In 2007 Intek was presented with performance enhancement requirements imposed on an existing Westinghouse condenser. The objective was to determine if the condenser performance could be improved from design capability and to estimate the achievable amount of improvement. The principal drivers for the retrofit were load limiting conditions in the summer time and a desire to switch tube material from Admiralty to SS. The results of the initial study were positive and led to a second effort for Intek to design the retrofit to achieve the projected performance level during a retubing outage whereby the copper bearing tubes would be replaced with stainless steel tubes (a lower heat transfer coefficient material).
The retrofit was engineered to include parts manufacturing and assembly drawings along with an assembly guideline document. The results, after implementing the retrofit during an outage in Spring 2008, are provided in the following Figures 1-4.
The projected key measured performance enhancements with new SS tubes were met or exceeded and included:
- compared to 1998-2007 data, the condenser project contributed to a 1-2% heat rate reduction,
- compared to 1998-2007 data, the condenser project contributed to a 1-2% emissions reduction,
- back pressure reduction of ~0.7”Hg at 85°F inlet circulating water temperature; shown in Figure 1,
- reduced condenser condensate DO, from 20ppb to as low as 2 ppb,
- increased air in-leakage removal effectiveness (for no excess back pressure or DO) from <25SCFM to
- >100SCFM at 90°F inlet circulating water temperature (no change in vacuum equipment), and
- condensate cation conductivity down from 0.16μS/cm to 0.11-0.12μS/cm (attributed to reduced circulating water in-leakage, less condenser corrosion solids, as well as less dissolved CO2 and its by products in condensate) with measured Powdex resin polisher run time increase of >300%.
The retrofit project payback was met in less than one year and included costs for engineering construction, (excluding the retubing costs), and was installed in ~2.5 weeks, mostly in parallel with the retubing schedule, and having minimum impact on the outage schedule. For comparison, this condenser improvement provides an equivalent Btu/kWhr reduction at 1/20th the cost of an HP turbine dense pack upgrade project.