China’s thermal power plant wet FGD (flue gas desulphurization) produces more than 80 million tons of gypsum each year. The factors affecting the quality of wet desulphurization gypsum are limestone quality, flue gas dust, gypsum slurry pH, slurry quality, gypsum water content, desulphurization system design features, and operating conditions, etc. There are many reasons for high gypsum moisture content, and the analysis and solution are particularly complex. Through a case analysis of a power plant with high moisture content of desulphurization gypsum, the main reasons are that the unit has been operating under low load conditions for a long time with low sulphur coal, limestone supply slurry is high, slurry pH is high, and the volume of gypsum crystals generated is small, resulting in gypsum dehydration difficulty and high moisture content. The measures were to add the crystal seeds into the slurry and to lower the operation pH. The slurry quality is improved, and the gypsum dehydration returns to normal. The design margin of the desulphurization system is large, even in a long-term low sulphur and low load operation. There are no similar cases, and this situation generally does not attract attention. It is worth further analysis and reference.
The boiler flame contains a lot of information,among which the pulsation frequen-cy is closely related to the combustion efficiency and thermal efficiency of the boiler,which has a practical guiding significance for the economic operation of the boiler.In this paper,the boiler flame during stable combustion was taken as the research object.With the help of im-age processing and spectrum analysis technology,the average pulse frequency of the boiler flame during stable combustion was obtained from the perspective of the change of flame are-a.Combined with the working condition data of the boiler,the relationship between the aver-age pulsation frequency and the boiler load,thermal efficiency and carbon content of fly ash is established.Within a certain range,the larger the average pulsation frequency,the greater the load corresponding to the operating conditions,the higher the thermal efficiency,and the less carbon content in fly ash.
Cyclone separator is one of the important equipment in the combustion system of circulating fluidized bed boiler.The falling off of central cylinder is a common problem affecting the safe operation of cyclone separator.In this paper,taking the cyclone separator of a 350 MW circulating fluidized bed boiler as the research object,the Reynolds Stress Model is used to simulate and analyze the gas flow characteristics in the cyclone separator before and after the center cylinder falling off.The calculation results show that the air flow structure in the cyclone separator does not change before and after the central cylinder falls off,including external swirling flow and internal swirling flow.When the central cylinder falls off,the longitudinal circulation and short-circuit flow in the upper part of the outer cylinder disappear,and part of the air flow flows directly from the central cylinder;The axial velocity and tangential velocity distribution of the air flow are similar,but the local velocity distribution and magnitude are different;The pressure distribution is similar,and the pressure difference between inlet and outlet decreases.
Due to the nonlinearity,large inertia and large delay of selective catalytic reduction(SCR)flue gas denitration system in coal-fired power plants,the traditional identification methods have the problems of slow convergence speed and low identification accuracy.In this paper,the ideas of adaptive dynamic inertia weight,adaptive variation of particles and natural selection are introduced on the basis of fundamental particle swarm algorithm.The improved particle swarm algorithm is applied to model identification of SCR flue gas denitration system of an ultra-supercritical 660 MW unit.Based on the field operation data of the unit,the transfer function models between the position opening of the regulating valve and the mass flow of ammonia,between the mass flow of ammonia and the concentration of NOx in the outlet,and between the concentration of NOx in the inlet and that in the outlet were established.The results of the study show that the particle swarm algorithm optimization improves the model identification accuracy,and effectively improves the defects of basic particle swarm algorithm which is easy to fall into the local optimum and the loss of population diversity in the later stage.Meanwhile,the simulation results demonstrate the effectiveness of the proposed method.
The serious fouling and blocking problems of several rows at first layer catalysts near the front wall were investigated in this paper,which are common in the selective catalyt-ic reduction(SCR)de-NOx device of coal-fired boilers.Taking a 350 MW coal-fired unit as an example,CFD numerical simulation and field test were used to carry out diagnostic analysis,and the catalyst anti blocking modification was carried out using fly ash interception and uni-form layout.Studies have shown that bias flow of coarse ash leads to a significantly higher fly ash concentration in the area near the front wall upstream of the top catalyst,and the accu-mulation of coarse fly ash in this area aggravates the wear of the catalyst.After adopting the plan of intercepting large particles at the economizer outlet and evenly distributing fly ash in the ascending flue gas duct,the serious fouling and blocking problems at several rows of top layer catalysts has been solved effectively.
During the construction period of the double reheat boiler,the steam and water system should be cleaned by chemical cleaning,steam blowing and unit start-up steam water quality optimization three stages of trial operation.Under the current steam blowing measures of double reheat boiler,there are problems such as long construction period,low super-heater blowing coefficient,many times of reduced pressure steam blowing,serious over temperature of steady pressure steam blowing,the noise pollution and emission loss of steam blowing have increased substantially.In order to solve the problems of poor blowing control and low cost performance,and efficiently complete the boiler steam-water system cleaning work,the cleaning measures of the three stages are improved:Expanding the scope of chemical cleaning to create conditions for reducing the steam blowing;Formulating steam blowing measures for the structure and parameter characteristics of the double reheat boiler to improve the blowing efficiency;Before the steam turbine flushing,the bypass system is used for large flow steam purging to remove corrosion produced after the steam blowing.Through the overall use of three cleaning processes,it can not only reduce the workload of steam blowing,but also ensure the cleaning quality,forming a more safe,environmental friendly,economical double reheat boiler comprehensive cleaning technology.
In the article,two calculation methods of air preheater air leakage rate in GB 10184-88 Power Station Boiler Performance Test Regulations and GB/T 10184-2015 are discussed.The data results show that the relative deviation rate of the air leakage calculated by the two methods is about 3％.Taking into account the limitations of the old method of the standard and the test complexity of the new one,an improved calculation method that mixes the two standards is proposed.After the improvement,the air leakage rate is between the old and the new standard,and the calculation workload can be reduced accordingly.
The combustion and NOx emission characteristics on pulverized coal moderate &intense low oxygen dilution(MILD)combustion of International Flame Research Foundation(IFRF)test system are analyzed by computational fluid dynamics(CFD)method.The effects of different turbulence-chemistry interaction models,volatile combustion mechanisms and char combustion models are compared.By comparing the numerical and experimental values of velocity fields,temperature fields and components fields,the EDC-WD-MSR combined model can better predict pulverized coal MILD combustion.Based on the EDC-WD-MSR model,the NOx formation and reduction for pulverized coal MILD combustion are analyzed.The results show that fuel-NO is dominant in pulverized coal MILD combustion,while thermal-NO,prompt-NO and intermediate-N2 O account for less than 10％.Strong homogeneous and heterogeneous reductions exist in pulverized coal MILD combustion,where the heterogeneous reduction makes fuel-NO accounting for 71.1％of the sum of char-NO and volatile-NO calculated independently.
In order to solve the problem of high ammonia escape rate in the selective catalytic reducation(SCR)denitrification system of the waste heat boiler of the gas-steam combined cycle unit,the mechanism of high NO2 content and slow reaction rate of excessive NO2 in the flue gas NOx emitted by the gas steam combined cycle unit was studied.The reasons and hazards of high ammonia escape rate in the waste heat boiler SCR denitrification system were analyzed;Technical measures such as combustion adjustment,replacement of new catalysts,flow field optimization,and precise ammonia injection have been proposed to effectively reduce ammonia escape rate.
The corrosion and protection of thermocouple protective casing pipe used in refuse incinerator were studied in this article.The layered Al(Fe,Ni)intermetallic compound coating was prepared on 1Cr18Ni9Ti matrix by arc spraying Al+high temperature diffusion method.The outer layer of the coating is Al75Ni10Fe15 intermetallic phase,which is the Al3M type aluminum rich phase formed by the solution and replacement of Fe,Ni and Cr elements.The inner side of the coating is homogeneous and compact Al(Fe,Ni)type intermetallic compound single phase layer,in columnar crystal shape.The average microhardness of the single-phase layer of the intermetallic compound is 836.1HV0.1,and it shows good salt corrosion resistance at 900 ℃.
Aiming at the problems existing in the coordinated control system of a 1 000 MW unit,the main reasons that restrict the regulation quality of unit coordinated control system are analyzed.This paper proposes a strategy that the set value of main steam pressure follows up with the actual main steam pressure within a certain margin.At the same time,the coor-dinated control system of the unit is optimized by means of fuel and feedwater feedforward correction,water fuel ratio control strategy modification,feedwater pump turbine speed con-trol PID parameters and valve flow curve optimization,and the adjustment quality and load response rate of the unit after optimization are analyzed through load variation test.The results show that the optimized parameters of the unit control system are stable,have good dynamic control quality,and can meet the requirements of safe,stable and economic opera-tion of the unit.
Failure analysis on the final superheater tube that has experienced leakage is con-ducted.A comprehensive evaluation of the cause of tube leakage is conducted through macro-scopic examination,metallographic examination,hardness test,and SEM analysis.The re-sults indicate that:The leakage of the final superheater tube was caused by improper control of the forming process of the tube during the manufacturing process,resulting in a large number of axially distributed linear defects existed on the inner wall.The defect spreads to the inside of the tube during service,resulting in a great reduction in the effective wall thick-ness of the tube.With the aging of the pipe organization,the performance is gradually deteri-orated,which leads to a decrease in the pressure-bearing capacity of the tube.Finally,the unstable expansion of cracks leads to leakage,causing multiple cracks to expand,forming a skylight-shaped explosion.
In order to promote energy conservation and emission reduction,and improve the economic as social benefits of the unit,the second phase expansion project of Huaneng Ruijin Power Plant(2×1 000 MW ultra-supercritical double reheat unit)adopts clean and high-effi-cient double reheat ultra supercritical coal-fired power generation technology,efficient and energy-saving back pressure extraction steam turbine(abbreviation:BEST small turbine)technology with integrated frequency conversion power generation and system,as well as a 12 stage regenerative system with 5 HP heaters,6 LP heaters,and 1 dearator.The flue gas desulfurization and denitrification facilities were built at same time,and the unit parameters has been increased from the conventional 31 MPa/600 ℃/620 ℃/620 ℃ to 31 MPa/605 ℃/622 ℃/620 ℃,and BEST small turbine technology has been adopted,achieving a unit effi-ciency of 49.25％;The flue gas collaborative treatment technology route is adopted to mini-mize the emission concentration of nitrogen oxides,particulate matter,sulfur dioxide,PM2.5,etc.,with the desulfurization efficiency of more than 99.4％and SO2 concentration of less than 20 mg/mt(O2=6％);The denitrification efficiency shall not be less than 90％,and the NOx value shall not exceed 28 mg/m3(O2=6％).
This paper aims at a 900 t/d municipal solid waste incinerator,and simulates the combustion condition and high temperature corrosion of the heating surface by CFD method.Firstly,this paper simulates the incinerator by using the bed combustion model+STAR CCM+coupling method,and the results are basically consistent with the actual combustion process,indicating that this method can accurately simulate the waste incineration boiler and provide a basis for the optimization of operating parameters.Secondly,this paper establishes a calculation model of high temperature corrosion of heating surface,taking the surface tem-perature of heating surface as the main influencing factor.And combined with the specific corrosion rate data of different alloy materials,the high temperature corrosion rate of differ-ent heating surface materials at different temperatures is obtained.Then,this paper calcu-lates the high temperature corrosion of the three-stage superheater,and the results show that the maximum corrosion rate is 1.04 mm/a,which occurs in the bundle without chromium-nickel-iron alloy layer.Finally,this paper optimizes the operating conditions of the incinera-tor,improves the combustion performance,and reduces the high temperature corrosion of the three-stage superheater.The maximum corrosion rate of the three-stage superheater is re-duced by 3％,and the area ratio of high corrosion rate is reduced by 4％.
为提高电站锅炉受热面的运行安全,通过优化吹灰器控制回路冗余触点,增加触点故障报警和监视,同时在分散控制系统(DCS)增加急退、退超时报警和智能检漏识别等功能,可有效预防吹灰器在运行过程中潜在的风险,防止吹灰器未退到位,内漏损坏锅炉受热面.某660 MW机组通过优化后,运行过程中未发生内漏情况,降低运行和检修人员维护工作强度的同时,保证机组运行安全,提高机组运行经济性.
为研究不同二次风风速对锅炉炉膛内温度、NOx浓度、烟气停留时间分布及热效率的影响,针对某600 t/d城市生活垃圾焚烧锅炉的燃烧过程进行了数值模拟.结果表明:当后墙二次风风速在42～66 m/s、前墙二次风风速不变时,随着后墙二次风风速增大,第一烟道出口处NOx浓度先升高后降低;当第一烟道出口处O2含量从6.47％增加到7.02％,NOx质量浓度从106.98 mg/m3降低到100.18 mg/m3,降低了 6.36％;前墙二次风风速为42 m/s,后墙二次风风速为66 m/s时,焚烧炉内温度梯度相较其他工况更加均匀,烟气在焚烧炉内温度大于1 123 K区域停留时间超过2 s,有利于抑制二英的生成;前墙二次风风速为45 m/s,后墙二次风风速为70 m/s时,相较原始工况第一烟道出口处平均温度降低19.51 K,排烟热损失降低0.83％,固体未完全燃烧热损失降低0.16％,焚烧炉热效率提高0.99％.该研究对垃圾焚烧锅炉低污染、高效率运行具有重要的指导意义.
针对某电厂四角切向燃烧锅炉12Cr1MoV高温过热器管近年来发生多次爆管事故,结合其锅炉结构、爆管现场检验结果与爆管失效分析结果,研究其过热器爆管失效模式及机理.研究发现:过热器爆管均为过热失效,爆口位置主要在管屏迎烟侧,其迎烟侧和背烟侧材料力学性能、组织球化和氧化皮厚度普遍存在明显的差异.研究表明:在炉内高温烟气作用下,过热器局部管屏迎烟侧管壁超温,由此引起其组织球化、材料力学性能劣化、蠕变裂纹的生成,多项因素的叠加导致最终爆管.
为了提高垃圾焚烧发电效率,分析了垃圾焚烧发电不同蒸汽参数对汽轮机、锅炉、焚烧炉、运行和经济成本方面的影响,找到了不同蒸汽参数的优缺点.结果表明:提高锅炉蒸汽参数可以提高垃圾焚烧电厂垃圾处理效率和经济效益;中温中压参数适用于小规模、低热值垃圾的处理;随着垃圾热值的提高和处理需求的增加,中温次高压参数具有更好的适应性和经济性;蒸汽温度的提高对发电经济性的贡献大于蒸汽压力的提高.
实现燃煤电站锅炉底部渣量在线检测,进而实现干排渣机冷却风量有效调整,对提高干排渣机运行的可靠性和经济性具有重要意义.提出一种基于主动双目视觉的炉渣体积流量在线检测方法,通过线型激光照射干排渣机输送带上炉渣表面,有效地增强了图像的亮度、纹理等特征,进一步利用改进的自适应Census算法实现了双目视觉系统准确匹配.在此基础上,开发了炉渣体积流量检测系统,开展了评价研究,并在某660 MW超临界机组上进行了现场应用.结果表明:该系统能够准确可靠的获得灰渣的深度信息,误差小于8％,整体精度较高.660 MW超临界机组现场应用结果进一步验证了渣量在线检测系统的可靠性和准确性,满足工业现场应用要求.
针对污泥燃烧氮氧化物排放超标的问题,采用涡耗散模型,对市政污泥(含水率40％)在污泥焚烧过程中低氮燃烧排放特性进行模拟与分析,得到了二次风平行射流角度、过量空气系数、二次风风口高度对污泥低氮燃烧的影响规律,以及烟气温度场与组分变化情况.研究结果表明:当二次风入射角度从90°降低到60.8°时,低氮燃烧效果最佳,烟气出口NOx质量浓度从256 mg/m3降低至176 mg/m3,降低了 31％;当过量空气系数从1.3减小到1.2,烟气中的NOx 质量浓度由330 mg/m3降低至176 mg/m3,继续减小过量空气系数到1.1时,NOx质量浓度降低至131 mg/m3,但烟气中CO 浓度大幅升高,过量空气系数宜选择1.2;当风口高度为1.3 m时烟气NOx质量浓度大幅增加到283 mg/m3,1.8 m高度下送风烟气NOx质量浓度与2.3 m相比略微升高,CO 浓度与1.3 m高度相比变化不大,二次风风口高度推荐设置为1.8 m.
