Magnesium Recycling

Dry sand is the best way to extinguish a Mg fire.

Yes, it can be recycled.

Depends on what your 'dry sand' is composed of...

Silicon dioxide and Magnesium constitute a type of thermite. While it requires a high temp for ignition, a magnesium fire can certainly provide a high temp. Once initiated it releases a significant amount of heat....sufficient in some cases to partially vaporize the resulting silicon.

Since Magnesium fires are difficult to extinguish and burn very hot, the firefighting procedures which are standard for most materials will not work.

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The threat is enough that, the procedure the US Navy specifies only 'Jettison', meaning no attempt should be made to fight the fire and salvage whatever equipment happens to have burning magnesium attached; the equipment should be immediately sacrificed by pushing it overboard.

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For me this was one of a myriad of absurdities: 'Jettisoning' burning metal isn't really an option on a sub.

I was in the Navy. My first three years was in an aircraft squadron. Then I went thru the nuke program (two solid years of schooling), and went to a nuclear powered aircraft carrier. EVERYONE in the Navy attends firefighting school. Book-learning and hands-on. A magnesium fire cannot be extinguished with water. Smothering it with sand is about the only thing that works. Jettisoning the offending part overboard was the only method endorsed because magnesium burns extremely hot and the potential danger to the vessel, equipment, and occupants makes it not worth the risk to try to save whatever the burning magnesium might be attached to. So, jettisoning the burning magnesium and whatever it might be attached to would be the actual method used. Fortunately, we never got an aircraft wheel burning on either carrier I served on. That would have been expensive.

Volatile? Maybe extremely flamable but I don't think it evaporates prior to ignition...

Enough nitpicking. Oxygen deprivation will stop the burn. A bit tough to do if its getting the oxygen by reduction of an oxide (eg rust) though....

Jettison from a submarine would work, just push out the flyscreens when you open the windows.

Certainly NOT volatile! Not even flammable under ordinary circumstances. I haven't used it recently, but I've had a magnesium pancake/frying pan for camping for around 50 years. I've used it directly over open fires many a time.

It takes extreme temperature to ignite magnesium. If it is a fine powder mixed with a lot of air, that temperature can be achieved with a match (with rather spectacular results), but for massive chunks of the metal it takes a lot more heat.

No ignition can continue without an oxidizer, so as someone else implied, anything non-flammable that can cover it completely will extinguish the fire.

'....anything non-flammable that can cover it completely will extinguish the fire....'

You consider water to be non-flammable, right? And by that logic, dropping magnesium into a pool of water deep enough so that it is fully submerged, will extinguish the fire, right?

Lots of non-flammable things will increase the intensity of a magnesium fire, by increasing the availability of things like oxygen, chlorine or fluorine.

Of course you are right! I should have said "...anything that won't itself provide an oxidizer..."

When I was a kid in the 60's, my Dad used to bring used/reject magnesium printing plates home and I would cut them into narrow triangular shapes with a narrow apex angle (a few degrees) and light them in our backyard incinerator (a 60's institution in Aus). The very fine end would get it started and the thicker sections would light the whole place up! Drill swarf was similarly employed!

I fear any burrs on the frypan could provide very effective (if unintended) backlighting for your camp cooking some day.

When machining magnesium castings in the late 70's we had a bucket of fire retardand dry powder on hand but didn't have any cause to use it.

The frying pan does indeed have all edges well rounded.

I have machined magnesium several times, and am happy to say that all the magnesium fires I've seen were intentional, and none anywhere near a machine. I really should get rid of the two bags of drill cuttings I still have...

I think in the firefighting profession this is called a Class D fire--burning metal. There are Class D extinguishers, but I'm not sure what the extinguishant is.

From Wikipedia:

Class D A class D fire extinguisher for various metals

There are several Class D fire extinguisher agents available, some will handle multiple types of metals, others will not.

• Sodium Chloride (Super-D, Met-L-X or METAL.FIRE.XTNGSHR) contains sodium chloride salt and thermoplastic additive. Plastic melts to form an oxygen-excluding crust over the metal, and the salt dissipates heat. Useful on most alkali metals including sodium and potassium, and other metals including magnesium, titanium, aluminum, and zirconium.

• Copper based (Copper Powder Navy125S) developed by the U.S. Navy in the 70s for hard-to-control lithium and lithium-alloy fires. Powder smothers and acts as a heat sink to dissipate heat, but also forms a copper-lithium alloy on the surface which is non-combustible and cuts off the oxygen supply. Will cling to a vertical surface-lithium only.

• Graphite based (G-Plus, G-1, Lith-X, Pyromet or METAL.FIRE.XTNGSHR) contains dry graphite that smothers burning metals. First type developed, designed for magnesium, works on other metals as well. Unlike sodium chloride powder extinguishers, the graphite powder fire extinguishers can be used on very hot burning metal fires such as lithium, but unlike copper powder extinguishers will not stick to and extinguish flowing or vertical lithium fires. Like copper extinguishers, the graphite powder acts as a heat sink as well as smothering the metal fire.

• Sodium carbonate based (Na-X) used where stainless steel piping and equipment could be damaged by sodium chloride based agents to control sodium, potassium, and sodium-potassium alloy fires. Limited use on other metals. Smothers and forms a crust.

• Some water based suppressants may be used on certain class D fires, such as burning titanium and magnesium. Examples include the Fire Blockade and FireAde brands of suppressant.^[16] Some metals, such as elemental Lithium, will react explosively with water, therefore water-based chemicals should never be used on such fires due to the possibility of a violent reaction.

Most Class D extinguishers will have a special low velocity nozzle or discharge wand to gently apply the agent in large volumes to avoid disrupting any finely divided burning materials. Agents are also available in bulk and can be applied with a scoop or shovel.

all ga's. the second part of my ? was, can it be recycled?

In the first response, Lyn answered that in the affirmative.

Magnesium can indeed be recycled.

I figure if somebody is buying scrap magnesium then it must be recyclable.