JP2014100623A - Amine recovery method, amine separation apparatus and acid gas separation and recovery apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amine recovery method capable of recovering a reusable amine component with low energy, an acid gas separation and recovery apparatus and an amine separation apparatus.SOLUTION: An amine separation apparatus comprises a first separation membrane and a second separation membrane. The first separation membrane is formed with a first pore size separation material corresponding to the molecular size of a deteriorated amine and separates the deteriorated amine from an amine solution. The second separation membrane is formed with a second pore size separation material and separates a reusable amine selectively from the amine solution passed through the first separation membrane. A second pore size is smaller than a first pore size.

Description

  Embodiments described herein relate generally to an amine recovery method, an amine separation device, and an acid gas separation and recovery device.

  Due to the recent global warming, technologies for reducing greenhouse gas emissions have been addressed globally, and one of them is the use of natural energy and nuclear power to suppress the emission of carbon dioxide with a greenhouse effect. Efforts related to power generation systems such as promotion of power generation, energy saving, and improvement of power generation efficiency are being actively carried out. In addition, as a means for suppressing carbon dioxide emission by improving and improving the current power generation technology, a technology for recovering acidic gas such as carbon dioxide has been developed for combustion exhaust gas using fossil fuel that occupies most of power generation.

  Considering installation in plants such as thermal power plants and steelworks, it is the most desirable method to separate and recover acid gas in exhaust gas discharged after burning fossil fuel. As such a separation and recovery method, a method using an amine-based absorbing solution such as alkanolamine, for example, monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, is widely adopted.

  In the amine-based absorbing liquid, deteriorated amine accumulates in the liquid with use over time. Since the effective amine component contained in the absorbent is relatively reduced due to the generation of the deteriorated amine, it is necessary to periodically replace the absorbent to maintain the performance of the absorbent.

  However, if all of the used absorption liquid is discarded as waste liquid in spite of containing reusable amine components, it is necessary to carry out neutralization treatment with chemicals, detoxification treatment of contained amine, etc. Will be produced. In addition, when a heat source or the like is used to selectively recover only the amine that is the original absorption component from the waste amine aqueous solution, the cost when viewed in the whole plant becomes large.

JP 2011-104559 A

  The problem to be solved by the present invention is to provide an amine recovery method, an amine separation device and an acid gas separation and recovery device capable of recovering a reusable amine component with low energy.

  The amine separation device of the embodiment has a first separation membrane and a second separation membrane. The first separation membrane is formed of a separation material having a first pore size corresponding to the molecular size of the degraded amine, and separates the degraded amine from the amine solution. The second separation membrane is formed of a separation material having a second pore size, and selectively separates a reusable amine from the amine solution that has passed through the first separation membrane. The second hole diameter is smaller than the first hole diameter.

1 is a diagram illustrating a schematic configuration of an amine separation device according to Embodiment 1. FIG. FIG. 4 is a diagram illustrating a schematic configuration of an amine separation device according to a second embodiment. The figure which shows schematic structure of the acidic gas separation-and-recovery apparatus by Embodiment 1. FIG. The figure which shows schematic structure of the acidic gas separation-and-recovery apparatus by Embodiment 2. FIG. The figure which shows schematic structure of the acidic gas separation-and-recovery apparatus by Embodiment 3.

  Hereinafter, some embodiments will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals, and redundant description thereof is omitted.

(A) Amine separator (1) Embodiment 1
FIG. 1 is a diagram illustrating a schematic configuration of an amine separation apparatus according to the present embodiment. The amine separation device SU1 shown in FIG. 1 includes two-stage separation membranes SF1 and SF2 and pumps 3 and 6. The separation membranes SF1 and SF2 have a molecular sieving function and are formed of separation materials having different pore sizes. Each pore diameter is controlled in advance according to the molecular size required for separation / recovery. For example, in this embodiment, the pore diameter is generally in the range of 0.1 nm to 1 nm. The amine separator SU1 selectively separates and recovers the reusable amine component depending on the difference in the pore size of each separator.

  Furthermore, the pore diameter of the separation material of the separation membranes SF1 and SF2 is desirably a pore diameter having a margin of 10% or more with respect to the effective diameter of the amine molecule to be recovered. For example, when recovering monoethanolamine from an aqueous solution of monoethanolamine and triethanolamine, the effective diameter of each component is 0.32 nm for water, about 0.5 nm for monoethanolamine, and about 0.6 nm for triethanolamine. is there. At this time, the first-stage separation membrane SF1 has a pore diameter of about 0.55 nm through which water and ethanolamine can permeate, and the second-stage separation membrane SF2 has a water permeability of 0. A separating material having a pore diameter of about 36 nm can be applied.

  As a separation material for each of the separation membranes SF1 and SF2, a zeolite membrane capable of selectively removing molecules having a specific molecular size can be used. As the zeolite used here, any kind can be used. For example, natural zeolite, synthetic zeolite and the like can be used. As the separation membranes SF1 and SF2, it is also possible to use nonporous polymer membranes excellent in chemical resistance. In the present embodiment, the separation membranes SF1 and SF2 correspond to, for example, the first and second separation membranes, respectively.

The amine solution that is the liquid to be treated containing the deteriorated amine is pressurized by the pump 3 and supplied to the separation membrane SF1 through the amine solution supply line 2. The supplied amine solution is separated into a concentrated liquid containing an amine having a large molecular size and a first treatment liquid that has permeated through the separation membrane SF1 through the separation material of the separation membrane SF1. The first treatment liquid contains a lot of water and CO _{2 in} addition to the reusable amine component. The concentrate containing the amine having a large molecular size is discharged through the polymer amine concentrate discharge line 4 and processed.

The first processing liquid that has passed through the first-stage separation membrane SF1 is boosted by the pump 6 and supplied to the second-stage separation membrane SF2 through the processing liquid discharge line 5. The supplied first treatment liquid contains a concentrated liquid containing an amine component that can be reused by the separation membrane SF2 composed of a separation material having a pore size smaller than that of the separation material of the separation membrane SF1, and a large amount of water and CO _2. It isolate | separates into a 2nd process liquid.

The concentrated liquid obtained in the second-stage separation membrane SF2 is returned to the absorbing liquid flowing in the plant such as a thermal power plant through the reusable amine concentrated liquid discharge line 8, and thereby the absorbing liquid The amine component contained therein is regenerated.
On the other hand, the second processing liquid separated by the second-stage separation membrane SF2 is discharged through the low molecular amine processing liquid discharge line 9 and processed as a waste liquid.

The amine separation device of this embodiment can be used separately from the acid gas separation and recovery device, but can be used by being incorporated in the acid gas separation and recovery device. By introducing the amine separation apparatus of the present embodiment into the acid gas separation and recovery process, it is possible to prevent contamination of piping and heat exchangers provided in plants such as thermal power plants and steelworks, and CO _2. Separation and recovery energy can be suppressed.

(2) Embodiment 2
In the first embodiment described above, the amine separation device SU1 including the two-stage separation membranes SF1 and SF2 has been described. However, when a plurality of amine components are to be recovered, the number of amine components to be recovered is increased by one. If a separation step is added, each component can be recovered.

FIG. 2 is a diagram showing a schematic configuration of an example of an amine separation apparatus in a mode suitable for separation / recovery of a plurality of amine components. The amine separator SU11 shown in FIG. 2 enables recovery of two amine components A and B (component A molecular diameter> component B molecular diameter), and includes three-stage separation membranes SF11 to SF13. In FIG. 2, the booster pump is omitted.
The separation membrane SF11 in the first stage separates a polymer amine having a large molecular size from the supplied amine solution, similarly to the separation membrane SF1 in FIG. The separated polymeric amine is discarded.

  The first treatment liquid that has passed through the first-stage separation membrane SF11 is supplied to the second-stage separation membrane SF12, and the amine component A is separated by the separation membrane SF12 and returned to the absorbing solution in the plant. Further, the second treatment liquid that has passed through the second-stage separation membrane SF12 is supplied to the third-stage separation membrane SF13, and the amine component B is separated by the separation membrane SF13 and returned to the absorption liquid in the plant. . The third treatment liquid that has passed through the third separation membrane SF13 is discarded.

  In the present embodiment, the aspect in which the two amine components A and B are recovered has been described. However, the present invention is not limited to this, and an amine separation device that enables three or more amine components is also possible. In the present embodiment, the separation membranes SF11 and SF12 correspond to, for example, the first and second separation membranes, respectively.

According to the amine separation device of at least one embodiment described above, the first-stage separation membrane formed of the separation material having the first pore size corresponding to the molecular size of the deteriorated amine allows the polymer amine and the other components to be separated. Separation of components (medium to low molecular amine, water, CO _2, etc.), and separation of medium to low molecular amine in the second and subsequent separation membranes to obtain an amine concentrate, without using a heat source The amount of amine discarded can be reduced.

(B) Acid gas separation and recovery device and amine recovery method (1) Embodiment 1
FIG. 3 is a block diagram illustrating a schematic configuration of the acidic gas separation and recovery device according to the first embodiment. In addition to the absorber 10, the regenerator 13, the heat exchanger 12, the coolers 41, 21, 16 and the reboiler 19, the acidic gas separation and recovery device of the present embodiment is provided between the absorber 10 and the heat exchanger 12. Provided with the amine separator SU1.

  The absorber 10 is composed of, for example, a counter-current gas-liquid contact device, and normally, an absorption liquid (hereinafter referred to as “lean liquid”) that receives the gas to be treated 31 from its lower part and absorbs carbon dioxide from its upper part. be introduced. The treated gas 31 supplied to the absorber 10 is an acid gas containing carbon dioxide derived from a coal combustion process, and is usually introduced into the absorber 10 through a denitration, dust removal, and desulfurization process.

  The absorber 10 absorbs the gas 31 to be treated by gas-liquid contact with the lean liquid and absorbs the acid gas, and discharges an amine solution that has absorbed the acid gas (hereinafter referred to as “rich amine solution”) from its lower part.

  The lean liquid is composed of an amine-based absorbing liquid in the present embodiment, and an amine solution such as alkanolamine, such as monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, or the like. used. The operating temperature of the amine solution in the absorber 10 is arbitrary depending on the composition and components, but in this embodiment, the operating temperature is about 20 ° C. to about 100 ° C.

  The deacidified gas from which the acid gas has been removed by the absorber 10 is cooled by the cooler 41 provided on the upper portion of the absorber 10, and then discharged through the processing gas discharge line 40.

  The rich amine solution discharged from the absorber 10 is introduced into the heat exchanger 12, heated and introduced into the regenerator 13.

  The regenerator 13 releases the acidic gas contained in the rich amine solution by heating the introduced rich amine solution using the reboiler 19, thereby regenerating the amine solution. The acidic gas containing carbon dioxide released from the amine solution passes through the processing gas cooler 21 and is then discharged from the discharge line 20 to the outside of the plant. The operating temperature of the amine solution in the regenerator 13 is also arbitrary according to the composition and components of the amine solution, the carbon dioxide content, etc., as in the absorber 10, but in this embodiment, it is about 80 ° C. to about 300 ° C. Operated at ℃.

  The regenerated amine absorbing liquid passes through the regenerated amine absorbing liquid discharge path 14 and is again introduced into the absorber 10 as a lean liquid through the heat exchanger 12.

  In the present embodiment, the amine separator SU1 is attached to the rich amine solution feed line 11 from the absorber 10 to the heat exchanger 12. The amine solution in the absorber 10 is immediately after absorbing the gas to be treated 31, and not only the acidic gas component such as carbon dioxide absorbed in the absorber 10 but also the acidic gas in the absorber 10 is contained in the liquid. Degraded amine produced by contact with components is included.

  In addition to carbon dioxide, the gas to be treated 31 contains nitrogen and oxygen, for example, solids such as dust, other acidic gas components, nitrogen oxides, sulfur oxides, hydrogen chloride, and the like. In general, since the amine-based absorbent is alkaline, it absorbs an acidic gas component in addition to carbon dioxide in the exhaust gas. In addition, calcium, sodium, silicon, and the like, which are components thereof, are slightly eluted as ions from the dust taken in the amine-based absorbent. Furthermore, by circulating the amine-based absorption liquid in the device, the corrosion of the structural material of the acid gas separation and recovery device gradually proceeds, and metal ion components such as iron ions and chromium ions eluted from the surface of the structural material. Accumulate in amine solution. In addition, since amine is an organic substance, the thermal decomposition of the amine component proceeds by repeating heating and cooling cycles of the solution, and organic acids such as formic acid, acetic acid, and oxalic acid are generated. Due to impurities in the amine absorption liquid, these products are difficult to remove from the amine absorption liquid only by applying heat, and these products accumulate in the system of the acid gas separation and recovery device. As a result, the modification of the amine absorbent component is promoted, and the amine absorbent component is decomposed or polymerized. These components generate scales particularly in the heat exchanger 12 and increase the amount of energy for releasing carbon dioxide from the amine solution, and the decomposed amine is released into the atmosphere and contained in the amine absorbing solution. The amine component is greatly lost. Therefore, it is necessary for the absorbing solution to replenish periodically lost amine.

  However, since amines generally have a high viscosity, it is necessary to reduce the viscosity by diluting to some extent with water and supply the amine. Further, among the deteriorated amines, the polymerized amine remains in the absorption liquid, so that it is very difficult to completely return to the initial absorption liquid composition.

Since the acidic gas separation and recovery device according to the present embodiment includes the amine separation device SU1, it is possible to increase the concentration of amine contained in the amine absorbent. That is, since it is obtained by concentrating the amine component, the moisture concentration contained in the absorption liquid can be lowered, and the latent heat of vaporization and sensible heat of water in the regenerator are reduced, so that the reboiler in the regenerator is reduced. Heating can be reduced. Therefore, it is possible to reduce CO ₂ separation and recovery energy.

In addition, since the amine separator SU1 is attached to the rich amine solution feed line 11, it becomes possible to remove deteriorated amine before the temperature is raised in the heat exchanger 12 and the regenerator 13, and particularly in the plant. Generation of scale in the heat exchanger 12 can be suppressed. Thereby, it is possible to suppress an increase in CO ₂ separation and recovery energy.

  In addition, it is also possible to introduce an impurity removing device, for example, an apparatus for removing ionic components, a decolorization process, etc. before or after the acidic gas separation and recovery device of the present embodiment. It is desirable that it is attached to the front stage.

(2) Embodiment 2
FIG. 4 is a block diagram illustrating a schematic configuration of the acidic gas separation and recovery device according to the second embodiment. As is clear from comparison with FIG. 3, the acid gas separation and recovery device of the present embodiment is characterized in that the amine separation device SU <b> 1 is provided between the heat exchanger 12 and the regenerator 13.

Since the amine solution in the regenerator 13 is heated by the reboiler 19 or the like, the decomposition reaction and the polymerization reaction of the amine are promoted, and thus a large amount of deteriorated amine is contained. Therefore, as shown in FIG. 3, by installing an amine separation device SU1 in the lean liquid feed line 14 from the regenerator 13 to the heat exchanger 12, the contamination of the piping is suppressed, and the scale to the heat exchanger 12 is reduced. Generation is suppressed. Thereby, it is possible to suppress an increase in CO ₂ separation and recovery energy. When the amine separation device SU1 is installed in the lean liquid feed line 14 from the regenerator 13 to the heat exchanger 12 as in the present embodiment, the separation membranes SF1 and SF2 are not non-porous polymer membranes and are not resistant. It is desirable to use a zeolite membrane having excellent temperature characteristics.

(3) Embodiment 3
FIG. 5 is a block diagram illustrating a schematic configuration of the acidic gas separation and recovery device according to the third embodiment. As apparent from the comparison with FIG. 3, the acid gas separation and recovery device of the present embodiment is characterized in that the amine separation device SU1 is provided between the heat exchanger 12 and the absorber 10, and the regenerator 13 is connected to the lean liquid. The amine aqueous solution (lean liquid) fed by the liquid feed line 14 is installed before being introduced into the absorber 10 after passing through the heat exchanger 12.

  Since the lean liquid is cooled by the heat exchanger 12 and the cooler 16, by installing the amine separation unit SU1 at this position, contamination of piping and the like can be prevented, and changes in amine solution characteristics can be prevented. It becomes possible. In addition, since the amine solution in the lean liquid feed line 14 is in the lowest temperature state in the acidic gas separation and recovery apparatus shown in FIG. 5, an ion removal process or the like can be further added using, for example, an ion exchange resin. For example, the ions contained in the amine solution such as the metal ions described above can be efficiently removed.

  In the acidic gas separation and recovery device according to the above-described embodiment, the case where each of the single amine separation devices SU1 for selectively separating the reusable amine from the rich amine solution or the lean amine solution is provided has been described. Of course, a plurality of amines may be arranged as long as they selectively separate reusable amines from at least one of a rich amine solution and a lean amine solution. Also, the amine separation apparatus has been described with respect to the case where the amine separation apparatus SU1 shown in FIG. 1 is provided. However, the present invention is not limited to this, and the amine separation apparatus SU11 shown in FIG. Of course, it is also possible to incorporate an amine separation device that makes it possible to the acidic gas separation and recovery device.

According to the acidic gas separation and recovery device of at least one embodiment described above, the reusable amine contained in the amine solution is provided with the amine separation device that selectively separates the reusable amine from the amine solution. Can be recovered with low energy, and this makes it possible to reduce amines that have been disposed of despite being reusable. Moreover, by removing the polymer amine contained in the amine solution, scale generation can be suppressed, and increase in CO ₂ separation and recovery energy can be suppressed. Further, by concentrating the reusable amine component from the waste amine and returning it to the plant, it is possible to maintain the original absorption liquid composition and concentration.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  DESCRIPTION OF SYMBOLS 10 ... Absorber, 11 ... Rich amine solution feed line (1st path | route), 13 ... Regenerator, 14 ... Lean amine solution feed line (2nd path | route), SU1, SU11 ... Amine separator, SF1, SF2 , SF11 to SF13 ... separation membrane.

Claims (5)

An acid gas containing an acid component is brought into contact with an amine solution to produce a rich amine solution that is rich in an acid component that has absorbed the acid component, and the rich amine solution is heated to release the acid gas. It is used in an acidic gas separation and recovery device that produces a certain lean amine solution and reuses it for absorption of acidic gas.
An amine recovery method for concentrating an amine by selectively separating a reusable amine from at least one of the rich amine solution and the lean amine solution. A first separation membrane formed of a separation material having a first pore size corresponding to the molecular size of the degraded amine and separating the degraded amine from the amine solution;
A second separation membrane that selectively forms a reusable amine from an amine solution that is formed of a separation material having a second pore size smaller than the first pore size and has passed through the first separation membrane;
An amine separator comprising: An acid gas containing an acid component and an amine solution are introduced, and an absorber that generates and discharges a rich amine solution that is rich in acid gas by absorbing the acid component by contacting the acid gas with the amine solution;
A regenerator that releases the acidic gas by heating the rich amine solution discharged from the absorber, generates a lean amine solution that is an acidic gas slime, and returns the lean amine solution to the absorber;
An amine separator that selectively separates a reusable amine from at least one of the rich amine solution and the lean amine solution;
An acid gas separation and recovery device comprising:   The acidic gas separation and recovery device according to claim 3, wherein the amine separation device includes a plurality of separation membranes formed of separation materials having different pore sizes.   The amine separation device includes at least a first path through which the rich amine solution is transferred from the absorber to the regenerator, and a second path through which the lean amine solution is transferred from the regenerator to the absorber. The acidic gas separation and recovery device according to claim 3 or 4, wherein the acidic gas separation and recovery device is provided in any one of the above.

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