Study on Dry Deashing and Desulfurization of Pulverized Coal via Pulsating Circulating Airflow Technology

In practical coal preparation processes, influenced by mining methods and mechanization levels, the proportion of fine and even ultrafine pulverized coal continues to increase. However, due to the small particle size, significant inter-particle interactions, and the low efficiency of conventional physical separation techniques, the efficient deashing of fine coal remains a significant technical challenge. Consequently, in the face of growing demand for fine coal processing, efficient and mature dry separation technologies are still lacking. To address this issue, a pulsating circulating airflow separation device was designed and developed in this study to deash and desulfurize pulverized coal with a particle size of less than 1 mm. The effects of gas velocity and pulsating airflow frequency on the deashing performance were investigated. Using Design-Expert software (version 13), an optimized formula for deashing efficiency was established, and the optimal operating parameters were evaluated. The separation results demonstrated that under the optimal conditions of fluidization, the number N = 1.2 and pulsating airflow frequency f = 2.375 Hz, the standard deviation of ash segregation (σ_ash) reached 25%, and the ash content in the cleaned coal was reduced from 37.28% to 22.32% in the cleaned sample. Furthermore, the sulfur content decreased significantly from 0.971% in the raw coal to 0.617% in the cleaned coal, indicating effective desulfurization. In addition, the concentrations of other harmful elements in the raw coal were also reduced to varying degrees. These findings demonstrate that the application of pulsating airflow can effectively enhance ash and sulfur removal from pulverized coal particles smaller than 1 mm. This approach offers a novel and promising method for the dry beneficiation of fine coal particles.