车用沼气提纯净化工艺技术研究

概述了车用沼气提纯净化工艺技术现状,评价了目前车用沼气脱除硫化氧、二氧化碳和水的工艺技术,重点论述了生物法、活性炭和变压吸附联合脱硫化氢,氢氧化钠溶液法吸收二氧化碳工艺和冷分离法除水工艺.指出提纯净化工艺具有较为广阔的发展前景.     

太阳能加热沼气发酵系统数值方法的研究

以太阳能加热沼气发酵系统为对象,应用Fluent软件进行模拟计算,分析沼气池内的温度场,同时对非稳态计算的数值方法进行研究。对同一计算模型分别采用定迭代方式和变迭代方式进行计算,结果发现,应用Fluent软件进行非稳态计算时,可以根据实际情况适当调整时间步内的迭代次数,从而减少计算时间,这对非定常计算有很大的实用意义。同时,对换热管内的经济流速进行了计算,结果显示,水流速度宜采用0.8～1.0m/s。     

甘氨酸钠溶液提纯沼气性能的试验研究

对新型有机胺-甘氨酸钠溶液吸收CO2提纯沼气的适宜条件进行了试验研究,并采用加热再生的方法对甘氨酸钠溶液的再生性能进行了研究。考察了不同浓度(0.5～3 mol/L)甘氨酸钠溶液对CO2吸收速率和吸收负荷随时间的变化关系,气流速度对于甘氨酸钠溶液对CO2吸收速率和吸收负荷的影响以及温度对于甘氨酸钠溶液对CO2吸收速率的影响。试验结果表明,甘氨酸钠溶液的浓度越高,吸收量也越大,但吸收负荷越小;气流速度对甘氨酸钠吸收CO2速率影响较为明显;温度对甘氨酸钠吸收CO2速率影响较小。另外,甘氨酸钠溶液具有稳定的再生性能,适宜的再生温度和再生时间分别为108℃和3 h。     

Optimized mixed reforming of biogas with O2 addition in spark-discharge plasma

Adding O₂ into biogas to achieve partial oxidation and CO₂ mixed reforming can not only increase H₂ + CO concentration, but also reduce energy cost for H₂ production. In this study, optimized mixed reforming of biogas with O₂ addition in spark-discharge plasma was pursued in combination with thermodynamic-equilibrium calculation. With respect to mixed reforming of biogas with O₂ addition in spark-discharge plasma, combination coefficients of independent reactions were given to quantitatively evaluate the mixed extent at various O₂/(CH₄–CO₂) ratios. Compared thermodynamic-equilibrium with experimental results, it can be concluded that the optimal O₂/(CH₄–CO₂) ratio for optimized mixed reforming of biogas in spark-discharge plasma was about 0.7. When total-carbon conversion was relatively high (>75%), H₂ + CO concentration on wet basis was the highest and energy cost for H₂ production was the lowest at O₂/(CH₄–CO₂) = 0.7, and their experimental results were closest to their thermodynamic-equilibrium values.     

Pressurization effect on dry reforming of biogas in kilohertz spark-discharge plasma

To produce high-concentration syngas (CO + H₂) from biogas, the effect of pressurization on dry reforming of biogas (CH₄/CO₂ = 60%/40%) in kilohertz spark-discharge plasma was reported for the first time by elevating the pressure from 1 bar to 2 bar. It was found that elevating the pressure could not only increase the reactant conversions, but also reduce energy cost and increase fuel-production efficiency at the same specific energy input (SEI). In particular, pressurization exhibited a significantly positive effect on increasing CO₂ conversion and decreasing energy cost for converting CO₂. Syngas concentration as high as 83% (H₂/CO = 1.4) was achieved with a ratio of the flow rates of product gas (dry basis) to feeding gas, 1.7, at 2 bar and SEI = 753 kJ/mol. The by-product, H₂O, was produced with only about 5% of hydrogen-based selectivity in this work. At 2 bar, the effect of SEI was investigated by varying the power and flow rate, respectively. Compared with those at 1 bar, with the increase in SEI, reactants conversion increased fast, energy cost rose slowly and fuel-production efficiency decreased slowly at 2 bar.     

Micro‐modeling of porous composite anodes for solid oxide fuel cells

A new anode micromodel for solid oxide fuel cells to predict the electrochemical performance of hydrocarbon‐fuelled porous composite anodes with various microstructures is developed. In this model, the random packing sphere method is used to estimate the anode microstructural properties, and the complex interdependency among the multicomponent mass transport, electron and ion transports, and electrochemical and chemical reactions is taken into account. As a case study, a porous Ni–YSZ composite anode operated with biogas fuel is simulated numerically and distributions of the current density, polarization, and mole fraction and rate of flux of the fuel components along the thickness of the anode are determined. The effect of the anode microstructural variables including the porosity, thickness, particle‐size ratio, and particle size and volume fraction of Ni particles on the anode electrochemical performance is also studied. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1893–1906, 2012     

Determining the limiting reaction in anaerobic digestion processes. How has this been tackled?

The rate‐limiting step concept has been widely used in anaerobic digestion processes as well as in many different biological processes. Sometimes it is described as part of the study introduction, but many times is used to support the specific objectives of the work. However, there is no clear consensus of how to define this step or how to determine it. This review presents a critical revision of several methods and procedures proposed to determine the rate‐limiting step in the anaerobic digestion field. The review is structured as follows: first, the justification of this revision is presented, followed by the very basic original definition and the latest applications in determining the rate‐limiting step. It ends with a discussion about the existing methodologies and the possible directions for addressing this issue. Different experimental approaches have been used for determining the rate‐limiting step which, in general terms, can be grouped into two procedures: steady states and batch test evaluation. Modeling applications have rarely been employed despite them allowing a more detailed picture of the anaerobic digestion system Copyright © 2012 Society of Chemical Industry     

火花点火式沼气发动机高效燃烧的研究

国内对火花点火式沼气发动机的研究甚少，生产的沼气发动机在运行中出现热负荷高、可靠性与经济性差的问题．本文从分析沼气燃烧特点出发，提出了改善火花点火式沼气发动机性能的快速燃烧方法，并开发出具有风扇形燃烧室的新型快速燃烧系统。实验研究表明这种新型燃烧系统对改善火花点火式沼气发动机的可靠性与经济性具有明显的效果     

Biodegradation of heavy oil by fungal extracellular enzymes from Aspergillus spp. shows potential to enhance oil recovery

Microbial enhanced oil recovery makes a substantial contribution to the recovery of heavy oils; however, most methods use bacteria, with less attention paid to the potential of fungi. In this study, we investigated the efficiency of fungal extracellular enzymes in biotransformation of heavy oil fractions into light compounds. Two Aspergillus isolates (A. terreus and A. nidulans) with the ability to biodegrade heavy oil were isolated from bitumen. The extracellular enzymes from these Aspergillus isolates exhibited dehydrogenase and catechol 2,3-dioxygenase activities. The biodegradation of heavy oil was coupled with abundant production of gases, mainly CO₂ and H₂. Gas chromatography analysis revealed a redistribution of n-alkanes in heavy oil after treatment with crude enzyme extracts, which resulted in an increase in individual n-alkanes. The viscosity of heavy oil was decreased considerably by enzymatic degradation. These results demonstrate the potential of fungal extracellular enzymes from Aspergillus spp. for applications in enhanced heavy oil recovery.