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​Evaporating Pan or Steam Jacketed Kettle


The steam jacketed kettle or evaporating pan is an example of natural circulation evaporators. It is made up of a hemispherical shape with large surface area for the evaporation. The pan can be permanent and emptying is done through the outlet. The pan is mounted in a way that they can be tilted to take out the product. The pans are heated by the steam that comes out of the steam jacket.


The tool that is used in the evaporation process is convection and conduction whereby the heat is conveyed by the pan to the extract. The steam that provides the heat is then transferred to a jacketed kettle where aqueous extracts are placed. The temperature would then rise and the tendency of the molecules to escape to the vapor thus increases and enhances the vaporization of the solvent matter.


The evaporating pan consists of a hemispherical shaped piece that is composed of an inner pan “kettle” and outer pan “jacket”. There are several metals that are used in the construction of the kettle; an example would be copper, which has a good conductivity. Some materials maybe acidic, which can react with the copper and as such tinned copper, may be used. Iron is used as a material for jackets due to its minimum conductivity and to prevent rusting, the iron is tinned or enameled. At the top of the jacket, an inlet is placed to let the steam out; at the bottom area, a vent is added to help condensate leave the pan. Products are discharged at the bottom area as well.

How it Works

Aqueous substances that need to evaporate are placed in the kettle and then steamed. The steam, which is the heat source, is provided through the inlet, the condensate then leave through the outlet.

Smaller amount of content needs to be stirred manually, large volumes on the other hand can be done automatically. In the initial stage, the evaporation rate is rapid.

To prevent fog formation of condensed vapor in the area, good ventilation is important as it helps remove the vapor. Fans may be fitted to allow vapor to clear and prevent condensation in the area.

Depending on the needs, the kettle can be permanent or made to tilt; an example is if 90 liters is needed, then tilt option is available. The bottom part or outlet is then used to collect the products.


  • For concentrated aqueous liquid
  • For concentrated thermos stable liquors (ex. Liquorice extracts)


  • Pans can be constructed for small to large batch operations
  • Easy to operate, maintain and has simple construction
  • Low cost of installation and maintenance
  • Wide variety of materials available (ex. Copper, aluminum, stainless steel)
  • Can be manually stirred and product removal is fast and easy


  • The natural circulation of the product causes poor heat transfer resulting to the solids being deposited and decomposition of the product.
  • The heating surface is limited and lowers with the increase of the pan size.
  • It is not ideal for thermos labile ingredients as the liquid matter is heated constantly at an open atmosphere and there are no guidelines as to the evaporation if under reduced pressure.
  • The pan is open and as such the vapors can move around the room causing discomfort among workers and this also slows down the evaporation process.

LFA does not supply any of this type of equipment. We specialise in Tablet Presses and Capsule fillers but can source equipment not on our website or recommend a supplier.