Optimal thermodynamic and economic volume of a heat recovery steam generator by constructal design

The ratios of gas flow to steam flow are huge in heat recovery steam generators (HRSGs) compared to other steam generators. So the volume which is occupied by components of the HRSG such as economizer, evaporator and superheater is important factor when the HRSG is applied in structures including buildings and ships. The optimum volume of a HRSG is deduced through optimization of entropy generation and cost evaluation. By increasing volume, second law of thermodynamics is improved, but this improvement may not be economical. In this work, the best dimensions and arrangements of flows in HRSG are obtained by constructal design and the optimization method is algorithm genetic. In this case, super heater temperature, pinch point, water/steam flow rate and gas pressure drop are derived from configuration which designed by constructal theory for HRSG. The effects of gas flow rate and inlet gas temperature are examined on the values of optimum volume.     

Thermodynamic optimization of design variables and heat exchangers layout in HRSGs for CCGT,using genetic algorithm

The heat recovery steam generator (HRSG) is one of the few equipments that are custom made for combined cycle power plants, and any change in its design affects all performance parameters of a steam cycle directly. Thus providing an optimization tool to optimize its design parameters and the layout of its heat exchangers is of great importance. A new method is introduced for modeling a steam cycle in advanced combined cycles by organizing non-linear equations and their simultaneous solutions by use of the hybrid Newton methods in this article. Thereafter, optimal thermodynamic performance conditions for HRSGs are calculated with the help of the genetic algorithm. In the conclusion, the results obtained for different types of HRSGs are compared. The results show that the use of several pressure levels in HRSGs increases the power production in the steam cycle, and similarly, reheating is very beneficial in three pressure heat recovery steam generators.     

Thermoeconomic optimization of combined cycle gas turbine power plants using genetic algorithms

This paper shows a possible way to achieve a thermoeconomic optimization of combined cycle gas turbine (CCGT) power plants. The optimization has been done using a genetic algorithm, which has been tuned applying it to a single pressure CCGT power plant. Once tuned, the optimization algorithm has been used to evaluate more complex plants, with two and three pressure levels in the heat recovery steam generator (HRSG).The variables considered for the optimization were the thermodynamic parameters that establish the configuration of the HRSG.Two different objective functions are proposed: one minimizes the cost of production per unit of output and the other maximizes the annual cash flow. The results obtained with both functions are compared in order to find the better optimization strategy.The results show that it is possible to find an optimum for every design parameter. This optimum depends on the selected optimization strategy.     

Thermoeconomic optimization of heat recovery steam generators operating parameters for combined plants

The optimization of the heat recovery steam generator (HRSG) is particularly interesting for the combined plants design in order to maximise the work obtained in the vapour cycle. A detailed optimization of the HRSG is a very difficult problem, depending on several variables. The first step is represented by the optimization of the operating parameters. These are the number of pressure levels, the pressures, the mass flow ratio, and the inlet temperatures to the HRSG sections. The operating parameters can be determined by means both of a thermodynamic and of a thermoeconomic analysis, minimising a suitable objective function by analytical or numerical mathematical methods. In the paper, thermodynamic optimization is based on the minimization of exergy losses, while the thermoeconomic optimization is based on the minimization of the total HRSG cost, after the reduction to a common monetary base of the costs of exergy losses and of installation.     

Optimization of fire tube heat recovery steam generators for cogeneration plants through genetic algorithm

In the present paper, a small cogeneration system including a gas microturbine and a fire tube heat recovery steam generator (HRSG) is considered. The HRSG system is optimized considering two different objective functions. Sum of the exergy losses resulting from the gases leaving the stack and the exergy destruction due to the internal irreversibility is considered as the first objective function while the second objective function is considered to be the sum of annualized values of the capital cost and the cost of the energy loss. The cost of energy loss includes the cost of the loss by hot gases leaving the stack and the cost of the reduction in the power production in the microturbine as the result of the pressure drop in the HRSG. Finally multi-objective optimization method via genetic algorithm is employed to find the optimum values of the design parameters. A decision making process based on finding the closest point to the ideal point is used. Results of different optimum points on the Pareto front are compared and discussed. The results show that the thermodynamic optimization doesn’t lead to major improvement of the total cost of the HRSG although the thermoeconomic and multi-objective methods improve the total cost of the system due decrease in the cost of energy loss due to decrease in the pinch point.     

燃气-蒸汽联合循环余热锅炉技术研究现状

燃气-蒸汽联合循环技术发展迅速，余热锅炉处于燃气轮机和蒸汽轮机之间，是燃气-蒸汽联合循环电站的三大主要设备之一。论述了国内外关于余热锅炉在受热面布置、烟气流动特性、热力参数优化、快速启停和变工况运行等方面的研宛现状，并指出了其中的不足。对联合循环余热锅炉的研宛开发和优化谩计有一定的参考意义。     

Study of a deaerator location in triple-pressure reheat combined power cycle

Deaerator is an essential open feed water heater in the steam bottoming cycle to improve the efficiency and also to remove the dissolved gasses from the feed water. Heat recovery steam generator (HRSG) plays a key role on the performance of the combined cycle (CC). In this work, attention has been focused to improve the performance of a triple pressure (TP) CC with a deaerator location. In this work, two options for deaerator location, one at condenser (deaerator–condenser) and the other in between low pressure (LP) and intermediate pressure (IP) heaters have been studied to increase the heat recovery from the gas turbine exhaust. The compressor pressure ratio is not fixed initially and evaluated from HRSG inlet condition. The LP and IP in HRSG have been evaluated from the local flue gas temperature to get the minimum possible temperature difference in the heaters. The results show that the deaerator placed in between the LP and IP heaters, gives high efficiency compared to a deaerator–condenser arrangement. The optimum conditions for the HRSG, deaerator and steam reheater are evaluated through the thermodynamic study. The results are validated by comparing with the published results.     

Comparative performance analysis of cogeneration gas turbine cycle for different blade cooling means

The paper compares the thermodynamic performance of MS9001 gas turbine based cogeneration cycle having a two-pressure heat recovery steam generator (HRSG) for different blade cooling means. The HRSG has a steam drum generating steam to meet coolant requirement, and a second steam drum generates steam for process heating. Gas turbine stage cooling uses open loop cooling or closed loop cooling schemes. Internal convection cooling, film cooling and transpiration cooling techniques employing steam or air as coolants are considered for the performance evaluation of the cycle. Cogeneration cycle performance is evaluated using coolant flow requirements, plant specific work, fuel utilisation efficiency, power-to-heat-ratio, which are function of compressor pressure ratio and turbine inlet temperature, and process steam drum pressure. The maximum and minimum values of power-to-heat ratio are found with steam internal convection cooling and air internal convection cooling respectively whereas maximum and minimum values of fuel utilisation efficiency are found with steam internal convection cooling and closed loop steam cooling. The analysis is useful for power plant designers to select the optimum compressor pressure ratio, turbine inlet temperature, fuel utilisation efficiency, power-to-heat ratio, and appropriate cooling means for a specified value of plant specific work and process heating requirement.     

Exergy and Energy Analysis of Combined Cycle systems with Different Bottoming Cycle Configurations

The paper deals with thermodynamic analysis of cooled gas turbine‐based gas‐steam combined cycle with single, dual, or triple pressure bottoming cycle configuration. The cooled gas turbine analyzed here uses air as blade coolant. Component‐wise non‐dimensionalized exergy destruction of the bottoming cycle has been quantified with the objective to identify the major sources of exergy destruction. The mass of steam generated in different configurations of heat recovery steam generator (HRSG) depends upon the number of steam pressure drums, desired pressure level, and steam temperature. For the selected set of operating parameters, maximum steam has been observed to be generated in the case of triple pressure HRSG = 19 kg/kg and minimum in single pressure HRSG = 17.25 kg/kg. Plant‐efficiency and plant‐specific works are both highest for triple‐pressure bottoming cycle combined cycle. Non‐dimensionalized exergy destruction in HRSG is least at 0.9% for B3P, whereas 1.23% for B2P, and highest at 3.2% for B1P illustrating that process irreversibility is least in the case of B3P and highest in B1P. Copyright © 2012 John Wiley & Sons, Ltd.     

Performance Improvement of Combined Cycle Power Plant Based on the Optimization of the Bottom Cycle and Heat Recuperation

Many F class gas turbine combined cycle(GTCC)power plants are built in China at present because of less emis-sion and high efficiency.It is of great interest to investigate the efficiency improvement of GTCC plant.A com-bined cycle with three-pressure reheat heat recovery steam generator(HRSG)is selected for study in this paper.In order to maximize the GTCC efficiency,the optimization of the HRSG operating parameters is performed.Theoperating parameters are determined by means of a thermodynamic analysis,i.e.the minimization of exergylosses.The influence of HRSG inlet gas temperature on the steam bottoming cycle efficiency is discussed.Theresult shows that increasing the HRSG inlet temperature has less improvement to steam cycle efficiency when itis over 590℃.Partial gas to gas recuperation in the topping cycle is studied.Joining HRSG optimization with theuse of gas to gas heat recuperation,the combined plant efficiency can rise up to 59.05% at base load.In addition,the part load performance of the GTCC power plant gets much better.The efficiency is increased by 2.11% at75% load and by 4.17% at 50% load.     

A general method for the optimum design of heat recovery steam generators

The optimization of the heat recovery steam generator (HRSG) is one of the key elements for increasing the efficiency of combined plants. According to the current technical practice, it can be organized at different levels of complexity with objectives sequentially defined: operating parameters, geometrical details and technological elements.

According to this point of view, in the paper a complete strategy for the optimum design of the HRSG is outlined. The optimization is organized at two levels: the first one enables to obtain the main operating parameters of the HRSG, while the second involves the detailed design of the component concerning the geometric variables of the heat transfer sections. The output of the first-level optimization is the input of the second level. In particular, the second level of the optimization can be articulated in two different steps. The first step can be aimed to the minimization of the pressure drop for a given heat flow. The second step leads to a reduction of the overall dimensions, maintaining the imposed performance of the HRSG in terms of heat flow and pressure drop. The whole procedure is tested with reference to a case of existing HRSG structures; it shows the possibility of improving performance maintaining a constrained packaged size.     

纯低温双压余热发电系统性能分析及参数优化

针对新型干法水泥窑纯低温双压余热发电系统,进一步完善了性能评价方法,以 5 000t/d水泥生产过程为实例分析了窑头AQC、窑尾SP余热锅炉废气参数、高压段、低压段蒸汽参数、公共省煤器出口水温对余热发电系统性能的影响以及各参数之间的耦合关系.结果表明:在确定的水泥窑废气参数下,通过对纯低温双压余热发电系统热力参数的优化,能够进一步提高余热发电量.     

IGCC系统关键部件的选择及其对电厂整体性能的影响——(3)气化炉合成气冷却器与余热锅炉的匹配

带有合成气冷却器的气化炉,因能将高温合成气中的显热提供给余热锅炉,其系统效率高且更具有研究价值．采用GT PRO软件,研究了余热锅炉和合成气冷却器联合运行的工作过程．模拟和对比了余热锅炉在不同位置抽取和回送冷却介质对系统整体技术、经济性能造成的影响．综合分析之后,提出了几种性价比较高的流程布置．     

A performance analysis of integrated solid oxide fuel cell and heat recovery steam generator for IGFC system

Solid oxide fuel cell (SOFC) is a promising technology for electricity generation. Sulfur-free syngas from a gas-cleaning unit serves as fuel for SOFC in integrated gasification fuel cell (IGFC) power plants. It converts the chemical energy of fuel gas directly into electric energy, thus high efficiencies can be achieved. The outputs from SOFC can be utilized by heat recovery steam generator (HRSG), which drives the steam turbine for electricity production. The SOFC stack model was developed using the process flow sheet simulator Aspen Plus, which is of the equilibrium type. Various ranges of syngas properties gathered from different literature were used for the simulation. The results indicate a trade-off efficiency and power with respect to a variety of SOFC inputs. The HRSG located after SOFC was included in the current simulation study with various operating parameters. This paper describes IGFC power plants, particularly the optimization of HRSG to improve the efficiency of the heat recovery from the SOFC exhaust gas and to maximize the power production in the steam cycle in the IGFC system. HRSG output from different pressure levels varies depending on the SOFC output. The steam turbine efficiency was calculated for measuring the total power plant output. The aim of this paper is to provide a simulation model for the optimal selection of the operative parameters of HRSG and SOFC for the IGFC system by comparing it with other models. The simulation model should be flexible enough for use in future development and capable of predicting system performance under various operating conditions.     

A performance analysis of integrated solid oxide fuel cell and heat recovery steam generator for IGFC system

Solid oxide fuel cell (SOFC) is a promising technology for electricity generation. Sulfur-free syngas from a gas-cleaning unit serves as fuel for SOFC in integrated gasification fuel cell (IGFC) power plants. It converts the chemical energy of fuel gas directly into electric energy, thus high efficiencies can be achieved. The outputs from SOFC can be utilized by heat recovery steam generator (HRSG), which drives the steam turbine for electricity production. The SOFC stack model was developed using the process flow sheet simulator Aspen Plus, which is of the equilibrium type. Various ranges of syngas properties gathered from different literature were used for the simulation. The results indicate a trade-off efficiency and power with respect to a variety of SOFC inputs. The HRSG located after SOFC was included in the current simulation study with various operating parameters. This paper describes IGFC power plants, particularly the optimization of HRSG to improve the efficiency of the heat recovery from the SOFC exhaust gas and to maximize the power production in the steam cycle in the IGFC system. HRSG output from different pressure levels varies depending on the SOFC output. The steam turbine efficiency was calculated for measuring the total power plant output. The aim of this paper is to provide a simulation model for the optimal selection of the operative parameters of HRSG and SOFC for the IGFC system by comparing it with other models. The simulation model should be flexible enough for use in future development and capable of predicting system performance under various operating conditions.     

Energetic and exergetic analysis of a hybrid combined‐nuclear power plant

Combined‐cycle power plants are currently preferred for new power generation plants worldwide. The performance of gas‐turbine engines can be enhanced at constant turbine inlet temperatures with the addition of a bottoming waste‐heat recovery cycle. This paper presents a study on the energy and exergy analysis of a novel hybrid Combined‐Nuclear Power Plant (HCNPP). It is thus interesting to evaluate the possibility of integrating the gas turbine with nuclear power plant of such a system, utilizing virtually free heat. The integration arrangement of the AP600 NPP steam cycle with gas turbines from basic thermodynamic considerations will be described. The AP600 steam cycle modifications to combine with the gas turbines can be applied to other types of NPP. A simple modeling of Alstom gas turbines cycle, one of the major combined‐cycle steam turbines manufacturers, hybridized with a nuclear power plant from energetic and exergetic viewpoint is provided. The Heat Recovery Steam Generator (HRSG) has single steam pressure without reheat, one superheater and one economizer. The thermodynamic parameters of the working fluids of both the gas and the steam turbines cycles are analyzed by modeling the thermodynamic cycle using the Engineering Equation Solver (EES) software. In case of hybridizing, the existing Alstom gas turbine with a pressurized water nuclear power plants using the newly proposed novel solution, we can increase the electricity output and efficiency significantly. If we convert a traditional combined cycle to HCNPP unit, we can achieve about 20% increase in electricity output. This figure emphasizes the significance of restructuring our power plant technology and exploring a wider variety of HCNPP solutions. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermoeconomic modeling and parametric study of hybrid SOFC–gas turbine–steam turbine power plants ranging from 1.5 to 10 MWe

Detailed thermodynamic, kinetic, geometric, and cost models are developed, implemented, and validated for the synthesis/design and operational analysis of hybrid SOFC–gas turbine–steam turbine systems ranging in size from 1.5 to 10 MWe. The fuel cell model used in this research work is based on a tubular Siemens-Westinghouse-type SOFC, which is integrated with a gas turbine and a heat recovery steam generator (HRSG) integrated in turn with a steam turbine cycle. The current work considers the possible benefits of using the exhaust gases in a HRSG in order to produce steam which drives a steam turbine for additional power output. Four different steam turbine cycles are considered in this research work: a single-pressure, a dual-pressure, a triple pressure, and a triple pressure with reheat. The models have been developed to function both at design (full load) and off-design (partial load) conditions. In addition, different solid oxide fuel cell sizes are examined to assure a proper selection of SOFC size based on efficiency or cost. The thermoeconomic analysis includes cost functions developed specifically for the different system and component sizes (capacities) analyzed. A parametric study is used to determine the most viable system/component syntheses/designs based on maximizing total system efficiency or minimizing total system life cycle cost.     

Solar thermodynamic plants for cogenerative industrial applications in southern Europe

The paper deals with the preliminary design and optimization of cogenerative solar thermodynamic plants for industrial users. The considered plants are all based on proven parabolic trough technology, but different schemes have been analyzed: from a conventional configuration with indirect steam cycle and a heat transfer fluid such as synthetic oil or molten salts, to a more innovative arrangement with direct steam generation in the solar field. Thermodynamic parameters of the steam cycle have been optimized considering some constraints due to the heat requirements of the user, leading to a preliminary design of the main components of the system and an estimation of costs. Resulting net electric efficiency is about 10% for conventional synthetic oil plant, while 13% for innovative molten salts and DSG.A comparison with conventional solar thermodynamic systems for electricity production and photovoltaic power plants shows the economic and energetic benefits of the cogenerative solution. Cost of electricity for solar plant is cheaper of about 20 €/MWh than conventional solar power application. Moreover, heat recovery allows to achieve a further 50% of CO₂ emission savings compared to reference solar plants for only electricity production.     

Thermo‐Economic Analysis and Multiobjective Optimization of Dual Pressure Combined Cycle Power Plant with Supplementary Firing

The heat recovery steam generator (HRSG) and duct burner are parts of a combined cycle which have considerable effect on the steam generation. The effect of the gas turbine, duct burner and HRSG on power generation is investigated to reduce exergy destruction and power loss in the gas turbine. The results show that with an increase in duct burner flow rate, pressure loss in the recovery boiler increases, steam generation increases on the HP side while it decreases on the LP side. With a reduction in the HP pinch point, thermal recovery increases while the LP pinch point does not have a significant effect. Then, power loss due to pressure drop in the gas turbine and the electricity cost are considered as two objective functions for optimization. Finally, the sensitivity analysis on ambient temperature, compressor pressure ratio, fuel lower heating value, duct burner fuel rate, condenser pressure and main pressure are performed and results are reported. It is concluded that with an increment in compressor pressure ratio, the duct burner flow rate and consequently steam generation increases while electricity cost decrease.     

BCHP系统中余热锅炉结构参数的热经济学优化

本文建立以BCHP系统的产品平均（yong）成本为目标函数,以余热锅炉排烟温度、蒸发器和省煤器中螺旋翅片管排数、每排管数、管束横向节距和纵向节距为决策变量的余热锅炉优化模型。应用所建立的优化计算模型,对BCHP系统不同工况分别进行优化计算,结果表明,无论在何种工况下,余热锅炉参数优化后其效率比优化前有所提高,冷量分摊的成本、系统的产品平均(yong)成本比未优化时均有所降低。