Exploring new approach for resource utilization of crab shell waste: Optimized microwave torrefaction parameters and efficient self-desulfurization.

Finding alternative energy sources and reducing the impact of waste on the environment are pressing global challenges. Crab shells possess the dual characteristics of a pollutant and a resource; therefore, transforming them into clean energy is an urgent issue that needs to be addressed for reducing environmental pollution. This study uses microwave torrefaction to treat crab shell waste efficiently and optimizes the torrefaction conditions through response surface methodology to rapid prepare derived fuel. At a microwave power of 2500 W, temperature of 225 °C, and a treatment duration of 11 min, the specific surface area of the crab shell derived fuel increased by 21.2%; furthermore, its high heating value increased from 14.41 to 18.18 MJ/kg and combustion and desulfurization performances improved considerably. As a proof-of-concept, these derived fuels were utilized as substitutes for fossil fuels and as desulfurization agents to capture SO2 in situ during coal combustion. Results indicated that after microwave torrefaction, the desulfurization capability of the crab shell derived fuel increased by 16.6%. At a derived fuel and coal blending ratio of 35%, SO2 emissions were reduced by 85.27%, with more desulfurization efficiency compared with conventional calcium-based dry desulfurization. To the best of our knowledge, this is the first report on using crab shell waste as derived fuel to achieve in situ SO2 capture. Given the low cost and renewability of crab shell, our study provides a promising strategy for the large-scale utilization of solid waste and its harmless disposal.