Combined Cycle Cogeneration Plant Research Articles

Hourly electricity CO[formula omitted] intensity profiles based on the real operation of large-scale natural gas combined cycle cogeneration plants

The decarbonization of energy systems is a major challenge that requires complex cross-sectoral strategies that need to be supported by energy modeling. As many technologies rely on electricity, an accurate estimation of its CO2 intensity is of utmost importance for the reliability of modeling results. When electricity is generated from fossil sources, its CO2 intensity depends on several parameters. This research paper presents an hourly calculation of the CO2 intensity of power generation from natural gas combined cycles, based on real data from several years of operation of three plants. As these plants are also operated in combined heat and power mode, two alternative allocation methods are compared. The results confirm the variability of CO2 intensity based on the different operation strategies of the plants and the share of heat and electricity generated. The hourly analysis shows average values in the range of 230–250 gCO2/kWh in winter, rising to around 330–370 gCO2/kWh in summer. The real CO2 intensity profiles presented in this paper can be integrated into energy planning models to improve their ability to estimate the potential benefits of different decarbonization solutions by including the effect of the operational profiles over the day and the year.

Optimal working-fluid selection for organic Rankine cycle integrated into a combined cycle cogeneration plant

Optimal working-fluid selection for organic Rankine cycle integrated into a combined cycle cogeneration plant

Optimization of schemes and ways to expand the adjustment range for the power supply of combined heat and power plants

The article assesses the possibility of using low-flow operating modes at steam turbine with an additional boiler and steam and combined-cycle cogeneration plants for heat supply schemes, taking into account the storage properties of heat networks and buildings. It is shown that the use of low-flow operation modes of the turbine plant during the night period allows the combined heat and power plant to participate more effectively in covering the variable part of the electric load schedule. The dependence of the share of participation of an additional boiler in covering the heat load on the prices for fuel and electricity is determined. Comparison of the performance indicators of the steam turbine CHPP in low-flow modes with the release of the thermal energy necessary to the consumer from an additional boiler with the mode of its complete shutdown and the release of thermal energy from the peak hot water boiler made it possible, taking into account the accumulating properties of heat networks and buildings, to recommend a low-flow operation mode at night. For a combined-cycle cogeneration plant it is shown that it is advisable to reduce the electric power at night, while ensuring the nominal heat supply, by unloading the gas turbines with the transfer of the steam turbine to the motor mode.

Оценка эффективности использования ПГУ-ТЭЦ для регулирования графика электрических нагрузок с учетом износа оборудования

Uneven power consumption in electrical grids is challenging for maintaining daily power load schedule. Existing power generation facilities are required to contribute to electrical load control. This paper is a result of efficiency evaluation for a combined-cycle cogeneration plant under a variable mode based on equivalent operating hours and equipment wear and tear for PGU-4T turbine as an example.

Research of the two-circuit combined-cycle cogeneration plant’s behavior according to the temperature chart

THE PURPOSE. To consider the actual problem of determining the optimum value of the connected heat load to the cogeneration combined cycle gas turbine (CCGT) of the heat generation profile. METHHODS. Simulation modeling of operation modes using the "United Cycle" software is applied as a research method of the considered power unit operation. We studied several regimes of heat supply from the considered CCGTs during the heating period with the determination of integral annual indicators, as well as the relative fuel savings compared to the separate generation and the increase in the specific integral economic effect for different values of the cogeneration coefficient.RESULTS. We found that the optimal cogeneration coefficient for the object of study is 0.49. However, the value of the optimal cogeneration coefficient, determined by the condition of maximizing the specific integral economic effect for the object of research, is also 0.49. CONCLUSION. Determining the optimal unit commitment, which influences not only the initial investment, but also the expected operating (fuel) costs, is a pressing issue in power plant design. We present a basis for the possibility of using the indicator of relative fuel economy compared to separate generation as an optimization criterion. This parameter is widely used for optimization of combined heat and power units under conditions of planned economy. Under current economic conditions, it is possible to obtain a direct link between the incremental net discounted income from combined production and the relative fuel savings. This method can be used to analyze and optimize the mix of CCGT equipment regardless of geographical area, type of power system, energy resources cost, market conditions, as well as the characteristics of the used equipment.

The Upgrading of the Combined-Cycle Cogeneration Plant with Heat-Recovery Steam Generators for Large Cities of the Russian Federation

In most large cities of Russia, the annual heat consumption exceeds the annual electricity consumption more than twice as a rule. On the contrary, the electric power of the combined-cycle cogeneration heat-power plant (CCCHPP) with heat-recovery steam generators (HRSG) is much higher than the thermal power of the cogeneration extraction of its steam turbine plant. This necessitates equipping combined-cycle gas turbine–combined heat and power plants (CCGT–CHPP) with additional heat sources to cover the heat loads of the heating season, which exceed the heat capacity of the cogeneration extractions of the combined-cycle gas turbines. The article shows that the use of water-heating boilers in this capacity has a number of serious disadvantages. These disadvantages can be eliminated by equipping HRSGs with afterburner units (ABUs), which burn the gas fuel in the residual oxygen of the exhaust gases of the gas turbine engine (GTE) directly in the HRSG. The range of thermal loads can be expanded, and the efficiency of the ABU application can be significantly increased by mounting the ABUs in the HRSG downstream from the high-pressure steam superheater upstream from the high-pressure evaporator. Furthermore, it is necessary to integrate a number of new components into the HRSG configuration, such as a water low-pressure steam superheater (WLPSSH) used instead of the gas LPSSH, a reduction device, and a peak network heater included in the heating plant of the steam turbine unit as the third stage of the network water heater at high (peak) thermal loads. By the example of the PGU-450T CCCHPP, the fundamental possibility of implementing the proposed modernization of its complete HRSG without making any changes to the design of the steam turbine is shown. Since the low-pressure drum of this HRSG is additionally equipped with a deaeration unit, the upgraded HRSG of the PGU-450T plant had also to be equipped with a water condensate heater upstream from the deaerator and additional shut-off and control valves that maintain the pressure in the deaerator and assure the subcooling of the water condensate at the deaerator inlet within the permissible range of all operating modes as well as under changing thermal loads all the year round.

Flexible operation of a combined cycle cogeneration plant – A techno-economic assessment

The need for flexibility in combined heat and power (CHP) plants is expected to increase due to the strong expansion of wind power in electricity systems. Cost-effective strategies to enhance the flexibility of CHP operation are therefore needed. This paper analyzes three types of flexibility measures for a combined cycle CHP plant and their relative impact on the plant operation and revenue. The types of flexibility are: operational flexibility of the fuel conversion system, product flexibility with variable plant product ratios (heat/electricity/primary frequency response), and thermal flexibility in a district heating network. A modeling framework consisting of steady-state and dynamic process simulation models and optimization model is developed to combine static, dynamic, technical and economic perspectives on flexibility. A reference plant serves as a basis for the process model development and validation, and an energy system model provides input profiles for future electricity price scenarios. The results indicate that product flexibility and thermal flexibility have the highest value for the cogeneration plant (up to 16.5 M€ increased revenue for a 250 MWel plant), while operational flexibility (ramp rate) has a comparatively small impact (<1.4 M€). A wide load span and plant versatility, e.g. electricity and heat generating potential between 0 and 139% of nominal capacity, is beneficial in future energy system contexts, but has a marginal value in the current system. Electricity price volatility is a main driver that increases the value of flexibility and promotes operating strategies that follow the electricity price profile rather than the heat demand.

복합열병합발전소의 성능향상을 위한 유기랭킨사이클의 적용 및 경제성 분석

Purpose: The performance of a combined cycle cogeneration plant (CCCP) degrades with time owing to various causes. To solve this problem, the total turbine output of the CCCP must be improved. This paper proposes methods to improve the total turbine output of CCCPs by applying the Organic Rankine Cycle (ORC).<BR>Methods: Three models are proposed to apply ORC to a 120 MW CCCP. Case 1 uses pure waste heat from a heat recovery steam generator (HRSG) and residual heat from district heating. Case 2 uses the waste heat from the exhaust gas generated after heat exchange in a vapor power cycle. Case 3 is an integration of Case 1 and 2. Detailed conditions and additional outputs of each model are analyzed, and their actual applicability is analyzed through economic analysis.<BR>Results: Compared with the power output of the CCCP, the output range of Case 1 is 0.3%~1.6%, that of Case 3 is 2.5%~3.7%, respectively, and the output of Case 2 is 2.2%. All the models have actual applicability.<BR>Conclusion: For CCCPs, additional power and economic value can be generated by selecting an appropriate ORC model according to the conditions of the target plant.

CO&lt;sub&gt;2&lt;/sub&gt; Emission and Energy Assessments of a Novel Pre-Purification Unit for Cryogenic Air Separation Using Supersonic Separator

Thermal power plants with oxy-combustion CO2 capture are featured by large scale oxygen demand, where cryogenic air separation is most suitable. In such context, a Pre-Purification Unit (PPU) is required, prior to air fractionation, to remove hazardous air contaminants – H2O, CO2 and several trace-species – preventing ingress into the Cold Box. The conventional PPU – named FULL-TSA – remove those contaminants by means of Temperature Swing Adsorption (TSA), ordinarily using double-layered bed with activated alumina for adsorbing H2O and zeolitic molecular sieve for adsorbing CO2 and further trace-species, which implicates in relatively high demand of low-pressure steam for impurities desorption. A novel pre-purification concept (SS-TSA) embraces a Supersonic Separator (SS) performing the bulk of separation service, abating nearly 98.5% of H2O, followed by a finishing single-bed molecular sieve (MS) TSA step, which is featured by its relatively small size, for removing CO2 and remaining impurities. This work presents the energy analysis, as well as the related indirect CO2 emissions, of such a novel concept (SS-TSA) comprising air compression, cooling, SS dehydration and finishing MS-TSA against the conventional method fully based in TSA purification (FULL-TSA). Process simulation in HYSYS 8.8 assisted technical evaluation and comparison of alternatives, which included the use of two Hysys Unit Operation Extensions – SS-UOE and PEC-UOE – for rigorous thermodynamic SS modeling with phase equilibrium sound speed. SS was designed to impose only 1.4% of head loss, while shrinking TSA service to about 10% of FULL-TSA counterpart, also recovering super-cooled aqueous condensate that reduces water make-up and N2 consumption for cooling. Changing from FULL-TSA to SS-TSA the average demand of low-pressure steam reduced from 1.37 to 0.16 MW. In terms of electricity demand the difference was quite small, referring to a tiny increase of 0.07 MW in SS-TSA comparatively to total power demand of 14.97 MW in FULL-TSA. Assuming a natural gas combined cycle cogeneration plant matching requirements to air compression and pre-purification process, equivalent reduction in CO2 indirect emission was 20 kg/h for SS-TSA. These results point superiority of SS-TSA.

Influence of ambiguity of reliability indices information on configuration shaping of combined cycle plant

Methodology for accounting of ambiguity of reliability indices information on configuration shaping of combined cycle plant (CCP) is elaborated. Ambiguity of calculated failure density of heat-recovery steam generators (HRSG) will have no impact on configuration shaping of combined cycle cogeneration plant (CCCP), if calculated value is about 10-12 percent.

The Investigation of Fuel Type Influence on the Energy Indicators of the Electrochemical Generator in the Cogeneration Unit

The paper presents a generic technique to calculate the consumption of synthetic gas and fuel for the specified electrical power, temperature in the anode fuel utilization factor, specific expenses of fuel equivalent to develop electric and thermal energy, power efficiency for various natural fuels (methane, coal, petroleum products, etc.) and synthesized ones (methanol, ethanol, etc.) in synthesis gas with subsequent use of it in the SOFC. The paper researches into the influence of fuel types: hydrogen, methane, motor diesel fuel, ethanol, gasoline and methanol – on fuel utilization factor, specific expenses for the production of electrical and thermal energy, efficiencies of the catalytic burner, fuel cell solid-oxide battery and electrochemical generator. The overall level of fuel utilization for the cogeneration power plant based on SOFC with hydrogen fuel and methane surpasses the level of modern combined-cycle cogeneration plant, and with diesel, ethanol, gasoline, and methanol surpasses the level of cogeneration combined heat and power plant CHPP on the basis of the internal combustion engine. The investigation has shown that the best fuel is hydrogen and the worst is methanol on the level of energy performance. For hydrogen, fuel utilization factor and specific expenses of fuel for production of electric and thermal energy releasing in heat networks equal to 1; 0.122 kg equivalent fuel/kWh and 34 kg of equivalent fuel/GJ, respectively, while for methanol, these indicators equal to 0.359; 0.475 kg equivalent fuel/kWh and 83,7 kg of equivalent fuel/GJ. For other fuel types, these energy indicators lie between the specified values.

System effectiveness analysis of combined cycle cogeneration plant

Methodology for thermodynamic analysis, fuel efficiency determination, and mathematical economic calculation model of comparative economic effectiveness of combined-cycle cogeneration plant (CCCP) are elaborated. CCCP with a single, dual and triple pressure heat-recovery steam generators (HRSG) are investigated with account for real-time use in Heating System. Employment of CCCP with a triple pressure HRSG ensure high value of system effectiveness. Modes of CCCP, conditional and functional scope of electricity and heat, and condition of construction investment financing of CCCP are main factors have an impact on effectiveness of different schemes of CCCP.

The Ways to Improve the Efficiency of Binary Cogeneration Plant Operation by Use Additional of the Exit-Gas Heat Behind the Recovery Boiler

The exit-gas temperature behind the recovery boiler depends on the location, climate conditions, operation modes of the gas and steam turbine equipment at the combined-cycle cogeneration plant and can be slightly higher than the minimum admissible value. It leads to emergence of additional of exit-gas heat behind the recovery boiler. However the high-grade heat of the steam turbine extraction not only for own flows needs but also system water is used for heating. It reduces profitability of work of all power plants. The ways of use of the additional of the exit-gas heat behind the recovery boiler system water heating and chemically treated water of district heating makeup heating are offered. It leads to production the extra power by steam turbine and to improve the efficiency of binary combined-cycle cogeneration plant operation.

Prediction of power generation capacity of a gas turbine combined cycle cogeneration plant

A precise prediction of the power generation capacity of each power plant in an electric grid is important for managing the grid stably by preventing mismatch between the electric demand and power production. This prediction also helps power plant owners maintain their facilities because it allows effective performance monitoring. This paper proposes a unique analysis tool for predicting the near-term power generation capacity of cogeneration combined cycle power plants using correction curves and real operating data. The plant operation was simulated using the well-simulated design performance and an off-design calculation model consisting of performance correction curves and thermodynamic modeling. Real operation data of several seven-day periods were simulated using the developed tool. The data of the first five days was used as a tool set up leading to a calculation of the power correction factor. The obtained power correction factor reflected the performance degradation quite well. The data of the last two days was used for tool validation. The discrepancy between the predicted and measured power outputs were less than 2%. The proposed method can be used for both performance monitoring and a prediction of the power generation capacity of gas turbine-based power plants.

복합열병합발전소에 적용된 유기랭킨사이클의 성능 및 경제성 평가

복합열병합발전소에 적용된 유기랭킨사이클의 성능 및 경제성 평가

Off-design performance analysis of organic Rankine cycle using real operation data from a heat source plant

There has been increasing demand for cogeneration power plants, which provides high energy utilization. Research on upgrading power plant performance is also being actively pursued. The organic Rankine cycle (ORC) can operate with mid- and low-temperature heat sources and is suitable for enhancing performance of existing power plants. In this study, an off-design analysis model for the ORC was developed, which is driven by waste heat or residual heat from a combined cycle cogeneration plant. The applied heat sources are the exhaust gas from the heat recovery steam generator (Case 1) and waste heat from a heat storage unit (Case 2). Optimal design points of the ORC were selected based on the design heat source condition of each case. Then, the available ORC power output for each case was predicted using actual long-term plant operation data and a validated off-design analysis model. The ORC capacity of Case 2 was almost two times larger than that of Case 1. The predicted average electricity generation of both cases was less than the design output. The results of this paper reveal the importance of both the prediction of electricity generation using actual plant operation data and the need for optimal ORC system sizing.

Energy System Diagnosis by a Fuzzy Expert System with Genetically Evolved Rules

The problem of malfunction diagnosis in energy systems can be approached using an expert system which compares the experimental data measured by the plant acquisition system and the calculated data evaluated by a plant simulator under the same operating conditions. In this paper the rules that form the knowledge base of the expert system are not assigned heuristically by trying to code the expertise of plant personnel, as it is usually done, but they are artificially and randomly generated by the recombination and selection operators of an evolutionary algorithm. A two-objective optimization problem is set up, in order to search for the optimal sets of rules having the minimum complexity but simultaneously maximizing the number of correct fault identifications for a given set of malfunctioning operating conditions. A global and a local approach are applied to a real test case, a two-shaft gas turbine used as the gas section of a combined-cycle cogeneration plant, in order to evaluate the potentialities and the limits of this methodology.

A methodology for energy savings verification in industry with application for a CHP (combined heat and power) plant

A methodology is proposed to assess the savings achieved from the implementation of ECMs (energy conservation measures) in industrial plants with application for a combined cycle cogeneration plant. The analysis begins with the study of the operation of the system and a qualitative assessment of the changes resulting from the ECMs in the plant. The control volume is subsequently selected with the objective of minimising and focusing the efforts exclusively on the areas of the system actually influenced by the ECMs. An ANN (artificial neural networks) approach is proposed for the modelling stage and it is used to mimic the production and consumption of the system during the post-retrofit period in its configuration prior to the changes. Special attention is given to the selection of the variables used as predictors in the developed models, as well as to the determination of the relative influence of the inputs on the final models. Finally, the savings are calculated, and a critical analysis of the results is presented based on the comparison with the predictions obtained from the preliminary qualitative assessment.

On the enhancement of the efficiency of the energy complexes of crude hydrocarbon processing plants

A method for circuit-parametric analysis of the efficiency of the heat-and-power system of the energy complexes at gas and natural-gas condensate processing plants is proposed. An energy complex of an alternative structure with an independent source of thermal and electric energy integrated into the production line has been developed. The energy carriers are produced accompanied by recovery of the secondary energy resources, waste, and effluents. Using the developed information-analytical software, multicriterion assessment of the efficiency of the alternative energy complexes and its systems based on independent energy sources of the combined-cycle cogeneration plant type has been performed for the gas processing plant in Astrakhan and the most effective equipment composition variant has been determined. The effect of the basic technical and economic factors on the economic efficiency has been established. The investments in construction of the power- and water-supply system within the plant’s energy complex pay off in 8–9 years.

Cogeneration unit with an absorption heat pump for the district heating system

The Imanta district heating plant began operation in 1974 as one of the main heating plants for the Riga district heating system. Until now, it has undergone several reconstructions. First, the ordinary boiler plant with steam and hot water boilers was reconstructed to be a natural gas-fueled combined cycle cogeneration plant supported with hot water boilers. Then, one of the cooling towers of the cogeneration section was replaced by an absorption heat pump/chiller, thus providing the closed cooling water circulation system and recovering 2 MWth (7 MMBTU/h) low-grade heat otherwise lost in the atmosphere. The driving force for the absorption heat pump is steam produced by the steam boiler (3 MWth = 10 MMBTU/h) already located at the boiler plant. The efficiency of the absorption heat pump is closely related to the operation of the cogeneration unit, outside temperature, and district heating water temperature regimes. The case study confirms that a more efficient energy production system reduces the fuel consumption with the same amount of the produced energy, thus lowering the expenses on energy production and reducing the amount of the polluting emissions into the atmosphere.