The influence of the synergistic effect of airflow and vibration in compound dry separation bed on upgrading of 6–0 mm fine-grained low-grade high-sulfur lignite

Abstract

Coal is the important support to guarantee the national energy security system. China is the largest coal producer and consumer country and the lignite reserves are abundant. In recent years, as the high-quality coal resources decrease and the difficulty in mining increases, low-grade lignite resource has been the important component of China’s energy production and supply. Promoting the clean and efficient utilization of low-grade lignite is an important approach to realize the goal of carbon peak and carbon neutrality. In this paper, compound dry separation bed was used for the desulfurization and ash reduction of fine-grained low-grade high-sulfur lignite. The synergistic effect of airflow and vibration on particle force characteristics was emphatically investigated and the leading action stage under different airflow and vibration conditions was determined. The spatial migration acceleration variation rule and spatial migration trajectory of particles in different areas under the synergistic effect of airflow and vibration were systematically analyzed. Meanwhile, the spatial distribution characteristics of sulfur content of fine-grained low-grade high-sulfur lignite on the compound dry separation bed and the segregation rule of particles on the different areas along the bed transverse direction were explored, and the spatial distribution layer of the materials on the bed area was determined. The experimental results demonstrate that under condition of Γ = 10.14, when the gas velocity U = 0.125 m/s, vibration plays a leading role in the particle migration on the bed surface; when the gas velocity U = 0.148 m/s, vibration plays a leading role and the airflow plays a surrounding role; when the gas velocity U = 0.229 m/s, the synergistic effect of airflow and vibration dominates in the particle migration. The motion trajectories of particles in each cross section are all oval shape. The variation of acceleration amplitude along OX-axis determines the transverse migration trajectory of particles; the variation of acceleration amplitude along OY-axis determines the peak force characteristics of particles; the variation of acceleration amplitude along OZ-axis determines the stratification law of particles. Meanwhile, it is determined that the top layer of area Ⅰ is the low density particle distribution layer; the top layer of area II is the medium–low density particle distribution layer; all of the top, middle and bottom layer in area III are the high density particle distribution layer. The separation and upgrading for fine-grained low-grade high-sulfur lignite were conducted and the results were as follows. The yield of clean coal is 66.56 % and its sulfur content is 0.97 %; the yield of gangue is 33.44 % and its sulfur content is 22.41 %; the probable error Ep is 0.105 g/cm3, which means that the efficient and clean desulfurization and ash reduction for fine-grained low-grade high-sulfur lignite have been realized.