CO2 Removal from Plant Stacks 3

[MJCronin]

I was wondering,.....with the current emphasis on "greenhouse gases" and global warming, how practical is it to remove CO2 from the effluent of a Combustion turbine power plant ? Are there any demo or pilot plants in operation ?

How is the CO2 collected and where does it go ?

How about a gas-fired combined cycle installation ? (The kind, of course, that is now being constructed all over the USA) If the plant emitts less CO2, don't we end up with a big pile of "something" that requires disposal ?

I realize that nuclear plants really are bad in the eyes of many, and that nobody want's them on the planet.... but, after we burn through all of our natural gas and had a few more war's in the mid-east over control of oil...... what is our only real option ??

Who knows something about the practicality of CO2 removal ?

Any websites ?

Thank You !!!

MJC

 

[davefitz]

The specific emission of CO2 from a gas fired combined cycle power plant is 2.5 times less than that from a conventional coal fired power plant, in units of (ton CO2/MWe-hr).

Currently, the coal plants are based loaded and the gas fired combined cycle plants in the US have a capacity factor of about 35% ( ie, they are shut down at night).

In order to reduce the US emission of CO2, one would need to reverse this schedule, ie, base load the gas fired combined cycle plants and load cycle the coal plants. Such a scenario would require:
a) LNG terminals to incrase the available gas supplies
b)modify the coal boilers for variable pressure cycling operation
c)a carbon tax to provide a finacial incentive to switch the load schedules

For this reason, there is proposed the Carper bill in the US congress to tack on a $20/ton CO2 tax to coal fired plants.

 

[rmw]

Yeah, that'll work, like all the taxes tacked on to motor fuel has reduced people's driving.

rmw

 

[bimr]

davefitz,

Your idea and Carpers seems to be a particularly bad one now that there is a natural gas shortage.

In addition, it should be noted that base loaded plants are built differently than cycling plants. It is not as simple as turning a switch to stop and start a plant. The powerplants must be designed mechanically and thermally to be able to accept the thermally induced stresses that occur when the heat goes on and off. For that reason, there will be major consequences from the recent construction of all the turbines units. Gas turbines are not generally designed for cycling operation.

Coal gasification may be the better way to go.

rmw,

I don't know why you make the statement about people's driving and taxes. There definitely is a point when the price of fuel will cause a change in driving habits.

 

[rmw]

Right now the percentage of the total price of fuel that is attributable to state, federal and local taxes is a lower percentage of the total cost of fuel than some months ago when the taxes, which are generally fixed amounts rather than percentages, were higher on a percentage basis.

(I know, I know, there are always the exception out there to my generality.)

When taxes as a percentage of the (formerly lower) total fuel cost were higher, it didn't slow us down much then. So, unless taxes are raised substantially, I don't see that making much difference.

I don't think our politicians have the will, nor would I have the will to permit them to raise taxes along the lines of the european model where gov'ts keep the price of fuel artificially high via the use of taxes.

I don't think americans in general want to drive european type 'wind up' cars over the vast expanses of our landscape. On the other hand, I would drive a hybrid for a commuter car in a heartbeat if I were in the market for a new auto.

Now, not to confuse that with your point, which I actually agree with. Higher prices, wherever they come from, raw material and/or operating costs or taxes, are going to drive markets to different solutions. Further, I predict that driving habits and vehicle types will soon change, as they did back in the '70's. Bye Bye SUV's as the commuter car of choice.

And, I don't mind being part of the change based on my personal choices. I just don't want politicians doing it by taking my hard earned dollars and doing with them the type of things that politicians are famous for doing with tax dollars.

rmw

 

[athomas236]

I have come across a planned project where carbon is removed from the natural gas and the resulting hydrogen burned in a combined cycle plant.

The CO2 that is left is pumped into oil wells. Apparently it gives a better oil recovery rate than traditional methods.

athomas236

 

[rmw]

CO2 has long been used for secondary recovery methods for depleted oil wells.

But, one has to have an available oil field fairly near to the source of CO2 in order for their to be a market for that by product.

Ammonia plants produce CO2 as a by product (they want the H from CH4) and I heard of one plant, Enid OK, as I remember, that sold its CO2 for that purpose. I knew of others located closer to oil fields that couldn't give the stuff away, and just vented it to the greenhouse.

Not many operating ammonia plants in the USA today due to the price of CH4.

rmw

 

[davefitz]

bimr:

True, a cycling plant is built differently than a base loaded plant. True, few US coal fired units are designed for cycling; in fact to date, ASME section I does not even recognize cyclic fatigue damage.

Most US gas fired combined cycle power plants are operated in a 2-shift mode of operation ( ie, shut down at night) , due to the high cost of fuel, yet their HRSG's were not designed to handle this mode of operation well,and these units are experiencing accelerated fatigue damage to their components. This is partly due to the fact that design code used ( ASME I ) does not recognize fatigue damage, partly due to the conventional use of a horizontal gas flow/ vertical tube orientation yields a thermo-mechanical design that does not tolerate the high , transient ,tube-to tube temperature unabalances which occur during frequent startups, but mostly due to fact that the extremely competitive market conditions cause the designers to cut too many corners . So the comment about cycling damage is actually universally applicable to nearly all US power plants, not just coal fired units.

Two shift cycling ( ie shut down at night) is far more dmaging than load cycling ( drop load to 30% MCR at night), and for that reason one would only contemplate cycling a base load desinged coal fired plant to 30% load at night . This is due not only to limt fatigue damage to pressure parts, but also becuase many units have been retrofit with SCR's and scrubbers in a manner that indicates they cannot operate this equipment at lower loads.

Load cycling can be successfully applied at many coal fired units, with (minor) modfications in many cases . First, to limit the heat rate penalty associated with constant throttle pressure operation, the boiler would need to be modified to variable pressure operation. The minimum cost change to effect this would be to use the older B+W patent of "dual pressure " operation, that is , a pressure reducing valve PRV is placed at the primary superheater outlet; the drum , waterwall, and economizer are operated at constant pressure, while the final superheater operates at sliding pressure. Other physical changes would likely include adding relief valves upstream of the PRV and upgrades to control logic, spray attemporator, and pressure part fatigue monitoring as per TRD 301 annex 1. If this method is not used, then the more costly change of upgrading the superheater tube materials and supports would be required.

For those that need to frame everything in dollars, the Carper solution ( ie adding a $20/Ton CO2 tax) could only be rationalized if the long term "externality" associated with emitting CO2 was proven to be at least as large as $20/ Ton . But in any event, a political solution is a political solution, which means, logic and rational thinking is purely optional.

 

[DougMSOE]

We took a different approach, we burn up the CO, NO JOKE!

 

[cryotechnic]

rmw: "I knew of others located closer to oil fields that couldn't give the stuff away, and just vented it to the greenhouse."

The company I work for, just finished a CO2 saving project in Holland.

The company usses an old, unused pipeline that goes right through a large greenhouse area in the country. They buy the CO2 from a refinery, (the CO2 is pure enough to use) then we compress it to about 50bar and distribute it through the pipeline. The greenhouses are connected to the large pipeline. At the greenhouse the CO2 is reduced in pressure.

The greenhouse farmers were first using tanks with liquied CO2 and an evaporator to supply extra CO2 to their greenhouse, others are heating extra during the summer time, not that they need the heat, but they use the CO2 that is produced in the burningproces of natural gas.
In this case, they save on natural gas.

Totaly a lot of CO2 is saved every year.

I also know of other projects where they pump CO2 into old gaswells or old saltwells and store the CO2 in there.

Cryotechnic.

"Math is the ruler of your potential succes...."

 

[MJCronin]

to all..

Here is what the feds plan to do....

http://www.fe.doe.gov/programs/sequ...gramplans/2005/sequestration_roadmap_2005.pdf

-MJC