Limitations of the Approach Temperature Concept

For processes with high exit gas temperature (e.g., GE, Shell, Siemens), the approach temperature concept has much more an empirical than a physical character. I app I 100 K are necessary to achieve, for example, certain amounts of CO2 or CH4 in the product gas (e.g.. Table 6.3). CH4 is in reality a non-decomposed pyrolysis product, rather than a product of constrained metha-nation reactions. 

the results of process assessment must be always seen with reference to these idealizations and accuracies. The influence of further technical parameters was investigated in separate sensitivity analyses, see Sections 5.6.4.S and 7.1.2. 

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