G. V. WOODY Allis-Chalmers Manufacturing Company, Pittsburgh, Penna.
because of the combination of carbonizing at a low temperature and at a rapid rate of heating. The process is simple and therefore the first or capital cost is low. The net result is the production of a smokeless fuel costing only slightly more than the domestic sizes of a good grade of bituminous coal usually marketed in the same district and shipped from the same mines as the fine sizes of coal from which the low-temperature coke is produced.
This paper describes the Hayes process for carbonizing coal at low temperatures and the production of low-temperature coke in two forms-namely, char and briquets. Both of these fuels are low in volatile content and are therefore considered smokeless fuels. The indicated cost of production of this fuel is occasioned by the high credits due to the high yields of by-products. These high yields are characteristic of this process
not be sold in quantities large enough to promote the abatement of objectionable smoke. Two kinds of low-temperature coke can be produced by the Hayes process-namely, char and briquet. The low-temperature char is an ideal smokeless fuel for use in stokers, and can be produced and sold in most places a t a price equal to or below that of high-volatile bituminous stoker coal. This fuel would be ideal for boiler plants serving office buildings, hotels, apartment houses, or domestic stokers. Briquetting this char for use in hand-fired furnaces, stoves, and fireplaces increases its cost, but even a t a higher price it would be fairly competitive with a high grade of bituminous coal for similar uses.
HE fuel-consuming public is showing a definite trend toward the burning of a fuel which will not produce objectionable smoke. High-volatile bituminous coal can be burned in stokers and perhaps in other furnaces by experienced firemen so as to accomplish these results. Generally, however, i t would seem that the best way to produce no objectionable smoke would be to burn a fuel which would not produce the smoke. Under this heading comes gas, anthracite coal, high-temperature coke, low-volatile bituminous coal, and, as a recent addition, low-temperature coke. The advantage of low-temperature coke is that it can be produced from the high-volatile coal normally sold in many communities at a cost only a little higher, if any, than that of a good grade of high-volatile bituminous coal now normally burned in the same location. I n addition to the price, lowtemperature coke combines several satisfactory burning characteristics; it ignites easily, burns evenly, and maintains combustion with a minimum amount of air. A good grade of low-temperature coke can be produced only by carbonizing a good grade of bituminous coal, and the same care must be used as when selecting coal for a good grade of high-temperature coke. I n common with all high- and low-temperature carbonization methods the Hayes process will operate best when the coal fed to the retort is or - 1 1 4 inch in size. One other general characteristic must be attained to make any low-temperature carbonization plant a successful venture. I n a community where bituminous coal delivered to the domestic consumer has been comparatively low in price, the cost of the domestic low-temperature coke must be kept near the cost of a good grade of bituminous coal, If this is not possible, then a great majority of purchasers using hard fuel in stoves and furnaces cannot purchase the low-temperature coke. It would be a luxury fuel and as such could
T
Commercial Installations The first commercial plant using the Hayes process was put into operation at Moundsville, W. Va., in 1928. The coal processed wm, for the most part, mined from Pittsburgh No. 8 seam by the Ben Franklin Coal Company whose operation was immediately adjacent to the carbonizing plant. Minus l/rinch screenings were used as they came from the mine without cleaning. Analysis of this coal was as follows: Proximate Moisture, % ' Volatile Fixed d r k i , % Ash, % Sulfur, 5% Ash fusion (spprox.), F. B. t. u./pound
1.26 38.17 50.04 9.63 4.0
2000 12,240
.
Ultimate (of One Channel Sample) Hydrogen Fixed oarLon, yo % 5.1 44.6 1.3 Nitrogen. % 10.1 Oxygen, % Sulfur % 5.5 11.8 Ash.
?k
The plant consisted of seven retorts mounted in one brick furnace setting, had a capacity of approximately 50 tons per 24 hours feed, and produced 35 to 40 tons of low-temperature char. During the first several years of operation the char 841
842
INDUSTRIAL AND ENGINEERING CHEMISTRY
from the plant was briquet,ted with petroleum pitch as a binder. This briquetted coke was for the most part' sold locally, and during the burning season there was never any trouble in disposing of it even though the selling price was from $2.00 to $3.00 higher per ton than the bituminous coals used in the vicinity. This statement does not conflict with one made previously because a t Moundsville the briquets were sold as a luxury fuel, and this was possible because of the plant's small producing capacity. Also adjacent to this plant was located a zinc 1,eductionfurnace which used a considerable amount of high-temperature coke breeze as the reducing agent. Experiments with the low-temperature char showed that it had certain characteristics which made it preferable to the high-temperat'ure coke breeze preriously used. By an arrangement isetn-een the two companies the entire production of the lorn-t,emperature char was shipped t)o the zinc plant during the last three or four years of operation. The Moundsville plant is not now functioning because a flood in 1936 damaged the carbonization plant and permanently closed the adjacent mine. Therefore, because of the much higher coal cost which would ensue if they were to obtain coal elsewhere, the owners did not feel justified in spending several thousand dollars to rehabilitate the carbonization plant. A single-retort pilot plant employing the Hayes process is in operation at Pueblo, Colo., making char for mixing with high-volatile coal. The mixture is charged in high-temperature ovens to produce an improved metallurgical coke for the blast furnace.
HAYESPROCESS
Vol. 33, No. 7
Operation at: Moundsville
The installation a t RIounclsville involved the use of a n alloy steel tube or retort 17 inches in inside diameter and 20 feet long inside the furnace. This tube was placed in a furnace setting and was support,ed by rollers a t each end (Figure 1). Stationary feed and discharge castings were located at t'he opposit'e ends of the retort, and were connected to it through packing glands. The retort tube was rotated in one direction a t 1.5 r. p. in. Within the retort was a specially const,ructed screw convcyor, 16 inches in outside diameter with 12-inch pitch flights. The flights werc hard-surfaced nn the outside edge to redace wear to a minimum. The bearings supporting the screw wei'e set 0.5 inch below the center line of the retort, which allowed the screw to rest 011 the bottom of the retort throughout its entire length. The screw was driven by a, train of gears which gave it a progressive oscillating motion. The motion was such that the screw moved the coal toward the discharge end of the retort a given distance when rotating in one direction, and on the reverse oscillation or direction the coal was returned a distance somewhat less than the forward movement. It required 16.5 oscillations to advance the coal 1 foot through the retort or 330 oscillations to carry the coal entirely through. Because of this forward and backward motion the coal had a theoretical travel of 220 feet iii passing through the 20-foot lengt,h of the retort. The problem of coal carbonization resolves itself into a question of heat transfer. In some processes of low-teniperature carbonization, owing to the relatively low heat head available, i t is dificult to raise the temperature of the layer of coal to a point where complete distillation is effected in R reasonable time. In this process, as a result of the motion of the retort screw, every p a r h l e of coal i s repeatedly brought into contact with the hot walls of the retort, and the carhonizat,ion is compIetely effected in about 20 minut,es, which is the approximate lengt,h of time for a piece of coal to pass through the retort. Not only does this oscillating motion mix and agitat,e the coal thoroughly as it passes through the retort, but it overcomes the tendency of the plastic mass of partly carbonized coal t o st,ick or adhere to the retort ~vallsand screw flights. This is due t o the fact that the carbonized and partly carbonized coal is continually kneaded together; t,liis movement is imparted to the coal by short quick t,lirusts of the screw flights which rotate a t a comparatively high speed. The wiping action of the screw on the retort walls as the retort is rotated keeps it clear of any adhering particles of coal. Since the speed of rotation of the screw has an important bearing on its operation, it might be well t.o compare this motion and that of a similar retort and screw in which the screw is driven continuously in one direction, the coal remaining in the retort for the same period. A screw rotating in only one direction would carry the coal forward 1 foot per revolut'ion and would be driven a t a speed of 1 revolution per minute to keep the coal in the PILOT-PL.4XT COAL CARBONIZATIOK INSTALLATION A T retort for 20 minutes. The peripheral COLORADO FUEL& IROK COMPANY
INDUSTRIAL AND ENGINEERING CHEMISTRY
July, 1941
MOTOR FOR
843
--
R E T O R T T U B E ___,_,. DRIVE, ,.'
L L E R SUPPORTS SECTION VIEW
VARIABLE SPEED MOTOR FOR FEED SCREW '
@xjjjl DISCH. FEEDER-
i
CHAR DISCHA~GE STAR GATE T Y P E
'REVERSING MOTOR FOR DRIVING RETORT SCREW
DISCHARGE
COMBUSTION CHAM0
FOR FIGURE 1. HAYESRETORT
CARBONIZING COAL AT
speed of the screw flight in this case would be approximately 4.25 feet per minute. With the oscillating screw, which rotates a t a speed equivalent to 13.5 r. p. m., the peripheral speed of 56.25 feet per minute is obtained. This comparison indicates the factors which combine to create a condition of agitation and cleaning action inside the Hayes retort and thus produce satisfactory operation, prevent clogging, and permit of long periods between cleaning operations. I n the Moundsville unit seven retorts were located in a battery type of furnace. Each retort was heated externally by a gas burner and was independent in its operation of the other six. Removable one-piece covers formed the top of the furnace, and any retort could be removed for inspection and cleaning without interfering with the setting or the operation of the others. The seven reversing gears were driven from a common line shaft. Power was supplied to this shaft by a motor and a speed reducer through a silent chain drive. The retorts were rotated by a countershaft, driven by a pinion gear mounted on a shaft extension from each reverse gear. Coal was fed to each of the retorts by a screw feeder, located on the feed-end casting. The rate of feed was 550 to 650 pounds per hour for each retort. The char was discharged from each retort into a collecting conveyor which ran the entire length of the retort setting. From this conveyor the char dropped into a quenching conveyor where it was partially cooled by water sprays and was then discharged through a rotary seal valve into the char conveyor. The gas and tar vapors were removed from the retorts through offtake connections located a t the discharge end of
LOW
TEMPERATURES
the retorts, and were conducted through standard condensing and cleaning apparatus where the tar was removed and the gas sent to the holder. All the firing was done in a combustion chamber located underneath the feed end of the retort. The hot gases of combustion, after passing through a baffle which formed the top of the combustion chamber, passed around the outside of the retort to the waste gas flue a t the discharge end of the retorts. A temperature of 1100" to 1300" F. was maintained automatically a t the feed end of the retort, depending upon the nature of the products desired and the character of the coal being processed. It was produced by a furnace temperature of 1200" to 1400" F. This method of firing had the effect of removing the moisture from the coal and raising it to the distillation temperature in the shortest possible time. The heat required for carbonization was approximately 1100 B. t. u. per pound of coal carbonized. When starting operations with a cold furnace, 36 to 48 hours were needed to bring the temperature of the retort up to the point where coal mas fed into it for carbonization. The temperature of the combustion chamber was regulated by automatic control devices operating in conjunction with pyrometers. After operation'for approximately 45 days, it was found advisable to stop a retort to clean a deposit of hard carbon which gradually built up a t several points on the interior. This cleaning was one of the regular duties of operation and was accomplished with comparative ease. The life of retorts and screws could only be estimated.
INDUSTRIAL AND ENGINEERING CHEMISTRY
a44
VOl. 33, No. 7 ~
TABLEI. ESTIMATED COSTOF PRODOCIKG LOW-TEMPERATURE COKEBY Cincinnati, Ohio Briauets Char 51,000,000 $800,000
Estimated plant cost Capacity tons Feed cbal/day Feed coal/year (330 days) Char/year (based on 70% of feed) Binder/vear (based on 7 % b v wt.) Briquetted coke/year
1,000 330,000 231,000 16,170 247,170
Yearly yield of by-products Gas, cu. f t T a r 30 gal /ton feed L i g h oil, 3 gal./ton feed
Credits Gas T a r a t 4C/gal. Light oil a t 8t/gal. Total Net cost a t plant Net operating cost Fixed charges, 0% of capital cost (15-year depreciation) Interest, 4 % on ~ 2 0 0 , 0 0 0working capital Sales a n d advertising Total Piant profit (15%) Total selling price a t plant
Based on 2000 cu. ft. per ton of feed. b Based on 1000 cu. f t . per ton of feed. A t $2.40 per ton. d At $2.10 per ton. a
1,000 330,000 231,000
1,000 330,000 231,000 16,170 247,170
,....
.....
1,000 330,000 231,000
.....
.
660,000,000a
8792,OOOC 194,040 146,900 71,000 14,300 39,600
8792,OOOC ...., 116,400 50,000 14,300 33,000
S693,OOOd 194.040 146,900 71,000 14,300 39,600
1,257,840
1,008,700
9,900,000 990,000
1,158,340
.
1
.
.
660,000,000Q
9,900,000 990,000
S693,000d
St. Louis, Mo. Briquets Char91,000,000 $800,000
1,000 330,000 231,000 16,170 247,170
330,000,000~ 9,900,000 660,000
50,000
14,300 33,000 __ 906,700
5759,000e 194,040 146,900 71,000 14,300 39,600 1,224,840
...
I .
116,400
1,000 330,000 231,000
...., I . . . .
330,000,000b 9,900,000 660,000 8759,000s .I...
116,400 50,000 14,300 33,000 -9
99,0001 396,000 79,200 574,200
99,OOOJ 396,000 79,200 574,200
132,OOOQ 396,000 79,200 607,200
132,0008 396,000 79,200 607,200
396,000 52,800 ___ 498,300
49,500/ 396,000 52,800 498,300
683,640
431,500
551,640
299,500
926,540
474,400
90,000 8,000 25,000 806,640
72,000 8,000 25,000 536,500
90,000 8,000 25,000 674,640
72,000 8,000 25,000 404,500
90,000 3,000 25,000 849,540
25,000 579,400
150,000 9 56,640
120,000 656,500
150,000 824,640
120,000 524,500
160,000 999,540
120,000 699,400
2.27 2.00 4.27
2.00 ___
s~
3.87
Cost per ton a t plant Dealer margin and transportation cost Domestic selling price
HAYESPROCESS
Pittsburgh, Penna. Brianets Char $1.000,000 8800,000
G60,000,000~ 9,900,000 990,000
660,000,000" 9,900,000 990,000
THE
2.00 __
5.87
2.84
2.00 4.84
3.34
2.00 5.34
.__
49,500/
4.05
6.05
72,000 8,000
3.03
2.00 __
5.03
At $2.30 per ton. I At 15 cents per 1000 cu. it. At 20 cents per cu. it.
e
The original retorts installed in 1928 were still in operation in 1936, and appearances did not indicate that early replacement would have been necessary. It i s probable that the screws would require more attention and repairs, but practice up t o that time did not indicate their life. Other parts, such as the conveyors collecting the char, quenching conveyors, and feeders, had shown no undue wear and required little maintenance. The material handling equipment, p r e s s e s , a n d other equipment in the plant were not of unusual design, and maintenanoe was normal.
20 inches 0 . d. and it was made from a 20-inch seamless steel pipe. For continuous operation, however, it is suggested that consideration be given to some kind of an alloy steel tube suitable for higher temperatures; carbon-molybdenum steel containing 0.50 per cent molybdenum would seem t o be satisfactory and not too high in cost. If really high temperatures were involred, chrome-nickel steel tubes suitable for withstanding temperatures in excess of 2000" F. are avail-
Improvements I n t h e recently built pilot plant which is now operating certain changes were made, none of which were fundamental. The rotating speed of the drum was increased t o approximately 4 r. p. m. and was driven by a chain and sprocket from a gear motor. The diamet e r of t h e d r u m was increased t o
DISCHARQE END
OF
FURNACE ROOF,HAYESLOW-TEMPERATURE ClRBONIZATION VILLE,
w.
'VA.
PLANT AT
MOUNDS-
July, 1941
INDUSTRIAL AND ENGINEERING CHGMISTRY
845
by the U. S. Bureau of Mines in conjunction with the American Gas Association should be consulted for estimates on other coals until such time as the coal to be used for carbonizing can be put through a pilot plant. I n this case the pilot plant is one unit of a completed plant. No changes in the dimensions of the retort or screw are contemplated, and when the proper speed of operation and the proper number of reversals are determined for one retort, they are the same for the multiple-retort plant.
Operating Figures at Moundsville Throughout the eight years of operation a t Moundsville, many figures were taken which are available to those interested. Early in 1930, after the plant had been operated for more than a year, a client interested in low-temperature carbonization retained the services of a firm of consulting engineers to make a test on this plant entirely independent of the operating crew. This test was summarized as follows:
*
Coal Approx. analysis as fed to t h e plant %xhe(d?arbon, % Volatile yo M o i s d e Q/ Ash.fusidn ?appro=.), O E'. Total input tone Av. i n p u t pkr hour, tons Av. i n p u t per day, tons
9.85 50.9 38.0 2.4 2000 519.37 2.26 54.24 13.5 9.2 1.0 1392
HAYESPROCESSPILOT-PLANTCOAL CARBONIZATION INSTALLATION AT COLORADO FUEL& IRON COMPANY Tar
Total t a r yield, gal. Av. water content % T o t a l dry t a r ield gal. Total t a r yieldr/toi of coal, gal. S , gr. of crude t a r (one teat) raotions by dietillation % r. 0.86, heutral oil) i:g2%Js8 $sp gr 0 948 40% tar acids) 236-270O C: (sp. gr: 1:OOd. 45'7 t a r acids) 27&300° C. (sp. gr. 1.004, 3 5 3 t a r acids) P!us 300' C. (185' C. m. p., 2% insol.) Liquor Loam
able. This drum was also increased in length by 20 per cent, but the diameter and pitch of the conveyor flights remain the same-that is, 16 inches. This permitted of more free space above the screw for the free passage of gases. The screw itself, instead of being driven through a mechanical reversing gear, was driven directly by a reversing alternating-current motor. The controller for this reversing motor is so designed that the time of the forward and reverse motion can be regulated as well as the number of reversals per minute. This is much more flexible than the mechanical reversing gear. No specific problem occurs in the feeding of coal to the retort or the taking of char away from the retort. The tar recovery system is no different than that used in other coke plants, and a description of it would be of no particular interest. The operation of this plant is extremely simple, but the results which can be obtained when using a given feed coal must vary as the coal varies. The operating results given here apply to the particular coal used; carbonization work
2
G a s (avera e values) Gas yieldg cu. ft./hour Gas yield cu. ft./ton of ooal Heat value of gas produced, B. t. u./cu. ft. Gas burned in furnace, cu. ft./hr. Gas burned for oarbonieing, yo H e a t t o oarbonize 1 lb. of coal, B. t. U.
21,500 5.3 20,360 39.2 1.080 4.97 14.25 9.09 12.56 53.62 3.5 2.01 10,150 4442 939 5332.5 52.5 1098.6
The four main variables which affect, more than other items, the cost of producing low-temperature coke are (1) the cost and type of the coal, (2) the selling price of the byproducts, (3) the plant cost, and (4)labor rates. Since there is a variation in these items, there must necessarily be considerable variation in the cost of a ton of low-
AND LABOR CHARQES TABLE11. SUPERVISION
Supervision (for Either Process) Yearly Position salary $8 000 5,'OOO
Two stenographers One chemist a n d helper T w o salesmen Total supervision a Of 8 hours each. r
3,000 2 400 2:700 6,000
4,800 31,900
Position Retort attendants Reooverv d a n t attendants B r i i i e t t h ' g crew Maintenance crew Boiler a n d engine operator Labor Foreman T o t a l daily labor cost Yearly labor cost, 360 days Total labor a n d supervision
Labor for Low-Temp. Char Men p w Np. of Man- Hourly shift shifts0 hours r a t e 3 3 48 $0.80 2 3 48 0.80
i
i
4
3
1
1
3 3
32
24 48 24
o'.io
0.90 0.70 1.00
Prooess Daily cost $57.60 38.40 25:80 21.60 67.20 24.00 234.46
84 500 00 116:400: 00
Labor for Low-Temp. Briquet Prooess Men er No of Man- Hourly Daily sgift shiits hours rate cost 157.60 48 $0.80 38.40 4s 0.80 38.40 48 0.so 38.40 0.80 48 24 21.60 0.90 72 100.80 0.70 24 24.00 1.00
319.20
115,000.00 146,900.00
846
INDUSTRIAL AND ENGINEERING CHEMISTRY
temperature coke. Therefore no reliable figures can be made on the cost of producing coke in a particular plant unless it is possible to make fairly accurate assumptions pertaining t o the variables mentioned. Many estimates have been made of the first cost of building a low-temperature coke plant using the Hayes process. The location of the plant, general schematic arrangement, and plant capacity will cause much variation-hence, the general statement: For a plant built t o produce char only in capacities of 400 tons per day or greater, the cost would be about $800 per ton per day feed capacity, and if built to produce low-temperature coke briquets, the cost would be about $1000 per ton per day feed capacity. The amount of by-products fiom the Hayes plant \Till de-
Vol. 33, No. 2’
pend upon the coal being carbonized, but generally the quantity of tars, which is the most important by-product, is considerably higher from the Hayes rctorts than from other low- or high-temperature proceases. To present tangible figures which might apply for different locations and for carbonizing different kinds of coal, Table 1 gives the estimated cost of producing lomtemperature coke by the Hayes process in plants having a capacity for carbonizing 1000 tons of coal per day; these plants are hypothetically located a t Pittsburgh, St. Louis, and Cincinnati. The item of repairs and supplies refers only to the cost of materials entering into the repairs and supplies since the cost of labor for making these repairs is included in the labor cost. Labor and supervision are figured as shown in Table 11.
H. J . R O S E llellon Institute, Pittsburgh, l’enna.
Anthrarite is a smokeless fuel under all combustion conditions. It does not release even a Lrace of Lar when heated. AnthraciLe i s closely sized, hard enough to resist breakage, and noncaking, and usually has a high ash-softening temperature. Therefore, it provides fuel beds of uniform and dependable character. It is the densest and most concentrated of all solid fuels. For these and other reasons, anthracite permits hand firing with maximum cleanliness and convenience, and is readily used for automatic firing. More than 99 per cent of the country’s anthracite production of 50 million tons annually comes from Pennsylvania, whose reserves are sufficient to last for about 150 years at the present rate of depletion.
NTHRACITE is the only natural fuel which is inherently smokeless under all conditions of use. Liquid and gaseous fuels, as well as coals containing more volatile matter than anthracite, will produce smoke unless they are burned with sufficient air properly mixed with the volatile fuel a t adequate furnace temperatures. Anthracite, however, will not produce smoke in any type of equipment, irrespective of the method of firing, the condition of equipment, or carelessness on the part of users. For a hundred years Pennsylvania anthracite has been the principal smokeless fuel used for heating homes and commercial buildings in the United States. Year after year it has continued to hold first place among the fuels which are burned smokelessly for this purpose. Table I shows its dominant position during the past ten years. According t o available statistics, less than 10 million tons of anthracite are used annually by manufacturing industries, power plants, gas plants, and railway locomotives. After allowing for these uses, it is evident that the amount of anthracite used for heating homes and buildings during the past ten years has been nearly equal to the combined equiva-
A
lent tonnage of all domestic coke, heating oils, and manufactured and natural gas used for domestic and house-heating purposes in the whole United States! X o s t of this anthracite is used in the S o r t h Atlantic states, which explains why that area, in spite of its high population density, has never had a smoke problem comparable to that of many cities elsewhere. The smoke which does occur in the East comes largely from railroads, industries, and heating plants which fail t o obtain smokeless combustion with substitute fuels. Potential Anthracite Production It is fortunate that anthracite pioduction can be greatly increased, becauie the present widespread interest in smoke prevention, stimulated by St. Louis’ successful campaign, comes at a time when unusual demands are being made on fuel production. A recent report from the Office of Production Management t o the President ( 3 ) estimates a shortage of metallurgical coke amounting to 5,360,315 tons during 1941, and states that this should be met by diverting coke from home and commercial uses.
