'Removing Sulphur From Coal

Press, Volume CX, Issue 32394, 5 September 1970, Page 5

'Removing Sulphur From Coal

WASHINGTON. A new process that prevents coal-flred power plants from emitting toxic sulphur dioxide fumes promises to produce a breakthrough in controlling air pollution. The method calls for removing sulphur from coal inside the furnaces of the electricity-generating plants. Next to motor-vehicles, coal-fired plants are the greatest source of air pollution in the United States, annually releasing millions of tons of sulphur dioxide fumes, which can cause serious respiratory problems and even be fatal. The new process completely prevents the formation of the toxic sulphur dioxide fumes. In other industrialised countries—Japan, the United Kingdom, Western Europe—-coal-burning electric power plants, added to coal-fired heavy industry are the greatest source of air pollution.

The new process is so promising that the United States Government, on the advice of the National Academy of Science, on July 8 announced the award of a contract to a Pittsburgh firm to build a pilot plant to prove the process’s technical and economic feasibility. In the new kind of combuster, coal is pneumatically injected, under high pressure, beneath a blanket of molten iron. The sulphur in the coal, as it is dissolved by the heat, immediately bonds to the iron because of the strong chemi-

cal affinity between the two elements. The sulphur is then removed from the iron by its affinity for the slag of another raw material in the furnace limestone. The limestone-sulphur slag is periodically removed from the furnace. In conventional combusters in such plants, the coal merely is burned in air-fed burners, which allows the formation of gaseous sulphur dioxide and its release into the atmosphere. In the new process the sulphur is .removed by conveyer belt as a solid slag. The slag is treated to recover elemental sulphur of high grade, which is readily marketable. The remaining slag can be sold for use as a road subsurface or as a solid ground fill. Another byproduct is granulated iron, since coal contains iron which dissolves into the molten iron already present. None of the other processes, he said, removes all the sulphur and none promised to do so even after further development. The good news of the new process came only a few months after a gloomy academy report had said much effort must go into removing sulphur from coal because no current technology was adequate or economically attractive. At the same time, the academy noted, demand for electric power will triple in the United States by the year 2000, making the already serious air pollution situation “intolerable.”—U.S.l.S. * 1V