A fixed-grid model to track the interface and porosity of a chemically reacting moving char particle

Simulation Study on the Interaction between Chemically Reacting Double Coal Char Particles

Due to the complex atmosphere of the entrained flow gasifier, it is difficult to obtain reactivity properties of coal char particles under high-temperature conditions by experiment. The computational fluid dynamics simulation method is a key way to simulate the reactivity of coal char particles. In this article, the gasification characteristics of double coal char particles under H₂O/O₂/CO₂ atmosphere are studied. The results show that the particle distance (L) has an influence on the reaction with particles. With the gradual increase of L, the temperature first rises and then falls among the double particles due to the migration of the reaction area, and the characteristics of double coal char particles gradually approach that of single coal char particles. The particle size also has an influence on the gasification characteristics of coal char particles. As the particle size varies from 0.1 to 1 mm, the reaction area of particles becomes smaller at high temperature and finally attaches to the surface of the particles. The reaction rate and carbon consumption rate increase with increasing particle size. As the size of double particles is changed, the reaction rate trend of double coal char particles at the same particle distance is basically the same, but the change degree of reaction rate is different. With the increase of the distance between coal char particles, the change of the carbon consumption rate is larger for the small particle size.

Direct Numerical Simulation of Reactive Fluid-Particle Systems Using an Immersed Boundary Method

In this paper, direct numerical simulation (DNS) is performed to study coupled heat and mass-transfer problems in fluid-particle systems. On the particles, an exothermic surface reaction takes place. The heat and mass transport is coupled through the particle temperature, which offers a dynamic boundary condition for the thermal energy equation of the fluid phase. Following the case of the unsteady mass and heat diffusion in a large pool of static fluid, we consider a stationary spherical particle under forced convection. In both cases, the particle temperatures obtained from DNS show excellent agreement with established solutions. After that, we investigate the three-bead reactor, and finally a dense particle array composed of hundreds of particles distributed in a random fashion is studied. The concentration and temperature profiles are compared with a one-dimensional heterogeneous reactor model, and the heterogeneity inside the array is discussed.