garbage incinerator

[robbie]

Traditionally, rural folks burn their trash and throw everything that's nonflammable into a ditch somewhere. I've found several garbage dumps on my property, with old furniture, appliances, jars and cans, and lots of roofing shingles for some reason. I don't care for this kind of dumping, so we do the same thing we did when I was a kid. We use a burn barrel, which is dumped at the landfill when full.

Burn barrels tend to fill quickly when things don't get burned completely, which is always. It's just a barrel with holes in it for air induction, and it's not efficient.

I have always wanted to build an incinerator for cleaner burning and to get more use out of a barrel. I had an unusable 80 gallon pressure tank left by the former owner of the property. I had always thought to build a barbecue out of it, but it turned out to be too thin. So I made holes in the bottom, cut a door, and cut a big hole in the top. Then I added feet to sit on top of a barrel. It's pretty simple, and it works great. It gets so hot that the metal glows.

In the photos you can see a typical burn barrel, then the incinerator. There's one photo that doesn't look so obvious. It shows the inside of the incinerator with not-very-visible holes in the bottom.

 

[robbie]

My wife took some photos of this thing in action at night and posted them on facebook. I'll see if I can find them.

 

[robbie]

Here are a couple of the night photos. It really lights the place up.

 

[mckutzy]

Ya that is cool. When I used to work at repair/building electric motors, we had a rig like that for burning wire.. but smaller, a metal paint bucket with a coffee can(2 actually) chimney.

What makes it efficient is having a back pressure for the initial heat to build up and start the reaction, and a good draft upwards.

With the wire burner, we would have a bit of wood to start it lit with a torch or the modified furnace burner it was setup on. air from a compressor was used to feed the fire, and once the wood started the main heat was turned off and it would be self sustaining for about 10 min or so. we also had another pipe for air leading to the lid way up the chimney for an after burner, which helped the process burn cleaner and the draft needed. .
We had flames just like the ones you had there, except they were blue and of course they were shorter.
This one was without the after burner pipe, we needed it later, cause the flames were getting bigger.

cool setup none the less.

 

[robbie]

I have a job delivering solar panels for my sister and brother in law in Kansas City 3 or 4 times a month. We usually end up with a little bit of cardboard in the truck at the end of the day. We used to burn this in the barrel, which was cool because you can roll it and make a chimney, but the bottom burns away pretty quickly and it falls over. This is what finally got me to build the incinerator after talking about it for so long. You can see in the photo where we have a big piece of cardboard rolled up and sticking out the top. Yesterday I had one of these in there with a plastic bucket at the bottom and I thought the whole thing was going to melt down and collapse.

When we were working yesterday I asked my son if he wanted to save any extra cardboard, and he decided to save four crates worth. These are big boxes about the size of large desk, and a little bit taller, made of triple thick corrugated cardboard. We filled the back of the truck with them. It was sort of like the time when I used to work at a pizza restaurant 25 years ago. We always wanted to steal chocolate pudding from the buffet, so one night the assistant manager just opened a can and had us all dig in. We were all sick of it pretty soon and never touched it again. This is what happens when you come home with a giant load of cardboard to burn. I still have several pieces left.

 

[mckutzy]

If they are the Gaylord plastic pellet material type bins, There are guys out there that will buy those if they are unmolested and clean.
When I used to work in injection molding, we had big stacks of them we used to sell to other companies, I think for like $40-$50 each.

 

[robbie]

I have a good story now to illustrate how well this incinerator works. My wife has a large drawer full of socks. She's been adding to them for longer than she's known me, probably 30 years. She finally decided to get rid of a bunch of them. Imagine two 5 gallon buckets full of old socks. Now imagine them in a regular burn barrel. You would probably end up with a pile of socks with only the top 3 inches burned. That's what would have happened without the incinerator.

I put them in there with the kitchen trash. Five minutes later it was a roaring inferno hot enough to keep me at least 5 feet away. When it burned out there was nothing but a few ashes.

 

[landuse]

I have a good story now to illustrate how well this incinerator works. My wife has a large drawer full of socks. She's been adding to them for longer than she's known me, probably 30 years. She finally decided to get rid of a bunch of them. Imagine two 5 gallon buckets full of old socks. Now imagine them in a regular burn barrel. You would probably end up with a pile of socks with only the top 3 inches burned. That's what would have happened without the incinerator.

I put them in there with the kitchen trash. Five minutes later it was a roaring inferno hot enough to keep me at least 5 feet away. When it burned out there was nothing but a few ashes.

That must have been something to see.

 

[robbie]

Yeah, there was some really evil looking smoke that was glowing orange right at the top of the tank. I've been having a lot of fun.

 

[mckutzy]

IF it get hot enough quickly, it will smoke far less. Try to put a smaller hole on the chimney. I reckon that will help bring up the temps quicker.
How do you start the reactor?

 

[robbie]

The way to start this thing is to just throw garbage in it and light it with a match. The only thing really special about it is that it allows massive airflow, which is created by gravity. The hot air rises and is replaced by new air from the bottom, the increased flow creates more combustion, which creates more heat, which creates more gravitational displacement and faster airflow, and so on. This just doesn't happen when you burn anything piled on the ground or in a barrel. Literally, this is the way a jet engine works. Because jet engines are horizontally oriented, you have to start them with compressed air. My garbage tank just starts with gravity. It's a beautiful thing. (I'm talking about the OLD jet engines of course. Modern ones have turbines built into them to cram air in and are started by electric motors.)

At first it had a smaller hole in the top, which caused a lot more smoke. Then I enlarged it, which made a huge improvement. The way to get less smoke and higher temperatures is to increase the fresh air supply with larger inlet holes in the bottom. I'm thinking of doing that, but it works well enough now that I'm not extremely motivated. Also, if I enlarge the holes too much the trash will fall out the bottom of the tank. At any rate, for optimal performance you always make sure there is plenty of outflow for the amount of inflow. This is critical because there is so much expansion going on in between. Generally, you want the area of the outlet to be twice the area of the inlet. If i ever do increase the inlet, I'll probably have to simply cut the entire top off the tank. Currently the top is about 60% open.

This reminds me of a project I've been wanting to do for at least 20 years. I had a mechanic friend in Texas who burned used motor oil in a barrel stove to heat his shop. The oil was in a small tank with a small copper pipe that entered the barrel and dripped into a dish made from a single disc from a disc harrow. He would open a small valve which allowed the oil to drip into the burner, then put in lots of wadded newspaper to start it burning. With some effort it would start and create sufficient heat to keep his shop warm in the Texas winter, which isn't saying much. His chimney was a piece of exhaust pipe with an air fitting on it. Every couple of days he would close the damper at the top of the barrel and fit an air hose to the fitting to blow out the massive amount of soot that collected whenever he used the stove. Then his dad would complain when he found soot all over his collection of meticulously restored antique cars which were kept in an adjacent shop. My idea is to connect the oil tank to the compressed air supply, fit a compressed air inlet to the barrel stove, and direct the oil tube into the air stream. The chimney would be very large to ensure adequate draw to suck up all the air being blown into the barrel. This setup would create a jet of oil mist, which would burn with a very hot flame but virtually no soot. I'll probably never build anything like that because I have more trees on my property than I know what to do with, and my pile of already cut firewood is enough to last me 2 years. But I think it would be a nifty project for somebody who works on cars a lot, has a lot of used oil but no trees, and lives in a colder climate than here.

 

[exenos]

I've been thinking about making a waste oil furnace as well because i can get a fairly steady supply of used oil from a guy I work for. The only thing holding me back is the sheer amount of heat that can be generated, hot enough to make steel sag and to melt cast iron. I'm not sure how to contain it properly.

 

[robbie]

Maybe just set it up to make a smaller flame?

 

[mckutzy]

Rob- gravity has no real influance in this respect to air movement, it is a vacuum that draws air into the bottom from heat going out the top.

Wase oil funaces that are getting hot quickly are of a pretty efficient design. You will need fire bircks to contain the heat. all this is getting into forge and foundry work if you are getting that heat for Iron.

 

[robbie]

I don't want to be disagreeable, but it is totally about gravity. Hot air is less dense than cold air. Gravity causes air of lesser density to rise and be replaced by air of greater density. Try building a furnace with the air inlet on the top and the chimney on the bottom.

Regarding waste oil furnaces, fire bricks are not necessary. My friend's barrel stove heated a shop and didn't get anywhere close to melting the barrel or even making it glow. The difference between his stove and an efficient design with a hot jet of flame is that they both could make the same amount of heat, but my friend's stove also consumed a bunch of extra oil and turned it into soot.

Regarding the difference between Texas and Canada, here are some more anecdotal observations. My trash burner glows red hot when burning large pieces of cardboard, but it's not enough to make it deform, so I'd say that red hot glowing isn't an inherently bad thing. My friend's stove wasn't anywhere close to red, and it heated a large shop in 45 degree weather. I think an efficient flame in the middle of the barrel would heat a shop in Canada without any trouble at all, and if it isn't enough you could safely increase the heat until you see red spots on the barrel.

I think the basic issue is that although waste oil burned efficiently will create tremendous amounts of heat, you can just build a smaller burner.

I'd love to build a test stove to prove this, but I just don't have a need for it.