Multi-Pollutant Formation and Control in Pressurized Oxy-Combustion: SOx, NOx, Particulate Matter, and Mercury

Abstract

Oxy-combustion is a promising carbon-capture technology, but atmospheric-pressure oxy-combustion has a relatively low net efficiency, limiting its application in power plants. In pressurized oxy-combustion (POC), the boiler, air separation unit, flue gas recirculation unit, and CO₂ purification and compression unit are all operated at elevated pressure; this makes the process more efficient, with many advantages over atmospheric pressure, such as low NO_x emissions, a smaller boiler size, and more. POC is also more promising for industrial application and has attracted widespread research interest in recent years. It can produce high-pressure CO₂ with a purity of approximately 95%, which can be used directly for enhanced oil recovery or geo-sequestration. However, the pollutant emissions must meet the standards for carbon capture, storage, and utilization. Because of the high oxygen and moisture concentrations in POC, the formation of acids via the oxidation and solution of SO_x and NO_x can be increased, causing the corrosion of pipelines and equipment. Furthermore, particulate matter (PM) and mercury emissions can harm the environment and human health. The main distinction between pressurized and atmospheric-pressure oxy-combustion is the former’s elevated pressure; thus, the effect of this pressure on the pollutants emitted from POC—including SO_x, NO_x, PM, and mercury—must be understood, and effective control methodologies must be incorporated to control the formation of these pollutants. This paper reviews recent advances in research on SO_x, NO_x, PM, and mercury formation and control in POC systems that can aid in pollutant control in such systems.