| Popis: |
Since vanadium is a dispersed element characterized by a low Clark parameter (0.15), ores in which its content amounts to tenths of a percent are considered promising as feedstock for its isolation on an industrial scale. In view of the acute shortage of vanadium in the world market, an intense search is being carried out to find non-mineral types of feedstock for vanadium production. In heavy crude oils the vanadium concentration is comparable with its concentration in ores, but during atmospheric and vacuum distillation of crude oil the vanadium content in the residual products (fuel oil and tar) can be increased by factors of 2 and 4 respectively. A possible means of further concentrating "petroleum" vanadium is to burn boiler fuel (fuel oils) and collect the vanadium-rich ash. However, the presence of vanadium in boiler fuel leads to corrosion of the boiler equipment. The problem of catching the volatile vanadium oxides also arises [1]. Furthermore, it is necessary to burn boiler fuel with a high sulphur content, while the vanadium present in fuel oils poisons the catalysts of secondary oil refining processes, in particular hydrodesulphurization processes. Thus problems of the refining of heavy oil residues (OR) and industrial isolation of vanadium are interrelated and should evidently provide for the concentration of vanadium in solid oil residues and their separation from the liquid part of heavy OR. Vanadium was isolated from solid OR using cokes produced in the processes of slow coking, thermocontact cracking, flexicoking, and thermolysis of tar and fuel oil. From the viewpoint of more thorough oil refining, an important parameter characterizing the effectiveness of these processes is the liquid product/coke ratio. Certain indices of the given processes [2-6] are presented below |
