A NEW FUEL.
An experiment as carried on by the contractors for the Forth Bridge at their works near South Queensferry, to determine whether crude shale oil can be advantageously employed as a substitute for coal in feeding boiler furnaces, possesses no slight interest; for should the new material fulfil the expectations of its introducers, the method cannot fail to be extensively adopted in the numberless manufacturing arts, where a heating agent combining efficiency and economy with cleanliness, is a desideratum. The general principles of the method adopted and the apparatus employed will be readily understood, when it is borne in mind that the process depends on the perfect combustion of crude shale oil, vapourised in connection with superheated steam and atmospheric air. The apparatus consists mainly of a cylindrical cast-iron retort, around which two pipes are coiled spirally, one externally, the other internally, meeting each other in a burner beneath the retort. Through the external pipe oil is forced by hydraulic pressure; through the internal pipe water is similarly driven.
To start the apparatus, the retort must first be heated, which may be readily effected by a small coal fire. The water valve is then slightly opened, and the water, after traversing the pipe coiled internally around the retort, issues at the burner beneath—a powerful jet of superheated steam. The oil is then similarly admitted through its pipe, namely, that coiled externally around the retort, and vapourised, or nearly so, by the heat, reaches the burner below. Here it is caught by the superheated steam, and hurled against the convex bottom of the retort, the force of the impact breaking up into finely divided vapour any portion of the oil which the heat may not have already converted into gas. In a short time the retort and tubes become red hot, chemical action is set up, and perfect combustion of the steam, the carbon from the oil, and atmospheric air, drawn in by the partial vacuum formed, ensues. The perfect combustion and intense heat generated consumes all the products, and leaves little or no residue requiring removal. The absence of ashes or other refuse necessitating constant attendance and cleaning; and the almost entire exemption from smoke, due to the completeness of combustion, are amongst the advantages claimed by the inventors of the apparatus.
With reference to the economy of the process, it may be added that crude shale oil is almost a waste substance, for that used during the recent experiments was the residue left in the process of obtaining the oil of commerce by distillation from the shale. In appearance the crude shale oil resembles butter, and so viscid is it, that a match, cinder, or even a red-hot poker fails to ignite it. Even in those localities where the cheapness of coal would equalise the cost of the two substances, it is yet claimed for the shale oil, that economy results from the comparatively little labour required in connection with its employment; an immense gain is moreover made in space for storing purposes; whilst a saving is effected by the decreased amount of work expended in keeping the furnace and machinery clean, heat with cleanliness being a marked characteristic of this method.
Other advantages may be briefly enumerated: Reduced bulk and weight as compared with coal, by which a saving correspondingly great is effected in carriage, often a considerable factor in the cost of the latter material. Economy resulting from the instantaneous extinction of the fire, whenever the day’s work is completed; whilst the facility with which the fire can be started, and the readiness with which the apparatus can be attached to furnaces at present consuming coal, are powerful arguments in favour of this new fuel.
It is estimated that if given quantities of crude shale oil and coal be taken, equal to each other as regards heat-giving efficiency, the former will occupy less than one-fifth the bulk of the latter. So great a reduction in space set aside for fuel, would, in our large ocean-going steamers, whose coal forms upwards of one-third of their tonnage, mean an enormous addition to cargo room, and consequently to earning power. ‘Of seventy stokers to handle two hundred tons per day, and put out the ashes, sixty may be left at home. Instead of two thousand tons of dead-weight in coal, the steamer may carry four hundred. In carrying and consuming large quantities of coal, the matter of ballast is a serious consideration. A hydrocarbon liquid, carried in several tanks, would be expelled therefrom to the furnaces by pumping water into the tanks, the ballast remaining nearly the same.’ There can be no question that such fuel is eminently suited to fast-sailing cruisers, which may be required to remain at sea for lengthened periods, without touching at port.
In conclusion, it will readily be perceived from the foregoing brief description of the method of employing crude shale oil as a fuel, how considerable are the advantages therefrom accruing; how important is the attempt—the first it is stated that has been made in Scotland—to utilise a substance hitherto regarded as little beyond a waste product.