Using moderately low pressure for evaporation, steam, and distillation

[Dave]

Had a look at graphs of boiling points of ethanol and water. Looks like
ethanol boils at about 50 Celsius at 0.3 atmospheres, which shouldn't be
that difficult to get. Also have a feeling that at that pressure
standard materials and construction should be OK, plate glass, mild
steel, motor trade quality gaskets, aluminium etc.

There is this page:
https://en.wikipedia.org/wiki/Vacuum_distillation

So really asking are distillers using low pressure to make it easier to
get the ethanol boiled off. Also is there a low pressure need for
desalination? Solar heated flat pond, with condensate collector on the
glass roof at normal temperatures. Might be more energy efficient than
reverse osmosis.

Not seeing a use for a low temperature steam (ethanol vapour) engine
generator since solar PV is so good, but would be nice to have one ready
to roll, in case of supply chain issues - 100% locally maintainable.

Since the science is well known, there must be reasons why not being
widely used, but the energy price may have changed the economics. Plus
with the motor trade shifting there will be a lot of production capacity
which might otherwise might go to waste e.g. the fuel pump factories.

[Dave]

On 06/07/2022 08, Dave wrote:
...

Post by Dave
Since the science is well known, there must be reasons why not being
widely used, but the energy price may have changed the economics. Plus
with the motor trade shifting there will be a lot of production capacity
which might otherwise might go to waste e.g. the fuel pump factories.

Just realised this may be one of the reasons why they want to replace
gas boilers with air to water heat pump heating systems.

Also fans and vacuum pumps have their own noises. Cars and car exhausts
have had over a century of work to get a nice acoustic profile -
generally no annoying whistle or hum. Unfortunately HVAC fans and pumps
come from a different tradition - industrial not domestic. Annoying
noise is not just about decibels.

[Dave]

On 06/07/2022 08, Dave wrote:
.

Post by Dave
Not seeing a use for a low temperature steam (ethanol vapour) engine
generator since solar PV is so good, but would be nice to have one ready
to roll, in case of supply chain issues - 100% locally maintainable.

There are options to create a no moving parts solar generator, with
using one of the new relatively safe low melting point alloys. e.g.
Field's metal 62 Celsius. Kind of bubble the ethanol vapour through a
pool of metal with a siphon tube exit, so when the vapour leaves it has
to force out some metal up through a fountain, and the current is
captured by a magnetohydrodynamic generator. Wouldn't say it would do
much more than charge a mobile device, with a 0.25m^2 surface in the
sun, but it should keep working for 40-50 years, if you can get ethanol
from somewhere.

Came across this:
https://www.ijsrp.org/research-paper-0613/ijsrp-p18106.pdf
but not sure what is new. The basics were well known and taught in the
1980s.

[Dave]

Had a look at graphs of boiling points of ethanol and water.  Looks like
ethanol boils at about 50 Celsius at 0.3 atmospheres, which shouldn't be
that difficult to get.  Also have a feeling that at that pressure
standard materials and construction should be OK, plate glass, mild
steel, motor trade quality gaskets, aluminium etc.
https://en.wikipedia.org/wiki/Vacuum_distillation
So really asking are distillers using low pressure to make it easier to
get the ethanol boiled off.  Also is there a low pressure need for
desalination? Solar heated flat pond, with condensate collector on the
glass roof at normal temperatures. Might be more energy efficient than
reverse osmosis.
Not seeing a use for a low temperature steam (ethanol vapour) engine
generator since solar PV is so good, but would be nice to have one ready
to roll, in case of supply chain issues - 100% locally maintainable.
Since the science is well known, there must be reasons why not being
widely used, but the energy price may have changed the economics. Plus
with the motor trade shifting there will be a lot of production capacity
 which might otherwise might go to waste e.g. the fuel pump factories.

There are ways, I believe, easy ways to get a vacuum with a water head.
The problem that it is like 10m you need. I think you can blend
materials, but mercury is too toxic, but gallium could be used, as it
melts about 30 Celsius and is 5 times denser than water. You should
therefore be able to get a still in a regular room less than 3 high.
Expect this was done, with mercury in the 1870s or so, but zero or next
to zero heating a requirement for bio-ethanol extraction, seems like it
is worth having a rummage in the archive.