大型火电机组热经济性的在线计算
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摘要
国家“十一五”节能规划制定的节能降耗目标以及“竞价上网”的市场竞争政策的深入实施,使得降低生产成本、实现火电节能成为火电工业当前形势下亟待解决的一个现实问题。调查表明,火电机组的实际供电煤耗要比设计值高的多,运行水平低是其中的一个主要原因。通过火电机组运行性能的在线监测,指导机组运行,提高运行水平,已被证明是针对火电机组运行管理的一条行之有效的节能途径。
为了实时监测火电机组运行性能、确定影响机组热经济指标的主要因素及其影响程度,从而及时、合理地为运行人员提供操作指导,降低运行因素导致的不必要的损失,提高机组运行的热经济性,有必要对火电机组实时运行性能的定量评价方法进行研究。为此,基于某300MW大型火电机组,本文开展了以下几方面的工作:
1.全面分析了发电机组热经济指标的计算模型及方法,并针对该机组进行了不同工况下的热力计算。计算结果表明:额定负荷下,其锅炉效率为91.68%,汽轮机绝对内效率为43.0%,全厂热效率为38.2%。
2.研究了调节级的变工况计算原理。针对机组采用的顺序阀控制方式,依据喷嘴配汽原理建立了调节级的变工况计算模型,根据特性参数的计算结果绘制了调节级特性曲线,并拟合了曲线方程。计算表明:调节级轮周效率ηu与压比ε呈抛物线关系,ηu=-1.223ε~2+2.345ε-0.321;而流量系数μ与压比ε为线性关系,μ=-3.424ε+3.716。
3.研究了适合汽轮机排汽焓在线计算的方法。由于汽轮机排汽处于湿蒸汽区,其焓值与压力、湿度有关,而现场并不具备测量排汽湿度的有效手段。本文从机组能量平衡的角度,建立了排汽焓在线计算模型,避开了湿度的影响,同时避免了其它算法的迭代计算过程。利用该模型计算得额定负荷下排汽焓为2482.4kJ/kg,与设计值2447.5kJ/kg相比,相对误差仅1.4%。
4.研究了负荷变化时,机组变工况计算的原理和运行参数目标值的确定方法。经过分析,将机组运行参数分为三类,分别采用设计值、热力试验结果和变工况热力计算三种不同的方法确定其目标值。
5.建立了机组主要运行参数耗差的计算模型,并针对该机组的不同负荷进行了参数的耗差分析。额定负荷下,该汽轮机绝对内效率偏差使供电标准煤耗增加6.19g/(kW·h),热力系统各项参数偏差导致供电标准煤耗增加总计5.93g/(kW·h),二者相对误差为4.38%。分析表明经济性下降主要是由新蒸汽压力降低和排汽压力升高导致的。
6.基于建立的模型,利用VB语言和Access数据库开发了火电机组运行性能在线监测分析程序。该程序能够实时监测火电机组当前的运行状况、计算机组的热经济指标并对主要运行参数的耗差进行分析。
For fire power generating units, realizing energy conversation has become an urgent problem solved at present, as a result of the 11~(th) five-year energy-saving layout and the competitive power market. Actual energy consumption is much higher than the planned value, due to the low operating level, showed in a survey. To increase operating level, by on-line monitoring performance and guiding operation, has been proved to be an effective way to save energy.
So as to evaluate their operating performance, ascertain main factors caused unnecessary energy losses, increase thermoeconomic indicators, it is necessary to study the methods of quantitatively evaluating operating performance. So based on a 300MW unit, several aspects were studied as follows:
1. Mathematic models and calculation methods of thermoeconomic indicators were analyzed respectively, and calculations under variable loads were carried out. It showed that, under the rated load, thermal efficiency of the boiler and the turbine was respectively 91.68% and 43.0%, and that of the unit was 38.2%.
2. The theory of off-design calculations for governing stage was deeply studied. Based on the control of sequence valve, calculation models were founded according to the nozzle governing. Characteristic parameters for the governing stage were calculated and characteristic curves were drawn. The curves were described as follows:η_u=-1.223ε~2+2.345ε-0.321,μ=-3.424ε+3.716.η_u,εandμrespectively represent the circumference of wheel efficiency, the pressure ratio and the flow coefficient.
3. On-line calculation methods of steam turbine exhaust enthalpy were studied. For exhaust steam is wet steam, its enthalpy is related to pressure and moisture, but the moisture cannot be obtained in field measurement. On-line calculation models were founded according to energy balance of the unit for avoiding iterative calculation. Under the rated load, the calculated exhaust enthalpy is 2482.4kJ/kg. Compared to the designed value 2447.5kJ/kg, relative error is only 1.4%.
4. The Principle and method of off-desigen calculation for the unit were studied, and determining of the target values for operating parameters was analyzed. Parameters were divided into 3 kinds, and their target values were determined respectively by the design data, the performance test data and the data obtained from off-design calculation.
5. Energy consumption deviations related to key operating parameters and their relationships with loads were studied. Under the rated load, the deviation of turbine efficiency leaded to a 6.19g increase for standard coal consumption, and several key parameters leaded to 5.93g, relative error was 4.38%. The loss was mainly caused by pressure deviations of the new steam and the exhaust, showed analysis results.
6. Based on founded models, software of on-line performance monitoring for a coal-fired power generating unit was developed by using VB language and Access database. It can monitor present operating conditions, calculate thermoeconomic indicators and analyze energy consumption deviations.
为了实时监测火电机组运行性能、确定影响机组热经济指标的主要因素及其影响程度,从而及时、合理地为运行人员提供操作指导,降低运行因素导致的不必要的损失,提高机组运行的热经济性,有必要对火电机组实时运行性能的定量评价方法进行研究。为此,基于某300MW大型火电机组,本文开展了以下几方面的工作:
1.全面分析了发电机组热经济指标的计算模型及方法,并针对该机组进行了不同工况下的热力计算。计算结果表明:额定负荷下,其锅炉效率为91.68%,汽轮机绝对内效率为43.0%,全厂热效率为38.2%。
2.研究了调节级的变工况计算原理。针对机组采用的顺序阀控制方式,依据喷嘴配汽原理建立了调节级的变工况计算模型,根据特性参数的计算结果绘制了调节级特性曲线,并拟合了曲线方程。计算表明:调节级轮周效率ηu与压比ε呈抛物线关系,ηu=-1.223ε~2+2.345ε-0.321;而流量系数μ与压比ε为线性关系,μ=-3.424ε+3.716。
3.研究了适合汽轮机排汽焓在线计算的方法。由于汽轮机排汽处于湿蒸汽区,其焓值与压力、湿度有关,而现场并不具备测量排汽湿度的有效手段。本文从机组能量平衡的角度,建立了排汽焓在线计算模型,避开了湿度的影响,同时避免了其它算法的迭代计算过程。利用该模型计算得额定负荷下排汽焓为2482.4kJ/kg,与设计值2447.5kJ/kg相比,相对误差仅1.4%。
4.研究了负荷变化时,机组变工况计算的原理和运行参数目标值的确定方法。经过分析,将机组运行参数分为三类,分别采用设计值、热力试验结果和变工况热力计算三种不同的方法确定其目标值。
5.建立了机组主要运行参数耗差的计算模型,并针对该机组的不同负荷进行了参数的耗差分析。额定负荷下,该汽轮机绝对内效率偏差使供电标准煤耗增加6.19g/(kW·h),热力系统各项参数偏差导致供电标准煤耗增加总计5.93g/(kW·h),二者相对误差为4.38%。分析表明经济性下降主要是由新蒸汽压力降低和排汽压力升高导致的。
6.基于建立的模型,利用VB语言和Access数据库开发了火电机组运行性能在线监测分析程序。该程序能够实时监测火电机组当前的运行状况、计算机组的热经济指标并对主要运行参数的耗差进行分析。
For fire power generating units, realizing energy conversation has become an urgent problem solved at present, as a result of the 11~(th) five-year energy-saving layout and the competitive power market. Actual energy consumption is much higher than the planned value, due to the low operating level, showed in a survey. To increase operating level, by on-line monitoring performance and guiding operation, has been proved to be an effective way to save energy.
So as to evaluate their operating performance, ascertain main factors caused unnecessary energy losses, increase thermoeconomic indicators, it is necessary to study the methods of quantitatively evaluating operating performance. So based on a 300MW unit, several aspects were studied as follows:
1. Mathematic models and calculation methods of thermoeconomic indicators were analyzed respectively, and calculations under variable loads were carried out. It showed that, under the rated load, thermal efficiency of the boiler and the turbine was respectively 91.68% and 43.0%, and that of the unit was 38.2%.
2. The theory of off-design calculations for governing stage was deeply studied. Based on the control of sequence valve, calculation models were founded according to the nozzle governing. Characteristic parameters for the governing stage were calculated and characteristic curves were drawn. The curves were described as follows:η_u=-1.223ε~2+2.345ε-0.321,μ=-3.424ε+3.716.η_u,εandμrespectively represent the circumference of wheel efficiency, the pressure ratio and the flow coefficient.
3. On-line calculation methods of steam turbine exhaust enthalpy were studied. For exhaust steam is wet steam, its enthalpy is related to pressure and moisture, but the moisture cannot be obtained in field measurement. On-line calculation models were founded according to energy balance of the unit for avoiding iterative calculation. Under the rated load, the calculated exhaust enthalpy is 2482.4kJ/kg. Compared to the designed value 2447.5kJ/kg, relative error is only 1.4%.
4. The Principle and method of off-desigen calculation for the unit were studied, and determining of the target values for operating parameters was analyzed. Parameters were divided into 3 kinds, and their target values were determined respectively by the design data, the performance test data and the data obtained from off-design calculation.
5. Energy consumption deviations related to key operating parameters and their relationships with loads were studied. Under the rated load, the deviation of turbine efficiency leaded to a 6.19g increase for standard coal consumption, and several key parameters leaded to 5.93g, relative error was 4.38%. The loss was mainly caused by pressure deviations of the new steam and the exhaust, showed analysis results.
6. Based on founded models, software of on-line performance monitoring for a coal-fired power generating unit was developed by using VB language and Access database. It can monitor present operating conditions, calculate thermoeconomic indicators and analyze energy consumption deviations.
引文
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[2]北京康电信息技术有限公司,机组性能监测与运行优化EtaPRO产品介绍
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[7]郑体宽,热力发电厂,北京,中国电力出版社,2001.3,144-150
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[2]北京康电信息技术有限公司,机组性能监测与运行优化EtaPRO产品介绍
[3]Westinghouse Process Control Inc.,SmartProcess Overview
[4]许继刚,郑慧莉,电厂管理控制-体化信息系统的发展,电力系统自动化,2001,25(7),59-63
[5]侯子良,再论火电厂厂级监控信息系统,电力系统自动化,2002.8,26(15),1-3
[6]侯子良,SIS发展到推广应用新时间面临的两大问题,中国电力,2005.1,38(1),62-64
[7]郑体宽,热力发电厂,北京,中国电力出版社,2001.3,144-150
[8]马芳礼,电厂热力系统节能分析原理,北京,水利电力出版社,1992
[9]林万超,火电厂热系统节能理论,西安交通大学出版社,1994,22
[10]张春发,郭民臣,电厂热力系统分析中的两个重要参量,工程热物理学报,1993.11,14(4),365-368
[11]张春发,张明智,周健等,再热机组热经济性分析的两个重要参数,中国电力,1993.12,54-58
[12]郭江龙,张树芳,宋之平等,火电厂热力系统热经济性矩阵分析方法,中国电机工程学报,2004.1,24(1),205-209
[13]郭江龙,张树芳,宋之平等,基于等效热降理论的热力系统热经济性矩阵分析方法及其应用,工程热物理学报,2004.9,25(5),729-732
[14]郭丙然,火电厂计算机分析,北京,水利电力出版社,1991
[15]陈国年,钟史明,电厂热力系统矩阵计算法,汽轮机技术,1991.10,33(5),39-45
[16]郭民臣,王清照,魏楠等,电厂热力系统矩阵分析方法的改进,热能动力工程,1997.3,12(2),103-106
[17]郭民臣,王清照,魏楠,电厂热力系统的定功率方程及热效率,现代电力,1997.6,14(2),11-16
[18]郭民臣,王清照,魏楠等,热(汽)耗变换系数法-分析电厂热力系统的新方法,中国电机工程学报,1997.7,17(4),227-229
[19]郭民臣,魏楠,刘文毅,“自由路径法则” 在电厂热力系统分析中的应用,中国电机工程学报,2002.4,22(4),122-126
[20]Valero A.,Lozano M.A.etc.On-line Monitoring of Power-plant pertormance using Exergetic cost Techniques,Applied thermal engineering,1996,16(12),933-948
[21]王加旋,王清照,宋乃辉,热经济学研究的使命与任务,热能动力工程,2002-3,17(98),79-82
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