A PROBLEM SOLVED.

Star (Christchurch), Volume XLIV, Issue 301, 19 December 1931, Page 9

A PROBLEM SOLVED.

Turning Slack Coal into Briquettes. SUCCESSFUL TESTS. (Special to* the “Star.”) WELLINGTON, December 19. Efforts to utilise the whole product of our coal mines by turning the slack into briquettes have been made over a long period of years, with varying success. The Waikato coal companies, who combined to establish a briquetting .plant, made a definite forward move, but this does not dispose of the problem for other classes of coal. Briquettes have been made in the past which have been quite successful, but the amount .of expensive material needed to bind the coal mixture put the process out of the question in a commercial sense. However, the associated coalowners of the Dominion financially assisted the investigations of the Department of Scientific and Industrial Research, and a point has now been reached with briquetting experiments on bituminous coals which may be regarded as definitely promising success.

The process has passed the laboratory stage, for the preliminary work in the laboratory was sufficiently conclusive to warrant the establishment of a small plant capable of turning out briquettes for commercial use. It is known as a “pilot” plant, about onequarter the size which would be operated in commercial practice, but sufficiently large to give experience of practical value. This plant is at work in the State coal yard in Wellington, and can turn out three tons of briquettes daily. An Object Achieved.

Various coals and mixtures of coals are being used in experiments. The former briquetting plants have failed because the proportion of pitch or bitumen needed to produce a satisfactory briquette for storage and handling was too large. This binding material costs £6 10s per ton, and the aim of the research workers was to produce results with the minimum quantity of bitumen or pitch in the coal mixture. The

“ pilot ” plant has achieved the object in view. If it is necessary—as was the case in past experiments—to use 10 per cent of binder material, this added 13s per ton to the cost of the briquetting material, but the plant now at work has cut the proportion of the expensive material down to 6 per cent, and it is considered possible by studying the degree of screening of the coal, and the mixtures, to further reduce the proportion of binder to 5 per cent, which would mean a cost of 6s 6d per ton in addition to that of the slack coal which can be utilised. If the coal mines of the Dominion are provided with a cheap process of briquetting, a profitable future opens to them, as it will be possible to find a market for the whole run of the coal produced. The great development of oil burning for steamers has considerably reduced the demand for slack coal, and with some mines this is almost a total loss. However, in the briquette form it will be capable of storage without deterioration, and can also be used by the largest coal consumer in the country, the Railway Department, which for locomotive use at present is obliged to restrict orders to screened coal.