Gu Hong (Electrical Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China)~60%. This paper gives a general introduction to the basic principles, main methods, development process and application of magnetic fluid power generation.
1 Introduction of a coal-fired power generation system currently used in China requires a large amount of S02 and NOx black smoke to be emitted into the atmosphere, which is more likely to cause more serious secondary environmental pollution. Therefore, it is an important strategic task to develop clean coal power generation technology, reduce pollutant emissions, and improve coal-fired power generation efficiency.
2 Definition and classification of magnetic fluid power generation and magnetic fluids (also known as magnetic liquids, iron suspicion fluids or magnetic fluids) are made up of a mixture of ferromagnetic particles, base fluid (also called media) and surfactants. . A stable gelatinous solution. The fluid has no magnetic attraction when it is static, and exhibits magnetic properties when applied by a magnetic field.
Magnetic fluid power generation is a new type of power generation method. It is defined as when a plasma with a magnetic fluid crosses a magnetic field and is cut by magnetic lines of force according to the law of electromagnetic induction; on the channel through which the magnetic fluid flows. When the mounting electrode is connected to an external load, power can be generated.
In order to make the magnetic fluid have sufficient conductivity, it is necessary to add an alkali metal such as potassium or barium and an inert gas (such as helium, argon, etc.) with a small amount of alkali metal as a working medium at a temperature and a high speed to utilize unbalanced ionization. The principle is to improve the degree of ionization. The former directly uses the combustion gas to pass through the magnetic field, which is called open-loop magnetic fluid power generation. The latter uses a heat exchanger to heat the working medium and then pass through the magnetic field to generate electricity by a closed-loop magnetic fluid.
Coal-fired magnetic fluid power generation technology, also known as plasma power generation, is a typical application of magnetic fluid power generation. When a high-plasma gas of 2.6×10: or more is obtained by burning coal and flows through a strong magnetic field at idle speed, the electrons in the gas are subjected to magnetic force. The function flows along the parties perpendicular to the magnetic lines of force to the electrodes, and sends a direct current, which is sent to the alternating current grid via the direct current inverter.
The efficiency of magnetic fluid power generation itself is only about 20%, but because of its high smoke exhaustion, the gas discharged from the magnetic fluid can be sent to the general boiler to continue to burn into steam, which drives the steam turbine to generate electricity, and constitutes a combined combined cycle power generation. The thermal efficiency can reach 50 ~ 60%. It is the most embarrassing of the power generation technology currently under development. Similarly, it can effectively desulfurize and effectively control the production of NO. It is also a low-pollution coal gasification combined cycle power generation technology.
3 The development of magnetic fluid power generation and its difficulties The first to propose the principle of magnetic fluid power generation is Faraday, who had envisaged the idea of ​​using ocean currents to generate electricity through the Earth's magnetic field. In 1940, Karl Roebitz of Westinghouse of the United States did a test of burning gas through a magnetic field, but it was unsuccessful. Inspired by aerospace technology in the 1950s, the dust in the temperature circle formed by the return of the artificial satellite to the earth has the function of magnetic fluid to control the falling of the satellite, thus generating potassium for use in the warm flue gas. The idea of ​​the alkali metal seed crystal to improve the ionization degree of the magnetic fluid was successfully tested in 1959.
With the development and application of superconducting technology, plasma technology and high temperature ceramic technology, the practical pace of magnetic fluid power generation is gradually advanced. At present, although electromagnets and superconducting generators for nuclear fusion and accelerators made of superconducting materials at liquid helium temperature are still in the development stage, applications in medical machinery and semiconductor fields are widespread and form a certain scale. Therefore, once the technology breaks through, it can form a certain scale. At the same time, superconducting materials at liquid nitrogen temperature have been successfully developed. Once the processing technology has made a breakthrough, the simplification and cost of the superconducting magnet device will be greatly reduced. Plasma technology has a great relationship with magnetic fluid power generation. Lowering the working temperature has a significant effect on reducing heat loss and lifting channel life. Plasma applications have been extensive, such as fluorescent lamps, plasma welding, plasma heating, and plasma melting of metals, but the difference is that the above applications are the energy to convert electrical energy into plasma, while the magnetic fluid power generation is the plasma. The energy is converted into electrical energy.
Quenched ceramics is not only related to the normal working temperature of 2000-3000K magnetic fluid, but also relates to the life of the channel, that is, the key to the normal operation of the coal-fired magnetic fluid power generation system. At present, the high temperature ceramics can withstand the highest temperature. 3090K. 4 Types of magnetic fluid power generation and preparation status of major national research and development 4.1 The development of ring magnetic fluid power generation is faster in the former Soviet Union. It works in the long-term research and development program centered on the Institute of Thermal Sciences of the Academy of Sciences. First, in the 1970s, the U-02, U-25 units (2MW and 25MW each) were used, and many tests were carried out with natural gas, which has reached 250 hours of accumulated operation. After the disintegration of the Soviet Union, Russia has carefully considered this form to be inferior to the gas and steam combined cycle economy. The future development focus is on coal-fired magnetic fluid generator sets. To this end, first test the coal-fired condition on the Y-25M (MHD10MW, steam power generation 15MW) unit. In 1993, Y-25G was built as a coal-fired power generation test, focusing on large-scale disk-type magnetic fluid power generation experiments and theoretical studies.
The research work on magnetic fluid power generation in the United States was the world leader in the late 1950s and 1960s. After the first oil crisis, the Ministry of Energy built a CDIF device in Montana, focusing on coal-fired open-loop magnetic fluid power generation tests, and achieved many individual results. For example, the magnetic fluid generator electrode life of the Afco Institute has exceeded 1,300 hours, which is expected to reach several thousand hours; the development of TRW's high-load coal burner; the CDIF device for coal-fired simulation test proves that through the variable flow The device can directly supply power to the grid. By 1993, the upper and lower parts had been combined to complete the 50MW engineering test. The next step was to build an industrial demonstration power station in Montana with a total power of 76MW and an investment of 460 million US dollars.
Japan's magnetic fluid power generation test began in the 1960s. After Toshiba's magnetic fluid power generation output reached 100 kW, it was included in the large-scale experimental research plan by the Industrial Technology Institute. After the oil crisis in 1976, it turned to the coal-fired magnetic fluid power generation test. Study the magnetic fluid power generation test of burning coal slurry. However, it was found in the test that the slag generated by coal at 3000K has a great influence on the life of the channel. Therefore, it has been included in the first-time technical basic project in the Moonlight Project since 1988, focusing on individual technical research and industrial development test engineering. stop.
In addition, Poland, Yugoslavia, Romania, Finland and India, with the assistance of the former Soviet Union, also carried out experimental research. Both the development of coal burners in Poland and the water and gas magnetic fluid power generation in India have achieved certain results. Basic research is also being carried out in countries such as Australia.
4.2 Closed-loop magnetic fluid power generation and open-loop working fluid are discharged into the atmosphere. The working fluid (rare gas and liquid gold) of closed-loop magnetic fluid power generation is closed-loop use, and the non-equilibrium magnetic fluid is used to generate electricity. Liquid metal is called liquid metal magnetic fluid to generate electricity. The United States Jiebate Company researched the use of magnetic fluid power generation as the pre-stage. After the transformation of the existing 125MW thermal power plant, the power of the power plant can reach 190MW, the efficiency is 38%, which is 3-5% higher than the original. However, due to the high temperature heat exchanger Helium compressors are expensive, resulting in higher unit investment and higher costs, so their practical development research lags behind the open loop system. Countries have also transferred individual studies and achieved certain results.
For liquid metal magnetic fluid power generation, it can be used in the temperature range of 450~1600K and power generation by various energy sources through reasonable selection of working fluids. The conductivity of liquid metal is more than 10,000 times that of general combustion gas and rare gas, so that the power generation device can be lightened and occupied, and it is possible to use AC power to input the existing power grid. Now consider using both gas and liquid. Two kinds of working fluids, gas as a thermodynamic task, liquid metal as an electrical task to fully improve the overall power generation efficiency.
Since the 1960s, China has carried out research on open-loop magnetic fluid power generation, and gradually formed a joint research group of the Institute of Electrical Engineering of the Chinese Academy of Sciences, Nanjing Institute of Technology and Shanghai Electric Complete Set. It has achieved some individual results and listed its own "863 High-Tech". The plan has progressed well.
5 Summary coal-fired open-loop magnetic fluid power generation, currently has demonstration projects, is expected to be partially commercialized in 2010, which will make a significant contribution to energy conservation and reduction of CO2 emissions to achieve green production in the power industry.
Unbalanced ionization closed-loop magnetic fluid power generation, due to its low operating temperature, is also suitable for medium-sized units of 100-300 MW and for the development of coal-fired gas-fired power generation industry with great potential. Liquid metal closed-loop magnetic fluid power generation, from the working temperature range and energy type adaptability and high conductivity can be applied to small power generation devices, the development prospects are broad, but countries are still in the basic research stage. mouth
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