Influence of the particle distribution on dust explosions in the 20 L sphere

TL;DR

This study investigates how the distribution of particles within a 20 L sphere affects dust explosion safety characteristics, revealing that near-wall particle concentration significantly influences explosion pressure and rate of pressure rise.

Contribution

The paper introduces a novel radial homogeneity parameter Phi to quantify near-wall particle concentration and demonstrates its impact on explosion safety parameters through simulation and benchmarking.

Findings

Higher near-wall particle concentration increases explosion pressure and pressure rise rate.

Moderate near-wall concentration can reduce explosion intensity below that of uniform distribution.

Simulation results align with experimental data, validating the model.

Abstract

It is essential to standardize the safety characteristics of dust explosions to mitigate their impact on the process industries. The 20 L sphere primarily investigates the safety characteristics, namely explosion pressure (P_ex) and the rate of pressure rise ((dP/dt)_ex), of dust explosions at the laboratory level. Ensuring uniform dust distribution inside the sphere is essential for accurate data acquisition and standardization. However, whirls created by the incoming flow through the nozzle yield particles to concentrate near the wall before ignition. This study simulated the explosion inside a 20 L sphere to investigate the impact of near-wall particle concentration on the safety characteristics. The OpenFOAM model based on the Euler-Lagrangian approach was benchmarked against experimental data of lycopodium dust explosions. A novel radial homogeneity parameter Phi (0 <= Phi <= 1) quantifies the near-wall particle concentration. The parameter Phi is calculated using a power law based on the radial component of particle coordinates, where Phi = 1 indicates a uniform distribution, and Phi = 0 represents all particles concentrating on the wall. Different particle distributions (Phi = 0.1, 0.2, ..., 1) are initiated before ignition. As Phi decreases from 1, P_ex and (dP/dt)_ex first decrease, but beyond a certain point, both parameters increase. At Phi = 0.1, both P_ex and (dP/dt)_ex reach their highest values, which are 1.75% and 10.1% higher than the uniform distribution, respectively. The lowest values arise at Phi = 0.7, with reductions of 0.25% and 5.6% compared to the uniform distribution. Thus, high near-wall concentrations enhance explosion intensity, while moderate concentrations result in lower intensity than the uniform distribution.