Yongjie Yan

Liquefaction of sawdust for liquid fuel

Abstract Pressurized liquefaction of sawdust was carried out in an autoclave in the presence of solvent under cold hydrogen pressure ranging from 2.0 to 5.5 MPa at the temperature range of 150C–450°C. The reaction time varied from 5 to 30 min. Investigations were made on the effects of temperature, reaction time, cold hydrogen pressure and solvent on the liquefaction process. Results indicate that liquefaction of sawdust can start at a temperature of 200°C, much lower than that for coal in a hydrogen-donor solvent, e.g., tetralin which was used in this run of experiment. Oil yield increase with the rise either in temperature and in cold hydrogen pressure or with the longer reaction time.

Study on co-liquefaction of coal and bagasse by factorial experiment design method

Abstract Co-liquefaction of a Chinese bituminous coal with bagasse — a biomass waste — has been carried out in an autoclave of 300-ml capacity at a temperature range of 350–450°C, reaction time 15–45 min and cool hydrogen pressure 300–700 psig (2.04–4.76 MPa). The addition of baggasse and tetralin are beneficial to liquefaction. Optimization of the co-liquefaction process was carried out with respect to oil yield by the Factorial Experiment Design Method. The oil yield reached 48% at optimum conditions of temperature 420°C, cool hydrogen pressure of 500 psig and reaction time of 40 min. A polynomial mathematical model-second order response surface model has been obtained for correlating the oil yield response factor as well as conversion with the major process variables. The equation derived by us holds well in determining the effect of process variables on response factors for any regime condition in the range of our experimental design within ±5%.

Original preasphaltenes and asphaltenes in coals

The preasphaltene (PA) and asphaltene (A) fractions from untreated coal show a direct relationship of PA/A (w/w) to the carbon content of coal. Their thermal stability was investigated by in-situ pyrolysis FTIR, and the results show that PA has higher thermal stability than A. By means of a vacuum FTIR method, five types of hydrogen bonds formed by hydroxyl groups were clearly observed in PA and A, i.e., OH-π, self-associated OH, OH–ether oxygen, cyclic OH groups, and OH–N. The self-associated OH and OH–ether oxygen are the two main hydrogen bonds. The insolubility of PA in benzene and A in hexane is determined by the hydrogen bond strengths of the acid/base fraction but is not strongly related to their structural parameters and molecular weight. The acid/base associated strength of preasphaltenes and asphaltenes is estimated to be within the following ranges, asphaltenes, <5.15 kJ/mol; preasphaltenes, 5.15–30.9 kJ/mol.

Kinetics of transesterification crude soybean oil to biodiesel catalysed by magnesium methoxide

The apparent activation energy of transesterification of soybean oil with methanol was investigated by the use of magnesium methoxide as solid base catalyst. The effect of variations in reaction time and temperature (50-65°C) on the macro reaction rate were studied while the molar ratio of methanol to oil (9 : 1) and the mass ration of catalyst to oil (8 wt%) were held. The experimental data were curve-fitted by using Origin software, and the relationship of FAME concentration with the reaction time was given, and the apparent activation energy was calculated. The total apparent activation energy was 46.3878 kJ mol−1 and k0 was 5.9112 × 105 L mol−1 min−1. And the apparent activation energies of each fatty acid composition were 36.16, 39.54, 54.23, 43.50 and 32.15 kJ mol−1 for the palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid, respectively.

Model for predicting catalytic and non-catalytic liquefaction of coal

Abstract Based on the non-uniform constitution of coal, coal liquefaction is conveniently described by a mathematical model, in which the overall liquefaction is achieved in two stages. Both stages consist of a series of parallel irreversible reactions, of which the activation energies obey normal distribution. When catalysts exist in the reaction system, they can decrease the activation energies of the second stage, but have little effect on the reactions of the first stage. This model improves the understanding of why some coal constituents are easy to liquefy while others are not. It successfully predicts that apparent activation energies increase with conversion. The predicted conversion values derived from this model show good agreement with our experimental data as well as with the data reported in the literature.

Heat transfer and kinetics of lignite devolatilization in wire-mesh apparatus

A model of lignite devolatilization in a wire-mesh apparatus is proposed in this paper. The model couples the heat transfer between grid and particle with a multiple-reaction kinetic model. The kinetic parameters are derived from the experiments, in which two Chinese lignites are devolatized. The model predictions of heating-rate and particle-size dependence of particle temperature, devolatilization rate and weight loss are presented. An index is suggested to assess the cumulative effect of heat transfer limitation on devolatilization. The model reveals that under a typical condition (particle size 50 μm, heating rate < 1000°Cs−1), the heat transfer limitation could be negligible. However, with further increasing particle size and heating rate, the heat transfer limitation seems to become somewhat important.