Modern Gasworks Practice

734 MODERN GASWORKS PRACTICE that the pores of the concrete are closed and a resistant skin fonned. The details of construction of a reinforced concrete tank suitable for oil storage are shown in Fig. 452. MATERIALS REQUIRED FOR MANUFACTURE With. different installations and in different localities a good deal of variation is found in the quantity of materials used in the manufacture of water gas. The coke consumed varies largely in accordance with its quality and physical condition, and whether or not it is carried (by telpher or other means) direct to the generators in an incandescent state or is charged cold. The type of plant, ratio of “ run ” to “ blow,” etc., also have their effect. Oil, of course, may be varied in quantity at will, and merely depends upon the quality of gas it is desired to produce. Steam, again, is dependent largely upon the steps which are taken to ensure as thorough decomposi-tion as possible. That is to say, the consumption will be reduced in those cases where the steam flow is gradually curtailed during the “run” in accordance with. the temperature of the fuel-bed.1 Tn general, the following figures may be taken as conforming with average practice :■— Coke (generator only) Oil (for 18 candle-power gas) „ (for 10 „ „ ) Steam (if flow is constant) „ (if flow is controlled) . Air (for “ blow ”) . Fuel for steam raising . 35 to 45 1b. per 1,000 cubic feet of gas. 2J to 2| gallons „ „ „ I| to If „ „ „ „ 32 to 35 1b. „ „ „ 28 to 32 1b. 2,000 to 2,500 cu. ft. „ „ „ 12 to 17 1b. A figure of 35 1b. for coke consumption is probably the most favourable obtained with plants of the Lowe type, but some reduction on this may be expected in those ■cases where the pan coke is extracted from the generator refuse and deducted from the total weight of coke shot into the generator. Plants designed essentially for the production of “blue gas are generally able to economize in the direction of fuel, and figures so low as 25 1b. of coke per 1,000 cubic feet have been claimed. As an average, ho wovor, the quantity will vary between 32 and 361b. These figures as in the case of those given for carburetting plants, are exclusive of the fuel required in the Boilers for steam raising. The steam-raising plant will, with the mixture of breeze and coke usually employed on gasworks, require an additional 12 to 171b. of fuel per 1,000 cubic feet of gas made. The cost of manufacture of water gas must depend largely upon the current market valnes of the raw products, coke and oil, the latter accounting for from 50 to 65 per cent, of the whole. Fot this reason it will be seen that the manufacture of blue gas is a very much. less costly undertaking than is the case with a carbur-etted gas. In general, the following statement shows how matters stood prior to 1914:— 1 See page 717.