燃煤过程痕量元素动力学机理的研究进展

由于痕量元素在煤中的含量低微、检测困难,加之其原子量一般较大,可能的反应途径多,使得相关的反应机理研究难度极大。本文结合作者的研究成果,介绍了煤燃烧过程中痕量元素化学反应动力学的国内外研究进展,包括痕量元素化学动力学机理的建立;相关的典型实验、计算模拟及其实验验证、动力学机理模型的简化;痕量元素反应动力学机理的完善和发展,包括采用简单碰撞理论、活化络合物理论(亦称过渡态理论,或绝对反应速率理论)对痕量元素化学反应动力学机理的修正;最后指出煤燃烧过程中痕量元素动力学研究的若干方向是: (1)痕量元素反应动力学模型数据库的建立;(2)煤燃烧过程中,主量元素和次量元素的动力学机理的完善; (3)各痕量元素之间动力学研究的开展; (4)实际燃烧过程中痕量元素动力学行为的研究。     

燃煤易挥发微量重金属元素行为的试验研究

为了解煤燃烧过程中易挥发微量重金属元素的行为及其控制因素,对黔西南烟煤和无烟煤进行了层燃实验和流化床燃烧实验。结果表明,层燃实验,煤中Hg在150℃挥发率达50.25％。到815℃几乎全部释放,Se的挥发率平均在98％以上。950℃下煤中As、Sb的挥发率平均为36.77％和34.47％。流化床燃烧,煤中绝大部分Hg以气态排放到大气中,部分Se以气态排放;微细颗粒吸附Hg、Se、As和少量的Sb以吸附态排放。赋存状态、燃烧方式以及燃烧工况等对微量重金属的挥发性有明显的控制作用。     

O2/CO2煤粉燃烧时细灰颗粒中痕量元素分布特性的实验研究

通过三个煤种在沉降炉中的燃烧实验,采用X-射线荧光光谱仪对实验收集的细灰颗粒物的元素组成进行定量测定,研究了O2/CO2煤粉燃烧对痕量元素行为的影响.结果表明,与O2/N2燃烧相比,O2/CO2燃烧对LPI颗粒物中Cu、Zn和Mn元素的分布形式没有影响,但显著增加了Cu、Zn元素在亚微米颗粒中的富集程度, Mn元素住细灰颗粒上没有出现富集,但O2/CO2燃烧时Mn在亚微米和超微米颗粒中的含量均显著减少.     

铁系矿物对煤灰相变过程的内在影响规律研究

为深入研究煤燃烧与煤气化过程中煤中矿物的熔融变化行为对煤灰物理相变变化过程的内在影响规律,本文采用高温热显微镜、SEM-EDX等分析测试手段,实验研究了不同条件(煤燃烧与煤气化)下煤中矿物演变规律与煤灰物理相变变化行为间的内在联系和影响规律。研究结果表明:高铁含量的煤灰A在气化条件下发生初始熔融温度(T_(in))及快速熔融温度(T_(max))要比其在燃烧条件下对应的温度分别低144℃和113℃,而低铁含量的煤灰B则对应气化条件下的T_(in)和T_(max)分别比燃烧条件下的对应温度低25℃和62℃;不同气氛下灰中Fe的不同价态是导致这种差别的主要原因,高温下煤灰相变发生、发展过程中,灰中方铁石、铁铝榴石以及铁做榄石等铁系矿物是引发煤灰发生初始熔融的主要矿物。     

煤在燃烧过程中表面灰层内气体扩散传质特性的研究

煤在燃烧过程中表面灰层内气体扩散传质特性的研究严建华，倪明江，张宏焘，岑可法（浙江大学能源工程系杭州３１００２７）关键词：灰层扩散，煤燃烧，孔隙率一、引言就流化床燃烧锅炉通常燃用的较大粒度的煤而言，其焦碳的燃尽时间占了煤粒燃尽所需时间的绝大部分，粗略...     

燃煤锅炉中痕量元素排放因子的研究

目前国内外对煤燃烧过程中痕量元素的排放和控制作了大量的研究工作,但是对痕量元素的排放因子的研究却鲜见报道。本文通过实验数据和一些经验数据对痕量元素排放因子进行了研究,了解了燃煤电厂锅炉容量和负荷对痕量元素排放因子的影响,并考察了除尘装置及脱硫装置等与痕量元素排放因子的关系,结果发现大容量锅炉痕量元素排放因子要相对小一些,且随着负荷降低,痕量元素排放因子会增加。     

刚玉床料对高钠煤循环流化床气化中钠迁移转化的影响

选择刚玉作为床料,利用循环流化床对天池木垒煤进行了气化实验研究,研究了刚玉对失流的抑制作用、矿物元素在不同粒径颗粒中分布以及煤中Na经过气化反应后的迁移转化规律。研究结果表明,以刚玉作为床料会降低底渣表面包覆层黏性,避免颗粒聚团导致失流;在刚玉诱导下,煤中Al、Si、Ca、Fe、Na和Mg等绝大多数矿物质元素在底渣和循环灰中富集,并导致物料粒径不断增大;935℃床温下(以刚玉为床料),天池木垒煤中Na在底渣、飞灰和煤气中的分布率分别为39.6%、45.4%和15%,相对于以石英砂为床料的情形,刚玉有效抑制了Na的挥发,降低了尾部沾污发生的机率;在刚玉作用下,固留在底渣中的Na主要以NaAl_(11)17、NaAlSi_2O_6和NaAlSi_3O_8等形式存在,并且刚玉与煤中矿物质元素反应生成的物质具有较高的熔点,避免低温共熔现象发生。     

氧燃烧方式下矿物质与重金属行为特征的研究

在沉降炉试验台上,进行空气气氛及O2/CO2气氛燃煤试验,通过X射线衍射分析和ICP-AES分析研究了不同气氛下煤灰中矿物质组成及痕量元素的挥发特性.并根据热力学多相平衡原理对矿物质与重金属在两种气氛下的挥发行为进行了计算和比较分析.结果表明,氧燃烧气氛下的矿物质组成与空气气氛下并无明显不同,矿物质元素的蒸发气化亦没有受到明显的影响,但在氧燃烧气氛下矿物质的晶相向非晶相的转化得到了较大改善,有可能使电站锅炉沉积得到缓解;氧燃烧气氛下灰中痕量元素相比空气气氛下在底灰中有明显的富集.     

PM2.5和PM10排放的一维炉煤燃烧实验研究

我国煤烟污染十分严重。燃煤排放的PM10和PM2.5表面富集了大量的有毒痕量元素,进入大气后,对环境的危害极大。本文在一维炉中对不同煤种分别在650℃,850℃,950℃下燃烧PM的排放进行实验研究,发现PM10和PM2.5的排放量随温度升高有增加的趋势;随煤种含S量的增加,其排放量也增加;随着煤灰分的增加,PM10和PM2.5的排放量也有增大的趋势,煤中矿物质的种类和形态对其排放有明显的控制作用。     

氧燃烧方式下痕量元素形态转化的试验和模拟研究

结合热重试验及XRF测量,采用化学热平衡分析方法对煤中易挥发的有毒痕量元素砷、铬、锑和汞在不同燃烧方式下的化学形态及分布进行了研究。计算表明,在常规燃烧方式下,痕量元素在400-1800 K的温度范围内容易蒸发,生成气相单质或氧化物。富氧燃烧条件下,高浓度的CO2(g)以及碳颗粒温度的降低在一定程度上会抑制痕量元素的蒸发,同时CO2(g)也会抑制痕量元素向气相次氧化物及单质的转化。     

单脉冲BOXCARS技术在瞬态燃烧场测温中的应用

 用单脉冲交叉相干反斯托克斯喇曼散射技术测量了两种不同固体燃剂的瞬态燃烧场的温度。对燃烧场进行了优化，给出了在燃烧场中取得的部分典型单脉冲CARS光谱及其理论拟合结果，得到了燃烧场的温度及其随高度的分布；稳定燃烧时两种燃剂燃烧场的温度基本保持不变，平均值分别为2 260，2 090K；测量了实验的纵向空间分辨率。结果表明，BOXCARS技术能较好地完成复杂的瞬态燃烧场温度的测量工作。     

FTIR遥测固体推进剂燃烧温度

应用遥感FTIR对固体推进剂燃烧火焰的温度进行了研究。遥感FTIR光谱仪在光谱分辨率为4cm^-1时,连续收集燃烧火焰的发射光谱。分别利用分子基带转振光谱测温法,以及分子发射光谱最大强度谱线测温法,对燃烧温度进行了遥感实时测定。文中列出了两种方法测得的各时刻的火焰温度。结果表明。两种方法在测量快速、剧烈燃烧的火焰温度时,都是很可靠的方法,当火焰的燃烧比较稳定时,分子发射光谱最大强度谱线测温法更为简便、快速。     

Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C11H17NO（s）

This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.     

注蒸汽燃气轮机燃烧室和后燃室中燃料系数的计算方法

注蒸汽燃气轮机燃烧室和后燃室中燃料系数的计算方法杨玉顺，周伏秋，严家（哈尔滨工业大学动力工程系哈尔滨１５０００１）关键词：注蒸汽燃气轮机循环，湿燃气，燃料系数，注蒸汽比一、前言燃气轮机燃烧室（或后燃室）出口的燃气温度，是一个很重要的性能参数。它受设备...     

Interactions of potassium vapor with reactor tubes made of different materials and their impacts on particulate matter emission during pulverized biomass combustion

During the combustion of biomass in drop-tube furnace (DTF) systems, the released alkali metal (e.g., potassium, K) inevitably reacts with reactor tube at high temperatures, affecting the experimental results on the emission of particulate matter with aerodynamic diameters of <10 μm (PM₁₀). This study reports the interactions between K vapor and tube reactors made of silicon carbide, corundum, and mullite and their impacts on PM₁₀ emission. Demineralized wood samples loaded with potassium chloride (KCl) or ion-exchanged K respectively were combusted in a DTF at 1300 °C under air or oxy-fuel atmosphere. Another series of experiments was conducted to collect and analyze the PM₁₀ from the combustion of KCl-loaded wood, K-exchanged wood, and two typical biomass samples (cotton stalk and wheat straw) in the three reactor tubes under air atmosphere. Experimental results show that 4.1‒72.5% of K is retained in the three tubes when burning the KCl-loaded wood in air, and the combustion in oxy-fuel atmosphere slightly increases the K retention. For K-exchanged wood combustion in air, only 3.7‒23.6% of K is released from the reactor tubes. In all conditions, the reactivity of the reactor tubes with K vapor follows a sequence of mullite > corundum > silicon carbide. The retained K is unstable, 49.0‒64.8% of which can be re-released during polyvinyl chloride combustion. In addition, the results demonstrate that, compared with silicon carbide tube, the use of corundum and mullite tubes leads to a 16.2‒54.3% decrease in PM₁ yields and a significant drop in fine mode peaks in PM₁₀ during the combustion of biomass samples in air, while the PM_1–10 yields and the coarse mode peaks remain largely unchanged. These are attributed to the enhanced retentions of alkali metals in corundum and mullite tubes, which reduce the yields of Na, K, and Cl in PM₁₀, but has negligible effect on those of refractory elements such as Mg and Ca.     

Velocity of deflagration combustion at high pressures and temperatures

The article presents additional calculated data on combustion velocity for typical gas mixtures at pressures up to 6000 atm and temperatures up to 4000 K. It was determined that combustion velocity is mainly influenced by initial temperature, and the dependence on pressure is rather low. For fuel-oxygen and air-fuel mixtures in three-dimensional space (pressure-temperature-velocity of deflagration combustion), we have found a single surface of combustion velocities and continuous dependence of flame velocity on initial conditions.     

External combustion of high-speed multicomponent hydrocarbon-air flow under conditions of low-temperature plasma

The stabilization of external combustion (at the plate surface) of high-speed multicomponent (air, alcohol, and propane) flows is realized experimentally. It is shown that heat fluxes during alcohol combustion rise by a factor of about 7 and during propane combustion by a factor of 15, in comparison with the heat flux from a discharge in a high-speed air flow. The electron concentration measured at a distance of 10 cm down-stream from the electrode ends is approximately 10⁹ cm^?3 in the case of the discharge in an air flow, whereas during alcohol combustion it attains 2 × 10¹¹ cm^?3 and during propane combustion it is 3 × 10¹¹ cm^?3. The flame temperature in the area of the discharge existence varies from 2000 up to 2500 K and outside the discharge at the distance of z = 20 cm from electrodes is 1800 K, gradually decreasing downstream. It is shown that the combined discharge in the subsonic flow allows for complete combustion of liquid and gaseous hydrocarbons. The completeness of combustion in supersonic flows attains 95%, depending on the flow velocity.     

Single particle ignition and combustion of pulverized pine wood,wheat straw,rice husk and grape pomace

This work examines the combustion behavior of single pulverized biomass particles from ignition to early stages of char oxidation. The biomass residues investigated were pine wood, wheat straw, rice husk and grape pomace. The biomass particles, in the size range 224–250 µm, were injected upward into a confined region with hot combustion products, produced by a flat flame McKenna burner, with a mean temperature of 1610 K and a mean O₂ concentration of 6.5 vol%. Temporally and spectrally resolved images of the single burning particles were recorded with an intensified charge-coupled device camera equipped with different band-pass spectral filters. Data are reported for CH*, C₂*, Na* and K* chemiluminescence, and thermal radiation from soot and char burning particles. The data on CH* and C₂* chemiluminescence and soot thermal radiation permits to identify important differences between the ignition delay time, volatiles combustion time and soot formation propensity of the four biomass residues, which are mainly affected by their volatile matter content. The Na* and K* emission signals follow the same trends of the CH* and C₂* emission signals until the end of the volatiles combustion stage, beyond which, unlike the CH* and C₂* emission signals, they persist owing to their release from the char burning particles. Moreover, during the volatiles combustion stage, the Na*/CH* and K*/CH* ratios present constant values for each biomass residue. The CH* and thermal radiation emission data suggest that all biomass char particles experienced heterogeneous oxidation at or immediately after the extinction of the homogeneous volatiles combustion.     

Analysis of Aluminum Dust Cloud Combustion Using Flame Emission SpectroscopySCIEI北大核心CSCD

In this study, aluminum flame analysis was researched in order to develop a measurement method for high-energy-density metal aluminum dust cloud combustion, and the flame temperature and UV-VIS-IR emission spectra were precisely measured using a spectrometer. Because the micron-sized aluminum flame temperature was higher than 2 400 K, Flame temperature was measured by a non-contact optical technique, namely, a modified two-color method using 520 and 640 nm light, as well as by a polychromatic fitting method. These methods were applied experimentally after accurate calibration. The flame temperature was identified to be higher than 2 400 K using both methods. By analyzing the emission spectra, we could identify AlO radicals, which occur dominantly in aluminum combustion. This study paves the way for realization of a measurement technique for aluminum dust cloud combustion flames, and it will be applied in the aluminum combustors that are in development for military purposes.     

Characterization and luminescence of Eu/Sm-coactivated CaYAl3O7 phosphor synthesized by using a combustion method

A novel red-emitting phosphor, CaYAl3O7 : Eu 3+ , Sm3+ , is synthesized by a combustion method at a low temperature (850℃), and the single phase of CaYAl3O7 is confirmed by powder X-ray diffraction measurements. The photoluminescence property results reveal that the red emission intensity of Eu3+ is strongly dependent on the Sm3+ concentration. Only the Eu 3+ luminescence is detected in the Eu 3+ -Sm3+ co-doped CaYAl3O7 phosphor with 393 nm excitation. However, under the characteristic excitation (402 nm) of Sm3+ , not only the Sm3+ emission but also the Eu 3+ emission are observed. A possible mechanism of the energy transfer between Sm3+ and Eu 3+ is investigated in detail.