THE DRY PURIFICATION OF CO AL GAS 613
from H2S) enters the plant by a main (H) and passes into the heat interchangers (G). The last-named vessels are constructed ou the lines of a multitubular boiler, being filled with 3-inch tubes. The hot gas leaving the plant passes through the heat interchangers in the opposite direction to that of the inflowing gas, and in this way gives up a large proportion of its heat to the cold imtreated gas. The gas is further raised in temperature in the heating chambers, and then flows in parallel currents through the tubes containing the catalyser, passing thence to the coHector tube (D) and through the heat interchangers. After midergoing treatment in this manner
7 .... ? .... y_______20
scale of feet SECTIONAL ELEVATION
Fig. 375.—The Cakpentek-Evans Hot Purification Plant.
A Furnace, B Combustion Chamber, C Heating Chamber, D Collector Tube, F Tubes containing Catalyst, G Heat Interchangers, H Gas before treatment, J Gas after treatment, K Coke Hopper, L Coke Handling Plant.
the gas will usually contain about 20 to 30 grains of sulphuretted hydrogen per 100 cubic feet. This is removed by a series of s econdary purification vessels containing oxide of ir on.
A 15 million cubic feet plant consumes approximately 5J tons of coke in the furnaces per day, this being fed into the producer by a hopper (/<) receiving its supply from a telpher (Z). The approximate cost of purifying the gas in this manner is now roughly 0-8tZ. per 1,000 cubic feet. The expenditure is accounted for as follows :—