Challenge
An eastern US, 885 MW, 3x1 combined cycle power plant was looking to improve asset protection during cycling operations while maximizing power generation through improved steam surface condenser efficiency. The customer turned to Veolia for a solution. The team recommended the use of Veolia’s proprietary volatile filming corrosion inhibitor, Polyamine Plus*.
Steamate* PAP7010 uses Veolia’s Polyamine Plus filming chemistry, and forms a hydrophobic barrier film on metal surfaces, protecting all water and steam touched surfaces including piping, boiler/evaporator and surface condenser. The filming technology minimizes outages and maintenance cost by improving corrosion control both on and offline and limiting the transport of metal oxides to the boiler. The hydrophobic barrier film developed by PAP7010 also has a positive impact on steam surface condenser performance. The film promotes dropwise as opposed to filmwise condensation (Figure 1) which has been documented to improve heat transfer. Our research in collaboration with the US Department of Energy (DOE) demonstrated this application in a laboratory scale (1), but field applications had yet to be conducted.
Solution
The Veolia technical team worked closely with the customer to develop a plan to introduce Steamate* PAP7010 into the condensate system coming out of the plant’s spring outage. At the same time, the team deployed Veolia’s Empower* advanced condenser analytics program. Empower would be utilized as the critical digital monitoring tool to evaluate the efficiency improvement in the condenser during treatment. The goal was to replicate the laboratory results observed during the DOE study in a full-scale field application. Power plant improves condenser efficiency through dropwise condensation with Polyamine Plus* filmer CASE STUDY I Power 2.
It took approximately 90 days for the entire steam circuit to be completely treated with the filmer using a stepwise and methodical approach for the introduction of the new chemistry. Once the system was fully passivated, the improvement in condenser efficiency was measurable and sustained.
Result
The Empower advanced analytics calculated a 1.6% improvement in their condenser cleanliness factor (CCF), a standard performance indicator approved by the industry. The improvement began 3 months after initiating treatment with Polyamine Plus when the system was fully passivated, as seen in Figure 1. The condenser efficiency gains are impressive considering they were realized at full load during the heat of the summer when inlet cooling water temperatures were at their peak. The resultant improvement in condenser efficiency captured by Empower produced an annualized excess fuel savings greater than $50,000 per year, utilizing $2.50/MMBtu’s as an average fuel cost for natural gas. The efficiency gain from dropwise condensation also reduced the projected carbon dioxide emissions from the station’s stack by ~4,200 lbs./hr, or over 16,500 MT CO2 per year if considering full load.
As further proof that the transition from filmwise condensation to dropwise had a positive impact on power generation performance, the team plotted the condenser backpressure during the year prior to the addition of Polyamine Plus against the condenser backpressure during the application. At similar inlet cooling water temperatures and load, the PAP7010 filmed condenser demonstrated a 0.5 in Hg (abs) (0.25 psi) reduction in backpressure. This reduction can be seen clearly in Figure 2. The reduction in backpressure lowers the enthalpy of the steam turbine outlet, allowing more power to be generated.
The Steamate PAP7010 addition to the power plant’s steam circuit not only delivered improved asset but also produced measurable improvement in condenser efficiency. The condenser efficiency gains agree with previous laboratory studies validating the ability of Polyamine Plus to facilitate dropwise condensation in the steam surface condenser and thus improve heat transfer, delivering significant operational and environmental value to operators.