Being a slow day, I thought I'd pass along a short story which happened in my early days, when I was a engineering student. I suspect many woodworkers on this NG may have similar backgrounds. Our class was allowed to visit the Bergen Generating Station in the NJ medowlands.
We were shown around the facility and then treated to a chalk talk about the ME aspects of of the boiler and steam turbines we saw. The power station at that time could be fired by steam coal or natural gas. Our lecturer explained that the thermal efficiency of the plant could be calculated by dividing the temperature of the cold body by that of the hot body.
Thus the efficiency was controlled by the temperature of the cooling water in Overpeck Creek which cooled the condensers and the maximum steam temperature which the turbine fan blades could withstand on a sustained basis.
We were told the plant ran at the highest possible thermal efficiency and that your reputation as a future engineer would be made if you could improve it one tenth of one per cent.
They have tried justabout everything. The big pisser is the latent heat of water. They have tried other fluids, but that created a whole new set of problems, like corrosiveness. They have tried super- critical systems, but the plumbing had to be sooo huge as to be cost prohibitive, like a steam line with 12" ID and 36" OD, just think of the flanges.
That's not so...there are some 600 supercritical plants in operation dating to as early as the 60's. TVA's Bull Run went on line in 1967 and routinely has had one of the best if not leading heat rate and availability in the US since, winning the annual efficiency rating fairly frequently until some of the newer units came on line. It's still routinely in the top five.
most-efficient coal-fired plant in the nation 13 times and is
I don't know the actual steam line dimensions, but while it is very thick-wall as compared to normal Sch 40/60/80 indeed, I'm pretty sure
12" walls are extreme (and 12" ID is way too small, I think they're more like 30" ID).
I looked in my old B&W _Steam_ book; they don't have any typical supercritical plant steam line dimensions unfortunately, but state that the Barberton fabrication facility could manufacture up to 8" wall thickness. There are almost no flanges in a supercritical facility; it's virtually all welded (for obvious reasons). I'll ask one of my old buddies what is a typical steam line dimension. (BTW, at least in the olden days, thick-wall pipe of these dimensions was made by boring solid material; I presume probably still is).
I'm not up to date on current statistics; quite a number of the recent and current boilers being built in China are supercritical units so they're certainly not out of style.
As an aside, an unfortunate disadvantage of nuclear units of all types (other than the oddballs that did not prove out like the HTGR or liquid-Na) are limited as compared to fossil owing to the limitation of core power density required to prevent either DNBR (PWRs) and/or centerline fuel melt (both) of the fuel. This limits them to lesser thermal efficiency than fossil units. One reason for the B&W OTSG was its ability to have 30-40F of superheat that compensated somewhat (as compared to conventional SG's). I'd have to look up CANDU but I don't think it's power density rates any higher than that of conventional LWRs; it's advantage is low-enrichment cost and the continuous refueling facility.
So, the supercritical boiler is alive and well... :) (At least outside the US where progress hasn't had the plug pulled, anyway....)
-------------------------------------------- Which is why generating plants are more efficient in winter; however, what is a truly a kick in the rear is the thermal efficiency of a generating station or an internal combustion engine.
On Jun 7, 3:49=A0pm, dpb wrote: =A0I'd have to look up CANDU but I don't
CANDU's are fuelled on the fly, but initial capital cost is very high. Ontario Power Generation is now considering a LWR. A lot of people I know/knew has worked or now works for OPG. Their scrapping the SuperCritical plans had everything to do with the cost of plumbing. None of those to be found in this network. Mind you, those studies were done in the 30's. 12" walled pipe? Prolly not. But thick and expensive nonetheless.
Our biggest generators are 850's and that's already a bit of a pain in the ass when taking spinning reserve into account. Everybody was always happy to see Big Alice come on line....not.
Speaking spinning reserve... I always thought that super tankers should have at least 30% of empty tanks on board... a set of big transfer pumps and presto... spring a leak, dump the leaking tank into an empty one.
Probably the wiser choice...(says an old PWR guy... :) )...
I'd think the $/MWe would quite possibly be higher for CANDU given layout.
Ages and ages ago had number of acquaintances at Chalk River but nobody at OPG.
With current technology the overall plant is often actually cheaper/smaller owing to the reduction elsewhere in fuel handling equipment sizing, pulverizer size/numbers, ash handling, etc., etc., etc. despite the complications required for the supercritical working fluid.
There's no reason one couldn't build smaller supercritical units for smaller grids that I can see...it's just that the current market is primarily overseas at the moment although B&W has a couple of current projects in that size range (altho I think they're both at least two-unit stations).
When I was doing coal analyzers and SaskPower was one customer, there was a new B&W-supplied unit finishing up just east of Weyburn (this
15(?) years ago or maybe longer now...my where does time go? :( ). I don't recall particulars on it other than another mine-mouth plant but it was pretty large (at least that of Poplar River and Koronach and probably larger) iirc. Not sure of cycle constants for it.
Interesting thought, but how often is there/has there been a significant tanker leak that wasn't associated w/ serious trouble rather than just a single/simple tank leak? Seems to me my recollection is they're generally in extreme circumstances (albeit sometimes of own making a la Exxon Valdez). Maybe not; just a conception, not data/researched...
That used to be quite common; not so much any longer w/ restricted limits altho may be some places that still have to. Detroit Edison Monroe plant did so routinely; we had online sulfur meter there to monitor in real time.
One major advantage in going to the super-critical cycle; it could reduce coal consumption 20% or even more depending on the age/efficiency of generation it replaced.
Over the last 30 years or so, SO2 and NOx reduction through scrubbing and selective catalytic reduction technologies has made significant differences in those smog/acid rain contributors. Fabric filters and improvements in electrostatic precipitators have reduced particulate emissions and more recently, technologies such as wet electrostatic precipitators and sorbent injection are capable of further reductions including fine particulates. Commercially available mercury control, for both eastern and western coals are being deployed in the US now.
Eventual C sequestration is undoubtedly on the horizon.
That said, nukes have major advantages in regard to operating emissions but the closure of the backend of the fuel cycle is still an impediment in the US owing to lack of political resolve primarily.
...
Bull Run is CE tangential-fired. I, too, like the tangential furnace despite being a B&W retiree (altho I was NPGD, not FPGD; I only drifted into the fossil side years later in the consulting gig).
NG fired cogen turbines are kinda cool. Quick start for peak load, but time will tell about their reliability. Dunno what they're running in terms of efficiency, but they are building them all over.
On Mon, 7 Jun 2010 19:51:21 -0700, "Lew Hodgett" wrote the following:
Rein in those asshole ecoterrorists, put a politician with a brain in office (or just throw -anyone- off the street in office) and nuke fuel is recycled, waste becomes a very small issue, and everyone is happy.
See if your library has a copy of Tucker's _Terrestrial Energy_. It's the least political, most open-minded, well-researched tome on the subject yet.
Like all the Wally World stores, or SONGS?
-- Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity. -- George S. Patton
Nor was it in any other industries' initial model, either.
Times change; generation is changing as well. Whatever the transition is, unless it's economic it'll cause major disruption in economic terms and that won't be good...
Coal still emits massive quantities of CO2, and the idea of burning it then somehow "sequestering the carbon" is whackadoodle. If we can "sequester" millions of tons of CO2 for all eternity we should be able to use the same technology to sequester a few truckloads of nuclear material for all eternity.
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