On better utilization of gas turbines in Kuwait

The Kuwaiti Ministry of Electricity and Water installed 16 gas turbine (GT) units of 2000 MW total generating capacity at Azzour South power plant (PP) and Sabbyia PP. These units are operating as a simple GT cycle by gas or oil fuel. The GT unit power output in Azzour PP is 163 MW at 15 °C ambient temperature (ISO conditions), and 125 MW at 46 °C (design outside air conditions). This paper suggests four variants for better utilization of these GT units. The first variant is to utilize these GT during off-peak hours to operate seawater reverse-osmosis desalting system. This increases the badly needed installed desalting capacity, decreases the specific energy consumed for desalting, and solves the problem of low water-to-power production ratio. The second variant is to add heat recovery steam generator to produce steam. This steam is used to operate multi-stage flashing units for more desalted water with no additional fuel energy. In the third variant, a gas/steam combined cycle is proposed to increase significantly both the installed capacity and efficiency. The fourth variant deals with cooling intake air to the compressor to increase the unit capacity when needed in hot days.     

Energy savings in single-purpose desalination systems

In this paper, an energy efficient combination is suggested for single-purpose desalination systems. The present analysis is based on data for existing units known for their reliabilities and high performances. For a specific steam power cycle, the generated power drives a RO, RO/MSF or RO/MEB system. In these combinations, the pretreated hp brine discarded by the RO is introduced as the feed for the distillation unit. Thus, the feed treatment, as well as the feed pumping required, is saved. The TBT and the bottom temperature in the distillation unit are set at 112 and 47°C, respectively.

Results show that, using the same steam power cycle, a water production of 4, 4·26 or 6·2 MGD can be produced if it drives a RO, RO/MSF or RO/MEB system, respectively. Moreover, the energy consumed per unit of fresh water produced (in kJ/kg) is 281, 265 or 182 for the RO, RO/MSF or RO/MEB system, respectively.     

Thermoeconomic analysis of a power/water cogeneration plant

Cogeneration plants for simultaneous production of water and electricity are widely used in the Arabian Gulf region. They have proven to be more thermodynamically efficient and economically feasible than single purpose power generation and water production plants. Yet, there is no standard or universally applied methodology for determining unit cost of electric power generation and desalinated water production by dual purpose plants.A comprehensive literature survey to critically assess and evaluate different methods for cost application in power/water cogeneration plants is reported in this paper. Based on this analysis, an in-depth thermoeconomic study is carried out on a selected power/water cogeneration plant that employs a regenerative Rankine cycle. The system incorporates a boiler, back pressure turbine (supplying steam to two MSF distillers), a deaerator and two feed water heaters. The turbine generation is rated at 118 MW, while MSF distiller is rated at 7.7 MIGD at a top brine temperature of 105 °C. An appropriate costing procedure based on the available energy accounting method which divides benefits of the cogeneration configuration equitably between electricity generation and water production is used to determine the unit costs of electricity and water. Capital charges of common equipment such as the boiler, deaerator and feed water heaters as well as boiler fuel costs are distributed between power generated and desalinated water according to available energy consumption of the major subsystems. A detailed sensitivity analysis was performed to examine the impact of the variation of fuel cost, load and availability factors in addition to capital recovery factor on electricity and water production costs.     

洛阳石化炼油装置节能潜力分析及优化措施

对洛阳石化炼油装置节能潜力进行了分析,并针对电、蒸汽和燃料气三项节能重点制定了优化措施。节约燃料气的措施为:优化常减压换热网络;连续重整扩能消缺改造,停运制氢装置;降低加热炉排烟温度,提高加热炉整体效率;更换高活性催化剂,降低加氢反应温度。节约电的措施为:对催化裂化装置烟机及再生器旋分器进行检修改造,提高烟机效率;负荷富裕的往复式压缩机增设无级气量调节系统;更换高能耗变压器,降低无功损耗;对部分能力过剩的机泵进行节能改造。节约蒸汽的措施为:气分装置取消蒸汽;焦化装置大吹汽改用凝结水;关闭蜡油加氢装置循环氢压缩机反飞动阀;整合乙醇胺溶剂系统;优化蒸汽管网运行,停用部分蒸汽线。措施实施后,洛阳石化每年可节约燃料13705t,节约用电21786MW·h,节约蒸汽150800t,综合能耗实现57.87kg标油/t原油的目标。     

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.     

脱硫低压省煤器在200 MW机组中的应用

介绍了山东百年电力股份发展有限公司4#机组在采用脱硫增压风机后加装低压省煤器,利用锅炉尾部烟气余热从汽轮机过来的凝结水,从而达到降低进入脱硫吸收塔烟气温度和提高凝结水温度,从而达到了进一步节约燃料和降低污染的目的。     

Exergy analysis of a cogeneration plant using coal gasification and solid oxide fuel cell

This paper presents exergy analysis of a conceptualized combined cogeneration plant that employs pressurized oxygen blown coal gasifier and high‐temperature, high‐pressure solid oxide fuel cell (SOFC) in the topping cycle and a bottoming steam cogeneration cycle. Useful heat is supplied by the pass‐out steam from the steam turbine and also by the steam raised separately in an evaporator placed in the heat recovery steam generator (HRSG). Exergy analysis shows that major part of plant exergy destruction takes place in gasifier and SOFC while considerable losses are also attributed to gas cooler, combustion chamber and HRSG. Exergy losses are found to decrease with increasing pressure ratio across the gas turbine for all of these components except the gas cooler. The fuel cell operating temperature influences the performance of the equipment placed downstream of SOFC. Copyright © 2005 John Wiley & Sons, Ltd.     

Major auxiliary equipment needs for the world energy network project

Many national energy projects have been pursued in Japan. Some of them are very important to control the emission of CO₂ from fossil fuel. The world energy network (WE-NET) project based on a hydrogen combustion gas turbine is one of the national projects and has a high target of thermal efficiency up to 60% or more (HHV) [Proc. IJPGC, Vol. 2, Baltimore, 1998, p. 293; Proc. IJPGC, Vol. 2, Baltimore, 1998, p. 433; Annual Summary Report on WE-NET, 1997; J. JSME, 100 (947) (1997) 1034; J. GTSJ, 27 (4) (1999) 217]. However, this new technology has to be developed by an application of a combined cycle for gas and steam turbines and special auxiliary equipment such as an oxygen supply plant and heat exchangers. The hydrogen combustion gas turbine will be operated by pure hydrogen and oxygen supplied and kept to produce a pure water vapor only. If other gaseous components are included in the combustion gas, the thermal efficiency of the combined cycle is decreased by the breakdown effect of a condenser vacuum. In this project, hydrogen may be imported from some foreign countries where it has to be produced by using clean and renewable energies, for example, hydropower or solar energy. On the other hand, the oxygen to be distilled from the air has to be supplied by auxiliary equipment of a liquid oxygen plant. This auxiliary equipment, however, will consume much power.In an existing type of the liquid oxygen plant, about 10% of the total power plant output has been consumed for the additional power of oxygen supply. In addition, the WE-NET combined cycle of the hydrogen combustion gas turbine will be supported by many heat exchangers that have to be checked for their technical problems. This paper has been highlighted at high performance design and setup of the major auxiliary equipment of the oxygen supply plant and the heat exchangers. The R&D prospect of their auxiliary equipment to attain a high thermal efficiency of the combined cycle in the WE-NET project will be discussed.     

Performance analysis of a heavy duty combined cycle power plant burning various syngas fuels

This paper presents a performance analysis of state of the art combined cycles power plants burning a number of syngas fuels. The first part of the analysis focuses on the effect of gas composition on the rated performance of the plant drawing two main conclusions. First, higher pressure ratio and lower firing temperature are found at turbine inlet. Second, the pressure at which fuel is supplied to the gas turbine plays an essential role in the power capacity of the engine. With respect to the steam cycle, no major effects are appreciated except for very low LHV fuels. In the second part of the work, the annual performance of the engine subjected to a typical load profile and real ambient and market conditions is studied. Differences in total incomes are appreciated depending on fuel composition and the concern about carbon emissions is highlighted.     

Analysis of biomass-residue-based cogeneration system in palm oil mills

Palm oil mills in Malaysia operate on cogeneration system using biomass residue as fuel in the boiler. The boiler produces high pressure and temperature steam which expands in a backpressure steam turbine and produces enough electric power for the internal needs of the mill. The exhaust steam from the turbine goes to an accumulator which distributes the steam to various processes in the mill.The study were made on seven palm oil mills in the Perak state in Malaysia. The primary objectives of the study are to determine boiler and turbine efficiencies, energy utilization factor, oil extraction rate and heat/power ratio for various palm oil mills working under similar conditions and adopting same processes. The palm oil industry is one of those rare industries where very little attempt is made to save energy. The energy balance in a typical palm oil mill is far from optimum and there is considerable scope for improvement. Bench-marking is necessary for the components in the mill. Energy-use bench-marking can give an overview of energy performance of the mills. The calculations were done to get net gain in power when back pressure turbine is replaced by a condensing turbine.It was found that the boiler and turbine have low thermal efficiencies compared to conventional ones used in power plants due to non-homogeneity and non-uniform quality of the fuel. The extraction rate was around 0.188. The use of condensing turbine increase the power output by 60% and the utilization factor was found to be 65% for the cogeneration system.     

Thermodynamic analysis of combined electric power generation and water desalination plants

The performance of three systems combining reverse osmosis (RO) to produce drinkable water and a steam power plant is modeled and calculated. The RO subsystem incorporates a power recovery unit: a hydraulic turbine in the first two cases and a pressure exchange unit (PES) in the third case. The coupling between the RO and power plant subsystems is only mechanical in the first case (the power plant provides mechanical power to the pumps of the RO subsystem) while in the two other cases the coupling is both mechanical and thermal (part of the heat rejected by the condenser of the power plant is transferred to the seawater). The effects of feed water flow rate and salinity, energy recovery system (hydraulic turbine or pressure exchanger) and operating pressures on the energy and exergy efficiencies and on the permeate quantity and quality are analyzed. Energy and exergy fluxes for all the components, as well as the quantity of drinkable water produced by each of these systems, are also compared for identical operating conditions.     

AE94.3A型燃气轮机进气冷却的应用可行性研究

对AE94.3A型燃气轮机燃气-蒸汽联合循环热力系统平衡进行研究进而发现,与同类型、同等级不同型号机组相比,AE94.3A型联合循环机组余热锅炉的排烟温度较高,排烟余热仍有进一步利用的空间。通过设计优化,扩大省煤器受热面,回收烟气余热加热给水,驱动热水型溴化锂制冷机制冷,用于机组满负荷调峰时的压气机进气冷却或厂房及办公区域空调供冷,对改善燃气轮机联合循环的运行性能,实现能源梯级利用,提高能源利用率和机组经济性运行起到了很大作用。     

Simulation of the operation of a gas turbine installation of a thermal power plant with a hydrogen fuel production system

The growth in demand for the production of heat and electricity requires an increase in fuel consumption by power equipment. At the moment, the most demanded thermal equipment for construction and modernization is gas turbine units. Gas turbines can burn a variety of fuels (natural gas, synthesis gas, methane), but the main fuel is natural gas of various compositions. The use of alternative fuels makes it possible to reduce CO₂ and NO_x emissions during the operation of a gas turbine. Under conditions of operation of thermal power plants at the wholesale power market, it becomes probable that combined cycle power units, designed to carry base load, will start to operate in variable modes. Variable operation modes lead to a decrease in the efficiency of power equipment. One way to minimize or eliminate equipment unloading is to install an electrolysis unit to produce hydrogen.In this article the technology of “Power to gas” production with the necessary pressure at the outlet of 30 kgf/cm² (this pressure is necessary for stable operation of the fuel preparation system of the gas turbine) is considered. High cost of hydrogen fuel during production affects the final cost of heat and electric energy, therefore it is necessary to burn hydrogen in mixture with natural gas. Burning a mixture of 5% hydrogen fuel and 95% natural gas requires minimal changes in the design of the gas turbine, it is necessary to supplement the fuel preparation system (install a cleaning system, compression for hydrogen fuel). In addition, the produced hydrogen can be stored, transported to the consumer. For the possibility of combustion of a mixture of natural gas and hydrogen fuel in a gas turbine the methodology of calculation of thermodynamic properties of working bodies developed by a team of authors under the guidance of Academician RAS (the Russian Academy of Sciences) V.E. Alemasov has been adapted, resulting in a program that allows to obtain an adequate mathematical model of the gas turbine. The permissible range of the working body temperature is limited to 3000 K. This paper presents the developed all-mode mathematical model of a gas turbine.On the basis of mathematical modeling of a gas turbine, a change in the main energy and environmental characteristics is shown depending on the composition of the fuel gas. Adding 5% hydrogen to natural gas has little effect on the gas turbine air treatment system, the flow rate remains virtually unchanged. CO₂ emissions decrease, but there is an increase in the amount of H₂O in the turbine exhaust gases.     

燃机电厂天然气调压站配置探讨

天然气用于燃气轮机发电在我国越来越多,但燃气轮机对天然气的压力、温度等都有一定的要求。天然气调压站是天然气的主要处理系统,直接影响到燃气轮机的安全稳定运行。根据已投产燃气轮机的运行经验,对天然气调压站的系统设备配置作了分析探讨,对设备提出了经济合理地配置的建议。     

Comparative studies of augmentation in combined cycle power plants

The attractive features of a combined cycle (CC) power plant are fuel flexibility, operational flexibility, higher efficiency and low emissions. The performance of five gas turbine‐steam turbine (GT‐ST) combined cycle power plants (four natural gas based plants and one biomass based plant) have been studied and the degree of augmentation has been compared. They are (i) combined cycle with natural gas (CC‐NG), (ii) combined cycle with water injection (CC‐WI), (iii) combined cycle with steam injection (CC‐SI), (iv) combined cycle with supplementary firing (CC‐SF) and (v) combined cycle with biomass gasification (CC‐BM). The plant performance and CO₂ emissions are compared with a change in compressor pressure ratio and gas turbine inlet temperature (GTIT). The optimum pressure ratio for compressor is selected from maximum efficiency condition. The specific power, thermal efficiency and CO₂ emissions of augmented power plants are compared with the CC‐NG power plant at the individual optimized pressure ratios in place of a common pressure ratio. The results show that the optimum pressure ratio is increased with water injection, steam injection, supplementary firing and biomass gasification. The specific power is increased in all the plants with a loss in thermal efficiency and rise in CO₂ emissions compared to CC‐NG plant. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermodynamic analysis of an LNG fuelled combined cycle power plant with waste heat recovery and utilization system

This paper has proposed an improved liquefied natural gas (LNG) fuelled combined cycle power plant with a waste heat recovery and utilization system. The proposed combined cycle, which provides power outputs and thermal energy, consists of the gas/steam combined cycle, the subsystem utilizing the latent heat of spent steam from the steam turbine to vaporize LNG, the subsystem that recovers both the sensible heat and the latent heat of water vapour in the exhaust gas from the heat recovery steam generator (HRSG) by installing a condensing heat exchanger, and the HRSG waste heat utilization subsystem. The conventional combined cycle and the proposed combined cycle are modelled, considering mass, energy and exergy balances for every component and both energy and exergy analyses are conducted. Parametric analyses are performed for the proposed combined cycle to evaluate the effects of several factors, such as the gas turbine inlet temperature (TIT), the condenser pressure, the pinch point temperature difference of the condensing heat exchanger and the fuel gas heating temperature on the performance of the proposed combined cycle through simulation calculations. The results show that the net electrical efficiency and the exergy efficiency of the proposed combined cycle can be increased by 1.6 and 2.84% than those of the conventional combined cycle, respectively. The heat recovery per kg of flue gas is equal to 86.27 kJ s^?1. One MW of electric power for operating sea water pumps can be saved. The net electrical efficiency and the heat recovery ratio increase as the condenser pressure decreases. The higher heat recovery from the HRSG exit flue gas is achieved at higher gas TIT and at lower pinch point temperature of the condensing heat exchanger. Copyright © 2006 John Wiley & Sons, Ltd.     

Study of an incrementally loaded multistage flash desalination system for optimum use of sensible waste heat from nuclear power plant

Existing practice of nuclear desalination cogeneration incurs loss of nuclear plant power generation because it competes for live steam with nuclear plant steam turbine. Such loss is completely avoided with the nuclear desalination plant design proposed in the present study. The plant called GTHTR300 is based on a high‐temperature gas reactor rated at 600 MWt. Gas turbine is used to replace steam turbine as power generator. The gas turbine converts about a half of the reactor's thermal power to electricity while rejecting the balance as sensible waste heat to be utilized in a multistage flash (MSF) plant for seawater desalination. A new MSF process scheme is proposed and optimized to efficiently match the sensible waste heat source. The new scheme increments the thermal load of the multistage heat recovery section in a number of steps as opposed to keeping it constant in the traditional MSF process. As the number of steps increases, more waste heat is utilized, and top brine temperature for peak water production is increased. Both tend to increase water yield. Operating with a similar number of stages, the new process is shown to produce 45% more water than the traditional process operating over the same temperature range. As a result, the GTHTR300 yields 56,000 m³/d water and generates 280 MWe power at constant efficiency with and without water cogeneration. Copyright © 2012 John Wiley & Sons, Ltd.     

Economic evaluation of reverse osmosis desalination system coupled with tidal energy

A reverse osmosis (RO) desalination system coupled with tidal energy is proposed. The mechanical energy produced by the tidal energy through hydraulic turbine is directly used to drive the RO unit. The system performances and the water cost of the conventional and tidal energy RO systems are compared. It is found that the proposed tidal energy RO system can save water cost in the range of 31.0%-41.7% in comparison with the conventional RO system. There is an optimum feed pressure that leads to the lowest water cost. The tidal RO system can save more costs at a high feed pressure or a high water recovery rate. The optimum feed pressure of the tidal energy RO system is higher than that of the conventional RO system. The longer lifetime of the tidal energy RO system can save even more water cost. When the site development cost rate is lower than 40%, the water cost of the tidal energy RO system will be lower than that of the conventional RO system. The proposed technology will be an effective alternative desalination method in the future.     

基于天然气管网压力能回收的联合循环构思

随着天然气大量应用及其相关技术的不断发展,天然气管网的输送压力也越来越高,蕴含巨大的压力能。本文提出一种回收天然气管网压力能的燃气蒸汽联合循环系统：高压天然气通过在膨胀机内膨胀回收一部分能量,承担部分压气机消耗功,膨胀后的低温天然气用来依次冷却压气机进气和蒸汽轮机排气,然后回收部分排烟余热。本文定性分析了该系统流程相关部分给联合循环带来的收益,显示出提高联合循环效率和能源综合利用率的潜力。