Part one of our discussion about distillation focused on the internals of the distillation tower. While distillation refers to how the separation of liquids by boiling point, this doesn’t include how the vapor reaches the top of the tower, which is done by using reboilers.
Essentially, a reboiler is a heat exchanger or a fired heater, providing heat that is needed for the distillation column to perform its function. Heat is often provided through shell and tube heat exchangers that are typically filled with steam or a thermal fluid (Hot Oil). Some systems receive their heat from a gas fired heater on the feed to distillation unit.
Learn more about the several different types of reboilers available for use and find out which one is right for your distillation process.
Kettle reboilers are the easiest type of reboiler design you could use for your distillation process. A kettle reboiler is designed to allow a heating fluid to pass through tubes that are covered in the liquid you want to be distilled.
As the liquid heats up and boils, it is sent to the distillation column and condensed by cooling liquid. Any vapor that is created then passes up to be collected and the liquid byproduct drops to the bottom of the kettle making its way back to the tubes.
Kettle reboilers can sometimes maintain pressure head on their own depending on the temperature of the process. If the temperature is inadequate, your kettle reboiler may need to be fitted with a pump or some other way of getting the condensed liquid phase back to the tubes.
A more complex type of reboiler is the thermosyphon, which comes in two primary types: vertical and horizontal. The type of thermosyphon that is used will depend on the orientation of the heating fluid tubes and the flow of the liquid. Aside from that, operative principles are the same as with kettle reboilers.
Thermosyphons operate by passing liquid from the bottom of the tower to the reboiler by gravity, which is then passed through the inside of the heated tubes in order to create a two-phase liquid-vapor product. The liquid-vapor product is transferred through a pipe back into the tower, where separation occurs before the non vaporized liquid is passed back into the reboiler.
Thermosyphons are also able to provide their own liquid head, meaning that the use of pumps is usually not necessary.
Pump Around Reboiler
Pump around reboilers are forced circulation heat exchangers that create two phase flow on the outlet that goes back to the column and creates the necessary vapor traffic in the column.
Leverage COSTELLO’s Expertise for Your Reboiler
Do you have the engineering expertise needed to design your process reboiler? If not, then let COSTELLO do the work for you. Our team of experts has years of experience with reboiler design and process simulation. We can help ensure that your design is the best fit for your process and business needs.
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If you like this series read part 1 here!