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Sun Dec 17, 2017, 08:32 PM

A Nice Discussion of the Use of Desalination Brines for the Production of Caustic Soda (NaOH).

Many years ago, in this space, back when I was still a fan of so called "renewable energy," I wrote a brief discussion of the potential use of California's Salton Sea as a tool for energy recovery and desalination.

That post is here: I offer a crazy energy idea about which I've fantasized: The Salton Sea.

Many of my energy ideas have changed since I wrote that piece 12 years ago. This was, for example, before the planetary community invested trillions of dollars in so called "renewable energy," dominated by the useless solar and wind industries.

In November of 2005, the mean concentration of the dangerous fossil fuel waste as reported at the Mauna Loa carbon dioxide observatory was 378.29 ppm. In November of 2016, the most recent posted monthly mean posted there, the concentration was 405.14 ppm.

The average for all year to year monthly comparison figures recorded as increases in the 20th century was 1.30 ppm/year. Since November of 2005 to November of 2017, the same type of average is 2.24 ppm/year.

So called "renewable energy" is a grotesque failure. It has not worked; it is not working; it will not work, if the goal is to address climate change rather than to post "feel good" stuff on the internet about how wonderful solar and wind are and how wonderful it is to subsidize the billionaire Elon Musk to the tune of billions of dollars because he's so, um, "green."

However this may be, and however much I may have changed my mind about so called "renewable energy" since 2005, I am still very concerned about our absolute indifference on this planet to address climate change. Now, as the end of my life approaches filled with existential guilt about what my generation is leaving for future generations, I am very much trying to spend some portion of my time to thinking about ways to remove carbon dioxide from the atmosphere, in other words, how future generations might, to whatever extent possible, clean up the planetary superfund site with which we've left them.

Once consequence of climate change will almost certainly involve access to clean and fresh water. We have seen this in many places on this planet, most graphically and recently for those Americans who give a shit - this would leave out anyone involved with the Trump crime family - in California, where I used to live decades ago, and where I used to think all the time about water.

It does seem to me that the only approach to addressing this issue in places like California, and for that matter in places where water supplies depend on glaciers, which they do for billions of people will involve seawater desalination.

Desalination is not, in any way, environmentally benign, however. One of the most important issues involved is of course, energy. Unless clean carbon free sustainable energy is available - I never tire of pointing out that in my opinion only nuclear energy meets this criteria - all desalination schemes will be counter productive.

The other problem with desalination concerns the resulting brine. Most schemes for desalination return the concentrated brine directly to local waters. On a grand scale this has the potential for further environmental destruction not only because of the impact on local ecosystems, but also on the further destabilization of oceanic salt gradients, which in turn further destabilize climatic and temporal weather.

Although I still favor, for certain reasons, the same thing I proposed in 2005 for the Salton Sea, formally reduced pressure distillation, over all in the scientific literature, at least in my overall impression, much of the discussion has focused on membrane separation.

A very nice overview of a potential solution for the brine problem (with some impact on the energy problem as well) was recently published in the wonderful scientific journal ACS Sustainable Chemistry and Engineering by scientists out of MIT.

The paper is here: Utilization of Desalination Brine for Sodium Hydroxide Production: Technologies, Engineering Principles, Recovery Limits, and Future Directions (John Leinhard V, et al, ACS Sustainable Chem. Eng., 2017, 5 (12), pp 11147–11162)

All of the energy ideas I've had in my lifetime involve the utilization of by products of processes - often referred to as "waste" in our common parlance - as starting materials or tools to accomplish other tasks. (Mostly this involves material by products but also can include heat.) This is why this paper so pleases me. It proposes to use a waste product (brine) to make another value added product (caustic soda, NaOH).

The introduction to the paper addresses this nicely:

Environmental and economic factors have long motivated interest in reducing the amount of brine discharged back into the ocean by seawater desalination plants. Modern designs for brine outfalls can limit adverse environmental impacts to “tens of meters” from the discharge source(1, 2) but are high cost.(3) An emerging class of solutions, broadly titled waste-to-resource, aim to reduce brine discharge by transforming it into useful compounds.(4-7)

Many previous such studies focus on recovering salts, of which the largest by mass is sodium chloride. But in many countries, NaCl exists in abundant, cheap supply as rock salt or brine, meaning any competing source must be extremely low cost. [The US Geological Survey reports average US rock salt and brine prices ranging from 38–50 USD/ton and 8–9 USD/ton, respectively, from 2011–2015.(8)] Its chemical derivatives, primarily soda ash, caustic soda (“caustic”), and chlorine, however, may be much higher value. Nearly 30% of NaCl sold in the US(8) is used as a feedstock in the chlor-alkali process to manufacture the most common of these at large scale: NaOH and Cl2. Also, NaOH is frequently used within the desalination plant itself.

Consequently, producing NaOH from seawater reverse osmosis (SWRO) brine for reuse within the SWRO facility has the potential to benefit environment and plant economics. By replacing NaOH manufactured off-site using chlor-alkali by an on-site, lower-energy process (e.g., one producing HCl as a byproduct instead of Cl2), the environmental and economic footprints of NaOH generation and transport are reduced. By diverting a portion of the brine discharge, less salt flows into the ocean, resulting in lower salt concentrations around brine discharge ports, which lessen the plant’s impact on marine life. Further, since both benefits scale with the amount of NaOH produced, any other nearby consumers of the NaOH produced would serve to increase the positive environmental and economic impacts of this technology.


In the following text, the authors point to the use of NaOH within a desalination plant, albeit in this case of a "SWRO" plant (Seawater Reverse Osmosis) plant.

They write:

Caustic soda has myriad uses both internal and external to the desalination plant. Internally, treating seawater feed with caustic soda increases the pH. At higher pH, several compounds are better rejected by the RO membrane. Around pH 9, the better-rejected borate anion B(OH)4– supplants boric acid as the dominant aqueous boron species.(11) The dissolved silica system behaves similarly, with the dominant SiO(OH)3– and SiO2(OH)22– species above pH 9 yielding better silica rejection,(12) and above pH 8, dissolved inorganic carbon exists as bicarbonate and free carbonate, which are better rejected than aqueous carbon dioxide.(13) Evidence also shows reduced organic fouling at high pH.(14) Finally, caustic soda is an ingredient in cleaning solutions to remove organic, biological, and organic/inorganic colloidal foulants and silica scale.(15)

For internal reuse, caustic soda purity requirements are moderate. Membrane manufacturers manuals for reverse osmosis(16) rate technical grade as sufficient purity for membrane and system compatibility.


I should point out at this point that while this situation applies to SWRO plants, NaOH would be useful in brine resulting from other processes. In particular it might prove of great utility in the recovery of certain metals from seawater, notably magnesium and calcium (but also including others) and another constituent of prime importance which is much more concentrated in seawater than it is in the atmosphere, carbon dioxide, along with certain carbon compounds. This would, however, probably involve a huge scale up of NaOH production, although there are some very cool approaches to in situ partitioning of seawater into HCl and NaOH fractions which I have no time to discuss here.

The authors further discuss the economic importance and current production methods for the production of sodium hydroxide:

n addition to its use in controlling pH and neutralizing acids, caustic soda is used as a reagent in the production of many chemicals. About 59% of NaOH in the EU and North America is used in the pulp and paper, inorganic, and organic chemical industries.(19) Soaps and detergent manufacture also account for significant demand. For external reuse, quality requirements are application specific, and some commercially produced caustic soda is of insufficient purity for certain industries. For example, caustic soda produced using the diaphragm process is not suitable for manufacturing viscose, also known as rayon.(20, 21)

Industrial production of caustic soda is massive. Global manufacture exceeded 59 million tons in 2004,(19) with significant growth in demand and capacity expected in Asia.(20) Production is also scalable, with plant capacities ranging from about 4.4 kt/yr (Kapachim, Inofita Viotias, Greece) to 1744 kt/yr (Dow, Stade, Germany) in the EU(22) and about 2 to 3333 kt/yr (Olin, Freeport, TX) in the US(20, 23) on a dry basis. [Estimated from chlorine capacity at 1.1 kt NaOH/kt chlorine,(18) which is slightly less than stoichiometric.] On the small end, ThyssenKrupp Uhde GmbH offers standardized skid-mounted plants at up to 17 kt/yr, and AVS Technology AG offers plants as small as 1.1 t/d.

About 99.5% of global caustic soda production is by the chlor-alkali process.(24) Briefly, the process produces caustic soda and chlorine gas in equimolar amounts by electrolysis of aqueous sodium chloride. Direct synthesis of process products can also produce hydrochloric acid, though less than 10% of HCl is manufactured this way.(25) (Technical aspects of the chlor-alkali process and other methods are discussed in-depth below.) Three variants of the process exist in widespread commercial use, generally distinguished by how catholyte and anolyte are separated. The variants are known as the membrane, diaphragm, and mercury processes.


The authors then discuss that the chlor-alkali process produces equal molar amounts of chlorine gas and NaOH and that the demand for these two commodities is not always matched, even if some of the chlorine is diverted to make another commodity, HCl, hydrochloric acid. (Hydrochloric acid is often a waste product needing disposal. There are huge waste disposal issues with it, and one dubious approach to dealing with it has been deep welling it.)

This mismatch has lead to wide fluctuations in the price of NaOH, as a graph from the paper shows:



It is worth noting that the "mercury process" - which is happily being phased out - has resulted in a large contribution to the widespread contamination of the environment with mercury. Although the amount of mercury from this source is definitely dwarfed by mercury contamination deriving from coal exhaust, fly ash and ash, it is still significant.

(Sometimes I think the whole world is developing "mad hatter disease." How else can we account for the placement of incredible fools like the orange nightmare in the White House, and his foreign equivalents, Kim Jung Un, Rodrigo Duarte, Recip Erdoğan, to name just a few.)

The authors graphically show the current chlor-alkali processes industrially in use:



The rest of the article is involved with thermodynamic and the always related economic issues, along with some technical arguments connected with membrane technology (which is the focus of the paper.)

Also discussed is heat, which is also an issue in the reduced pressure schemes about which I often privately muse.

Overall, I like these kinds of papers and I thought I'd share this one for anyone who may find it interesting. Interested readers who can manage access, are invited to look the paper up.

Esoteric I know, but important.

Enjoy the coming work week.


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Response to NNadir (Original post)

Sun Dec 17, 2017, 08:57 PM

1. ...

"So called "renewable energy" is a grotesque failure. It has not worked; it is not working; it will not work, if the goal is to address climate change rather than to post "feel good" stuff on the internet"

So, Germany should just STOP trying? When the authors make assertions like the one above, I have to question the remainder of the article also. Maybe I'm missing something. I certainly don't have a PHD.

"Germany raised the proportion of its power produced by renewable energy to 35 percent in the first half of 2017 from 33 percent the previous year, according to the BEE renewable energy association.

Germany is aiming to phase out its nuclear power plants by 2022. Its renewable energy has been rising steadily over the last two decades thanks in part to the Renewable Energy Act (EEG) which was reformed this year to cut renewable energy costs for consumers.

Germany has been getting up to 85 percent of its electricity from renewable sources on certain sunny, windy days this year."

http://www.independent.co.uk/news/world/europe/germany-green-technology-record-power-generation-35-per-cent-renewables-solar-wind-turbines-a7820156.html

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Response to Ferrets are Cool (Reply #1)

Sun Dec 17, 2017, 09:15 PM

2. I understand the enthusiasm for the fad, but the trillions spend on this scheme, given the...

...results are unambiguous.

406.55 ppm, week ending December 10, 2017, at the Mauna Loa Carbon Dioxide Observatory

Here's a picture of what's happening, in case you don't get it, of the annual increases of carbon dioxide from Mauna Loa :



This is the measurement of carbon dioxide in the planetary atmosphere, increases in which are accelerating, no decelerating, all the useless bullshit about Germany notwithstanding.

I have no use whatsoever for the German energy program. It's a waste of money and time, and is, in fact, counter productive.

If it were working, this news item would not have appeared last month:

As Germany hosts green summit, an energy firm is razing a nearby forest

They're destroying an old growth forest to dig coal.

I don't give a shit, in general, about journalistic crap however and am unimpressed by decade after decade after decade of "percent talk" about what happened on some sunny windy day. It's illiterate.

I've been hearing this bull here for more than 15 years, and elsewhere, much longer. I'm not drunk on wishful thinking. I'm soberly facing some hard cold reality.

The only amount of dangerous fossil fuels that should be utilized in percent terms is um, zero percent, not just on windy sunny days when journalists somewhere are drooling all over themselves, but every day, every night, every damned second.

The mere fact that this useless scheme to provide so called "renewable energy" is so damned popular is probably a function of the fact that one cannot get a journalism degree on this planet if one has passed an introductory college level science course.

I read the primary scientific literature, a lot of it, and the conclusion I've come to have 30 years of nearly obsessive reading is that the German, and by extension the world approach to addressing climate change as expressed in the faith based worship of the toxic, expensive and unsustainable solar and wind industries is not merely ill advised but is, in fact, a crime against all future generations.

The German program is a very, very, very, very, very bad joke.

Enjoy the coming work week.

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Response to NNadir (Reply #2)

Sun Dec 17, 2017, 09:59 PM

3. Do you understand what kind of energy plan that he wants to

move toward? I do not.

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Response to NNadir (Reply #6)

Tue Dec 19, 2017, 11:00 AM

7. It is a wonderful essay....

quite a bit over my head, but I get the gist of it. It is, however, idealistic at best. While I realize it is not your intention to discuss the negatives of this idea coming to fruition, the political and economic realities will not allow the end of coal and oil in our, or our childrens lifetimes. There are too many people making billions from those operations to abandon them for the good of the planet. JMO

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Response to Ferrets are Cool (Reply #7)

Tue Dec 19, 2017, 01:47 PM

8. Thank you. I understand the difficulties people have with idealism but...

...even as an old man, I believe it has a place.

One of my political heros from the 19th century is Frederick Douglass, the escaped slave and abolitionist who held the radical idea that all men are really created equal.

Even Abraham Lincoln felt he was a bit of an idealist.

Nevertheless it is absolutely true, as true is it is that African Americans are not, and should have never been treated as, little more farm animals, that nuclear energy is the best, and frankly, the only form of sustainable energy.

I note that when slavery was abolished, the economic impact eliminated, on paper at least, much of the "wealth" of the United States, clearly not in moral terms, but at least in dollar terms.

Nevertheless, it was the only thing that was possible in order for this country to survive. The stakes in climate change are much greater than those of this country alone, or any country.

Just as Americans in 1860 needed to wake up, citizens of this entire planet need to wake up.

Thanks again for your kind words.

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Response to NNadir (Reply #8)

Wed Dec 20, 2017, 10:08 AM

9. You are quite welcome. I love that you are so passionate about this issue. And yes,

the citizens of this entire planet need to wake UP. And YES, when the world is devoid of idealist, the world is doomed forever.

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Response to NNadir (Original post)

Mon Dec 18, 2017, 09:10 PM

4. Wouldn't rising sea levels more then compensate for an uptike in concentrated brine?

The rise in sea levels caused by the massive infusion of fresh water.

And couldn't desalinization plants in the Southern California region be powered by solar powered farms located on bases such as Edwards AFB? Some of which are so large that a 100 square miles on a base could be dedicated to solar farms with little to no impact on the military use of the base?

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Response to Kaleva (Reply #4)

Mon Dec 18, 2017, 11:56 PM

5. The ocean features pretty pronounced salt gradients and they in fact drive currents.

While the average salt concentration of the oceans might well remain constant, or less saline, locally it is very possible to disrupt ecosystems by radical changes in salinity.

A famous example of this is the destruction of the Colorado delta system.

The solar industry can't even power a grid; it remains after more than half a century of wild eyed cheering for it, a trivial source of energy.

Covering huge tracts of California, or any other area, with fairly toxic semi-conductors, particularly those that are periodically covered with dust that will be need to be, um, washed off, using water, is a very bad idea environmentally, and it won't work.

Since the solar industry has not produced at any time in its long history driven by wishful thinking and handwaving, even two of the 570-580 exajoules consumed by humanity, desalination - an energy intensive task - cannot be supported by solar energy. Wind energy might be marginally better, although it is also inadequate not only for desalination, but for everything else, and it would represent a huge risk to California's avian ecosystem.

From my perspective, beyond membranes, as are described in the reference in the opening post, reduced pressure distillation and/or supercritical water separations are the only viable schemes. Only nuclear energy can provide access to these in an environmentally acceptable fashion.

The Diablo Canyon nuclear plant in California is one of that state's largest single desalination plants. In earlier times it utilized flash distillation - the reduced pressure system to which I referred - which was ultimately replaced by RO. That single power plant produces more electricity than all the solar facilities in the entire state built, again, in over half a century of cheering.

Flash distillation was abandoned because of materials science issues which I now believe can be addressed.

In supercritical water - water in a state where there is no distinction between the gas and liquid phases - which exists at temperatures higher than 373C, salts are more or less completely insoluble.

The largest source of electrical energy in California as of 2016 dangerous natural gas (34.02%), followed by imports (28.76%), hydroelectricity (9.97%) and nuclear (6.52%, in a single building.) Solar PV energy produces 5.93%, with tens of thousand, if not hundreds of thousands of semi-conductor future electronic waste distributed all over the state.

If California desalinates under current conditions, it will do so with dangerous natural gas, which given climate change, would be extremely counter productive.

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Response to NNadir (Reply #5)

Wed Dec 27, 2017, 10:14 AM

12. Interesting! You are way above my paygrade!

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Response to NNadir (Original post)

Wed Dec 20, 2017, 02:24 PM

10. A story about the Salton Sea was recently posted in E/E...

Dust Storms Worsen Around Disappearing Salton Sea

https://www.democraticunderground.com/1127113439

Using Laguna Saluda as a forebay for any Salton Sea energy storage or shoreline stabilization project might mitigate some of the environmental concerns.

http://www.desertsun.com/story/news/environment/2016/03/23/how-water-mexico-can-save-salton-sea/82163024/

You are correct in your opinion that natural gas will be used to desalinate water for the small fraction of the human population who can afford it. It seems the wealthy will never suffer water shortages, nor will they suffer the consequences of their fossil fuel use.




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Response to hunter (Reply #10)

Thu Dec 21, 2017, 10:32 AM

11. What the wealthy seem to have forgotten...

... is that wealth is a social construct dependent on the passive acquiesce of the larger social structure.

History records that one of the wealthiest persons in his time was Louis XVII.

He died violently because the society beneath him lost hope and basic security.

I certainly opposed with every bone in my body to violence but it is not in my power, or for that matter even the power of the wealthy to prevent that outcome.

Bankrupting the US government to enrich the wealthy may come back to bite them in the cake they propose for the rest of us to eat.

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