Environmental impacts of cement kiln co-incineration sewage sludge biodried products in a scale-up trial.

[Display omitted] • Co-incineration biodried products in cement kilns were researched. • Combustion performance of biodried products was better than that of sewage sludge. • Heat efficiency of biodried products during co-incineration was 93.7%. • Co-incineration leads to increased SO 2 and NO X emission concentrations. • Biodried product as fuels have greater potential to reduce carbon emissions. The biodrying technology as a pretreatment technology can overcome the limitations of cement kilns co-incineration sewage sludge (SS) on energy consumption. But the impact of SS biodried products on cement kilns and the route carbon reduction potential of biodrying + cement kilns have not been studied. In this study, SS biodrying and cement kiln co-incineration biodried product trials were conducted to highlight the matrix combustion characteristics, and the impact of biodried products on cement kilns (clinker capacity, coal consumption, and pollutant discharge). The carbon emissions of the four scenarios were assessed based on these results. The results showed that water removal rate reached 65.5 % after 11-day biodrying, and the wet-based lower heating value of the biodried product increased by 76.0 % compared with the initial matrix. Comprehensive combustibility index of the biodried product (0.745 × 10−7 %2℃−3min−2) was better than that of SS (0.433 × 10−7 %2℃−3min−2) although a portion of the organic matter was degraded. Cement kiln co-incineration of biodried products (150 t/d) resulted in per tonne of clinker saved 5.61 kg of coal due to the heat utilization efficiency of biodried products reached to 93.7 %. However, it led to an increase in the emission concentrations of NO X and SO 2. Assessment results indicated that the biodrying + cement kiln pathway reduced CO 2 emissions by 385.7 kg/t SS. Biodried products have greater potential to reduce emissions as alternative fuels than as fertilizers. This study indicated the advantages of SS biodrying + cement kiln co-incineration route. [ABSTRACT FROM AUTHOR]