掺混比对半焦与烟煤混合燃烧及NO_x排放特性影响的试验研究

在350 kW中试煤粉锅炉上研究了热解半焦掺混比对神华烟煤与神木半焦混合燃烧时着火特性、燃尽特性以及NO_x排放特性的影响,测量了不同轴向位置处炉膛温度以及O_2体积分数、CO体积分数和NO_x质量浓度等参数。结果表明:随着掺混比的增大,着火性能变差,着火距离增加且着火温度升高,主燃烧区出口NO_x质量浓度逐渐增大;采用EGA气体释放法分析燃料着火点时,CO释放法对掺混比为60%和100%的燃料适合,NO_x释放法在分析高挥发分烟煤的着火时效果更好;纯半焦燃烧时燃尽率最低,掺混高挥发分烟煤对整体燃尽有较大改善。     

三种催化剂对半焦燃烧特性的影响

用热天平研究了四种半焦的燃烧特性,结果表明：添加催化剂制得的半焦具有较好的反应活性。炭燃烧反应前需要吸附的氧量也相对较小,具有较小的ＭＩ值;并通过燃烧动力学计算发现添加氧化钙制得的半焦燃烧活性最高;最后,提出了平均活化能的概念来作表示半焦燃烧活性的一个指标,提出了平均活化能的概念来作表示半焦燃烧活性的一个指标,并与其它研究者提出的可燃性综合指标Ｓ进行了比较。     

半焦粒子着火与燃烧过程实验研究

实验研究了半焦粒子着火与燃烧过程,测定了几种尺寸的半焦粒子在不同环境温度下的着火温度、着火滞燃期、燃尽时间和燃烧过程中的粒子温度等与燃烧过程相关的参数变化,对影响半焦粒子燃烧的因素进行分析讨论,并将实验结果与理论计算结果进行了对比分析,两者在一定范围内有较好的一致。     

典型煤质富氧着火特性试验研究

针对火电机组低负荷条件下燃烧不稳定等问题,采用哈尔滨锅炉厂有限责任公司煤燃烧特性试验炉对三种典型煤质进行不同富氧条件下的着火特性试验。试验结果表明:随着一次风氧气浓度增加,三种煤质着火温度都有所降低,但半焦(SH)着火温度降低幅度较小,而贫煤(XY)和烟煤(HB)着火温度降低幅度都呈现先大后小的趋势。此外,通过比较三种煤质着火温度,发现贫煤着火温度明显高于其他两种煤质,而烟煤除了在一次风氧气浓度为21%条件下着火温度高于半焦,其他工况下都低于这两种煤质。本次研究为今后火电机组低负荷稳燃和灵活性改造提供依据和数据。     

中温下热解对半焦燃烧反应性的影响

用热天平（TGA）和粉末X射线衍射方法（XRD）分别测量了两种低变质程度烟煤和一种无烟煤的半焦在400-1400℃热解过程中燃烧反应性及其结构的变化，探讨了低变质煤的反应性变化的原因。研究发现，半焦反应性下降主要与热解过程中半焦晶格化与矿物质催化作用的逐渐消失有关，温度低于900℃，原煤脱去大部分挥发份形成的半焦进一步热解时，晶格化现象不很显著，但反应性明显下降，反应性的降低主要与煤中矿物质在热解过程中的失活有关。     

热解温度对生物质半焦特征的影响

对稻壳和稻秸进行了机理性热解试验,并采用TG、SEM、EDS和XDR方法研究和分析了半焦的孔隙结构、结渣特性、氯和硫元素迁移和无机化合物晶相等物化特性的变化规律．结果表明：在500～800℃,生物质热解半焦孔隙结构的变化较大．当热解温度为1000℃时,稻壳半焦的凸面呈现熔融现象,稻秸半焦呈现熔融黏结现象．在800～1000℃,半焦中剩余的氯和硫大部分会析出;在稻壳和稻秸热解过程中,当终温为1000℃时,物相发生较大变化并且出现非晶态的无机化合物．     

生活垃圾燃烧特性实验研究

选取了城市生活垃圾中的厨余、纸张、织物、含氯塑料和不含氯塑料，进行元素分析、工业分析和热重分析，并在此基础上进行了几种垃圾混合物的燃尽实验。实验结果表明：生活垃圾的着火温度、活化能明显低于混合烟煤。而且塑料的燃烧规律与其它垃圾样品有显著区别。实验发现，随条件的不同，垃圾燃烧过程中会不同程度地产生CO、SO2和NOx，因此需要合理的燃烧组织，以降低污染的排放。     

气化半焦加压着火特性及燃烧稳定性研究

在单炉膛双吊蓝加压热重分析仪上对气化半焦的加压着火特性和燃烧稳定性进行了较为系统的试验和理论研究，考察了半焦种类、总压、氧浓度、粒径和加热速率等因素对半焦着火特性和燃烧稳定性的影响规律。并以纯碳测试数据为基准，提出了燃烧稳定性的判别指数RW。研究表明，半焦的挥发份含量、固定碳含量以及孔结构是影响半焦着火温度的主要因素。随着总压和氧浓度的提高以厦粒径的减小，半焦的着火温度下降，燃烧稳定性提高；随着加热速率的增加，半焦的着火温度明显上升。     

热解终温度对生物质半焦结构特性的影响

利用固定床制备不同终温生物质半焦。对所制半焦采用热重分析仪、扫描电镜、比表面积及孔径分析仪对半焦孔隙结构、在固定床中反应过程、半焦孔隙结构变化规律等进行分析,对所得实验数据采用分型FHH方程对进行拟合计算。结果表明:热解制焦终温越高,燃烧过程中半焦碳转化率越低;所制取的终温为600℃的半焦,表面最粗糙,孔隙最大;热解制焦终温越高,半焦表面越粗糙,半焦吸附性能越强,且分形维数D_(FHH)越大。     

O_2_CO_2气氛下痕量元素迁移特性试验研究

在管式炉上进行徐州烟煤的燃烧试验,采用电感耦合等离子体光谱质谱联用仪(ICP-MS)对燃烧剩余灰渣进行测定.研究了不同温度和不同燃烧气氛(空气气氛和O2/CO2气氛)下痕量元素的迁移特性.结果表明,煤燃烧过程中,痕量元素Cr、Mn、Ni、Zn、Cd、Pb在灰渣中富集,As挥发率达70%以上.随着温度的升高,大部分痕量元素在灰渣中的含量降低,Mn、Ni、Cr在灰渣中的含量相对比较稳定.O2/CO2气氛下,各元素随温度的变化趋势并未受到影响,但整体上O2/CO2气氛下各痕量元素在灰渣中的含量要大于空气气氛下的,随着温度的升高,O2/CO2气氛和空气气氛下痕量元素在灰渣中的含量越来越接近,说明燃烧气氛对痕量元素迁移的影响随温度升高而减弱.     

Characterization of Egyptian semi-cokes using Mössbauer spectroscopy at room temperature

Well characterized, an Egyptian coal sample (EM-87) has been carbonized in an Argon atmosphere of pressure 10⁵ Pa at different temperatures from 700–1000 K. The analysis of the Mössbauer spectra collected at room temperature for the produced semi-cokes, showed that pyrite FeS₂ was starting to be transformed to pyrrhotite Fe_1-xS at 700 K. This transformation was found to be increased when the pyrolysis temperature was increased.     

O_2/CO_2气氛下生物质半焦加压燃烧特性的实验研究

利用Thermax500加压热重分析仪（PTGA）,研究了压力对木屑半焦富氧燃烧反应特性的影响。结果表明,压力从0 MPa升高到1.0 MPa,半焦燃烧反应向低温方向移动,反应速率加快,促进了燃烧反应的进行。压力由1.0 MPa继续升高,其对燃烧的促进作用减弱。当压力由1.3 MPa升高到1.6 MPa时,半焦燃烧反应反而向高温方向移动,同时反应速率减慢,过高的压力对燃烧反应起抑制作用。     

Process and product characteristics for carbonization of liquid–solid mixtures from coal liquefaction

In this paper, a carbonization process for valid liquid–solid separation and upgrading of coal liquefaction residues was proposed and practiced using batch-type devices. The effect of carbonization times and temperatures on the efficiency of liquid–solid separation and product distributions were investigated using self-prepared liquid–solid mixtures (CSMs) from direct coal liquefaction. It was suggested that the carbonization temperature and blowing gases were essential to the efficient liquid–solid separation in this process, and the carbonization process was characterized by the efficient liquid–solid separation. The n-hexane soluble fractions (HS) can be largely separated from CLMs. It was remarkable that over 0.06–1.50% of HSs can be additionally produced at the higher temperatures (430 °C–500 °C). On the other hand, the obtained semi-cokes (SCs) were mainly characterized as a rich carbon-containing material with high heating values. Some of the SCs were characterized by the better caking property with the caking index (G) from 68.5 to 75.2. In addition, it was proved that the caking property of SCs is directly affected by the asphaltenes (ASs) instead of pre-asphaltenes (PAs).     

Analysis and application of variable conductance heat pipe air preheater

The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature trans-fer matrix was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could be easily calculated for a given air preheater and inlet fluid temperatures. The active length of condenser in a variable conductance heat pipe is determined according to the flat interface model. With the same initial conditions, the comparisons between variable conductance heat-pipe air preheater and regular heat pipe air preheater has been analyzed and tested in terms of heat pipe wall temperature, heat transfer surface area and outlet fluid temperatures. Based on the real industrial applications, it has been confirmed that the variable conductance heat pipe air preheater has excellent performance of anti-corrosion and anti-ash-deposition especially at the variable working condition and the sulfur coal (5%-6% mass fraction of sulfur) condition.     

Comparing product distribution and desulfurization during direct pyrolysis and hydropyrolysis of Longkou oil shale kerogen using reactive MD simulations

The product distribution and organic sulfur removal during direct pyrolysis and hydropyrolysis of oil shale kerogen were investigated via reactive molecular dynamics (RMD) simulations with reactive force field (ReaxFF). Two structural models for direct pyrolysis and hydropyrolysis of kerogen were constructed about kerogen extracted from Longkou oil shale to investigate the impact of H₂ at different temperatures on the product distribution and reaction processes of oil shale. The experimental results show that hydropyrolysis could increase light shale oil (the most important product in shale oil industry), and improve the removal rate of organic sulfur simultaneously. It was found that comparing to the direct pyrolysis, hydropyrolysis can provide more H free radicals to participate in the reaction and therefore promoting the pyrolytic reaction of kerogen. In addition, hydropyrolysis greatly promoted the desulfurization due to the contribution to the production of H₂O molecules, and the transfer of sulfur to the gas products requires the participation of H₂O molecules. This work is an intensive study on hydropyrolysis mechanism at different temperatures at the atomic level. These conclusions could be helpful for the clean utilization technology of oil shale industry.     

Microwave-enhanced pyrolysis of Yunnan lignite for improving rich hydrogen syngas production

This study aimed to obtain the maximum possible gas yield and the high-quality syngas production from microwave pyrolysis of lignite. The microwave pyrolysis experiments have explored the influence of the using of microwave stir device and different coke ratios on gas production rate and gas yield. The results show that the influence of microwave stir device on both gas production rate and gas yield was substantial. Adding appropriate semi-cokes can accelerate the lignite microwave pyrolysis rate, and increase the production of gas.     

Ash transformation and deposition characteristic during straw combustion

The main objective of this study was to determine ash transformation and deposition characteristic for three types of straw (corn straw, oat straw, and rice straw) combustion at temperatures between 500 and 1000°C. The collected deposits on the sampling probe were characterized with X-ray diffraction and scanning electron microscopy combined with energy dispersive X-ray analysis. The results indicated that the ash forming processes of straw were influenced by fuel composition and temperature. The quantity of corn straw ash collected from deposition probe was noticeably lower than that of oat straw and rice straw due to different contents of K, S, and Si in fuels. The deposition amounts of corn straw and oat straw followed a linear pattern at temperatures below 800°C, while rice straw followed a nonlinear pattern as a function of temperature. Corn straw was an ideal fuel compared to oat straw and rice straw from the points of deposition amounts and appearance. It also can be found that silicon, calcium, potassium, and sulfur were key points in the forming process of ash deposits.     

Combustion Characteristics of 24 Lignite Samples

Abstract

In this study, the combustion characteristics such as thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), burning profile, ignition temperature, and peak temperature were analyzed for 24 lignite samples from different areas of Turkey. The samples were heated up to 900°C at a constant rate of 10°C/min in a 5 mL/min flow of dry air. The burning profiles of the samples studied, combined with proximate, sulfur analysis and calorimetry results, contribute to a clearer identification of lignite samples' structure and a better understanding of the coalification process. The lignite samples have been tested with particle size of 0–0.05 mm. Ignition temperatures of the samples have been determined from their burning profiles.     

Molecular dynamics simulation study of proton diffusion in polymer electrolyte membranes based on sulfonated poly (ether ether ketone)

Molecular dynamics (MD) simulation technique was employed to investigate the effect of degree of sulfonation (DS) on structural and dynamical characteristics of sulfonated poly (ether ether ketone) (SPEEK) membranes at different temperatures. MD Simulations were performed for the cell containing SPEEK chains, hydronium ions and water molecules under NVT and NPT conditions. By evaluating the pair correlation functions, it was observed that with increasing the DS of SPEEK, the distance between sulfur atoms increases, more water molecules solvate the sulfur atoms and hydronium ions, the average sulfur–hydronium ion separation distance increases and larger water clusters are formed. It was also found that with increasing DS and temperature, the diffusion coefficient and conductivity of hydronium ions enhance. It was also understood, the simulated ionic conductivities qualitatively follow the experimental data.