mollwollfumble said:
Tau.Neutrino said:
World first: Dutch brewery burns iron as a clean, recyclable fuel
Many industries use heat-intensive processes that generally require the burning of fossil fuels, but a surprising green fuel alternative is emerging in the form of metal powders. Ground very fine, cheap iron powder burns readily at high temperatures, releasing energy as it oxidises in a process that emits no carbon and produces easily collectable rust, or iron oxide, as its only emission.
more…
> If burning metal powder as fuel sounds strange, the next part of the process will be even more surprising. That rust can be regenerated straight back into iron powder with the application of electricity. The iron acts as a kind of clean battery for combustion processes, charging up via one of a number of means including electrolysis, and discharging in flames and heat.
> Recently, Swinkels Family Brewers in the Netherlands has become the first business in the world to put this process to work at an industrial scale. The company has been working with the Metal Power Consortium and researchers at TU Eindhoven to install a cyclical iron fuel system at its Brewery Bavaria that’s capable of providing all the heat necessary for some 15 million glasses of beer a year.
OMG, what an enormous waste of electricity. Much less electricity would be needed if electricity were used directly as a heat pump.
But is there a way in which it really could work? Perhaps.
I’ve had a soft spot for burning metal powders for energy ever since I heard the idea. I’ve thought of the difficulty of turning metals into a sufficiently fine powder as a major problem. But …
(Many ideas churning together in my brain here):
- It’s very much easier to powder a metal if it’s brittle
- Making iron brittle generally requires a high carbon content
- The carbon would burn off when the iron combusts so more carbon would have to be added
- Unless there was some other way of making brittle iron
- Much more efficient overall to avoid using a cyclic process and instead run it on scrap iron
- But scrap iron would not necessarily be brittle
- Turning rust into iron with electricity requires nearly as much electricity as making aluminium
- In electrolysis, water is a problem, you’d need to make sure that that rust is dry
- Can you partially turn the rust back into iron, enough to be burnable but retain some oxygen to aid brittleness
- Small scale iron manufacture like this wastes a lot of energy as heat and produces crap quality iron
- But is this heat captured and used or only the heat from burning iron
- Crap quality iron is better for pulverisation
Too many questions and not enough answers. Looks like a good research project.
Let’s look at efficiency.
> High-efficiency electrolysis of iron oxide can store as much as 80 percent of your input energy in the iron fuel, according to this 2018 paper – a figure similar to what you get with modern hydrogen splitting. Using this kind of cyclical process to generate electricity could approach a theoretical efficiency around 40 percent, again according to this 2018 paper.
That 40% would be a theoretical maximum. Extremely difficult to achieve in practice.
Electrical heat pumps have an energy efficiency greater than 100% if I remember correctly. That’s because the electricity isn’t used to generate heat, it’s used to amplify heat. (Checks web). Yes. “A leading edge residential heat pump can deliver heat at 600% efficiency, compared with a gas heater at 50% to 95% efficiency. When the electricity is produced using renewable electricity, this delivers astounding reductions in greenhouse gas emissions.”
So we’re talking a theoretical maximum of 40% for a cycle based on iron vs a current technology of 600% for an electrically operated heat pump.
> It might seem a little odd to generate renewable energy, then toss 60 percent of it out in the form of inefficient steam turbine generation processes, but this could end up being a flexible and cost-effective way to capture, distribute and even export renewable energy that’s generated at inconvenient times when there’s no demand for it to be fed directly into the grid.
It’s the “distribute and export” that is of interest. Unfortunately, iron is still heavy. Magnesium and aluminium would both be better. If we change that to the even lighter lithium then we’re back to lithium ion batteries.