Energy Analysis of Power Plant Thermal System

Abstract: The energy is clean, easy to use secondary energy, but in the production of electricity while consuming a large amount of primary energy. This paper briefly analyzes the current energy situation, summarize the main system calculation method, that the power plant Thermal analysis of the problems still exist, and recommendations are given power energy saving and energy saving strategy analysis.

Keywords:: thermal system energy-saving technologies calculation of economic indicators
Introduction
As we all know, energy has become a common concern of countries in the world, this phenomenon is more prominent in our country. Because of the extensive economic growth mode, but also speed up the upgrading of consumption structure in the historical period, energy consumption is too large, thus saving energy will be a long-term and arduous task. According to the United States and China's power Industry survey showed that China's average higher than in developed countries, coal consumption rate of 30 ~ 60g/kWh, this is a big gap, shows that China's power plants have great energy saving potential can be tapped. Therefore, the power plant thermal system are related to the energy global energy and the sustainable development of the event. Therefore, the Department of the thermal environment, reveal a variety of energy-saving theory intrinsically linked, in-depth study and development of energy to the theoretical and practical significance to the plant's energy consumption has a very strong guidance.

First, the thermal system of economic indicators
The thermal power plant in China commonly used indicators of economic efficiency and energy consumption rate of the main two.

(A thermal efficiency of the audience ηcp:
Where, Nj is the net power of the Internet, B for the coal burning, Ql for the coal calorific value.

The whole plant thermal efficiency indicators are a comprehensive index to run power plants, during the system analysis is often the decomposition of the composite indicator to distinguish between the responsibility of the manufacturers and the main direction, it can be rewritten as:
Which, ηb: boiler efficiency, coal-fired boiler and effective absorption of heat and low heat ratio
ηp: pipeline efficiency, turbine and boiler circulation heat ratio of the effective heat absorption,
ηi: steam turbine cycle plant efficiency, turbine power and the internal circulation heat ratio
ηm: mechanical efficiency, turbine output power and internal power ratio;
ηg: generator efficiency, and front-end power generators online power ratio
Σξi: power consumption rate, all the auxiliary power consumption and electric power of the Internet with the power ratio generator.

(B heat consumption rate and the standard coal consumption rate
Synthetic evaluation of heat rate heat economy turbine generators, each generator and its essence is power 1kWh, refrigerant absorbs heat from the boiler value. Defined type is as follows:

Coal consumption rate indicators can be divided into two types: standard coal consumption rate and power generation standard coal consumption rate.

Second, the calculation of thermal system status
Steam turbine power plant thermal system is set to run performance analysis, thermal testing and system improvements in the common calculation, the calculation of the thermal system is intended to determine the heat index unit, so choose the appropriate system calculation methods is a unit of heat economy an important prerequisite. system many types of calculation, according to the thermodynamic basis on which they can be divided into: first law analysis and the second law analysis.

Conventional heat balance method is combined with mass balance and energy balance, based on the actual thermal system of numerical calculation methods. Calculations need to heat the system changed working conditions calculated to determine the turbine extraction port and the exhaust side of the steam parameters and return the corresponding parameters of the thermal system, and its essence is to determine the turbine expansion process of new lines and system parameters, the core and difficult is the calculation of steam turbine conditions change.

Equivalent Heat Drop is the new steam flow, cycling and thermal parameters of the initial end of the process line remain unchanged as the premise, less power (equivalent heat down) by the variation of thermal systems heat economy. In the local thermodynamic system analysis, the equivalent heat drop method to improve the deficiencies of conventional thermal calculation proposed the concept of equivalent heat drop and the thermal system based on a new analysis method, calculation of the thermodynamic analysis with the system.

Cycle function under the second law of thermodynamics, the cycle is not reversible (or cold source and the loss of turbine cycle energy analysis of qualitative criteria to recycle energy functional quantitative calculation for the steam turbine cycle loop function of work is a thermodynamic system complexity a good way.

Entropy analysis is balanced by the entropy of the system, calculated to strike the size and distribution of entropy, entropy analysis of the factors that determine the entropy production and irreversible loss of the relationship, as the imperfections of the evaluation process and improve the process based on the degree .

Exergy analysis method [4] is based on the quantitative thermodynamic two, combined with environmental conditions from the full understanding of the nature of energy, starting from the energy utility's an idea and method, which is from the perspective of energy conversion device or thermal process that the scientific integrity indicators.

Algebraic method is a thermodynamic analysis of thermal analysis of the system energy. The method used to describe the incident matrix of each subsystem of a system of energy out into the relationship between the matrix defines the exergy exergy of the value stream, fire with branches defines a single system, the relationship between inflow and eventually get the structure matrix [FP], the height of the matrix from the overall study to develop a full, new trends in the relationship between subsystems.

Links to Research Papers Download http://www.hi138.com Third, the current problems still exist
1. Common sense is still a lack of systems engineering analysis, mathematical tools are still yet to be developed, the use of computers for analysis of thermal system less energy. Are currently run by local optimization method, system energy analysis remains to be further developed .

2. In essence, the present system belongs to steady state. Study is based on the thermodynamic parameters of some of the same power system, and in constant operation, which of course would greatly simplify the complexity of the study, but also to limitations. Thermal System Energy Analysis in Applied Research Unit less variable conditions.

3. Different Thermal System theory is to study different aspects of the thermal system objects, the relationship between the different theoretical Research is still not sufficient.

4. Whether the design parameters of large capacity units with high or improving the operating level of existing units, excavators group of energy-saving potential, we need an effective and accurate guidance to energy saving theory, energy-saving measures can be targeted. And reasonably determine the optimal performance index, the right systems and processes to build mathematical models still need to increase Research.

Fourth, energy-saving technology measures thermal system
There are many ways to heat the system can achieve energy saving. For the new design unit, through optimized design, reasonable support for energy conservation, and for running unit, can be diagnosed through energy conservation, optimization of transformation, monitoring energy loss, guiding operation and achieve energy conservation goals.

The development of the power plant, which have been used both regenerative and reheat cycle ways, making the cycle efficiency greatly improved. At present, the possible energy-saving technological transformation include:
Part of the implementation of turbine flow transformation. The current transformation can be divided into two types: one is to improve the efficiency of steam turbine to achieve the purpose of saving the other is saving while increasing turbine output. Specific reform measures are replaced cylinder, the double-row control stage to adjust the level so separate.

Transformation using the new seal boiler air preheater. Air preheater of the leakage issue has been the impact of combustion, reduce the efficiency of the threat. Through the use of new sealing technology to reduce air preheater leakage rate, not only to reduce exhaust losses, reduce fly ash carbon content, but also saves power plants to reduce power consumption rate.

Boiler Milling System Plant. Through the transformation of coal mill system, sealing system, can improve the milling efficiency and reduce flour consumption, thereby reducing coal consumption.

Waste heat power station cooling water re-use. Through condenser cooling water away from the heat transport usually accounts for 15% of the total energy, and some even as high as 25% or more, resulting in great waste of energy. If we can use waste heat use this part of the energy use of technology together to improve the efficiency of power plants will inevitably produce significant results.

V. Concluding Remarks
At present, faced with increasingly scarce energy resources and increasing total energy demand in the dual challenges of energy-saving imperative, especially in energy-hungry industries. Brunt plant system, and compared with developed countries, China's energy-saving heating system there is great potential for saving space and can be fully tapped. reason to believe that, with the thermal system analysis related to the progressive development and improvement of energy-saving plant system will achieve more long-term progress.

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