EP2780098A1

EP2780098A1 - Method and device for the separation of acidic gases from a gas mixture

Info

Publication number: EP2780098A1
Application number: EP12773311.1A
Authority: EP
Inventors: Jörn Rolker; Matthias Seiler; Ralf Meier; Udo Knippenberg; Rolf Schneider; Muhammad Irfan; Hari Prasad MANGALAPALLY
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2011-11-14
Filing date: 2012-10-15
Publication date: 2014-09-24
Also published as: WO2013072147A1; CA2855855A1; MX2014005746A; AU2012339061A1; CO6960534A2; BR112014008497A2; US20130118350A1; EA201400577A1; EA025928B1; US20160045857A1; TN2014000090A1; AU2012339061B2; US9221007B2

Abstract

In a method for the separation of acidic gases from a gas mixture, the gas mixture is brought into contact with an absorption medium comprising water and at least one amine and having a separation temperature in the range from 0 to 130°C. Acidic gases are desorbed from the loaded absorption medium by means of stripping with water vapour in a desorption column, wherein the desorption is executed at a temperature at which a separation into a watery liquid phase and a low-water liquid phase takes place in the desorption column. The resulting watery phase and low-water liquid phase are separated from each other, the watery liquid phase is advanced to an evaporator in which water vapour is generated which is used to strip the acidic gases and the low-water liquid phase and watery phase are returned to the absorber as an absorption medium. A device for this method comprises an absorber (1), a desorption column (2) with a material exchange zone (3) that has a liquid drain (4), an evaporator (5) and a phase separation device (6) with an inlet point (7) and outlet points (8, 9) for the liquid phases, wherein the evaporator (5) is arranged separated from the phase separation device (6), the liquid drain (4) of the material exchange zone (3) is connected to the inlet point (7) of the phase separation device and the device has connecting lines (10, 11) from the outlet point (8) for watery liquid phase to the evaporator (5) and from the outlet point (9) for low-water liquid phase to the absorber (1).

Description

Process and apparatus for the separation of acidic

from a gas mixture

The invention relates to a method and a device for separating an acidic gas, in particular CO2, from a gas mixture.

Many industrial and chemical processes produce gas streams that have an undesirable content of acid gases, in particular CO2, whose content must be reduced for further processing, transportation or avoidance of C02 emissions.

On an industrial scale, for the absorption of CO2 from a gas mixture, usually aqueous solutions of

Alkanolamines used as absorption medium. The

loaded absorption medium is regenerated by heating, releasing to a lower pressure or stripping, whereby the carbon dioxide is desorbed. After this

Regeneration process, the absorption medium can be reused. These methods are described, for example, in Rolker, J .; Arlt, W .; "Separation of carbon dioxide from flue gases by absorption" in Chemie Ingenieur Technik 2006, 78, pages 416 to 424 and in Kohl, A.L .; Nielsen, R. B., "Gas Purification", 5th ed., Gulf Publishing,

Houston 1997 described.

However, these methods have the disadvantage that the

Separation of CO2 by absorption and subsequent

Desorption requires a relatively large amount of energy, and desorbs only part of the absorbed CO2, so that in one cycle of absorption and desorption, the capacity of the absorption medium is insufficient. In addition, upon desorption by heating, thermal and oxidative degradation of the amine occurs at the hot heat exchange surfaces. In WO 2008/015217 it is proposed to use an absorption medium for a process for the separation of CO ₂ from gas mixtures, which on heating shows a separation into two liquid phases in order to reduce the energy requirement for the gas

Desorption of CO ₂ decrease. In this process, the desorption of CO ₂ takes place at a high level

C0 ₂ partial pressure, so that in a cycle of absorption and desorption only an insufficient capacity of

Absorption medium is achieved. US 2009/199709 and US 2010/104490 describe processes with such an absorption medium, in which the acidic gas-laden absorption medium is heated so that form two liquid phases, these phases are separated and only the acidic gas-rich liquid phase of a Desorption is supplied while the acidic gas poor liquid phase is recycled directly into the absorption. In these methods, however, part of the gas bound in the loaded absorption medium is already released in the apparatus in which the

Phase separation takes place. In practice this leads to

Problems, since the acidic gas is usually released from the heavier phase and rising gas bubbles of the

Counteract phase separation. In addition, the method of US 2009/199709 and US 2010/104490 can not be operated stably with the devices used in US 2009/199709 and US 2010/104490, although it can also be found in the US Pat

Desorption column for the formation of two liquid phases comes.

US 4,251,494 describes a process with a

An absorption medium comprising water, a hindered amine and an alkali metal carbonate. In this

Method, the composition of the absorption medium is chosen so that the absorption medium after desorption in the evaporator of the desorption by the

Evaporation of water and the temperature increase two forms liquid phases, which are separated in the evaporator and recycled at different locations in the absorber. The process requires an absorption medium with a high content of alkali metal carbonate, which has an undesirably high corrosivity. It also occurs in the same way as when using a single-phase

Absorption medium, a thermal and oxidative degradation of the amine on the hot heat exchange surfaces of the evaporator. There is therefore still a need for a method and an apparatus for the separation of acidic gases from a

Gas mixture in which by the formation of two

liquid phases in the desorption of energy requirements is reduced and does not have the disadvantages of the known from the prior art methods and devices.

The invention therefore relates to a process for the separation of acidic gases from a gas mixture which comprises absorbing acid gases by contacting the gas mixture with an absorption medium comprising water and at least one amine in an absorber to obtain a loaded absorption medium and a desorption of acidic gases from the loaded absorption medium by stripping with steam in a desorption column, wherein the absorption medium used in at

Heating over a demixing temperature in the range of 0 to 130 ° C shows a separation into two liquid phases. In the method according to the invention, the desorption is carried out at a temperature at which in the

Desorption a separation into a water-rich liquid phase and a low-water liquid phase takes place, the resulting water-rich liquid phase and

low-water liquid phase are separated from each other, water-rich liquid phase becomes an evaporator

fed, is generated in the water vapor, with the in the Desorption be stripped acid gases and

low-water liquid phase and water-rich liquid phase are returned as absorption medium in the absorber.

The invention also relates to an apparatus for the separation of acidic gases from a gas mixture comprising an absorber (1), a desorption column (2) with a mass transfer zone (3), an evaporator (5) and a

Phase separation device (6) for the separation of two liquid phases with a feed point (7) and separate

Entnahmestellen (8, 9) for the liquid phases comprises. The evaporator (5) is separate from the

Phase separation device (6) arranged. The

Phase separation device (6) has removal points (8, 9) for a low-water liquid phase and a water-rich liquid phase. The mass transfer zone (3) has a liquid outlet (4), which is connected to the feed point (7) of the phase separation device. The

The device according to the invention also has

Connecting lines (10, 11) from the discharge point (8) for water-rich liquid phase to the evaporator (5) and from the discharge point (9) for low-water liquid phase to the absorber (1).

In the inventive method for the separation of acidic gases from a gas mixture, the gas mixture can

Natural gas, a methane-containing biogas from a

Fermentation, composting or treatment plant, a

Combustion exhaust gas, an exhaust gas from a

Calcination reaction, such as the burning of lime or the production of cement, a residual gas from a

Blast furnace process for the production of iron or a resulting from a chemical reaction gas mixture, such as

for example, a carbon monoxide and hydrogen

containing synthesis gas or a reaction gas of a

Be hydrogen production by steam reforming.

Preferably, the gas mixture is a combustion exhaust gas Natural gas or a biogas, more preferably a

Combustion exhaust gas, for example, from a power plant.

The gas mixture contains at least one acidic gas,

preferably one or more acidic gases from the series CO2, COS, H ₂ S, CH ₃ SH and S O ₂ , particularly preferably CO ₂ . One

Combustion exhaust gas is preferably previously desulfurized, i. S O2 is extracted from the gas mixture with a desulfurization process known from the prior art,

preferably by washing with lime milk, before the process of the invention is carried out.

The gas mixture preferably has a content of CO2 in the atmosphere before being brought into contact with the absorption medium

Range of 0.1 to 50% by volume, more preferably in the range of 1 to 20% by volume, and most preferably in the range of 10 to 20% by volume.

The gas mixture can still be added to acidic gases

Contain oxygen, preferably in a proportion of 0.1 to 25% by volume and more preferably in a proportion of 0, 1 to 10% by volume. In the process of the present invention, the gas mixture in an absorber is contacted with an absorption medium comprising water and at least one amine which, when heated above a demixing temperature ranging from 0 to 130 ° C, segregates into two liquid phases , The demixing temperature refers to the unloaded absorption medium without acidic gases. Amines, their mixtures with water one

Demixing temperature in the range of 0 to 130 ° C.

are known to those skilled in the art, for example from WO 2008/015217, US 2009/199709 and US 2010/104490. Preferably, amines are used which have a solubility of less than 100 g of amine in 1 l of water at 100 ° C., more preferably less than 60 g of amine in 1 liter of water and most preferably less than 10 g of amine in 1 liter of water.

The content of alkali metal salts in the absorption medium is preferably below 10 wt .-%, more preferably below 5 wt .-% and in particular below 2 wt .-%.

In a preferred embodiment, the

Absorption medium at least one amine of the formula (I)

(I) where the radicals R and R independently

Hydrogen or aliphatic radicals of 1 to 10

Carbon atoms are those with amino groups or

Alkylamino groups may be substituted.

In a further preferred embodiment, the absorption medium comprises at least one amine of the formula (I), for which the radicals R ¹ and R ^{2 are} independently hydrogen or alkyl radicals having 1 to 6 carbon atoms, more preferably R ^{1 is} hydrogen and R ^{2 is} an alkyl radical 1 to 6 carbon atoms. Most preferred are the compounds 4- (n-propylamino) -

2, 2, 6, 6-tetramethylpiperidine and 4- (n-butylamino) -

2, 2, 6, 6-tetramethylpiperidine, for which R ^{1 is} hydrogen and R ^{2 is} n-propyl or n-butyl.

In a particularly preferred embodiment, the absorption medium comprises a first amine of the formula (I), for which the radicals R ¹ and R ^{2 are} independently hydrogen or alkyl radicals having 1 to 6 carbon atoms and a second amine of the formula (I), for the R ¹ hydrogen and R ^{2 is} a radical (CH ₂ ) _n NR ³ R ⁴ is where n = 2 to 4, R ³ = hydrogen or alkyl radical having 1 to 4 carbon atoms and R ⁴ =

Alkyl radical having 1 to 4 carbon atoms. For the first amine of the formula (I), R ¹ is preferably hydrogen and R ^{2 is} an alkyl radical having 1 to 6 carbon atoms, R ² particularly preferably n-propyl or n-butyl. The second amine of the formula (I) is preferably 4- (3-dimethylamino-propylamino) -2,2,6,6-tetramethylpiperidine, for which n = 3 and R ³ , R ⁴ = methyl, or 4- (2 Ethylamino-ethylamino) - 2, 2, 6, 6-tetramethylpiperidine, for which n = 2, R ³ = methyl and R ⁴ = hydrogen. The weight ratio of the first amine of the formula (I) to the second amine of the formula (I) is preferably in the range from 10: 1 to 1:10, particularly preferably in the range from 3: 1 to 1: 5 and in particular in the range from 1 : 1 to 1: 3. The absorption medium preferably comprises from 25 to 85% by weight of water and from 15 to 75% by weight of amines of the formula (I), based in each case on unloaded absorption medium without acidic gases.

By using an absorption medium containing amines of formula (I), a high capacity for the absorption of CO _{2 can be achieved} even at low C0 ₂ partial pressure. In addition, such absorption media are less corrosive, show good stability against

oxidative and thermal degradation and show in the

inventive method no foaming. The absorption medium may contain, in addition to water and amines of the formula (I), at least one sterically unhindered primary or secondary amine as activator. A sterically unhindered primary amine in the sense of the invention is a primary amine in which the amino group is attached to a

Carbon atom is bound to the at least one

Hydrogen atom is bonded. A sterically unhindered secondary amine in the sense of the invention is a secondary amine in which the amino group is bonded to carbon atoms to which in each case at least two hydrogen atoms are bonded. The content of sterically unhindered primary or secondary amines is preferably 0.1 to 10 wt .-%, particularly preferably 0.5 to 8 wt .-%. Suitable activators are activators known from the prior art, for example ethanolamine, piperazine and 3- (methylamino) -propylamine. Also suitable is 4-amino-2, 2, 6, 6-tetramethylpiperidine. The addition of an activator leads to an acceleration of the absorption of CO ₂ from the gas mixture without loss of absorption capacity. The absorption medium may contain, in addition to water and amines, one or more physical solvents

contain. The proportion of physical solvents can be up to 50 wt .-%. As a physical

Solvents are sulfolane, aliphatic

Acid amides, such as N-formylmorpholine, N-acetylmorpholine,

N-alkylpyrrolidones, in particular N-methyl-2-pyrrolidone, or N-alkylpiperidones, and also diethylene glycol,

Triethylene glycol and polyethylene glycols and their

Alkyl ethers, in particular diethylene glycol monobutyl ether. Preferably, however, the absorption medium does not contain a physical solvent.

The absorption medium may additionally have additives, such as corrosion inhibitors, wetting-requiring additives and defoamers. As corrosion inhibitors, it is possible in the absorption medium to use all substances which are known to the person skilled in the art for the absorption of CO ₂ using alkanolamines as suitable corrosion inhibitors, in particular the corrosion inhibitors described in US Pat. No. 4,714,597. The amount of corrosion inhibitors can be significantly lower when using amines of the formula (I) than in a conventional

Ethanolamine-containing absorption medium, since absorption media containing amines of formula (I), compared to metallic materials significantly less are corrosive than the commonly used ethanolamine-containing absorption media.

The wetting-requiring additive used is preferably the nonionic surfactants known from WO 2010/089257 page 11, line 18 to page 13, line 7, zwitterionic surfactants and cationic surfactants.

Defoamers which may be used in the absorption medium are all substances which are suitable for the person skilled in the art for the absorption of CO ₂ using alkanolamines

Defoamers are known.

Preferably, the gas mixture is in a

Absorption column brought into contact with the absorption medium, wherein the absorption column is preferably operated in countercurrent, in order to achieve a low residual content of acidic gases in the gas mixture after absorption.

The absorption is preferably carried out at a temperature in the range of 0 ° C to 70 ° C, more preferably 20 ° C to 50 ° C, wherein the temperature of the absorption medium when entering the absorber below the

Demixing temperature is. Within the absorber, the temperature can also be above the segregation temperature

increase if the absorption of acid gas in the absorption medium from the amine salts are formed, which have a higher water solubility than the amine. When using a countercurrent

Absorption column is the temperature of the

Absorbent medium preferably 30 to 60 ° C when entering the column and 35 to 70 ° C when exiting the column. The absorption is preferably carried out at a pressure of

Gas mixture in the range of 0.8 to 50 bar, more preferably 0.9 to 30 bar performed. At a

Separation of CO ₂ is the initial partial pressure of CO ₂ in the gas mixture preferably 0.01 to 4 bar,

more preferably 0.05 to 3 bar. In a particularly preferred embodiment, the absorption at a total pressure of the gas mixture in the range of 0.8 to 1.5 bar, in particular 0.9 to 1.1 bar, performed. This particularly preferred embodiment is advisable in the absorption of CO ₂ from the combustion exhaust gas of a power plant without compression of the combustion exhaust gas.

In the method according to the invention, the laden absorption medium obtained in the absorber is a

Fed desorption in the acidic gases from the loaded absorption medium by stripping with steam. The desorption is carried out at a temperature at which separation takes place in the desorption column into a water-rich liquid phase and a water-poor liquid phase. The temperature in the desorption is preferably in the range of 50 ° C to 200 ° C, more preferably in the range of 80 ° C to 150 ° C. The desorption is preferably carried out at a pressure in the range from 10 mbar to 10 bar, particularly preferably in the range from 100 mbar to 5 bar.

The water-rich liquid phase resulting from the desorption and the water-poor liquid phase are separated from each other. Part of the water-rich liquid phase is fed to an evaporator in which water vapor is generated, which is fed into the desorption column and stripped with the in the desorption column of acidic gases. The low-water liquid phase and the remaining part of the water-rich liquid phase are called

Absorption medium returned to the absorber. The low-water liquid phase and the remaining part of the water-rich liquid phase are preferably mixed together at a temperature below the demixing temperature before being returned to the absorber. The proportion of water-rich in the evaporator not evaporated liquid phase can optionally be supplied to the desorption column or the absorber.

With the method according to the invention, a high capacity of the absorption medium in a cycle can be

Absorption and desorption can be achieved because in the process, the desorption can be carried out to a low residual content of acidic gases and absorption media can be used with a high proportion by weight of amines with which a high loading is achieved in the absorption. The thermal and oxidative degradation of the amines used for absorption is low in the inventive method, since only a small part of the amines enters the evaporator and is exposed there to the high temperatures at the heat exchange surfaces. The energy requirement of the method according to the invention is compared to

Methods using a single-phase absorption medium are significantly lower. The process according to the invention requires no auxiliary substances in addition to water and amine and can be carried out in simple and inexpensive apparatuses.

Figure 1 shows a flow diagram of an embodiment of a device according to the invention, in which the

Phase separator (6) separated from the

Desorption column (2) is arranged. Figure 2 shows a flow diagram of a preferred embodiment of a device according to the invention, in which the

Phase separation device (6) within the desorption column (2) below the mass transfer zone (3) is arranged.

The device according to the invention for the separation of acidic gases from a gas mixture comprises an absorber (1) in which the gas mixture (20) containing acidic gases is brought into contact with a liquid absorption medium. As absorber, all known from the prior art devices for the absorption of a gas from a Gas mixture are used in a liquid. As an absorber, a washing column is preferably used, preferably internals to increase the

Phase interface between the gas mixture and the

having liquid absorption medium. Suitable internals are, for example, packing, e.g. Raschig rings or Pall rings, structured column packs, e.g.

Sheet metal packings, as well as column bottoms, e.g. Sieve trays.

Alternatively, a membrane contactor, a radial flow scrubber, a jet scrubber, a venturi scrubber or a rotary scrubber can be used as the absorber. The absorber used is particularly preferably a scrubbing column for countercurrent operation, in which the gas mixture containing acidic gases in a lower region of the

Washing column is supplied and the liquid

Absorption medium is supplied in an upper region of the wash column.

The device according to the invention comprises a

Desorption column (2) with a mass transfer zone (3), which is arranged within the desorption column. The desorption column is laden with the acidic gas

Absorption medium supplied from the absorber. The absorption medium laden with the acidic gas is preferably fed to the desorption column above the mass transfer zone. As a desorption column, all known from the prior art columns for the desorption of a gas from a liquid can be used. The

Mass transfer zone (3) is preferably in the form of

Built-in executed, which cause an increase in the surface. Column trays, random packings or structured packings are preferably used as internals. As column trays, for example, bubble trays, sieve trays, tunnel trays, valve trays, slotted trays, sieve slotted trays, sieve bubble trays, nozzle trays or

Centrifugal trays. Examples of suitable packings are Raschig rings, Lessing rings, Pall rings, Berl saddles or Intalox saddles. Suitable structured packings are, for example, the column packings of the type Mellapak from Sulzer, the type Rombopak from Kühni or the type Montz-Pak from Montz. In the mass transfer zone, sections with column bottoms, random packings and structured packings can be combined as desired. The mass transfer zone (3) has a liquid outlet (4), on which liquid is collected, which emerges at the lower end of the mass transfer zone. The device according to the invention comprises an evaporator (5) in which steam is produced, which is fed to the desorption column (2) to supply heat for the desorption of acidic gas from the loaded absorption medium and with the vapor stream acidic gases from the liquid

Separate absorption medium. As evaporator, all known from the prior art evaporators can be used, for example, natural circulation evaporator,

Forced circulation evaporator, falling film evaporator or

Thin-film evaporator. The device according to the invention comprises a

Take-off points (8, 9) for the liquid phases, a

Withdrawal point (8) for water-rich liquid phase and a discharge point (9) for low-water liquid phase. Of the

Evaporator (5) and the phase separator (6) are arranged separately. The liquid outlet (4) of the mass transfer zone (3) is connected to the feed point (7) of the phase separation device in order to remove from the

Mass transfer zone exiting liquid the

Feed phase separation device. When

Phase separation device can all from the state of

Technique known apparatus for the separation of mixtures of two liquid phases can be used. Suitable, for example, settling tanks, in which a separation of the Phases are done by gravity. Alternatively, separators may be used in which the phases are separated by centrifugal forces. In a

In a preferred embodiment, the phase separation device (6) is arranged within the desorption column (2) below the mass transfer zone (3)

The device according to the invention comprises a

Connecting line (10) from the discharge point (8) for water-rich liquid phase to the evaporator (5), is supplied to the liquid-rich liquid phase to the evaporator to produce steam therefrom. The inventive

Device also comprises a connecting line (11) from the discharge point (9) for low-water liquid phase to the absorber (1), is returned to the low-water liquid phase in the absorber. Preferably, the device according to the invention additionally comprises a

Connecting line (16) from the discharge point (8) for water-rich liquid phase to the absorber (1), is recycled to the water-rich liquid phase in the absorber.

In a preferred embodiment, the

Device according to the invention additionally

Connecting line (16) between the removal point (8) for water-rich liquid phase and the absorber (1), wherein in the connecting line a control valve (17) or a controllable pump is arranged. The phase separation device (6) in this embodiment has a level control (18) for a liquid-liquid phase interface in the phase separation device (6), with which the control valve (17) or the controllable pump is driven. Alternatively, the connecting line (16) with a

additional discharge point for water-rich liquid phase to be connected to the phase separation device (6) from the sampling point (8) connected to the evaporator (5)

is connected, is disconnected. By such Level control can regulate the amount of water-rich liquid phase, which is returned to the absorber, so that no water in addition to the absorber must be supplied for a stationary operation of the device. In a further preferred embodiment, the device according to the invention additionally comprises a

Mixing device (19) which is arranged in the connecting line (11) from the discharge point (9) for low-water liquid phase to the absorber (1) and with the

Extraction point (8) for water-rich liquid phase

is connected and liquid from the discharge point (9) for low-water liquid phase with liquid from the

Removal point (8) for water-rich liquid phase mixes. As a mixing device, all known in the art devices for mixing two liquids can be used. As a mixing device are, for example, stirred containers, containers with a liquid circulation via an external circuit or static mixer.

Preferred are containers with a liquid circulation via an external circuit and a supply of low-water liquid phase and water-rich liquid phase in the external circuit. Preferably, in the lines with which are water-poor liquid phase and

Water-rich liquid phase of the mixing device (19) is supplied, heat exchangers (21, 22) arranged, with which let the two phases to a temperature below the demixing temperature of the absorption medium used in the absorber to cool. Particularly preferably, the heat exchangers (21, 22) are arranged so that they heat exchange between the loaded

Absorbent medium absorbed by the absorber (1) of the

Desorption column (2) is supplied, and the liquid phases, which are supplied to the mixing device (19) cause. By using the mixing device, a uniform flow can be achieved during operation of the device

Composition of the absorption medium in the absorber ensure that variations in the control of the device do not affect the effectiveness of the absorption.

The device according to the invention preferably additionally comprises a condenser (23), which is connected to the head of the desorption column (2) and connected to the

Water, which leaves the desorption column in vaporous form together with the desorbed acidic gas, is condensed and returned to the desorption column. Figure 1 shows an embodiment of the device according to the invention, in which the phase separation device (6) is arranged separately from the desorption column (2) and is designed as a settling tank with an overflow weir. In this embodiment, the floor drain of

Desorption column as a liquid outlet (4) of

Mass transfer zone (3) used. In the connecting line between the liquid outlet (4) and the inlet point (7) of the phase separation device koaleszenzufde internals can be arranged, such as

Coalescing filter to achieve a more complete phase separation in the phase separation device.

Figure 2 shows a preferred embodiment of

Device according to the invention, in which the

Phase separation device (6) within the desorption column (2) below the mass transfer zone (3) is arranged. The phase separation device (6) is characterized by a

Overflow weir (13) formed in the column sump (12), which separates the column sump in a first zone (14) and a second zone (15), and by a feed point (7) to the first zone (14), wherein the feed point with the

Liquid outlet (4) of the mass transfer zone (3) is connected. The liquid drain (4) is preferably formed as a collection tray for liquid with a liquid drain above the first zone. The feed point to the first zone (14) may be above the first zone (14) be arranged as shown in Figure 2, or within the first zone (14) below the upper edge of the overflow weir (13) to be arranged. For use with

Absorption media in which the water-lean phase is lighter than the water-rich phase, as shown in Figure 2, in the first zone (14) a removal point (8) is arranged, which via a connecting line (10) connected to the evaporator (5) is and arranged in the second zone (15) has a removal point (9), which has a

Connecting line (11) with the absorber (1) is connected. For use with absorption media in which the water-lean phase is heavier than the water-rich phase, the sampling points (8) and (9) are reversed compared with FIG. The device according to the invention may comprise additional pumps, measuring devices, control valves, shut-off valves and buffer containers which are not shown in FIGS. 1 and 2 and which the person skilled in the art has been aware of

described operation of the device according to its general expertise can add.

The device according to the invention has a simple structure and can be carried out with commercially available apparatuses. It enables stable operation without

Fluctuations in the separation performance of acid gases even when using absorption media used in the

Desorption show a separation into two liquid phases, of which one phase is poor in water, so that from this phase no water vapor can be produced in the evaporator. When using such absorption media in the devices known from US 2009/199709, US 2010/104490 and US 4,251,494, however, there are strong fluctuations in the generation of steam in the evaporator, which lead to an unstable operation. Since in the device according to the invention, only the water-rich liquid phase containing a small proportion of amines, with the hot heat exchange surfaces of the Evaporator comes into contact, it comes in operation only a small thermal and oxidative degradation of the amines used in the absorption medium.

The following examples illustrate the invention, but without limiting the scope of the invention.

Examples:

In Table 1 are compositions of for the

inventive method suitable absorption media and the separation temperatures of these absorption media

(Loading with CO ₂ and without loading).

To determine the demixing temperature of loaded with CO ₂ absorption medium, the absorption medium was placed in a pressure-resistant glass vessel and saturated at 20 ° C and atmospheric pressure by the addition of dry ice with CO ₂ . The glass jar was then capped and the CO ₂ -loaded absorption medium was slowly heated in an oil bath until separation into two liquid phases, that of turbidity of the previously clear mixture

was recognizable.

Abbreviations in Table 1:

Propyl TAD: 4- (n-propylamino) -2,2,6,6-tetramethylpiperidine

Butyl TAD: 4- (n-butylamino) -2,2,6,6-tetramethylpiperidine

DM-TAD: 4- (dimethylamino) -2,2,6,6-tetramethylpiperidine TAT: 4- (3-dimethylamino-propylamino) -

2, 2, 6, 6-tetramethylpiperidine or triacetonetriamine

EAE-TAD: 4- (2-ethylamino-ethylamino) -

2,2,6,6-tetramethylpiperidine

MEA: ethanolamine

DEA: diethanolamine

MDEA: methyldiethanolamine

AMP: 2-amino-2-methyl-1-propanol

nb: not determined Table 1

Table 1 (cont

For a mixture of water and 4- (n-butylamino) -2,6,6,6-tetramethylpiperidine (butyl-TAD), the

Composition of the two liquid phases in the biphasic area as a function of the temperature studied. The results reproduced in Table 2 show that the water-rich liquid phase, which in the process according to the invention corresponds to the

Evaporator is supplied, containing only small amounts of amine.

Table 2

Temperature in ° C Water content Water content

upper phase lower phase

in% by weight in% by weight

60 17.5 98, 3

67 12, 5 98, 9

75 9.3 99, 2

82 6, 8 99, 3

93 4.5 99, 4

Claims

Patent claims:

1. Process for the separation of acidic gases from a

Gas mixture comprising absorption of acidic gases by bringing the gas mixture into contact with an absorption medium comprising water and at least one amine in an absorber to obtain a loaded absorption medium and desorption of acidic gases from the loaded absorption medium by stripping with steam in a desorption column, wherein the absorption medium when heated over a

Separation temperature separates into two liquids

phases shows

characterized,

that the absorption medium has a demixing temperature in the range from 0 to 130 ° C, the desorption is carried out at a temperature at which in the

Desorption column separation into a water-rich liquid phase and a water-poor liquid phase takes place, the resulting water-rich liquid phase and water-poor liquid phase are separated from each other, water-rich liquid phase is fed to an evaporator in which

Water vapor is generated, with which acidic gases are stripped in the desorption column and water-poor liquid phase and water-rich liquid phase are used as absorption medium

Absorbers are returned.

2. Method according to claim 1,

characterized,

that the absorption medium comprises an amine which has a solubility of less than 100 g of amine in 1 liter of water at 100 ° C.

3. Method according to claim 1 or 2,

characterized,

that the absorption medium comprises at least one amine of the formula (I). (I) where the radicals R ¹ and R ² are independently hydrogen or aliphatic radicals with 1 to 10 carbon atoms, which can be substituted with amino groups or alkylamino groups.

Method according to claim 3,

characterized,

that the radicals R ¹ and R ² are independently hydrogen or alkyl radicals with 1 to 6 carbon atoms.

Method according to claim 3,

characterized,

in that the absorption medium comprises a first amine of the formula (I), for which the radicals R ¹ and R ² are independently hydrogen or alkyl radicals with 1 to 6 carbon atoms, and a second amine of the formula (I), for which R ¹ is hydrogen and R ² is a radical (CH ₂ ) _n NR ³ R ⁴ with n = 2 to 4, R ³ = hydrogen or alkyl radical with 1 to 4 carbon atoms and R ⁴ = alkyl radical with 1 to 4 carbon atoms.

Method according to one of claims 3 to 5,

characterized,

that the absorption medium comprises 25 to 85% by weight of water and 15 to 75% by weight of amines of the formula (I).

Device for separating acidic gases from a

Gas mixture comprising an absorber (1), a

Desorption column (2) with a mass transfer zone (3) which has a liquid outlet

(4), an evaporator (5) and a phase separation device (6) for separating two liquid phases with an inlet point (7) and separate removal points (8, 9) for the liquid phases,

characterized,

that the evaporator

(5) separate from the Phase separation device (6) is arranged

Phase separation device

(6) has withdrawal points (8, 9) for a water-poor liquid phase and a water-rich liquid phase, the liquid outlet (4) of the mass transfer zone (3) with the inlet point

(7) is connected to the phase separation device and the device has connecting lines (10, 11) from the withdrawal point (8) for water-rich liquid phase to the evaporator (5) and from the withdrawal point (9) for

has a low-water liquid phase to the absorber (1).

8. Device according to claim 7,

characterized,

that the phase separation device (6) within the

Desorption column (2) is arranged below the mass transfer zone (3).

9. Device according to claim 8,

characterized,

that the desorption column (2) has a column bottom (12), which is separated by an overflow weir (13) into a first zone (14) and a second zone (15), which

Liquid outlet (4) of the mass transfer zone (3) is connected to an inlet point (7) to the first zone (14), a removal point (8) in the first zone (14) via a

Connecting line (10) is connected to the evaporator (5) and a removal point (9) in the second zone (15) is connected to the absorber (1) via a connecting line (11).

10. Device according to one of claims 7 to 9,

characterized,

that it additionally has a connecting line (16) between the removal point (8) for water-rich liquid phase and the absorber (1), with a

Control valve (17) or a controllable pump is arranged, and the phase separation device (6) has a level control (18) for a liquid-liquid phase interface in the

Has phase separation device with which the control valve (17) or the controllable pump is controlled.

11. Device according to one of claims 7 to 10,

characterized, that in the connecting line (11) from the removal point (9) for the low-water liquid phase to the absorber (1).

Mixing device (19) is arranged, which is connected to the

Withdrawal point (8) for water-rich liquid phase is connected and liquid from the withdrawal point (9) for low-water liquid phase mixes with liquid from the withdrawal point (8) for water-rich liquid phase.