Optimization of Industrial Process 1
To illustrate the application of the method described in the previous chapter, the multi-objective optimization problem of the regenerative steam power plant with superheat and reheat shown in Fig. 6.1 is taken as an example. It consists of one stage of steam reheat and two closed feed water heaters with drains cascaded backward that operates at different pressure levels. Each feed water heater is a heat exchanger that receives steam bled from the turbine and feed water or high-pressure subcooled liquid water from the condenser. The water stream passes through successive steam-fed preheaters from the turbines and the condensation of which causes the heat to flow to the boiler feed stream to preheat. As the bled steam condenses in each feed water heater, it is passed through a pressure reducing valve to flow to a lower pressure region, such as either the next lower-pressure feed water heater or the condenser. In the condenser, cooling water provided by a wet-cooling tower removes the waste heat from the turbine exhaust steam at the lowest pressure level of the plant, leaving subcooled liquid water or condensate for reuse in the cycle. A pump is placed after the condenser to deliver water through the three-high-pressure closed feed water heaters to the boiler. The boiler generates high-pressure superheated steam from boiler feed water by combusting natural gas. Superheated high-pressure steam from the boiler is used to generate electric power in HP, IP, and LP turbines.