Sources and Temperature Ranges of Waste Heat
The temperature stages, and the position of the waste heat streams associative to the user’s requirement, are important in WHR. Three temperature ranges are generally used to categorize waste heat:
High-temperature Waste Heat:
Above 650oC, the utmost hypothetical temperature for combustors is around 2000oC, and most of the practical combustors are operated under 1650oC. Most of the waste heat in this temperature range outcomes from direct fuel-fired procedures; it must be employed to perform work by means of gas or steam turbines before employment as waste heat.
Medium-temperature Waste Heat:
250oC to 650oC. Most of the waste heat in this temperature variety comes from the exhausts of directly-fired procedure units. This waste, heat is not hot sufficient to allow extraction of mechanical work by steam or gas turbines.
Low-temperature Waste Heat:
Below 250oC. In this temperature variety, it is generally not practical to extract work from the waste heat source; it might be used for pre-heating, and for producing low-pressure steam or hot water.