Hence, for the basic process, spare converters must be provided, so that there may always be some of them re-lining, either while standing in the same place as when in use, or, as in Holley's arrangement, in a separate repair house, to which these gigantic vessels are removed bodily.
A pair of working converters has made 4958 charges of 10 tons each, or a total of 50,547 tons, in one month, or at an average rate of a charge every seven minutes and twenty-four seconds throughout every working day.
The mould-train now carries its empty moulds to a cooling yard, and, as soon as they are cool enough to be used again, carries them back to the neighbourhood of the converters to receive a new lot of steel.
Indeed, the whole German production of acid Bessemer steel in 1899 was at a rate but slightly greater than that here given for one pair of American converters; and three pairs, if this rate were continued, would make almost exactly as much steel as all the sixty-five active British Bessemer converters, acid and basic together, made in 1899.
Hence the progressive increase which has occurred in the size of converters, until now some of them can treat a 20-ton charge, is not surprising.
The matte is treated either in reverberatory furnaces (English process), in blast furnaces (German process), or in converters (Bessemer process).
Blast furnaces of large size, built of brick, have been constructed for treating the richest and more silicious ores of Rio Tinto, and the Rio Tinto Company has introduced converters at the mine.
The difficulty of effecting this double object in one operation was so great that in subsequent experiments the aim was merely to concentrate the matte to metallic copper in converters of the Bessemer type.
Vessels of several designs are used - some modelled exactly after steel converters, other barrelshaped, but all with side tuyeres elevated about io in.
This is so rapidly consumed that the converters must be cooled and partially relined after 3 to 6 charges, dependent on the iron contents of the matte.
Ganister, a slightly plastic siliceous sand, is similarly used for the lining of Bessemer steel converters; it is found in the neighbourhood of Sheffield.
The other items of cost are labour, the quantity of which depends on the mechanical appliances provided for handling the converter shells and inserting the lining; and the blast, which in barrel-shaped converters is low and in vertical converters is high, and which varies therefore from 3 to is lb to the square inch.