Jan., 1 9 2 1
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 the comparative value of byprbduct coke, anthracite, and Pittsburgh coal, based
31
on tests made a t the fuel laboratory of the Bureau of Mines, Pittsburgh, Pa. The paper also describes the 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 the 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 in mind when comparing the results of the 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 the size ordinarily used for heating the 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 the week. until Friday or Saturday morning. During each 24 hrs. the 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 the other 16 hrs. t o develop a determined percentage of thle rating of the 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 the medium rating tests about 6 hrs. apart, and on the high rating tests about 4 hrs. a p a r t . On the DESCRIPTION O F
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING. C H E M I S T R Y
32
tests a t higher ratings the firings were made closer together, because not enough fuel could be put in the furnace t o last over longer periods. Between firing periods the fires were given no attention. Steam was generated under a 3-lb. gage pressure and discharged into the atmosphere. A large steam separator was placed in the steam line t o take the water out of the steam. Water was weighed and fed into the boiler every hour t o keep the height of water in the boiler nearly constant as i t would be under actual heating conditions. E C O N O M I C R E S U L T S O F TESTS-A summary of the economic results of the tests is given in Table 111. The third column under each fuel gives the number of B. t. u. absorbed by the boiler per pound of fuel. ‘The value per pound of anthracite is high because the coal contained an unusually low percentage of ash. Ordinarily the ash in the anthracite runs about the same as the ash in by-product coke. TABLE111-ECONOMIC RESULTSOF TGSTS(Averages of Dunning and -----COKE--
EffiRating ciencv 52.5 68.9 99.6 70.6 133.0 64.7 Averaae Efficiency All Ratings 68.1 Heat Value per t b . B. t. u.
B. t. u. Absorbed 8105 8330 7490
... . 11,756
Arc0 Boilers) -ANTHRACITE--
B. t. u.
Rating 52.6 89.6 128.7
., ...
Effi- Abclencv sorbed 6 5 . j 8300 68.40 8640 66.3 8380 66.8
,
12,636
COA4B. t. u. Abciencv sorbed 55.8 7390 55.3 7350 54.4 7200
-PITTSBURGH
Rating 48.0 89.6 108.5
... .... .
Effi-
52.2
,
. ..
13,239
The table shows t h a t the efficiency obtained with the coke was a little better than t h a t obtained with anthracite coal, and I O t o 17 per cent better than t h a t obtained with Pittsburgh coal. The lower efficiency with the anthracite coal is due t o the fact t h a t the coal cracks in the fire and the small pieces of coal t h a t are cracked off fall through the grate and increase the losses in the ashes. The low efficiency obtained with the Pittsburgh coal is due t o incomplete combustion of coal gases and high-flue gas temperatures for a period of I t o 2 hrs. after each firing. If the value of the three fuels is based on the amount of heat actually absorbed by the boiler per pound of fuel burned, then the coke is about 15 per cent better than the Pittsburgh coal, and the anthracite coal is about g per cent better than the coke. However, as previously stated, the anthracite coal used on the tests was cleaner than is the coal marketed a t present. With the present market qualities of the two fuels, the results of the coke and the anthracite coal would be closer together. Pittsburgh coal is usually low in ash and high in heat value, so t h a t the comparison of the coke with the Pittsburgh coal, as shown in the table, is about right. No partipular trouble was experienced with clinker on any of the three fuels. Although the coke made considerable more clinker than either of the coals, i t was light and porous. I t formed a circular disk covering the central part of the grate, and if the fire was not too hot the whole disk was easily removed in one piece through the firing door. With a hot fire the clinker was soft and broke into small pieces when attempt was made t o remove it. It should be borne in mind t h a t the coke has some
Vol. 13, No.
I
advantages over Pittsburgh coal which cannot be expressed in dollars and cents. Coke is a clean, smokeless fuel, requires much less attention when burned in an ordinary house heating apparatus, and gives a uniform heat between long firing periods. ACTUAL H O U S E H E A T I N G T E S T
I n order t o obtain d a t a on the relative value of coke and Pittsburgh coal under actual heating conditions, the writer used coke a t his house during t h e months of Kovember and December 1919, and Pittsburgh coal during the months of January, February, The heated part of the house conand March 1920. sisted of 8 large rooms and a bath room. The outside walls of the house were built of solid concrete with the wall paper pasted directly on the concrete walls. On account of this construction the house was rather difficult t o keep warm. The heating plant consisted of a hot-water boiler rated a t 1100 sq. f t . of radiation surface. The radiating surface of the radiators was about 600 sq. f t . I n two of the upstairs rooms the heat was turned on about 8 P. M. and off about 7 A. M . Heat in the other rooms was on all the time. A larger boiler was installed in order t o make i t possible to run the fire with two firings a day; one about 7 A . M. and the other about 8 P. hc. The most important data for the period between November I and March 31 a r e given in Table IV. TABLE IV-FUEL USED AND WEIGHTOF REFUSE:IN HEATINGAN 8-Roo1.3 HOUSE Wt. of Fuel Wt. of -Burned Lbs.- Ashes MONTH Day Night Lbs. November.. . . . 1200 1200 December .... ... 1940 2000 645 January.. . . . . . . 2890 2000 .720 February., , , , 1981 2162 413 March 1570 1545 237
. .. . . ... .... . . .. . .
....... . .....
...
W t of Clinker Lbs.
FUEL USED
245 None None None
Coke Coke Pittsburgh coal Pittsburgh coal Pittsburgh coal
. .. ..
During December, when coke was burned, the total refuse was 890 lbs., of which 645 lbs. were ash pulled out of the ash pit. T h e refuse was about 2 3 per cent of the fuel fired, a n d 7 7 per cent of the refuse was ash. I n January the total refuse amounted t o 7 2 0 lbs., all of which was ash from the ash pit. There was n o clinker. The refuse was 14.7 per cent of the coal fired. These figures show t h a t the coke had very high percentage of ash, which is the principal drawback from the standpoint of the user. The clinker had t o be removed from the furnace every day or not less often than every other day. The best time t o remove t h e clinker was in the morning or in the evening before firing, and while the fire was not hot. The clinker could then be removed in’one piece, and the removal was easy. After the clinker was removed the fire was leveled, and a charge of 60 t o 1 2 0 lbs. of coke was put into the furnace. Owing t o the greater bulk of the coke the new charge covered the fire completely, so t h a t it took an hour or more before all of the new charge was completely ignited. After the coke once started t o burn a very even rate of heating could be maintained. The draft needed varied from 0.01 t o 0.04 in. of water. The ability t o maintain an even rate of heating depends on the accuracy of draft regulation. For this reason i t is necessary t o have a sensitive draft gage which will easily measure drafts of 0.01 in. of water. Regulation of draft by t h e
Jan.,
T H E J O U R N A L OF I N D U S T R I A L A N D .ENGINEERING CHEMISTRY
1921
position of t h e damper is unreliable and very unsatisfactory, and is probably responsible for the many failures in burning coke. The coke is a clean fuel and there is no soot deposit on the surfaces of the boiler. After about z mo. of burning coke there was a thin deposit of fine ash on t h e surfaces of t h e boiler varying from one-thirty-second to one-eighth of an inch in thickness.
/
A
33
door with large lumps. Fig. I shows the furnace after firing. This method of firing virtually changes the furnace into a coke oven. The coal in the front part of t h e furnace is changed into coke, and the escaping coal gases pass over the hot coke in the rear part of t h e furnace and most of them burn. After 1 2 hrs., t h e coal has been changed into coke; i t is then moved onto t h e rear part of the furnace and a fresh charge of coal is put into the front part. The best tool for moving the coke into the rear part of the furnace was found t o be a spading fork. The prongs of t h e fork are inserted between the coke and the lower inside edge of the firing door frame, and the coke is moved by a prying motion. Twelve-hour firing periods are made possible only with a large furnace with sufficient capacity to hold enough fuel for T 2 hrs. The writer is of the opinion that heating boilers should not be rated on the amount of heating surface they contain, but on the capacity of t h e furnace t o hold large firings so t h a t the furnace can be run long periods without attention. The I 2-hr. period is preferable for most houses because t h e attention t h e furnace needs can be supplied by the man, and t h e housewife and other members of the family need n o t disturb the fires a t all.
SOME FACTORS AFFECTING THE SULFUR CONTENT O F COKE AND GAS IN THE CARBONIZATION OF COAL1 By Alfred R. Powell PITTSBURGH EXPERIMENT STATION, BUREAUOS MINES, PITTSBURGE, PA.
SULFUR I N COAL
L-
SECTION TUROUGH AB
FIG. 1
With t h e Pittsburgh coal there was no clinker. However, t o offset this, there was a heavy deposit of soot on the surfaces of the boiler. If good results are t o be obtained t h e soot should be swept off of t h e boiler surfaces every day or preferably before each firing. With a proper design of the boiler, the soot can be swept back into the fire pot, covered with fresh coal, and burned. It was found t h a t all t h e soot t h a t will stick t o t h e surfaces of the boiler will accumulate in one day. After one day further accumulation is stopped by the soot burning off. The cubical volume of one week’s accumulation of soot is about the same as one day’s accumulation, but it is somewhat heavier owing t o t h e fact t h a t a larger percentage of t h e soot layer is ash. The best method of firing Pittsburgh coal was found t o be as follows: Immediately before firing, the hot coals were pushed against the rear wall of the fire pot and the space in t h e front part of the furnace was completely filled with fresh coal. I n cold weather t h e fresh charge completely filled the front part of the furnace u p t o the roof of the furnace, even blocking the
It is now known t h a t sulfur exists in coal in three general forms-pyrite or marcasite, organic sulfur compounds, the exact mature of which has not yet been determined, and small quantities of sulfates. Methods of analysis have been devised for the determination of these different forms, which have furnished the basis for investigations of a practical nature on this most undesirable coal impurity. Organic sulfur occurs in bituminous coal in quantities ranging from 0.5 t o 2 . 0 per cent. The quantity present is very uniform for any given locality and seam, and i t is impossible t o remove i t from t h e coal by any known method. Pyrite comprises practically all the remainder of the coal sulfur, and the amount of pyrite present is variable, even in the same mine. Pyrite may be partially removed from the coal by washing processes. Sulfates are almost absent in freshly mined coal, but may increase as the coal stands in storage. PRIMARY
REACTIONS
O F COAL S U L F U R BONIZATION
DURING
CAR-
Amratherdetailed’lstudy has been made of the changes these forms of sulfur undergo when subjected t o t h e coking process. This work has been done in t h e laboratory on small quantities of coal in such a manner that,the-temperatures could be closely controlled, a n d 1
Published by permission of the Director, U. S Bureau of Mines.
