The effect of the operating parameters of heat recovery steam generators on combined cycle/sea-water desalination plant performance

Combined gas/steam turbine cycle plants have been proposed for cogeneration of electricity and process steam. Examples are combined-cycle power plants coupled with sea-water desalination, district heating plants, chemical industries, etc. In combined heat and power plants, the gas turbine exhaust heat is utilized through the use of heat recovery steam generators (HRSG's). As a result, these waste heat generators (boilers), whether fired or unfired, control the performance of the combined plant lower side (bottoming cycle). Moreover, any changes made in the HRSG operating parameters (i.e. the pinch point, approach temperature, first and second stage pressures, and mass ratios) can greatly affect the HRSG performance and will eventually affect the overall combined plant performance. This paper presents a method to predict the performance of the heat recovery steam generators (HRSG)/steam bottoming cycle combined with sea-water desalination plant at various steam and exhaust gas conditions.     

Coordinated optimization of the parameters of the cooled gas-turbine flow path and the parameters of gas-turbine cycles and combined-cycle power plants

In the present paper, we evaluate the effectiveness of the coordinated solution to the optimization problem for the parameters of cycles in gas turbine and combined cycle power plants and to the optimization problem for the gas-turbine flow path parameters within an integral complex problem. We report comparative data for optimizations of the combined cycle power plant at coordinated and separate optimizations, when, first, the gas turbine and, then, the steam part of a combined cycle plant is optimized. The comparative data are presented in terms of economic indicators, energy-effectiveness characteristics, and specific costs. Models that were used in the present study for calculating the flow path enable taking into account, as a factor influencing the economic and energy effectiveness of the power plant, the heat stability of alloys from which the nozzle and rotor blades of gas-turbine stages are made.     

Gas turbine exhaust gas heat recovery at South Baghdad (Iraq) power plant

Gas turbine exhaust is usually relatively clean, especially the exhaust from natural gas turbines. The use of such gases to improve the overall thermal efficiency of a steam power plant has the advantage of reducing the cost of cleaning the equipment and reducing the maintenance costs of the heat recovery equipment used in the application.In this paper, two proposals for recovering the waste energy of the exhaust gases from a gas turbine unit, fuelled by natural gas at south Baghdad Power Plant (Iraq) are discussed. The proposals cover improvements to the thermal efficiency of a steam power plant installed near the gas turbine unit. The first proposal is to use the exhaust gases to preheat the feed water at four feed water heaters, in order to increase the power output. This arises because of the savings in the amount of steam extracted at a different level used for preheating the feed water line. The second proposal is to use the thermal energy in the exhaust gases to reheat the extracted stream, at five points at a high thermal potential, to increase the thermal gain at the preheating feed water line. This avoids the complexity associated with rejection of the extracted steam. The first roposal shows that a 1.22–14.9% saving in fuel consumption is achievable and the overall thermal efficiency of the steam power plant becomes 29–34% (at different gas turbine plant loads). The second proposal shows that a 2.3–7.35% saving in fuel consumption can be attained and the corresponding thermal efficiency will be 30.3–32%.     

Waste heat recovery of dura (Iraq) oil refinery and alternative cogeneration energy plant

The first part of this paper presents a waste heat recovery scheme for the Dura (Baghdad, Iraq) oil refinery energy plant. Both the wasted heat of the process return condensate and the flue gases are utilized for low temperature feedwater and fuel heating. The steam saved, both from the main steam line and turbine extraction system, was found to increase the steam and plant overall efficiency by 18%.An alternative cogeneration energy plant is presented in the second part of this study. The proposed plant utilizes the gas turbine exhaust, in conjunction with a heat recovery boiler, to produce the process steam requirement. With this alternative plant, the overall efficiency increases by 31.6%, while the steam efficiency increases by 19%. The outstanding features and advantages of the proposed plants are highlighted.     

650℃超超临界1000 MW机组回热系统的参数优化

发展更高参数超超临界汽轮机组是提高发电热效率和降低燃煤消耗量的主要方向。随着高温合金材料技术的发展,目前已具备发展主蒸汽650℃超超临界机组的条件,主蒸汽和再热蒸汽温度的提高,对回热系统的设计也提出了新的要求。本文设计了超超临界1000 MW汽轮机组的回热系统,分析了主蒸汽和再热蒸汽压力对机组热力性能的影响规律,采用遗传算法优化了各级抽汽参数,汽轮机发电热耗率低于6940 kJ·(kW·h)^-1。     

Solar thermal power plants

The solar thermal power plant technology, the opportunities it presents and the developments in the market are outlined. The focus is on the technology of parabolic trough power plants, a proven technology for solar power generation on a large scale. In a parabolic trough power plant, trough-shaped mirrors concentrate the solar irradiation onto a pipe in the focal line of the collector. The thermal energy thus generated is used for electricity generation in a steam turbine. Parabolic trough plants can be combined with thermal storage and fossil or biomass fired heat exchangers to generate electricity even when the sun is not shining. Solar Millennium AG in Erlangen has developed the first power plant of this kind in Europe. After two years of construction the plant started operation in Southern Spain in 2008. This one and its sister projects are important steps leading the way for the whole market. The paper also covers the technological challenges, the key components used and the research and development activities concerning this technology. Solar thermal power plants are ideal for covering peak and medium loads in power grids. In hybrid operation they can also cover baseload. The Solar Chimney power plant, another striking technology for the conversion of solar into electric energy, is described briefly. The paper concludes with a look at the future – the import of solar energy from the deserts of North Africa to central Europe.     

Refuse-fired,pressurized, fluidized-bed combustion combined cycle analysis

Use of pressurized, fluidized-bed combustion (PFBC) has given a new opportunity to use municipal refuse as fuel for combined gas and steam power cycles keeping the pollutants of sulphur and nitrogen oxides to a minimum at reduced capital cost.In combined gas and steam power cycles, the heat energy in the exhaust gases of a simple gas turbine cycle is used to generate steam in a waste-heat boiler and the generated steam is used in the steam turbine for power generation.The effects of gas turbine pressure ratio and inlet temperature on the main parameters of refuse-fired, pressurized, fluidized-bed combustion combined cycles are determined.The results indicate a maximum combined cycle thermal efficiency and work output at a possible range of optimum pressure ratios between 10 and 12 for a range of gas turbine inlet temperatures of 750–1000°C.     

The key role of heat exchangers in advanced gas-cooled reactor plants

The use of helium as a nuclear reactor coolant has been successfully demonstrated in plants built and operated in the U.K., U.S.A., and Germany. Following the pioneering proof of principle plant, two small power plants were operated for several years and this led to the construction of two commercial power stations. For the next generation of gas-cooled reactors new criteria have been developed, namely, the plants will be smaller, simpler, safer and of lower cost. The base case Modular High-Temperature Gas-Cooled Reactor (MHTGR) utilizes existing technology to offer a tried and proven power generating plant using a conventional steam turbine power conversion system that could be in utility service just after the turn of the century. The capability of the MHTGR to operate at very high temperatures will be exploited early in the next century in the form of advanced variants to meet the needs of the power generation and process industries. A key component in the MHTGR is the heat exchanger, since this is where the reactor thermal energy is transferred to the prime-mover or process system. This paper addresses the various roles that heat exchangers will play in advanced MHTGRs, recognizing that the requirements for the steam cycle, gas turbine (direct- or indirect-cycle), and process heat reactor are unique. Topics include thermodynamic considerations, differing configurations, and construction types; materials (metals, composites, ceramics); germane technology bases; and advanced heat exchanger technologies.     

Performance of gas turbine co-generation power desalting plants under varying operating conditions in Kuwait

Recent developments in gas turbines have led to their utilization to carry both base and emergency loads in single purpose power plants as well as in cogeneration (e.g. power and desalting) plants. Gas turbines are usually rated at certain environmental design conditions (e.g. low ambient temperatures) which differ from hot environments like that in Kuwait. Consequently, their actual power output and thermal efficiency are much lower than their rated design values during hot and humid weather that prevails most of the year in Kuwait. This study is concerned with the prediction of gas turbine cogeneration (power/desalting) plant performance under different environmental and loading conditions.     

A case study of cogeneration for Jeddah and Yanbu petromin refineries in Saudi Arabia

The Petromin refineries in Jeddah and Yanbu, Saudi Arabia produce power and process steam separately. The Jeddah refinery gas turbines that have an installed capacity of 88 MW, run at less than 50% utilization factor. The refinery demand of steam is 70–120 tons h⁻¹.The electric power demand of Yanbu refinery is supplied by The Royal Commission of Yanbu at a rate of 16–25 MW. The steam consumption is 68 tons h⁻¹. Data were collected for the performance and requirement for both plants. An integrated system for cogeneration is proposed which consists of a gas turbine, heat recovery steam generator equipped with a supplementary duct burner and economizer. The thermal and economical analyses have proved the feasibility of the proposed system with payback periods of 23 and 36 months for Jeddah and Yanbu refineries, respectively. However, the payback period for Jeddah refinery can be reduced to 15 months if the utilization factor is improved, and the excess power generated by the gas turbines is connected to the public utility grid. In fact, it is worth mentioning that the present study is considered the first to be carried out in Saudi Arabia; more studies and investigations could lead to tremendous saving in the fuel consumption in this country.     

High-speed mathematical models of cogeneration steam turbines: Optimization of operation at heat and power plants

The approach was developed for creation of high-speed mathematical models of cogeneration turbines; these models are the tools for fast optimization of operation modes of large-scale cogeneration heating plants. The approach was developed for identification of mathematical models of steam turbines via measuring its parameters. The example of parameters identification is presented for steam turbine T-100/120–130. The optimization computations of operation modes for a cogeneration heating plant were the basic ones for plotting equivalent energy characteristics at a given consumer heat load.     

Heat and electricity consumption of large industrial energy users in The Netherlands

On the basis of information that can be extracted from existing databases, combined with information from literature and interviews, a database called BIN has been constructed containing data about the consumption of fuel, steam and electricity by approximately the 300 largest energy-consuming industrial plants in The Netherlands. Comparison with national statistics shows that the industrial plants incorporated in the database are responsible for 80% of the total industrial demand on primary energy carriers (excluding their use as feedstock). Thirteen industrial plants already cover 50% of this demand. The paper and board industry, the refineries, the chemical industry, and the basic metal industry are almost consumption over size classes has been derived. This article also gives the temperature distribution of the industrial steam consumption in The Netherlands. Of the 64 million tonnes of steam produced in boilers in the industrial plants included in the database the weighted average enthalpy is 3.17 MJ/kg and the average exergy is 1.29 MJ/kg, both with liquid water of 10°C as the reference. The plant-specific data included in the database can be used for research into industrial energy conservation measures, e.g. the combined generation of heat and power (CHP).     

Methods for analysis and synthesis of technological schemes of thermal power plants based on solving auxiliary problems of linear programming

The paper describes the developed method for analyzing technological schemes of thermal power plants based on solving problems of auxiliary linear programming. This method involves solving the linear programming problems to evaluate the effect of supply and removal of heat or material flows of various sizes at different points of the technological scheme of a thermal power plant (TPP). The method effectiveness is demonstrated by the example of the coaldust steam turbine unit with nominal electrical output of 660 MW. As a result of its application, the change of the technological scheme of the unit was found to provide reduction in electricity cost by 0.3%.     

Combined cycles with gas turbine engines

Simple cycle gas turbine engines suffer from limited efficiencies and consequential dominance of fuel prices on generation costs. Combined cycles, however, exploit the waste heat from exhaust gases to boost power output, resulting in overall efficiencies around 50%, which are significantly above those of steam power plants. This paper reviews various types of combined cycles, including repowering, integrated gasification and other advanced systems.     

Simulation of a combined cycle power plant based on a pressurized circulating fluidized bed combustor

A comprehensive mathematical model for the simulation of a pressurized circulating fluidized bed combustor will be presented. The model consists of a combustor model describing the combustion chamber, the cyclone and the external heat exchanger as well as of a gas turbine model. The results of the simulation for the combustor at full load and different pressures and for the combined cycle power plant at full and part load are presented in form of temperature-, flue gas composition- and heat transfer-profiles in the combustor. Especially, energy fluxes from the combustor to the water-/steam cycle and the output of gas- and steam-turbine will be shown. The validity of the model will be shown by comparative simulation of an existing plant for the special case of atmospheric conditions.     

新型燃煤发电-CO2捕获-供热一体化系统

本文在深入分析燃煤电站CO₂捕获和汽水系统热平衡的基础上,提出一种新型燃煤发电-CO₂捕获-供热一体化系统。该系统通过汽水流程、碳捕获流程及地暖供热流程的有效集成,实现了系统中、低温余热的高效利用,降低了碳捕获对电厂效率的影响。分析结果显示,本文提出的一体化系统,在CO₂回收率90%时,供电效率可达31.32%,供电效率降低8.96%,而传统化学吸收法碳捕获电站效率惩罚普遍在10～12个百分点或更高。同时,该系统可供热350 MW,全厂（火用）效率达34.49%,全厂热效率高达55.88%;该系统以较少的能耗代价实现高效供电、供热与CO₂减排,为燃煤发电机组碳减排提供了独特的学术思路与技术方案。     

环境温度对燃气轮机功热并供装置及联合循环变工况性能的影响

采用动力机械变工况性能解析分析方法,研究了大气温度变化对燃气轮机功热并供和联合循环装置性能影响．指出燃气轮机在带有余热利用的条件下,大气温度的影响明显减弱,并对不同燃气轮机设计参数和蒸汽设计参数影响做了分析比较。     

中低温太阳能品位间接提升及系统集成

本文提出了中低温太阳热能品位间接提升的概念、方法和系统集成,其核心是热集成和热化学转换的有机结合。在所提出的太阳能和化石能源综合互补的化学回热循环系统(SOLRGT)中,中低温太阳热能首先提供蒸汽蒸发潜热从而转化为蒸汽内能;其次通过蒸汽参与重整反应进一步转化为合成气化学能,实现品位提升;最后得以在高效的燃气轮机系统中实现热功转换。由于太阳能的引入,燃气轮机透平排气余热回收部分的热匹配得到极大改善,并减少了化石能源消耗;同时,蒸汽产率的增加有助于增进系统化学回热和物理回热收益。系统中太阳能热转功净效率可达26.5%;和常规化学回热循环相比,化石能源节约率可达20%～30%,实现相应数量的CO_2减排,系统中实现了中低温太阳能的高效热功转换和与化石燃料的梯级互补。     

直接空冷凝汽器理论最佳背压的研究

为了更好地提高直接空冷机组系统运行的经济性,本文以直接空冷系统为研究对象,以空冷系统的热力模型为基础,综合考虑汽轮机功率与空冷风机耗功率,从理论上探索研究运行工况下的最佳背压以及有关主要因素对最佳背压影响的基本规律,从而为直接空冷机组的冷端优化和经济运行提供指导.     

Gas turbine waste heat recovery distillation system

This article presents a method for improving the gas turbine's performance through an efficient utilization of the waste heat in a distillation system with a special arrangement. This consists of two trains of VTE/MEB connected to increase the fresh water produced. Exhaust gases from the gas turbine are used in a multi-temperature level heat recovery system with five feed heaters, and gases are released to ambient at 130°C. Distillation top train has nine effects and evaporation range from 130 to 82°C while the bottom train has six effects with evaporation range from 76 to 46°C and is supplied with the steam leaves the last effect in the top train.Thermal analysis using a 32.67 MW gas turbine showed that the present arrangement can produce 3.2 million gallons per day (mgd) of fresh water with more than 4 g/kWh at a performance ratio (PR) of 8.8. This is 34% more than that produced in an existing gas-turbine distillation combination and 14% more than that expected from a reverse osmosis plant driven by a bottoming Rankine power cycle.