|
Multi-Effect Evaporation is
an important procedure adopted to economize the consumption of
energy.
Multi Effect Evaporators are the instruments in which steam
from an outside source is condensed in the heating element of
first effect. The boiling temperature at which the first effect
operates is high enough so that the evaporated water can serve
as the heating medium for second effect. The vapors so formed
are then sent to a condenser if it is a double effect
evaporator.
The feed for the multi-effect type evaporator is generally
transferred from one effect to another. This leads to the
ultimate product concentration to reach only in the one effect
of evaporator.
|
MULTI EFFECT EVAPORATORS |
There are two feed operations - backward feed
and forward feed operations. A brief explanation of these
operations:
In the backward operation, the raw feed enters the last (coldest)
effect and the discharge from this effect becomes a feed for the
next to last effect. This technique of evaporations is advantageous,
in case the feed is cold, as much less liquid must be heated to the
higher temperature existing in the early effects. The procedure is
also used if the product is viscous and high temperatures are
required to keep the viscosity low enough to produce good heat
transfer coefficients.
In the case of a forward feet
operation, the raw feed is introduced in the first effect and is
passed from effect to effect parallel to steam flow. The product is
withdrawn from the last effect. This procedure is highly
advantageous if the feed is hot. The method is also used if the
concentrated product may be damaged or may deposit scale at high
temperature. |
