沼气发酵猪粪管理系统对温室气体排放的影响

基于生命周期清单分析以及清洁发展机制,引入"碳足迹"概念,对我国散养猪以及规模化养猪场引入沼气发酵系统后猪粪管理系统温室气体排放及减排进行了估算。农户散养猪粪处理系统中,12 m3沼气池厌氧发酵过程碳足迹为223.40 kg CO2e/a,沼气代替原煤燃烧减少444.33 kg CO2e/a温室气体,沼气发酵净减少220.93 kg CO2e/a温室气体,我国散养生猪产生的猪粪以此沼气池发酵可减少温室气体20 984.62 Gg CO2e/a;分析运行规模约1 000 m3大型沼气工程的碳足迹,保守估计为2 835.32 t CO2e/a,运行沼气工程替代煤炭以及减少猪粪排放的温室气体共约2 914.23 t CO2e/a,故沼气工程年减少温室气体78.91 t CO2e,该项目共可减排1 578.20 t CO2e。在猪粪管理系统中采用沼气发酵系统可以更好地促进温室气体减排的进行。     

生物质制取高品位液体燃料的生命周期评价

采用生命周期评价方法(LCA)对稻秸热解提质制取液体燃料和稻秸气化合成液体燃料4种工艺进行环境影响评价。将CO2、NOX、SO2等污染物分为7种环境影响类型,用货币化方法量化不同污染物对环境的影响。结果表明,生命周期环境影响成本由低到高分别为二甲醚11.54$/GJ、精制油16.79$/GJ、乳化油17.86$/GJ、柴油18.04$/GJ和费托油20.30$/GJ;生物燃料(乳化油除外)的生产上游环境性能较好,液体燃料的消费排放亦比柴油有所改善,生产过程环境影响较大;以化石柴油为基准,生物质制取液体燃料的温室效应降低9.4%~121.1%,二甲醚酸化和光化学污染分别降低27.8%~34.7%和15.6%~53.8%,但其他3种生物燃料酸化增加5.0%~61.2%。     

生物质气化发电能耗和温室气体排放分析

利用混合式生命周期分析方法对1 MW和5.5 MW生物质气化发电系统的能耗和温室气体(GHG)排放进行分析,结果表明:每输出1 GJ电力,1 MW和5.5 MW生物质气化发电系统一次化石能源消耗分别为0.238 GJ和0.258 GJ,GHG排放分别为40.4 kg CO_2-eq和49.8 kg CO_2-eq,其中发电阶段的能耗和温室气体排放最高;两个系统的能源替代率在90%以上,GHG减排率在80%以上;生物质气化发电系统具有良好的可持续性,可在节能减排中发挥重要作用。     

中国农业沼气工程生命周期评价

文章系统回顾了中国农业沼气工程的生命周期评估（LCA）研究,以生产利用1 MJ沼气为统一功能单位,对其环境影响进行了定量的对比分析。研究结果表明：受系统边界和参考系统选择等因素的影响,中国农业沼气工程LCA研究的结果差别很大,但大都能显著减少化石能源消耗和温室气体（GHG）排放;中国农业沼气工程生命周期能耗为0.01～0.76 MJ/MJ,节能收益最高可达2.27 MJ/MJ,利用煤炭加热保温是高能耗的最主要因素;中国农业沼气工程生命周期的GHG排放为9～219 g/MJ,GHG减排收益为33～787 g/MJ,其在环境酸化、富营养化和光化学氧化等环境影响方面的效益有待更多的研究确认。     

基于SimaPro利用废弃餐饮油脂炼制生物柴油的生命周期环境影响评价

基于生命周期评价(LCA)理论和SimaPro(Version7.3.3)软件,利用Eco-indicator99(生态指数法)环境影响评价指标体系,分析生物柴油生命周期环境影响;并将其与具有相同功能单位的石化柴油进行比较。结果表明:1 MJ生物柴油生命周期环境负荷单一值为0.006 8 Pt,其中,生产阶段造成的环境负荷较显著。1 MJ石化柴油生命周期环境负荷单一值为0.014 8 Pt,表明生物柴油产品较石化柴油更具环境协调性。     

大中型沼气工程增温及控制系统运行管理策略

针对北方地区大中型养殖场沼气工程,制定一套发酵罐体增温及控制系统的运行管理策略,它分为供暖期与非供暖期两种模式。阐述两种系统的工作原理,对系统的热负荷、发电余热回收、沼气锅炉采暖及锅炉回水余热回收进行理论计算,并进行设备选型。计算可得:发酵系统平均每日热负荷为3.26 GJ,余热锅炉每日可提供的发电尾气余热回收量为3.64 GJ,发电量为1300 k Wh/d;通过板式换热器与沼气锅炉回水换热,每日集热量为4.41 GJ,可满足维持发酵罐体正常发酵温度的要求,从而保证厌氧发酵系统的稳定运行。     

畜禽养殖场沼气工程运行温度的确定方法

为实现沼气工程运行的净产能最大化,以万头猪场配置的500 m3发酵罐为分析对象,建立计算模型,计算净沼气产量,从而确定发酵温度。结果表明：发酵罐的能量产出效率指标k和能量输入效率指标η是发酵温度选择的决定性因素；在现有设计条件(k=55%、w=45%、发酵温度35 ℃)下运行,年增温所需沼气量为总沼气产量的42.4%,其中,冬季为65.2%,春季为42.1%,秋季为40.4%,夏季为22.3%,年平均净沼气产量为285.6 m3/d;只有当k≥55%和w≥45%时,运行净能产出最大的发酵温度为35 ℃,当k或η值随工程运行下降,降低发酵运行温度方可获得最大净能产出；结合我国沼气工程的实际工况,建议选择30 ℃作为发酵运行温度,并及时对发酵设备进行维护,以确保工程的长期运行效率。     

畜禽养殖场沼气工程发酵温度的确定方法

为实现沼气工程运行的净产能最大化,以万头猪场配置的500m3发酵罐为分析对象,建立计算模型,计算净沼气产量,从而确定发酵温度。结果表明:发酵罐的能量产出效率指标k和能量输入效率指标η是发酵温度选择的决定性因素;在现有设计条件(k=0.55、η=0.45、发酵温度35℃)下运行,年增温所需沼气量为总沼气产量的42.4%,其中,冬季为65.2%,春季为42.1%,秋季为40.4%,夏季为22.3%,年平均净沼气产量为285.6m3/d;只有当k≥0.55和η≥0.45时,运行净能产出最大的发酵温度为35℃,当k或η值随工程运行下降,降低发酵运行温度方可获得最大净能产出;结合我国沼气工程的实际工况,建议选择30℃作为发酵运行温度,并及时对发酵设备进行维护,以确保工程的长期运行效率。     

车用沼气燃料生命周期的评价

利用国际标准化组织的生命周期评价(LCA)标准,确定了城市垃圾厌氧发酵车用沼气燃料的生命周期评价的边界和清单分析参数,提出了生命周期清单分析(LCI)的计算方法,对垃圾厌氧发酵车用沼气燃料进行了生命周期评价.结果表明:在车用沼气燃料生命周期中,改善厌氧发酵过程是减少能源消耗的主要途径;沼气车辆运行阶段是影响环境污染物排放的关键;全球变暖对环境影响负荷贡献最大.城市垃圾厌氧发酵为城市垃圾的处理找到了可持续发展的途径.     

增强型地热系统能耗及CO_2排放强度的生命周期评价

以装机容量10 MW的增强型地热系统(EGS)为例,对其生命周期内能耗和CO2排放进行详细核算,结果表明:EGS能耗以造井和储层建造阶段能耗为主,分别占生命周期能耗的80.04%和12.73%。EGS能耗强度和CO2排放强度(合标准煤)分别为3.45 g/kWh和8.25 g/kWh,能耗强度略高于风电,显著低于光伏发电与火电;CO2排放强度以EGS为最低,相较国内单位发电量764 g/kWh的碳排放,EGS服役期满20 a后,可实现减排CO2106万t。     

小型锅炉烟尘测试时锅炉出力的计算

锅炉烟尘测试时,必须对锅炉出力进行测试。但监测中,许多小型锅炉往往不具备相关的计量装置和仪表,为解决这一问题,文章提出了用烟气量和空气过剩系数来计算锅炉的出力的公式,在实际使用中,该方法简单易行,其结果和实测值具有很好的一致怀。     

Unerroric of control of mutual compliance of the efficiency of hydrogen engines of unmanned vehicles in the conditions of mass production

The issues related to the reliability of hydrogen engines of unmanned vehicles and increasing the efficiency of using hydrogen as fuel when using the method of its production during the decomposition of hydrogen-containing molecules of liquid-phase organic compounds in a plasma discharge under the action of intense ultrasonic exposure are considered. Experiments have shown that as a result of decomposition in the acoustoplasma discharge of liquid hydrocarbons, solid-phase carbon-containing products are formed, chemical transformations occur in the liquid phase and hydrogen-containing combustible gas is formed. Hydrogen-containing gas can be used as fuel immediately after synthesis, i.e. it does not require separation, since in addition to hydrogen it contains only impurities of CO₂ and water vapor. The purpose of the study is to formalize the basic conditions for tightening the control of mutual compliance with the efficiency of hydrogen engines of the same series in the conditions of their mass production. Methods of mathematical statistics and hardware-software modeling were used in the study. The term “unerroric of quality mutual compliance control” is introduced to describe a set of hardware and software tools for such control. The principle of in-depth testing of the technical condition of such engines of one series is described in a multidimensional formulation of the quality control problem for three of their operating parameters at once. The conditions for increasing the mutual correspondence of the measured values of such parameters in the conditions of serial production of hydrogen engines are formalized.     

中国煤炭地下气化技术的发展

本文综述了煤炭地下汽化技术的国内外发展现状,对我国“长通道、大断面”煤炭地下气化新工艺给予了技术经济评述,并提出了发展煤炭地下汽化技术的政策建议。     

Review of theory of distortion and disintegration of liquid streams

Linear and nonlinear analyses of the instabilities and distortion of liquid streams injected into a gaseous media are discussed. The various fundamental mechanisms and the predictive capabilities for the distortions are emphasized. Round jets, planar sheets, annular sheets, and conical sheets are discussed in detail. The balance between capillary and inertial forces is primarily examined. The method for simplifying the analyses in the case of thin liquid sheets is discussed. The capabilities for representing the droplet size distribution that follows the stream disintegration are outlined.     

MgO膨胀剂细度对MgO水化和水泥浆体膨胀的影响

基于《水工混凝土掺用氧化镁技术规范》中的Ⅰ型氧化镁（MgO）,研究了该型MgO膨胀剂（MEA）细度对掺粉煤灰水泥浆体膨胀性能的影响。即采用X射线衍射分析(XRD)及同步热分析（TG DSC）分析了掺MEA水泥浆体中MgO的水化性。结果表明,养护温度相同时,MEA的细度对水泥浆体内MEA中MgO的水化和水泥浆体的膨胀无显著影响,产生的膨胀均能补偿水泥浆体的收缩;MEA的细度可从试验设计采用的45 μm筛筛余15%左右增加到30%左右,这将有利于MEA生产企业的节能降耗。     

机车车轮多轴疲劳强度安全评定的研究

使用ANSYS8.0软件对高速列车车轮进行了三维有限元分析,计算出车轮在直线、曲线和道岔条件下牵引、制动共6种工况时孔边薄弱部位的应力,分别通过Mises等效平均应力方法、Sines平均主应力方法和应力分量中考虑平均应力方法计算出应力在极值位置时的等效应力幅、等效平均应力,从而进一步算出车轮的安全系数,对其疲劳强度进行评定,并对3种方法进行了比较研究。     

Constructal optimization of the geometry of an array of micro-channels

This paper documents the geometric optimization of an array of circular and non-circular ducts. The optimization was carried out numerically using finite volume method. As optimal dimensions were independent of the array configuration, the numerical simulation was performed on a unit cell. Numerical optimization for circular, square and isosceles right triangle cross-sections of channels was performed. Based on the results of this investigation, some correlations were proposed to predict the optimal hydraulic diameter and dimensionless heat transfer per unit volume. In addition to examining the effect of pressure drop on these parameters, it was showed that among the different geometries of this study, square cross-section has the most efficiency for a given volume. The numerical results of the present study were compared with approximate results reported in the literature which a good agreement was observed.     

固体热辐射Yong性能分析

本文对漫灰均温物体在常物性条件下对外辐射传热的Ｙｏｎｇ值计算建立了数学模型。通过与物体内能Ｙｏｎｇ公式的数值计算比较,得出了辐射能量的Ｙｏｎｇ值不大于内能Ｙｏｎｇ值的结论。从初步的热射Ｙｏｎｇ值计算公式发现。Ｙｏｎｇ与物体表面辐射率有关。     

Measurements of concentration distribution of hydrogen jet using deflection of center of the laser spot

The main purpose of this work is to propose a new method to evaluate the concentration distribution of the hydrogen jet by using a He–Ne laser through the jet. This research attempts to apply the expression of concentration Gaussian distribution, the refraction formula of inhomogeneous refractive index medium, and the concentration inversion function to disclose the displacement of the center of the laser spot at different heights in the gas jet. The spot images of the laser beam passing through the gas jet at three vertical heights z = 10d, 20d, 30d, and different radial positions are obtained. The radial spatial asymmetry of the gas jet is also found in the experiment. Finally, the calculated concentration distribution curve and the fluent simulation curve, it is found that the two results are very similar. Our findings show that the error between the concentration distribution of this method and the simulated concentration distribution reaches 2.43%.     

Heat of vaporization of mixtures

General expressions for the heat of vaporization of mixtures at constant pressure; at constant temperature; and at constant pressure, temperature, and composition are proposed. The last one is related to the liquid-vapor interface where steady vaporization or condensation is taking place. Numerical examples by the proposed expressions are shown for binary mixtures of HCFC22(R22) and (HCFC123(R123) © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(1): 12–24, 1996