116 MODERN G AS WORKS /PRACTICE
120 B.Th.U. gross, and the analysis averages 29 per cent, carbon monoxide, 4 per cent, carbon dioxide and 8 per cent, hydrogen, which gives a waste gas in the shaft contaming 19 per cent, carbon dioxide, 0.5 per cent, oxygen. The waste gas on its way to the shaft imparts some of its heat to the incoming producer gas and also to the secondary air, thereby effecting some heat recovery. The average temperature of the combustion cham-
Fig. 61.—Mond Pkoduceb.
bers is 1,300° C.
In. the construction of producers of this kind it is most advisable to fit a curtain wall in the producer so as to ensure that the gas passing to the retort settings is taken off well below the upper sur-face of the fuel. In this way the steam which. is evolved from the freshly charged coke is prevented from passing out with. the gas before being decom-posed.
THE MOND PRODUCER
The Mond producer is probably too well known to need detailed description ; but it may be recalled that a complets Mond gas installation was erected at the Saltley works of the Birmingham Corporation in 1912, for the purpose of heating a battery of coke-ovens for the carbonization of coal.
A general idea of the producer, complete with apparatus for the recovery of by-products, is shown in Fig. 60, whilst a section of the generator is given in Fig. 61. The producer may be fed with a mixture of coke or breeze and coal slack, and is capable of gasifying about 18 tons of thesefuels per 24 hours. The Birmingham plant consists of five producers. The base of eacli is sealed in water, into which the ash descends, this being periodically removed without interfering with the process of gas-making. The producers can, if desired, be fitted with automatic