KR20120020198A - Method for reducing the emission of carbon dioxide and device - Google Patents

Abstract

The present invention relates to a method for reducing carbon dioxide emissions into the atmosphere and a tank for carrying out the method. According to the invention, the carbon dioxide generated due to the combustion process is separated from the gas. The carbon dioxide is then provided with a pressure of at least 10 bar in absolute pressure, preferably at least 15 bar in absolute pressure, particularly more preferably at least 18 bar in absolute pressure, and at a temperature of -10 ° C, preferably -20 ° C. Cools down. Preferably, the temperature of liquefied carbon dioxide is -40 ° C. The temperature of the liquefied carbonic acid during transport into the tank is preferably from -25 ° C to -35 ° C. The temperature required for liquefaction depends on the storage pressure. To provide a tank with a relatively high wall thickness, for example, a relatively high 18 bar g absolute pressure is required. Of course, a relatively high proportion of hydrogen and nitrogen in carbon dioxide gas is made possible through this high pressure. According to the prior art, it is not necessary to separate all of hydrogen and nitrogen before liquefying carbon dioxide that carbon dioxide has been separated.

Description

METHOD FOR REDUCING THE EMISSION OF CARBON DIOXIDE AND DEVICE}

The present invention relates to a method for reducing carbon dioxide emissions into the atmosphere and an apparatus for implementing the method. In particular, the carbon dioxide (CO ₂ ) is generated when the fuel containing carbon is burned. The carbon dioxide thus emitted is released into the atmosphere and affects global warming. Such environmental problems are known, for example, from German patent application DE 198 340 73 A1.

What is needed to prevent the carbon dioxide from being released into the atmosphere is to separate the carbon dioxide generated by combustion and to store it properly and permanently. In order to transport the collected carbon dioxide to a suitable reservoir located at a distance from the power plant, it has often been provided that the carbon dioxide is preferentially liquefied. For example, liquid carbon dioxide is transported from a power plant where carbon dioxide is generated by combustion to a reservoir.

The peculiarity of ship transport is that CO ₂ occurs continuously at the power plant, while ship transport can only be carried out in stages. This creates a need for buffer capacity to be provided.

The liquefied carbonic acid may be filled in a tank and stored after being transported to a reservoir, for example a depleted oil field or gas field or salt cave, via a transport such as a ship or vehicle.

It is already known to liquefy a gas for transport and to transport it in liquid form from a source to a desired destination using a tank. For example, natural gas is cooled to -161 to -164 ° C, thereby liquefying. In particular, liquefied natural gas (LNG) is carried by ship. In the case of LNG, materials that are resistant to low temperatures must be selected for storage in tanks. Of course, the materials used do not always have to have high robustness at low temperatures, since the LNG can be carried at normal pressure or at some excess pressure. However, there are also efforts to transport the LNG at high pressure and at high temperatures with high pressure.

It is known to store LPG under pressure. Since the gas can only be liquefied through pressure rise, the storage pressure is up to 18 bar in absolute pressure. This is the case when the ambient temperature is up to 45 ° C. In general, 45 ° C. corresponds to a high design temperature, which is calculated for gas tankers in service around the world. It is also known to cool the LPG to be conveyed to -42 ° C in order to deliver it to a high volume tank where no specific pressure is required. The storage pressure of the LPG to be conveyed can be reduced to ambient pressure.

In some cases, since a relatively expensive metal must be used, those skilled in the art do not allow the temperature of the liquefied gas to be cooled below -50 ° C. In particular, this is true even when the tank pressure is in an overpressure (overpressure) state. If the temperature of the liquefied gas is -50 ° C and above, it is generally possible to use low temperature fine grain steel such as P355NL2 or 13MNNI63. The tank made of the low temperature fine grain steel may be formed to be relatively pressure-resistant. Of course, for large volume tanks (greater than 1000 cubic meters), it is difficult and technically expensive to produce tanks that withstand relatively high excess pressures, for example of 5 to 10 bar g. In the case of transportation in large volumes, those skilled in the art should select the temperature of the liquefied gas so as to avoid using a pressure resistant tank or to lower the required pressure resistance in order to use a relatively large tank without problems.

If the tank for liquefied gas is to be subjected to pressure resistance, those skilled in the art should limit the wall thickness of the tank to about 50 mm. In particular, the following physical relationship is important: Micro-grained steels are affected by so-called low temperature embrittlement, which can be used for pressure tank construction where the micro-grained steel is no longer below a certain service temperature. Do not. The unit for this is the notched impact strength for individual temperatures. Among them, the numerical value depends on the structural conditions of the metal. The thicker the iron plate, the greater the risk of nonuniformity of the structure. In addition, there is an increased risk in areas affected by heat when welding, for example, to fabricate a rolled steel sheet during fabrication in machining. As such, the values for the test grids may not be applicable to all locations in the tanks produced. A pragmatic approach to testing thick iron plates at temperatures lower than the use temperature arises from the foregoing. This should ensure that the notched impact strength values identified are practically carried out throughout the iron plate at the operating temperature. The figures considered in this application reflect the pressure / temperature and sheet thickness for special micro-grained steels such as, for example, P690 QL2, which are generally used to construct gas storage tanks for sailing vessels. From the foregoing, the wall thickness is 50 mm, the test temperature is a storage temperature of −40 ° C., and the steel mill manufacturing the metal at the test temperature reaches the required notch impact value.

If a person skilled in the art would like to transport the carbon dioxide generated in the combustion process to the reservoir, the person skilled in the art should liquefy the carbon dioxide for the reasons described above, and transport it at a temperature of -50 ° C and a pressure of about 6.6 bar g. In order not to be provided with a low temperature or high pressure, and those skilled in the art will first purify the carbon dioxide, and in particular the separation of oxygen and nitrogen, a small amount inevitable in known in the art how to separate the CO ₂ from the power plant gas pollutants CO ₂ Oxygen and nitrogen are generated.

It is an object of the present invention to transport carbon dioxide generated in the combustion process industrially and possibly as completely as possible to the reservoir.

This object of the present invention is solved through a method of separating carbon dioxide generated from a combustion process from a gas. The carbon dioxide is then provided with a pressure of at least 10 bar in absolute pressure, preferably at least 15 bar in absolute pressure, particularly more preferably at least 18 bar in absolute pressure, and at a temperature of -10 ° C, preferably -20 ° C. Cools down. Preferably, the temperature of liquefied carbon dioxide is -40 ° C. The temperature of the liquefied carbonic acid during transport into the tank is preferably from -25 ° C to -35 ° C. The temperature required for liquefaction depends on the storage pressure. According to the invention, a temperature which is not too low can be selected. For example, a relatively high 18 bar g pressure is needed to provide a tank with a relatively high set pressure of 19 to 21 bar g (bar gauge) and a high wall thickness with it. Of course, the high pressure can withstand a relatively high proportion of hydrogen and nitrogen in carbon dioxide gas. According to the prior art, with regard to the separation of carbon dioxide, it is not necessary to separate all of hydrogen and nitrogen before liquefying carbon dioxide. The corresponding part of the carbon dioxide has the disadvantage of being released to the atmosphere in this way. In accordance with the present invention, the separated carbon dioxide is typically liquefied and transported to the reservoir due to the −50 ° C. temperature difference typically sought, without the large amount of hydrogen and nitrogen being separated beforehand.

There is no need to provide relatively pure carbon dioxide. The higher the amount of hydrogen and nitrogen that is separated, the more inevitably the disadvantage is that more carbon dioxide is separated and released into the atmosphere.

According to the invention, the temperature of the carbon dioxide is not cooled to -50 ° C in order to carry the liquid gas at the lowest possible pressure. Instead, it is necessary to separate nitrogen and hydrogen, or to attain a relatively high pressure to at least minimize such separation, unlike this conventional approach. In the case of tanks, it is necessary to relatively thicken the wall thickness. However, the foregoing does not increase the overall cost because the cost is reduced elsewhere. For example, the cost can be reduced because a large amount of hydrogen, oxygen and / or nitrogen does not have to be separated from the carbon dioxide to obtain the pure carbon dioxide.

In order to optimally process the steel used in the tank, the maximum wall thickness for the tank is about 50 mm.

When the ratio of nitrogen to carbon dioxide is not more than 0.7% mol, or the ratio of oxygen is not more than 0.99% mol, or the ratio of hydrogen is not more than 0.14% mol, preferably separated carbon dioxide Separation of oxygen, nitrogen or hydrogen from water can be completely abandoned, i.e. not separated, when the temperature of CO ₂ is about -30 ° C and the pressure is about 18 bar absolute. If CO ₂ different lot of toxic gases necessary for the undesirable increase in pressure or temperature drop to the liquid present in the CO _2, and another upper limit value is commonly used depending on the ingredients. In an embodiment of the present invention the carbon dioxide is cooled to -30 ° C and the pressure is selected such that the noxious gas can be separated from the separated carbon dioxide.

In an embodiment of the invention, the harmful gases and in particular nitrogen, oxygen and hydrogen are removed from the separated CO ₂ in order to save the energy required for liquefaction.

To remove the carbon dioxide, the carbon dioxide is pumped into a bore hole in, for example, an old oil field or gas field or salt cave.

First, CO ₂ basically generates saturated steam. Therefore, in the embodiment of the present invention, the carbon dioxide is dried before transporting the carbon dioxide in the liquid state. In some cases, cryogenic fluids produce ice and hydrates. If the formation of ice and hydrate is suppressed through drying, this can suppress blockage of narrow cross sections of filters, valves, pumps and the like. Preferably, when the carbon dioxide reaches a high pressure is to dry the carbon dioxide. This reduces drying.

The invention relates in particular to the case where the carbon dioxide is separated from the soot gas of the power plant. During the combustion of power plants, carbon dioxide causes enormous environmental pollution. Therefore, the present invention is particularly used for this case.

In addition, a tank having the features of the dependent claims is provided for solving the invention. Preferred embodiments are the subject of the dependent claims. The present invention also relates to a barge, the barge having carbon dioxide and / or sufficient pressure resistance to store the liquid carbonate at a temperature of -20 ° C to -40 ° C, preferably about -30 ° C. A device for liquefaction of the tank is provided. The tank has sufficient pressure resistance when the pressure required to liquefy CO ₂ increases. The tank volume of the tank in the barge is in particular at least 2000 cubic meters, particularly preferably at least 3000 cubic meters, in order to store a large amount of CO ₂ , in which case it is not expensive to produce the tank.

In particular, the barge,

-No building site is used in the power plant;

It is preferable if the barge has a longer drying period than fixed installations.

The individual tanks of the barge can be large because the tank is not carried. Therefore, in the embodiment of the present invention, liquefied carbonic acid is transferred from the tank of the barge to the tank of the vessel having a small volume. The vessel carries the liquefied carbonic acid to a suitable reservoir.

In older power plants, the buffer reservoir is fed from one power plant to another to continue using the buffer stroage in embodiments of the present invention. In this respect, the use of the barge is superior to fixed installations.

In an embodiment of the invention, the barge is anchored outside a commercial port to overcome the limitation of the shuttle-ship's access depth.

Since a large amount has to be conveyed, the volume of the tank carrying the liquefied carbonic acid to the reservoir is preferably at least 2000 cubic meters, particularly preferably at least 3000 cubic meters for the above reasons. The largest individual pressure tank with a set pressure of 18 bar g to 20 bar g, which can be prepared according to the prior art for storing CO ₂ at 18 bar α and −30 ° C., is 5000-6500 m ³ . Here, the combination of any of a number of tanks allows the construction of a corresponding buffer volume or transport volume on a ship.

This places high demands on the tanks in relation to temperature and pressure, in particular the tanks are made of high strength special steel according to EN 10028-6, for example with an elastic limit> 500 MPa to 900 MPa. This material is known as material number P690QL2 or 1.8888.

Tanks with a volume of 2000 cubic meters and more are carried by ship. However, another vehicle, for example a tank transport train or a van, may be used to transport the liquefied carbonic acid from the place where the combustion process is carried out to the reservoir. Of course, the tank volume of the vehicle is small. The tank is simple and in particular can be implemented with pressure resistance. Thus, the present invention first relates to the case of transporting a large amount of carbon dioxide to a suitable reservoir by ship. The vessel, of course, generally does not have a single tank, but rather a plurality of tanks (storage tanks). The total volume is at least always 5000 m ³ .

In overview, the present invention may be described as follows with respect to numbered embodiments:

1. A method of reducing the emission of carbon dioxide, in which the carbon dioxide generated through the combustion process is separated, wherein the separated carbon dioxide is at least 10 bar in absolute pressure, preferably at least 15 bar in absolute pressure, particularly more preferred. Preferably an absolute pressure of at least 18 bar is provided, the separated carbon dioxide is provided at a temperature of -10 ° C, preferably -20 ° C, particularly preferably -40 ° C, and the separated carbon dioxide is liquefied. Is transferred to the tank, which is transported to the carbon dioxide reservoir.

2. The method according to embodiment 1, wherein the pressure of the liquefied carbonic acid is not at least 25 bar in absolute pressure, preferably at least 18 bar in absolute pressure.

3. The method according to one of the embodiments 1 or 2, wherein the maximum wall thickness of the tank is not more than 50 mm.

4. The method according to one of embodiments 1-3, wherein the set pressure of the tank is not more than 20 bar.

5. One of the embodiments 1-4, wherein the proportion of nitrogen in the liquefied carbonic acid is not greater than 0.7% mol, or the proportion of oxygen is not greater than 0.99% mol, or the proportion of hydrogen is not greater than 0.14% mol. The method according to the embodiment of the invention. Embodiment 1, wherein up to 75%, preferably up to 50%, particularly preferably up to 25% of the total volume of non-carbon dioxide gases such as nitrogen, oxygen, hydrogen are separated from the carbon dioxide prior to liquefaction of the carbon dioxide The method according to one of the embodiments.

6. The process according to any one of embodiments 1 to 5, wherein no oxygen or nitrogen is separated from the separated carbon dioxide prior to liquefaction.

7. The method according to any one of embodiments 1 to 6, wherein the carbon dioxide is conveyed to the reservoir through one bore hole or a plurality of bore holes.

8. The method according to any one of embodiments 1 to 7, wherein said carbon dioxide is dried and conveyed to a reservoir in a dried state.

9. The method according to one of embodiments 1 to 8, wherein the tank consists of steel having material number P690QL2.

10. The method according to one of embodiments 1 to 9, wherein the tank consists of steel or equivalent steel having an elastic limit> 500 MPα, in particular> 620 MPα, particularly preferably> 690 MPα and P690QL2.

11. The method according to one of the embodiments 1 to 10, wherein the carbon dioxide is discharged from the power plant process in gaseous form, in particular separated from the soot gas of the power plant.

12. The method according to any one of embodiments 1 to 11, wherein the carbon dioxide is liquefied and / or temporarily stored in a barge.

13. The method according to any one of embodiments 1 to 12, wherein the liquefied carbonic acid stored in the barge is transported to a ship with its own drive.

14. The method according to any one of embodiments 1 to 13, wherein the tank or carbon dioxide-tank of the ship with its own drive is smaller than the tank or carbon dioxide-tank of the barge.

15. A carrier tank having liquefied carbonic acid contained in the tank and a tank volume of at least 2,000 m ³ , wherein the pressure of the tank is at least 10 bar g, preferably at least 15 bar g, particularly more preferably at least 18 bar g, and the temperature of the carbon dioxide is -30 ° C to -20 ° C. Basically, a vehicle tank with liquefied carbonic acid contained in the tank is produced according to the method according to embodiments 1 to 14.

16. Tank according to one of the two embodiments described above constructed from P690QL2.

17. In particular, a storage tank having a plurality of tanks with liquefied carbonic acid contained in said tank according to one of the two embodiments described above, wherein the pressure of each tank is at least 10 bar g, preferably At least 15 bar g, particularly preferably at least 18 bar g, the temperature of the carbon dioxide is from -30 ° C to -20 ° C, and the total volume of the tank is at least 5,000 m ³ , preferably 10,000 m ³ .

18. Barge with tank where liquefied carbonic acid can be stored at a temperature of -30 ° C. and a pressure of 18 bar g.

19. Barge according to embodiments 1 to 18, in particular having a device for the liquefaction of carbon dioxide.

20. A barge with one or multiple tanks in which the liquefied carbonic acid is stored at a temperature of about −30 ° C. and a pressure of about 18 bar g.

The present invention is described in detail below according to the embodiment.

In general post-combustion capture processes, the total soot gas of a power plant is subjected to an additional cleaning process (amine absorption process) according to conventional treatment methods (dust removal, desulfurization, denitrification). CO ₂ is preferably removed at the bottom of the washing tower through the concentrate because it is absorbed in the amine solution. In amine regeneration the CO ₂ is withdrawn from the amine solution due to the heat supply, and the raw CO ₂ is generated as saturated steam at atmospheric pressure. In several stages of compression, the carbon dioxide is provided at an absolute pressure of the desired liquefaction pressure of 12 to 40 bar. In the scope of the preferred embodiment, CO ₂ is carried at an absolute pressure of 18 bar and the liquid phase pressure is chosen slightly higher according to the invention (about 19 bar at absolute pressure). In the case of higher compression pressures, several stages of compression are required, which intermediately cool and separate the condensate produced in accordance with the invention. The gas is then dried. This is first done in a refrigerant dryer up to a pressure dew-point temperature of about 4 ° C. and then in an adsorption dryer. The dried CO ₂ is then liquefied, for example using a refrigerant condenser. Here, different refrigerants and processes may be carried out. In an embodiment, R410 is used as the refrigerant. A refrigerant is vaporized at low pressure and at a temperature of about -30 ° C and condensed with CO ₂ . The refrigerant is then compressed and condensed at about 30 ° C. for cooling water. Here, another method (e.g., condensation on air, etc.) is also possible, which is subject to different pressures and component choices. An advantage of the selection according to the invention, devised mainly in Northern Europe, is the use of conventional components in efficient energy use and cooling techniques.

Compression of the gas is carried out in power plants to enable industrial transport. Along with this, drying is also carried out in a power plant according to the invention because condensation takes place during transportation.

If another conveyance is to be carried out in stages for the reasons mentioned above, a buffer capacity is provided. This buffer capacity can also be carried out in several stages of compression if buffer storage is provided directly where the plant is located. If the power plant and the reservoir are spatially separated from one another, further compression (compared to the transport loss) is preferably carried out in a liquefier. Boil-off-gas (evaporating gas), which is inevitably generated due to heat input to the buffer tank, may again reach liquefaction pressure through a corresponding booster. In this embodiment (booster in the apparatus for CO ₂ liquefaction) compressors are less used.

Liquefaction and temporary storage may be performed in a spatially separate state (but not necessarily). In addition to the buffer storage, it is also possible to install it on a ship, for example, near a port. Preferably the liquefaction and temporary storage is carried out on a barge, ie on a ship without a self-drive. The barge reduces the need for land and can be installed at low cost in a short time compared to fixed installations. Basically, as modernization of the power plant, the barge can be carried out more easily than the corresponding fixed installation. The liquefaction and buffer storage and also when the vessel is spatially separated, the liquid conveyance is each carried out via a suitable pump.

Carrying vessels pump the CO ₂ on the holders to store service pressure rise and heating to, or pump the corresponding configuration CO ₂ in a vessel equipped with an element, and directly to the bore hole (bore hole) connected to the store ( CO ₂ , for example, through temporary coupling with deep-sea pipelines. Since pressure is applied to the reservoir, and having a bore hole is not suitable for low temperatures, pressure rise and heating are required.

In an embodiment of the invention, the storage pressure was 18 bar absolute. The liquefaction pressure was easily above the storage pressure described above. The temperature of the liquefied carbonic acid was about -35 ° C. The tank was a 3000 cubic meter volume cylindrical tank consisting of P690QL2 with a set pressure of 19 bar g.

Storage pressure The limit values at which carbon dioxide with nitrogen and oxygen can be contaminated for transport at about 18 bar at absolute pressure and at a temperature of about −30 ° C. are detailed in the examples below.

Mixture I:

CO ₂ 99.1992 mol%

N ₂ 0.4004 mol%

O ₂ 0.4004 mol%

Liquid temperature is -29.75 ℃ at 18 bar absolute pressure

Mixture II:

CO ₂ 99.1305 mol%

N ₂ 0.3498 mol%

O ₂ 0.5197 mol%

Liquid temperature is -30 ℃, 18 ℃ at 18 bar absolute pressure

Mixture III:

CO ₂ 99.2303 mol%

N ₂ 0.5496 mol%

O ₂ 0.2201 mol%

Liquid temperature is -30 ° C at 18 bar absolute pressure

If the carbon dioxide is to be transported at -30 ° C and 18 bar at absolute pressure, then much contaminated by the nitrogen and oxygen can first be purified to obtain sufficiently pure carbon dioxide free of nitrogen and oxygen. This also applies to other pressures and temperatures.

Claims (15)

As a way to reduce carbon dioxide emissions,
a) separating carbon dioxide generated in the combustion process from the gas;
b) bringing the separated carbon dioxide to an absolute pressure of at least 10 bar;
c) cooling the separated carbon dioxide to a temperature of -10 ° C;
d) liquefying the separated carbon dioxide to a tank;
e) conveying said tank for said carbon dioxide storage. The method of claim 1,
Said separated carbon dioxide having an absolute pressure of at least 18 bar. The method according to claim 1 or 2,
Cooling the separated carbon dioxide to a temperature of -40 ° C. 4. The method according to any one of claims 1 to 3,
And the pressure of the liquefied carbonic acid is not more than 25 bar in absolute pressure. 5. The method according to any one of claims 1 to 4,
And wherein the median wall thickness of the tank for liquefied carbonic acid is less than 50 mm. The method according to any one of claims 1 to 5,
And a set pressure of the tank for liquefied carbonic acid is not more than 20 bar. The method according to any one of claims 1 to 6,
The liquefied carbonic acid meets at least one of the criteria that the ratio of nitrogen is not more than 0.7% mole, the ratio of oxygen is not more than 0.99% mole, and the ratio of the proportion of hydrogen is not more than 0.14% mole. To reduce carbon dioxide emissions. The method according to any one of claims 1 to 7,
And no oxygen or nitrogen is separated from the separated carbon dioxide prior to liquefaction. The method according to any one of claims 1 to 8,
And said carbon dioxide is liquefied and stored in a barge. A tank of at least 2000 cubic meters for conveying liquefied carbonic acid, the tank being at least partially filled with liquid carbon prepared according to a method for reducing the carbon dioxide emissions of any one of claims 1 to 9, wherein the pressure of the tank is at least 10 bar tank, characterized in that g. The method of claim 10,
The tank has a pressure of at least 18 bar g. The method according to claim 10 or 11, wherein
The temperature of the carbon dioxide is a tank, characterized in that -30 to -20 ℃. The method according to any one of claims 10 to 12,
Wherein the liquid carbon is at a temperature of -30 ° C. at a pressure of 18 bar g. A storage tank provided with a plurality of tanks according to any one of claims 10 to 13. Barge provided with the tank in any one of Claims 10-13.