Forced circulation Evaporator
Forced Circulation Evaporators are short tube evaporators and are ideally used when the boiling of feed liquid on the heating surfaces is to be avoided due to the salting and fouling characteristics of the liquid. Hence in these evaporators the flow velocity in the tubes is kept very high.
The forced circulation system is a combination of a heat exchanger, for product heating, and a flash vessel. A high flow pump circulates the solution to be evaporated inside the heater where it is heated a few degrees over the boiling temperature by steam or another heating fluid. The heated solution then evaporates by flashing in the vessel.
In forced circulation evaporators the liquid is circulated at high velocities in the tubes of the heat exchanger while steam is provided in the chest. This liquid is partially evaporated when the pressure is reduced in the vapour-liquid separator to the corresponding boiling temperature. High volume , low head axial flow circulation pumps are used for recirculating the crystal laden slurry in the evaporator and hence the operation of this evaporator is independent of the temperature difference.
In the crystallizing operation crystals can be separated from the crystallizing slurry by adjusting the velocity of the circulating stream. Forced circulation evaporators are ideal for handling liquors with high viscosity or which have a tendency to salt and scale during evaporation.
Features:
- Suitable for widest variety of evaporator applications.
- Ideal for crystallizing operation.
- High heat transfer coefficients.
- Positive circulation.
- Freedom from salting, scaling and fouling.
- Suitable for corrosive and viscous solutions.
