SLACK COAL

Hokitika Guardian, 8 April 1933, Page 6

SLACK COAL

POSSIBILITIES OF BRIQUETTES

RESEARCH REPORT ISSUED

CHRISTCHURCH, April 4

In it report issued by the Mew Zealand Department. ol' Scientific and .Industrial Research on the briquetting of Mew Zealand coals, the conclusion is advanced that-briquettes of Reef ton slack coal, or of blends of Reefton slack and coking bituminous coal, can be produced in Christchurch in competition withs crcened coal, allowing a fair margin ef profit. The report is the outcome of research at the Dominion’s Laboratory, Wellington, undertaken. as an extension of the investigation of the briquetting of Mew Zealand coals which was started in 1925.

The report states that in the mining of coal, a portion of the production consists unavoidably of small coal often did not find a ready market, and its utilisation had long been a problem of considerable magnitude t 0 mining undertakings. Small coal could readily be applied to the generation of steam, and with the development of pulverised fuel low temperature carbonisation, and hydrogenation had been provided. Briquetting provided another means of converting small coal into a product equal, nnd, in some cases superior, . to : lump .coal. By blending coals, tiie-' hur.rJi;ng. quality and other properties of briquettes could be varied, within limits. From this point of view the manufacture of briquettes might help to meet competition from other fuels, the chief advantage. of which lay in their ease of application, cleanliness, and uniformity of quality.

THE PROCESS

Briefly put, the process of briquot- ! ting consisted of mixing the ground coal with some agglomerating agent or hinder, and . moulding under pressure into blocks of various shapes and sizes. It was not till the introduction of coal-tar pitch as a binding material, about TOO years ago,, that briquetting began to assume industrial importance. The application of briquetting to Mew Zealand coal was not a new. idea. .About 20 years ago a plant was erected at Wesport, but the cost of manufacture was too high, Pud the factory had to close down. At present the briquetting of carbonised Waikato coal was being carried out at the works at the Waikato Carbonisation Ltd.,, Rotowaro. When in full operation the plan was capable of a daily output of about 150 tons of briquettes.

CHOOSING A BINDER

One of the most important factors in briquetting manufacture was the choice of a suitable binder, from the points of view of both cost and effi--cicney.- ..In the development, of . briquetting. binding materials used had included' clay, cements, water, glass, WnaUtaiy pitch, petroleum pitch, bitumen or asphalt, sulphite liquor from the paper pulp industry, molasses, flour, and other starchy substances, casein, and pulp binders. In practice, the portion of hinder might run from 5 to 10 per, cent, or more. In the Mow Zealand investigations, work was confined chiefly tp bituminous slack and blends of ; brown—sub-bituminous—coal, with a proportion oS bituminous coking coal. The coals used were Paparoa, Dennis-t-on, and Millerton, Liverpool, James, Reefton, and blends of coking coals with Waikato and Reefton. Coal-tar pitch and bitumen hinders were mainly used, as these were readily available and gave promise of satisfactory result's.