Modeling and experiments (in a cold flow model reactor) to study char-wall interaction and segregation phenomena during slagging entrained-flow coal gasification

Aim of this communication is to report on the recent findings by this research group on modeling and experiments, the latter carried out in a cold flow model reactor, to study char-wall interaction and segregation phenomena during slagging entrained-flow coal gasification. This work illustrates how different modeling approaches can be jointly used to understand segregation patterns of char particles. RANS-based simulations of the full-scale geometry with coal particle injection and tracking aimed to obtain the behaviour of the flow field and particle trajectories. Simulations enabled to estimate the effect of swirl and tangential flow on the bulk-to-wall char particle deposition rate. Then, RANS results were adopted in a more detailed model based on the solution of the filtered Navier-Stokes equations, where a turbulence LES approach for the Eulerian gas phase was applied. This enabled the assessment of the char particle deposition rates and the nature of char-slag interaction. This paper also reports on preliminary results of an experimental investigation aimed at the development of a phenomenological model of the fate of coal/ash particles. The study specifically addresses the interaction between the lean-dispersed particle phase and the reactor walls, and the establishment of a particle segregated phase in the near-wall region of the gasifier. A lab-scale cold flow reactor has been designed and set up, where molten wax is air-atomized into a mainstream of air to simulate the fate of char/ash particles in a real hot environment. Characterization of the hydrodynamics of the lean-dispersed phase, of its interaction with the wall, of the build-up of the liquid wall layer has been accomplished with a focus on the 'sticky wall-sticky particle' subregime. The particle deposition rate at the wall and the wax droplets partitioning between the leandispersed phase and the wall liquid layer have been assessed under a range of operating conditions.