Coal of the Pikes Peak Region Evolution of G a s e s during Low-Temperature Carbonization FRANK W. DOUGLAS
Colorado College, Colorado Springs,Colo.
FIGURE1. DIAGRAM OF ELECTRIC DISTILLATION FURNACE Electric furnace 6‘. Water heater Retort (liter Pyrex 5ask) H. Tar bottle I. Cold water oondensor Thermocouple D. High-temperature thermometer J. Collecting bottle for water and light oils E. Rheostats, one for each coil K. Gas sample remover F. Hot water condenser L. Aspirator bottles for gas storage M. Outlet for water from aspirator bottles A. B. C.
OT
HE coal of the Pikes Peak region occurs in a single seam a t depths varying from approximately 30 to 600 feet. It is called lignite but is apparently a sub-bituminous coal. It is black in color, of shiny luster, and with little remaining evidence of ligneous nature. When carbonized a t high temperatures, the coal of the Pikes Peak region yields water, gas, and tar, but falls into powder. Therefore it cannot be used for coke making by the usual process and for this reason has not been found profitable for gas making since coke is a necessary by-product of that industry in order to make it a commercial success. The high percentage of matter volatilized and the low temperature a t which it is evolved give low efficiency in burning the raw coal and, therefore, make such methods of utilization very wasteful. The coal of the Pikes Peak region forms a section of the deposits which lie along the eastern slope of the Rocky Mountains and extend northward into the Dakotas. The coals in this field vary from lignite to sub-bituminous, differing mainly in content of moisture and volatile matter. Under distillation they behave similarly. Conservation of these valuable deposits demands a more efficient method of utilization. Lowtemperature carbonization seems promising for the following reasons :
5 . The coke ignites easily, holds fire well, and requires little
draft.
6. The gas is of good quality with high heating value. 7. The tar appears to give a good yield of motor fuels and
other valuable products.
For a number of years work in the low-temperature carbonization of coal of the Pikes Peak region has been in progress in this laboratory. Its special objectives have been: 1. The treatment of the coal to prevent slaking. 2. The strengthening of the coke to permit handling. 3. The determination of the conditions of distillation to give the most valuable products. 4. A study of the results of distillation under increased pressures. 5. Distillation accompanied by cracking of the tar to give a greatly increased yield of gas and higher hydrogen content. 6. A study of the tars under different conditions to determine which yield the most valuable products.
It is the principal purpose of this paper to report on the amounts and compositions of the gases evolved under different conditions of distillation.
Coal Used Two samples of coal were used in this work. The first was taken from the Corley Mine, 7 miles north of Colorado Springs. Samples were obtained from four rooms in the mine by making vertical cuts across the working face. The portions from the four rooms were crushed and mixed together. The sample thus obtained was stored in sealed bottles. During transportation and preparation the coal was exposed to the air. Effort was made to reproduce approximately the conditions to which the coal would be subjected in the usual methods of handling. This gave a partially air-dried sample, commonly designated “coal as received.’, The analysis gave :
1. The coal slakes badly so that it is unsuitable for shipment or storage. 2. The region has no available and adequate supply of smokeless fuel, making an urgent need and giving promise of a good market. 3. Carbonization takes place at 600’ C. or below, making possible the use of inexpensive apparatus and waste heat. 4. The coal is noncoking, thus eliminating trouble with the clogging of the retort and the conduction of heat.
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moisture, 16.15 per cent; volatile matter, 37.65; and ash, 7.81. The volatile matter was determined by making a one-gram pellet, using the press of an Atwater bomb calorimeter, heating with a low flame for 3 minutes and then with the full flame of a Bunsen burner for 4 minutes. The compression into pellets has given more consistent results in this laboratory. The second sample was taken in a similar manner from the Pikeview Mine, about 2 miles north of Colorado Springs, and was prepared in the same way. The analysis gave the following results, volatile matter being determined by the usual modified method (3) : moisture, 16.54 per cent; volatile matter, 37.48; fixed carbon, 40.78; ash, 5.20; and sulfur, 0.47. The sample of about 100 pounds (45.4 kg.) was stored in sealed bottles and used for further work. It seemed to change little over a period of several years.
Electric Distillation Furnace The apparatus used for most of the distillations is shown diagrammatically in Figure 1: The furnace was a double-walled, cubical, sheet steel box, the space between the walls being packed with asbestos cement. The top was removable for charging. It was heated by means of two coils of nichrome wire, one on the bottom and one on the sides. Each coil was connected separately to the power supply. A double mica window permitted observations of the progress of the distillation. The retort was a liter Pyrex flask resting on a wire support. Connections with the condensing apparatus were made by means of a hard-baked plug of asbestos cement, set in place with a mixture of litharge and linseed oil. In case of leakage, a coating of asbestos cement, moistened with water glass solution, successfully closed it. Temperature control was obtained by means of rheostats, and measurements were made by means of high-temperature thermometers and thermocouples. The condensing system contained a straight condenser through which flowed a current of hot water to prevent the clogging by the tar. The latter was collected in a bottle connected to the condenser. The uncondensed products next flowed through a cold water spiral condenser into a bottle where the water and light oils were collected. A series of aspirator bottles followed and were so arranged that any portion of the gas could be collected as desired. A T-tube in the circuit permitted the removal of a sample of gas at any time.
Rapid Heating of Furnace to Maximum Temperature Two distillations were made, using 500 grams of Pikeview coal, the heating was gradual but as rapid as possible. I n the first distillation, the furnace was raised to a maximum temperature of 650" C. in 4 hours and held there for one-half hour. The rate of heating was about 2.5" C. per minute except a t the beginning. In the retort a maximum of 565" C. was obtained in 4.5 hours, the rate of increase being 2" C. per minute. No gas was given off below 100" C. The distillation was practically complete a t 475 " c. In the second distillation, the furnace was heated to a maximum of 500" C. in 3.5 hours, the rate being 2.36" C. per minute. In the retort the increase was 3" C. per minute for the first loo", and 2.10" C. per minute thereafter. A third distillation was heated a t the rate of 3.0" per minute but gave off tar so fast that it clogged the apparatus and blew out the connections. The two distillations were fair duplicates. No differences were discernible due to time, temperature, or manner of heating. The yield of gas was 3338 cubic feet per ton with a density of 1.178 grams per liter. The average of twenty-seven analyses (in per cent) gave: Carbon dioxide Illuminants Oxygen Carbon monoxide
37.7 1.26 4.0 9.80
Methane Hydrogen Nitrogen
25.11 7.25 14.81
VOL. 28. NO. 2
Stepwise Distillations A series of seven distillations of the Corley coal was made in a stepwise manner, the maximum temperature reached was 400" C. At each temperature the apparatus was held a t constant conditions until practically no more gas was given off. For instance, in the seventh distillation the periods were as follows: 100' C. 200 250
300' C. 350 400
4.0 hours 4.5 3.0
2.5 hours 3.5 5.0
No gas was evolved below 100" C. At that temperature the yield was small and appeared to be occluded gas. The distillate was entirely water. At 200" C. the evolution of gas was slow and steady. The distillate was still water with a barely visible film of oil. At 245' C. the first discernible drops of clear colorless oil condensed. At 260" C. the gases issuing from the delivery tube began to take on a cloudy appearance. When condensed, they gave a clear, light-colored oil. At 300" C. the condensate was a dark yellow oil with very little water. Below 350" C. the gas evolved would ignite but would not burn a Bunsen burner. The most marked evolution of gas occurred a t this temperature. At 400" C. the condensate was a dark colored oil and very thick. Above 300" C. the oils clogged the condenser if hot water were not used. The last distillation gave, per kilogram of coal, 3.0 liters of gas a t 100" C.; 5.2 a t 200"; 31.0 a t 300"; 66.8 a t 400". The data obtained in these distillations are shown in Tables I and 11. The composition of the gases obtained a t the different intervals of temperature was fairly constant, and averages are given. Calorific values are calculated but have been shown to be consistent with calorimeter determinations. DISTILLATIONS OF CORLEY COAL TABLEI. STEPWISE Distillation No.: Coal, grams Coke, grams Coal volatilized % Volatile matter i n ooke, % Water, grams Water, %
3 500 295 41.0 12.8 126 25.2 19.0 3.8 0.6 0.1 59.5 51,500
4 500 294 41.2 12.7 127 25.4
5 500 295 41.0 12.8 126 25.2
6 500 296 40.8 12.9 125 25.0
7 500 295 41.0 12.8 126 25.2
19.5 19.0 18.0 19.0 3.9 3.8 3.6 3.8 0.5 0.5 0.5 0.5 0.1 0.1 0.1 0.1 59.0 59.6 60.5 59.5 53,500 52,500 51,000 53,000
OF GASES~ FROM STEPWISE DISTILLATABLE 11. COMPOSITION TIONS OF CORLEY COAL
Temp.
c.
0
COz
Illuminants
0 2
CO
%
%
%
%
6.5 250 80.0 0.0 0.0 8.5 300 70.5 1.0 0.1 0.5 10.0 48.0 2.5 350 5.5 0.8 400 28.5 0.7 Average of twenty-seven analyses.
CH4
Hz
%
%
3.5 17.0 33.8 49.9
1.3 3.0 3.9 12.5
Calcd. Calo-
Nz rific Values % cat. (Warns)/ 8.7 0.0 1.3 2.1
liter 1708.8 3150.6 4690.3 5028.5
Distillation with Furnace at Fixed Temperatures Another series of distillations of the Pikeview coal was made by heating the furnaces rapidly to a given temperature and holding it there until no more gas was given off. The results per kilogram of coal are shown in Table 111. The first distillation apparently shows the effects of air enclosed in the apparatus and occluded in the coal. The yield was small. The distillate was water with only traces of tar and oil. Between 250" and 300" C . there was a distinct increase in tar and oil and not much water. A moderate amount of gas was given off which was nearly all carbon dioxide.
FEBRUARY. 1936
IXDUSTRIAL AND ENGINEERING CHEMISTRY
221
hottest part of the retort. Distillation 4 was similar, but the TABLE111. DISTILLATIOXS OF PIKEVIEW COALAT CONSTANT products were removed from the top of the retort. I n distilTEMPERATURES lation 3 the gases collected below 250' C. (11.53 liters) were Yield IllumiCalcd. Calodiscarded because of their high content of carbon dioxide. Temp. per Kg. COz nants 0 2 GO CH4 Hz rific Value This raised the percentage of the other constituents in proCal. (grams)/ ' C. Liters % % % % % lzter portion. Temperatures were measured by means of thermo200 N o gas ... ... .... couples at the center of the retort. The distillations proceeded 250 1.8 47:6 0.0 l2:2 310 510 0.67 258.1 350 23.5 46.0 0.7 4.7 6.0 11.4 4.5 1691.0 in about the same manner as in the electric furnace, but the 530 27.9 33.6 1.1 4.8 8.2 28.7 22.5 3640.1 temperatures were not quite the same.
Gas-Heated Cast-Iron Retort The next series of distillations was carried on in another form of apparatus (Figure 2) : The retort consisted of a 3.5-inch (8.9-cm.) cast-iron pipe, 28 inches (71.2 om.) long, closed at both ends by collars and plugs. Into each plug was fitted a 0.5-inch (1.3-cm.) pipe. Glass connections were fitted into these pipes by the method previously described. A sheet-iron jacket, lined with an inch (2.5 cm.) of asbestos cement, surrounded the retort. The annular space between the retort and jacket was about one inch. Through this assed the hot gases for heating the retort. The offset a t the ottom of the jacket was so constructed that the retort was heated by refleotion rather than by direct contact with the flames. The base of the jacket had holes for six burners. Between these were three holes for draft which had sliding doors for draft control. The top of the jacket was connected with a flue by means of a yip". The retort was mounted on a tripod. Three precision eker burners, operating on natural gas, gave a uniform temperature of 600" C. and satisfactory control up to that temperature. The condensing system was similar to the one already described but a column of cotton was inserted t o take out the fog. Also, a telescopic gas holder of about 9 cubic feet (0.25 cubic meter) capacity was substituted for the aspirator bottles, and a small gas meter was used for the measurements of volume.
t:
TABLE IV. ANALYSES OF GASESFROM DISTILLATIONS OF 1750 GRAMSOF PIKEVIEW COAL
--
Distillation No.: 1 2 3 4544 590 625 500 Temp., C . 500-600 Total 136.33 115.15 187.27 195.33 9 1 . 3 5 2 8 6 . 6 8 Vol. (STP) liters 28.8 31.3 43.9 45.25 13.0 34.9 Carbon didxide, % 0.0 0.0 0.0 0.35 0.1 0.2 Benzene % 0.9 1.2 1.5 1.95 ~~lurnina'nts, % 0.3 1.4 2.1 0.4 0.4 0.4 0.3 0.4 Oxygen % 11.6 11.2 10.0 Carbon'monoxide, % 9.4 13.6 10.8 26.0 27.8 25.3 23.15 21.0 22.5 Methane % 21.1 24.1 16.6 17.3 44.3 25.9 Hydrogeh % 10.8 4.2 2.3 2.2 7.4 3.9 Nitrogen '% Calcd. dlorific value, cal. . . . . . . . . 3488.8 3 4 3 5 . 4 3853.7 3 5 9 5 . 6 (grams)/liter
TABLEV.
YIELDSPER TONIN DISTILLATIONS OF COALOF
Coal source: Furnace used: Distillation No.:
PIKESPEAKREGION
Corley Mine Electric
Pikeview Mine Cast-Iron Retort 3 4
400 59.0 12.8 3354.0
626 600 44.00 43.7 6.57 6.26 3639.9 5249.2 3488.8 3595.6 69.74 75.21 5.56 8.89 .. . . 5.04
....
....
60.49 9.78
....
Distillations in Cast-Iron Retort The results of four distillations are given in Table IV. Distillation 1 was carried out in the electric furnace, and the products were passed through the coal in the cast-iron retort. Most of the tar was absorbed by this coal. Distillation 2 was carried out on this coal after it had stood in the cast-iron retort for 2 weeks. The purpose was the strengthening of the coke, which occurred to some extent but was not sufficient. Distillation 3 todk place in the cast-iron retort, and the products were removed from the bottom which was obviously the
Conclusions 1. Coal of the Pikes Peak region can be almost completely
carbonized at temperatures between 500' and 600' C. At lower temperatures some volatile matter is retained, but a good fuel is produced which can be stored or shipped. 2. Of the two forms of apparatusused in these experiments, the electric furnace gives the more uniform heating. An iron retort should be substituted for the glass since the latter softens around 600' C.- The cast-iron retort seems to give somewhat higher temperatures I Cl in the distillation, probably because of less uniform distribution of heat. 3. Little or no gas is given off below 100' C. At that temperature water is distilled over. 4. At a temperature between 250" and 300" C. distillation of the water is nearly complete. A considerable part of the water is formed by decomposition of the compounds in the coal. The gas up to this point is 80 to 90 per cent carbon dioxide and amounts to approximately 4 to 5 per cent of the total gas. Probably i t would be profitable to discard the gas up to this point or use i t to recover the carbon dioxide. 5. Most of the valuable gas is given off between 350' and 500" C. Above this temperature the yield is small. 6. Evolution of carbon dioxide decreases rapidly as the t e m p e r a t u r e r i s e s above 350" C., but all of the d i s t i l l a t i o n s show a s u r p r i s i n g l y l a r g e amount evolved a t all temperatures. The amount of i l l u m i nants is low, as might b e e x p e c t e d , i n -
INDUSTRIAL AND ENGINEERING CHEMISTRY
222
creasing slightly with the temperature. The actual amount of oxygen is probably small at all temperatures. Larger amounts appear to be accidental. Carbon monoxide evolution is small up to 250" C. and increases with the temperature, although a maximum a t 350" C. seems to be established for the Corley coal. Rapid evolution of methane begins around 300 " C. and increases rapidly with increasing temperature. However, little change is found between 500" and 600" C. Hydrogen is not given off appreciably up to 400" C . Above that temperature its formation is very marked, the percentage increasing greatly between 500" and 600" C. Nitrogen is low as in most coal gas. Larger percentages recorded probably are accidental. B. t. u. values increase rapidly with the temperature of carbonization. The heating power would be high if the carbon dioxide were washed out, probably 550 to 700 B. t. u. 7. As far as gas is concerned, complete carbonization a t about 600" C. is indicated. Rapid carbonization with collection of all of the gas above 250" C . would seem to be satisfactory. It is possible that carbonization a t 500" C., giving a coke in which a little of the volatile matter is retained, might prove even more profitable.
VOL. 28, NO. 2
Acknowledgment The work on low-temperature-carbonization was done in collaboration with the following students: undergraduates Harold Milner, Henry Waller, Harold Robinson; Charles A. Bordner, candidate for master of arts degree.
Bibliography (1) Brownlie, Chem. & Met. Eng., 26,23 (1922). (2) Canadian Dept. Mines, Summary Report 586 (1923). (3) Cooper, H. M., Osgood, F. D., and Solomon, R. E., Bur. Mines, Rept. oflnvestigations 3168 (1932). (4) Davis and Galloway, IND. ENG.CHEM.,20,612 (1928). (5) Fieldner and Davis, Ibid., 2,304 (1910). (6) Gentry, "Technology of Low Temperature Carbonization,' 1928. (7) Manuel and Carpenter, Coal &e, 34, 547 (1929). (8) Monnet, Chem. & Met. Eng., 23, 1246 (1920). (9) Parr, J. IND.ENQ.CHEM.,3, 900 (1911); 4,352 (1912).
(IO) Porter, "Coal Carbonization,'' New York, Chemical Catalog Co., 1924. (11) Yancey, H. F., Johnson, K. A., and Selvig, W. A., Bur. Mines, Tech. Paper 512 (1932). R E C ~ I VAugust ~D 19, 1935. Presented before the Division of Gas and Fuel Chemiatry at the 90th Meeting of the American Chemical Society San Francisoo, Calif., August 19 to 23, 1935.
PHOSPHORIC ACID AS THE CATALYST FOR
ALKYLATION OF AROMATIC HYDROCARBONS V. N. IPATIEFF, HERMAN PINES, AND V. I. KOMAREWSKY Universal Oil Products Company, Riverside, Ill.
QT
HE use of phosphoric acid as a catalyst for the alkylation of aromatic hydrocarbons with olefins has not been reported in the literature, Malishev (9) described the use of a mixture of phosphorus pentoxide, cresol, and lampblack as a catalyst for the alkylation of aromatic hydrocarbons with olefins. This paper deals with (1) the alkylation of benzene, naphthalene, and tetrahydronaphthalene with ethylene a t 300" C., and (2) the alkylation of naphthalene and fluorene with propene a t 200" C. under pressure. The products obtained from these reactions consisted of the corresponding mono-, di-, and polyalkyl aromatic hydrocarbons, The propene underwent both polymerization and alkylation. The apparatus consisted of an electrically heated Ipatieff rotating autoclave provided with a gage, thermocouple well, and valve. A glass liner was inserted to prevent corrosion of the walls of the autoclave by the phosphoric acid. The conditions under which the experiments were carried out, and the amount of the total product obtained from the reaction aresummarized in Table I. Benzene-Ethylene Alkylation In experiment 1, 30 per cent of the charged benzene remained unchanged. For each mole of benzene that entered the reaction, 3 moles of ethylene reacted. The reaction product was fractionally distilled using Podbielniak's high-temperature distilling apparatus (4):
Per Cent Baaed on Boiling Range, O C. Alkylated Benzene 1 79-130 4.2 2 130-137 18.5 137-174 3.4 3 4a 174-204 28.8 5" 204-238 16.6 64 238-283 12.6 Above 263 17.0 7 a Distilled under 5 mm. of mercury pressure. The boiling points were correoted to 760 mm. of mercury pressure using Brown's chart (1). Fraction
Eighty-five to eighty-nine per cent orthophosphoric acid can be used as a catalyst for the direct alkylation of aromatic hydrocarbons. The ethylation of benzene, naphthalene, and tetrahydronaphthalene was studied, and the following were identified: mono-, m-di-, sum-tri-, and tetraethylbenzene ; diethylnaphthalene ; mono- and diethyltetrahydronaphthalene. The direct propylation of naphthalene and fluorene was made. Monopropylnaphthalene and monopropylfluorene were formed.
