Further, the supply of air and steam should be regularly distributed, so that the velocity of the gases through the fuel shall be as nearly as possible regular across its whole area.
In some cases the by-products of a producer, such as ammonia, tar, etc., have a commercial value, and if a large amount of gas is generated it will sometimes pay to select a fuel that is rich in these particular substances.
(16) Coal.
Coal which is the basis of producer gas, is composed generally speaking of the combustible matter, moisture, ash and sulphur. The combustible element may be subdivided into the HYDROCARBONS, OR VOLATILES, and the solid fixed carbon. The exact composition of coal is generally given by what is known as PROXIMATE analysis, which analysis divides the constituents of the coal into five groups, viz.: MOISTURE, VOLATILES, FIXED CARBON, ASH, and SULPHUR. Ultimate analysis resolves the coal into its ultimate chemical elements, such as hydrogen, carbon, nitrogen, sulphur, etc., and being a difficult and tedious process it is not much used.
The proximate analysis gives all the necessary information and takes less time to perform.
| VALUES OF COAL | ||||||
|---|---|---|---|---|---|---|
| Location of Mine | PROXIMATE ANALYSIS | Calorific Value in B.T.U. per Lb. of Coal | ||||
| Moisture | Volatile Matter | Fixed Carbon | Ash | Sulphur | ||
| ANTHRACITE | ||||||
| Northern Pa. | 3.39 | 4.41 | 83.30 | 8.17 | .73 | 13,200 |
| Eastern Pa. | 3.70 | 3.07 | 86.42 | 6.18 | .63 | 13,440 |
| Western Pa. | 3.12 | 3.76 | 81.60 | 10.61 | .53 | 12,875 |
| SEMI-ANTHRACITE | 1.25 | 8.15 | 83.30 | 6.27 | 1.63 | 13,900 |
| SEMI-BITUMINOUS | ||||||
| Pennsylvania | .80 | 15.60 | 77.40 | 5.35 | .85 | 14,900 |
| Pennsylvania | 1.55 | 16.45 | 71.50 | 8.63 | 1.87 | 14,200 |
| Pocahontas Va. | 1.00 | 21.00 | 24.40 | 3.02 | .58 | 15,100 |
| West Virginia | .90 | 17.83 | 77.70 | 3.30 | .27 | 15,230 |
| BITUMINOUS | ||||||
| Youghiogheny Pa. | 1.00 | 36.50 | 59.00 | 2.59 | .86 | 14,400 |
| Sample No. 2 | 1.20 | 30.18 | 59.00 | 8.84 | .78 | 14,400 |
| Hocking Valley | 6.5 | 35.06 | 48.80 | 8.05 | 1.59 | 12,100 |
| Kentucky | 4.00 | 34.00 | 54.70 | 7.00 | .03 | 12,800 |
| Indiana | 8.00 | 30.20 | 54.20 | 7.60 | 12,500 | |
| Illinois | 10.50 | 36.15 | 37.00 | 12.90 | 3.45 | 10,500 |
| Colorado | 6.00 | 38.01 | 47.90 | 8.09 | 12,200 | |
| LIGNITE | 9.00 | 42.26 | 44.30 | 3.27 | 1.18 | 11,000 |
The CALORIFIC VALUE of a fuel may be calculated from its analysis, or may be determined by means of the CALORIMETER from a sample of the coal; the latter method is the most reliable. Table gives approximately the calorific values, and the proximate analysis of several representative coals from various sections of the country. The values given in the table are not exact, as the coal from each locality varies considerably in quality, but the figures will indicate what may be expected from each type of coal.
Connellsville, Pa., Coke has a calorific value of approximately 13,000 B.T.U.’s per pound, contains no volatile matter, and has an approximate content of 10% ash. Coke is a valuable fuel for the gas producer, but is rather expensive. It is clean and the absence of volatile matter reduces the “scrubbing” problem to a minimum.
Small coal such as buckwheat and pea contain a much higher percentage of moisture than given in the table, running from 5% to 10% higher than the given values.
Bituminous coal is high in hydrocarbons or volatiles which condense easily and form tar. If the tar is not removed or converted into a permanent gas, it will clog the passages of the producer and the engine and cause trouble.