pls can anyone tell me the efficiency of the boilers with super-heater and without superheaters..!
The boiler efficiency is roughly the same with and without superheat. The efficiency of a utility boiler will be over 90%. You obtain the efficiency savings in the turbine cycle where you convert the thermal energy of the steam into mechanical energy to turn a generator. In most modern coal fired boiler, there are two superheat circuits, one called superheat and one called reheat. The heat rate of one boiler I know of with the reheat circuit is over 13,000 BTU/KWHr, while the heat rate of a two superheat boiler is around 10,000 BTU/KWHr. (Divide the heat rate by 3412 to get the efficiency.) But it depends on design. Most nuclear units do not have any superheat, they operate on a saturated steam steam cycle. Their heat rates are not that far off from a coal unit, look at the figures in the link below:
