Dengyu Chen

Effects of heating rate on slow pyrolysis behavior, kinetic parameters and products properties of moso bamboo.

Effects of heating rate on slow pyrolysis behaviors, kinetic parameters, and products properties of moso bamboo were investigated in this study. Pyrolysis experiments were performed up to 700 °C at heating rates of 5, 10, 20, and 30 °C/min using thermogravimetric analysis (TGA) and a lab-scale fixed bed pyrolysis reactor. The results show that the onset and offset temperatures of the main devolatilization stage of thermogravimetry/derivative thermogravimetry (TG/DTG) curves obviously shift toward the high-temperature range, and the activation energy values increase with increasing heating rate. The heating rate has different effects on the pyrolysis products properties, including biochar (element content, proximate analysis, specific surface area, heating value), bio-oil (water content, chemical composition), and non-condensable gas. The solid yields from the fixed bed pyrolysis reactor are noticeably different from those of TGA mainly because the thermal hysteresis of the sample in the fixed bed pyrolysis reactor is more thorough.

Combined pretreatment with torrefaction and washing using torrefaction liquid products to yield upgraded biomass and pyrolysis products

This study presented an approach to upgrade biomass and pyrolysis products using a process based on torrefaction liquid washing combined with torrefaction pretreatment. The torrefaction of cotton stalk was first conducted at 250°C for 30min and then the resulting torrefaction liquid products were collected and reused to wash cottonstalk. The pyrolysis of the original and pretreated cotton stalk was performed at 500°C for 15min in a fixed-bed reactor. The results indicated that the combined pretreatment obviously reduced the metallic species in cotton stalk, decreased the water and acids contents while promoted phenols in bio-oil, declined the ash content in biochar, as well as improved the heating value of non-condensable gas. Overall, the combined pretreatment did not only allow to reuse the liquid products issued from torrefaction pretreatment but also improved the quality of biomass and the pyrolysis products, making it a novel promising pretreatment method.

Pyrolysis polygeneration of pine nut shell: Quality of pyrolysis products and study on the preparation of activated carbon from biochar.

A lab-scale pyrolysis reactor was utilized to investigate the effect of pyrolysis temperature (300-700°C) on the yield, quality, and energy distribution of products issued from the pyrolysis polygeneration of pine nut shells. Afterward, activated carbon was prepared from biochar using the steam activation method. Pyrolysis temperatures ranging from 500 to 600°C were found to be optimal in inducing products with improved properties, such as higher heating values of non-condensable gas, lower water content and elevated heating values of bio-oil, and substantial fixed carbon content and greater specific surface area of biochar. In addition, it was noticed that the activation conditions had a significant effect on the yield and adsorption performance of the activated carbon. As a result, activated carbon with elevated specific surface area reaching 1057.8m(2)/g was obtained at the optimal conditions of 850°C activation temperature, 80min activation time, and 1.5 steam/biochar ratio.

An approach for upgrading biomass and pyrolysis product quality using a combination of aqueous phase bio-oil washing and torrefaction pretreatment

Bio-oil undergoes phase separation because of poor stability. Practical application of aqueous phase bio-oil is challenging. In this study, a novel approach that combines aqueous phase bio-oil washing and torrefaction pretreatment was used to upgrade the biomass and pyrolysis product quality. The effects of individual and combined pretreatments on cotton stalk pyrolysis were studied using TG-FTIR and a fixed bed reactor. The results showed that the aqueous phase bio-oil washing pretreatment removed metals and resolved the two pyrolysis peaks in the DTG curve. Importantly, it increased the bio-oil yield and improved the pyrolysis product quality. For example, the water and acid content of bio-oil decreased significantly along with an increase in phenol formation, and the heating value of non-condensable gases improved, and these were more pronounced when combined with torrefaction pretreatment. Therefore, the combined pretreatment is a promising method, which would contribute to the development of polygeneration pyrolysis technology.

Pyrolysis polygeneration of poplar wood: Effect of heating rate and pyrolysis temperature

The pyrolysis of poplar wood were comprehensively investigated at different pyrolysis temperatures (400, 450, 500, 550, and 600°C) and at different heating rates (10, 30, and 50°C/min). The results showed that BET surface area of biochar, the HHV of non-condensable gas and bio-oil reached the maximum values of 411.06m(2)/g, 14.56MJ/m(3), and 14.39MJ/kg, under the condition of 600°C and 30°C/min, 600°C and 50°C/min, and 550°C and 50°C/min, respectively. It was conducive to obtain high mass and energy yield of bio-oil at 500°C and higher heating rate, while lower pyrolysis temperature and heating rate contributed towards obtaining both higher mass yield and energy yield of biochar. However, higher pyrolysis temperature and heating rate contributed to obtain both higher mass yield and energy yield of the non-condensable gas. In general, compared to the heating rate, the pyrolysis temperature had more effect on the product properties.

Effect of torrefaction pretreatment and catalytic pyrolysis on the pyrolysis poly-generation of pine wood.

Torrefaction of pine wood was performed in a tube furnace at three temperatures (220, 250, and 280°C) for 30min. Then catalytic pyrolysis of raw and torrefied pine wood was performed using HZSM-5 catalyst in a fixed-bed pyrolysis reactor at 550°C for 15min. Torrefaction pretreatment and catalytic pyrolysis have an very important effect on the yield, property, and energy distribution of pyrolysis products. The results showed that the yield of biochar rapidly increased, while that of bio-oil decreased with increasing torrefaction temperature. The oxy-compound content of bio-oil, such as acids and aldehydes, sharply decreased. However, the aromatic hydrocarbon content not only increased but also further promoted by HZSM-5 catalyst. With highest mass yields and energy yields, biochar was also the very important product of pyrolysis. The oxygen content in biomass was mainly removed in the form of CO2 and H2O, leading to increasing CO2 content in non-condensable gas.

Effect of pyrolysis temperature on the chemical oxidation stability of bamboo biochar

Biochar produced by biomass pyrolysis has the advantage of carbon sequestration. However, some of the carbon atoms in biochar are not very stable. In this study, the effect of pyrolysis temperature on the chemical oxidation stability of bamboo biochar was investigated using the atomic ratios of H/C and O/C, Fourier transform infrared spectroscopy, and potassium dichromate (K2Cr2O7) oxidation spectrophotometric method. The results show that the carbon yield and ratios of H/C and O/C decreased from 71.72%, 0.71, and 0.32 to 38.48%, 0.22, and 0.06, respectively, as the temperature was increased from 300°C to 700°C. Moreover, the main oxygen-containing functional groups gradually decreased, while the degree of aromatization increased accordingly. The biochar showed a better stability at a higher pyrolysis temperature. The proportion of carbon loss, i.e., the amount of oxidized carbon with respect to the total carbon of the biochar, decreased from 16.52% to 6.69% with increasing temperature.

In-depth study of rice husk torrefaction: Characterization of solid, liquid and gaseous products, oxygen migration and energy yield

Torrefaction is a promising method for biomass upgrading, and analysis of all products is the essential way to reveal torrefaction mechanism. In this study, torrefaction of rice husk was performed at 210-300 °C. Results showed that the fuel properties of solid products were greatly enhanced upon removal of oxygen. The gaseous products were mainly CO2 (52.9-73.8 vol%), followed by CO (26.3-39.2 vol%). The liquid product was mainly water and some tar, and the latter contained acids, furans, ketones, aldehydes, and phenols, among which the relative content of acids was the highest. Torrefaction temperature has obvious effects on the oxygen migration. Within the temperature range of 210-300 °C, 9.5-63.2% of oxygen in rice husk was migrated to the gaseous and liquid products. The H2O was the major contributor to deoxygenation, followed by CO2 and CO. Thus, formation of H2O, CO2, and CO during torrefaction is important as it achieves the purpose of intense deoxygenation.