TREATMENT OF COAL

Hawke's Bay Tribune, Volume XXIII, Issue 71, 6 March 1933, Page 5

TREATMENT OF COAL

GREAT SCOTTISH PROJECT PRODUCTION OF OIL. ELECTRIC-POWER ECONOMIES. A revolution in the Scottish coal industry is predicted as the result of a great project which is about to be launched with a capital of £1,000,000 to exploit the low-temperature carbonisation process invented by a Glasgow engineer, Mr Charles Turner. The formation of the company follows 10 years of painstaking experiment by Mr Turner, who has been operating a large-scale experimental plant at Coalburn, Ayrshire, since 1926. One result of the process is claimed to be the perfection of a method of making electricity from coal at a fraction of the cost at which it is now produced in the most up-to-date plants in Britain. In addition it is stated that many byproducts can be obtained at astonishingly low prices, including fuel oil and motor spirit.

Already Mr Turner’s organisation has secured rights of purchase over collieries sufficient to supply a plant designed to treat up to 200,000 tons of bituminous coal daily. When in full operation these pits will give employment to 1200 miners, and it is estimated that 200 men will be required to operate the treatment plant. At latest advices, according to the Glasgow “Weekly Herald,” Mr Turner had expressed his willingness to accept an offer by the Ayrshire Electricity Board to purchase power from his company at 80 per cent, less than the price at present paid by the board. USE OF SUPERHEATED STEAM.

Among a number of processes for the low-temperature carbonisation of coal, Mr Turner’s invention appears to be singular in that heat is applied to coal, not by an external furnace or by the injection of burned gases, but by the use of super-heated low-pressure steam. The Turner retort is a vertical conical vessel made entirely of iron and steel, into which steam is passed uninterruptedly from the bottom. The material in the retort is fed in continuously near the top and rests upon an archimedean screw placed at the base. By this means it is allowed to sink slowly and is gradually discharged after treatment by the slow rotation of the screw on its vertical shaft. At the top of the retort there is an outlet pipe for the steam and gaseous products, the escape of which is governed by a valve operating only so long as a certain pressure is maintained within the retort. This pressure is sufficient to allow the steam to penetrate all the voids in the material, which, by chemical action, attains a higher temperature than the steam itself. On being released through the valve the mixture of steam and hydrocarbon vapours expands and cools. It is then treated for the separation of the various gaseous and liquid hydrocarbons and other products. It is claimed that the process enables an exceedingly high percentage of these to be rccoverd, and there is only a small production of gas. LIGHT AND HEAVY OILS. The residual fuel, or semi-coke, has a calorific value of 13,750 British thermal units to the pound and burns freely without smoke in an ordinary grate. One important advantage is that the sulphur content is less than one-half per cent., making the fuel very suitable for domestic use in cities.

It is estimated that 1000 tons of Ayrshire bituminous coal will produce 600 tons of residual fuel, 20,000 gallons of light oil and 10,000 gallons of heavy oil. With coal at 14s a ton, the cost of treating this quantity is put down at £lOOO and the value of the products at £1375, allowing 25s a ton for the residual fuel and 6d and 3d a gallon for the light and heavy oils respectively. If the plant were erected alongside a power station, low-pressure exhaust steam could bo obtained practically free of cost and a saving of 2s 6d a ton of coal could be effected. For superheating the steam the “fines” from the retorts are used, only the large fuel being sold. CHEAPER ELECTRIC POWER. What makes the process important from the aspect of electric-power production is that the residual fuel is claimed to have greater steam-raising power than its calorific value might indicate. The reason given for this is that it produces little water-vapour and no smoke at all. While raw coal is burned in a furnace the mixture of vapour and smoke tends to form a screen or blanket which hinders the transference of heat by radiation to the boiler plates. According to one authority the new fuel has 25 per cent, more evaporative pow-er than the best Scottish coal, and by its use the present average cost of electricity from British coal-burning plants can be reduced from onc-halpenny to one-fifth of a penny a unit.

M Turner looks forward to the time when smokeless fuel will entirely supersede coal for domestic purposes in Britain. When this comes about the smoke nuisance in cities will almost disappear, together with the huge annual waste and loss caused by the pollution of the air by acids which corrode building stone and ironwork. Unfortunately, conservative British householders are still very unwilling to do without the bright yellow flame of the ordinary coal fire.