In this paper, three detection methods were analyzed to determine the chlorine precipitation from the flue gas: Silver nitrate volumetric analysis (SNVA), Volhard method (VM) and Mercuric thiocyanate spectrophotometric method (MTSM). Results indicated that SNVA and VM were simple and convenient, but unsuitable for the detection of blend fuel due to the high lower limit. MTSM was suitable for biomass and coal co-combustion for its low lower limit and high sensitivity. In addition, MTSM needed less sample solution, which made it more suitable for multiple measurements to reduce errors, and the maximum proportional error was only 3.5%.

The ash characteristics is closely related to the fuel compositions, and chemical reactions happened between the compounds of ash during co-combustion of biomass and coal. Through the phase compositions analysis of ash from co-combustion of biomass and coal, the results show that KCl(g)mainly reacts with aluminosilicates to form potassium-aluminosilicates and part of KCl(g)also can be sulfated by SO2during co-combustion. In the fuel, CaO and MgO may react with aluminosilicates to form CaAl2Si2O8and Mg3Al2Si3O12with low melting temperature, which can reduce the content of potassium-aluminosilicates and drop the ash melting point temperature.