JP5625627B2 - Ammonia storage device and selective catalytic reduction system - Google Patents

Description

  The present invention relates to an ammonia storage device and a selective catalytic reduction system, and in particular, an ammonia storage device for using the stored ammonia as a reducing agent for NOx in exhaust gas from a diesel vehicle, and a selection comprising the ammonia storage device Relates to a catalytic catalytic reduction system.

  Diesel vehicles have good fuel efficiency, but reducing NOx emissions is one of the major challenges.

  However, since exhaust gas from diesel vehicles has a high oxygen content, it is difficult to decompose and remove NOx by catalytic reduction using a three-way catalyst used in ordinary gasoline vehicles.

  Therefore, a selective catalytic reduction (SCR) type exhaust gas purification system (SCR system) is generally used to remove NOx from the exhaust gas of diesel vehicles.

  In the SCR system, ammonia is generally used for NOx reduction, but liquefied ammonia, aqueous ammonia solution, and aqueous urea solution are usually used as the ammonia source.

  The SCR system using liquefied ammonia as an ammonia source has a potential danger and a problem of ammonia leakage due to filling and using ammonia in a high-pressure vessel. The SCR system using an aqueous ammonia solution as an ammonia source does not have the danger of using a high-pressure vessel, but the problem of ammonia leakage remains.

  In an SCR system that uses an aqueous urea solution as an ammonia source, urea is decomposed by injecting the aqueous urea solution into a high-temperature exhaust gas to generate ammonia. There is no serious danger or leakage of ammonia. Therefore, in recent years, an aqueous urea solution is generally used as an ammonia source.

  However, the SCR system using an aqueous urea solution as an ammonia source has several problems as described below.

  In an SCR system, about 30% by weight urea aqueous solution is usually used, and in this SCR system, water occupies about 70% of the capacity of a container for storing urea aqueous solution.

Further, in an SCR system using an aqueous urea solution as an ammonia source, urea is hydrolyzed with water in the aqueous urea solution to generate ammonia, but urea has a chemical structure represented by the chemical formula CO (NH ₂ ) ₂ . When urea is hydrolyzed, two molecules of ammonia and one molecule of carbon dioxide are produced. Therefore, ammonia generated by hydrolysis of urea is only about 50% by weight of urea, and therefore the ratio of ammonia generated by hydrolysis of urea aqueous solution to only about 15% by weight is liquefied ammonia as an ammonia source. This is lower than the weight ratio of the ammonia actually used to the ammonia source when using ammonia or when using aqueous ammonia.

  The SCR system also requires an injection system for injecting an aqueous urea solution into the exhaust gas. Furthermore, since the urea aqueous solution is frozen at a temperature of −11 ° C. or lower, it is necessary to consider that the urea aqueous solution does not freeze when it is extremely cold.

（但し、Ｍは、アルカリ土類金属および／または、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、およびＺｎからなる群から選択されるカチオンであり、
Ｘは、１つ以上のアニオンであり、
ａは、単位塩分子１個当りのカチオン数であり、
Ｚは、単位塩分子１個当りのアニオン数であり、
ｎは、２〜１２の配位数である。）
で示されるイオン塩を含有するアンモニア貯蔵および移送用材料が考案された（特許文献１） So the following general formula:

(However, M is an alkaline earth metal and / or a cation selected from the group consisting of Mn, Fe, Co, Ni, and Zn,
X is one or more anions,
a is the number of cations per unit salt molecule,
Z is the number of anions per unit salt molecule,
n is a coordination number of 2-12. )
A material for storing and transporting ammonia containing an ionic salt represented by the above has been devised (Patent Document 1).

Special table 2008-508186

  Since the ammonia storage and transfer material is solid at room temperature both in a state where ammonia is occluded and in a state where ammonia is released, compared with the case where liquefied ammonia is used as an ammonia source or when ammonia water is dropped, It is unnecessary and has high safety.

  However, since the material for storing and transporting ammonia has a low bulk specific gravity of about 0.1, it needs to be compressed into a tablet by using a press or the like in order to use it in an SCR system. However, there is a possibility that ammonia that is harmful to the human body is generated during work due to decomposition of the above materials due to heat generated by the press machine and released to the outside. The possibility that ammonia is generated and released is considered to be remarkable at high temperatures such as in summer.

  The present invention has been made to solve the above problems, and unlike the SCR system using liquefied ammonia as an ammonia source, there is no danger due to the use of a high-pressure vessel, and there is no leakage of ammonia during handling. It is an object of the present invention to provide an ammonia storage device that is free of danger and an SCR system that uses the ammonia storage device.

According to a first aspect of the present invention, ammonia is occluded, and the occluded ammonia is released by heating, and the ammonia occlusion material whose volume increases at the time of occlusion of ammonia, the ammonia occlusion material, and the ammonia occlusion material An ammonia storage tank in which the internal volume of the portion to be stored is smaller than the free volume of the ammonia storage material when storing ammonia, an ammonia introduction path for introducing ammonia into the ammonia storage tank, and ammonia stored in the ammonia storage tank Accommodated in the ammonia occlusion tank, an ammonia deriving path for deriving the ammonia released from the occlusion material to the outside, a porous filter provided in a communication portion of the ammonia occlusion tank with the ammonia introduction path and the ammonia egress path Added ammonia storage material Comprising heating means for the wall surfaces of the ammonia storage tank is a double structure composed of inner and outer walls, when allowed to absorb ammonia to the ammonia absorber is between the inner and outer walls of the ammonia storage tank The present invention relates to an ammonia occlusion device that circulates a cooling fluid in the space .

In the ammonia storage device, the ammonia storage material expands when ammonia is stored. The internal volume of the portion of the ammonia storage tank in which the ammonia storage material is stored is smaller than the volume of the ammonia storage material when ammonia is stored in free space, and the ammonia storage material in the ammonia storage tank is stored. A porous filter is disposed between the portion and the ammonia introduction path and the ammonia extraction path. Therefore, since the ammonia storage material expanded by storing ammonia has no escape, the volume difference between the internal volume of the ammonia storage material in the ammonia storage tank and the free volume of the ammonia storage material at the time of ammonia storage. Compressed by the amount, the bulk density of the ammonia occlusion material becomes higher than when ammonia is occluded in a free state. Therefore, the ammonia storage amount per unit volume can be increased as compared with the case where ammonia is stored in the ammonia storage material in a free state. For this reason, since the ammonia storage device as a whole can be made compact, the mountability to an automobile is improved.

Further, since the ammonia occlusion material is automatically compressed by occlusion of ammonia, it is not necessary to compress the ammonia occlusion material occluded with ammonia by a press or the like and then store it in the ammonia occlusion tank. Therefore, it is not necessary to put the ammonia occlusion material that occludes ammonia into and out of the ammonia occlusion tank, and therefore it is possible to prevent leakage of ammonia due to the ammonia occlusion material being taken in and out of the ammonia occlusion tank.

Further, since the ammonia storage material generates heat when storing ammonia, it is necessary to cool the ammonia storage material in order to store a large amount of ammonia. Since the cooling fluid is circulated through the space between the inner wall and the outer wall to cool the ammonia storage material, more ammonia can be stored compared to an ammonia storage device that does not cool the ammonia storage material.

  In the ammonia storage device, for example, cooling water can be used as the cooling fluid, and a heater can be used as the heating means.

According to a second aspect of the present invention, ammonia is occluded, and the occluded ammonia is released by heating, and the ammonia occlusion material that increases in volume at the time of occlusion of ammonia, the ammonia occlusion material, and the ammonia occlusion material An ammonia storage tank in which the internal volume of the portion to be stored is smaller than the free volume of the ammonia storage material when storing ammonia, an ammonia introduction path for introducing ammonia into the ammonia storage tank, and ammonia stored in the ammonia storage tank Accommodated in the ammonia occlusion tank, an ammonia deriving path for deriving the ammonia released from the occlusion material to the outside, a porous filter provided in a communication portion of the ammonia occlusion tank with the ammonia introduction path and the ammonia egress path Added ammonia storage material Heating means, and the wall surface of the ammonia storage tank has a double structure consisting of an inner wall and an outer wall, and when releasing ammonia from the ammonia storage material, between the inner wall and the outer wall of the ammonia storage tank The present invention relates to an ammonia storage device that evacuates the space.

Since the ammonia storage material absorbs heat when releasing ammonia, it is necessary to heat the ammonia storage means with a heating means when releasing ammonia. In the ammonia storage device of the second aspect, when releasing ammonia, the space between the inner wall and the outer wall of the ammonia storage tank is evacuated, so the ammonia storage device does not have the space, Even if the ammonia storage tank has the space, heat from the heating means is more efficient because heat dissipation from the wall surface of the ammonia storage tank is suppressed compared to an ammonia storage device that does not evacuate the space when ammonia is released. Is transferred to the ammonia storage material.

According to a third aspect of the present invention, in the ammonia storage device of the first aspect, when ammonia is released from the ammonia storage material, the space between the inner wall and the outer wall of the ammonia storage tank is evacuated.

Since the ammonia storage material absorbs heat when releasing ammonia, it is necessary to heat the ammonia storage means with a heating means when releasing ammonia. In the ammonia storage device of the third aspect, when ammonia is released, the space between the inner wall and the outer wall of the ammonia storage tank is evacuated.

  Therefore, in the ammonia storage device of the first aspect, heat radiation from the wall surface of the ammonia storage tank can be suppressed as compared with the case where the space is not evacuated when ammonia is released. Heat from the heating means is more efficiently transferred to the ammonia storage material.

A fourth aspect of the present invention relates to an ammonia storage device in which the inside of the ammonia storage tank is divided into a plurality of chambers by porous partition walls.

In the ammonia storage device, the inside of the ammonia storage tank is divided into a plurality of chambers by the porous partition walls, so that the ammonia storage passage is inside the ammonia storage tank in a state where the ammonia storage material is accommodated in the ammonia storage tank. Can be secured. Therefore, ammonia can be occluded and released more quickly than in the case where the inside of the ammonia occlusion tank is not divided into a plurality of chambers by the porous partition walls.

Further, since the strength of the ammonia storage tank is improved by being divided into a plurality of chambers by the porous partition wall, the ammonia storage material absorbs ammonia and expands, so that the wall of the ammonia storage tank is expanded. Safety against the outward stress that occurs is improved.

Further, as the porous partition wall, a ceramic porous body and a metal porous body are used. However, when a metal porous body is used, the thermal conductivity of the metal porous body is high, and the porous partition wall and the ammonia storage material Since the contact area is large, the heat from the heating means can be quickly transferred to the entire ammonia storage material. Therefore, ammonia can be released more rapidly.

A fifth aspect of the present invention relates to an ammonia occlusion device that circulates exhaust gas from a diesel engine in a space between an inner wall and an outer wall of the ammonia occlusion tank when releasing ammonia from the ammonia occlusion material .

In the ammonia storage device, when the ammonia is released, the exhaust gas from the diesel engine is circulated through the space between the inner wall and the outer wall of the ammonia storage tank, so that the ammonia storage material can be heated by the heat of the exhaust gas. . Therefore, the load on the heating means can be reduced. Further, when the ammonia storage material can be sufficiently heated only by heating with the exhaust gas, the space itself can function as a heating means.

According to a sixth aspect of the present invention, the ammonia storage material is selected from strontium chloride, calcium chloride, and magnesium chloride. A seventh aspect of the present invention is an ammonia storage device in which the ammonia storage material is magnesium chloride. About.

  In addition to magnesium chloride, compounds that increase in volume when ammonia is occluded include strontium chloride and calcium chloride. However, strontium chloride and calcium chloride release ammonia at a temperature close to room temperature, and handling is dangerous.

On the other hand, the magnesium chloride used in the ammonia storage device of the seventh aspect releases ammonia at a higher temperature, not at a temperature close to room temperature like strontium chloride or calcium chloride. Therefore, even when the ammonia lead-out path is accidentally opened while left at room temperature, ammonia is hardly released unless the heating means is operated.

According to an eighth aspect of the present invention, there is provided an ammonia storage device according to the first to seventh embodiments, an ammonia injection device for injecting ammonia released from the ammonia storage device into exhaust gas from a diesel engine, and the exhaust gas. A selective reduction catalytic converter that holds a catalyst for reacting introduced ammonia with NOx contained in the exhaust gas and into which the exhaust gas supplied with ammonia by the ammonia injection device is introduced; It relates to a reduction system.

In the selective catalytic reduction system, that is, the SCR system, ammonia is stored in the ammonia storage device in advance, and ammonia is released from the ammonia storage device that stores the ammonia, which is discharged from the diesel engine by the ammonia introduction means. By introducing the exhaust gas into the catalyst portion, NOx in the exhaust gas reacts with ammonia and is finally decomposed into water and nitrogen.

According to the first aspect of the present invention, a large amount of ammonia can be occluded and released while being more compact, so that it can be easily mounted on an automobile and the ammonia occlusion material occluded with ammonia can be occluded. Since the operation of taking out from the tank and pressing it is unnecessary, a highly safe ammonia storage device is provided.

Also, unlike the ammonia storage device in which the wall surface of the ammonia storage tank does not have a double structure, ammonia can be stored more rapidly by circulating a cooling fluid through the section formed on the wall surface. An occlusion device is provided.

According to the second aspect of the present invention, the ammonia storage agent is more efficient in the heat from the heating means compared to the ammonia storage device that does not evacuate the space between the outer wall and the inner wall of the ammonia storage tank when ammonia is released. Energy transmitted to the heating means can be saved. In addition, an ammonia storage device capable of more rapid ammonia release is provided.

According to the third aspect of the present invention, in the ammonia storage device of the first aspect, the heat from the heating means compared to the case where the space between the outer wall and the inner wall of the ammonia storage tank is not evacuated when ammonia is released. Is more efficiently transmitted to the ammonia storage agent, so that energy input to the heating means can be saved. In addition, an ammonia storage device capable of more rapid ammonia release is provided.

According to the fourth aspect of the present invention, it is possible to occlude and release ammonia more rapidly than an ammonia occlusion device that does not have a porous partition wall, and the ammonia occlusion tank has an expansion pressure against the ammonia occlusion material. An ammonia storage device with high strength is provided.

According to the fifth aspect of the present invention, the heat from the heating means is more efficiently converted into the ammonia storage agent as compared to the ammonia storage device that does not circulate the exhaust gas in the space between the outer wall and the inner wall of the ammonia storage tank. Since it is transmitted, energy input to the heating means can be saved. In addition, an ammonia storage device capable of more rapid ammonia release is provided.

The sixth aspect of the present invention is an example of the ammonia storage material used in the present invention. According to the seventh aspect of the present invention, strontium chloride or calcium chloride is used as the ammonia storage material. Unlike the ammonia storage device, even if the ammonia lead-out path is accidentally opened, ammonia is hardly released unless the heating means is operated, and a highly safe ammonia storage device is provided.

According to the eighth aspect of the present invention, the safety is far superior to the SCR system using liquefied ammonia as the ammonia source, and the tank is compared with the SCR system using ammonia water or urea as the ammonia source. An SCR system is provided that can occlude and release more ammonia per volume.

FIG. 1 is a schematic cross-sectional view taken along the longitudinal direction showing the configuration of the ammonia storage device according to the first embodiment. FIG. 2 is an explanatory diagram showing that the ammonia occlusion material that occludes ammonia in the ammonia occlusion apparatus according to Embodiment 1 is automatically compressed in the ammonia occlusion tank. FIG. 3 is a schematic cross-sectional view taken along the longitudinal direction showing the configuration of the ammonia storage device according to the second embodiment. FIG. 4 is a cross-sectional view showing a cross section of the ammonia storage device according to Embodiment 2 cut along a plane XX in FIG. 3. FIG. 5 is a schematic cross-sectional view taken along the longitudinal direction showing the configuration of the ammonia storage device according to the third embodiment. FIG. 6 is a schematic cross-sectional view taken along the longitudinal direction showing the configuration of the ammonia storage device according to the fourth embodiment. FIG. 7 is a block diagram illustrating a configuration of the SCR system according to the fifth embodiment. FIG. 8 is a graph showing changes in the amount of ammonia stored when the mass of magnesium chloride as the ammonia storage material in Example 1 is changed. FIG. 9 is a graph showing the change in the amount of occluded ammonia when the filtration capacity of the porous filter is changed in Example 2. FIG. 10 is a graph showing changes in the ammonia occlusion rate when the filtration capacity of the porous filter is changed in Example 2. FIG. 11 shows the amount of ammonia released per kg and 1 liter of ammonia storage material in Comparative Example 3 using magnesium chloride as the ammonia storage material, and urea water (Comparative Example 1) or ammonia water (Comparative Example 2) as the ammonia source. It is a table | surface which shows the comparison of the amount of ammonia discharge | released per 1kg of ammonia sources when 1 is used, and 1 liter.

1. Embodiment 1
Hereinafter, an example of the ammonia storage device of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an ammonia storage device 1 according to Embodiment 1 includes an ammonia storage tank 11 that stores an ammonia storage material 10, and an ammonia introduction pipe 12 that serves as an ammonia introduction path for introducing ammonia into the ammonia storage tank 11. And an ammonia lead-out line 13 as an ammonia lead-out path for leading ammonia to the outside from the ammonia storage tank, and a portion communicating with the ammonia introduction pipe 12 and the ammonia lead-out line 13 inside the ammonia storage tank 11. A porous filter 14 and a heater 15 as a heating means for heating the ammonia storage material 10 accommodated in the ammonia storage tank 11 are provided.

  An open / close valve 16 and an open / close valve 17 are respectively provided in the ammonia introduction pipe line 12 and the ammonia lead-out pipe line 13 so as to be opened and closed.

  The ammonia storage material 10 is stored in a space 11 </ b> B between the bottom surface 11 </ b> A and the porous filter 14 in the ammonia storage tank 11. The internal volume of the space 11B is set smaller than the volume when the ammonia occlusion material occludes ammonia in a free space.

  As the ammonia storage material 10, a material whose volume increases when ammonia is stored is used. Specifically, magnesium chloride is used. Other compounds that increase in volume when ammonia is occluded include calcium chloride and strontium chloride. When ammonia is occluded in these compounds, ammonia is released at a temperature close to room temperature. Is inappropriate. In contrast, magnesium chloride occluded with ammonia does not release ammonia at room temperature, but is released only when heated to a temperature of 150 ° C. to 200 ° C., and therefore is preferable as the ammonia occlusion material 10.

The bulk density of the ammonia storage material 10 is preferably 0.4 to 1.3 g / cm ³ , particularly preferably 0.6 to 1.3 g / cm ³ in the state of being stored in the ammonia storage tank 11. The particle size is preferably about 10 to 200 μm.

  The porous filter 14 preferably has a filtration capacity of 2 to 90 μm. Here, the filtration capacity of the porous filter 14 can be expressed as the minimum value of the diameter of the particles that can be blocked by the porous filter 14.

  Hereinafter, the operation of the ammonia storage device 1 of Embodiment 1 will be described. As shown in FIG. 2 (A), the volume of the ammonia storage material before storing ammonia is smaller than the internal volume of the space 11B in the ammonia storage tank.

  When the on-off valve 16 is opened and ammonia is supplied from the ammonia introduction pipe 12 to the ammonia storage tank 11, the ammonia storage material 10 stores the supplied ammonia and expands. However, since the ammonia storage material 10 cannot pass through the porous filter 14 provided in the ammonia storage tank 11, it cannot expand beyond the internal volume of the space 11B as shown in FIG.

  Therefore, the volume when ammonia is occluded in the ammonia occlusion material 10 without compression, that is, the volume when ammonia is occluded in the ammonia occlusion material in free space, in other words, when the ammonia occlusion material occludes ammonia. The ammonia storage material is compressed by the difference ΔV between the free volume V1 (see FIG. 2C) and the internal volume V2 of the space 11B in the ammonia storage tank 11.

  Therefore, although the internal volume V2 of the space 11B in the ammonia storage tank 11 is set smaller than the free volume V1 when ammonia is stored in the ammonia storage material, it is the same as that stored in the free space. A certain amount of ammonia can be occluded.

  When the amount of ammonia stored in the ammonia storage material 10 reaches the saturation amount, the on-off valve 16 is closed, the ammonia introduction path 12 is closed, and the introduction of ammonia is terminated.

  When the ammonia occluded in the ammonia occlusion material 10 is released, the on-off valve 17 is opened to open the ammonia outlet line 13 and the heater 15 is energized to heat the ammonia occlusion material 10. When the ammonia storage material 10 is heated to, for example, 150 to 200 ° C., release of the stored ammonia is started. The released ammonia is released through the ammonia outlet line 13.

  In the ammonia storage device 1 of the first embodiment, as described above, the internal volume V2 of the space 11B of the ammonia storage tank 11 is set to be smaller than the free volume V1 when ammonia is stored in the ammonia storage material. Nevertheless, the ammonia storage material 10 can store the same amount of ammonia as that stored in the free space. Therefore, although it can be made compact, the ammonia occlusion amount is large, so that it can be mounted on a diesel vehicle.

  When ammonia is stored in the ammonia storage material 10, the ammonia storage material 10 is automatically pressed by the wall surface of the ammonia storage tank 11 or the porous filter 14 if the ammonia storage material 10 tries to expand beyond the internal volume V <b> 2 of the space 11 </ b> B. Compressed. Therefore, the operation of pressing the ammonia storage material 10 storing the ammonia and then storing it in the ammonia storage tank 11 is unnecessary, so that leakage of ammonia accompanying the operation is prevented and the safety is high.

  Further, the ammonia storage device 1 can be constituted by the ammonia storage tank 11, the porous filter 14, the ammonia introduction pipe 12, the ammonia lead-out pipe 13, and the heater 15, so that the configuration is simple.

2. Embodiment 2
Hereinafter, another example of the ammonia storage device of the present invention will be described with reference to the drawings.
As shown in FIGS. 3 and 4, the ammonia storage device 2 according to the second embodiment includes an ammonia storage tank 11 that stores the ammonia storage material 10, and ammonia introduction as an ammonia introduction path that introduces ammonia into the ammonia storage tank 11. The pipe 12, the ammonia lead-out line 13 as an ammonia lead-out path for deriving ammonia from the ammonia storage tank to the outside, and the part that communicates with the ammonia introduction pipe 12 and the ammonia lead-out pipe 13 inside the ammonia storage tank 11 A porous filter 14 provided, and a heater 15 as a heating means for heating the ammonia storage material 10 accommodated in the ammonia storage tank 11 are provided.

  The inside of the ammonia storage tank 11 is divided into a plurality of small chambers 11C by a porous partition wall 20 extending in the longitudinal direction, and the ammonia storage material 10 is accommodated in the small chamber 11C. The porous partition 20 may be formed from an aggregate of porous cylinders 18 as shown in FIG. 4 (A), or may be formed in a honeycomb shape as shown in FIG. 4 (B). Good.

  The material of the porous partition 20 is not particularly limited as long as it can withstand the heating by the heater 15, but a ceramic porous body and a metal porous body are preferable, and a metal porous body is particularly preferable in terms of high thermal conductivity.

  The porous partition 20 preferably has a filtration capacity of 2 to 90 μm. The filtering ability is as described in the first embodiment.

  Although the heater 15 is arrange | positioned at the bottom part of the ammonia storage tank 11, it is not limited to this, For example, what was integrated in the porous body inside may be used.

  Regarding the points other than the above, the ammonia storage device 2 has the same configuration as the ammonia storage device 1 of the first embodiment. Therefore, the ammonia storage material 10, the ammonia storage tank 11, the ammonia introduction pipe line 12, the ammonia lead-out pipe line 13, and the porous filter 14 are as described in the first embodiment.

  In addition to the features of the ammonia storage device of the first embodiment, the ammonia storage device 2 of the second embodiment has a structure in which the porous partition wall 20 becomes an ammonia passage when storing and releasing ammonia. It has the feature that it can be done quickly.

  In addition, since the space 11B is divided into a plurality of small chambers 11C by the porous partition wall 20, the ammonia storage tank 11 has a higher strength against the expansion pressure of the ammonia storage material 10.

3. Embodiment 3
Hereinafter, another example of the ammonia storage device of the present invention will be described with reference to the drawings.
As shown in FIG. 5, in the ammonia storage device 3 according to the third embodiment, the wall surface other than the bottom surface 11 </ b> A of the ammonia storage tank 11 has a double structure of an outer wall 112 and an inner wall 111. The space between is a cooling water passage 21 which is a cooling water passage as a cooling fluid. The bottom surface 11A of the ammonia storage tank 11 may also have a double structure of an outer wall and an inner wall.

  The cooling water passage 21 is connected to a cooling water introduction conduit 22 through which cooling water is introduced and a cooling water outlet conduit 23 through which the cooling water is derived. The cooling water introduction conduit 22 and the cooling water outlet conduit 23 can be opened and closed by an on-off valve 24 and an on-off valve 25, respectively.

  Regarding the points other than the above, the ammonia storage device 3 has the same configuration as the ammonia storage device 1 of the first embodiment. Therefore, the ammonia storage material 10, the ammonia storage tank 11, the ammonia introduction pipe 12, the ammonia discharge pipe 13, the porous filter 14, and the heater 15 are as described in the first embodiment.

  In the ammonia occlusion device 3, when the ammonia occlusion material 10 occludes ammonia, the on-off valve 24 and the on-off valve 25 are opened to allow cooling water to flow through the cooling water passage 21, and the ammonia occlusion material 10 occludes ammonia. Remove generated heat.

  On the other hand, when desorbing the ammonia stored in the ammonia storage material 10, the inside of the cooling water passage 21 is evacuated, and then the on-off valve 24 and the on-off valve 25 are closed to maintain the inside of the cooling water passage 21. In this state, the heater 15 is energized to heat the ammonia storage material 10, thereby preventing the heat from the heater 15 from escaping from the wall surface of the ammonia storage tank 11 to the outside.

  The ammonia occlusion device 3 cools the inside of the ammonia occlusion tank 11 by circulating cooling water through the cooling water channel 21 during occlusion of ammonia, and evacuates the heat from the heater by evacuating the inside of the cooling water channel 21 when ammonia is released. Therefore, the energy stored in the heating means can be saved as compared with that of the one-soup structure in the wall of the ammonia storage tank 11. In addition, it has a feature that ammonia can be stored and released more quickly.

4). Embodiment 4
Hereinafter, another example of the ammonia storage device of the present invention will be described with reference to the drawings.
As shown in FIG. 6, the ammonia storage device 4 according to the fourth embodiment is similar to the ammonia storage device 3 according to the third embodiment in that the wall surfaces other than the bottom surface 11 </ b> A of the ammonia storage tank 11 are formed between the outer wall 112 and the inner wall 111. It has a double structure. The space between the outer wall 112 and the inner wall 111 is a flow path for cooling water as a cooling fluid, and a cooling heating flow path 30 that is a flow path for diesel engine exhaust gas as a heating fluid. Has been.

  A pipe 31 is connected to one end of the cooling / heating flow path 30, and a pipe 32 is connected to the other end.

  Regarding the points other than the above, the ammonia storage device 3 has the same configuration as the ammonia storage device 1 of the first embodiment. Therefore, the ammonia storage material 10, the ammonia storage tank 11, the ammonia introduction pipe 12, the ammonia discharge pipe 13, the porous filter 14, and the heater 15 are as described in the first embodiment.

  In the ammonia occlusion device 4, when the ammonia occlusion material 10 occludes ammonia, the cooling water is introduced from the conduit 31 to the cooling heating passage 30, and this cooling water is led out from the conduit 32, thereby storing the ammonia. The heat generated when the material 10 occludes ammonia is removed.

  On the other hand, when releasing ammonia, the exhaust gas of the diesel engine is supplied from the pipe line 32 to the cooling heating flow path 30 to heat the inside of the ammonia storage tank 11 and from the ammonia storage material stored in the inside. Promotes the release of ammonia.

  The ammonia occlusion device 4 cools the inside of the ammonia occlusion tank 11 by flowing cooling water through the cooling / heating channel 30 during occlusion of ammonia, and exhaust gas discharged from the diesel engine into the cooling / heating channel 30 during ammonia release. Since the inside of the ammonia storage tank 11 is heated through circulation, ammonia can be stored more quickly compared to an ammonia storage device that does not cool and heat the ammonia storage tank 11. The load on the heater 15 is reduced. When the temperature of the exhaust gas is high or the flow rate of the exhaust gas is large, the ammonia storage material 10 is sufficiently heated only by the heat of the exhaust gas, so that the heating of the ammonia storage material 10 by the heater 15 becomes unnecessary.

  The example in which the ammonia introduction pipe 12 and the ammonia lead-out pipe 13 are provided as separate pipes has been described above. However, in the ammonia storage tank of the present invention, one ammonia introduction pipe and one ammonia lead-out pipe are provided. Needless to say, the pipe may be used in combination.

5. Embodiment 5
Hereinafter, the SCR system which is an example of the selective catalytic reduction system of this invention is demonstrated using drawing. As shown in FIG. 7, the SCR system 5 of Embodiment 5 includes an oxidation catalyst converter 51 provided on the exhaust system 50 of the diesel engine 200 and an SCR catalyst provided on the downstream side of the oxidation catalyst converter 51 in the exhaust system 50. Converter 52, slip catalytic converter 53 provided on the downstream side of SCR catalytic converter 52, ammonia injection device 54 for injecting ammonia between oxidation catalyst converter 51 and SCR converter 52 in exhaust system 50, and ammonia injection device An ammonia storage device 55 connected to 54, and a controller 56 that controls the current flowing through the heater 15 of the ammonia storage device 55 according to the flow rate of ammonia flowing through the ammonia injection device 54. The SCR converter 52 corresponds to a selective catalytic reduction converter included in the selective catalytic reduction system of the present invention.

  The ammonia storage device 55 has a function of supplying ammonia to the ammonia injection device 54. For example, the ammonia storage device described in the first to fourth embodiments is preferably used. The ammonia storage device 55 is connected to the ammonia injection device 54 in the ammonia outlet line 12.

In the SCR system 5, the oxidation catalytic converter 51 oxidizes hydrocarbons and CO contained in the exhaust gas of the diesel engine 200 to water and CO _2, and NO to NOx.

  The ammonia injection device 54 has a function of injecting ammonia into the exhaust gas oxidized by the oxidation catalytic converter 51.

  The SCR catalytic converter 52 has a function of reducing NOx in the exhaust gas into nitrogen gas and water by the ammonia injected by the ammonia injection device 54.

  The slip catalytic converter 53 has a function of oxidatively decomposing and removing the discharged ammonia when ammonia is discharged together with the exhaust gas from the SCR catalytic converter 52.

  Hereinafter, the operation of the SCR system 5 will be described.

The exhaust gas discharged from the diesel engine 200 is introduced into the oxidation catalytic converter 51, where hydrocarbons and CO in the exhaust gas are oxidized into water and CO ₂ and NO is oxidized into NOx, respectively.

  In the ammonia injection device 54, the ammonia released from the ammonia storage device 55 is injected into the exhaust gas that has passed through the oxidation catalytic converter 51 in an amount corresponding to the NOx concentration of the exhaust gas.

  In the SCR catalytic converter 52, NOx in the exhaust gas is reduced to nitrogen and water by the injected ammonia and removed. If ammonia is excessively injected in the ammonia injection device 54, the excess ammonia is discharged together with the exhaust gas. However, since the slip catalytic converter 53 is provided on the downstream side of the SCR catalytic converter 52, the ammonia discharged together with the exhaust gas is oxidized and removed by the slip catalytic converter 53. Therefore, surplus ammonia is hardly discharged to the outside world.

  The controller 56 controls the heater 15 of the ammonia storage device 55 according to the amount of ammonia injected by the ammonia injection device 54. That is, when the ammonia injection amount decreases in the ammonia injection device 54, the controller 56 decreases the amount of ammonia released from the ammonia storage device 55 by decreasing the current flowing through the heater 15. On the other hand, when the ammonia injection amount increases in the ammonia injection device 54, the controller 56 increases the amount of ammonia released from the ammonia storage device 55 by increasing the current flowing through the heater 15.

  Further, in the controller 56, for example, when the temperature of the exhaust gas and the NOx concentration are low, the current flowing through the heater 15 is reduced, and when the temperature of the exhaust gas and the NOx concentration is high, the heater 56 The current flowing through 15 may be increased.

  Alternatively, the pressure in the ammonia storage device 55 is adjusted by the heater 15 so that the pressure in the ammonia storage device 55 becomes substantially constant (a pressure regulating valve is arranged downstream of the ammonia storage device 55 so that ammonia at a substantially constant pressure is supplied to the ammonia injection device 54). Alternatively, a predetermined amount of ammonia is supplied by controlling the opening area or the opening time of the ammonia injection device 54.

  In the SCR system 5, since the high pressure is not used in the ammonia storage device 55, the safety is far superior to the SCR system using liquefied ammonia as an ammonia source. In addition, a large amount of ammonia can be injected into the exhaust gas with a small ammonia storage tank capacity compared to an SCR system using ammonia water or urea as an ammonia source.

  Further, in the controller 56, the amount of ammonia released from the ammonia storage device 55 is controlled by controlling the heater 15 in accordance with the amount of ammonia injected by the ammonia injection device 54, so that ammonia is excessive in the exhaust gas. It is possible to prevent the injection or the ammonia injection amount from being insufficient.

の右辺で示されるアンモニア吸蔵塩を形成する。図８において、実線は、アンモニア吸蔵量の理論値を示し、白丸はアンモニア吸蔵量の実測値を示す。なお、アンモニア吸蔵量の理論値は、上記化学式２に基いて求めたアンモニア吸蔵量である。 (1) Example 1
The ammonia occlusion apparatus 1 according to Embodiment 1 was used to occlude ammonia using magnesium chloride as the ammonia occlusion material 10. The internal volume of the space 11B of the ammonia storage tank 11 provided in the ammonia storage device 1 was 3.5 cm ³ . Moreover, the weight of the magnesium chloride accommodated in the space 11B was set to three points of 0.83 g, 1,15 g, and 1.5 g. The pressure of ammonia introduced into the ammonia storage device was set to 0.3 MPa, and the ammonia introduction time was 90 minutes. The results are shown in FIG. In addition, when magnesium chloride occludes ammonia, the following chemical formula 2:

The ammonia storage salt shown on the right side of is formed. In FIG. 8, the solid line indicates the theoretical value of the ammonia storage amount, and the white circle indicates the actual measurement value of the ammonia storage amount. The theoretical value of the ammonia storage amount is the ammonia storage amount obtained based on the above chemical formula 2.

  As is apparent from FIG. 8, in the ammonia storage device 1, it was found that the measured value of the ammonia storage amount was in good agreement with the theoretical value.

Further, since the bulk density of the magnesium chloride used in Example 1 is about 0.6 g / cm ^3, the volume of the magnesium chloride 0.83g is 1.38Cm ^3, and the volume of the magnesium chloride 1.5g 2 .5 cm ³ . Therefore, when the amount of magnesium chloride is 0.83 g, the magnesium chloride occupies about 40% of the internal volume of the space 11B of the storage tank 11, and when the amount of magnesium chloride is 1.5 g, the magnesium chloride is It occupies about 71% of the internal volume of the space 11B of the storage tank 11.

Here, since the bulk density of the ammonia occlusion salt produced when magnesium chloride occludes ammonia is about 0.1 g / cm ³ , the volume of magnesium chloride increases about 6 times when ammonia is occluded in a free state.

  However, since the space 11B is a space surrounded by the ammonia storage tank 11 and the porous filter 14, the storage salt cannot expand beyond the internal volume of the section 11B. Therefore, even when the amount of magnesium chloride is 0.83 g and 1.5 g, the occluded salt produced by occlusion of ammonia is compressed in the ammonia occlusion tank 11.

(2) Example 2
Next, 1.15 g of magnesium chloride was used as the occlusion material, and those having filtration capacities of 2 μm, 15 μm, 60 μm, and 90 μm were used as the porous filter 14, and the ammonia occlusion amount was measured. FIG. 9 shows the amount of occlusion after 90 minutes, and FIG. 10 shows the change over time of the occlusion amount.

  As shown in FIG. 9, the occlusion amount after 90 minutes, in other words, the occlusion amount when the equilibrium state is reached, is about 2 μ, 15 μm, 60 μm, and 90 μm as the porous filter 14 in any case. There was no change of 1.2 g, which was a value almost equal to the theoretical value of the amount of occlusion of ammonia determined based on Chemical Formula 2. In addition, as shown in FIG. 10, the ammonia occlusion amount after 5 minutes, 10 minutes, and 25 minutes after the start of ammonia occlusion is also different when the filtration capacity of the porous filter 14 is 2 μm, 15 μm, 60 μm and 90 μm. It was hardly seen. From this, it can be seen that the filtration capacity of the porous filter 14 is preferably in the range of 2 to 90 μm.

(3) Example 3, Comparative Example 1, Comparative Example 2
Next, using the same ammonia occlusion apparatus as used in Example 1, using magnesium chloride (Example 3) as the ammonia occlusion material 10, and urea water (Comparative Examples 1, 32.5) as the ammonia source % Aqueous solution) or ammonia water (Comparative Example 2, 25% aqueous solution), and the amount of ammonia released was measured per kg and 1 liter of occlusion material (ammonia source) based on the results. . The results are shown in FIG.

  As apparent from FIG. 11, in Example 3, the ammonia release amount per kg of magnesium chloride was 0.52 kg, and the ammonia release amount per liter of magnesium chloride was 0.62 kg. In contrast, in Comparative Example 1 using urea water as the ammonia source, the amount of ammonia released per kg of the ammonia source was 0.18 kg, and the amount of ammonia released per liter of the ammonia source was only 0.20 kg. . In Comparative Example 2 using ammonia water as the ammonia source, the ammonia release amount per kg of the ammonia source was 0.28 kg, and the ammonia release amount per liter of the ammonia source was only 0.25 kg. From this, the amount of ammonia released per kg and 1 liter of the ammonia storage material in Example 3 is more than double the amount of ammonia released in Comparative Example 1 using urea as the ammonia source and Comparative Example 2 using aqueous ammonia. It turns out that there is.

DESCRIPTION OF SYMBOLS 1 Ammonia storage device 2 Ammonia storage device 3 Ammonia storage device 4 Ammonia storage device 5 SCR system 10 Ammonia storage material 11 Ammonia storage tank 12 Ammonia outlet line 12 Ammonia inlet line 13 Ammonia outlet line 14 Porous filter 15 Heater 16 Opening and closing Valve 17 On-off valve 18 Cylinder 20 Porous partition wall 21 Cooling water passage 22 Cooling water introduction conduit 23 Cooling water outlet conduit 24 On-off valve 25 On-off valve 30 Cooling heating passage 50 Exhaust system 51 Oxidation catalytic converter 52 SCR catalytic converter 53 Slip catalytic converter 54 Ammonia injection device 55 Ammonia storage device 56 Controller 200 Diesel engine

Claims (11)

Storing ammonia, releasing the stored ammonia by heating, and an ammonia storage material whose volume increases when storing ammonia;
An ammonia storage tank containing the ammonia storage material, and an internal volume of a portion in which the ammonia storage material is stored is smaller than a free volume of the ammonia storage material when storing the ammonia;
An ammonia introduction path for introducing ammonia into the ammonia storage tank;
An ammonia lead-out path that leads out to the outside the ammonia released from the ammonia storage material stored in the ammonia storage tank;
A porous filter provided in a communication portion between the ammonia introduction path and the ammonia outlet path in the ammonia storage tank;
Heating means for heating the ammonia storage material housed in the ammonia storage tank;
Equipped with a,
Wall of the ammonia storage tank is a double structure composed of inner and outer walls, when allowed to absorb ammonia before Symbol ammonia absorber, a cooling fluid into the space between the inner and outer walls of the ammonia storage tank Ammonia storage device to be distributed . Storing ammonia, releasing the stored ammonia by heating, and an ammonia storage material whose volume increases when storing ammonia;
An ammonia storage tank containing the ammonia storage material, and an internal volume of a portion in which the ammonia storage material is stored is smaller than a free volume of the ammonia storage material when storing the ammonia;
An ammonia introduction path for introducing ammonia into the ammonia storage tank;
An ammonia lead-out path that leads out to the outside the ammonia released from the ammonia storage material stored in the ammonia storage tank;
A porous filter provided in a communication portion between the ammonia introduction path and the ammonia outlet path in the ammonia storage tank;
Heating means for heating the ammonia storage material housed in the ammonia storage tank;
With
A wall surface of the ammonia storage tank has a double structure consisting of an inner wall and an outer wall. When releasing ammonia from the ammonia storage material, the space between the inner wall and the outer wall of the ammonia storage tank is evacuated. /> Ammonia storage device. The ammonia storage device according to claim 1, wherein when ammonia is released from the ammonia storage material, a space between the inner wall and the outer wall of the ammonia storage tank is evacuated. The ammonia storage device according to claim 1 or 3, wherein the cooling fluid is cooling water. The ammonia storage device according to any one of claims 1 to 4, wherein the heating means is a heater. The ammonia storage device according to claim 1, wherein the inside of the ammonia storage tank is divided into a plurality of chambers by a porous partition wall. The ammonia storage device according to claim 6, wherein the porous partition is formed of a material selected from a ceramic porous body and a metal porous body. When releasing the ammonia from the ammonia storage material is ammonia storage device according to the exhaust gas from a diesel engine in claim 1, circulating in the space between the inner and outer walls of the ammonia storage tank. The ammonia storage device according to any one of claims 1 to 8, wherein the ammonia storage material is selected from strontium chloride, calcium chloride, and magnesium chloride. The ammonia storage device according to claim 9 , wherein the ammonia storage material is magnesium chloride. The ammonia storage device according to any one of claims 1 to 10 ,
An ammonia injection device for injecting ammonia released from the ammonia storage device into exhaust gas from a diesel engine;
A selective reduction catalytic converter in which a catalyst for reacting ammonia introduced into the exhaust gas with NOx contained in the exhaust gas is held, and the exhaust gas supplied with ammonia by the ammonia injection device is introduced;
A selective catalytic reduction system.

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