Upgrading of low-grade high-sulfur lignite using differential dynamic field dry cascade cleaning apparatus

Abstract

Coal is an important cornerstone to ensure national energy security under the new situation. China is rich in lignite reserves. In recent years, with the increasing consumption of high-quality coal resources, the development and utilization of low-grade lignite resources has become extremely urgent. Promoting the clean and efficient utilization of low-grade lignite resources is an important way to achieve the goal of carbon emission peak and carbon neutrality. In this paper, the low-grade high-sulfur lignite is desulfurized and ash-reduced by using the differential dynamic field dry cascade separation bed. The temporal and spatial migration and distribution law of material sulfur content in the cascade separation bed are mainly studied, and the dominant period of particle migration is determined. The effects of vibration intensity and airflow velocity on the density uniformity and stability of differential dynamic field cascade separation bed are systematically analyzed. At the same time, the cascade distribution characteristics of low-grade high-sulfur lignite in different transverse areas of the separation bed are explored, and the transverse separation functional area is determined. The experimental results show that when the separation time T = 0–6 s, the particle system is dominated by mixed migration; when T = 0–12 s, the particle system is dominated by mixed-regional layering migration; when T = 0–18 s, the particle system is dominated by stratified migration; when T = 0–24 s, the particle system is dominated by inspective stratification. It is determined that the area of 0–700 mm along the X axis is the transverse separation domain of the materials; the area of 700–1400 mm along the X axis is the transverse transition domain of the materials, and the area of 1400–2000 mm along the X axis is the transverse diffusion domain of the materials. When the operating parameters are in the range of A = 3.1 mm, f = 29 Hz, and v = 0.212–0.314 m/s, the uniformity and stability of the bed density are the best. The low-grade high-sulfur lignite was separated and upgraded by cascade separation bed and the separation result are shown as follows. The sulfur content of clean coal was 0.98%, the ash content was 8.96%; the yield was 67.32%. The sulfur content of gangue was 16.77%, the ash content was 69.59% and the yield was 32.68%. The probable error Ep is 0.1 g/cm3, which means that the high-efficiency desulfurization and ash reduction of low-grade and high-sulfur lignite are realized.