Attemperator Design and Configuration for HRSG

Subject:

Comments:
: : Would like to get some feedbacks on the following. The boiler in question is a HRSG with supplementary firing. : 1) Single inter-stage attemperator vs. Multi inter-stage attemperator : Single inter-stage attemperator is an attemperator where the water injection is in between 2 superheater banks. The water injection is controlled by a temperature controller at the final outlet of the HRSG (i.e.secondary or the last superheater bank) : Multi inter-stage attemperator is - in my case - 2 attemperators where the water injection are in between first and second superheater banks, and between second and third/final superheater banks, respectively. : The water injection for the 1st attemperator (between 1st and 2nd superheater banks) is controlled by a temperature controller at the final outlet of the HRSG and for the 2nd attemperator is by a temperature controller at the inlet of the 2nd superheater bank. : What are the reasons and the advantages of the multi inter-stage attemperator? : 2) Degree of superheat (value of temperature above saturation point) of steam at in between superheater banks : What are the reasons and the advantages of having lower degree of superheat for steam at in between of the superheater banks? : This was achieved through design of the superheater banks and controlled of water injection at the 1st attemperator (for multi inter-stage attemperator design).