Study on thermal behavior and gas pollutant emission control during the co-combustion of rice straw-modified oily sludge and coal

Oily sludge (OS) is a solid waste generated from oil industry activities that can threaten the ecological environment and human health if not properly treated or disposed of. In this paper, the thermal behavior and emission of gas products during the co-combustion of rice straw (R) modified OS (OS5-R5) and coal (C) were investigated using an automatic calorimeter and model analysis. The effect of combustion atmosphere and additives on the gas products emission during the co-combustion of C, R, OS5-R5, and mixed fuels were investigated. The results show that as the content of OS5-R5 increased in mixed fuels, the performance of mixed fuels worsened gradually. When the mass content of OS5-R5 is 30 %, the lower heating value (LHV) was about 20 MJ/kg, which is about 16 % lower than that of C, but the comprehensive combustion index had no significant decrease. The additives could control the emission of pollutant gases. The increase of heating rate from 5 °C/min to 20 °C/min resulted in an increase of the overall combustion performance of the mixed fuel by 5.07-time. Similarly, increasing the oxygen concentration from 10 % to 100 % led to a 3.09-time increase in the combustion index of the mixed fuel. The adsorption of polar molecules by montmorillonite was conducive to reducing the emission of pollutant gases. BaO and CaO do not affect NO and NO2 emission control but reduce H2S and SO2 emissions because BaO and CaO could react with H2S and SO2 to form sulfate resulting in reduced emission. The research provides a theoretical basis for OS's safe disposal and efficient resource utilization.