CO2 assisted Ca-based additives on pyrolytic characteristics and products from the co-pyrolysis of sewage sludge and biomass

In this study, the CO2-looping system was firstly attempted to build for exploring the effect of calcium-based (Cabased) additives on pyrolytic characteristics and products in co-pyrolysis of sewage sludge (SS) and biomass. Then, an innovation method for the consumption of CO2 (CPCO2) evaluation was proposed and carried out in the CO2-looping system, in which it was evaluated based on the syngas volume and CO2 proportion. The results revealed that the addition of CaO and Ca(OH)2 could significantly improve CPCO2 by 21.2% in the co-pyrolysis of 500 degrees C, while the CaCO3 addition decreased the CPCO2 by 1.0%. Besides, the co-pyrolysis temperature more than 700 degrees C would play more significant role on the CPCO2 than the addition of Ca-based additives. Then the effect of Ca-based types on biochar characteristics was also identified accompanied by the bio-oil composition. Results showed that the CaO and Ca(OH)2 additives not only increased biochar mass and pH, but also enhanced the dissolved organic carbon content and the variety of dissolved organic matter, and reduced the total HMs content. Meanwhile, it was 15 types of components that was identified in bio-oil by NIST mass spectral library, found that the intensity of heptadecanenitrile and estra-1,3,5(10)-trien-17 beta-ol was influenced by Ca-based additives. Moreover, the CaO and Ca(OH)2 played important roles for improving the CPCO2 in the CO2-looping system, which was further verified by Fact Sage. Finally, the mechanism for the Ca-based additives on CPCO2 was proposed at different co-pyrolysis temperatures. These findings can widen paths for biochar application and development of CO2 capture materials.