Efficiency Of Thermal Power Plants Research Articles

Development of a model to evaluate the water level impact on drain cooling in horizontal high pressure feedwater heaters

Feedwater heaters play an important role in improving power plant thermal efficiency. High pressure feedwater heaters are generally of shell and tube type of heat exchangers which have three shrouded zones in the shell. In present study, a mathematical model is suggested for performance evaluation of a three-zone feedwater heater. Proposed model is capable of predicting the effects of variation in liquid level and load condition. The model is verified by experimental results existing in literature. Then impact of increase or decrease of liquid level on performance characteristics are evaluated for a typical horizontal high pressure feedwater heater. The influence of water level and load on drain cooler approach is analyzed quantitatively. Results show sharp variation in drain cooler approach in low water level condition. It is also shown that at full load condition, heater is more sensitive to liquid level changes.

Energy Efficiency of Low-Temperature Deaeration of Makeup Water for a District Heating System

It is shown that the temperature of makeup water in district heating systems has a strong effect on the energy efficiency of turbines of thermal power plants. A low-temperature deaeration process that considerably improves the energy efficiency of thermal power plants is developed. The desorbing agent is the gas supplied to the burners of the boiler. The energy efficiency of the process for a typical unit of thermal power plant is assessed.

Study on Magnetic Separation Device for Scale Removal From Feed-Water in Thermal Power Plant

To improve thermal power plant efficiency, we proposed a water treatment system with a high gradient magnetic separation (HGMS) system using a superconducting magnet, which is applicable in high-temperature and high-pressure conditions. This is a method to remove the scale from feed-water utilizing magnetic force. One of the issues for practical use of the system is how to extend the continuous operation period. In this paper, we succeeded in solving the problem by eliminating the deviation of captured scale quantity by each filter. In fact, in the HGMS experiment using the solenoidal superconducting magnet, it was shown that a decrease in separation rate and an increase in pressure loss were prevented, and the total quantity of captured scale increased by proper filter design. The design method of the magnetic filter was proposed and will be suitable for long-term continuous scale removal in the feed-water system of the thermal power plant.

Development of a Magnetic Separation System of Boiler Feedwater Scale in Thermal Power Plants

We are developing a superconducting magnetic separation system to remove scale or iron oxide from boiler feedwater in thermal power plants. The reduction of scale improves energy conversion efficiency of thermal power plants and reduces discharged CO 2 . We have studied suitable installation locations and operation conditions and examined the separation ability of the system located near the boiler where the water is at high temperatures and pressures. We have concluded that the magnetic separation system is effective to remove scale of boiler feedwater and that the use of a superconducting magnet is essential for the system.

Lower electricity prices and greenhouse gas emissions due to rooftop solar: empirical results for Massachusetts

Monthly and hourly correlations among photovoltaic (PV) capacity utilization, electricity prices, electricity consumption, and the thermal efficiency of power plants in Massachusetts reduce electricity prices and carbon emissions beyond average calculations. PV utilization rates are highest when the thermal efficiencies of natural gas fired power plants are lowest, which reduces emissions of CO2 and CH4 by 0.3% relative to the annual average emission rate. There is a positive correlation between PV utilization rates and electricity prices, which raises the implied price of PV electricity by up to 10% relative to the annual average price, such that the average MWh reduces electricity prices by $0.26–$1.86 per MWh. These price reductions save Massachusetts rate-payers $184 million between 2010 and 2012. The current and net present values of these savings are greater than the cost of solar renewable energy credits which is the policy instrument that is used to accelerate the installation of PV capacity. Together, these results suggest that rooftop PV is an economically viable source of power in Massachusetts even though it has not reached socket parity.

Management Index Systems and Energy Efficiency Diagnosis Model for Power Plant: Cases in China

In recent years, the energy efficiency of thermal power plant largely contributes to that of the industry. A thorough understanding of influencing factors, as well as the establishment of scientific and comprehensive diagnosis model, plays a key role in the operational efficiency and competitiveness for the thermal power plant. Referring to domestic and abroad researches towards energy efficiency management, based on Cloud model and data envelopment analysis (DEA) model, a qualitative and quantitative index system and a comprehensive diagnostic model (CDM) are construed. To testify rationality and usability of CDM, case studies of large-scaled Chinese thermal power plants have been conducted. In this case, CDM excavates such qualitative factors as technology, management, and so forth. The results shows that, compared with conventional model, which only considered production running parameters, the CDM bears better adaption to reality. It can provide entities with efficient instruments for energy efficiency diagnosis.

Frequency reduction effect on the performance of thermal power plants

This research study the effect of frequency reduction of national electric net on the thermal power plant efficiency. The Baiji thermal station was selected as mathematical model. This steady showed that the frequency reduction due to the increasing of load in the national electric net from 50 Hz to 49 Hz causes that the plant efficiency decrease from (35.9%) to the (33.5%), and the overall efficiency was decreased to 31.3% at 48 Hz because the relationship between this decreasing with the induction working motor in the plant

Thermodynamic analysis of a novel power plant with LNG (liquefied natural gas) cold exergy exploitation and CO2 capture

The LNG (liquefied natural gas) regasification process is a source of cold exergy that is suitable to be recovered to improve the efficiency of thermal power plants. In this paper, an innovative power plant with LNG (liquefied natural gas) exergy utilisation and the capture of CO2 proceeding from the flue gases is presented. It is characterised by the recovery of LNG cold exergy in a closed Brayton cycle and through direct expansion in an expander coupled to an electrical generator. Moreover, this novel power plant configuration allows CO2 capture, through an oxy-fuel combustion system and a Rankine cycle that operates with the flue gases themselves and in quasi-critical conditions. The greatest advantage of this plant is that all the recoverable LNG exergy is used to increase the efficiency of the CBC (closed Brayton cycle) and in direct expansion whereas, in other power cycles found in literature that associate LNG regasification and CO2 capture, part of the LNG exergy is used for condensing flue gas CO2 for its subsequent capture. As a result, a high efficiency power plant is achieved, exceeding 65%, with almost zero greenhouse gas emissions.

Research on Heat Recovery System of Turbine Exhaust Steam Using Absorption Heat Pump for Heating Supply Based on Heating Load Characteristics

Abstract In order to improve the energy utilization efficiency of thermal power plants and to solve the heating shortage problem in China, the absorption heat pump is usually employed to recover the heat of turbine exhaust steam for heating supply. In the existing references, few researchers considered the heating load characteristics when designing the recovery system. In this paper, the design thought of heat recovery system of turbine exhaust steam using absorption heat pump for heating supply based on heating load characteristics was presented. With an engineering case, the heat recovery system was designed and its economic efficiency was calculated.

Algorithms for striking material and energy balances in calculating the technical-and-economic indicators of thermal power plant equipment based on the ill-posed problem regularization method

The problem of striking material and energy balances from the data received by thermal power plant computerized automation systems from the technical accounting systems with the accuracy determined by the metrological characteristics of serviceable calibrated instruments is formulated using the mathematical apparatus of ridge regression method. A graph theory based matrix model of material and energy flows in systems having an intricate structure is proposed, using which it is possible to formalize the solution of a particular practical problem at the stage of constructing the system model. The problem of striking material and energy balances is formulated taking into account different degrees of trustworthiness with which the initial flow rates of coolants and their thermophysical parameters were determined, as well as process constraints expressed in terms of balance correlations on mass and energy for individual system nodes or for any combination thereof. Analytic and numerical solutions of the problem are proposed in different versions of its statement differing from each other in the adopted assumptions and considered constraints. It is shown how the procedure for striking material and energy balances from the results of measuring the flows of feed water and steam in the thermal process circuit of a combined heat and power plant affects the calculation accuracy of specific fuel rates for supplying heat and electricity. It has been revealed that the nominal values of indicators and the fuel saving or overexpenditure values associated with these indicators are the most dependent parameters. In calculating these quantities using different balance striking procedures, an error may arise the value of which is commensurable with the power plant thermal efficiency margin stipulated by the regulatory-technical documents on using fuel. The study results were used for substantiating the choice of stating the problem of striking material and fuel balances, as well as the method for solving it. With the problem statement and the solution method implemented in the real thermal power plant computerized automation systems, less biased calculation of actual thermal efficiency indicators of equipment is obtained.

Simulation of an integrated gasification combined cycle with chemical-looping combustion and carbon dioxide sequestration

Chemical-looping combustion is an interesting technique that makes it possible to integrate power generation from fuels combustion and sequestration of carbon dioxide without energy penalty. In addition, the combustion chemical reaction occurs with a lower irreversibility compared to a conventional combustion, leading to attain a somewhat higher overall thermal efficiency in gas turbine systems. This paper provides results about the energetic performance of an integrated gasification combined cycle power plant based on chemical-looping combustion of synthesis gas. A real understanding of the behavior of this concept of power plant implies a complete thermodynamic analysis, involving several interrelated aspects as the integration of energy flows between the gasifier and the combined cycle, the restrictions in relation with heat balances and chemical equilibrium in reactors and the performance of the gas turbines and the downstream steam cycle. An accurate thermodynamic modeling is required for the optimization of several design parameters. Simulations to evaluate the energetic efficiency of this chemical-looping-combustion based power plant under diverse working conditions have been carried out, and a comparison with a conventional integrated gasification power plant with precombustion capture of carbon dioxide has been made. Two different synthesis gas compositions have been tried to check its influence on the results. The energy saved in carbon capture and storage is found to be significant and even notable, inducing an improvement of the overall power plant thermal efficiency of around 7% in some cases.

Исследование тепловой экономичности ТЭС с турбоустановкой К-300-240-2 ХТГЗ и абсорбционным тепловым насосом при переменных режимах работы

Исследование тепловой экономичности ТЭС с турбоустановкой К-300-240-2 ХТГЗ и абсорбционным тепловым насосом при переменных режимах работы

Removal of Iron Oxide With Superconducting Magnet High Gradient Magnetic Separation From Feed-Water in Thermal Plant

By the accident of Fukushima Daiichi Nuclear Plant, all the nuclear plants have stopped in Japan. As a result, the operation rate of thermal power plants has been increased. It caused growth in CO 2 emission, which requires some kind of countermeasure. We focused on the iron oxide scales deposited on the piping system and boiler which declines the heat exchange efficiency of thermal power plants. In this study we attempt to remove the iron scales from the piping system and the boiler to maintain the power generation efficiency. In the current thermal plant treated by All Volatile Treatment (AVT) the iron elutes to the feed water in the low-temperature part which changes into iron ion or the paramagnetic fine iron oxide particles. On the other hand at the high-temperature part the main component of the scales is large ferromagnetic particles of magnetite. Therefore the magnetic separation at the high-temperature part is the more effective to remove the scale than that at the low-temperature part. For the reason, the existing method using the electromagnetic filter placed in the low-temperature part is not effective to remove the scales. We studied the high gradient magnetic separation (HGMS) at high-temperature part to remove a large amount of the scale. In this study, we assumed to install the HGMS system using the superconducting magnet at the inlet of the boiler.

Technical and economic aspects of oxygen separation for oxy-fuel purposes

Abstract Oxy combustion is the most promising technology for carbon dioxide, originated from thermal power plants, capture and storage. The oxygen in sufficient quantities can be separated from air in cryogenic installations. Even the state-of-art air separation units are characterized by high energy demands decreasing net efficiency of thermal power plant by at least 7%. This efficiency decrease can be mitigated by the use of waste nitrogen, e.g., as the medium for lignite drying. It is also possible to store energy in liquefied gases and recover it by liquid pressurization, warm-up to ambient temperature and expansion. Exergetic efficiency of the proposed energy accumulator may reach 85%.

Combustion distribution control using the extremum seeking algorithm

Quality regulation of the combustion process inside the furnace is the basis of high demands for increasing robustness, safety and efficiency of thermal power plants. The paper considers the possibility of spatial temperature distribution control inside the boiler, based on the correction of distribution of coal over the mills. Such control system ensures the maintenance of the flame focus away from the walls of the boiler, and thus preserves the equipment and reduces the possibility of ash slugging. At the same time, uniform heat dissipation over mills enhances the energy efficiency of the boiler, while reducing the pollution of the system. A constrained multivariable extremum seeking algorithm is proposed as a tool for combustion process optimization with the main objective of centralizing the flame in the furnace. Simulations are conducted on a model corresponding to the 350MW boiler of the Nikola Tesla Power Plant, in Obrenovac, Serbia.

Development of energy efficient methodology of carbon materials drying and fragmentation

The development of heat power engineering in the modern conditions requires high-quality fuel with low sulfur content. Unlike liquid and gaseous fuels, brown coal has a high ash content and humidity. In order to improve the efficiency of thermal power plants, it is necessary to modernize the brown coal preparation process to lower sulfur content and reduce harmful emissions into the atmosphere during combustion. Therefore, the development and introduction of new energy-saving heat technological installations for drying and fragmentation of carbon materials is an important scientific-technical problem which is solved in the framework of the scientific area - industrial heat power engineering.In the paper, new energy-saving methodology, allowing highly efficient continuous drying and simultaneous fragmentation of dispersed materials was developed at the newly created highly productive thermal vacuum installation.During the research on thermal vacuum drying of dispersed materials, analytical and experimental methods for determining moisture withdrawal from the investigated objects depending on the regime parameters of the thermal vacuum installation were used.Based on the results of scientific and technical research it was found that brown coal with the initial humidity of 40% and size of up to 8 mm is converted into a fine powder with a humidity of less than 1.0% for 14 seconds during drying in the thermal vacuum installation. The temperature of the dried brown coal at the heating element outlet did not exceed 76οC at the heater temperature of 250oC. Brown coal drying proceeds uniformly, the color changes from brown to black. This suggests that the sulfur content in the brown coal reduces. In our case, the sulfur amount in the dried brown coal has decreased by more than twice from 4.8% to 2.2%.The developed process of thermal vacuum drying and simultaneous fragmentation of brown coal allows to reduce energy costs per unit of the dried product, accelerate the drying process, obtain a fine powder of the dried coal with low sulfur content, which leads to reducing harmful emissions into the environment during combustion.

Energy and environment, challenges and driving forces for the future heat treatment and surface engineering

exploration, which is heavily dependent on heat treatment and surface engineering. The paper has clearly demonstrated with statistical data how stabilising and improving product quality as the result of the improvement of scientific, technical and management level of HT during the last decade in the petroleum machinery manufacturing industry in China has raised the equipment utilisation rate and reduced the energy consumption. We hope it may trigger a series of studies on various important industrial branches. In general, any scientific achievements in materials science in HT and SE, as well as technical innovations and upgrading in process efficiency, energy efficiency, furnace design and construction, measurement and process control, etc. contribute to the solution of energy-environment problems. In this relatively ‘old’ field of HT, many interesting and practically important effects still need to be reinvestigated and clarified, such as those presented in the paper by Dong and Zhu 2 . Energy and environment are, from the optimistic viewpoint, the external driving forces for the future of HT and SE. No doubt, clean energy generation and supply systems require not only upgrading of conventional HT and SE, but also new materials and methods for their processes. The energy transition may not be realised without innovation of new types of steels and highly developed steel processing. For example, the offshore wind power station demands high corrosion resistant steels for its foundations and towers. The efficiency of thermal power plant may be much improved when its pressure and temperature are raised, which may only be possible with new high-performance alloys. Recently the 2 nd International Conference on Energy and the Future of Heat Treatment and Surface Engineering 3 organised by Chinese Heat Treatment Society (CHTS) took place in Beijing. Following its predecessors the conference addresses the main themes of energy management in HT and SE and the HT and SE in the manufacture of clean energy generation and supply systems. In the coming IHTSE issues we will introduce selectively most interesting papers to our readers.

Process-circuit and layout solutions for steam-turbine units and performance efficiency of thermal power plants

Criteria for evaluating process-circuit and layout solutions adopted in designing steam-turbine units are presented together with their values for a number of steam-turbine units produced by the Ural Turbine Works. The presented values of the criteria are recommended for being used as tentative ones in designing new thermal power plants or in upgrading them with the use of steam turbine units operating both as basic power installations and as part of combined-cycle power plants. The influence of process-circuit and layout solutions adopted for steam-turbine units on the effectiveness of thermal power plant construction and plant performance efficiency is shown.

Simulation study on lignite-fired power system integrated with flue gas drying and waste heat recovery – Performances under variable power loads coupled with off-design parameters

Lignite is a kind of low rank coal with high moisture content and low net heating value, which is mainly used for electric power generation. However, the thermal efficiency of power plants firing lignite directly is very low. Pre-drying is a proactive option, dehydrating raw lignite to raise its heating value, to improve the power plant thermal efficiency. A pre-dried lignite-fired power system integrated with boiler flue gas drying and waste heat recovery was proposed in this paper. The plant thermal efficiency could be improved by 1.51% at benchmark condition due to pre-drying and waste heat recovery. The main system performances under variable power loads were simulated and analyzed. Simulation results show that the improvement of plant thermal efficiency reduced to 1.36% at 50% full load. Moreover, the influences of drying system off-design parameters were simulated coupled with power loads. The variation tendencies of main system parameters were obtained. The influence of pre-drying degree (including moisture content of pre-dried lignite and raw lignite) on the plant thermal efficiency diminishes gradually with the decreasing power load. The dryer thermal efficiency and dryer exhaust temperature are also main factors and the influences on system parameters have been quantitatively analyzed.

Development Trend of Chinese Hydroelectric Generation Technology of Hydro Power Plant (HPP)

Water power is a renewable energy which is economically cheap, clean and reliable. Theoretical hydropower resources of China amounted to 680 million kW, the greatest in the world. For the water maintains circulating according to a certain hydrologic cycle continuously and uninterruptedly, the water resources are considered to be a renewable energy. Therefore Hydropower is low cost due to firstly, the energy carried by the water flow is the only energy required for the power generation in the hydropower station. Secondly, the applied equipment is simpler than that of thermal power plant, thus costing less in maintenance and overhaul. If taking the fuel consumption into consideration, the annual operation cost of thermal power plant is 10~15 times higher than that of hydropower plant. Beside hydropower is clean during the course of hydropower generation, neither harmful gas, smoke, dust, ash will nor nuclear pollution will be caused. Hydropower generation has a high efficiency and conventional hydropower plant can make use of 80% water resources, while the heat efficiency of thermal power plant only reaches 30%~50%. In this paper, the study is established in the necessary Engineering development of hydropower plants and hydroelectric generation technology in China. The Chinese model base of hydropower plants features, functions, flow analysis chart and ecologic Issues are also discussed in this paper.