Back-pressure Steam Turbine Research Articles

Predicting Steam Turbine Power Generation: A Comparison of Long Short-Term Memory and Willans Line Model

This study focuses on using machine learning techniques to accurately predict the generated power in a two-stage back-pressure steam turbine used in the paper production industry. In order to accurately predict power production by a steam turbine, it is crucial to consider the time dependence of the input data. For this purpose, the long-short-term memory (LSTM) approach is employed. Correlation analysis is performed to select parameters with a correlation coefficient greater than 0.8. Initially, nine inputs are considered, and the study showcases the superior performance of the LSTM method, with an accuracy rate of 0.47. Further refinement is conducted by reducing the inputs to four based on correlation analysis, resulting in an improved accuracy rate of 0.39. The comparison between the LSTM method and the Willans line model evaluates the efficacy of the former in predicting production power. The root mean square error (RMSE) evaluation parameter is used to assess the accuracy of the prediction algorithm used for the generator’s production power. By highlighting the importance of selecting appropriate machine learning techniques, high-quality input data, and utilising correlation analysis for input refinement, this work demonstrates a valuable approach to accurately estimating and predicting power production in the energy industry.

Modifikovani Rankinov ciklus parne turbine bez odbacivanja toplote kondenzacije ciklusa, pokretan termokompresorom koji radi u oblasti vlažne pare

The disclosed concept relates to a novel modified and simplified steam-turbine Rankine cycle without rejection of the cycle waste heat of condensation, which is driven by a thermocompressor (ejector) operating in the wet-vapor region. The thus modified steam-turbine Rankine cycle can theoretically achieve the maximum possible thermal efficiency (~100%). The wet-vapor mixture circulating within the thermocompressor is being separated in a dedicated cylindrical separation tank, so that the saturated water is pumped to a water heater where it receives the cycle heat input, while the saturated vapor is expanded in a backpressure steam turbine producing useful mechanical work and is then recirculated back to the thermocompressor, where it is being re-pressurized by means of the primary fluid (pumped and heated saturated water). The concept can be applied to steam-turbine-cycle power-plants fueled by: coal or solid/liquid/gaseous fuel, waste heat, nuclear fuel (used by boiling water reactors, pressurized water reactors, pressurized heavy-water reactors, gas-cooled reactors, molten salt reactors or liquid-metal-cooled fast reactors) or renewable energy sources (Solar energy, biomass, geothermal). The concept can also be applied as the “bottoming” steam-turbine-cycle part of a combined gas-turbine/steam-turbine cycle power plant.

Techno-economic and carbon dioxide emission assessment of carbon black production

The over 15 million metric tonnes of carbon black produced annually emit carbon dioxide in the range of 29–79 million metric tonnes each year. With the renaissance of carbon black in many new renewable energy applications as well as the growing transportation sector, where carbon black is used as a rubber reinforcement agent in car tires, the carbon black market is expected to grow by 66% over the next 9 years. As such, it is important to better understand energy intensity and carbon dioxide emissions of carbon black production. In this work, the furnace black process is studied in detail using process models to provide insights into mass and energy balances, economics, and potential pathways for lowering the environmental impact of carbon black production. Current state-of-the-art carbon black facilities typically flare the tail gas of the carbon black reactor. While low in heating value, this tail gas contains considerable amounts of energy and flaring this tail gas leads to low overall efficiency (39.6%). The efficiency of the furnace black process can be improved if the tail gas is used to produce electricity. However, the high capital investment cost and increased operating costs make it difficult to operate electricity generation from the tail gas economically. Steam co-generation (together with electricity generation) on the other hand is shown to substantially improve energy efficiency as well as economics, provided that steam users are nearby. Steam co-generation can be achieved via back-pressure steam turbines so that the low-pressure exhaust steam (∼2 bar/120 °C) can be used locally for heating or drying purposes. Furthermore, the potential of utilizing hydrogen to reduce carbon dioxide emissions is investigated. Using hydrogen as fuel for the carbon black reactor instead of natural gas is shown to reduce the carbon dioxide footprint by 19%. However, current prices of hydrogen lead to a steep increase in the levelized cost of carbon black (47%).

An Evaluation Method of Comprehensive Performance of Retrofitted CHP District Heating Systems

There is a big wave in China of retrofitting single-purpose coal-fired systems for district heating into heat-oriented combined heat and power (CHP) systems to save energy. Back-pressure steam turbines (BPSTs) and extraction steam turbines (ESTs) are both common in retrofitted systems, but contrastive analyses of their effects on the systems’ operation performance are lacking. Moreover, comprehensive evaluation methods of the retrofitted systems remain unknown. In this paper, exergy, exergoeconomic, and exergoenvironmental analyses were conducted to evaluate the thermodynamic, economic, and environmental performances of two real CHP systems: system A using a BPST and system B using an EST. Additionally, a new multi-criteria evaluation method based on rank correlation analysis was proposed for the retrofitted system. The results show that system A is better than system B in thermodynamic and environmental aspects but poorer in the economic aspect. Overall, the multi-criteria evaluation result indicates that system A has a better comprehensive performance than system B. Therefore, the BPST has a better effect than the EST on the retrofitted CHP system for district heating in this study. The findings could provide a reference point for retrofitting work in the future.

Bagasse Electricity Potential of Conventional Sugarcane Factories

Sugar industries have huge potential to contribute to the sustainable energy transition through electricity generation and production of biofuels. Sugar-producing countries generate huge volumes of sugarcane bagasse as a byproduct of sugarcane production. In this study, the performance of an operating traditional sugar factory is analyzed for electricity generation and export potential. The study presents characteristics and energy potential of modern and traditional sugar factories. The challenges facing a traditional sugar mill are inefficient boilers, less efficient and back pressure steam turbines, and wasteful and inefficient use of steam turbine drives as prime movers instead of modern electric drives for the mills and cane knives. Others are the use of inefficient and energy intensive cane mill rollers instead of the diffusers which have low energy requirements. It was demonstrated that the cogeneration potential of sugar factory is quite significant but currently underutilized. Sugar factories can make significant contribution towards mitigation of greenhouse gas emission mitigation through supply of green electricity to the public grid. The study showed that the factory uses very old and inefficient boilers aged over 39 years which contributes to poor performance and low electricity generation capacity. Modernization is required to increase the generation and electricity export capacity through investment in new and modern high-pressure boilers, replacement of inefficient back pressure boilers (BPSB) with more efficient condensing extraction turbines (CEST), and reduction of factory steam consumption by electrification of mills and cane knife turbine drives among other measures. This study showed that the 3,000 TCD factory can invest in a 15 MW power plant based on current average factory performance indicators and more if the throughput and overall performance is close to design parameters.

Comparison of District Heating Supply Options for Different CHP Configurations

The article discusses the evaluation of potential heat production options for a large-scale district heating system in Narva (Estonia). Heat is currently generated at the Balti Power Plant’s CHP unit using local oil shale mixed with biomass. The CHP unit consists of two circulating fluidised bed boilers and a reheat steam turbine. According to the development strategy, the district heating system is expected to achieve carbon neutrality in the future. Various options and parameter variations should be analysed. The following scenarios were compared: (1) baseline scenario featuring an existing CHP extraction steam turbine; (2) alternative Scenario I featuring a CHP backpressure steam turbine; and (3) alternative Scenario II featuring a CHP gas turbine. To evaluate the above scenarios, a comprehensive energy/exergy analysis was performed, and economic indicators were calculated. The primary energy consumed, as well as the heat and electricity generated, were all taken into account. Based on this analysis, a scenario was selected using multiple-criteria decision-making that will improve energy efficiency and reliability of the system.

Influence of temperature of return district water on the performance of a backpressure steam turbine installation

The district heating systems supply heat to a wide range of consumers. In the heat source of such systems, highly efficient technologies are used for the combined production of electrical and thermal energy mainly based on steam turbine installations with backpressure turbines or turbines with adjustable steam extractions. Combined production leads to a reduction in fuel consumption (fuel saving) compared to the separate production of the two energy products. The fuel saving resulting from cogeneration reduces carbon dioxide emissions. Combined production affects the amount of fuel saved, leading to a reduction in emitted emissions, both the size of the heat load realize to consumers and the temperature of the water that enters from the return pipeline of the district heating systems into the heat source. In backpressure steam turbine installations, the district water is heated by the steam that enters the boiler-condenser, and in steam turbine installations with adjustable steam extraction, it is heated in a district heater by steam extracted from the turbine. The purpose of this paper is to study the influence of the temperature of return district heating water on the performance of a backpressure steam turbine installation for cogeneration.

Feasibility Study of Converting Boiler Houses in Moscow into Mini Combined Heat and Power Plants

The effectiveness and feasibility of modernizing boiler houses with converting them for operation as combined heat and power plants (CHPP) in a megalopolis are analyzed taking the city of Moscow as an example. The following boiler house modernization versions are considered: dependent generation of electricity from heat consumption and independent generation of electricity. The advantages and drawbacks of each version are studied by way of comparison, based on which the most appropriate version in the megalopolis environment is selected. In selecting a turbine for topping the boiler house, gas turbine and steam turbine units were compared. With taking into account the operational possibility, technical constraints, and studied literature, a backpressure steam turbine was selected for the modernization of generating facilities. The choice of the most suitable boiler house for modernization was based on the production program of Mosenergo's boiler houses for 2022, and the Yuzhnoye Butovo district thermal network’s boiler house was chosen as the most appropriate one for modernization. To determine the amount of electricity generated and the consumption of equivalent fuel after the modernization of this boiler house with taking heat from the turbine and not from the boiler, a thermal calculation was made. Based on the data obtained from the thermal calculation, a feasibility study of the modernization was carried out. It is shown that under the current conditions, the modernization of a boiler house with shifting it to operate as a CHPP is not a feasible and profitable project for the generating company in Moscow.

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.

Comparative Analysis of Low-Grade Heat Utilization Methods for Thermal Power Plants with Back-Pressure Steam Turbines

Thermal power plants (TPPs) with back-pressure steam turbines (BPSTs) were widely used for electricity and steam production in the Union of Soviet Socialist Republics (USSR) due to their high efficiency. The collapse of the USSR in 1991 led to a decrease in industrial production, as a result of which, steam production in Russia was reduced and BPSTs were left without load. To resume the operation of TPPs with BPSTs, it is necessary to modernize the existing power units. This paper presents the results of the thermodynamic analysis of different methods of modernization of TPPs with BPSTs: the superstructure of the steam low-pressure turbine (LPT) and the superstructure of the power unit operating on low-boiling-point fluid. The influence of ambient temperature on the developed cycles’ efficiency was evaluated. It was found that the usage of low-boiling-point fluid is thermodynamically efficient for an ambient temperature lower than 7 °C. Moreover, recommendations for the choice of reconstruction method were formulated based on technical assessments.

Operation Strategy of Supercritical Reheat Double Suction Back Pressure Steam Turbine

Operation Strategy of Supercritical Reheat Double Suction Back Pressure Steam Turbine

Research on Adding Post-unit for Back Pressure Steam Turbine

Research on Adding Post-unit for Back Pressure Steam Turbine

Performance Analysis Based on Experimental Data of Backpressure Steam Turbine for Cogeneration in Saturated Steam Applications

This paper aims to validate the performance capabilities of a Pressure Reducing Turbine (PRT) with respect to initial predictions based on analytic calculations. The designed equipment was installed in a beverage facility, located in Brazil. The validation procedure consists of analyzing the data collected in several periods of PRT’s operation, accessed remotely via an online server. The analysis of empirical data identifies the behavior of two key variables: generated power and effective efficiency. However, the observed boundary conditions differed significantly from expected values, forcing the turbine to operate in off-design conditions. The turbine model was hence refined and used to predict the PRT’s performance in such conditions. Results showed satisfactory accuracy for both power and efficiency predictions.

Mathematical Models of the Energy Characteristics of a Backpressure Steam Turbine Based on a Simulation Study

The backpressure steam turbine installations for combined production generate thermal energy and electricity. The produced electricity depends on the heat load determined by consumers. Heat energy is released in the district heating system through water, which is heated with the exhausted steam in boiler-condenser (district heater). The operation regime of the installation is influenced by load of the released district heat and the temperature of the district heat water at the input and output of the boiler-condenser. The variables are heat load of the district heating system and temperature of district heat water at power plant output. The temperature of the district heat water at the boiler-condenser input is an uncontrollable variable, whose value depends on heat consumption. It influences the steam pressure in the boiler-condenser and the available enthalpy drop of the cogeneration installation. In this report, a verified simulation model is applied on a backpressure steam turbine installation, type SST-300 CE2L/V36S. A multivariate simulation is carried out, studying the performance of the installation in off-design regimes. The results obtained are used for the creation of regression models of the installation’s energy characteristics. They reveal the dependence between the energy characteristics of the cogeneration steam turbine by the released heat load in the district heating system and the temperature of incoming and outgoing district heat water. The accuracy of the developed models is evaluated through multiple correlation coefficients. The mathematical models could be successfully used to optimize the operating regime of the backpressure steam turbine installation.

Оценка показателей работы теплофикационной ПТУ при изменении внутреннего относительного КПД отсеков паровой противодавленческой турбины

The authors carried out the circuit-parametric optimization studies of a promising cogeneration STU, which includes a backpressure steam turbine and a gas-fired steam boiler capable of heat recovery from flue gases. A mathematical model was employed to analyze how the internal relative efficiency of the steam turbine compartments in such an STU could affect the core operating parameters and the design characteristics of the heat exchange equipment of the unit. Mathematical modeling and circuit-parametric optimizations were run in the Machine Programming System, a software package developed by the Department of Heat and Power Systems, Melentiev Energy Systems Institute, Siberian Branch of the Russian Academy of Sciences. The optimization criterion was the price of STU-supplied electricity at the given prices of supplied heat and fuel with the adjustment for the internal rate of return on investment. Circuit-parametric optimizations show that the price of electric energy from a cogeneration STU linearly depends on the internal relative efficiency of the turbine compartments, and when it changes from 0.82 to 0.9, the price of electric energy decreases by 0.03 cents/kW. The cost effect of the increase in efficiency can be up to 98.79 thous. USD/year given the quantitative supply of electricity from the STU. The methodological approach used in this work enables feasibility testing of the attempts to improve the internal relative efficiency of the steam turbine compartments and can be useful both in the design and operation of thermal power plants. The estimated effects of internal relative efficiency of the turbine compartments on the core operating parameters and the characteristics of the unit will help determine the reliability and efficiency of its operation.

Feasibility study of the energy and economic gain that can be achieved by driving the boiler feedwater pump with a backpressure steam turbine

The low-pressure steam requirement in the iron and steel production plant is obtained through pressure reduction stations with unrestrained expansion. In this study, the feasibility of obtaining the low-pressure steam that is needed in the plant in a backpressure turbine instead of pressure reduction stations has been studied. In this way, it is foreseen that a significant amount of wasted energy during the unrestrained expansion in pressure reduction stations, can be recovered as shaft work during the expansion process performed in the turbine. The obtained shaft work is planned to be used in the boiler feedwater pump drive. It is aimed to increase the efficiency of the system by the deactivation of boiler feedwater pump electric motors and as well as bringing the energy that is lost during the unrestrained expansion of the superheated steam to the system through the pump drive. The estimated size of energy saving of the system could be reached to 33.74%. The annual size of achievable saving has been determined by approximately 8,094,810 kWh and economically $509,973. The payback period of the estimated $683,079 investment is 1.34 years. A determined amount of saving is also equivalent to the reduction of 7,285,329 kg CO2 emission, annually.

Performance improvement of low-pressure cylinder in high back pressure steam turbine for direct heating

It is the general retrofit to remove the last stages in the low-pressure cylinder of steam turbine for high back pressure direct heating, which can avoid the exergy loss caused by the traditional extracting steam heating mode of combined heat and power. However, the flow field of low-pressure cylinder will change. In this study, the last stage flow field of low pressure cylinder of such high back pressure turbine, as well as the temperature distribution, is analyzed and optimized by setting the diversion ring. Low-pressure cylinder of the 300 MW steam turbine is selected as the research object. The optimal scheme is obtained after analyzing vortex distribution, static pressure recover coefficient and total pressure loss coefficient in flow field under different heating conditions. The results show that adding appropriate diversion ring bringing about vortex effectively reduced, leading to a sharp increase of 7.84% in efficiency of low-pressure cylinder and 0.63in statistic pressure recover efficient. It is also contributing to an apparently decrease of 0.95 in total pressure loss efficient. All results indicate that the aerodynamic performance of low-pressure cylinder has obvious promotion. Under high back pressure heating condition, the structure of low-pressure cylinder of steam turbine changed.

ENERGY AND EXERGY ANALYSIS OF SHAKARGANJ LIMITED JHANG THERMAL POWER PLANT

Exergy analysis has sparked interest within the scientific community to require a more in-depth check up on the energy conversation devices. Exergy analysis gives entropy generation, irreversibility percentage exergy loss and second law efficiency. The exergy loss or irreversibility is the maximum at boiler. Thus to know about actual flow of exergy in the cycle thermodynamic analysis based on second law is desirable. In this report exergy analysis of operating condition of boiler has been carried out based on mass and exergy balance. The power plant boiler was simulated based on the measured operating data and the thermodynamic states of the plant components. . It has been found that maximum exergy destruction occurs due to combustion process. Exergy efficiency of boiler according to second law analysis and the exergy analysis of back pressure steam turbine is performed. It is found that at minimum flue gas outlet temperature second law efficiency is the maximum.

Implementing multiple-effect distillation and reverse osmosis thermal coupling to improve desalination process performance in combined water and power plants

Cogeneration has recently been an appropriate engineering approach to supply increasing energy demands. The present study demonstrates a significant influence on increase in productivity and reduction of utility consumption of thermal desalination, considering a novel internally coupled multiple-effect distillation and reverse osmosis desalination process in a cogeneration of water and power plant. The proposed power generation unit, consisting of two SGT600 gas turbines as prime movers, two heat recovery steam generators and one back-pressure steam turbine, has been applied. The objective is to propose a modified multiple-effect distillation process, due to availability of sufficient cooling water, provided by reverse osmosis reject water. The basic configuration comprises a hybrid desalination using a dual purpose condenser, results of which showed a 45% reduction in electrical energy consumption of multiple-effect distillation, accompanying a 67% decrease in intake water cost. In modified configuration, condenser temperature decreases from 48 to 45℃, allowing number of effects to increase from 5 to 7. Therefore, produced water rate and gain output ratio of the modified multiple-effect distillation increase by 30% and 31%, respectively, while specific energy consumption decreases by 6%, causing a two-year reduction in cogeneration of water and power plant pay-back period compared to the basic configuration.

Thermo-economic and environmental multi-objective optimization of a novel arranged biomass-fueled gas engine and backpressure steam turbine combined system for pulp and paper mills

For gaining both the maximum profit and the minimum exergy loss, a novel arranged gas engine combined heating and power system is proposed. This system was modeled in four aspects of energy, exergy, economic and environmental. By defining two objective functions including percentage of exergy destruction to the total inlet exergy and relative annual benefit, Genetic Algorithm was used for system multi-objective optimization. Modeling two strategies including selling mode and no-selling mode during system lifetime was another novel part of the present research. Modeling and optimization results in selling mode for Mazandaran pulp and paper plant in Iran showed that combined heating and power cycle included five gas engines each one with 6737 kW nominal power output and one steam turbine which had 667.4 kW power output. The overall efficiency of the above CHP system was 80.5% with about 1.07 years as the payback period. Comparison of results with that for traditional system showed 3.1 × 107 m3/year fuel saving, 2.63 × 106 US $/year fuel cost saving, and 1.84 × 108 kgCO2/year reduction in emission production. With no-selling mode condition, relative annual benefit decreased for about 19% and payback period increased for about 11.6%.