Condensing Steam Turbine Research Articles

CFD approach for determining the losses in two-phase flows through the last stage of condensing steam turbine

Analyzing and simulating wet steam flows within steam turbines holds significant importance, especially due to the presence of a liquid phase in the low-pressure stages of the turbine, resulting in consequential losses that demand careful consideration. Considering these conditions, this study employs advanced predictive CFD models to simulate the wet steam flow within the actual 3D geometry of the final stage in a 200 MW steam turbine, which is observed in the least research due to the complexity of modeling and analysis of three-dimensional flows. This advancement promises more precise and reliable results. Employing the ANSYS CFX software, this study engages in numerical simulations of steady-state compressible two-phase flow. Furthermore, the study offers practical equations to quantify the losses within the entire stage, which serves as a valuable metric for assessing loss levels and offers a benchmark for design improvements aimed at loss reduction. Based on the results, 10 % of losses occur along the stator and 1 % along the rotor, and a total of 11 % of losses occur along the entire stage. Finally, the efficiency of the stage is calculated to be 89 %. Steam condensation strengthens the shock waves, changes their location, diminishes Mach number and the flow velocity, and alters the flow angle. It reduces the efficiency of the turbine by 1.27 % and also reduces the work done by the turbine by 13.97 %. This emphasizes the significant influence of condensation on flow characteristics, emphasizing the necessity of conducting comprehensive investigations into this phenomenon.

Evaluation of the Effectiveness of Using Various Methods for Calculating Steam Turbine Condensers Equipped with Built-In Bundles

Evaluation of the Effectiveness of Using Various Methods for Calculating Steam Turbine Condensers Equipped with Built-In Bundles

Research and Development of the Oxy-Fuel Combustion Power Cycle for the Combined Production of Electricity and Hydrogen

Modern trends in improving environmental safety have determined the urgency in creating innovative technologies that allow the production of electricity and hydrogen without the emission of harmful substances. However, at the moment, there are not so many technical solutions offering the combined production of these useful products with a high degree of efficiency and environmental friendliness. The transition to oxy-fuel combustion power cycles for the co-production of electricity and hydrogen is a prospective way to decrease carbon dioxide emissions into the atmosphere from the energy sector. To achieve zero emissions, the semi-closed oxy-fuel combustion cycle is combined with a steam methane reformer, which has a high energy efficiency through reducing losses in the steam turbine condenser. The modeling methodology has been described in detail, including the approaches to defining the working fluid properties and mathematical models of the different steam methane reforming plants and the oxy-fuel combustion power plant. According to the results of the thermodynamic analysis of the steam methane reforming plant, it was found that an increase in the temperature from 850 to 1000 °C leads to a decrease in the mass flow fuel by 16.3% due to the shift towards a direct reaction. Moreover, the optimal temperature in the reformer lies in the range of 900–950 °C. A comparison of the energetic and ecological characteristics of various steam methane reformer units showed that the scheme with oxy-fuel combustion is better compared to the scheme with CO2 capture by absorption in monoethanolamine; the efficiency is 6.9% higher and emissions of carbon dioxide are 22 times lower. According to the results of the thermodynamic analysis of a novel oxy-fuel combustion power cycle, it was found that its performance varied regarding the range of electricity production (123.6–370 MW) and hydrogen production (0–10.8 kg/s). The efficiency of the oxy-fuel combustion power cycle varies in the range of 47.2–70.1%. Based on the results of the operation regimes analysis, the energy complex performance map has been developed, allowing identification of the efficiency and working fluid massflow by net power and produced hydrogen massflow.

INFLUENCE OF FOULING OF HEAT-EXCHANGE SURFACES OF CONDENSERS OF STEAM TURBINES ON THE CARBON OXIDE EMISSIONS

According to the strategy of environmental development of Ukraine until 2030, in order to increase the Environmental Performance Index (EPI), it is planned to reduce the energy intensity of GDP. One of the most polluting industries is the thermal power industry, and therefore reducing the emission of harmful gases, in particular nitrogen dioxide, is an important environmental problem. The share of electricity production by thermal power plants and thermal power plants in the electric power complex is significant, which leads to environmental risks due to large emissions and discharges of harmful substances by these enterprises into the environment. The magnitude of such emissions depends on the efficiency of the circulating cooling systems, which affects the rational use of fuel and water resources and, accordingly, the state of the environment. Increasing the temperature of the exhaust steam by reducing heat transfer through the contaminated heat exchange surface increases the pressure in the condenser of steam turbines and reduces the power of the turbine, which increases fuel consumption and increases the amount of emissions of harmful substances. One of these emissions is nitrogen dioxide, which is a harmful toxic compound and is classified as a greenhouse gas. The Purpose of the work is to calculate oxide carbon emissions depending on the thickness of the deposited layer on the heat exchange surface of the condensers of steam turbines of TPP. The concept of a particle of harmful emissions associated with the emergence and growth of a layer of pollution of the heat exchange surface of the condensers of steam turbines of TPP, expressed in fractions of a unit, is introduced, and an analytical expression is obtained for this value. Based on the theories of fuel combustion, heat transfer, as well as the concept of a part of harmful emissions associated with the emergence and growth of a pollution layer, the dependence of the amount of harmful emissions associated with fuel combustion at TPPs on the thickness of the pollution layer of the heat exchange surface of steam turbine condensers is obtained. Keywords: environmental pollution, thermal power plants, carbon monoxide, heat exchange surfaces.

Recovery boiler back-end heat recovery

Sustainability and efficient use of resources are becoming increasingly important aspects in the operation of all industries. Recently, some biomass-fired boilers have been equipped with increasingly complex condensing back-end heat recovery solutions, sometimes also using heat pumps to upgrade the low-grade heat. In kraft recovery boilers, however, scrubbers are still mainly for gas cleaning, with only simple heat recovery solutions. In this paper, we use process simulation software to study the potential to improve the power generation and energy efficiency by applying condensing back-end heat recovery on a recovery boiler. Different configurations are considered, including heat pumps. Potential streams to serve as heat sinks are considered and evaluated. Lowering the recovery boiler flue gas temperature to approximately 65°C significantly decreases the flue gas losses. The heat can be recovered as hot water, which is used to partially replace low-pressure (LP) steam, making more steam available for the condensing steam turbine portion for increased power generation. The results indicate that in a simple condensing plant, some 1%–4% additional electricity could be generated. In a Nordic mill that provides district heating, even more additional electricity generation, up to 6%, could be achieved. Provided the availability of sufficient low-temperature heat sinks to use the recovered heat, as well as sufficient condensing turbine swallowing capacity to utilize the LP steam, the use of scrubbing and possibly upgrading the heat using heat pumps appears potentially useful.

The Influence of Moisture Content on Energy Losses in the Steam Turbine Last Stages

A method for calculating energy losses due to moisture content is presented, which takes into account the intra-channel and peripheral separation in condensing steam turbine LPC last stages and the actual moisture distribution over the stage height. It is shown that with the consideration of peripheral and intra-channel separation in the stage with a 1200-mm long rotor blade, the losses due to moisture content are decreased by 1.3% and, accordingly, stage efficiency hrist is increased by the same value. If the separated moisture is distributed taking into account the location of the intra-channel separation slots, and the separated peripheral moisture is distributed according to a linear law in the stage upper quarter, the real moisture content value at the periphery will decrease by 8%. This will make it possible to more accurately take into account the rotor blade droplet impingement erosion at the blade peripheral zone inlet section. It is recommended to calculate the energy losses due to moisture content not in the internal relative efficiency hri as part of additional losses, but inside the blade efficiency hrb, because these losses take place in the stage cascades, unlike other types of additional losses. This approach will help more accurately determine the following flow characteristics in the stage: relative velocities M1 and M2, velocity coefficients in the nozzle j and rotor y cascades, stage reaction ratio r, etc.

INFLUENCE OF PRESSURE IN THE TURBINE CONDENSER ON HEAT SUPPLY EFFICIENCY OF NPP WITH HEAT PUMP

The use of a heat pump for heat supply makes it possible to practically stop thermal pollution of the environment during the operation of thermal and nuclear power plants in winter. If a steam turbine condenser is used as a low-potential energy source for heat pump, the amount of released thermal energy will be equal to the sum of the thermal power of the NPP condenser and the power of the heat pump compressors. From the point of view of environmental safety, heat supply by combining power plant with a heat pump is an urgent task. But it is known that the due to the lack of steam extraction for water heating, the additional electrical power of the cogeneration heat and power plant will be less than the capacity of the heat pump compressors. Thus, in terms of thermodynamic efficiency, the use of a heat pump loses to a traditional cogeneration plant. The purpose of the work is to determine the influence of the final pressure in the turbine condenser on the thermodynamic efficiency of a nuclear power plant with a heat pump. A mathematical model of the thermal scheme of the K-1000-5.8/1500 NPP turbo-plant during summer and winter operation with heating plant has been developed. With the heating plant capacity of 230 MW, the electric capacity of NPP unit decreases by 43.5 MW. A mathematical model of a heat pump has been developed, for which a steam turbinecondenser is used as a low-potential energy source. To ensure the release of 230 MW of heat, the power of the heat pump compressor must be 48.4 MW. Thus, if the heating plant is replaced with a heat pump of the same capacity, the electric power will decrease by 4.8 MW. Calculations were made regarding the influence of the final pressure in the condenser on the exergetic efficiency of the NPP with heat pump, which uses the entire capacity of the turbine condenser. The analysis of the obtained results showed that the exergetic efficiency due to the increase in electric power released in winter increases with the increase of the final pressure in the condenser. This is explained by an increase in the heat pump coefficient of performance.

Aspects of ecology and automation in the forecasting of sulfur dioxide emissions associated with contamination of the heat exchange surfaces of steam turbine condensers

Aspects of ecology and automation in the forecasting of sulfur dioxide emissions associated with contamination of the heat exchange surfaces of steam turbine condensers

INFLUENCE OF HEAT-EXCHANGE SURFACES FOULING FOR TPP STEAM TURBINES CONDENSERS ON THE AMOUNT OF NITROGEN DIOXIDE EMISSIONS

Problem statement. One of the most polluting industries is the thermal power industry and therefore reducing the emission of harmful gases, in particular nitrogen dioxide, is an important environmental issue. Despite the decrease in the production of TPPs and CHPs of electricity compared to 2020 (by 12,5 %), at present their share remains significant in the entire electric power complex, which leads to environmental risks due to large emissions and discharges of harmful substances by these enterprises into environment. The magnitude of such emissions depends on the efficiency of the circulating cooling systems, which affects the rational use of fuel and water resources and, accordingly, the state of the environment. Increasing the temperature of the exhaust steam by reducing heat transfer through the fouled heat exchange surface increases the pressure in the condenser of steam turbines and reduces the power of the turbine, which increases fuel consumption and increases the amount of harmful substances emissions. One of these emissions is nitrogen dioxide, which is a harmful toxic compound and is classified as a greenhouse gas. The purpose of the work is to calculate nitrogen dioxide emissions depending on the thickness of the deposited layer on the heat exchange surface of the TPP steam turbine condensers. Conclusions. The concept of harmful emissions’ share associated with the emergence and growth of a pollution layer on the heat exchange surface of the TPPs’ steam turbines condensers, expressed in fractions of a unit, is introduced, and an analytical expression is obtained for this value. Based on the theories of fuel combustion, heat transfer, as well as the concept of harmful emissions’ share associated with the emergence and growth of a pollution layer, the dependence of the amount of harmful emissions associated with fuel combustion at TPPs on the thickness of the pollution layer on the heat exchange surface of steam turbine condensers is obtained.

Improving the efficiency of condensation installations of steam turbines by applying liquid-vapor ejector

This paper considers the possibility of using liquid-vapor ejectors in condensing units of steam turbines. This unit is designed for pumping out a steam-air mixture from a steam turbine condenser, in which the process occurs at a pressure lower than atmospheric. In the traditional scheme, this is provided by a two-stage steam-jet ejector unit. The proposed scheme involves the use of a single-stage liquid-vapor ejector and its possible pre-vacuum mode of operation in conjunction with a liquid-ring vacuum pump. A working process of the liquid-vapor ejector does not require the supply of working steam from the outside since its generation occurs in the active nozzle of the liquid-vapor ejector. A description of the traditional scheme and the proposed options is given, which are different both in the scheme solution and in the operating parameters. The object of this study is a liquid-vapor ejector, which is used in the condensing system of a steam turbine. Thermodynamic calculation of the proposed circuit solutions was carried out. As a result, the necessary mode parameters of the schemes were determined. To assess the feasibility of using a liquid-vapor ejector in the condensation systems of steam turbines, an exergy analysis was performed. The proposed scheme makes it possible to increase efficiency by 2.3 times, and when used with a liquid-ring vacuum pump – by 2.44 times. To assess the economic efficiency of the modernization of the condensing system, thermoeconomic analysis was performed. The use of the proposed scheme makes it possible to reduce the cost of generating boiler steam and reduce the cost of the resulting product of the steam turbine unit by about 51 %. The estimated cost of a unit of the amount of boiler steam consumed per ton of product and the unit cost of steam were established.

Tri-objective optimization of two recuperative gas turbine-based CCHP systems and 4E analyses at optimal conditions

In this study, optimal performances of two combined cooling, heating and power systems are presented using energy, exergy, exergoeconomic, and environmental analyses. The topping cycle is a recuperative gas turbine cycle, which is common in both. The bottoming cycle of the first system comprises a steam turbine, a recuperative-regenerative organic Rankine cycle, two absorption cooling systems and a water heater while in the second, the recuperative-regenerative organic Rankine cycle is replaced entirely with a condensing steam turbine cycle. A parametric analysis is performed first to determine the impact of key operating conditions on the performance of the proposed systems. Then those operating conditions are used for performing a tri-objective optimization applying Pareto Envelope-based Selection Algorithm-II considering energy efficiency, exergy efficiency and total cost rate as the objective functions. Thereafter, a multi-criteria decision analysis is performed to determine the best optimal solution from the Pareto front. Further, to show the benefit of optimization, the values of the objective functions are compared at the optimal and the base case conditions. After optimization, it was observed that the energy and exergy efficiencies improve modestly in both systems, while the total cost rate decreased by 9% and 5.3%, respectively. Further, the first system has a payback period of 10.83 years, while the second system has 13.27 years. It was also found that at their optimum condition, the overall energy output and efficiencies of the two systems are nearly the same. However, the total cost rate of the first system is substantially lower compared to the second.

Control of condensate dissolved oxygen in steam surface condenser. Reconstruction experience

Dissolved oxygen concentration in the steam turbine condenser significantly influences the failure-free operation of the power unit.Despite the wide range of recommendations and operating experience, there are still condenser working regimes with abnormal dissolved oxygen concentration.Taking into account the importance of water chemistry, there is a need to pay additional attention to the root causes of the described problem.This paper contains the results analysis of the deaerating tests on the full and part loads before and after condenser reconstruction. The main reason for the high dissolved oxygen concentration was determined. After the reconstruction, the average concentration of dissolved oxygen decreased from 174 μg to 22.7. At the nominal load of the turbine, the average concentration before the reconstruction was 99 μg. After the reconstruction, it was possible to reach values of 14 μg, meanwhile the increase in electricity consumption for own needs amounted to 21.6 MW per month.Despite the test codes recommendations, this study methodology involves changing the drainage input and studying its effect on the dissolved oxygen concentration over a wide range of changes in steam turbine loads. This made it possible to evaluate the effect of a specific drainage flow on the dissolved oxygen concentration.

Analysis of High Back-pressure Heating System of 350MW Wet Cooling Unit

In order to solve the problem of increasing heating demand of 350MW supercritical condensing steam turbine unit in a power plant, this paper introduces a high back pressure heating technology of wet cooling unit, and describes the key problems in this technology. By increasing the pressure of low-pressure cylinder exhaust, the condenser transformation fully makes use of the steam latent heat heating circulating water of low-pressure cylinder exhaust. The double-rotor exchange technology can form high back pressure in the heating season and low back pressure in the non-heating season, which can not only improve the exhaust parameters of steam turbines in the heating period, but also can operate in pure condensing conditions in the non-heating season.

Cumulative solar exergy allocation in heat and electricity cogeneration systems

Heat and electricity cogeneration is effective to improve energy efficiency but with no a unified allocation method. Both the emergy and cumulative exergy methods could evaluate the resources consumption, with the issues caused by total inheritance principle and inequivalence of primary exergy, respectively. This paper takes solar exergy as the basis for cumulative exergy, proposing a concept of cumulative solar exergy (CSE), which provides a new insight for allocation problems and sustainability evaluation. The CSE allocation is performed by taking the CSE transformities (TrCSE) in the stand-alone heat and electricity generation systems (alternative systems) as baselines. The CSE method is applied in the biomass and coal gasification cogeneration systems, with back pressure steam turbine (BPT), extraction condensing steam turbine (ECT) and gas-steam combined cycle (GSC) taken as power generation facilities. The results show that the TrCSE of biomass-based systems are lower than those of the coal-based systems. The resource utilization efficiencies can be improved by cogeneration according to the TrCSE of cogeneration and alternative systems. The allocation results of CSE and exergy methods are in the range of energy and enthalpy drop methods. The electricity coefficients of the CSE method are higher than those of the exergy method.

Justification of the power of the heat pump used in the cooling system of the steam turbine condenser of the CCGT-CHP

THE PURPOSE. Determination of the permissible power of the heat pump (HP) used in the cooling system of the steam turbine condenser for a thermal power plant (TPP) based on double-circuit combined-cycle gas turbine (CCGT).METHODS. Mathematical modeling of the operating modes of a heating CCGT with a HP in the cooling system was used as a research method. The research was conducted using statistical data on technical parameters and economic indicators of CCGT-450, for climatic and market conditions of St. Petersburg. The research of the most characteristic modes of operation of the main power equipment, in the annual context, was carried out. The maximum permissible capacity of the HP, from the point of view of the organization of stable heat supply to the consumer, available low-potential resources and breakeven operation of TPP in the electricity market was determined.RESULTS. It was found that lowpotential energy resources in the cooling system of the steam turbine condenser are formed in significant volumes and the thermal power of the consumer is consistently high, including in summer. Therefore, market restrictions related to the break-even operation of TPP in the wholesale electricity market are the most essential condition determining the permissible level of HP power. It was found that for the object of study, with an average annual electrical capacity of 650 MW, the maximum power of the HP is 160 MW.CONCLUSION. The main factors limiting the permissible level of HP power were analyzed using the example of a real power facility. A direct connection between the maximum capacity of the HP and external economic conditions, as well as the level of energy efficiency of the TPP equipment was established. This approach can be used to select and justify the HP capacity regardless of the location region, the type of power system, the cost of energy resources, market conditions, as well as the type and characteristics of the equipment used.

Infrared thermal image based steam turbine condenser air ingress test

This paper looked at the findings and analysis of a practical investigation into measuring air ingress to a steam power plant condenser using an infrared (IR) thermal imaging camera. The transient circumstances heat transfer of the condenser's surfaces were researched in order to use a single heating element with changing heat flow contributions. The investigation was conducted out on a condenser with a changing load, with thermal images taken with an infrared sensor and saved on a computer. The thermal resistance of the condenser was found to be about 40% lower than that of the damaged condenser.

Optimization of Condenser Backwash Method to Maintain Condenser Performance During the Backwash Process in PLTGU Grati

The condenser is a device used to change the water vapor phase that has been used to rotate the turbine blade into a liquid phase by condensing it. When the condenser tube is dirty, it can disrupt the steam condensation process which affects the efficiency of the condenser. To overcome this problem a condenser backwash is carried out.  Condenser backwash has a good influence on unit efficiency but backwash activities also reduce production by decreasing vacuum condensers and steam turbine loads. When the vacuum condenser backwash process decreases + - 24 mmHg and the steam turbine load decreases + - 8 MW.The condenser backwash process is carried out from the control room with the observation of parameters from the local area or equipment. Backwash condensers are done one by one as needed. The condenser type in PLTGU Grati Block I is a type of crossflow with two sides, namely, side A and side B. Each side of the condenser has a different sequence backwash condition. This study will be carried out a backwash method that is different from the sequence of automatic sequences.In the normal condenser backwash activity of data table 3 we can know there is a decrease in steam turbine load ± 8MW and a decrease in vacuum ± 24 mmHg. This is because at a certain period the condenser performance is reduced because at the time of switching valve one side of the condenser is not irrigated by seawater so that the heat transfer in the condenser is reduced which has an impact on a load of steam turbine and vacuum condenser. After the research was obtained that the greater the opening of the valve inlet when the condenser backwash then the decrease in vacuum and steam turbine load decreased even no decrease in load.The backwash method that can be done to keep the vacuum condenser and steam turbine load stable is by maneuvering the valve inlet, outlet, and condenser backwash valve. The results of the analysis obtained were a more stable decrease in steam turbine production in 0 MW and a decrease in the vacuum of 14 mmHg.

An economic assessment method for flexibility enhancement technologies of thermal power plants

High-level renewable energy integration imposes significant uncertainties into power systems. The negative peak load regulation (NPLR) and frequency regulation (FR) are needed for the security of the system’s operation. Thermal power plants are urgent to carry out flexibility enhancement to provide NPLR and FR. However, there are diverse flexibility enhancement technologies to be chosen. This paper proposed an economic assessment method of flexibility enhancement technologies to conduct thermal power plants to choose the best scheme. Firstly, the framework for the economic evaluation is proposed. The various flexibility enhancement technologies are classified based on the revenue model. Then, the revenue function of NPLR and FR are formulated under the ancillary service market. Finally, the economic indexes, such as, the internal rate of return (IRR), net present value (NPV), and payback period are calculated. The proposed methods are validated using a 200 MW power unit with a condensing steam turbine. The results demonstrated the effectiveness of the proposed framework.

Computer simulation of the reliability of the heat exchange surface of the steam turbine condenser

The aim of the article is to demonstrate the relationship between the adaptive regulation of the heat exchange surface to specific operating conditions of a steam turbine condenser and the reliability and availability of this surface in a specific period of time. The article exemplifies the relationship between the settings of the condenser heat exchange surface and the resulting changes in the reliability structures of this surface. The method of creating a mathematical model of reliability estimation, which is characterized by the variability of the reliability structures of the heat exchange surface in relation to specific operating conditions in a specific period of time, was indicated. Then, exemplary simulations of the adaptation of reliability structures of specific pipe systems constituting the condenser’s heat exchange surface to specific processes of operation of this condenser are presented. The simulations refer to the time-varying thermal loads of the condenser, the time-varying mean thickness of the sediments, and changes in the temperature of the cooling water at the point of its intake over time. The adaptation of certain reliability structures consists in the adaptation of specific systems of pipes through which the cooling water flows to the currently existing operating conditions of the condenser in order to maintain the desired reliability of the heat exchange surface for a specified time. This is done by enabling or disabling the flow of cooling water through a given number of pipes in specific systems under given operating conditions. On the basis of computer simulations, the reliability functions, and the availability functions of the subsystem under consideration were estimated.

Prediction of the influence of pollution of heat-exchange surfaces of steam turbine condensers on harmful substance emissions of TPP

Prediction of the influence of pollution of heat-exchange surfaces of steam turbine condensers on harmful substance emissions of TPP