Design and Test Furnace Sorbent Injection for SO2 Removal in a Tangentially Fired Boiler

Abstract

The furnace sorbent injection (FSI) process involves injection of dry sorbents into the upper furnace of a coal-fired boiler for reduction of SO2 emissions, forming solid products that are captured in the plant particulate control equipment. Key parameters that impact SO2 removal rates are sorbent reactivity, flue gas temperature at the sorbent injection elevation, and degree of mixing between the sorbent and the flue gas. Several potential impacts on boiler performance, such as increased fouling and increased opacity, need mitigation during design and operation. An FSI demonstration project was recently conducted in a 188 Mega Watt generation (MWg), tangentially fired twin-furnace boiler. An integrated design approach combining computational fluid dynamics modeling, isothermal physical flow modeling, and boiler thermal modeling was applied to (1) understand boiler thermal profiles and flow patterns, (2) specify the optimum sorbent injection design, and (3) predict SO2 removal rates. Field measurements and performance indicators during the test after the installation of the FSI system revealed that SO2 reduction levels were generally consistent with modeling predictions. At the calcium-to-sulfur molar ratio of 2.5, SO2 reduction ranged from approximately 40% to 55%. The highest SO2 reduction achieved during the long-term trial was 72%, at a Ca/S ratio of 3.8.