JP2016169612A - Internal combustion engine exhaust purification device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately treat nitrogen oxide separated through a regeneration treatment of an absorbing solution with the nitrogen oxide absorbed therein or to perform the regeneration treatment of the absorbing solution with the nitrogen oxide absorbed therein more appropriately than ever before.SOLUTION: An exhaust purification device 10 comprises: a first absorbing device 16 which makes a first absorbing solution 18 absorb nitric acid in exhaust from an internal combustion engine 12; a regeneration device 22 which performs a regeneration treatment to separate the nitric acid from the first absorbing solution 18; and a second absorbing device 26 which makes a second absorbing solution 28 absorb the nitric acid separated from the first absorbing solution 18. A control section 34: starts the regeneration treatment of the regeneration device 22 when a concentration of the nitric acid in the first absorbing solution 18 is equal to a first concentration threshold or more and a temperature of the second absorbing solution 28 is within a predetermined range; and stops the regeneration treatment of the regeneration device 22 when the concentration of the nitric acid in the first absorbing solution 18 is less than a second concentration threshold smaller than the first concentration threshold or the temperature of the second absorbing solution 28 is outside the predetermined range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine for purifying nitrogen oxides contained in the exhaust gas of the internal combustion engine.

Conventionally, techniques for purifying nitrogen oxides (NO _x ) contained in exhaust gas from internal combustion engines such as engines have been proposed.

  For example, Patent Document 1 discloses an absorption device that absorbs nitrogen oxides modified to nitric acid by bringing them into contact with an absorption liquid. Nitrogen oxides contained in the exhaust gas are separated and removed by the absorption device.

Patent Document 2 discloses an absorption device that absorbs nitrogen oxides in contact with an absorption liquid, and has an ionic liquid that hardly evaporates even in a high-temperature environment as the absorption liquid. Patent Document 2 also discloses that NO _x can be absorbed again by separating NO _x absorbed in the ionic liquid from the ionic liquid.

JP 2014-62543 A JP2012-217918A

  For example, when nitrogen oxides are separated from an absorbing solution that has absorbed nitrogen oxides as in the technique described in Patent Document 2, the treatment of the separated nitrogen oxides becomes a problem. In this regard, Patent Document 2 does not mention the treatment of nitrogen oxides separated from the absorbing solution by the regeneration treatment.

  An object of the present invention is to suitably treat nitrogen oxides separated by regeneration treatment of an absorbing solution that has absorbed nitrogen oxides. Alternatively, an object of the present invention is to more suitably perform the regeneration treatment of the absorbing solution that has absorbed nitrogen oxides.

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine for purifying nitrogen oxides contained in exhaust gas from the internal combustion engine, comprising a first absorption liquid, wherein the exhaust gas from the internal combustion engine is circulated. A first absorption device that absorbs the nitrogen oxides in the first absorption liquid; a separation unit that performs a separation process for separating the nitrogen oxides absorbed in the first absorption liquid from the first absorption liquid; And a second absorption device that absorbs the nitrogen oxide separated from the first absorption liquid into the second absorption liquid.

  Desirably, the absorption rate of the nitrogen oxides fluctuates depending on the temperature of the second absorption liquid, and the exhaust gas purification apparatus of the internal combustion engine further includes a temperature detection unit that detects the temperature of the second absorption liquid, The separation means performs the separation process when the temperature of the second absorbent is within a predetermined range.

  Desirably, it further includes temperature adjusting means for adjusting the temperature of the second absorbing liquid to be within the predetermined range.

  Preferably, exhaust gas flow detection means for detecting whether or not exhaust gas from the internal combustion engine is flowing through the first absorption device, and the separation means is connected to the first absorption device from the internal combustion engine. The separation process is not performed when the exhaust gas is in circulation.

  Preferably, when the exhaust gas from the internal combustion engine is circulated through the first absorber, the exhaust gas from the internal combustion engine is also circulated through the second absorber, and the second absorber is fed from the internal combustion engine. The nitrogen oxide contained in the exhaust gas is absorbed by the second absorption liquid.

  Desirably, a plurality of the first absorption devices are provided, and the exhaust gas purification device of the internal combustion engine switches the flow path of the exhaust gas from the internal combustion engine, and exhausts the exhaust gas from the internal combustion engine of the plurality of first absorption devices. A flow path switching device that circulates to any one of the plurality of first absorption devices, wherein the separation means absorbs the nitrogen absorbed in the first absorption device in which exhaust from the internal combustion engine is not circulated. The oxide is separated.

  Desirably, it further comprises a concentration detection means for detecting the nitrogen oxide concentration of the first absorption liquid, and the separation means performs the separation process when the nitrogen oxide concentration of the first absorption liquid is a predetermined value or more. It is characterized by performing.

  ADVANTAGE OF THE INVENTION According to this invention, the nitrogen oxide isolate | separated by the reproduction | regeneration process of the absorption liquid which absorbed nitrogen oxide can be processed suitably. Or according to the objective of this invention, the reproduction | regeneration process of the absorption liquid which absorbed the nitrogen oxide can be performed more suitably than before.

1 is a schematic configuration diagram of an exhaust emission control device according to a first embodiment. It is a figure which shows the structural example of a 1st absorber. It is a figure which shows the example of the temperature characteristic of the absorption factor of a nitrogen oxide. It is a flowchart which shows the flow of a process of the exhaust gas purification apparatus in 1st Embodiment. It is a block schematic diagram of the exhaust emission control device according to the second embodiment. It is a figure which shows the structural example of the 1st absorber in 2nd Embodiment. It is a block schematic diagram of the exhaust emission control device according to the third embodiment. It is a flowchart which shows the flow of a process of the exhaust gas purification apparatus in 3rd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments described below.

<First Embodiment>
FIG. 1 is a schematic configuration diagram of an exhaust emission control device 10 according to the first embodiment.

An internal combustion engine (engine) 12 generates power by burning fuel in a cylinder. Here, the internal combustion engine 12 may be a spark ignition engine such as a gasoline engine, or may be a compression ignition engine such as a diesel engine. Exhaust gas after combustion in the internal combustion engine 12 is discharged to the reformer 14. Exhaust gas discharged from the internal combustion engine 12 to the reformer 14 contains harmful components such as nitrogen oxides (NO _x ). Examples of nitrogen oxides include NO (nitrogen monoxide), NO ₂ (nitrogen dioxide), N ₂ O (zincated nitrogen), N ₂ O ₅ (dinitrogen pentoxide), and N ₂ O ₃ (dinitrogen trioxide). ), N ₂ O ₄ (dinitrogen tetroxide), HNO ₃ (nitric acid), NO ₃ (nitrate ion), HNO ₂ (nitrous acid), and the like. Nitrogen oxide is separated and removed from the exhaust gas in the first absorber 16 described later.

Preferably, the exhaust purification device 10 is provided with a reforming device 14. The reformer 14 reforms nitrogen oxides contained in the exhaust gas from the internal combustion engine 12 into nitric acid in order to perform the nitrogen oxide separation and removal process in the first absorber 16 more efficiently. The reformer 14 has a nitric acid generation catalyst for promoting a reaction for converting nitrogen oxides to nitric acid (HNO ₃ ), and converts the nitrogen oxides contained in the exhaust from the internal combustion engine 12 to nitric acid on the nitric acid generation catalyst. To reform. The nitric acid production catalyst can be constituted by a catalyst having an acid point or a catalyst in which a metal such as silver (Ag), iron (Fe), copper (Cu) is supported on a carrier having an acid point. In order to further promote the oxidation reaction in the reformer 14, it is also preferable to add ozone (O ₃ ) as an oxidant to the exhaust gas from the internal combustion engine 12. Although the 1st absorber 16 can also process nitrogen oxides other than nitric acid, this embodiment is described hereafter about the example in which the 1st absorber 16 processes nitric acid as nitrogen oxide.

  Exhaust gas from the reformer 14 is discharged to the first absorber 16. Hereinafter, the exhaust from the reformer 14 is referred to as “exhaust from the internal combustion engine 12” for convenience.

  The exhaust gas from the internal combustion engine 12 is circulated through the first absorption device 16, and nitric acid is separated and absorbed from the exhaust gas. Specifically, the first absorption device 16 has a first absorption liquid 18, exhaust gas from the internal combustion engine 12 is brought into contact with the first absorption liquid 18, and nitric acid in the exhaust gas is absorbed by the first absorption liquid 18. .

  As the 1st absorption liquid 18, the liquid which can absorb nitric acid and can isolate | separate the absorbed nitric acid later as nitric acid is used. That is, a liquid that can absorb nitric acid with almost no chemical reaction (defined as “physical absorption type” in this specification) is used. Examples of the liquid that satisfies such conditions include various physical absorption type ionic liquids.

Absorption liquids containing not only various ionic liquids but also water and alkaline aqueous solutions have a feature that the absorption rate of nitrogen oxides varies depending on the temperature. That is, these absorbing liquids have temperature characteristics of nitrogen oxide absorption rate (hereinafter simply referred to as “temperature characteristics”). Here, the absorption rate of nitric acid is the amount of nitric acid absorbed with respect to the amount of nitric acid input to the absorber, and is specifically defined by the following equation.
{(N _in −N _out ) / N _in } × 100 (Formula 1)
In Equation 1, N _in is the amount of nitric acid input to the absorber, and N _out is the amount of nitric acid discharged from the absorber.

  The first absorbing liquid 18 is brought into contact with the exhaust from the internal combustion engine 12, so that the temperature rises due to the heat of the exhaust. The temperature rise of the first absorbent 18 varies depending on the temperature of the exhaust from the internal combustion engine 12 or the amount of exhaust. That is, the temperature of the first absorbing liquid 18 is varied depending on the exhaust conditions of the internal combustion engine 12. The temperature of the first absorbent 18 is also influenced by the outside air temperature and the like, but the fluctuation factor of the temperature is mainly exhaust conditions.

  Therefore, as the first absorbent 18, it is preferable to use an absorbent that exhibits a high absorption rate at a wider temperature. In the present embodiment, 1st-butyl-3-methylimidazolium triflate ([BMIM] [OTf], hereinafter simply referred to as “ionic liquid”), which is a physical absorption type ionic liquid, is used as the first absorbing liquid 18 that satisfies the above conditions. Use). The temperature characteristics of the ionic liquid will be described later with reference to FIG.

  The exhaust gas from which nitric acid is separated in the first absorption device 16 is discharged to an exhaust pipe 20 connected to an exhaust outlet. The exhaust gas discharged from the exhaust outlet is in a state where nitric acid as nitrogen oxide is removed. That is, the purified exhaust is discharged to the exhaust outlet.

  The regenerator 22 performs a process of separating the nitric acid absorbed in the first absorbent 18 from the first absorbent 18. When the first absorbing liquid 18 has absorbed nitric acid to the limit (saturated state), it can no longer absorb nitric acid, but the nitric acid can be absorbed again by separating the nitric acid from the first absorbing liquid 18. That is, the regeneration device 22 performs a regeneration process for the first absorbent 18. Note that the greater the amount of the first absorbent 18, the greater the amount of nitric acid that can be absorbed before the first absorbent 18 is saturated. The regeneration device 22 starts or stops the regeneration process of the first absorbent 18 based on an instruction signal transmitted from the control unit 34 described later.

  When the ionic liquid that has absorbed nitric acid is heated, the nitric acid absorbed in the ionic liquid is separated from the ionic liquid. Therefore, in the present embodiment, heating that heats the ionic liquid that is the first absorbent 18 in the regenerator 22. Use the device. In the said heating apparatus, an ionic liquid is heated to about 150 degreeC. Of course, other devices can be used as the playback device 22. For example, it is possible to use a method in which a voltage applying device is used as the regenerating device 22 and nitric acid is reduced and separated from the ionic liquid by applying a voltage to the ionic liquid.

  The nitric acid separated from the first absorbent 18 by the regenerator 22 becomes a gas and is circulated to the second absorber 26 via the separated nitric acid flow path 24 provided separately from the exhaust pipe 20. Hereinafter, nitric acid separated from the first absorbent 18 is referred to as separated nitric acid.

  The second absorption device 26 absorbs separated nitric acid. Specifically, the second absorption device 26 has a second absorption liquid 28, and the separated nitric acid is brought into contact with the second absorption liquid 28 and absorbed by the second absorption liquid 28. As the second absorbing liquid 28, various liquids can be used as long as the separated nitric acid can be absorbed, such as water, an alkaline aqueous solution, and various ionic liquids. In the present embodiment, water is used as the second absorbing liquid 28. The second absorber 26 is disposed at a position that is not on the exhaust passage of the exhaust gas from the internal combustion engine 12. Therefore, in the present embodiment, the exhaust from the internal combustion engine 12 is not circulated through the second absorber 26.

  The temperature sensor 30 detects the temperature of the water that is the second absorbing liquid 28. As the temperature sensor 30, a thermocouple, a thermistor, an infrared temperature sensor, or the like is used. Temperature data indicating the temperature of the second absorbing liquid 28 detected by the temperature sensor 30 is sent to the control unit 34 or read by the control unit 34.

  The concentration sensor 32 is a sensor that measures the concentration of nitric acid in the first absorbent 18. In the present embodiment, a pH meter that measures the hydrogen ion index (pH (pH)) of the first absorbent 18 is used as the concentration sensor. The more nitric acid is absorbed by the first absorbent 18, the higher the acidity of the first absorbent 18. Therefore, the nitric acid concentration in the first absorbent 18 can be grasped by a pH meter that measures the degree of acidity. Of course, as long as the concentration of nitric acid in the first absorbent 18 can be detected, a measuring device other than a pH meter may be provided as the concentration sensor 32. Concentration data indicating the nitric acid concentration of the first absorbent 18 detected by the concentration sensor 32 is sent to the control unit 34 or read by the control unit 34.

  The control unit 34 is composed of, for example, a microcomputer, and controls the playback device 22 or identifies the operating state of the internal combustion engine 12. The control unit 34 transmits an instruction signal instructing the playback device 22 to start or stop the operation. In the present embodiment, the control unit 34 controls the start or stop of the regeneration process of the regeneration device 22 based on both the temperature of the second absorbent 28 and the nitric acid concentration of the first absorbent 18. Specifically, the detected temperature of the temperature sensor 30 is compared with information indicating a predetermined range stored in a storage unit (not shown in FIG. 1) (such as a temperature threshold) and the detected concentration value of the concentration sensor. The playback device 22 is controlled by comparison with a density threshold value set in advance and stored in the storage unit. Details of the control of the playback device 22 by the control unit 34 will be described later with reference to the flowchart of FIG.

  Preferably, the exhaust gas purification device 10 is provided with a temperature adjustment device 36. The temperature adjusting device 36 is for adjusting the temperature of the second absorbing liquid 28. As described above, the absorbing liquid has temperature characteristics, and the temperature adjusting device 36 allows the second absorbing liquid 28 to absorb nitric acid more suitably, that is, to increase the nitric acid absorption rate. Then, the temperature of the second absorbing liquid 28 is adjusted.

  In the present embodiment, water is used as the second absorption liquid 28, and as will be described later, water exhibits a relatively high nitric acid absorption rate at less than 70 ° C. Therefore, in the present embodiment, a cooling device (a radiator or the like) is used as the temperature adjustment device 36 in order to prevent water from becoming 70 ° C. or higher. The cooling device always cools the second absorbent 28 at least while the internal combustion engine 12 is operating.

  FIG. 2 is a schematic view showing a structural example of the first absorption device 16. FIG. 2A shows a structural example of the first absorption device 16 used in this embodiment, and FIG. 2B shows a modified example thereof.

  The first absorption device 16a shown in FIG. 2A is configured to include a gas-liquid contact portion 40. The gas-liquid contact part 40 makes exhaust gas from the internal combustion engine 12 come into contact with the first absorbent 18 (not shown in FIG. 2A), and the first absorbent 18 absorbs nitric acid in the exhaust. . In the first absorption device 16 a, the first absorption liquid 18 is stored in a storage unit provided in the gas-liquid contact unit 40.

  As a contact method between the exhaust gas from the internal combustion engine 12 and the first absorbent 18, a known technique such as bubbling, scrubber, gas-liquid contact film, or the like can be used. In the present embodiment, the exhaust flow path and the first absorption liquid 18 are separated from each other by a porous film in the gas-liquid contact portion 40, and nitric acid contained in the exhaust is passed through the porous film from the exhaust flow path through the first absorption liquid. 18 is contacted. As the porous membrane, a porous PTFE (polytetrafluoroethylene) membrane or the like can be used. As the first absorbent 18 stored in the gas-liquid contact part 40 absorbs nitric acid in the exhaust from the internal combustion engine 12, the concentration of nitric acid increases. Note that the contact amount of the first absorbent 18 with respect to the exhaust gas in the gas-liquid contact portion 40 may be set as appropriate.

  In the first absorption device 16a, the regeneration device 22 is provided in the gas-liquid contact portion 40 or in the vicinity of the outside thereof. The concentration sensor 32 is provided in the gas-liquid contact portion 40. Further, a valve 42 for switching a discharge flow path from the gas-liquid contact unit 40 is provided at the discharge port of the gas-liquid contact unit 40. The valve 42 can be switched between positions 42a and 42b. When the exhaust from the internal combustion engine 12 is flowing through the first absorber 16a, the valve 42 is in the position 42a, and the exhaust from the gas-liquid contact portion 40 flows to the exhaust pipe 20. During the regeneration process by the regeneration device 22, the valve 42 is in the position 42 b, and the separated nitric acid separated from the first absorbent 18 flows into the separated nitric acid flow path 24. The position of the valve 42 may be switched based on an instruction signal transmitted from the control unit 34. Thus, in the first absorption device 16a, a part of the discharge flow path of the gas-liquid contact portion 40 is shared by the exhaust flow path from the internal combustion engine 12 and the separated nitric acid flow path.

  Moreover, as the 1st absorber 16, the structure as shown in FIG.2 (b) is also employable. In the first absorption device 16 b shown in FIG. 2B, the storage portion 44 that stores the first absorption liquid 18 has a separate structure provided outside the gas-liquid contact portion 40.

  In the first absorption device 16 b, the first absorption liquid 18 stored in the storage unit 44 is pumped up to the gas-liquid contact unit 40 by the pump 46. In the gas-liquid contact portion 40, the first absorbent 18 is brought into contact with nitric acid in the exhaust from the internal combustion engine 12. The first absorption liquid 18 that has absorbed nitric acid in the gas-liquid contact part 40 is returned to the storage part 44. Thus, the 1st absorption liquid 18 circulates between the storage part 44 and the gas-liquid contact part 40. FIG. By the circulation, the nitric acid concentration of the first absorbent 18 is increased.

  In the first absorption device 16b, the regeneration device 22 is provided in the storage portion 44 or in the vicinity of the outside thereof. A concentration sensor 32 for measuring the nitric acid concentration of the first absorbent 18 is provided in the storage unit 44. In the first absorption device 16 b, the separated nitric acid flow path 24 through which the separated nitric acid is discharged is connected to the storage unit 44. That is, in the first absorption device 16b, there is no shared portion between the flow path of exhaust from the internal combustion engine 12 and the flow path of separated nitric acid.

  In addition, although the typical example of the 1st absorber 16 was shown in FIG. 2, the apparatus of another structure can be used as the 1st absorber 16.

  As the 2nd absorber 26, the structure similar to the 1st absorber 16b shown, for example by FIG.2 (b) is employable. Therefore, description of the basic structure of the 2nd absorber 26 is abbreviate | omitted. Of course, the second absorption device 26 may have any structure as long as the separated nitric acid can be suitably absorbed by the second absorption liquid 28. In the second absorption device 26, the temperature sensor 30 is provided in or near the gas-liquid contact portion, and detects the temperature of the second absorption liquid 28 at the contact position with the separated nitric acid. Further, a temperature adjusting device 36 is provided in the gas-liquid contact portion or in the vicinity of the outside thereof.

  FIG. 3 is a graph showing temperature characteristics of water and ionic liquid. In FIG. 3, the horizontal axis represents the temperature of the absorbing solution, and the vertical axis represents the nitric acid absorption rate of the absorbing solution or the weight of the absorbing solution. In the graph shown in FIG. 3, the white square indicates the nitric acid absorption rate of water, and the black square indicates the nitric acid absorption rate of the ionic liquid. The ionic liquid has a stable nitric acid absorption rate in the range of 20 ° C. to 120 ° C., and has a nitric acid absorption rate of at least 50% at any temperature. On the other hand, water absorbs nitric acid at a temperature of less than about 70 ° C., which is 60% or higher, and exhibits a relatively high absorption rate. In other words, it can be said that the ionic liquid preferably has a relatively wide temperature range in which nitric acid can be absorbed, and water has a relatively narrow temperature range in which nitric acid can be suitably absorbed.

  The nitric acid absorption rate also varies depending on the contact amount of the absorbing solution with nitric acid. For example, if the contact amount of the ionic liquid with nitric acid is increased, the black square graph shown in FIG. In this embodiment, the nitric acid contact amount of the ionic liquid is about 70% of the contact amount of water, and FIG. 3 shows the temperature characteristics in that case.

FIG. 3 shows the remaining weight ratio of water and ionic liquid. The white triangle indicates the remaining weight ratio of water, and the black triangle indicates the remaining weight ratio of the ionic liquid. The remaining weight ratio is a ratio of the weight of the absorbing liquid after a lapse of a predetermined time to the weight before the lapse of a predetermined time when maintained at a certain temperature, and is specifically defined by the following equation.
(Q _after / Q _before ) × 100 (Expression 2)
In Equation 2, Q _after is the weight of the absorbing solution after a predetermined time has elapsed, and Q _before is the weight of the absorbing solution _before the predetermined time has elapsed. The weight of the absorbent varies (decreases) due to evaporation of the absorbent. In other words, it means that the smaller the remaining weight ratio, the easier the absorbing liquid evaporates.

  The remaining weight percentage of water decreases as the temperature increases. That is, water is more likely to evaporate as the temperature increases. In particular, in a temperature range exceeding 70 ° C., it is very easy to evaporate, and as a result, nitric acid can hardly be absorbed. On the other hand, the remaining weight ratio of the ionic liquid is maintained almost 100% in the range shown in the graph of FIG. That is, the ionic liquid hardly evaporates at least up to around 120 ° C.

  FIG. 4 is a flowchart showing the flow of processing of the exhaust emission control device 10 in the first embodiment. Specifically, the control procedure of the playback device 22 by the control unit 34 is shown. Hereinafter, each step of the flowchart of FIG. 4 will be described with reference to FIG.

  In step S <b> 10, the control unit 34 determines whether or not the exhaust gas from the internal combustion engine 12 is circulated through the first absorber 16. In the exhaust purification device 10, all the exhaust from the internal combustion engine 12 is circulated to the first absorption device 16 via the reformer 14. Therefore, the control unit 34 detects the operating state of the internal combustion engine 12, and if the internal combustion engine 12 is operating, determines that the exhaust from the internal combustion engine 12 is circulating to the first absorber 16, and the internal combustion engine 12 If it is stopped, it is determined that the exhaust from the internal combustion engine 12 is not distributed to the first absorber 16.

  If the exhaust gas from the internal combustion engine 12 is circulated through the first absorber 16 in step S10, the process of step S10 is repeated again. That is, the control unit 34 stands by until the exhaust from the internal combustion engine 12 does not flow through the first absorption device 16.

  When the exhaust gas from the internal combustion engine 12 is not circulated through the first absorption device 16, in step S12, the control unit 34 determines that the nitric acid concentration of the first absorption liquid 18 is equal to or higher than the first concentration threshold and the second absorption. It is determined whether or not the temperature of the liquid 28 is within a predetermined range.

  When the condition in step S12 is not satisfied, the process returns to step S10 again. That is, the controller 34 is configured such that the exhaust gas from the internal combustion engine 12 is not flowing through the first absorber 16, the nitric acid concentration of the first absorber 18 is equal to or higher than the first concentration threshold, and the temperature of the second absorber 28 is Wait until the three conditions of being within the predetermined range are satisfied.

  When the condition in step S12 is satisfied, in step S14, the control unit 34 instructs the regeneration device 22 to start the regeneration process of the first absorbent 18. The playback device 22 starts operating according to the instruction. The nitric acid absorbed in the first absorbent 18 is separated from the first absorbent 18 by the regeneration process. The separated nitric acid is circulated to the second absorption device 26 and is absorbed by the second absorption liquid 28 in the second absorption device 26.

  In step S <b> 16, while the regeneration device 22 continues the regeneration process, the control unit 34 has the nitric acid concentration of the first absorbent 18 that is equal to or higher than the second concentration threshold smaller than the first concentration threshold, and the second absorption. It is determined whether or not the temperature of the liquid 28 is within a predetermined range.

  If the condition is satisfied, the process of step S16 is performed again. That is, the control unit 34 continues to monitor the nitric acid concentration of the first absorbent 18 and the temperature of the second absorbent 28. Then, the regeneration device 22 continues the regeneration process of the first absorbent 18 until the nitric acid concentration of the first absorbent 18 and the temperature of the second absorbent 28 do not satisfy the above conditions.

  When the condition is not satisfied in step S16, in step S18, the control unit 34 transmits a regeneration processing stop instruction to the regeneration device 22, and the regeneration device 22 that has received the instruction regenerates the first absorbing liquid 18. Stop.

  As described above, according to this embodiment, since the physical absorption type ionic liquid is used as the first absorbing liquid 18, the nitric acid absorbed in the ionic liquid can be separated by the regeneration process. The separated nitric acid generated by the regeneration process of the first absorbent 18 is absorbed by the second absorbent 28 in the second absorbent 26, and thus the separated nitric acid is unintentionally released outside the exhaust purification apparatus 10. There is nothing. Then, the separated nitric acid absorbed in the second absorbing liquid 28 can be processed by an appropriate method.

  In the present embodiment, the second absorber 26 is not on the exhaust path of the exhaust from the internal combustion engine 12, and therefore the exhaust is not circulated. Therefore, the second absorbing liquid 28 has few temperature fluctuation factors, and the temperature is relatively stable. That is, it is easy to control the temperature of the second absorbing liquid 28. Therefore, as the second absorbing liquid 28, water that is a very inexpensive liquid can be used although the temperature range in which nitric acid can be suitably absorbed is relatively narrow. Further, since the amount of fluctuation in the temperature of the water as the second absorbent liquid 28 is small, that is, it is difficult to reach a high temperature, the evaporation amount is also reduced.

  In the present embodiment, the regeneration process of the first absorbent 18 is started or stopped based on the temperature of the second absorbent 28. For example, the temperature of the second absorption liquid 28 fluctuates due to factors such as high outside air temperature or contact between the separated nitric acid and the second absorption liquid 28 for a long time, resulting in a region where the nitric acid absorption rate is low. There are also cases where In such a case, since the 2nd absorption liquid 28 cannot absorb nitric acid suitably, in this embodiment, regeneration processing of the 1st absorption liquid 18 is not performed. Therefore, the temperature range in which the nitric acid absorption rate of the second absorbent 28 is most excellent is set as the predetermined range in step S12. In the present embodiment, water is used as the second absorbing liquid 28 and, as shown in FIG. 3, the nitric acid absorption rate of water is excellent at less than about 70 ° C., so that the predetermined range is set to less than 70 ° C. The

  In the present embodiment, since the temperature adjusting device 36 is also provided, the temperature of the second absorbent liquid 28 is maintained at a suitable temperature at which the nitric acid absorption rate of the second absorbent liquid 28 becomes high, that is, a temperature within the predetermined range. Or temperature fluctuations of the second absorbent 28 can be suppressed. Thereby, while maintaining the 2nd absorption liquid 28 on the conditions which can perform the reproduction | regeneration process of the reproduction | regeneration apparatus 22, the 2nd absorption liquid 28 can absorb separation nitric acid more suitably. Note that the regeneration process of the first absorbent 18 may be performed regardless of the temperature of the second absorbent 28 as long as the temperature of the second absorbent 28 can be maintained within a predetermined range.

  In the present embodiment, in the first absorption device 16, a part of the discharge flow path of the gas-liquid contact portion 40 is shared by the exhaust flow path from the internal combustion engine 12 and the separated nitric acid flow path (FIG. 2). (See (a)). Therefore, in the present embodiment, when the exhaust gas from the internal combustion engine 12 is flowing through the first absorber 16, the regeneration process of the first absorbent 18 is not performed. As a result, the exhaust gas from the internal combustion engine 12 is appropriately discharged to the exhaust pipe 20 without flowing into the separated nitric acid flow path 24, and the separated nitric acid is appropriately discharged to the separated nitric acid flow path 24 without flowing into the exhaust pipe 20. Discharged. The exhaust from the internal combustion engine 12 is the main cause of the temperature fluctuation of the absorbing liquid. By preventing the exhaust from the internal combustion engine 12 from flowing through the second absorbing device 26, the temperature of the second absorbing liquid 28 varies. Can be prevented. Note that the structure of the first absorber 16 is, for example, the structure shown in FIG. 2B, that is, if there is no shared portion between the exhaust flow path from the internal combustion engine 12 and the separated nitric acid flow path, Since the exhaust gas does not flow to the separated nitric acid flow path 24 and the separated nitric acid does not flow to the exhaust pipe 20, regardless of whether or not the exhaust gas from the internal combustion engine 12 is flowing through the first absorber 16. First, the regeneration process of the first absorbent 18 may be performed.

  In the present embodiment, the regeneration process of the first absorbent 18 is started or stopped based on the nitric acid concentration of the first absorbent 18. If the regeneration process is performed when the first absorbent 18 hardly absorbs nitric acid, not only the effect of the regeneration process is obtained, but also the energy for operating the regeneration device 22 is wasted. Become. Therefore, in this embodiment, when the nitric acid concentration of the first absorbent 18 becomes equal to or higher than the first concentration threshold, the regeneration process of the first absorbent 18 is started, and the nitric acid concentration of the first absorbent 18 is the second concentration. When it becomes less than the threshold value, the regeneration process of the first absorbent 18 is stopped. Here, the first concentration threshold may be set to a concentration of nitric acid that can sufficiently exert the regeneration capability of the regeneration device 22 based on the regeneration capability (reproduction speed) of the regeneration device 22 or the like. The first concentration threshold may be set by taking into account the amount of the first absorbing liquid and the amount of nitrogen oxides discharged from the internal combustion engine 12. For example, a value of 50% or more is set as the first concentration threshold. On the other hand, since the second density threshold is a threshold that triggers the stop of the reproduction process, for example, a value of 1 to 10% is set. In addition, you may make it perform the reproduction | regeneration process of the 1st absorption liquid 18 irrespective of the nitric acid concentration of the 1st absorption liquid 18. FIG.

  Further, in the present embodiment, the regeneration process of the first absorbent 18 is started or stopped based on the nitric acid concentration of the first absorbent 18 and the temperature of the second absorbent. However, only one of the conditions is used. Based on this, the reproduction process may be started or stopped.

  According to the exhaust gas purification device 10, since the first absorbing liquid 18 can be regenerated, nitric acid in the exhaust gas from the internal combustion engine 12 can be removed for a long time even if the amount of the first absorbing liquid 18 is reduced. Absorbable. In particular, since the ionic liquid used as the first absorbing liquid 18 is relatively expensive, reducing the amount thereof is beneficial from the viewpoint of cost. On the other hand, since relatively inexpensive water or the like can be used as the second absorbent, the amount of the second absorbent 28 can be increased while suppressing the cost. By increasing the amount of the second absorbent, the amount of separated nitric acid that can be absorbed by the second absorbent 28 is increased, and the separated nitric acid can be absorbed for a longer time. That is, the regeneration process of the first absorbent 18 can be performed for a longer time without replacing the second absorbent 28. This reduces the frequency of replacement of the second absorbent liquid 28.

Second Embodiment
FIG. 5 is a schematic configuration diagram of an exhaust emission control device 60 according to the second embodiment. In FIG. 5, illustration of the internal combustion engine and the reformer is omitted. In the exhaust purification apparatus 60, the same components as those in the exhaust purification apparatus 10 according to the first embodiment are denoted by the same drawing numbers as those in FIG. 1, and the description of the same functions as those in the first embodiment is omitted. To do. Also in the second embodiment, the first absorbent 18 is an ionic liquid, and the second absorbent 28 is water.

  In the exhaust purification device 60, the exhaust gas after the nitric acid absorption exhausted by the first absorption device 16 and the separated nitric acid flow in a common flow path after the first absorption device 16. Specifically, both the exhaust from the first absorption device 16 and the separated nitric acid are discharged to the exhaust pipe 62. A valve 64 is provided in the middle of the exhaust pipe 62.

  The valve 64 switches the exhaust gas from the first absorption device 16 and the flow path of the separated nitric acid. Specifically, the flow path of the exhaust gas and the separated nitric acid is switched to either the exhaust pipe 62a that is the flow path to the second absorption device 26 or the exhaust pipe 62b that is the flow path that is discharged to the exhaust outlet. Switching of the flow path by the valve 64 is performed based on an instruction signal transmitted from the control unit 34.

  FIG. 6 shows a structural example of the first absorption device 16 in the second embodiment. As shown in FIG. 6, the first absorption device 16c used in the second embodiment has the same structure as the first absorption device 16a shown in FIG. There is no valve at the outlet.

  According to the exhaust purification device 60, first, the same processing as that of the exhaust purification device 10 according to the first embodiment can be performed. First, when the exhaust gas from the internal combustion engine 12 is flowing through the first absorption device 16 (during operation of the internal combustion engine 12), the control unit 34 distributes the exhaust gas from the first absorption device 16 to the exhaust pipe 62b. The valve 64 is switched. As a result, the exhaust from the first absorber 16 bypasses the second absorber 26 and is discharged to the exhaust outlet. Next, when the exhaust gas from the internal combustion engine 12 is not flowing, the nitric acid concentration of the first absorbent 18 is not less than the first concentration threshold, and the temperature of the second absorbent 28 is within a predetermined range. In some cases, the regeneration device 22 performs a regeneration process of the first absorbent 18. At this time, the control unit 34 switches the valve 64 so that the separated nitric acid discharged from the first absorption device 16 flows through the exhaust pipe 62a. Thereby, the separated nitric acid is circulated to the second absorption device 26 and absorbed by the second absorption liquid 28.

  Second, the second absorption device 26 can be used as a device that absorbs nitric acid in the exhaust gas from the internal combustion engine 12. In this case, when the exhaust gas from the internal combustion engine 12 is flowing through the first absorption device 16 (during operation of the internal combustion engine 12), the control unit 34 sends the exhaust gas from the first absorption device 16 to the exhaust pipe 62a. By switching the valve 64 to circulate, the exhaust from the internal combustion engine 12 circulates through the first absorber 16 and the second absorber 26. By flowing the exhaust gas from the internal combustion engine 12 through the two absorption devices, a larger amount of nitric acid can be absorbed. In this case as well, it may be determined whether exhaust from the internal combustion engine 12 is brought into contact with the second absorbent 28 based on the temperature of the second absorbent 28. For example, when the temperature of the second absorption liquid 28 is 70 ° C. or higher, the nitric acid absorption rate of water is low, so there is little significance in contacting the exhaust with the second absorption liquid 28. The exhaust from the first absorption device 16 may be directly discharged to the exhaust outlet via the exhaust pipe 62b. In addition, this prevents the water temperature from being maintained at 70 ° C. or higher, and the amount of water evaporation can be reduced. Thus, in the first embodiment, when the exhaust from the internal combustion engine 12 is flowing through the first absorption device 16, the second absorption device 26 did nothing, but according to the second embodiment. Even when the exhaust gas from the internal combustion engine 12 is flowing through the first absorber 16, the second absorber 26 can be suitably used.

<Third Embodiment>
FIG. 7 is a schematic configuration diagram of an exhaust emission control device 70 according to the third embodiment. Also in FIG. 7, illustration of the internal combustion engine and the reformer is omitted. In the exhaust purification device 70, the same components as those in the exhaust purification device 10 according to the first embodiment are denoted by the same reference numerals as those in FIG. 1, and description of the same functions as those in the first embodiment is omitted. To do.

  In the exhaust purification device 70, two absorption devices for absorbing nitric acid contained in the exhaust from the internal combustion engine 12 are provided in parallel with the exhaust flow path (the first absorption device 16 and the third absorption device 72). ) Is provided. Exhaust gas from the internal combustion engine 12 is exhausted to an exhaust pipe 74 connected to the two absorbers. A valve 76 is provided in the middle of the exhaust pipe 74.

  The valve 76 switches the exhaust flow path from the internal combustion engine 12. Specifically, the exhaust flow path is switched to either the exhaust pipe 74 a that is a flow path to the first absorption device 16 or the exhaust pipe 74 b that is a flow path to the third absorption device 72. Switching of the flow path by the valve 76 is performed based on an instruction signal transmitted from the control unit 34.

  The third absorption device 72 has the same structure as the first absorption device 16. The first absorption device 16 and the third absorption device 72 in this embodiment have a structure shown in FIG. That is, the exhaust gas from the internal combustion engine 12 and the separated nitric acid flow path are partly shared. Moreover, the 3rd absorption apparatus 72 has an ionic liquid as the 1st absorption liquid 18b similarly to the 1st absorption apparatus 16. FIG. In the present embodiment, the second absorbing liquid 28 is water.

  The exhaust purification device 70 is provided with two regeneration devices. Specifically, a regeneration device 22a that performs the regeneration process of the first absorbent 18a included in the first absorber 16 and a regeneration device 22b that performs a regeneration process of the first absorbent 18b included in the third absorber 72 are provided. .

  The exhaust gas purification device 70 is also provided with two concentration sensors. Specifically, a concentration sensor 32a that detects the nitric acid concentration of the first absorption liquid 18a that the first absorption device 16 has, and a concentration sensor 32b that detects the nitric acid concentration of the first absorption liquid 18b that the third absorption device 72 has. Provided.

  In the exhaust emission control device 70, the flow path of the exhaust gas from the internal combustion engine 12 is switched as follows. First, when the nitric acid concentrations of both the first absorbents 18a and 18b are less than a third concentration threshold value that is determined in advance and stored in the storage unit, the exhaust gas from the internal combustion engine 12 is preferentially sent to the first absorber 16. To be distributed. When the concentration of nitric acid in the first absorbent 18a becomes equal to or higher than the third concentration threshold, the valve 76 is switched to allow the exhaust from the internal combustion engine 12 to flow through the third absorber 72. As described later, the regeneration process of the first absorbent 18a is performed during this period. When the nitric acid concentration of the first absorbing liquid 18b becomes equal to or higher than the third concentration threshold, the valve 76 is switched, and the exhaust from the internal combustion engine 12 is circulated to the first absorbing device 16 again. The above processing is repeated. In this embodiment, the same value as the first density threshold described in the first embodiment is set as the third density threshold, but a value equal to or higher than the first density threshold is set as the third density threshold. May be.

  FIG. 8 is a flowchart showing a processing flow of the exhaust purification device 70 in the third embodiment. Specifically, the control procedure of the playback devices 22a and 22b by the control unit 34 is shown. Hereinafter, each step of the flowchart of FIG. 8 will be described with reference to FIG.

  In step S30, it is determined whether or not the temperature of the second absorbing liquid 28 detected by the temperature sensor 30 is within a predetermined range. When the temperature of the 2nd absorption liquid 28 is not in the predetermined range, it returns to Step S30 again. That is, the control unit 34 stands by until the temperature of the second absorbent liquid 28 falls within a predetermined range.

  When the temperature of the second absorbing liquid 28 is within the predetermined range, in step S32, the control unit 34 determines to which absorbing device the exhaust from the internal combustion engine 12 is circulated. The control unit 34 has information indicating the current state of the valve 76 in order to transmit a switching instruction signal to the valve 76. Based on the information indicating the state of the valve 76, the control unit 34 identifies the absorption device through which the exhaust gas is circulated.

  When the exhaust from the internal combustion engine 12 is circulated through the third absorber 72, in step S34, the control unit 34 determines that the nitric acid concentration of the first absorbent 18a included in the first absorber 16 where the exhaust is not circulated. It is determined whether or not it is equal to or higher than the first density threshold. If the nitric acid concentration of the first absorbent 18a is less than the first concentration threshold, the process returns to step S30.

  When the nitric acid concentration of the first absorbent 18a is equal to or higher than the first concentration threshold, in step S36, the controller 34 instructs the regeneration device 22a to start the regeneration process of the first absorbent 18a. The playback device 22a starts operating according to the instruction. By the regeneration process, nitric acid absorbed in the first absorbent 18 is separated from the first absorbent 18a. The separated nitric acid is circulated to the second absorption device 26 and is absorbed by the second absorption liquid 28 in the second absorption device 26.

  In step S38, while the regeneration device 22a continues the regeneration process, the control unit 34 has the nitric acid concentration of the first absorbent 18a equal to or higher than the second concentration threshold smaller than the first concentration threshold, and the second absorption. It is determined whether or not the temperature of the liquid 28 is within a predetermined range.

  If the condition is satisfied, the process of step S38 is performed again. That is, the control unit 34 continues to monitor the nitric acid concentration of the first absorbent 18a and the temperature of the second absorbent 28. Then, the regeneration device 22a continues the regeneration process of the first absorbent 18a until the nitric acid concentration of the first absorbent 18a and the temperature of the second absorbent 28 do not satisfy the above conditions.

  If the condition is not satisfied in step S38, in step S40, the control unit 34 transmits an instruction to stop the reproduction process to the reproduction apparatus, and the reproduction apparatus that receives the instruction stops the reproduction process.

  If it is determined in step S32 that the exhaust gas from the internal combustion engine 12 is distributed to the first absorber 16, the process proceeds to step S42. In steps S42 to S46 and S40, only the regeneration process target and the comparison target with the concentration threshold value are changed from the first absorption liquid 18a to the first absorption liquid 18b, and the processing content is the same as the processing of steps S34 to S40. Since it is the same, the description is abbreviate | omitted.

  As described above, according to the present embodiment, the first absorber 16 and the third absorber 72 are provided in parallel in the exhaust flow path from the internal combustion engine 12, and the regenerator 22 includes the internal combustion engine 12. A regeneration process is performed on the first absorbing liquid 18 of the absorbing device in which no exhaust gas is distributed. For example, when the exhaust from the internal combustion engine 12 is circulated through the first absorber 16, the regenerator 22b performs a regeneration process on the first absorbent 18b of the third absorber 72 where the exhaust is not circulated. When the concentration of nitric acid in the first absorbent 18a is equal to or greater than the third concentration threshold, the exhaust from the internal combustion engine 12 is circulated to the third absorber 72, and the nitric acid in the exhaust enters the regenerated first absorbent 18b. Preferably absorbed. Meanwhile, the regeneration device 22a performs a regeneration process on the first absorbent 18a. When the concentration of nitric acid in the first absorbent 18b becomes equal to or greater than the third concentration threshold, the exhaust from the internal combustion engine 12 is circulated to the first absorber 16 again, and the nitric acid in the exhaust is regenerated in the first absorption. The liquid 18a is suitably absorbed.

  In this way, in the exhaust purification device 70, the absorption processing of nitric acid in the exhaust from the internal combustion engine 12 is performed in one of the absorption devices, and at the same time, the regeneration processing of the absorption liquid of the other absorption device is performed. Accordingly, even when the internal combustion engine 12 is continuously operated, that is, when exhaust gas is continuously exhausted for a long time, while preventing the exhaust gas from flowing to the second absorber 26, While the nitric acid is absorbed, the first absorbent 18a or 18b can be regenerated.

  For example, the exhaust gas from the internal combustion engine 12 is circulated to the first absorber 16 because the nitric acid concentration of the first absorbent 18b becomes equal to or higher than the third nitric acid concentration during the regeneration process of the first absorbent 18a. If this happens, the regeneration process of the first absorbent 18a is immediately stopped.

  In the present embodiment, two absorption devices are provided in parallel in the exhaust flow path from the internal combustion engine 12, but three or more absorption devices may be provided in parallel. Even in this case, the regeneration process is performed on the absorbing liquid of the absorbing device that does not circulate the exhaust gas from the internal combustion engine 12 among the plurality of absorbing devices.

  Further, as in the present embodiment, when a plurality of absorbers that absorb nitric acid in the exhaust from the internal combustion engine 12 are provided in parallel, a plurality of absorbing liquids included in the plurality of absorbers are regenerated in one regenerator. You may do it. In this case, the absorbing solution is sent from each absorbing device to the regenerating device and the regenerating process is performed. The regenerated absorbent is returned to each absorbent. According to this aspect, there is no need to provide the regenerator 22 for each absorber, and cost reduction is realized.

  10, 60, 70 Exhaust purification device, 12 Internal combustion engine, 14 Reforming device, 16 First absorption device, 18, 18a, 18b First absorption liquid, 20 Exhaust pipe, 22 Regeneration device, 24 Separation nitric acid flow path, 26 2 absorption device, 28 2nd absorption liquid, 30 temperature sensor, 32 concentration sensor, 34 control part, 36 temperature adjustment device, 64,76 valve, 72 3rd absorption device.

Claims (7)

An exhaust purification device for an internal combustion engine for purifying nitrogen oxides contained in exhaust from the internal combustion engine,
A first absorption device that has a first absorption liquid and causes the first absorption liquid to absorb the nitrogen oxides by passing exhaust gas from the internal combustion engine;
Separation means for performing a separation treatment for separating the nitrogen oxides absorbed in the first absorption liquid from the first absorption liquid;
A second absorption device that has a second absorption liquid and causes the second absorption liquid to absorb the nitrogen oxides separated from the first absorption liquid;
An exhaust emission control device for an internal combustion engine, comprising: The absorption rate of the nitrogen oxide varies depending on the temperature of the second absorption liquid,
The exhaust gas purification device for the internal combustion engine includes:
Temperature detecting means for detecting the temperature of the second absorbent,
Further comprising
The separation means performs the separation process when the temperature of the second absorbent is within a predetermined range;
The exhaust emission control device for an internal combustion engine according to claim 1, wherein: Temperature adjusting means for adjusting the temperature of the second absorbent to be within the predetermined range;
The exhaust emission control device for an internal combustion engine according to claim 2, further comprising: An exhaust gas flow detecting means for detecting whether or not the exhaust gas from the internal combustion engine is distributed to the first absorber;
Further comprising
The separation means does not perform the separation process when exhaust gas from the internal combustion engine is circulated through the first absorber.
The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust gas purification device is an internal combustion engine. When exhaust gas from the internal combustion engine is circulated through the first absorption device, exhaust gas from the internal combustion engine is also circulated through the second absorption device, and the second absorption device serves as exhaust gas from the internal combustion engine. Absorbing the nitrogen oxide contained in the second absorption liquid;
The exhaust emission control device for an internal combustion engine according to claim 4, wherein the exhaust gas purification device is an internal combustion engine. A plurality of the first absorption devices are provided,
The exhaust gas purification device for the internal combustion engine includes:
A flow path switching device that switches a flow path of the exhaust gas from the internal combustion engine and distributes the exhaust gas from the internal combustion engine to any of the plurality of first absorbers;
Further comprising
The separation means separates the nitrogen oxides absorbed by the first absorption device in which exhaust from the internal combustion engine is not circulated among the plurality of first absorption devices.
The exhaust emission control device for an internal combustion engine according to claim 4, wherein the exhaust gas purification device is an internal combustion engine. Concentration detecting means for detecting the nitrogen oxide concentration of the first absorbing liquid;
Further comprising
The separation means performs the separation process when the nitrogen oxide concentration of the first absorption liquid is a predetermined value or more.
The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust gas purification device is an internal combustion engine.

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