Characteristics of kukersite oil shale, some regularities and features of its retorting

Over the seventy years of commercial scale retorting of Baltic oil shale (kukersite) considerable studies have been carried out on its physical, chemical and technological properties. The results of these studies combined with operational experience have greatly contributed to further perfection of oil shale retorts now in operation in Estonia and in Leningrad district. However, no generalized evaluation of these data and experience has been published so far. It will therefore be of interest for further development of new retorts to discuss here some technological properties of kukersite characterizing it as raw material for thermal processing. As for the essential effect of specific air consumption upon the process on retorting lump shale one has to bear in mind that contrary to other oil shales it is fairly difficult to obtain high oil yields from kukersite. It may be explained by the fact that on thermal processing of kukersite, unlike the oil shales of other deposits, it elevated moisture percentage and the predominance of calcium carbonate in it mineral part result in high values of specific heat consumption in the process. That is why on thermal processing of kukersite the specific consumption of air must be kept at a high level which, however, decreases the oil yield. Therefore the reduction of specific heat consumption and, consequently, specific consumption of air in order to decrease the concentration of oxygen in the reaction zone has become one of the most actual problems in utilizing kukersite. The Oil Shale Research Institute and the Oil Shale Processing Association have developed a new retort design with a circular semi coking chamber to improve the distribution of heat carrier across the shale bed. It has already been demonstrated in practice that in these units, as compared with the retorts presently in operation, the distribution of heat carrier across the shale bed has indeed improved resulting in a decrease of the temperature of oil vapours at the gas off take from 200-250 deg C to 140-160 deg C and a decrease of specific air consumption from 340-360 to 240-260 m3/t. tab., 10 refs