Paul_D_North_Jr Murphy Siding [snip] I was even more surprised to see a mine-mouth power plant being built north of Gillette, in the Powder River basin of Wyoming. I lived in Gillette for a couple of years. There is a Wyodak power plant that has been on the outskirts of town for maybe 40 years. It is almost a desert. In an area that dry, how do they deal with a lack of cooling water? We need a mechanical engineer with knowledge of such things to provide an authoritative and detailed answer, but in the meantime I'll take a stab at addressing it: Coal-fired power plants use the water - in the form of steam - mainly as a heat-transfer medium between the firebox and the turbine-generator, not for cooling per se.
Murphy Siding [snip] I was even more surprised to see a mine-mouth power plant being built north of Gillette, in the Powder River basin of Wyoming. I lived in Gillette for a couple of years. There is a Wyodak power plant that has been on the outskirts of town for maybe 40 years. It is almost a desert. In an area that dry, how do they deal with a lack of cooling water?
We need a mechanical engineer with knowledge of such things to provide an authoritative and detailed answer, but in the meantime I'll take a stab at addressing it:
Coal-fired power plants use the water - in the form of steam - mainly as a heat-transfer medium between the firebox and the turbine-generator, not for cooling per se.
It really depends on the location of the plant as to which method of cooling can be used to condense the used steam from the turbine back to condensate water to be used again in the cycle. In dry areas, such as the location of the Wyodak power plant, air-cooled condensers can be employed because of the low atmospheric humidity levels...there is sufficient heat transfer via evaporative cooling to obtain the required pressure drop across the condenser. But for steam plants, say, in the southeast where huimdity levels are typically high, evaporative cooling alone is not possible and water-based cooling must be employed.
Paul_D_North_JrCooling water is mainly needed by nuclear power plants, which produce so much heat - sometimes even when not wanted, because they're hard to 'turn off' like a coal plant - so that something of that kind has to be provided for both the generating cycle and for emergency back-up cooling purposes.
Cooling water is actually needed at all steam power plants that cannot employ an air-cooled condenser, not just nuclear plants. There has to be a cooling medium to condense the used steam back to condensate and maintain a vacuum inside the condenser.
Cooter:Are you on the IP side of the river?
Ed
No, sorry to say I am on the Mo side, cousins live within sight of the Coffeen stacks.
Illinois is getting a Mine/mouth plant at Marissa, trying to utilize the coal that lays untouched for the last two decades due to high sulfur content; major scrubbers, major challenge as to power output if they choke down on stack gas flow.
Nukes(where I work) do need a lot of cooling water but no more than a coal plant, heat is heat and it has to be reduced to maintain a differential for steam flow through a condenser. many western state plants use waste water (purified) or large lakes with convoluted path cooling ponds to remove the heat. A coal burner sits in downtown Columbia Mo, it has a small lake fed from local sewerage plant discharge and mechanical draft cooling towers.
New plants are being built continuously. Until nuclear gets the green light, coal is the most efficient source out there. Omaha Public Power turned on unit 2 at Arbor (Nebraska City). Mid-American Energy (Iowa) turned on unit 4 at Council Bluffs, with unit 5 on the drawing board. Unit 3 at Mid-American just went through a 2 year modification to come into further EPA compliance. In Kansas there are three plants either currently being built or under contract.
As far as building near railroads, in this area the utilities try to keep competition. At Arbor, they are served by UP. But OPPD owns the old CBQ line from Lincoln to Neb City as a "back-up to UP rate increases". They have occasionally run single unit trains over it. MAE is also served by UP but their location is at the end of a service loop also served by BNSF. Where possible.... Another thing as far a location, in the midwest running wire is cheap. In congested or heavily populated areas, leasing and air rights are more costly, hence plants located closer to the end user.
Natural gas turbines are being built more often out here, but usually as back-up or peak-demand units.
Cooter50We are currently getting scrubbers for CO2 and to remove more particulates, these new units will use lime slurry to pass the exhaust gas stream through and then we will have to pit the residue as the lime loads up, this stuff will not be sellable. Our chief facility of power delivery uses 12000 tons of coal per 24 hrs, the new scrubbers will use 6000 tons of lime per week.
Thanks to Chris / CopCarSS for my avatar.
Railway Man................and partially due to inability of some projects to demonstrate purpose-and-need to state or federal regulators, but most of all because the economic downturn has caused a severe decline in electric consumption. In fact, there are some in the industry who are predicting the decline might be permanent, that the U.S. will never need as much power as it can generate right now..................
Murphy Siding Cooter50We are currently getting scrubbers for CO2 and to remove more particulates, these new units will use lime slurry to pass the exhaust gas stream through and then we will have to pit the residue as the lime loads up, this stuff will not be sellable. Our chief facility of power delivery uses 12000 tons of coal per 24 hrs, the new scrubbers will use 6000 tons of lime per week. Am I reading this right, that the power plant uses 6000 tons of lime per week, and that the used lime will have to be buried? On site? Or will it have to be hauled out by truck or rail? Isn't that the equivilent of 60 carloads a week?
Am I reading this right, that the power plant uses 6000 tons of lime per week, and that the used lime will have to be buried? On site? Or will it have to be hauled out by truck or rail? Isn't that the equivilent of 60 carloads a week?
I'm reading it the same way, Murphy. So the 12,000 TPD coal consumption creates a need for about 850 TPD of lime, at least inward-bound, or about 7 per cent more tonnage/ carloads. And I suppose at least as much if not more tonnage/ carloads if the 'loaded up' lime is then shipped out by rail for final disposal in a landfill or abandoned mine or quarry someplace, as they tend to do around here.
So as the anti-coal, anti-carbon, and anti-CO2 crowd force the power plants to cope with those new requirements, it seems that may result in rail traffic increasing by 7 to 14 or more per cent ? What's that old saying about ''It's an ill wind that blows no good ?'' Gee, maybe we ought to go out and buy some railroad stocks again soon . . .
- Paul North.
csmitherman -
First, to the Forum !
Thanks much for responding above with your insights and corrections to what I wrote previously about cooling water and the like. That's exactly the kind of information I was hoping for, because I knew there was something like that which applied, but I don't have the knowledge of the fundamentals to explain it as it should be. I still don't know why a condenser needs a pressure drop or a vacuum across it, or how it uses that, or what it does with it - - but that's OK, I'll take it on faith and your say-so because it does seem to make sense.
Thanks again, and we look forward to your future posts.
Paul: Do you recall the Carnot cycle from college physics. It's what every heat engine such as a powerplant follows.
This is a good explanation: http://en.wikipedia.org/wiki/Heat_engine
Mechanical work (spinning a generator) is proportional to heat differential between the hot side and cold side. Narrowing the temperature differential and getting the same mechanical work out of the system would be a pretty neat trick; you be on your way to creating a perpetual motion machine.
RWM
The quote on the lime was a estimate by our engineers, the lime will be used to further scrub acids from the flue gasses while at the same time removing CO2; as it loads with CO2 it will need to be removed from the process and will have to be entombed as unusable in retention pits. 6000 tons/week maybe more maybe less as the process is tweaked for emissions.
Go to Google Earth, along the Mississippi is Portage Des Sioux Missouri, to the east is our Sioux plant which has supercritical Cyclone CE boilers of 3600psig output, to the south of the plant is a rough rectangle bordered by rail south and west, hwy.94 north and roads to the east, this has already been bermed for the retention pits, 460 acres +/- to start with an additional 200 acres to expand 30-50 feet deep. There are three circles to the east of the plant buildings, this is where the new scrubbers and stack now sit, the large area encompassed by the rail line expansion is the lime storage yard east of there.
In my facility we lose 13-16000 gal/min. from our cooling tower, a lake cooled unit only loses around 1000-1800 g/m to evaporation in high heat summer. The condensers operate to remove latent heat from the steam with circulation water at 85-90 degrees on entry and 110-115 on exit in summer, volume is the key and quick flow of volume is essential. In winter we shut down one circ pump and choke flow internally on the tower to keep from going too cold. A misconception is the steam is as hot leaving the turbine as entering, you lose 60-75% of heat in driving the turbine and only latent heat of vaporization remains to be removed to the point the steam becomes saturated condensate liquid.
RWM -
I do remember the name ''Carnot cycle'' - but not much else, so thanks for that link. It's a little too extensive for the little bit of time I have available this afternoon, but I do appreciate your kindness in posting it.
I can follow your 2-sentence explanation; also, on further reflection, csmitherman's comment about condensers makes sense, too. Specifically, I can see that a pressure drop across a condenser is physically necessary to induce or motivate the fluid/ water to move through the condenser - otherwise, there's no gradient to force it to do that past the pipe friction and fittings and the like. But I don't yet see why there needs to be a vacuum at the other end, unless that is just relative to the input pressure, and not referenced to an absolute pressure such as atmospheric, etc.; but I suppose that light will dawn on me someday, too.
Withal, I can see that I'm going to be dragged into knowing more about thermodynamics, kicking and screaming, whether I want to be or not. As Calvin (of the ''Calvin & Hobbes'' cartoon strip) once said: ''Careful - we don't want to learn anything from this !'' Previously, I was happy just as a steel and concrete civil/ structural engineer not knowing anything about this stuff - then we built a new house with geo-thermal water-to-air heating and cooling, so I have to be able to explain at least the basics of it to visitors and colleagues. But it's still almost magic to me . . . [see Arthur C. Clarke quote about advanced technologies]. You guys will make something out of me yet .. .
Thanks again.
P.S. - Only very marginally related, but: Did you see the article in the Wall Street Journal last Thurs. or Fri. on the ascent of Nikolai Tesla as something of a 'cult personality' in certain aspects of popular culture ? Without his inventions and innovations, alternating current as produced by the subject coal-fired power plants would have been a lot longer in becoming technically and commercially practical. But there's something ironic or maybe even strange with this latest twist of history, it seems to me. - PDN.
Cooter50 [snip] . . . only latent heat of vaporization remains to be removed to the point the steam becomes saturated condensate liquid.
This is the kind of thing that I don't understand . . . . . . the rest of Cooter50's post I could follow just fine. No offense intended - it's just MechEng technical jargon and concepts that I'm not familiar with - yet.
Sorry to be too techno guys, vacuum is applied to better utilize the steam flow energy otherwise it requires more pressure to send the steam through the turbine, with a vacuum it is 'drawn' through the turbine not pushed.
As to heat, once water vaporizes into steam there is a heat value that if removed returns the vapor back to water(latent heat of vaporization), it is that transition point where water turns to steam with a pressure drop or back to water with a pressure rise and we have to be below there to keep the water as a liquid to pump it. The action of condensing our steam propagates the vacuum with the collapsing volume of steam returning to water( 1 lb steam is 1000 times the volume of 1 lb water), we aid this by vacuum pumps to remove non-condensable gasses from the condenser during the transition(primarily nitrogen or air).
In yesterday's (Thurs., Jan. 21st, 2010) Wall Street Journal , a very small paragraph at the end of a short article on or analysis of something else in the right-hand column of page B-16 (if I recall rightly) basically said that in light of the Massachusetts Senate seat election results, whatever the fate of health care reform might be, without a doubt the 'cap and trade' legislation was dead for the foreseeable future.
That would appear to be good news and a benefit for the coal-hauling railroads.
Paul_D_North_Jr In yesterday's (Thurs., Jan. 21st, 2010) Wall Street Journal , a very small paragraph at the end of a short article on or analysis of something else in the right-hand column of page B-16 (if I recall rightly) basically said that in light of the Massachusetts Senate seat election results, whatever the fate of health care reform might be, without a doubt the 'cap and trade' legislation was dead for the foreseeable future. That would appear to be good news and a benefit for the coal-hauling railroads. - Paul North.
On one hand, it takes the steam out of cap and trade. However, if cap and trade is not done by congress, much of its costly CO2 restrictions can readily be imposed by the EPA. Moreover, the EPA has vowed to regulate CO2 if congress does not get in front of them with cap and trade legislation.
So congress was as concerned about getting one step ahead of the EPA as they were about selling cap and trade to the public. Senator Byrd was urging congress to get out in front of the EPA with cap and trade in order to prevent the EPA from killing Byrd’s West Virginia coal industry.
So, with cap and trade being dead in congress, we may have gone from the frying pan to the fire, in terms of railroading.
I would sincerely hope not as to the EPA running amok, they ran over the auto industry yet the results are a mixed bag guesstimate at best, they dropped a wall on diesels yet that too has had little to negligible results except to both costing the consumer greatly at a net gain of nothing.
Coal has a place in US economics but it is waning much as steam locos waned after only a short time in service in comparison to relative time; coal steam stations are also on the decline as no one wants the dirty mess they leave behind. I work at a nuke, I do not see these returning simply out of costs, 6-12 billion each is nothing to sneeze at.
The Trains forum might not be the appropriate place to discuss the value of cap-and-trade legislation, or compare the cost-benefit ration of the longer lives and fewer illnesses that result from cleaner air, against the cost of implementing emissions reductions. Nor may this be the appropriate place to root for either the delay of cap-and-trade implementation or the acceleration of its implementation. These questions concern values that are not within the authority of the business of railroading to dictate. They are "boxtop rules" in which the business of railroading operates.
From a railroad's strategic perspective, there are far more important things to concern oneself than cap-and-trade, carbon emissions reductions, air emssions reductions, and so forth. If nothing like cap-and-trade is implemented, ever, coal traffic is not going to increase radically from the level it would obtain anyway. If something is implemented, soon, coal traffic is not going to decline radically from the level it would obtain anyway. If threats to rail traffic is what compells you to lose sleep at night, this is not even in the top 10.
The EPA is a creature of Congress. Congress can pull CO2 out from under EPA jurisdiction. This Congress isn not likely to do that, but the next Congress, Who knows? I do feel that Global Warming/Climate Change is losing steam fast.
Paul_D_North_Jr But I don't yet see why there needs to be a vacuum at the other end, unless that is just relative to the input pressure, and not referenced to an absolute pressure such as atmospheric, etc.; but I suppose that light will dawn on me someday, too. .
But I don't yet see why there needs to be a vacuum at the other end, unless that is just relative to the input pressure, and not referenced to an absolute pressure such as atmospheric, etc.; but I suppose that light will dawn on me someday, too. .
Paul:
The term vacuum refers to the fact that the absolute pressure in the condenser is below atmospheric pressure. Any condensing temperature below 212F (assuming an absolute atmospheric pressure of 14.7 psi) will result in a condenser pressure below atmospheric.
For example, if the condenser is cooled by water at 80F and the temperature of the condensing steam is 100F, then the absolute pressure of the condensing steam would just under 1 psi There is no "need" to have a vacuum in the condenser, it just happens as a result of the thermodynamic properties of water.
Anthony V.
Anthony, we draw a vacuum on our condenser at my plant with vacuum pumps as we start up, then leave one of three running to maintain removal of non-condensible gasses as nitrogen from the steam. Vacuum makes a turbine run more efficiently, the steam is drawn through the turbine as much or more than the pressure from the boiler is pushing it; this in turn allows the turbine to cool somewhat as the steam has no time to linger. Steam condensers have been around for the major life of ship engines, adding vacuum added power, minimized corrosion and aided in keeping the engine cool. Our steady state vacuum or negative pressure is around 27" water or close to 3 lb/sq.in. absolute.
Paul_D_North_Jr P.S. - Only very marginally related, but: Did you see the article in the Wall Street Journal last Thurs. or Fri. on the ascent of Nikolai Tesla as something of a 'cult personality' in certain aspects of popular culture ? Without his inventions and innovations, alternating current as produced by the subject coal-fired power plants would have been a lot longer in becoming technically and commercially practical. But there's something ironic or maybe even strange with this latest twist of history, it seems to me. - PDN.
Yes, I too read last week's WSJ piece about Nikolai Tesla and was not surprised to learn that he's become something of a cult figure among the technoids.
If I recall correctly, the late Mr. Tesla, while out for an afternoon walk, sketched out in his mind what we might today call the modern electric power industry. With alternating current, it was easy to boost voltages by means of transformers and then miles down the line lower it again, by means of additional transformers, to useful voltage levels. What Tesla intuitively knew that Edison had a hard time accepting was this idea: That an alternating current system could move power much further with far less line losses than a pure direct current system.
If, in the early 1890s, Chicago had adopted the Edison direct current system, the area we today call the Chicago Loop would have required a system of power plants equal in area to that well known central business district.
At one time Samuel Insull, the Chicago-based utilities magnate who created the mighty Commonwealth Edison Company, actually considered a compromise of sorts: A.C. to the electric meter, then run it through individual residential rectifiers to produce D.C. current for use within a house.
Cooter50 Anthony, we draw a vacuum on our condenser at my plant with vacuum pumps as we start up, then leave one of three running to maintain removal of non-condensible gasses as nitrogen from the steam. Vacuum makes a turbine run more efficiently, the steam is drawn through the turbine as much or more than the pressure from the boiler is pushing it; this in turn allows the turbine to cool somewhat as the steam has no time to linger. Steam condensers have been around for the major life of ship engines, adding vacuum added power, minimized corrosion and aided in keeping the engine cool. Our steady state vacuum or negative pressure is around 27" water or close to 3 lb/sq.in. absolute.
What is the parasitic load of the vacuum pump, or how much power does the vacuum pump use versus how much it contributes to the functioning of the power turbine?
Railway ManIf nothing like cap-and-trade is implemented, ever, coal traffic is not going to increase radically from the level it would obtain anyway. If something is implemented, soon, coal traffic is not going to decline radically from the level it would obtain anyway.
Minnesota has already enacted a renewable energy policy that will clearly force a reduction in coal consumption.
RWM:Would you mind sharing the top 10?
This is a bit late, and a bit aside from the current flow, but to return a bit to the vacuum and condensation efficiency phenomenon, it reminds me a lot of the processes necessary for an injector to work on steam locomotives. The use of steam injected into the ventury at the same time as water is forced across it causes a massive vacuum that accelerates the water jet toward the check valves at the forward side of the boiler.
Or, so I gather.
-Crandell
Bob-FrymlIf I recall correctly, the late Mr. Tesla, while out for an afternoon walk, sketched out in his mind what we might today call the modern electric power industry.
If I recall correctly, the late Mr. Tesla, while out for an afternoon walk, sketched out in his mind what we might today call the modern electric power industry.
What Tesla invented was the polyphase system for AC power generation and use. I seem to recall that he also invented the induction motor. The use of single phase AC along with the use of transformers predated Tesla, but the polyphase system made it much more practical. A polyphase generator (which is almost always an alternator) feeding a balanced load will have a constant driving torque, thus eliminating the vibration problem inherent with single phase alternators.
If, in the early 1890s, Chicago had adopted the Edison direct current system, the area we today call the Chicago Loop would have required a system of power plants equal in area to that well known central business district. At one time Samuel Insull, the Chicago-based utilities magnate who created the mighty Commonwealth Edison Company, actually considered a compromise of sorts: A.C. to the electric meter, then run it through individual residential rectifiers to produce D.C. current for use within a house.
I don't know for sure if Chicago was or was not wired with the Edison system back in the 1880's, but the downtowns of many major cities were so equipped. In later years, these were fed by substations that converted AC to +/- 125VDC typically using synchronous converters. These substations were often equipped with battery back-ups, so power would still be available if the AC grid was temporarily down.
- Erik
BucyrusRailway ManIf nothing like cap-and-trade is implemented, ever, coal traffic is not going to increase radically from the level it would obtain anyway. If something is implemented, soon, coal traffic is not going to decline radically from the level it would obtain anyway. I understand what you say about coal traffic being unaffected if no carbon policy is enacted; but I do not understand your belief that coal traffic could not be forced downward by the enactment of a carbon policy.
I wonder about that as well. A combined cycle combustion turbine plant running on natural gas can produce around 4 times as much electrical energy per pound of CO2 as a coal fired steam plant with emissions controls. (Assumptions are 14,000 BTU per pound of carbon from coal, 30,000 BTU per pound of methane, 33% thermal efficiency for a coal plant and 60% thermal efficiency for a combined cycle plant.)
beaulieu, our vacuum pumps are what are considered as 'Hoggers' in the industry; they are very efficient single impeller, water media compressors that take suction on the condenser. The are slow speed operating off 480v 3ph motors of around 60hp through a reduction gear. it takes all three to establish the correct vacuun then as the steam flow initiates we cut back to one.
The current to operate is minimal for the addition of near to 25,000hp on the turbine by enhanced steam flow. The facility generates 1250 megawatts electric every hour on the hour as long as we are up; to start the plant from cold takes three to four days, a few bad sequences then a final roll and connect to grid, our house power loads are close to 58 megawatts/hour for the pumps, compressors and remaining support equipment. A small city of 5-8000 will use around 60 megawatts per hour. Our turbine is rated at 1,250,000 hp.
A minor point on terminology, I believe you mean "megawatts" when you wrote "megawatts per hour". As you said, 60 hp is small potatoes when compared with the plant output. If I'm not mistaken, their purpose is to remove any air or other gases that leak into the condenser.
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