TW201323062A - Flue gas recirculation with CO2 enrichment membrane - Google Patents

Abstract

The present invention relates to a system (1) for capturing CO2 from a flue gas deriving from combustion of hydrocarbons which has been generated in a gas turbine (12) wherein the system comprises means for recirculating the flue gas (18, 24, 25) to the inlet of a gas turbine; means for CO2 separation (15); means for capturing CO2 (16). The invention relates also to a method capturing CO2 in the system.

Description

Flue gas recirculation with enriched CO 2 membrane

The present invention relates to a flue gas system of CO ₂ enriched, wherein the flue gas recirculation system has been combined with a system having an enrichment of CO ₂ film.

The general goal is to increase the CO ₂ concentration in the gas produced in a gas turbine based power plant.

In terms of the power cost of a power plant based on a gas turbine and equipped with a CO ₂ capture system, if the CO ₂ concentration in the flue gas is increased before the flue gas is treated in the CO ₂ capture unit of the power plant, then Improve overall performance.

Different methods can be used to perform the so-called "CO ₂ enrichment", that is, to increase the concentration of CO _{2 in} the flue gas.

Flue Gas Recirculation (FGR) is a method for increasing CO _{2 in} flue gas. This method is described in further based (e.g.) US 19800113635 and US 3 866 411, in which the gas turbine system and the _separation of hydrogen and CO combustion composition.

Also it is known in the flue gas recirculation (FRG) in combination to the gas turbine means and thereby facilitate the CO ₂ capture.

In EP 0 744 987, a system comprising an offshore gas turbine, a flue gas recirculation, a heat recovery steam generator (HRSG) and a CO ₂ capture system is described. Contains this system for enhanced oil recovery.

In WO 00/48709, a method of removing CO ₂ from exhaust gas and recovering it is described.

Another method of increasing the CO ₂ concentration in the flue gas is via membrane separation. The membrane provides a different range of selectivity for the particular species present in the flue gas.

Several types have been developed or membrane separation of CO ₂ is being developed, comprising a polymer film, a membrane contactor and facilitate the transfer film. Among these films, the polymer film is the most mature. A large-scale polymer membrane for CO ₂ separation is operated in the natural gas production industry, which processes a gas flow rate of about 400 m ² /s (Cakerwala natural gas production in Gulf of Thailand). Polymer membranes for CO ₂ separation in coal-fired power plants with optimum selectivity and permeability have been described in "TCMerkel et al., Power plant post-combustion carbon dioxide capture: An opportunity for membranes, Journal of membrane science 359 (2010) 126-139". These membrane systems are commercially available. For pilot plant testing, they can be designed to separate 20 tons of CO ₂ /day.

Furthermore, in WO 02/060561 it is described to capture CO ₂ by a CO ₂ frosting capture system. The CO ₂ capture is carried out by anti-sublimation. Previously, a combined flue gas recirculation configuration, membrane and high pressure solvent scrubbing method were proposed. The spent CO ₂ gas stream is reintroduced into the gas turbine for combustion in the form of a high pressure stream.

However, there is still a need for a method in which a high concentration of CO ₂ is obtained.

The present invention relates to an integrated system comprising a gas turbine based power plant having a flue gas recirculation and a CO ₂ capture system. Furthermore, CO ₂ enrichment can be further enhanced if combined with another enriched CO ₂ system, even referred to as a CO ₂ capture system.

The present invention objective to provide a self-derived hydrocarbon have occurred in a gas turbine combustion flue gas capture CO (part thereof) of the system _2. The system comprises: a) means for recirculating the first portion of the flue gas to be mixed with the flue gas at the gas turbine inlet; b) means for separating the CO ₂ from the second portion of the flue gas ; c) means for trapping the second portion of CO ₂ ; and if desired d) means for recycling the spent gas stream after trapping CO ₂ to the flue gas recycle.

According to step a), the first portion of the flue gas produced by the gas turbine is recirculated to the gas turbine inlet and mixed with the flue gas prior to the gas turbine inlet. The amount of recycled flue gas can be varied and determined by the ratio of flue gas recirculation (FGR) showing the percentage of flue gas recycled to the gas turbine inlet. The CO ₂ concentration in the flue gas is about 5% by volume prior to any flue gas recirculation. To double the CO ₂ concentration, about 50% of the flue gas needs to be treated and recycled to the gas turbine inlet. The recycled flue gas can be cooled before it is mixed with fresh air before the gas turbine inlet. The gas may have a temperature of about 40 to 45 degrees Celsius before being combined with fresh air and reintroduced into the gas turbine.

An embodiment of the invention is the system above, wherein the gas turbine system is coupled to a heat recovery steam generator (HRGS). The HRGS is present in the integrated system of the present invention as needed.

An embodiment of the invention is the system above, wherein the CO ₂ capture unit is located on the rich steam side downstream of the CO ₂ separation unit.

An embodiment of the invention is the system above, wherein the CO ₂ capture device can be selected from the group consisting of a CO ₂ frosting capture system, a gas processing unit (GPU), and a CO ₂ scrubbing capture system.

An embodiment of the invention is the system as above, wherein the apparatus for the CO ₂ frosting capture system is a continuous processing system wherein the CO ₂ in the gas phase is at a low temperature (e.g., -120 ° C to -56 ° C) Frosting to partially remove CO ₂ .

An embodiment of the invention is the system above, wherein the CO ₂ separation unit is a membrane that typically has limited CO ₂ selectivity and has an enriched flue gas stream (which is subsequently processed into the CO ₂ capture unit) A film of the nature of CO ₂ concentration.

It is an object of the present invention to provide a method for capturing CO ₂ from flue gas that has been combusted by a hydrocarbon in a gas turbine (as needed in combination with a heat recovery steam generator (HRSG)), comprising the following steps : a) separating the first portion of the flue gas and recirculating the first portion of the flue gas to the inlet of the gas turbine and mixing with the air; b) passing the second portion of the flue gas through the CO ₂ separation unit To generate a CO ₂ rich gas; c) to capture CO ₂ ; and if necessary d) to recycle the spent gas stream after CO ₂ capture to the flue gas recycle (FGR stream).

The flue gas separated in step a) may comprise 8 to 9% by volume of CO ₂ .

An embodiment of the method is wherein the CO ₂ separation device is a membrane, preferably a membrane having limited CO ₂ selectivity. The CO ₂ concentration can be further increased by a subsequent CO ₂ trap.

One embodiment of the invention is a method wherein the CO ₂ capture device can be selected from, for example, a CO ₂ frosting capture system, a gas processing unit (GPU), and a CO ₂ scrubbing capture system. The CO ₂ capture as in step c) above is carried out by CO ₂ frosting. One example is based on CO ₂ frosting anti-sublimation of CO _2, which is preferably carried out at atmospheric pressure.

It is advantageous to obtain a high concentration of CO ₂ in the gas. This is common to any post-combustion capture system, such as the following systems: chemical washing methods (higher amine method (AAP), cold ammonia method (CAP)), physical washing methods by absorption of CO ₂ in the liquid phase (eg , Rectisol) and by separating the solid phase from the vapor phase of the flue gas CO ₂ (e.g., an anti-sublimation) or liquid CO ₂ (hereinafter, such as examples of GPU gas processing unit) of the physical washing process. The purpose of increasing the CO ₂ concentration is to lower the energy required to cool and/or compress the flue gas (in terms of the same CO ₂ mass).

One embodiment of the present invention provides a method wherein the CO ₂ capture in step c) is performed by a gas processing unit (GPU). In the gas processing unit (GPU), the compressed air system, cooled, dried, liquefied and compressed to 90-99% of the CO ₂ rich stream.

According to one embodiment of the above method, the CO ₂ capture is carried out in a washing system, preferably a low pressure washing system.

According to an embodiment of the invention, the washing system is based on an amine washing system. According to an embodiment of the invention, the washing system is based on an ammonia system.

According to an embodiment of the invention, the CO ₂ removal rate in the flue gas obtained after step c) is greater than 90% (from the flue gas to the chimney).

Thus, flue gas recirculation system combines CO ₂ separation means (preferably non-selective membrane-based) of a system and method that provides cost of CO ₂ capture reduced.

This is achieved due to the reduced mass of flue gas to be treated. A higher partial pressure of CO _{2 is} also obtained, which results in an increase in energy input efficiency of the power plant by 15-70%, thereby reducing energy consumption.

In addition, a CO ₂ gas stream containing a small portion of O ₂ -depleted gas can be reused and the cooling load of the circulating flue gas cooler can be reduced.

In addition, it is also possible to provide a gas stream having a higher O ₂ amount than the surrounding air. This means that higher FRG obtained and a higher _{concentration} than in the airflow from the gas turbine of CO.

The present invention relates to an integrated system comprising a gas turbine based power plant having a flue gas recirculation and a CO ₂ capture system.

1 is a schematic representation of an integrated system in accordance with an embodiment of the present invention. The integrated system (1) of the present invention includes a gas turbine (12) that can feed air via a conduit (21). Natural gas is fed to the gas turbine (12) via a conduit (22). The gas turbine (12) is additionally combined with a heat recovery steam generator (HRSG) (14) to which the gas flows via a conduit (23).

The CO ₂ concentration in the flue gas is about 4 to 5% by volume without any flue gas recirculation. To double the CO ₂ concentration, about 50% of the flue gas must be treated and recycled to the gas turbine inlet. Therefore, to optimize the process, the amount of flue gas recirculation (FRG) can be specified.

The flue gas obtained after HRSG (14) contains about 8 to 9% CO ₂ . Then, the flue gas by a splitting point (32), wherein a portion of the flue gas line 15 towards the CO ₂ separation means (e.g., membrane) flow.

Another portion of the flue gas flows toward the flue gas cooler (18). Depending on the plant specific cooling system, the temperature of the flue gas is reduced from about 80 ° C to about 20-45 ° C after passing through the flue gas cooler ( 18 ). Then, the flue gas Recirculated to the inlet of the gas turbine via conduit (25).

The flue gas stream flowing to the CO ₂ separation unit (15) (e.g., membrane) is split into two streams, the nitrogen-rich exhaust gas flowing forward via conduit 26 and the carbon dioxide rich gas flowing forward through the conduit (27). The film should have the ability to CO ₂ is concentrated to about 50% (preferably up to about 60%) of. Thus, the pipeline (27) a flow of the flue gas may contain greater than 50% of the CO ₂ concentration (e.g., 50% to 60%) of.

In addition, membranes with limited (CO ₂ ) selectivity should be operable at a flue gas temperature of 85 ° C to 95 ° C. The membrane should also be capable of selectively treating a high quality stream of about 300 kg/s with relatively low driving force and limited CO ₂ selectivity. The driving force is provided by a blower or compressor 35 based on the optimum feed pressure to the CO ₂ trap (16).

Typically, the CO ₂ rich flue gas obtained after initial separation of CO ₂ comprising about 60% by volume of CO ₂ (carbon dioxide), about 10% by volume of O ₂ (oxygen), and about 30% by volume of N ₂ (nitrogen) .

The carbon-rich flue gas is then passed through a compressor 35 to obtain a CO ₂ rich stream. The CO ₂ capture device (16) then further enriches the CO ₂ concentration to a level suitable for its final storage or reuse via the conduit (28). a spent air stream comprising primarily N ₂ and O ₂ , which can be vented to the atmosphere or recirculated to the flue gas recirculation FGR pipe (25) via conduit (29) if it is due to from mixing with the cooling pipe (24) because of the O ₂ content of air or O ₂ content is higher than the conduit (21) in the fresh air line and useful).

The CO ₂ capture device (16) can be, for example, a CO ₂ frosting, liquefaction, and compression system. The spent gas stream after passing through the CO ₂ frosting device preferably has an O ₂ concentration that is higher than O _{2 in} the air.

The spent CO ₂ gas stream passing through the CO ₂ capture unit contains high levels of nitrogen (N ₂ ) and oxygen (O ₂ ).

The gas content can be adjusted by the capture rate of the CO ₂ frosting system. Devices with limited (CO ₂ ) selectivity can also affect the gas content.

Another option for capturing CO ₂ is via gas processing unit (GPU) technology.

GPU-based CO ₂ rich stream for processing, and compression processing by limiting selective membrane ₂ CO obtained. The gas will be compressed and purified as it passes through the GPU. The parameters that optimize the content of the gas stream can be specified.

The processing in the GPU includes the steps of compressing a gas, cooling a gas in which water vapor will condense into a water liquid, drying, liquefaction, and compression.

For purposes of this invention, the flue gas after the GPU obtained based CO ₂ removal rate of greater than 90% (from the flue gas to the stack), for example greater than 95%.

In another alternative, the CO ₂ capture device is based on a scrubbed CO ₂ capture system. For example, the washing system can be based on an amine or ammonia wash. The CO ₂ capture system (16) is preferably located downstream of the finite CO ₂ selective membrane. The system can be based CO ₂ capture system of the washing-based, object-based capture via a CO ₂ absorption solvent, so that the release of the product CO ₂ solvent regeneration. The CO ₂ capture is preferably carried out in a low pressure scrubbing system. Then, the purified and compressed CO ₂ -rich gas and adapted to be stored or used for other purposes. Typically, the CO ₂ rich gas so purified to recovery of 90%.

Further, in this embodiment, since the removal of the CO ₂ enriched gas stream can be recycled to the flue gas prior to its introduction in the gas turbine. The N ₂ and O ₂ rich recycle gas has a lower temperature than the recycle flue gas and, therefore, can be used to adjust the temperature of the recycle flue gas stream.

The washing process can be, for example, based on an amine or based on ammonia. Amines suitable for use in the washing process are generally selected from alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA). Other examples of amines to be used in the washing process are diisopropylamine (DIPA) and aminoethoxyethanol (diethylene glycol amine) (DGA). Mixtures of such amines can also be used in the washing process.

By capturing ammonia-based washing system, or CO ₂ capture by an amine-based CO ₂ scrubbing system.

According to step a), the first portion of the flue gas after the gas turbine is recycled to the gas turbine inlet and mixed with fresh air.

Thus, flue gas recirculation system in combination with the membrane of the system and to provide a method for reducing the cost of the CO ₂ capture.

This is achieved due to the reduced mass of flue gas to be treated. A higher partial pressure of CO _{2 is} also obtained, which results in a higher energy input efficiency of the power plant, thereby reducing energy consumption. In addition, a CO ₂ gas stream containing a small portion of O ₂ -depleted gas can be reused and the cooling load of the circulating flue gas cooler can be reduced.

It is also possible to provide a gas stream having a higher O ₂ amount than the surrounding air. This means that higher FRG obtained and a higher _{concentration} than the gas flow from the gas turbine in the CO.

While the invention has been described with respect to the preferred embodiments embodiments illustrated embodiments In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention. Therefore, the invention is not intended to be disclosed as the invention The specific embodiments of the preferred embodiments are limited, and the invention will include all embodiments within the scope of the appended claims. In addition, the use of the terms first, second, etc. does not denote any order or importance. Instead, the terms first, second, etc. are used to distinguish one element from another.

1‧‧‧CO2 capture system

12‧‧‧ gas turbine

14‧‧‧heat recovery steam generator

15‧‧‧CO ₂ separation device

16‧‧‧CO ₂ capture device

18‧‧‧ Flue gas cooler

21‧‧‧ Pipes

22‧‧‧ Pipes

23‧‧‧ Pipes

24‧‧‧ Pipes

25‧‧‧ Pipes

26‧‧‧ Pipes

27‧‧‧ Pipes

28‧‧‧ Pipes

29‧‧‧ Pipes

32‧‧‧Distribution point

35‧‧‧Blowers/Compressors

1 is a schematic representation of one example of an integrated system including flue gas recirculation, membrane, and CO ₂ capture systems.

1‧‧‧CO2 capture system

12‧‧‧ gas turbine

14‧‧‧heat recovery steam generator

15‧‧‧CO ₂ separation device

16‧‧‧CO ₂ capture device

18‧‧‧ Flue gas cooler

21‧‧‧ Pipes

22‧‧‧ Pipes

23‧‧‧ Pipes

24‧‧‧ Pipes

25‧‧‧ Pipes

26‧‧‧ Pipes

27‧‧‧ Pipes

28‧‧‧ Pipes

29‧‧‧ Pipes

32‧‧‧Distribution point

35‧‧‧Blowers/Compressors

Claims (14)

A self hydrocarbon has occurred from the gas turbine (12) in the combustion flue gas capture CO ₂ (partially) of the system (1), which comprises: a) the first portion of the recirculated flue gas to the gas turbine (12) of the inlet means (24,25,18); b) means for the CO ₂ from the second portion of the separated flue gases (15); c) CO ₂ trapping device (16 And; as needed d) means for recycling the spent gas stream after CO ₂ capture to the flue gas recirculation (29). The system of claim 1 wherein the gas turbine system is coupled to a heat recovery steam generator (HRGS) (14). The system of claim 1, wherein the CO ₂ capture device (16) is located on the rich gas stream side downstream of the CO ₂ separation unit (15). The system of claim 1, wherein the CO ₂ capture device (16) is selected from the group consisting of a CO ₂ frosting capture system, a gas processing unit (GPU), and a CO ₂ wash trap system. The system of claim 4, the apparatus wherein the frost-based CO ₂ capture systems for continuous processing apparatus, which via the CO ₂ in the gas phase at a low temperature portion of the frost to remove CO _2. The system of claim 1 wherein the CO ₂ separation unit (15) is a membrane that typically has a non-concentrating nature of the CO ₂ concentration in the flue gas stream (which is subsequently processed into the CO ₂ capture unit). Selective membrane. A method for capturing CO ₂ from flue gas that has been combusted by a gas turbine (12) (as needed in combination with a heat recovery steam generator (HRSG) (14)), comprising the following steps : a) separating the first portion of the flue gas (containing 8-9% CO ₂ ) and recycling the first portion of the flue gas to the inlet of the gas turbine and mixing with the air; b) making the flue The second part of the gas passes through the CO ₂ separation unit (15) and generates a CO ₂ rich gas; c) captures the CO ₂ ; and optionally d) recycles the spent gas stream after capturing the CO ₂ to the flue gas Recycling. The method of claim 7, wherein the flue gas in step a) comprises from 8 to 9% CO ₂ . The method of claim 7, wherein the separation device (15) is a membrane, preferably a membrane having limited CO ₂ selectivity. The method of claim 7, wherein the CO ₂ capture (16) in step c) is performed by CO ₂ frosting. The method of claim 7, wherein the CO ₂ capture (16) in step c) is performed by a gas processing unit (GPU), wherein the gas system is compressed, cooled, dried, liquefied, and compressed into a CO ₂ rich stream. The method of claim 7, wherein the CO ₂ capture (16) is carried out in a scrubbing system, preferably a low pressure scrubbing system. The method of claim 12, wherein the washing system is an amine based washing system or an ammonia based washing system. The method of claim 7, wherein the CO ₂ content after step c) is greater than 90%.