An Arrhenius reaction rate based burning model for simulation of dust explosions

Abstract

The handling of combustible dust poses inherent risks, potentially leading to dust explosions whose strength and consequences hinge on various factors. Computational Fluid Dynamics (CFD) simulations of dust explosions can effectively incorporate these factors, contributing to the design of safer processes and equipment. The FLACS DustEx CFD code has demonstrated notable efficacy in simulating explosions in organic dusts such as maize starch, even in substantial structures like a 236-m³ silo. This code, formerly known as DESC, has been utilized by multiple industries for over a decade. The accurate functioning of the DustEx code relies on the combustion properties of the dust, influenced by factors like dust concentration and particle size. These crucial properties are derived from P_max and (dP/dt)_max values obtained through standardized experimental tests conducted in 20-L and 1-m³ environments.

The enhanced combustion modeling in DustEx comprises three key components. First, the burning rate is linked to an Arrhenius reaction rate based on the product temperature. Second, the impact of particle size distribution and dust concentration on the burning rate is considered by making it a function of the total surface area of all particles. Third, a substantial database at Gexcon is leveraged to formulate the burning rate model across a spectrum of dust types, particle sizes, and dust concentrations. These models are fine-tuned through optimization using least square fitting to align with experimental data.

In contrast to previous iterations of DustEx, which necessitated experimental tests for all combinations of dust concentrations and particle size distributions for each dust sample, the new models significantly reduce the need for such extensive testing. This innovation facilitates a more streamlined process, wherein experimental testing of dusts before CFD simulations can be minimized. The efficacy of these new models has been validated through simulations of large-scale explosion experiments, as well as experiments conducted in 20-L and 1 m³ spherical bombs. This comprehensive testing approach ensures the reliability and applicability of the improved combustion model across a range of scenarios and conditions.