762
MODERN GASWORKS PRACTICE
Thermal Efficiency of (Single-sta Heat Sufplied. B.Th.U. 1 ton of coal = 30,000,000 Fuel for steam used for gasmak- ing, fan, etc., at 12,100 B.Th.U. per Ib. 600 Ib = 7,260,000 COMPLETE GaSIFICATION ge process.) Heat Recovebed. B. Th.TJ. 57,400 c. ft. gas at 374 B.Th.U. per c. ft =21,467,600 132 Ib. tar at 15,500 B.Th.U. per Ib = 2,046,000 10 Ib. free sulphur at 4,100 B.Th.U. per Ib = 41,000
Total recovered .... 23,554,600 Heat used and lost .... 13,705,400
Total 37,260,000 Total 37,260,000
23 5 Thermal efficiency of process = 54,600 nrir> „„ o , ’ x 100 == 63-2 per cent. 60,000
Thermal effi.cien.cy of gas production. = 35 x 100 = 60-1 ?er cent
If the fuel employed for generating steam is neglected (an error too common in the calculation of thermal efficiency) tlien the result will be as given below. This figure, in. faet, represents the thermal efficiency which would result if it were possible to derive from the process sufficient heat for carbonization as well as for steam raising.
Thermal efficiency of gas production. =
21>467>000_________X 100 = 77 per cent.
21,467,000 + 6,445,400
50«. per ton.
45s. jj
15.s. „ „
7|rf. „ gallon.
8d.
£ s. d.
2 10 0 £ s. d.
= 1 2 6\
= 0 0 9
= 0 6 10 -1 13 0
= 0 2 2
= 0 0 97
0 17 0
= 3-01<Z. per therm.
COMPARISON OF COST
From a financial standpoint a comparison between the various gasmakmg processes dealt with above must esséntially be influenced by th.e prevailing valnes, of raw materials and by-products. In the following statements the prices of various materiale have been. considered as follows:—
Coal ....•■•• Coke ....•■■• Breeze
Tar . ...
Liquor ....■■■■
(a) Straight Coal Gas (horizontal retorts)—
1 ton coal ....■•••
Less 10 cwt. coke .....
1 cwt. breeze .....
11 gal. tar
32 gal. liquor . . • , - •
Sulphur and carbon ....
1 ton coal (net cost) . . . . •
yielding 6,760,000 B.Th.U. in gas.
Cost of gas .