Controlling Chemistry during Startup and Commissioning of Once-Through Supercritical Boilers: An Overview from the EPC Contractor’s Perspective

摘要

With new power plants committing to once-through supercritical boilers and the rush to put them online with the shortest schedule possible, any EPC contractor with turn-key responsibilities faces a dilemma with respect to both short-term and long-term chemistry concerns. This dilemma is related to Oxygenated Treatment (OT) that will be implemented on these boilers during long-term normal operation. Whereas most of the industry experience is based on converting existing once-through boilers from All Volatile Treatment (AVT) to OT, there is relatively much less information on newer boilers operating on OT. EPRI startup guidelines provided for AVT(O) (All Volatile Treatment (Oxidizing)) and AVT? (All Volatile Treatment (Reducing)) to facilitate conversion to OT for these boilers are sound but not tested on new boilers. Additional considerations such as “No Deaerators Cycles” are not included and must be treated on a case-per-case basis. The startup/commissioning cycle is still the EPC turn-key contractor’s responsibility, which includes startup on AVT and quick conversion to OT. This technical paper addresses these chemistry issues and provides a practical approach to achieving steam purity and the specified feedwater chemistry requirements.