What factors need to be considered when converting the two reboilers in a distillation tower into one?
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The distillation column was originally designed with two reboilers; one of them had to be replaced temporarily with a larger reboiler due to equipment corrosion. After the replacement, it was found that the larger reboiler alone was sufficient to meet the temperature requirements of the material. I would like to ask the experts here: if only one large reboiler is used, will it affect the mass transfer as intended in the original design? Could there be delays in the flow of materials at the bottom of the tower, or dead zones?
A reboiler is what is commonly referred to as a “heat exchanger”. This issue is primarily considered in terms of the heat exchange area. It is acceptable to consider only the heat exchange area. If uniform heat transfer of the material is considered, it is necessary to examine the actual conditions of the material on site to see whether such a possibility exists. Typically, when a reboiler operates at the bottom of a tower, it is completely submerged in liquid. If the liquid does not have a high viscosity, it circulates upward and downward within the reboiler, resulting in a convective flow with heat moving upward and cold fluid moving downward. So, the issue of dead corners need not be considered. Additionally, are two reboilers installed with the aim of ensuring continuous operation in case one is damaged and replacement cannot halt production? One as a backup and one in use? ? For reference.
Take a look at the drawings: do the inlets of the two reboilers designed originally come from one location in the bottom of the tower or from two different locations? If it comes from one location, it might be designed with one in use and one as a backup; if it comes from two locations, the load of two reboilers may be required to meet production needs. Now, one unit is sufficient to meet those needs – does this mean that the production load has decreased? Or has the quality of the materials changed? Have the distillation conditions changed? There are many reasons.
It is not an outlet, as one of them has been replaced with a reboiler having a larger heat exchange area. It is roughly equivalent to the capacity of the original two small reboilers.
It was changed from two small ones to one large and one small; the small one developed problems and can no longer be used, so currently only the large one is in use. There is concern that mass transfer will be affected.