JP2016164373A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of exhaust emission control performance even when the operation state of an internal combustion engine changes.SOLUTION: An exhaust emission control device captures moisture in exhaust contacting with a demister part 22 together with water-soluble gas in exhaust by the demister part 22, and thereby purifies water-soluble gas in exhaust. At that time, by adjusting temperature of the demister part 22 with a temperature adjustment part 23, even when the operation state of an internal combustion engine 10 changes, such as the phenomenon that steam concentration in exhaust from the internal combustion engine 10 is made low, and the phenomenon that exhaust temperature from the internal combustion engine 10 is made high, the exhaust emission control device can stably condense steam in exhaust by the demister part 22, and can suppress deterioration in performance of purifying water-soluble gas in exhaust.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine for purifying harmful components contained in exhaust gas from the internal combustion engine.

  As a technique for purifying harmful components contained in exhaust gas, for example, techniques disclosed in Patent Documents 1 and 2 below are known. In Patent Document 1 below, in a wet desulfurization apparatus that is brought into gas-liquid contact with an absorption liquid in order to remove sulfur oxides contained in exhaust gas, a steam pipe for blowing water vapor into a desulfurization tower body is provided. When steam is blown into the main body of the desulfurization tower, it is cooled by the surrounding gas, the steam becomes a saturated concentration at that temperature, and the excess steam condenses into droplets, and these droplets nucleate dust etc. floating in the gas. As these grow, the fine particles appear to be enlarged. When the particles become large, the droplets are likely to collide and be collected due to inertia, and the collection efficiency of dust and the like is improved.

  Further, in Patent Document 2 below, in order to remove nitrogen oxides (NOx) in the gas to be treated, NOx in the gas to be treated is subjected to ozone oxidation, and the residual NOx component in the gas to be treated after the ozone oxidation is removed. Absorbed and removed by absorption liquid. At that time, ozone is added to both the gas to be treated and the absorption liquid.

JP 7-178314 A JP2013-717A

In exhaust from internal combustion engines such as gasoline engines and diesel engines, water produced by the combustion of fuel exists as water vapor, and nitrogen oxides in the exhaust react with water (water vapor). Nitric acid (HNO ₃ ) is produced. Therefore, by absorbing water-soluble gas such as nitrogen oxide (for example, NO ₂ ) and nitric acid in exhaust gas into water condensed water vapor in the exhaust gas, water-soluble gas such as nitrogen oxide and nitric acid in exhaust gas is absorbed. It becomes possible to purify. However, when the water vapor concentration in the exhaust gas is lowered due to the air-fuel ratio of the internal combustion engine being separated from the stoichiometric air-fuel ratio, such as lean combustion with excess oxygen, the dew point temperature at which the water vapor in the exhaust gas is condensed is lowered. Further, when the exhaust temperature of the internal combustion engine increases, the saturated water vapor concentration in the exhaust increases. In the operating state of these internal combustion engines, the water vapor in the exhaust gas is less likely to condense, and the ability to purify the water-soluble gas such as nitrogen oxides and nitric acid in the exhaust gas by absorbing it in the condensed water tends to be reduced. .

  The exhaust gas purification apparatus for an internal combustion engine according to the present invention aims to suppress a decrease in exhaust gas purification performance even when the operating state of the internal combustion engine changes.

  The exhaust gas purification apparatus for an internal combustion engine according to the present invention employs the following means in order to achieve the above-described object.

  An exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a demister portion that comes into contact with exhaust gas and a temperature adjustment unit that adjusts the temperature of the demister portion in a container into which exhaust gas from the internal combustion engine flows, and contacts the demister portion. The gist of the invention is to have a temperature-adjustable demister unit that captures moisture in the exhaust gas together with the water-soluble gas in the exhaust gas in the demister section.

  In one embodiment of the present invention, it is preferable that the temperature adjusting unit adjusts the temperature of the demister unit so that the water vapor concentration in the exhaust gas flowing into the container is higher than the saturated water vapor concentration.

  In one aspect of the present invention, the water vapor concentration in the exhaust gas can be controlled by controlling the air-fuel ratio of the internal combustion engine so that the water vapor concentration in the exhaust gas flowing into the container is higher than the saturated water vapor concentration. Is preferred.

  In one embodiment of the present invention, it is preferable to have a water addition device that adds water to the exhaust gas from the internal combustion engine so that the water vapor concentration in the exhaust gas flowing into the container is higher than the saturated water vapor concentration.

  In one aspect of the present invention, the temperature adjustment unit has a water addition device for adding water to the exhaust gas from the internal combustion engine, and the priority order for making the water vapor concentration in the exhaust gas flowing into the container higher than the saturated water vapor concentration. It is preferable that the temperature is set in the order of the temperature adjustment of the demister unit by the air-fuel ratio control of the internal combustion engine, and the water addition by the water addition device.

  In one aspect of the present invention, it is preferable that the temperature adjustment type demister unit includes a cooling pipe through which a refrigerant flows as a temperature adjustment unit.

  According to the present invention, the water-soluble gas in the exhaust gas can be purified by capturing the moisture in the exhaust gas in contact with the demister portion together with the water-soluble gas in the gas exhaust gas. In that case, even if the operating state of the internal combustion engine changes, such as the water vapor concentration in the exhaust gas becomes low or the exhaust gas temperature becomes high, by adjusting the temperature of the demister unit by the temperature adjustment unit, Water vapor can be stably condensed in the demister section, and a decrease in performance for purifying water-soluble gas in the exhaust can be suppressed.

1 is a diagram showing a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. It is a figure which shows the structural example of a demister part and a temperature control part. It is a figure which shows the structural example of a demister part and a temperature control part. It is a figure which shows the relationship of the saturated water vapor | steam density | concentration with respect to temperature. It is a diagram illustrating an example of a relationship of HNO ₃ absorptance with respect to the temperature of the demister. It is a flowchart which shows an example of the process performed by the electronic control apparatus at the time of driving | operation of an internal combustion engine. It is a figure which shows the other schematic structure of the exhaust gas purification apparatus of the internal combustion engine which concerns on embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. The exhaust emission control device according to the present embodiment is mounted on a vehicle together with, for example, an internal combustion engine. An internal combustion engine (engine) 10 generates power by burning fuel in a cylinder. The internal combustion engine 10 here 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 10 is discharged into the exhaust pipe 12. The exhaust gas discharged from the internal combustion engine 10 into the exhaust pipe 12 contains harmful components such as nitrogen oxides (NOx). In this embodiment, the nitrogen oxides in the exhaust gas from the internal combustion engine 10 are removed. In order to purify the harmful components contained therein, a temperature adjustment type demister unit 20 is provided at a position downstream of the exhaust pipe 12.

  In the temperature control type demister unit 20, an inlet 21 a and an outlet 21 b are formed in the container 21. Exhaust gas discharged from the internal combustion engine 10 into the exhaust pipe 12 flows into the container 21 from the inlet 21 a. Then, it flows out of the container 21 from the outlet 21b. In the container 21, a demister unit 22 that comes into contact with the exhaust gas flowing in from the inflow port 21 a and a temperature adjusting unit 23 that adjusts the temperature of the demister unit 22 are accommodated.

  Configuration examples of the demister unit 22 and the temperature adjusting unit 23 in the container 21 are shown in FIGS. FIG. 2 shows an example of the structure per layer, and FIG. 3 shows an example of a structure in which the structure of FIG. As shown in FIG. 2, a cooling pipe 23 is provided meandering as a temperature adjusting portion, and a wire 22 is wound around the cooling pipe 23 as a demister portion and is formed in a stitch shape. A large number of structures in which the wire 22 is wound around the cooling pipe 23 are arranged along the exhaust flow direction (the direction indicated by the arrow A) in the container 21 as shown in FIG.

  2 and 3, the liquid refrigerant such as cooling water flows in the cooling pipe 23 to cool the demister part (wire) 22 in contact with the cooling pipe 23 and adjust the temperature of the demister part 22. Is done. The cooling water is stored in a cooling water storage tank 24 installed outside the container 21, supplied to the cooling pipe 23 by driving of the electric pump 25 and circulated. The cooling water amount level Lw in the cooling water storage tank 24 is monitored by the water amount level sensor 26, and the cooling water amount level Lw is maintained within a specified range by the water amount level maintaining device. The cooling water temperature Tw passing through the cooling pipe 23 is monitored by the water temperature sensor 27, and the cooling water temperature Tw is adjusted to the set temperature by the water temperature adjusting device.

In the exhaust gas discharged from the internal combustion engine 10 such as a gasoline engine or a diesel engine into the exhaust pipe 12, water generated by the combustion of the fuel exists as water vapor, and NOx in the exhaust gas is water (water vapor). ) And nitric acid (HNO ₃ ) and nitrate ions are produced. In the temperature adjustment type demister unit 20, the exhaust gas flowing into the container 21 from the inlet 21 a flows in the direction of arrow A in FIGS. 2 and 3, and is in contact with the demister section (wire) 22 between the stitch-shaped wires 22. Pass through the gap. At that time, water vapor in the exhaust is condensed to form water droplets (liquid) and adheres to the wire 22, and NOx (for example, NO ₂ ), nitric acid, nitrate ions, aldehyde, etc. are soluble in water in the exhaust. As the gas dissolves, these water-soluble gases are separated and removed from the exhaust together with the water. The water droplets in which the water-soluble gas has dissolved fall vertically downward by gravity and are stored in the aggregate liquid storage tank 28. Regarding nitric acid and nitrate ions absorbed in the water in the coagulated liquid storage tank 28, it is preferable to monitor the amount of nitric acid using a nitrate ion concentration meter, a pH meter or the like. Further, the exhaust gas that has passed through the gap between the wires 22 flows out of the container 21 from the outlet 21b. As described above, the temperature-adjusting demister unit 20 purifies the water-soluble gas in the exhaust gas by capturing the moisture in the exhaust gas that contacts the demister unit 22 together with the water-soluble gas in the exhaust gas with the demister unit 22. The configuration of the demister unit 22 may be any configuration as long as it can capture moisture in the exhaust gas, and is not limited to the configuration of FIGS. The configuration of the temperature adjustment unit 23 may be any configuration as long as the temperature of the demister unit 22 can be adjusted, and is not limited to the configuration of FIGS.

The water vapor in the exhaust gas is condensed at the dew point temperature to liquid water when the temperature is lowered, but the dew point temperature changes according to the water vapor concentration in the exhaust gas, and the dew point is reduced against the decrease in the water vapor concentration in the exhaust gas. The temperature drops. The saturated water vapor concentration in the exhaust gas changes according to the exhaust gas temperature, and as shown in FIG. 4, the saturated water vapor concentration in the exhaust gas decreases with a decrease in the exhaust gas temperature. Therefore, the ability to condense the water vapor in the exhaust gas in the demister unit 22 and absorb the water-soluble gas varies depending on the temperature of the demister unit 22 and the water vapor concentration in the exhaust gas. As an example, the relationship of the HNO ₃ absorption rate to the temperature of the demister section 22 is shown in FIG. As shown in FIG. 5, the HNO ₃ absorption rate increases as the temperature of the demister section 22 decreases.

Further, the water vapor concentration in the exhaust gas from the internal combustion engine 10 changes according to the air-fuel ratio A / F of the internal combustion engine 10. For example, the exhaust gas when combusted at the theoretical air-fuel ratio A / F = 14.7 theoretically contains about 15% of water vapor, but when the oxygen excess atmosphere is A / F = 40, it is contained in the exhaust gas. Water vapor is reduced to about 6%. Also, when the air-fuel ratio A / F is rich (smaller than the stoichiometric air-fuel ratio), the water vapor contained in the exhaust gas is reduced compared to the stoichiometric air-fuel ratio. Therefore, the dew point temperature at which the water vapor in the exhaust gas condenses changes in accordance with the air / fuel ratio A / F of the internal combustion engine 10, and the air / fuel ratio A / F moves away from the stoichiometric air / fuel ratio, for example, lean combustion with excess oxygen. As the dew point temperature decreases. When the concentration of water vapor in the exhaust gas decreases and the dew point temperature decreases, such as when the air-fuel ratio A / F moves away from the stoichiometric air-fuel ratio, the water vapor in the exhaust gas is less likely to condense in the demister section 22, and water such as HNO ₃ Sexual gas is less likely to be absorbed. In order to improve the performance of absorbing the water-soluble gas by condensing the water vapor in the exhaust gas in the demister unit 22, the water vapor concentration in the exhaust gas flowing into the container 21 becomes higher than the saturated water vapor concentration, that is, in the demister unit 22. It is desirable that a dew condensation condition is established in which the moisture in the exhaust gas that comes into contact is lower than the dew point temperature.

  Therefore, the temperature adjusting unit 23 adjusts the temperature of the demister unit 22 so that the water vapor concentration in the exhaust gas flowing into the container 21 is higher than the saturated water vapor concentration. As shown in FIG. 1, a water vapor concentration sensor 32 is attached to the exhaust pipe 12 upstream of the temperature control type demister unit 20, and the water vapor concentration D in the exhaust gas flowing into the container 21 is changed by the water vapor concentration sensor 32. Detected and input to an electronic control unit (ECU) 40. The electronic control unit 40 causes the electric pump 25 to flow through the cooling pipe 23 so that the water vapor concentration D becomes higher than the saturated water vapor concentration, that is, the demister 22 atmosphere temperature Td in the container 21 is lower than the dew point temperature. Control the coolant flow rate. The dew point temperature here can be calculated as the dew point temperature corresponding to the water vapor concentration D, and the saturated water vapor concentration here can be calculated as the saturated water vapor concentration corresponding to the demister section 22 ambient temperature Td. As for the demister unit 22 ambient temperature Td, the ambient temperature in the container 21 may be directly detected by the temperature sensor, or the coolant temperature Tw detected by the water temperature sensor 27 may be used as the temperature of the demister unit 22. It is. As a result, the water vapor concentration D in the exhaust gas flowing into the container 21 becomes higher than the saturated water vapor concentration corresponding to the demister portion 22 ambient temperature Td, that is, the water content in the exhaust gas contacting the demister portion 22 is the water vapor concentration D in the exhaust gas. The demister section 22 is cooled by the cooling pipe 23 so that the dew condensation condition lower than the dew point temperature corresponding to is established. As described above, since the water vapor concentration D in the exhaust gas has a correlation with the air-fuel ratio A / F of the internal combustion engine 10, the water vapor concentration D in the exhaust gas is detected not only directly by the water vapor concentration sensor 32 but also in the internal combustion engine. It is also possible to calculate from the air-fuel ratio A / F of the engine 10 (for example, detected by an air-fuel ratio sensor).

According to the present embodiment described above, water vapor in the exhaust is condensed in the demister section 22 and water-soluble gases such as NOx (eg, NO ₂ ), nitric acid, nitrate ions, aldehyde, etc. in the exhaust are absorbed into the condensed water. By doing so, the water-soluble gas in exhaust gas can be purified. In that case, the temperature adjustment unit 23 performs temperature adjustment (cooling) of the demister unit 22 so that the above dew condensation condition is satisfied, thereby reducing the water vapor concentration in the exhaust from the internal combustion engine 10 Even if the operating state of the internal combustion engine 10 changes, such as when the exhaust temperature from the engine 10 increases, the water vapor in the exhaust can be stably and efficiently condensed in the demister unit 22, and the water-soluble gas in the exhaust can be It is possible to suppress a decrease in the performance to be purified.

  The electronic control unit 40 controls the air-fuel ratio A / F of the internal combustion engine 10 so that the water vapor concentration D in the exhaust gas flowing into the container 21 is higher than the saturated water vapor concentration, so that the water vapor concentration in the exhaust gas is increased. It is also possible to control D. At that time, the water vapor concentration D is higher than the saturated water vapor concentration corresponding to the demister unit 22 ambient temperature Td (the moisture in the exhaust gas contacting the demister unit 22 is lower than the dew point temperature corresponding to the water vapor concentration D). The air-fuel ratio A / F of the internal combustion engine 10 is controlled so that is established. As a result, even if the operating state of the internal combustion engine 10 changes, for example, the exhaust temperature from the internal combustion engine 10 increases, the water vapor in the exhaust can be stably and efficiently condensed in the demister unit 22, A decrease in the performance of purifying water-soluble gas can be suppressed.

  Further, as shown in FIG. 1, a water addition device 34 is provided in the exhaust pipe 12 (position upstream of the water vapor concentration sensor 32), and water (water vapor) is added from the water addition device 34 to the exhaust gas in the exhaust pipe 12. Thus, the water vapor concentration D in the exhaust gas flowing into the container 21 can be adjusted. The water addition device 34 can also add water (water vapor) to the exhaust gas from the internal combustion engine 10 so that the water vapor concentration D in the exhaust gas flowing into the container 21 is higher than the saturated water vapor concentration. At that time, the electronic control unit 40 causes the water vapor concentration D to be higher than the saturated water vapor concentration corresponding to the demister unit 22 ambient temperature Td (the water content in the exhaust gas contacting the demister unit 22 is higher than the dew point temperature corresponding to the water vapor concentration D). The water vapor concentration D in the exhaust gas flowing into the container 21 is controlled by controlling the amount of water vapor added by the water addition device 34 so that the dew condensation condition is satisfied. As a result, even if the operating state of the internal combustion engine 10 changes, such as when the concentration of water vapor in the exhaust from the internal combustion engine 10 decreases or the exhaust temperature from the internal combustion engine 10 increases, the demister 22 Therefore, it is possible to stably and efficiently condense, and it is possible to suppress a decrease in the performance of purifying the water-soluble gas in the exhaust gas. The water addition device 34 may have any configuration as long as the water vapor concentration D in the exhaust gas flowing into the container 21 can be adjusted. For example, water may be sprayed into the exhaust pipe 12 with a spray nozzle or the like. Alternatively, a porous membrane type humidifier may be used.

  Further, when the internal combustion engine 10 is in operation, the electronic control device 40 can execute the processing shown in the flowchart of FIG. First, in step S101, the water vapor concentration D is higher than the saturated water vapor concentration corresponding to the demister unit 22 ambient temperature Td (the moisture in the exhaust gas contacting the demister unit 22 is lower than the dew point temperature corresponding to the water vapor concentration D). Whether or not is established is determined. When the dew condensation condition is satisfied (when the determination result in step S101 is YES), the execution of this process ends. On the other hand, when the dew condensation condition is not satisfied (when the determination result of step S101 is NO), the process proceeds to step S102.

  In step S <b> 102, the temperature adjustment (cooling) is performed so that the temperature of the demister unit 22 is decreased by controlling the flow rate of the cooling water flowing into the cooling pipe 23 by the drive control of the electric pump 25. In that case, the rotation speed of the electric pump 25 is limited to the set rotation speed or less, whereby the flow rate of the coolant flowing through the cooling pipe 23 is limited to the set flow rate or less. Next, in step S103, it is determined whether or not the above dew condensation condition is satisfied by cooling the demister section 22 under the condition that the flow rate of the coolant flowing through the cooling pipe 23 is equal to or less than the set flow rate. When the dew condensation condition is satisfied under the condition where the cooling water flow rate is equal to or lower than the set flow rate (when the determination result in step S103 is YES), the execution of this process is terminated. On the other hand, if the dew condensation condition is not satisfied even if the cooling water flow rate is increased to the set flow rate (if the determination result in step S103 is NO), the process proceeds to step S104.

  In step S104, the water vapor concentration D in the exhaust gas flowing into the container 21 is increased by controlling the air-fuel ratio A / F of the internal combustion engine 10 to approach the stoichiometric air-fuel ratio. Next, in step S105, it is determined whether or not the above dew condensation condition is satisfied by performing air-fuel ratio control of the internal combustion engine 10. When the dew condensation condition is satisfied by increasing the water vapor concentration D in the exhaust by the air-fuel ratio control of the internal combustion engine 10 (when the determination result in step S105 is YES), the execution of this process is terminated. On the other hand, if the dew condensation condition is not satisfied even when the air-fuel ratio A / F of the internal combustion engine 10 is controlled to the stoichiometric air-fuel ratio (when the determination result of step S105 is NO), the process proceeds to step S106.

  In step S <b> 106, water vapor is added to the exhaust gas in the exhaust pipe 12 by the water addition device 34, thereby increasing the water vapor concentration D in the exhaust gas flowing into the container 21. At that time, the amount of water vapor added to the exhaust gas is controlled by the water addition device 34 so that the above dew condensation condition is satisfied. Then, the execution of this process ends.

  According to the flowchart of FIG. 6, the priority order for making the water vapor concentration D in the exhaust gas flowing into the container 21 higher than the saturated water vapor concentration (making the moisture in the exhaust gas in contact with the demister unit 22 lower than the dew point temperature). The temperature adjustment of the demister unit 22 by the temperature adjustment unit 23, the air-fuel ratio control of the internal combustion engine 10, and the water addition by the water addition device 34 are set in this order. When the temperature adjusting unit (cooling pipe) 23 adjusts the temperature of the demister unit 22, if it is determined that the above dew condensation condition is not satisfied under the condition that the cooling water flow rate flowing through the cooling pipe 23 is equal to or lower than the set flow rate, the internal combustion engine By increasing the water vapor concentration D in the exhaust by controlling the air-fuel ratio of the engine 10, the power consumption of the electric pump 25 can be reduced. Then, when it is determined that the above dew condensation condition is not satisfied even when the air-fuel ratio A / F of the internal combustion engine 10 is controlled to the stoichiometric air-fuel ratio, the water vapor concentration D in the exhaust gas is increased by adding water from the water addition device 34. By increasing the amount, the amount of water required for water addition by the water addition device 34 can be suppressed.

  FIG. 7 shows another schematic configuration of the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment. In the configuration example of FIG. 7, compared to the configuration example of FIG. 1, the reformer 14 is provided at a position upstream of the water addition device 34 in the exhaust pipe 12, and upstream of the reformer 14 in the exhaust pipe 12. The heat exchanger 13 is provided at the position.

The reformer 14 includes a nitric acid generation catalyst 14a for promoting a reaction for converting nitrogen oxides to nitric acid (HNO ₃ ), and converts nitrogen oxides contained in harmful components in exhaust from the internal combustion engine 10 to nitric acid. It reforms to nitric acid on the produced catalyst 14a. The nitric acid generation catalyst 14a 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. Examples of the catalyst / support having an acid point include zeolite such as ZSM-5, BEA, MOR, SAPO, SiO ₂ / Al ₂ O ₃ , SO ₄ / TiO ₂ , SiO ₂ / TiO ₂ , WO ₃ / Composite oxides such as TiO ₂ , WO ₃ / ZrO ₂ , WO ₃ / SnO ₂ , SO ₄ / ZrO ₂ can be used. For the oxidation reaction in the reformer 14, an ozone addition valve 19 is provided at a position upstream of the reformer 14 in the exhaust pipe 12 (position between the heat exchanger 13 and the reformer 14). It has been. By injecting ozone (O ₃ ) as an oxidant from the ozone addition valve 19 toward the reforming device 14, ozone is added to harmful components in the exhaust gas flowing into the reforming device 14. In the reformer 14, nitrogen oxides such as nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) are contained in ozone (O ₃ ) added by the ozone addition valve 19 and exhaust from the internal combustion engine 10. By contacting the nitric acid generation catalyst 14a together with moisture, it is oxidized and reformed to nitric acid (HNO ₃ ). Exhaust gas containing harmful components converted into nitric acid is supplied to the temperature-controlled demister unit 20 on the downstream side.

  In order to generate ozone added to harmful components flowing into the reformer 14, an ozone generator 18 is provided, and the ozone generated by the ozone generator 18 passes through the ozone conduit 17 to add ozone. The fuel is injected from the valve 19 toward the reformer 14. In the ozone generator 18, ozone may be produced by any method, and examples thereof include a water electrolysis device and plasma discharge. In particular, the use of a water electrolysis device makes it possible to generate and supply ozone having a high concentration and high purity, which is advantageous in terms of efficiency, cost, space, and the like. A water electrolysis device is a device that generates ozone and hydrogen by electrolysis of water, and decomposes water on the anode side separated by a cation exchange membrane to generate ozone, while positively generating on the cathode side. Hydrogen gas is generated from hydrogen ions that have passed through the ion membrane. About the water used for electrolysis with a water electrolysis apparatus, it is also possible to supply from the outside, and it is also possible to collect | recover and supply the water in exhaust_gas | exhaustion.

  The heat exchanger 13 provided on the upstream side of the reformer 14 adjusts the temperature of the exhaust gas flowing into the reformer 14 by exchanging heat with the exhaust gas from the internal combustion engine 10. As a result, the temperature of the nitric acid generation catalyst 14a in contact with the exhaust is adjusted. For example, by supplying a refrigerant to the heat exchanger 13 and cooling the exhaust from the internal combustion engine 10, the temperature of the exhaust flowing into the reformer 14 can be lowered, and the temperature of the nitric acid generation catalyst 14a can be lowered. . Thus, the heat exchanger 13 functions as a temperature adjusting device for adjusting the temperature of the nitric acid generation catalyst 14a. In addition, when the temperature of the nitric acid generation catalyst 14a increases, ozone used to generate nitric acid is easily decomposed and the generated nitric acid is easily returned to nitrogen oxides by a reverse reaction. Therefore, the heat exchanger 13 changes the temperature of the nitric acid generation catalyst 14a by heat exchange with the exhaust from the internal combustion engine 10 so that the temperature of the nitric acid generation catalyst 14a is maintained at 350 ° C. or lower (more preferably 300 ° C. or lower). It is preferable to adjust. For example, when the temperature of the nitric acid generation catalyst 14a detected by the temperature sensor exceeds 350 ° C. (more preferably 300 ° C.), the refrigerant is supplied to the heat exchanger 13 to reduce the temperature of the exhaust gas that contacts the nitric acid generation catalyst 14a. The temperature of the nitric acid generation catalyst 14a is preferably lowered to 350 ° C. or lower (more preferably 300 ° C. or lower).

  According to the configuration example of FIG. 7, the nitrogen oxide in the exhaust gas is converted into nitric acid before being absorbed and captured by the demister unit 22, thereby greatly improving the absorption rate in water. And the purification rate of nitrogen oxides can be further improved. Furthermore, nitric acid can be continuously produced on the nitric acid production catalyst 14a at a high reaction rate by bringing the nitrogen oxides into contact with the nitric acid production catalyst 14a having an acid point together with ozone and water.

However, as the coexisting gas of NOx, when unsaturated hydrocarbons (olefins) such as propylene (C ₃ H ₆ ) and ethylene (C ₂ H ₄ ) and aromatic hydrocarbons coexist, these hydrocarbons and O _Since the reactivity of ₃ is high, O ₃ is consumed in the reaction with these hydrocarbons, and the amount of O ₃ used in the HNO ₃ production reaction decreases. Accordingly, in the configuration example of FIG. 7, an oxidation catalyst 16 is further provided at a position upstream of the reformer 14 and the heat exchanger 13 in the exhaust pipe 12. The oxidation catalyst 16 includes hydrocarbons (THC) contained in the exhaust gas from the internal combustion engine 10, particularly unsaturated hydrocarbons (olefins) such as propylene (C ₃ H ₆ ) and ethylene (C ₂ H ₄ ), and aromatics. Is oxidized to water (H ₂ O) and carbon dioxide (CO ₂ ), and carbon monoxide (CO) contained in the exhaust gas is oxidized to carbon dioxide (CO ₂ ). Further, the oxidation catalyst 16 oxidizes nitrogen monoxide (NO) contained in the exhaust from the internal combustion engine 10 to nitrogen dioxide (NO ₂ ).

According to the configuration example of FIG. 7, unsaturated hydrocarbons and aromatic hydrocarbons contained in the exhaust gas are oxidized and removed by the oxidation catalyst 16 on the upstream side of the reformer 14, so that they react with these hydrocarbons. Thus, consumption of O ₃ can be suppressed, and a decrease in the amount of O ₃ used in the HNO ₃ production reaction in the reformer 14 can be suppressed. Further, the NO contained in the exhaust is oxidized to NO ₂ by the oxidation catalyst 16 upstream of the reformer 14, thereby suppressing the decrease in the amount of O ₃ used for the HNO ₃ generation reaction in the reformer 14. can do. Therefore, it is possible to suppress a decrease in the NOx purification rate without increasing the amount of ozone added.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

  DESCRIPTION OF SYMBOLS 10 Internal combustion engine, 12 Exhaust pipe, 13 Heat exchanger, 14 Reformer, 14a Nitric acid production catalyst, 16 Oxidation catalyst, 17 Ozone conduit, 18 Ozone generator, 19 Ozone addition valve, 20 Temperature control type demister unit, 21 Container 21a Inlet, 21b Outlet, 22 Demister section (wire), 23 Temperature adjusting section (cooling pipe), 24 Cooling water storage tank, 25 Electric pump, 26 Water level sensor, 27 Water temperature sensor, 28 Condensate storage tank, 32 Water vapor concentration sensor, 34 Water addition device, 40 Electronic control device.

Claims (6)

An exhaust purification device for an internal combustion engine,
A vessel into which exhaust from the internal combustion engine flows is provided with a demister portion that comes into contact with the exhaust and a temperature adjustment unit that adjusts the temperature of the demister portion, and water in the exhaust that comes into contact with the demister is removed from the water-soluble gas in the exhaust. An exhaust gas purification apparatus for an internal combustion engine having a temperature adjustment type demister unit that is captured by the demister unit. An exhaust emission control device for an internal combustion engine according to claim 1,
The temperature adjusting unit adjusts the temperature of the demister unit so that the water vapor concentration in the exhaust gas flowing into the container is higher than the saturated water vapor concentration. An exhaust emission control device for an internal combustion engine according to claim 1 or 2,
An exhaust gas purification apparatus for an internal combustion engine in which the water vapor concentration in the exhaust gas is controlled by controlling the air-fuel ratio of the internal combustion engine so that the water vapor concentration in the exhaust gas flowing into the container is higher than the saturated water vapor concentration. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3,
An exhaust gas purification apparatus for an internal combustion engine having a water addition device for adding water to the exhaust gas from the internal combustion engine so that the water vapor concentration in the exhaust gas flowing into the container is higher than the saturated water vapor concentration. An exhaust emission control device for an internal combustion engine according to claim 1,
A water addition device for adding water to the exhaust from the internal combustion engine;
Priorities for making the water vapor concentration in the exhaust gas flowing into the vessel higher than the saturated water vapor concentration are set in the order of temperature adjustment of the demister unit by the temperature adjustment unit, air-fuel ratio control of the internal combustion engine, and water addition by the water addition device. An exhaust purification device for an internal combustion engine. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 5,
The temperature adjustment type demister unit is an exhaust gas purification apparatus for an internal combustion engine, which includes a cooling pipe through which a refrigerant flows as a temperature adjustment unit.