Haiping Yang

Biomass-based pyrolytic polygeneration system on cotton stalk pyrolysis: influence of temperature.

To study the process of biomass-based pyrolytic polygeneration and its mechanism in depth, the pyrolysis of cotton stalk was investigated in a packed bed, with focus on the evolution of the chemical and physical structures of the solid, liquid and gaseous products. The evolution of product characteristics could be good explaining the process mechanism of biomass pyrolysis. A relationship between the pore distribution of solid products and the fused aromatic rings system revealed by Raman analysis might be exist and need to quantify in further study. Regarding the optimum conditions for obtaining high-quality pyrolytic products from the polygeneration system, the optimum temperature is 550-750°C, with a higher calorific value of the obtained charcoal (≈ 28 MJ/kg) and a higher surface area (>200 m(2)/g). Meanwhile, the calorific value of the gas reaches 8-9 MJ/m(3) and the liquid oil would be used as a platform product in biorefinery.

Torrefaction of agriculture straws and its application on biomass pyrolysis poly-generation

This study investigated the properties of corn stalk and cotton stalk after torrefaction, and the effects of torrefaction on product properties obtained under the optimal condition of biomass pyrolysis polygeneration. The color of the torrefied biomass chars darkened, and the grindability was upgraded, with finer particles formed and grinding energy consumption reduced. The moisture and oxygen content significantly decreased whereas the carbon content increased considerably. It was found that torrefaction had different effects on the char, liquid oil and biogas from biomass pyrolysis polygeneration. Compared to raw straws, the output of chars from pyrolysis of torrefied straws increased and the quality of chars as a solid fuel had no significant change, while the output of liquid oil and biogas decreased. The liquid oil contained more concentrated phenols with less water content below 40wt.%, and the biogas contained more concentrated H2 and CH4 with higher LHV up to 15MJ/nm(3).

Combustion behaviours of tobacco stem in a thermogravimetric analyser and a pilot-scale fluidized bed reactor.

Despite its abundant supply, tobacco stem has not been exploited as an energy source in large scale. This study investigates the combustion behaviours of tobacco stem in a thermogravimetric analyser (TGA) and a pilot-scale fluidized bed (FB). Combustion characteristics, including ignition and burnout index, and combustion reaction kinetics were studied. Experiments in the FB investigated the effects of different operating conditions, such as primary air flow, secondary air flow and feeding rates, on the bed temperature profiles and combustion efficiency. Two kinds of bed materials cinder and silica sand were used in FB and the effect of bed materials on agglomeration was studied. The results indicated that tobacco stem combustion worked well in the FB. When operation condition was properly set, the tobacco stem combustion efficiency reached 94%. In addition, compared to silica sand, cinder could inhibit agglomeration during combustion because of its high aluminium content.

Hydrogen production from biomass gasification using biochar as a catalyst/support.

Biochar is a promising catalyst/support for biomass gasification. Hydrogen production from biomass steam gasification with biochar or Ni-based biochar has been investigated using a two stage fixed bed reactor. Commercial activated carbon was also studied as a comparison. Catalyst was prepared with an impregnation method and characterized by X-ray diffraction, specific surface and porosity analysis, X-ray fluorescence and scanning electron micrograph. The effects of gasification temperature, steam to biomass ratio, Ni loading and bio-char properties on catalyst activity in terms of hydrogen production were explored. The Ni/AC catalyst showed the best performance at gasification temperature of 800°C, S/B=4, Ni loading of 15wt.%. Texture and composition characterization of the catalysts suggested the interaction between volatiles and biochar promoted the reforming of pyrolysis volatiles. Cotton-char supported Ni exhibited the highest activity of H2 production (64.02vol.%, 92.08mgg(-1) biomass) from biomass gasification, while rice-char showed the lowest H2 production.

Process simulation of single-step dimethyl ether production via biomass gasification.

In this study, we simulated the single-step process of dimethyl ether (DME) synthesis via biomass gasification using ASPEN Plus. The whole process comprised four parts: gasification, water gas shift reaction, gas purification, and single-step DME synthesis. We analyzed the influence of the oxygen/biomass and steam/biomass ratios on biomass gasification and synthesis performance. The syngas H(2)/CO ratio after water gas shift process was modulated to 1, and the syngas was then purified to remove H(2)S and CO(2), using the Rectisol process. Syngas still contained trace amounts of H(2)S and about 3% CO(2) after purification, which satisfied the synthesis demands. However, the high level of cold energy consumption was a problem during the purification process. The DME yield in this study was 0.37, assuming that the DME selectivity was 0.91 and that CO was totally converted. We performed environmental and economic analyses, and propose the development of a poly-generation process based on economic considerations.

Novel bi-functional Ni–Mg–Al–CaO catalyst for catalytic gasification of biomass for hydrogen production with in situ CO2 adsorption

Catalytic gasification of biomass in the presence of CaO is a promising route for CO2 capture and thereby high yield hydrogen production. However, the instability of the CaO sorbent for CO2 adsorption is a challenge for the process. A novel bi-functional Ni–Mg–Al–CaO catalyst has been prepared with different contents of CaO by integration of the catalytic and CO2 adsorbing materials to maximise hydrogen production. The prepared catalysts were tested for hydrogen production via the pyrolysis-gasification of wood biomass using a two-stage fixed-bed reaction system. The carbonation/calcination results using thermogravimetric analysis (TGA), in an atmosphere of N2 or CO2, showed that the reactivity of CaO with CO2 decreased even after several cycles of carbonation/calcination, while the Ni–Mg–Al–CaO catalyst showed a comparatively stable CO2 adsorption even after 20 cycles. Adding CaO to the Ni–Mg–Al catalyst leads to an increase in hydrogen production and selectivity due to the enhancement of the water–gas shift reaction by in situ CO2 adsorption. An optimal content of CaO was suggested to be 20 wt% (weight ratio of CaO/Ni–Mg–Al) which gave the highest hydrogen production (20.2 mmol g−1 biomass) in the presence of the Ni–Mg–Al–CaO catalyst. Temperature-programmed oxidation (TPO) showed that carbon deposition was significantly decreased with the addition of CaO in the Ni–Mg–Al catalyst, and with the increase of CaO content, coke deposition on the reacted catalyst was further decreased.

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.

Characterization of products from hydrothermal liquefaction and carbonation of biomass model compounds and real biomass

Abstract The main properties of products from real biomass (water hyacinth, rice straw) and biomass model compounds (microcrystalline cellulose, xylan) by hydrothermal liquefaction (300°C for 30 min) and carbonation (220°C for 4 h) were examined in a batch reactor. The results showed that rice straw (RS) has the highest heavy oil yield of 21.62% from the hydrothermal liquefaction (HTL). The oil yields from HTL are 15.00%, 11.61%, and 12.19% for microcrystalline cellulose (MC), xylan (XL), and water hyacinth (WH), respectively. The yields and composition of the heavy oil depend on the chemical ingredients in real biomass. The major compounds of the liquid products from HTL were identified by TOC and GC-MS. The heavy oil mainly contains ketones, phenols, aldehydes, alcohols, and a few acids from different materials. The hydro-char, analyzed by SEM and TEM, is composed of carbon micro-spheres in the form of core-shell during HTC. MC, WH, and RS have higher char yield. Finally, the formation of carbon micro-spheres of the xylan was proposed.

Application of biomass pyrolytic polygeneration technology using retort reactors

To introduce application status and illustrate the good utilisation potential of biomass pyrolytic polygeneration using retort reactors, the properties of major products and the economic viability of commercial factories were investigated. The capacity of one factory was about 3000t of biomass per year, which was converted into 1000t of charcoal, 950,000Nm(3) of biogas, 270t of woody tar, and 950t of woody vinegar. Charcoal and fuel gas had LHV of 31MJ/kg and 12MJ/m(3), respectively, indicating their potential for use as commercial fuels. The woody tar was rich in phenols, while woody vinegar contained large quantities of water and acetic acid. The economic analysis showed that the factory using this technology could be profitable, and the initial investment could be recouped over the factory lifetime. This technology offered a promising means of converting abundant agricultural biomass into high-value products.