MOx Energy Metal as Fuel Cycle — The MOx Cycle

MOx Energy FAQ Frequently Asked Questions

What does MOx mean?

MOx is a metal oxide. When metal fuels burn, they release a lot of energy, and are converted into oxides – for example, iron becomes iron oxide, or rust.

Does metal burn?

Yes. When metals rust or corrode they react with the oxygen in the air, which is a slow oxidation. This process releases a small amount of heat. If the metal particle reaches ignition temperature it will oxidise rapidly, or burn, releasing all that heat energy quickly. For iron powder, the ignition temperature is around 1300°C, less than the temperature of a cigarette lighter.

Here is a good explanation (link)
Or a video (link)

How do you start the MOx fuel burning?

MOx fuel can be ignited by any flame hotter than the ignition temperature, around 1300°C. Most traditional fuel flames are around 2000°C, which is more than sufficient. The flame then sustains itself by its own heat release.

How hot does MOx fuel burn?

Around 2000°C-3000°C, approximately the same temperature as fossil fuels. The temperature can be tuned by altering the formulation of the MOx fuel.

How advanced is the MOx Energy technology?

Key components of the technology have been demonstrated by various groups globally to date from laboratory to small pilot scale. It is at a technology readiness level (TRL) of 5-6.

What equipment is needed?

Burning – MOx fuel is in powder form. In powder form, metal is easily carried in an airstream to be fed to burners, where it can burn like any other fuel. This can be with conventional burners, or even in piston engines. The MOx fuel system can be retrofit into many current industrial processes. This heat can be used to generate steam, drive turbines, convert heat in Rankine cycle machines, all the same things as burning conventional fossil fuels.

Recycling – Once the MOx fuel is burnt it is captured with filters, cyclones, etc. and then recycled. The burnt fuel is a metallic oxide, with iron it is more commonly known as rust. With aluminium it is aluminium oxide. This waste is then converted back to its metal state using electrolysis, or hydrogen reduction.

Here is a good video showing how hydrogen reduces iron oxide back to iron. The temperature required here is about 600°C.

What emissions are generated?

Burning – In the burning stage, there are zero greenhouse gas emissions. The combustion uses oxygen from the air, which when combining with the MOx fuel releases heat. Theoretically there is a small potential at very high temperatures to convert some of the nitrogen in the ambient air into nitrogen oxides (NOX gases). Real world examples in pilot systems have shown this is negligible, an important advantage over fossil fuels. MOx fuel is completely clean, a true zero emission solution.

Recycling – If the recycling stage is implemented with renewable electricity such as solar or wind then there are no carbon emissions. If hydrogen is used in the recycling, the hydrogen atoms strip oxygen from the MOx waste, producing very pure water vapour (H₂0). This can be seen in the video above.

Is it fully recycled?

Yes. The captured ash is fully recyclable, and the only losses are due to material handling, typically less than 0.1% per cycle

How many times can MOx fuel be recycled?

The MOx fuel itself is 100% recyclable.

Can it be stored?

Yes, easily in bulk, safely, and for long periods of time. If the MOx fuel gets wet it will oxidise slowly (i.e. rust). Humid environments may rust the outer layer of the storage pile. The bulk of the fuel can still be used, however, and all the particulate can be recycled. This should be contrasted with Hydrogen, which slowly leaks from any container, and fuels such as diesel and gasoline, which will degrade over a few months.

Is it safe to store and transport?

Yes. The fuel will not ignite until exposed to flame and fluidised in an air stream, under very specific conditions. It will not explode. As the conditions suitable for combustion do not happen naturally, it is very safe to store and transport.

What metals can be used as fuels?

Many metals can be burnt, such as iron, aluminium, copper, lithium, boron, magnesium, potassium, sodium and more. The easiest metals to recycle and hence use as a fuel are iron and aluminium. They also have a very high energy potential, and burn at temperatures equivalent to fossil fuels. They are abundant, and cheap.

How long can the fuel be stored?

In a dry environment the MOx fuel can be safely stored indefinitely.

How is it transported?

MOx fuel can be transported with standard bulk carriers such as road, rail, or cargo ships.

Can it explode when stored?

The risks of explosion are negligible, especially when compared to those of stored fossil fuels, and particularly Hydrogen.

Why doesn’t everyone do this?

Metal combustion has already been used for a long time in rocket propulsion. It’s use in industrial processes and for industrial heat requires in-depth process know-how. Retro-fitting the incumbent fossil fuel-based processes takes time, investment and foresight. MOx Energy is at the forefront of such market disruptions.

Is this technology ready or is it academic?

The combustion of iron and production of steam has been demonstrated on a laboratory scale (TRL 3-4). Demonstration in an environment relevant to practice (TRL 4-5) has been shown in Europe. The combined MOx Energy system remains to be demonstrated as an integrated sustainable industrial energy solution.

Will this replace hydrogen?

All sustainable energy technologies will be required for full decarbonisation of the global energy systems. Metal powder is safe to handle, stores indefinitely, and can be easily moved with existing bulk carriers like rail. Hydrogen is a required part of the energy mix. However significant challenges remain in the use of hydrogen for the applications we have identified.

Storing useful amounts of hydrogen generally involves high pressure and extreme cold. This is a significant limitation when trying to distribute or transport energy at a distance.

What is Green Hydrogen?

Green hydrogen is hydrogen that is generated with no carbon emissions. In the same sense, green steel, and green aluminium are metals made with no carbon emissions. In the traditional manufacturing sense, the production of hydrogen and steel are heavy users of fossil fuels for their manufacture, and aluminium uses a significant amount of electricity. It is possible to generate hydrogen with renewable electricity and fuel cells, or electrolysis. If the electricity is from renewable sources (solar/wind), then the hydrogen is labelled green. If you use green hydrogen to make steel, it is green steel. If you use renewable electricity for aluminium production it is green aluminium.

Does using MOx Fuels attract Carbon Credits and Reduce Carbon Emissions?

Yes. Using MOx fuel completely displaces fossil fuel use, which generates carbon emissions.