A heat recovery steam generator (HRSG) is a common sight in many modern power plants. Due to its greater energy efficiency when compared to a traditional gas or steam turbine, this machine has become a staple of modern industry. However, the vast majority of the public remains woefull under-informed about the different types of HRSGs available. Here’s a quick look at how these amazing heat exchangers can be classified.
A heat recovery steam generator is most often classified according to its purpose. The most commonly seen incarnation is the combined cycle HRSG where the machine’s purpose is to harness super-heated steam from a hot gas stream to drive a steam turbine. However, recent innovations have seen HRSGs used to generate steam for use in important industrial processes. This process, known as cogeneration, traps heat emitted during the heat recovery process for useful purposes such as heating water, thus eliminating he energy wastage associated with combined cycle HRSGs.
Another important classification for HRSGs categorizes them based on the direction of gas flow. A vertical heat recovery steam generator uses horizontal coils to generate a vertical gas flow while horizontal versions use vertical coils to generate a horizontal gas flow. Although the initial start up costs are similar for both types of HRSGs, horizontal HRSGs tend to incur greater maintenance and inspection fees and are hence more costly in the long run.
Lastly, HRSGs may be classified based on the number of pressure circuits or levels. Smaller scale industrial operations tend to use only one pressure circuit to vaporize water to steam. Industry experts agree, however, that the optimum efficiency for the heat recovery and steam generation process occurs when three pressure circuits are used as this maximizes heat absorption.
As HRSGs become an increasingly pivotal part of the modern industrial landscape, it is important that we familiarize ourselves with the options available. Now you have the knowledge you need to pick the type of HRSG that best fits your needs!