3 replies to this topic

[mykid]

Hi Anyone has any guideline in designing the kettle (shell) for an electric reboiler? As this is an electric heater, the heating elements are normally supplied by a separate vendor, and the kettle or the shell side is considered as the pressure vessel. As such, the dimension of the kettle with overflow weir is to be supplied by process?

I have the dimention of the heating elements and the quantity, but would like to find out if there is any guideline in designing the vapour space, location of overflow weir. The volume in the overflow compartment can be based on the residence time requirement. And the flange connected to the electric heater can be estimated based on the quantity of elements required.

Appreciate for any input that may help.. thanks

[djack77494]

You could probably contact a vendor like Chromalox or Gaumer and get a complete design. THis is basically a kettle type heat exchanger with the tubes being electric.

[Zauberberg]

Hello mykid,

Good references for kettle reboiler design can be found in D. Kern's "Process heat transfer" and "Chemical engineering" by Coulson/Richardson.

Heating element will be designed based on maximum allowable heat flux for a given service, as it is the case in pool boiling applications.

Best regards,

[bmk]

The vapour space must be sufficiently large to accomodate any foaming in the boiling liquid, boliling liquid entrainment.

The weir height is such that the inserted heating elements are immersed completely under the liquid.

The surface area of heaters is determined by the electric flux rated for the type of liquid to be heated. For highly viscous liquids like furnace oil it is around 8 watts/sq.in and for normal liquids it is 14 w/sq.in. The heater suppliers design the wattage/length of the heaters on this basis and we have to select the dimensions of the vessel accordingly. I suggest you to use cartridge heaters enclosed in side SS304 pipes for your purpose. I have used them for a reboiler cum cracker for castor oil at 350 deg C. thanks.