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In normal multi-stage flash distillation desalination, after
the feedwater has been heated, it sprays through a
nozzle into a gas/liquid separator; the liquid (now
slightly more concentrated) then passes through another
nozzle into a slightly lower pressure gas/liquid
this idea, imagine there are three stages of
gas/liquid separator, called A, B, and C. A is the lowest
pressure and temperature, C is the hottest and highest
Instead of having liquid simply move through a nozzle
from C to B, it moves from C, through an eductor
pump, to a nozzle in B, pulling some of the steam from
A into B.
If there are more than three stages, this can be done
for every adjacent trio of stages.
What does this accomplish, you ask? Because we are, in
effect, compressing the steam that we are pulling from
A to B, we are raising the temperature of that flow of
Since a greater mass of steam condenses at a higher
temperature than a lower temperature, the
temperature of the coolant moving from B to C is
higher... since the coolant is our feedwater, this means
that our boiler will need to add less heat than it
On recycling heat energy
Your Idea mentions some stuff that this one seems to describe, also. [Vernon, Aug 09 2011]
||I thought it said "Educator assisted multi-stage distillation"
||//Since a greater mass of steam condenses at a higher temperature than a lower temperature// eh ?
||Vernon, your vacuum desalting idea is basically a form
of mechanical vapor compression distillation. It works,
but one the mechanical power that's used to run the
vacuum pump can be considered "high grade" power,
which is more valuable than the "low grade" thermal
power that's being used in my idea.
||Basically, one BTU of electricity (to run a vacuum pump
in your idea) costs more money than one BTU of heat (to
supply the seawater boiler in my idea).
||FT, let's imagine that in normal Multi Stage Distillation,
we have stages A, B, and C, as I described in the main
idea; suppose that in each stage, 10 pounds of water
evaporate per minute, and 10 pounds of steam condense
||Now, with the ejector pump added, 10 pounds of water
per minute evaporates in each section, but the
saltwater moving from C to B through the ejector sucks
1 pound of steam per minute from A into B... so 9
pounds of steam per minute condenses in A (the lowest
temperature section), and 11 pounds of steam per
minute condenses in B (the middle temperature
||Those 11 pounds of steam are warmer than those 9
pounds of steam.
||The water that's being used as coolant to cause that
condensation, and which will eventually go to the
boiler, will absorb more high temperature heat in B
(from that extra 1 pound of steam) than it would have
gotten if the ejector hadn't been there.