Economic analysis and calculation of the cogeneration upgrade for large fossil fired generation unit

The theoretical calculation involved in the district heating upgrading of the existing large fossil fired generation units was described. A feasibility study example for an existing 600MW unit was put forward in detail. It is shown that in the feasibility study of heating upgrading scheme, more effort should be made to analyze the part load performance change of the unit except for the full load performance change, in order to get a complete overview of the upgrading effect. It is also shown that for the cogeneration upgrading schemes where the IP and LP turbine crossover piping is the steam source, there exists one balancing operation condition for each operation load condition. When the heating steam supply is lower than the balancing operation condition, the economic negative benefit due to heating supply increases rapidly, and the unit operation under this kind of condition should be avoided if possible.