Incineration

[Geo]

if you just dry the chemical, it forms a salt. when you add water, it hydrates back to the chemical it was. to completely remove the nitric or the hcl from material, it needs to be brought to (at least) a dull red heat for a few minutes. you cant do this in a glass container. Harold recommends a stainless steel pan. any heat source that can get the material that hot will work. if the material contains carbon, it needs to be kept at a red heat until all the black carbon is gone and chalky white ash remains, if its solids (like ceramics or metal) just a dull red heat for a few minutes will work.

 

[kjavanb123]

Thanks a lot Geo, I saved some left over solution after nitric leach and it seems positive for gold.

Regards,
Kevin

 

[pesco]

Hi guys,
I know its an old topic, but situation have changed, at least from point of view :mrgreen:

Back in early nineties every two weeks I was getting bucket load of sand papers and around 1.5 kg workbench dust (mainly paste) along with spent electrolytes. Propane costed me next to nothing, so all solids were incinerated. I never used steel pan and would not recommend it as some values form alloys with steel very easily. Container of choice was around 3 litres, deep ceramic dish and was doing all papers and paste in small batches.
The yield was good enough to return more then twice as much values as my competitor (to be clear - he wasn't sloppy or uneducated, he was just greedy :x ) and still make very nice profit. Problem were losses and I was joking to my mates that if I carry on like that for next 20 years or so I will be proud creator of new gold ore deposit around my garden :mrgreen:

Today I would rather experiment with pyrolysis. Last year I have done pilot batch of RJ45 connectors, gold plated tapes and sim cards. Plastics simply vanished, but still there is a bit of carbon left from paper labels, some tapes etc.. That batch is still waiting for further processing but I am thinking of replacing incineration by heating the batch up on hotplate and very slowly blowing oxygen over it. Should work in theory, but practice is often quite different animal. Anyone tried ? :mrgreen:

 

[Geo]

Hi guys,
I know its an old topic, but situation have changed, at least from point of view :mrgreen:

Back in early nineties every two weeks I was getting bucket load of sand papers and around 1.5 kg workbench dust (mainly paste) along with spent electrolytes. Propane costed me next to nothing, so all solids were incinerated. I never used steel pan and would not recommend it as some values form alloys with steel very easily. Container of choice was around 3 litres, deep ceramic dish and was doing all papers and paste in small batches.
The yield was good enough to return more then twice as much values as my competitor (to be clear - he wasn't sloppy or uneducated, he was just greedy :x ) and still make very nice profit. Problem were losses and I was joking to my mates that if I carry on like that for next 20 years or so I will be proud creator of new gold ore deposit around my garden :mrgreen:

Today I would rather experiment with pyrolysis. Last year I have done pilot batch of RJ45 connectors, gold plated tapes and sim cards. Plastics simply vanished, but still there is a bit of carbon left from paper labels, some tapes etc.. That batch is still waiting for further processing but I am thinking of replacing incineration by heating the batch up on hotplate and very slowly blowing oxygen over it. Should work in theory, but practice is often quite different animal. Anyone tried ? :mrgreen:

what you describe is the general process for incineration. heat the material until only a small bit of carbon remains and then play oxygen over the heated material to convert the last bit of carbon to carbon dioxide.

 

[pesco]

As far as I am aware :
incineration -> is exothermic process where treated material is burned with a help of external source of fire,
pyrolysis -> endothermic, dry distillation, no fire involved
oxidation by heating up in presence of oxygen -> I don't know if that has its own name, but it is also endothermic, no fire involved

Lets take a piece of timber and place it in a shallow dish (assuming no wind involved):
incineration -> set it on fire, no external energy required (but could help), lots of flue gases and ash movement, small amount of ash left as big part of it flies away
pyrolysis -> put a lid on top of the dish and heat it up, wood breaks down to carbon and gases, gases fly away, carbon and all ash stays on the dish
oxidation in presence of oxygen -> just like previous, lid on top of it, heat it up, supply oxygen, in theory carbon should oxidise to CO₂ leaving all ash on the plate


I've done the pyrolysis and wonder if anyone tried removing carbon by heating the sample in presence of oxygen.
Not sure if it works in reasonable temperatures.
It might be not worth the hassle as the small amount of carbon left after pyrolysis could be quickly incinerated with minimal losses.


Any thoughts Deano? You are the expert in pyrolysis and related :mrgreen:

 

[yossarian]

I know this might seem like a silly question, but I am totally new at all laboratory procedure and am trying to figure it all out from scratch.

I am currently in experimentation phase of my refining. That means I am doing the Hoke acquaintance experiments as well as other refining processes but on a very small scale. everything is being done with a few grams of material and a few milliliters of acids.

Anyway, for Incineration steps to get rid of excess acids before adding other acids, I am using an ordinary MAPP gas blow torch. I use this because it is what I have and am not ready to purchase an acetylene torch yet.

I am wondering if this is good enough for these purposes? Also, when I try to Incinerate the foils and powder on the used filter paper, the pressure from the torch blows everything all over the place, no matter how low I set the flame, and a lot of it gets lost. I am currently using a ceramic evaporating dish as the container. I was considering getting a crucible with a cover and just heating the crucible but I don't know if it will get hot enough inside without direct contact with the flame.
Is there some kind of trick I could use to prevent this?

 

[maynman1751]

Mapp torch is more than adequate. You might try incinerating in a larger vessel. Do you have a stainless steel pot to use? When incinerating, keep the flame up off of your material. Once it's partially burned you can move the flame closer. It will take a little practice to figure out what works, but I really think you need something larger with sides.

 

[qst42know]

I know this might seem like a silly question, but I am totally new at all laboratory procedure and am trying to figure it all out from scratch.

I am currently in experimentation phase of my refining. That means I am doing the Hoke acquaintance experiments as well as other refining processes but on a very small scale. everything is being done with a few grams of material and a few milliliters of acids.

Anyway, for Incineration steps to get rid of excess acids before adding other acids, I am using an ordinary MAPP gas blow torch. I use this because it is what I have and am not ready to purchase an acetylene torch yet.

I am wondering if this is good enough for these purposes? Also, when I try to Incinerate the foils and powder on the used filter paper, the pressure from the torch blows everything all over the place, no matter how low I set the flame, and a lot of it gets lost. I am currently using a ceramic evaporating dish as the container. I was considering getting a crucible with a cover and just heating the crucible but I don't know if it will get hot enough inside without direct contact with the flame.
Is there some kind of trick I could use to prevent this?

Heat from below to red hot in stainless, corning pyroceram, or vision ware dish. It will stick for a time as the salts melt, keep heating and the salts will give up as well and your material will begin to release from the surface. If you don't have oxygen stir gently to put all material in contact with the red hot bottom eventually virtually all carbon will be eliminated it just takes a bit longer without additional oxygen.

 

[srlaulis]

Thank you Harold for taking the time to write such an informative article. I really enjoy the opportunity to be a student of your teachings. Your vast knowledge and experience is such a treasure in this forum and nice addition to my collection of notes.

 

[lysdexic]

There are losses by various procedures, so a filtered fume hood is a great idea. Even when dissolving values, if there's the slightest bit of effervescence, the tiny bubbles that surface burst with enough energy to carry off minuscule traces of vales. A filtered fume hood can capture the bulk of the losses and return them, assuming it's filtered and can be cleaned appropriately on occasion. I used 20" x 25" fiber glass furnace filters in my hood, which were easy to change. Once fully contaminated, I'd pull the filter and incinerate, then store the wastes that were generated. It the filter had punched steel faces, that portion went in the stock pot, and the incinerated ashes were stored, just as I recommend.
Harold

Harold,

I've read a number of your posts concerning incineration (and many other topics) and I have a question, if I may ask. I saw a picture of your hood and read how you coated the blower with epoxy. Was your hood made of stainless steel and what had to be done to protect it from corrosive vapors? (sorry that was two questions)

Doug

 

[FrugalRefiner]

Doug,

Sadly, Harold doesn't spend much time here these days, so I'll attempt to answer your questions. After a bad experience with fiberglass, he built his hood from an asbestos material called transite. I don't recall him ever mentioning coating it with anything, so I'm guessing the material was fairly resistant to chemical action as well as heat. Since asbestos is now considered evil, transite is no longer available.

Dave

 

[butcher]

You can still find asbestos, in many places, and in many older building materials, in old fume hoods, inside older flammable storage, and chemical storage cabinets (many times between the sheet metal of these), older house siding, asbestos, in old stoves, or backings, old refractory, or insulating materials.

I have worked with asbestos most of my life, it was used in many things, refractory and insulation, and many building materials, this natural rock had so many very useful purposes, and was an excellent material for many applications.

Asbestos can be extremely dangerous if worked with improperly, which is the main problem with it, I remember working on boilers mixing 55 gallon drums of powdered asbestos, we would reach into the drum and grab handfuls of the dust and throw it into a bucket of water to make a mud to replace refractory in the boiler, the fine powdered dust would fill the boiler rooms air, back then we wore no masks, we would also cut the insulation off of steam piping that dust dropping all over us, blowing out brake drums with compressed air, crawling through layers of asbestos insulation...

Through all of my years of working in the trades that I have, I have breathed an awful lot of this dust, and will most likely suffer from lung problems because of it.

I still think asbestos is a great material, superior to many of the materials we are using to try and replace it with today.

The rock itself is not deadly, in fact I believe this rock has helped to save many lives, from its fire resistant properties, breathing the fine fibers of the dust from this rock is what makes it so dangerous, it is what we do with the rock or how we handle it that makes it so dangerous.


A big problem is how asbestos is worked with, another problem was that it was so useful that it was used in so many different products, and in many different forms in construction material, because of its fibrous properties and fire resistant qualities, these construction materials when worked on later, it may have not been known to the workers that the material contained asbestos, and he could be cutting the materials with a power saw or some other work, and be exposing himself and his lungs to this dangerous dust without even knowing it.

Older industrial buildings, and even homes, can still contain tons of this rock in many different building materials used back then.

 

[lysdexic]

Thank you Dave and Butcher,

I kind of like Harold's to the point and kick in the seat when needed approach. I hope he's well and enjoying retirement.

Well asbestos seems out of the question and the best suited modern materials out of my reach. I would like to be able to incinerate and melt inside a fume hood as well as use it for chemical reactions. My budget is near $0.00. I do have some perfect sized steel components and some 1/4" tempered glass. I have second thoughts but was considering using an epoxy appliance paint on steel. I can build my own centrifugal fan using Unka Dave Gingerly's book on the subject. I just am unsure if it would last long enough to make it worth the effort.

Doug

 

[butcher]

Melting metals, welding indoors, well first what type of shop do you have, concrete floors, wide open non flammable areas, non combustible walls and work area...

If the shop you work out of can handle it safely, a large fan in a door way with an open window on the opposite side of the shop.

I would prefer to work outdoors most of the time; a carport type roof can help keep the rain and snow off your back in bad weather.

You can build a fume hood on a low budget from building materials you can find, they make a hardie board (fiber-reinforced cement board), as an underlayment for tile floors, a similar fire resistant (not fire proof material) is used in house siding, coating this with an acid resistant epoxy coating may help if using acids in the fume hood.

Large ceramic tiles, grout may suffer some and need replacing now and then, the grout can be coated with a acid resistant coating.

If you plan on using glass be sure to use tempered safety glass, I have some tempered glass from old wood stoves and ovens that would work fairly well in this area.

Build a brick fireplace, with a tile chimney coat the cement... :lol:

 

[gold4mike]

Butcher described almost exactly the materials I used for my fume hood. The Hardee backer board was used on 2X4 framing, and RTV Silicone to caulk the joints. When it was done I bought 2 cans of pickup truck bed liner coating from the auto parts store and brushed it on thick.

The fumes from that stuff are almost as bad as those from our processes. Let it cure for a couple of days. I haven't had any spills penetrate it yet.

 

[lysdexic]

I guess I'm guilty of not providing all the pertinent information. My work area is a garage built on a concrete slab. It's basically a one car garage that's almost two cars deep. A regular roll up door in front and a large sliding (rolling actually) door in the back on the right when looking in. There's usually quite the natural draft when both doors are open but I still don't weld inside (not much of a welder and don't do much of it) or use the torches. Incinerating indoors, I refer only to the type Harold spoke of in this topic, filters and other wastes, PM's or concentrates that contain PM's. I have a wood stove where I'd like to put a hood. The stove hasn't been fired up in years but I've spent many cold winter days and nights out there with the stove burning hotter than a fume hood would get doing what I'm proposing. Metal melting I mentioned I meant only the few grams of gold I'll get here and there, maybe some silver, but nothing more than would fit in a melting dish. I was thinking perhaps a "micro" version of a crucible furnace fired with a mapp torch, something along the lines of lazersteves fire brick furnace but with more refractory. I wouldn't want to melt anything else indoors, even lower temp potmetal (zinc casting alloy), on one hand the fumes and on the other it's too much to safely manage in a fume hood... anything bigger than a button would need to go outdoors. Gold indoors (to quote Harold) for all the wrong reasons. The old woodstove (outside for this one) would make a nice incinerator for flatpacks and such... seal it up with some stove cement line it with refractory cement and the exhaust gasses could be piped to an afterburner. I'm toying with an idea for that too but I've already cover way too much ground here so I'll save that for when I get that far. I'm not suggesting this is the best route or the safest. I know my environment, I know to cease and desist if there's a safety concern, I know to be very careful testing and go slow, checking, double checking and then checking a few more times while looking for other things to check on to make sure the structure and system can handle the work I want them to acomplish. I say this not to be cocky but so that someone doesn't go off half baked and burn down their house or garage. I have fire extinguishers and a full cylinder of CO₂ that I could flood a fumehood with. When working with anything that can burn... cutting torch, welding, melting metal (people here talk of shoting or making cornflakes of metal by slowly pouring molten metal into water... NEVER however introduce water into a crucible of molten metal) I always have the water hose there and charged.

If I do go forward with this idea I'm thinking I'll build and test it outside so I can push it a bit and see how it holds up, see how hot it gets incinerating etc. That way if it's a failure it will already be close to the scrap pile and I can just tip it over onto the rest of the junk

Doug

 

[Macleight]

Hello,

I recently dissolved some base metals off various types of scrap with nitric. I have washed the materials well, and filtered them off. They are safely trapped in my filter. I would like to boil in HCL next to further remove base metals. Obviously, I don't want to create AR, and so incineration is the next step. I have setup something very similar to what Harold describes, with a stainless steel cup on a propane stove.

However, I do not see much information on safety during this procedure. I was a firefighter in a past life, and know how to keep my backyard from catching on fire, so I am more worried about fumes and vapors. I want to stay nearby and monitor the process, do I need a respirator? Earlier in this thread, there is mention of values volatilizing and being lost, and Harold put this to rest, but what of the base metals? There is still likely some solder remnants in the filtrate. I know lead fumes are bad. Butcher has said heating silver chloride can cause some to volatilize. There is a chance some silver chloride is trapped on the papers. (How could silver chloride have gotten into the mix, you ask? From some of the wash water. I distilled some for washing, but I don't have a test for chlorides and won't completely rule it out.) Some of the scrap was escrap, so there is the chance that there is unknown material in the mix, maybe even dangerous things like cadmium. Probably not much, but better safe than sorry.

Any thoughts on safety during incineration of filter papers?

 

[butcher]

When working outdoors, if you have a breeze it can help to blow fumes away, but many times like a camp fire, the smoke seems to try and follow you around the campfire, you now smoke likes the good looking one, a box fan can help keep the fumes traveling in one general direction, away from you, and you do not have to stand over it the whole time, in fact most of the time I spend well away from the process, if done the way I do it, it takes time, and I can let it work, with me far away from any of the fumes.

It does take some practice knowing where to set the heat, before walking for a while.

There is some of the time you will need to work next to it, the fan and a respirator will help (I normally do not wear the mask although at times I should).

If you live in town on a city block you may find all your neighbors very mad at you for stinking up the whole neighborhood. I live out in the country with plenty of room between me and any neighbors.

Much of the stuff I have incinerated I surely would not want to do this in town. without a good fume hood and a scrubber or an afterburner, this stuff stinks terrible, the smoke is toxic and is a danger to other people who may be in the area to breath it.

How bad your filters will be, can depend what is in your filters and the volume...

The fumes from this is definitely something you do not want in your lungs.

Even outdoors it would not be a bad idea to have something like a make shift fume hood on the back of your incineration table, to keep the dangerous fumes away from you, an old metal box with a fan and some old duct work would help pull the fumes a distance off from where you need to stand, or work.


On a hot plate in a corning Pyro Ceram casserole dish, I wash the material in a fairly strong solution of sodium hydroxide and water, stirring and crushing lumps, add some heat then lower heat to let everything settle well, this will help any base metal chloride give up the chloride to the sodium, (or other acid component of the salts), and the hydroxide to help form base metal oxides or hydroxides, after the powders settle well, the newly formed sodium chloride (or sodium salt of the acid as the case may be), the salt solution formed can be decanted, a couple of heated water washes, with time for the powders to settle well, before decanting (or siphoning off the soluble liquid salts), this will help to remove the soluble salts.

Then we can set the heat on the hot plate for drying, normally you need a fairly low heat, too hot and once most of the water is gone, it would form large gas bubbles which can pop and splash out your goodies.

Slow low heat will evaporate water and not form the large gas bubbles, now the powders will dry out, and need crushing after dry, after crushing to powder we can raise the heat for a while, this will begin to drive off acids, the powders may fuse and begin to form a syrup after a period of time, in this case you need to lower the heat, as the syrup will again form the large popping bubbles, at a lower heat the syrup will again dry out as it removes most of the acids, it will take a while.

Keeping an eye on it checking it more often as it becomes more dryer.

I try to catch it before it completely dries to a hardened cake, where it is easier to crush to powders again, after crushing to powders I can raise the heat in fairly larger increments, driving off the last of the acids, and then bring the temperature up to full heat of the hot plate, driving off the harder to remove acid as gases.

After this I can use my torch to increase the heating of the powders to get them glowing red hot heat, and stirring the powders to expose them well to the oxygen while holding them at red hot for a period of time, (normally 20 to 30 minutes) to complete the incineration process, before the cooling and the washing of the powders.

 

[Dude4ever]

Hello again my fellow intellects.

I'm toying with a thought that seems awfully logical in my mind, so I want to do the most reasonable thing and share it with you, so that it can be disassembled by those who can see it's resulting reality;

I want to make a incinerator, but as mentioned before in countless threads, the fumes produced by burning scrap is not preferred by your lungs, or even by the local authorities.
But I have looked into how to make a DIY Induction Heater lately. For those who not instantly knows this device, it is basically a thick & large copper coil that you run electricity through, more specifically a high current through (Ampere).
That produces a moving magnetic field (eddy currents), and that will in turn induce a even larger current in anything that is made of iron, placed inside of the mentioned copper coil (This link shows it all: http://www.mindchallenger.com/inductionheater/).

Anyways, my thought is; if you construct a induction heater, that couples with a heavy iron- or an even more heat resistant container, and this container were to be filled with chips and whatever wanted, and then you seal it so that it behaves like a preassure cooker does with water, having a safety valve of course, and then my logic tells me that if you were able to rapidly heat the container to near melting point, while keeping the gas pressure generated inside, you would eventually combust the worst toxic fumes as well? I include in my reasoning that you may connect a supply of oxygen that feeds the container, or even include some kind of chemical or substance in the container that will react with the gases to render it neutral or at least manageable, given the extreme heat combined with very rapid heating

This way gases would at the very least, in my mind be invisible by the time they reach air
I welcome any aspiring "mythbuster" to replicate this suggestion, I'm not at all a electrician, but I intend to make some small prototypes throgh "trying and failing", regardless of any opinion some may respond with.
I will of course consider the educated opinions of the more expirenced refiners, that I know from earlier in this forum.

Food for thought?

 

[jason_recliner]

I can't contribute much on your idea but I'll share something as a transformer manufacturer.
Induction is not actually proportional to Amps, rather Amps * Turns.
Putting 5A of current through 2 turns of copper is equivalent in magnetomotive force to 1A through 10 turns. This gives you the ability to reduce your current enormously for the sake of a tad more copper wire. Of course, the longer the copper the higher the resistance, and the more turns the higher the inductance which may reduce AC current. You will eventually run into the law of diminishing returns.
HTH.