Valorization of slow pyrolysis vapor from biomass waste: Comparative study on pyrolysis characteristics, evolved gas evaluation, and adsorption effects

Energy consumption and environmental impact analysis of biomass graded deconstruction activation catalytic deoxygenation for rich single-ring aromatic bio-oil preparation

The graded deconstruction activation catalytic deoxygenation (GDACD) technology positively influenced biomass pyrolysis product quality, but the energy consumption and environmental impact for industrial applications were still uncertain. To realize the requirement of biomass conversion for high energy efficiency and low environmental impact, this study developed a poly-generation system of GDACD, syngas combustion, and waste energy power generation to produce high-quality oil with a high content of single-ring aromatic and industrial steam. The poly-generation system was investigated and evaluated according to the energy and exergy balance and environmental pollutant emissions. Inconsistency of the analysis baseline resulted in a relatively large error between simulated and experimental results. The simulation result of oil components closely matched the experimental results with the largest error of 5.88 % for the N-containing compounds in the bio-oil. The high water and oxygen content in pine sawdust led to the designed poly-generation system not being energy self-sufficient and required an additional external energy supply of 270801.33 MJ·h-1. The exergy loss of the poly-generation system was mainly related to the PREPY240, PY650, ACT650, and REFOR650 modules, which were 32.90 %, 20.59 %, 9.35 %, and 26.61 % of the entire poly-generation system exergy loss, respectively. When thermal power is the source of supplied energy, global warming and ash are more harmful with 22.56 kgCO2eq·kg-1oil and 5.38 kgAsheq·kg-1oil, respectively. The interactive power supply method of thermal, wind, and solar power should be adopted to supplement the energy consumption for the cogeneration system.

In-situ DRIFTS insights into the evolution of surface functionality of biochar upon thermal air oxidation

Biochar surface functionality is crucial for its application. Herein, the evolution of biochar surface functionality upon thermal air oxidation (TAO) was investigated in-situ by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and thermogravimetric analysis (TGA). The results show that, although the surface functionality of biochar is remarkably changed during TAO at the initial low temperature range, the biochar weight is still stable in the initial low temperature range, suggesting the chemisorption of O2 as intermediate oxygenated functional groups (OFGs) on biochar surface. Moreover, the evolution of biochar surface functionality upon TAO is highly affected on its preparation temperature and intrinsic minerals. Specifically, biochar produced at a high temperature is more resistant to TAO, and more favorable for the formation of ketone groups during TAO. While the biochars prepared at low or medium temperatures show a remarkable formation of carboxyl/lactone groups upon TAO, and the maximum temperature for the formation of carboxyl/lactone groups can be achieved at 400 °C. It's worth noting that the intrinsic minerals in biochar catalyze the TAO reaction, resulting in a much higher mass loss of biochar upon TAO. Furthermore, with the catalysis of intrinsic minerals, TAO is more suitable for enhancing the performance of biochar with intrinsic minerals. These results facilitate the design of engineered biochar via TAO for enhanced applications.

Pyrolysis of exhausted biochar sorbent: Fates of cadmium and generation of products

Biochar is a promising sorbent for Cd removal from water, while the disposal of the exhausted Cd-enriched biochar remains a challenge. In this study, pyrolysis was employed to treat the exhausted biochar under N2 and CO2 atmospheres at 600-900 °C, and the fate of Cd during pyrolysis and characteristics of high-valued products were determined. The results indicated that higher temperature and CO2 atmosphere favored the volatilization of Cd. Based on the toxicity characteristic leaching procedure (TCLP) results, the pyrolysis treatment under both atmospheres enhanced the stability of Cd, and the leached Cd concentration of regenerated biochar obtained at high temperatures (>800 °C) was lower than 1 mg/L. Compared with the pristine biochar, the regenerated biochar demonstrated higher carbon content and pH, whereas the contents of oxygen and hydrogen declined, and exhibited promising sorption properties (35.79 mg/g). The atmosphere played an important role in modifying biochar properties and syngas composition. The N2 atmosphere facilitated CH4 production, whereas the CO2 atmosphere increased the proportion of CO. These results implied that pyrolysis can be a valuable and environmental-friendly strategy for the treatment and reuse of exhausted biochar sorbent.