This may have been covered before…
According to Wikipedia (I know, I know…) fly ash contains “trace amounts” of nickel, vanadium, arsenic, beryllium, cadmium, barium, chromium, copper, molybdenum, zinc, lead, selenium, uranium, thorium, and radium.
No mention in that passage of mercury, however a preceding passage on fly ash brick touts the prevention of mercury release into the environment, presumably by capturing it in the brick.
From Wikip.: “The US EPA has said in the past that coal fly ash does not need to be regulated as a hazardous waste. However, a revised risk assesment may change the way ccw is regulated”
The wiki article offers the reassurance that you can trust the EPA because the EPA’s building is made of concrete with fly ash… probably safe as long as you don’t disturb it, right?…
Anyone know more?
K
k
Replies
Coal fly ash is what's left over when you burn coal. Folks have been burning coal for centuries, and while the result has not been a Utopian world, you and I are more or less OK in spite of it.
Why do you care?
Well, I care because I mix, drill, cut, grind, core and generally work with concrete from time to time. I'd really care a lot if I was mixing in fly ash in bulk... Also, a previous message on slab work veered into fly ash q's.
Coal plants are the biggest dispersers of methylmercury in the world, and fly ash is the stuff that's filtered from the chimneys. (flying ash) It is filtered to stop that stuff (mercury etc.) from getting into the world at large. I then get to work with it? Seems reasonable to ask some questions, no?
I'm actually just wondering if anyone has facts and stats...
k
when we are inside the precipitator, we wear full body harnesses, gloves, Tyvek suits and close up the sleeves and legs with duct tape disposable dust masks are not required and a few of the cowboys just don't bother with them but you never know when an air hose gets cut or a big clump of the ash will come down from above ..I prefer the 3M #9211 but will also use a mask for fumes when I have to weld on our stuffthe two things to remember when working around anything that poses a health risk are time AND distance..keep your exposure time short and stay away from someone who is working with a questionable material.
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I'm really glad to hear about the tyvek suits. Seems smart to me. Thanks again for the posts about the mechanics, I find it fascinating. Fly ash is in drywall?
k
Fly ash is processed into gypsum.
[On reviewing the available info I see that the above statement is wrong -- the gypsum comes from the sulfur removal systems in power plants. But it's convenient since you can mix the fly ash and gypsum together to get a serviceable concrete, and some fly ash is often mixed with the gypsum in drywall to serve as a binder.]
If your view never changes you're following the wrong leader
Edited 3/22/2008 7:07 pm by DanH
at another powerhouse south of me the fly ash is delivered by conveyor to the gypsum plant outside the fence, on the left of the picture.the big black spot at the bottom is the coal pile, since there are four boilers at this one the pile is huge and from the look of it only two units are running, you can see the stack plumes just above the coal pile.
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Madddog,, I have spent many a uncomfortable hour in in the belly of E.S.P.'s also , most don't know what kind of He'' that is .I worked at a cement plant and we used bunkers and bunkers of Fly Ash and synthtic gypsum in the grinding/ manufactoring process of portland cement.
M.S.H.A. would run random blood tests /ambient enviromentale checks on all workers who worked with the Fly ash and E.S.P.'s, esp. the maintanance workers who welded or oxy-act cut on the rapper plates , screw conveyors or any of the thousands of yards insulated ductwork. My hats off to you there feller, esp's bring back bad memories.....
D.W. former member in good standing, D314 Boilermakers, Cement Div.
my hat is off to you dedubya, you literally had to eat this stuff, and my job is just temporary but I will say the BMs on this one have their hands full ..all the new plates are bowed, and the customer has rejected all 572 of them.
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Ya - know while working at the plant, I developed pumonia at least twice a year , the last 10 years I was there, it took 3 years after leaving that job/ he'' hole before my breathing straightened out , no pumonia and or sinus infections in 4 yrs .. one of the hardest, best things I ever did.
You want to see something that would make a person sick, look at a smoke stack of a cement plant in full operation, when the esp's lose power, Your could almost literley walk across the exhaust stream from the stacks.
A lot of e.s.p's are being phased out in the cement industry , instead they are cleaning their stacks using Hi-Temp dust collectors/ baghouses in the grinding of raw materials . The e.s.p's are still haveing to be used on the Kiln exhausts because of the high temps .
One of these days when I become more puter savy about posting pics and such I will do a thread about how cement is made and the humongous equip. it takes to do it ,pretty interesting process, some of the largest earth moving and stationary equip. on the planet ,one of a kind type stuff.
I'd like to see those picturesI know what you're talking about with the lung problems too, every time I do one of these things I get sick as a dog for a couple weeks.
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Maddog and Dedubya both,
This stuff is fascinating to me. Thanks for sharing your knowledge. And since I'm drawing juice from the grid right now, I gotta say thanks for your work too.
I'm looking into the fly ash bricks- they're writing about setting up brick plants right and the end of the ash conveyers on the same site. The study that says they're totally safe is kind of funny, I'll post more info or a link in a bit.
thanks. k
The position that fly ash is a safe additive for concrete to me seems reasonable. "Trace amounts" can be very, very small. The EPA is in the business of evaluating risk based on real data, so is definitely an authority in the field. The elements you listed are mostly metals and would not be volitile at room temperature. Radium would evaporate during combustion of the fuel, but any uranium that remained would continue to produce new radium over time.
I would tend to think that the mercury level would be exceptionally low, since mercury evaporates readily. It may bind to other elements, but most of them may break down at high temperatures. If it did not release during the heat of combustion, it won't come out at ambient temperature.
I appreciate your level-headed analysis. I'm not sure if I generally trust the EPA or not, but from what I read, they're re-evaluating whether it is safe, so it sounds like they're not sure either. As far as how much mercury, chromium, radium, etc. is in the stuff or not, and whether it is released when you grind it or not, that's my question. Is it no big deal? Or is it no big deal like asbestos- no big deal unless you mess with it too much?
The Wikipedia (someone please direct me to a better source) article talks about a new brick made of fly ash & water, saying:
"The manufacturing method is said to save energy, reduce mercury pollution, and cost 20% less than traditional clay brick manufacturing. Liu intends to license his technology in 2008."
I take the "reduce mercury pollution" part to mean that instead of dumping mercury laden fly ash in the landfill, they put it in the brick. I could be wrong. Dumping it is problematic too, obviously, but for the moment I'm curious about working with it.
k
"The EPA is in the business of evaluating risk based on real data, so is definitely an authority in the field."Like when they said the air in and around ground zero was safe. To be fair I suspect they were under a lot of presure from the Bush administration to say so.
Right, and they're under a lot of pressure to find something to do with the 70 million tons of crud that's filtered from the stacks at coal plants.
Again, I'm just looking for facts and stats if anyone has them. The epoxy I use is probably worse...
k
Here's a bigger thing to worry about.
Silicosis
From Wikipedia, the free encyclopedia
Classification & external resources
Silicosis (also known as Grinder's disease and Potter's rot) is a form of occupational lung disease caused by inhalation of crystalline silica dust, and is marked by inflammation and scarring in forms of nodular lesions in the upper lobes of the lungs.
Silicosis (especially the acute form) is characterized by shortness of breath, fever, and cyanosis (bluish skin). It may often be misdiagnosed as pulmonary edema (fluid in the lungs), pneumonia, or tuberculosis.
This respiratory disease was first recognized in 1705 by Ramazzini who noticed sand-like substances in the lungs of stonecutters. The name silicosis (from the Latin silex or flint) was attributed to Visconti in 1870.
The full name for this disease when caused by the specific exsposedness to fine silica dust found in volcanoes is pneumonoultramicroscopicsilicovolcanoconiosis, and at 45 letters it is the longest word in any of the major English dictionaries. (The name has been described as a "trophy word"—its only job is to serve as the longest word.[1])
Silica
Silica is the second most common mineral on earth. It is found in sand, many rocks such as granite, sandstone, flint and slate, and in some coal and metallic ores. The cutting, breaking, crushing, drilling, grinding, or abrasive blasting of these materials may produce fine silica dust. It can also be in soil, mortar, plaster, and shingles. Silicosis is due to deposition of fine dust (less than 1 micrometre in diameter) containing crystalline silicon dioxide in the form of alpha-quartz, cristobalite, or tridymite.
The induction period between initial silica exposure and development of radiographically detectable nodular silicosis is usually 10 years. Shorter induction periods are associated with heavy exposures, and acute silicosis may develop within 6 months to 2 years following massive silica exposure.
“The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.” —Albert Einstein
You're right. And people have ridiculed me when i bring that up too. How many times have you seen someone cutting backerboard with a grinder and no respirator... yikes. Point taken. still...
k
I do highrise residential, which is predominantly PT slab decks.
If we catch people grind without a dust collection system, or floor sweeping without a sweeping compound we shut the activity down.
It is well known that we will call L&I if they don't.
“The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.” —Albert Einstein
I tip my hat. Is that Union work? A lot of the jobs I've been on are like the wild west compared to that.
but back to fly ash...
k
Yes union.
My jobs can have about 350 workers on them during peak times.
“The world is a dangerous place, not because of those who do evil, but because of those who look on and do nothing.” —Albert Einstein
You da man.
k
this is weird, since I am presently working inside an electrostatic precipitator making sure the electrical wires and spikes are not damaged by the boilermakers when they change out the old plates..
the ash is, to say the least all over the place..
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So far all the industry specs people are showing only talk about silica/silicosis, so if you're not making dust, or are wearing a respirator, it is apparently o.k. I personally wouldn't wash my coveralls with junior's footy pajamas though...
What exactly is an electrostatic precipitator? Is that a negative ion generator? I'm curious what the capturing system is- ash, charged particles, vapors all in the same charged plates/filters? different stages? You're the first person posting from inside a coal plant filter housing.
k
I can tell what I know, which is somewhat limited since I am not an engineer.yes, a precip is a negative ion generator, this one operates at 50,000 volts DC there are two styles used at this powerhouse the oldest is a wire that resembles a single strand of a typical chain link fence, while the newer style is an array of rigid spikes welded to a vertical post , these both hang alternately between rows of grounded platesthe wires /spikes and plates are in frames that are 36' tall and 12' wide there are 25 plate frames ad 25 wire frames in each cell and there are 24 cellsthe operation is continuous ..
the high negative DC voltage causes a discharge which ionizes the air around the wires / spikes which charges the ash and smoke as it passes by and then is attracted to the grounded plate .the solids accumulate on the plate and then automatic rappers pound the frames to loosen the buildup which falls into the hopper and is transported to a collection point where the stuff is sold to places that make drywall and other building materials including concretethe volume of air is around 600,000 CFM thanks to 17,000 hp of forced and induced draft fans ....so the process happens rather quickly !
one of the things that is still in the gas stream after the precip process is NOx which is captured using another process called SCR which is Selective Catalytic Recovery, so that virtually the only thing coming out of the stack is visible water vapor...steamsome plants are capable of reducing the moisture to a point that you cannot see anything in the dischargein the picture the precip is the little box inside the triangle of the crane boom,
the SCR is the horizontal box in front of the stack and the tall brown structure on the right side of the picture.
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> so that virtually the only thing coming out of the stack is visible water vapor...steamAnd carbon dioxide.
If your view never changes you're following the wrong leader
yep that too... tons of it.
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Here is something that could fix that problem:http://www.news.com/2300-13838_3-6220159-1.html?tag=ne.gall.pg
talk about serendipity..He then went to his PC and began to research the subject on Google. He didn't find a lot of answers, but one posting referred to a 1973 textbook Jones remembered. He'd bought it for a class at the University of Texas. In fact, it was on the shelf right behind him.He opened it up to the relevant page and there was the passage he wanted, underlined years earlier by Jones himself.I wish him great success I hope the idea takes off and real soon.
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Thanks, Mr. Maddog.
That's a great description. So if the only thing coming out of the stack is water vapor, where does all the chemical byproduct of combustion go? in the fly ash?
K
according to the precip guy almost all solids are collected or are chemically bonded to render them inert...except of course the copious amounts of CO2.well after snooping around a bit I found this, earlier I wrote "......recovery " when it is "reduction" as in Selective Catalytic ReductionSCR Systems work similar to a catalytic converter used to reduce automobile emissions. Prior to exhaust gases going up the smokestack, they will pass through the SCR System where anhydrous ammonia reacts with nitrogen oxide and converts it to nitrogen and water..
.. . . . . . . . Edited 3/22/2008 3:58 pm by maddog3
Edited 3/22/2008 5:26 pm by maddog3
http://www.titanamerica.com/products/msds/pdf/sti_coal_fly_ash.pdf
First, a comment about the EPA. Like any Federal agency, it is a politically controlled position, where the head is appointed by the president. Our current president appointed Stephen Johnson as the chief. There have been any number of articles saying that Mr. Johnson's job was to gut the EPA of any power because they inconvenience industry and businessmen who happen to support Mr. Bush.
One example was the recent statement by Mr. Johnson that California could not impose stricter laws on certain types of emissions, in spite of the fact that California has had the right to do so, and has done so repeatedly.
Now, about fly ash. The mercury, chromium, etc. are all present as compounds, not as the metal. They are also embedded in the structure of the fly ash, which consists of other, far less toxic materials. The compounds to not leach out easily. So, if the compounds are encapsulated, they are safe to be around since they cannot get at you.
As to the bricks being useful: The bricks are cured in a kiln, and that further encapsulates the fly ash.
Also, there is an admixture of portland cement and fly ash that cures to be almost watertight and is almost shrink-free. Apparently it is the silica (silicon dioxide; glass) in the fly ash that does the trick. In the alkaline environment of the concrete, the silica reacts to form sodium silicate (waterglass). This material takes up MORE volume that silica, and in the right proportions it fills the voids caused by the shrinking concrete.
In the case
John,
I don't much doubt that they could be safe to "be around", my question regards working with it. For instance, my current remodel job is on a house with loads of lead paint and all the siding is cement-asbestos shingles. Since the asbestos is not friable and the paint is not peeling, I'm not at all worried for the client's health.
But I understand that I need to take serious precautions while working, for my sake and my 10 month old daughter's sake (I don't want to come home covered in lead dust, give her a big hug and wash my clothes with her jammies). That's the type of question I have.
K
Wow! You've got a list of potent elements listed there in your first post. It sounds like a prescription from my alternative Dr. If you leave out the lead, arsenic and the radium and a few others things they would sell like hot cakes in an attractive pill bottle. :>)
And furthermore, and with a more serious note, I have a place where you can send that CO2 stuff. My trees in northern WI love it. They even promise that if they get enough they will grow 50% faster. Not only that but they will pay for it in a very fair trade in pure oxygen. How's that for fair?
And with a yet more serious note, a mature forest that is never harvested and the growth is all left to rot on the forest floor, returns all the CO2 that it used back into the atmosphere. Thus the moral of the story is to utilise the wood in whatever manner is it's most valuable way, such as furniture or housing, thereby keeping the CO2 out of the atmosphere.
Fact----A half billion years ago the amount of CO2 in the atmosphere was 20 times what it is now.
Fact----Even a ventilated green house has to introduce CO2 into the atmosphere to keep healthy plants.
Ever notice the great feeling you get when you walk in a deep woods? I sure have and I guess you could say "there's something in the air". Because there is.
um, not a lot of human life on the planet a half billion years ago, I'm not sure I'd use that as an acceptable measure.
Actually, I appreciate your sense of humor and healthy scepticism, even if I might disagree with your conlcusions. Not sure what your conclusion was, but I think it was related to co2?
Which brings the discussion back to fly ash. Peformance aside, one of the best reasons to use it is that it displaces portland cement, which has a huge carbon footprint. No one would argue with that.
The other big reason to use it in buildings is that no one knows what to do with it. There have been a couple of big problems with arsenic and other pollutants in ground water and air near fly ash disposal sites. The ones I heard about were in Pa. and Md. The USGS says that concentrations of heavy metals in fly ash are 10x what they are in the coal, which makes sense.
But is it safe to work with? The only building materials test I saw was focused on mercury offgassing over time, and didn't address working with it. It was also a joke- they did two runs of air in a sealed unit past fly ash brick, the first of which they threw out because apparently sample a and sample b were mis-labeled (can't keep two samples straight? not real confidence inspiring...). The second run said that the bricks were absorbing mercury from the air, which doesn't make a lot of sense, but they liked it, so that's the published conclusion, which no one is in a rush to question.
k
what does safe mean to you ?there are all sorts of things in construction that are "safe" if handled properly fiberglass insulation is " safe " but inhaling the stuff all day long is a poor choice to makeAsbestos was just used for literally everything , with little thought for safety. ####, safety was hardly discussed on jobsites until the 80sthere are fumes of all sorts but a prudent person doesn't snort themelectricians used to stick their fingers in sockets to test for voltage, because it was
" only 110 "Fall Protection at one time consisted of a heavy belt and rope .... around your waistear plugs were for sissieswe wore hard hats only if work was directly over your headfor that matter highly educated scientists and physicists used to take vials of PLUTONIUM home in a shirt pocket to show the kids.......... that happened regularly at a DOE lab in Illinois, it was so out of control they had to begin weighing the stocks to determine if any was missingearlier I wrote time and distance were your two best friendsif you feel you need to wear all that PPE, by all means you should, since everything to protect is out there Tyvek suits, gloves, full face respirators, Powered Air Purifying Respirators or PAPR, HEPA filters, water in a spray bottle, a garden hose, use it all, it is your health after all because an entire industry is not going to change due to your concerns about something you do occasionally .
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Yes. My problem is exactly that-I can't begin to guess what "safe" is with this stuff.
The info isn't there, or is contradictory. That's what started this whole question for me. For the most part the question is dismissed out of hand. The only hard study I've found was the previously mentioned one on offgassing of fly ash brick; it was not applicable to working with the brick, and also was not very convincing.
There's no question the stuff is nasty. The USGS says fly ash has at least 10x whatever heavy metals were in the coal. There have been two serious recent cases of polluted air and groundwater from fly ash landfills (Md. & Pa) that I found with about 10 min. of Googling. And of course there's the cases of lung problems shared on this thread.
There are also clear reasons why it makes sense to use it in building materials(performance, carbon footprint of portland cement, and toxic landfill issues). I know I'm not going to change the fly ash (and coal) industry. And, we all accept a lot of risk, or we wouldn't be in the trades. I just wish I could get better info on this risk, and the fact that I can't makes me wonder.
k
I understand your dilemma now
one would think after all this time that everything has been thought of, discussed. tested or been done apparently not because atour safety meeting yesterday morning we were warned NOT to chew on the plastic insulation for building wire, because it may contain high levels of Lead......... WTF? I do recall one crazy Boilermaker who used say the dust was harmless and to prove it he would wet his finger, dunk it in the ash and eat it....he's dead now, so we all decided he was wrong.
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Edited 3/25/2008 5:52 am by maddog3
Here's hoping that they can come up with a clean way to utilise coal because that could well be the major source of fuel in the forseeable future. Which very probably means more and more fly ash in that future. I doubt if anyone can say with much authority which of all the nasty elements in fly ash are ones to be concerned about. But I can say this much and that is that this generation is a generation of guinea pigs. We are all living "canaries in the mine shaft" because the end results of a vast amount of knowledge is not yet known.
It's tough to put your confidence in science when 50% say one thing and the other 50% say the opposite as the global warming debate shows. Therefore my position is to be a wide awake skeptic. That might be the best you can do too, LOL.
bump
(as a sidebar to the toxic drywall thread)
k
Edited 1/20/2009 9:47 pm ET by KFC
Take a look at the recent Government report on Fly Ash....
http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html
There was a program on one of the Science Channels that reported on the medical problems of our soldiers from the first round of Desert Storm in the early 1990's.
The initial research of the use of depleted Uranium in weapons such as artillery shells, showed that there was no problem from exposure and handling the shells. The newest data sighted in that TV program showed that the government research didn't take into account where soldiers were exposed to areas of exploded shells where the depleted Uranium was floated in the air where they exploded when hitting their targets. INHALING the depleted Uranium lodged into the lungs and the low level began to expose itself to lung tissue and blood passing through the lungs which research showed all the complications the soldiers were showing. Now, the Fly Ash, concentrated with all the heavy metals, are easily put in the air and exposing all who are near it at the plant, down wind, or on the railway pathways as it is loaded on railcars and hauled away are being exposed in the same way and to the same problems... SCARY....
Bill
Right, or in the air as we're shaving and zipping drywall. I don't know about you, but when I work with drywall, I'm covered head to toe in a fine white powder.
And it's a similar situation, where the material in question has some legitimate performance advantages, but is being pushed for use largely as a way to dispose of waste material.
I did not know that fly ash was in drywall until I started this thread last year.
k
KFC,
There is a large drywall mfg. company in Sweetwater, Texas. There have been "rumors" about unknown future problems with the new "NO fungus" drywall that uses fiberglass on the outside faces instead of paper the black mold feeds on. Man, talk about a using it as a dumping/hiding place for fly ash and making both the proposed NEW future coal fired generator plant owners AND the drywall Mfg. company SUPER RICH!!! One palm greases the other....????
The rumor is that no one knows what the life expectancy of the fiberglass/glue material on the faces of each drywall sheet. Some are expecting this type of drywall to begin crumbling...Some others are saying that the process of making fiberglass insulation uses Formaldehyde which impacts those living around it... Heck, on another Science Channel program, the host said that when a human body is embalmed, compared to the same size person in the 1920's, it now takes HALF as much today because of all the formaldehyde that's in every living person....
It would seem that the other bad thing about this mold resistant type of drywall is that working with it and its fine dust is much like installing fiberglass insulation...it ITCHES... Do you see any future problems with this fungus free drywall and does it itch?
Bill
I have no idea. Like I said, I didn't even know fly ash was in drywall until I posted that thread. I think most guys covered in drywall dust are assuming it's simply gypsum, which is relatively inert.
As far as the fiberglass layering and possible formaldehyde glues, that certainly is an obvious concern. My take on fiberglass (formaldehyde notwithstanding) is similar to my take on crystalline silica. It's an obvious hazard, but there are basic precautions that can be taken. At the risk of oversimplifying, if I don't directly breath it, it probably won't kill me (again, setting aside formaldehyde, for now).
I know you can get fiberglass insulation with little or no formaldehyde, and my local yard sells only formaldehyde-free plywood.
But as the toxic drywall thread noted, some materials are offgassing or irradiating even if not physically disturbed, or can be absorbed in other ways. Those are the ones that scare me.
Especially since their presence isn't generally known, and there is a huge push and pressure to find ways to get rid of the 70 million tons of fly ash produced annually in the U.S. And in China too, no big surprise. Sell it to me to work with? thanks a lot!
k
They were, IIRC, putting fly ash in concrete blocks--something about it reacting with the lime to make CO2 to make the block less dense. Seems like that would almost be okay because blocks are not cut that much. I suppose there would be some leachate from rainwater hitting, but.... For a while, road builders were using fly ash (and bottom ash too, I think) as road bed material. Again, that makes sense because it would be pretty much protected by the actual road material (although I suppose there would be considerable leaching into the ground water).
Yeah, it's used in a number of concrete products. That's great, in theory, because it offsets portland cement, which is a huge greenhouse gas contributor. Fly ash adds some curing advantages as well. And if you encapsulate it in block, bricks or slabs, you have less of it to spill into the Tennessee Valley's rivers... It is a "green" product by most definitions.
The thing that worries me is that there is a huge pressure to do something, anything with this stuff, and that we are getting it in building materials without any acknowledgement of potential hazards.
k
I'm re-bumping this thread b/c the general issue of fly ash keeps coming up in the toxic drywall thread.
According to coonass, the fly ash wastestream is different from the "synthetic gypsum" wastestream. If so, then general questions about fly ash safety and disposal/use in building problems might be better served here.
I don't claim to be an expert, just trying to help.
k
I've worked a lot in power plants too, and spent a lot of time with the engineers and designers. What is called flyash is the direct product of combustion of coal. It (largely) drops out in the bottom ash hopper, and the precip. This is then often used in the production of concrete.
The artificial gypsum (CaSO4+nH2O) is a resultant of a chemical reaction in the scrubber. Lime slurry (H20 + CaCO3) is sprayed into the flue gas and the following (generalized) reaction occurs H2SO4+CaCO3 = H2O + {CaSO4+H2O} + CO2
This artificial gypsum is often incorporated into drywall.
So then, flyash is not part of drywall manufacturing
Thanks for the description of the process, that is in line with what coonass said in the toxic drywall thread.
That's the reason I re-opened this thread; the toxic drywall thread was veering into a general discussion of fly ash, and I thought this thread might be a better venue for general fly ash concerns.
When I started this thread a year or so ago, I was only concerned about fly ash in concrete and masonry products. The drywall issue came up later...
Incidentally, USG admits "some" fly ash gets in their synthetic gypsum. How much "some" is I do not know.
But, for now anyway, I encourage posters to put general fly ash posts in this thread, and keep the drywall thread more focused... Not that I can direct traffic anyway.
Thanks for your info, please share anything else you know about it- there's been a lot of conjecture, but few people with firsthand knowledge such as yourself.
k