The Influence of Particle Size on Sulfur Dust Explosion Properties

Abstract

Despite sulfur’s extensive use in the industry, there is little information in the literature on its key dust explosion properties such as the Minimum Explosible Concentration (MEC) and Minimum Ignition Energy (MIE). This research aimed to fill in the knowledge gaps of sulfur dust MEC and MIE. First, sulfur dust samples were collected from a sulfur production facility in Qatar, characterized, and their MEC was determined using the Modified Hartmann Tube. The results showed that dust samples generated in the process units are capable of causing dust explosions. The influence of the particle size of sulfur dust MEC was investigated using the Modified Hartmann Tube and the 20 L Sphere. The MEC of sulfur was found to increase with increasing particle size in the Modified Hartmann Tube. However, the influence of particle size on sulfur MEC could not be quantified using the 20 L Sphere. This was due to the phenomenon of particle breakage induced by the sphere’s dispersion mechanism. Further experiments confirmed the occurrence of sulfur particle breakage in the 20 L Sphere and showed that it is inversely proportional to dust concentration and proportional to the dust’s original particle size distribution. These experiments highlighted the need for a novel approach for the prediction of sulfur dust MEC and MIE. A model was developed based on the heat and mass transfer occurring when a sulfur particle in a control volume is exposed to a hot planar surface acting as an ignition source. The model describes the heat transfer from the hot surface to the particle and the particle’s fusion and vaporization. Ignition criteria are based on the lower flammability limit (LFL) of sulfur vapor in air and the activation energy of the sulfur vapor-air combustion initiation reaction. The model includes a correlation describing a time to ignition which accounts for necessary dynamic changes like the dust’s exposure time to the hot surface. The model is capable of predicting the influence of the particle diameter on the MEC and MIE of sulfur dust and was validated with experimental data.