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Mon Jun 15, 2020, 07:51 PM

Quiz: Electrification of the Chemical Industry: What's wrong with this picture?

Here's a news item from the current issue of Science: Electrification of the chemical industry (Barton, Science 12 Jun 2020 Vol. 368, Issue 6496, pp. 1181-1182)

Curbing carbon emissions while maintaining quality of life is a global challenge for manufacturing processes that will require process innovation. One approach is replacing energy from the burning of carbon-based fuels with energy supplied by “green” electrons. This goal can be achieved in some cases by simply replacing heat supplied by combustion with electrical heating (1). In chemical synthesis, it can also more elegantly supply reaction energy through electrochemistry. On page 1228 of this issue, Leow et al. (2) propose an electrochemical route to ethylene oxide (EO) and propylene oxide (PO) that promises cleaner, more efficient, and more selective processing. Ethylene and propylene were epoxidized electrochemically to EO and PO, respectively, at industrially relevant current densities with Faradaic (electron-specific) selectivities ∼70% to the target epoxide (2).

Leow et al. coupled an electrochemical flow cell to homogeneous reactions for an overall reaction, C2H2 + H2O → C2H2O + H2, for EO synthesis (see the figure). Two electrochemical reactions drive this reaction. Chlorine evolution occurs at the anode, 2Cl− → 2e− + Cl2, and hydrogen evolution occurs at the cathode, 2H2O + 2e− → H2 + 2OH−, where e is the charge on the electron. These reactions are not particularly interesting; what is innovative is coupling these two simple reactions with three subsequent, homogeneous chemical reactions. Dissolved chlorine in the anodic solution dissociates into hydrochloric and hypochlorous acid (HCl and HOCl, respectively)...

...Technoeconomic analysis by Leow et al. suggests that this process could scale to produce EO at a cost comparable with current industrial practices with a lower carbon footprint when supplied with renewable energy (2). Such a process would be a carbon-negative path to an important, large-scale commodity chemical. Improvements are still possible, particularly in product selectivity and catalyst selection. Nonetheless, the electrochemical productivity of EO reported in this study is a factor of 10 higher than that of the electrochemical process of Simmrock and Hellemanns (3).

As usual, it sounds wonderful, does it? (By the way there is nothing particularly surprising or innovative in the chemistry here; it should be obvious to a strong undergraduate in a decent chemistry program.)

The full paper, open sourced, is here: Chloride-mediated selective electrosynthesis of ethylene and propylene oxides at high current density (Leow, et al., Science Vol. 368, Issue 6496, pp. 1228-1233)

In the United States, chemical manufacture accounts for 28% of total industrial energy demand (1). At present, this demand is largely met by the consumption of fossil fuels, resulting in substantial carbon dioxide (CO2) emissions (2, 3); a recent report showed that the plastics industry alone releases 1.8 billion metric tons of CO2 per year and that replacing fossil fuels–based production methods with ones powered with renewable energy offers a route to reduce net greenhouse gas emissions associated with plastics manufacture (4).

One attractive strategy involves the development of electrochemical systems that produce the necessary raw materials by using renewable electricity (5–8).

I have added the bold and italics.

I am of course, a critic of so called "renewable energy," but I hold the possibly naive notion that some things are so absurd that they should be obvious. To me, this one has a hole so large that one can drive a zepplin sufficient to hold the carbon dioxide that drove that atmospheric concentration of CO2 up by 45.34 ppm since May 28, 2000 and now right through it. (I note, with bitter and tragic schadenfreude, that since May, 28, 2000, almost exactly 20 years ago, we've all been cheering wildly for so called "renewable energy," for the whole period, claiming that so called "renewable energy" is a positive good that cannot be questioned.)

I'm curious whether there is anyone with enough of a knowledge of Chemical Engineering to see what that hole is.

I'd guess there isn't any such person who will read this, but if someone wants to surprise me, I'm open to hearing it. (Hint: Consider what types of processes are the most economic for producing high volume chemical commodities.)

Have a pleasant evening.

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Response to NNadir (Original post)

Mon Jun 15, 2020, 10:44 PM

1. I'm not a Chemical Engineer and only have a laymans understanding of this stuff...

Last edited Tue Jun 16, 2020, 01:55 AM - Edit history (2)

...but, what the heck, I'll take a stab at this. Does it have to do with the energy required to produce chlorine gas, or hydrochloric acid, being equivalent to or greater than the energy used in the usual industrial thermal processes to make these products? Please be kind and let me down gracefully if I'm wrong, or worse, too simplistic. A dirty, coal fired plant makes electricity that is used to produce the products required to be utilized to effect another, slightly "greener" industrial process?

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Response to EarnestPutz (Reply #1)

Tue Jun 16, 2020, 08:23 AM

2. No, that's not it, but it's a perfectly respectable answer, particularly since you're...

...not an engineer.

In a purely thermodynamic sense, this process is no winner for sure, but the point was to make sacrifices to reduce the carbon impact. Ethylene's existing process utilizes dangerous fossil fuel starting materials.

It is however true that any process for making ethylene other than from dangerous fossil fuels will be a thermodynamic loser, unless the process involves high temperatures and process intensification.

Here's another hint:

The answer is also tied to the reason that the most expensive household electricity is that in Germany and Denmark.

From a recent IEA report:

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Response to NNadir (Reply #2)

Tue Jun 16, 2020, 04:01 PM

3. O.K., let me think out loud for a minute. Your chart shows how energy prices have changed...

.... in various countries over the past 40 years. Prices have gone up 5.2 times in Denmark and 4.1 times in Germany to make these two countries the most expensive today, that is that each household spends the most on electricity. I don't know why "households" are relevant as I'd guess there is variation in size among different countries. Canada started out with very low costs 40 years ago, but these have gone up 4.6 times, even though they are still quite low. Germany has undertaken to move away from coal-fired and nuclear power plants over the last few years. Denmark has built more wind farms. So lets put them in the "renewable energy dependent" column. Canada I would guess is has been and continues to be dependent on hydro power. So put them in that column too. Prices in the U.S. have gone up 3.0 times as we continue to use coal, oil and natural gas. France has a reputation for building many cookie cutter nuclear plants (are they still doing that?) has one of the lowest increases at 2.5 times. So an increased emphasis on renewable energy equals higher prices and costs. No surprise so far.

How am I doing so far? Another hint?

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Response to EarnestPutz (Reply #3)

Tue Jun 16, 2020, 04:25 PM

4. OK, I'll give another hint.

But first let me explain that "household" could be replaced with "residential." This is not like one of those news accounts where they report the capacity - nonsensically I might add - of a wind farm in "households." The unit here is dollars/unit of energy (MWh), not "households."

Here's the hint: Iceland relies almost 100% on so called "renewable energy," for electricity but the "renewable energy" in question is geothermal and hydroelectricity, not solar and wind.

Iceland is also the site of huge electrochemical plants that make aluminum.

Kaiser Aluminum historically also built aluminum plants in Washington State for the same reason that Alcoa in a subsequent generation opened plants in Iceland.

(Aluminum production in Iceland has some opposition.)

Electrochemisitry is the only way that aluminum can be made economically, even though electricity is a thermodynamically degraded form of energy. The only greenhouse gases emitted by aluminum plants, excluding the source of electricity, in operation is CF4, tetrafluoromethane, and CO2 from the oxidation of petroleum coke anodes.

To make the hint broader: Aluminum plants operate at high temperatures in molten salts.

What's the most economical way to operate an aluminum plant?

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Response to NNadir (Reply #4)

Tue Jun 16, 2020, 11:47 PM

5. Wow, I really am in over my head at this point. Please continue to be kind...

...to me as I try to learn, with your help and a bunch of google searches. Aluminum smelting has usually been located near sources of cheap and abundant electricity, as here in Spokane, my home town, where Kaiser built a huge smelter and rolling mill for wartime production of aluminum for Seattle's aircraft industry. The source of the electricity was Grand Coulee Dam, about fifty miles away. Reading now about the smelting process tells me that the process require large amounts of electricity because it not only uses a dense current flow to heat to melt the ore, but that the reduction of aluminum oxide consumes a lot of electrons directly into the process. Is that right? It seems that the formulas in the article you bring forward indicate this.
Is that the problem with "renewable" sources of electricity, that they can't economically keep up with the demands of an electrical reduction or electrolysis process that requires more than just heat? Are the industrial production of aluminum and EO and PO similar because of the electrolysis component in the production? Does not analysis in the paper just consider electrons in the electrolysis and not in the heating of the molten mass? Like I said, I'm in over my head, but please humor me.

"What's the most economical way to operate an aluminum plant?" I'd guess on as large a scale as possible, running as continuously as possible, like most industrial processes. Though aluminum is a batch process, rather than something that can run continously.

I'd looked at Iceland on your chart and wondered why their costs had also gone up so much as well as why they consumed so much electricity for such a small population. They must use their geothermal and hydro electric resources to make a lot of aluminum. Just read, in your linked article, some horror stories about horrible working conditions in Iceland's smelters and how huge amounts of fluorocarbon byproduct poison the landscape.

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Response to EarnestPutz (Reply #5)

Wed Jun 17, 2020, 10:28 PM

6. It appears you are not over your head at all, as you have uncovered the correct answer.

You write:

"What's the most economical way to operate an aluminum plant?" I'd guess on as large a scale as possible, running as continuously as possible, like most industrial processes. Though aluminum is a batch process, rather than something that can run continously.

I have added the bold and italics.

A Hall-Heroult plant - an aluminum plant - is not a batch process but is a continuous process however. Alumina, which is the main component of bauxite is a well known refractory, with a very high melting point, 2,072 °C. It is however easily dissolved in a strong basic solution, for example sodium hydroxide. This is how the alumina in bauxite is separated from the other constituents, iron oxides, titanium oxides, calcium oxides and silica. This process is known as the Bayer process. The resultant sodium aluminates can be calcined to give alumina, Al2O3.

The alumina is then dissolved in molten cryolite, trisodium hexafluoroaluminate. This is a relatively rare mineral, historically mined in another Scandinavian province, Greenland, but it has been mined to extinction. Almost all of the cryolite now used in the aluminum industry is now synthetic. The melting point of cryolite is around 1000 °C, and you are correct that it is maintained at this relatively high temperature by electrical resistance. It follows then that if the electric current is not available, because, let's say the sun isn't shining and the wind isn't blowing, the mixture of alumina and cryolite will solidify, as it cools. The cooling is rejecting energy to the atmosphere, wasting it. To restart the electrolyzer because the sun is shining and the wind is blowing, one will need to reheat the solid in the reactor, which will involve an energy investment that produces nothing at all, since the mixture must be completely molten for the electrolysis reaction to resume.

Economically, the fixed costs, the costs of salaries, the depreciation of the reactor, the interest payments on the facility, facility maintenance, roads and/or rails and/or docks to deliver raw materials and to carry away aluminum metal will all accrue whether the plant is operating or not. If the plant is only able to run a few hours a day, depending on the weather, or is entirely unavailable for long stretches of time, it will require all of these costs to be recovered by sales of the smaller amount of aluminum that it would produce were it operating 24/7, 365.24 days per year. Thus the aluminum will be more expensive, and less available to the lower classes. The environmental costs, will also be higher, since many more plants will be required to meet demand, and building roads, reactors, facilities all imply an external cost, usually dangerous fossil fuels, in particular, petroleum products.

On reflection, one can see that this will apply to any kind of plant, including a dangerous natural gas plant of the kind that are essential wherever dependence on so called "renewable energy" is widely used. This accounts for the high cost of electricity in that offshore oil and gas drilling hellhole Denmark, and that gas dependent country Germany.

It is completely ignorant to insist that batteries can solve the problem, since batteries are producing nothing of value when being recharged; they waste energy; and their external costs are huge and producing them on a vast scale - an exajoule scale - may easily deplete important resources while inducing severe environmental penalties. If one looks into the chemistry of batteries - I have - and their social and moral costs, one should be appalled, but apparently most people aren't.

Let's shout out thousands of cheers for that asshole Elon Musk.

The Hall-Heroult process can be continuous by the way because the melting point of aluminum 660.3°C is lower than the melting point of cryolite, and thus can be removed in a flow process. The development of the Hall-Heroult process was quite literally a major event in human history. Aluminum metal is a critical material in multiple industries, notably aircraft - as you point out - but in other industries as well.

Another electrochemical process, the FCC Cambridge process, has the potential to offer as much as of an impact as the Hall-Heroult process, since it will make "difficult" metals, notably titanium, cheap and readily available.

All major chemical commodities are produced in continuous processes, including gasoline, ethane, ethylene, propene and, for that matter, where electricity is cheap, electricity itself. This is because continuous processes provide continuous revenue: There are no points at which an idle facility is generating fixed costs with no output.

From time to time, you hear people cheering for negative costs associated with so called "renewable energy" as if this was a good thing. It isn't if you own a wind farm, however, since your commodity is worthless but the fixed costs of your wind farm - both the environmental (external) and economic - steel, lanthanide magnets, copper and aluminum as well as maintenance - are expenses with no return on value.

This is why the so called "renewable energy" nirvana is a fool's paradise. Denmark has strewn its country side with junk that will be rotting soon enough to produce unreliable electricity that could reliably produced in two or three small buildings containing nuclear reactors. Incredibly Germany has chosen to emulate this bit of stupidity, and as usual, the people who will suffer in both countries are the poor people. The costs of the affectations of the wealthy almost always fall on the poor.

Give yourself some credit; you got to the point and needed only a minor correction.

I have been writing quite a bit about this issue of stranded costs and so called "renewable energy" but haven't published it anywhere. Charles Forsberg of MIT has written excellent pieces on this topic, and what I am writing is purely derivative.

Thanks for playing.

By the way, your last post - the one to which I'm responding - contains a huge amount of empty space at the end.

Be safe and be healthy.

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Response to NNadir (Reply #6)

Thu Jun 18, 2020, 02:27 AM

7. That was fun. Thank you so much for helping me along. I learned a lot....

....both from your question and the process of doing a little research. I've mentioned to you before that you've turned me around on the question of nuclear energy. This problem illustrated what you've preached quite well.
I don't know how all that white space appeared other than it was some errant keystroke I made and my lack of computer skills left me unable to correct at the time. Sorry about that.

"365.24 days" is a nice touch for a scientist.

One last thought. You mention the energy needed to reheat a crucible, or aluminum for that matter, was well illustrated here in Spokane where the two Kaiser plants are at opposite ends of the city. Molten aluminum was trucked through town in crucibles from the smelter to the rolling mill so that it could be cast into ingots and rolled into sheet without reheating. It was a dangerous proposition but they pulled it off for quite a few years. The truck with the molten metal would slowly make its way through town with lead and chase safety cars accompanying it. They avoided disaster even when a locomotive hit it in 1990. Following from the newspaper:

One of the locomotives chased the runaway cars but struck a Kaiser Aluminum & Chemical Co. truck at a crossing and derailed, Kallio said.

He said the truck was carrying two 15,000-pound crucibles of molten aluminum.

The containers, carrying its load from Kaiser’s Mead smelter to its Trentwood rolling mill, remained intact, spokeswoman Susan Ashe said. To save energy costs, the company has been hauling molten metal from its smelter to its rolling plant since 1971 without a major incident, Ms. Ashe said.

Thanks again.

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Response to EarnestPutz (Reply #7)

Fri Jun 19, 2020, 03:24 PM

8. My pleasure. When we started this discussion...

...I had no idea you actually lived in a town having an aluminum plant.

My knowledge of aluminum processes falls merely on general reading and knowledge so I appreciate the added color.

Part of my career was definitely involved with process chemical engineering but primarily in the pharmaceutical industry where historically almost every process was a batch process.

That is likely to change. I recently attended a fabulous symposium discussing in line continuous processing for active pharmaceutical ingredients. It was something I never expected to see, being an old man, but it's quite real.

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