Sweeps burner- detailed wanted

In Roland Loewens book - Small Scale Refining of Jewelers Wastes- he has a diagram for a sweeps burner made out of large diameter pipe that resembles an outdoor grill of sorts on Page 25. It is fueled by natural gas with an afterburner set up.

The diagram is not detailed enough for me to follow to try to make one. Does anyone have more detailed plans for a sweeps burner like this one?

I would like to make one to slow burn buffing wheels and floor sweeps-

Thanks

Grains of gold

Ghetto Sweeps Burner:

Take 1 large cast iron frying pan. Spread sweeps evenly around inside of pan. Add enough Methanol to make everything damp. toss in a match.

After it burns down, put pan on a grill with lots of charcoal. Light coals and fry the sweeps to make sure you oxidized everything.

This works for polishing sweeps which generally do not have fines carried off in the air. (The wax from the polishing compounds melts first, and traps really fine stuff.) Something like dried paper towels with solution spills should be kept in an enclosed area with a screen above to stop paper floaters.

Here's something to think about.

I incinerated polishing wastes, filters, old buffing wheels and floor sweeps on a regular basis for over 20 years.

I avoided cast iron like the plague.

Here's why. It's desirable to raise the temperature of the ash near a red heat to insure you eliminate all traces of carbon. Hard to do when you're heating a cast iron pan.

I had excellent success with old stainless pans, which are relatively thin, and resist oxidation well. Steel doesn't hold up well at all due to the excessive temperature.

Harold

Harold_V said:

It's desirable to raise the temperature of the ash near a red heat to insure you eliminate all traces of carbon. Hard to do when you're heating a cast iron pan.

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Actually, it's not hard at all. A pile of briquettes will get it dull red if the pan is placed directly on the coals. Also, most gas burners such as found on a home stove, will get a small to medium sized pan red hot. A gas fired barbecue will do it too, if the pan is close to the flame. Use a pan large enough to spread out the sweeps, do not pile them high in a cone. You want an even coat on the pan.

That being said Harold, stainless is a good idea. I was just suggesting the cheapest way to set up. A thin stainless pan will warp, and then the bottom can spring upon the next heating, bumping stuff out of the pan. A heavy stainless pan will cost more but will work fine.
I guess the best idea is to pick up heavy stainless used stuff from the Salvation Army. In fact, that is what I did 2 months ago for some experiments i am doing.

BTW this is only for small lots. Large lots we just burned in out gas fired incinerator.

GeeDub said:

Harold_V said:

It's desirable to raise the temperature of the ash near a red heat to insure you eliminate all traces of carbon. Hard to do when you're heating a cast iron pan.

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Actually, it's not hard at all. A pile of briquettes will get it dull red if the pan is placed directly on the coals.

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For the occasional incineration, perhaps. I refined on a daily basis, processing polishing wastes routinely. Charcoal would have been worthless in my case.

Also, most gas burners such as found on a home stove, will get a small to medium sized pan red hot.

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Yes, they will, but only in a given area. I used burners exactly like you describe, taking advantage of 1 pound of natural gas pressure (my natural gas service was installed to serve my refining business----it was not the typical 4 ounce delivery). I adjusted the flame to maximum, strictly for incineration. When the pan was as hot as it was going to get, and burning had subsided, it required torch heating to increase the temperature so remaining carbon would ignite. There were no exceptions. That was with thin pans. Cast iron would have been far worse.

A gas fired barbecue will do it too, if the pan is close to the flame.

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From my experience, I'd say that is a poor idea. Incineration causes dusting, and dusting results in losses. To incinerate without some means of capturing potential losses was not a good idea, and proven in practice by having a filtered hood. Cleaning out the hood on about a two year cycle resulted in a recovery of roughly eight ounces of gold. That does not take into account the amount of gold that was trapped in filters.

Use a pan large enough to spread out the sweeps, do not pile them high in a cone. You want an even coat on the pan.

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I used the largest diameter pans I could acquire from second-hand stores. Always stainless. It was not unusual to have a yield of a half gallon of ash after incineration.

That being said Harold, stainless is a good idea. I was just suggesting the cheapest way to set up.

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That's why I used stainless pans. Not only were they inexpensive ($1.00 maximum), but they are far easier to heat to redness. The amount of energy it would take to heat a cast iron pan is enormous, and playing a torch on one would most likely result in a cracked pan. Cast iron does not enjoy uneven heating, something that is very obvious to anyone that has done any cast iron welding.

A thin stainless pan will warp, and then the bottom can spring upon the next heating, bumping stuff out of the pan

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Interesting comment, but not true in practice. Like I said, I used stainless pans for more than twenty years. Never had that problem, although they do tend to deform somewhat.

A heavy stainless pan will cost more but will work fine.

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Not likely to be encountered. Stainless is a poor conductor of heat as compared to many metals. When they are thicker, they become less desirable. What you will encounter is stainless pans with copper bottoms, or even aluminum bottoms, on the outside, of course. They were not the best choice, due to the red heat I spoke of.

I guess the best idea is to pick up heavy stainless used stuff from the Salvation Army. In fact, that is what I did 2 months ago for some experiments i am doing.

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Indeed! I did exactly that, then when the pans had finally corroded to the point of having a pinhole, they would be transferred to the stock pot, where they slowly dissolved, resulting in recovery of traces of values.

Everything but the squeal was my motto. I was rewarded handsomely for my process methods.

BTW this is only for small lots. Large lots we just burned in out gas fired incinerator.

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Depends on what you call small lots. I had only my hood for incineration, and it served me perfectly well for the entire run of my humble refining business (more than 20 years, including processing carpets). I processed thousands of ounces of gold. It's a matter of running more than one pan when necessary. It's like eating an elephant - a bite at a time.

Harold

Harold_V said:

That's why I used stainless pans. Not only were they inexpensive ($1.00 maximum), but they are far easier to heat to redness.

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Well, we won't get into a pissing match over this one...
You liked stainless. I used cast iron, stainless, and even large steel campfire pans. They all worked. I just gravitated toward the cast iron over time.

My instructions were for a cheap setup for a beginner. That is what most guys on this forum seem to want to do. Haven't seen the post where the guy says I have half a million to set up a refinery, what should I do?

If you are doing polishing sweeps from individual jewelers, many will be small lots. I did each separately on a pan on a gas stove under a hood. Didn't have to always use the gas. Sometimes just alcohol was enough. Larger stuff like rugs, wood flooring, etc., went in the incinerator.

As far as dusting, the presumption was for setting up on the cheap. Working in a room away from the (high) window will have the dust land within the room. Every refiner should have a doormat outside of his refining area to wipe his feet on to recover dust and spills. The cheapest (free) is to go to a carpet store and ask for a few of the old sample pieces they have.
-Gee

After reading through this topic again I have come to the conclusion that it may be confusing for people new to the game. Please understand that Harolds' and my methods are 2 different solutions to the same task.
They also appear to be designed for people in different stages of ability, capitalization and equipment.
Since the topic began with a reference to a book designed for the casual jeweler, my suggestion was tailored to that level of use.
You may be tempted to take what you think are the best of both ideas and combine them, I do not believe this is a good idea. Parts of each are mutually exclusive. I do not think you can synthesize a new process by combining the 2.
Let me "flesh out" some of the basic things in my method. I invite Harold to do the same, and provide more detail on his method for the inexperienced. I also realize he is a moderator and has to read and answer lots of posts, so we can only hope he gets some spare time.
Since polishing sweeps can be easily divided, you can easily try both ways, and make your own choice.

The post was about polishing sweeps, therefore my answer is tailored to polishing sweeps.
First, let me point out that for those sweeps (my method) you do not need to heat the pan on a stove after the alcohol burn. It is nice, and it does help, but in this particular case it is not absolutely necessary.
The carbon in those sweeps is generally from the waxes in the polishing compounds, the fiber from the buffing wheels, and the felt and wax from the lap wheel (if used). This carbon can be adequately burned with just an alcohol burn, it just will have to be repeated a number of times.
The other thing I want to point out is, unlike the other method, do not use a torch. It will only serve to blow metal out of the pan.
Choose a large shallow pan over a small tall one. If you have a lot of sweeps, use larger pans or break into smaller burns. You want to cover the pan evenly with a layer of about (a maximum) of 2 inches of unburned sweeps.
How much Methanol? Wet the lot totally. You don't want to make a soup, but there can be slight pools of alcohol in the depressions. The purpose of the alcohol is not just to burn the wax of the polishing compounds. It is also to raise the temperature of the mass so that it has sufficient heat content to support independent combustion of the cotton or felt fibers. Think of it as burning wood. You get the fire hot enough to create self sustaining embers which slowly oxidize. Before you get to the fibers, you have to burn off the volatiles. Think of them as like a candle. As the candle wax burns through capillary action, the wick also burns down because of the heat in the center of the flame. The alcohol, although being a low temperature flame, has enough heat to volatize the waxes, which burn alongside the alcohol adding BTU content and raising the temperature.
That is why I gravitated toward a cast iron pan. The pan will heat more slowly, but the specific heat of cast iron works to hold the heat and radiate it back to the mass being processed ensuring that it stays hot long enough to oxidize embers. In burning, it is not the temperature, but the heat content which is important.
There is no reason to stay and watch the burn, nothing spectacular is going to happen. You can leave the room and go have a cup of coffee. I had a small window in the door, so I could see when it was finished.
When it is done (no smoking or embers lit), the pan will still be warm. That is good. It won't be hot enough to spontaneously combust the next batch of alcohol. Smoking at the end of the burn is a sign another burn is needed. On each successive burn, the pan will be warmer because it will take you less time to turn over the burnt sweeps (assuming you didn't go walk the dog).
Take a large spoon or spatula. Break up any clumps you see by gently mashing them down and breaking them apart. Then turn over everything in the pan, so that what was on the bottom (and not as well burned) is now on the top. This is why you use a shallow pan, you want ambient air to reach the sweeps and burn as embers. Do not pick up and drop while you are turning, you're not mixing cake batter. The edge of the turner need never leave the pan. Check your technique, If you do the turning over a clean piece of sheetrock, and dust falls outside the pan onto the sheetrock, you are being too vigorous. If you choose to stir, be gentle, stirring will raise dust. Being gentle cuts down on dust. (If you vacuum your work area regularly, it's not that big a worry.)

Wet with alcohol, burn again, turn again.

Repeat again as needed.

Also note, if you do it in a closed room (with a window high and away, and the door closed), you don't need a fume hood to catch the dust. The amount of dust raised will be negligible, and you can vacuum the room every 6 months. I am presuming you are starting on a budget. Fume hoods aren't free. If somehow a few dollars worth of metal drifted out the window, how many lots would you process to break even on the cost of the hood? I am not saying don't (ever) get a fume hood, I am just saying for this procedure, it is not your first priority. I am inferring from the initial post, this will only be done a few times a year.

Methanol is not the only alcohol you can use. Use what you get cheapest. I used to buy out the chemical rooms at auctions. Got all types of alcohols for pennies a gallon. They all work. Some burn hotter than methanol.
-G

Excellent presentation of your method.

The method I pursued required a hood, plus a setup that is fire resistant. No accelerant was required. Because the temperature of the pan is critical, unlike your example, I can see why you felt cast iron served adequately. It would not be by the method I pursued, which included heating the pan to a dull red heat. My one attempt with an iron pan proved a failure, so I avoided them religiously from that point forward.

You alluded to the hazard of heating the waste material directly with the torch, but that was not a problem in that a low velocity flame was used when that was necessary, so little, if any, dusting occurred. A direct flame was generally used only to ignite the heated material, which often would not self ignite. I also played oxygen on the material towards the end, insuring that any traces of carbon were consumed. It served as a measure of the completeness of the incineration process. If any pockets of carbon remained, they were readily identified. End product, assuming it was heavy in value, was a nice deep purple color, absent of black. The sole exception would be with materials from benchmen that used the green buffing compound instead of rouge and Tripoli.

I'm not suggesting for a moment that my method is the only way to incinerate, but it provided a product absent of carbon. Not a bad idea considering carbon has the ability to absorb values, so eliminating all carbon was top priority for me.

I designed my operation around incineration. Nothing got processed without seeing heat first, even if it was nothing more than to burn off oils that are common to items that have been handled.

The one distinct advantage to my method is the ability to convert a pan full of waste to ash in short order. By heating the pan from below, the oils and waxes, of which you speak, liquefy, at which point they burn well. There is a reasonable amount of smoke, however, so this method would not be suited to processing without a hood. It could be performed in the open, but I was always concerned about losses, thus the filtered hood.

Many of my customers sent their polishing wastes, along with filters, in a large plastic bag. In order to process the lot with minimal loss, I incinerated the bag. They don't burn well until they have been converted to oil, at which time they burn with a vengeance. That is one of the reasons I preferred the method I chose.

I also benefited greatly by the excessive heating in that fiber glass filters were reduced to a fine dust easily.

As you have alluded, assuming we were discussing polishing wastes, I, too, leached for values. I paid no attention to silver unless the material came from a silversmith. If so, my process was entirely different than for wastes from a goldsmith. I didn't process for silver in that case, giving the resulting waste material a heavy boil in HCl, then a series of rinses until the rinse was clear of color. At that point I processed for values.

By giving materials of this nature a boil in HCl, the resulting pregnant solution will filter without issues. The difference in doing so, or not, was so pronounced that when I processed silver bearing materials, I'd remove silver with nitric, then I'd incinerate the solids once again, to kill the nitrates, then they would be screened a second time, then subjected to a boil in HCl to improve the handling qualities of the resulting solution.

If readers don't get a single thing of value from these posts, the one thing they should understand and use is the HCl wash. It truly is the magic bullet one seeks when filtration is troublesome.

Harold

When I process bench sweeps I use a method like Harold's. I work outdoors because the amount of smoke is huge. I cover the stainless steel pan with a stainless steel grease splash guard to prevent stray embers from escaping the pan. I avoid breathing the toxic smoke by handling the frying pan with a long PVC pipe extension slipped over the handle of the frying pan. I only do this on a day when there is a strong wind and I process the lot in batches of 1 pound of sweep material or less.

Once the sweeps are reduced to fine ash, I pass the ashes through a stainless steel mesh to collect any metal objects, gemstones, and unburnt items. I re-burn the items that are combustible until the whole lot is a consistent color. I typically see purple or green ash as an end result of this process. I use an old paint brush to gently coax the ash through the stainless steel mesh.


I have a video of the entire process that needs editing and posting.

I'll try and extract some photos from the footage and post them here soon.
Steve

We had a large steel box incinerator about 4' x 3' x 6' tall. We put the sweeps in large SS trays, about 4" - 6" deep, with a screen on them, and used a 50/50 mix of gasoline/diesel (or gasoline/kerosene) to burn the sweeps. We let everything cool and settle overnight before slowly opening the door. Very little was lost. After removing the tray, the inside was vacuumed. The ash was then ball milled, screened, and a magnet was used to remove the steel.

We ended up with what is known in the trade as "prepared sweeps". The sweeps were fire assayed for all PMs and these plus the oversize and magnetic fractions were sent to a large refiner. The settlements were excellent and their assays were within a percent, or so, of mine. I don't remember who the refiner was.

All sweeps were purchased and we didn't have to account to anyone.

Harold_V said:

If readers don't get a single thing of value from these posts, the one thing they should understand and use is the HCl wash. It truly is the magic bullet one seeks when filtration is troublesome.Harold

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I know I have said something to the effect of "how many posts of I agree" does a forum need?.
However, I have to say it here.
Your one post here will save a newbie soooo much time, anger and frustration, that you deserve a medal just for posting it. A lot of guys will have trouble on their early sweeps leaches. My Commendations Sir.

I am also very pleased with the direction this post has gone. As we have shown, there are many ways to do these things. We now have several very distinct methods that newcomers can apply according to their needs and circumstances.

Just a question. What is the purpose of incineration?

hosef said:

Just a question. What is the purpose of incineration?

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To eliminate unwanted substances that can be troublesome, including carbon. Oils of all types are another example. Anything that is absorbent and combustible is another.

Incineration just makes sense. It is ultra critical if you refine jeweler's wastes, where polishing compounds, hair, fingernails, bits of wood, string, buffing lint, cat hair, part of someone's lunch, and countless other substances and objects get included in the refining lot.

Harold

cat hair, part of someone's lunch,


.......body parts of jewelers that didnt quite make the grade......

...organic matter when refining dental waste!
[img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]

peter i said:

[img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]

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Where is that coming from lol ?

peter i said:

...organic matter when refining dental waste!
[img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]

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Oh, yeah! But you have to be careful! It is common to find gold crowns that have been installed over teeth that have silver amalgam fillings. I highly recommed teeth be broken with a hammer before incineration to insure that one does not breath any mercury vapors.

Harold

@ Harold
Yes, dental waste is ugly in all aspects.

Should I do it again, I think I would start with a good long boil in strong sodium hydroxide to break down any organics. Then sort it carefully.

Noxx said:

peter i said:

[img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]

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Where is that coming from lol ?

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its a .gif like the others.

Right click it, "save as", then you can add it to the smiley-file.




Sorry for going off-topic! (I have a few others that I would not dare to add, even though it's tempting)

peter i said:

@ Harold
Yes, dental waste is ugly in all aspects.

Should I do it again, I think I would start with a good long boil in strong sodium hydroxide to break down any organics. Then sort it carefully.

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Excellent idea. One must consider the ramifications of dealing with dental wastes. Hepatitis C and AIDS being amongst the possibilities.

Harold

I understand and appreciated both process's in getting the polishing waste to the burnt and shifted state. Once all carbon and trash has been removed, Whats next. I saw a mention of a HCL wash, and something about a leach. Knowing this material will be full a different kinds of abrasive grit, can it be processed in one of the traditional manners. Which one is best. Too, my bench sweeps are about 80% volume boric acid ( flux dripping into my pan). What method is best for processing this, and do I need to remove the boric before processing.