(Please excuse the nod to Battlestar Galactica fans, heh)
Yeah, the business of energy is dirty, and everybody's acting surprised, even when Duke Energy was involved in a bottom ash spill. Yeah, I know that nobody called that stuff "bottom ash", but I do because I used to be a power plant employee and know the difference between fly ash and bottom ash. Fly ash is what gets scrubbed from the smoke stack and is highly acidic. Bottom ash comes from rendered slag mixed with water in a slag crusher, then is flumed out to a holding pond. Every coal fired power plant does it and has done it ever since nationwide electrification has taken place.
And y'all act like you were born just yesterday. Pffft. Cry me a river--y'all get outraged over an ash spill and don't even ask where the water that got it there went to, or what that water has been contaminating over the years. I don't hear all the proponents of solar-electric panels whining about where the wastewater generated from THAT manufacturing process goes to, or what THAT wastewater is contaminating either. You guys can cry me a river, too.
There are two basic types of coal-fired boiler designs: recirculation (drum), and once-through. Those terms refer to how the water circulates inside the boiler, and that stuff has hydrazine in it. Great for the recirc boiler--but where does it go once it's been through a once-through boiler, hmm? Nobody has ever screamed about that.
Yeah, natural gas is "cleaner" as a final product, as are solar-voltaic panels...ah, but when you consider how they're produced, and the water that's used and therefore contaminated in the process of producing these things, it's a whole 'nother ballgame.
Well, friends n neighbors, brace yourself for a power generation tutorial in this post as soon as I put my mitts on my old boiler book...to which I'll add some stuff about semiconductor manufacturing, which is what I did at Motorola after I left Illinois Power Company. Stay tuned.
First I'm going to begin with silicon technology, with a show-n-tell I did for a speech class at Arizona State in the engineering program. Current solar panels are made from silicon processed thus:
All silicon integrated circuit chips are born this way, in a furnace, that grows an ingot of silicon in which the silicon molecules are aligned in crystalline form because the lattice structure of the crystal is crucial. The seed is already in proper lattice form, and this is dipped into molten silicon contained in a quartz vat. It is then very slowly withdrawn with the molten silicon attached and the molten silicon attains the desired lattice structure of the seed. It takes several hours to draw up a full ingot.
When the ingot is fully grown, it is removed from the furnace and separated from the seed, and then is sent to be x-rayed to establish the exact orientation of the lattice. Once the lattice orientation is established, the ingot is ground down on one side to produce a flat. Some ingots have one major flat; some get a major and a minor flat ground into it, and when the ingot is sliced into wafers, they look something like the following illustration, but they don't have that grid on it yet:
The grid you see here is the result of growing more silicon (epitaxial layers) on top of the original wafer (substrate), but that part of the story is getting ahead of things at the moment. Consider how the manufacturing equipment needs to be cleaned between one ingot and another. Soap and water doesn't cut this stuff. Hydrofluoric acid and straight chlorine gas are used to etch the quartz clean, and both are highly fatal to the human being upon immediate exposure. Straight chlorine rips your lungs and skin to pieces, while hydrofluoric acid penetrates your skin and attacks your bones. Sweet, huh.
Pure silicon is electrically an insulator. To turn it into a semiconductor, you need to "dope" it with some other nasty stuff. Whether N type or P type, the subsequent epitaxial layers are doped alternating substances, and a solar cell is more like a diode (2-layer). One of those dopants is arsenic. For those folks who can handle engineering-level information, here's a link to a more detailed description.
But I was raising an issue about contaminated water, wasn't I. First, when the ingot is sawed into wafers, all that poisonous doped silicon dust gets washed off as a slurry--so, where does that get disposed of? And here's where the grid comes into the picture. After each epitaxial layer on a wafer, a circuit is photographed onto the layer, developed with more chemicals, etched in more acid, and then cleaned with water. And then run through a dicing saw, which uses more water. What's in the water in the first case are photochemical pollution, and in the second case, all the nasty dopants plus silicon of the wafer as the saw creates curfs in the dicing operation, as more slurry. And to think nobody ever asks how that water is disposed of while they're moaning about one single ash spill. Please.
The following illustration is of a lead frame that has pads upon which each die is mounted, and then a wire bonder stitches the ports on each die to each of the leads on the frame...which then runs through a plastic molder which creates the encapsulation of the die, and then run through a stamper which cuts the package from the frame and bends the leads to become the contact pins of the package.
...for the skeptics who still don't believe I'm more science than liberal arts, despite my beginnings in the liberal arts at first...here's an artifact from my own history, circa 1988, 1989...
The following is a flow diagram of a Westinghouse once-through boiler that drove a 600 megawatt turbine, and it looks like it's supposed to be a closed loop until you look at it closer and notice that the only thing that gets recirculated is the condensate...
You can more clearly see that I wasn't fibbing about the hydrazine injection. That's real rocket fuel in them thar boiler tubes. It's in there to "getter" the extra dissolved oxygen out of the system; whatever oxygen there may be in the system necessarily has to be attached two atoms to every hydrogen atom and no more, or the boiler tubes will rapidly corrode via oxidation under such heat, not to mention the turbine blades. Issues with the turbine blades is why silica content of the water is important--its buildup on the blades can cause imbalance in operation.
The (treated) lake water comes in at the boiler feed pump on the left and exits via a flume back into the lake--and people fish in that lake, including the power plant employees on graveyard shift because nobody superior is looking and the game warden's gone home. "LP Heater" = Low Pressure Heater, and HP is high pressure. In basic physics, water holds more heat the higher the pressure it's under, which is why you have LP and HP, and it's the HP that feeds the superheater. Only when the water is superheated into superheated steam does it get to pass through the blades of a turbine, and it's hell when there's a superheated steam leak inside the turbine housing. It's invisible, and you could walk into it without a single clue that it's even there.
There's another turbine hazard, just below the shaft: hydrogen gas. And to think y'all thought that electricity was just as easy as plugging sumpin into da wall.
Next is a diagram of the air flow through the Westinghouse once-through. Notice the smoke stack, and the fan ductwork leading to the smoke stack. The bottom part is an ID fan (4) (Induction Draft, because of the direction of the draw on the furnace, not the stack--the other kind is the FD, or Forced Draft; this furnace is also known as a Universal Pressure--UP--boiler because of the fan arrangement). Notice the 90 degree drop-down to ID fan (4), then notice the box with two hoppers underneath it. Those are the fly ash precipitators, where the fly ash is collected and disposed of, NOT in a pond.
Now take notice of item number 12...
Item 12 is where the furnace's firebox connects to the slag tank, which is full of water and into which hot coal slag drops to get crushed and then pumped out to the pond. Every stinkin' coal-fired power plant in the country disposes of bottom ash this way, so don't expect me to get teary-eyed over one oopsie in North Carolina. Bottom ash toxic? Try sulfur-rich fly ash on for size if you think it's a problem. Working around precipitators in the heat of the summer means that your sweat turns into battery acid. Been there, done that.
Sure, the precip hoppers are automated, but when the controls break because of the harsh environment, take a wild guess who gets to fix 'em or replace 'em. The bulk of the fly ash is collected there, and the rest is collected in the stack scrubber. (Note to George--you can see how I got comfortable with climbing radio towers: climbing 12 1/2 storeys of boilers, sharing that rarified air with all them damn pigeons.)
...continued...
I wasn't entirely sure about who to credit for the materials provided on the topic of the Westinghouse generating unit, but now I know--it's the defunct company of boilermakers, Babcock & Wilcox.The boiler wasn't made by Westinghouse but it was made to Westinghouse specifications, while Westinghouse concerned itself primarily with the design of the electrical generation (turbine) end of things. Babcock & Wilcox specialty is boiler engineering; it's Leeds & Northrup's specialty to provide various digital/analog/hydraulic/pneumatic controls which interface to a control computer. It's the specialty of Bailey Controls to control start-up, shut-down, and continuous combustion control, and so on.
The following is a simplified block diagram of the major systems involved in boiler operation; it should be noted that this book contains a rather interesting account of the history of steam technology beginning with Hero's steam engine.
The next few pages constitute the official key to the numbers in the previously posted illustration of the boiler...
To explain a cyclone further--there are multiple cyclones and the term is descriptive of how powdered coal dust is carbureted and combusted as it swirls. Man, you should see the coal pulverizers that make that stuff, which is still abrasive and will cause coal chute fires when the walls get too thin from the abrasion. Yeah--this was a fun job. As a matter of fact, compared to Motorola, I still like it better. I jumped from a job that was too dirty to a job that was too clean and wound up missing the dirty one. If Motorola hadn't made a better job offer, I would have stuck with the power plant. Seriously.
The following summarizes basic boiler construction:
Next, the explanation as to why hydrazine is used in the boiler's circulating water:
Heh--we now pause for a break to consider a meme now making the rounds on Facebook. No fan of God over here, but the sentiment is certainly shared because I've got awesome friends:
Found another good one...
Finally, here's a boilermaker's technical take on slag, bottom ash, and fly ash:
...well...thus, the discussion gets even more painfully arcane, and so at this point, I'll leave it at that, except to say this--with gas, you get water pollution problems; with solar-voltaic, you get water pollution problems; with nuclear, you get Fukushima/Daiichi-sized epic water pollution problems; with traditional coal-fired plants, you have always had water pollution problems that you've ignored until recently. What it boils down to, so to speak, is.....................
..................pick your poison.
Thank you, Daily Kos & Greenpeace Africa, for the next graphic--
SATURDAY MINI-UPDATE: A mini article of interest regarding a vote by the PEGASYS board to dissolve itself, which makes mention of the court case previously mentioned elsewhere in this blog, and missing any mention of the amicus curiae, which mentioned the Oklahoma Attorney General.
Something to worry about? Well, another article says that the AG is paying closer attention to goings-on in Enid, indicating that the best is yet to come...
A certain timelord we all know is famous not only for his travels in time/space, but also saving the universe. He's always been the man with a plan. Well, every once in a while it befalls the lot of a human time traveler to save the human universe. I guess it's my turn because of the plan. ;)
Oh, it's not that I think I can save this particular universe; it's yet another case where I've gotta do it, or die trying, and like the fictional Clara Oswald, I've already died a number of times. What's one more time?
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