Study On Reaction And Interaction Mechanism Between High-temperature Molten Slag Layer And Deposited Coal Char Particles

Liquid slag discharge technology is adopted in entrained flow gasifier.Slag flow is an important factor to ensure stable operation of the gasifier.In this paper,high temperature molten slag and coal char were chosen as samples.The effect of alkali metal(K)in molten slag on the gasification reaction of coal char particles was studied.The migration and structural evolution of residual carbon in slag layer and its effect mechanism on mineral transformation were investigated.The influence of iron valence state on molten slag rheology was investigated.The main contents are as follows:1.The effect of alkali metal(K)in molten slag on the gasification of coal char particles was studied by visualization technique.K in the slag accelerated the gasification reaction rate of coal char on the slag surface.In the process of coal char gasification,the alkali metal K was found to migrate and accumulate to the interface between particles and slag,and the accumulation amount increased with the increase of carbon conversion rate and K content.It was found that the low temperature zone below the coal char particles was the key to the migration of K,Si,A1 and other elements in the gasification process.Through theoretical analysis,the migration mechanism of K in the char/molten slag interface during the coal char gasification process is revealed.2.The migration and structure evolution of the carbon in the slag layer and its effect on the coal slag transformation were studied and revealed.The results showed that the carbon reacted with the iron bearing material to form metallic iron at the carbon/slag interface.With the increase of slag temperature and residence time,the morphology of metallic iron changed from lamellar to spherical,and the mass ratio of the carbon that consumed by the slag to initial carbon layer and the disorder degree of residual carbon structure both increased.The increase of disordered structure of carbon residue promoted carbon thermal reaction.Carbon migration and carbon thermal reaction promoted mineral transformation and crystallization behavior of slag layer.3.The influence of the valence state of iron(Fe0/Fe3+)on the phase transformation and viscosity temperature characteristics of molten slag was studied and revealed.Fe0 reacted with minerals in high temperature molten slag to form minerals such as hercynite.In addition,the addition of Fe3+promoted the mineral transformation from anorthite to hercynite and diopside in the slag.With the increase of Fe0 addition in slag,the tcv of slag decreased first and then increased,and then continued to decrease.However,the effect of Fe3+ addition on tcv of slag was opposite.Adding a small amount of Fe0 and Fe3+ reduced the melting temperature,but also facilitated slag discharge,so that the gasifier can operate at a more economical operating temperature.