Principles of reboiler operation
In total, three main types of reboilers may be distinguished according to their principle of operation. The first one is a thermosyphon reboiler. The factor there is the difference in the densities of working fluids at different temperatures. This means that circulation occurs naturally, without the use of pumps or other additional equipment. This principle is the most economical and not expensive, but not suitable for fluids with high viscosity. Besides, it needs additional space for installation at the required elevation marks so that sufficient pressure is created to ensure circulation. And at the manufacturing site, sometimes there may not be extra free space for this kind of equipment.
The second type is a forced circulation reboiler. Here the flow of working fluids is ensured by pumps. For this reason, it is possible to work with almost any product. However, there are additional costs for secondary equipment.
The third type is a steam space reboiler. Such a heat exchanger is always immersed in the liquid of towers. When the cooling agent is supplied to the unit, the surrounding liquid instantly begins to evaporate. This provides a high rate of vaporization. Besides, a similar type of reboilers may operate under vacuum. But the low heat transfer coefficient and the dirt retention of oil products make this type of reboiler very unpopular.
