Question

Consider a cogeneration power plant that is modified with reheat and that produces 3 MW of power and supplies 7 MW of process heat. Steam enters the high pressure turbine at 8 MPa and 500 C and expands to a pressure of 1 MPa. At this pressure, part of the steam is extracted from the turbine and routed to the process heater, while the remainder is reheated to 500 C and expanded in the low pressure turbine to the condenser pressure of 15 kPa. The condensate from the condenser is pumped to 1 MPa and mixed with the extracted steam, which leaves the process heater as a compressed liquid at 120 C. The mixture is then pumped to the boiler pressure. Assuming the turbine to be isentropic, show the cycle on a T-s diagram with respect to saturation lines, and disregarding pump work, determine (a) The rate of heat input to the boiler and (b) the fraction of steam extracted for process heating. (c) The utilization factor of the plant.

Answer 1