Thermal behavior and general distributed activation energy model kinetics of Lignite-Chinese herb residues blends during co-pyrolysis

Investigation of ash fusion characteristics on co-combustion of coal and biomass (straw, sludge, and herb residue) based on experimental and machine learning method

Co-combustion of coal and biomass has the potential to reduce the cost of power generation in plants. However, because of the high content of the alkali metal of biomass ash, co-combustion of these two fuels leads to unpredictable ash fusion temperature (AFT). This study conducted experiments to measure the AFT of straw, sludge, and herb residue when they were blended with coal at different ratios. Additionally, a machine learning algorithm called tuna swarm optimization (TSO) was employed to optimize the support vector regression (SVR) model to predict the softening temperature (ST) of samples. The results indicate that straw and sludge were found to be suitable for blending in small proportions, while herb residue was suitable for blending in larger proportions. In comparison to the traditional grid search optimization model, the TSO algorithm significantly enhances the prediction accuracy of both training and test sets, and improves the generalization ability of SVR.

Energetic, bio-oil, biochar, and ash performances of co-pyrolysis-gasification of textile dyeing sludge and Chinese medicine residues in response to K2CO3, atmosphere type, blend ratio, and temperature

Hazardous waste stream needs to be managed so as not to exceed stock- and rate-limited properties of its recipient ecosystems. The co-pyrolysis of Chinese medicine residue (CMR) and textile dyeing sludge (TDS) and its bio-oil, biochar, and ash quality and quantity were characterized as a function of the immersion of K2CO3, atmosphere type, blend ratio, and temperature. Compared to the mono-pyrolysis of TDS, its co-pyrolysis performance with CMR (the comprehensive performance index (CPI)) significantly improved by 33.9% in the N2 atmosphere and 33.2% in the CO2 atmosphere. The impregnation catalyzed the co-pyrolysis at 370°C, reduced its activation energy by 77.3 kJ/mol in the N2 atmosphere and 134.6 kJ/mol in the CO2 atmosphere, and enriched the degree of coke gasification by 44.25% in the CO2 atmosphere. The impregnation increased the decomposition rate of the co-pyrolysis by weakening the bond energy of fatty side chains and bridge bonds, its catalytic and secondary products, and its bio-oil yield by 66.19%. Its bio-oils mainly contained olefins, aromatic structural substances, and alcohols. The immersion of K2CO3 improved the aromaticity of the co-pyrolytic biochars and reduced the contact between K and Si which made it convenient for Mg to react with SiO2 to form magnesium-silicate. The co-pyrolytic biochar surfaces mainly included -OH, -CH2, C=C, and Si-O-Si. The main phases in the co-pyrolytic ash included Ca5(PO4)3(OH), Al2O3, and magnesium-silicate.

Thermal Behavior and Pyrolysis Kinetics of Mushroom Residue with the Introduction of Waste Plastics

Co-pyrolysis is considered a very promising technology for the treatment of solid wastes as it can rapidly realize the volume reduction of raw materials and obtain high value-added products. To realize the resource utilization of newly emerging solid wastes in relation to edible fungi residue and waste plastics, mushroom residue (MR), a representative of edible fungi residue, was co-pyrolyzed with waste plastic bags (PE), waste plastic lunch boxes (PP), and waste plastic bottles (PET). The thermal behavior and pyrolysis kinetics of the mixtures were investigated. It was found that the softening of the plastics in the mixtures led to an increase in the initial pyrolysis temperature of MR by 2-27 °C, while the pyrolytic intermediates of MR could greatly promote the decomposition of the plastics, resulting in a decrease in the initial pyrolysis temperatures of PE, PP, and PET in the mixtures by 25, 8, and 16 °C, respectively. The mixture of MR and PE (MR/PE) under different mixture ratios showed good synergies, causing the pyrolysis peaks attributed to MR and PE to both move towards the lower temperature region relative to those of individual samples. The increase in heating rate led to enhanced thermal hysteresis of the reaction between MR and PE. The strength of the interaction between plastics and MR based on mass variation was subject to the order PE > PP > PET. The pyrolysis activation energies of MR, PE, PP, and PET calculated from kinetic analysis were 6.18, 119.05, 84.30, and 74.38 kJ/mol, respectively. The activation energies assigned to MR and plastics were both reduced as plastics were introduced to co-pyrolyze with MR, indicating that MR and plastics have a good interaction in the co-pyrolysis process. This study provides theoretical and experimental guidance for the resource utilization of agricultural solid wastes via thermochemical conversion.

Co-pyrolysis of different torrefied Chinese herb residues and low-density polyethylene: Kinetic and products distribution

In present work, the synergistic effects during co-pyrolysis of low-density polyethylene (LDPE) and torrefied Chinese herb residues (CHR) have been investigated by thermogravimetric analysis. The kinetic parameters of co-pyrolysis were calculated by Coats-Redfern method, and the difference values of experiment and theoretical were also investigated for gas and oil compounds. The results show that the extent of synergistic or inhibitory effects of co-pyrolysis was connection with the severity of CHR torrefaction, and the activation energy depend on the blend ratio of LDPE and CHRs. In addition, co-pyrolysis tends to generate more small molecule products and reduce oil yield, and increase the CO content but decreases CH₄ in the gas product. The results also found that the liquid products have a significant interaction during the co-pyrolysis process, because the content of aliphatic hydrocarbons and alcohols in the blends pyrolysis oil has been greatly increased, and improving the quality of oil.