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
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
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.
Pushing the envelope of technology is not easy!
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
Better look for cheap heat. Like a CANDU.
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
So, the supercritical boiler is alive and well... :) (At least outside
the US where progress hasn't had the plug pulled, anyway....)
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
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
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...
I never did find the eng'g drawings online for Bull Run and my TN
buddies are busy and I told 'em to not waste their time if didn't either
know it or have it directly at hand...
So, I did a very rudimentary minimum wall thickness calculation for
seamless tubing based on the ASME B31.1 criterion based on allowable
stress and got a number otoo 4" for 30" nominal diameter, 3500 psi
working pressure w/ steel derated to 12000 psi for temperature. I don't
think that's _way_ out of line, but it's certainly not a design
Higher tensile strength values would reduce that at about an 80%
proportionally to the ratio of strengths. I didn'tfind the applicable
ASME table for temperature factors online and it's one I don't have at
hand (I'm a nuc-e, not mech, ... need cross-sections? I got those or
shielding data or ... :) ) so reduced another 20% based on a
subcritical system calculation. OTOH, one might reasonably expect
better alloys which would be higher at temperature, to compensate. So,
as is it's a guesstimate. Better data would be nice but only tables
and/or piping calculators I found were all for purchase, none were
online modules like the sagulator the likes of which I was hoping I
Thanks...I had seen it before but it didn't come up in my searches this
time. Looking, I found a pressure vessel calculator that gives somewhat
higher values at similar conditions but it has no references to the
basis for the computation, unfortunately, so I can't tell what's causing
them. Clearly it's not the same as B31.1 but doesn't reference either a
Standard nor the criterion behind it so can't tell.
Unfortunately, they don't have a link to the pertinent ASME Standard,
either...so, useful site for much but didn't help me out on this
particular sidelight trivia quest...it got me to wondering in that I
really don't know what the dimensions actually are, myself. I've got
the TVA design book for a couple of the older plants we did some
technology demonstration projects at but they're not of any help for the
supercritical units, unfortunately.
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.
Both are less than 20%.
There's not been a sizable central-station generation plant that had a
thermal efficiency <30% built since before WW-II I'd think. Even the
old Kingston Fossil units, still operate in the low 30% range after 50+
From B&W (Babcock & Wilcox) site...
One big difference in pollutants is to burn that ' clean coal' those
adverts on US TV talk about. *smirk*
Seriously, one plant I worked at had a pile of 'summer coal' for those
One of OPG's stations had a blend B&W and CE boilers. Circ pumps and
tangential fires made the CE's my favourites. Those were only 500'MW
single shaft two-pole, the B&W were tandems. Big wheels on the LP
side. None were over 30% efficient.
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).
Something the utility industry has fought at every turn.
Pollution control has not been in their economic models.
A possibility until than transition away from fossil fuels which is
going to happen.
It will be one hell of a fight, but it will happen.
Solve the "backend" problem and you have a winner.
A serious question.
Based on the total cost of electrical generation
including pollution controls as well as responsible disposal costs,
What are the relative cost differentials between coal, oil and
natural gas as a fuel source?
SFWIW, it's amazing how much co-gen there is in SoCal.
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
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.
Oh, I agree wholeheartedly it's a seemingly asinine thing to do, but w/
current politics in charge it appears it will be either that or...well,
just what, specifically??? There doesn't appear to be a substitute of
the magnitude required in the short term to simply quit.
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