A numerical study on parametric sensitivity of the flow characteristics on pulverized coal gasification

摘要

In order to analyse the sensitivity on pulverized coal flames of variables such as initial turbulent intensity, steam addition, primary/secondary momentum ratio, and radiation heat transfer, a numerical study was conducted at the gasification process. Eulerian approach is used for the gas phase, whereas Lagrangian approach is used for the solid phase. Turbulence is modeled using the standard k- ε model. The turbulent combustion model incorporates the eddy dissipation model. The radiation heat transfer is solved using a Monte-Carlo method. One-step two-reaction model is employed for the devolatilization of a Kideco coal. In pulverized flame of long liftoff height, the initial turbulent intensity is an important factor to predict the accurate flame front position. The radiation heat transfer and wall heat loss ratio distort the temperature distributions along the reactor wall, but do not affect the reactor performance such as coal burnout, residence time and flame front position. The primary/secondary momentum ratio only affects the position of flame front, but the coal burnout is slightly influenced. It is confirmed that the momentum ratio is a variable only associated with the flame stabilization. The addition of steam in the reactor has a detrimental effect on all the aspects, particularly in reactor temperature and coal burnout. The increase of liftoff height and dropped gas temperature mean the harm of flame stabilization in the reactor, and so the gasification reaction may be deactivated.