Mining waste for cheaper hydrogen fuel production

[Astronuc]

TL;DR

feldspars, aluminosilicate from mining waste may be combined with selected, expensive metals, e.g., Pt ($1450/oz), Ir ($1370/oz) and Ru ($367/oz) or cheaper Co ($70,000/t), Ni ($26,000/t) and Fe ($641/t) to form effective 'water splitting' catalysts

Water splitting reactions that produce hydrogen are triggered using rare platinum ($1450/ounce), iridium ($1370/ounce) and ruthenium ($367/ounce), or cheaper but less active metals—cobalt ($70,000/ton), nickel ($26,000/ton) and iron ($641/ton).

Professor Ziqi Sun from the QUT School of Chemistry and Physics and QUT Centre for Materials Science and Dr. Hong Peng from the School of Chemical Engineering at the University of Queensland led research to create a new catalyst using only a small amount of these reactive metals.

They combined them with feldspars, aluminosilicate rock minerals found in mining waste that Professor Sun said some companies pay about $30/ton to dispose of.

In the experiment, featured on the August cover of Advanced Energy & Sustainability Research, the researchers triggered a water splitting reaction using heated-activated feldspars nanocoated with only 1–2 percent of the cheaper reactive metals.

https://phys.org/news/2021-09-ingredient-cheaper-hydrogen-fuel-production.html

"Water splitting involves two chemical reactions—one with the hydrogen atom and one with the oxygen atom—to cause them to separate," Professor Sun said.

"This new nanocoated material triggered the oxygen evolution reaction, which controls the overall efficiency of the whole water splitting process," he said.

Professor Sun said cobalt-coated feldspar was most efficient and optimizing the new catalysts could see them outperform raw metals or even match the superior efficiency of platinum metals.

 

[Andrew Mason]

Very interesting. Just a few comments:

Are there not other, possibly cheaper, processes other than electrolysis? How about high temperature thermo-chemical processes using solar furnaces, for example?

The need for a non-carbon energy dense chemical fuel is going to become more and more pressing as the world realizes the we will eventually have to eliminate combustion of sequestered hydro-carbon. Some things will continue to need a chemical fuel source. It is going to be hard to develop electric aircraft, for example.

Hydrogen seems to be a very good fuel alternative. I was a bit surprised to see that Hydrogen has about 3 times the energy density (energy/unit mass) of diesel fuel.

AM

 

[Bystander]

I was a bit surprised to see that Hydrogen has about 3 times the energy density (energy/unit mass) of diesel fuel.

One is less than twelve.

 

[berkeman]

One is less than twelve.

Wakarimasen...

Spoiler

I was going to try to be more polite, and say "Lo siento, wakarimasen", but I was worried that might break Google Translate...

 

[Astronuc]

Wakarimasen...

Atomic mass H = 1, although H₂ = 2, and C = 12.

 

[berkeman]

Atomic mass H = 1, although H₂ = 2, and C = 12.

Whelp, that clears things right up. Guess I should have paid more attention in chem class. Bueller?

 

[Andrew Mason]

One is less than twelve.

Material ....Specific Energy (MJ/kg) (combustion)

Hydrogen .....141.86
Methane ......55.6
Gasoline ......46.4
Diesel fuel....45.6

See: https://en.wikipedia.org/wiki/Energy_density and sources cited therein.

 

[Ygggdrasil]

Hydrogen seems to be a very good fuel alternative. I was a bit surprised to see that Hydrogen has about 3 times the energy density (energy/unit mass) of diesel fuel.

It's important to note that hydrogen's numbers fall off a cliff once you consider the weight of the tanks needed to safely store the hydrogen. For the wikipedia source you cited above:

High-pressure tanks weigh much more than the hydrogen they can hold. The hydrogen may be around 5.7% of the total mass,[19] giving just 6.8 MJ per kg total mass for the LHV.

Of course, future technological developments may be able to change this. However, because of storage issues, I think hydrogen is less likely to play a role in transportation than in large scale power generation, where hydrogen could be a good solution to store excess energy from the grid for use later.

 

[grandbeauch]

Very interesting. Just a few comments:

Are there not other, possibly cheaper, processes other than electrolysis? How about high temperature thermo-chemical processes using solar furnaces, for example?

The need for a non-carbon energy dense chemical fuel is going to become more and more pressing as the world realizes the we will eventually have to eliminate combustion of sequestered hydro-carbon. Some things will continue to need a chemical fuel source. It is going to be hard to develop electric aircraft, for example.

Hydrogen seems to be a very good fuel alternative. I was a bit surprised to see that Hydrogen has about 3 times the energy density (energy/unit mass) of diesel fuel.

AM

What about in cars. The suggestion that has been brought up is way to big and cumbersome. I am all for getting into the hydrogen economy. The cheaper the catalyst the sooner the pollution will go down.

 

[Arthur R.]

Fossil fuels are a potentially abundant source of hydrogen, which can be separated from natural gas with solid carbon as the waste product. The process is called methane pyrolysis. Can also work on any other hydrocarbon including waste plastic. Chemical company BASF has a pilot plant in Germany, see https://tinyurl.com/2hk8tzzv
Another approach is to heat catalysts with microwave energy in the presence of natural gas. Go to the 29:10 mark in the following video:
There are other approaches as well. Finally, it appears that hydrogen is trapped in the Earth's crust and can be drilled out. If such natural hydrogen is abundant, this would probably be the cheapest source of hydrogen. See
Cheers !

 

[N1206]

"I was a bit surprised to see that Hydrogen has about 3 times the energy density (energy/unit mass) of diesel fuel."

You were a bit surprised only because that statement isn't right. From #7 from Andrew Mason, you will see that Specific Energy (MJ/kg) for hydrogen gas is 141.86 (HHV) and 45.6 for diesel (3x larger) but Energy Density (MJ/L) is 10.044 (HHV) for hydrogen gas liquified and 38.6 for diesel (3x smaller)

And energy density is what matters for mobile applications--and hydrogen (and methane for that matter) are very energy intensive to to compress or liquify and need strong and heavily insulated containers. Rocket fuel is about the only mobile application where those liquid fuels make sense. LNG happens for ocean transport--and for virtually no other reason--and usually gets fluffed/heated back to reasonable temps and psi for dumping into pipelines

 

[Andrew Mason]

Well there is volumetric energy density (energy/unit volume) and gravimetric energy density (energy/unit mass). I thought I made it clear that I was using energy/unit mass.

AM

 

[N1206]

Well there is volumetric energy density (energy/unit volume) and gravimetric energy density (energy/unit mass). I thought I made it clear that I was using energy/unit mass.

AM

You had cross-mixed the terms from your reference. You wrote '3 times the energy density (energy/unit mass)' but your reference defines energy density as energy per volume and specific energy as energy per mass and doesn't use 'volumetric' or 'gravimetric' at all. And when it comes to fuels for mobile applications, energy per volume is the important thing, along with container weight, 'transformer' weight, and effective 'transformation' speed. Elon Musk has contempt for hydrogen because he figures the economics of hydrogen will never beat those of batteries: that the weight of a hydrogen tank, the weight of a fuel cell, the fuel cells ability to provide wattage on demand and the costs of all of that (both fuel cell and compressing hydrogen) will never beat that of batteries you can charge at home with renewables.

There would have to be massive improvements in both cost, weight and output of fuel cells for him to be wrong. The physics of compressing and containing hydrogen have no give to them. Hydrogen may be a good substitute for methane in industrial and residential heating applications (furnace fuel) but I don't think hydrogen, LNG or CNG have much future as transportation fuel. CNG has been around for 30 years and made no inroads other than the utility's own vehicles. LNG-for-Diesel has been around for 5 years or so, but the local attempt to put a filling station near the truckstop only was in operation for about 6 months before being gated off. Certarus will haul CNG to site as a 'virtual pipeline' for when propane would be prohibitively expensive and you need large volumes of heating fuel--but that is really a niche operation. Hydrogen has all the same impediments.

 

[Andrew Mason]

And when it comes to fuels for mobile applications, energy per volume is the important thing, along with container weight, 'transformer' weight, and effective 'transformation' speed.

I am not sure the actual container weight should matter as much as the proportion that the container + fuel has in relation to the total vehicle mass. In at least one mobile application - rockets - energy per unit mass is the most important thing.

your reference defines energy density as energy per volume and specific energy as energy per mass and doesn't use 'volumetric' or 'gravimetric' at all.

My reference was to the Wikipedia page on "Energy Density" the first paragraph of which reads:

"In physics, energy density is the amount of energy stored in a given system or region of space per unit volume. It is sometimes confused with energy per unit mass which is properly called specific energy or gravimetric energy density."​

​

AM​

​

 

[N1206]

"In at least one mobile application - rockets - energy per unit mass is the most important thing."
Well, not most important, since not all rockets actually use hydrogen.
Space-X rockets have been using rocket grade kerosene (RP-1) and Space-X is playing with methox rockets. The shuttle main engines were LH2, but the boosters were solid fuel.

And what makes liquid hydrogen work for rockets is that you are only likely keeping it at STP for short periods of time, and boiling it off to gas is actually what you want as you consume it. But anyway...

 

[Borek]

"In at least one mobile application - rockets - energy per unit mass is the most important thing."
Well, not most important, since not all rockets actually use hydrogen.

So you are saying that for rockets that don't use hydrogen, energy per unit mass is not important, and they could be run even by a biogas reactor?

 

[Andrew Mason]

And what makes liquid hydrogen work for rockets is that you are only likely keeping it at STP for short periods of time, and boiling it off to gas is actually what you want as you consume it. But anyway...

I think you will find that liquid Hydrogen-Oxygen is the most efficient rocket fuel in terms of the impulse generated per unit mass of fuel. That is the reason it was used by NASA in all its pre-shuttle programs.

But it is difficult to make H2 fueled rockets reusable because of the extremely low temperature required to keep H2 in a liquid state. That is why the Space Shuttle's reusable rocket boosters did not use H2. That may also be why Space-X does not use H2 fuel.

AM

 

[N1206]

So you are saying that for rockets that don't use hydrogen, energy per unit mass is not important, and they could be run even by a biogas reactor?

No one--NO ONE-- said anything like that.
Only that it is not perhaps the most important thing.
The economics of rockets are a minimization of $/(kg of operational payload delivered) + (% probability of non-operational outcomes)*(cost of payload)
You want the cheapest possible delivery of payload with the least risk of the payload not arriving operational. A perfect rocket would deliver operational payloads 100% of the time with no failures.

Space-X played with carbon fibre before concluding that stainless steel remained the better choice in terms of present technology. They have played with chilling RP-1 to its lowest density to try and squeeze out better economics. They are working on methox rockets. H₂ is already an old technology that is not supplanting other technologies, at present.