TRIPLE COMBINED POWER CYCLE WITH MAGNETOHYDRODYNAMIC (MHD)GENERATOR

TRIPLE COMBINED POWER CYCLE WITH MAGNETOHYDRODYNAMIC (MHD) GENERATORPRESENTED BY M.HARISH KUMARNALLA MALLA REDDY ENGINEERING COLLEGE

CONTENTSIntroductionCombination of cyclesPrinciple of MHD generatorAnalysis of MHD cycleAnalysis of Brayton cycleAnalysis of Rankine cycleEfficiency of combined cycleAdvantages and disadvantagesconclusion

INTRODUCTION:More demand for power generationIncrease in efficiency of the system by combining two or more cyclesThough dual cycles produce more power, going for triple cycle increases efficiency of the plantSeveral triple combined power cycles were proposed 1. With SOFC 2. With MHD generatorEfficient usage of natural resources

Combination of cycles:

Triple combined cycle consists of following cyclesMagnetohydrodynamic (MHD) cycle as topping cycleBrayton cycle (Gas turbine) as intermediate cycleRankine cycle (Steam turbine) as bottoming cycle

Principle and working of MHD generatorFaradays law of electro magnetic inductionConventional generator copper strips as conductorsMHD generator ionized gas as conductor

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NVOutput current Hot gaseous conductorThe direction of current (Potential) is perpendicular to both the direction of moving gas particle and to the magnetic field.

90 90 Potential (E) Ionized gas (Q)Magnetic field (B) Constructional details of MHD generatorS

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combustion

ChamberVIonized GasWorking fluidWater coolerThermal resistance sealingMagnet Stream outLoad output NozzleElectrodeInletAnalysis of MHD cycle

MHD cycle consists of following parts 1. Combustion Chamber 2. Convergent-Divergent Nozzle 3. MHD Generator 4. Heat ExchangerFuel employed- Natural gas and coalIonization of gases at high temperatures Seed materialAir preheatingDirect Current

The MHD systems are broadly classified into two types. 1. OPEN CYCLE SYSTEM 2. CLOSED CYCLE SYTEM a. Seeded inert gas system b. Liquid metal system

Figure shows open MHD cycle

Figure shows closed MHD cycle Acts as Brayton cycle Heat sources and working fluid are independent Helium or Argon with Cesium seedingAnalysis of Brayton cycle

Brayton cycle consists of following components 1. Compressors (1&2) with an intercooler between them 2. High temperature air heater (HTAH) 3. Gas turbine 4. Recuperator At intercooler preheating of fuel and working fluid of Rankine cycleWorking fluid is fresh air drawn from atmosphere

Analysis of Rankine cycle

Figure shows the combined MHD generator with Rankine cycle

The parts in the Rankine cycle 1. Heat recovery steam generator (HRSG) 2. Steam Turbine 3. Condenser 4. Pump 5. IntercoolerInput heat to boiler is from exhaust gases coming out from MHD generatorSteam acts as working mediumAgain it is converted into water during condensation process

Efficiency of combined cycle

In a triple combined cycle power generation system, an MHD power generation system is placed before the GTCC system.By generating power at three stagesthe MHD generator, gas turbine, and steam turbinethe resulting combined cycle system achieves outstanding efficiency in generating power from natural gas.The combined cycle system is expected to achieve the worlds highest power generation efficiency exceeding 70% (LHV) for several hundred MW class power generations and over 60% (LHV) efficiency for several tens of MW class power generation.

Figure shows the increase in efficiency of the power plant for every year with different types of cycles.

Advantages and disadvantagesAdvantages:Present efficiency of the cycle is 50% t0 53% Still efficiency of 65% can be achievedLarge amount of power is generated.It has less moving parts, so more reliable.The closed cycle system produces power, free of pollution.It has ability to reach the full power level as soon as started.Although the cost cannot be predicted very accurately, yet it has been reported that capital costs of MHD plants will be competitive to conventional steam plants.

It has been estimated that the overall operational costs in a plant would be about 20% less than conventional steam plants.Elimination of turbine in MHD cycleThese systems permit better fuel utilization. The reduced fuel consumption would offer additional economic and special benefits and would also lead to conservation of energy resources.It is possible to use MHD for peak power generations and emergency service. It has been estimated that MHD equipment for such duties is simpler, has capability of generating in large units and has the ability to make rapid start to full load.

Disadvantages:MHD Systems suffer from the reverse flow (short circuits) ofelectrons through the conducting fluids around the ends of the magnetic field.There will be high friction losses and heat transfer losses. The friction loss may be as high as 12% input. The MHD system needs very large magnets and this is a majorexpense.Coal, when used as a fuel, poses the problem of molten ash which may short circuit the electrodes. Hence, the restriction on the use offuel makes the operation more expensive.Flue gases should pass only for less time in the MHD generator

conclusion The threat of disappearing of the fossil fuels within few decades compel the human beings to search for new energy sources will last for a longer time.Extensive research is going on in different countries throughout the world to find out the new resources to replace the conventional fossil one.With the present research and development programmes, the non-conventional power resources play an important role in the power industry.This power resource plays a minor role presently and its use on a vast scale is yet to be confirmed as it is in its childhood stage.THANK YOU