Zhihe Li

Enhancing biogas production of corn stover by fast pyrolysis pretreatment

A new thermo-chemical pretreatment by a lower temperature fast pyrolysis (LTFP) was applied to promote anaerobic digestion (AD) efficiency of corn stover (CS). The pretreatment experiment was performed by a fluidized bed pyrolysis reactor at 180, 200 and 220°C with a carrier gas flow rate of 4 and 3m(3)/h. The components characteristics, Scanning Electron Microscope (SEM) images and Crystal Intensity (CrI) of the pretreated CS were tested to explore effectiveness of the pretreatment. The results showed that the cumulative methane production at 180°C for 4 and 3m(3)/h were 199.8 and 200.3mL/g TS, respectively. As compared to the untreated CS, the LTFP pretreatment significantly (a<0.05) increased the methane production by 18.07% and 18.33%, respectively. Methane production was well fitted by the Gompertz models, and the maximum methane potential and AD efficiency was obtained at 180°C for 3m(3)/h.

Mechanical Properties of Rice Husk Biochar Reinforced High Density Polyethylene Composites

Rice husk biochar was utilized to reinforce high-density polyethylene (HDPE) and to prepare biochar/plastic composites (BPC) by the extrusion method. Morphologies, non-isothermal crystallization behavior, and mechanical properties of the composites were investigated. The SEM (scanning electron microscope) showed that HDPE was embedded into the holes of the rice husk biochar. The DSC (differential scanning calorimeter) showed that biochar could reduce the crystallization rate and the higher the content of rice husk biochar, the slower the crystallization rate. Significantly, the bending and tensile strength of BPC could reach 53.7 and 20 MPa, far beyond WPC (wood plastic composites). With the increase of filler content, BPC were still stronger than WPC, although the impact strength of BPC and WPC all showed a general decline in the trend. The strong interaction was achieved by the utilization of rice husk biochar to reinforce HDPE.

Supercritical CO2 Extraction of Corn Stalk Pyrolysis Oil

Supercritical CO 2 extraction was employed to separate simulated and real bio-oil. Effects of adsorbents on enrichment were investigated for a simulated bio-oil, which is composed of acetic acid (AC), propanoic acid (PA), furfural (FR), acetylacetone (AA) and 2-methoxyphenol (MP). Extraction of spiked bio-oil shows adsorbents are able to influence extraction efficiency and selectivity. Appropriate water content in the simulated bio-oil favors in improving extraction efficiency. Extraction with methanol (or ethanol)-modified CO 2 affords higher extraction efficiency than that with pure CO 2 , but might lead to lower extraction selectivities. Using 5A molecular sieve as adsorbent, the extraction efficiencies for MP, FR, PA, AA and AC under 45°C and 20.0 MPa respectively reach up to 100%, 84.9%, 57.8%, 57.1% and 22.8%. In addition, supercritical CO 2 extraction of a real bio-oil showed that water content and acidity of the bio-oil after extraction dropped significantly, suggesting remarkable upgrading in heat value and corrosiveness of the bio-oil.

Comparative study on fast pyrolysis of agricultural straw residues based on heat carrier circulation heating

Fast pyrolysis of agricultural straw residues based on ceramic ball circulation heating was studied by using an originally developed V-shaped drop tube pyrolysis unit. The yields of bio-oil, bio-char and pyrolysis gas from these straw residues were in the range of 41-46, 26-30 and 26-29 wt%, respectively, with maize straw giving the highest bio-oil yield. A quadratic model was developed to correlate the cellulose-to-lignin-ratio (CLR) and hemicellulose-to-lignin-ratio (HLR) with bio-oil yield. For a given HLR above 1.12, the bio-oil yield continued to increase as the CLR increased. However, when the HLR was between 0.86 and 1.12, it tended to decrease first and then increase with the increase of CLR. In contrast with CS, the proportions of acids and ketones in the bio-oils increased by 13.3% and 14.8% for MS and 9.2% and 30.5% for WS, respectively, while the proportion of phenols decreased by 9.9% and 14.3%.

Thermal and Kinetic Behaviors of Corn Stover and Polyethylene in Catalytic Co-pyrolysis

The burning of cattle manure for domestic use, and plant biomass left out in fields, is a common practice in South Asia, specifically Pakistan. According to the 2014 government of Pakistan (GOP) survey, Pakistan had 171 million head of cattle that would produce 345 billion kg of manure, which could easily be converted into 150 billion m3 of biogas. The focus of the present study was to evaluate the benefits from co-digestion of cattle manure (CM) with Dalbergia sissoo leaves (DSL) and Malus domestica leaves (MDL), with a focus on changes in the biodegradability, C/N ratio effect, and synergistic effect. The idea was to adjust the C/N ratio to increase biodegradability at mesophilic range to help the process to produce more methane than 100% manure-based digestion. First, the ideal pH and temperature conditions for mesophilic anaerobic digestion (AD) were optimized to carry out further co-digestion under the same conditions. The results of co-digestion revealed a 40% (251 NmL CH4/g VS) increase in methane yield by replacing 20% of volatile solid in CM-based AD reactors with MDL. This combination also presented a biodegradability of 59% and a synergistic effect (θ) value of 1.40, which corresponded to highly positive synergism reflecting the optimum growth conditions. The DSL/CM co-digestion also followed the same pattern, and the maximum methane yield of 229 NmL CH4/g VS was obtained using a 20/80 DSL/CM combination.

Influence of inherent hierarchical porous char with alkali and alkaline earth metallic species on lignin pyrolysis

This study aimed to explore the influence of inherent hierarchical porous char with alkali and alkaline earth metallic species (AAEMs) during pyrolysis of lignin derived from agricultural crop residues in a laboratory fixed-bed at 550 °C. A catalytic strategy was implemented to investigate volatile-char interactions based on ex situ lignin pyrolysis. The physico-chemical properties of the AAEMs-loaded char were characterized by FTIR, XRD, SEM-EDX and N2 nitrogen adsorption analyses. Results indicated that AAEMs-loaded char had a large specific surface area, hierarchical porosity, amorphous carbon structure, surface-active functional groups and highly dispersed metal species. Specifically, the specific surface area of AAEMs-loaded char was significantly reduced owing to coke deposition after interaction with pyrolysis vapours. Bio-oil composition revealed substantial increases in phenol, o-cresol, p-cresol and catechol. These increases were mainly attributed to demethylation, demethoxylation, or alkyl substitution reaction. The experimental results confirmed the occurrence of significant volatile-char interactions during lignin pyrolysis.

Fast pyrolysis of corn stovers with ceramic ball heat carriers in a novel dual concentric rotary cylinder reactor

Fast pyrolysis of corn stovers with ceramic ball heat carriers in a dual concentric rotary cylinder reactor was studied to explore the product yields and characteristics in response to temperature. The reactor was confirmed to successfully scale up to a 25 kg/h pilot plant, with its performance being excellent. The highest bio-oil yield of 48.3 wt% at 500 °C was attained with the char and gas yields being 26.8 and 24.9 wt%. Phenols content was reduced from 22.3% to 18.9% when elevating temperature from 450 until 600 °C, with guaiacols and alkyl phenols being the predominant compounds, while ketones accounted for 15.8-23.0% and their content showed a continuous increase, with hydroxyacetone being the paramount ketonic one. Acetic acid was the dominant acidic compound with its peak content of 9.4% at 500 °C. The char characteristics in response to temperatures were determined for subsequent processing and high value-added utilization.