Forced Compressed Air Cooling System for a 300 MW Steam Turbine in Waigaoqiao Power Plant

The 300 MW steam turbine installed in Waigaoqiao Power Plant with combined HPIP cylinders of double casing structure is a product of the Shanghai Turbine Works utilizing licensed technology. It has a large heat storage capacity and good thermal insulation, so the metal temperature of first stage of HP cylinder (FSMTI) may reach 400-450℃ after shut down and it takes 7-8 days to cool to 150℃ by natural cooling, Now with a forced cooling system the cooling time may be reduced to 40 hours, so that the turbine may be opened for repair work in about 5-6 days. The cooling system for #2 unit and test procedure are briefly described below.

Transient Heat Transfer Study of Direct Contact Condensation of Steam in Spray Cooling Water

We conducted a transient experimental investigation of steam–water direct contact condensation in the absence of noncondensible gas in a laboratory-scale column with the inner diameter of 325 mm and the height of 1045 mm. We applied a new analysis method for the steam state equation to analyze the molar quantity change in steam over the course of the experiment and determined the transient steam variation. We also investigated the influence of flow rates and temperatures ofcooling water on the efficiency ofsteam condensation. Our experimental results show that appropriate increasing of the cooling water flow rate can significantly accelerate the steam condensation. We achieved a rapid increase in the total volumetric heat transfer coefficient by increasing the flow rate of cooling water, which indicated a higher thermal convection between the steam and the cooling water with higher flow rates. We found that the temperature ofcooling water did not play an important role on steam condensation. This method was confirmed to be effective for rapid recovering ofsteam.

Feasibility Analysis of Back-Pressure Steam Feeding Water Pump for Direct Air-Cooled Unit

As the performance of an air-cooled condenser is apt to be affected by the fluctuating ambient condition, some difficulties are brought to the use of a steam feeding water pump in an air-cooled unit. This paper introduces a new design of for steam feeding the water pump of an air-cooled unit using the back-pressure steam turbine as the prime motor. Using variable condition analysis on a 600 MW direct air-cooled unit, and with consideration of the effect on the ambient conditions, the feasibility, economy, and adaptability of the design are verified.

Calculation of the Choked Back Pressure for Steam Turbines with Air Cooled Condensers

The choked back pressure characteristic of the steam turbine unit with air cooled condenser is very different with the unit with wet cooling technology, and the understanding of the choked back pressure performance change with operation load is important to guide the economic operation of the unit. One simplified Variable Operation Condition Analysis Method was put forward for calculation of the unit output-turbine back pressure characteristics. Based on this method, the choked back pressure for each operation load can be determined. An example was given for a super-critical, regenerative single-shaft, 2-casing with 2-exhaust steam turbine generation unit with air cooled condenser. The calculation result was provided and compared with the result of the unit with wet cooling technology.

Influence of thermal flow field of cooling tower on recirculation ratio of a direct air-cooled system for a power plant

In order to get thermal flow field of direct air-cooled system,the hot water was supplied to the model of direct air-cooled condenser(ACC). The particle image velocimetery (PIV) experiments were carried out to get thermal flow field of a ACC under different conditions in low velocity wind tunnel,at the same time,the recirculation ratio at cooling tower was measured,so the relationship between flow field characteristics and recirculation ratio of cooling tower can be discussed. From the results we can see that the flow field configuration around cooling tower has great effects on average recirculation ratio under cooling tower. The eddy formed around cooling tower is a key reason that recirculation produces. The eddy intensity relates to velocity magnitude and direction angle,and the configuration of eddy lies on the geometry size of cooling tower. So changing the flow field configuration around cooling tower reasonably can decrease recirculation ratio under cooling tower,and heat dispel effect of ACC can also be improved.

Influence of Different Vortex Generators on Heat Transfer in Direct Air-Cooled Condensers

通过数值模拟研究了矩形小翼、三角小翼、梯形小翼、柱面梯形翼、柱面三角翼和柱面矩形翼等6种涡流发生器分别安装于直接空冷凝汽器单排蛇形翅片扁管中的压降和换热性能。Re数在600~1800范围内,涡流发生器采用相同高宽比、尾高、攻角以及安装位置。结果表明：矩形小翼的换热及压降增大最多,Re=1729时,相比平直翅片分别增加了14.27%和18.32%。Re=1 729时,柱面梯形翼的压力损失比矩形小翼少4.7%,换热低1.5%。当以（j/j0）/（f/f0）1/3作为综合换热性能评价标准时,柱面梯形翼的综合换热性能最好。另外,考察了柱面梯形翼倾角的影响（0°、6°、12°、20°、24°和26°）,相同工况下,倾角为12°的柱面梯形翼换热最好（较平直翅片增强4.29%~14.1%）、压降最小（增大7.5%~12.8%）且综合换热性能最好。柱面梯形翼因其迎流面积与斜边长度的匹配以及流线型柱面,具有良好的强化传热效果以及较小的压降。

Waste heat water pumping model with direct contact cooling

The performance of a patented water pumping model with steam-air power was presented, which operates automatically by direct contact cooling method. The main objective was to study feasibility of a pumping model for underground water. In this model, a heater installed within the heat tank represented sources of waste heat as energy input for finding appropriate conditions of the 10 L pump model. The system operation had five stages: heating, pumping, vapor flow, cooling, and water suction. The overall water heads of 3, 4.5, 6 and 7.5 m were tested. At the same time, it was found that the pump with 50% air volume is sufficient for pumping water to a desired level. In the experiment, the temperatures in the heating and pumping stages were 100-103 °C and 80-90 °C, respectively. The pressure in the pumping stage was 12-18 kPa, and the pressure in the suction stage was about-80 kPa, sufficient for the best performance. It could pump 170 L of water at a 2 m suction head, 120 L at a 3.5 m suction head, 100 L at a 5 m suction head, and 65 L at a 6.5 m suction head in 2 h. A mathematical model for larger pumps was also presented, which operates nearly the same as the present system. Economic analysis of the 10 L pump was also included.

空冷机组汽轮机主轴直接驱动给水泵的变工况运行仿真试验

汽轮机主轴直接驱动给水泵技术是一种全新的给水泵驱动方式,目前国内尚无成熟的运行经验。针对采用该技术的某350 MW直接空冷机组进行了系列变工况运行仿真试验。结果表明:对于配置1台100%容量主机泵和1台50%容量备用泵的机组,该技术完全能够满足在机组背压快速变化、负荷变化及给水泵故障等工况下给水流量的需求。

光热电站主机直接空冷系统优化探讨

光热发电是一种比较有发展前景的可再生能源发电形式,具有良好的储能和调峰能力。受制于水资源条件,目前我国光热电站的主机冷却系统多采用直接空冷系统。直接空冷系统配置对机组经济性和盈利能力均会产生较大影响。在总结和分析光热电站投资构成及运行特点的前提下,依托某案例工程进行直接空冷系统优化计算和分析。对光热电站直接空冷系统气象数据选取与处理、以及电价敏感性分析进行初步探讨。由于上网电价及成本电价普遍较高,与常规火电厂直接空冷系统相比较,光热电站直接空冷系统配置倾向于初始温差(ITD)值较低、风速较小、空冷凝汽器面积较大的方案。

直接空冷机组尖峰冷却系统冷却倍率优化

为了提高燃煤直接空冷机组尖峰冷却系统的经济性,提出了尖峰冷却系统冷却倍率优化计算的方法;在参照EPC招标文件要求的基础上确定了尖峰冷却系统的凝汽量,并重点探讨了带表面式凝汽器的尖峰冷却系统的最优冷却倍率。研究表明,“表面式凝汽器+机力塔+循环泵”的尖峰冷却系统在设计凝汽量、设计温度35℃下的最佳冷却倍率为35倍,随着环境温度的降低,对应温度下的最佳冷却倍率增大;600 MW超临界直接空冷发电机组,尖冷凝汽量280 t/h时,扣除水资源费用后,年收益为886.92万元。

Improved Design of a 25 MW Gas Turbine Plant Using Combined Cycle Application

This paper presents the improved design of a 25 MW gas turbine power plant at Omoku in the Niger Delta area of Nigeria, using combined cycle application. It entails retrofitting a steam bottoming plant to the existing 25 MW gas turbine plant by incorporating a heat recovery steam generator. The focus is to improve performance as well as reduction in total emission to the environment. Direct data collection was performed from the HMI monitoring screen, log books and manufacturer’s manual. Employing the application of MATLAB, the thermodynamics equations were modeled and appropriate parameters of the various components of the steam turbine power plant were determined. The results show that the combined cycle system had a total power output of 37.9 MW, made up of 25.0 MW from the gas turbine power plant and 12.9 MW (an increase of about 51%) from the steam turbine plant, having an HRSG, condenser and feed pump capacities of 42.46 MW, 29.61 MW and 1.76 MW respectively. The condenser cooling water parameters include a mass flow of 1180.42 kg/s, inlet and outlet temperatures of 29.8°C and 35.8°C respectively. The cycle efficiency of the dry mode gas turbine was 26.6% whereas, after modification, the combined cycle power plant overall efficiency is 48.8% (about 84% increases). Hence, SIEMENS steam turbine product of MODEL: SST-150 was recommended as the steam bottoming plant. Also the work reveals that a heat flow of about 42.46 MW which was otherwise being wasted in the exhaust gas of the 25 MW gas turbine power plant could be converted to 12.9 MW of electric power, thus reducing the total emission to the environment.

The Experimental Investigation of Recirculation of Air-Cooled System for a Large Power Plant

The paper introduces thermal buoyancy effects to experimental investigation of wind tunnel simulation on direct air-cooled condenser for a large power plant. In order to get thermal flow field of air-cooled tower, PIV experiments are carried out and recirculation ratio of each condition is calculated. Results show that the thermal flow field of the cooling tower has great influence on the recirculation under the cooling tower. Ameliorating the thermal flow field of the cooling tower can reduce the recirculation under the cooling tower and improve the efficiency of air-cooled condenser also.

不同单元型式的直接空冷岛数值试验对比研究

利用ANSYS Fluent软件研究某2×660MW直接空冷岛,以期提高其整体换热性能。对不同单元型式、散热器管束和风机布置方式下的空冷岛方案进行流动和传热特性的数值模拟、分析和研究。在环境风速风向的影响下,不同布置型式的空冷岛出现一定的性能差异。静风状态下,不同布置方案的空冷岛通风量及换热量之间的差别很小,均在1%以内。TRL考核风速各风向下,与常规空冷布置方案相比,双小“A”风机低位布置方案的机组背压较低。炉后风向下,双小“A”风机低位布置方案的机组平均背压低于常规布置方案约1.57kPa。

电厂汽轮机空冷系统优化及节能降耗研究

汽轮机真空度是衡量汽轮机组运行效果的核心指标,真空系统的严密性则是影响汽轮机真空的重要因素。受凝汽器真空严密性差的影响,某电厂汽轮机组负荷逐年下降。本文结合该电厂汽轮机空冷系统运行现状,探寻电厂汽轮机空冷系统的优化方法,以期进一步降低汽轮机单位发电煤耗,有效促进电厂节能降耗,最终实现绿色发展。

耦合碳捕集的直接空冷燃煤机组特性分析和背压优化

配置碳捕集技术将大幅改变直接空冷燃煤机组中汽机–给水和冷端系统的工质与能量分配,导致安全风险和经济损失。为提高耦合碳捕集的直接空冷燃煤机组发电效率,该文建立发电–碳捕集系统的全工况动态机理模型,分析变捕集率条件下子系统状态和整体经济性,揭示出捕集率对背压–发电功率和背压–风机耗功的影响规律,提出以热耗率最小为优化目标,以捕集率、锅炉负荷和环境参数为边界条件的背压优化方法。结果表明:每增大1%的CO_(2)捕集率对应1.06MW发电功率损失和15.2kJ/(kW·h)热耗率增量;背压优化降低了发电热耗约200~260kJ/(kW·h);捕集率为90%时,最优背压低至3.85kPa;高温、大风和高负荷时,捕集率的变化对最优背压影响较大。结果可为空冷燃煤–碳捕集整体系统的变工况高效运行提供决策依据。

先进超超临界空冷汽轮发电机组高位布置技术及工程应用

提高燃煤发电机组效率是实现节能降碳的直接手段,700℃超超临界发电的工程应用受制于高温合金材料价格成本阻碍,有必要探索新布置、新结构、缩短高温蒸汽管道以降低工程造价。本文以锦界电厂三期为例,介绍了超超临界空冷汽轮发电机组高位布置技术取得的工程化创新实践。该工程实践表明,锦界电厂三期作为世界首例高位布置示范工程,主厂房采用钢筋混凝土框架-剪力墙结构,可有效降低整体重心、提高抗震性能,通过技术攻关有效保障主厂房结构、高温蒸汽管道和汽轮发电机组的安全性;与常规布置(运转层12.6~17 m标高)相比,高位布置(运转层65 m标高)主蒸汽、再热蒸汽管道分别可节省材料约34.2%、20.9%,空冷岛排汽管道可节省的材料达93%,还可以较设计值节省供电煤耗4.5~5.1 g/(kW·h),整体技术经济性显著提高;此外,项目投产后的运行监测数据显示,主厂房结构实时在线监测系统各参数均在安全阈值范围内,厂房结构、关键设备均处于安全状态。研究建议,加快发展清洁高效燃煤发电技术,统筹协调我国富煤缺水“三北”地区清洁高效先进空冷煤电机组应用高位布置技术,为未来700℃超超临界煤电机组建设节约高温蒸汽管道提供实践经验。

环境风向对自然通风直接空冷塔散热影响

自然通风直接空冷系统既不需要机械通风风机,也不需要间接空冷系统的循环水泵,大幅度降低了噪声、厂用电率和供电煤耗,符合“低碳”时代发展要求。自然通风直接空冷系统在大容量机组尚未应用,需掌握环境风向对自然通风直接空冷塔散热的影响规律。利用流体力学模型仿真FLUENT软件,对2×660 MW机组的直接空冷塔不同风向进行数值模拟,得到不同风向下各散热三角的通风量和散热量分布特点、直接空冷塔总体散热性能以及风向对直接空冷塔和主厂房总体布置的影响。结果表明,2台机组的自然通风直接空冷塔的中心连线优先与主导风向平行。

直接空冷乏汽提质供热系统变工况特性研究

直接空冷机组高背压供热方式受热网循环水回水温度和空冷岛换热单元协调控制的限制,运行经济性和发电出力两者之间难以平衡。为解决上述矛盾,采用商业软件Ebsilon Professional对直接空冷乏汽提质供热系统在不同负荷下的空冷岛背压、汽轮机出力、汽轮机热耗和喷射器引射比等关键性能进行了变工况计算和分析。计算结果表明,乏汽提质供热系统在冬季低负荷时最佳运行背压为13~20 kPa,可以实现供热能量的梯级利用和机组出力的平衡,并满足防冻安全的运行要求。

直接空冷系统技术改进及能效提升研究

为实现火电厂“提效-节能降耗”目标,解决常规直接空气冷风系统换热效率低、运行背压高等问题,通过对其排汽管道系统、散热器管束型式及风机组布置方式进行技术改进和能效提升研究,提出了一种新型直接空冷系统布置方案。新方案采用风机低位布置双“A”型散热器空冷布置型式,通过结构应力计算和流场数值模拟,相比常规的空冷系统,可得以下结论:(1)在满足系统结构安全性的前提下,新型排汽管道布置方式的出口至蒸汽分配管入口总阻力压降减少约400 Pa,排汽管道内流量分配更均匀;(2)双小A型散热器管束布置,可缩短管束长度约一半,加快蒸汽冷却,减少不凝结气体的堆积,防冻性能更好;(3)在冷却三角布置标高不变的条件下,将风机下移至钢桁架底部,使风机出口至冷却三角底部之间存在一定空间可对新空气起“导流、梳理”作用,在散热器出口面,同样形成风速带,沿高度方向增大,蒸汽分配管附近高速区域进一步增大,冷却单元的换热效果将进一步得到增强,散热器出口风速优于常规布置,进而使进入冷却三角的空气流动状态稳定,提高冷却三角散热效率。经过某电厂现场应用,其空冷机组夏季运行背压降低约2 kPa,全年平均运行背压降低约0.8 kPa,煤耗减少约1 g/(kW·h),单台机组每年可为电厂节省煤炭费用约276万元(标煤价1 000元/t)。该方案在降低机组背压的同时,可减少膨胀节组合数量、钢结构重量等,也降低了空气侧风阻,缓解了空冷凝汽器的防冻问题。因此,所提方案既可降低设备的一次性投资,又具有在运行费用方面(节省煤耗)的明显优势,可实现电煤的清洁和高效利用,取得良好的社会效益,具有很大的推广价值和广泛的应用前景。