RI 2469 The Desulfurization of Coke by Air

In another paper the writer has described an investigation in which the forms of sulphur in coke were determined and described. Coke was found to contain four characteristic forms of sulphur- namely, ferrous sulphide, sulphates, ad- sorbed free sulphur, and sulphur held in solid solution in the carbon. While the coke is still in the oven, only two forms of sulphur are present namely, the ferrous sulphide and the sulphur in solid solution in the carbon. During the quenching, however, the sulphur of the coke is subjected to considerable oxidation, a portion of the ferrous sulphide being oxidized to free sulphur and sulphates, while the solid solution form remains unchanged. The coke, however, loses no sulphur during this process, since the free sulphur which is formed ie retained by the coke in an adsorbed form. Since this oxidation of the ferrous sulphide took place so easily, an inves- tigation was undertaken to determine whether this property could not be taken ad- vantage of in some industrial process for the desulphurization of coke. Although it is true that such a roasting process would not touch the solid-solution form of sul- phur, still the removal of the ferrous sulphide sulphur would undoubtedly benefit the coke from the standpoint of the metallurgist. This improvement in the coke would result not only from the decrease in total sulphur, but also from the large decrease in the ferrous sulphide, which is responsible for the contamination of the iron in the upper part of the blast-furnace. The de sulphurization of coke by roasting in air it a new idea, but dates back to the earliest days of coke manufacture. In 1871, Philipparts published the results of some work done by him on the de sulphurization of coke by air, as well as a review of the results of earlier investigators. In the se earlier experiments, nothing was known of the forms in which the sulphur existed in the coke, while the temperature measurements were only approximate, so that altogether the results were not very conclusive nor complete. The de sulphurisation figures given by the se early investigators generally showed a low efficiency for the process, but some extraordinary results were claimed by certain inventors. In the light of our new knowledge concerning the coke sulphur, it seemed to be important enough to warrant investigation.