Mitigation of ash deposition problem during co-combustion of coal and refuse-derived fuel using aluminium-rich anti-slagging additives

Processing MSW into refuse-derived fuel (RDF), which has a high heating value, can substitute for coal in power plants, but the high content of alkali and chlorine in RDF easily exacerbates ash deposition problems for boiler pipes during co-combustion. In order to alleviate these problems, the co-combustion experiment of coal with a dosage of 20 wt% of two typical RDFs (biodegradable-rich RDF and blended RDF) at 1250 °C was studied in a laboratory-scale furnace. The effectiveness of two kinds of aluminum-rich anti-slagging additives (aluminosilicate (Al-Si) and aluminum-sulfate (Al-S) based) for ash deposition was comprehensively evaluated at doses of 0.1 and 1.0 wt%. The results showed that severe fouling occurred at the co-combustion ratio of 20 wt% RDFs. The dosage of 1.0 wt% Al-Si-based additive effectively reduced the formation of sticky particles and low melting point minerals, and the deposits on the probe surface were more easily removed. The anorthite mineral in the biodegradable-rich RDF phase transforms to anhydrite and was not present when Al-Si-based additives were added. These findings are essential for clarifying the fact that the Al-Si-based additive with a low adding ratio can potentially mitigate ash deposition problems in coal-fired boilers.