Simulation Study of the Formation of Corrosive Gases in Coal Combustion in an Entrained Flow Reactor

Maximilian von Bohnstein,Jochen Ströhle,Bernd Epple,Lorenz Frigge,Coskun Yildiz

doi:10.3390/en13174523

Abstract

Gaseous sulfur species play a major role in high temperature corrosion of pulverized coal fired furnaces. The prediction of sulfur species concentrations by 3D-Computational Fluid Dynamics (CFD) simulation allows the identification of furnace wall regions that are exposed to corrosive gases, so that countermeasures against corrosion can be applied. In the present work, a model for the release of sulfur and chlorine species during coal combustion is presented. The model is based on the mineral matter transformation of sulfur and chlorine bearing minerals under coal combustion conditions. The model is appended to a detailed reaction mechanism for gaseous sulfur and chlorine species and hydrocarbon related reactions, as well as a global three-step mechanism for coal devolatilization, char combustion, and char gasification. Experiments in an entrained flow were carried out to validate the developed model. Three-dimensional numerical simulations of an entrained flow reactor were performed by CFD using the developed model. Calculated concentrations of SO2, H2S, COS, and HCl showed good agreement with the measurements. Hence, the developed model can be regarded as a reliable method for the prediction of corrosive sulfur and chlorine species in coal fired furnaces. Further improvement is needed in the prediction of some minor trace species.

Highlights

Coal is one of the most abundant energy sources and accounts for up to one-third of the world’s primary energy consumption in 2018 [1], and forecasts see only a slight decrease in coal consumption over the twenty years [2]
The reducing conditions prevailing in the air staging area cause the formation of corrosive sulfur species, such as H2 S and COS, which can lead to high-temperature corrosion on the furnace walls [3,4]
To describe the sulfur reactions in detail, elaborate reaction mechanisms are necessary, which are not applicable to be linked to Computational Fluid Dynamics (CFD) Simulations

Summary

Introduction

Coal is one of the most abundant energy sources and accounts for up to one-third of the world’s primary energy consumption in 2018 [1], and forecasts see only a slight decrease in coal consumption over the twenty years [2]. Air staging as a primary measure to reduce NOx emissions is generally applied in furnaces. The reducing conditions prevailing in the air staging area cause the formation of corrosive sulfur species, such as H2 S and COS, which can lead to high-temperature corrosion on the furnace walls [3,4]. Despite their importance, the reaction kinetics causing the formation of these sulfur species are still not fully understood. The computing time of CFD simulations with several million grid cells becomes manageable when reduced reaction mechanisms are used. The mechanism has to be chosen carefully regarding the operation conditions of the investigated facility

Methods

Results

Conclusion