Conference Dates

May 1-5, 2011


Oxy-fuel circulating fluidized bed combustion (CFBC) can use calcium based sorbents, primarily limestone, for the in-situ capture of much of the sulfur dioxide in the fuel. Under oxy-fuel CFBC conditions, the CO2 content is usually high, and at high combustor temperatures sulfur capture can occur in two steps, calcination and then sulfation. The typical Ca utilization ratio in oxy-fuel CFBCs is less than half. When temperature is below the calcination temperature while remaining exposed to a high CO2 environment, recarbonation of unused CaO may occur. This reaction between calcium oxide and carbon dioxide has the potential to create serious operational problems and boiler maintenance issues. The main purposes of this study were to design a test method to study recarbonation of limestone under oxy-firing fluidized bed conditions using a test reactor and to carry out test runs using this method. The test runs were carried out in a test reactor at Metso Power Research and Development Center in Tampere, Finland.