Applied Mechanics and Materials Vols. 672-674

Abstract: Four commonly-used temperatures (37°C, 30°C, 55°C, and 70°C) were examined on mixed-culture H₂-producing behavior with corn stover hydrolyzate as the substrate. Experimental results indicated that the optimum biogas (1505.7 mL/L) and H₂ (717.2 mL/L) production was achieved at 55°C. For soluble metabolites, the highest acetate/butyrate concentrations and the lowest ethanol production were also found at 55°C. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was employed to analyze corresponding microbial community structure. At 55°C, most bacteria were identified as Clostridium spp., which might be responsible for higher H₂ yield in this case. Totally, fermentation temperation of 55°C was probably preferable for H₂ production from corn stover hydrolyzate.

Abstract: In this paper, using TG-DTG and single pellets hot air ignition experiment to study the hot air ignition characteristics of biomass forming granule, analyzes the hot air temperature, velocity, flow rate of its influence on ignition performance. It was found that the weight loss rate of surface material significantly higher than the center materials of the pellet at different heating rates through the experiment, and lignin pyrolysis accelerated leading to substantially coincide of hemicellulose, cellulose and lignin pyrolysis, With the increase of air temperature, maximum weight loss rate increased, the pellet heating rate accelerated, sped up the pellet ignition, the ignition temperature should be above 500°C. As the increase of gas flow, the weight loss of corn stalks is reduced after increased first, little change in the final weight loss. Weight loss rate is decreased first and then increased. The maximum weight loss rate is essentially the same at low flow, but the maximum weight loss rate reduced and the time extension after more than 50ml/min.

Abstract: Liquefaction is one of the useful and effective techniques for utilizing lignocellulosic biomass, expressly, heterogeneous catalytic liquefied technology receive ever-increasing attention due to the mild reaction, such as medium temperature, usually at 150°C, and atmospheric pressure. Based on lacking of enough understanding to the direct heterogeneous catalytic liquefied behavior of biomass and the impact caused by the ingredient of the liquefaction to the properties of the polymer, meanwhile, with lacking of enough theoretical support results in the liquefaction and the quality of its polymer product is not stable, this work gives out the studies of chemical structure and composition variation before and after corn bran liquefaction. The results show that lignin and hemicellulose are rapidly liquefied at the beginning of liquefaction, and cellulose, which is the main component of residue, is difficult to liquefy. The solvolysis and condensation reaction are occurred between the component of corn bran and phenol during liquefied process. The phenol is introduced into the structure of corn bran.

Abstract: To study the saccharification conditions of cellulase on lignocellulose material, this paper used corn straw as the material to do research on the effect of cellulase. The hydrolysis factors, including reaction temperature, reaction time and cellulase concentration, were measured in order to determine the optimal saccharification conditions for fuel ethanol production. The results showed that, when the reaction temperature was 45°C, reaction time was 72 h and cellulase concentration was 60 IU/g, the hydrolysis rate can respectively reach 6.25 %, 14.7 % and 14.4 %. By the analysis of orthogonal test, the main factors effects the saccharification was reaction time. And the optimal combination of saccharification conditions was the reaction time of 54 h, the reaction temperature of 45 °C, and the cellulase concentration of 55 IU/g.

Abstract: This paper presents an overview of biogas purification technology and industry status, studies the purified rules in biogas purification processing and a lot of experiments are made to verify the influence of purification efficiency by various influencing factors. Carbon dioxide in biogas, which occupies at least 30%, can be absorbed by the lye based on the acid-base neutralization reaction and the absorption efficiency can be improved by controlling the inlet pressure and other factors in the biogas purification processing. The experimental results show the purification rules that purification efficiency of biogas is proportional to concentration ratio of methane and carbon dioxide before reaction, inlet pressure, fluid volume of lye, lye concentration and volume of filler, but inversely proportional to the total inlet flow, which builds theoretic foundation for the later design of the biogas purification device.

Abstract: Modern control theory has been used to design a variable pitch controller based on disturbance accommodating. The controller realizes the optimal control which minimized the controller action and drive-train torque. A torque controller based on pole clustering had been designed to enhance drive system damping and to suppress torque ripple. The federated control of variable pitch and torque is adopted to reduce drive system dynamic torsional load, and has been verified by software MATLAB and FAST. Simulation result illustrated that drive system dynamic torsional load can be controlled to improve reliability of wind turbine and extend life of critical components by active control method.

Abstract: For the volatility and intermittency of intermittent new energy like wind power, traditional dispatch model and technology are severely challenged. According to the characteristics that the prediction accuracy of wind power increases as time scale increases, this paper presents a multi-time scale active power dispatch model based on the traditional dispatch model, and proposes an active power dispatch hierarchical predicting control method on the base of model predictive control and multilevel hierarchical control during industrial control course. Finally, it gets the online rolling dispatch model and strategy for the access of intermittent energy.

Abstract: The accurate prediction of wind power is an important way to improve the safety and economy of wind power system operation in large scale. On one side, the accuracy of wind power prediction depends on the characterized degree of accuracy for wind power fluctuations under the used prediction method. On the other side, it depends on the inherent degree of predictability in the characteristics of wind power fluctuations. This text will focus on the predictability of wind power, and use recurrence plot and recurrence rate to analyze it in the qualitative and quantitative view, and analyze change rule of recurrence plot and recurrence rate under different time scales. The real case of a wind farm has been analyzed to demonstrate that predictability of wind power will be poorer when the sampling interval becomes large.

Abstract: This paper designed the wind-solar hybrid electricity generation system, it might offer users reliable power supply when the climate and other factors change. The system has a variety of operation modes, can be either manually or automatically transforms. Each mode can be selected manually switching storage batteries to achieve the reliable power supply and prolong the battery service life. Through Matlab simulation analysis, the feasibility of the control system has been verified. Simulation results show that the system output stability, it can satisfy user demand.

Abstract: In this paper, voltage fluctuation and stability analysis of critical buses was performed using multiple indexes to power system with wind farm connected. Considering the intermittency and randomness of wind speed, this paper constructed three voltage fluctuation indexes according to the characteristic of voltage random distribution. Bus voltage stability index was also calculated with the help of PV and QV curves in the paper. The simulation analysis performed in the DIgSILENT/PowerFactory basing on three machines nine nodes system with double-fed wind farm was carried out to reveal the impacts of wind generation uncertainty on voltage fluctuation and stability.