Jingai Shao

Torrefaction of cedarwood in a pilot scale rotary kiln and the influence of industrial flue gas

Torrefaction of cedarwood was performed in a pilot-scale rotary kiln at various temperatures (200, 230, 260 and 290°C). The torrefaction properties, the influence on the grindability and hydroscopicity of the torrefied biomass were investigated in detail as well as the combustion performance. It turned out that, compared with raw biomass, the grindability and the hydrophobicity of the torrefied biomass were significantly improved, and the increasing torrefaction temperature resulted in a decrease in grinding energy consumption and an increase in the proportion of smaller-sized particles. The use of industrial flue gas had a significant influence on the behavior of cedarwood during torrefaction and the properties of the resultant solid products. To optimize the energy density and energy yield, the temperature of torrefaction using flue gas should be controlled within 260°C. Additionally, the combustion of torrefied samples was mainly the combustion of chars, with similar combustion characteristics to lignite.

The densification of bio-char: Effect of pyrolysis temperature on the qualities of pellets

The densification of bio-chars pyrolyzed at different temperatures were investigated to elucidate the effect of temperature on the properties of bio-char pellets and determine the bonding mechanism of pellets. Optimized process conditions were obtained with 128MPa compressive pressure and 35% water addition content. Results showed that both the volume density and compressive strength of bio-char pellets initially decreased and subsequently increased, while the energy consumption increased first and then decreased, with the increase of pyrolysis temperature. The moisture adsorption of bio-char pellets was noticeably lower than raw woody shavings but had elevated than the corresponding char particles. Hydrophilic functional groups, particle size and binder were the main factors that contributed to the cementation of bio-char particles at different temperatures. The result indicated that pyrolysis of woody shavings at 550-650°C and followed by densification was suitable to form bio-char pellets for application as renewable biofuels.

MSW oxy-enriched incineration technology applied in China: Combustion temperature, flue gas loss and economic considerations

To investigate the application prospect of MSW oxy-enriched incineration technology in China, the technical and economical analyses of a municipal solid waste (MSW) grate furnace with oxy-fuel incineration technology in comparison to co-incineration with coal are performed. The rated capacity of the grate furnace is 350 tonnes MSW per day. When raw MSW is burned, the amount of pure oxygen injected should be about 14.5 wt.% under 25% O2 oxy-fuel combustion conditions with the mode of oxygen supply determined by the actual situation. According to the isothermal combustion temperature (Ta), the combustion effect of 25% O2 oxy-enriched incineration (α = 1.43) is identical with that of MSW co-incineration with 20% mass ratio of coal (α = 1.91). However, the former is better than the latter in terms of plant cost, flue gas loss, and environmental impact. Despite the lower costs of MSW co-incineration with mass ratio of 5% and 10% coal (α = 1.91), 25% O2 oxy-enriched incineration (α = 1.43) is far more advantageous in combustion and pollutant control. Conventional combustion flue gas loss (q2) for co-incineration with 0% coal, 20% coal, 10% coal, 5% coal are around 17%, 13%, 14% and 15%, respectively, while that under the condition of 25% O2 oxy-enriched combustion is approximately 12% (α = 1.43). Clearly, q2 of oxy-enriched incineration is less than other methods under the same combustion conditions. High moisture content presents challenges for MSW incineration, therefore it is necessary to dry MSW prior to incineration, and making oxy-enriched incineration technology achieves higher combustion temperature and lower flue gas loss. In conclusion, based on technical and economical analysis, MSW oxy-enriched incineration retains obvious advantages and demonstrates great future prospects for MSW incineration in China.

Co-gasification of coal and biomass: Synergy, characterization and reactivity of the residual char.

The synergy effect between coal and biomass in their co-gasification was studied in a vertical fixed bed reactor, and the physic-chemical structural characteristics and gasification reactivity of the residual char obtained from co-gasification were also investigated. The results shows that, conversion of the residual char and tar into gas is enhanced due to the synergy effect between coal and biomass. The physical structure of residual char shows more pore on coal char when more biomass is added in the co-gasification. The migration of inorganic elements between coal and biomass was found, the formation and competitive role of K2SiO3, KAlSiO4, and Ca3Al2(SiO4)3 is a mechanism behind the synergy. The graphization degree is enhanced but size of graphite crystallite in the residual char decreases with biomass blending ratio increasing. TGA results strongly suggest the big difference in the reactivity of chars derived from coal and biomass in spite of influence from co-gasification.

Physicochemical properties and hygroscopicity of tobacco stem biochar pyrolyzed at different temperatures

The physicochemical properties and hygroscopicity of biochar derived from tobacco stem pyrolysis were investigated to get the effect of pyrolysis temperature (250–950 °C). The chemical composition and structure of biochar were characterized with proximate and ultimate analysis, X-ray fluorescence, and two-dimensional perturbation-based correlation infrared spectroscopy (2D-PCIS) based on Fourier-transform infrared spectroscopy. The physical pore structure was analyzed by Brunauer-Emmett-Teller surface area. Results showed that surface area and pore volumes of biochar increased, while biochar yield, volatile matter, H/C and O/C ratios decreased with the increasing pyrolysis temperature. The 2D-PCIS analysis suggested that the intensity of hydroxyl groups and aromatic skeletal changed greatly with pyrolysis temperature. Tobacco stem biochar was abundant in Ca and K and contained P, Mg, S, and Cl, while N was low and decreased with temperature. Tobacco stem biochar produced at 550 °C has the lowest hygroscop...

Preparation of nitrogen-doped microporous modified biochar by high temperature CO2–NH3 treatment for CO2 adsorption: effects of temperature

Nitrogen-rich agricultural waste, soybean straw, was used as a raw material to prepare high efficiency CO2 adsorbents (nitrogen-doped porous modified biochars). Three different modification methods for the preparation of these adsorbents were compared, i.e. activation with carbon dioxide, ammonification with ammonia (NH3) and high temperature treatment with the mixture of CO2 and NH3. Effects of modification temperature on physicochemical properties of the modified biochars and influences of adsorption temperature on their CO2 capture performances were both investigated. Activation with CO2 obviously developed the pore structure of modified biochars, especially micropores, while the ammonification with NH3 and modification with the mixture not only developed porosity, but also introduced nitrogen functional groups, and the modification with the mixture was better than the ammonification with NH3. As the modification temperature increased, the micropore surface area and N/C ratio of the modified biochars by the modification with the mixture both increased first, and reached the maximum at 800 °C, and then decreased. Furthermore, at the lower adsorption temperature, the micropore structure played an important role to influence the CO2 capture performance, while at the higher adsorption temperature, the chemical properties, especially the nitrogen functional groups, contributed more to the CO2 capture.

Influence of torrefaction with Mg-based additives on the pyrolysis of cotton stalk

The study presented an approach to introduce Mg-based additives into cotton stalk for strengthening deoxygenation effect during torrefaction. Then catalytic pyrolysis of torrefied feedstock with Mg-based additives residue as catalyst was performed at 550 °C for 10 min in a fixed-bed reactor. The effects of torrefaction temperature (200, 230, 260, 290, 320, 350 °C), type of Mg-based additive (MgO and MgO-K2CO3), mass ratio of additive to biomass (0.5, 1 and 2) on pyrolysis were investigated. The results indicated that yields of bio-char and bio-oil significantly increased and decreased with torrefaction temperature rising to 350 °C. MgO inhibited pyrolysis bio-char yield increase with torrefaction severity. MgO-K2CO3 increased H2 yield a lot from 1.39 to 3.67 mmol/g. It also effectively improved the aromatic hydrocarbons in bio-oil and the reduction of acids. A maximum aromatic hydrocarbons yield of 16.05% was obtained with MgO-K2CO3 (the mass ratio of 0.5:1) at torrefaction temperature of 320 °C.

Effects of the physicochemical properties of biochar and soil on moisture sorption

To investigate the correlation between the physicochemical and hygroscopic properties of biochar and soil, the moisture sorption properties of typical biochars and soils were observed inside a thermostatically controlled incubator at a temperature of 30 °C and humidity of 70%. Results showed that the equilibrium moisture content (EMC) of tobacco stem biochar, rice husk biochar, Hubei paddy soil, and Jiangxi red soil were 7.66%, 6.40%, 3.34%, and 2.92%, respectively. There was a synergistic interaction between biochar and soil, resulting in a higher EMC of biochar-soil mixtures with increases ranging from 0.16% to 2.52%. The porosity of tobacco stem biochar, rice husk biochar, Hubei paddy soil, and Jiangxi red soil were 82.58%, 65.05%, 59.02%, and 56.71%, respectively. Additionally, according to our findings, the biochar had higher carbon content, C/N ratio, and carbonyl groups, and lower bulk density, oxygen content, O/C ratio, and carboxyl groups than the soil. The linear correlation analysis indicated that there was a positive correlation between EMC and the physicochemical properties of biochar and soil, including porosity, carbon content, nitrogen content, and carboxyl groups. Consideration of the physicochemical properties of biochar and soil will significantly improve the overall properties of biochar used for soil amendment.

The conversion of biomass to light olefins on Fe-modified ZSM-5 catalyst: Effect of pyrolysis parameters

Light olefins are the key building blocks for the petrochemical industry. In this study, the effects of in-situ and ex-situ process, temperature, Fe loading, catalyst to feed ratio and gas flow rate on the olefins carbon yield and selectivity were explored. The results showed that Fe-modified ZSM-5 catalyst increased the olefins yield significantly, and the ex-situ process was much better than in-situ. With the increasing of temperature, Fe-loading amount, catalyst to feed ratio, and gas flow rate, the carbon yields of light olefins were firstly increased and further decreased. The maximum carbon yield of light olefins (6.98% C-mol) was obtained at the pyrolysis temperature of 600°C, catalyst to feed ratio of 2, gas flow rate of 100ml/min, and 3wt% Fe/ZSM-5 for cellulose. The selectivity of C2H4 was more than 60% for all feedstock, and the total light olefins followed the decreasing order of cellulose, corn stalk, hemicelluloses and lignin.

Utilization of pyrolytic char derived from bamboo chips for furfural removal: Kinetics, isotherm, and thermodynamics

ABSTRACT Bamboo charcoal obtained from the pyrolysis of bamboo chips was used to remove furfural, a representative fermentation inhibitor in hydrolyzates or pyrolysis oil. Kinetics, isotherm, and thermodynamic calculations were performed. The adsorption process can be well depicted by Ho’s pseudo-second-order model. The particle diffusion of homogeneous particle diffusion model (HPDM) and shrinking core model (SCM) was found to be the controlling step. Isotherm analysis indicated the adsorption feature took place by a nonideal adsorption. Thermodynamic calculation suggested that ΔH° > 0, ΔG° < 0, ΔS° > 0, and Ea value was 2.02 kJ/mol. The comparison results demonstrate bamboo charcoal is a promising adsorbent for furfural removal.