99.5%? Is it possible?

[Oz]

I have been seeing a lot of talk recently about the Miller Chlorine Process on the forum. I have to question whether that those that are recommending it to others have practical experience in using this process themselves. The process is not all that complicated from a technical viewpoint but I have yet to see it as a low cost process for small quantities of gold. With all this talk I would like to see someone come forward with how they are setting up and using it for processing lots of 5 ounces and up and how they can justify the capital investment to do it on that scale.

Theoretical thought processes are fine for discussion but it is a hard sell to advise someone to use a process that they have not used successively themselves. Beyond that one must look at if it is cost effective on the volume they run in a typical week. I would like to hear from someone that is currently doing this for a cost that is less than traditional refining on lots of 5 ounces Au. I chose the 5 ounce mark since it fits with a moderate refiner as a per week through-put (I do not see how one can pay their bills on less than 5 ounces per week). That is also more gold than 95% of our typical forum members will process in a year.

 

[HAuCl4]

You can't bubble neither air nor chlorine through a 5 Oz melt. I have done it/seen it done in 3 Kg/15 Kg (around 100/400 Oz) of material.

This process is not cost effective for 1-off batches, and I would not use it unless a minimum steady 100 Oz per week of material could be sourced.

I do not professionally refine gold/silver these days.

Properly setup this has less fumes than the equivalent size acid operation. Especially if you use an electric furnace. All the "fumes problem" has been blown out of proportion in the literature, but it is understandable if you use a gas-fired furnace and just start blowing chlorine in an open crucible...all the fumes mix with the flue from the furnace and then you have a huge "fumes problem".

And you are right, I do not currently process even 5 Oz of material per year, and all this is just a hobby/mental exercise to avoid Alzheimers for me and keep myself busy somehow.

But since I visited the Royal Canadian Mint and also met/spent several hours with Mr. Robert Trepanier (ex Refinery Manager of same) in Caracas in 1988, and setup a small refinery using same process back then, maybe I have a clue or two, but then maybe not. I remember at the time discussing how they were changing all parting furnaces to induction from gas. And how he was very impressed at what we had achieved locally with a normal electric (non-induction) furnace.

Since I was screwed in business from that deal, for one reason or another, I never re-entered the "gold business", till I joined this forum, first as JohnW, but since I lost my password to my email account, I decided to create another without making any noise.

I have read passionately the info in this forum, where I learned a lot, especially from Steve and his ideas of chemical loops, where little/no chemicals are wasted, and the per-sulfuric cell process which was completely new to me.

I have been "advised" to blow myself up once, to shut up because I'm a newbie that knows nothing, and that I am always asking the wrong questions... just for being creative.

Now even my credibility is attacked/questioned/whatever. I have no desire, time or inclination to defend my views or knowledge anymore.

From now on I will just shut up, read, learn whatever is there to learn, and wish you all a happy refining experience using whatever methods you like.

 

[nickvc]

You can't bubble neither air nor chlorine through a 5 Oz melt. I have done it/seen it done in 3 Kg/15 Kg (around 100/400 Oz) of material.

This process is not cost effective for 1-off batches, and I would not use it unless a minimum steady 100 Oz per week of material could be sourced.

I do not professionally refine gold/silver these days.

Properly setup this has less fumes than the equivalent size acid operation. Especially if you use an electric furnace. All the "fumes problem" has been blown out of proportion in the literature, but it is understandable if you use a gas-fired furnace and just start blowing chlorine in an open crucible...all the fumes mix with the flue from the furnace and then you have a huge "fumes problem".

And you are right, I do not currently process even 5 Oz of material per year, and all this is just a hobby/mental exercise to avoid Alzheimers for me and keep myself busy somehow.

But since I visited the Royal Canadian Mint and also met/spent several hours with Mr. Robert Trepanier (ex Refinery Manager of same) in Caracas in 1988, and setup a small refinery using same process back then, maybe I have a clue or two, but then maybe not. I remember at the time discussing how they were changing all parting furnaces to induction from gas. And how he was very impressed at what we had achieved locally with a normal electric (non-induction) furnace.

Since I was screwed in business from that deal, for one reason or another, I never re-entered the "gold business", till I joined this forum, first as JohnW, but since I lost my password to my email account, I decided to create another without making any noise.

I have read passionately the info in this forum, where I learned a lot, especially from Steve and his ideas of chemical loops, where little/no chemicals are wasted, and the per-sulfuric cell process which was completely new to me.

I have been "advised" to blow myself up once, to shut up because I'm a newbie that knows nothing, and that I am always asking the wrong questions... just for being creative.

Now even my credibility is attacked/questioned/whatever. I have no desire, time or inclination to defend my views or knowledge anymore.

From now on I will just shut up, read, learn whatever is there to learn, and wish you all a happy refining experience using whatever methods you like.

This is an open forum and ideas and discussion of ideas is part of what makes it work.The comments I made are based on what little I could glean from the literature on the Miller process and from some one I know who is at present trying to install it into his new refinery, if im wrong please enlighten me, I dont claim to be an expert in any field so I would love to hear how you or anyone else set up and ran the Miller process and at what cost what equipment you used and what problems you encountered and how you over came them .The same im sure goes for Oz,we just dont see how you can set up and use this process at reasonable cost and safely so again please tell us your story im sure the whole forum will be reading your posts with rapt attention but do expect questions and no doubt some cynicism until the whole story is told.Get typing you have me fascinated already even though i,ll never do it now

 

[Oz]

HAuCl4,

I have seen the Miller process brought up here and in other threads. Perhaps my choice of threads to reply in was poor but it was the most recent I read. I had gathered the impression from these different threads that some might have felt that this might be viable for smaller lots. It is possible that someone here may have experience that shows smaller scale as viable, I am doubtful. You were clear that you were recommending this for 100 ounces and up.

I would think it was reasonable to ask if any that were recommending the process were actually using it, as well as if they are using it if they are able to do so on small lots. To be clear I have no practical experience with it so I was asking for clarification from those that do. I would enjoy any discussion of it but find it helpful to know whether what is being presented is theoretical or from personal experience.

Since you have clarified by saying that you set up and ran the Miller Chlorine Process successfully in a small refinery of your own I would be particularly interested in what you have to say of it. You are the first that I know of on the forum that has instituted this process into their refinery.

 

[nickvc]

Oz I believe there are several but their lips seem sealed, actual hands on experience is really hard to uncover and Im really looking forward to having a tour round my friends refinery when its up and running,I know that his costs in setting up his refinery is over $750,000, admittedly it covers a furnace that can melt around 100 kilos a time but the cost of the extraction equipment is horrendous apparently due to the fact that the gold chloride is happy to be follow the extracted fumes into the system so recovery is a must to collect the values.I hope our friend HAuCl4 will give us all an insight into what he did and how employing the Miller process, it might well be out of nearly all of our reach on the forum but I for one will be reading every word that he hopefully posts recalling his experiences.

 

[HAuCl4]

Considering that my equipment setup costs were less than $7,500 complete and that I never lost more than 1/1000 th of the gold processed, you probably don't want to hear my story, because it is already unbelievable for most.

$750,000...whew...what a waste. I'm hoping that he spent 95% of that in the vault, the building and other security mechanisms...

I'll type 1 or 2 pages with tips and will try to answer questions to the best of my ability...

My "fumes problem" processing equipment was an state of the art $300.00 vacuum cleaner and 2 drums filled with soda ash and water. We got some silver out of the sludge and insignificant amounts of gold, and no fumes on the exhaust only dry air. I carefully processed this sludge once only to establish the what is what, and then it was just mixed with the low grade slags, sweeps, etc. and smelted once a year.

The gold stayed 97-99% in the crucible charge, in the copper/silver chloride slags 1-3% (recovered as a silver dore cullot inmediately with a sprinkle of soda ash, and re-melt), and maybe a 0.2% as metal in the cracks of the crucible, fully/mostly recovered every 4-5 melts when the crucible was taken out of commission and crushed. The bigger the charge the smaller % that stayed "in transit".

We used AP Green #14 crucibles (Same as the Royal Canadian Mint at the time, why reinvent the wheel right?) at a cost around $15 a piece at the time, and crucible covers for same, in which we drilled a hole for the clay tube used for injecting. If I had to do it again today, I'd try to use state of the art nonporous sintered zirconia crucibles at slightly higher cost, but much higher number of melts per crucible, and a cheap induction furnace.

We built and optimized an electric furnace around that crucible setup. A simple but not trivial cheap furnace setup was reached after a little trial and error.

All the fumes came out from around the inyecting clay tube and were promptly sucked in by the vacuum cleaner, and soda ash drum. The biggest amount of fumes occurred when pouring the chlorides slags into another crucible, the vacuum cleaner took care of it, but we also used masks for safety. A couple good electric fans kept the air circulating.

The batches were mainly mine dore at around 90% gold, but sometimes a batch of scrap karat here and there. We injected a little pure air first instead of chlorine to scorify instead of chloridize. The difference in costs was negligible, but I believe it helped on the total removal of copper and other base metals before starting with the chlorine.

9985 was the best we achieved even with extended exposure to chlorine. (And no we did not lose any significant amount of gold as chloride. This is a myth. I can see how one could lose a lot of gold in the flue in a gas fired, open crucible, chlorine splashing operation, but not with this setup.)

Maybe the crucible cover and the mix of glass and borax I used for the flux was a factor in the negligible losses of gold as chloride. There was also a very clear transition when reaching the end of operation, and where chlorine injection had to be slowed down in the ellimination of the last remaining silver. If you were paying attention this posed no problems. The purple stain on the clay tube was very distinctive, and marked the near-end of the process. We pushed this point often at a slow chlorine rate in the hopes of ever increasing the fineness of the final product, but after a while it was just a waste of time and chlorine, and negligible gold chloride. Remember all these losses get smaller as a % as the charge gets bigger, and even 1 gram of gold makes A LOT of gold chloride fumes to be detected. And we always had the $300 vacuum cleaner!. :roll:

The silver chloride we recovered using sulphuric and iron, like explained in the literature. We did not refine silver except for a small amount in a thum cell, to be used in the fire assays. This is another story and fully documented in the literature.

Everyone that I have ever met that used Miller to this date (a handful maybe), still regards this process as "secret" and few if any are forthcoming with details. Mr. Trepanier was a notable exception 20+ years ago, and now you are stuck with me, as far as I know... :lol:, but maybe others that have been quiet till now, will share their experience.

There were no platinum group metals present.

 

[nickvc]

Now I love this and your right the process is clouded in mystery and rumour and hard facts and figures are non existent to anyone outside of the companies using it.Im shocked that there was so little fume after been led to believe that was the main concern but not surprised as it helps keep the process supposedly beyond the educated amateur.Im going to read your post over again and try not to be so shocked at the simplicity.Fantastic information,I bet you will not be popular with the big boys in the refining world for sharing this with the forum.I think my friend is installing other refining equipment but until I get a look round I wont know but I do remember him saying he was having trouble getting the clay pipes to use?

 

[HAuCl4]

Now I love this and your right the process is clouded in mystery and rumour and hard facts and figures are non existent to anyone outside of the companies using it.Im shocked that there was so little fume after been led to believe that was the main concern but not surprised as it helps keep the process supposedly beyond the educated amateur.Im going to read your post over again and try not to be so shocked at the simplicity.Fantastic information,I bet you will not be popular with the big boys in the refining world for sharing this with the forum.I think my friend is installing other refining equipment but until I get a look round I wont know but I do remember him saying he was having trouble getting the clay pipes to use?

Morgan crucible makes and sells clay pipes. Nowadays I know how to make my own, but I don't need to!. Back in that day (there was no internet I remind you!), we obtained tubes made of zirconia that were used in the manufacture of thermocouples for harsh environments. (We got them free at first from the discards!). Each tube would last forever with certain care. There are many internet sources now, just google "clay tubes". So easy now. The hard part is getting the material to refine!. At $1,200 an ounce this is no mystery. Too little gold going around, and too many "refiners".

Re. the "fumes" and the "chlorine": Any pool boy that maintains a medium sized swimming pool at a country club, handles more chlorine per year than most refiners... . He keeps it dilute in water though!. :shock:

 

[nickvc]

Well I have re read your post twice and all I can say is FANTASTIC..... :lol: I never would have believed that a process that is over a century old could still be so little documented until I tried to find out how it worked and what dangerous fumes and by products :roll: were likely to be encountered, now I know why. Thank you for sharing that and for once the information really is gold....Im pleased you came back onto the forum as an active member, lets see if anyone can fault this who has actually done it!

 

[qst42know]

If clay pipes are hard to find, isn't fused quartz tubing capable of doing this job?

 

[HAuCl4]

Here are 3 photos taken this afternoon by a friend. Quality is not the best.

One is of a new/untreated crucible with the inyection tube in position. Missing (don't have them them), are the slotted crucible cover, the furnace, and the vaccuum cleaner "fume processing" device. Maybe I'll make a diagram later this week.

Then you have the tube with characteristic purple stain (this tube bottom part was broken). And another of same tube with the latest new all time high price of last friday for the August delivery of COMEX gold.

That ceramic tube is about the only "evidence" I still have that I once processed gold using Miller chlorination. An expert connoisseur will recognize it inmediately as authentic.

 

[HAuCl4]

Im shocked that there was so little fume after been led to believe that was the main concern

Oh no. There are enough fumes to be dangerous, but no fumes problem if you control them at the source before they get mixed with more air.

This was easily controlled with the vacuum cleaner during the process. When pouring the slags, the chlorine injection was stopped and the tube removed, so no more chlorine, and a fume hood was connected to the vaccum cleaner and brought close to the pouring spout, and we wore masks at this point. This was the point of "maximum amount of fumes".

Also this pouring of chloride slags (into another cold crucible) had to be done carefully, because silver chloride at that temperature looked like chicken soup, only more fluid, and it was fuming. Gold stayed in the crucible, and we added more borax and glass at that point after most of the slags were out. Fumes after that were a lot less.

My guess is that with a comparable acid system for the same volume of material, the volume of fumes to control would have been bigger, although of a different nature, and not necessarily easier to process.

 

[4metals]

The corrosivity of the chlorine gas is an issue, the piping to the furnace and the storage of the bottles of gas were a major concern to local firemen. I never had much issue with the gas coming out of the reaction either. I never used an expensive Cottrell electrostatic exhaust either. I exhausted into a 6" quartz glass tube which switched over to CPVC when it was cooler at a distance of 10 feet from the furnace. The chloride fume is water soluble so it actually scrubbed easier than a NOx fume. The base metals were easily dropped from the scrubber water for waste treatment using caustic.

Not pushing the reaction to get three nines is also smart. If you stop when the clay tube turns purple all of the gold is in the pot. I melted 700 ounce lots of karat (fine gold content) and used French Clay parting crucibles which were used for 1 melt. When the clay tube indicated the reaction was complete I pulled the tube and removed the crucible to let it cool. I never bailed chlorides off the top. In the morning the cold crucible was smacked with a hammer and the 99% fine gold was on the bottom and the silver chlorides had solidified to look like the top of a lemon meringue pie. These chlorides contain between 1/2 and 1 percent by weight fine gold beads which were trapped in the thick foamy chloride. They were crushed and reduced to metal and processed in a silver cell to recover the gold as a slime.

There have been many authors who have detailed the process used at large refineries, these reports combined with a knowledge of chemistry and the ability to experiment helped detail the process.

I still wouldn't take the chlorine gas lightly, it will kill you if there is an accident and it will be a painful choking death. For this reason I advise people to stay away, it requires meticulous maintenance of the delivery system and safety systems for the one time when it goes bad. Continued success makes us complacent, then it happens. Look at what happened in the Gulf.

Considering the non chemical backgrounds of some members I would never recommend the process.

 

[Barren Realms 007]

The corrosivity of the chlorine gas is an issue, the piping to the furnace and the storage of the bottles of gas were a major concern to local firemen. I never had much issue with the gas coming out of the reaction either. I never used an expensive Cottrell electrostatic exhaust either. I exhausted into a 6" quartz glass tube which switched over to CPVC when it was cooler at a distance of 10 feet from the furnace. The chloride fume is water soluble so it actually scrubbed easier than a NOx fume. The base metals were easily dropped from the scrubber water for waste treatment using caustic.

Not pushing the reaction to get three nines is also smart. If you stop when the clay tube turns purple all of the gold is in the pot. I melted 700 ounce lots of karat (fine gold content) and used French Clay parting crucibles which were used for 1 melt. When the clay tube indicated the reaction was complete I pulled the tube and removed the crucible to let it cool. I never bailed chlorides off the top. In the morning the cold crucible was smacked with a hammer and the 99% fine gold was on the bottom and the silver chlorides had solidified to look like the top of a lemon meringue pie. These chlorides contain between 1/2 and 1 percent by weight fine gold beads which were trapped in the thick foamy chloride. They were crushed and reduced to metal and processed in a silver cell to recover the gold as a slime.

There have been many authors who have detailed the process used at large refineries, these reports combined with a knowledge of chemistry and the ability to experiment helped detail the process.

I still wouldn't take the chlorine gas lightly, it will kill you if there is an accident and it will be a painful choking death. For this reason I advise people to stay away, it requires meticulous maintenance of the delivery system and safety systems for the one time when it goes bad. Continued success makes us complacent, then it happens. Look at what happened in the Gulf.

Considering the non chemical backgrounds of some members I would never recommend the process.

Can I recomend SCH80 PVC insted of CPVC. CPVC is not what I would recomend from an insallation stand point.

And the chlorine gas is bad I'v inhaled large doses 2-3 times it is hard to get over. And hurt

 

[qst42know]

Can I recomend SCH80 PVC insted of CPVC. CPVC is not what I would recomend from an insallation stand point.

:?:

Both are available in SCH80 and CPVC has a higher temperature rating and improved acid resistance compared to PVC.

 

[Barren Realms 007]

Can I recomend SCH80 PVC insted of CPVC. CPVC is not what I would recomend from an insallation stand point.

:?:

Both are available in SCH80 and CPVC has a higher temperature rating and improved acid resistance compared to PVC.

You are correct that CPVC has a higher temperature rating than PVC. CPVC also has a tendency to be more brittle than PVC as time goes and has more of a tendency to shatter. SCH80 is a type of PVC but it is chemical resistant, It takes heat better without damage.

 

[HAuCl4]

The corrosivity of the chlorine gas is an issue, the piping to the furnace and the storage of the bottles of gas were a major concern to local firemen. I never had much issue with the gas coming out of the reaction either. I never used an expensive Cottrell electrostatic exhaust either. I exhausted into a 6" quartz glass tube which switched over to CPVC when it was cooler at a distance of 10 feet from the furnace. The chloride fume is water soluble so it actually scrubbed easier than a NOx fume. The base metals were easily dropped from the scrubber water for waste treatment using caustic.

Not pushing the reaction to get three nines is also smart. If you stop when the clay tube turns purple all of the gold is in the pot. I melted 700 ounce lots of karat (fine gold content) and used French Clay parting crucibles which were used for 1 melt. When the clay tube indicated the reaction was complete I pulled the tube and removed the crucible to let it cool. I never bailed chlorides off the top. In the morning the cold crucible was smacked with a hammer and the 99% fine gold was on the bottom and the silver chlorides had solidified to look like the top of a lemon meringue pie. These chlorides contain between 1/2 and 1 percent by weight fine gold beads which were trapped in the thick foamy chloride. They were crushed and reduced to metal and processed in a silver cell to recover the gold as a slime.

There have been many authors who have detailed the process used at large refineries, these reports combined with a knowledge of chemistry and the ability to experiment helped detail the process.

I still wouldn't take the chlorine gas lightly, it will kill you if there is an accident and it will be a painful choking death. For this reason I advise people to stay away, it requires meticulous maintenance of the delivery system and safety systems for the one time when it goes bad. Continued success makes us complacent, then it happens. Look at what happened in the Gulf.

Considering the non chemical backgrounds of some members I would never recommend the process.

Nice idea of using the crucible just once and crushing it. I bet you had hardly any "fumes problem". We recovered most of the gold inside the slags by sprinkling soda ash in the molten slags (in another crucible).

The chlorine cylinder (we had one at a time only) was kept inside a large water tank outside the room (in case of leaks), and a plastic hose inside a hard plastic tube was ran into the furnace room. We never had any incidents, so probably I was taking more risks than I knew at the time.

 

[4metals]

I chose CPVC because of the temperature. Something about exhausting over a furnace with plastic made me nervous, that's why I fed the fume directly over the furnace into a quartz glass pipe for 10 feet before transitioning to CPVC. (Did you ever see a PVC fueled fire? I did once in a plating shop it was like someone threw kerosene on it.) I suppose the physical scrubber could have been PVC but the deal I got at the time had it all in schedule 80 CPVC. The scrubber could have also been fiberglass, I like the vinyl ester resin as it withstands the corrosivity well.

Using a single cylinder and having it in a water tank is a good approach but we were doing 6 to 10 melts per day so we needed a bank of 8 tanks. Because of the way they were delivered and the distance, we purchased chlorine 4 tanks at a time. They were outside, 100 feet away from any building and enclosed by fire department rules. All of the delivery piping was double walled and we even ran it inside a dedicated 6" exhaust duct constantly pulling air out of the shop. That duct ended about 5 feet from the point of use. A pressure gauge told us the line pressure and in case of a leak in the feed the air was already going out. Fortunately the exhaust ducting on feed piping was never put to the test. When I design something I always make it like I have to be the guy over the furnace, sometimes I was, so I'm kind of anal about the safety I build into a process.

We never processed the crucibles separately from the regular melting room crucibles and stir rods, so I don't know how much metal was in the crucibles but I do know that our accountability of the gold between the melting and the slimes from the silver cell ran inside the margin of error for fire assays so it was negligible.

My point again about Chlorine gas is you can make it safe, even super safe, but I don't believe you can make it backyard safe!

 

[qst42know]

Schedule 80 (abbreviated SCH80) is a heavier wall thickness of pipe and fittings for an increased pressure rating.

My experience with CPVC was just the opposite. In a hot acidic iron phosphate tank at 135F PH4 the PVC lasted only 2 years. The CPVC was still running after 8 years. The PVC in the two cold rinse tanks were original we had no trouble with these. All of it was Schedule 80.

 

[Barren Realms 007]

Schedule 80 (abbreviated SCH80) is a heavier wall thickness of pipe and fittings for an increased pressure rating.

My experience with CPVC was just the opposite. In a hot acidic iron phosphate tank at 135F PH4 the PVC lasted only 2 years. The CPVC was still running after 8 years. The PVC in the two cold rinse tanks were original we had no trouble with these. All of it was Schedule 80.

Regular SCH40 PVC is a diffrent piping than SCH80 PVC the SCH80 is desighned for uses like the processes that are done here. CPVC will stand up to the heat better than SCH40 PVC because it is desighned for use in hot water applications where as SCH40 PVC is not and will fail sooner in a hot application. SCH80 is desighned for use in hot and harsh applications. CPVC is more likely to fail in cold weather because it gets brittle sooner than SCH40, And SCH80 is very durable in the cold.

Here is what you can do. Take a piece of SCH40 PVC and heat it up lightly with a tourch and it will heat up and you can bend it. I have done it with up to 6" SCH40 PVC to make odd bends. I have taken a piece of 3"SCH80 and tried to heat it up to bend it, won't happen with out burning the pipe to a crisp.

Do another test take all 3 types in 1/2" down to 0 F and then start tapping them a little harder each time you tap and see what sequence they crack in.