What is a major disadvantage of a controlled circulation HRSG?

A controlled circulation heat recovery steam generator (HRSG) has a significant disadvantage in that it requires expensive pumps to maintain the necessary flow. Controlled circulation systems utilize forced circulation to ensure adequate water flow through the evaporator and superheater sections, which is essential for efficient heat exchange and steam production. This forced circulation helps to overcome issues such as evaporation and boiling within the tubes, but it also means that high-capacity pumps are needed to operate the system effectively.

These pumps need to be robust and capable of handling high pressures and temperatures, which increases both initial capital costs and ongoing maintenance costs. While this technology allows for better handling of varying loads and enhances thermal efficiency in certain scenarios, the requirement for more complex and costly pumping systems can be a significant disadvantage compared to simpler natural circulation designs that do not necessitate such equipment. This aspect can impact the overall economic viability of using controlled circulation HRSGs in some applications.

In contrast, other options either refer to advantages of the HRSG technology or do not align with the recognized challenges presented by controlled circulation systems. For instance, a smaller physical footprint is often considered an advantage rather than a disadvantage, and being less prone to steaming can actually be a benefit of controlled circulation designs. Low thermal efficiency is not typically associated