Techno-economic performance of HCl and SO2 removal in waste-to-energy plants by furnace direct sorbent injection

With the impending release of Best Available Techniques (BAT) conclusions on waste incineration, existing European waste-to-energy (WtE) plants will be required to achieve a higher efficiency in the removal of several target pollutants, such as acid gases (above all, HCl and SO2). The direct injection of a sorbent in the furnace as a primary deacidification stage may be a cost-effective option to achieve the required performances. The present study investigated the furnace injection of a specific dolomitic sorbent, with the aim of identifying the techno-economic optimum for the sorbent feed rate considering different scenarios of flue gas composition. A full-scale test run campaign was carried out on two WtE plants and a phenomenological model linking HCl and SO2 conversion to reactant feed rate was developed. The model allowed assessing the cost-effectiveness of dolomitic sorbent furnace injection for WtE plants equipped with either a single or a two-stage acid gas treatment system. The addition of dolomitic sorbent resulted particularly suitable for WtE plants equipped with a single stage treatment coping with a high SO2 concentration in the flue gas, where the injection of dolomitic sorbent can increase the redundancy of flue gas treatment with a reduction of the total operating costs.