26
T H E J O U R N A L O F I N L I L T S T R I A L AiVD E X G I N E E R I N G C H E M I S T R Y
day and, besides t h e main plant, includes equipment for working u p t h e by-products into the usual crude products for t h e market. The coal is mined b u t a few miles away, and is a good grade of high volatile bituminous coal. As t h e coal comes from t h e cars i t is dumped into a track hopper and elevated t o a crusher, where i t is crushed t o pass a three-eighthsinch screen. It is then delivered t o six 80-ton bins in t h e primary retort building. There are 2 4 primary retorts, arranged in four batteries of six each. Each retort is about 7 ft. in diameter and 20 f t . long, with a capacity of a ton a n hour. The crushed coal is fed into t h e retorts by self-sealing screw conveyors and is stirred and advanced slowly through t h e retorts by a paddle mechanism. The by-products are led off t h e discharge end of the retorts and handled as in coke-oven practice.
YOI, 1 3 , N O .
I
DISCUSSION
PROF.PARR:Mr. Chairman, I would like to ask Dr. Curtis how nearly the pitch residue from the oil or tar in the process met the requirements of the binder for the briquets. DR. CURTIS:It is about an even break on most high volatile coals. The point is not one which bothers us a t all. Having a t a r plant as a part of the equipment, we can if necessary bring in outside tar and distil i t a t a profit, giving the required additional pitch. I n the case of one plant there is a small shortage and this is being done. The question ol pitch yield depends, of course, on the coal which is being used in t h e process. MR. SPERR: I should like t o ask about the amount of gas produced. As I understand it, t h e comparison of the yields of this process with those obtained in by-product coke-oven practice was made on the basis of the entire gas prodltction. That is evidently why the figure of 10,000 tu. f t . was given lor coke-oven production. Have you any figures that we could use to compare the surplus gas produced by this process with that obtained from the by-product coke oven? DR. CURTIS:The plant a t Clinchfield has not been ruiuiiiig long enough to give a n accurate figure, but judging from results obtained a t the Irvington plant i t takes about 7000 cu. ft. of gas per ton of coal to run the process. At Clinchfield we do not consider gas as one of the salable products of the plant, but in case a plant were located near a city or industrial center, there would be a few thousand cubic feet of gas which could be disposed of. The gas yield depends, of course, on the coal used in the process, and with most high volatile coals is somewhat more than necessary for the retorts. BY-PRODUCT COKING By F. W. Sperr, Jr., and E. H.Bird THEKOPPERS C O M P A N Y LABORATORY, 3fELLON
T O P VIEW O F
SECONDARY RETORTS
The semi-coke which is discharged continuously from the primary retorts is carried by covered conveyors t o storage bins in t h e briquet building. Here it is ground, fluxed with pitch, and briquetted. There are two of these roll presses having a combined capacity of about 24 tons of briquets per hour. The raw briquets are carried slowly up a long cooling conveyor t o t h e storage bins a t t h e secondary retorts. From these bins they are drawn into larry cars and charged into t h e secondary retorts. The secondary retorts are built in two batteries of six and four, t e n retorts in all. Each retort consists of six rectangular chambers, 2 1 ' f t . long and inclined a t about 30°, with six charging and three discharging doors per retort, t h e capacity of t h e retort being approximately I 5 tons of raw briqueks. The finished briquets are discharged into steel quench cars and carried t o a quenching and loading station from which they are finally loaded into railroad cars. The by-products from t h e secondary carbonization are combined with those from t h e primary, after a preliminary cooling. The usual by-product equipment is provided, including a light oil plant, and a tar-distilling plant.
INSTITUTE, Pl'l"rSBU1Z(;H,
L'A.
For nearly two years t h e production of by-product coke in America has held t h e lead over t h a t of beehive coke. By-product coke manufacture is now firmly established and continually growing, while beehive coke is certain t o decline t o a position of minor importance. Although t h e bulk of t h e coke and gas manufactured i n by-product ovens is now consumed by iron and steel plants, there is a n increasing tendency for t h e by-product coke industry t o assuine t h e position of an independent fuel industry, and its relations are broadening t o such a n extent t h a t they must be considered i n t h e study of almost every phase of fuel economy. I S C X E A S I N G S H O R T A G E O F h-ATUR.4L F U E L S
Among t h e underlying causes of t h e many-sided development of this comparatively new industry, there is, first of all, t h e increasing shortage of t h e important natural fuels-anthracite, natural gas, and petroleum. The difficulty of obtaining adequate supplies of anthracite and t h e inferior quality of t h e material have combined t o favor t h e substitution of coke. Natural gas finds its most satisfactory supplement i n coke-oven gas and has a further accessory in water gas made from by-product coke. Fuel oil is being replaced t o a n increasing extent with t a r and t a r oils, while benzene has been successfully introduced as a motor fuel distinctly superior t o gasoline, although on account of t h e comparatively limited amount of t h e former available, there is n o question of competition between t h e two. The high price and poor quality of t h e gas oils now available are having
Jan., 1921
T B E J O C R N A L O F I S T D C S T R I A L A Y D EA7GINEERILVG C H E M I S T R Y
t h e effect of discouraging t h e large-scale manufacture of carbureted water gas, and, here again, coke-oven gas appears as t h e most economical substitute. An important factor in this connection is the high cost of labor, which has made the ordinary retort process of manufacturing coal gas an expensive proposition, and has forced t h e artificial gas industry t o a recognition of t h e advantages of carbonizing coal in relatively large charges, as is done in t h e by-product coke oven.
27
TABLSI-FEEL PROPERTIES OF COKE, TAR,PITCH, AND MOTOR SPIRIT Air Requirement Sp. Lbs. per -B. t. u. per Lb.- Cu. Ft. Gross Net per Lb. Gr. Cu. Ft. Coke 12,900 12,860 132 Tar . . . . . . . . 1.165 72.7 16,120 15,575 162 Pitch.. . . . . . 1.250 78.0 15,660 15,370 155 Motor spirit. 0.877 54.7 18,060 17,360 176
...........
Flame -Temp. C.With WithAir Cold Preheated Air to500'C. 1875 2085 1900 2115 1980 2230 1915 2165
BY-PRODUCT C O K E I N T H E I R O N AND S T E E L I N D U S T R Y
Although, as has been stated, t h e use of by-product coke is rapidly being extended outside of the iron and T H E BY-PRODUCT O V E K AS A F U E L P R O D U C E R steel industry, the bulk of this fuel is still employed With t h e exception of ammonia and its compounds, in this industry, largely in the blast furnace and, t o each of t h e primary products of the modern coke a smaller extent, in the iron foundry. The achieveoven has a technically important fuel value. I t is ments in t h e utilization of by-product coke in t h e with t h e primary products t h a t we are the most con- blast furnace are of t h e utmost importance from cerned. Popular fancy likes t o speak of a by-product t h e standpoint of fuel economy. With modern coke plant as if i t were a factory for dyes and drugs; methods of manufacture, and with a better underbut this is, of course, a misconception. I n America standing of the conditions affecting coke quality on it is very seldom t h a t the organization of a by-product the part of t h e producer and of t h e conditions requisite coke plant proceeds farther t h a n t h e production of for efficient utilization on t h e part of t h e consumer, t h e primary products, and although some of these the old prejudice in favor of beehive coke has been products are indispensable t o our rapidly growing almost entirely wiped out. It has been shown in American chemical industries, it must be recognized regular operation t h a t t h e consumption of by-product t h a t , no matter how interesting and important this coke per ton of pig iron is from I O O t o 300 lbs. less sort of utilization may be, it is far outstripped, in t h a n the consumption of beehive coke, and blastterms of dollars and cents, by t h e utilization of these furnace managers, as a rule, are now just as favorable and t h e other products as fuel. t o t h e use of by-product coke as they were formerly skeptical. COMPARISON W I T H T H E B E E H I V E O V E N S o remarkable a revolution in both opinion and praeIt is of some interest from this standpoint t o examine tice would have been impossible without t h e developthese fuel values in detail. Such an examinatioh will, ment of t h e modern by-product oven with its flexifor instance, enable us t o appreciate t h e great economy of a by-product coke oven as compared with t h e bee- bility of regulation and its means for exact heat conhive oven which i t is displacing. I n coking one ton trol a t every point. Having such an apparatus, a of high-grade coal in a beehive oven, the following proper study could be made of t h e various factors affecting t h e quality of coke by-products, such as the fuel must be consumed: Equivalent kind of coal and its preparation, oven dimensions, B. t. u, Lbs. Coal and oven operating conditions. Simultaneously, t h e Gas, 11,000 cu. f t . .. . . . . . . . . . . 6,160,000 440 Tar, 9 gal., . . . . . . . . . . . . . . . . . . 1,401,000 100 effect of variation in coke quality upon blast-furnace Light oil, 4 g a l . . . . . . . . . . . . . . . 527,000 38 Coke, 100 lbs.. . . . . . . . . . . . . . . . . 1,300,000 93 operation had t o be determined. It was necessary TOTAL . . . . . . . . . . . . . . . . . . . 9,388,000 671 t o go even farther t h a n this-to break away from I n coking one ton of t h e same coal in t h e by-product old traditions of blast-furnace practice with beehive oven, we consume simply: Gas 4300 cu. f t . = 2,408,000 coke and t o determine what operating conditions of B. t. u., equivalent t o 1 7 2 lbs. coal. For every pound t h e blast furnace would be necessary t o give t h e best of coal coked, t h e beehive oven consumes 9,388,000 results with by-product coke of a given quality. B. t. u., or 33.5 per cent of t h e heating value of t h e It has not always been possible t o make this sort of coal, while the by-product oven requires only 2,408,000 investigation as a systematic procedure; b u t our knowledge. of t h e general subject has been gradually B. t . ti., or 8.6 per cent. 48,166,719 tons of coal were coked in beehive built up t o a point of considerable practical value. ovens in 1918. If this had been coked in by-product There is still a wide field for further development of ovens there would have been saved t h e equivalent this important subject. of 11,993,513 tons of coal. DEVELOPMENT O F OTHER USES FUEL PROPERTIES
OF
COKE
AND
BY-PRODUCTS
Some d a t a regarding t h e fuel properties of coke, tar, pitch, and motor spirit (obtained by purifying t h e benzenes recovered from coke-oven gas) are given in Table I, while Table I1 gives information regarding coke-oven gas obtained by different operating methods, as compared with producer gas and water gas made from by-product coke. The figures in these tables are given as fairly typical, b u t there may naturally be considerable variation, depending upon the kind of coal used and upon operating conditions.
A point which i t is especially desired t o emphasize here is t h a t t h e advances scored in t h e use of byproduct coke in t h e blast furnace may be repeated in other lines of application if similar methods are pursued. What is especially needed is cooperation between t h e producer and consumer of coke, t o arrive at a correct understanding of t h e requirements for each particular application. Since we have in t h e by-product oven an apparatus of t h e utmost reliability, capable of treating a very wide range of coals, t h e possibilities of future development in t h e further
28
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
TAB&@ 11-TYPICALANALYSESOF
Vol. 13, No.
I
GAS, WITH HEATINGVALUE, AIR REQUIREMENT, A N D FLAWE TEMPERATURE Air Require- Flame Temp. "C. B . t. u. ment Cu. Ft. With With Air per Cu. Ft. per Cu. Ft. Cold Preheated CO Ha CH4 Nz (Gross) Sp. Gr. Gas Air t o 500° C. 6.8 47.3 33.9 6.0 591 0.44 5.08 1865 2095 6.9 47.8 34.2 6.0 562 0.42 4.99 1870 2100 6.3 46.3 35.0 5.3 630 0.45 5.25 1870 2100 6.4 46.8 35.4 5.4 605 0.42 5.15 2105 1875 6.0 57.0 27.0 5.6 528 0.38 4.40 1875 2105 , 6.1 57.5 27.3 5.7 497 0.35 4.31 1850 2110
COKE-OVEN, P R O D U C E R AND WATER
..... ...... ........ ......... ........ ......... .............................. ..................... ......
Straight coal gas before removing benzenes.. Straight coal gas after removing benzenes.. Rich coal gas before removing benzenes.. Rich coal gas after removing benzenes.. Lean coal gas before removing benzenes.. Lean coal gas after removing benzenes.. Blue water gas. Coke producer gas cold) Coke producer gas !preheated t o 500' C.)..
COz 2.2 2.2 2.6 2.6 2.1 2.1 6.0 5.0 5.0
Illuminants
0 2
3.5
0.3
2.6 4.3
0.3
3.2
2.0
1.0
...
0.2 0.2 0.3
0.3
... 1.0 ... .. .. ..
39.0 23.0 23.0
utilizatiorl of by-product coke are very great. One of t h e most prominent phases of such development is in relation t o domestic fuel, and t h e systematic investigations now being conducted by t h e U. S. Bureau of Mines, proving t h e merit of coke for this purpose, are typical of what ought t o be done in connection with other important applications. There is no good reason for replacing a single pound of antthracite with any solid fuel other t h a n by-product coke, and there is every reason why t h e utilization of by-product coke ought t o go much further t h a n t h e replacement of anthracite. Other leading uses of coke, outside of t h e manufacture of iron and steel, are in nonferrous metallurgy, in t h e production of water gas, as railroad fuel, and as fuel for general industrial heating, especially where t h e avoidance of smoke is desirable. T h a t quality, physical or chemical, which is best suited for one application is not necessarily t h e best for another. The iron foundry needs coke of different characteristics from t h a t required by t h e blast furnace, and still other characteristics become essential when we consider t h e use of coke in a water-gas machine. These considerations are important i n making it possible for a wide variety of coals, producing cokes of different quality, t o be economically and profitably treated in t h e by-product oven. UTILIZATION O F C O K E B R E E Z E
One of the most interesting developments in fuel economy resulting from by-product coke manufacture has been in t h e utilization of coke breeze-a material which, not more t h a n a few years ago, was regarded as nearly useless. This material, containing as much as 85 per cent fixed carbon (dry basis) and having a heating value of 11,500t o 12,500 B. t. u. per pound, was formerly disposed of for filling purposes or else completely wasted Of late years, with t h e development of improved stoking machinery, it' has been found possible t o burn coke breeze for steam-raising purposes with a high degree of efficiency, and i t is the general practice for by-product coke plants t o obtain their entire steam requirements from this fuel. After satisfying plant requirements a surplus of breeze may still be left for sale, and its utility as fuel is becoming more and more recognized in t h e general market. TAR A S M E T A L L U R G I C A L F U E L
The yield of t a r obtained in by-product coking varies with t h e kind of coal used. It may be as low as 4, or as high as 1 2 gal. per t o n of coal. With t h e majority of coals now being coked i n America, t h e yield is from g t o I O gal. per ton. The use of t a r for fuel, especially in steel manufacture, has rapidly
49 .O 14.0 14.0
....
....
....
5.0 58.0 58.0
305 128 128
'0.55 0.87 0.87
2.17 0.89 0.89
1920 1495
2110 1650
1665
1815
increased during t h e past few years, and many of t h e larger steel companies, operating their own by-product coke plants, do not sell any of their t a r for distillation purposes, but use it exclusively for fuel. I n openhearth practice, t h e consumption of t a r per t o n of steel is I O per cent less t h a n t h e consumption of fuel oil. It is advantageously employed in combination with producer gas. The resulting flame has a much better melting efficiency t h a n t h a t of straight producer gas, and t h e increase in t h e capacity of the furnace is much greater than would be accounted for on t h e basis of the heating value of t h e fuel used. These considerations are of great moment, in view of t h e increasing price of fuel oil, and a t a time when the maximum output per unit of investment is essential.
.
TAR O I L S AND P I T C H
The various t a r distillates have been extensively used in Europe for fuel purposes; but t h e demands for such products in American creosoting and chemical industries will undoubtedly prevent this sort of utilization here for some time t o come. There has, however, been a surplus production of one t a r product, namely, pitch, and its burning warrants some consideration. It melts readily to a liquid similar t o raw tar, and, with a simple preheating arrangement, could probably be used in t h e same way as tar. The employment of pitch as fuel by direct combustion offers some present promise, but, in view of the increased demand for it, particularly in t h e electrochemical industries, it is a question whether such application can be counted o n as permanent. T H E B E N Z E N E S A S XOTOR F U E L S
Although t h e products from t h e crude light oils, recoverable from coke-oven gas, are largely used in chemical industries, t h e surplus production of these materials since t h e close of t h e war has required their sale as motor fuel, supplementing gasoline a t an opportune time. The lower boiling fractions of t h e crude benzene (benzene, toluene, and xylene) are purified and used alone or in mixture with gasoline. This sort of utilization is very important in Europe, where there is much less petroleum available t h a n in t h e United States. Here, even if all our coke were manufactured in by-product ovens, t h e amount of benzene recoverable would be only about I O per cent of t h e annual consumption of gasoline. However, t h e demonstrated superiority of benzene motor fuels over gasoline gives them considerable local importance i n districts where they are pr0duced.l 1 In a certified dynamometer test by the Automobile Club of America, 20 per cent benzene showed 12.3 per cent less fuel consumption than gasoline. 4 t the same time the horse power was increased, depending on the speed. 4t 2000 r. p. m. this was 19.4 per cent greater than t h a t 3f gasoline. The 1iigher ignition point of benzene also eliminates knocking (pre-ignition).
'
\
Jan., 1921
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERIN G CHEMISTR Y COKE-OVEN
GAS
I n recent years, a n increasing number of by-product coke plants have been built for t h e primary purpose of supplying gas for industrial a n d domestic consumption. T h e Koppers. oven, using part of its gas production for its own heating requirements, delivers a surplus amounting t o 60 per cent, or even more, of t h e total gas. This surplus is about 6600 cu. f t . per net t o n of coal charged, and, after the recovery of benzenes, t h e gas has a heating value of 560 B. t. u. per cu. f t . T h e heating value may be increased by retention of t h e benzenes, by gas separation, or by enrichment; b u t each of these courses of procedure is, in t h e long run, uneconomical both t o t h e consumer a n d the producer of t h e gas, and is justifiable only where arbitrary local standards of high heating values are enforced. Straight coke-oven gas of 540 t o 560 B. t. u. per cu. f t . constitutes an ideal gaseous fuel for domestic a n d industrial heating, and t h e demand for i t is continually increasing. I t is, when manufactured a t the r a t e of I,OOO,OOO cu. f t . or more per day, t h e cheapest high-grade artificial gas. The carbonization of coal in bulk, as in coke-oven practice, naturally effects great economy in fixed charges, maintenance, and operating labor as compared with t h e old retort process €or the manufacture of coal gas, while the quality of t h e coke produced simultaneously with high-grade gas is far superior. Among t h e principal causes for the rising demand for coke-oven gas are the increasing recognition of the utility and convenience of gaseous fuel in general and t h e growing shortage of natural gas. T h e relations of t h e centers of production of by-product coke t o districts in which natural gas is largely used are peculiarly fortunate. Coke-oven gas will be increasingly employed t o replenish t h e depleted supplies of natural gas in these districts. For example, i t has been shown t h a t the total amount of by-product coke-oven gas manufactured in t h e Cleveland-Pittsburgh district, which is t h e largest natural-gas consuming district in t h e United States, is considerably more t h a n the annual production of natural gas in the s t a t e of Pennsylvania. T H E C O M B I N A T I O N O V E N I N R E L A T I O N T O GAS S U P P L Y
Considerations of this nature have given great importance t o the combination oven, which is t h e only t y p e of by-product coke oven t h a t can be economically heated with either coke-oven gas or producer gas. If producer gas is used, the entire output of high-grade gas is rendered available for outside consumption. T h e combination oven is being generally adopted by those plants which are built primarily for gas manufacture. Hitherto, the by-product coke ovens installed in connection with iron and steel plants have been designed t o use their own gas exclusively, and such ovens cannot be converted into t h e combination type without rebuilding. I n t h e future, however, t h e price obtainable for coke-oven gas will make i t profitable for iron and steel companies t o build combination ovens whenever i t becomes necessary t o replace or enlarge existing plants or t o build new plants. Combination ovens have been in con-
29
tinuous and successful operation in Europe for a number of years, and one of t h e several installations in America has been operating during t h e past 18 mo., partly on coke-oven gas and partly on producer gas, i n accordance with the demand for surplus gas and coke. I n considering the possible advantages offered by t h e combination oven, i t should be pointed out t h a t i t can be heated with producer gas made either from breeze and other small-sized coke, or from low-grade coal containing either high ash, high sulfur, or both. A high percentage of sulfur in t h e gas is not detrimental t o its use for oven heating. Furthermore, t h e combination oven may be heated with blastfurnace gas, which under certain conditions may be a profitable procedure. W A T E R GAS F R O M B Y - P R O D U C T C O K E
The growing importance of gaseous fuels for industrial or domestic heating is such t h a t we must look beyond the direct production of coke-oven gas proper and consider other gases t h a t may be made i n connection with t h e operation of a by-product coke plant. Carbureted water gas is being largely manufactured from by-product coke t o augment the supply of cokeoven gas; but, as has been mentioned, t h e unsatisfactory supply of gas oil has had a discouraging effect upon t h e manufacture of this fuel. Blue water gas, on t h e other hand, offers considerable promise. It has a heating value of 300 B. t. u. per cu. f t . and t h u s stands midway between coke-oven gas and t h e lowgrade gases, such as producer gas and blast-furnace gas. It can be used for a wide variety of heating purposes without the necessity of preheating gas or air, which is not true of low-grade gases. P R O D U C E R GAS A N D C O M P L E T E GASIFICATIOh'
Producer gas manufactured from coke also deserves some consideration in this connection. Coke producer gas may be manufactured in connection with the operation of a by-product coke plant, not only for heating t h e ovens, but also for furnishing an additional supply of gas a t relatively low cost t o mix with and augment the supply of coke-oven gas. This, together with the possibilities offered in the manufacture of blue water gas, brings up the question of complete gasification of coal. With a process of complete gasification which has been urged by many authorities on fuel economy, the plant would ultimately produce no solid fuel, but would convert all of t h e coke into gas t o be mixed with the regular coke-oven gas and sold. Complete gasification offers more attraction in rather densely populated industrial districts t h a n in localities where the gas would have t o be distributed over long distances. There can be no question b u t t h a t in t h e former case i t will eventually be undertaken on a large scale, and it is of interest t o know the amount and quality of the gas t h a t would be produced. Of course, in each case, allowance must be made for the requirements of the by-product coke plant with i t s necessary auxiliary equipment. If complete gasification were accomplished with t h e producer gas system, t h e plant would produce 86,100cu. f t . of mixed gas per t o n of coal having a heating value of 183
30
T H E JOURRNAL O F I A T D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
B. t. u. per cu. f t . With t h e blue water gas system, there would be produced per ton of coal 33,100 cu. f t . of mixed gas having a heating value of 380 t o 38; B. t. u. per cu. f t . The latter gas would be satisfactory for all domestic and industrial purposes, while the former would be of more limited application. TECHNICAL PROGRESS A S D FUEL E C O S O N Y
I t remains t o mention very briefly t h e technical developments in t h e by-product coke industry which have contributed t o fuel economy. There is, first of all, t h e fundamental heating principle of t h e oven with its provisions for economical heat regeneration, accessibility, and convenient and exact temperature regulation. This heating principle not only has effected an improvement in coke quality and saving of gas over any other oven system previously introduced, b u t it has also made possible t h e combination oven in which t h e regenerative system is adapted t o t h e necessary preheating of producer gas as well as air. The same principle is retained i n t h e new triangularflued oven system, and in a new t y p e of gas oven t h a t is now being introduced. The use of silica brick i n t h e construction of byproduct coke ovens is now universal i n American practice and has been a n important factor in fuel economy. By its superior heat conductivity, this material has not only made possible a considerable saving i n t h e heat requirements of t h e oven, b u t has effected a reduction in t h e time required in coking a charge of coal, and t h u s has increased t h e carbonizing capacity per oven. I t s highly refractory quality makes possible t h e employment of higher flue temperatures, which have also contributed t o reduction of coking time. From t h e standpoint of durability, it is superior t o any other available refractory material. I t s use has a n important p a r t i n t h e acknowledged superiority of American coking practice over European. Of t h e number of new developments t h a t are just a t their beginning, there should be especially mentioned those t h a t are related t o t h e bylproduct gas producer, which is admirably adapted t o economical operation i n combination with t h e by-product coke plant. The by-product producer is used t o a large extent i n Europe; b u t so far, conditions have not been favorable t o its introduction into America. The future will, however, see much important progress in this direction, and it is expected t h a t t h e same degree of superiority will be attained as has been achieved in t h e introduction and development of t h e by-product coke oven. Work is actively in progress in connection with other developments and improvements in by-product coking. One general statement might be made in relation t o these. It has been our experience t h a t improvements made primarily for t h e betterment of coke quality generally have a favorable effect upon t h e by-products. I n dealing with any given coal supply, i t is not a t all necessary t o sacrifice coke quality for good by-product yields, as used t o be supposed. This is important because t h e profitable disposal of coke is a n essential factor in t h e success of any enterprise of by-product coking.
Vol. 13, No. I
DISCUSSION
DR. E. W. SMITH: Mr. Chairman, Mr. Sperr gave us a very low figure, a figure of 8 per cent for fuel on by-product coking plants. I should be very glad if he could tell us in connection with that very low figure what percentage of by-product gas he used for heating the ovens, and what was the temperature of the combustion chambers, the volatile matter in his coke, and the duration of charge. The figures that we are used to on the other side are figures that are higher than those he has been fortunate enough to get here. ILlr. Sperr will probably be well acquainted with the fact that the advance that he hopes t o make in this country in by-product producers was made in Birmingham, England, in 1912, and has worked successfully ever since. There they have a battery of 66 ovens heated by means of by-product producer gas, and heated very successfully. Those ovens were put in as being the cheapest form of gas making, because of low labor costs. Since that time, however, there have been other developments, and that particular undertaking is installing on wholesale lines the vertical retort, which with slight steaming yields up to about 6000 cu. f t . to the ton of water gas; gas is made at a cost on a B. t. u. basis (and that is about the only basis on which we can compare them) much lower than those obtained from by-product coking, in spite of the fact that in by-product coking there is a receipt of nearly one pound per ton more for coke than is obtainable from the coke from the vertical retorts, so that there are advances being made in continuous working vertical retort practice of a very large order, which I think the by-product retort people will have to watch, if they are going to hold the position that they have taken in this country. Coke ovens are being installed here for the purpose of supplying city gas, and the coke used for the production of water gas and for domestic purposes. In so far as this is true, I am very strongly of the opinion that gas engineers are not adopting either the cheapest or the best means of producing city gas. It is an accepted fact in England that hard coke such as is obtained from coke ovens or from intermittent verticals does not give anything like as good results as the special highly porous coke obtained from continuous working vertical retorts, particularly in watergas manufacture, Domestic coke here is usually hard coke, but when the consumer has been educated into the use of more porous coke, I am quite satisfied that here, as in England, a market can be: created where this is necessary. The other advantages of installing continuous working vertical retorts are too well known to require elaboration and, of course, by-product recovery is carried out in a similar way to methods employed in cokeoven practice. I shall be glad if Mr. Sperr can give me those figures. MR. GEORGE K. BROWN: Mr. Chairman, I would like to ask one other question: Is it possible to use a vertical continuous retort similar to the Woodal type as installed by the Porter Company on a by-product coke? Has it been used, or if it has not, briefly, why not? MR. SPERR: Answering Dr. Smith’s question I would say that the figure for the amount of gas used in coking is based on the actual operating records of several American plants, such a s the Minnesota By-product Coke Company a t St. Paul, the Jones & Laughlin Steel Company at Pittsburgh, and the RaineyWood Coke Company near Philadelphia. I would say in a well operated plant, not calling for perfection but what you would reasonably expect in regular operation, you should use from 38 t o 42 per cent of the total gas for coking; the rest you would recover as surplus. The kind of coal used is an important factor in the amount of gas required. The fact that much larger amounts of gas are used for coking in English practice is diie to differences in oven design, to smaller oven capacities, and to the use of fire clay brick instead of silica
I
Jan., 1921
T H E J O L ' R N A L O F I N D U S T R I A L A N D E N G I N E E R I N G CH E M I S T R Y
brick. A s a rule, overcoking is somewhat prevalent in English plants. Of course, in many cases allowance must be made for the fact that most of the British plants have to use washed coal, which is charged with a comparatively high percentage of moisture; but those American plants which also use washed coal show 'considerably less gas consumption than the British plants. Answering the question as to the percentage of volatile matter in the coal, I mould state that this ranges from 3 I to 33 per cent atfthe plants mentioned. With the ovens operating a t 16 hrs. coking time, the flue temperatures may be from 2 5 0 0 ' to 2600' F. Now as regards the use of gas producers in by-product coking practice, we are very glad t o give full credit and appreciation -to European technologists for the successful development and application of the by-product producer. Conditions in Europe have hitherto been more favorable to the application of by-product producers than in this country, but it is certain that the next few years will witness a great development in this direction here. With reference t o the installation of vertical retorts, adapted to steaming, Dr. Smith will be interested to know that some of our newest ovens are also adapted for steaming, and that this method of increasing the gas production can be employed when desired. Naturally this is of more interest where the by-product coke oven is employed primarily as a source of gas than where coke is the main product. Answering the question of Mr. Brown, regarding the use of vertical ovens, working on the principle of the continuous vertical retort, I would say that I do not know of any such ovens that have been in successful operation. The principle of the continuous vertical retort is such that it cannot be expected to produce first-class coke. To attempt to explain the difference between the functioning of the vertical retort and the functioning of the coke oven would be rather too long a story for this afternoon. MR. LAYKG: Are there any ovens in the West using Illinois coal entirely for coking purposes, and if not what percentage .of Illinois coal may be used in mixtures with Eastern class coals i n the West? MR. SPERR: That is a question that always arouses great interest, particularly here in Chicago. The plant of the Indiana Coke and Gas Company a t T a r e Haute, Ind., has used, for long periods, straight Indiana coal, which is very similar to Illinois coal. From time to time they have also used varying amounts of Pocahontas coals in combination with the Indiana coal. These amounts might range from 8 to 15 per cent. Illinois coal has also been coked in other by-product plants, either straight or mixed with different amounts of Eastern coals. I would say t h a t a large proportion of Illinois coals can be successfully coked straight in the modern by-product coke oven. The coke has been found by actual test to be suitable for blast-furnace purposes, providing the percentage of sulfur is sufficiently low. It is also adapted for domestic use, for the manufacture of water gas, and for many other purposes. It is more difficult to make good foundry coke from Illinois coals, and where the production Qf foundry coke is important i t is often advantageous to mix some Eastern coal k i t h the Illinois coal. The statistics which Dr. Porter includes in his paper for the year 1917 are, as he explains, not correct in respect to the present relative proportions of by-product coking and beehive coking. For nearly two years, beginning, I think, two years ago this November, the production of by-product coke has been in excess of the production of beehive coke.
BY-PRODUCT COKE, ANTHRACITE, AND PITTSBURGH COAL A S FUEL FOR HEATING HOUSES By Henry Kreisinger BUREAUo r XINES, PITTSBURGN, Pa.
This paper discusses t h e comparative value of byprbduct coke, anthracite, and Pittsburgh coal, based
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on tests made a t t h e fuel laboratory of t h e Bureau of Mines, Pittsburgh, Pa. The paper also describes t h e methods of firing by-product coke and Pittsburgh coal t h a t were found t o give the best results in actual heating service. E X P E R I M E h-TAL
FUELS-In the tests made a t t h e Bureau's laboratory, the three fuels were of the same size, passing over a 0.;-in. screen and through a 2-in. screen. Their chemical composition is given in Table I . DESCRIPTION
OF
OF FUELS USED I N TESTS Piozzmate d n n l y s e r as Recezved By-Product Pittsburgh CONSTITCE\T A4nthracite Coke Coal Moisture. . . . . . . 4.11 0.79 2.23 Volatile matter 6.36 2.80 37.21 Fixed carbon, . . 77.97 79.27 52.10 Ash.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.56 17.14 8.46 'r4BL,E I-*'XALYSES
TOTAL ...........................
__-
-_
100.00 100.00 Liltimote A n a l y s e s of Dry Fuel Hydrogen . . . . . . . . . . . . . . . . . . . . ..... 2.58 0.60 Carbon. . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.13 79.24 Kitrogen . . . . . . . . . . . . . . . . . . . . . . ..... 0.87 1.27 Oxvnen . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.32 0.72 Sulfur. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.04 0.89 Ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.06 17.28 TOTAL ........................... Calorific value per lb.,as received, B. t. u. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Weights of fuels per cu. f t . , Ibs. . . . . . . .
-__ 100.00
5.00 75.38 1.36 7.66 1.95 8.65
___
--_
100.00
100.00
___
100.00
12636 52.5
11756 34.5
13239 47.0
The anthracite coal was taken from t h e Bureau's stock purchased in 1916. It was a very clean, goodlooking coal, and in fact was considerably lower in ash t h a n t h e coal now obtainable on t h e market. This fact must be kept i n mind when comparing t h e results of t h e tests. The Pittsburgh coal was sized coal purchased from a local dealer. I t was of average quality as sold in Pittsburgh. The by-product coke was a mixture of 60 per cent of 21-hr. and 40 per cent of 19-hr. by-product coke. It was made from a mixture of coals coming from nine different mines. The composition of a composite sample of these coals is given in Table 11. TABLEII--AVERAGE COMPOSITION OF COALS USEDFOR BY-PRODUCT COKE CONSTITUENT P E R CENT Moisture., ......................... 2.77 Volatile m a t t e r . . . . . . . . . . . . . . . . . . . . . 34.17 Fixed carbon ....................... 56.94 A s h . . ............................... 8.89 Sulfur.. ............................ 1.37 TOTAL...........................
100.00
TESTS-The tests were made in two steam boilers of t h e size ordinarily used for heating t h e average 7-room house, and were conducted under conditions conforming t o those existing in actual house heating practice. The tests were started Monday morning and continued through t h e week. until Friday or Saturday morning. During each 24 hrs. t h e fires were run a t low rating for a periqd of 8 hrs. in a manner similar t o t h a t existing over night under actual heating conditions, and were r u n t h e other 16 hrs. t o develop a determined percentage of thle rating of t h e boilers. Three tests were made with each fuel, one a t about 5 0 per cent, one a t 80 t o I O O per cent, and one a t 1 2 0 t o 13; per cent of boiler rating. On the low rating tests the firings were 8 hrs. apart, on t h e medium rating tests about 6 hrs. apart, and on the high rating tests about 4 hrs. a p a r t . On t h e DESCRIPTION O F
