DEM-CFD coupled simulation of limestone calcination and fuel combustion in beam type lime shaft kiln

Abstract

This paper presents the development and simulation analysis of a coupled DEM-CFD model of the gas–solid heat and mass transfer process in an industrial-scale beam lime shaft kiln, which uses Computational Fluid Dynamics (CFD) to simulate the combustion of gaseous fuels and the three-dimensional transport of mass, momentum and energy in the gas, and the Discrete Element Method (DEM) to simulate the movement of limestone particles and calcination reactions in the kiln are simulated using the Discrete Element Method. A beam lime kiln uses five burner beams staggered up and down to provide heat for the decomposition of limestone particles in the kiln, and natural gas is injected as fuel from the burners on the burner beams into the limestone bed of the kiln for combustion, while cooling air enters the kiln from the bottom air cap to cool the calcined products and then enters the calcination zone as secondary air to participate in the combustion. In this paper, a 250 m3 beam lime shaft kiln in normal production is used as the research object to simulate and analyze the data of temperature, gas and solidity field and limestone decomposition rate in the kiln. The simulation results show that the overall limestone calcination temperature in the kiln is low and the temperature distribution is uneven, and the decomposition degree of limestone near the kiln wall is higher than that in the center of the kiln. It's caused by the wall effect, the particle porosity is larger near wall, and combustion gas penetration is therefore enhanced in the vicinity. Meanwhile, the simulation results are in good agreement with the actual measured data, which verifies the reasonableness of the model for application in industrial-grade lime kiln.