p o rta n t f a c t o r and i f so , how i t o p e r a te s . A ll o f th e o th e r p r o p e r t i e s l i s t e d a t th e end of S e c tio n 1 excep t c e l l w a ll th ic k n e s s and p o re p e r m e a b ility a re r e g u la r ly d eterm in ed , many on a r o u t i n e b a s i s .

A ttem pts to c o r r e l a t e

th e s e p r o p e r tie s w ith b l a s t fu rn a c e perform ance have met w ith l i t t l e su c c e s s .

T his i s i n la r g e m easure due to th e in h e re n t

com plexity o f th e problem i n w hich th e number of v a r i a b l e s i s la r g e and t h e i r d e g re e s o f in te r-d e p e n d e n c e o b scu re. One u n a v o id a b le d i f f i c u l t y i s t h a t coke i s e s s e n t i a l l y a v e ry h etero g en o u s m a te r ia l and i s th e r e f o r e s u b je c t to se v e re sam pling e r r o r s .

T his h e te ro g e n e ity i s a consequence o f th e

method of m an u factu re and a lth o u g h modern coke oven o p e r a tio n aims a t th e p ro d u c tio n o f th e most u n ifo rm coke p o s s i b le , th e r e a r e l i m i t s to what i s p o s s ib le , and th e s e a re n o t always a t t a i n ­ ed. E xam ination of any o v en -lo ad of coke r e v e a ls a wide v a r i ­ a t io n in th e appearance o f th e in d iv id u a l p ie c e s .

There a re

d if f e r e n c e s in c o lo u r, s iz e and sh ap e; a p p a re n tly in s tr e n g t h and in d eg ree o f f i s s u r i n g ; in p o r o s i t y ; and in th e g ra d a tio n o f c o lo u r from end to end.

N e v e rth e le s s th e re i s a g e n e ra l

11. s i m i l a r i t y i n th e p ro d u c t o f any one b a t t e r y Which f r e q u e n tly m arks i t a s a d i f f e r e n t coke from o th e r s made elsew h ere. The v a r io u s d if f e r e n c e s l i s t e d can each b e a t t r i b u t e d to one o r more o f th e fo llo w in g c a u se s , (1)

The te m p e ra tu re g r a d ie n t a c ro s s th e oven and i t s v a r i a t i o n a t d i f f e r e n t p a r t s o f th e oven due to (a ) boundary e f f e c t s a t d o o rs , s o le e t c . , (b) d if f e r e n c e s in th e p a c k in g o f th e ch a rg e ,

(2)

The v a r i a t i o n in th e p ack in g o f th e charge from th e bottom to th e top where th e f a l l o f th e c o a l i s g r e a t e s t and l e a s t r e s p e c tiv e ly w i l l have th r e e e f f e c t s . (a ) The te m p e ra tu re g r a d ie n t and hence th e r a t e o f h e a t­ in g o f th e charge and th e p o r o s ity o f th e p ro d u c t w ill be a ffe c te d . (b) p o r o s ity may be a f f e c te d more d i r e c t l y by th e v a ry ­ in g r e s is ta n c e to s w e llin g in d i f f e r e n t p a r t s o f th e c h a rg e . (c ) (a ) w i l l le a d a ls o to d i f f e r e n t f i n a l te m p e ra tu re s in d i f f e r e n t p a r t s . A s m a lle r v a r i a t i o n i n p ack in g d e n s ity w i l l o ccur from

end to end o f th e oven i t b e in g h ig h e r a t any le v e l immed­ i a t e l y u n d er th e ch arg in g h o le s . (3)

A c c id e n ta l or u n av o id ab le v a r i a t i o n s i n oven w a ll tem per­ a tu re .

(ij.)

The e f f e c t o f w a ll ta p e r w hich th o u g h only ab o u t 2» i s 124$ on a 1 6 " oven.

(5)

The p o s s i b i l i t y c o a ls

in a d e q u a te m ix in g

of

th e

c o n s titu e n t

c a n n o t b e ig n o re d .

V a ria tio n s a ls o u p s e ts

of

o c c u r b e tw e e n o v e n s d u e t o

c h a n g in g b le n d ,

in tim e s c h e d u le s and n o rm a l te m p e r a tu r e d i f f e r e n c e s .

T hese l o c a l v a r i a t i o n s

in

c o k e q u a l i t y may h a v e l i t t l e

e f f e c t on th e u s e f u ln e s s o f th e f u e l in

th e fu rn a c e b u t a re

a lw a y s im p o r t a n t w hen s a m p le s a r e b e in g ta k e n f o r an y t e s t . S a m p le s m u s t b e t r u l y r e p r e s e n t a t i v e o f t h e b a t c h b e i n g t e s t e d , and th e q u a n tity

s u b je c te d

to

th e t e s t s u f f i c i e n t to

t h a t th e m ean v a l u e o f th e in d e x s o u g h t i s a b le a c c u ra c y .

e n su re

o b ta in e d w ith s u i t ­

I t i s f r e q u e n tly im p o s s ib le to

a tta in a de­

s i r e d a c c u r a c y w i t h o u t e m p lo y in g i n c o n v e n i e n t l y l a r g e

s a m p le s .

T he s i z e o f s a m p le r e q u i r e d c a n u s u a l l y b e d e t e r m i n e d b y s t a t i s t i c a l m e th o d s , ly .

F o r e x a m p le ,

c e rta in

and s a m p lin g te c h n iq u e p la n n e d a c c o r d in g ­

i n d e te rm in in g th e s iz e d i s t r i b u t i o n o f

c o k e s t h e a u t h o r f o u n d t h a t a s a m p le o f 20 i n c r e m e n t s ,

e a c h o f 50 -

60 l b . w e i g h t — t h a t i s a b o u t h a l f a t o n o f

m a t e r i a l —w a s n e c e s s a r y c o rre c t i 0*1»,

a s th e

l e s s th a n 1*0 in c h ,

if

a v e ra g e s i z e w as to b e d e te rm in e d

t o t a l r a n g e o f s i z e b e in g o b ta in e d w as

i t w i l l b e a p p r e c i a t e d t h a t s a m p le s i z e w as

lim it e d by p r a c t i c a l c o n s id e r a tio n s and n o t ch o sen a s b e in g a d e q u a te f o r re q u ire m e n ts o f a c c u ra c y . D a t a a r e o f t e n a v e r a g e d o v e r p e r i o d s o f a w e e k o r a m o n th i n o r d e r t h a t d i f f e r e n c e s b e tw e e n p e r i o d s may b e c o m e s i g n i f i c a n t and la r g e

s c a le

c o r r e l a t i o n w o rk m u s t c e r t a i n l y b e o r g a n i s e d o n

a l o n g te rm b a s i s i f ed .

re a lly

s ig n if ic a n t r e s u lts a re

T h e r e i s p r o b a b l y w id e s c o p e i n

to b e o b ta in

th e in d u s try f o r

th e

13. a p p l ic a tio n o f th e more advanced s t a t i s t i c a l methods p o p u la rly known a s " o p e r a tio n a l a n a ly s is " . The p r e s e n t work has been c a r r ie d o u t la r g e ly by c l a s s i c a l m ethods, w ith elem en tary s t a t i s t i c a l s a fe g u a rd s .

When new

methods w ere b ein g co n sid e re d th e im p o rtan ce o f sam pling was re c o g n is e d ,

p r e fe re n c e was g iv e n to methods w hich could be

a p p lie d to re a s o n a b ly sm all q u a n t itie s o f broken coke su ch as could be o b ta in e d from a l a r g e r " f a i r " sample by s ta n d a rd coning and q u a r te r in g te c h n iq u e .

Methods in v lo v in g exam ination of

specim ens — by th e m icroscope f o r example — were avoided b ecau se o f th e s e rio u s sam pling e r r o r s in e v ita b ly in c u rre d . The d e te rm in a tio n o f a p p a re n t d e n s ity i s a n o ta b le e x c e p tio n to t h i s ru le .

A s u i t a b l e method u s in g a " f a i r " sample could n o t be

found b u t th e o p p o rtu n ity was ta k en of making a c a r e f u l stu d y o f th e sam pling e r r o r s o b ta in e d . Throughout th e work, where e r r o r s a r e e s tim a te d by s t a t i s ­ t i c a l means, th ey a re assumed to be d i s t r i b u t e d n o rm ally ab o u t t h e i r mean M and th e ra n g e quoted as M±G io (where g = 2 x th e sta n d a rd d e v ia tio n ) i s t h a t w ith in w hich 95i of v a lu e s a r e ex­ p e c te d to f a l l .

I t was n o t alw ays p o s s ib le to ap p ly th e s e

m ethods r ig o u r o u s ly and in c e r t a i n e a ses accuracy e s tim a tio n i s le s s re lia b le . The m a te r ia l s u s e d (a rg 2 jn t h i s r e s e a r c h , l i s t e d below i n T able I w ith code irumbers and n o te s on t h e i r o r ig in .

S a n p lin g

was n o t u n d er c o n tro l a s cokes were o rd e re d by l e t t e r from v a r io u s p a r t s o f th e c o u n try .

The s e l e c t i o n i s g e o g ra p h ic a lly

f a i r l y w ide, b u t th e s i m i l a r i t y among I , I I , and IV on th e one

hand and VI and V II on th e o th e r may be u s e f u l i n r a i s i n g th e s ig n if ic a n c e o f any d if f e r e n c e s found betw een th e s e g ro u p s.

It

was hoped t h a t th e in c lu s io n o f a b e e h iv e coke m ight y ie ld in ­ fo rm a tio n on th e a lle g e d s u p e r io r ity o f t h a t ty p e as a m e ta ll­ u rg ic a l f u e l.

The o th e r im p o rta n t d if f e r e n c e s a re t h a t VI was

made i n r a t h e r o ld w ide ovens and t h a t I I was of v ery low a sh c o n te n t,

coke p had v e ry l a r g e p o re s and was in c lu d ed as an

extrem e case o f a p o ro u s m a te r ia l l i k e coke, w h ile th e Q uartz

Q

r e p r e s e n tin g th e o th e r extrem e, has been employed a t v a r io u s s ta g e s o f th e work a s a sta n d a rd n on-porous m a te r ia l. A p r e lim in a r y to th e measurement o f p o re s iz e d i s t r i b u t i o n m ust b e th e d e te rm in a tio n o f a b s o lu te p o r o s ity .

T his has le d to

i n v e s tig a tio n s i n t o th e measurement of a p p a re n t and r e a l d e n s i­ t i e s and to an a tte m p t to m easure th e a p p a re n t d e n s ity o f sm all p a r t i c l e s (a s opposed to t h e i r r e a l d e n s ity ) by a new method d is p la c in g a p l a s t i c m a te r ia l .

T his p a r t o f th e r e s e a r c h i s

r e p o r te d in p a r t I I . i n p a r t I I I a re c o n sid e re d v a r io u s methods w hich have been in v e s tig a te d f o r th e d e te rm in a tio n o f p o re s iz e d i s t r i b u t i o n , in c lu d in g th e s u c c e s s fu l »cou n tin g " method i n S e c tio n 1 0 .

The

r e s u l t s o f th e s e ex p erim en ts and th e in f e r e n c e s drawn from them a re d is c u s s e d i n P a r t IV, w h ile i n th e A P P e^ ix some s u b s id ia r y work on s ie v in g and th e d e t a i l s o f th e r e a l d e n s ity in v e s t i g a t i o n a r e r e p o r te d .

15

TABLE I . - L i s t o f M a te ria ls Examined. Code Ho.

I

II

Sour ce

S c o t t i s h b l a s t fu rn a c e coke from

D u ll

l o c a l c o a ls b len d ed 15^ Durham c o a l.

B lack Blocky, hard s ilv e ry .

S c o t t i s h E le c tro d e coke from low v o l­ a t i l e co al washed to g iv e v e ry low ash

III

ipp e a ra n c e .

As I I b u t r e c e iv e d a y e a r e a r l i e r

i

As I I .

(Appendix A only) S im ila r to I . O btained from same ovens

D u ll

ab o u t one y e a r l a t e r .

b la c k .

V

S outh W elsh b l a s t fu rn a c e coke.

S ilv e r y .

VI

Durham fo u n d ry coke from 201’ ovens.

S ilv e r y b u t b la c k in n e r ends.

V II

Durham b e e h iv e coke.

Mixed.

p

p a r a f f i n coke from s h a le o i l r e s id u e s .

V itre o u s b la c k .

Q

Mined q u a rtz w ith sm all p r o p o r tio n

IT

o f m usco v ite p r e s e n t. C

Household c o a l.

P art Twe.

THE POROSITY OP

I

COKE.

SECTION 3 *

THE ORIGIN OF PORES. B e fo re d i s c u s s i n g th e m e a su re m e n t o f p o r o s i t y a s h o r t a c c o u n t o f th e fo rm a tio n o f p o re s in e s p e c ia lly

a s th e r e s u l t s

c o k e may b e d e s i r a b l e

o f t h e r e s e a r c h d o H ave a n im ­

p o r t a n t b e a r i n g o n c o k i n g m e c h a n is m . The o r i g i n o f p o r o s i t y

is

m e e h a n is m o f c o k i n g a n d t h i s G e n e ra lly a c c e p te d

o f c o u rse bound up w ith th e

i s n o t a t p r e s e n t w e ll u n d e rs to o d .

th e o r y s u g g e s t s t h a t c o k in g c o a ls becom e

s o f t b e tw e e n 350° a n d i*.50°C d u e t o t h e fu s ib le

c o m p o n e n ts o r d e c o m p o s i t i o n p r o d u c t s ( o f u n k n o w n n a t u r e )

and d i s p e r s a l o f th e i n f u s i b l e p a r t i n s o r t o f c o llo id

of p la s tic

o f th e f u s ib le m a te ria l i s

c o n s is te n c y .

e v o lv e f a s t e r

t h a n th e y

E lim in a tio n o f th e f u s i b l e re -s o lid ific a tio n

t h e m e l t t o f o r m som e F u r th e r d e c o m p o s itio n

th e n su p p o se d to fo rm g a se o u s p r o ­

d u c t s w h ic h fo rm b u b b le s and c a u s e t h e g ases

" m e l t i n g 11 o f som e e a s i l y

coke to s w e ll i f

th e

c a n e s c a p e fro m t h e m a s s .

com ponent b y d e c o m p o s itio n l e a d s

o f th e s w o lle n c h a r w ith en h an ced

to

c a rb o n con­

te n t. R e c e n tly B e rk o w itz

(8 )

has c ritic iz e d

th is

th e o ry a d v e rs e ly

m a in ly on th e g ro u n d s t h a t t h e r e i s no e x p e r im e n ta l e v id e n c e o f th e f u s ib le n o t re a lly tic u la r,

com ponent and t h a t i n any c a s e c a r b o n iz in g behave as i f

he say s,

s u c h a com p o n en t w e re fo rm e d .

t h a t i n i t i a l m e ltin g o f th e

coal does In p a r­

c o m p o n e n t w o u ld

b e e x p e c t e d t o b e a c c o m p a n ie d b y a s h r i n k a g e a s t h e l i q u i d o c c u p ie d

t h e p o r e s p a c e w h ic h i s

c o k in g c o a l.

a b o u t 5 $ o f t h e v o lu m e o f a

17. He p r o v i d e s a n a l t e r n a t i v e

th e o r y w h ic h i s

c o m p a tib le

w i t h t h e kn o w n b e h a v i o u r o f c o a l s o f d i f f e r e n t r a n k a n d a p p e a r s m o re a c c e p t a b l e , S o fte n in g i s

th o u g h la c k i n g r i g o r o u s p r o o f .

e x p la in e d a s b e in g s im ila r to

p l a s t i c s - f o r w h ic h s u g g e s t i o n t h e r e i s Gras e v o l u t i o n i s

s till

t h a t o f p o ly m e ric

som e e m p i r i c a l e v i d e n c e .

c o n s id e re d to b e d u e to d e coup o s i t io n o f

c o a l m a t e r i a l b u t t h e s i z e o f p o r e s fo r m e d i n

th e coke d ep en d s

o n t h e d e g r e e t o w h ic h t h e c o a l h a s s o f t e n e d a n d o n t h e p o r e s tr u c tu r e o f th e p a re n t c o a l. c o n s tric te d

T h is i s b e lie v e d to b e h ig h ly

and h e n c e l e s s p e rm e a b le to g a s e s ,

in th e s o -c a lle d

c o k in g c o a l s t h a n - i n t h o s e o f h i g h e r o r o f lo w e r r a n k , fo r m a tio n o f th e f a m i l i a r b u b b le p o r e s i n g a s e s b e in g e v o lv e d f a s t e r th a n th e y p o r e s y s te m . h ig h p o r o s i t y

th e

In th is

coke i s due to th e

can escap e v ia th e e x is tin g

H o n - c o k in g c o a l s d o n o t s w e l l a n d d o n o t d e v e l o p e i t h e r b e c a u s e th e y a r e d e f i c i e n t i n v o l a t i l e s ,

b e c a u se th e v o l a t i l e s s y s te m i n

and t h e

can escap e e a s ily

or

th r o u g h a p e rm e a b le p o re

c o a l. e x p la n a tio n p o r e s a r e d e p i c t e d a s b e in g fo rm e d

w i t h i the p a rtic le s

o f c o a l,

s o fte n in g ,

th e m e c h a n ic a l p r e s s u r e s d e v e lo p e d d u e to

h o w e v e r,

c o m b in e d w i t h

s w e llin g i n

a c o n fin e d

s p a c e m u s t p ro m o te th e c o a le s c e n c e o f t h e c o a l p a r t i c l e s and t h i s p r e s e n ts th e p o s s i b i l i t y

t h a t b u b b le s fo rm a l s o b e tw e e n

th e o r ig in a l co al p a r t i c l e s . I n d e e d B angham , McKee a n d p i r a n i { $ ) h a v e sh o w n b y h e a t i n g t o g e t h e r g r o u n d g l a s s a n d a l k a l i n e e a r th c a rb o n a te s t h a t i f

th e g la s s

co n p o ses a p o re s tr u c tu r e l i k e

s o fte n s b e fo re

th e s a l t d e -

t h a t o f coke can b e p ro d u c e d .

I t seems p ro b a b le t h a t b o th mechanisms o p e ra te and t h a t t h e i r r e l a t i v e im p o rtan ce w i l l depend on th e r e l a t i v e r a t e s o f s o f te n in g and gas e v o lu tio n .

The p o re s iz e d i s t r i b u t i o n

o b ta in e d w i l l b e shown to b e co m p atib le w ith t h i s s u g g e s tio n .

19. SECTION k* THE APPARENT DENSITY OP COKE (%). The l i t e r a t u r e on th e measurement o f th e ap p a re n t d e n s ity of coke h a s been review ed by R e if (1 0 ).

The meaning o f th e term

as i t a p p l ie s to p o ro u s m a te r ia l i s d is c u s s e d , and i t i s v e ry p r o p e r ly d e fin e d a s " th e r a t i o o f th e mass to th e g eo m etric volume o f a r e p r e s e n t a t i v e cube o f th e m a t e r i a l 1'.

Thus any p o ro u s

m a te r ia l w ith a d e f i n i t e u p p er l i m i t o f p o re s iz e has a d e f in a b le a p p a re n t d e n s ity b u t i t s measurement depends on th e p ro d u c tio n o f a " r e p r e s e n ta tiv e cube".

T his sample need n o t be c u b ic .

Any

g eo m etric form bounded by "smooth" s u r fa c e s would be e q u a lly s u ita b le .

The e s s e n t i a l f e a t u r e i s t h a t th e volume can be

u n iq u e ly d e f in e d . The s u r fa c e o f bro k en coke i s n o t "smooth" i n th e s p e c ia l se n se t h a t th e rim s o f th e open p o re s a r e n o t u n ip la n a r so t h a t th e r e i s no u n iq u e d e f i n i t i o n o f th e bounding s u rfa c e o f th e p a r t i c l e , and hence i t s volume i s u n c e r ta in .

T his u n c e r t a i n i t y

i s p r o p o r tio n a te ly l e s s f o r l a r g e r p a r t i c l e s and te n d s to z e ro f o r p a r t i c l e o f i n f i n i t e s iz e .

A r e p r e s e n ta ti v e cube may b e r e ­

g arded a s a p o r tio n o f an i n f i n i t e p a r t i c l e such t h a t i f an i n f i n i t e number o f s im ila r cubes w ere b u i l t in to a s in g le mass th e a p p a re n t d e n s ity would n o t be a l t e r e d . A part from th e "boundary" e r r o r s d e s c rib e d above, th e measurement o f Da i s s u b je c t to sam pling e r r o r s , s iz e d e g ra d a tio n e r r o r s and th e e r r o r of d e te rm in in g f i s s u r e volume as p o re volum e.

20. Sam pling e r r o r s can be red u ced to any d e s ire d l e v e l by ta k in g more and more p ie c e s i n th e sam ple.

For convenience t h i s u s u a lly

means ta k in g sm a lle r p ie c e s b u t i t i s n o t alw ays p r a c t i c a b l e to do so .

Sm all p ie c e s o f coke a re s u b je c t to a v a ria n c e due to

p o s it io n i n th e o r ig in a l p ie c e s , so t h a t th e number of sm all p ie c e s must be l a r g e enough to c a n c e l t h i s new e r r o r . S iz e d e g ra d a tio n e r r o r s a r e n e g l i g i b l e a s lo n g as th e p ie c e s a r e much l a r g e r th a n th e l a r g e s t p o r e s . F is s u r e e r r o r s can be m inim ized only by r e j e c t i n g b ad ly f i s s ­ u re d p ie c e s from th e sample and t h a t u s u a lly l i m i t s th e s iz e of p ie c e s t h a t can b e u s e d . The norm al method o f d e te rm in in g Da i s by a soaking or b o i l ­ in g method w hich may b e a p p lie d e i t h e r to h a l f oven w id th p ie c e s ( 6) or to bro k en lumps o f 3« - 4 11 s iz e ( 7 ) .

B r ie f ly , a w eighed

mass o f coke i s soaked in w ate r and th e n re-w e ig h ed i n w ater and a g a in i n a i r a f t e r d r a in in g .

From th e s e th r e e w eig h ts th e

a p p a re n t d e n s ity can be c a lc u la te d . R e if h a s shown th a t su ch methods a re v e ry in a c c u r a te , y i e l d ­ in g v a lu e s 5 o r 6 p e r c e n t h ig h e r th a n th o s e o b ta in e d by a «geom etric» m ethod.

The d is c re p a n c y i s due to th e f a i l u r e of th e

w a t e r / a i r i n t e r f a c e a f t e r d r a in in g to c o in c id e w ith th e s t a t i s ­ t i c a l l y " tr u e " boundary o f th e lum ps.

I f th e p o s it io n of th e

s u r fa c e a s d e fin e d by th e w a t e r / a i r in t e r f a c e under (more or l e s s ) sta n d a rd c o n d itio n s i s in e r r o r by say d e n s ity w i l l depend upon s iz e , b e in g 2 ” lum ps; and 1 8 $ f o r 1»» lum ps.

th e n th e e r r o r in fo r

lum ps; 9f0 f o r

T his e r r o r i s se v e re and

c e r t a i n l y d is c o u ra g e s a tte m p ts to m easure Da on sm all p ie c e s ,

21. no m a tte r how much b e t t e r th e sam pling may b e . I t was d e c id e d to work d i r e c t l y from R e if *s d e f i n i t i o n and en^loy th e fo llo w in g g eo m etric m ethod.

About 25 p ie c e s o f coke

w ere ta k e n from th e g ro s s sample a s random ly a s p o s s i b le b u t b ad ly f i s s u r e d p ie c e s b e in g r e j e c t e d .

A specim en was cu t from

each p ie c e w ith a diamond edged c u ttin g d i s c .

The specim en was

to b e bounded by p la n e s u r f a c e s ; was to be as la r g e a s p o s s ib le from th e p a r e n t p ie c e ; and fre e; of a l l b u t th e f i n e s t f i s s u r e s . These specim ens were d r ie d , d u s te d and w eighed, and th e n soaked in h o t p a r a f f i n wax, ta k e n o u t and c o o le d .

A r e - d ip i n c o o le r

wax was u s u a lly n e c e s s a ry i n o rd e r t h a t each p ie c e should be com­ p l e t e l y enveloped and th e wax firm ly a tta c h e d to th e coke s u rfa c e . A r a z o r b la d e was th e n u sed to c le a n o f f th e excess wax down to th e l e v e l o f th e p la n e s u r fa c e s bounding th e specim ens.

The volume of

th e coke was th e n d eterm in ed by th e d isp la c e m e n t o f m eth y lated s p i r i t s from a Eureka can.

A lcohol was u se d in p r e f e r e n c e to

w a te r b ec au se (a) some p ie c e s o f coke f lo a te d in w a te r and (b) a i r b u b b le s were l e s s l i k e l y to c lin g e s p e c ia lly where i t had been n e c e s s a ry to c le a n wax o u t of a s l i g h t f i s s u r e on th e coke su rfa c e . T his te c h n iq u e a v o id s boundary e r r o r s and d e g ra d a tio n e r r o r s a -lm o s t e n t i r e l y , and f i s s u r e e r r o r s a re b e lie v e d to have been r e ­ duced to a minimum.

The a p p a re n tly crude measurement o f volume

was s u b je c te d to r e p e t i t i v e checking and found to g iv e good r e p r o ­ d u c ib ility .

The p ie c e s u sed had each a volume o f 50 - 100 com.

and th e p e rc e n ta g e e r r o r in th e m easured volume o f 25 o f them was

22. v e ry s m a ll.

The sam pling e r r o r however h as b een found to be

v e ry l a r g e , in c o r p o r a tin g no d o u b t th e v a ria n c e due to th e p o s i t i o n o f th e specim en in th e o r i g i n a l p ie c e , and t h a t o f th e p ie c e i n th e oven, (n o t to m ention th e d if f e r e n c e s betw een o v e n s). The o v e r a ll v a r i a b i l i t y was examined by d e te rm in in g th e a p p a re n t d e n s i t i e s o f in d iv id u a l p ie c e s o f th e sam ples o f IV and The d a t a o b ta in e d a r e p r e s e n te d i n T able I I w hich in d ic a te d

V II#

t h a t e r r o r s a r e p ro b a b ly d i s t r i b u t e d n o rm ally and t h a t when a sam ple o f 25 p ie c e s i s u sed as su g g e ste d th e mean v a lu e of Da i s s u b je c t to an e r r o r o f '2.3 $ #

To h a lv e t h i s e r r o r i t would be

n e c e s s a ry to p r e p a r e 100 specim ens]

T his confirm s R e i f ’ s a n a l­

y s i s o f Mott and W heeler1s d a ta on some 900 f u l l le n g th p ie c e s r e p r e s e n tin g 200 v a r i e t i e s from w hich th e co rresp o n d in g r e p r o ­ d u c i b i l i t y i n Da from a sam ple of 25 p ie c e s has been c a lc u la te d to be

2.-2$. The m agnitude o f e r r o r o b ta in e d i s i n i t s e l f o f c o n s id e ra b le

im p o rtan ce as i t i s im p o s s ib le to e n v isa g e a more a c c u r a te d i r e c t method f o r d e te rm in in g a p p a re n t d e n s ity , th a n t h a t d e s c r ib e d above.

The u se o f l a r g e r p ie c e s would re d u c e sam pling e r r o r s a t

th e expense o f f i s s u r e e r r o r s .

The u s e o f a s i g n i f i c a n t l y l a r g e r

number o f p ie c e s would be j u s t i f i e d o n ly i n v e ry s p e c ia l c a se s su ch a s th e c a l i b r a t i o n o f some i n d i r e c t method.

T a b le j i . ■i

■■



-

T he A c c u r a c y o f D _ #



a

j

M ean i n d i v i d u a l V a lu e s o f Ba .

C oke

Da

S td . D ev.

* + E rro r

0.746 0 .8 0 0 0 . 8 1 4 , 0 . 8 1 8 , 0 .8 2 3 0 . 8 3 0 , 0 . 8 4 3 , 0 .8 4 8

IV

0.850,0.854,0.855,0.856,0.864,0.874.

0 . 862.

0.056 ±2.3#

0.865

0.043 1 2 . 0 /.

0 . 8 7 5 , 0 . 8 8 3 , 0 . 8 8 8 , 0 .890•

0 .9 1 0 . 1.005

0 .7 8 6 . 0.834,0.840,0.848. 0.850,0.859,0.865.

V II

0 .9 0 0 . 0.934,0.935. On a s a m p le o f 25 p i e c e s .

T he v a l u e s o f Da o b t a i n e d f o r t h e g iv e n i n

T a b le I I I .

The c o k e s s e l e c t e d

c o k e s e x a m in e d a r e h a v e a w id e r a n g e o f

a p p a r e n t d e n s i t i e s w h ic h c a n b e d e d u c e d fro m l a t e r d a t a d u e t o w id e d i f f e r e n c e s b o t h i n p o r o s i t y a n d i n r e a l d e n s i t y .

TABLE I I I . - A pparent D e n s i tie s and t h e i r R e la tio n s h ip w ith Bulk D e n s i tie s .

I

Coke

!' i ii I

i

■°a

0.88

Db

-

RVDb

-

IV

i ; V 1

| 0o86 j 0.92 i j o.i+55 i o .5 o 5 j 0.514i

j 0.78

11.72

! 1.71 11 .7 1 .I1 — —

VI

V II

P

Q

0.995

0 .8 8

0 .5 4

2.65

0.5 6

0.495

0.305

1.43

1 .7 8

1.78

1 .7 7

1 .8 5

The developm ent o f a method i n w hich a f a i r sam ple of broken coke could be u se d would be v e ry d e s i r a b l e , and a s u i t a b l e i n ­ d i r e c t method w hich could be c a l i b r a t e d by th e above d i r e c t method can now be s u g g e ste d .

i n T able I I I a re g iv en th e v a lu e s

of b u lk d e n s ity (Db ) and a r a t i o R = Da/Dt).

The d e te rm in a tio n of

Db i s th e s u b je c t o f S e c tio n 11, and th e v a lu e s g iv e n a r e th o se o b ta in e d from la r g e s iz e s (above \ i n eh) o f each coke, w here Db i s p r a c t i c a l l y in d e p en d en t of s i z e .

The r a t i o R i s n o t q u ite

c o n s ta n t and may depend upon th e shape o f th e coke p a r t i c l e s , as i s d is c u s s e d in S e c tio n 1 2 . N e v e rth e le s s , i f th e mean v a lu e of R== 1.74- i s u sed , th e n v a lu e s of Db a re a l l w ith in y/0 o f th e v a lu e s o b ta in e d by d i r e c t m easurem ent.

When i t i s remembered t h a t v a lu e s o f Da a r e them­

s e lv e s l i a b l e to a sam pling e r r o r o f over 2$ , i t seems p ro b a b le t h a t th e sim ple r e l a t i o n s h i p Da =R Db could p ro v id e th e b a s is o f a s u i t a b l e i n d i r e c t m easurem ent of a p p a re n t d e n s ity .

Accuracy

b e t t e r th a n ± 3$ would have to be a s s u re d of co u rse b u t could p ro b a b ly be a t ta i n e d by s ta n d a r d iz a tio n o f method and c a r e f u l d e te rm in a tio n o f th e b e s t v a lu e o f R u n d er th e sta n d a rd con­

d itio n s .

R* might be made more co n stan t fo r d if f e r e n t cokes

by modifying the p a r ti c l e shape by trom melling the sample.

SECTION 5 .

THE REAL DENSITY OF COKE (Dr ) . I t i s obvious th a t the t o t a l p o ro sity of coke can be c a l­ cu lated from the v alu es of i t s apparent and r e a l d e n s itie s .

The

r e a l d en sity of a porous m a te ria l may be defined as the r a ti o of i t s mass to i t s volume excluding the volume of a l l pores#

The

measurement of r e a l d en sity thus defined th ere fo re depends upon the p o s s ib ility of f i l l i n g a l l the pores w ith a s u ita b le d is ­ placement flu id # p revious stu d ie s of r e a l d en sity d eterm ination have shown th a t pores e x is t of siz e s probably down to m olecular dimensions and th a t to f i l l them is n ot an easy m atter*

D e n sitie s obtained

by displacem ent of helium are g en erally accepted as being most n early co rre c t b ut th a t method was not a v a ila b le .

The use of

liq u id displacem ent media have never been found very s a tis fa c to r y as d if f e r e n t liq u id s give d if f e r e n t values of d e n sity fo r the same coke.

U n til re c e n tly no s a tis fa c to r y theory had been put

forward to explain irre g u la r r e s u l ts obtained. A s e rie s of experiments has been c a rrie d out to determ ine i f p o ssib le the most s u ita b le method of measuring Dr fo r the purposes of th is in v e s tig a tio n of p o ro sity .

As the d e ta ils of

th ese experiments and most of the conclusions drawn are i r r e l e ­ v an t to the main theme of the re se a rc h the account of them has been p u t in to an appendix (A). r e s u l t s are summarized below.

The im portant conclusions and

27.

(1)

I t was confirmed, by in feren ce, th a t very small pores

p o ssib ly down to m olecular dim ensions, do e x is t in coke. (2)

The method p re fe rre d as giving the most c o n siste n t r e s u l ts

from coke to coke i s th a t u sin g benzene as the displacem ent medium a f te r a degassing treatm ent a t 500°C.

The values thus

obtained may be ra th e r lower than by helium displacem ent but the discrepancy i s probably small and very sim ilar from one coke to ano th er. (3)

The values of the r e a l d e n s itie s of the cokes studied as

obtained by the p re fe rre d method are given in Table IV along w ith r e a l d e n s itie s of Quartz, p a r a ffin coke and Coal obtained by d i s ­ placement of w ater. Table IV - Real D e n sitie s to be employed in p o ro s ity C alculations M aterial. Coke I

Method

D ensity (gm./ccm)

Evacuation and Benzene

1.88

Coke IV

*» ••

t• ••

•• ••

1.885

Coke V

••

«•

••

1.965

Coke VI

:

:

s

2.01

Coke VII

i

5

S

1.88

Coke I I

Coke p Quartz Coal C

B o ilin g w ith Water q

1.9k

i.kkS

J

1

2

2.65

:

:

t

1.33

28 e

SECTION 6. I n t e r m e d i a t e D e n s i t i e s b y D ia k o n D i s p l a c e m e n t (D a ) The p r e s e n c e o f m i n u t e p o r e s , p o s s i b l y o f m o l e c u l a r d i ­ m e n s io n s h a s b e e n i n f e r r e d fro m th e r e s u l t s

o f th e e x p e rim e n ts

on r e a l d e n s it y o f c o k e . W hen t h e p o r e

s i z e d i s t r i b u t i o n s r e p o r t e d l a t e r w e re

»wwl

measured i t was found th a t no pores sm aller than O.Oij. were being detected*

the same time i t could be deduced th a t the

(counting) method used was probably f a il i n g to record, a small p ro p o rtio n of the p o ro s ity . T hese c o n s id e r a tio n s p o in te d to v e s tig a tin g

th e s e

s m a lle s t p o re s .

m e a su re th e

a p p a re n t d e n s ity

th e d e s i r a b i l i t y

I t w as d e c id e d to

o f c e ll w a ll m a te r ia l in

d e te rm in e th e am ount o f any s u c h p o r o s i t y ta in .

o f in ­ a tte m p t to o rd e r to

t h a t i t m ig h t con­

The f o l l o w i n g m e th o d w h i c h h a s b e e n d e v e l o p e d e m p lo y s

d i a k o n a s t h e d i s p l a c e m e n t m e d iu m .

Diakon i s a therm o p lastic m aterial which can be moulded w ith high p re ssu re a t tem peratures of 120 - l k 0 ° C, and which i s used fo r mounting specimens fo r m etallographic examination.

It

i s used here as the displacem ent medium In d en sity determ ination in the b e lie f th a t i t does not p e n e tra te the f in e s t pore s tr u c t­ u re of the coke. One g ra m o f c o k e ( o r a s i m i l a r v o lu m e o f o t h e r m a t e r i a l s ) w a s m ix e d w i t h a b o u t 8 c cm . o f d i a k o n p o w d e r a n d p l a c e d i n a 1 " d ia m e te r c y lin d r ic a l a b o v e an d b e lo w .

s t e e l m o u ld w i t h a t h i n l a y e r o f d i a k o n

T he m i x t u r e w a s m o u ld e d a t

in c h p r e s s u r e a p p lie d

as

lj.000

t h e m o u ld h e a t e d u p f r o m

lb * p e r sq u are

90°

to

130°C

29. and m a in ta in e d d u r in g

c o o lin g b a c k to

kO°G»

The d e n s i t y o f t h e

c o m p o s i t e m o u ld in g w a s f o u n d b y t h e m e th o d o f A r c h i m e d e s . d e n s ity

o f d ia k o n a lo n e p r e p a r e d i n

s e p a ra te ly ,

th e

sam e way w a s d e t e r m i n e d

a n d t h e v a l u e o f t h e d e n s i t y Dd o f t h e c o k e b y t h e

d is p la c e m e n t o f d ia k o n w as c a l c u l a t e d . to

The

D e n s iti e s w e re a d ju s te d

t h e b a s i s o f t h a t o f w a t e r a t 25 °C e q u a l t o o n e t o b e i n l i n e

w ith th e r e a l d e n s ity d a ta . to b e n e c e s s a ry t l / 2 n d ly a m uch l a r g e r c o u n t w o u l d

have b een n e c e s s a ry i n o r d e r th a t th e o b ta in e d w ith s u f f i c i e n t a c c u ra c y .

t o t a l w e ig h t c o u ld be The f o l l o w i n g t e c h n i q u e w as

d e v e l o p e d w h i c h e n a b l e d Ws t o b e d e t e r m i n e d dow n t o 1 7 0 / 2 0 0 m e s h . A c o u n t i n g b o a r d w as p r e p a r e d ,

a te n in c h square o f in c h

a n d t e n t h s g r a p h p a p e r b e i n g m o u n te d o n a s t i f f fit

e x a c tly .

One h u n d r e d s a m p l i n g a r e a s ,

h u n d re d ,o n e in c h s q u a r e s on th e b o a r d ,

c a r d tr i m m e d t o

one i n e a c h o f th e one

e a c h 0 . 3 n x 0 . 4 tr i n

siz e 3

w e re m ark ed o f f . A su ita b le

p o r t i o n o f th e

siz e

o b ta in e d by c o n in g and q u a r t e r i n g . b o ard ,

sp illa g e

f r a c t i o n b e i n g t e s t e d w as I t w as s c a t t e r e d o v e r t h e

o v e r t h e e d g e s b e i n g c a u g h t on w h i t e p a p e r and

re s c a tte re d u n til of n e g lig ib le

p ro p o rtio n .

s c a t t e r e d fro m a r e l a t i v e l y c o a r s e

The c o k e w as

s i e v e w i t h a m a sk o f p a p e r

w ith ab o u t a dozen q u a rte r in c h h o le s in i t

l y i n g on to p o f th e

60

c lo th .

T h i s s i e v e w as s h a k e n o v e r t h e b o a r d a n d g a v e a f a i r ­

l y u n ifo rm d i s t r i b u t i o n

of p a r tic le s upon i t .

The n u m b e r o f p a r t i c l e s

i n e a c h s a m p l i n g a r e a w as t h e n

c o u n te d u s in g a m a g n ify in g g l a s s

of su ita b le

sum m u l t i p l i e d b y 8 . 3 3 t o g i v e a n e s t i m a t e on th e b o a r d .

pow er and t h i s

o f th e t o t a l num ber

The b o a r d w a s t h e n s w e p t c l e a n o f c o k e w h i c h

was w e ig h e d . P a rtic le s

ly in g a cro ss

th e b o u n d a r ie s o f th e sa m p lin g

a r e a s w ere c o n v e n t i o n a l l y c o u n te d i n o r o u t d e p e n d in g on w h e th e r th e y la y a c ro ss

th e

S

S am p lin g o f th e g r o s s

a n d W, o r siz e

N

and

E

edges r e s p e c tiv e ly .

f r a c t i o n had to be b y c o n in g and

q u a r t e r i n g a s ran d o m s a m p lin g g a v e v e r y e r r a t i c

re su lts

o f th e c lo s e

th e

siz e r a tio

w as n o t p e r m i t t e d 0 .0 4 g ram s. checked i f

(1 .2 ).

On t h e b o a r d ,

t o f a l l b e lo w 1000 n o r t h e

Ws

in

sp ite

to ta l count

t o t a l w e ig h t b e lo w

was a lw a y s d e t e r m i n e d i n d u p l i c a t e a n d r e ­

g o o d a g r e e m e n t w as n o t o b t a i n e d .

Q u a rtz

( i n th e

c a l i b r a t i o n ) w as c o u n t e d o n a b o a r d o n w h i c h t h e c o u n t i n g a r e a s w ere in k e d b l a c k . (6)

The a c c u r a c y o f t h e c o u n t i n g o p e r a t i o n i s

m ig h t be e x p e c t e d . a tta in e d

n o t as h ig h as

S i g n i f i c a n t l y h ig h e r a c c u ra c y c o u ld be

o n l y b y m o re a n d m ore r e d u p l i c a t i o n b u t t h e m e th o d i s

a l r e a d y c u m b e r s o m e a n d t e d i o u s a n d f u r t h e r l e n g t h e n i n g w o u ld h a r d ly be j u s t i f i e d by th e in c r e a s e T h ere i s o f th e

siz e ,

an in e v ita b le

in accu racy o b ta in a b le .

sa m p lin g e r r o r due to th e v a r ia n c e

shape and d e n s i t y o f th e p a r t i c l e s

s iz e f r a c tio n .

E v en w hen t h e

1 .2 th e w e ig h t r a t i o r

sie v e

of p a rtic le s

siz e r a tio

in a sin g le w as a s lo w a s

o f q u a r t z was f o u n d t o b e o f

61 t h e o r d e r o f 100«

The v a r i a n c e

such th a t th e accu racy of i t s w as o n l y if

t 4 .7 %

o f Ws

i n 5 / 6 m . q u a r t z w as

d e te r m in a tio n fro m 1000 p ie c e s

(9 5 °/o l e v e l o f p r o b a b i l i t y ) ,

o rt3 .3 ° /0

t h e a v e r a g e o f d u p l i c a t e d e t e r m i n a t i o n w as t a k e n .

s i m i l a r v a l u e w as o b t a i n e d f o r 1 4 / l 6 m . q u a r t z . ev er v ery ir r e g u la r in

Q u a r t z i s how ­

sh a p e a n y sam p le c o n t a i n i n g a w id e r a n g e

o f sh a p e s fro m n e e d le s to p l a t e s fin d

A

a n d i t w as n o t s u r p r i s i n g

to

t h a t t h e c o r r e s p o n d i n g a c c u r a c y o b t a i n e d f r o m t h e m o re

u n i f o r m l y s h a p e d c o k e IV w as i 2 ° / 0

on th e d u p l i c a t e d e t e r ­

m in a tio n a t 5 /6 m .. T h a t e r r o r w i l l p r o b a b l y n o t v a r y dow n t o 5 2 / 6 0 m . t h o u g h m i s t a k e s i n c o u n t i n g may t e n d t o b e m o re f r e q u e n t a t s m a l l e r s iz e s.

When t h e c o u n t i n g b o a r d i s u s e d t h e

q u ite d if f e r e n t.

e rro r p a tte rn is

As t h e n u m b e r o f p a r t i c l e s

in c re a se s

th e e r r o r

due to sh ap e and s i z e

s a m p lin g r a p i d l y becom es n e g l i g i b l e

th e m a jo r e r r o r i s

th e

th e b o a rd .

in

of th is

An e r r o r o f ± 4 ° / o

d u p l i c a t e was o b t a i n e d . and p r a c tic e

sa m p lin g o f th e p o p u la tio n d e n s i t y o f

An i n v e s t i g a t i o n

6 0 / 7 2 m . C oke P .

e r r o r w as made u s i n g o n t h e m ean o f t h e

T h is was d o n e a t r a t h e r a n e a r l y

a n d i m p r o v e d t e c h n i q u e may h a v e r e d u c e d i t

T h is v a r i a n c e w o u ld p r o b a b l y b e r a t h e r l e s s w here th e h i g h e r r a t i o p a rtic le

sta g e

la te r.

a t sm a lle r s iz e s

o f b o a rd o r s a m p lin g p a tc h a r e a to

p r o j e c t e d a r e a w o u ld i m p r o v e t h e

p o p u la tio n d e n s ity .

and

s a m p lin g o f th e

C e rta in ly re a so n a b ly c lo se d u p lic a te s

( 3 ° / o mfcjtimum d i f f e r e n c e ) w e r e n o r m a l l y o b t a i n e d . A p a rt fro m random e r r o r s

i n Ws

su ch as th o se d is c u s s e d

above t h e r e h a v e b e e n e n c o u n te re d o c c a s i o n a l v a l u e s w h ic h , w h ile r e a d ily re p ro d u c ib le l i e

w ild ly o ff th e b e s t li n e

th ro u g h th e r e s t o f th e p o in ts . th e se

a n o m a lie s t h a t can b e s u g g e s te d

consequence o f th e r a th e r sie v in g , in

T he o n l y is

e x p la n a tio n of

t h a t th e y a r e a

e rra tic d is trib u tio n s

a lre a d y p o in te d o u t on page

th e c a l i b r a t i o n by q u a r tz ,

55*

o b ta in e d by

They o c c u r r e d

and o c c a s i o n a l l y ,

o r n e a r a n o g iv e in a coke c u rv e have re n d e re d

o c c u rrin g a t th e d ra w in g o f

th e b e s t l i n e r a th e r d i f f i c u l t . At th e v e ry th e

sm a lle st s iz e s

i t w as a l r e a d y n o te d t h a t i n

c a l i b r a t i o n w i t h Q u a rtz and co k e

o b ta in e d . th e se

T h is s u g g e s ts a f a l l i n g

s m a l l s i z e s and w h i l e t h a t i s

P

p o o r a g re e m e n t w as

o ff of re p ro d u c ib ility

at

q u ite l i v e l y due to th e

d iffic u lty

o f h a n d l i n g and w e ig h in g o f s m a l l am o u n ts o f s m a l l

p a rtic le s,

to th e

sta g e s, siz e s,

chance o f c o n ta m in a tio n by d u s t a t v a r io u s

and to th e r a t h e r l e s s

s a tisfa c to ry

s ie v in g o f th e se

a c o m p l e t e l y new f a c t o r b e c o m e s o f i n c r e a s i n g i m p o r ­

ta n c e - n am ely e y e s t r a i n .

The e x t e n s i o n o f t h e

c o u n tin g to

3 00m . w o u l d h a v e b e e n d e s i r a b l e i f 2 ^ 0 a n d 3 0 0 m e s h s i e v e s o f su ffic ie n tly

h ig h a ccu racy had been a v a ila b le .

b e i n g p r o d u c e d w hen t h i s w o rk w as c a r r i e d o u t ) .

(T hey w e re n o t Im p ro v ed

c o u n t i n g m e t h o d s w o u ld h a v e h a d t o b e f o u n d h o w e v e r p r o b a b l y b y m a k i n g u s e o f a b i n o c u l a r m i c r o s c o p e o f lo w p o w e r m o u n t e d o ver th e

c o u n tin g b o a rd .

(7)

The r e l a t i o n s h i p b e t w e e n d Q

o n ly by m ic ro s c o p e « p o lish e d s e c tio n s

L arg er s iz e s

and

S

o f p o r e s w ere ex am in ed on

o f coke w ith a b in o c u la r m ic ro sc o p e .

S m a lle r p o r e s w ere ex am in ed i n p o l i s h e d of s u ita b le

can be d e te rm in e d

s e c tio n s

of p a rtic le s

s i z e m o u n te d e i t h e r i n W ood*s m e t a l o r i n d i a k o n .

A m e t a l l u r g i c a l m i c r o s c o p e w as u s e d a t s u i t a b l y h i g h m a g n i f i ­ c a tio n .

D i a k o n w as m o re c o n v e n i e n t f o r m o u n t i n g b u t s o m e t i m e s

t h e l a r g e r p i e c e s w ere c r u s h e d an d t h e i r p o r e s t r u c t u r e s d e ­ s tr o y e d d u r in g m o u ld in g . P o r e s i z e w as c o m p a r e d w i t h p a r t i c l e th e u p p erm o st and lo w e st o g iv e s i z e s .

(It

siz e

p a rtic u la rly at

sh o u ld be e x p la in e d

t h a t tw o r a n g e s o f p o r e s i z e w e r e f o u n d a n d h e n c e t h e r e fo u r o g iv e s i n s iz e

t h e l o g Ws /

lo g

S curve o f each c o k e .)

The

o f th e l a r g e s t p o re s d e te c te d i n any coke o b v io u s ly

c o rre s p o n d s w ith th e p a r t i c l e

siz e

a t th e u p p e rm o st o g iv e .

Tile l a r g e s t p o r e s f o u n d i n p a r t i c l e s th e lo w e s t o g iv e w ere u s e d t o com pare I t m ig h t be th o u g h t t h a t th e in

are

th is

of siz e

c o rre sp o n d in g to

d g and

S

a t th a t siz e .

s m a l l e s t s h o u ld have b e e n m easu red

c a s e , b u t t h e r e w e re a lw a y s a v e r y few m in u te p o r e s d e ­

t e c t a b l e by m ic ro sc o p e ,

so s m a ll and o f s u c h i n s i g n i f i c a n t t o t a l

v o lu m e t h a t t h e y w e r e p r o b a b l y n o t i n c l u d e d i n trib u tio n .

th e p o re d i s ­

T h e s e " p o r e s ” may o n l y h a v e b e e n s m a l l c h o r d s o f

m u ch l a r g e r s p h e r e s , a n d i t w a s t h o u g h t j u s t i f i a b l e th em a t t h i s

sta g e .

to ig n o re

P o r e s w e re e x a m in e d a t a few o t h e r s i z e s

i n te r m e d ia te b e tw ee n th e l a r g e s t and s m a l l e s t ,

and th e i n f o r ­

m a t i o n o b t a i n e d h a s b e e n su m m a riz ed f o r a l l t h e s e e x p e r i m e n t s i n T ab le V I I .

'

64 TABLE V I I . C oke

- D e t e r m i n a t i o n o f t h e R a t i o R®

P a rtic le Pore S ix e I S iz e S cm s. d s cms . . * . . .

1 1 ds/ s |

^ s/ s .

M e th o d o f M e a s u r e m e n t

j

II

0*51

0 .2 0

0 .3 9

S fro m u p p e rm o st o g iv e o f

IV

0 .5 1

0 .2 3

0 .4 5

l o g Ws /

V

0 .5 1

0 .2 0

0 .3 9

VI

0 .4 1

0 .1 3

0 .3 2

d s fro m l a r g e s t p o re s on

V II

0 .5 1

0 .2 0

0 .3 9

p o lish e d s u rfa c e s .

P

1 .9 0

0 .9 1

0 .4 8

II

0 .1 9

0 .0 6 4

0 .3 4

lo g S

cu rv e.

S fro m u p p e r o g iv e o f lo w er r a n g e . d s from l a r g e s t p o re s i n 5 /6 m . c o k e .

V

0 .0 3 8

0 .0 1 8

0 .4 7

L a r g e s t p o r e s i n $ 6 /4 4 m . coke o

XI

0 .0 2 3

0 .0 1 1 5

0 .5 0

L a r g e s t p o r e s i n 6 0 /7 2 m .c o k e

p

0 .0 6 1

0 .0 2 5

0 .4 1

S fro m lo w e r o g iv e

ds

fro m p o r e s i n 2 2 /2 5 m . c o k e . 0 .0 1 2 5

0 .0 0 3 8

0 .3 1

S fro m lo w e st o g iv e s .

II

| 0 .0 1 2 5

0 .0 0 5 1

0 .4 1

d s fro m l a r g e s t p o re i n

IV

0 .0 1 1 5

0 .0 0 3 8

0 .3 3

p a rtic le s

V

0 .0 1 4

0 .0 0 7 6

0 .5 4

( a b o u t 1 0 0 - 1 2 0 m .)

VI

0 .0 1 4

0 .0 0 2 5

0 .1 8 *

V II

0 .0 1 6

0 .0 0 5 1

0 .3 2

I

* No e x p l a n a t i o n c a n h e f o u n d f o r t h i s

o f o g iv e s iz e

v e r y lo w v a l u e o

P ro m t h e d a t a i n T a b l e V I I I t v a lu e

o f th e ra tio :a

R = d s/

S

is

can be deduced th a t th e a p p ro x im a te ly 0 .4 .

v a lu e c a n n o t be d e te rm in e d p r e c is e ly * av erag e v a lu e o b ta in e d i s m o re p r o b a b l e

th a t dg

It

Is

th o u g h t t h a t th e

p r o b a b l y r a t h e r lo w b e c a u s e i t

w as m e a s u r e d lo w t h a n h i g h .

coke c o u ld b e ex am in ed - f o u r o r f i v e

o f th e la r g e

sm a lle r p a r t i c l e s .

is

S a m p lin g

w as m o s t i n a d e q u a t e , f o r o n l y a s m a l l n u m b e r o f p i e c e s

a few d o z e n s o f t h e

T h is

o f any

p ie c e s

or

Each o f th e se p ie c e s

w as e x a m in e d i n one s e c t i o n o n ly w h ic h n e e d n o t i n t e r s e c t t h e la rg e s t p o re, c a lly . Is

or i f

i t d o e s w i l l p r o b a b ly n o t do so d i a m e t r i ­

The p r o b a b i l i t y o f d e t e c t i n g

th e re fo re

s m a ll b u t on th e

th e l a r g e s t p o re o f a l l

o th e r hand an u n u s u a lly la rg e

p o r e may b e f o u n d o f w h i c h t h e r e may b e t o o f e w t o b e o f a n y consequence. For th is

r e a s o n t h e c o u n t i n g m e th o d c a n n o t b e e x p e c t e d t o

g iv e p o re s i z e d i s t r i b u t i o n i n te rm s o f a b s o l u t e p o re s i z e b u t th e d i s t r i b u t i o n s coke to co k e.

m easu red w i l l p r o b a b ly be c o m p a ra b le fro m

A c o m p l e t e c r o s s - c h e c k o n t h e m e th o d u s i n g a n

i n d e p e n d e n t t e c h n i q u e w o u ld b e n e c e s s a r y i f m easure o f p o re s i z e s

is

to be m ade.

c e r t a i n t y i n th e v a lu e a d o p te d f o r

a m o re p r e c i s e

The e f f e c t o f t h e

un­

R , upon th e p ore s u rfa c e

a r e a s and c e l l w a ll t h i c k n e s s e s d e d u ce d fro m th e d i s t r i b u t i o n s w ill be in d ic a te d in

th e a p p r o p r ia te

se c tio n s.

66 C ritic ism s

of

t h e m e th o d *

T h ere a r e f o u r p o s s i b l e c a u s e s b y w h ic h th e c o u n tin g m e th o d may f a i l

to in d ic a te

p r o p e r ly th e v a r i a t i o n i n a p p a re n t

d e n s ity w ith siz e * F irstly , o n ly i n

t h e s h a p e f a c t o r may c h a n g e *

th e l i g h t o f th e r e s u l t s

T h is c an be d is c u s s e d

o b t a i n e d a n d w i l l :b e d e a l t w i t h

l a t e r i n S e c t i o n 12* S e c o n d l y , d i m i n u t i o n o f p o r o s i t y a t b r o k e n s u r f a c e s may cause an in c re a s e

i n D0 s a t a siz e

d i f f e r e n t i a l p o re ru p tu r e

occurs*

l a r g e r th a n t h a t a t w h ic h The d a t a o b t a i n e d h a v e b e e n

e x am in ed and t h e r e i s no s i g n o f t h i s e ffe c t*

phenom enon h a v in g a n y

Some e x p e r i m e n t s w e r e c a r r i e d

o f le a d sh o t

( o f know n s i z e

a n a ly sis)

(

o u t on an a g g lo m e ra te

in c o n c re te ,

i n w h ic h th e

s h o t w as t o r e p r e s e n t p o r e s a n d t h e c o n c r e t e c o k e - c a r b o n i n a n a n a lo g o u s

"coke"*

m easu re th e

The c o u n t s m e th o d w as a p p l i e d b u t f a i l e d

to

"p o re s iz e d i s t r i b u t i o n ” b ecau se o f " p o r o s ity ” l o s t

a t th e b ro k e n s u rfa c e s * out ra th e r re a d ily ,

In t h a t c ase how ever th e

and th e h o le s

l e f t b e h in d w ere i n e f f e c t

" n e g a tiv e p o r o s ity o f v e ry h ig h r e l a t i v e e f f e c t w as v e r y n o t i c a b l e o n ly a sm a ll f r a c t i o n

shot f e l l

in d e e d .

d e n sity "

and th e

B ut p o re s in coke can lo s e

o f t h e i r v o lu m e a s t h e y a r e e x p o s e d ,

g r e a t e r p a r t o f t h e m b e i n g d i v i d e d am ong t h e p a r t i c l e s

th e

fo rm ed

by th e f r a c tu r e * A th ird p o s s ib ility is

th a t a s im ila r d im in u tio n o f p o r­

o s ity o c c u rrin g a t a l l p a r tic le

siz e s

m i g h t d i s t o r t t h e Dg

c u r v e s o t h a t t h e r e w o u l d a p p e a r t o b e a m uch l o w e r p o r o s i t y o f sm all s iz e s

th a n th e re r e a l l y i s .

T h is p o i n t c a n n o t be

67 checked w ith o u t fin d in g

a c o m p l e t e l y i n d e p e n d e n t m e an s o f

m e asu rin g p o re s i z e d i s t r i b u t i o n ,

s u c h a s m ig h t hav e b e e n

a f f o r d e d b y t h e m e r c u r y p e n e t r a t i o n m e th o d *

I t may b e r e ­

m arked h o w e v er t h a t t h e r e h a s b e e n fo u n d a s u r p r i s i n g l y h i g h p r o p o r tio n o f p o r o s ity o f v e ry sm a ll siz e * F o u rth ly ,

th e re

is

th e p o s s i b i l i t y

o f t h e c o k e t h e m o re p o r o u s , e n d s w i l l b r e a k dow n f a s t e r s o t h a t Ws f o r l a r g e sm a ll s iz e s siz e s

fro m th e

(r e a l) dense in n e r

th a n th e h a rd d ense c a u lif lo w e r ends

T h is p o i n t was s u c c e s s f u l l y ex am in ed *

At

a s 5 / 6 m . o r ® / l 6 n - ^ / 8 n t h e v a l u e s o f Ws o b t a i n e d

sm a ll s iz e s

t h a t from th e

s o f t e r and l e s s

th e c o m m in u tio n

s i z e s w i l l be u n d u ly h ig h and t h a t f o r

t o o lo w *

as la rg e

th a t in

screen ed out a f te r

la rg e r siz e s

w ere i d e n t i c a l *

a fte r

th e f i r s t b reak d o w n and

th e f i n a l c ru s h in g in th e r o l l s

At v e r y s m a ll s i z e s no d i f f e r e n c e

c o u ld be

d e t e c t e d b e tw e e n th e v a lu e s

o f Ws f r o m t h e n o r m a l s a m p l e

and

t h a t o b ta in e d by c ru sh in g a

sam p le a s f i n e l y a s p o s s i b l e

in r o l l s «

T h is p o s s i b l e

so u rce o f e r r o r can be d is c o u n te d .

R e su its* The c o u n t i n g m e th o d h a s b e e n a p p l i e d t o a l l and th e d a ta a re a g a i n s t lo g b u t th e d ic a tin g

S*

su m m a riz ed The c u r v e

o f C oke P i s

Ws i s

p lo tte d

o f th e ty p e p r e d i c t e d

s i x m e t a l l u r g i c a l c o k e s show tw o ws t e p s ” a p p a r e n t l y i n ­ tw o d i s t i n c t r a n g e s o f p o r e

a t s im ila r siz e s in a l l is

i n F i g u r e 4 w here lo g

seven cokes

six cokes.

siz e .

The tw o r a n g e s o c c u r

The e x t e n t o f t h e u p p e r r a n g e

in each case v ery in a d e q u a te ly d e fin e d

t h e r e b e in g one p o i n t

o n ly i n th e m id d le o f th e " s t e p ” p a r t o f th e c u r v e . The l o w e r e n d o f t h e r a n g e o f s m a l l p o r e s u n f o r t u n a t e l y

c o rre sp o n d s w ith th e

s m a lle s t sie v e

siz e s

W_ a r e d e t e r m i n e d w i t h m o s t d i f f i c u l t y , s t i o n w as l e a s t

s a tisfa c to ry .

f o r w h ic h th e v a l u e s o f

and f o r w h ic h c a l i b r a -

The d r a w i n g o f t h i s

th e c u rv e s h a s o c c a s io n a ll y b een d i f f i c u l t

and i t

lo w e r end o f was f o r t h i s

r e a s o n t h a t e x t e n s i o n o f t h e c o u n t i n g t o 300m* w o u l d h a v e b e e n v ery u s e f u l. The v a l u e s

o f Ds h a v e n o t b e e n p r e s e n t e d a s t h e y a r e n o t

r e q u ir e d in th e c a lc u la tio n o f p o re o f no i n t e r e s t i n

and a re

th e m selv e s*

The t o t a l d i s p l a c e m e n t o f t h e p a r a l l e l to th e

siz e d is tr ib u tio n

l o g Ws a x i s

lin e a r p o rtio n o f th e cu rv es

is u su a lly le ss

f r o m t h e e x p e r i m e n t a l v a l u e s o f Da a n d

th a n th a t c a lc u la te d

D r

of

k.

th e

" d i a k o n " m e th o d o f m e a s u r i n g d e n s i t y ,

a ssu m in g c o n s ta n c y

I t was t h i s d i s c r e p a n c y w h ic h l e d t o

th e d e v e lo p m e n t o f

and th e d is p la c e m e n t

c a l c u l a t e d f r o m Da a n d D^ c o r r e s p o n d s f a i r l y w e l l w i t h t h a t found by c o u n tin g e x p e rim e n ts .

I n o t h e r w o r d s t h e maximum

v a l u e s o f Ds h a v e b e e n f o u n d t o b e a p p r o x i m a t e l y e q u a l t o D^* T he g r e a t e s t d i f f e r e n c e b e t w e e n t h e m w a s f o u n d i n C oke V a n d a m o u n ted t o a b o u t 6 p e r c e n t . The i n t e r p r e t a t i o n

of th is

m easu res th e d i s t r i b u t i o n

Is

t h a t t h e c o u n t i n g m e th o d

o f th e b u b b le p o re s o n ly .

q u e s tio n of th e c o n sta n c y o f

k

The

idfc d i s c u s s e d i n S e c t i o n 1 2 a n d

th e c a lc u la tio n o f th e p o re d i s t r i b u t i o n i s

S e c t i o n 13*

69 SECTION 11 INTERMEDIATE DENSITIES (Ds ) BY BULK DENSITIES (D b) An a l t e r n a t i v e s iz e

is

to

t h e c h a n g e s i n Ds w i t h

th ro u g h th e v a lu e s o f th e b u lk d e n s i t i e s

siz e d m a te r ia l• F irstly ,

m e th o d o f t r a c i n g

T h i s m e th o d w a s i n v e s t i g a t e d f o r tw o r e a s o n s .

i t w as h o p e d t h a t i t w o u l d p r o v i d e a n e a s i e r a l t e r n a t i v e

th e c o u n t i n g m e th o d , and s e c o n d ly ,

b e t t e r u n d e rsta n d in g

th a t i t

m ig h t le a d to a

o f shape f a c t o r s .

The t h e o r y o f t h e m e th o d i s m e th o d .

of c lo se ly

s im ila r to t h a t o f th e c o u n tin g

F ro m g e o m e t r i c c o n s i d e r a t i o n s

th e b u lk d e n s ity o f a non-

p o r o u s m a t e r i a l w o u ld b e e x p e c t e d t o b e i n d e p e n d e n t o f s i z e b u t it

w i l l d e p e n d on a p p a r e n t d e n s i t y , on s h a p e ,

a f f e c t in g p a c k in g . d o n d itio n s

lik e

e le c tro s ta tic p a rtic le s, in e rtia

Some o f t h e s e

ro u g h n ess,

fo rces.

fa c to rs

adsorbed la y e rs

O th e rs in c lu d e

and on any f a c t o r

a re due to s u rfa c e as of m o istu re ,

and

a i r - c u s h i o n i n g b e tw e e n

th e num ber o f f r i c t i o n p o i n t s i n th e b e d , and th e

o f th e p a r t i c l e s .

These l a s t

e f f e c t , b e i n g m uch m o re i m p o r t a n t i n s u l t b u lk d e n s ity is

th re e v ary in th e ir

sm all s i z e s ,

and a s a r e ­

g e n e r a l l y lo w er w ith s m a ll m a t e r i a l th a n

w ith la r g e . N e v e r t h e l e s s B u l k D e n s i t y may b e e x p r e s s e d a s Db = f • w here f p

is

Ds

a f a c t o r d e p en d in g on s h a p e , and th e p a c k in g f a c t o r

d e p e n d s on t h e v a r i o u s

e ffe c ts

p.

a lr e a d y m e n tio n e d .

S e c t i o n 10* a n d i s ,

su rface p ro p e rtie s Ds h a s t h e

and m e c h a n ic a l

same s i g n i f i c a n c e

as in

o f co u rse c o n s ta n t f o r non -p o ro u s m a te r ia ls ,

o r i n coke s iz e ra n g e s o f c o n s ta n t p o r o s i t y .

t

Z e v o P o v o s i tV

Constant Maxt»nu*u Povosity.

2

Q

FIGURE 5 . - S c h e m a t i c C u rv e ;

o f B u lk

te n s i ty v S iz e .

T h e n i f Dt> i s

p lo tte d

f o r a po ro u s m a te r ia l l i k e i n c r e a s e s f r o m Da t o Dr lik e

a g a in st

S,

th e p a r t i c l e s

c o k e i n w h i c h t h e v a l u e o f Ds

over a c e r ta in

siz e ran g e,

t h a t i n F ig u re 5 w i l l be o b ta in e d .

c o n s ta n t th e r a t i o

siz e ,

a cu rv e

I f f and p a re

o f t h e maximum t o t h e m inim um v a l u e o f

w o u l d b e e x p e c t e d e q u a l t o Dr / D a , a n d t h a t o f a n y i n t e r ­ m e d ia te v a lu e

o f Db t o

V ery l i t t l e siz e

on th e

t h e m inim um e q u a l t o Ds / D a

a p p ears in th e l i t e r a t u r e

on th e e f f e c t o f

shape o r p a c k in g f a c t o r s r e l a t i n g

In d eed v e ry l i t t l e

to b u lk d e n s ity .

h a s b e e n p u b l i s h e d on c l o s e l y s i z e d m a te r ­

i a l a t a l l except th e o r e tic a l c o n sid e ra tio n s

on th e p a c k in g

71

of spheres# la rg e

in c re a s e

R o lle r

( 2 6 ) h a s p u b l i s h e d some d a t a s h o w i n g a

i n v o i d a g e o f s i z e d m a t e r i a l s b e l o w 20yM (2 0 0 m . i s

7 6 / a) .

G ypsum , p o r t l a n d c e m e n t a n d a n h y d r i t e b e h a v e d s i m i l a r l y o / w ith v o id a g e s o f 4 3 -4 5 / 0 a t l a r g e r s i z e s w h ile th e s m a l le s t o / v o i d a g e g i v e n b y c h ro m e y e l l o w w a s 5 5 / 0 . The d i f f e r e n c e may be due to shape b u t th e know n. due to

B e lo w 2 0 / i

th e

c o n d itio n of R o lle r* s m a te ria ls sudden in c r e a s e

o n e o r m o re o f t h e f a c t o r s

is

not

i n v o i d a g e w as p r o b a b l y

a ffe c tin g

p a c k in g b eco m in g

o f in c r e a s in g im p o rta n c e a t d im in is h in g s i z e .

The o n l y o t h e r

in f o r m a tio n found i s

(2 5 ) i n T a b le V I I I

su m m a riz ed fr o m D a l l a v a l l e

TABLE V I I I . . V o i d a g e s f o u n d i n V a rio u s Packed M a t e r i a l s .

M a te ria l

V o id s ° / 0 o f

1 6 /3 8 m .T y le r

T o t a l V o lum e

S p h e r i c a l Pb S h b t

3 7 .1 8

S p h e ric a l S Shot

3 7 .3 5

D une S a n d

3 7 .6 0

B ea c h Sand

3 6 .5 5

M arin e ! Sand

,

3 4 .7 8

C ru sh ed Q u a rtz

4 1 .2

C rushed C a l c i t e

4 0 .7 6

C rushed H a lite

4 3 .5 1

M ic a

8 6 .6 2

.......................... The m a t e r i a l s w e r e s i z e d i n

72

t h e r a t h e r w id e r a n g e 1 6 /3 8 m .

T y l e r , (S iz e r a t i o = 2 ), and t h i s

p ro b a b ly a c c o u n ts f o r th e

m uch s m a l l e r v o i d a g e s t h a n a r e o b t a i n e d i r y b h i s w o r k . d e m o n strates c le a r ly

th e d ep en d en cy o f v o id a g e upon s h a p e .

S p h e r e s g a v e v a l u e s a b o u t 37 0/ 0 > o b l i q u e 3 5 % ; and a n g u la r p a r t i c l e s s i z i n g w o u ld i n c r e a s e w ith a s iz e r a t i o never le ss

T a b le V I I I

s o m e t h i n g o v e r 4 0 ° / o ..

th e se a l l ro u n d .

o f 1 .2

s p h e re s lo w e r,

about

C lo se r

I n t h e p r e s e n t w ork

t h e v o i d a g e o f c r u s h e d q u a r t z w as

th a n 4 7 ° /0 and t h a t o f la r g e

c o k e a b o u t 41 - 4 7 ° / 0 .

T h ese f i g u r e s w ere fo u n d t o i n c r e a s e b e tw e e n 51 and 5 5 ° /o

fo r

coke a t th e s m a lle s t s i z e s . The m e a s u r e m e n t s o f p o ssib ilitie s i s by f a r

is

v e ry sim p le .

T h ere a r e

- lo o s e p a c k in g and c l o s e s t p a c k in g .

t h e m o re r e p r o d u c i b l e .

tw o

The l a t t e r

C oke w as s i z e d a s f o r t h e

c o u n t i n g m e th o d b u t r a t h e r m o re o f e a c h f r a c t i o n w as r e q u i r e d . E a c h s i z e w as c o n e d c a r e f u l l y a n d p o u r e d i n t o c y lin d e r o f s u ita b le d im e n sio n s. tim e s th e d ia m e te r o f th e p a r t i c l e s

a m e a su rin g

T h is had to be a t l e a s t 8 and h a d t o be f i l l e d

h e ig h t a t l e a s t 6 tim e s th e d ia m e te r o f th e c y l i n d e r c y l i n d e r w as t a p p e d u n t i l made t o

to a

(2 6 ).

The

th e l e v e l o f th e coke c o u ld n o t be

f a l l any f u r t h e r .

The v o lu m e i t

o c c u p ie d i n th e

c y l i n d e r w as t h e n n o t e d a n d i t w as p o u r e d o u t a n d w e i g h e d , was t h e n s im p ly t h e r a t i o When t h e

o f t h e m a ss t o t h e m e a s u r e d v o l u m e .

s i z e w as b e l o w 44 m . t h e c y l i n d e r w as e v a c u a t e d

d u rin g th e p a c k in g p r o c e s s .

T h is sp p ed ed up p a c k in g o f th e

5fcarsfer o f t h e s e f r a c t i o n s a n d r e n d e r e d c l o s e p a c k i n g o f t h e

73 fin e s t fra c tio n s

p o ssib le

seem s t o c o n t r i b u t e fin e

as a i r c u s h io n in g b e tw e e n th e p a r t i c l e s

to w a rd th e p o o r p a c k in g n o r m a lly m et w i t h i n

pow d ers. The a c c u r a c y o f t h e d e t e r m i n e d b u l k d e n s i t y d e p e n d s o n t h e

re p ro d u c ib ility

o f t h e v o lu m e m e a s u r e m e n t .

g e n e r a l l y m ore a c c e p t a b l e p a c k in g d e n s i t y erro rs

are

th a t is

t h a n lo w o n e s b e c a u s e i t

b e in g m easu red .

sm a ll b u t p a c k in g a p p e a rs

h ad b e e n m ix e d .

H ig h v a l u e s a r e

C o n in g o f t h e

is

a maximum

S ie v in g and s a m p lin g

t o d e p e n d o n how t h e

sam p le b e f o r e p o u r in g i n t o

c y l i n d e r w as a d o p t e d a s s t a n d a r d p r o c e d u r e b e c a u s e i t re p ro d u c ib ility .

sie v e s in

th e

im p ro v e d

D u p l i c a t e s w i t h i n 2 ° /o w ere g e n e r a l l y o b t a i n e d e

The n e c e s s i t y o f e m p l o y i n g l a r g e r s i z e r a t i o s B .S .S .

sam p le

th e l a r g e r s iz e s

le d

on b u lk d e n s i t y b e in g i n v e s t i g a t e d . o f 1 .2 and a b o u t 1 .5

th e

to th e e f f e c t of s iz e r a t i o B etw een t h e s t a n d a r d v a l u e

e f f e c t w as n e g l i g i b l y

ra n g e c o v ers th e re q u ire m e n ts

th a n th e 1 .2 o f th e

sm a ll.

T h is

o f t h i s w o rk .

The b u l k d e n s i t y o f q u a r t z w as d e t e r m i n e d t o f i n d how i t v a rie d w ith s iz e The r e s u l t s V II and P .

as a g u id e

are p lo tte d

in

sta n t,

its

i n F ig u re 6 a lo n g w ith th o s e o f cokes

They a r e e r r a t i c

d e n s ity w ith s iz e . P

to w hat m ig h t be e x p e c te d o f c o k e .

b u t show a m a r k e d f a l l

On t h e o t h e r h a n d t h e b u l k d e n s i t y o f Coke

r a n g e o f z e r o p o r o s i t y b e l o w 25m . i s

c o rre s p o n d in g to a v o id a g e o f 5 2 ° /o

t h a t o f sm all q u a r tz . may b e d u e s i m p l y t o i t s a ttrib u te d

in b u lk

The e r r a t i c

re m a rk a b ly con­

th a t is

th e

sam e a s

v a lu e s o b ta in e d of q u a rtz

v e r y w i d e r a n g e o f s h a p e s t o w h i c h w as

i n S e c t i o n 10 t h e l a r g e

a v e r a g e p a r t i c l e w e i g h t Ws .

v a ria n c e

of its

v a lu e of

FIGURE

6#

OO ^ with

of

S iz e .

Bulk

te n sitie s

of

I,

V II

hf

P ana

- V a ria tio n s

74

OiP

75 The f a l l i n b u l k d e n s i t y o f q u a r t z d o e s s e e m t o b e r e a l h o w e v e r . It

o c c u rs m a in ly i n s i z e s

above 2 2 m ..

B e lo w t h a t s i z e b u l k

d e n s i t y may b e c o n s i d e r e d a l m o s t c o n s t a n t b u t v e r y e r r a t i c . c au se o f th e f a l l (c o u n tin g )

can n o t be e x p la in e d e s p e c i a l l y as th e

shape f a c t o r

B u lk d e n s i t i e s m esh s i z e s

k

w as c o n s t a n t .

of cokes I ,

V II,

and P w ere d e te r m in e d a t a l l

a n d V I I a n d P a t some l a r g e r s i z e s

a lso .

c o k e s w e re d e t e r m i n e d a t s m a l l an d l a r g e m esh s i z e s la rg e r

siz e s,

i n t e r e s t h a v in g f o c u s s e d on th e

s ta n t p o ro sity .

D a ta f o r c o k es I ,

g r a p h i c a l l y i n F i g u r e 6 w h e r e Db i s cu rv es are

o f th e

in d ic a tin g

th e

e x p e c te d form .

tw o r a n g e s o f p o r e

V II,

and P a r e

p lo tte d

siz e

of con­

su m m a riz ed

a g a in st

S •

The

a s d i d t h e c o u n t i n g m e th o d . D a ta a t l a r g e

C urves f o r th e

o th e r

o f I and V II and a r e n o t p r e s e n te d

a s th e y add n o th in g o f v a lu e a t t h i s siz e s

a n d a t a fe w

C oke V I I s h o w s t h e d o u b l e s t e p

s i z e s w e r e n o t o b t a i n a b l e f o r C oke I . c o k e s w ere i n l i n e w i t h th o s e

The o t h e r

s iz e ran g es

C oke P h a d o n e p o r e s i z e r a n g e o n l y a s e x p e c t e d .

to th e l a r g e s t

The

sta g e .

The d a t a p e r t a i n i n g

o n ly h av e b e e n in c lu d e d i n T a b le I I I

fo r

a n o th e r p u rp o se . B ro a d ly sp e a k in g th e

” s t e p s ’1 o b t a i n e d i n d i c a t e

r a n g e s a s w ere o b t a i n e d fro m th e ences in d e ta i ls .

th e

sam e p o r e

c o u n t i n g m e th o d b u t w i t h d i f f e r ­

O g iv e s a r e g e n e r a l l y l e s s

s h a rp and th e

lo w e r p o r e r a n g e s r a t h e r w id e r th a n b y th e c o u n tin g m e th o d . The v a l u e o f D r / D a i s

i n v a r i a b l y m uch l o w e r t h a n t h a t o b t a i n e d

fro m d e n s i t y m e asu re m e n ts o f fro m th e

c o u n tin g m e th o d .

T h is

co n fo rm s w ith th e b e h a v io u r o f q u a r t z

and m ust b e du e t o

some

change in p r o p e r tie s

a f f e c tin g p a c k in g .

T h is q u e s tio n i s d i s -

76 c u s s e d i n f u l l i n S e c t i o n 12 a l o n g w i t h o t h e r r e l e v a n t fo rm a tio n i n a g e n e r a l c o n s id e r a tio n o f th e p r o p e r tie s p a rtic u la te

in ­ of

m a tte r.

On t h e w h o l e t h e s e e x p e r i m e n t s h a v e c o n t r i b u t e d l i t t l e th e u n d e rs ta n d in g o f shape f a c t o r s u s e fu l as an a lte r n a tiv e

to

to

a n d show n o s i g n o f b e i n g

t h e c o u n t i n g m e th o d for., e s t i m a t i n g

p o re s i z e d i s t r i b u t i o n b e c a u se o f th e change i n p a c k in g c h a r a c ­ te ris tic s T h is i s

i n a s i z e ra n g e w h ic h c a n n o t be d e te r m in e d e x a c t l y .

p a r tic u la r ly u n fo rtu n a te

sin c e

th e

te ch n iq u e has been

fo u n d t o be so s im p le and r e p r o d u c i b i l i t y r e a s o n a b l y g o o d .

PART FOUR • L

CONCLUSIONS,

77 SECTION 1 2 . SHAPE FACTORS. T o t a l i g n o r a n c e o f s h a p e f a c t o r s w as a m a t t e r f o r some c o n c e r n w h e n t h e w o r k w as c o m m e n c e d .

S o m e th in g h a s b e e n

l e a r n e d on th e w ay, b u t th e in f o r m a t io n o b ta in e d i s a few m a t e r i a l s

o n l y a n d e v e n among t h e s e

lim ite d

some f e a t u r e s

to

la c k

e x p la n a tio n . The s h a p e f a c t o r s g i v e n i n T a b le IX . th e

k

o b t a i n e d b y t h e c o u n t i n g m e th o d a r e

Two v a l u e s a r e g i v e n f o r e a c h m a t e r i a l -

c o n s t a n t v a lu e f o r l a r g e p i e c e s w h ic h h ad l o s t no p o r o s i t y ,

and t h a t f o r

sm all p a r t i c l e s

w h ic h w ere f r e e

of p o res.

A lo n g ­

s id e a r e g iv e n th e v o id a g e s a p p ly in g to th e b u lk d e n s i t y m easu re­ m e n t s - a g a i n tw o v a l u e s f o r e a c h m a t e r i a l . w ere o f c o u r s e in te rc e p ts p a rts

in

o b ta in e d from th e th e o r d in a te

of th e c u rv es

be b e t t e r

D is

lo g S = 0

lo g S

(k .D ) w hence

e i t h e r Da o r

th a n t h a t o f th e

fro m th e

k

can be o b ta in e d i f D k

a p p ro p ria te d e n s ity v a lu e .

D

is

k

The i n t e r c e p t s

Da., a n d t h e a c c u r a c y o f

a c c u r a c y o f th e V o id a g e f i g u r e s

t 3 ° / 0 a s t h e y d e p en d on

g raph s,

of

( S « l c m . ) o f th e l i n e a r

(p ro d u ced i f n e c e s s a r y . ) .

g iv e th e v a lu e s o f lo g i s known.

l o g Wg/

The v a l u e s

p ro b a b ly n o t b e t t e r

a lso ,

cannot The

th a n

and on th e b u lk d e n s i t y

d e te rm in a tio n . An i m p o r t a n t f e a t u r e g ra d ie n ts

o f th e lo g w /lo g S

o f th e l i n e a r p o r tio n s

T h is a p p l i e s

to th e v e ry la rg e

in te rm e d ia te

s i z e s i n w h ic h t h e r e

to

p lo ts

a re a l l v ery c lo se

siz e s is

is

t h a t th e

to 3 .

o f p o ro u s c o k e s ;

to th e

a p p a r e n t l y no p o r e r u p t u r e ;

th e s m a l l s i z e s w here th e c o k e s a r e n o n - p o r o u s ; an d p a r t i c ­

u la rly

to q u a r tz and th e n o n -p o ro u s ra n g e o f s i z e s

o f C oke P .

78 I t w o u ld seem t h a t a n e a r l i e r little

w ith s iz e

or zero p o ro s ity .

is

a ssu m p tio n t h a t v a lu e s

p ro b a b ly j u s t i f i e d The a s s u m p t i o n i s

fo r m a te ria ls

s till

of

k

v ary

o f c o n sta n t

s u b je c t to th e n a tu re

o f t h e m a t e r i a l h o w e v e r a n d may n o t h o l d f o r t h o s e w i t h s t r o n g d i r e c t i o n a l c le a v a g e su c h as c o a l o r m ic a .

TABLE I X . -

Shape F a c to r s and V o id a g e s.

Shape F a c t o r

k

V o id a g e

° /0

C oke t L arge

S m a ll

S m a ll

L arge

I

0 .6 0 4

0 .6 1 8

-

5 3 .1

II

0 .5 8 9

0 .5 5 7

4 3 .0

5 5 .0

IV

0 .6 3 5

0 .6 1 9

4 1 .4

5 4 .5

V

0 .6 5 6

0 .6 3 8

4 1 .6

5 1 .7

VI

0 .6 5 0

0 .6 2 8

4 3 .7

5 3 .0

V II

0 .6 4 0

0 .6 1 8

4 3 .7

5 3 *3 .

p

0 .6 5 0

0 .6 2 6

4 3 .5

5 2 .0

Q

0 .6 4 2

0 .6 4 2

4 6 .3

5 1 .0

The g e n e r a l i m p r e s s i o n g a i n e d f r o m T a b l e IX i s

t h a t shape

f a c to r s have a r a th e r lim ite d ra n g e of p o s s ib le v a lu e s b u t w ith ­ in

t h a t ra n g e th e v a r i a t i o n a p p e a rs q u i t e random .

e x am p le i s

C oke I I

fo r

a b lo c k y coke f o r w h ic h a h i g h f a c t o r m ig h t hav e b e e n

e x p e c te d , b u t i t h as th e lo w e st f a c t o r ;

P

on th e o t h e r hand I s

a s o f t m a t e r i a l f o r m i n g f o u n d e d lu m p s f o r w h i c h a lo w v a l u e o f

79 k its

a p p r o a c h i n g t h a t f o r s p h e r e s w o u ld h a v e b e e n p r e d i c t e d , v a lu e i s

one o f th e h i g h e s t .

Then e v e n w h e re t h e r e i s

change i n p o r o s ity th e change i n w i l l p r o b a b ly be s m a l l.

k

w ith in th is

The a s s u m p t i o n t h a t

c o n s ta n t even f o r non -p o ro u s m a te r ia ls i s The d i f f e r e n c e b e t w e e n t h e v a l u e s sm all s iz e s

o f th e

sam e c o k e i s

of

k

w o u ld b e n e a r l y

th e re fo re k

ju stifie d #

fo r la rg e

k

to have a s m a lle r v a lu e

( T a b l e IX ) a r e o f l i t t l e

in g to i n t e r p r e t th e v a r i a t i o n s

in

k .

siz e s

th e v a r ia tio n s i n

is

a p p a re n tly q u ite

The v o i d a g e s o b t a i n e d a t

c o rre s p o n d f a i r l y w e ll w ith th o s e g iv e n i n T a b le V III

f o r cru sh ed m a te ria ls ra tio

k .

use in h e lp ­

They to o v a r y w i t h i n

a n a rro w r a n g e b u t i n a ran d o m f a s h i o n t h a t i s

la rg e

p o r­

c an n o t be e x p la in e d .

The v o i d a g e f i g u r e s

u n re la te d to

and

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The a b v i o u s t e n d e n c y f o r

a t sm a lle r s iz e s

a

lim ite d ran g e

a c c u r a c y w i t h w h i c h t h e c o u n t i n g m e th o d h a s m e a s u r e d i t s o sity *

but

in th is

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c a s e m uch s m a l l e r

t h a t th e

(1 .2 a g a in s t 2 . 0 ) .

siz e These

a r e b e in g c o n s id e r e d "n o rm a l" v o id a g e s and th o s e o b ta in e d a t s m a lle r s iz e s a re b e in g c o n s id e re d d e n sitie s

" h ig h ".

M o st o f t h e b u l k

m e a s u r e d h a v e t h e r e f o r e b e e n " lo w " f o r r e a s o n s

th a t

w ill be d isc u sse d l a t e r . The d i f f e r e n c e s b e t w e e n t h e v o i d a g e s o f t h e l a r g e a n d s m a l l s iz e s

o f th e c o k e s h a s b e e n fo u n d v e r y l a r g e

ponds to a b ig e r r o r i f d e n sity d a ta . trib u tio n

p o ro sity is

T h is a lo n e i s

and t h i s

co rres­

b e in g e s ti m a te d fro m b u lk

s u f f i c i e n t re a so n th a t po re d i s ­

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show how t h e A p p a r e n t

( Ds/ D a ) m easure(3- b y t h e tw o m e t h o d s d i f f e r .

The g r a p h s h a v e b e e n d r a w n f o r C o k e s V I I a n d

P

and f o r Q u a rtz *

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t y p i c a l o f t h e m e t a l l u r g i c a l c o k e s a n d w as c h o s e n

because i t s

d a t a w ere m ost c o m p le te .

by th e

In t h a t case th e r e s u l t s

tw o m e t h o d s d i v e r g e m o s t m a r k e d l y a t l a r g e

d iffe re n c e

e sta b lish e d

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th e

a t 5 /6 m . b e in g m a in ta in e d w i t h o n ly

s l i g h t i n c r e a s e dow n t o a b o u t 6 0 m . .

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th e f a c t o r by b u lk d e n s it y f e l l

lo w e r th a n t h a t b y c o u n t­

in g .

s till

sm a lle r s iz e s

The b u l k d e n s i t y a t v e r y s m a l l s i z e s w as n o t q u i t e

s ta n t b u t c o n tin u e d to in c re a s e

con­

s l i g h t l y a lth o u g h th e c o u n tin g

m e th o d i n d i c a t e d n o p o r e r u p t u r e .

C oke

fa c to rs

s iz e s and th e d if f e r e n c e

to d iv e rg e r a p id ly a t la rg e

b e c a m e p r a c t i c a l l y c o n s t a n t b e t w e e n 6m.

P a g a i n show ed t h e

and

16m .

th e n

b u t a g a in

i n c r e a s e d r a p i d l y f o r t h e c o u n t i n g m e th o d i n d i c a t e d p o r e r u p t u r e t o 22 m . s i z e , In th is

w h ile

t h e b u l k d e n s i t y w as c o n s t a n t b e l o w 1 6 m . .

c a s e v o id a g e and

k

w ere b o t h c o n s t a n t o v e r a v e r y

w i d e r a n g e o f s i z e s dow n t o 2 0 0 m . . and h a v in g a c o n s ta n t

k

i n t h i s w ay t o o , b u t i t s is

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w o u ld h a v e b e e n e x p e c t e d t o b e h a v e a p p a re n t d e n s ity f a c t o r by b u lk d e n s ity

show n t o h a v e d i m i n i s h e d

(ra th e r e r r a tic a lly )

w ith d im in ish ­

i n g s i z e . (s