When you complete this lesson, you will be able to identify some auxiliary systems that may be found in an HRSG and recall their purpose and benefit to the unit. • Recall the purpose of the following systems: – Supplementary firing – Bleed air – Deaerator – Attemperator – Sampling – Dosing – Selective Catalytic Reduction (SCR) – CO catalyst – Nitrogen • Identify the general location of the following systems: – Supplementary firing – Deaerator – Selective Catalytic Reduction (SCR) – CO catalyst • Relate the operating conditions in which supplementary firing would be impactful • Describe the mechanism by which deaerators fulfill their purpose • List some qualities for which analyses are frequently performed in the steam/water cycle • State why SCR systems and CO catalyst systems have been put in place • Relate what operating conditions a nitrogen system would be used in