Carbon dioxide separation and recovery method, and carbon dioxide recycling method

Abstract

The present invention realizes a simple method for preventing deterioration and loss of function of an absorption device caused by solid deposition, which is a phenomenon peculiar to phase separation type carbon dioxide absorbents, without a significant increase in the complexity of a CO2 separation and recovery device in comparison with a conventional CO2 separation and recovery system.　This carbon dioxide separation and recovery method includes: a first step for using an absorption device 100 to bring a carbon dioxide absorbent solution 150 containing a phase separation type carbon dioxide absorbent into contact with a CO2-containing gas that contains carbon dioxide to obtain an absorption solution 160 in a reaction stage A in which solidification is limited by causing the carbon dioxide absorbent solution 150 to absorb the carbon dioxide; a second step for moving the absorption solution 160 to a solidification device 200; and a third step for transferring the absorption solution to a reaction stage B, in the solidification device 200, in which the carbon dioxide absorbent and the carbon dioxide react with each other to form a reaction solidified product, to obtain a liquid containing the reaction solidified product.

Description

Method for separating and capturing carbon dioxide and method for recycling carbon dioxide

[0001] The present invention relates to a method for separating and recovering carbon dioxide and a method for regenerating carbon dioxide.

[0002] Curbing the rise in global average temperature caused by anthropogenic greenhouse gas emissions is one of the important challenges in modern society. ２ CO2 emissions from sources or from the atmosphere ２ There is a strong desire for technological development and early social implementation that will enable low energy costs for separation, recovery, transportation, and storage.

[0003] Conventionally, carbon dioxide absorbents used to remove carbon dioxide from combustion exhaust gases and the atmosphere, such as monoethanolamine solutions, remained in the liquid phase even after absorbing carbon dioxide. Therefore, separating the absorbent from the liquid solvent after absorption was difficult. Consequently, when regenerating the absorbent by heating, the solvent had to be heated simultaneously, resulting in the consumption of excess thermal energy.

[0004] To solve this problem, carbon dioxide absorbents that combine with carbon dioxide to form a solid-phase precipitate, i.e., phase-separation type carbon dioxide absorbents, are known (see Patent Documents 1 and 2). Such phase-separation type carbon dioxide absorbents can separate the solid precipitate from the liquid-phase solvent containing the carbon dioxide absorbent, thus reducing the heating energy required for the regeneration of the absorbent. Examples of phase-separation type carbon dioxide absorbents include monoxylenediamine (MXDA), paraxylenediamine (PXDA), and isophoronediamine (IPDA).

[0005] However, when attempting to commercialize a phase-separation type carbon dioxide separation and recovery process, there are concerns that problems not anticipated in conventional processes may occur, such as pipe clogging due to solid deposition everywhere inside the absorber, for example, on the inner walls, pipes, and surfaces of internal structures, and that the absorber's function may deteriorate or be lost. Therefore, in order to commercialize a phase-separation type carbon dioxide removal system, it is necessary to develop effective solid handling methods in the absorption tower.

[0006] Therefore, a gas treatment apparatus has been proposed comprising: a treatment tower that contains a treatment liquid and has a nozzle at its lower part for blowing the gas to be treated into the treatment liquid, and has an outlet at its upper part for discharging the treated gas; a regeneration tower that has a heating device and has a recovery outlet at its upper part for recovering the recovered gas; and a connecting pipe that connects the lower part of the treatment tower and the lower part of the regeneration tower and is inclined to become lower from the treatment tower side to the regeneration tower side, wherein the treatment tower has a partition plate that divides the inside of the treatment tower vertically into a nozzle area including the nozzle outlet and other areas, except for the upper end of the treatment tower (see Patent Document 3).

[0007] Patent No. 7026938 Patent No. 7441557 Patent No. 7616304

[0008] When implementing the phase-separation type carbon dioxide separation and recovery method described in Patent Documents 1 and 2, there are concerns that problems such as pipe clogging, deterioration or loss of function of the absorber may occur due to the precipitation of solids, which are reaction products with carbon dioxide, throughout the absorber, such as on the inner walls, pipes, and surfaces of internal structures. Furthermore, the slurry containing the precipitated fine particles has high viscosity and requires a large amount of energy to pump, thus reducing CO2 levels. ２ There is a problem that the entire separation and recovery system becomes large and complex. For example, in Patent Document 3, in order to handle the high-viscosity slurry generated in the absorption device, a conventional CO2 ２ The absorption device has a mechanism that is not present in the separation and recovery system.

[0009] This invention is CO ２ The separation and recovery device is a conventional CO ２ The challenge is to develop a simple method that prevents the deterioration and loss of absorption device function caused by solid precipitation, a phenomenon unique to phase-separated carbon dioxide absorbents, without significantly increasing the complexity compared to separation and recovery systems.

[0010] As a result of repeated research to solve the above problems, the inventors have found that the reaction in which a phase-separation type carbon dioxide absorbent absorbs carbon dioxide and precipitates a solid is composed of two reaction stages, that is, reaction stage A in which the carbon dioxide absorbent absorbs carbon dioxide, and reaction stage B in which the liquid-phase absorbent that has absorbed carbon dioxide undergoes crystallization to precipitate a solid, and thus the present invention has been completed.

[0011] According to a first aspect of the present invention, an absorption device is used to bring a carbon dioxide absorbent solution containing a phase-separation type carbon dioxide absorbent into contact with a CO ２ 2-containing gas, obtaining an absorption solution in the reaction stage A where the carbon dioxide is absorbed into the carbon dioxide absorbent solution and solidification is restricted; a second step of transferring the absorption solution to a solidification device; and a third step of advancing the reaction of the absorption solution in the solidification device to shift the reaction to reaction stage B where a reaction solidified product is formed, thereby obtaining a reaction solidified product-containing liquid.

[0012] In a second aspect of the present invention, in the first step, the CO containing carbon dioxide and the carbon dioxide absorbent solution ２ 2-containing gas, the contact method, contact ratio, and contact temperature are controlled to limit the generation of the reaction solidified product to a predetermined range or less.

[0013] In a third aspect of the present invention, the absorption device is configured such that the CO in the carbon dioxide absorbent solution ２ 2-containing gas is bubbled through the device; a spray type device that blows the CO ２ 2-containing gas into the upper space accommodating the carbon dioxide absorbent solution; a tray column type device that brings the CO ２ 2-containing gas into contact with the carbon dioxide absorbent solution on trays stacked in multiple stages; and a packed column type device that brings the carbon dioxide absorbent solution into contact with the CO ２ 2-containing gas in a packed column packed with packing material, wherein the absorption device is any one selected from the group consisting of the above.

[0014] In a fourth aspect of the present invention, there is provided the method for separating and recovering carbon dioxide according to the above aspect, wherein the carbon dioxide absorbent solution comprises at least one selected from the group consisting of m-xylylenediamine (MXDA), p-xylylenediamine (PXDA), and isophoronediamine (IPDA), and a non-polar solvent.

[0015] In a fifth aspect of the present invention, there is provided a method for regenerating carbon dioxide, wherein carbon dioxide is regenerated from the reaction solidified product-containing liquid obtained by the method for separating and recovering carbon dioxide according to any one of the first to fourth aspects.

[0016] In a sixth aspect of the present invention, there is provided the method for regenerating carbon dioxide according to the above aspect, comprising: step a of, after carrying out the method for separating and recovering carbon dioxide with the solvent of the carbon dioxide absorbent solution in the first step being a polar solvent, treating the obtained reaction solidified product-containing liquid with a non-polar solvent, removing the polar solvent to obtain a non-polar suspension containing the reaction solidified product and the non-polar solvent or a non-polar reactant which is a slurry obtained therefrom; step b of heating the non-polar reactant obtained in step a under pressure, normal pressure or reduced pressure, separating and recovering carbon dioxide to regenerate the carbon dioxide absorbent from the non-polar reactant, thereby obtaining a non-polar solution of the carbon dioxide absorbent; and step c of treating the non-polar solution of the carbon dioxide absorbent obtained in step b with the polar solvent to replace the solvent, thereby obtaining a polar solution of the carbon dioxide absorbent.

[0017] According to the present invention, the separation and recovery of carbon dioxide using a phase-separation type carbon dioxide absorbent can be performed with a simple absorption device and a simple solidification device, and the separation and recovery of carbon dioxide can be realized while omitting complicated countermeasures against solid precipitation such as a precipitated solid removal function and a solid precipitation suppression function.

[0018] A diagram showing a process where an absorption liquid having absorbed carbon dioxide is transferred from a spray-type absorption device and crystallization is performed at another location. A diagram showing a process where an absorption liquid having absorbed carbon dioxide is transferred from a bubbling-type absorption device and crystallization is performed at another location. A graph showing the time-dependent change in viscosity of the carbon dioxide absorbent solution in Test Example 1. A graph showing the time-dependent change in temperature of the carbon dioxide absorbent solution in Test Example 1. A graph showing the time-dependent change in viscosity of the carbon dioxide absorbent solution in Test Example 2. A graph showing the time-dependent change in temperature of the carbon dioxide absorbent solution in Test Example 2. A graph showing the time-dependent change in viscosity and temperature of the carbon dioxide absorbent solution in Test Example 3.

[0019] Hereinafter, the present invention will be described in further detail. The method for separating and recovering carbon dioxide of the present invention uses an absorption device to mix a carbon dioxide absorbent solution containing a phase-separation type carbon dioxide absorbent with carbon dioxide-containing CO ２ 2-containing gas, comprising: a first step of obtaining an absorption solution in reaction stage A where solidification is restricted by having carbon dioxide absorbed into the carbon dioxide absorbent solution; a second step of transferring the absorption solution to a solidification device; and a third step of advancing the reaction in the absorption solution in the solidification device to shift to reaction stage B where a reaction solidified product is formed, thereby obtaining a reaction solidified product-containing liquid.

[0020] That is, according to the present invention, even when a carbon dioxide absorbent solution containing a phase-separation type carbon dioxide absorbent is brought into contact with a carbon dioxide-containing CO ２ 2-containing gas, if the contact is performed under predetermined conditions, even after carbon dioxide is absorbed into the carbon dioxide absorbent solution, only the reaction of carbon dioxide being absorbed by the carbon dioxide absorbent occurs, and a state where solid precipitation has not yet occurred can still be maintained at this point. This state can be set as reaction stage A where solidification is restricted. The first point of the present invention is that even when the absorption solution in reaction stage A is conveyed to another device by a pump or the like, solidification does not occur, no precipitation occurs in the pump or the conveying pipe, and the absorption solution can be solidified in a solidification device separate from the absorption device.

[0021] On the other hand, reaction stage B is the stage where a reaction in which carbon dioxide absorbed inside the carbon dioxide absorbent crystallizes through a chemical reaction occurs. In reaction stage B, the absorption solution from reaction stage A has CO ２Further contact with the contained gas is unnecessary. In reaction step B, CO2 is added to the absorption solution obtained in step 1. ２ The second key point is that the carbon dioxide absorbent in the absorption solution can be reacted with carbon dioxide to form a solidified product without further contact with the contained gas.

[0022] Here, the reaction mechanisms of reaction step A and reaction step B are not necessarily clear, but in reaction step A, firstly, it is thought that the carbon dioxide absorbent in the absorption solution reacts with carbon dioxide (reaction a), producing compounds derived from the carbon dioxide absorbent and carbon dioxide, but without solidification. Secondly, it is thought that the carbon dioxide absorbent and carbon dioxide react, and some or most of it becomes a solidified reaction product, but it is dissolved in the solution and, in some cases, supersaturated with respect to the solution. Thirdly, it is thought that the solidified reaction product produced by the reaction of the carbon dioxide absorbent and carbon dioxide (reaction a) is ionized, or that reaction intermediates associate and aggregate and dissolve in the solution. Furthermore, it is possible that several of the above states coexist, and it is also possible that carbon dioxide that has not reacted with the solidified reaction product is dissolved in the absorption solution.

[0023] On the other hand, in reaction step B, a reaction solid is formed in the absorption solution from reaction step A. However, the reaction mechanism by which a reaction solid is formed and a liquid containing the reaction solid is obtained in reaction step B is not clear. Firstly, the reaction between the carbon dioxide absorbent and the carbon dioxide compound formed in reaction step A proceeds further to form a reaction solid (reaction b). Secondly, the carbon dioxide absorbent and carbon dioxide compound formed and dissolved or overdissolved in reaction step A solidifies further (reaction b). The reaction solid is ionized and dissolved in the absorption solution, or the reaction intermediates associate and aggregate and solidify (reaction b). Or, the carbon dioxide dissolved in the absorption solution reacts with the unreacted carbon dioxide absorbent to form a reaction solid, or a combination of these states. Some of these may not be considered reactions, but in this invention, all of these are referred to as reactions, and the state until this reaction is completed is called reaction state B.

[0024] This invention utilizes the fact that, although the reaction mechanism is not always clear in the reaction between a carbon dioxide absorbent, particularly isophorone diamine (IPDA), and carbon dioxide, the reaction mechanism and the time required for the reaction in which carbon dioxide is absorbed into the carbon dioxide absorbent and the reaction in which intermediate products resulting from the carbon dioxide absorbent and carbon dioxide further react to form a reaction solidified product are different, and the invention takes advantage of the time difference between these reactions. Here, the reaction in which carbon dioxide is absorbed into the carbon dioxide absorbent is reaction step A, and the reaction in which intermediate products resulting from the carbon dioxide absorbent and carbon dioxide further react to form a reaction solidified product is reaction step B.

[0025] The time difference between these two reactions depends, for example, on the concentration of the carbon dioxide absorbent solution and the CO2 gas being treated. ２ The process can be controlled by various factors, such as the contact time and temperature between the contained gas and the carbon dioxide absorbent, the addition of liquids, solids, or gases to promote or inhibit crystallization, the selection of carbon dioxide absorbents or mixtures of different carbon dioxide absorbents, and the selection of solvents.

[0026] In particular, by adjusting the time required to transition to reaction stage B to be sufficiently longer than the time required for reaction stage A, after obtaining the absorption solution in reaction stage A where carbon dioxide is absorbed, the absorption solution can be transferred to the outside of the absorption apparatus using the time difference and proceed to reaction stage B in another location. After transferring the absorption solution to another location, the process may be made more efficient by adding operations to accelerate reaction stage B, such as temperature control, the addition of liquid, solid, or gaseous additives that accelerate reaction stage B, or shock.

[0027] A crucial factor in ensuring that components within the absorption device do not become obstacles during transfer to other devices is whether or not solids are formed by the reaction. This is because solid precipitation can cause adhesion to internal structures and pipe blockages. In comparison, the importance of increases in viscosity and temperature of the absorption solution is smaller. However, measuring viscosity is useful as an indicator of whether or not solids have been formed, because continuous measurement of solid precipitation is difficult.

[0028] The present invention utilizes the above-mentioned matters to maintain reaction stage A, in which carbon dioxide and carbon dioxide absorbent react to form an absorbent solution that is substantially free of solidified material, for as long as possible, and to delay the timing of reaction stage B, in which the reaction of the reaction intermediate between carbon dioxide and carbon dioxide absorbent proceeds, solidified material substantially begins to form throughout the absorbent solution, and the reaction is completed until it becomes a completely solidified material. The carbon dioxide absorption reaction is carried out in the reaction absorption device, and the absorbent solution is transferred from the absorption device while it is still in reaction state A, in which carbon dioxide has been absorbed but solid precipitation has not yet begun, or only minute solid precipitation has occurred that does not significantly affect the viscosity, and the reaction is carried out in a place other than the absorption device, for example, in a storage device or regeneration device, to reach reaction state B, thereby allowing the solidification reaction, which could cause malfunction of the absorption device, to proceed.

[0029] The present invention has the effect of solving process problems such as the formation of high-viscosity slurries within the absorption device, as well as pipe clogging and loss of absorption device function due to solid deposition.

[0030] In other words, the present invention makes it possible to adapt existing carbon dioxide removal processes that use monoethanolamine, N-methyldiethanolamine, potassium hydroxide, sodium hydroxide, etc., as carbon dioxide absorbents to phase-separation type carbon dioxide absorbents without adding or modifying complex mechanisms. The structure of existing absorbents is, for example, bubbling type, spray type, tray type, packed column type, etc., but is of course not limited to these.

[0031] The carbon dioxide separation and recovery method of the present invention will be described in detail below with reference to the drawings.

[0032] Figure 1 shows the CO2 separation and recovery method of the present invention. ２ This is a schematic diagram showing an example of a separation and recovery device. The gas treatment device shown in Figure 1 consists of an absorption device 100, a solidification device 200 which is a storage device or a regeneration device, and a connecting pipe 300 that connects the two.

[0033] The absorption device 100 is used to process air or exhaust gas, which is CO2. ２ Inlet 110 for contained gas, CO ２ The absorption device 100 has an outlet 120 for the gas after carbon dioxide has been absorbed and removed from the contained gas. The absorption device 100 is connected to the solidification device 200 by a connecting pipe 300, and a liquid transfer pump 310 is interposed in the connecting pipe 300.

[0034] The absorption device 100 has a spray nozzle 130 inside, and the carbon dioxide absorbent solution 150 sprayed by the liquid transfer pump 140 and this spray nozzle 130 adsorbs carbon dioxide inside the absorption device 100 and accumulates in a liquid phase inside the absorption device 100. This absorbent solution 160 containing the carbon dioxide absorbent that has absorbed the carbon dioxide is sent by the connecting pipe 300 and liquid transfer pump 310 to the solidification device 200, which is a storage device or regeneration device, before the solidification reaction proceeds.

[0035] Inside the solidification device 200, which is a storage or regeneration device, the solidification reaction of the absorption solution 210 containing the carbon dioxide absorbent, which is the liquid phase supplied from the absorption device 100, proceeds, and a solid phase 220 gradually appears.

[0036] Figure 2 shows the CO of the present invention. ２ This is a schematic diagram showing another example of a separation and recovery device. Here, a bubbling method is employed as the contact method between the gas to be treated and the carbon dioxide absorbent. That is, the absorbent liquid introduced via the liquid transfer pump 140A is stored in the absorption device 100A, and the gas to be treated is CO ２ It is equipped with piping 110A for bubbling the contained gas into the absorption solution, and the absorption solution becomes absorption solution 160A containing a carbon dioxide absorbent that has absorbed carbon dioxide, CO ２ The gas remaining after carbon dioxide has been absorbed from the contained gas is discharged from outlet 120A.

[0037] The absorption device 100A is connected to a solidification device 200A, which is a storage or regeneration device, via a connecting pipe 300A and a liquid transfer pump 310A. The absorption solution 160A containing the carbon dioxide absorbent that has absorbed carbon dioxide is transferred to the solidification device 200A via the connecting pipe 300A and the liquid transfer pump 310A before the solidification reaction proceeds.

[0038] Inside the solidification device 200A, which is a storage or regeneration device, the solidification reaction of the absorption solution 210A containing the carbon dioxide absorbent, which is the liquid phase supplied from the absorption device 100A, proceeds, and the solid phase 220A gradually appears.

[0039] The present invention is carried out using the apparatus shown in Figure 1 or Figure 2 as described above. In the first step, the carbon dioxide absorbent solution is brought into contact with carbon dioxide in the absorption apparatus, and an absorbent solution is obtained in reaction step A, in which the carbon dioxide absorbent solution absorbs the carbon dioxide and solidification is limited.

[0040] In other words, the method comprises a first step of absorbing carbon dioxide into a solution containing a carbon dioxide absorbent, which is a compound that absorbs carbon dioxide and precipitates a solid, and a solvent, thereby obtaining an absorption solution in which carbon dioxide has been absorbed, or in which a liquid state containing a very small amount of solid precipitate that does not significantly affect the viscosity of the solution (this state is called reaction state A); a second step of removing the absorption solution obtained in the first step from the absorption device in a state in which almost no solid precipitate has occurred, or even if minute solid precipitate has occurred, it is so small that it does not significantly change the viscosity, and transferring it to a solidification device which is a storage device or regeneration device; and a third step of performing solid precipitation from the absorption solution obtained in the second step in the solidification device which is a storage device or regeneration device.

[0041] In the first step, the carbon dioxide absorbent solution and the CO2 containing carbon dioxide are used. ２ The method of contact with the contained gas, the contact ratio, and the contact temperature are controlled to limit the formation of the reaction solid to a predetermined range, that is, to a state where, for example, even if minute solid precipitation occurs, it is so slight that it does not cause a significant change in viscosity.

[0042] To maintain this state, the carbon dioxide absorbent solution and the CO ２ The method of contact with the contained gas, such as bubbling or spraying, the contact ratio, contact temperature, and contact pressure, are appropriately controlled to ensure that the absorbent solution is transferred to the solidification device without adversely affecting the absorption device, and that solid deposition occurs within the solidification device.

[0043] Furthermore, the suspension or slurry containing the solidified reaction product within the solidification device can be treated using conventional methods.

[0044] The carbon dioxide absorbent that can be used in the present invention is not particularly limited as long as it is a phase-separation type carbon dioxide adsorbent, but examples include isophorone diamine (IPDA), or monoxylenediamine (MXDA), paraxylenediamine (PXDA), etc. Alternatively, a mixture of amine compounds containing these may also be used.

[0045] The carbon dioxide absorbent is dissolved in a solvent to form an absorption solution. The solvent is not limited as long as it is compatible with the amine compound, but at least one polar solvent selected from, for example, water, methanol, ethanol, acetone, acetic acid, ammonia, dimethyl sulfoxide (DMSO), sulfuric acid, etc. may be used, although a nonpolar solvent may be mixed in if necessary.

[0046] In any case, the type of solvent and the concentration of the carbon dioxide absorbent are selected, as described above, so that reaction state A is maintained for as long as possible. The concentration of the carbon dioxide absorbent is selected, for example, from 0.05 to 10 M, preferably from 0.08 to 3 M. Note that the concentration unit "M" represents "mol / L".

[0047] Furthermore, as mentioned above, the temperature of the absorption solution is selected so that reaction state A is maintained for as long as possible, for example, from a range of 0 to 90°C, preferably 5 to 60°C. In addition, the pressure inside the absorption apparatus is also one of the conditions selected so that reaction state A is maintained for as long as possible.

[0048] As described above, the carbon dioxide separation and recovery method of the present invention can be carried out using conventionally used simple absorption and solidification devices, and has the effect of achieving carbon dioxide separation and recovery without the need for complicated solid precipitation countermeasures such as solid precipitation removal and solid precipitation suppression functions.

[0049] Furthermore, the method for regenerating carbon dioxide from the reaction solidified product-containing liquid obtained by the carbon dioxide separation and recovery method of the present invention is not particularly limited, but one example is described below.

[0050] The carbon dioxide regeneration method of the present invention involves the following steps: a) performing the carbon dioxide separation and recovery method in the first step using a polar solvent for the carbon dioxide absorbent solution; a) treating the resulting reaction solidified product-containing liquid with a nonpolar solvent to remove the polar solvent and obtain a nonpolar reaction product which is a nonpolar suspension or slurry containing the reaction solidified product and the nonpolar solvent; b) heating the nonpolar reaction product obtained in step a under pressure, atmospheric pressure or reduced pressure to separate and recover carbon dioxide and regenerate the carbon dioxide absorbent from the nonpolar reaction product to obtain a carbon dioxide reagent nonpolar solution; and c) treating the carbon dioxide nonpolar solution obtained in step b with a polar solvent to replace the solvent and obtain a carbon dioxide reagent polar solution.

[0051] The reaction solidified product-containing liquid obtained by the separation and recovery method can be obtained as a suspension or slurry in a polar solvent. However, if this is first treated with a nonpolar solvent, the reaction solidified product will migrate into the nonpolar solvent, and the polar solvent can be separated and removed. This allows for the production of a nonpolar reaction product, which is a nonpolar suspension or slurry containing the reaction solidified product and the nonpolar solvent.

[0052] Furthermore, when the nonpolar reactant obtained in this manner is heated under pressure, atmospheric pressure, or reduced pressure, carbon dioxide can be separated and recovered, regenerating the carbon dioxide absorbent from the nonpolar reactant and yielding a nonpolar solution of the carbon dioxide reactant.

[0053] Here, at least one nonpolar solvent can be used, such as hexane, octane, nonane, decane, benzene, toluene, xylene, diethyl ether, or cyclohexane.

[0054] Then, when the nonpolar carbon dioxide solution obtained in this way is treated with a polar solvent, the solvent can be replaced, and a polar solution of the carbon dioxide reactant can be obtained, which can be reused as the reactant solution used in the separation and recovery method of the present invention. By using such a carbon dioxide regeneration method, CO ２ CO2 is absorbed from the reactants. ２ By lowering the regeneration temperature during regeneration, the energy input can be reduced. Furthermore, even if regeneration is performed without separating the reactants, the energy input is sufficiently reduced.

[0055] The present invention will be described in more detail below with reference to specific test examples and embodiments. However, the present invention is not limited in any way to the embodiments shown below. In the test examples, the degree of crystallization is evaluated by real-time measurement of the viscosity of the solution. For real-time measurement of viscosity and temperature, an A&D Company, Limited tuning fork vibration viscometer SV-10A was used. ２ For measuring the concentration, Vaisala Corporation's CO2 ２ Probe GMP251 (CO ２ Concentration 0-20% and GMP252 (CO ２ (Concentrations of 0 to 10,000 ppm were used.)

[0056] [Test Example 1]: Control of crystallization time by IPDA concentration. IPDA is used as a phase-separated carbon dioxide absorbent, and water is used as the solvent. 40 g of an aqueous IPDA solution containing 10 wt%, 50 wt%, or 90 wt% IPDA is prepared in a beaker and used as the absorbent solution. In this example, by changing the concentration of the IPDA solution, CO ２ This demonstrates that the time difference between absorption and crystallization can be controlled.

[0057] These three types of IPDA concentrations of CO ２A mixed gas consisting of 90% nitrogen and 10% carbon dioxide was blown into each of the absorbents at a rate of 500 mL / min for 5 minutes, and CO2 was released by bubbling. ２ Absorb it into the solution.

[0058] After blowing for 5 minutes, the blowing of the mixed gas is stopped, thereby reducing IPDA and CO2 levels. ２ The reaction a is completed, and the solution is allowed to stand. In this state, reaction state A is maintained. Next, without contact with the mixed gas containing carbon dioxide, reaction b, which involves crystallization (solidification) within the solution, proceeds, and the solution transitions to reaction state B.

[0059] The degree of crystallization can be evaluated by measuring the viscosity of the solution in real time. Figures 3 and 4 show the results of real-time measurements of the viscosity and temperature of the solution, respectively. Measurement of the viscosity and temperature of the solution began at elapsed time t=0 (unit: minutes). For 1 minute from t=0 to t=1, the solution was left undisturbed. For 5 minutes from t=1 to t=6, the solution was stirred with a stirring bar while a mixed gas consisting of 90% nitrogen and 10% carbon dioxide was blown in at a rate of 500 mL / min for 5 minutes. After that, the blowing of the mixed gas and stirring were stopped, and the solution was left to stand for about 2 to 4 hours.

[0060] From Figure 3, it can be seen that in all cases of IPDA concentration, CO ２ It was found that there is a time lag between the point at which blowing stops (t=6) and the start of the rapid increase in the viscosity of the solution, i.e., the progression of crystallization. The rapid increase in viscosity occurred fastest with a 50 wt% IPDA concentration, and a point of inflection was observed on the graph at around t=50. That is, the time lag Δt (in minutes) from the stop of blowing to the start of the rapid increase in viscosity was Δt = 50 - 6 = 44. For a 10 wt% IPDA solution, Δt = 60 - 6 = 54, and the largest time lag was observed with a 90 wt% IPDA solution, with Δt = 120 - 6 = 114. Therefore, CO ２ There is a time lag between absorption and crystallization, and this time lag can be controlled by the IPDA concentration. In particular, by avoiding the IPDA concentration range of 40% to 60% and adjusting it to a higher or lower concentration, it is possible to delay the crystallization time.

[0061] [Test Example 2]: Control of crystallization time based on the flow time of the gas to be treated. IPDA is used as a phase-separated carbon dioxide absorbent, and water is used as the solvent. 40 g of an IPDA aqueous solution containing 90 wt% IPDA is prepared in a beaker and used as the absorbent solution. In this test example, CO ２ By changing the injection time of the mixed gas containing CO, ２ This demonstrates that the time difference between absorption and crystallization can be controlled.

[0062] To this IPDA solution, a mixed gas consisting of 90% nitrogen and 10% carbon dioxide is blown in at a rate of 500 mL / min for 5 or 10 minutes, and CO2 is released by bubbling. ２ The solution was absorbed. After blowing for 5 or 10 minutes, reaction A was terminated by stopping the blowing of the mixed gas, and the solution was allowed to stand. Due to reaction B, crystallization proceeded within the solution without contact with the gas containing carbon dioxide.

[0063] Figures 5 and 6 show the results of real-time measurements of the viscosity and temperature of the solution, respectively. Measurement of the viscosity and temperature of the solution began at elapsed time t=0 (unit: minutes), and for 1 minute from t=0 to t=1, the solution was left undisturbed. In the case of a blowing time of 5 minutes, a mixed gas consisting of 90% nitrogen and 10% carbon dioxide was blown into the solution at a rate of 500 mL / min while stirring with a stirring bar for 5 minutes from t=1 to t=6. In the case of a blowing time of 10 minutes, a mixed gas consisting of 90% nitrogen and 10% carbon dioxide was blown into the solution at a rate of 500 mL / min while stirring with a stirring bar. After that, the blowing of the mixed gas and stirring were stopped, and the solution was left to stand for about 2 to 4 hours.

[0064] Figure 5 shows that when the mixed gas injection time is 5 minutes, there is a time difference of Δt = 120 - 6 = 114 from the cessation of injection until the rapid progression of crystallization begins, whereas when the injection time is 10 minutes, the viscosity increase due to rapid crystallization occurs in less than 10 minutes after the cessation of injection. Therefore, by changing the injection time of the mixed gas, CO ２ It is possible to control the time difference between absorption and crystallization.

[0065] [Test Example 3]: Control of crystallization time by selection of absorbent. MXDA is used as a phase-separated carbon dioxide absorbent, and water is used as the solvent. 40 g of an MXDA aqueous solution containing 10 wt% MXDA is prepared in a beaker and used as the absorbent solution. In this test example, CO ２ This demonstrates that the time difference between absorption and crystallization can be controlled, even when MXDA is used as the absorbent.

[0066] To this MXDA solution, a mixed gas consisting of 90% nitrogen and 10% carbon dioxide is blown in at a rate of 500 mL / min for 10 or 15 minutes, and CO2 is released by bubbling. ２ The gas was absorbed into the solution. After blowing for 10 or 15 minutes, reaction a was terminated by stopping the gas blowing, and the solution was allowed to stand. Due to reaction b, crystallization proceeded within the solution without contact with the gas containing carbon dioxide.

[0067] Figure 7 shows the results of real-time measurements of the viscosity and temperature of the solution when the blowing time was 15 minutes. Measurement of the viscosity and temperature of the solution began at elapsed time t=0 (unit: minutes), and for 1 minute from t=0 to t=1, the solution was left undisturbed. In the case of a 15-minute blowing time, a mixed gas consisting of 90% nitrogen and 10% carbon dioxide was blown into the solution at a rate of 500 mL / min while stirring the solution with a stirring bar for 15 minutes from t=1 to t=16. After that, the blowing of the mixed gas and stirring were stopped, and the solution was left to stand for more than 8 hours. After the blowing of the mixed gas was stopped, the solution remained colorless and transparent for at least 2 hours, but after 3 hours, turbidity of the entire solution and the progression of solid precipitation were observed. From 9 to 16 hours after the blowing was stopped, crystallization progressed further, and the sensor part of the viscometer impregnated in the solution, i.e., the two tuning forks, became one due to the growth of plate-like transparent crystals, making it impossible to continue measuring viscosity using the tuning fork vibration viscometer.

[0068] On the other hand, when the mixed gas was blown in for 10 minutes, the solution began to become cloudy within 10 minutes of stopping the blowing. Therefore, MXDA was converted to CO ２ Even when used as an absorbent, by changing the injection time of the mixed gas, CO ２It was found that it is possible to control the time difference between absorption and crystallization. Furthermore, this result suggests that CO is a similar phase-separated type. ２ Even with absorbents, IPDA and MXDA use CO ２ It was found that there was a difference in the time difference between the absorption time and the crystallization time. In other words, two or more different phase-separated CO2 molecules were found. ２ By mixing absorbents, such as IPDA and MXDA, CO ２ It is also possible to control the time difference between the absorption time and the crystallization time.

[0069] [Test Example 4] CO2 of the gas to be treated ２ Control of crystallization time by concentration: IPDA is used as a phase-separated carbon dioxide absorbent, and water is used as the solvent. 700 g of an aqueous solution of IPDA containing 10 wt% IPDA is prepared in a beaker and used as the absorbent solution. In this test example, CO ２ The time difference between absorption and crystallization is due to the amount of CO injected. ２ This demonstrates that the concentration can also be controlled.

[0070] This IPDA concentration of CO ２ When compressed air, specifically air containing approximately 400 ppm of carbon dioxide, was blown into the absorbent solution at a flow rate of 3 L / min, the solution remained colorless and transparent for the first 20 hours. However, 20 to 22 hours after blowing, the solution gradually began to become cloudy. 10 mL samples of the solution were taken into vials at 20, 22, and 24 hours after blowing, and allowed to stand with the lids closed. The samples taken at 22 and 24 hours showed slight cloudiness at the time of sampling, but after more than 20 hours of standing, it was visually confirmed that the amount of white solid precipitate had clearly increased several times over. In other words, even at atmospheric levels with a blown-in carbon dioxide concentration of around 400 ppm, CO ２ We confirmed that there is a time lag between absorption and crystallization, and that this time lag can be changed by adjusting the carbon dioxide concentration of the gas being treated.

[0071] [Example 1] IPDA is used as a phase-separated carbon dioxide absorbent, and water is used as the solvent. 10 kg of an aqueous IPDA solution containing 10 wt% IPDA is prepared and placed inside the absorption tower as the absorbent solution. A mixed gas consisting of 90% nitrogen and 10% carbon dioxide is blown into the solution at 125 L / min for 5 minutes. In Test Example 1, there is almost no change in viscosity within 60 minutes after the blowing stops, meaning that solid precipitation hardly progresses. Therefore, it is preferable to transfer the absorbent solution to the solidification device using a liquid transfer pump within this time to avoid solid precipitation inside the absorption device.

[0072] However, as a guideline, significant solid precipitation begins when the viscosity of the liquid phase exceeds 1.5 times the initial viscosity before carbon dioxide absorption. Therefore, if a small amount of solid precipitation is acceptable, it is sufficient to transfer the material within 100 minutes from the cessation of injection, i.e., when the viscosity reaches 1.5 times the initial viscosity. Similarly, in the case of a continuous process, solid precipitation in the absorption device can be avoided by transferring the material to the solidification device within 60 minutes, preferably no more than 100 minutes, of residence time in the absorption device.

[0073] According to Test Example 1, when the IPDA aqueous solution concentration is 50 wt% and when it is 90 wt%, the time it takes for the viscosity to become 1.5 times the initial viscosity is 60 minutes and 80 minutes, respectively, after the injection stops. Therefore, in this case, the residence time in the absorption device should be kept to a maximum of 60 minutes and 80 minutes, respectively.

[0074] On the other hand, as shown in Test Example 2, when the concentration of the IPDA aqueous solution is 90 wt% and the bubbling time is 10 minutes, the viscosity already becomes more than 1.5 times the initial value immediately after the bubbling stops, and solid precipitation proceeds rapidly, making it difficult to transfer the absorption solution to the solidification device while it is still in the liquid phase.

[0075] [Example 2] MXDA is used as a phase-separated carbon dioxide absorbent, and water is used as the solvent. 10 kg of an MXDA aqueous solution containing 10 wt% MXDA is prepared and placed inside the absorption tower as the absorbent solution. A mixed gas consisting of 90% nitrogen and 10% carbon dioxide is blown into the solution at 125 L / min for 5 minutes. As shown in Test Example 3, the change in viscosity is very small within 120 minutes from the cessation of blowing, and after 160 minutes the viscosity increases to 1.5 times the initial viscosity. Therefore, by preferably limiting the residence time in the solidification device to within 120 minutes, and at most 160 minutes, and transferring to the precipitation device, it is possible to avoid the problem of solid deposition in the absorption device.

[0076] [Example 3] IPDA is used as a phase-separated carbon dioxide absorbent, and water is used as the solvent. 7 kg of an aqueous IPDA solution containing 10 wt% IPDA is prepared in the absorption apparatus. According to Test Example 4, this CO ２ When air containing approximately 400 ppm of carbon dioxide is blown into the absorbent solution at a flow rate of 30 L / min, the solution remains colorless and transparent for the first 20 hours or so. However, 20 to 22 hours after the initial injection, the solution gradually becomes cloudy due to solid precipitation. By transferring the solution to the solidification device within one hour, either just before this clouding begins or immediately after slight solid precipitation starts (20 to 24 hours after injection), it is possible to avoid the problem of solid precipitation in the absorbent device.

[0077] This invention is CO ２ Fixation, CO ２ CO2 recovery ２ It can be used in all areas of transportation.

[0078] 100, 100A: Absorption device 110: Air or exhaust gas inlet 110A: Piping 120, 120A: Gas outlet 130: Nozzle 140, 140A: Liquid transfer pump 150: Carbon dioxide absorbent solution 160, 160A: CO ２ Absorbent solution that absorbed CO2 200, 200A: Solidification device 210, 210A: CO2 ２ Absorption solution that absorbed the substance; 220, 220A: solid phase; 300, 300A: connecting pipe; 310, 310A: liquid transfer pump

Claims

1. Using an absorption device, a carbon dioxide absorbent solution containing a phase-separated carbon dioxide absorbent and CO2 containing carbon dioxide are separated. ２ A method for separating and recovering carbon dioxide, comprising: a first step of bringing the carbon dioxide absorbent solution into contact with a contained gas to obtain an absorbent solution in reaction step A, in which carbon dioxide is absorbed by the carbon dioxide absorbent solution and solidification is restricted; a second step of moving the absorbent solution to a solidification device; and a third step of advancing the reaction of the absorbent solution in the solidification device to move to reaction step B, in which a reaction solidified product is obtained, thereby obtaining a liquid containing the reaction solidified product.

2. In the first step, the carbon dioxide absorbent solution and the CO2 containing carbon dioxide are used. ２ A method for separating and recovering carbon dioxide according to claim 1, wherein the method of contact with the contained gas, the contact ratio, and the contact temperature are controlled to keep the formation of the reaction solidified product below a predetermined range.

3. The absorption device puts the CO into the carbon dioxide absorbent solution. ２ A bubbling device for blowing in the contained gas; the CO2 in the upper space containing the carbon dioxide absorbent solution ２ A spray-type device for blowing in the contained gas; the CO ２ A tray-type apparatus that brings the contained gas into contact with the carbon dioxide absorbent solution on trays stacked in multiple stages; and a packed column filled with packing material and the carbon dioxide absorbent solution and the CO ２ A method for separating and recovering carbon dioxide according to claim 1, wherein the device is one selected from a group of packed-tower type devices that bring the device into contact with the contained gas.

4. The method for separating and recovering carbon dioxide according to claim 1, wherein the carbon dioxide absorbent solution comprises at least one selected from monoxylenediamine (MXDA), paraxylenediamine (PXDA), and isophoronediamine (IPDA), and a polar solvent.

5. A method for regenerating carbon dioxide, comprising regenerating carbon dioxide from a reaction solidified liquid obtained by the carbon dioxide separation and recovery method according to any one of claims 1 to 4.

6. A method for regenerating carbon dioxide according to claim 5, comprising: step a, performing the carbon dioxide separation and recovery method in the first step using a polar solvent as the solvent for the carbon dioxide absorbent solution; treating the resulting reaction solidified liquid with a nonpolar solvent to remove the polar solvent and obtain a nonpolar reaction product which is a nonpolar suspension or slurry containing the reaction solidified product and the nonpolar solvent; step b, heating the nonpolar reaction product obtained in step a under pressure, atmospheric pressure or reduced pressure to separate and recover carbon dioxide and regenerate the carbon dioxide absorbent from the nonpolar reaction product to obtain a carbon dioxide absorbent nonpolar solution; and step c, treating the carbon dioxide absorbent nonpolar solution obtained in step b with the polar solvent to replace the solvent and obtain a carbon dioxide absorbent polar solution.

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