Actual cogeneration plant

Example 4.20 Energy dissipation in an actual cogeneration plant A cogeneration plant uses steam at 900 psia and 1000°F to produce power and process heat (see Figure 4.26). The steam flow rate from the boiler is 16 lb/s. The process requires steam at 70 psia at a rate of 3.2 lb/s supplied by the expanding steam in the turbine. The extracted steam is condensed and mixed with the water output of the condenser. The remaining steam expands from 70 psia to the condenser pressure of 3.2 psia. If the turbine operates with an efficiency of 80% and pumps with an efficiency of 85%, determine the work loss at each unit. 

Figure 4.26. (a) Schematic of actual cogeneration plant and (b) T-S diagram. 

Table 4.8a State properties of the actual cogeneration plant in Example 4.20...

Finally, EVO had decided to accept the helium turbine from the manufacturer in spite of nonconformance with the supply contract. This decision was made because helium-specific experiences could nevertheless be gained with the actual plant conditions and because the plant could be operated (in spite of the lower electrical power) as a cogeneration plant satisfying the required district heat demand. 

Because the 43 bar-cogeneration system is relatively new in the plant, two options (base cases) were considered when evaluating the actual energy costs for the plant ... 

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