Upgrading low-quality oil shale using high-density gas-solid fluidized bed

Abstract

Oil shale is a high-value fuel resource and its global output is gradually increasing with time. Based on the analysis of physical properties of oil shale, a sorting process for high-density dense-phase gas-solid separation using fluidized bed is proposed. During the separation process in a gas-solid separation fluidized bed, a binary mixture of oil shale’s mineral powder and ferrosilicon powder is formed. This paper systematically analyzes the separation characteristics of ferrosilicon powder. Furthermore, the influence of different factors (fluidization number N, and oil shale’s powder grade) on the degree of mixing of particles in the binary mixture and the influence of binary heavy medium ratio on the stability of bed are also studied. The results show that the weight of ferrosilicon is prone to stratification and grading in the fluidized bed due to its own particle size composition. The mixing process of oil shale mineral powder and ferrosilicon powder plays a crucial role in the adjustment of bed density. The density gradually narrows with the increase in the value of fluidization number. For the same fluidization number, the bed density decreases with the increase in the mass fraction of oil shale's mineral powder. The oil shale is separated under optimized operating conditions (particle size of 0.5–0.9 mm, mixing ratio of 10%, and fluidization number of 1.4). The yield of concentrate is 27.18%, while the oil content is 10.76%. Furthermore, the yield of tailings is 77.61%, whereas the oil content is 1.46%. Additionally, the separation precision (possible error) E has the value of 0.113.