In three-effect evaporation, how to determine the height of the U-shaped bend where the second-effect condensed water enters the third-effect shell side?
Thread Content
Please tell me heroes: The third effect evaporates downstream, and the second effect condensed water enters the third effect shell side. In order to maintain the pressure stability between each effect, a U-shaped bend is set on the condensed water pipe. The second-effect shell side pressure is 0.2MPa (G), and the third-effect shell side pressure is 0.15MPa (G). How long is the U-shaped bend height? Thanks
I would like to ask if any users have encountered this kind of problem, or have seen multi-effect evaporation equipped with U-shaped tubes? Thanks
Add a small jar between the second and third effects for liquid sealing to prevent cross-pressure, and there is no need for U-shaped bends.
What is the purpose of passing the second-effect condensed water into the third-effect?
Flash evaporation to recover as much heat as possible
The function of the U-shaped bend is to ensure that there is no cross-pressure between the two evaporator shell sides and each can work smoothly. According to the given operating pressure, the height is preferably above 5m.
The pressure difference between the second and third effects is 0.05MPa. Regardless of pipeline losses, the "resistance" at the liquid seal or U-shaped pipe should be 0.05MPa. How should the liquid seal be designed?
Thanks. My idea is similar to yours. To achieve a pressure difference of 0.05MPa, the height of the U-shaped tube is about 5m. But in production, I have never seen such a tall U-shaped tube. Have you added a restrictor orifice to the pipeline?
The main purpose of adding a U-shaped bend is to form a liquid seal so that there is no air leakage between the two effects. There is no need to add anything (valves or orifice plates) to the pipeline. The minimum height should be the pressure difference between the effects (0.2-0.15=0.05Mpa, 5 meters). However, in actual design, orifice plates or valves will be added to increase pipeline pressure drop and reduce U-shaped height to meet process requirements.
Thanks for the guidance. While setting the valve/orifice plate to increase the pressure drop, the flow rate will be affected by the valve opening/orifice plate size. For example, the smaller the valve opening, the greater the pressure drop, but the passing flow rate must remain unchanged. How should this be considered?