Purpose of the Vacuum Equipment
The vacuum equipment's function is to remove the incondesible gases that find their way into the vapour stream. The incondensible gases come from the following sources:
- leakage of air into the vessels;
- inherently in the juice;
- air in the heating steam
- air in the cooling water
Quantity of Air to be Removed
A number of authors have expressed an opinion on the the amount of incondensible gas to be removed from the condensers. Sadly, and as is typical there is little agreement among them.
Peter Rein's Cane Sugar Engineering gives guidance for the estimation of the quantities of air to be removed as follows.
- leakage of air [kg/h] = 0.345·V, where V is the volume of the vessel [m3]
- air in the juice [kg/h] = 0.1·mj, where mj is the flow of juice [t/h]
- air in the cooling water [kg/h] = 0.035·mw, where mw is the flow of cooling water [t/h]
- air in the heating steam is not counted
Liquid ring vacuum pumps are commonly used to handle wet gas mixtures (i.e., mixtures containing condensable vapors).
Steam Jet Ejectors
Steam jet ejectors are a simple alternative to mechanical pumps for vacuum - raising applications. The steam jet ejector utilizes high pressure steam to compress low pressure vapours or gases.