IiVD USTRIAL SiVD ENGINEERING CHEMISTRY
612
Vol. 20, No. 6
Low-Temperature Carbonization of Lignites and Sub-Bituminous Coals' Yield of Products and Comparison of Assay Methods J. D. Davis and A. E. Galloway PITTSBURGH EXPERIMENT STATION, U. S. BURBAU OF MINES,PITTSBURGH. Pa
ABORATORY-SCALE carbonization tests (assays) do The overflow tube is connected to the automatic leveling not, as a rule, give results directly convertible into device shown. By measuring the displaced water and the industrial-scale yields because it is impossible to simu- temperature the volume of the gas is determined. The liquid late operating conditions exactly. Furthermore, different in the gas holder is a mixture of glycerol and water, a satuindustrial processes do not give the same yields, so that if rated solution of magnesium chloride in water, or water satuone should devise a laboratory test to give the same yields rated with gas from a previous run. Magnesium chloride was as a specified type of process it would not apply exactly to used by the writers. any other. Assay methods tend to give high oil and low gas METHOD-The coal is ground to pass a 60-mesh sieve and yields because application of heat is so controlled that mini- dried at 105" to 110" C. The retort tube is charged with a mum cracking of oil vapors 20-gram sample, and a loose takes place. I n d u s t r i a l asbestos plug is placed in scale carbonization in inert the forward end. The coal Comparative low-temperature assay tests were made gases-for e x a m p l e , in is so placed in the tube that on twenty-four sub-bituminous coals and lignites by s u p e r h e a t e d steam-also it will be in the middle of the three different methods: the oil-shale method, deminimizes cracking; accordfurnace, and is shaken down veloped by the Bureau of Mines; the Gray and King ingly, the yields obtained to allow a free passage for method, developed in England; and the Franz Fischer by processes of this type apthe gas in the upper half of method as used in Germany. The results, which are p r o a c h very closely those the tube. After the furnace given in tabular form, give a general idea of the yield obtained b y assay. In has been heated to 300" C., of products to be expected from coals of this rank. other types of processes, the tube is inserted and conThe writers find that the Franz Fischer method gives when no particular effort is nected to the train. This the most concordant results: accordingly, they prefer taken to prevent cracking, cools the furnace somewhat. this method. oil yields may drop to 70 The tar condenser is cooled b y i m m e r s i o n in a water per cent of that given by assay, with increased yields bath, the glass beads in the of Doorer gas. ammonia scrubber are drenched with sufficient sulfuric acid, kssaysare valuable, however, for indicating comparative and the gas holder is adjusted to receive gas and release water. yields of different coals, provided that the methods employed When the furnace temperature has again reached 300" C., it can be relied upon to give results that can be duplicated. is raised to the maximum of 550" C. in one hour a t a constant I n this paper comparative results obtained by three different rate and held constant a t that temperature for one hour. The methods are given for twenty-four representative American rate of gas formation can be determined a t intervals by measlignites and sub-bituminous coals. These methods are the uring the overflow water for a definite period. By weighing Bureau of Mines oil-shale, Gray and King, and Fischer, the retort tube plus the asbestos plug empty, then with the used in the United States, England, and Germany, respec- coal, and a t the end of the run, the weights of the coal and tively. coke are determined. At the end of the run the formation of gas for this temperaFuel Research Board (Gray and King) Method ture will have ceased and screw clamps may be placed over APPARATUS-Figure 1shows the Gray and King apparatus.2 the rubber-tube connections to close off the ammonia abA hard glass tube 30 cm. long and 2 cm. in diameter, open a t sorber, the tar condenser, and the gas reservoir. The volume one end, with a side tube 1 cm. in diameter close to this end, of gas may then be determined by noting the temperature and is heated in an electric furnace; the open end of the tube is pressure in the holder and measuring the overflow water, or closed by a rubber stopper, Temperature is measured by a the water may be weighed. The yield of ammonia is deterthermocouple extending midway into the furnace between the mined by collecting the aqueous distillate in the tar conglass tube and furnace wall. A U-shaped tu%e with a short denser and the washings from the ammonia absorber, making tube and stopcock sealed on at the bottom for drainage it strongly alkaline, absorbing the distillate in standard serves as a tar condenser. Connected to the condenser is an acid, and titrating. The tar and oils are determined by armrronia scrubber. This is a tube 2 or 3 cm. in diameter, weighing the tar condenser empty and before and after filled with glass beads drenched with sulfuric acid. A stop- removal of the water a t the end of the run. The runs were made in duplicate; the first run was precock is sealed on at the bottom. The gas from the tar condenser is led downward by means of a small tube and enters liminary and the gas was used to displace all air by passing the bottom of the scrubber. The gas reservoir is a large it back through the apparatus when it was again assembled. bottle closed by a rubber stopper, through which pass a ther- The gas sample taken for analysis was collected from the mometer for measuring the gas temperature, an overflow tube second run. All determinations of the first run were used to reaching to the bottom, and a T-tube connected to the check those of the second. ammonia scrubber at one end and a manometer a t the other. Bureau of Mines Oil-Shale Method
L
1 Received February 11, 1928. Published by permission of the Director, U . S. Bureau of Mines. (Not subject to copyright.) a Gray and King, Fuel Research Board, Tcchnical Paper 1 (1921).
The second method and apparatus used by the writers waa that designed and used by the Oil Shale Laboratory of the
I,YDCSTRIAL AND ENGIATEERILVGCHEMIPTHY
June, 1928
Bureau of Mineb at Boulder. Colo.. and described in detail elsewhere.3 APPARATUS-The retort (Figure 2) is made of cast iron with a clamped-on cover, and is the one commonly supplied for mercury distillation. The lid is carefully ground to fit tightly. The greatest dimensions of the retort without the clamp are 5 inches (12.7 em.) in height by 4.5 inches (11.4 cm.) in diameter. The vapor offtake is a 0.25-inch (6-mm.) pipe 20 inches (51 em.) long with a “street ell” on one end which screws into the lid and a tee on the other end. Into the lower end of the tee is screwed a 3.5-inch (8.9-cm.) length of pipe, ground to a dropping point on one end. To this short pipe a 100-c~.graduate with lip smoothed over is connected by means of a rubber stopper bored at a n angle to allow the graduate to stand perpendicularly. To the upper end of the tee a 1- to 0.25-inch (25.4- to 6-mm.) reducing coupling is connected by a short nipple. A long Liebig condenser is connected to the reducing coupling by a cork which is made gas-tight with a glycerol-litharge cement. Condensates will thus drain back into the graduate receiver. From the top of the condenser a long tube leads downward to a U-tube filled with activated carbon to retain mists which pass the condenser, light oils, and tar. The clean gas now passes through a meter to a holder or is wasted. The retort 1s surrounded by an asbestos box with a hole in the bottoni for a large Fischer gas burner and a hole in the top for ventilation. The heating is regulated by a needle valve connected in the gas line, the gas pressure being given by a sensitive manometer.
613
_____Figure 2-Oil-Shale
.4pparatus
the weight of oil, but usually it was negligible. The volume of the total tar, oils, and watery liquid was measured in the graduate receiver. With the oil-shale assay, for which this method was designed, it is an easy matter to determine the oil and water in the graduate receiver, because they separate by gravity and can be read directly. With coals and lignites there was no sharp separation in the graduate. Accordingly, the total volume of the distillate was read and its weight determined, the volume and weight of water being subsequently determined by distillation with xylene, as in the Fischer method described later. Water and oil were thus separately determined on a volume and on a weight basis. The time required for an assay distillation was usually 41/2hours, and the samples were run in duplicate by mounting two retorts beside each other and regulating them as nearly alike as possible. The gas from one retort was collected in a holder over water and afterwards measured by discharging through a meter. The gas from the other retort passed through the meter and was wasted. Franz Fischer Method
Figure 1-Fuel
Research Board Apparatus
%hTHoD-The coal or lignite as received was crushed to pass a 10-mesh screen and a sample of 225 grams taken for assay. The usual form of apparatus for oil-shale assay work does not include a means of measuring the temperature; therefore, none was used by the writers. For this method the basis of regulation is not rate of temperature rise but a uniform accumulation of the distillate. The gas pressure on the burner was therefore increased at intervals to give a regular accumulation of distillate, as noted by the dropping of liquid and by the volume increase of distillate per unit time. The desired curve, therefore, of the distillate accumulation plotted against time is a straight line, and in carrying out an assay this curve was made to approach a straight line as nearly as possible. The heating was continued until the distillate ceased to come over. At this point the Liebig condenser was drained and steam slowly admitted at the top to melt out the small quantities of tar and heavier distillates which had condensed there. The small amount of light oils caught in the activated carbon was taken into account in determining 8 Gavin, U S Bur Mines, Bull 210 (1922), Karrick, I b t d , Repts Inuesfigatmns 2229 (March, 19211, Karrick, l b i d . , Bull 249 (1926).
APPARATUS-T~~S apparatus was especially designed by Fischer4 and his associates for the lowtemperature assay of brown and bituminous coals. It was purchased directly from Fischer’s instrument maker, Andreas Hofer, Miilheim-Ruhr, 4 Fischer and Schrader, Z. anpew. Chcm., 39, 172 (1920); Schrader, Brennsloff-Chem, 12, 182 (1921).
Figure 3-Franz
Fischer Retort a n d Apparatus
INDUSTRIAL AND ENGINEERING CHEMISTRY
614
T a b l e I-Analyses ~~
of SamDles
~
PROXIMATE LOCALITY, MINE, ETC.
Mois- Vola- Fixed tile carhre matter bon
Big Vein mine, Roundup, Musselshell County, Mont. (250 feet SE of slope mouth) Wilton mine, Wilton, Burleigh County, N. Dak. (face of room 3 on 2 south off 6 west)
1” 2 3 1 2
3
1 2 3 1 Reclamation mine, Williston, Williams County N. Dak. (in room 13, 40 feet in from 9th so& 2 entry, on rib) 3 Pratt Corporation mine Zap Mercer County, 1 N. Dak. (at fresh fac; in S’W part of rib) 2 3 1 Wright mine, Matheson, Elbert County, Colo. (at freshest face in strip pit, about center of pit) 2 3 1 Northwestern Improvement Co. mine, Colstrip Rosebud County, Mont. (near northern end bf 2 pit) 3 1 Flagstaff mine, Manderson, Big Horn Country, Wyo. (face a t end of west entry) 2 Larson’s strip pit mine, Terry, Prairie County,
L Mont. (at outcrop)
3
Krogman mine, Upton, Weston County, Wyo. (150 feet from slope mouth, on rib in No. 1 room) Hotchkiss No. 2 mine, Sheridan, Sheridan County, Wyo. (No. 6 room off 3rd north, entry, face of room) Ellis mine, Gobert, Harding County, S. Dak. (in last crosscut between main entry and air course) Chupp mine, Bloomfield, Dawson County, Mont. (from fresh face 80-90 feet from slope mouth)
Olson mine, Scobey; Sheridan County, Mont. (center of north pit)
1 2 3 1 2
3 1 2 3
1 2 3
1
2 3 No. 4, Union Pacific Coal Co. mine, Hanna, Car- 1 bon County Wyo. (room 13, E Plane, 3 north 2 entry; last l i f t crosscut 500 feet from room neck) 3 Raeder mine, Chinook, Blaine County, Mont. (at 1 end of main entry 250 feet from slope mouth) 2 3 1 Pittsburgh mine, Dickinson, Stark County, N. Dak. (on rib a t end of 1st west entry) 2 3 Curran & Marengo mine, Broadus, Powder River 1 2 County, Mont. (from face a t west end of out3 crop) 1 Lee mine, Plentywood, Sheridan County, Mont. [face of 1st right entry (air course)] 2 3 1 Truax mine, Columbus, Burke County, N. Dak. (east pit) 2 3 Knopp mine, New Leipzig, Grant County, N. 1 Dak. (face of room neck, 100 feet from slope 2 mouth, east off main entry) 3 No. 4, Union Pacific Coal Co. tnine, Hanna, Car- 1 hon County, Wyo. (13 room, E plane, 3 north 2 entry; east left crosscut, 500 feet from room neck) 3 Poposia No. 1 mine, Poposia, Fremont County, 1 Wyo. (comp. of A 4706, A 4707, A 4708) 2 3 M and M mine, Thermopolis, Hot Springs 1 County, Wyo. (200 feet from main slope 2 3 mouth, face of entry) a
%
%
Vol. 20, No. 6
%
15.7 31.4 46.2 .. 37.2 54.9 . . 4 0 . 4 59.6 39.7 2 7 . 5 2 6 . 8 45.6 44.4 . . 50.7 4 9 . 3 2 6 . 1 25.2 31.2 . . 3 4 . 1 42.2 . . 44.7 5 5 . 3 36.1 20.5 33.5 32.0 5 2 . 5 . . 37.8 62.2 3 3 . 6 2 7 . 2 33.0 . . 41.0 49.7 . . 45.2 5 4 . 8 31.4 2 7 . 4 2 8 . 8 . . 39.9 4 2 . 1 . . 48.7 5 1 . 3 24.3 28.0 40.5 . . 3 7 . 0 53.4 . . 40.9 59.1 16.5 34.3 38.0 .. 41.0 45.6 47.452.6 3 1 . 9 25.5 3 4 . 5 38.9 50.7 4 3 . 4 56.6 20.8 3 2 . 8 4 2 . 1 .. 41.4 53.1 .. 43.8 56.2 4 1 . 0 23.2 28.4 .. 3 9 . 3 4 8 . 2 . . 45.0 5 5 . 0 38.3 2 4 . 4 30.0 .. 3 9 . 5 48.7 44.7 5 5 . 3 34.1 2 4 . 7 3 2 . 1 . . 37.6 48.6 43.6 56.4 11.2 40.6 4 4 . 1 . . 45.7 49.7 .. 47.9 5 2 . 1 2 1 . 0 28.8 39.9 . . 36.4 5 0 . 5 .. 41.958.1 4 2 . 6 24.7 2 7 . 0 . . 43.0 47.2 47.7 52.3 3 0 . 8 26.8 3 4 . 6 .. 38.8 5 0 . 0 .. 43.7 56.3 37.2 26.4 3 0 . 8 . . 4 2 . 0 49.1 46.153.9 3 2 . 2 27 0 3 2 . 3 . . 39.9 4 7 . 5 45.6 54.4 34.1 2 8 . 1 2 7 . 7 42.7 4 2 . 0 .. 50.4 49.6 1 2 . 7 4 1 . 2 40.6 . . 47.2 4 6 . 6 .. 5 0 . 4 4 9 . 6 2 0 . 8 3 3 . 0 43.2 41.7 5 4 . 5 43.3 56.7 1 0 . 4 3 5 . 5 41.9 .. 3 9 . 6 46.8 45.8 54.2
..
..
.. .. ..
.. ..
.. ..
.. ..
.. .. ..
ULTIMATE
Ash
% 6.7 7.9
..
6.0 10.0
..
17.5 23.7
..
9.9 15.5
..
6.2 9.3
..
H
C
%
%
5 . 9 61.2 4.9 72.6 5.4 78.8 7 . 1 38.6 4 . 5 64.0 5 . 0 71.1 5.5 41.0 3 . 6 55.5 4 . 7 72.7 6 . 6 40.8 4.0 63.8 4.7 75.5 6.6 43.8 4.2 66.0 4.7 72.8
12.4 18.0
... ...
..
7.2 9.6
5,6 3.8 4.2 6.0 5.0 5.7 6.4 4.3 4.7 6.3 5.0 5.3 7.0 4.2 4.8 6.8 4.1 4.7 6.3 3.7 4.3 6.0 5.4 5.6 5.7 4.3 4.9 7.3 4.5 4.9 6.4 4.3 4.8 6.9 4.4 4.8 6.4 4.1 4.7 6.7 4.4 5.2 6.0 5.3 5.6 6.2 4.9 5.1 5.5 4.8 5.6
53.6 70.8 78.3 54.9 65.7 75.9 46.2 67.8 75.7 57.3 72.4 76.6 37.8 63.9 73.1 40.4 65.5 74.3 42.0 63.8 74.0 65.8 74.1 77.7 51.9 65.7 75.6 37.3 64.9 72.0 44.9 65.0 73.2 41.4 65.9 72.4 43.6 64.4 73.6 40.5 61.5 72.6 61.8 70.7 75.5 57.3 72.4 75.2 60.4 67.4 78 0
..
..
11.2 13.4
..
7.1 10.4
..
4.3 5.5
,.
7.4 12.5
..
7.3 11.8
..
9.1 13.8
..
4.1 4.6
..
10.3 13.1
..
5.7 9.8
..
7.8 11.2
..
5.6 8.9
..
8.5 12.6
..
10.1 15.3
..
5.5 6.2
..
3.0 3.8
..
12.2 13.6
.
OFTEN:ALORIFIC
..
N
0
S
%
%
%
%
24.2 12.2 13.3 46.7 18.9 21.0 34.9 15.8 20.7 41.0 13.9 16.5 42.1 18.5 20.3
1.0 1.2 1.2 1.0 1.6 1.8 0.4 0.5 0.7 1.0 1.6 1.9 0.6 1.0 1.1 0.5 0.8 0.9 0.9 1.2 1.4 2.1 2.5 2.9 0.5 0.8 0.9 0.7 0.8 0.9 2.2 3.7 4.2 0.3 0.4 0.5 0.4 0.6 0.7 0.3 0.3 0.4 0.7 0.8 1.0 0.6 1.0 1.1 0.3 0.4 0.5 0.4 0.6 0.6 0.4 0.6 0.7 1.5 2.3 2.7 0.5 0 6 0.6 0.3 0.4 0.4 1.3 1.4 1 6
6.7 7.9
...
...
.. ..
0.9 1.1 1.3 1.1 1.3 1.5 0.8 1.2 1.4 1.0 1.3 1.4 0.5 0.9 1.0 0.6 1.0 1.2 0.6 0.9 1.1 0.9 1.0 1.1 1.2 1.5 1.7 0.5 0.9 1.0 0.7 1.0 1.1 0.7 1.1 1.2 0.7 1.1 1.2 0.6 1.0 1.1 1.1 1.3 1.4 1.2 1.5 1.6 1.2 1.3 1.5
31.8 13.5 14.8 24.7 12.1 14.0 39.0 15.5 17.3 30.4 15.0 15.8 45.1 14.8 16.9 44.6 17.2 19.3 41.6 17.2 19.9 22.9 14.6 15.2 30.2 14.6 16.8 48.6 18.9 21.0 39.9 18.1 20.4 45.0 19.1 21.0 40.4 17.2 19.8 40.6 1.5.5 18.4 25.1 15.9 16.9 32.0 17.0 17.7 19.4 11.5 13.3
..
6.0 10.0
..
17.5 23.7
..
9.9 15.5
..
6.2 9.3
.. ..
..
..
7.2 9.6
..
11.2 13.4
..
7.1 10.4
..
4.3 5.5
..
7.4 12.5
..
7.3 11.8
..
9.1 13.8
..
4.1 4.6
..
10.3 13.1
..
5.7 9.8
..
7.8 11.2
..
5.6 8.9
..
8.5 12.6
..
10.1 15.3
..
5.5 6.2
..
3.0 3.8
..
12.2 13 6 ,.
in0
TEMP.
Ash
1.0 1.2 1.3 0.6 1.0 1.1 0.7 0.9 1.2 0.7 1.2 1.4 0.7 1.0 1.1
. . . .. ... ..
VALUE
Cal. B. t . u. 5956 10,720 7061 12,710 7667 13,800 3650 6,570 6050 10,890 6722 12.100 3728 6,710 5044 9,080 6611 11,900 3817 6,870 5967 10,740 7056 12,700 4067 7,320 6128 11,030 6756 12,160 3828 6,890 5578 10,040 6806 12,250 5128 9,230 6772 12,190 7489 13,480 5411 9,740 6478 11,660 7483 13,470 4244 7,640 6233 11,220 6956 12,520 5456 9,820 6889 12.400 7289 13,120 3544 6,380 6000 10,800 6861 12,350 3628 6,530 5883 10,590 6667 12,000 3806 6,850 5778 10,400 6700 12,060 6367 11,460 7172 .12,910 7522 13,540 4878 8,780 6167 11,100 7094 12,770 3478 6,260 6056 10,900 6717 12,090 4200 7,560 6067 10,920 6839 12,310 3806 6,850 6061 10,910 6656 11,980 4050 7,290 5972 10,750 6828 12,290 3867 6,960 5872 10,570 6933 12,480 6111 11,000 7000 12,600 7467 13,440 5517 9,930 6961 12,530 7239 13,030 5856 10,540 6539 11,770 7567 13,620
F. 2450 2390 2355 1940 2110 2290 2150 2180 2230 2090 2060 2260 2110 2410 2510 2150 2260 2340 2090 2060 2410
2680
The form of analysis is denoted by number as follows: 1, sample as received; 2, moisture free; 3, moisture and ash free.
Germany. The particular retort used by the writers (Figure 3) is not of the type designed for distillation in superheated steam, because those on hand with this provision were too small. It is a heavy-wall, cast-aluminum, cylindrical retort with a triangular side projection or “nose” through which the outlet tube extends downward a t an angle of 45 degrees. Because of the large heat capacity of this nose the outlet tube is kept hot so that heavy tars do not condense in it. The cover is a heavy aluminum plug fitting into the retort top on a carefully ground taper joint. A thermometer well in the retort wall takes a special high-temperature mercury thermometer furnished with the apparatus. An ordinary iron tripod is used to support the retort, which is heated by a large gas burner; the type of MBker burner designed for air blast
will be found convenient. The receiver is a 250-cc. Pyrex distilling flask with a large side tube (about 8 mm. bore) in order to have ample space for refluxing the condensate from the Liebig condenser which is connected to it. The receiver is connected to the outlet tube by a soft perforated cork. This will burn and leak, however, unless covered by a glycerollitharge cement. A tube of activated carbon is connected to the outlet end of the Liebig condenser to catch any light oils and tar mists which escape condensation, and the receiver is immersed in an ice bath for rapid cooling. The gas leaving the carbon tube is led through a meter and then is either wasted or collected in a gas holder for subsequent analysis as desired. The retort plug should be lubricated with a thin film of graphite and oil to prevent sticking.
INDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1928
of Average Assay R e s u l t s
T a b l e 11-Comparison COAL
370.
F.a O.S.aF.R.B.C
1 Lignite, Fort Lupton, Colo. 2 Sub-bituminous, Roundup, Mont. 3 Lignite, Wilton, N. Dak. 4 Lignite Terry Mont. 5 Lignite: Willis;on, N. Dak. 6 Lignite Zap N. Dak. 7 Lignite: Maiheson, N. Dak. 8 Sub-bituminous coal, Colstrip, Mont. 9 Sub-bituminous coal, Manderson, Wyo. 10 Sub-bituminous coal. UPton Wyo. 11 Sub-bituminous coal, Sheridan, Wyo. 12 Ljgnite,Harding Co., S. Dak 13 Lignite, Bloomfield, Mont. 14 Lignite Scobey, Mont. 15 Sub-biLuminous coal (top), Hanna, Wyo. 16 Sub-bituminous coal, Chinook Mont. 17 Lignite: Dickenson, N. Dak. 18 Lignite, Broadus, hlont. 19 Lignite, Plentywood, Mont. 20 Lignite, Columbus, N. Dak. 21 Lignite, h-ew Leipzig, . . N. Dak. 22 Sub-bituminous coal (bottom), Hanna, Wyo. 23 Sub-bituminous coal, Lander Wyo. 24 Sub-dituminous coal, Thermopolis, Wyo. Average
I
WATER
COKE
TAR
-
%I%
F.
O.S.
TAR
GAS
GAsb
0,s. F.R.B. F. 0,s. F.R.B.
F.
615
F.R.B.
%
%
%
70 27.6
27.6
5.8
5%. 6
%
56.0
4% .4
%
55.4
2 970. 2
%
58.4
7.9
9.9
10.8
64.8 43.0 56.5 41.8 45.0 49.0
64.9 41.5 53.6 42.5 46.1 49.4
63.0 41.5 54.6 40.9 44.3 48.4
21.4 20.0 42.6 40.6 32.0 31.8 43.6 41.7 39.8 37.2 36.6 34.1
21.4 42.6 32.0 43.6 39.8 36.6
7.1 6.3 3.4 4.0 2.5 2.5 4.5 3.9 3.6 2.9 4.2 4 . 4
5.9 2.9 1.8 3.5 3.2 3.5
7.9 11.5 9.1 10.1 11.6 10.2
9.0 14.4 12.2 12.2 12.6 11.3
9.7 13.0 11.6 13.0 12.7 11.5
57.6
57.0
56.0
28.0
27.2
28.0
5.5 6.0
5.3
8.0
61.2
59.7 57.1
9 . 3 10.7
F.
0,s.
F.
F.R.B.
Cu. f t . per f o n 2500 3020 3130
Gallons p e r ion 13.8 1 0 . 5 13.5 16.9 1 5 . 1 14.2 8.1 9.6 7.0 6.9 5.9 4.3 9.5 9 . 3 8.4 9.9 8.6
2790
13.2
14.4 12.7 17.1 22.6
23.0
22.0
23.0
6.8 7.1
9.4
10.5
2920
3230 2970
16.4
33.7
34.2
33.7
3.2
2.8
3.5
10.6 1 3 . 0 1 2 . 1
2880
3290 3160
7.7
5 4 . 8 53.9 45.2 4 3 . 8 47.8 46.0 50.0 48.3
50.8 43.2 45,s 49.7
2 9 . 6 2 8 . 8 29.6 4 1 . 7 41.8 41.7 38.7 3 9 . 0 3 8 . 7 36.8 33.0 3 6 . 8
5.6 3.0 3.3 1.8
6.1 2.5 2.5 3.0
8.3 3.0 3.4 1.6
9 . 6 10.3 10.6 11.1 10.0 11.8 15.4
11.3 12.1 12.1 11.9
2910 2650 2570 2490
3.730 2870 3090 4960
10.0
1 0 . 1 14.6
11.9
8.4 19.9 7.2 8.2 3.6
3220 5220 3240
1 8 . 0 1 7 . 7 24.0
12.9 8,9 17.3 13.9 16.8 13.8 16.1 12.8 15.2 12.6
2390 4810 2980 5240 3140 5570 3140 5250 2850 5510
2600 3280 3200 3210 2910
9.7 10.3 8.6 8.3 8.2
4.4
8.0
12.1
17.8 12.7
2930
8.7 7.7
10.7
18.2
18.1 18.2
7 . 5 7.4
57.2 42.9 46.3 42.8 45.0
59.8 42.0 48.2 45.1 47.5
26.0 37.6 33.3 37.2 35.2
26.5 36.2 33.2 38.1 36.1
26.0 37.6 33.3 37.2 35.2
4.0 4.3 3.6 3.5 3.4
3.5 3.3 3.2 2.5 2.9
49.4
44.6
45.2
34.1
3 3 . 0 34.1
5.0
62.8
57.4
58.7
17.6
1 7 . 8 17.6
58.4
5 3 . 5 54.2
26.4
25.2
5.7
16.4 1 6 . 6 16.4 3 1 . 5 30.9 3 1 . 5
6.7
13.4 14.6 7.2 5.9 8.0 6.0 4.6 7.2
7.8 11.6 11.8 11.5 10.6
59.5 59.r
62.3 46.3 51.1 47.6 50.2
61.2 51.0
3000 2640 2890 2710
5.3 6.5 4.7 4.9 4.7
63.3
67.2 62.0 53.6 50.9
7 8.7 4
2730
50.7
26.4
160..97
2550
5 2 . 3 49.6
9 . 5 10.9
O.S. F.R.B.
8 . 9 17.0
13.0
8.5 7.8 8.8 6.0 6.9
12.7 15.6 11.3 11.8 11.3
5530
3050
12.1
10.5 19.2
3270 5930
3350
20.9
18.5 15.7
3130
13.6
13.0 19.7
5.4
8.2
8.2
16.0 11.2
2700
5780
9 . 1 8.5 4.8 4.5
12.4 5.7
5.7 9.8
12.1 10.0 13.3 11.8
2250 4660 2780 2793 4097 3005
21.7 20.5 29.8 11.4 10.8 13.2
~~
Sum of average convtituents: F. 99.7 ; O.S. 99.9; F.R.B. 100.0 per cent a
b
Fischer ( F J , oil-shale (C Calculated weight from I
,),
and Fuel Research Board (F.R.B.) methods.
; analysis.
T a b l e 111-Variations
in Yields of Products-Differences
between D u p l i c a t e D e t e r m i n a t i o n s
~
DIFFERENCES I N YIELDS OF COKE
No.
~~~
F. R. B.a
%
a
9 10 11 12 13 14 15 16 17
1s
19 20 21 22 23 24
Average Maximum variation 0
DIFFERENCES IN YIELDSOB TARA N D OIL
2.03 1.33 2.66 0.52 1.33 0.54 1.18 1.06 0.31 0.07 0.36 0.13 0.30 1.34 1.91 0.82 0.41 0.52 0.22 0.75 1.43 1.14 1.94 0.14 0.935 2.66
0. S.O
% 2.86 0.26 2.91 0.35 1.42 0.54 1.67 0.77 0.40 0.61 1.94 1.29 0.87 0.34 0.84 0.20 0.49 0.20 1.64 0.93 0.20 0.44 1.00 1.20 0.974 .2.91
F.Q
%
DIFFERENCES IN GAS YIELDS
~
F. R. B.
0. S.
%
%
F.
% 0.11 0.20 0.01 0.06 0.54 0.42 0.14
0.32 0.38 0.21 0.28 0.26 0.23 0.35 0.43 0.52
0 : ii 0.04 0.23 0.03 0.04 0.07 0.37 0.00 0.22 0.16 0.16 0.14 0.52 0.25 0.10 0.02 0.171 0.54
0.Oi 0.10 0.38 0.87 0.00 0.24 0.37 0.28 0.72 0.67 0.36 0.52 0.54 0.44 0.59 0.3&0 0 87
F. R. B.
0. s.
F.
Cu. It. per 100 grams coal
0.1976 0.0199 0.0272 0.0008 0.0233 0.0130 0.0122 0.0189 0.0072 0.0004 0.0094 0.0169 0,0091 0.0467 0.0120 0.0143 0.0110 0.0056 0.0010 0.0217 0.0225 0.0216 0.0107 0.0160 0.02245 0.0467
0.05505 0.1506
0.0036 0.0128 0.0040 0.0140 0.0080 0.0020 0.0580 0.0028 0.0180 0,0068 0.0144 0.0096 0.0040 0.0340 0.0188 0.0088 0.0032 0.0016 0.0024 0.0252 0.0460 0.0020 0.0464 0.0088 0.01480 0,0580
Fischer ( F . ) , oil-shale ( O . S . ) , and Fuel Research Board (F.R.B.) methods
hfETHOD-The coal as received was ground to pass a 10-mesh screen and 250 grams were taken for assay. Duplicate determinations were made simultaneously, two retorts being mounted side by side and heated in as nearly the same manner as possible. After the burners were lighted, the temperature was raised as quickly as possible to a maximum of 550' C., but care was taken to avoid heating so rapidly that an excessive amount of tar in the form of mist passed through the condenser into the activated carbon. Heating to 550" C. required about 1 hour; then the temperature was held constant until the distillation was finished, as shown by cessation of gas evolution. The gas from one retort was collected in a holder for sampling and afterward discharged through a meter; that from the other retort was passed through a meter and wasted. The water in the
Liebig condenser was now replaced by steam, SO that tars which solidified there melted and ran down into the receiver. The receiver containing the total distillate was then disconnected and weighed; xylene was added and the mixture distilled. The distillate was caught in a graduate in which the water separated so that its volume could be read. The volume and weight of tar and oils and of water were calculated from the data so obtained. Results of Comparative Tests
Tables I to IV, inclusive, and Figure 4 show the results of the work. Table I gives the origin and complete analysis of the samples; Table 11, all the assay results; Table 111, the variations between duplicates for the three methods used; and Table IV, the analysis of the gases. Figure 4 shows the
616
INDUSTRIAL AND ENGINEERING CHEMISTRY
F'ol. 20, No. 6
relation between oxygen content of the samples and their yield of tar oils, by the Fischer method. As previously stated, in the case of the oil shale and the Fischer methods the coal is tested on the as-received basis, whereas the Grey and King method calls for drying the sample a t 105" C. I n order to render all results comparable and still adhere to the procedure as published, the results given for the Grey and King method in Table IV have been corrected to the as-received state by calculation. The gross samples from which all samples for test were taken were kept in carbide cans with tightly fitting covers to prevent changes in moisture content. Yield and Quality of Products
The assay yields obtained are characteristic.of coals below the coking rank. Table I indicates that the oxygen content of all these coals is well above 19 per cent, the upper limit usually set for coking coals. None of the samples gave a sintered residue; it was powdery in all cases and small in amount, ranging in round figures from 41 to 67 per cent (Table 11). The yield of tar was low, varying from 3 to 10 per cent or 6 to 20 gallons per ton. Figure 4 shows how this varies directly with the rank of the coal, as indicated by its oxygen content. The yield of gas is about normal, but its quality is poor; this is due to its high content of oxides of carbon, which is to be expected from high-oxygen coals. The averages of analytical results given in Table I1 give an idea of what yields can be expected of coals in this range of rank. To show how these figures compare with assay results from a high-rank coal, it may be said that a good gas coal (35 to 37 per cent volatile matter) will yield about 72 per cent of coke, 34 gallons of tar per ton, and 3000 cubic feet of 900 to 1005 B. t. u. gas. It should be emphasized again that these assay methods tend to give high tar yields as compared with those from industrial processes other than the types involving distillation in inert gases. In other processes cracking usually takes place to a greater extent than in an assay retort. A low oil yield is, of course, not necessarily a process defect; oil may be sacrificed for the production of better coke and more gas. Agreement of Methods
Because of the high moisture content and ease of oxidation of these low-rank coals the comparative assay results obtained constitute rather a severe test of the methods. The agreement is not close. For example, the figures for coke, which should be the easiest constituent to determine, often vary 2 per cent, and inseveral cases as much as 5 per cent. With these individual comparisons (Table 11) the variation shown is due in part to variation between duplicate runs by the same method-that is, only two determinations were made and the results averaged to obtain the figures reported; if more determinations were included in the averages, the comparison between methods would undoubtedly show better agreement. This is indicated on comparing the average results for all coals by the several methods. Averages of constituents in
INDUSTRIAL A N D ENGINEERIXG! CHEMISTRY
June, 1928
617
Board method gives results that agree more closely with the oil-shale method than with the Fischer method. Yields of tar by this method are usually high, owing to experimental error. The small sample of 20 grams yielded only a small amount of tar, which was hard to separate accurately from the watery distillate. Comparative Reliability of Methods
-1
-
Figure 4-Relation
G
~_______
- _
2:
35 40 45 O \ > G E \ ( I S H FPEE PER CE\T)
ZD
20
_, 4,
between Tar Yield a n d Oxygen Content
each case sum up to nearly 100 per cent, except Fischer. off 3 per cent, so there are no consistent errors inherent in the method favoring wrong figures. On an average, the oil-shale method gives somewhat low yields of tar and high yields of gas. The residue and water are also slightly low, but hardly to a significant extent. Evidently this method, as compared with the other two, makes gas a t the expense of tar. This could result from higher retort temperatures and more extensive cracking. It will be recalled that temperature is not measured in this method; control is effected solely by observing the rate of formation of the distillate. The Fischer method gives the largest residue and the lowest gas figures, together with a slightly higher tar yield than the oil-shale method. Cracking was therefore minimized in this method. The Fuel Research
With all empirical methods such as these, careful attention to details of procedure is required to insure that the tests are all carried out in exactly the same manner. Long experience with a given method will render this easy, and an experienced analyst will turn out results of a quality impossible to the beginner. Realizing this, the writers believe that all three methods can give fair results in the hands of their originators or of others with more experience than themselves. Nevertheless, on the basis of their work, the writers believe that the Fischer method is superior to the other two, both for accuracy and facility of manipulation. The oil-shale method was not designed for the assay of coal, and for coal the rate of distillation does not give such satisfactory control as that based on temperature measurement. The iron retort corrodes and is difficult to keep gas-tight. The main difficulty with the Fuel Research Board method is that the sample taken for assay is so small as to render difficult the accurate handling of recovered distillation products. Table I11 gives variations between duplicate determinations for each constituent determined by the several methods, also the maximum variation found in each case. Agreement between duplicates is clearly best by the Fischer method. Between the two other methods there does not seem to be much choice.
Effect of Physical Characteristics of Coke on Reactivity’pz J. D. Davis and D. A. Reynolds PITTSBURGH
E X P B R I M I ~S TXATT I O N ,
u. s. BCREACOF
?rXI.?.ES, P I T T S B U R G H , P A .
Results of reactivity tests of low- and high-temperar e a c t i n g w i t h substances S APPLIED to coke ture cokes in air, steam, and carbon dioxide over temother than oxygen, but such the term “reactivity” perature ranges from 800” to 1100” C. are given. The a distinction hardly seems is rather i n d e f i n i t e . effects on reactivity of bulk density, volatile matter, warranted. “Reactivity” is Every coke user thinks of that adsorptive power, size of test particles, and varying quality in connection with the perhaps the best general term reactivity of particles of the same sample have been use of which he intends to to use; where it is necessary estimated. put the coke. Thus, if he to be more s p e c i f i c , t h e method of test should also wants to make water gas, he thinks of the rate a t which the coke will produce water gas be stated. under practical working conditions. The producer man The character of coal used and the method of coking deis interested in rate of reduction of carbon dioxide. Others termine the physical characteristics of the coke and hence consider ease of ignition, rate of combustion, etc. As a its reactivity. I n measuring the effect of physical properties result, various empirical test methods have been developed one should have a test method for reactivity applicable to as for determining reactivity, each being based on a particular wide a range of uses as possible, that conclusions of general use for the coke. The quantity measured is usually called significance may be drawn. The test method used in this reactivit3, although it is realized that all test methods by paper was selected after comparing various available methods which it is determined do not measure the same thing. The (in modified form when this seemed advisable) for sensiterm “combustibility” is also used. Smith and his collabo- tivity and reproducibility of results. The physical characterr a t o r ~define ~ “combustibility” as the property of com- istics studied were: (1) bulk density, (2) volatile-matter bining with oxygen, and “reactivity” as the property of content, (3) adsorptive power, (4) size of particles, and (5) coke luster. 1 Presented before the Division of Gas and Fuel Chemistry at the 74th
A
Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. 2 Published by permission of the Director, U. S. Bureau of Mines (Not subject to copyright ) 8 Smith, Finlayson, Spiers and Townsend, Gas J . , 1926, Coke No.3-16.
Cokes Used
With the exception of the one made in superheated steam, the cokes used in this investigation were produced on an
