polyphenyl samples and 30 wt % solutions of hydrocracked polyphenyl samples in Santowax-OJIP are shown in Table V. I n every case hydrocracked polyphenyl samples gave polymer yields which do not vary greatly from t h a t of SantowaxOMP (except run 4), considering t h a t the accuracy of the measured dose varies by +25%. This is significant since these samples contained approximately 20 wt yG alkylpolyphenyl (mostly methyl and ethyl derivatives). Other workers have also shown t h a t slightly lower radiolytic polymer yields are obtained from reclaimed hydrocracked polyphenyl coolant samples which also contained alkylated compouiids than from those of Santowax-OhlP (Gardner and Hutchinson, 1964). The results suggest t h a t reconstituted hydrocracked polyphenyl coolant containing methyl or ethyl substituents may have possible use as a heat transfer medium in a radiation environment. Acknowledgment
The authors are indebted t o William H. Yanko and Mark Gutzke, Monsanto Research Corp., Dayton Laboratory, Dayton, Ohio, for performing the electron irradiations. The nuclear irradiations were performed by California Research Corp., Richmond, Calif., under the supervision of R. 0. Bolt. literature Cited
Bolt, R. R.,Carroll, J. G., Proc., “International Conference on Peaceful Uses of Atomic Energy,” Geneva, 7, ,546 (1936), also text “Radiation Effects on Organic Materials,” Academic Press, New York, N.Y., 1963. Campbell, R. H., Bekebrede, A. E., Gudzinowicz, B. J., Anal. Chem., 35 ( l a ) , 1989 (1963). Carroll, J. G., Bolt, R. O., Sucleonzcs, 18 (9), 78 (1960). Charlesworth, D . H., “Status of Fouling Experience in OrganicCooled Systems at A.E.C.L.,” CEI-132, May 1961. DeHalas, D. R., “Pyrolytic and Radiolytic Decomposition of Organic Reactor Coolant,” USAEC Rept. TID-4500, 13th ed. rev., Nov. 25, 1957. Freeman, G. R., J . Chem. Physzcs, 33 ( l ) ,71 (July 1960). Gardner, L. E., Hutchinson, W. U., Znd. Eng. Chem. Prod. Res. Develop., 3 (1) 28 (1964).
Gilman. H.. Weioert. E. A.. J . Ora. Chem.. 22. 446 (1957). Huber,’F. h’., Renoll, AI.: Ross”ow, A. G., ’Mowiy, D’. T., J . Amer. Chem. SOC.,6 8 , 1109 (1946). Johns, I. B., RIcElhill, E. A,, Smith, J. O., J . Chem. Eng. Data, 7 (2), 277 (1962). Leny, J. C., Orlowski, S., Charrault, J. C., Lafontaine, “Orgel, A European Power Factor Design,” European Atomic Energy Community, Euratom, Eur., 85e (1962). Schoepfle, C. S., Fellows, C. A., Znd. Eng. Chem., 23 (12), 1396 11931). Scola, D.A., Adams, J. S., “Reckmation of Nuclear Reactor Coolant by Solvent Treatment, USAEC Rept. IDO-11057, Aug. 22, 1963a. Scola, D. il., Adams, J. S., “Studies of the Reclamation of Organic Nuclear Reactor Coolant by Partial Hydrogenation of Polyphenyls,” USAEC Rept. IDO-11058, May 15, 1963b. Scola, D. A., Adams, J. S., Bekebrede, A. E., Znd. Eng. Chem. Prod. Res. Develon.. 9 13). 413-19 (1970). Scola. D. A,. Adams. J.”S.. Richiusa. ’C. C.. Kafesiian. R.. “Fburth Annual Report, Organic Coolant Reclamatio; and Coolant Chemistry,” USAEC Rept. IDO-11055, May 10, 1 qfi.?
-I--.
Scola, D. A,, Kafesjian, R., “Catalytic Hydrocracking of Polyphenyl Systems for Use in Reclamation of Organic Nuclear Reactor Coolant,” USAEC Rept. IDO-11056, June 30, 1963. Scola, D. A., Wineman, R. J., Znd. Eng. Chem. Prod. Res. Develop., 2 . 3 2 2 (1963). Seymour, H., Chem. Age (London) 43,43 (1940). Sweeney, AI. A., Hall, L. H., Bolt, R. O., J . Phys. Chem., 71 (6), 1564-71 (1967). Trilling, C. A., “The OMRE-A Test of the Organic ModeratorCoolant Concept,” Proc. Second United Nations International Conference on Peaceful Uses of Atomic Energy, Geneva (Sept. 1958) Geneva, United Nations, 1958, 1‘01 9, pp 421, 468. USAEC Rept. K;AA-SIi-5688, Organic Coolant Reactor Forum, Proc. (Oct. 6-7, 1960). Woods, G. F., “Preparation and Properties of Some Polyphenyls,” WADC Tli 39-496, p 93 (Sept. 1959). Yanko, W. H., Ellard, J. A,, “Thermodynamic Properties of BiDhenvl and the Isomeric Terohenvls.” USAEC Reot. IDOllb08 (“Oct.31, 1963). I
~~
\
I
,
RECEIVED for review July 20, 1970 ACCEPTED June 29, 1971 This work was supported by the United States Atomic Energy Commission under contract AT(10-1)-1088.
Production of Carbon Black from Assam Coal R. Haque,l
R. K. Chakrabarti, M. 1. Dutta, and M. S.
lyengar
Regional Research Laboratory, Jorhat, Assam, India
The direct conversion of the high-volatile vitrain-rich coals of Assam to thermal-type carbon black was investigated. The reaction takes place in a high-temperature transport reactor in which heat i s supplied by partial combustion of the coal feed a t high volumetric production rates. Factors, such as air-to-coal ratio, feed rate, reaction temperature, and the nature of coal and its mineral matter, determine the yield and quality of carbon black, The product is compared with that obtained b y conventional methods. Data o n compounding of the carbon black in rubber mixes are given.
C a r b o n black is mainly produced by the cracking of natural gas, petroleum hydrocarbon, and coal t a r oils. Prior t o 1950, 95% of the world’s supply of carbon black was based on using natural gas as ram material, and 75yG of the world’s supply came from the CSh. Today, however, the major amount of carbon black is produced by the oil furnace process which allows location of the unit near the consumer. To whom correspondence should be addressed. 420 Ind. Eng. Chern. Prod.
Res. Develop., Vol. 10, No.
4, 1971
The first production of carbon black from coal was reported by Johnson et al. (1967a,b). Coal crushed through 325 mesh was dropped in a free fall through a temperature zone of 125OOC in the presence of air, ammonia, nitrogen, or argon to produce a black costing about $0.03-0.04/lb. The same workers, in producing hydrogen cyanide from highvolatile coal and ammonia, reported that about 6-107, of the coal was converted to carbon black. The process was carried out a t 125OOC and produced fine thermal-grade
WATER
ELEClROSTATtc PRECIPITATOP
PRIMARY CYCLONE
w
T HERMOCOUPLE
EXHAUS1
\
r *in BLOWER
:s
COIL
ROTAMETER
Figure 1.
FEED PIN
.CYCLONES
w REACTOR
CHAR STORAGE
I
WATER SEPARATOR
CARBON BLACK S T O R A G E
WATER TO DRAIN
Flow diagram of unit for production of carbon black from coal
carbon black. RIischenko (1969) made a comparative study of the carbon blacks obtained from various coals. Opinions regarding the mechanism of formation of carbon black vary considerably. R a y and Long (1964) and Street and Thomas (1955) separately put forward theories of carbon formation in which they have described the formation of carbon as involving processes of both aggregation and dehydrogenation. Their views differ mainly in the order in which these processes occur. Smith (1940) in his theory has assumed t h a t the fuel molecules first undergo dehydrogenation giving carbon (C,) molecules which then condense t o give carbon black. Wolfhard and Parker (1950) think that fuel molecules initially polymerize giving rise t o saturated polymers which are then dehydrogenated to yield carbon. Other workers suggest intermediate routes. When oil or natural gas is used as raw material, the primary determinants of quality and yield are fuel characteristics, air-to-fuel ratio, preheat temperatures, and furnace or burner designs. Coal as raw material for production of carbon black is unconventional because the product contains a high percentage of ash. Analysis of the coal used here for the production of carbon black is given in Table I. This coal is unique in t h a t it has low carbon, high volatile matter, low ash, and cakes easily. On low-temperature carbonization, i t yields nearly double the quantity of t a r of other Indian coals, but a high percentage of sulfur restricts its use. At present there is practically no use for vast deposits of this type of coal, but carbon black can be produced from it. Thermal-type carbon black from Assam coal (ACB)
has been produced by pyrolysis a t 950-1250°C. 'The various factors influencing the yield and quality of the product are discussed, and their propert'ies have been compared with the other commercial blacks. Experimental
The flow diagram of the unit for production of ACB is shown in Figure 1. Lump coal from Baragolai Colliery, Upper Xssam, is ground t o -72 mesh BS size and charged into a coal feed bin. Flow into the reactor is regulated through a gate valve. The coal is then subjected to flash pyrolysis in a sillimanite reactor tube, 80 in. long and 3l/, in. in diameter. Air is the fluidizing medium. Initial heat is supplied electrically, but the partial combustion of the coal supplies the subsequent necessary heat. The temperature is raised to 1250°C maximum. The volatile matter evolved is instantaneously cracked into carbon black and flue gases. The residence time is of the order of 1 sec. Flue gases laden with carbon black and char pass through a series of cyclone separators where the char is separated. Carbon black is carried over with the flue gases. About 407, is collected by water scrubbing, and the rest is recovered from the flue gases by electrostatic precipitation. The carbon black is t'hen pelletized and dried a t 400-450OC. Process variables, such as air-to-coal ratio, feed rate, reaction temperature, and nature of the coal, are studied along with their influence on t'he quality of the product. Material and Energy Balance of Process. About 50% of t h e coal is consumed in supplying heat' for t'he process; of the other half, 30YG is converted to char and 20% to carbon black. Of t h e supplied heat, 43.2% is lost as sensible heat, 11% in radiation, and 20.87G through t h e flue gases.
Table 1. Analysis of Coal Sample Used to Produce Carbon Black
%
%
%
Volatile matter, % DAF
2.5
2.5
44.5
Ash,
Moisture,
Fixed carbon, % DAF
Float over specific gravity, 1.30
55.5
90
C% DAF
H% DAF
DAF
N and 0 (by difference) DAF, %
81.6
5.6
2.3
10.5
S%
Yield per ton of vorious products of low-temperature Gray-King carbonization assoy Gas, Coke liquor, Coke, Tar, quality gal ft3 cwt gal
13.4
37.6
13.4
3930
G-Gltype
Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No. 4, 1971
421
Table II. Comparison of ACB with Normal Rubber-Grade Carbon Black, HAF
Details of sample
Reaction temperature, 'C
Ash,
Volatile Moisture, matter,
%
. %
Residue on
325 BS,
%
Acetone extract,
%
%
Benzene discoloration, transmission at 420 rnM
Specific gravity
pH
Iodine adsorption no., ASTM, mg h/g of carbon black
Surface area, M2/g
Average Partic! size, A
Bulk density, Ib/ft3
ACB
1.0-1.5 9501250
2 4
1-6
0.5 max
0.5 max
78-95
5.5 1.5
60-110
40-80
500-900
20-25
HAF
1200- 0.1-0.5 1400
2-3
5max 0.1 max
0.5 max
85-97
6 . 9 1.8-1.9
82k7
60*5
500
23-29
5'0
.
-z
.) 4 ' 0 -
2 w c
$-
L 0 m W
E
3'0
-
3
1
F
Y
G
E 0 0
2Q-
1'0
TE MP E R ATU R E
-
C '
Effect of reaction temperature on iodine number
Figure 2.
-
The remaining 25y0 of the heat is used in devolatilizing the coal and cracking the hydrocarbon components. Testing of Carbon Black. Different properties of the carbon black produced are studied using ASTM or BS procedure. Surface area and particle size are determined by indirect methods. Smith and co-workers (1941) have shown t h a t iodine adsorption values (mg/g) bear a definite relationship to the surface area (h!12/g) ; therefore, the specific surface has been calculated from the iodine adsorption values. The average particle size has been calculated from the specific surface from the relationship, SDd = 60,000, where S is the :pecific surface in M2/g, D is the average particle size in A, and d is the density in g/cc. The experimental results are shown in Table 11, and different curves are plotted.
Figure 3. Effect of air-coal ratio on volatile matter content of carbon black
carbon black can be adjusted to the desired level by adjustment of the reaction temperature. Effect of Air-to-Coal Ratio. Volatile matter decreases with increase in the ratio of air t o coal (Figure 3), but no significant change is noticed in the ash content. For a variation of air-to-coal ratio between 60-100 fta/lb, ash
Discussion
Carbon black is produced, probably according to:
+ 202(g)
+ 2Hz0, AH = -191,800 cal CHI +C(amorphous) + 2Hz(g), AH = +20,300 cal
CH4(g)
----f
COz
The relatively high volatile matter of Assam coal with its high vitrain content is a distinct advantage as carbon black formation takes place owing to the pyrolysis of volatile components. Effect of Reaction Temperature. Product quality varies with reaction temperature, the iodine number being taken as a measure of quality (Figure 2). The iodine value of the 422
Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No. 4, 1971
5
6
COAL
?
FECD
8 PATE
9
10
@&/A*.)
Figure 4. Effect of coal feed rate on volatile matter content of carbon black
* h
c
ta 0 W
I
1
W
r
P
2
.I,
550
loo0
1100
T€MPERATURL
I200
k
50 0
I'O
20
ID
40
50
6'0
VOLATILE MATTERX
Figure 5. Effect of volatile matter content on iodine value of carbon black
content of the product varies between 1.0-1.570. Air-tocoal ratio of less than 60 ftaair/lb of coal causes agglomeration of the coal particles inside the reactor. On the other hand, a higher air-to-coal ratio (>100 ft3/lb) causes excessive combustion inside the reactor resuking in a lower yield. Effect of Feed Rate. From Figure 4 it may be concluded t'hat t o maintain a volatile matter content of 2-3% in the final product', a feed rate of about 7 lb coal/hr in this system-Le., a solid mass velocity of about 100 lb coal/ft* area/hr and a corresponding mass velocity of air of 625 lb/ ft*/hr-is to be maint'ained t,o produce a standard rubber-grade product. For a variation of coal feed rate between 6.6 and 9.7 lb/hr, the ash content of the product varies between 1.0 and 1.3Yob. Effect of Volatile Matter Content. Comparison of Figure 2 with Figure 5 may appear t o indicate that. volatile matter content increases with increase of reaction temperature. This is not really the case. Besides reaction temperature, feed rate, air-to-coal ratio of the charge, and residence time of solids in the reactor play a prominent role in determining the volatile matter content of the product. Similar effect of feed rate on the volatile matter content of carbon black was noticed by Newman and eo-workers (1968) in their study on the hydrogen plasma pyrolysis of coal and coal tar 'fractions. It is difficult t o study the variation of the volatile matter content of the product with an individual factor, a t the same time keeping the other factors constant under the present set of reaction conditions. Effect of Reaction Temperature on Particle Size. As it has been shown in Figure 2 t h a t iodine adsorption values increase wit'h increase of react'ion temperature and as the iodine values bear a definite relationship t o the surface area which in its t u r n is related to t'he particle size, t.he latter decreases with increase of reaction temperature (Figure 6). Relationship Between Surface Area and Volatile Matter. Figure 7 shows t h a t surface area also increases with the increase in volat.ile matter content of t'he sample, and the same arguments as those discussed for explaining Figures 2 and 5 hold true. Effect of Nature of Coal. All the coals of Assam will not be equally suitable for the production of carbon black.
Figure 6. Effect of reaction temperature on average particle size of carbon black
Besides the high volatile nature of the coal, the nature and amount of the coal ash play a prominent role. The volatile matter and the vitrain content of the coal are responsible for the yield, whereas the nature and amount of ash in the coal are responsible for the ash content of the final product. Table I11 shows that coal ash containing lower percentages of silica and alumina tends to give a product containing a desirable lower ash. A higher percentage of silica and alumina in the coal ash increases the ash content of the product, indicating that besides the total ash content of the coal, analytical makeup of the ash is also responsible for the amount of ash in the final product. Table IV shows that reduction of the size of coal feed beyond 72 BS does not affect the yield and ash content of the product appreciably. X-ray Studies. ACB samples were examined by X-ray diffraction with a Debye Scherrer camera and copper K, radiation. The X-ray pattern is shown in Figure 8 and is compared with a standard carbon black (HA4F).ACB, unlike the standard, shows presence in traces of quartz
W
a
< W
60
V
8 E v) 3
5s
0
P
3
VOLATILE
MATTER
I
4
5
6
%
Figure 7. Effect of volatile matter on surface area of carbon black Ind. Eng. Chern. Prod. Res. Develop., Vol. 10, No. 4, 1971
423
Table 111. Effect of Nature
of
Coal Ash, Volatile Matter on Quality of Carbon Black Ash content
VM, Sample
Assam coal from Baragolai Colliery, Upper Assam.
Ah,
%
2.5
%
Yield of corbon
of carbon block obtoined from
block,
%
there CODIS,
DAF
%
of coal
44.5
1.5max
20
22
1% of different mineral4 SiO,, 32.5; PzOS, trace; ALO,, 14.1; SOO,1.2; Fe,O,, 48.1; alkalies (by difference), 1.3; TiOe, 1.2; CaO, 0.9; MgO, 0.7 Nature of the cod orh
SiOl, 52.3; SO,, trace; Altos, 40.5; alkali, nil; FezOs, 5.5; TiO,, 1.4; CaO, trace; MgO, 0.4; PzOa, 0.1
Figure 8. X-ray diffraction pattern of (top) Arram cool black(ACB);(' '
_.."
Compoundi-,
rVYYY...b
~
_.
I
~."
of carbon black, after mixing in t h e rubber mixes, have been done by Firestone Rubber & Tyre Co., Ltd., Bombay. The results are shown in Table V and Figure 9. Modulus a t 300'% elongation of ACB, which gives the reinforcing capacity of the black. is eomnarativelv lower than t h e industrial-g,rade blacks, hut it has a higher ball rebound percentage, i ndicating development of lower heat during service in the pro#ductmade from the mixes. ACB is unique in having ~ , . 1 ~ 1 ~~ 1 ~ . . . 1 1 - - . L l 1..-...--L:L:-- - c :A I ^ a low strucura -wiiieii SRUU~U ~ i i i a u ~ rage c ~ U L L U U U L WUL 111 LIV 1,e used in a rubber mix. ~~
~~L..-.
YOILL,
I1,6"-*"'YY"Y
*IyIuI.L-LIyII
y"'"ll
y"I.I""u."&
" I
direct production of thermal-type carbon black by the 1
,... ~
ot
3000/,elongation
--
Table V. Comparative Compounding Test Performance of ACB and Standard Blacksa ACB
GPF black
SRF
FEF
black
black
Modulus a t 300y0 eloiigation, psi Ball rebound
-1025 -350 -425 +lo0 Actual 1225 +13 $10 $11 +9 % Actual 62 a The blacks were mixed with rubber mixes using ASTM test formula which is: Parts by wt 100.0 Natural rubber grade RSS 1 llercaptobenxothiazol disulfide 0.6 2.5 Sulfur Zinc oxide 5.0 Stearic acid 3.0 Carbon black 50.0 __ Total 161.1 The test results are expressed in the customary way which is different from industry Reference Black No. 1.
process of flash pyrolysis of the coal in a high-temperature transport reactor, using air as the medium. The quality of carbon black produced directly from coal compares well with commercially available products. The chemical and compounding tests in rubber mixes reveal that the carbon black produced here has a low structure so t h a t large quantities
can be used in a rubber mix to lower the cost of rubber products. Acknowledgment
Grateful acknowledgment is made t o J. Samson of Firestone Tyre & Rubber Co., Ltd., Bombay, without whose help i t would have been difficult t o perform the compounding tests of the carbon black in rubber mixes. The authors also thank A . K. Singh, J. L. Ghose, and K. S . Goswami for helpful cooperation. References
Johnson, G. E., Decker, W. A., Forney, A. J., Field, J. H., Rubber World, 156 (3), 63-8 (1967a). Johnson. G. E.. Decker. W. A , . Fornev. A. J.. Field. J. H.. U.S. Bur. $lines, Report of Investigation“6994 (Aug. 1967b). Kirk, R. E., Othmer, D. F., Eds., “Encyclopedia of Chemical Technology,” Vol. 3, 53, Interscience Encyclopedia Inc., Sew York, N.Y., 1949. Kirk, R . E., Othmer, D. F., Eds, “Encyclopedia of Chemical Technology,” Vol. 4, 243-82, Interscience Publishers, New York, X.Y., 1964. llischenko, AI. L., Kham. Tverd. Topl., No. 2, 139-41 (hIarchApril 1969). Newman, J. 0. H., Coldrick, A. J. T., Evans, P. L., Kempton, T. J., O’Brien, D. G., Woods, B., Proc., Seventh International Conference on Coal Science, Prague, Sect. 4, Paper No. 26, 1968. Ray, S. K., Long, R., Combust. Flame, 8 , 139 (1964). Smith, E . C. W., Proc. Roy. SOC.,174A, 110 (1940). Smith, R. It.,Thornhill, F. S., Bray, 11. I., Ind. Eny. Cheni., 33, 1303 (1941). Street, J . C., Thomas, A., Fuel, 34, 4 (1935). Warren, B. E., Biscoe, J., J . A p p l . Phys., 13,364 (1942). Wolfhard, H. G., Parker, U’.G., J . Chem. Soc., 1950, p 2038. RECCIT ED for review November 17, 1970 ACCEPTED June 16, 1971
Ortho Esters as Hydrogen Chloride Scavengers George Kesslinl and Olaf Nifontoff Research Department, Kay-Fries Chemicals, Inc.,2 West Haverstraw, N . Y . 10993
Ortho esters react rapidly and essentially quantitively with trace amounts of anhydrous hydrogen chloride in several organic solvents. The speed of reaction i s a function of ortho ester structure and of solvent medium and can b e complete in less than 1 min at room temperature. The stoichiometry of the reaction is established, and the products of reaction are demonstrated to be the alcohol, normal ester, and alkyl chloride derived from the ortho ester used.
E t h y l chloride and ethyl formate were previously identified as products of the reaction of anhydrous hydrogen chloride with triethyl orthoformate (Arnhold, 1887). Although quantitative data were lacking, and the presence of alcohol was not demonstrated, Arnhold postulated the reaction as R’C(0R)s
I
+ RC1+ R
1
=
R’C02R
C,H,; R’
=
+ ROH + RC1 H
To whom correspondence should be addressed. Present address, Stony Point, N.Y. 10980.
(1)
As recently as 1943, stoichiometry and mechanism were still uncertain; it was even suggested that if ethyl chloride were formed, it might be assumed to have resulted from the action of hydrochloric acid on ethyl alcohol (Post, 1943). Because of our interest in the frequently unique chemistry of ortho esters (Kesslin and Bradshaw, 1966), it seemed warranted to resolve the uncertainty of the stoichiometry and products from their reaction with hydrogen halides. I n addition, further study to accumulate data for the design of structural features of ortho esters most suited for hydrogen chloride scavenging appeared worthwhile because of the reported stabilization of chlorinated hydrocarbons by a n Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No. 4, 1971
425
