FUEL ECONOMY

Dominion, Volume 10, Issue 3188, 12 September 1917, Page 5

FUEL ECONOMY

THE ART OP BRIQTJETTING GOAL. The object of briquetting is to give a commercial yi;!ud to coal products that would not otherwise find a market, but inasmuch as coals differ ,materially -in their composition, some being dry and hard, others 6oft and. earthy lignites, containing much moisture, methods of treatment have to be arranged to meet particular requirements. In the one case briquetting can only be effected by the addition of a binding material, such as pitch, to give the necessary firmness and cohesion. In the other, simple pressure without adhesive material is 'sufficient to make coal fragments adhere, but having a much higher water content, prolonged drying operations are necessary. In neither, case are these operations- many or complicated, but wherever material has to be handled in large masses, the several processes must be arranged to reduce the expenses of manufacture to a minimum. Whatever the nature of the raw material, the process of briquetting is. designed to give a degree o» cohesion to the finished product that shall bo equal to that of good coal, in order to prevent loss by attrition and crumbling;- during transport. The calorific value as. determined by evaporating power must not fall below that of coal. The btiquette must not contain more than 5 per cent, of water, nor be capable of absorbing moisture, and the ash should not exceed 10 per cent. If the briquette is required for domestio heating, in addition, it must not soil the hands, be odourless, easy to ipiute, and make little soot or, smoke. Finally, it must be produced of that weight and form which is best adapted for the purpose for which it is intended, the special circumstances under which, it is to be transported, stored, and fired. Naturally only small coal) and waste are used for briquetting, the particles varying in size from it powder to grains about 10 mm. in length, and smithy or hard ooals aro found best adapted for the purpose. The proportion of fine dust to thajnrger grains is of no greatconsequence, but a uniform distribution of some dust among the ooarser grains is not only of' advantage, but absolutely essential to the formations of dense, strong,, briquettes. Where this dust is present in large quantities the amount of binding material has to be increased, and the cost of this ingredient may make the- manufacture imreiminerative. This binding "agent fixes a limit to the utilisation of the waste material. Briquetting is only possible by the admixture of the'coal with pitch or other binder, and not the least important problem in the progress of the industry is to find the most economical way in which the due cohesion may bo effected. To a gTeat extent the whole possibility of tho industry as a profit-ma Sing concern turns' on the price of pitch. If the price is low, or -if the quantity of pitch can be reduced from 7 per cent, to 6 2-3 per' cent., a slightly less, but a sufficient profit, can be earned, and the business is remunerative in ordinary times. But in any case the margin of profit is narrow, even where the output is much increased and the expenses can be distributed more favourably. Cheaper binders have been tried, but without great success, and in any case all the operations have to be conducted as economically as possible. Labour-saving devices operated by automatic contrivances, have, says "Engineering," to be employed everywhere, waste heat has to to be utilised, and frugality has to be stndied.