COAL CARBONISATION.

Waikato Times, Volume 109, Issue 18350, 9 June 1931, Page 3

COAL CARBONISATION.

THE ROTOWARO PLANT. OPENING CEREMONY TO-MORROW The Minister of Railways, Hon. W. A. Veitch, and the Minister of Hon. A. J. Murdooh, will ofllciallv open the coal carbonisation plant at Rotowaro to-morrow. The main product Is a high-grade steaming fuel in the form of briquettes which burn without sparks and practically without smoke. Nearly two years ago four of the Waikato collieries faced with only a small market for their slack owing to the advent of hydro-electric power from Arapuni formed a subsidiary company, Waikato Carbonisation, Limited, with a nominal capital of £IOO,OOO, to undertake the treatment of coal by the German Lurgi process. The latter was selected after exhaustive trials of Waikato coal at plants in South Germany. A site for the plant was selected close to the pit-head of the Rotowaro Mine, and the installation was carried out by German engineers in co-operation with the company’s general manager, Mr W. G. Heptinstall, who has had wide experience of the process in Canada. The production of briquettes was commenced towards the end of May. The Plant. The plant consists of a great array of cauldrons, pipes, tanks and combustion chambers, some in the open and the others in buildings of steel and brick. There are numerous belt conveyors by which coal, carbonised residue and briquettes are _ carried about and other clever mechanical devices used In handling the various materials:' Carbonisation is continuous, and when in full operation the plant is guaranted to deal with 250 tons of slack dally. Rather more than half this weight of residual fuel will be produced. The immediate by-products are a gas akiu to producer-gas and tar. The latter is distilled to divide It Into oil and pitch, which Is used as a binder for the briquettes. The tar distillation plant is not yet In working order, and all the briquettes so far made are bound with imported asphalt pitch. The oil extracted from the tar is estimated to bulk about eight gallons a ton of slack. It is capable of being refined to extract motor spirit and other components, but there Is no immediate intention of doing thi3 at Rotowaro, and the oil w'll be disposed of as it Is, probably for heavy fuel purposes. The slack coal is fed Into large hoppers at the top of the twin carbonisers. In the first stage of the process hot burned gas is forced through, driving off 18 per cent, of moisture contained in the coal. From the driers the coal falls into the carbonlsers, where gas at a higher 'temperature is passed through, separating the gas and tar. Lower still, cool gas is circulated to reduce the temperature of the residue before it reaches the open air. It is then carried to storage hoppers, and so to the briquetting pitch, where it is crushed, mixed with heated and pressed between honeycombed rollers into 3oz. briquettes, which are cooled on wire-mesh belts while being conveyed to the storage bins.