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I’d like to add that an ACC can handle whatever you give it (obviously within reasonable limits), the question is what saturation temperature you will operate at. If you increase steamflow, you’ll produce more MW but you’ll pay for it in efficiency if your ACC was not designed for it. Usually in our case, the turbine last stage blades have some limit and you shouldn’t operate at higher values than that. Sometimes, we find that even at design steamflow, our backpressures are so high (because of wind etc.) that we have to “deload” i.e. reduce steam flow.
Cleaning tubes (the presence of fouling), changing fan pitch etc. all just try to help you to get the saturation temperature down for a given heat load and that could change over time for various reasons.
In our case, which is not combined cycle, only coal, you can increase steamflow until you reach a upper backpressure limit – then you’ve reached “capacity” but obviously you’re less efficient (burning more coal) at that specific operating point.
The best way to know is to run it up slowly and see what happens 🙂
Hi Maikol. I agree with Desmond. Are you trying to get back past performance or are you trying to increase performance relative to design?
Hi Noah.
Maybe a little late but here goes. I’m not a specialist in the area myself but I have a colleague or two and I ask them since it’s quite an interesting problem.
We don’t know if the problem is with the DA. Here’s why…
We have tray types DA’s at an old station of ours (wet cooled) – 1960s. These particular trays have a lot of vibration and are on fairly small brackets and mostly break out later. As the trays failed in one of the units we simply took them out. At the end there were only one or two trays left (probably 6 months back), but the DA still worked as he should do with DO’s in spec. We believe the saturated conditions in the DA with condensate falling from the top with a reasonable spread (1 tray) are sufficient…
Having said that no one really knows exactly what’s going on in the DA. This specific DAs had two tanks, each 50m^3 each. You have condensates and distillates that come in, feed water suction that goes off, RFT filling in, balancing lines between the two tanks above and below, the vents that go out and then you try to control the level quite accurately by adding more water in the condenser or dumping condensate to the RFT i.e. many things going on!
To answer the question, we’ve noted ASME PTC 12.3: Performance Test Code on Deaerators. We’ll start there.
Nick, I agree BNF/RPM is one possible cause (as it is a bit close for comfort) but we can’t do too much about that now – it’s been running for 25 years like this. We have to typically re-torque every 3 months and it occurs across all fans (young and old).
We’ve found that it becomes worse with windy stretches which is kind of expected but I was just wondering if this is common among other users.
