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It is well known that man had always been trying to fined something new to achieve a new aims 80% of total electricity produced in the world is hydral while remaining 20% is produced from nuclear, thermal, solar, Geothermal energy and from magneto hydro dynamic power generation. MHD power generation is a new system of electric power generation which is said to be of high efficiency and low pollution. In advanced countries MHD generator are widely used but in developing countries like India it is still under construction. This construction work is in progress at Tiruchirapalli in Tamilnadu unders joint efforts of BARC (Bhabha Atomic Research Centre), BHEL, Associated cement corporation and Russian technologists. As its name implies, magneto-hydro-dynamic (MHD) is concerned with the flow of conducting fluid in presence of magnetic and electric field. This fluid may be gas at elevated temperature or liquid metal like sodium or potassium. A MHD generator is a device for converting heat energy of fuel directly into electric energy without a conventional electric generator. The basic difference between conventional generator and MHD generator is in the nature of conductor.
Govt. Polytechnic, Khamgaon .
Govt. This is the principle of the conventional generator also. where the conductors consists of copper strips. In MHD generator the solid conductors are replaced by a gaseous conductor. This is the principle of MHD generator.e. A MHD conversion is known as direct energy conversion because it produced electricity directly from heat source without the necessity of the additional stage of steam generation as in a steam power plant.MHD Power Generation PRINCIPLE OF MHD POWER GENERATION The principle of MHD generation is simple. a current would flow through the resistance. Polytechnic. A Positively charged particles as forced upward and negatively charged particle is forced downward. A magnetic force ‘F’ acts on the charged particle. an ionized gas. which produced an electric current. If the P 1 and P 2 are externally connected through a resistance.e. and negative ions would be accelerated towards the plate P 2 . a emf. Is induced in it. The developed view of an MHD channel in show in fig. i. discovered by faraday when an electric conductor moves across a magnetic field. . Khamgaon . i. If such gas is passed at high velocity through a powerful magnetic field. Show in fig. Thus gas energy directly converted into electrical energy. The positive ions would be accelerated towards the upper plate P. suppose we have a charged particle (having charge q) moving at a high velocity ‘V’ towards right and a perpendicular magnetic field is applied.
In open cycle system working fluid is air.MHD Power Generation MHD SYSTEM There are two types of MHD System 1. In a closed cycle system the working fluid is recycled to the heat sources and thus used again and again. . In closed cycle system helium or argon is used as the working fluid. Polytechnic. Govt. The operation of MHD generator directly on combustion products in an open cycle system.) Closed cycle System In open cycle system the working fluid after generating electrical energy is discharged to the atmosphere through a stack. Khamgaon .) Open cycle System 2.
Polytechnic. .MHD Power Generation Gas Flow Gas Flow Magnetic field Cathode Govt. Khamgaon .
Khamgaon . The plasma is then seeded with small fraction (1%) of an alkali metal (potassium) introduced usually as a carbonate powder or solution. . is shown in fig. The gas expand through the generator surrounded by powerful magnet. The hot gas is then seeded with a small amount of an ionized alkali metal (cesium or potassium) to increase the electrical conductivities of gas. The above cycle is not suitable for commercial use. The exhaust gases of MHD unit are still at a sufficiently hot temperature it is possible to use for additional power generation in a steam turbine alternator unit. The seed material is recovered for successive use. coal is processed and burnt in the combustor at high temperature (2750 to 3000 °K) and pressure (7 to 15 at atmosphere). The nitrogen and sulphur are remove for pollution controlled and then gasses are discharged to the atmosphere. Such cycle is known as hybrid MHD-steam plant cycle. Figure shows hybrid MHD steam cycle. During the motion of gas the positive and negative ions move to the electrodes and constitute an electric current.MHD Power Generation OPEN CYCLE MHD SYSTEM An elementary open cycle MHD system. The rejected gas passes through an air heater for preheating the inlet air. This is increase the efficiency of process. The MHD generator resembles a rocket engine surrounded by a magnet the coal is burnt to produced hot gas. With preheated air to form the plasma. Polytechnic. Govt.
Khamgaon .MHD Power Generation HYBRID STEAM OPEN MHD PART CYCLE The resulting having an mixture electrically conductivity of about 10 ohm/m is expanded through a nozzle to increase its velocity and then Govt. . Polytechnic.
. For efficient practical realization a MHD system must have following features: 1) Air superheating arrangement to heat the gas to around 2500 °C so that the electrical conductivity gas is increased. 2) The combustion chamber must have low heat losses 3) A management to add a low ionization potential seed material to the gas to increase. Electrodes channel provided electric contact between flow and external load. 5) A magnet capable of producing high magnetic flux density. Khamgaon . The seed material is recovered from the gas the harmful emissions (sulphur) are also removed from gas before it is discharged to atmosphere through a stack. The gas coming out of MHD generator is still sufficiently hot and is used to raise steam.MHD Power Generation passed through the high magnetic field (5 to 7 teslas) of the MHD generator. A part of this steam is also used in a steam turbine which driver a compressor for compressing air for the MHD cycle. CLOSED CYCLE MHD SYSTEM The closed cycle inert gas MHD system was conceived 1965. 4) A water cooled but electrically insulating expanding dust with long life electrodes. its conductivity. Polytechnic. The power o/p is dc and it is necessary to use to change it to ac before the power can be fed to an electric grid. which generates additional energy in a steam in a steam turbine alternator unit. The main disadvantages of the open cycle system is very high Govt. 6) Seed recovery apparatus necessary for both environmental and economics reasons.
MHD Power Generation temperature requirement and a very chemically active flow could be removed. The loop shown on the right hand side in fig is the steam loop for further recovering the heat of the working fluid and converting this heat into electrical energy. In the heat exchanger HX. As the name suggests the working fluid in closed cycle. This steam is used partly for during a turbine which runs the compressor partly for turbine Govt. The complete system has three distinct but interlocking loops. by the inverter and is then feed into the grid.35 MJ/kg and temperature of about 530°C is burnt in a combustor to produce heat.C. Polytechnic. Khamgaon . Figure show a closed cycle MHD system. by closed cycle MHD system. The combustion products after passing through the airpreheater (to recover a part of the heat of combustion product) and purifiers (To remove harmful emissions) and discharged to atmosphere. is circulated in a closed loop. The loop in the centre is the MHD loop. The fluid passes through the heat exchanges HX 2 where it imparts its heat to water which gets converted to steam. coal is gasified and the gas having a high heat value of about 5. The hot argon gas is seeded with cesium and passed through MHD generator. The working fluid is helium or argon with cesium seeding. . On the left is the external heating loop. this heat is transferred to argon the working fluid of MHD cycle. The dc power output of MHD generator is converted to A.
A closed system can provide more useful power Govt. . The output of the alternator is also to the grid. Polytechnic. The working fluid goes back to the heat exchanges HX) after passing through compressor and intercooler.MHD Power Generation driver an alternator. Khamgaon .
Polytechnic. NEED FOR FURTHER RESEARCH The commercial use of MHD concept has not been possible Govt.MHD Power Generation conversion at lower temperatures (around 1900 o K as compared to 2500 o K for open cycle system). Khamgaon . .
MHD Power Generation because numerous technological advancements are needed prior to commercialization of MHD systems. Search is on for better insulator and electrode materials which can with stand the electrical. Khamgaon . Most of these are related to material problem created by the simultaneous presence of high temperature and a highly corrosive and abrasive environment. thermal. Polytechnic. . 1) The conversion efficiency of a MHD system can be 50% as compared to Govt. ADVANTAGES OF MHD GENERATION MHD generation offers several advantages as compared to other methods of electric generation. magnetic and electric fields. mechanical and thermo-chemical stresses and corrosion. The MHD channel operates extreme conditions of temperature.
2) Large amount of power is generated. Pollutant emission m tons per day based on use of coal having-3 percent sulphur contents. the overall generation cost of an MHD plant will be less.MHD Power Generation less than 40 percent for the most efficient steam plants. Govt. 6) The more efficient heat utilization would efficient heat utilization would decreases the amount of heat discharged to environment and the cooling water requirements would also be lower. Polytechnic. Khamgaon . so more reliable. 4) It has ability to reach the full power level as soon as started. 8) The Closed cycle system produces power free of pollution. The reduce fuel consumption would offer additional economic and social benefits. . 3) It has no moving parts. Following table show the pollutant emission of an MUD plant and a conventional steam plant. 5) Because of higher efficiency. 7) The higher efficiency means better fuel utilization.
Khamgaon . . CONCLUSIONS Govt. 3.) Defense application.MHD Power Generation 1000 MWC Conventional steam plant. Polytechnic.) Power generation in space craft. 3 3 4 Applications 1.) Hypersonic wind tunnel experiments. 2. Particulate matter Sulphur oxides Nitrogen oxides 33 450 80 1000MWC MHD Plant using coal as a fuel.
. The answer to this is in non conventional energy. In the country is sure to fall short of the energy demand by the first decade of next century. It will not be long before the technological problem of MHD generate are overcome and MHD power generation transform itself from nonconventional to conventional energy sources. Govt. REFERENCES 1) Non-Conventional energy source. Polytechnic. Khamgaon .MHD Power Generation With the increased industrial and agricultural activities. The MHD power generation is in advanced stage today and closer to commercial utilization significant progress has been made in development of all critical component and sub system technologies coal burning MHD combined steam power plant promise significant economic and environmental advantages compared to other coal burning power generate technologies. power demand is also highly increased. This means an additional capacity of power is required next 10 year.
D. Rai 2) Electrical Power System By : Dr. Inamdar 3) Generation Distribution & Utilization of Electrical Energy. By : C.L.MHD Power Generation By : G.Wadwa Govt. Polytechnic. Khamgaon . .
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