Experimental study on the impact of airflow velocity and pipeline diameter on dust explosions in vessel-pipeline pneumatic conveying

To ensure the process safety of powder particles during pneumatic transport, a dust explosion experimental apparatus was designed to simulate the dust transport process. The system is supplied with a stable airflow by a high-pressure fan, capable of continuously transferring dust from the vessel to the pipeline at a controllable speed. Dust explosion experiments were meticulously executed by applying 1 kJ of ignition energy to the transported dust particles at airflow velocities of 5, 10, and 15 m/s. This study examines the effects of dust concentration, airflow velocity, and pipe diameter on explosion characteristics and delves into the mechanisms these effects through a detailed analysis of experimental results. The results demonstrate that the starch explosion flame progresses through four distinct stages within the vessel: flame development, flame stretching towards the pipe, intense combustion of starch particles, and complete combustion of the particles. As airflow velocity and pipe diameter increase, the stretching effect on the flame becomes more pronounced. At an airflow velocity of 15 m/s within a pipeline, a balance is struck between intensified particle combustion rates and unconstrained discharge, resulting in a maximum explosion pressure of 135.56 kPa for a 100 mm diameter pipe, with a maximum pressure rise rate of 7.27 MPa/s. Additionally, flame propagation velocity is higher at the pipe inlet. Different flame behaviors were observed inside the pipeline under varying airflow speeds. Compared to previous studies that utilized high-pressure gas to create dust clouds within vessels for explosion experiments, the results of this study underscore the crucial impact of airflow velocity on dust explosions. This research provides critical parameters for explosion prevention and presents a case study on the safety of dust handling processes.