氧化钙添加剂对烟气中汞分布的影响

在一个大气压下,273．15～l273．15K温度范围里,采用化学热力平衡分析方法研究了煤燃烧过程中CaO和HCl对痕量元素汞的形态及分布的影响。化学热力平衡分析结果表明,在煤燃烧的最高温度区域里,单质汞是汞的主要形式。随着在烟气中温度的降低,单质汞将发生化学反应而生成二价汞的化合物,其中主要是HgCl2(g);预测结果还表明氯元素的增加可以增强汞元素的蒸发、排放,而CaO(s)对汞元素在烟气中的行为特性的影响不大。尽管化学热力平衡分析结果与实验结果之间存在较大差异,但是通过与实验结果的比较,仍可以推断CaO(s)主要是通过减少灰粒表面积或改变飞灰矿物学和形态学特性影响烟气中汞元素分布特性。     

燃煤过程中易挥发有毒痕量元素的相互作用

采用化学热平衡分析方法研究了煤中最易挥发的有毒痕量元素汞、砷和硒在煤燃烧过程中的化学形态及分布,着重考虑了痕量元素和氯元素之间、多种痕量元素之间的相互作用.在300～2000K温度范围内,考察了痕量元素在还原性气氛和氧化性气氛的烟气中的化学形态和物理相.结果发现,在燃煤过程中,汞、硒、砷三种痕量元素的挥发性大小依次为汞＞硒＞砷;氯元素能大大增强汞的蒸发,而对硒和砷的蒸发影响不大.     

煤裂解或燃烧条件下汞的析出规律研究

进行了加热时间、反应条件、煤种等因素影响煤中汞析出规律的试验研究。首先对煤样裂解或燃烧产物中残留汞进行分析，发现煤中汞在燃烧条件下能很快析出，而在裂解时则析出相对缓慢。其次利用管式炉系统，在还原性气氛（载气为氮气）或氧化性气氛（载气为氮、氧体积比为4：1的混合气体）下进行煤样裂解或燃烧后汞的析出及形态迁移转化试验。研究认为，煤在裂解或燃烧后，汞主工以气态方式进入烟气，烟气中的汞主要以二价汞（Hg^2 ）和零价汞（Hg^0）形式存在，且汞的形态分布与反应条件和煤种有关。随加热温度升高，烟气中的二价汞含量升高，零价汞含量降低；裂解与燃烧相比，燃烧时零价汞被氧化的程度更高。     

溴元素对烟气中汞的形态和分布的影响

采用化学热力平衡分析方法研究了煤燃烧过程中溴对烟气中痕量元素汞的形态及分布的影响.在一个大气压下,25～825℃温度范围内,研究了汞-煤-溴系统中高氯煤和低氯煤在添加溴前后汞化学形态和分布的变化,着重探讨了溴对汞在烟气中的形态和分布的影响.对于高氯煤,当烟气中加入溴后,氯化汞的分布区域明显受到了抑制;而对于低氯煤,氯化...     

燃煤过程中元素Na和Fe在可吸人颗粒物中的形态与分布

通过对平顶山烟煤在沉降炉内的燃烧试验,结合热力学平衡计算分析,研究了两种选定的矿物质成灰元素Na和Fe在可吸入颗粒物中的形态与分布。燃烧试验条件为:煤粉粒径小于63μm,燃烧温度在1400°C,炉内燃烧气氛为空气气氛。试验采用低压撞击器(LPI)按不同粒径大小从0.03~10μm共分为13级,分别采集燃烧后的可吸入颗粒物。并采用热力学平衡计算分析方法研究了氧化性气氛中元素Na和Fe的化学形态和物理相。试验和计算结果显示:钠元素主要以Na单质的形式气化,大部分以NaO、Na2SO4、NaCl、Na3PO4的形式存在于亚微米颗粒中,极少量以NaAlSi3O8相存在于PM1.0-10中;Fe元素主要以FeO的形式气化,部分以Fe2O3的形式存在于亚微米颗粒中,部分以Fe3O4和Fe2O3的形式存在于PM1.0-10中。图1表2参6     

燃煤过程中痕量重金属的形态与分布研究

采用化学热平衡分析方法研究了不同煤种的燃烧过程中痕量元素的化学形态及其分布。选用的煤种为河南平顶山烟煤、河南焦作无烟煤和贵州六盘水贫煤3个煤种,分析的痕量元素为Pb、Cd和Cr3种痕量重金属元素。在400K～2000K温度范围内,比较讨论了3种元素在氧化性和还原性气氛中的化学形态和物理相。结果表明:在燃煤过程中,Pb、Cd和Cr都是不易挥发的元素,他们的挥发性大小依次为Cd>Pb>Cr;在还原性气氛下,高温时主要以气态单质存在;烟煤与贫煤的分析结果一致,而无烟煤的分析结果在低温时存在差异。图6表3参5     

燃煤汞形态分布和排放特性研究

概述了燃煤烟气中汞的形态(元素态,氧化态和颗粒态)分布规律,综述了烟气温度和组分、烟气中硫和氯元素、燃煤飞灰、除尘和脱硫设备对汞形态分布的影响规律。分析了煤气化和燃烧过程的气体产物中汞形态转化的条件,以及烟气中硫和氯元素对汞排放的影响。指出除尘和脱硫设备的应用能有效地促使元素汞向氧化汞的转化,并提高汞的脱除效率。     

循环流化床内污泥与煤混烧时汞的浓度和形态分布

在循环流化床燃烧试验台上进行了污泥与煤的混烧试验,研究了污泥与煤的质量掺混比、燃烧温度、Ca/S摩尔比、脱硫剂种类以及过量空气系数等对重金属汞在烟气、飞灰和炉渣中的形态、浓度分布的影响.结果表明,元素汞是烟气中汞的主要存在形态,运行参数对烟气和灰渣中汞的浓度和形态分布均有较大的影响.     

烟气汞形态分布及其受氯化物添加剂影响的研究

在自行设计的一维煤粉燃烧试验台上,研究了烟气汞形态的分布特征,并分析了NaCl作为添加剂与煤混烧对汞形态分布的影响.结果表明:在试验煤种烟气中,气态汞是烟气汞最主要的排放形式,二价汞是气态汞的主要形式,飞灰中的汞含量比底渣中的汞舍量高;NaCl的添加使气态二价汞和单质汞占总汞的百分比都有不同程度的下降,而颗粒态汞的比例相应增加,但随着NaCl添加量的增加,颗粒态汞的增加量逐渐趋于平缓,单质汞的减少量也相应降低,趋势趋于平缓.     

模拟烟气中Hg排放形态的数值分析

为了深入研究燃煤Hg排放控制技术,在分析Hg形态转化过程及其影响因素基础上,通过控制变量法设定模拟烟气组分(HCl、O_2、NO、H_2O、CO_2和SO_2)的初始浓度值,利用化学动力学计算软件Chemkin进行数值模拟.结果表明:Cl原子的存在会促进单质Hg(Hg~0)向氧化态Hg转化,在一定范围内增加HCl的量有利于Hg的氧化;O_2会促进Hg的氧化但作用不如HCl明显;根据其所处的烟气气氛,NO既能促进Hg的氧化也能抑制Hg的氧化,在氧化性气氛中,NO的存在会提高Hg的氧化率;H_2O有利于Hg的氧化,而CO_2的存在会造成局部很强的还原性气氛,会抑制Hg的氧化;在不同条件下,SO_2可以促进或抑制Hg氧化.     

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