________________________________________________________________________________________
coal2thorium.com
Converting Large Coal Burning Power Plant Boilers
to Nuclear Boilers
Big Bend is about in the
middle of the world's 1,200 "Mega-sized Coal Burning Power Plants" range.
These are the very few power plants that are causing over 30% of ALL Global
Warming.
http://carma.org/plant/detail/4540
CARMA report for Big Bend, Tampa, FL, Units 1 thru 4,
2007 Carbon Emissions:
Global Rank: 222nd, Short Tons CO2
10,500,000, MegaWatt-hour
9,146,898, CO2
Intensity 2.289.
MegaWatt-hour Energy: Annual megawatt-hours of electricity produced. CO2
Intensity: Pounds of CO2
emitted per megawatt-hour of electricity produced.
Introduction and Orientation:
Tampa Electric Company (TECO) Big Bend Power Station,
1,821 megaWatt (MVA)
Big Bend power station located on Tampa bay at Apollo Beach, near Tampa, Florida.
(Notes from Feb. 14, 2011, Conference: CCS is 2.5 MW slipstream, Big Bend claims 5 megatons coal per year.)
The basic repowering concept:
Introduction: This system uses unpressurized melted salt in pipes to carry heat, via two heat exchangers, to the steam generators. The original power plant's turbine steam pipes would be disconnected from the old coal burning boiler and then reconnected to the new steam generators. The melted salt coming out of the reactor's containment building (blue) is not radioactive.
In Big Bend's case, the four 445 megaWatt (mW) turbines could be repowered with a pair of 1,000 mW Molten Salt Reactor barges.
To explain a bit:
This is how a couple of Molten Salt Reactor (MSR) barge-boilers next to Big Bend's turbine gallery (white and tan roof) would look.
(Big Bend, Tampa Electric Company, (TECO) quad 445 mWe unit coal burning power plant, located at Apollo Beach, Florida.)
Since the Molten Salt nuclear boilers are 1,000 mWe each, each MSR can drive two of Big Bend's 445 mWe units. The "U" in the steam lines is for pipe expansion.
Notice how long the green and blue steam lines from the new reactors to the turbines in the turbine building are? There would actually be 16 lines: 12 steam and 4 feedwater, or possibly only 4 HITEC salt lines if the steam generators could be located where the boilers are currently located.
The two turbines driven by a single reactor concept:
Two original 445 MegaWatt turbines (total 890 MWe), both being driven by new 1,000 MW nuclear boiler.
(Below) How they would be connected.
Nuclear repowering concept, Big Bend specific.
NUCLEAR
REPOWERING: BIG BEND
SPECIFIC
Big Bend has 3 445 MWe and 1
486 MWe turbines = 1,821 MWe
2 ORNL-TN-1060 1,000 MWe high temperature fast reactors
= 2,000 MWe
Nuclear Repowering:
Zero shortfall assuming 100% efficiency of conversion units.
Clean Coal: 455 MWe shortfall
over 4 units assuming 75% efficiency
of "Clean Coal's" Carbon Capture and Sequestration.
About the "Nuclear Boiler on a Barge" concept.
Big Bend (Up is North.)
Three 445 MWe Riley and one 486 MWe Combustion
Engineering boilers (all in a row, left to right) with the turbine gallery - white and tan roof
- located just North of them.
For scale, automobiles are about 16 feet long.
Not to forget that Big Bend also has three 60 MWe natural gas turbines for emergency "Dark Restarts" and short term peak load service. If I owned Big Bend, I'd just keep them and bite the CO2 bullet anytime I needed them.
Additional baseload capacity units with a big future are Babcock and Wilcox's mPower 125 MWe underground silo small modular reactors (SMRs). As many as ten 125 MVA expansion modules can be added to a single central plant over time as load grows. http://www.babcock.com/products/modular_nuclear/
Powering two large steam turbines with one large nuclear boiler. (Larger image: click on image, then click again.)
(Above) With proper isolation valves on the tertiary salt loop, dual 445 megaWatt (e) pair of turbogenerators such as found at TECO's Big Bend plant can be driven by a single 1,000 megaWatt electrical (or 2,500 megaWatt thermal) T-FRR reactor. (Click for larger, sharper image.)
In a like manner, all 5 of Muskegon, Michigan's, B C Cobb plant's small steam turbogenerators (which happen to add up to exactly 500 mWe) PLUS an additional new low-cost generic Korean, Chinese, or Indian 500 mWe turbogenerator could be driven by a single T-FRR reactor. A great way for the United States to salvage the great power plant value and the skilled trade jobs that remain in its hundreds of B C Cobb-like power plants.
________________________________________________________________________________________
Why the author
thinks these nuclear boilers have the "Right Stuff" to replace coal.
The author thinks engineers
who have spent their careers around boilers and turbines like these will agree
that, while this is not a perfect fit,
it is certainly "Good Enough." (If you
have candidate boiler and can get the government to expense the engineering
costs of an emissions feasibility study,
the author knows of a utility engineering firm that's looking for work.)
The 1,300°F promised by the Molten Salt Reactor (MSR) - LFTR folks is hot enough to be beyond question. The somewhat lower temperatures of liquid metal cooled Integral Fast Reactors (IFR) is clearly cause for concern since the superheated steam is 90°F cooler than the GE turbine's original design.
________________________________________________________________________________________
Thermodynamics: Extremely low-cost Molten Salt reactor heat can compete very well indeed with coal, natural gas, and oil fires.
Here's what a typical supersized steam turbine needs and what a conventional solid-fuel PWR reactor can deliver:
________________________________________________________________________________________
Old Turbine Rebuilds
General Electric may be able provide turbine blades and buckets to restore performance and to better match the old turbines to the new nuclear boilers. http://www.gepower.com/prod_serv/serv_for/gas_steam_turbines/en/cmus/cmus_ist/index.htm
________________________________________________________________________________________
The Big Bend, Tampa, Florida, Power Plant
Big Bend's
Boilers
The boilers have to supply the
following steams
Note: As a "bogey" reference for a large typical modern coal-fired power plant, I picked the 4-unit TECO (Tampa Electric Company) "Big Bend" 1.8 GigaWatt plant located on the Alafia River near Apollo Beach, Florida, in the Tampa South Bay region. It's equipped with state-of-the-art emissions controls. In addition to its 4 steam driven electricity generating units, Big Bend also has three 60 MegaWatt combustion turbines (large stationary jet engines connected to electricity generators) to provide quick short-term peaking power.
Big Bend is unusual in that a reverse-osmosis desalination plant that supplies over 10% of the Tampa area's fresh water is also located on their site. The Big Bend site has become a recognized national wildlife refuge for manatees that winter in the plant's slightly warm discharge water.
TECO also operates a super-high-efficiency, low-emissions gasified coal combined cycle plant in nearby Polk County - only one of several in the entire country in addition to their lower CO2 emissions gas-fired Bayside plant (natural gas produces only 2/3 the CO2 of coal). TECO's current electricity mix is: Purchased Power 13%, Oil & Gas 35%, and Coal 52%. Through this engineer's eyes, TECO is a world-class operation.
According to the press, TECO is experiencing a 150 megaWatt increase in electricity demand every year.
Three of Big Bend's four boilers are 445 MWe (MegaWatts electric) Riley Turbo® opposed wall-fired, wet-bottom coal units, and one is a 486 MWe Combustion Engineering tangentially fired coal unit.
Typically, the boilers are designed for a safe drum operating pressure of 2,875 psig and can produce about 2,868,000 lb/hr of steam continuously at 2,600 psig and 1,000°F at the superheater outlet when supplied with feedwater at 487°F at the economizer inlet. The steam outlet temperatures of the superheater and high temperature reheater are both 1,000°F, and the pressures are 2,600 psig and 552 psig, respectively.
The boilers are fired with low-sulfur bituminous coal. Everything running flat-out for a year might burn 6.4 million tons of 25 million BTU/Ton coal, or 17,000 tons of coal per day at 33% efficiency. http://www.tecocoal.com/COpremier.html - TECO's Elkhorn coal mine near Myra, Kentucky. At average coal spot prices spring 2007 of $35/ton, 6.4 million tons = $224 million per year. That much energy is about the same as 2 days worth of oil for the entire United States.
(Note: Boilers can be rated in either (or both) MegaWatts thermal and MegaWatts electrical, depending upon the final application. Electrical generators are rated in Mega Volt-Amperes or MVA. A watt is one Volt-Ampere, so "MegaWatts" is also used.)
________________________________________________________________________________________
The basic repowering concept again, in greater detail:
Thorium-Fueled
Model "T" reactor
Molten Salt Reactor
Nuclear boiler on the left, steam generators middle, old coal fired
steam plant on the right, energy flowing from left to right.
(As far as the author knows,
this is the only drawing in the world that shows how to drive a standard
superheated steam coal burning power plant with a nuclear reactor of any type,
much less a molten salt reactor. To see it, the author had to sketch it
himself. Notice how stone-simple the MSR is?)
Unpressurized shell-type molten salt-to-water shell and tube heat exchangers provide pre-heated water, water evaporation (saturated steam), superheated steam, and reheated steam. The tall evaporation-superheat unit is from an 880 mWe Russian Rosatom BN-800 sodium cooled fast-neutron reactor. (Unneeded coal boiler and stack shown faded in background.) Larger, sharper View. To power two turbines from the same large reactor, simply add a second set of pipes in the first heat exchanger.
The reactor on a barge is a radical innovation that is easily overlooked. It is as if the fire was in one building and the boiler's kettle in another. Such a configuration confers new advantages and flexibilities. Only the barge needs to be "nuclear-rated."
Big Bend is on Tampa Bay, a location subject to hurricane storm surges that could go as high as 20 feet. The air-tight reactor silo protrudes 40 feet above sea level to prevent being inundated. The reactor is in a 9 foot thick reinforced containment building with 5 feet of concrete and dual passive 2 foot thick heat exchanger downcomers and risers. (Concrete is cheap, we make roads out of it.) Radiation is straight-line, and since everything radioactive is hot salt that could, if desired, be behind a berm, if any leaks out, it can't anything other than cooling and turning solid within the confines of the barge. Again, this particular reactor goes largely automatically for 30 years between refuelings.
Shipyards, now equipped with computer controlled cutting and precision welding machines, are well-suited for mass-producing large objects made out of heavy metal such as the MSR T-FRR reactor and its heat exchangers shown above. Mass production always drives costs down and quality up.
MSRs have the “high ground.” Never underestimate the power of price. Repowering a coal burning power plant generating unit is estimated to salvage half the value of the equipment impacted – perhaps as much as ½ billion dollars. MSR technology is, by its very nature, frugal, safe, inexpensive, and durable. MSR’s unpressurized “Shell and Tube” components are extremely simple and safe compared to their conventional reactor counterparts. This translates into a highly profitable mass-market product.
Over half of the 1,200 supersized power plants are on navigable water, making shipyard mass produced concrete “Reactor Barges” a cost-attractive approach. They would be parked in filled-in slips cut next to a power plant’s turbine gallery. If desired, a great deal of physical security can be economically added. Such “Reactor Barges” would act as catch basins in the event of an accidental spill, “float” on the ground during an earthquake, be “high and dry” in the more likely event of a storm surge, be easily returned to a factory for its 30-year refurbishing-refueling, and be easily removed forever when no longer needed, leaving no residual radiation or nuclear power site decommissioning costs.
REACTOR: Since the reactor is UNPRESSURIZED, the reactor vessel can be made from relatively inexpensive 1/2 inch thick welded nuclear-rated Hastelloy-N instead of the massive 10 inch thick steel forgings needed for conventional nuclear reactors. Also, since the reactor is filled with nothing but blocks of graphite with tubes drilled through them, (that is why the reactor cut-away is shown as black in the sketches) we have a relatively easy to construct system. The shape of the reactor reflects the Gen-IV sketch rather than the less readily understandable 1,000 mWe EBASCO design. ORNL's 1,000 mWe reactor vessel design called for: 20'-2" dia., 1.7" thick INOR-8, max temperature 1,400°F, weight including internals 125 tons, radiation heating in support plates 2 watts/cm3 , radiation heating in vessel wall 0.6 watts/cm3 , maximum temperature rise in wall 40°F.
HEAT EXCHANGERS: ALL the salt heat exchangers are UNPRESSURIZED shell and tube types so they are also very cheap to build. In essence, they are unpressurized shells with steam pipes running through them. The only pressurized containers or vessels in the entire system are the steam pipes.
CONTAINMENT VESSEL: Since there is nothing nuclear that can explode, there is ZERO need for a containment vessel, just a conventional "NRC Nuclear Hot Room" but building it as a containment silo for added safety will add only about 10% to the construction costs.
GOING SOLID: The salt will go solid when cold, so all vessels, pipes, and pumps that carry molten salt will have to be traced with Nichrome wires to re-melt the salt. Also the dump tanks for the fuel salt loop, clean salt loop, and HITEC water heat exchanger loops should be equipped with a package gas fired boiler to reheat their dump tanks for "dark" start up in case the grid is down.
I've shown one of those Russian BN-800 superheated steam generators located at the reactor - making the right steam for the high pressure stage, plus just a heat exchanger to do the reheat for the intermediate turbine stage. Hitec salt, a commercial heat salt, which has a relatively low melting temperature and good nucleonics seems to be the salt of choice for the third - water contact - salt loop.
Following from: ESTIMATED COST OF ADDING A THIRD SALT-CIRCULATING SYSTEM FOR CONTROLLING TRITIUM MIGRATION IN THE lOOO - MW(e) MSBR
ABSTRACT
"Controlling tritium migration to the steam system of the 1000-MW(e) reference design MSBR power station by interposing a KN03-NaNOa-NaN03 salt-circulating system to chemically trap the tritium would add about $13 million to the total of $206 million now estimated as the cost of the reference plant if Hastelloy N is used to contain the LiF-BFa salt employed to transport heat from the fuel salt to the nitrate-nitrite salt, and about $10 million if Incoloy could be used.
The major expenses associated with the modification are the costs of the additional heat exchangers ($9 million), the additional pumps ($5 million), and the 7LiF-BeFa inventory ($4.8 million).
Some of the expense is offset by elimination of some equipment from the feedwater system ($2 million), through use of less expensive materials in the steam generators and reheaters (about $2 million), and through an improved thermal efficiency of the plant (worth about $1 million).
In addition to acting as an effective tritium trap the third circulating system would make accidental mixing of the fuel and secondary salts of less consequence and would simplify startup and operation of the MSBR. A simplified flowsheet for the modified plant, a cell layout showing location of the new equipment, physical properties of the fluids, design data and cost estimates for the new and modified equipment are presented." - - (From ORNL-TM-3428)
________________________________________________________________________________________
How TECO can profit big time by
Overpowering Repowering their Big Bend site.
It all comes together - it's the orange barge and left turbine gallery - in the photograph below and here.
How much additional electricity could "Overpowered Repowering" mean?
Note: Due to the sizes of the units at Big Bend, repowering to avoid carbon emissions can be achieved with only two Molten Salt reactors. Overpowered Repowering would more than double the plant's capacity.
If a power plant with four 450 MegaWatt generating units,
such as Tampa’s “Big Bend” (Right,
click for larger image.),
were repowered with four MSR Boiler Barges at 1,000 MW each, the
extra electricity
produced would be:
1,000 MW minus 450 MW (for repower) or 550 MW per new unit.
Times four new units = 2,200 MegaWatts new electricity. In Big
Bend's case, adding a third Reactor Barge and one turbogenerator in the east
end of a new west turbine hall located in your old coal yard would get Big
Bend's foot solidly in Northwest Florida's future electricity market's door.
The second turbine would be dirt cheap.
That’s more additional electricity than you can get from a new
conventional nuclear power plant. At 10 cents per kiloWatt-hour and
90% capacity factor, that’s 1.4
billion dollars in additional revenue
every year.
Plus, you’ve just ended 10 million tons of CO2
per year from the old coal
boilers.
At Vattenfall’s average estimated Carbon Capture price of $50 per ton of postcombustion CO2, $500 million – or ½ billion – dollars of annual Carbon Capture expense or, if no capture was installed, carbon tax, was avoided.
How all that would come together.
________________________________________________________________________________________
The Carbon Capture and Sequestration Option
Real life repowering.
Wow, do we have options or what?
If the government is going to give the carbon capture folks a break on the CO2 that slips past their equipment, it will only be fair that a CO2 per kWh allowance would be given those who elect to repower with nuclear technology instead of carbon capture and storage. Initially, leakages of up to 50% are acceptable in the Waxman-Markey Bill.
Waxman-Markey Bill - as of May 18 - P46 to 97 .pdf
When you look at the combinations of CO2 leakage in Carbon Capture technology and match them up with the CO2 produced by heating saturated steam with natural gas to get superheated and reheated steam, a whole bunch of possibilities jump out at you.
Then, if you decide that replacing your turbine's high pressure stage with another intermediate stage is a possibility, an almost infinite combination of ways to repower almost any size and type of coal burning steam plant becomes obvious.
We don't have to wait for the 1,000°F next-generation reactors such as the 25 MWe Hyperions, 311 MWe PRISMs to show up in the United States market. We'll soon have several 550°F reactors to choose from: The 40 MWe NuScale, the 125 MWe mPower, and the 600 MWe IRIS, all of them with multiple steam generators for running either the reactors or the turbines in tandem to match sources with loads.
Nuclear electricity produces less than 1% of fossil fuel's carbon dioxide.
Vattenfall, the Swedish energy
company, produces electricity from Nuclear, Hydro, Coal, Gas, Solar Cell,
Peat, and Wind energy and has produced accredited Environment Product
Declarations for all these processes. Vattenfall finds that, averaged over the
entire lifecycle of their Nuclear Plant including Uranium mining, milling,
enrichment, plant construction, operating, decommissioning and waste disposal,
the total amount of CO2
emitted per KW-Hr of electricity produced is 3.3 grams per KW-Hr of produced
power. Vattenfall measures its CO2
output from Natural Gas to be 400 grams per KW-Hr
and from Coal to be 700 grams per KW-Hr. Thus
nuclear power generated by Vattenfall emits less than one hundredth the
GHG Emissions from Electric Supply Technologies DanielWeisser.pdf
Also:
http://atomicinsights.blogspot.com/2011/01/overcoming-mythology-real-analysis.html
(Above) From Daniel Weisser's paper. The two boxes are actually a single graph with the right hand box being an expanded-scale continuation of the left hand graph. This was done because the CO2 emissions from nuclear and the renewables is so much smaller than the fossil fuels. (Data sources in Daniel Weisser's paper.)
________________________________________________________________
________________________________________________________________
Notes:
http://www.tecoenergy.com/news/powerstation/bigbend/ Visit TECO's Big Bend plant and the other plants mentioned on TECO's web site.
TECO, Consumers Energy, Westinghouse, Combustion Engineering, Riley, ESKOM-PBMR, and General Atomics have nothing to do with this paper. They are entirely unaware I am using their plants and products as "concrete" examples in my advocating the principle of converting coal-burning power plants to nuclear power.
It's "Errors and Omissions" time.
Please, everyone, let me know what is wrong with my plan. Or, if you know of a
better idea, let me know about it also. You can always
________________________________________________________________
