Predicting Emissions from Coal Gasifiers using an Equivalent Reactor Network Approach with Detailed Chemistry

摘要

The concept behind the Equivalent Reactor Network (ERN) approach has been presented. The ERN model can afford the implementation of detailed chemistry in the simulations because it consolidates salient features of the geometry and the flow field into a network of idealized reactors. The connectivity among the reactors in the network is established from information in an existing 3-D CFD solution. The procedures of creating and running an ERN simulation for coal gasification are demonstrated through the application to the MHI 200-TPD gasifier. The MHI 200-TPD gasifier case is also used to validate the accuracy of the ERN model. With proper treatment of coal devolatilization and char oxidation, the ERN model, equipped with detailed chemistry, is a powerful tool to gain insights of gas-phase chemistry activities during coal gasification process. The ERN model has been shown to provide accurate predictions of syngas composition at the gasifier outlet. Furthermore, the ERN model can track the evolution of coal-originated pollutant species such as NH_3 and H_2S throughout the gasifier. The capability of identifying and quantifying pollutant emissions from the gasifier should greatly benefit the planning and design of after-treatment systems for the gasifier. In the CFD-ERN model setup employed in this study, the ERN model acts as a complementary chemistry processor to provide detailed information about species and reactions inside the coal gasifier. However, the ERN model is more than just a chemistry post-processor for the CFD simulations. Once an ERN is created from the CFD solution, the same reactor network can be used to explore sensitivities of chemical processes involved in the coal devolatilization to variations in inlet and operating conditions.