My personal experience with silver in an industrial environment

I know that there are a few chemistry and engineering buffs on this forum so I thought that it might be interesting to describe the multi-million dollar silver catalyst change that was completed in my unit last month.

I am a process operator (think Homer Simpson) for an ethylene oxide unit here in Louisiana. I have been working here as an operator for 7 and a half years. Our process involves using a silver catalyst to help combine ethylene and oxygen into ethylene oxide (EO). http://en.wikipedia.org/wiki/Ethylene_oxide

The plant I work in, as well as most petrochemical plants, run 24/7 365 barring any major process upsets (shutdowns) and turnarounds/catalyst changes. Every year or so our EO units shut down for about a month to fix broken equipment that could not be fixed while running, upgrade and add equipment and piping, and change catalyst if necessary. The catalyst change is what this post will focus on.

Without going into too much detail, because the catalyst technology is proprietary, I will explain silvers role in the catalyst change. The catalyst contains upwards of 30% silver by weight and is impregnated to an inert carrier. Now 30% silver doesn't sound like much, but consider that our catalyst change required roughly 300,000 lbs of catalyst. At 30% silver by weight that is 90,000 lbs of pure silver! In a nutshell as the catalyst produces more and more EO it begins to "age" over time and has to be changed out with fresh catalyst so that unit efficiency can improve and unwanted byproduct is minimized. During turnaround/catalyst change the old catalyst is removed and recovered. This recovered or "spent" catalyst is sent back to the manufacturer ,CRI, and the silver is recovered. After the reactor is empty of spent catalyst fresh catalyst can be loaded and the unit can be started up again.

I thought some of you would be interested to know of one of silver's major industrial uses. If you have any questions I'll try to answer them as accurately as possible as long as I don't think the answer will get me in trouble

Here is a picture of the inert catalyst carrier before the silver is added to it.



This is a link to our catalyst producer. It has a small picture of the catalyst impregnated with silver. Note the gray color.
http://www.cricatalyst.com/products/exo/High_Selectivity_Catalyst.aspx

 

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Great post. Do you have any idea of the silver recovery rate? I ask since some catalysts that aren't pure PM like yours have nearly 100% recovery of the metal, while some lose the vast majority of it in the reactions.

 

The recovery rate of the Silver was the very first thing that popped into my head. I am making the assumption that the recovery is less than the cost of replacing the Silver. But as with anything, current value is often directly linked to cost of replacement (mining, smelting, etc).

Thanks for sharing this.

gary

 

I'm not sure what the recovery rate is. I can tell you that the spent catalyst, as well as the fresh catalyst is shipped via multiple 18 wheelers in 53' box trailers. The catalyst is driven from Louisiana all the way to California where it is made and reclaimed. It can't be too cheap to send multiple fully loaded box trailers across country like that. I can ask the catalyst engineers at work if they know what the reclamation yield is. They usually stick around for a few weeks after the unit is started up and direct us how to run the catalyst for optimum performance.

On a side note, when the spent catalyst is being unloaded from the reactor it is very dusty and a dust collection system is used to reclaim the dust. The "silver dust" is then placed into drums, sealed up, and sent along with the other spent catalyst in the trailers. These drums are extremely heavy when full and if i had to guess yield a very high percentage of silver. I like to think of the catalyst swap out as kind a "core charge" system similar to the rebate you get back from an old car battery or alternator when you bring it to the store and replace it with a new one.

 

Very interesting topic. Thanks for sharing your knowledge.

 

+1

 

If it is a true catalyst, the reaction would only use the silver as a surface for the formation of ethylene oxide. But we know how reactive silver is in gases such as oxygen, so probably the "silver dust" and the reason the silver coated ceramic "carrier" needs to be reclaimed is silver's reaction with other than the ethylene. I would suspect the reclaiming rate would be very high. Swagger1, do you know if the reclamation just returns the silver to its original state on the ceramic, or if the silver is removed from the ceramic and reintroduced onto new ceramic. I would think that reacting it with hydrogen gas or such might reverse the reaction, but that might not be so, as they would probably have developed a process to do it in your ethylene oxide reactor by back flushing hydrogen through it. Thanks for the nice post. ethylene oxide blows up badly. Use to use it in autoclaving, but mixed it with inert gas

This may not be the patent on your material, but it reads close on the silver/ceramics catalyst.

http://www.freepatentsonline.com/5734068.html

Jim

 

Desertgem, I am pretty sure that the silver has to be removed from the ceramic to be reclaimed. The reason I believe this is the case is because due to the nature of the catalyst removal process the ceramic is often crushed, chipped, and severely damaged. The fresh catalyst that we receive is nice and uniform like in the pictures above. Also, the ceramic carrier has been changing shape slightly over the past few catalyst changes which means that it is indeed a new ceramic.

As far as EO being extremely volatile, flammable, and a poison to all living things, we take great care and caution at work to keep it inside the pipes and run our units within design parameters to keep leaks and runaway reactions from happening. We have EO monitors throughout the units that detect as low as 1 PPM EO in air. Here are 2 interesting EO videos.

This first video shows an EO explosion at a sterilization plant in Canada in 2004. It only took a few lbs of EO to destroy the inside of the building.
http://www.youtube.com/watch?v=_2UnKLm2Eag

This second video gives me the goosebumps. This is a video of a freight train going through a tornado and derailing. The white car you see throwing sparks everywhere and hitting the locomotive was a fully loaded EO rail car that was loaded at our site. There is some speculation is this was an EO car or a "shock fluid" car. Either way, an EO rail car from that tornado train derailment came back to our site all wrecked up and on a flatbed rail car. We had to purge it out so it could be repaired.
http://www.youtube.com/watch?v=WADnriWzJes

 

Are there any close substitutes for the silver in the process? If the price of silver rises, say, 50% will the process become uneconomic and be terminated?

 

Good question, but this answer would depend on the recovery rate no? I mean, if they recover 99% of the silver it really won't matter if silver is $5 or $150 an ounce since effectively they are not consuming any. This is why platinum is still used in some industrial catalysts where they recover the metal, while in some others palladium or other catalysts have been introduced because of pricing.

Great idea Cloud, that is why I asked about recovery rate since I knew you would ask it.

 

Excellent description of the unit and process....I've been doing internal/external inspections of petro-chemical processing units for a long time.

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It's just one more little piece of evidence that industrial demand for silver won't necessarily drop if the price rises.

 

If the recovery rate is around 99% then this existing industrial application of silver has virtually no impact on demand. The price of silver could increase to the point where the company would reclaim all the silver from the process, sell it and replace it with a substitute.

 

Well, if they recover 99% the price won't matter, if they don't and they consume a lot in the process, we don't know if there is another substitutable product that may be less effcient for the reaction by economically efficient. I knew you would bring this up, that is why I asked.

Think of this playing out times 100 industries. Every one will have a different answer, many will not be able to switch, but some will for a price. That is what I was getting at. Remember how silver was beginning to become popular in hand sanitizers? At $10 an ounce those projects were proceeding. I just heard from a friend at a consumer product manufacturer that they are putting that on hold due to concern about pricing for now. Even though inclusion is low, they cannot gamble on a new product what its inputs would be. Every industry will be different.

 

There's an old joke that a professor, when confronted by an economic event that went contrary to expectations said, "That might work in practice, but it will never work in theory." That's how I think about silver. Economic theory would predict that as silver prices rise, industrial demand would fall. But as silver prices rose from $5 to $20, this didn't happen because new uses for the special properties of silver are found all the time. And silver isn't copper. For many applications, nothing else performs nearly as well.

 

Silver is not gold, and copper is not silver, and aluminum is not copper, and steel is not aluminum, yet every single one of these displacements have occurred due to economic pricing. From $5 to $20 may not be enough of a shock, but I will guarantee you users of silver are right now looking at alternatives. In my previous firm we did just that with metals all of the time.

Before you mentioned that a small price difference will not make a change in industry. Well where I am currently we make changes monthly based upon a .002 cents a pound price difference in our finished product. Many industries are penny industries, and will change formulas if they can for much less than a penny a pound savings. When you make 400,000,000 pounds of product a year you cannot afford to not make that change. I know I said, "if they can". Some cannot change, but enough can that demand will go down over time at certain price points.

Like I have said, I love silver, always have, its just economic reality is that there never is a set demand at an unlimited price. Every user will have a price at which they HAVE to switch, except investors.

 

I should be able to find out tonight what the reclamation percentage is of the silver catalyst. I'll keep y'all posted.

 

I don't think I said that. I believe I said that since silver is a small percentage of the cost of many applications where it is used, it is unlikely that companies will undertake a redesign of the product in order to use a different material that results in inferior performance. This is just the history of the metal. For example, silver is used in a variety of medical and weapons applications where no other metal has the physical properties to act as an effective replacement for silver. Everyone knows that "there never is a set demand at an unlimited price" as you indicated, but that isn't the issue. The issue is whether we are close to the point where industrial usage of silver will decline because of price. I don't think there is any evidence that this is the case.

 

We agree, I don't know of any incidents right now forcing a change. My only point, which I believe you know but making clear, is that there IS some point out there, but it is variable for every industry.

We agree on a lot really Cloud, it just doesn't sound like it a lot of times.

 

thanks Swagge, I appreciate the video links. Sometimes workers ( and the public) don't realize what dangerous stuff is on the move. I guess ceramic forms are inexpensive enough to replace, as they can be extruded and fused very quickly. The ceramic is probably the key process.

Jim