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FLUE GAS COOLER SIMULATION PART 2.
I finally finished the application example of the flue gas cooler tower. Here is the second part of the story with a video summary.
Previously I talked about the cooling tower of a waste burner in which the 1000°C flue gas was cooled very fast to 220°C with water spray, to reduce nitrogen oxide content. But the water with chemicals from the flue gas accumulated on the bottom and destroyed the steel parts. With fluid flow simulation we showed that the mixing of flue gas and water vapor was not effective and there was excess water in the system.
Well, here came our next turn: to massively improve the mixing of the flue gas and the water vapor. We didn’t change too much on the tower itself but we redesigned the positions the water injectors. Many different versions were created, all based on CFD simulations. The injectors were placed to the opposite side of the flue gas inlet (they were removed from the top of the cooling tower), pointing a little upwards to face the gas flow. Also they were concentrated on a fairly small curve of the tower side, to improve mixing with this arrangement too.
Traces of water vapor show just that.
Traces of water vapor coming from the injectors
The water leaves the injectors pointing upwards and to the center of the tower. When it reaches the main flue gas flow, in the middle of the tower, the flow direction of the water vapor changes. Traces show how big, sometimes multiple curves the water particles travel while mixing with the flue gas.
Expecting such an intensive mixing, such an even concentration of the water vapour at the top section of the tower was impossible with the original design.
Here is the video of the application example (you can put it to full screen with the right icon of the VCR):
Like I said in the video a fine tuned injector configuration was built into the redesigned cooling tower, but of course because of secrecy reasons it is different from what was shown here.
Some other improvements were also carried out. New control electronics was developed and it measures the wall temperature of the tower in more than 30 points. The quantity of the water to be injected is set based on the temperature values near the injection points. This way the system can quickly follow the fluctuations in burner heat load and can add just the necessary cooling water.
The reconstruction of the cooling tower was finished at the end of August 2009. The system is running fine without corrosion or excess water.
Robert Dul
2010.01.13 - CFD Engineering Hungary Kft. |
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