Ronghou Liu

Comparison of the effects of five pretreatment methods on enhancing the enzymatic digestibility and ethanol production from sweet sorghum bagasse.

To improve the enzymatic digestibility of sweet sorghum bagasse and bioethanol production, five pretreatment methods have been investigated and compared, including (1) dilute NaOH solution autoclaving pretreatment, (2) high concentration NaOH solution immersing pretreatment, (3) dilute NaOH solution autoclaving and H(2)O(2) immersing pretreatment, (4) alkaline peroxide pretreatment and (5) autoclaving pretreatment. Among them, the best result was obtained when sweet sorghum bagasse was dilute NaOH solution autoclaving and H(2)O(2) immersing pretreatment. The highest cellulose hydrolysis yield, total sugar yield and ethanol concentration were 74.29%, 90.94 g sugar/100g dry matter and 6.12 g/L, respectively, which were 5.88, 9.54 and 19.13 times higher than the control. Moreover, the FTIR and SEM analysis illustrated significant molecule and surface structure changes of the sweet sorghum bagasse after pretreatments.

Effect of hot vapor filtration on the characterization of bio-oil from rice husks with fast pyrolysis in a fluidized-bed reactor

To produce high quality bio-oil from biomass using fast pyrolysis, rice husks were pyrolyzed in a 1-5 kg/h bench-scale fluidized-bed reactor. The effect of hot vapor filtration (HVF) was investigated to filter the solid particles and bio-char. The results showed that the total bio-oil yield decreased from 41.7% to 39.5% by weight and the bio-oil had a higher water content, higher pH, and lower alkali metal content when using HVF. One hundred and twelve different chemical compounds were detected by gas chromatography-mass spectrometry (GC-MS). The molecular weight of the chemical compounds from the condenser and the EP when the cyclone was coupled with HVF in the separation system decreased compared with those from the condenser and EP when only cyclone was used.

Steam reforming of bio-oil from rice husks fast pyrolysis for hydrogen production.

Steam reforming of two kinds of bio-oil from rice husks fast pyrolysis was conducted for hydrogen production at three temperatures (650, 750 and 850 °C) with Ni-based catalyst in a fixed-bed reactor. The gas composition and organic compounds in liquid condensate were detected by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), respectively. In addition, the carbon deposition was also investigated. The results showed that the mole fraction range of hydrogen was within 55.8-61.3% at all temperatures and more hydrogen was produced at the higher temperature. The highest H₂ efficiency of bio-oil steam reforming was 45.33% when extra water was added. The bio-oil with lower content of chemical compounds has a higher H₂ efficiency, but its hydrogen volume was less. Analysis of the liquid condensate showed that most of the organic compounds were circularity compounds. The carbon deposition can decrease the bio-oil conversion, and it was easier to form at the temperature of 750 °C.

Influence of particle size on performance of a pilot-scale fixed-bed gasification system

The effect of particle size on the gasification performance of a pilot-scale (25 kg/h) downdraft fixed bed gasification system was investigated using prunings from peach trees at five different size fractions (below 1, 1-2, 2-4, 4-6 and 6-8 cm). The gas and hydrocarbon compositions were analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC-MS), respectively. With increasing particle size, gas yield increased while tar and dust content decreased. The lower heating value of the gas decreased slightly with particle size. At a smaller particle size, more hydrocarbons were detected in the producer gas. Hydrogen and carbon dioxide contents increased with the decrease in particle size, reaching 16.09% and 14.36% at particle size below 1cm, respectively. Prunings with a particle size of 1-2 cm were favorable for gasification in the downdraft gasifier used in this study.

Biogas production from undiluted chicken manure and maize silage: A study of ammonia inhibition in high solids anaerobic digestion

The feasibility of co-digestion of chicken manure (CM) and maize silage (MS) without water dilution was investigated in 5-L digesters. Specific methane production (SMP) of 0.309LCH4g(-1) volatile solids (VS) was achieved but only at lower %CM. Above a critical threshold for total ammonia nitrogen (TAN), estimated at 7gNL(-1), VFA accumulated with a characteristic increase in acetic acid followed by its reduction and an increase in propionic acid. During this transition the predominant methanogenic pathway was hydrogenotrophic. Methanogenesis was completely inhibited at TAN of 9gNL(-1). The low digestibility of the mixed feedstock led to a rise in digestate TS and a reduction in SMP over the 297-day experimental period. Methanogenesis appeared to be failing in one digester but was recovered by reducing the %CM. Co-digestion was feasible with CM ⩽20% of feedstock VS, and the main limiting factor was ammonia inhibition.

Sensitivity analysis of three-parallel-DAEM-reaction model for describing rice straw pyrolysis.

The three-parallel-DAEM-reaction model was used to study the slow pyrolysis kinetics of rice straw based on thermogravimetric analysis (TGA) data. The kinetic parameters of the model were calculated using the pattern search method. A comparison between the predicted DTG data and experimental values showed good agreement. The influences of the kinetic parameters on the model for describing the experimental data of rice straw were analyzed by means of local parametric sensitivity analysis. The results indicated that the frequency factor and the mean value of the activation distribution for cellulose decomposition affect the model more strongly than other parameters, followed by the corresponding parameters for hemicellulose and lignin. The sensitivity of the model to the standard deviations of the activation energy distributions for all pseudocomponents is very slight.

Applicability of Fraser-Suzuki function in kinetic analysis of DAEM processes and lignocellulosic biomass pyrolysis processes

In this work, a new method for fitting the conversion rate curves of the distributed activation energy model (DAEM) and lignocellulosic biomass pyrolysis process was introduced. The method was based on the curve fitting technique using the Fraser–Suzuki function. Various simulated DAEM processes were analyzed. The results showed that the conversion rate curve of one DAEM process could be described well by a Fraser–Suzuki function. According to the obtained parameters of the fitted Fraser–Suzuki functions, the influences of the DAEM parameters on the conversion rate curves of the corresponding DAEM processes can be quantitatively obtained. The experimental data of the pyrolysis of cotton stalk, oilseed rape straw, and rice straw were fitted by the Fraser–Suzuki mixture model which involves three individual Fraser–Suzuki functions. It has been found that the Fraser–Suzuki mixture model can reproduce accurately the conversion rate curves of the pyrolysis of three lignocellulosic biomass samples. The Fraser–Suzuki mixture model provides an approach to separate lignocellulosic biomass pyrolysis into three parallel reactions which link to the decomposition of hemicellulose, cellulose, and lignin, respectively.

Comparison of anaerobic digestion characteristics and kinetics of four livestock manures with different substrate concentrations

Anaerobic digestions of pig manure (PM), dairy manure (DM), chicken manure (CM) and rabbit manure (RM) at initial volatile solid loading (VSL) of 8 g VS/L, 16 g VS/L, 32 g VS/L, 64 g VS/L were investigated under mesophilic conditions. The maximum methane yields of 410, 270, 377 and 323 mL CH4/g VSadded for PM, DM, CM and RM were all obtained at initial VSL of 8 g VS/L, respectively. The improvement of substrate concentration to 64 g VS/L not only decreased the methane yield and biodegradability both by 22.4%, 37.3%, 49.1% and 34.6% for PM, DM, CM and RM respectively, but also reduced the methane content in final biogas production. The Cone model (R(2): 0.9910-0.9974) showed a better fit to the experiment data and the calculated parameters indicated that anaerobic digestion of manures at higher loading has longer lag phase and lower hydrolysis rate.

A critical study of the Miura–Maki integral method for the estimation of the kinetic parameters of the distributed activation energy model

Using some theoretically simulated data constructed from known sets of the activation energy distribution f(E) (assumed to follow the Gaussian distribution [Formula in text] where E is the activation energy, E(0) is the mean value of the activation energy distribution, and σ is the standard deviation of the activation energy distribution) and the frequency factor k(0), a critical study of the use of the Miura-Maki integral method for the estimation of the kinetic parameters of the distributed activation energy model has been performed from three cases. For all cases, the use of the Miura-Maki integral method leads to important errors in the estimation of k(0). There are some differences between the assumed and calculated activation energy distributions and the differences decrease with increasing the assumed k(0) values (for Case 1), with increasing the assumed σ values (for Case 2), and with decreasing the b values (for Case 3).

Prediction of concentration profiles and theoretical yields in lignocellulosic biomass pyrolysis

This work involved the prediction of the concentration profiles and theoretical yields in lignocellulosic biomass pyrolysis under real pyrolysis conditions. The competing reaction model was used and verified by the experimental data of the pyrolysis of oilseed rape straw and sesame stalk. The pyrolysis kinetic behaviors of the pyrolysis of peach branch, cotton stalk, and corn stalk under various conditions were simulated based on the model and their chemical compositions. The influences of the heating rate and final temperature on the theoretical yields of pyrolysis products and the pyrolysis time were obtained. Under the same conditions, the pyrolysis of peach branch gave the highest yield of volatile products, while the pyrolysis of cotton stalk gave the highest yield of char. The method presented in this work enables us to predict the concentration profiles and theoretical yields of different lignocellulosic materials under various pyrolysis conditions.