[Illustration: FIG. 44.—Taylor Gas-producing Plant.]
The gaseous mixture, consisting of hydrogen, carbon monoxide, etc., produced in the generator has a heat of combustion of from 1400 to 1500 calories. The relative heating power compared with coal gas is therefore two-sevenths. A motor consuming 700 litres of coal gas would require 2500 litres of the poor gas produced by this system to develop the same power, and 550 grammes of anthracite would be consumed in the process.
The cost per horse-power hour varies according to the price of materials. Supposing we have an eight horse-power motor consuming 25 cubic feet of coal gas per horse-power hour, at 2_s._ 6_d._ per 1000 cubic feet, and working for 10 hours, the cost per day would be
8 × 25 × 30 × 10_d._ ———————————————————— = 5_s._ or ¾_d._ 1000
If, on the other hand, it were supplied with poor gas generated from anthracite costing 25_s._ a ton, it would burn about 1¼ lbs. per horse-power hour, costing 16_d._, which is about one-fifth the cost, and using cheap coal this cost can be still further reduced. These figures clearly show how much cheaper it is to burn poor gases than coal gas.
_Bénier gasogene._—Since the 1889 Exhibition, where a Simplex engine was to be seen working with poor gas generated on the Dowson system, engineers and others have fully recognized the advantages of this cheap motive power. In the last few years a very large number of these plants have been erected, and the experience gained by practice has shown, that in spite of the extreme cheapness there are serious faults to be found with this class of apparatus.
The gases are produced under pressure and are of an exceedingly poisonous nature, carbon monoxide being the same gas which is principally evolved from burning charcoal. Great care has therefore to be taken that there are no leaks, which might have fatal results if inhaled by the persons attending to the plant. The chemical operation of the production of the gas is a very delicate one, and requires skilled attendants if constancy in the quality of the gas is required. The Bénier gasogene has been designed to eradicate or circumvent these grave drawbacks. It presents many novel features, the most interesting of which is the device for absolutely ensuring no leaks. This is done by generating the gas below the pressure of the atmosphere. This low pressure is maintained throughout the plant right up to the valve which admits the explosive mixture to the motor cylinder. The only places in which the pressure is raised are surrounded by vacuum jackets leading to the gas reservoir. The gas-producing plant can therefore be installed anywhere, even in dwelling-houses or cellars, without running any risk of poisoning the inmates.