Effects of critical viscosity temperature and flux feeding ratio on the slag flow behavior on the wall of a coal gasifier

석탄 가스화시 회분의 임계점도온도 및 플럭스 비율 변화에 따른 벽면 슬래그 거동 특성 분석

In the entrained-flow coal gasifier, coal ash turns into a molten slag most of which deposits onto the wall to form liquid and solid layers. Critical viscosity refers to the viscosity at the interface of the two layers. The slag layers play an important role in protecting the wall from physical/chemical attack from the hot syngas and in continuously discharging the ash to the slag tap at the bottom of the gasifier. For coal with high ash melting point and slag viscosity, CaO-based flux is added to coal to lower the viscosity. This study evaulates the effect of critical viscosity temperature and ash/flux ratio on the slag behavior using numerical modelling in a commercial gasifier. The changes in the slag layer thickness, heat transfer rate, surface temperature and velocity profiles were analyzed to understand the underlying mechanism of slag flow and heat transfer.