Palladium, Not Carbon, May Be Used To Scrub Mercury From "Clean Coal" Plants
by John Laumer, Philadelphia on 06. 7.07
Because there is no "away" when it comes to economically useless, toxic, heavy metals found in coal, and because most commercially used activated carbon is made from coal (which of course means that the activation of carbon emits heavy metals), we have long wondered how what the industry calls a "clean coal" syn-gas plant would perform over the full production life cycle - mine to electricity distribution - when it comes to controlling the poisonous heavies. Now comes news that something other than activated carbon could be used to scrub out the heavy metals, indicating that life cycle performance might be better than one would assume if carbon were the control technology of choice. "Johnson Matthey company... has been granted an exclusive license by the U.S. Department of Energy’s National Energy Technology Laboratory (NETL) for its high temperature sorbent technology and patent to remove mercury, arsenic and potentially selenium, cadmium and phosphorous from syngas produced by coal gasification. This license was a natural extension of a two-year Cooperative Research and Development Agreement (CRADA) between Johnson Matthey and NETL to evaluate and optimize palladium (Pd) sorbent material properties and performance. Unlike conventional sorbents such as activated carbon, which operate at ambient temperature, high temperature Pd sorbents remove mercury and arsenic at temperatures above 500°F, resulting in a major improvement in overall energy efficiency of the power combustion process."
So, while this licensing development provides an insight as to how the toxic heavies might be cost-effectively removed from a publicly funded syn-gas stream, we still lack information about how the palladium-removed toxic metals will be managed in total. This leads to a key question which has never, to our knowledge, been addressed in the mainstream media. Under normal circumstances, the captured heavy metals would be regulated as hazardous waste if generated in excess of 1000 Kg/month at a US syn-gas plant. This regulatory threshold would apply as soon as that much palladium/heavy metal complex were removed from the syn-gas process for off site waste management purposes. Theoretical ways to avoid the expensive proposition of having a syn-gas plant regulated as a large quantity generator of hazardous waste would potentially include: keeping generation rate of the heavy metals under the 1000/Kg per month threshold [conditionally acceptable situation]; or, using some sort of national defense ruse to convince the US-Environmental Protection Agency to exempt the syngas metal waste stream from being regulated as a hazardous waste [bogus and lame if attempted]; or, find an economically viable market for the metals removed [best possible outcome].
Inquiring minds want to know how the clean coal industry and DOE intend for to this to go? What economically useful products might be made with the mercury, for example? Are we going to open up the decision process to the public. Because there is no away.
Amuzing asides.
It has been proposed, somewhat tongue-in-cheek we suppose, that the best economic use of cadmium would be to cast public statuary to keep the metal isolated from living organisms. Unfortunately, the same would not work for mercury.
Some of the most fantastic black and white photographs ever made are palladium prints.
Palladium is a rare metal, very expensive, and subject to price fluctuations (as pictured) based in part on demand for pollution control applications such as catalytic converters. If Chinese cars are required to use Pd converters, the market competition for the metal will greatly affect the economic viability of this licensed technology.
Update: Sending the spent Palladium complex offsite for recycling might potentially provide an exemption from hazardous waste regulation. That simply transfers all the issues and question to the recycling site. Where would that be?
Via:: Power Online
Image credit: HES Radio Palladium Investor Alert
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I know that gold mining creates tons of cyanide leachate and destroys the surrounding ecosystem. I can't imagine palladium mining (mostly in Russia, I think) can be any better for the environment. The impact of mining the palladium should be costed in, although I can't imagine that would be a deal-breaker for this technology.
As for the heavy metal waste, that's gonna be a problem, but I'd prefer dealing with pools of mercury and cadmium, rather than spent nooklear rods. Perhaps some kind of relatively inert mineral could be manufactured from the waste, which could then be warehoused.
So clean coal technology does not remove any CO2 WHATSOEVER?
Great. Just great.
This is NOT a solution.
==== author's response follows ====
C02 capture and sequestration can be accomplished in theory, but have not been done so at a commercial scale for that express purpose. Costs are high in general and imprecisely known; and, long term effectiveness is unproven.
On the semantic end of things, "Clean Coal" is a term of propaganda at worst and a tool for North American political advocacy at best. The "clean-ness" of the clean coal operating design depends as much on end of pipe pollution controls as it does process innovation.
As for the innovativeness, keep in mind that key parts of this process were invented by German chemical engineers to help Nazi Germany cope with WWII fuel shortages stemming from Allied blockades & territory losses in North Africa. I have read that some of the German former production sites were highly contaminated, similar to the way US 19th century "Coal Gas" production operations. As WWII drew to a close 'somehow' the knowledge of how to build this process re-appeared in South Africa, where it still is in use. The common thread among Germany, SOuth Africa, and North America is oil shortage.
There is no doubt that "synfuel" will one day be made at large scale in the US, driven largely by oil shortages and fear of dependency on hostile nations. The window of opportunity for setting environmental performance goals and informing the public about the tradeoffs is growing shorter. Plladium markets are one key aspect. That's why this post is important.
Climate change gets absolutely zero positive mitigation from synfuel, as you say. And, it certainly could make things worse.
Gold mining does tend to use a lot of cyanide, which ends up outdoors. However, the cyanide is oxidized and neutralized relatively quickly.
There are much bigger scars that the mining industry leaves on the environment, the cyanide is pretty much a non-issue.
==== author's response follows ====
This may be true as far as proper leachate management practices are followed. In the category of unintended consequences, however, cyanide wears a different face. A strong business exists in diverting cyanide from mining to where it h as a nice short term effect. "Fisherman" dump it into the waters around coral reefs to feed the Asian fish markets. Try googling fish cyanide coral hong kong.
The highest mercury content in coal is about a half a part per million. For a 6000 ton coal per day operation, that translates to 76 kg mercury per 28 days. The heavy metals are disposed only at the end of the plant's life and handled as normal hazardous waste.
=== author's response follows ===
Thanks for the insight into the numbers.
Are you hinting that Palladium regeneration will take place within battery limits of the synfuel operation?
My understanding is that metals content of coal varies quite widely depending on formation it came from and how benefaction takes place. Have read the USGS reports on this.
For even small quantity hazwaste generators there is a max quantity on site limitation of 10,000 Kg. Individual states may adjust that downward if they feel it is needed as a risk management measure.
What do you regard as "normal hazardous waste" management? (Mercury is a known developmental toxin that has impacts on the young and there are only trivial commercial uses remaining for it in western societies.)
I was actually talking about activated carbon. This is the first I've heard about palladium. The carbon beds are sized to meet a certain mercury specification in the cleaned syngas. To clean such concentrations to very very low concentrations requires a great deal of activated carbon. As I understand it, the beds are often large enough to last the lifetime of the plant without the need for regeneration. The activated carbon beds are disposed of as solid hazardous waste--that is, placed into leach resistant containers and landfilled at specially licenced facilities.
You are right in stating that the metal content of coal does vary widely, which is why I used a higher value. Most bituminous coals contain less than half that value. Some lignites may contain up to 5 times that, but no "clean coal" company I know of would touch the stuff as it adds a great deal of cost to the syngas cleanup equipment.
=== author's response follows ===
Thanks again.
Not having to drop that delta-T for the input to an activated bed is a big cost savings So the Palladium looks like an operational cost driven choice - until the international spot market price jumps an order of magnitude; and then they'll be back to activated carbon.