Slagging in Entrained-flow Gasifiers

Abstract

Gasification is a flexible technology which is applied in industry for electricity generation, hydrogen production, steam raising and liquid fuels production. Furthermore, it can utilize one or more feedstocks such as coal, biomass, municipal waste and petroleum coke. This versatility, in addition to being adaptable to various emissions control technologies (including carbon capture) renders it an attractive option for years to come. One of the most common gasifier types is the entrained-flow slagging gasifier. The behaviour of inorganic fuel components in these gasifiers is still ill-understood even though it can be the determining factor in their design and operation. A literature review of inorganic matter transformation sub-models for entrained-flow slagging gasifiers is provided. Slag viscosity was identified as a critical property in the sub-models. Slag viscosity models are only applicable to a limited range of slag compositions and conditions, and their performance is not easily assessed. An artificial neural network model was developed to predict slag viscosity over a broad range of temperatures and slag compositions. Furthermore, a toolbox was developed to assist slag viscosity model users in the selection of the best model for given slag compositions and conditions, and to help users determine how well the best model will perform. The slag viscosities of coal, petroleum coke and coal/petroleum coke blends were measured in the temperature range of 1175-1650ºC. Interaction of vanadium-rich slags with various materials was investigated. The results from the first two parts of a three-part research program which involves fuel characterization, testing in a 1 MWth gasifier, and computational fluid dynamics (CFD) modeling for entrained-flow slagging gasification are presented. The end goal is to develop a CFD model which includes inorganic matter transformations. Fuel properties were determined with prioritization based on their application; screening of potential fuels, ensuring proper gasifier operation, gasifier design and/or CFD modeling. Using CanmetENERGY’s 1 MWth gasifier, five gasification tests were completed with the characterized coals. Solid samples from the refractory liners, in-situ gas sampling probe sheaths and impingers, the slag tap, the slag pot, quench discharge water and scrubber water were collected and characterized.