Issues regarding the drum liquid level in the waste heat recovery system
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Dear experts: My installation is equipped with a waste heat recovery system that generates 40 kilograms of steam. It has just been connected to the medium-pressure pipeline network in recent days. After being connected to the network, the pressure in the steam drum is inevitably affected by fluctuations in the pressure of the medium-pressure pipeline network, and the liquid level in the steam drum also fluctuates constantly. Since the liquid level in the steam drum is a key parameter for monitoring, I would like to ask: under the conditions of a constant furnace temperature and a constant amount of water added to the steam drum, when the pressure in the pipeline network is low, does the liquid level in the steam drum first drop and then rise, or does it first rise and then drop? I just looked up the principles related to saturated vapor pressure, but I don’t quite understand them well. I hope an experienced expert can share their insights; thank you
Keep the pressure in your steam drum slightly higher than that of the pipeline network; this way, pressure fluctuations outside will not have a significant impact on your system, and it will be easier to control the liquid level.
Under the conditions of a constant furnace temperature and a constant make-up water volume to the drum, when the pressure in the pipeline network is low, the drum liquid level first rises and then falls.
With a constant water inflow rate, the pressure in the pipeline network decreases; as a result, the pressure acting on the liquid surface also decreases, causing the liquid level to rise. However, the decrease in pipeline network pressure also leads to an increase in the amount of vapor generated. With a constant water inflow rate, the liquid level drops.
I agree with what was said above – the control scheme for the drum liquid level should be quite mature by now, unless there is something wrong with the owner’s control system
To enable the steam to be connected to the grid, the boiler pressure needs to be slightly higher. As for the changes in liquid level, what has been said already covers it thoroughly
First it rises and then falls; as the pressure in the pipeline network decreases, the instantaneous gas generation rate in the drum increases, causing the volume inside the drum to expand and the liquid level to rise. After allowing steam to be released for a short while, and once it adjusts to the pressure in the pipeline system, the liquid level drops