Unfired plant

In Fig. 9.2a, the work output from the unfired plant is shown to be equal to unity and the heat supply F q = 4.0. Further, it is assumed that the useful heat supplied is (2u)cg = 2.25 and the unu.sed non-useful heat is (2nu)cg = 0-75. An important parameter of this CHP plant is the ratio of useful heat supplied to the work output, = (2u)cg cg = 2.25. 

For a site with a fixed power demand throughout the year, the unfired plant illustrated in Fig. 9.2a is suitable for summer operation when the heat load is light. 

TEMA-style shell-and-tube-type exchangers constitute the bulk of the unfired heat-transfer equipment in chemical-process plants, although increasing emphasis has been developing in other designs. These exchangers are illustrated in Fig. 11-35, and their features are summarized i n Table 11-11. 

Other parameters for the plant operating conditions—of HRSG unfired (WHR) and HRSG fired (WHB)—are as follows ... 

Direct fired pressure vessels Nuclear power plants Heating boilers Unfired pressure vessels... 

As unfired pressure vessels, stills will need biennial inspections, but if it is believed that corrosion may have taken place a prompt check should be made. If a process whose moderate corrosion has been predicted on the basis of laboratory results is due to be done on the plant, corrosion test coupons should be installed in the plant and inspected regularly. 

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