Potable Water - The Third Way.

Mark Borgerson wrote:
> In article <4709c5f6$0$497$815e3792@news.qwest.net>,
> keithahughes.TakeThisOut@qwest.net says...
> <<SNIP>>
>> You need to get back to the gas law to see where this error lies. You
>> have to *create* the vacuum. That requires a HUGE increase in volume
>> for whatever the initial headspace is. For this to happen you need a
>> much longer tube to start with.
>>
>
> You seem to have missed the fact that I proposed filling the tubes
> completely with water so that the initial head space would be zero.

No, it won't be zero. It can't be. If it is, then you have a solid
liquid stream, and it's just a siphon. You have to have headspace. And
it has to be sufficient to maintain separation of the seawater and
freshwater to prevent contamination when filling the tubes. And it has
to be large enough to prevent percolation carryover when boiling is
initiated.

> At that point you release the pressure on the water and it falls
> to the point where water weight plus vapor pressure equals 1ATm.

A solid liquid loop will not separate into two separate columns. They
have to be separated by a headspace. You can heat the seawater side and
create a headspace by liberating dissolved gases, then let the columns
drop to create vacuum, but you will have contaminated the freshwater side.

>
> At that point, you essentially have two water barometers,
> interconnected at the top. One is salty and warm, and
> one is fresh and cold. Neither need be too much longer
> than 33 feet. The actual height of the water will be
> less than 32 feet by a factor dependent on the temperature
> of the water in the warm side.
>
> The real practical problem lies in the addition of the dissolved
> gases in the seawater to the water vapor in the headspace.
> What we have here is a rather inefficient degassing column.
> I spent a lot of time degassing seawater while working on
> my MS in chemical oceanography. I was trying to measure
> the dissolved hydrogen in seawater, and the oxygen, nitrogen,
> methane, and other gases kept getting in the way!
>
> Getting rid of the disssolved gases in the headspace and
> as bubbles forming on the sides of the tube is going to
> be a major headache.

Not a headache, an impossibility (they're not really dissolved at that
point though) That, and the increase in pressure due to water vapor
will make this an oscillating, self-quenching system. It'll require
more and more heat as the partial pressures of the non-condensables
increases, and the column heights will drop as the pressure goes up,
with the diffusion path increasing the whole time.

Keith Hughes
 >> Stay informed about: Potable Water - The Third Way. 

In article <470a652c$0$505$815e3792@news.qwest.net>,
keithahughes.TakeThisOut@qwest.net says...
> Mark Borgerson wrote:
> > In article <4709c5f6$0$497$815e3792@news.qwest.net>,
> > keithahughes.TakeThisOut@qwest.net says...
> > <<SNIP>>
> >> You need to get back to the gas law to see where this error lies. You
> >> have to *create* the vacuum. That requires a HUGE increase in volume
> >> for whatever the initial headspace is. For this to happen you need a
> >> much longer tube to start with.
> >>
> >
> > You seem to have missed the fact that I proposed filling the tubes
> > completely with water so that the initial head space would be zero.
>
> No, it won't be zero. It can't be. If it is, then you have a solid
> liquid stream, and it's just a siphon. You have to have headspace. And
> it has to be sufficient to maintain separation of the seawater and
> freshwater to prevent contamination when filling the tubes. And it has
> to be large enough to prevent percolation carryover when boiling is
> initiated.
>
> > At that point you release the pressure on the water and it falls
> > to the point where water weight plus vapor pressure equals 1ATm.
>
> A solid liquid loop will not separate into two separate columns. They
> have to be separated by a headspace. You can heat the seawater side and
> create a headspace by liberating dissolved gases, then let the columns
> drop to create vacuum, but you will have contaminated the freshwater side.
>

The head space is generated by the evaporation (or boiling) of some of
the water in a column. It's exactly the same principle that you get it
you fill a closed tube full of mercury and then invert it, placing the
end in a reservoir of mercury. (We call these things barometers.)
You start with no head space, but when you invert it, VOILA!
head space appears as the mercury sinks to a level where the weight
of the mercury equals the atmospheric pressure. You get a much
better vacuum with mercury, since it has a much lower vapor pressure
at room temperature.

A column of water will behave the same way. The column just has
to be much taller.

Some of the historical references on water barometers mention that,
despite precautions, the water in the barometer eventually got
contaminated with dissolved gases and they lost their accuracy.
> >
> > At that point, you essentially have two water barometers,
> > interconnected at the top. One is salty and warm, and
> > one is fresh and cold. Neither need be too much longer
> > than 33 feet. The actual height of the water will be
> > less than 32 feet by a factor dependent on the temperature
> > of the water in the warm side.
> >
> > The real practical problem lies in the addition of the dissolved
> > gases in the seawater to the water vapor in the headspace.
> > What we have here is a rather inefficient degassing column.
> > I spent a lot of time degassing seawater while working on
> > my MS in chemical oceanography. I was trying to measure
> > the dissolved hydrogen in seawater, and the oxygen, nitrogen,
> > methane, and other gases kept getting in the way!
> >
> > Getting rid of the disssolved gases in the headspace and
> > as bubbles forming on the sides of the tube is going to
> > be a major headache.
>
> Not a headache, an impossibility (they're not really dissolved at that
> point though) That, and the increase in pressure due to water vapor
> will make this an oscillating, self-quenching system. It'll require
> more and more heat as the partial pressures of the non-condensables
> increases, and the column heights will drop as the pressure goes up,
> with the diffusion path increasing the whole time.\

I agree with that part---except for the oscillation part. I think
the processes are slow enough and the thermal and physical masses
are high enough that the oscillations will be damped out and you
will see a slow change to equilibrium with little or no overshoot.


Mark Borgerson
 >> Stay informed about: Potable Water - The Third Way. 

N:dlzc D:aol T:com (dlzc) brought forth on stone tablets:
> Dear Richard Casady:
>
> "Richard Casady" <richardcasady.RemoveThis@earthlink.net> wrote in message
> news:47093cad.33079812@news.east.earthlink.net...
>
>>On Sat, 29 Sep 2007 19:44:35 -0700, Keith Hughes
>><keithahughes.RemoveThis@qwest.net> wrote:
>>
>>
>>>Sounds like perpetual motion to me, but I'm
>>>having a hard time envisioning what you're
>>>describing above.
>>
>>Of course you are, since it is basically nonsense.
>>No mention of where the energy comes from.
>
>
> Links were provided. "waste heat" (from what process?) and / or
> "solar heat" have been cited so far. All the vacuum does is move
> boiling temperature closer to ambient. Making more common
> materials suitable for this application.
>
> David A. Smith
>
>


.... and much more importantly, making the process viable with far
lower quality heat.

bob
s/v Eolian
Seattle
 >> Stay informed about: Potable Water - The Third Way. 

Mark Borgerson wrote:
> In article <470a652c$0$505$815e3792@news.qwest.net>,
> keithahughes.RemoveThis@qwest.net says...
>> Mark Borgerson wrote:
>>> In article <4709c5f6$0$497$815e3792@news.qwest.net>,
>>> keithahughes.RemoveThis@qwest.net says...
>>> <<SNIP>>
>>>> You need to get back to the gas law to see where this error lies. You
>>>> have to *create* the vacuum. That requires a HUGE increase in volume
>>>> for whatever the initial headspace is. For this to happen you need a
>>>> much longer tube to start with.
>>>>
>>> You seem to have missed the fact that I proposed filling the tubes
>>> completely with water so that the initial head space would be zero.
>> No, it won't be zero. It can't be. If it is, then you have a solid
>> liquid stream, and it's just a siphon. You have to have headspace. And
>> it has to be sufficient to maintain separation of the seawater and
>> freshwater to prevent contamination when filling the tubes. And it has
>> to be large enough to prevent percolation carryover when boiling is
>> initiated.
>>
>>> At that point you release the pressure on the water and it falls
>>> to the point where water weight plus vapor pressure equals 1ATm.
>> A solid liquid loop will not separate into two separate columns. They
>> have to be separated by a headspace. You can heat the seawater side and
>> create a headspace by liberating dissolved gases, then let the columns
>> drop to create vacuum, but you will have contaminated the freshwater side.
>>
>
> The head space is generated by the evaporation (or boiling) of some of
> the water in a column. It's exactly the same principle that you get it
> you fill a closed tube full of mercury and then invert it, placing the
> end in a reservoir of mercury.

You seem to be forgetting that the whole purpose is to Purify/desalinate
the water. No initial headspace = single process stream = contamination
on the distillate side.

(We call these things barometers.)

Except when we call them Mcleod gauges...

> You start with no head space, but when you invert it, VOILA!
> head space appears as the mercury sinks to a level where the weight
> of the mercury equals the atmospheric pressure. You get a much
> better vacuum with mercury, since it has a much lower vapor pressure
> at room temperature.
>
> A column of water will behave the same way. The column just has
> to be much taller.

True, but you need to keep the context - water purification. The
contamination control features are as crucial to the operational
constraints as are the physical parameters. Thus, you have to *Start*
with headspace. Sure, you could purge the freshwater side until the
contaminants are removed, but by then most, if not all, of your
production will be wasted.

>
> Some of the historical references on water barometers mention that,
> despite precautions, the water in the barometer eventually got
> contaminated with dissolved gases and they lost their accuracy.

Yes, you can only deaerate so far prior to filling. Personally, I've
never seen an absolute pressure water barometer. IME they are primarily
used in an inverted u-tube configuration for DP measurements. BTW,
mercury barometers suffer the same fate, primarily through oxidation of
the mercury, changing the density. Just look at that almost black film
layer on any old barometer.

>
> I agree with that part---except for the oscillation part. I think
> the processes are slow enough and the thermal and physical masses
> are high enough that the oscillations will be damped out and you
> will see a slow change to equilibrium with little or no overshoot.

You may be right, but I doubt it. Unless you control the temperature
versus pressure relationship, which is virtually impossible with any
passive heating process, then I'd expect self quenching would result in
an oscillating system.

Keith Hughes
 >> Stay informed about: Potable Water - The Third Way. 

Jere Lull wrote:
> On 2007-10-08 18:17:58 -0400, Mark Borgerson <mborgerson.RemoveThis@comcast.net> said:
>
<snip>

> Though I consider this whole discussion impractical,

I don't know that I'd call the *discussion* impractical; the device
certainly. Kind of the point of the discussion.

> I haven't seen
> anyone mention that the fresh-water side will be drawn down fairly
> regularly. And, of course, the sea water side will be replenished from
> time to time.
>
> Suck hard enough on the fresh-water side and you get even better
> "vacuum" at the top. (Dissolved gasses are likely to be a problem,
> though.) Cool the fresh-water side and water vapor will condense there
> -- the whole point of the exercise.
>
> Thinking only momentarily on a problem that I have little interest in...
> if the fresh-water side is evacuated to the point that the salt-water
> side is slightly below the top, every once in a while (or perhaps
> often), the fresh-water side will be empty and only the
> previously-dissolved gasses evacuated.
>
> The required evacuation pumps and one-way valves sound like the problem
> at the moment.

The whole exercise was to get a passive system. If you're going to add
a vacuum pump, then you just provide continuous evacuation on the
freshwater side, using a demister that drains into the freshwater pool,
to separate the water vapor from the non-condensables. But if you
accept the need for a pump, why use this rather byzantine approach at all?


Keith Hughes
 >> Stay informed about: Potable Water - The Third Way. 

In article <470ad1d9$0$499$815e3792@news.qwest.net>,
keithahughes RemoveThis @qwest.net says...
> Mark Borgerson wrote:
> > In article <470a652c$0$505$815e3792@news.qwest.net>,
> > keithahughes RemoveThis @qwest.net says...
> >> Mark Borgerson wrote:
> >>> In article <4709c5f6$0$497$815e3792@news.qwest.net>,
> >>> keithahughes RemoveThis @qwest.net says...
> >>> <<SNIP>>
> >>>> You need to get back to the gas law to see where this error lies. You
> >>>> have to *create* the vacuum. That requires a HUGE increase in volume
> >>>> for whatever the initial headspace is. For this to happen you need a
> >>>> much longer tube to start with.
> >>>>
> >>> You seem to have missed the fact that I proposed filling the tubes
> >>> completely with water so that the initial head space would be zero.
> >> No, it won't be zero. It can't be. If it is, then you have a solid
> >> liquid stream, and it's just a siphon. You have to have headspace. And
> >> it has to be sufficient to maintain separation of the seawater and
> >> freshwater to prevent contamination when filling the tubes. And it has
> >> to be large enough to prevent percolation carryover when boiling is
> >> initiated.
> >>
> >>> At that point you release the pressure on the water and it falls
> >>> to the point where water weight plus vapor pressure equals 1ATm.
> >> A solid liquid loop will not separate into two separate columns. They
> >> have to be separated by a headspace. You can heat the seawater side and
> >> create a headspace by liberating dissolved gases, then let the columns
> >> drop to create vacuum, but you will have contaminated the freshwater side.
> >>
> >
> > The head space is generated by the evaporation (or boiling) of some of
> > the water in a column. It's exactly the same principle that you get it
> > you fill a closed tube full of mercury and then invert it, placing the
> > end in a reservoir of mercury.
>
> You seem to be forgetting that the whole purpose is to Purify/desalinate
> the water. No initial headspace = single process stream = contamination
> on the distillate side.
>
> (We call these things barometers.)
>
> Except when we call them Mcleod gauges...
>
> > You start with no head space, but when you invert it, VOILA!
> > head space appears as the mercury sinks to a level where the weight
> > of the mercury equals the atmospheric pressure. You get a much
> > better vacuum with mercury, since it has a much lower vapor pressure
> > at room temperature.
> >
> > A column of water will behave the same way. The column just has
> > to be much taller.
>
> True, but you need to keep the context - water purification. The
> contamination control features are as crucial to the operational
> constraints as are the physical parameters. Thus, you have to *Start*
> with headspace. Sure, you could purge the freshwater side until the
> contaminants are removed, but by then most, if not all, of your
> production will be wasted.

With the proper placement of the check valves, I think you could
start with the initial boiling happening in the freshwater side---
after all it is going to boil at a lower temperature.

The procedure might look like this:

1 Pump both fresh and salt water to near the top.
2. Shut offf the salt water side pump, but keep the
tube closed at the bottom.
3. Pump a bit more fresh water into the tube---where
it overflows to the saltwater side, displacing
the rest of the air out the check valve.

You now have no air in the tube and a small layer of
fresh water on top of the salt water.

4 Release the pressure at the bottom, and the fresh
water at the top will boil and create your head space
with little or no contamination of the freshwater
side.

5 Apply your heat differential and remove distilled
fresh water as it overflows the reservoir at the
bottom.

This should work until the dissolved gas problem lengthens
the vapor path to the point where you have to start over
at step 1.


>
> >
> > Some of the historical references on water barometers mention that,
> > despite precautions, the water in the barometer eventually got
> > contaminated with dissolved gases and they lost their accuracy.
>
> Yes, you can only deaerate so far prior to filling. Personally, I've
> never seen an absolute pressure water barometer. IME they are primarily
> used in an inverted u-tube configuration for DP measurements. BTW,
> mercury barometers suffer the same fate, primarily through oxidation of
> the mercury, changing the density. Just look at that almost black film
> layer on any old barometer.

That is mostly due to contaminants trapped in the glass and impurities
in the mercury. Production barometers didn't use glass that was
heated with a vacuum to remove contaminants.
>
> >
> > I agree with that part---except for the oscillation part. I think
> > the processes are slow enough and the thermal and physical masses
> > are high enough that the oscillations will be damped out and you
> > will see a slow change to equilibrium with little or no overshoot.
>
> You may be right, but I doubt it. Unless you control the temperature
> versus pressure relationship, which is virtually impossible with any
> passive heating process, then I'd expect self quenching would result in
> an oscillating system.

What do you mean by "self-quenching"?


Mark Borgerson
 >> Stay informed about: Potable Water - The Third Way. 

Mark Borgerson wrote:

<SNIP>

> With the proper placement of the check valves, I think you could
> start with the initial boiling happening in the freshwater side---
> after all it is going to boil at a lower temperature.

Well, except that 1) unless you fill the entire apparatus with fresh
water (ignoring for a moment how much fresh water that might take, and
how much system capacity is lost in re-distilling the fresh water), you
haven't eliminated the carryover contamination issue, since you still
have a contiguous water stream, and 2) the freshwater side of the system
is configured for *cooling* and the seawater for heating (passive system
remember), so boiling will always be initiated on the seawater side.
>
> The procedure might look like this:
>
> 1 Pump both fresh and salt water to near the top.
> 2. Shut offf the salt water side pump, but keep the
> tube closed at the bottom.
> 3. Pump a bit more fresh water into the tube---where
> it overflows to the saltwater side, displacing
> the rest of the air out the check valve.

And where is the barrier layer that keeps salt from moving into the
freshwater?
>
> You now have no air in the tube and a small layer of
> fresh water on top of the salt water.

But it won't stay that way. As soon as you begin to heat the seawater,
you'll almost certainly have seawater rising into the fresh (do to the
density change with heating) before you get boiling going on.
>
> 4 Release the pressure at the bottom, and the fresh
> water at the top will boil and create your head space
> with little or no contamination of the freshwater
> side.

Yeah, but "little" is not the goal. And you'd have to quantify that
"little" empirically, since there are many factors that contribute to
the process.
>
> 5 Apply your heat differential and remove distilled
> fresh water as it overflows the reservoir at the
> bottom.
>
> This should work until the dissolved gas problem lengthens
> the vapor path to the point where you have to start over
> at step 1.

Again, the design complexity involved in being able to heat the fresh
side to initiate the boiling there *first*, and then switching to
cooling mode when there is sufficient column separation puts paid to any
thoughts of this being a simple system. And then, you have a very
complex, and Horribly inefficient system.

There are lots of ways that you could make the system work, but why?
The *only* feature this concept has going for it to start with is
simplicity, and basically a passive (save for some human work input) system.

Keith Hughes
 >> Stay informed about: Potable Water - The Third Way. 

On Mon, 08 Oct 2007 10:13:17 -0700, Keith Hughes
<keithahughes.TakeThisOut@qwest.net> wrote:

>>...I proposed filling the tubes
>> completely with water so that the initial head space would be zero.

>No, it won't be zero. It can't be. If it is, then you have a solid
>liquid stream, and it's just a siphon.
....
>A solid liquid loop will not separate into two separate columns.
....
>Keith Hughes

Perhaps it would be better for you to check what is the maximal rise
(head) of a syphon. Can you guess what it might be?

Brian Whatcott Altus OK
 >> Stay informed about: Potable Water - The Third Way. 

Brian Whatcott wrote:
> On Mon, 08 Oct 2007 10:13:17 -0700, Keith Hughes
> <keithahughes.RemoveThis@qwest.net> wrote:
>
>>> ...I proposed filling the tubes
>>> completely with water so that the initial head space would be zero.
>
>> No, it won't be zero. It can't be. If it is, then you have a solid
>> liquid stream, and it's just a siphon.
> ...
>> A solid liquid loop will not separate into two separate columns.
> ...
>> Keith Hughes
>
> Perhaps it would be better for you to check what is the maximal rise
> (head) of a syphon. Can you guess what it might be?

Uhmmm, maybe you should follow the thread. If you *pump* the water up
the columns, evacuating the headspace as you go, until the columns meet,
you can siphon pretty much any height you want. Until outgassing
creates a headspace. If the bases of the columns are at differing
heights, you have a siphon until that happens.

Keith Hughes
 >> Stay informed about: Potable Water - The Third Way. 

In article <470acd29$0$499$815e3792@news.qwest.net>,
keithahughes.RemoveThis@qwest.net says...
> Brian Whatcott wrote:
> > On Mon, 08 Oct 2007 10:13:17 -0700, Keith Hughes
> > <keithahughes.RemoveThis@qwest.net> wrote:
> >
> >>> ...I proposed filling the tubes
> >>> completely with water so that the initial head space would be zero.
> >
> >> No, it won't be zero. It can't be. If it is, then you have a solid
> >> liquid stream, and it's just a siphon.
> > ...
> >> A solid liquid loop will not separate into two separate columns.
> > ...
> >> Keith Hughes
> >
> > Perhaps it would be better for you to check what is the maximal rise
> > (head) of a syphon. Can you guess what it might be?
>
> Uhmmm, maybe you should follow the thread. If you *pump* the water up
> the columns, evacuating the headspace as you go, until the columns meet,
> you can siphon pretty much any height you want. Until outgassing
> creates a headspace. If the bases of the columns are at differing
> heights, you have a siphon until that happens.

If you pump both the fresh and salt water to the top of the U-Tube,
then switch from the pumps to the reservoirs at the bottom,
you won't get a siphon. The boiling of water at the top will
break the siphon action.

Mark Borgerson
 >> Stay informed about: Potable Water - The Third Way. 

On Mon, 08 Oct 2007 05:33:39 -0700, Keith <keith77720032003 DeleteThis @yahoo.com>
wrote:

>Boiling Point Elevation
>The boiling point of a solution is higher than that of the pure
>solvent. Accordingly, the use of a solution, rather than a pure
>liquid, in antifreeze serves to keep the mixture from boiling in a hot
>automobile engine.....
>From:
>http://www.chemistryexplained.com/Ce-Co/Colligative-Properties.html


Actually, no. Ethylene glycol in its pure liquid state boils near
200 degC
http://www.dow.com/ethyleneglycol/about/properties.htm

It is usually cut to 50% dilution for use as an antifreeze.

Brian Whatcott Altus OK
 >> Stay informed about: Potable Water - The Third Way. 

Brian Whatcott wrote:
> On Mon, 08 Oct 2007 05:33:39 -0700, Keith <keith77720032003 DeleteThis @yahoo.com>
> wrote:
>
>> Boiling Point Elevation
>> The boiling point of a solution is higher than that of the pure
>> solvent. Accordingly, the use of a solution, rather than a pure
>> liquid, in antifreeze serves to keep the mixture from boiling in a hot
>> automobile engine.....
>> From:
>> http://www.chemistryexplained.com/Ce-Co/Colligative-Properties.html
>
>
> Actually, no. Ethylene glycol in its pure liquid state boils near
> 200 degC
> http://www.dow.com/ethyleneglycol/about/properties.htm
>
> It is usually cut to 50% dilution for use as an antifreeze.
>
> Brian Whatcott Altus OK

Since he used the term "solvent", the assumption, at least on my end, is
that he's talking about a solvent/solute system, not a solution of
miscible liquids.

Keith Hughes
 >> Stay informed about: Potable Water - The Third Way. 

In article <tudlg3lp905g7kg21s9qaenp9jtc8d6b74 DeleteThis @4ax.com>, betwys1
@sbcglobal.net says...
> On Mon, 08 Oct 2007 05:33:39 -0700, Keith <keith77720032003 DeleteThis @yahoo.com>
> wrote:
>
> >Boiling Point Elevation
> >The boiling point of a solution is higher than that of the pure
> >solvent. Accordingly, the use of a solution, rather than a pure
> >liquid, in antifreeze serves to keep the mixture from boiling in a hot
> >automobile engine.....
> >From:
> >http://www.chemistryexplained.com/Ce-Co/Colligative-Properties.html
>
>
> Actually, no. Ethylene glycol in its pure liquid state boils near
> 200 degC
> http://www.dow.com/ethyleneglycol/about/properties.htm
>
> It is usually cut to 50% dilution for use as an antifreeze.
>
True---when mixing liquids, the boiling point is somewhere between
the boiling points of the two.

Radiators and cooling systems are pressurized so that the system
can have an elevated boiling point.


Mark Borgerson
 >> Stay informed about: Potable Water - The Third Way.