Abstract:
Abstract: Pyrolysis technology is one of the main ways to treat biomass wastes. A typical agricultural and forestry waste, corn straw contains alkali metals and other catalytic components, showing the excellent pyrolysis behavior with high volatile matter while low ash content. Another typical municipal solid waste, the sludge contains a large amount of thermally degradable organic matter, pathogenic microorganisms, toxic and harmful organic matter. There are relatively high moisture and ash content in the sludge, compared with the corn straw. The co-pyrolysis of the sludge and the corn straw can be an effective way to improve energy efficiency, thereby enhancing the performance of the products. As such, it can fully realize the complementary advantages of two wastes. In this study, a ThermoGravimetric Analysis (TGA) test was performed on the mixed samples with the corn stalk and municipal sludge in the mass ratio of 9:1, 3:7, 5:5, 7:3, and 1:9 at different heating rates (10, 20, and 30 ℃/min), to explore the pyrolysis characteristics and the Degree of Synergy (DS) in the single and mixed samples. A Coats Redfern method was used to clarify the kinetic of weight loss curves. The results indicated that there were great differences in pyrolysis characteristics between corn stalks and municipal sludge, where the residual rate differed by 18.57 percentage points, the comprehensive pyrolysis index differed by 35.73×10-5, and the activation energy differed by 35.31 -46.88 kJ/mol. Specifically, the activation energy of sludge pyrolysis was lower than that of corn straw. Furthermore, the activation energy increased with the increase of heating rate, with a maximum of 30 ℃/min. The initial temperature of pyrolysis decreased from 360.3 ℃ to 440.3 ℃, with the content of municipal sludge varied from 10% to 90%, while the main pyrolysis interval of mixed samples became longer from 277.7-360.3 ℃, shifting to the high-temperature zone. The residual rate increased from 33.69% to 45.83%, whereas, the maximum weight loss rate decreased from 7.88 to 3.11%/min. There was a similar behavior in the comprehensive pyrolysis index, indicating a decrease from 8.5×10-5 to 1.7×10-5. The starting temperature of pyrolysis in the mixed samples was significantly improved by the municipal sludge, but some negative effects also occurred, including the longer interval time of pyrolysis, the higher residual rate, the slower weight loss rate, and the lower comprehensive pyrolysis index. The comprehensive pyrolysis index of mixed samples was lower than that of theoretical value, indicating an inhibitory effect in the co-pyrolysis of mixed samples. The activation energy required for the individual pyrolysis of corn stalks was greater than that of municipal sludge. The increase of activation energy varied at low and high temperatures in the mixed samples of corn stalks and municipal sludge, as the heating rate increased. The activation energy of pyrolysis in the mixed samples decreased from 66.01-46.16 kJ/mol to 44.47-17.04 kJ/mol, as the content of municipal sludge increased from 10% to 90%. The findings can provide insightful data support to the co-pyrolysis of corn straw and municipal sludge, and the further application of products in low-carbon agriculture.