Types of Jackets for Reaction Vessel

Types of Jackets for Reaction Vessel

 Different types of jackets used for reaction vessels are:
  1. Dimple jacket.
  2. Plain jacket.
  3. Halfpipe coil jacket.

Plain jacket

It can be termed as an extra covering all around the vessel or on some part of the vessel. The annular space between the vessel wall and jacket wall is used for the circulation of heating or cooling medium. Plain jackets are suitable for small capacity vessels and for operations where the pressure inside the vessel is more than twice the jacket pressure.
It is most suitable where heating is to be done with steam. Jacket height is usually up to the liquid height in the vessel. The jacket can be fabricated in one piece or can be divided into many parts and all parts operating in parallel. For a higher flow segmental jacket is preferred when downstream vapors are used as the heating medium, the plain jacket is preferred.

plain jacket

Spiral baffling can be provided in the jacket. It helps to induce turbulence and increase the heat transfer coefficient. A vessel with a plain jacket and spiral baffles.

Halfpipe coil jacket

The pipe is cut into 1wo pieces and half pipe coil is welded to the vessel wall. It helps to provide high velocity and high turbulence. It also helps to provide strength to the vessel wall and thereby reduce the cost of the vessel. It provides structural rigidity which is an advantage for high-temperature operation. To have the flexibility and high efficiency the half coil jacket can be divided into multiple zones.
Half coil jacket is usually made from carbon steel. Stainless steel. Inconel and other alloys can also be used for the fabrication of half coil jacket. Shows the half coil jacket welded to the shell.

half pipe coil jacket

If jacket pressure is the controlling parameter in estimating vessel wall thickness, then half coil jacket is preferred. These are used for high capacity vessels and where high velocities for circulating hot oils, glycols, etc. is required. In these jackets bypassing, short circulation is completely avoided.

Dimple jacket

It can be fabricated by using thin sheets. It is useful for high jacket pressure operation. Dimple jacket can induce turbulence even at very low flow velocity. It can be used for circulating steam and hot Oil.
A vessel can be provided either a jacket on a limpet coil for heat transfer. Which alternative should be selected depends upon the process requirements, ease of operation and the cost involved. Jacketed vessel ensures more heat transfer as compared to limpet coil but the heat transfer coefficient is less in jacket than in limpet coil. Pressure drop is less in jacket than in limpet coil.

Channeling of heating or cooling medium is not possible in the jacket unless spiral baffles are provided. Pumping cost is less for the jacket as compared to the limpet coil for the same operating pressure jacket requires more thickness than the limpet coil.

dimple jacket

Construction of jacket is easy as compared to limpet coil because, in limpet coil construction lot of cutting, bending, welding is involved. Therefore jacket construction is cheaper than limpet coils.
If the heat transfer areas for jacket and limpet coils are compared it can be seen than the jacket gives more surface area as compared to limpet coils.
A vessel can be provided with a jacket or a limpet coil for heat transfer in the vessel. The selection of any of the two depends upon the requirements of the process, ease of operation and the cost involved.

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