Measurement and simulation of viscosity characteristics of coal ash slag under water vapor condition in coal gasification

The long term and safe operation of entrained gasifiers strongly depends on smooth and steady removal of the ash slag. Management of slag behavior for safe slag-tapping requires the well understanding of slag viscosity temperature behavior and reliable prediction model for the slag viscosity in presence of water vapor. Based on the ratio of acidic to basic oxides (A/B) in coal ash, the viscosity temperature characteristics were studied under Ar with water vapor, and the optimization model for predicting the slag viscosity as a function of T and slag composition, including the constituent H2O was established. When water vapor is present in Ar, the slag viscosities decreased due to the breaking of Si-O-Si bridge bonds for the slags with A/B < 0.8. As A/B >= 0.8, the slag viscosities increased which ascribed to the formation of free hydroxyl. The viscosity prediction model for the fully molten slags and partly crystallized slags was developed under water vapor atmosphere based on the modified viscosity models in Ar. The modified Urbain model has been used to predict the completely molten slag and the remaining liquid phase for partly crystallized slags. The viscosities of heterogeneous slags were predicted by modified Roscoe model. These models can predict well the slag viscosity and Tcv. This work enables the prediction of slag viscosity at high temperature under water vapor condition and will provide a theoretical basis for the operation of entrained flow gasification, especially for the coal water slurry gasification.

Automated summary

This study investigated the viscosity temperature characteristics of slag under water vapor atmosphere and established an optimization model for predicting slag viscosity, which can effectively predict the viscosity and Tcv of the slag.