汽爆技术促进中药资源高值化利用

汽爆技术在中药资源高值化利用中发挥的作用正在逐渐体现:汽爆处理打破中药植物细胞壁的屏障结构,有利于有效成分的分离提取;汽爆过程物料自体水解发生去糖苷化作用使天然植物中的苷元与糖基分离,提高苷类物质提取和分离效率;汽爆应用于中药炮制和中药脱毒有高效、快速和避免有效成分流失等优点;汽爆处理有利于中药非药用组分如纤维素、半纤维素等的有效分离和利用,联产乙醇、丁醇等能源和化工产品。本文对汽爆技术在中药资源高值化利用中的研究进展进行了综述。     

Pd/ZnO催化甲醇水蒸气重整理论研究

随着化石能源的日渐枯竭和人们对环境保护的日益重视,发展清洁高效的新能源成为世界各国高度关注的战略课题。甲醇水蒸气重整是生产氢能的有效方法之一,Pd/ZnO催化剂热稳定性好、选择性高,是可能替代Cu/ZnO的催化剂。本文综述了近十年来采用理论方法对Pd/ZnO催化甲醇水蒸气重整制氢机理的研究工作。文章首先论述了催化剂的研究进展,然后对水在单体和聚集状态下在单层及多层平整的和阶梯状的合金表面的吸附和解离进行了总结;接着对甲醇、甲氧基和甲醛在合金表面的吸附和化学反应的热力学和动力学作了介绍;随后基于计算结果,对甲醇反应机理给予了详细的描述。最后对全文进行了总结并对未来的研究作了展望。     

Hydrogen Production by Steam Reforming of Ethanol: A Two Step Process

A two-layer fixed-bed catalytic reactor for hydrogen production by steam reforming of ethanol is proposed. In this reactor ethanol is first converted to acetaldehyde over a Cu-based catalyst and then acetaldehyde is converted to a hydrogen-rich mixture over a Ni-based catalyst. It is shown that the use of such type of reactor prevents coke formation and provides hydrogen yields closed to equilibrium.     

Numerical investigation of the effect of inlet condition on self‐excited oscillation of wet steam flow in a supersonic turbine cascade

Self‐excited oscillation can be induced due to the interaction between condensation process and local transonic condition in condensing flow, which is an important problem in wet steam turbine. With an Eulerian/Eulerian numerical model, the self‐excited oscillation of wet steam flow is investigated in a supersonic turbine cascade. Owing to supercritical heat addition to the subsonic flow in the convergent part of the cascade, the oscillation frequency decreases with increased inlet supercooling. Mass flow rate increases in the oscillating flow due to the greater supersaturation in condensation process, while the increase will be suppressed with the flow oscillation. Higher inlet supercooling leads to the fact that the condensation process moves upstream and the loss increases. Moreover, some predictions of oscillation effects on outflow angle and aerodynamic force are also presented. Finally, heterogeneous condensations with inlet wetness and periodic inlet conditions, as a result of the interference between stator and rotor, are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

黏胶废液对福建无烟煤水蒸气催化气化的动力学和补偿效应

采用黏胶废液为催化剂,对福建尤溪无烟粉煤在常压热分析仪中的水蒸气催化气化动力学进行了研究。在850℃～950℃测定了黏胶废液催化剂添加量（NaOH浓度为计算基准）从0～12%时的碳转化率随气化时间的变化,表明黏胶废液具有提高碳转化率和气化速率的作用,同时确定了该黏胶废液催化剂的加载饱和浓度。基此得出的尤溪无烟粉煤水蒸气催化气化反应动力学符合缩芯模型,并给出相应的动力学参数。进而分析表明,该催化气化过程存在明显的补偿效应,最后给出黏胶废液对尤溪无烟粉煤水蒸气催化气化包括补偿效应的动力学方程。     

The effect of copper content on the reactivity of Cu/Co6Al2 solids in the catalytic steam reforming of methane reaction

The steam reforming of methane over Cu/Co₆Al₂ mixed oxides with different copper contents was studied. The Co₆Al₂ support was prepared via the hydrotalcite route. It was thermally stabilized at 500 °C, impregnated with 5 wt.%, 15 wt.% or 25 wt.% copper using copper (II) nitrate Cu(NO₃)₂·3H₂O precursor and then calcined again at 500 °C under an air flow. The impregnation of copper enhanced significantly the reactivity of the solids in the considered reaction. The 5Cu/Co₆Al₂ solid was the most reactive one, with a methane conversion of 96% at 650 °C. The selectivities of H₂ and CO₂ were also better for the catalyst containing 5 wt.% copper compared to higher copper loadings. The decrease in the catalytic reactivity with increasing the copper content was attributed to the formation of agglomerated and less reactive CuO species, which were detected by XRD and TPR analyses.     

Potential Hydrothermal-Humification of Vegetable Wastes by Steam Explosion and Structural Characteristics of Humified Fractions

In this work, steam explosion (SE) was exploited as a potential hydrothermal-humification process of vegetable wastes to deconstruct their structure and accelerate their decomposition to prepare humified substances. Results indicated that the SE process led to the removal of hemicellulose, re-condensation of lignin, degradation of the cellulosic amorphous region, and the enhancement of thermal stability of broccoli wastes, which provided transformable substrates and a thermal-acidic reaction environment for humification. After SE treatment, total humic substances (HS), humic acids (HA_s), and fulvic acids (FA_s) contents of broccoli samples accounted for up to 198.3 g/kg, 42.3 g/kg, and 166.6 g/kg, and their purification were also facilitated. With the increment of SE severity, structural characteristics of HA_s presented the loss of aliphatic compounds, carbohydrates, and carboxylic acids and the enrichment of aromatic structures and N-containing groups. Lignin substructures were proved to be the predominant aromatic structures and gluconoxylans were the main carbohydrates associated with lignin in HA_s, both of their signals were enhanced by SE. Above results suggested that SE could promote the decomposition of easily biodegradable matters and further polycondensation, aromatization, and nitrogen-fixation reactions during humification, which were conducive to the formation of HA_s.     

Sorption-enhanced steam reforming of hydrocarbons with autothermal sorbent regeneration in a moving heat wave of a catalytic combustion reaction

A novel technological concept of sorption-enhanced steam reforming of hydrocarbons is suggested. The peculiarity of the concept is the autothermal regeneration of the carbon dioxide scavenger in the moving super-adiabatic heat wave of an exothermic catalytic combustion reaction performed directly inside the adsorption-catalytic bed. The capability and high efficiency of the proposed technological approach are confirmed by process simulation. The approach proposed is shown to open a way for the creation of an inexpensive, reliable and energy-saving adiabatic packed bed methane processors of unlimited processing capacity.     

Prediction of losses in the flow through the last stage of low‐pressure steam turbine

In this paper, the numerical modelling of the flow through the low‐pressure steam turbine last stage was presented. On the basis of predicted wet steam flow‐field, the aerodynamic as well as thermodynamic losses were estimated. For calculations of the wet steam steady flow‐field three numerical methods were employed. The first method was a streamline curvature method (SCM). The commercial CFD code (CFX‐TACflow) and an in‐house code, both solving the 3‐D RANS equations, were the next two methods. In the wet steam region, by means of all three methods, the equilibrium flow was modelled. Additionally, the in‐house CFD code was used for modelling of the non‐equilibrium steam condensing flow. In this work, the comparison of the cascade loss coefficient for stator and rotor and selected flow parameters for the stage were presented, compared and discussed. Copyright © 2006 John Wiley & Sons, Ltd.