Simulation analysis of biomass pyrolysis based on the improved CPD model with chain reaction dynamics

The complex composition and molecular structure of biomass lead to more complex and diversified chemical reactions in the pyrolysis. According to the structural characteristics of the reactants, this paper simplifies the pyrolysis process and extends the research focus from the micro-molecular elementary reactions to the macro reaction kinetics. The wheat straw is chosen as the investigated biomass, and the promoted chemical percolation devolatilization (CPD) with modified pseudo-grid and chain reaction kinetics (CRK) pyrolysis models were constructed for predicting the pyrolysis characteristics. Compared with the experimental results, the prediction errors of char, oil and gas production are in a reasonable range of < 10 %. Moreover, the reliability of the model is verified by comparing with the experimental thermogravimetric curve, which shows that the model could well predict the mass loss, product distribution and component characteristics, and provides a reasonable prediction for the pyrolysis of biomass.

Elucidating The Thermal Decomposition Mechanism and Pyrolysis Characteristics of Biorefinery-Derived Humins From Sugarcane Bagasse And Rice Husk

Biomass-derived humins produced in the biorefining of biomass represent an attractive feedstock for thermochemical processes and other carbon-derived platform chemicals. However, in most works, humins are merely a by-product that is not further analyzed. This work presents the purification and characterization of humins derived from sugarcane bagasse and rice husks (H-SCB and H-RH respectively), followed by the kinetic and thermodynamic analysis of its pyrolysis. Pyrolysis was examined via thermogravimetric analysis (TGA), and a global reaction model was adopted to address pyrolysis kinetics. To understand the pyrolysis process of humins and boost the quality of fit between the kinetic model and thermoanalytical data, the analyses were based on the Vyazovkin isoconversional method. The activation energy of H-SCB increased from 166.09 to 329.76 kJ mol-1. In contrast, the activation energy of H-RH decreased from 163.31 to 84.99 kJ mol-1. According to the results of the generalized master plot approach, the governing reaction mechanism shifted among order-based models, nucleation, and diffusion-controlled particle mechanisms. Derived thermodynamic properties showed that the heat absorbed helps the humins to achieve a more ordered state close to a conversion of 0.50. As far as we know, these findings are the first reported data on the forecast kinetic curves and pyrolysis mechanism of biorefinery-derived humins from sugarcane bagasse and rice husk, and these results will enable process design for the thermochemical conversion of these emerging materials to produce energy and other products.

Study of the Combustion , Pyrolysis Characteristics and Synergistic Effect of Co-hydrocharsation Products of Oil Shale and Rice HuskStudy of the Combustion , Pyrolysis Characteristics and Synergistic Effect of Co-hydrocharsation Products of Oil Shale and Rice Husk

Under the pressure of environmental problems and fossil energy shortage, countries all over the world are looking for fuel to replace fossil energy. Oil shale and rice husk are potential fuels, but they both have some problems, such as high ash content and low calorific value .In the present study,oil shale and rice husk were used as feedstock for the high quality fuel through hydrothermal approach,it provides a new way for the resource utilization of oil shale and rice.Thermogravimetric method was used to analyze the functional groups change and thermal transformation characteristics of mixed hydrochars prepared for oil shale(OS) and rice husk(RH) at different hydrothermal temperatures(150,200 and 250℃), including combustion and pyrolysis processes, and analyze the synergistic effects. Results showed that the co-hydrocharsization pretreatment had a significant effect on the thermal transformation behavior of oil shale and rice husk.On the one hand, the mixture of hydrocar has higher volatile content than its calculated value.On the other hand,a synergistic effect(promoting combustion and pyrolysis behavior) was found in both combustion and pyrolysis processes, and this effect was the most obvious when the hydrothermal temperature was around 200℃,and the characteristic peak of functional groups vibration was strong.Since the synergistic effect of pyrolysis process is lower than that of combustion process, co-hydrocharsation products are considered to be more suitable for combustion.These findings have positive significance of energy generation and utilization of organic waste by the combination of co-hydrocharsization modification and subsequent thermochemical process.