Explain the type of multiple effect evaporator feed arrangement used for handling viscous liquid.

Explain the type of multiple effect evaporator feed arrangement used for handling viscous liquid.
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1 Answer

Answer :

Backward feed arrangement 

If the liquid is very viscous, then we have to adopt backward feed arrangement. In this arrangement, the feed solution and vapour flow is in opposite direction. Fresh feed is admitted to the last effect and steam to the first effect.

Need pump for moving the solution from effect to effect. Solution is heated in each effect , result in better economy. The most concentrated liquor is in the first effect where temperature is highest and viscosity is lowest , Thus high overall coefficient. Maintenance charges and power cost are more. Not very common as it need pump. At low values of feed temperature higher economy.

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