Equivalent Enthalpy Drop Research Articles

Research on deep utilization technology of flue gas residual heat for large-capacity coal-fired units

The utilization of flue gas waste heat is an important measure to improve the power efficiency of coal-fired units. Traditional method is to arrange the heating surface after the air preheater, which can just recover the low-grade heat, low efficiency. For the engineering practice of a 1000MW double-reheat unit, three feasible schemes are proposed, namely scheme 1 “two-stage gas cooler plus cold air heater”, scheme 2 “air preheater bypass + two-stage flue gas cooler plus cold air heating” and scheme 3 “air preheater bypass + hot primary air temperature adjustment plus two-stage flue gas cooler plus cold air heater”. For the sake of evaluating the actual effects of different schemes objectively, the thermal characteristic calculation model of the four-part rotary air preheater was established by finite difference method, and then the effect of the inlet air temperature and the share of bypass flue gas on the thermal efficiency of the boiler were studied. The equivalent enthalpy drop method was used to establish the thermal characteristic model of steam turbine, and the influence of different heat distribution modes on the heat consumption rate of steam turbine was studied.. Considering the technical economy, the optimal bypass flue gas share of this scheme is 12%, which corresponds to the reduction of coal consumption for power supply of the unit by about 3.23g/kWh. Taking into account comprehensively, scheme 3 is recommended.

Thermal economy analysis of flue gas waste heat utilization system of 1000MW secondary reheat unit

Deep utilization of flue gas waste heat is an important means to ameliorate the power generation productivity of coal-fired units. Aiming at the waste heat cascade utilization system which is composed of “air preheater bypass + two-stage low-temperature coal economizer + thermal primary air temperature regulating device” proposed in a certain project, using the energy balance method and the equivalent enthalpy drop method, the mathematical model of the impact of waste heat utilization devices at all levels on the unit economy is established from the boiler efficiency and steam engine heat rate. Combined with the rated operation data of the unit, the thermal economy of the system is analyzed. The results show that the bypass of the air preheater and the temperature regulating device of the hot primary air can effectively improve the utilization efficiency of the waste heat of the flue gas at the tail of the boiler, the coal consumption of power supply can be reduced by 3.47 g/kWh under rated working conditions.

Thermo-economic analyses of the waste heat and water recovery system from flue gas by heat pump integrated with different heat utilization ways in coal-fired power plant

To recover the waste heat and water simultaneously from flue gas after wet desulphurization, a novel method by adding a flash evaporation device and heat pump system was proposed. The thermal-economic theoretical models for systems integrated with three different heat utilization ways were established based on the method of equivalent enthalpy drop. A typical 300 MW coal-fired power plant was selected as a case to compare the thermo-economic performance. Results show that when the flue gas temperature decreased from 50°C to 30°C, the amounts of recovered waste heat and water could be up to 65.2MW and 81.4t/h, respectively. At the same heat output of 11.3 MW from heat pump, the heat utilization way of pre-heating air exhibited the best energy-saving performance with the net efficiency of power plant increasing to 42.46% from 42.3%.

Advantages of thermal industry cluster and application of particle swarm optimization model

This paper first analyzes that the waste heat before the flue gas of thermal power company enters the desulfurizationwer can be heated by the low pressure economizer, and then the heated condensate can be incorporated into the regenerative system, so as to recover the waste heat and improve the unit efficiency. In this paper, the possible lay-out scheme of the low pressure economizer in the thermal system is constructed firstly, and then the mathematical model of the equivalent enthalpy drop increment of the unit is established with the water partition coefficient as the independent variable. Particle swarm optimization and co-ordinate rotation are used to optimize the model, and the results show that particle swarm optimization is more effective in solving the problem. After the low pressure economizer is added to the unit, the heat consumption of the whole plant of the unit is reduced by 61.131, the unit efficiency is increased by 0.783%, and the coal consumption of the whole plant is reduced by 2.293. Finally, from the perspective of industrial agglomeration, industrial diversification and economic resilience, this paper analyzes the advantages of diversified agglomeration of thermal power companies.

Compare the Calculations of Steam Extraction Efficiency of Power Plant Turbine by Simple Heat Balance Method and Equivalent Enthalpy Drop Method

At present, the calculation method of steam extraction efficiency of power plant turbine have five methods: heat balance method, equivalent enthalpy drop method, cyclicfunctional method, composite structure method and matrix method. In this paper, a 600MW grade subcritical thermal power plan is take as an examplefor comparing the calculation by the simple heat balance method and the equivalent enthalpy drop method. The result shows that the computational results of simple heat balance method agree with equivalent enthalpy drop method. So simple heat balance method can be used to replace equivalent enthalpy drop method in order to reduce calculation amount in practicalapplication.

Quantitative Analysis of Energy Storage in Different Parts of Combined Heat and Power Plants

To increase the flexibility of power generation, the coal-fired combined heat and power (CHP) plants should make full use of their own energy storage (ES). Available ES exists mainly in boiler steam-water systems, in units' condensed water systems (CW), and in district heating networks (DHN). The goal of the paper is to analysis the ES quantitatively. And ES is characterized by ES coefficient, the maximum ES capacity and ES respond speed for power load. ES coefficient, the key parameter of ES capacity, represents the change in ES when unit process variable changes. For pressure, flow, and temperature variables, three kinds of mechanism methods (volume increment method, equivalent enthalpy drop method, and specific enthalpy increment method) are proposed to calculate ES coefficients. Then, the maximum ES capacity can be obtained by the product of ES coefficient and the limit value of the variable. Finally, ES respond speed for power load can be drawn from simulation. Calculation results and simulations show that ES in CW has small capacity 1.2 GJ but fast speed; ES in boiler has larger capacity 2.6 GJ and slower respond speed; ES in DHN is 374 GJ, which is two orders of magnitude larger than the previous two, and the response is relatively fast. Therefore, recommendations to increase power load flexibility are using ES in boiler and DHN to reduce fuel fluctuation when power load change frequently, using ES in CW to reduce load responding time, and using ES in DHN to expand load regulation range.

Optimization of the Drain Mode for No. 0 High Pressure Heater

The addition of No. 0 high-pressure heater is a new technology with energy saving and emission reduction benefits, the economic analysis of No. 0 high-pressure heater under different loads and drain modes is provided on a 680 MW unit based on the Equivalent enthalpy drop method principle and the comprehensive economic drain mode for No. 0 high-pressure heater is recommended.

Analysis of high energy consumption of 1000MW ultra supercritical unit

A 1000MW ultra supercritical unit heat consumption rate was higher than design value 324.81 kJ/kW h, in this paper, by comparing the conventional test and assessment test, the result of the analysis of conventional test data at the same time, found out the factors that affect the unit heat consumption, low efficiency of unit mainly include cylinder and putting-in-service proactively reheat steam consumption reduction of warm water, small machine increase, feed water by-pass leakage, system other internal leakage, etc., application of equivalent enthalpy drop method, calculated the influence of the influence factors on the heat consumption of value.

Application and thermal economic analysis of plate low pressure economizer in flue gas waste heat recovery

Low pressure economizer is an important equipment to reduce exhaust gas temperature and recover waste heat of flue gas in power plants. In this paper, the welded plate heat exchanger is applied to the field of low pressure economizer. The waste heat of coal slag and flue gas is utilized comprehensively to raise the boiler feed water temperature and reduce coal consumption. The thermal economy of plate economizer and finned tube economizer is analyzed by the equivalent enthalpy drop method. The results show that the plate economizer has obvious advantages under the same pressure drop and heat load. Compared with the finned tube economizer, the heat transfer coefficient the of the plate economizer increases by more than 50%, and the volume decreases by about 2/3. After installing the slag cooler, the heat consumption rate decreases by 119.7 KJ/kWh, and the coal consumption decreases by 4.68 g/kWh.

Application Research and Thermal Economic Evaluation of Low-Pressure Economizer on Coal-Fired Units

The energy saving principle, layout and key parameters of low-pressure economizer on coal-fired units are introduced. Taking a 220MW unit as an example, the thermal economy of low pressure economizer is evaluated by equivalent enthalpy drop method.

Economic Analysis of Waste Heat Utilization for Coal-fired Power Units

Strict energy conservation policies require power plants to minimize energy consumption as much as possible. Low pressure economizer is an effective method to recycle waste heat from boiler exhaust gas. In this paper, the economic analysis model of coal-fired power plant is established by means of equivalent enthalpy drop method, and the waste heat utilization effect on thermal systems is investigated, including boiler efficiency, steam turbine power output, condensate pump, induced draft fan, electro static precipitator and desulfurization system. Then the economic effect on a 1000 MW ultra super critical unit in Shandong Province is calculated. The results show that waste heat utilization could comprehensively reduce standard coal consumption rate by 1.89 g/(kW·h), and the unit could save about 10.8 thousand tons standard coal and 1.29 billion dollars every year. Besides, the energy saving effect is more significant for lower load condition.

Energy Saving Effect Test and Operational Optimization of Low Pressure Economizer under Multi-variable Factors

The energy saving effect of low-pressure(LP) economizer of a 220MW unit was tested under multi-variable factors. Using the equivalent enthalpy drop method, the energy saving effect of LP economizer at different operational modes and different operating parameters has been calculated. When the higher water flow rate and inlet temperature of LP economizer is necessary, condensate water from NO.6 LP heater outlet should be used priority. Under the condition of 220MW, the optimal flow into LP economizer from NO.6 LP heater outlet is about 250t/h, the thermal efficiency of the unit could be increased 0.645%. If LP economizer inlet temperature is lower, the outlet of LP economizer should be connected to the outlet of NO.6 LP heater. And water temperature at LP economizer outlet should be slightly higher than the temperature of the NO.6 LP heater outlet. Otherwise, the energy saving effect will be decreased. Under the condition of 220MW, the thermal efficiency of unit increases 2.003%. For different LP economizer operation mode, there will be an optimal water returning location and optimal inlet flow rate.

Economic Analysis of a 660MW Supercritical Turbine for Steam Initial Parameters

Economic diagnosis of thermal power units is to determine the economy of its operating parameters and operating modes by quantitative and qualitative analysis, which is significant to economic operation and energy saving of power plant. On the basis of equivalent enthalpy drop method and the theory of variable conditions, the economic diagnosis model of operating parameters was established. As main steam temperature and main steam pressure for example, economic diagnosis of a 660MW supercritical steam turbine unit was performed. The result demonstrates that improving the main steam temperature or main steam pressure can reduce heat consumption of the unit. The essence of improving the initial steam parameters is to improve the average temperature of the steam cycle endothermic process, thus improving the circulation efficiency and reducing heat consumption. The economic impact of main steam temperature is up to 0.61g/(kW·h), while which of main steam pressure is little. Therefore, by increasing the initial steam parameters, especially the main steam temperature, to improve the economy of the entire power plant is the main way to enhance the efficiency of power plant in the current.

600 MW Direct Air-Cooling Unit Back-Pressure Optimization and Theoretical Analysis

In recent years, direct air cooling units have developed rapidly in China, but in the actual operation, the back-pressure often deviate from the optimal back-pressure, which affect the economy of the unit. The paper has figured out the optimum back-pressure, fan speed and power gain with the method of equivalent enthalpy drop; the paper also worked out the exergy loss of each device before and after the optimization. Through the exergy efficiency analysis of the devices before and after the optimization, we find out that after optimization, exergy loss of the turbine reduces by 0.954MW and the net amount of the generated power increases 130.5kW, the net exergy efficiency of units improves about 0.018 percent points.

Analysis on Thermal Economy and Peak-Shaving Capability for Combined Heat and Power (CHP) Unit in Varying Operating Conditions

Based on the principle of featured through-current area being constant, calculation model for parameters of regenerative steam extraction of CHP unit in different heating conditions is developed in this paper through using FROTRAN software. The generated output and thermal economy of the CHP unit are calculated by using the method of equivalent enthalpy drop, and the accuracy of the model is verified. With the purpose to analyze the rationality of different calculation methods, the distribution ratio of coal consumption for heat supply and coal consumption rate for power generation are calculated through method of equivalent enthalpy drop, heat quantity method and method of actual enthalpy drop under the same operating condition. Moreover, according to the operation test on the unit, the highest and lowest generated output of the CHP under various loads of heat supply are determined, which will provide a basis to the subsequent thermoelectric units in participating in peak shaving of power grid.

Research on the 330MW Double-Extraction Steam Turbine of Dynamic and Thermal Characteristics Analysis Model

This paper is study on the 330MW Double-extraction unit, made by Dongfang Steam Turbine Works manufactured, and the reference conditions of the unit was calculated. Thermal system analysis and calculated of double-extraction unit based on the equivalent enthalpy drop and variable condition calculation methods, and double-extraction steam turbine dynamic characteristics analysis model is established through a series of dynamic characteristics. The result showed that the smaller error between the calculated value and the design value of this model, and it can be applied to single extraction and condensed various working conditions. In addition, four variables of the unit main steam flow, low-pressure extraction flow, medium pressure extraction flow and electric power was fitted, resulting in multi-characteristic equation, which provides a theoretical basis for the follow-up study online load distribution.

大型供热机组深度参与电网调峰能力的研究与实践

针对我国北方寒冷地区冬季供暖期电网调峰能力严重不足的现状，以研究大型供热机组供暖期调峰能力为目的，根据等效热降理论得出供热机组调峰能力理论模型；以此为基础，本文采用现场试验核定的方法确定电网内每台供热机组不同抽汽供热量时机组所对应的调峰高限负荷和调峰低限负荷，采用多项式回归方法建立相应的调峰能力实际应用模型,为大型供热机组深度参与电网消纳风电提供理论依据和技术支持。在吉林省电网的应用也证明了模型的正确性和有效性。 In allusion to the serious capability inadequacy of peak-load regulation of power network during the heating seasons in north China, by making use of the basic theory of equivalent enthalpy drop method, a theoretical model is derived for the peak-load regulation capacity from large units during the heating period. Then based on it, the peak-load regulation capacity minimal load and maximal load of every large heating unit in different heating loads were obtained by field tests and the application models were established by polynomial fitting method which supplied theoretical basis and technical support for the large heating units deeply involved in peak regulation of power network. The accuracy and validity of the method are confirmed by the application in Jilinpower grid.

Equivalent Enthalpy Drop Method with Application in a 330 Mw Double Pumping Cogeneration Unit and its Thermal Characteristics Analysis

It is quite convenient and flexible to adopt the equivalent enthalpy drop method, in order to analyze a thermal system. In this report, a 330MW cogeneration unit will be chosen, as a case in point, to provide quantitative calculation and qualitative analysis in both global and local aspects. According to our research, this cogeneration unit is designed to operate in a double pumping status. It has such properties as follows: Under 85%BMCR double pumping condition, its highest efficiency of power generation is obtained. In pure condensing conditions with around 70% load, the steam consumption rate reaches minimal level. The reason for this phenomenon lies in the maximal net equivalent enthalpy drop of new steam, although with 70% load, the power generation efficiency is much lower than that in rated pure condensing conditions.

Optimal Design of Solar Aided Coal-Fired Electricity Generation System

In order to overcome deterioration of heat transfer caused by two-phase flow and avoid flow separation, using volume expanding evaporator instead of steam-water separator to make integration and optimization between parabolic trough solar energy collection system and coal-fired power plant regenerative heating system. Then based on equivalent enthalpy drop method, it analyses the thermal economy about 300MW coal-fired unit to discuss the optimal integration solutions and works out the unit thermal economy variation tendency and the best back water position of the drain in volume expanding evaporator when the different stage extraction steam of coal-fired unit replaced by the exit steam of solar collection system super heater region. The results show that the whole third stage extraction steam replaced by solar heat and drain water in volume expanding evaporator returned back to 3 heater exit of coal-fired unit feedwater pipeline is the best scheme.

Study on Application of Steam Ejector Heat Pump in Partial Innovation of Power Plant Thermal Regenerative System

The exhaust steam heat of steam driven feed pump small steam turbine is considerable in modern coal-fired power generating unit, most of which is adopted the way of wet cooling through the condenser as same as main steam turbine for condensing steam turbine unit, all the waste heat with it is taken away by circulating cooling water and not used effectively. This paper will propose the way of part of exhausted steam of small steam turbine recycled to the regenerative extraction steam system to heat condensate based on steam ejector heat pump, so as to use the exhausted steam effectively and analyze the thermal economic index of different schemes by using equivalent enthalpy drop method. The results show that it produces best economic benefits when exit steam of steam ejector heat pump is recycled to steam extraction of the fourth section.