Types of Jackets for Reaction Vessel
Types of Jackets for Reaction Vessel :- Different types of jackets used for reaction vessels are:
- Dimple jacket.
- Plain jacket.
- Half pipe 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 circulation of heating or cooling medium. Plain jackets are suitable for small capacity vessels and for operations where 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. Jacket can be fabricated in one piece or can be divided into number of parts and all parts operating in parallel. For higher flow segmental jacket is preferred when downstream vapors are used as heating medium, plain jacket is preferred.
Spiral baffling can be provided in the jacket.. It helps to induce turbulence and increase the heat transfer coefficient. A vessel with plain jacket and spiral baffles.
Half pipe coil jacket
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 vessel. It provides structural rigidity which is an advantage for high temperature operation. To have 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, monel. Inconel and other alloys can also be used for the fabrication of half coil jacket. Shows the half coil jacket welded to shell.
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 by passing, 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 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 jacket, unless spiral baffles are provided. Pumping cost is less for jacket as compared to limpet coil for the same operating pressure jacket requires more thickness than limpet coil.
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 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.
