Performance of Gas-Steam Combined Cycle Cogeneration Units Influenced by Heating Network Terminal Steam Parameters

The determination of source-side extracted heating parameters is of great significance to the economic operation of cogeneration systems.This paper investigated the coupling performance of a cogeneration heating and power system multidimensionally based on the operating characteristics of the cogeneration units,the hydraulic and thermodynamic characteristics of the heating network,and the energy loads.Taking a steam network supported by a gas-steam combined cycle cogeneration system as the research case,the interaction effect among the source-side prime movers,the heating networks,and the terminal demand thermal parameters were investigated based on the designed values,the plant testing data,and the validated simulation.The operating maps of the gas-steam combined cycle cogeneration units were obtained using THERMOFLEX,and the minimum source-side steam parameters of the steam network were solved using an inverse solution procedure based on the hydro-thermodynamic coupling model.The cogeneration operating maps indicate that the available operating domain considerably narrows with the rise of the extraction steam pressure and flow rate.The heating network inverse solution demonstrates that the source-side steam pressure and temperature can be optimized from the originally designed 1.11 MPa and 238.8°C to 1.074 MPa and 191.15°C,respectively.Under the operating strategy with the minimum source-side heating parameters,the power peak regulation depth remarkably increases to 18.30%whereas the comprehensive thermal efficiency decreases.The operation under the minimum source-side heating steam parameters can be superior to the originally designed one in the economy at a higher price of the heating steam.At a fuel price of$0.38/kg and the power to fuel price of 0.18 kg/(kW·h),the critical price ratio of heating steam to fuel is 119.1 kg/t.The influence of the power-fuel price ratio on the economic deviation appears relatively weak.

Application Research of Intake-Air Cooling Technologies in Gas-Steam Combined Cycle Power Plants in China

The generated power and efficiency of gas-steam combined cycle (GSCC) power plants depend on the temperature of the inlet air greatly. Based on the analysis of basic theory of inlet air cooling technologies, the application of evaporative cooling system and the absorption cooling system in GSCC power plants are discussed in this paper. Moreover, in China with high temperature and humidity, applied research and simulation analysis of the above two different cooling systems are conducted separately, the research results of which can provide certain reference for optimal design and economic operation of inlet air cooling system for GSCC power enterprises in China.

Dynamic simulation analysis of molten salt reactor-coupled air-steam combined cycle power generation system

A nonlinear dynamic simulation model based on coordinated control of speed and flow rate for the molten salt reactor and combined cycle systems is proposed here to ensure the coordination and stability between the molten salt reactor and power system.This model considers the impact of thermal properties of fluid variation on accuracy and has been validated with Simulink.This study reveals the capability of the control system to compensate for anomalous situations and maintain shaft stability in the event of perturbations occurring in high-temperature molten salt tank outlet parameters.Meanwhile,the control system’s impact on the system’s dynamic characteristics under molten salt disturbance is also analyzed.The results reveal that after the disturbance occurs,the controlled system benefits from the action of the control,and the overshoot and disturbance amplitude are positively correlated,while the system power and frequency eventually return to the initial values.This simulation model provides a basis for utilizing molten salt reactors for power generation and maintaining grid stability.

Optimization Potentials for the Waste Heat Recovery of a Gas-Steam Combined Cycle Power Plant Based on Absorption Heat Pump

A new waste heat recovery system is presented to recover exhausted steam waste heat from the steam turbine by absorption heat pump(AHP) in a gas-steam combined cycle(GSCC) power plant. The system can decrease energy consumption and further improve the energy utilization. The performance evaluation criteria are calculated, and exergy analysis for key components are implemented in terms of the energy and exergy analysis theory. Besides, the change of these criteria is also revealed before and after modification. The net power output approximately increases by 21738 kW, and equivalent coal consumption decreases by 5.58 g/kWh. A 1.81% and 1.92% increase in the thermal and exergy efficiency is respectively obtained in the new integrated system as the heating load is 401095 kJ at 100% condition. Meanwhile, the appropriate extraction parameters for heating have been also analyzed in the two systems. The proposed scheme can not only save energy consumption but also reduce emission and gain great economic benefit, which is proven to be a huge potential for practical application.

Thermal performance analysis of advanced partial gasification combined cycle

This paper presents the thermodynamic performance analysis and comparison of four kinds of advanced pressurized fluidized bed combustion combined cycle (APFBC-CC) system schemes, two based on pressurized fluidized bed (PFB) combustion and the other two based on atmospheric circulating fluidized bed (CFB) combustion. The results show that the first scheme avoids high temperature gas filter, but has the lower cycle efficiency and syngas heating value. The second scheme can gain the highest cycle efficiency, however it is better to now lower the filter operating temperature. The third and fourth schemes, based on CFB, have lower efficiencies than the second one. But the fourth one, with preheating air/steam for gasification, can obtain the highest heating value of syngas and gain higher efficiency than the third one.

Model Selection of Gas Turbine for Large Scale Gas-Fired Combined Cycle Power Plant

This paper briefs the configuration and performance of large size gas turbines and their composed combined cycle power plants designed and produced by four large renown gas turbine manufacturing firms in the world, providing reference for the relevant sectors and enterprises in importing advanced gas turbines and technologies.

Performance analysis of ammonia-water absorption/compression combined refrigeration cycle

In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.

Simulation and performance analysis of organic Rankine cycle combined heat and power system

To improve the overall thermal efficiency of the organic Rankine cycle（ ORC）, a simulation study was carried out for a combined heat and power（ CHP） system, using the Redlich-Kuang-Soave（ RKS） equation of state. In the system,R245 fa was selected as the working fluid. A scroll expander was modeled with empirical isentropic expansion efficiency.Plate heat exchangers were selected as the evaporator and the condenser, and detailed heat transfer models were programmed for both one-phase and two-phase regions. Simulations were carried out at seven different heat source temperatures（ 80,90, 100, 110, 120, 130, 140 ℃） in combination with eight different heat sink temperatures（ 20, 25, 30, 35, 40, 45, 50,55 ℃）. Results showthat in the ORC without an internal heat exchanger（ IHE）, the optimum cycle efficiencies are in the range of 7. 0% to 7. 3% when the temperature differences between the heat source and heat sink are in the range of 70 to90 ℃. Simulations on CHP reveal that domestic hot water can be produced when the heat sink inlet temperature is higher than40 ℃, and the corresponding exergy efficiency and overall thermal efficiency are 29% to 56% and 87% to 90% higher than those in the non-CHP ORC, respectively. It is found that the IHE has little effect on the improvement of work output and efficiencies for the CHP ORC.

Hydrate-based carbon dioxide capture from simulated integrated gasification combined cycle gas

The equilibrium hydrate formation conditions for CO2/H2 gas mixtures with different CO2 concentrations in 0.29 mol% TBAB aqueous solution are firstly measured.The results illustrate that the equilibrium hydrate formation pressure increases remarkably with the decrease of CO2 concentration in the gas mixture.Based on the phase equilibrium data,a three stages hydrate CO2 separation from integrated gasification combined cycle （IGCC） synthesis gas is investigated.Because the separation efficiency is quite low for the third hydrate separation,a hybrid CO2 separation process of two hydrate stages in conjunction with one chemical absorption process （absorption with MEA） is proposed and studied.The experimental results show H2 concentration in the final residual gas released from the three stages hydrate CO2 separation process was approximately 95.0 mol% while that released from the hybrid CO2 separation process was approximately 99.4 mol%.Thus,the hybrid process is possible to be a promising technology for the industrial application in the future.

Thermodynamic analysis and combined cycle research on recoverable pressure energy in natural gas pipeline

Current research and ways of capturing mechanical energy are discussed in this paper. By the aid of the comprehensive thermodynamic analysis and Aspen simulation tool, the amount of a vailable work that can be produced from capturing the pressure energy has been calculated. Based on the comprehensive thermodynamic analysis, two systems have been proposed to capture pressure energy of natural gas to generate electricity. In this study, the expression of exergy is given which can be used in evaluating purposes. A problem with this multidisciplinary study is the complicated boundary condition. In conclusion, a technical prospect on recoverable natural gas pressure energy has been presented based on total energy system theory.

Effects of ORC Working Fluids on Combined Cycle Integrated with SOFC and ORC for Stationary Power Generation

The purpose of this study is to explore the effects of working fluid on conventional combined cycle integrated with pressurized solid oxide fuel cell (SOFC) and waste heat recovery organic Rankine cycle (ORC) for stationary utility power generation. The mathematical model of a natural gas fueled design configuration is developed in Matlab and Simulink and simulated with 14 working fluids. The effluent gases of SOFC undergo combustion in the combustion chamber and it is utilized in the gas turbine, steam turbine cycle and ORC. The model is compared with those found in literature and the parametric studies of temperature, flow rate, fuel utilization factor and exhaust gas on the system efficiency are examined. Results revealed that working fluids show a closely related behavior in efficiency at low pressure ratio and high flow fraction, fuel utilization, and temperature. R-123 was found to perform the best among 14 working fluids studied, yielding a system energy efficiency of 70% in the combined cycle integrated with SOFC and ORC.

Short-Term Scheduling of Combined Cycle Units Using Mixed Integer Linear Programming Solution

Combined cycle plants (CCs) are broadly used all over the world. The inclusion of CCs into the optimal resource scheduling causes difficulties because they can be operated in different operating configuration modes based on the number of combustion and steam turbines. In this paper a model CCs based on a mixed integer linear programming approach to be included into an optimal short term resource optimization problem is presented. The proposed method allows modeling of CCs in different modes of operation taking into account the non convex operating costs for the different combined cycle mode of operation.

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.

Process Simulation of a 620 Mw-Natural Gas Combined Cycle Power Plant with Optimum Flue Gas Recirculation

The main objective of this investigation is to obtain an optimum value for the flue gas recirculation ratio in a 620 MW-Natural Gas Combined Cycle (NGCC) power plant with a 100% excess air in order to have a composition of the exhaust gas suitable for an effective absorption by amine solutions. To reach this goal, the recirculated flue gas is added to the secondary air (dilution air) used for cooling the turbine. The originality of this work is that the optimum value of a Flue Gas Recirculation (FGR) ratio of 0.42 is obtained from the change of the slope related to the effects of flue gas recirculation ratio on the molar percentage of oxygen in the exhaust gas. Compared to the NGCC power plant without flue gas recirculation, the molar percentage of carbon dioxide in the flue gas increases from 5% to 9.2% and the molar percentage of oxygen decreases from 10.9% to 3.5%. Since energy efficiency is the key parameter of energy conversion systems, the impact of the flue gas recirculation on the different energy inputs and outputs and the overall efficiency of the power plant are also investigated. It is found the positive effects of the flue gas recirculation on the electricity produced by the steam turbine generator (STG) are more important than its cooling effects on the power output of the combustion turbine generator (CTG). The flue gas recirculation has no effects on the water pump of the steam cycle and the increase of energy consumed by the compressor of flue gas is compensated by the decrease of energy consumed by the compressor of fresh air. Based on the Low heating value (LHV) of the natural gas, the flue gas recirculation increases the overall efficiency of the power plant by 1.1% from 57.5% from to 58.2%.

Assessment of Site Parameters and Heat Recovery Characteristics on Combined Cycle Performance in an Equatorial Environment

This paper investigates the effects of site based parameters such as ambient temperature, humidity, altitude and heat transfer characteristic of a dual pressure heat recovery system on the performance of the combined cycle power plant within an equatorial environment. The bulk heat utilization and configuration of a dual pressure heat recovery system are investigated. It is observed that the heat system configuration play a vital role in optimizing the combined cycle overall performance, which has proportionality relationship with the operating ambient temperature and relative humidity of the gas turbine. The investigation is carried out within the ambient temperature range of 24℃ to 35℃, relative humidity of 60% to 80%, and a high level steam pressure of 60 bar to 110 bar. The results show that at 24℃ ambient temperature, the heat recovery system has the highest duty of 239.4 MW, the optimum combined cycle power output of 205.52 MW, and overall efficiency of 47.46%. It further indicates that as the ambient temperature increases at an average exhaust gas temperature of 530℃ and mass flow of 470 kg/s, the combined cycle power output and efficiency decrease by 15.5% and 13.7% respectively under the various considerations. This results from a drop in the air and exhaust mass flow as the values of the site parameters increase. The overall results indicate that decreasing the ambient temperature at optimum exhaust gas flow and temperature increases the heat recovery system heat duty performance, the steam generation, overall combined cycle power output and efficiency, which satisfies the research objective.

DESIGN OF COMBINED CYCLE GENERATION SYSTEM WITH HIGH TEMPERATURE FUEL CELL AND STEAM TURBINE

For environment protection and high efficiency, development of new conceptpower plant has been required in China. The fuel cell is expected to be used in a power plant as acentralized power Station or distributed power plant. It is a chemical power generation device thatconverts the energy of a chemical reaction directly into electrical energy and not limited by Carnotcycle efficiency. The molten carbonate fuel cell (MCFC) power plant has several attractive featuresi.e. high efficiency and lower emission of NO_x and SO_x A combined cycle generation system withMCFC and steam turbine is designed. Its net electrical efficiency LHV is about 55 percent.

Combined Cycle Fatigue Testing with Ultrasonic FrequencyComponent of S350 Steel Welded Joint

A combined cycle fatigue （CCF） testing system with ultrasonic frequency component was developed toevaluate the CCF properties of S350 steel welded joints in this study. The fatigue testing results indicated that the S-Ncurves of CCF did not have fatigue limit, which agreed with those of pure high frequency fatigue of welded joints. TheS-N curves showed that the CCF strength of welded joints dropped greatly with the increasing interaction between highand low frequency fatigue loading. An approximation design method of CCF was presented using amplitude envelopeas the stress range.

Parameters and Trajectory Overall Optimization Design of the Combined Cycle Engine Reusable Launch Vehicle

Reusable launch vehicle is an important way to realize fast,cheap and reliable space transportation.A combined cycle engine system provides a more efficient and flexible form of power.The investigation on the research status of the combined cycle engine technology,including basic principle,research programs and classification of structure is firstly discussed in this paper.Then the bilevel hierarchical and integrated parameters/trajectory overall optimization technologies are applied to improve the efficiency and effectiveness of overall vehicle design.Simulations are implemented to compare and analyze the effectiveness and adaptability of the two algorithms,in order to provide the technical reserves and beneficial references for further research on combined cycle engine reusable launch vehicles.

Prediction of Electrical Output Power of Combined Cycle Power Plant Using Regression ANN Model

Recently, regression artificial neural networks are used to model various systems that have high dimensionality with nonlinear relations. The system under study must have enough dataset available to train the neural network. The aim of this work is to apply and experiment various options effects on feed-foreword artificial neural network (ANN) which used to obtain regression model that predicts electrical output power (EP) of combined cycle power plant based on 4 inputs. Dataset is obtained from an open online source. The work shows and explains the stochastic behavior of the regression neural, experiments the effect of number of neurons of the hidden layers. It shows also higher performance for larger training dataset size;at the other hand, it shows different effect of larger number of variables as input. In addition, two different training functions are applied and compared. Lastly, simple statistical study on the error between real values and estimated values using ANN is conducted, which shows the reliability of the model. This paper provides a quick reference to the effects of main parameters of regression neural networks.

Thermo-economic Investigation of an Enhanced Geothermal System Organic Rankine Cycle and Combined Heating and Power System

As a potentially viable renewable energy, Enhanced Geothermal Systems(EGSs) extract heat from hot dry rock(HDR) reservoirs to produce electricity and heat, which promotes the progress towards carbon peaking and carbon neutralization. The main challenge for EGSs is to reduce the investment cost. In the present study, thermo-economic investigations of EGS projects are conducted. The effects of geofluid mass flow rate, wellhead temperature and loss rate on the thermo-economic performance of the EGS organic Rankine cycle(ORC) are studied. A performance comparison between EGS-ORC and the EGS combined heating and power system(CHP) is presented. Considering the CO_(2)emission reduction benefits, the influence of carbon emission trading price on the levelized cost of energy(LCOE) is also presented. It is indicated that the geofluid mass flow rate is a critical parameter in dictating the success of a project. Under the assumed typical working conditions, the LCOE of EGS-ORC and EGS-CHP systems are 24.72 and 16.1 cents/k Wh, respectively. Compared with the EGS-ORC system, the LCOE of the EGS-CHP system is reduced by 35%. EGS-CHP systems have the potential to be economically viable in the future. With carbon emission trading prices of 12.76 USD/ton, the LCOE can be reduced by approximately 8.5%.