JP2015087082A - Chemical heat storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical heat storage device capable of enhancing heat conductivity of a reactor.SOLUTION: A chemical heat storage device 10 comprises: a ring-shaped reactor 11 which is arranged around an oxidation catalyst 4 with an exhaust pipe 9 placed in between; and a container which is connected to the reactor 11 through a medium supply passage 12 and stores NHby absorbing the same. The reactor 11 has a ring case 15 where a molded pellet 16 for chemical heat storage is arranged therein in a manner that contacts the exhaust pipe 9. The molded pellets 16 has a heat storage material 17 which generates heat through a chemical reaction with the NHand a metal section 18 which is made of a metal material having higher heat conductivity than the heat storage material 17. The metal section 18 is continuously extended from an outer peripheral surface of the molded pellet 16 to an inner peripheral surface thereof. The molded pellet 16 is manufactured in a manner that mixes the heat storage material 17 and the metal material making up the metal section 18 in a mold and simultaneously presses a mixture into a shape.

Description

  The present invention relates to a chemical heat storage device for heating an object to be heated such as a catalyst provided in an exhaust system of an engine.

  As a conventional chemical heat storage device, for example, a device described in Patent Document 1 is known. The chemical heat storage device described in Patent Literature 1 includes a reactor having a heat storage material (heat storage material) that is disposed around the catalyst ceramic portion and a water conduit that supplies water for generating heat from the heat storage material. . When water and the heat storage material are reacted exothermically, heat is generated from the reactor, and the catalyst ceramic part is heated by heat conduction.

JP 59-208118 A

  However, the following problems exist in the prior art. That is, a heat storage material that generates heat by a chemical reaction with a reaction medium such as water has a low thermal conductivity. Therefore, since the heat generated in the heat storage material is difficult to be transmitted through the reactor, the object to be heated such as the catalyst ceramic portion cannot be sufficiently heated.

  The objective of this invention is providing the chemical heat storage apparatus which can improve the heat transfer property of a reactor.

  The present invention relates to a chemical heat storage device for heating an object to be heated, which is disposed around or inside the object to be heated and generates a heat by chemically reacting with a reaction medium and a metal having a higher thermal conductivity than the heat storage material. A reactor having a molded pellet including a metal part made of a material, and a reservoir connected to the reactor and storing a reaction medium, and the molded pellet is press-molded by mixing a heat storage material and a metal material The metal part extends toward the object to be heated inside the molded pellet.

  Thus, in the chemical heat storage device of the present invention, a molded pellet formed by mixing a heat storage material with a metal material having a higher thermal conductivity than the heat storage material is provided, and the metal portion made of the metal material is heated within the molded pellet. By configuring the molded pellets so as to extend toward the object, the heat generated in the heat storage material due to the chemical reaction between the reaction medium and the heat storage material is transmitted to the object to be heated through the metal part. Thereby, the heat conductivity of the molded pellet of the reactor is improved. Moreover, since the void which inhibits heat transfer does not exist in the inside of a shaping | molding pellet by performing a press molding process and forming a shaping | molding pellet, the heat conductivity of a shaping | molding pellet further improves.

  Preferably, the metal part continuously extends toward the heating object inside the molded pellet. In this case, the heat generated in the heat storage material can be more easily transferred to the object to be heated through the metal portion, so that the heat transfer property of the molded pellets can be further improved.

  At this time, preferably, the molded pellet is arranged around the object to be heated, and the metal portion continuously extends from the surface on the opposite side of the object to be heated to the surface on the object to be heated inside the molded pellet. ing. In this case, the heat generated by the heat storage material present at a position away from the heating object is also reliably transmitted to the heating object through the metal portion. Thereby, the heat conductivity of a shaping | molding pellet can be improved further.

  Preferably, the metal part is formed of a metal porous body. In this case, the metal ratio per unit volume can be easily adjusted by changing the porosity of the metal porous body, and as a result, it is easy to arbitrarily change the thermal conductivity. Moreover, it becomes easy to make the dispersion | variation in a metal part uniform in a shaping | molding pellet. Thereby, adjustment of the heat conductivity of a molding pellet can be performed easily.

  Preferably, the molded pellet further includes a heat transfer material having a higher thermal conductivity than the metal material. In this case, since the metal parts are connected to each other through the heat transfer material, the heat generated in the heat storage material is more easily transmitted to the heating object through the metal part and the heat transfer material. Thereby, the heat conductivity of a shaping | molding pellet can be improved further.

  According to the present invention, the heat transfer property of the reactor can be improved. Thereby, it becomes possible to effectively heat the object to be heated by the heat generated in the reactor.

It is a schematic block diagram which shows the exhaust gas purification system provided with one Embodiment of the chemical heat storage apparatus which concerns on this invention. It is sectional drawing which shows the principal part of the chemical thermal storage apparatus shown in FIG. As a comparative example, it is sectional drawing which shows the principal part of an example of the conventional chemical heat storage apparatus. It is sectional drawing which shows the principal part of other embodiment of the chemical heat storage apparatus which concerns on this invention. It is a schematic block diagram which shows the modification of the exhaust gas purification system shown in FIG.

  Hereinafter, preferred embodiments of a chemical heat storage device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an exhaust purification system including an embodiment of a chemical heat storage device according to the present invention. In the figure, an exhaust purification system 1 is provided in an exhaust system of a diesel engine 2 (hereinafter simply referred to as an engine 2) of a vehicle, and purifies harmful substances (environmental pollutants) contained in exhaust gas discharged from the engine 2. System.

  The exhaust purification system 1 includes an oxidation catalyst (DOC) 4, a diesel exhaust particulate removal filter (DPF) 5, and a selective reduction catalyst that are sequentially provided from the upstream side to the downstream side in the exhaust passage 3 connected to the engine 2. (SCR) 6 and oxidation catalyst (ASC) 7 are provided.

The oxidation catalyst 4 is a catalyst that oxidizes and purifies HC, CO, etc. contained in the exhaust gas. The DPF 5 is a filter that collects and removes PM contained in the exhaust gas. The SCR 6 is a catalyst that reduces and purifies NOx contained in the exhaust gas by NH ₃ (ammonia) generated by hydrolysis from the urea water added from the addition valve 8. The oxidation catalyst 7 is a catalyst that oxidizes NH ₃ that has flowed downstream through the SCR 6.

  As shown in FIG. 2, the oxidation catalyst 4 is disposed inside a cylindrical exhaust pipe 9 that forms a part of the exhaust passage 3. The oxidation catalyst 4 has a temperature range (activation temperature) that exhibits the ability to purify environmental pollutants. Therefore, it is necessary to heat the oxidation catalyst 4 in order to bring the temperature of the oxidation catalyst 4 to the activation temperature.

  Therefore, the exhaust purification system 1 includes a chemical heat storage device 10 that heats the oxidation catalyst 4 without energy. The chemical heat storage device 10 normally stores the heat of exhaust gas and uses the stored heat when necessary.

As shown in FIGS. 1 and 2, the chemical heat storage device 10 includes a ring-shaped reactor 11 disposed around the oxidation catalyst 4 with an exhaust pipe 9 interposed therebetween, and the reactor 11 and the medium supply passage 12. And a reservoir 13 for adsorbing and storing NH ₃ as a reaction medium. The reservoir 13 contains activated carbon that physically adsorbs NH ₃ . An opening / closing valve 14 is provided in the medium supply passage 12.

  The reactor 11 has a ring case 15 made of metal (for example, SUS). Inside the ring case 15, a molded pellet 16 for chemical heat storage is disposed so as to contact the exhaust pipe 9. The molded pellet 16 is formed in a ring shape by connecting a plurality of tile-shaped molded pellets 16a.

The molded pellet 16 includes a heat storage material 17 that chemically reacts with NH ₃ to generate heat, and a metal portion 18 made of a metal material having a higher thermal conductivity than the heat storage material 17. The thermal conductivity of the heat storage material 17 is, for example, 0.1 to 1.0 W / m · K. The thermal conductivity of the metal material is, for example, 100 to 400 W / m · K.

  As the heat storage material 17, a material having a composition MXa of a halide is used. Here, M is an alkaline earth metal such as Mg, Ca, or Sr, or a transition metal such as Cr, Mn, Fe, Co, Ni, Cu, or Zn. X is Cl, Br, I or the like. a is 2-3. As the metal material, a material having high thermal conductivity such as Cu, Ag, Ni, Ci—Cr, Al, Fe, and stainless steel is used.

  The metal portion 18 continuously extends from the outer peripheral surface of the molded pellet 16 (the surface on the opposite side of the oxidation catalyst 4) to the inner peripheral surface of the molded pellet 16 (the surface on the oxidation catalyst 4 side). That is, the metal part 18 is formed so as to extend in a network shape toward the oxidation catalyst 4 inside the molded pellet 16.

  The metal portion 18 is formed of a metal block (metal porous body) such as a foam metal having pores therein, for example. At this time, the porosity of the metal block is desirably 50% or more. In this case, the heat storage material 17 is filled in the holes of the metal block.

  Moreover, the metal part 18 may be a metal fiber or a metal wire entangled in a wool shape (metal wool). In this case, the heat storage material 17 is filled in the gaps between the metal fibers or the metal conductors.

  However, in the metal block, it is easy to arrange uniformly in the molded pellet 16 as compared with the metal fiber or the metal wool. Further, in the metal block, the metal ratio per unit volume can be easily adjusted by changing the porosity, so that the thermal conductivity of the molded pellet 16 can be easily adjusted as compared with the metal fiber or the metal wool. Therefore, it is desirable that the metal portion 18 be a metal block.

  The molded pellet 16a is produced by simultaneously pressing and solidifying the heat storage material 17 and the metal material forming the metal portion 18 in a mold and mixing them. As a result, there is no space (void) inside the molded pellet 16a.

  A heat insulating material 19 is disposed between the molded pellet 16 and the ring case 15. The medium supply passage 12 is connected to the molded pellet 16 through the ring case 15 and the heat insulating material 19.

In the chemical heat storage device 10 configured as described above, when the temperature of the exhaust gas from the engine 2 is low, the NH ₃ gas stored in the storage device 13 is molded pellets 16 of the reactor 11 through the medium supply passage 12. The heat storage material 17 in the molded pellet 16 and NH ₃ chemically react and chemisorb (coordinate bond), and heat is generated from the heat storage material 17. That is, the reaction of the following reaction formula (exothermic reaction) occurs.
MX + _n NH ₃ → MX (NH ₃ ) _n + heat

  The heat generated in the heat storage material 17 is transferred to the oxidation catalyst 4 through the exhaust pipe 9, and the oxidation catalyst 4 is heated to the activation temperature suitable for the purification of the pollutant by the heat. At this time, the heat generated in the heat storage material 17 is transferred to the metal part 18, and the heat is transferred to the oxidation catalyst 4 through the metal part 18. That is, the metal part 18 becomes a heat conduction path.

On the other hand, when the temperature of the exhaust gas from the engine 2 increases, the heat of the exhaust gas is applied to the heat storage material 17 through the exhaust pipe 9, whereby the heat storage material 17 and NH ₃ are separated. That is, the reaction of the following reaction formula (regeneration reaction) occurs.
MX (NH ₃ ) _n + heat → MX + _n NH ₃

At this time, the heat of the exhaust gas is transmitted to the metal part 18, and the heat is transferred to the heat storage material 17 through the metal part 18. Then, the NH ₃ gas separated from the heat storage material 17 returns to the reservoir 13 through the medium supply passage 12 and is recovered.

FIG. 3 is a cross-sectional view showing a main part of an example of a conventional chemical heat storage device as a comparative example. In the chemical heat storage device 100 shown in FIG. 3, the molded pellet 101 is formed by press-molding only the heat storage material 17. However, since the thermal conductivity (described above) of the heat storage material 17 is low, such a molded pellet 101 has the following problems. That is, during the exothermic reaction, it is difficult to extract the heat generated by the chemical reaction between the heat storage material 17 and NH ₃ to the outside of the heat storage material 17. Further, during the regeneration reaction, the heat of the exhaust gas is not efficiently taken into the heat storage material 17, and it takes time to regenerate the NH ₃ gas. In particular, the heat generated from the heat storage material 17 disposed on the outer peripheral surface side of the molded pellet 101 is not easily transmitted to the oxidation catalyst 4 disposed across the inner peripheral surface of the molded pellet 101 and the exhaust pipe 9. For this reason, the heating efficiency of the oxidation catalyst 4 is deteriorated. In addition, even during the regeneration reaction, the heat of the exhaust gas flowing in the exhaust pipe 9 is not easily transmitted to the heat storage material 17 disposed on the outer peripheral surface side of the molded pellet 101, and the time for separating NH ₃ from the heat storage material 17 becomes longer. .

  In contrast, in the present embodiment, a molded pellet 16 is formed by mixing a metal material having a higher thermal conductivity than the heat storage material 17 into the heat storage material 17, and the metal portion 18 made of the metal material is an outer peripheral surface of the molded pellet 16. Since the molded pellet 16 is configured so as to continuously extend from the inner peripheral surface to the inner peripheral surface, the following effects are obtained.

That is, during the exothermic reaction, the heat generated by the chemical reaction between the heat storage material 17 and NH ₃ is transferred to the oxidation catalyst 4 through the metal portion 18, so that the heat storage material 17 existing at a position away from the oxidation catalyst 4 The generated heat is reliably transmitted to the oxidation catalyst 4. Further, during the regeneration reaction, the heat of the exhaust gas is transferred to the heat storage material 17 through the metal portion 18, so that the heat of the exhaust gas is reliably transmitted to the heat storage material 17 existing at a position away from the oxidation catalyst 4. . Thereby, the heat conductivity of the molding pellet 16 becomes high.

  In the present embodiment, since the molded pellet 16 is formed by press molding, as described above, the molded pellet 16 has no gap that hinders heat transfer. Thereby, the heat conductivity of the molding pellet 16 becomes still higher.

As described above, according to the present embodiment, the heat transfer property of the molded pellet 16 including the heat storage material 17 is sufficiently high. As a result, the oxidation catalyst 4 can be effectively heated and the regeneration time of the NH ₃ gas can be shortened.

  FIG. 4 is a cross-sectional view showing a main part of another embodiment of the chemical heat storage device according to the present invention. In the drawing, the same reference numerals are given to the same or equivalent members as those of the above-described embodiment, and the description thereof is omitted.

  In the figure, in the chemical heat storage device 10 of this embodiment, the molded pellet 16 of the reactor 11 has a heat conductivity higher than that of the metal material in addition to the heat storage material 17 and the metal portion 18 made of the metal material. A thermal material 20 is further included. As the heat transfer material 20, for example, a carbon fiber is used. The thermal conductivity of the carbon fiber is about 1000 W / m · K. The heat transfer material 20 is randomly arranged inside the molded pellet 16.

  The molded pellet 16 is produced by simultaneously pressing and solidifying the heat storage material 17, the metal material forming the metal portion 18 and the heat transfer material 20 in a mold and mixing them. Is done.

  In this way, by mixing the heat transfer material 20 with the heat storage material 17 and the metal material, the metal portions 18 are connected to each other via the heat transfer material 20, so that the heat conduction path further increases. Thereby, the heat conductivity of the molding pellet 16 containing the heat storage material 17 becomes still higher.

  In addition, this invention is not limited to the said embodiment. For example, in the above embodiment, the metal portion 18 made of a metal material continuously extends from the outer peripheral surface of the molded pellet 16 to the inner peripheral surface of the molded pellet 16 inside the molded pellet 16. It is not restricted and the metal part 18 should just extend toward the oxidation catalyst 4.

  Further, in the above embodiment, the ring-shaped molded pellets 16 are formed by joining a plurality of tile-shaped molded pellets 16a. Molded pellets may be formed. Further, the shape of the molded pellet may be a rectangular parallelepiped shape, a hollow cylindrical shape, a rectangular parallelepiped shape, a cubic shape, or the like.

  In the above embodiment, the reactor 11 is arranged around the oxidation catalyst 4. However, the arrangement location of the reactor is not limited to this, and may be in the oxidation catalyst 4.

Furthermore, in the above embodiment, the reaction medium NH ₃ and the heat storage material 17 having the composition MXa are chemically reacted to generate heat, but the reaction medium is not particularly limited to NH ₃ , For example, H ₂ O may be used. In this case, CaO, MnO, CuO, Al ₂ O ₃ or the like is used as a heat storage material to be chemically reacted with H ₂ O.

  Furthermore, although the said embodiment heats the oxidation catalyst 4 provided in the exhaust system of the diesel engine 2, this invention is what heats the other part provided in the exhaust system of the diesel engine 2. Is also applicable. An example is shown in FIG.

  In the exhaust purification system 1 shown in FIG. 5, the heat exchanger 30 is arranged on the upstream side of the oxidation catalyst 4. Here, the heat exchanger 30 is disposed in the middle of the exhaust passage 3 and has a honeycomb structure. The reactor 11 is arranged around the heat exchanger 30. Other configurations are the same as those of the exhaust purification system 1 shown in FIG.

  In addition, the present invention is for heating another exhaust catalyst provided in the exhaust system of the diesel engine 2 or the exhaust pipe 9 itself, or any exhaust catalyst or exhaust pipe provided in the exhaust system of the gasoline engine. It is also applicable to those that heat etc. The present invention can also be applied to a device that heats an object to be heated other than the engine exhaust system.

  4 ... oxidation catalyst (object to be heated), 10 ... chemical heat storage device, 11 ... reactor, 13 ... reservoir, 16 ... molded pellet, 17 ... heat storage material, 18 ... metal part, 20 ... heat transfer material, 30 ... heat Exchanger (object to be heated).

Claims (5)

In a chemical heat storage device that heats an object to be heated,
A reaction having a molded pellet that is arranged around or inside the heating object and includes a heat storage material that chemically reacts with a reaction medium to generate heat and a metal portion made of a metal material having a higher thermal conductivity than the heat storage material. And
A reservoir connected to the reactor and storing the reaction medium;
The molded pellet is formed by mixing the heat storage material and the metal material and performing a press molding process,
The chemical heat storage device, wherein the metal part extends toward the heating object inside the molded pellet.   The chemical heat storage device according to claim 1, wherein the metal part continuously extends toward the heating object inside the molded pellet. The molded pellet is arranged around the heating object,
3. The chemical heat storage device according to claim 2, wherein the metal part continuously extends from a surface on the opposite side of the heating object to a surface on the heating object side in the molded pellet.   The said metal part is formed with the metal porous body, The chemical heat storage apparatus as described in any one of Claims 1-3 characterized by the above-mentioned.   The chemical heat storage device according to any one of claims 1 to 4, wherein the molded pellet further includes a heat transfer material having a higher thermal conductivity than the metal material.

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