以小型热管式空气预热器试验平台为研究对象,测试热管换热器热管管束气流方向的温度梯度和高、中、低温区单位换热面积对应的换热功率,测试烟气侧、空气侧阻力,测试单支高、中、低温热管冷端温度和布置倾角随热源功率变化的趋势.验证了低流阻热管的换热性能和阻力特性,为电厂进行热管空预器设计和改造提供参考.

超超临界二次再热机组增加了一级再热系统导致其再热汽温偏低,为了保证再热汽温能达到设计要求,通常采用烟气再循环增加炉膛出口烟气焓值的办法提高再热汽温.烟气再循环改变了省煤器进口的烟气量和烟气温度,影响了省煤器受热面的局部风速和换热强度,同时加剧了尾部受热面的磨损速度.为了定量研究不同烟气再循环对1000 MW超超临界二次再热锅炉省煤器运行参数的影响,制定了两种烟气再循环方案:方案一热烟气再循环由省煤器出口烟道抽取(再循环烟气温度为379℃);方案二冷烟气再循环由引风机出口烟道抽取(再循环烟气温度为117℃).通过热力计算研究了烟气再循环抽取点、机组负荷及烟气再循环率对省煤器管壁最大磨损厚度和省煤器换热温升的影响.由于影响省煤器磨损量的因素较多且计算复杂,为了便于对比采用省煤器最大磨损厚度表征省煤器的磨损程度.计算结果表明方案二对应的省煤器磨损量>方案一中省煤器的磨损量;BMCR、THA和75％THA工况下,烟气再循环率为15％时,THA工况省煤器管壁最大磨损厚度增幅最大;两个方案省煤器中介质温升基本一致;不同负荷下,烟气再循环率每增加5％,省煤器中介质温升增加2℃ ～3℃,且随着机组负荷的升高省煤器中介质温升越高.研究结果对二次再热机组选择烟气再循环方案提供指导,为二次再热锅炉省煤器的磨损计算提供了依据.

为了缓解脱硝反应器内局部氨氮摩尔比不匹配,介绍了喷氨优化调整方法,并结合某厂600 MW超临界燃煤机组喷氨格栅(AIG)改造,给出涡流静态混合式AIG和分区控制式AIG下烟气脱硝系统喷氨支管喷氨覆盖面与出口测点位置的对应关系.试验结果表明,500MW负荷下,烟囱出口 NOx质量浓度值控制在40mg/m3左右,通过对涡流静态混合式AIG进行喷氨优化调整,脱硝反应器两侧出口 NOx 质量浓度分布不均匀度分别由72.8％、90.3％下降至39.3％、40.2％;氨逃逸体积浓度分别由2.39 μL/L、2.97 μL/L下降至0.97 μL/L、0.96 μL/L.通过对分区控制式AIG进行喷氨优化调整,脱硝反应器两侧出口NOx质量浓度分布不均匀度分别由36.2％、45.4％下降至13.2％、18.8％;氨逃逸体积浓度分别由0.78 μL/L、1.05 μL/L下降至0.57μI/L、0.68μL/L.结果表明,分区控制式AIG效果优于涡流静态混合式AIG,研究结果为燃煤机组脱硝系统喷氨格栅改造提供参考和借鉴.

为解决超超临界二次再热锅炉再热汽温偏低的问题,以1 000 MW超超临界二次再热锅炉为研究对象,提出采取增设壁式再热器的方法提高再热汽温,计算了壁式再热器面积对主再热蒸汽温度的影响.计算结果表明:增设壁式再热器可提高再热汽温,当一、二次再热器各增加350 m2受热面时,可使一、二次再热汽温满足设计要求,但也会导致主蒸汽严重欠温,无过热减温水时主蒸汽温度也低于设计值;采用增加壁式再热器同时提高煤水比,可使主再热蒸汽温度满足要求.

针对涡盘式喷氨系统存在的问题进行了摸底试验,发现脱硝出口的NOx浓度分布严重不均,尤其是深度方向.调节喷氨支管手动蝶阀来调节喷氨量,只能降低炉宽方向的NOx浓度不均匀度,无法降低深度方向的NOx浓度不均匀度.通过优化试验将脱硝出口A侧的NOx浓度不均匀度由77.5％降低到47.2％,脱硝出口B侧的NOx浓度不均匀度由49.7％降低到35.0％.针对NOx沿深度方向分布不均的特点,给电厂提供了两种改造技术路线:方案一是沿炉宽方向增加涡流盘数量,解决炉宽方向局部区域NOx浓度不均问题;调整涡流盘的倾斜角度或改为两行涡流盘结构,解决脱硝出口NOx浓度沿深度方向的不均.方案二是将NH3喷射装置由涡盘式改为格栅式,解决脱硝出口NOx浓度沿深度方向严重不均的现象.增加CEMS测点个数,使在线NOx浓度值具有代表性.

利用AKOMA煤粉取样系统对某电厂BBD4060型双进双出筒式钢球磨制粉系统进行试验研究,通过控制变量法逐一考察了磨煤机料位差压、分离器开度和钢球加装量对于煤粉细度的影响.综合煤粉细度要求和磨煤机耗电量给出了磨煤机分离器开度的最优值.试验发现料位差压变大,煤粉细度逐渐变小,但B磨煤机的煤粉细度仍然偏大.通过调节分离器挡板开度和加装钢球,降低了B磨煤机的煤粉细度.试验结果为电厂运行提供参考.

针对四角切圆锅炉出现的汽温偏差问题进行了燃烧优化调整.为解决炉内切圆偏斜,分析了墙式燃尽风和角式燃尽风开度、摆角对汽温偏差的影响.结果 表明:增大墙式燃尽风开度,汽温偏差减小;综合考虑垂直水冷壁后墙管屏壁温和高温过热器壁温,建议将角式燃尽风和墙式燃尽风的水平摆角控制在正切0°位置,角式燃尽风和墙式燃尽风垂直摆角控制在水平位置.

为解决某600 MW超临界对冲燃烧锅炉水冷壁高温腐蚀的问题,采用运行优化调整的方式,研究了燃烧器风量、外二次风旋流强度、燃尽风开度和运行氧量对近壁区CO和H2S体积分数的影响.结果 表明:采用“碗式配风”同时降低外侧燃烧器外二次风旋流强度,可显著降低近壁区还原性气体体积分数;通过增加运行氧量和调整燃尽风风量的方式,提高主燃烧器区过量空气系数,也有利于改善壁面还原性气氛,降低水冷壁高温腐蚀的风险.

针对国内已投产超超临界二次再热机组锅炉普遍存在再热汽温低的问题,对已投产的泰州电厂二期SG-2710/33.03-M7050型二次再热锅炉进行过热蒸汽和一、二次再热蒸汽的吸热量计算和分析,表明再热气温低的原因是受热面比例设计存在偏差.提出了烟气再循环的改造方案,在75％热耗保证(THA)工况采用5％烟气再循环率时,一、二次再热汽温可以达到610℃以上,50％ THA工况采用15％烟气再循环率一、二次再热气温也可以接近600℃.

以某1 000 MW超超临界二次再热锅炉为例,采用数值模拟与炉膛分区段热力计算相结合的方法,研究了不同负荷下再循环烟气量对炉膛内部温度场、各气体组分的浓度场及NOx生成的影响.结果 表明:引入再循环烟气后,在锅炉最大连续蒸发量(BMCR)负荷下烟气再循环率在0％～15％内每增加5％,可使屏底烟温平均下降约4.7K,屏底O2体积分数下降4.1％,CO体积分数上升31.81％,NO体积分数下降6.2％;随着负荷降低,在相同再循环率下,屏底烟温下降幅度增大,屏底O2体积分数下降幅度和CO体积分数上升幅度均减小.

为了分析不同再循环烟气抽取点和引入点对某1 000 MW超超临界二次再热锅炉运行参数的影响,提出分别从省煤器和引风机后抽取烟气,并引入到炉膛底部和上部共4种烟气再循环方案.进行热力计算,分析不同负荷、不同再循环率下各方案对锅炉参数的影响.结果 表明:烟气再循环会降低炉膛出口烟温和升高排烟温度,抽取点为引风机后,排烟温度升高幅度较大,引入点为炉膛上部时,炉膛出口烟温下降幅度较大;再循环烟气引入炉膛底部可以提高再热蒸汽温度和主蒸汽温度,引入点为炉膛上部不能明显提高再热蒸汽温度且会降低主蒸汽温度;随着再循环率的增加以及负荷降低,烟气再循环对蒸汽温度的影响程度增加;从省煤器后抽取烟气的方案对锅炉热效率的影响较小,但再循环风机磨损较严重,从引风机后抽取烟气对锅炉热效率影响较大.

探讨了二次再热机组烟气再循环对二次再热塔式锅炉炉膛沿高度换热的影响,通过编程实现了某超超临界1 000 MW二次再热塔式锅炉在不同的烟气再循环方案下的炉膛分区段热力计算.结果表明:烟气再循环会使炉膛各区段出口烟温降低,随着负荷的升高和再循环率的增加,烟温下降幅度增加;当烟气引入炉膛底部时,燃烧器区域烟温下降幅度最大,随炉膛高度升高,各区段出口烟温下降幅度减小,炉膛出口烟温略微下降,炉膛辐射换热量减少明显,可改变烟气对流和辐射换热比例,调节再热汽温;烟气引入炉膛上部时,烟气引入点区段烟温下降幅度最大,炉膛出口烟温下降明显,炉膛辐射换热量减少不明显,有利于减轻炉膛出口处结渣,但不能调节再热汽温.

介绍了国内外二次再热机组发展状况,结合国内超超临界二次再热1000 MW机组性能考核试验情况,分析比较了目前已投产的超超临界二次再热机组的主要性能指标,对今后二次再热机组的设计、制造、运行具有重要指导意义.

某电厂对冲燃烧锅炉水冷壁管存在大面积高温腐蚀现象,根据高温腐蚀机理,从锅炉燃用煤种、炉型参数、运行情况和炉内烟气氛围等方面分析了产生高温腐蚀的原因,有针对性地提出了防范措施,可为解决此类问题提供参考.

Lignite is a kind of high moisture low heat value coal.Power plant burning lignite directly will lead to coal pulverizing system output insufficient and low boiler thermal efficiency.Use the steam pipe rotary dryer to dry lignite,the power plant can realize burning lignite only,and the pulverizing system output will be improved.By taking a 300MW coal-fired unit as the research object,the paper studied the influence of the steam pipe rotary dryer for the thermal efficiency of power plants,and compared the economic benefit with fuel cost.Through theoretical calculation,it make power generation consume 4.07t/h more standard coal,the thermal efficiency of power plant declined;Burning lignite can also save great fuel cost for power plant because of its low price.

Numerical software FLUENT has been used to simulate the reburning condition of gasified gas of cornstalk,rice straw and wheat straw at 600 ℃ in a 600 MW supercritical coal-fired boiler with whirl burners in front and back wall cross collocation,so as to study how the category and flow rate of reburning gas influence the in-furnace combustion,outlet gas temperature and the production of NO,CO2 and CO.Results show that the maximum denitrification rate of gasified gas of wheat straw,cornstalk and rice straw is respectively 41%,40% and 38%,indicating a decreasing order of denitrification rate.With the increase of reburning gas flow rate,the emission concentration of both CO2 and NO reduces,but the outlet gas temperature and CO concentration rise.The reburning of biomass gas can effectively reduce the emission concentration of NO,and it hardly interrupts boiler＇s normal operation.

In order to reduce the power consumption of oxygen making for oxygen-enriched combustion power generating set,two schemes of ASU design output,respectively meeting daily oxygen demand and rated power generation demand,are proposed while three power supply modes recommended,by comprehensively considering the daily oxygen demand in peak/valley period and the peak/valley power price.Taking the 600 MW oxygen-enriched combustion power generating set as an object of study,the oxygen-making cost has been calculated in 6 cases in consideration of both the equipment investment and the running cost based on reasonable estimation of relevant parameters.Results show that via configuration optimization,the power consumption of the oxygen making can be reduced by 2.1%,and the net efficiency of the power generating set can be raised by 0.8%,indicating obvious energy-saving effect.

Based on the minimization of Gibbs free energy and energymass balance,the software ASPEN PLUS was adopted to simulate the process of biomass gasification in which pine sawdust and wheat straw were selected.And the accuracy of simulation results with experimental data was verified.Large extent variety of high air temperature and raw water content which were difficult to operate in the experimengts were investigated.Simulation results showed that the model can better imitate the process of biomass gasification,which could be provide some reference value for further biomass gasification expriments and scaling up.

A new wide band correlated-k distribution model was proposed to calculate the radiative heat transfer of the water vapor and carbon dioxide gas mixture at high pressure and concentration under pressurized O2/CO2 combustion mode.The radiation intensity and carbon dioxide 4.3 μm band cumulative distribution function between two cold and black parallel plates were calculated to verify the present model by combination of the present model and the discrete ordinate method at 1 000-2 500 K and 0.1-1.5 MPa in the furnace of a coal-fired boiler.The comparison shows that the results from the present model are more reasonably consistent with those by the line-by-line method with an increase in pressure.Moreover,the accuracy of the present model is higher than that of the full-spectrum correlated-k distribution model or the wide band correlated-k distribution model based on the exponent in literature.It seems that this new wide band correlated-k model is suitable to the radiative heat transfer of flue gas at high pressure.

Biomass gasification takes place at a certain temperature,and the gasifier should be preheated before gasification.Researches have been done on the preheating principles of the fluidized bed gasifier with the fluidized bed of 200 mm、300 mm、400 mm height and the air temperature of 500 ℃、550 ℃、600 ℃ respectively.The result shows that as the height of the fluidized bed raises,the steady fluidized bed temperature raises as well;the steady fluidized bed temperature raises with the raising of the air temperature.Through experiments,the data of the initial preheating stage of the fluidized bed have been collected,and the whole preheating process of the fluidized bed has also been improved.