Experimental study on performance of flow & desulfurisation of a gas-liquid screen scrubber for wet flue gas desulfurization

In the paper, the gas-liquid two-phase flow performance and desulfurisation performance of the gas-liquid screen scrubber were experimentally studied when limestone was used as absorbent. Experiments were carried out at varying the flue gas velocity and slurry flux in concurrent and countercurrent tower respectively. The experimental results showed that the flow resistance of absorber increased rapidly with an increase of the flue gas velocity whether in concurrent or in countereurrent tower, and the up trend of the flow resistance in the cotmtercurrent tower was higher than those in the concurrent one. The influence of the flue gas velocity on the flow resistance of absorber was more than those of the slurry flux density. Whether in the concurrent tower or in the cotmtercurrent one, increasing the flue gas velocity or the slurry flux density would enhance the desulphurization efficiency. The influence of the slurry flux density on the desulfurisation efficiency was greater than those of the flue gas velocity.

Miscibility of light oil and flue gas under thermal action

The miscibility of flue gas and different types of light oils is investigated through slender-tube miscible displacement experiment at high temperature and high pressure.Under the conditions of high temperature and high pressure,the miscible displacement of flue gas and light oil is possible.At the same temperature,there is a linear relationship between oil displacement efficiency and pressure.At the same pressure,the oil displacement efficiency increases gently and then rapidly to more than 90% to achieve miscible displacement with the increase of temperature.The rapid increase of oil displacement efficiency is closely related to the process that the light components of oil transit in phase state due to distillation with the rise of temperature.Moreover,at the same pressure,the lighter the oil,the lower the minimum miscibility temperature between flue gas and oil,which allows easier miscibility and ultimately better performance of thermal miscible flooding by air injection.The miscibility between flue gas and light oil at high temperature and high pressure is more typically characterized by phase transition at high temperature in supercritical state,and it is different from the contact extraction miscibility of CO_(2) under conventional high pressure conditions.

Retrofit of 350-MW Supercritical Boiler Based on the Analysis on Exhaust Gas Temperature

Since the first batch of 350-MW supercritical utility boilers was put into operation, the exhaust flue gas temperature of the boilers has always been higher than the designed value. The main reason is that the heat absorbed by the air heater is not sufficient. In Huaneng Dongfang Power Plant, the exhaust flue gas temperature is lowered through modifications to the economizer and the air heater. The experimental results reveal that every year, each boiler could save 3 850 tons of standard coal and reduce 85 tons of SO2 and 9 000 tons of CO2 respectively after retrofit.

Technical Measures and Selections for Reducing Flue Gas Heat Loss of Large Coal-Fired Boilers

The main technologies for reducing flue gas heat loss of pulverized coal-fired boilers are introduced, and the suitability of these technologies for boiler operation and the principles for selection of these technologies are explored. The main conclusions are： 1） the non-equilibrium control over flue gas flow rates at the inlet of the air heater and the reversal rotation of the air heater rotator should be popularized as regular technologies in large boilers; 2） increasing the area of the air heater to reduce the flue gas heat loss in pulverized coal-fired boilers should be the top option and increasing the area of the economizer be the next choice; 3） low- pressure economizer technology could save energy under special conditions and should be compared with the technology of increasing economizer area in terms of technical economics when the latter is feasible; 4） the hot primary air heater is only suitable to the pnlvefizing system with a large amount of cold air mixed.

Comparison and Optimization of Mid-low Temperature Cogeneration Systems for Flue Gas in Iron and Steel Plants

Three generation systems, namely, steam Rankine cycle （SRC）, organic Rankine cycle （ORC）, and steam-organic combined Rankine cycle （S-ORC）, were simulated using the Engineering Equation Solver fEES） to efficiently utilize flue gas emissions from 200 to 450 ℃ in iron and steel plants. Based on the simulation results for thermal efficiency, exergy efficiency, and power generation, the performances of the three power generation systems were compared and analyzed. To further utilize waste heat from the turbine exhaust steam of the ORC system, cas- cade （）RC （CORC） was designed for heat sources above 300 ℃. Based on a comprehensive performance comparison, the application of the ORC using R141b is preferable for 200 to 300 ℃ flue gas. For 300 to 450 ℃ flue gas, CORC is an alternative technology to improve the efficiency and quality of waste heat utilization. For flue gas above 450 ℃, S-ORC can achieve higher efficiency and power generation than conventional SRC, with a relatively small negative pressure and high dryness of the turbine outlet steam. Hence, S-ORC can be considered as a substitute for SRC.

Numerical Simulation Analysis of the Transformer Fire Extinguishing Process with a High-Pressure Water Mist System under Different Conditions

To thoroughly study the extinguishing effect of a high-pressure water mist fire extinguishing system when a transformer fire occurs,a 3D experimental model of a transformer is established in this work by employing Fire Dynamics Simulator(FDS)software.More specifically,by setting different parameters,the process of the highpressure water mist fire extinguishing system with the presence of both diverse ambient temperatures and water mist sprinkler laying conditions is simulated.In addition,the fire extinguishing effect of the employed high-pressure water mist system with the implementation of different strategies is systematically analyzed.The extracted results show that a fire source farther away fromthe centerline leads to a lower local temperature distribution.In addition,as the ambient temperature increases,the temperature above the fire source decreases,while the temperature and the concentrationof theupperflue gas layer bothdecrease.Interestingly,after thehigh-pressurewatermist sprinkler begins to operate,both the temperature distribution above the fire source and the concentration of the flue gas decrease,which indicates that the high-pressure water mist system plays the role of cooling and dust removal.By comparing various sprinkler laying methods,it is found that the lower sprinkler height has a better effect on the temperature above the fire source,the temperature of the upper flue gas layer,and the concentration of the flue gas.Moreover,when the sprinkler is spread over thewhole transformer,the cooling effect on both the temperature above the fire source and the temperature of the upper flue gas layer is good,whereas the change in the concentration of the flue gas above the fire source is not obvious compared to the case where the sprinkler is not fully spread.

Oxidation Behaviors of Different Grades of Ferritic Heat Resistant Steels in High-Temperature Steam and Flue Gas Environments

For steam tubes used in thermal power plant,the inner and outer walls were operated in high-temperature steam and flue gas environments respectively.In this study,structure,microstructure and chemical composition of oxide films on inner and outer walls of exservice low Cr ferritic steel G102 tube and exservice high Cr ferritic steel T91 tube were analyzed.The oxide film was composed of outer oxide layer,inner oxide layer and internal oxidation zone.The outer oxide layer on the original surface of tube had a porous structure containing Fe oxides formed by diffusion and oxidation of Fe.More specially,the outer oxide layer formed in flue gas environment would mix with coal combustion products during the growth process.The inner oxide layer below the original surface of tube was made of Fe–Cr spinel.The internal oxidation zone was believed to be the precursor stage of inner oxide layer.The formation of internal oxidation zone was due to O diffusing along grain boundaries to form oxide.There were Fe–Cr–Si oxides discontinuously distributed along grain boundaries in the internal oxidation zone of G102,while there were Fe–Cr oxides continuously distributed along grain boundaries in that of T91.

Study on Calculation Method for Partition of Heat Transfer in an Ultra-supercritical Boiler

Use a 1000MW ultra-supercritical tower boiler as the research object. On the basis of one dimensional model, simplify the tube heat transfer model and the radiation heat transfer model;establish the two-dimensional area calculation model with the regional method;?summarize the heat load distribution of flue gas temperature and water wall surface;and compare with the measured data. The error range of the result is acceptable on the project. The distribution of water wall surface heat load along the furnace width and the area where heat transfer deterioration?cause easily along the furnace height direction are studied with the model and algorithm on different boiler load conditions. All these provide the reference for the design and operation of the ultra supercritical boiler.

基于数值模拟对生物质循环流化床锅炉燃烧优化的研究

基于双流体模型对生物质燃料在循环流化床锅炉的燃烧过程开展模拟研究。模型中考虑固体燃料在炉膛内的干燥、热解和燃烧过程,并通过模拟结果调查下移燃料进口,减少屏式过热器受热面的面积,是否会影响烟气温度。通过对改变燃料进口位置的工况开展模拟研究,发现对于高水分燃料,可通过下移燃料进口,促使其提早干燥并燃烧,且有利于燃烧区整体下移,避免火焰直扫屏式过热器;而在减少屏式过热器的受热面后,烟气的平均温度略有上升,保证了屏式过热器的换热能力。模拟研究表明,合理改变燃烧区的燃烧组织形式,可以实现锅炉稳定运行及维持流化床锅炉热效率的主要因素。

再循环烟气引入位置对1000 MW超超临界锅炉影响的数值模拟研究

锅炉烟气再循环技术不仅能够减少煤粉燃烧过程中生成的NO_(x),还能起到调节再热蒸汽温度的作用,是锅炉低NO_(x)燃烧和调节再热汽温的主要手段之一,国内外对于烟气再循环技术开展了众多研究。但是,目前国内的研究主要集中在再循环烟气量对锅炉燃烧和换热的影响,仍然缺少大型燃煤发电机组中多种再循环烟气引入位置的详细对比研究与分析。本研究以某1000 MW超超临界二次再热四角切圆塔式炉为研究对象,对其建立三维模型并进行燃烧数值模拟,探究再循环烟气引入位置对锅炉燃烧、NO_(x)生成特性、屏底烟温和炉膛换热的影响。结果表明:在所选取的四种不同再循环烟气引入位置中,将再循环烟气与一次风混合后引入,强化了一次风与二次风之间的空气分级效果,能够获得较低的NO_(x)排放量和屏底烟气温度,降低炉膛宽度方向的屏底烟温偏差。引入再循环烟气后,再热器吸热量均有所上升,在炉膛底部引入再循环烟气对锅炉再热蒸汽温度的调整作用更好。

烟气炉烟气温度自动控制系统

为满足喷煤粉系统在制粉过程中对烟气温度的要求,设计了烟气温度自动控制系统。该系统以触摸屏为人机界面,西门子S7-200系列PLCCPU226作为控制核心,以电动机、电动阀、电动执行器为控制对象,通过Modbus通讯协议与远程控制系统通讯,实现了焦炉煤气点火后到高炉煤气的切换和对烟气温度的控制。应用表明,系统操作简单,控制可靠,既满足了工艺要求,又保证了设备安全。

Application of Response Surface Methodology for Analysis of Reheat Steam Temperatures in a Double Reheat Coal-Fired Boiler

For the improvement of reheat steam quality and performance of double reheat coal-fired utility boiler under wide load operation, a variety of temperature regulation ways were utilized to adjust the energy distribution between different heating surfaces. In this paper, thermodynamic calculation based on the fundamental heat transfer theory was conducted for the analysis of temperature regulation strategy effects to steam temperature. In consideration of the specific overlapping heating surface arrangement, the compartment model was adopted to solve this problem. Response surface methodology(RSM) was used to analysis the effect of each temperature regulating variables on the steam temperature and boiler efficiency;then the polynomial model was fitted to predict the primary and secondary steam temperature simultaneously. Results showed that the flue gas recirculation rate has a relatively significant influence on the steam temperature, the maximum temperature deviation between fitting value and calculation value is 3.85℃ in 75% THA;the quadratic model can well predict the steam temperature under different operation conditions in wide load change. The variation of flue gas baffle has a significant influence on the boiler efficiency, compared to the flue gas recirculation and angle of burner oscillation. The influence of various factors on the reheat steam temperature is flue gas baffle > flue gas recirculation > angle of burner oscillation.

Experimental and thermal stress investigation on side wall deformation at the pendent convective pass in a utility boiler

An experimental investigation is performed on side wall deformation at the pendant convective pass (PCP) in a 300 MW and a 600 MW utility boiler. The temperature distributions are measured on the side wall areas of the water-cooled wall, the PCP and the horizontal convective pass (HCP) in the two utility boilers. These experiments show that there are great temperature differences in the side wall areas during the startup process in both utility boilers. These temperature differences can reach 80～150 °C with the side wall temperature in the PCP area higher than those in the water-cooled wall and the HCP. The highest temperature in the PCP is close to the flue gas side temperature at the same position in the horizontal flue gas pass. Thermal stress analyses are conducted in the side wall areas in the water-cooled wall, the PCP and the HCP with the software ANSYS. The results show that, at great temperature differences, the PCP side wall undergoes negative thermal stresses that exceed the yield strength causing deformation in the PCP side wall.

Effects of Optimized Operating Parameters on Combustion Characteristics and NO_(x)Emissions of a Burner based on Orthogonal Analysis

To optimize the structure of the burner,improve the combustion performance,and reduce the emission of NO_(x),a self-circulating low NO_(x)combustion technology was used to design a new type of flue gas self-circulating low NO_(x)burner.Based on previous research on the numerical model of combustion and the composition of mixed gas on combustion and NO_(x)emissions,the effect of various factors on the ejection coefficient of the flue gas self-circulating structure was analyzed using the orthogonal test method,and the burner operating parameters,such as preheating temperature and excess air coefficient,were deeply studied through the three-dimensional finite element numerical model in this paper.The results show that the diameter ratio of the nozzle and the length of the cylindrical section of the flue gas self-circulating structure have great influence on its ejection and mixing ability.The optimal ejection coefficient was 0.4829.Overall,the amount of NO_(x)emissions greatly increased from 6.23×10^(-6)(volume fraction)at the preheating temperature 973 K to 3.5×10^(-3)at preheating temperature 1573 K.When the excess air coefficient decreased from 1.2 to 1,the maximum combustion temperature decreased from 2036.3 K to 1954.22 K,and the NO_(x)emissions decreased from 352.29×10^(-6)to 159.73×10^(-6).

电站锅炉屏底结渣的影响因素及预防措施

随着电站锅炉容量增大、参数提高,煤粉锅炉屏底结渣问题越来越突出,尤其是四角切圆锅炉。分析了影响锅炉屏底结渣的因素,包括烟温过高、煤质影响、烟温偏差等;并借助FLUENT模拟软件,对过量空气系数、燃尽风率和一次风速对屏底烟温的二维平面分布的影响进行了研究,结果表明屏底烟温随着过量空气系数增大而降低,随着一次风速增大而升高,而燃尽风率的影响则较复杂,烟温不再随燃尽风率的变化而单调变化;最后探讨了解决屏底结渣的相关措施与对策。