UTILISING WASTE COAL

Ashburton Guardian, Volume XLVI, Issue 10531, 24 October 1925, Page 7

UTILISING WASTE COAL

INTERESTING EXPERIMENTS. SOME PROMISING! RESULTS. (Per Press Association.) WELLINGTON, October 23. If the vast quantities of slack coal of the Dominion cannot ultimately be turned into profitable use it will not be because a wide field of experiment has not been fully availed of. On the contrary, tests that have been going on for some time at the Dominion Laboratory, at the expense of the Mines Department, are extremely encouraging, and the experiments are being conducted on a large scale. The principal methods that had been suggested were: (1) Dust firing, (2) low temperature carbonisation, and (3) briquetting. As the last-mentioned appeared to be the mast promising of the three methods, it was decided to investigate conditions necessary for its successful application to New Zealand waste coal.

The Mines Department secured an experimental hydraulic press, giving pressures up to 30 tons to the square inch. One of the first series of tests was on Waikato brown, or bituminous, coal, about 40 per cent, of which as mined was rejected as slack and was found practical:/ unsaleable. This was found to be friacie and of a soft nature without a binder. On the other hand, no difficulty was experienced in briquetting lignite from Alexandra, Otago Central. However, in all cases, experiments made with mixtures of other coals had shown definite results. One of the conclusions which the experimenters have como to is that it did not seem possible to briquet the Waikato coals successfully without using a binder, and coal tar pitch was the most suitable of binders examined. Tlie blending of 50 per cent, of Waikato coal with 50 per cent, of bituminous coal would' produce briquets which would bo free from the tendency to spark so characteristic of the AVaikato coal. In regard to the experiments made with bituminous coal alone, the briquets were hard, compact and brittle, whereas briquets made by blending brown coals with bituminous coals were more friable.

The experiments carried out are of a, particularly interesting nature. The waste coal is first put through a sieve before being put into the hydraulic press which consolidates the coal. The small tablet produced is then submitted to all sorts of tests. It is put into a corrugated tank with other tablets and briskly rotated. The manner in which it weathers this pummelling is a pretty good indication as to how it would stand transport. Just how brittle it is or just how friable is noted, and further experiments are made with the addition of "binder," and all grades of coal are tried with different kinds of binders, such as coal tar, pitch, etc! Then the tablet is placed under a miniature pile-driver, which, being of oven weight, falls dead on to the block. The manner in which it stands these hard knocks is also of interest to the experimenter. But there are dozens of other interesting processes used to determine what shall be absolutely the best method of dealing with the waste coals of the Dominion. Mr W. H. Penseler, B.Sc, 8.E., who is carrying out experiments under the direction of the Dominion Analyst, hasi hundreds of samples representing every conceivable "blond" and test, and he is still working away. Every single detail is taken, down carefully and the calorific value of the coal is also made a feature oi by the experimented. A comprehensive report is to be. made to the Minister shortly.