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Abstract

Содержание

Introduction

There is no doubt that thermal energy will remain dominant in the energy balance of the world and individual countries in the short term. The share of coal and other less clean fuels increases in energy generation. So we study some of the ways and methods of their use which can significantly reduce the negative impact on the environment. These methods are based mainly on improving the technology of fuel preparation and capture of pollutant emissions.

1. Theme urgency

TPP in the degree of influence are among the industrial objects, the most intense impact on the biosphere, so that electricity generation are associated with significant negative impacts on the environment, and this fuel economy is one way to reduce it. Reducing fuel consumption can be achieved different ways one of which is to use the simplest double- pipe heat exchanger.

2. Goal and tasks of the research

The main equipment of thermal power 175 MW this power plant is a boiler unit TP - 100 K and a steam turbine - 200 - 130 - 3. The boiler, which burns grade coal culm, is equipped with two individual systems of pulverizing with intermediate bunker. It provided transportation to the dust burner by spent drying agent with a temperature of 90-100 ? C. Input the root flare burner fuel mixture with a low temperature does not allow the conditions for reliable ignition of dust, it leads to excessive fuel consumption for lighting.

The aim is to consider the possibility of improving the work of systems of pulverizing on Starobeshevskaya TPP. To solve this goal the following objectives : review classification schemes of pulverization; study the individual circuit pulverization prombunkerom on Starobeshevo TPP; analyze the possibility and options to improve the scheme; make technical and environmental calculations, the calculation of fuel economy for version after the reconstruction.

3. Review of Research and Development

According to foreign data [1], the structure of power in modern coal-pulverization systems differed from those of our country. coal-pulverization systems prombunkerom and a spherical drum (ShBM) are used very rarely, most often used in ShBM coal-pulverization systems direct injection (for example, in one of the most modern power stations in England, "Ebersou" with blocks of 500 MW). Most new power plants for milling coal are equipped with medium low-waste mills , and for milling of brown coal mills-fans. Hammer mills operate largely on a relatively old power plants working on brown coal. In Germany, continues to use them, and at this time [2]

In the classical work of Kiselgof M.L. contains the necessary materials analysis and design of boiler installations coal-pulverization systems on power plants and industrial facilities. [3]

In the publications of Dobrokhotova V.I. and Levit G.T. to improve the performance of the equipment of coal-pulverization systems recommends a complex of work, not only to improve the mills, but also for the cleaning of fuel from foreign bodies, removal of fuel hung in the bunkers and chutes, feeders increase the reliability of fuel, the use of wear-resistant designs and materials to combat wear and tear of pipe. [4]

The problem of boilers for solid fuels with very variable loads and frequent shutdowns examined by Soviet scientists A.A Madoyan and K.Y. Polferov [5].

Soviet engineers' Rostovenergo "Kaminsky, VP and Chuevsky S. In his article review and analyze the factors that are important in the work node " firebox - coal-pulverization systems", such as temperature dust bin, the rationality of the scheme of the boiler ductwork, the number of operating coal-pulverization systems in the boiler and air distribution to burners of the boiler at different combinations of operating coal-pulverization systems, load of ball mill , the value of recycling mill agent, quality of dust, etc. [6]

In the master works of students of Donetsk National Technical University A. Studennikov and D Podoksenova also discussed measures to improve the ecological situation and fuel economy by developing new technologies of burning low-grade solid fuel boilers with circulating fluidized bed, by using of new types of burners and gas turbine superstructures. [7]-[8]

4. Using the double-pipe heat exchanger for additional heating of fuel mixture in the coal-pulverization systems on the Starobeshevska TTP

To solve the problem of additional heat to the burner fuel mixture to a temperature of 300 ºC is proposed to use regenerative double-pipe heat exchanger. It consists of of two round cylindrical tubes. A coolant (a mixture of dust and air) moves along the inner pipe, the other coolant (overheated steam, which are selected from the turbine) moves in the opposite direction of the annular gap between inner and outer tube (Fig.)

Construction of heat exchanger

1 - inner tube (pyleprovod), 2 - outer tube, 3 - connections

Figure - Construction of heat exchanger


For this heat exchanger was made heat and the design calculations with the following conditions: a mixture of air and coal dust is heated by the temperature t2н=90 ºС to t2к=300 ºС, the heating medium - steam, selected for the 18th stage of the turbine K-200-130, enter into the heat exchanger with t2н=390 ºС and p = 5,58 kgf/cm2. Results are presented in the table.


Table - Results of thermal and constructive calculations
Parameters of coolants
Coolant The average temperature tav, ºС Speed w,
 m/s		 Mass flow rate G,
kg/s		 The heat transfer coefficient α,
W/m2 K
Overheated steam 273,25 1,2 0,47 7696,9
Dusty air 195 25 4,6 38,12
The calculation of the heat exchanger
Given heat transfer coefficient αg,
W/m2k		 Coefficient of thermal transmission k, W/m K The average temperature head Δt,ºС The surface of heat exchan F, m2 Length L, m
2244,6 21,14 212,22 220,75 35

As a result of the reconstruction of coal-pulverization systems heat exchange surface will be 220,78 mm2, the length of the device (with fins) - 35 m.

Due to the increase of heating boilers and reducing the specific fuel consumption for the production of a 2,8% efficiency of the boiler to change in a positive way.

Reduction of emissions can make up for nitrogen oxides - 244,27 tons/year of sulfur oxides – 1452,8 tons/year of ash – 1500,74 tons/year. This reduction emissions undoubtedly result to improved environmental area.

Conclusion

In this work is proposed improving system for coal pulverization on Starobeshevskaya TPP by using a simple double-pipe heat exchanger heating a mixture of air and dust. In such a way an average reduction emissions by reducing fuel consumption can make for nitrogen oxides - 244,27 tons/year, sulfur oxides - 1452,8 tons/year, ash - 1500,74 tons/year, vanadium pentoxide - 0,0068 tons/year.

This master's work is not completed yet. Final completion: December 2012. The full text of the work and materials on the topic can be obtained from the author or his head after this date.

References

  1. Розенгауз И.Н. Зарубежные котельные агрегаты большой мощности. М.: Энергия, 1974, 172 с.
  2. Schuler U. Feinmahlanlagen in Kraftwerken in verschiedenen Landern // «Techn. Mitt.», 1973. - №2. – p.14-19
  3. Кисельгоф М.Л., Соколов Н.В. Нормы расчета и проектирования пылеприготовительных установок. – М.:Государственное энергетическое издательство, 1958.- 149 с.
  4. Доброхотов В.И., Левита Г.Т. К вопросу оптимизации схем пылеприготовления и типов мельниц мощных энергоблоков // Теплоэнегетика.- 1976. - № 8. – с. 4-8
  5. Мадоян А.А., Полферов К.Я. О требованиях, предъявляемых к пылесистемам с ШБМ и промбункером в связи с пиковым режимом работы котлоагрегатов // Теплоэнергетика. – 1978. - № 12. – с. 58-63
  6. Каминский В.П. , Чуевский С.В. Влияние работы пылесистем на экономичность котлов блоков 300 МВт при работе на АШ // Теплоэнергетика. – 1982. - № 4. – с. 43-46
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