PROCESS FOR THE ENHANCEMENT OF POWER PLANT WITH CO2 CAPTURE AND SYSTEM FOR REALIZATION OF THE PROCESS
Improved methods and systems for power plants with CO2 capture and especially power plants with CO2 capture for enhanced oil recovery (EOR) purposes.
The present invention generally concerns power plants with CO2 capture and especially power plants with CO2 capture for enhanced oil recovery (EOR) purposes.
BACKGROUND OF THE INVENTIONIt is known that power plants for the generation of electrical and thermal energy having gas and/or steam turbines driven by fossil fuels may be equipped with systems based on chemical solvent processes (amines, chilled ammonia and others) for the capture of carbon dioxide (CO2) from the flue gas resulting from the combustion of the fossil fuels; the so called “post combustion carbon capture process”.
It is also known that exhaust gas recirculation can be used in fossil-fired power plants to control the production of gaseous emissions, in particular to enrich the CO2 content of the exhaust gas, reducing or eliminating the need for costly CO2 capture.
It is also known that an alternative technology is the so called “oxyfuel process” based on combustion of fossil fuels in an oxygen-enriched stream instead of the ambient air (which contains approximately 21% by volume of oxygen only). If nitrogen is removed prior to combustion, the flue gas stream would then have less nitrogen and the concentration of CO2 becomes higher, reducing or eliminating the need for costly CO2 capture.
Following any necessary post-treatment, the separated CO2 can be forwarded into storage or used for enhanced oil recovery or other purposes.
Further information concerning this technical background can be found in “Developments and innovations in carbon dioxide (CO2) capture and storage technology”; Volume 1; Carbon dioxide (CO2) capture, transport and industrial applications; edited by M. Mercedes Maroto-Valer; Woodhead Publishing Limited, 2010, ISBN 978-1-84569-533-0.
In the post-combustion CO2 capture system the whole flue gas flow is processed at low pressure, therefore this system (apparatus, pipelines, etc.) becomes voluminous and expensive. Some vessels can become so large, that the system is not feasible as a one-train solution, therefore several trains working in parallel are required for realization of such a process.
One issue with the post-combustion CO2 capture system results from the low CO2 concentration in the flue gas (3-15% depending on the fuel and combustion system). The efficiency of the chemical solvent process plant depends on the CO2 concentration in the flue gas, a low CO2 concentration generally resulting in a low efficiency.
The oxyfuel-based system has a similar problem, i.e. a large amount of air is required to be treated in the air separation unit for the production of the oxygen that goes into combustion. The system therefore becomes large, possibly requiring a multi-train solution and inefficient.
Exhaust gas recirculation has the problem that the oxygen lean recirculation gas, when mixed with incoming ambient air results in a oxygen depleted/CO2 enriched air stream for the power plant that can affect the output, efficiency, stability and operation of the power plant.
For all of the above reasons, there remains a need in the art for improvements to CO2 capture from a power plant.
SUMMARY OF THE PRESENT INVENTIONThe present invention provides improved techniques for CO2 capture from a power plant and reuse thereof that is an improvement over the techniques known in the prior art.
The present invention provides improved techniques for CO2 capture from a power plant that is an improvement over the techniques known in the prior art and particularly to CO2 capture for EOR (Enhanced Oil Recovery) purposes. One goal of the present invention is to create an efficient power plant with CO2 combustion.
The process according to the present invention is based on a combination of the exhaust gas recirculation process, oxy-fuel process and post combustion process (chemical solvent process). A portion of the exhaust gas from the power plant is recirculated to the air inlet and mixed with both incoming ambient air and an oxygen rich gas stream. The oxygen content of the mixed stream is adjusted by addition of the oxygen rich stream that may be provided from an air separation unit, or other appropriate source. This mixture results in a CO2 enriched flue gas from the power plant that is partly recycled to the power plant with the remainder flowing to the chemical solvent process unit, where the CO2 is separated. This process of flue gas recycle and oxygen enrichment are used to control the parameters of the combustion process for the power plant and to make the CO2 separation easier.
The invention will be described in greater detail with reference to the drawing figures, wherein like components are labeled with like reference numerals. In particular,
The invention offers several advantages. By using oxygen enriched air from an ASU as part of the recycle feed to the power plant, the CO2 concentration in the recycle gas is greater than a feed stream because there is less nitrogen in the feed. This makes the power plant more efficient. In addition, since less nitrogen is entering the system, there is a greater concentration of CO2 in the flue gas. This makes the chemical solvent treatment process more efficient and increases the efficiency of the whole power plant system. In addition, only a fraction of the air required needs to be separated in the air separation unit when operating according to the invention. Therefore the irreversibility caused by the air separation is reduced. The air separation plant can be more compact in the invention because of the reduced air flow requirement and the size of the absorption plant is also reduced because of the lower nitrogen concentration in the flue gas. It is therefore possible for the system of the invention to be used in either a single-train- or double-train solution, which allows for simpler control methodology.
By using the invention, the mixed gas provided to the power plant is oxygen enriched and therefore the output, efficiency, stability and operation of the power plant is enhanced. Further, the system of the invention can advantageously be used for retrofitting of existing power plants, because only minor changes are required to the power plant input.
It is anticipated that other embodiments and variations of the present invention will become readily apparent to the skilled artisan in the light of the foregoing description, and it is intended that such embodiments and variations likewise be included within the scope of the invention as set out in the appended claims.
Claims
1. A power plant system comprising:
- a fossil fueled power plant having an inlet and an exhaust;
- a flue gas treatment unit communicating with the exhaust of the power plant;
- a recycle line communicating with the flue gas treatment unit and the inlet of the power plant;
- an air separation unit communicating with the inlet of the power plant;
- an ambient air source communicating with the inlet of the power plant;
- wherein at least a portion of a CO2 enriched gas stream from the flue gas treatment unit is mixed with oxygen enriched gas from the air separation unit and ambient air from the ambient air source to form a mixed gas stream that is delivered by the recycle line to the inlet of the power plant.
2. The power plant system of claim 1 wherein the power plant is a power plant for an enhanced oil recovery system.
3. The power plant system of claim 1 wherein the power plant is a gas turbine, a steam generator or a combined gas turbine and steam generator.
4. The power plant system of claim 1 wherein the air separation unit is a cryogenic air separation unit.
5. The power plant system of claim 1 further comprising a heater communicating with the flue gas treatment unit and with the recycle line, for preheating the CO2 enriched gas stream.
6. The power plant system of claim 1 further comprising a chemical processing unit communicating with the flue gas treatment unit wherein the portion of the CO2 enriched gas stream that is not recycled is treated in the chemical processing unit.
7. The power plant system of claim 6 wherein the chemical processing unit is an amine wash unit.
8. The power plant system of claim 1 wherein the flue gas treatment unit is a direct contact flue gas cooler or a chilled water direct contact flue gas cooler.
9. The power plant system of claim 1 wherein the portion of the CO2 enriched gas stream that is not recycled is provided to end users.
10. The power plant system of claim 9 wherein the end user is an enhanced oil recovery operation.
11. The power plant system of claim 1 wherein the air separation unit produces a nitrogen enriched gas stream that may be provided directly to an end user.
12. The power plant system of claim 11 further comprising a mixing unit communicating with the flue gas treatment unit and with the air separation unit wherein the portion of the CO2 enriched gas stream that is not recycled and the nitrogen enriched gas stream from the air separation unit are mixed for supply to end users.
13. A method of enhancing the operation of a power plant comprising:
- collecting flue gas from the power plant;
- recycling at least a portion of the collected flue gas to the power plant;
- mixing the recycled flue gas with air and oxygen enriched gas; and
- delivering the mixed gases to the power plant.
14. The method of claim 13 further comprising supplying the oxygen enriched gas from an air separation unit.
15. The method of claim 13 wherein the oxygen enriched gas is from 50% to 100% oxygen.
16. The method of claim 13 further comprising treating the flue gas prior to the step of recycling a portion of the flue gas.
17. The method of claim 16 wherein treating the flue gas comprises processing the flue gas through a direct contact flue gas cooler or through a chilled water direct contact flue gas cooler.
18. The method of claim 13 further comprising delivering the portion of the flue gas that is not recycled to an end user.
19. The method of claim 18 wherein the end user is an enhanced oil recovery operation.
20. The method of claim 13 further comprising
- producing a nitrogen enriched gas stream from the air separation unit; and
- delivering the nitrogen enriched gas stream to an end user.
21. The method of claim 20 further comprising
- mixing the portion of the flue gas that is not recycled with the nitrogen enriched gas stream; and
- delivering the mixture to an end user.
22. The method of claim 21 further comprising removing oxygen from the flue gas prior to mixing with the nitrogen enriched gas stream.
23. A method of enhancing the operation of a power plant comprising:
- collecting flue gas from the power plant;
- recycling at least a portion of the collected flue gas to the power plant; and
- delivering air and oxygen enriched gas to the power plant.
Type: Application
Filed: Dec 11, 2012
Publication Date: Jun 20, 2013
Inventors: Alexander Alekseev (Wolfratshausen), Rob Smith (Hampshire), Ramachandran Krishnamurthy (Chestnut Ridge, NY)
Application Number: 13/710,951
International Classification: F01N 3/00 (20060101);