# Incineration



## Harold_V

A recent inquiry by PM concerning incineration has prompted me to post on the subject. 

Those of you who have read my ravings know that I endorse the process, and recommend it for almost everything you may encounter. When your material gets incinerated and why may vary, but rarely will a process not benefit by the procedure. 

These are my thoughts, based on years of practice: 

Hoke, in her book, talks freely of tossing on gasoline when incinerating. That, of course, is insane. Gasoline should never be used as an accelerant, especially when working indoors. The risk of a fire out of control is immense. I strongly advise against using anything when incinerating aside from the material in question. None is required. 

Do not incinerate in a kiln. The most desirable condtion is one whereby the material in question can be ignited, not just heated and permitted to smolder. It's one way to limit the amount of smoke created by the roasting process. An ample supply of oxygen is required, which would be limited in a kiln. Open incineration is the answer. 

If plastic items (bags containing polishing waste, for example) are incinerated, they should be monitored closely. The bulk of plastic items don't burn well, turning to oil instead when heated. However, once they reach critical temperature, they often erupt in flame much like you'd expect from burning fuel. 

Do not incinerate in a hood that is flammable, nor on a countertop that has a wooden base under the burner. Prolonged heating will slowly convert the wood to charcoal, with a fire the outcome, assuming there is enough oxygen. A smoldering fire could result easily after prlonged incineration. 

My method for incinerating was simple. My heat source was the same one that I used for the refining process, although when incinerating no other process was in motion because of the excessive heat. 

The heat source in question was a three burner natural gas hotplate. They are relatively inexpensive (I used to pay $60), and were used as purchased, with one modification. I adjusted the valve on one position so it would be opened with greater flow, and adjusted the air full open. If natural gas is not an option, one could use propane, although with the propane tank out of doors, piping the gas inside. 

A discarded fry pan serves very well as the incineration container. It should *never* be made of aluminum, which would melt, nor cast iron, which will be difficult to heat well, plus they will crack when heated as is necessary for proper incineration. 

I found that stainless pans held up very well, and could be used for many cycles before they perforated. They do have a finite life, especially if acid bearing materials are incinerated, and that's one of the things you'll do routinely once you understand the benefits. 

Second-hand stores (Goodwill, for example) are an excellent source for pans of this nature. Boy Scouts used a small pan, about 6" in diameter, which serves very well for small lots, so if you encounter one, don't pass it by. 

I am assuming that the greatest interest here is the processing of E scrap. In that case, incineration may not be required until after the gold has been stripped. I would assume that the material would be stripped by a sulfuric cell, or one of the work-around methods promoted on the forum. 

Once the values have been removed from the base metals, the step I would recommend is to get all of them in a filter, where they can be drained and dried. When well drained, they should be introduced to the pan, filter and all. Heat the lot until the filter combusts, then add sufficient heat to the pan to achieve a dull red heat. Apply heat to the sides and bottom of the pan, not to the material inside, and do not melt the material. A Hoke type torch, or a rose bud serves very well for the additional heating. This should remove all oils and grease and plastic bits from the material, and burn off all carbonaceous substances. Heat should be maintained until there are no glowing embers. 

After incineration, crush the material well in a mortar, then screen the lot, removing anything that's magnetic, which should be added to the stock pot. It will likely carry traces of values, and they'll be recovered in the future when the stock pot is refined or furnace reduced. 

The now crushed and screened material can be treated by two methods, each of which will remove unwanted substances. If nitric is your choice, the material would be boiled in nitric/water until no more fumes evolve, then the beaker filled with water. Decant when the solids have settled well, and rinse once again, using water. 

If the material in question has the risk of containing tin, either from E scrap (solder) or it came from gold filled objects, which often have a soft solder bonding the gold surface, the material will benefit by a boil in HCl. This process will make for very easy filtration of the gold chloride solution that is yet to be produced. 

Going from nitric to HCl presents a serious risk of dissolving values prematurely. To get around the problem, once again, the material should be incinerated. Once well heated, all nitric would have been expelled. Once again, crush the material well in a mortar, then place it back in a beaker. There should be no need to screen after the first time. Cover the material with 50/50 HCl and tap water and bring to a boil, holding there for several minutes. Remove the beaker from the heat source, and add water. Allow to settle well, then decant. Rinse with water, stirring well, then allowing the material to settle. None of these processes require distilled water. Tap water should be more than adequate. 

After decanting, the material is ready to be dissolved to extract the gold. The resulting solution should be various shades of yellow, depending on the level of concentration. For the most part, the base metals will have been eliminated because of the acid washes. That serves to provide much cleaner gold.

All of these operations may sound like they are labor intensive, but they are routine-----easily accomplished, and paying huge benefits in the overall quality of gold recovered, plus ease in handling of the gold solution. Another benefit is you won't experience floating of precipitated gold, assuming you keep your vessels well washed, and don't get finger prints on the insides of beakers that are used in precipitation. 

If you are involved in refining wastes from the jeweler's bench, the only material that doesn't require incineration is large pieces of karat gold, which would be inquarted, thus freed of oils when they are melted. 

Something to ponder. 

Regardless of how much you may wash filters when filtering your gold chloride solutions, traces of values will usually remain. If you do not wish to spend the time, and prefer to not dilute your solutions by rinsing, do not discard the filter when finished with filtration and a fast rinse with water (I always used tap water). They should be dried, then incinerated, with the resulting ashes stored. By incinerating, any free acids are eliminated, limiting the amount of rust you'll experience in your work area. 

Don't discard anything that is in the filter. Everything should be stored for future processing by furnace. There is often silver chloride included, along with traces of other metals. They will serve to act as a collector when the material is processed, so they provide a valuable function. 

The bottom line here is that incineration should be a part of your refining processes. The benefits far outweigh the results of avoiding the process. 

Contrary to the belief of some, incineration does nothing to degrade the quality of gold, nor does it complicate refining. Yes, it is ugly from heating, but otherwise not changed.  Incineration will not complicate the refining process, and the washing process will restore the bulk of luster to the material. 

Harold


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## Buzz

Excellent post Harold, thanks.

How much of the values do you reckon actually "go up in smoke"?

Reason I ask is the fume hood.
Due to my location and facilities, i would have to incinerate outdoors and i doubt a fume hood would be very effective due to draughts etc.

I'd hate to stand there and watch all my precious just fly away!

Regards
Buzz


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## Harold_V

In my opinion, not much unless you incinerate polishing wastes. They were quite smoky and liberated a great deal of wax, especially if they were heated but not yet ignited. Once they ignited, they weren't bad. The vapors carried traces of the solids, but they were not lost, thanks to filtration. 

As for losses due to breezes, you'd have to design around that problem, but it's certainly possible. The size of the opening in the hood would serve well enough, or you could provide a complete cover, with fresh air vents placed in appropriate places. 

If you incinerate only small batches of materials, there really isn't much smoke. The worst things to incinerate are fume hood and polishing waste filters, along with the polishing wastes. Each of them smoke like crazy. I used to do a lot of my incineration in the dead of night to avoid the limited smoke plume being visible. Worked fine for years. My early refining years were in a sub-division, where houses were spaced 4 per acre. I had no complaints from neighbors while refining there.

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. 

If you incinerate out of doors, as long as you can keep the hood dry, there's no reason to not use one----especially a filtered one. A good paddle type blower would be clog free and provide enough draft to keep the exhaust running through the filter, assuming you designed the hood properly. You can even include a scrubber of sorts, which would also recover lost values. A little creativity could go a long ways towards designing something that functioned well. 

Assuming a scrubber is created, a cascading water type would likely work, but it, like the filters in a hood, should have provisions for the recovery of values. Anything solid that accumulated in the scrubber would be incinerated and processed by furnace. Assuming water was used, it could be introduced to the stock pot when it was changed, insuring that any values contained would be recovered. I had plans like that, but sold the business before they materialized. 

I don't feel comfortable disclosing the amount of gold, silver and platinum group I recovered from my waste materials (after more than 20 years of operation), but there's not a person reading this board that wouldn't be impressed. It was a wonderful savings plan-----especially with the inflated values of those metals on today's market. Damned shame I didn't keep the platinum group longer than I did. 

I encourage anyone that refines to pursue a hood and a scrubber of sorts. Do it for all the wrong reasons (recovering losses), if ecology alone isn't a good enough reason. You'll be justly rewarded, assuming you keep refining. 

Harold


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## skippy

I'd advise against anyone incinerating e scrap. Dioxins and brominated hydrocarbons are not something you or anyone else would want to breathe. If the incineration was nice and hot, with sufficient exygen I suspect most of the nasty stuff would be decomposed though. Watch out for the solid residue too, heavy metal oxides, etc.

http://www.aseanenvironment.info/Abstract/41015197.pdf


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## lazersteve

Excellent post Harold.. as is usual for you!  

Steve


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## Platdigger

Skippy is right about incinerating this E scrap stuff.

This is a whole different ball game.

Randy


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## Harold_V

skippy said:


> I'd advise against anyone incinerating e scrap. Dioxins and brominated hydrocarbons are not something you or anyone else would want to breathe. If the incineration was nice and hot, with sufficient exygen I suspect most of the nasty stuff would be decomposed though. Watch out for the solid residue too, heavy metal oxides, etc.
> 
> http://www.aseanenvironment.info/Abstract/41015197.pdf



I trust you took note of my comment:



> I am assuming that the greatest interest here is the processing of E scrap. In that case, incineration may not be required until after the gold has been stripped.



I made no recommendation to incinerate E scrap, but incinerating the stripped values *is* advised. Assuming you've done your work well, there would be precious little in the way of noxious fumes created, and the benefits of incineration would be far greater than ignoring the procedure. 

Harold


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## Harold_V

Thanks, Steve.

Harold


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## skippy

Harold, I know that you wern't recommending incinerating e-scrap. Though I can see how my message came across like that - sorry.
I just wanted to caution anyone against trying this with motherboards on their BBQ in their subdivision .


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## Harold_V

skippy said:


> Harold, I know that you wern't recommending incinerating e-scrap. Though I can see how my message came across like that - sorry.
> I just wanted to caution anyone against trying this with motherboards on their BBQ in their subdivision .


Chuckle!

Yep! I get your point. Especially if the barbeque were to become the heat source. I can't imagine food prepared after incineration of boards would be in anyone's best interest, to say nothing of the noxious fumes that would be generated in the process of incineration.

Fact is, if a person could get around the initial incineration, tossing entire boards in the furnace to be melted is not a bad idea. The base metals would serve as a collector for values, so you'd achieve quite good recovery with minimum effort. Problem is, you're left with a mess that would require parting with nitric. It's beyond that which the home refiner should entertain unless a cheap source of nitric is available. 

One of my customers was a recycler, many years ago. He had incinerated a huge quantity of E scrap, fusing it into a common mass. I processed enough of the material to determine values, and realized it was a losing proposition for a small scale operation. I ended up shipping the balance (over 20 pounds of metal) to a refinery that is known to me (now, not then) to be dishonest. They reported half the content that I had determined to be present----and took their fees from the half due my customer. That was the beginning of my negative experiences with major refiners. 

Harold

EDIT:

It has been brought to my attention that the very fact that I've discussed the process of incineration and furnace processing of boards may be an inducement for those that have less than good sense to attempt recovery of values by that method. I do not endorse the concept unless one has a certified incinerator. It has long been known that burning plastic compounds results in the liberation of toxic gases. It would also be an invitation for a visit from the local authorities. It would be difficult, if not impossible, to mask the stink and visual signs. 

I hesitate to remove the information above, if for no other reason, it's a fact of life. That's one of the processes that is used for recovery of values. That in no way should be construed as a suggestion for the home refiner to attempt the process. Those who don't have the wisdom to adhere to good practice would likely engage in it, in spite of being well informed of the hazards. We see that daily in other processes. Use good sense, folks. 

Harold


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## skippy

I suspect if the boards were charged into a retort and the gases generated upon heating were piped out and through a burner with sufficient oxygen that the toxins would be minimal. Improvise some sort of exhaust scrubber and it would be even. Might be an appropriate way to incinerate a small amounts for assay.


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## tamerakshar

Harold The Wise. :idea:


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## Anonymous

I used a old toaster oven or heat gun to depopulate the boards, catch a lot of the solder in a pan and all of the parts. Then I use a belt sander with 36 grit to wipe the traces off.

I have a slucie box to seperate the metal from the small amount of fiber from the boards.
I should add that obvius gold plating is removed by grinding seperately first.

I was doing pretty good till copper dropped so low.

I still have all of the chips and stuff to process.

Jim


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## butcher

James this can be so fine your tailings may also be rich, fine gold floats, and especially if stuck to solder mask etcetera,maybe catch tailings letting them settle, decant, and leach them to test for values.if you are not just after the copper in your processes, and the parts depopulated have value to electronic hobbiest.of coarse check switchs and older components for gold, tantalum capacitors, silver capacitors,and stuff like that. newer circuit boards are mutilayer and can have more copper in between fiberglass sheets than they have on the outside layers.
fiber Cpu's have multilayers with gold plating and copper between each fiberglass layer


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## kjavanb123

All,

Is this the same "incineration" process required after I nitric leached some CPUs to remove the base metals before I leach the materials with AP? Because last time, only 0.22 grams of gold powder was recovered from 3 of the following CPUs which is just a major loss in value somewhere.



I read Harold's piece on this, so after nitric leach, rinse and decant with water, I should boil in dilute hcl? then proceed with AP leach?

Thanks 
Kevin


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## maynman1751

kjavanb123 said:


> All,
> I read Harold's piece on this, so after nitric leach, rinse and decant with water, I should boil in dilute hcl? then proceed with AP leach?
> 
> Thanks
> Kevin



Incinerate between acids(nitric/HCl) or you could produce AR and lose values.


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## kjavanb123

hi,

what you mean by incinerate between acids? do i have to heat the CPUs after they are being leached with nitric to remove base metals?

Thanks and regards,
Kevin


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## Geo

incinerate between processes using nitric solutions and hcl solutions. you cant wash either acid out of the material. if you leach in nitric, and go to a hcl solution without incinerating to remove the nitric acid first, you will create a weak AR solution that will dissolve some of your values. if you did not know this beforehand, you could discard the solution and thus throwing out your gold with the wash water.


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## kjavanb123

hmm I still can't get the "incineration", I got the part leaching in nitric then adding hcl would create weak AR, so what do i do?? after I leached in nitric, then just heat the beaker with CPUs in it dry? boil in water? if you could elaborate on this part.

Thanks
Kevin


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## 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.


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## 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.


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## kjavanb123

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

Regards,
Kevin


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## 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:


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## Geo

pesco said:


> 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.


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## 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:


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## 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?


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## 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.


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## qst42know

yossarian said:


> 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.


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## 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.


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## lysdexic

Harold_V said:


> 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


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## 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


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## 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.


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## 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


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## 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:


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## 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.


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## 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


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## 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?


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## 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.


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## 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?


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## 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.


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## g_axelsson

It sounds more like a bomb than an incinerator. If you keep the gases inside and raise the heat the pressure will rise steeply. You also need an air or oxygen supply to burn the gases, only adding heat without air is called pyrolyzing.

To create eddy currents in small objects you need a higher frequency than if you have solid metal objects. To build an high frequency high power generator is more complicated than a lower frequency unit.

To make a proper incinerator you need a dwell time for the gases above a certain temperature for a minimum time with oxygen excess.

Göran


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## necromancer

i first read that at 4am & thought that was a crazy dangerous idea !!

the saying goes "there is no amount of gold worth dying for" :!:


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## Dude4ever

Hi

I kind of include in my post a little bit of written reasoning, that your answers actually adds to, I read them as more or less expanding my initial question with some further technicalities.
About the "bomb" part, you have take in concideration that a "Pressure cooker(exaggerated): http://upload.wikimedia.org/wikiped...d_by_Georg_Gutbrod,_Stuttgart,_about_1864.jpg".
One option is to design it to be sealed with a mechanical pressure release valve, that only opens if the pressure inside raises beyond a threshold, determined by using some kind of shape that fits in a tiny hole in the lid, with a heavy enough weight to match a certain pressure. I just throwing out some thoughts here.

I am also aware that the winding resistance and number of turns are critical, but the size of the coil and the container in relation would be the first to start with, but speaking from research, the induction coil will actually be the "L" in an RLC-circuit.In such a circuit, the capacitor bank and the induction coil determines the resonant frequency of the circuit, at resonance the current will naturally increase a lot, the trick is actually how the metal container to be the furnace inside the coil are constructed. Because the coil stores electrical energy in it's magnetic field, and when the magnetic field reach the full potential, it will then break down and pass the current to the capacitor who stores the electrical energy in a internal field, the time between this two operations would then be called one cycle, or for the sake of your comment 1Hz speaking in frequency. But the metal-container will act as a 1-winding secondary coil, and it will be coupled with the magnetic field, so when calculating the resonant frequency of the circuit, you will have to make sure that the disturbance and phasing of the circuit is right when the container are in place, and that the current is right, I figure about 900-1100°C max temperature in the iron pot, Because I do not want a melting furnace, only a IC-chip and other-stinky/small-chips-&-components-that-needs-to-be-pulverized-later-for-gold incinerator.

The link I added earlier shows a great example for ideas to making it work. The whole idea is to use a iron pot and a current to generate enough infrared heat to replicate & replace use of open flames and/or gas burners.
The container may not be a lot bigger than a PVC pipe Ø, and could for example have some fire-bricks as lid to hold off the worst fumes as chips warms up and burns.

I may add that the intended design is not meant to be a complicated idea, as all this technicalities may indicate


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## the iron dwarf

your pressure vessel would have to be tested to withstand many times the maximum pressure it could get to and you would probably want your safety valve to be the same diameter as the vessel with no restriction in it.
one thing I have seen a video of is a soup can half filled with water in an induction heater, the user hit the switch and ran for it to get out of the way of the massive geyser that erupted


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## Dude4ever

Water obviously have a higher vapour pressure than plastics :lol:


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## g_axelsson

Dude4ever said:


> Water obviously have a higher vapor pressure than plastics :lol:


At room temperature, sure. At the boiling point of water too, but at incineration temperature it's close to even. Water and plastic would have the same vapor pressure when your reactor breaks, it's just a question of a minor difference in temperature. The biggest difference is that water isn't flammable but pyrolyzed plastic vapors are.... or in words that a dude would understand. *Big kaboom!*

This is Not a joke!

Göran


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## Geo

Incineration and Pyrolysis is two very different things. Incineration is a thermochemical reaction by heat and oxygen to convert carbon to carbon dioxide. Pyrolysis is a thermochemical reaction to decompose organic material in the absence of oxygen leaving carbon behind.


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