超临界W火焰锅炉燃用劣质燃料燃烧优化研究

针对W火焰锅炉运行中热效率偏低问题,对燃用的烟煤、石油焦、越南无烟煤等主要煤种开展配煤掺烧,以降低燃料成本、提高锅炉效率。从燃用煤质适应性分析、W火焰锅炉燃烧过程数值模拟和混煤掺烧优化试验3方面,研究了石油焦和越南无烟煤不同掺混比例下热解和燃烧过程特性,制定了掺烧策略并通过燃烧过程模拟研究和掺烧优化试验找到了合适的配煤掺烧方法,解决了锅炉效率低、飞灰含碳量较高、锅炉排烟温度高等问题,实现了节能降耗、提高经济效益的目的。     

600MW“W”火焰直流锅炉烟煤启动及低负荷稳燃技术的研究及应用

贵州某电厂2×600MW超临界机组于2011年投产发电,锅炉使用北京巴威公司生产的BWB-1900/25. 4-M型超临界参数"W"火焰直流变压锅炉。锅炉设计煤种为普兴矿区的无烟煤,在锅炉启停、低负荷稳燃时采用0号轻柴油。由于超临界"W"火焰直流变压锅炉的设计结构特点,锅炉在启动过程中需严格控制水冷壁热偏差、管壁温度和升温升压速率。加上汽轮机暖机工作的需要,锅炉冷态启动时间较长,而磨煤机能够启动制粉参与燃烧的时间较晚,造成锅炉冷态启动油耗较大。经过分析研究并实际应用,利用烟煤来进行机组冷态启动、在机组低负荷时采用烟煤掺烧,不仅提高了锅炉燃烧的稳定性,还取得了很好的节油效果。     

电厂锅炉混煤燃烧技术应用现状及分析

为降低发电成本,拓宽煤炭供应渠道,国内各燃煤发电厂相继开展了锅炉非设计煤种的掺烧试验研究。首先介绍了电厂锅炉混煤掺烧常见的三种方式,分析了这三种混煤掺烧方法的优缺点,然后介绍了国内电厂掺烧烟煤、褐煤、无烟煤的情况;分析了目前电厂锅炉掺烧烟煤、褐煤、无烟煤时所存在的问题,并提出了一些切实有效的技术措施;最后分析了混煤燃烧对锅炉运行的影响,指出需要对燃烧混煤时锅炉性能的变化、掺烧经济性等问题做深入研究。     

W型火焰锅炉水冷壁结焦问题的分析

W型火焰锅炉普遍存在水冷壁的结焦现象,本文介绍了W型火焰锅炉的结构特点以及W型火焰锅炉结焦的因素,并从煤质特性、炉膛内温度、气氛条件、炉内空气动力场等因素对W型火焰锅炉结焦的原因进行了详细分析,同时提出了防止结焦的措施。     

600MW机组锅炉掺烧劣质烟煤的性能试验研究

对某电厂锅炉进行了劣质烟煤掺烧性能试验,分析了锅炉在高、低负荷运行下,不同劣质烟煤掺烧比例,对锅炉排烟热损失、固体未完全燃烧热损失、锅炉热效率及辅机电耗的影响。结果表明:锅炉在高、低负荷运行下,随着劣质烟煤掺烧比例的增加,锅炉排烟热损失升高、锅炉固体未完全燃烧热损失增大、锅炉热效率下降;在锅炉负荷和运行氧量相同的情况下,随着劣质烟煤掺烧比例的增加,辅机电耗增大;掺烧劣质烟煤工况的耗电率比单烧铁法煤工况的耗电率大,这将增加厂用电率,增加煤耗。     

350 MW机组锅炉褐煤掺烧技术探讨

阐述电厂结合HG-1165/17.45-YM1型锅炉的特性,进行以燃烧烟煤为主,掺烧褐煤的试验.文中提出掺烧褐煤的最优改造技术方案,讨论了褐煤掺烧技术应用中所面临的问题,并对掺烧褐煤的经济性进行分析.     

600 MW"W"火焰锅炉结焦原因分析与防止措施

针对山东聊城发电厂600MW"W"火焰锅炉运行中存在的严重结焦问题,结合实际运行情况、锅炉设备特性、燃煤特性等分析了锅炉结焦原因,并提出了相应的防止措施.     

基于“MBEL”W火焰锅炉结焦现象原因分析及其对策

介绍了国电菏泽发电厂"MBEL"W火焰锅炉的设计特点,该锅炉在运行中遇到了因结焦而被迫停炉的重大问题,通过对锅炉运行情况的分析研究,找出了造成结焦的原因,并通过对设备改造和运行调整等措施消除了W火焰锅炉结焦问题,对同类"MBEL"W火焰锅炉在运行中出现结焦问题的解决具有指导性作用。     

对冲燃烧锅炉热负荷分配对炉内燃烧影响的试验研究

介绍了某电厂超临界对冲燃烧锅炉运行情况,以东胜纳林庙烟煤作为设计煤种,以山西塔山煤矿烟煤作为校核煤种,指出实际运行中掺烧较大比例的印尼褐煤,在运行中多次发生锅炉结焦的原因主要是锅炉因热负荷分配不均、炉膛局部温度高、炉内流场紊乱等导致炉膛掉焦。阐述了通过调整优化炉内热负荷分配的措施,对热负荷分配的影响进行了分析,认为可有效解决锅炉掉焦的问题。     

1150t/h锅炉掺烧褐煤的性能试验研究

对某电厂1150 t/h锅炉进行了山西晋北烟煤与扎赉诺尔褐煤的掺烧试验,分析了不同掺烧比例、不同煤质及不同磨煤机掺烧时锅炉的综合性能.结果表明:扎赉诺尔褐煤能够在烟煤锅炉上稳定掺烧,当混煤水分Mar<20%时,A、B、C 3台磨煤机可以同时掺烧褐煤,全厂掺烧比例最高可达40%;混煤水分对磨煤机的干燥出力有较大影响,混煤水分降低时,磨煤机干燥出力提高;A、B、C磨煤机掺烧褐煤后,锅炉主燃烧器区域温度升高,炉膛水冷壁出现局部结渣,排烟和固体未完全燃烧热损失升高,导致热效率降低约1.2%.     

症状性大脑中动脉粥样硬化性狭窄支架植入术后血流动力学研究

【摘要】 目的 探讨症状性大脑中动脉粥样硬化性狭窄患者接受颅内支架植入术前后脑血流动力学变化。方法 回顾成功实施颅内支架植入术的39例症状性大脑中动脉粥样硬化性狭窄患者基线资料,对采用经颅多普勒超声检测术前、术后1周、术后3个月大脑中动脉狭窄段收缩期峰值流速（PSV）和脉动指数（PI）进行分析,比较手术前后病变血管血流动力学变化。结果 39例患者中1例术后狭窄改善不明显,38例动脉平均管径狭窄率由治疗前（80.3±8.5）%改善为术后即刻（16.3±9.2）%（P=0.011）。术后1周、术后3个月大脑中动脉狭窄段PSV与术前比较有明显降低（P=0.023）,PI也较术前明显降低（P=0.028）。术后3个月时2例患者平均PSV回复升高31%～39%;术后3个月与术后1周比较,平均PSV略有升高（P=0.129）,PI稍有增高（P=0.115）,但差异无统计学意义。结论 症状性大脑中动脉粥样硬化性狭窄患者接受颅内支架植入术后短期内脑血流得到有效增加,长期血流改善程度有待观察。

     

Thermovoltaic effect of <Emphasis Type="Italic">p</Emphasis>Si-<Emphasis Type="Italic">n</Emphasis>(Si<Subscript>2</Subscript>)<Subscript>1−x</Subscript>(ZnS)<Subscript>x</Subscript> structures

The pSi-n(Si₂)_1−x (ZnS) _x (0 ≤ x ≤ 0.92) structure, on which thermovoltaic effect is observed, has been obtained by means of liquid-phase epitaxy from tin solution-melt on plates of p-type technical silicon. This effect is explained by grain boundary defects and influence of ZnS impurities in a thin layer adjacent to the p-n-junction.     

The fabrication and investigation of <Emphasis Type="Italic">n</Emphasis>/CdS-<Emphasis Type="Italic">p</Emphasis>/CdTe-<Emphasis Type="Italic">n</Emphasis>/Si structures

Attempts to obtain heterojunctions between A²B⁶ (cadmium telluride and cadmium sulfide) compounds and silicon were made. The distributions of chemical components and some photoelectric properties of the surfaces of the produced layers were investigated.     

Antireflection coatings for solar elements based on Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and SiO<Subscript>2</Subscript> oxides

An alloy of a mixture of Al₂O₃ and SiO₂ oxides has been obtained under radiant heating. It is established that films of the Al₂O₃ and SiO₂ alloy, deposited on the surface of glass and silicon plates, have high mechanical strength and adhesion, are transparent in the SE sensitivity region, and can be used as antireflection coatings.     

Electrochemical oxidation behavior of Mg–Li–Al–Ce–Zn and Mg–Li–Al–Ce–Zn–Mn in sodium chloride solution

Mg–Li–Al–Ce–Zn and Mg–Li–Al–Ce–Zn–Mn alloys were prepared using a vacuum induction melting method. Their electrochemical oxidation behavior in 0.7 M NaCl solution was investigated by means of potentiodynamic polarization, potentiostatic oxidation, electrochemical impedance technique and scanning electron microscopy examination. Their utilization efficiencies and performances as anode of metal–hydrogen peroxide semi-fuel cell were determined. The Mg–Li–Al–Ce–Zn–Mn exhibited higher discharge activity and utilization efficiency than Mg–Li–Al–Ce–Zn, and gave improved fuel cell performance. The utilization efficiency of Mg–Li–Al–Ce–Zn–Mn is comparable with that of the state-of-the-art magnesium alloy anode AP65. The magnesium–hydrogen peroxide semi-fuel cell with Mg–Li–Al–Ce–Zn–Mn anode presented a maximum power density of 91 mW cm⁻² at room temperature. Scanning electron microscopy and electrochemical impedance studies indicated that the alloying element Mn prevented the formation of dense oxide film on the alloy surface and facilitated peeling off of the oxidation products.     

How to make the production of methanol/DME &#8220;GREENER&#8221;&#8212;Integration of wind power with modern coal chemical industry&#8212;

The urgency and necessity of alternative fuels give an impetus to the development of modern coal chemical industry. Coal-based methanol/DME is the key element of this industry. Wind power, whose installed capacity increased at a rate of more than 100% in recent years, has the most developed technologies in renewable energy. However, there still exist many unsolved problems in wind power for on-grid utilization. A new integrated system which combines coal-based methanol/DME production with wind power is proposed in this paper. In this system, wind power is used to electrolyze water to produce H₂ and O₂. The O₂ is fed to the gasifier as gasification agent. The H₂ is mixed with the CO-rich gas to adjust the H₂/CO to an appropriate ratio for methanol synthesis. In comparison with conventional coal-based methanol/DME system, the proposed system omits the expensive and energy-consuming ASU and greatly reduces the water gas shift process, which brings both advantages in the utilization of all raw materials and significant mitigation of CO₂ emission. This system will be attractive in the regions of China which have abundant wind and coal resources.     

A new weighted‐sum‐of‐gray‐gases model for oxy‐combustion scenarios

A new weighted‐sum‐of‐gray gases (WSGG) model that is based on the statistical narrow band model (SNB) RADCAL is proposed for use in computational fluid dynamic (CFD) simulations of air and oxy‐combustion. When employed in conjunction with the discrete ordinates (DO) method, the model predictions compare well against line‐by‐line benchmark data that have been made available recently that are based on the latest spectroscopic databases. Furthermore, the model compares well against the EM2C SNB model calculations that have served as benchmark data in three‐dimensional geometries. Radiative transfer calculations in these prototypical problems therefore confirm recent experimental observations that SNB RADCAL and EM2C SNB serve as good model databases to develop approximate radiative property models. To achieve an optimum balance of speed and accuracy in computationally intensive CFD simulations, non‐gray formulations of the WSGG model are also employed with the P1 model and solutions are compared against those generated by the DO model. While the P1 model gave favorable comparisons when cold, black walls were present, the errors in the surface incident radiative flux predictions increased in the presence of hot, reflecting walls. Finally, in fully coupled simulations of natural gas combustion under air‐firing and oxy‐firing modes, the predicted incident radiative flux profiles were distinctly different between the gray and non‐gray calculations at regions of high temperature gradients, while the centerline temperature predictions were comparatively unaffected. The effects of turbulence radiation interactions were also accounted for through the temperature self‐correlation term. However, the magnitudes of the temperature fluctuations were small and localized within this furnace and did not significantly alter our predictions. Copyright © 2012 John Wiley & Sons, Ltd.