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# Heat rate of coal fired power plant

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Heat rate is the single paramter that can tell the health of a power plant similar to the pusle rate of a person tells about ones health.

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### Heat rate of coal fired power plant

1. 1. HEAT RATE-THE PULSE RATE OF POWER PLANT PDMV Prasad , P Koteswara Rao Truth is ever to be found in simplicity…Sir Isaac Newton.The following are the facts which make the understanding on heat rate simple and makeengineers feel the practicality and ensure team preparation for achieving what is possible.Operating Heat Rate depends on three significant factors: Firing Boiler range coal, maintaininghigh Loading factor and Operating the plant at design parameters.Heat rate in simplicity is ratio between heat input and energy output. There are fourdefinitions. 1. Unit heat rate: - Heat input to boiler / gross electrical generation. 2. Net unit heat rate: - Heat input to boiler/net electrical generation (Aux consumption must be subtracted from gross generation). 3. Actual unit heat rate :-Total heat input to boiler/ actual net generation of the period ( Including fuel burnt in unit offline period) 4. Design unit heat rate: - Design heat rate is the heat rate anticipated at the design parameters at specific load like MCR (maximum continuous rating), VWO (valve wide open operation) etc. with design efficiencies of equipments.Now let us examine the order of significance in a power plant operation and performance. 1. Legal compliance. 2. Life of the plant. 3. Output of the plant. 4. Efficiency.Firstly legal and environmental compliance is very important for continuing operations.Secondly life of plant equipment is very important for it to live design expected life and thuscapable of producing power for its life time. Thirdly output is very important for sustainingoperations and ensuring accomplishment of purpose of plant. Efficiency comes in fourthposition and it will decide how well a power unit is performing in converting coal energy toelectrical energy. This order is written for guidance. For example, if life of plant is going todecrease by operations as derived from efficiency lessons then higher life is to be preferred. Forexample, if a reheater coil outlet metal temperature is going high reheater spray is to be giveneven if reheater temperature is going to reduce below design temperature. Subsequentlyproblem is to be studied why such phenomenon is taking place in the unit.
2. 2. Design Heat rate broadly depends on Rankine cycle –parameters of the unit and Design ofequipments and capacities.Heat rate deviation occurs due to some or more of the following Equipment degradation /ageing, Parameter deviations, Process Deviations and change in input conditions like fuel, CWwater etc.RANKINE CYCLEIn selection of the unit various options are available which are dependent on Rankine Cyclewith variety of sets of parameters.The higher the temperature and pressure parameters of main steam and reheat steam thehigher the cycle efficiency. The fixed cost of unit on per MW basis increases as higherparameters are chosen due to usage of costlier metals for withstanding higher parameters. Soonce design parameters are selected the heat rate limit is getting decided.Design of equipments and capacities make the selected rankine cycle reality .The turbineefficiency and condenser design, the boiler efficiency of heat absorption and converting intosteam etc achieved by designers and manufacturers decide the performance of equipment. Thedesigns are supposed to achieve the Rankine Cycle parameters, output etc.