Alkali removal from hot flue gas by solid sorbents in pressurized pulverized coal combustion

The limitation of fossil fuel resources and the necessity for reducing CO2 emission requires an increase in the efficiency of power plants by using combined cycle power systems. Pressurized Pulverized Coal Combustion (PPCC) is a potential concept to realize these objectives. The direct use of hot flue gas for driving a gas turbine requires a hot gas cleanup to achieve corrosion prevention of the turbine blading. One of the main problems is the alkali release during the coal combustion process. This investigation was conducted to find a sorbent material for alkali removal at 1400 °C under PPCC conditions sufficient to fulfill the demands of the gas turbine manufacturers. Using a flow channel reactor, an alkali chloride laden gas stream was passed through a bed of aluminosilicate sorbents. Qualitative and quantitative analysis of the hot gas downstream the sorbent bed was carried out using high pressure mass spectrometry (HPMS). The risk of hot corrosion using the found sorbent materials was estimated by thermodynamic calculations. The mechanism of the sorption process has been investigated.