Why are air coolers more commonly used at the top of towers and split-flow exchangers more commonly used at the bottom in the petrochemical industry?
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As the title suggests, I’ve noticed that several projects use similar designs: air cooling is commonly employed for the condenser at the top of the tower, while split-type heat exchangers are often used for the reboiler at the bottom
Compared to water cooling, air cooling is more energy-efficient and saves water. It dissipates heat through exhaust gases, so it is only suitable for installation at the top layer of the frame. It is generally used for cooling or condensation purposes. In cases where the material exiting from the bottom of the tower needs to be cooled, and there is sufficient power to lift it to the top layer of the frame, air cooling can also be utilized. The reboiler at the bottom of the tower must be heated by a heat source; heat exchangers can only be used.
I mean, why are these used more in the petrochemical industry? What are the differences between the petrochemical industry and other chemical industries?
The petrochemical industry has developed early and is quite mature; there is a wealth of practical experience regarding equipment and processes. This is why, in so many projects, the equipment configurations are all the same
Are you saying that air cooling is first used in the petrochemical industry, while other chemical industries have not yet begun to adopt it gradually?
If I remember correctly, air coolers were indeed developed for petrochemical projects and were first applied in such projects.
Is it because petrochemical processes require high energy consumption? When using air cooling, switching to water cooling increases equipment costs and energy usage. However, in the case of fine chemicals, such problems do not exist, so there is no need to use water cooling?
Well, that’s basically the consideration: with such large refining capacities, energy consumption is extremely high. Areas in the north that suffer from water shortages also face problems, as there are limits set on water usage. Fine chemicals generally cannot be produced on a large scale, so there is no need to use air cooling.
Air cooling is more energy-efficient and water-saving, making it suitable for projects located in areas with limited water resources. It is usually installed on the top layer of the frame, and is generally suitable only for cooling or condensation. The reboiler at the bottom of the tower requires a heat source for heating, and only heat exchangers can be used. The specific selection of a heat exchanger requires comprehensive consideration based on the properties of the process medium, as well as material and energy balances.
Air cooling is more effective for heat dissipation when installed at the top of the tower. Other types of heat exchangers facilitate maintenance and material transfer at the bottom.