O&M – Balance of Plant: Klamath Cogeneration Plant
Reuse of evap cooler water
Klamath Cogeneration Plant
Iberdrola Renewables500-MW, gas-fired, 2 × 1 combined-cycle cogeneration facility located in Klamath Falls, OR
Plant manager: Ray Martens
Key project participants: Greg Dolezal, maintenance manager; Bruce Willard, operations and engineering manager
Challenge.
Plants that utilize evaporative cooling for their turbine inlet air often have the sump blowdown going to a waste drain. In our case, that drain leads to the local water treatment plant. The treatment plant faces very high upgrade costs and is in the process of raising our sewer rates 70% over the next three years. The largest contributor to our wastewater discharge was the evaporative coolers, especially in the summer.
Solution.
The solution was to capture this water and find a way to reuse it. The only place that this water would be useful to us was boiler makeup water. Of course, it had to be demineralized first. We are fortunate because the condensate returning from our steam host enters our turbine building at the same end of the building as the combustion turbine inlets. From there it goes underground to our makeup water tank.We decided to tap into this line and allow gravity to be the motive force. Since the normal operating level of the storage tank is slightly lower than the evaporative cooler sumps, the water naturally tries to equalize with the tank at all times. This equalization causes flow that we can meter based on chemistry results.
The routing was simple: we came off the bottom of the sumps with a loop-seal type arrangement. If there are no obstructions to flow, the water goes to the tank. If the tank level is too high or the operator closes the isolation valve, the flow is diverted back to its original design and goes to the drain. This prevents us from overfilling the tank or the evaporative cooler sumps.
The only challenge to overcome was all the obstructions inside the building. These obstructions prevented us from getting the proper slope of pipe to our tie-in destination. Instead, the pipe was routed outside the building and underground utilizing flexible plastic pipe.Although some trenching was required, most of our outdoor piping used the plant storm drain system. The flexible pipe was routed inside the storm drain much like an electrical duct bank. The two units were joined inside the storm drain and a low point drain was installed for clearing the pipe before winter. See Fig 95 for design details.
Results.
The results are easy to quantify. Even without the 70% increase in sewer rates the cost of disposing this water is approximately $20,000 annually. Since we did not have to install any pumps, regulating valves or long runs of pipe, this project paid for itself in less than one summer. The system is extremely simple and operates itself, seamlessly. Other than draining the piping before winter there is no maintenance or operator intervention.
Aside from the monetary benefits, we feel that we are being good stewards of the resources in our care. This project reduces the amount of well water that our host must produce to cover the steam losses in their system, thus saving them money and allowing the aquifer water to stay in the aquifer
