Combustion of wooden particles

Be careful. Under certain conditions dusts can become potentially explosive. Guidance on assessing the extent of zones is given in EN61241-10.

May I ask why you wish to grind wood to micron sizes and what are you trying to achive? This will affect how you perform this operation safely, and safety is a concern because the dust you are creating is not only fully flammable it can be explosive!

I completely agree with the other posts .

This sounds like a potentially very hazardous situation. Even sawdust from a standard tablesaw, or other any other type of power saw, is explosive if enough of it becomes airborn in a closed area like a garage.

Be careful with your experiments -- good luck.

There have only been a few documented cases of incidents with wood dust exploding. Some grain silos also. It is not that easy to ignite or wood shops all over the world would blow up every day. You have to get just the right ratio of dust to air, just like gasoline and the right ignition source to get it to work.

You can put out a cigarrette in liquid gasoline and unlike the movies spilled gas will not light up so easily. They rig things with more easily combustible materials and devices.

Other than that I don't have an answer for the original question.

Yes you are correct in your assessment, but the potential is there and should be taken VERY seriously.

To state the obvious, such as; liquid gasoline does not burn (DOH), really isn't necessary --- but you are correct, and very few if any wood shops (that I am aware of) have burned because of dust in the air -- I'm certain it has happened and is something that should be taken seriously.

Anyone who puts cigarettes out in liquid gasoline is a complete fool, yet there are those who will just to prove a point.

The object of my post was to encourage the original poster to proceed with CAUTION as the potential is there.

Your assessment does not change my views on safety or my attempt to bring it to the forefront in the questioner's mind..

There is no doubt it can be potentially dangerous.

I am assuming he will do this in a completely controlled environment.

All safety pre-cautions should of course be taken.

I was not totally disagreeing, only noting that it is not that common. A unique set of circumstance needs to be present: air/fuel mixture has to be right, moisture, igniton, and combustion chamber have to be righ.

He will want that because that is what he is after.

I would be curious to know if he/she will find it easy to combust the wood dust or not in his/her research.

I have not, nor will not put out a cigarrette in liquid gas. I don't smoke.

As for stating the obvious, it was an example. I am glad you were observant to that.

Again, your pointing out the following is a valid point;

"I was not totally disagreeing, only noting that it is not that common. A unique set of circumstance needs to be present":

The possible reason explosions in wood shops, grain silos, bakeries etc. etc. is not a "common occurrence" -- is that this lesson was learned decades ago and have since been cautiously approached. "The unique set of circumstance" has been reduced or eliminated and this is what I hope the original questioner will do as part of his/her process.

All of the industries mentioned put great effort into proper ventilation systems for their processes, maybe this is the reason the danger has been reduced in current times.

Commercial wood shops, are generally equipped with dust extraction systems on each machine usually a vacuum of some kind, as well as a shop ventilation system, i.e. exhaust fans. Maybe lessons learned in the past have paid off. This is also encouraged in small home shops as it not only helps with the safety issue it helps keep a small shop clean.

I haven't been in a grain silo since the '60s but even then ventilation was a serious issue and was/is conscientiously addressed at all times.

I agree with you --- SAFETY is paramount in ALL industrial processes.

Ietech, YOU WERE AND ARE RIGHT!!!

Safety should always be paramount, let the others get put Post Mortem onto:-

http://darwinawards.com/

You and I will just read about them!!!

Why not treat wood with high pressure/temperature steam (±1400°F-±850°C) and burn the off gases?

Wood particles and virtually every other material containing material that will oxidize will undergo explosive reaction under appropriate conditions of particle size and concentration if a source of ignition is present.

Since this can occur because of static charge, this is particularly important for pneumatically conveyed materials; hence the reason for grounding and static charge arrestors on such systems. Please be careful.

I don't have any information on your first question, but in reply to your second question, we use a knife mill to pulverize wood. I don't know how fine you want the product, but it is difficult to grind a fibrous material like wood to pass a fine screen, such as 60-mesh (150 micron).

Bill Morrow

sandpaper does a great job of it.

If you don't mind having abrasive particles in the product. Otherwise they have to be separated out.

Bill Morrow

Think carborundum wheel! Sandpaper is a generic term to illustrate a method.

...you will still get bits of the wheel in the end product....

The problem with combustion is when your fuel to air ratio is in the correct proportion. Too much air or too little air no rapid combustion. To little air smolders, smothers or burns slow controlled by air circulation. To much air and heat gets absorbed by the air and lost from the fuel, extinguishing the ignition.

Most dusts at the perfect ratio will burn.

Is particle size or surface area your goal? The smaller the particle the higher the surface area.

The higher the surface area the more rapidly the oxidiser can combine with the fuel. This can be so fast that the reaction is explosive, in the correct or incorrect conditions depending on your circumstance.

Not knowing your intended purpose/application or anything about you my suggestion is be very careful with fuels, oxidisers and uncontrolled conditions.

Brad's 2 cents worth

....a prime example being the physics test in the school lab using a teaspoon full of common flour!!!