WO2015025666A1

WO2015025666A1 - Chemical heat storage device

Info

Publication number: WO2015025666A1
Application number: PCT/JP2014/069352
Authority: WO
Inventors: 研二森; 鈴木　秀明; 峻史水野
Original assignee: 株式会社豊田自動織機
Priority date: 2013-08-20
Filing date: 2014-07-22
Publication date: 2015-02-26
Also published as: JP2015040646A

Abstract

This chemical heat storage device (10) is provided with a reactor (11) and a storage unit (13). The reactor (11) has a reaction part (16) that contains particles of a heat storage material (17) which chemically reacts with a gaseous reaction medium and generates heat. The storage unit (13) is connected to the reactor (11) and stores the reaction medium. The surfaces of the particles of the heat storage material (17) are coated with a non-metallic heat conductive material (18) that has a higher heat conductivity than the heat storage material (17) and is permeable to the reaction medium.

Description

Chemical heat storage device

The present invention relates to a chemical heat storage device.

A chemical heat storage device described in Patent Document 1 is known. The chemical heat storage device described in Patent Document 1 is disposed around the catalyst ceramic portion, and includes a reaction portion including a heat storage material (heat storage material), a water conduit for supplying water (reaction medium) for generating heat from the heat storage material, and It has. Heat is generated from the reaction part by the exothermic reaction between water and the heat storage material. The heat generated in the reaction part is transferred to the catalyst ceramic part, and the catalyst ceramic part is heated.

JP 59-208118 A

However, the following problems exist in the above-described conventional technology. Since the heat storage material that generates heat by a chemical reaction with the reaction medium has high thermal resistance and low thermal conductivity, the heat generated in the heat storage material is difficult to be transmitted to the reaction part. For this reason, heating objects, such as a catalyst ceramic part, cannot fully be heated.

An object of the present invention is to provide a chemical heat storage device capable of improving the thermal conductivity of the reaction section.

The present invention relates to a chemical heat storage device for heating an object to be heated, a reactor having a reaction part that is disposed around or inside the object to be heated and includes a heat storage material that chemically reacts with a gaseous reaction medium to generate heat. The reaction part is a non-metallic heat transfer material having a higher thermal conductivity than the heat storage material and capable of passing the reaction medium. The particle surface is coated.

In the chemical heat storage device of the present invention, the surface of the particles of the heat storage material is coated with a heat transfer material having a higher thermal conductivity than the heat storage material, and the reaction unit is configured, thereby providing a plurality of heat transfer inside the reaction unit. The materials are connected. Therefore, the heat generated in the heat storage material due to the chemical reaction between the reaction medium and the heat storage material is effectively transmitted in the reaction section through the heat transfer material. By using a non-metallic material capable of passing a gaseous reaction medium as the heat transfer material, it is not necessary to form a gap (space) for securing a flow path for the reaction medium in the reaction section. For this reason, it is prevented that the heat generated in the heat storage material is hardly transmitted by the gap. As described above, the thermal conductivity of the reaction part is improved.

The reaction part may be formed by compacting the heat storage material in a state where the surfaces of the particles of the heat storage material are coated with the heat transfer material. In this case, since the reaction part is sufficiently dense, a plurality of heat transfer materials are reliably connected to each other inside the reaction part, and a gap that inhibits heat transfer is formed inside the reaction part. There is no. Thereby, the thermal conductivity of the reaction part is further improved.

The heat transfer material may be a carbon-based material. The carbon-based material has a sufficiently high thermal conductivity and easily passes through a gaseous reaction medium.

According to the present invention, a chemical heat storage device capable of improving the thermal conductivity of the reaction section is provided.

FIG. 1 is a schematic configuration diagram showing an exhaust purification system according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the chemical heat storage device shown in FIG. FIG. 3 is an enlarged view of the reaction unit shown in FIG.

Hereinafter, embodiments of 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 according to the present embodiment. As shown in FIG. 1, the exhaust purification system 1 is provided in an exhaust system of a diesel engine (hereinafter simply referred to as “engine”) 2 of a vehicle. The exhaust purification system 1 purifies harmful substances (environmental pollutants) contained in exhaust gas discharged from the engine 2.

The exhaust purification system 1 includes an oxidation catalyst (DOC) 4, a diesel exhaust particulate removal filter (DPF) 5, a selective reduction catalyst (SCR) 6, and an oxidation catalyst (ASC) 7. DOC4, DPF5, SCR6, and ASC7 are arranged in the order of DOC4, DPF5, SCR6, ASC7 from the upstream side toward the downstream side in the exhaust passage 3 connected to the engine 2.

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

As shown in FIG. 2, the oxidation catalyst 4 is arranged 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.

The exhaust purification system 1 includes a chemical heat storage device 10 that heats the oxidation catalyst 4 without requiring external energy such as electric power. The chemical heat storage device 10 normally stores the heat of the exhaust gas and warms up the oxidation catalyst 4 using the heat stored when necessary.

The chemical heat storage device 10 has a reactor 11 and a reservoir 13 as shown in FIGS. 1 and 2. The reactor 11 is arranged so that the exhaust pipe 9 is sandwiched between the reactor 11 and the oxidation catalyst 4. The reactor 11 is located around the oxidation catalyst 4 and has a ring shape. The reservoir 13 stores NH ₃ as a gaseous reaction medium. The reservoir 13 contains activated carbon that physically adsorbs NH ₃ . That is, the storage device 13 stores NH ₃ by the activated carbon physically adsorbing NH ₃ . The reactor 11 and the reservoir 13 are connected by a medium supply passage 12. An opening / closing valve 14 is disposed in the medium supply passage 12.

The reactor 11 has a ring case 15 made of metal (for example, stainless steel). In the ring case 15, a plurality of pellet-shaped reaction portions 16 are arranged so as to contact the exhaust pipe 9. A heat insulating material may be disposed between the reaction unit 16 and the ring case 15. The reaction unit 16 has, for example, a curved shape with a circular section.

As shown in FIG. 3, the reaction unit 16 includes a heat storage material 17 that chemically reacts with NH ₃ to generate heat, and a heat transfer material 18 that has a higher thermal conductivity than the heat storage material 17.

As the heat storage material 17, a halide represented by the composition formula MXa is used. 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 a number specified by the valence of M, and is 2 to 3. The thermal conductivity of the heat storage material 17 is, for example, about 0.1 to 3.0 W / (m · K).

As the heat transfer material 18, a non-metallic material that allows NH ₃ gas to pass is used. Examples of the non-metallic material through which NH ₃ gas passes include a carbon-based material (for example, carbon fiber) or a ceramic (for example, aluminum nitride, boron nitride, or silicon carbide). In the present embodiment, the heat transfer material 18 is a carbon-based material. The carbon-based material has a high thermal conductivity and is easy to pass NH ₃ gas. The heat conductivity of the heat transfer material 18 is, for example, about 5.0 to 900 W / (m · K).

The reaction section 16 is formed by coating the surface of secondary particles (polycrystalline particles) of the heat storage material 17 with the heat transfer material 18, and putting the heat storage material 17 into a mold and compacting. Thereby, as shown in FIG. 3, the secondary particles of the heat storage material 17 coated with the heat transfer material 18 are crushed, and the shape of the secondary particles of the heat storage material 17 becomes random. For this reason, there is no gap (space) inside the reaction section 16. Further, the heat transfer materials 18 coated on the surfaces of the secondary particles of the heat storage material 17 are connected to each other. The heat transfer material 18 serves as a heat transfer path through which heat generated in the heat storage material 17 passes. The heat transfer material 18 is in a random direction from the outer peripheral surface (surface on the opposite side of the oxidation catalyst 4) of the structure constituted by the plurality of reaction parts 16 to the inner peripheral surface (surface on the oxidation catalyst 4 side) of the structure. It extends continuously. In the present embodiment, the plurality of reaction portions 16 constitute a structure that exhibits a shape corresponding to the shape of the space formed in the ring case 15.

That is, in this embodiment, the heat storage material 17 is in the form of particles. Specifically, the heat storage material 17 has a form of secondary particles in which a plurality of primary particles are aggregated. The heat transfer material 18 is coated on the surface of the secondary particles of the heat storage material 17. The heat transfer material 18 constitutes a coating layer that covers the secondary particles of the heat storage material 17. The reaction unit 16 is formed by coating the surface of the secondary particles of the heat storage material 17 with the heat transfer material 18 and compacting the secondary particles coated with the heat transfer material 18. The reaction unit 16 is an aggregate of secondary particles of the heat storage material 17 coated with the heat transfer material 18. In the compacting, a mold is used. The secondary particles coated with the heat transfer material 18 are placed in a molding die, and the molding die is pressurized, whereby the pellet-shaped reaction section 16 is obtained.

Examples of the technique for coating the surface of the secondary particles of the heat storage material 17 with the heat transfer material 18 include hybridization, tight contact, and surface film formation. Hybridization combines the fine particles of the heat transfer material 18 on the surface of the secondary particles of the heat storage material 17 using a force mainly composed of impact force while dispersing the secondary particles of the heat storage material 17 in a high-speed air stream. Technology. The tight contact is a technique for forcibly physically mixing the secondary particles of the heat storage material 17 and the powder of the heat transfer material 18 using a mortar or a ball mill. The surface film formation is a technique for forming a film of the heat transfer material 18 on the particle surface of the heat storage material 17 using CVD or PVD. By employing these techniques, the coating layer of the heat transfer material 18 can be formed on the surface of the secondary particles of the heat storage material 17.

In the chemical heat storage device 10, when the temperature of the exhaust gas from the engine 2 is low, NH ₃ gas stored in the storage 13 is supplied to the reactor 11 through the medium supply passage 12. When NH ₃ gas supplied to the reactor 11 reaches each reaction section 16, the heat storage material 17 in the reaction section 16 and NH ₃ chemically react. In the chemical reaction, NH ₃ is chemisorbed on the heat storage material 17, that is, NH ₃ and the heat storage material 17 are coordinated and heat is generated from the heat storage material 17. That is, a reaction of the following reaction formula, that is, an exothermic reaction occurs.
MX + _n NH ₃ → MX (NH ₃ ) _n + heat

The heat generated in the heat storage material 17 is transmitted from the reactor 11 to the oxidation catalyst 4 through the exhaust pipe 9. Due to the heat transferred from the reactor 11, the oxidation catalyst 4 is heated to an activation temperature suitable for the purification of contaminants. At this time, the heat generated in the heat storage material 17 is transmitted to the heat transfer material 18. That is, the heat generated in the heat storage material 17 is transmitted to the oxidation catalyst 4 through the heat transfer material 18.

When the temperature of the exhaust gas from the engine 2 increases, the heat of the exhaust gas is given to the heat storage material 17 through the exhaust pipe 9. Thereby, the heat storage material 17 and NH ₃ are separated. That is, a reaction of the following reaction formula, that is, a 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 heat transfer material 18 through the exhaust pipe 9. That is, the heat of the exhaust gas is transmitted to the heat storage material 17 through the heat transfer material 18. NH ₃ separated from the heat storage material 17 returns to the reservoir 13 through the medium supply passage 12 as NH ₃ gas. As a result, the NH ₃ gas is recovered in the reservoir 13.

As described above, in the present embodiment, the surface of the secondary particles of the heat storage material 17 is coated with the heat transfer material 18, and the heat storage material 17 is compacted in this state, whereby the pellet-shaped reaction unit 16. To form. For this reason, the secondary particles of the heat storage material 17 coated with the heat transfer material 18 are arranged in a sufficiently dense state. By using a non-metallic material capable of passing NH ₃ gas as the heat transfer material 18, it is not necessary to form a gap (space) for securing the NH ₃ gas flow path in the reaction section 16. . For this reason, there is no problem at all even if the secondary particles of the heat storage material 17 are in a sufficiently dense state. Accordingly, the heat transfer materials 18 coated on the surfaces of the secondary particles of the heat storage material 17 are easily connected to each other, and a gap that hinders heat transfer is not formed inside the reaction portion 16. Therefore, heat is efficiently transmitted through the heat transfer material 18 in the reaction section 16.

At the time of the exothermic reaction, heat generated by a chemical reaction between the heat storage material 17 and NH ₃ is transmitted to the oxidation catalyst 4 through the heat transfer material 18, so that heat generated in the heat storage material 17 existing at a position away from the oxidation catalyst 4. Is also reliably transmitted to the oxidation catalyst 4. At the time of the regeneration reaction, the heat of the exhaust gas is transmitted to the heat storage material 17 through the heat transfer material 18, so that the heat of the exhaust gas is reliably transmitted also to the heat storage material 17 present at a position away from the oxidation catalyst 4.

Thus, according to the present embodiment, the thermal conductivity of the reaction section 16 including the heat storage material 17 can be sufficiently increased. Specifically, the thermal conductivity λ of the reaction part 16 when the reaction part 16 is composed only of the heat storage material 17 is 1 or less, whereas the heat storage material 17 is coded by the heat transfer material 18 as in this embodiment. In this case, the thermal conductivity λ of the reaction section 16 is 5-20.

Thereby, at the time of exothermic reaction, the heat output from the reaction part 16 is high, and it becomes possible to fully heat the oxidation catalyst 4. During the regeneration reaction, it is possible to reduce the time required for regeneration of NH ₃ .

In another aspect, the present embodiment is a chemical heat storage device 10, which includes a reactor 11 having a reaction section 16 including particles of a heat storage material 17 that chemically reacts with a gaseous reaction medium to generate heat, and a reactor. 11 and a reservoir 13 for storing the reaction medium, and the surface of the particles of the heat storage material 17 has a higher thermal conductivity than the heat storage material 17 and passes through the reaction medium. Material 18 is coated.

According to this aspect, the surface of the particles of the heat storage material 17 is coated with a nonmetallic heat transfer material 18 having a higher thermal conductivity than the heat storage material 17. For this reason, in the reaction part 16, several heat-transfer materials 18 which respectively cover the surface of an adjacent particle | grain are connected. Therefore, the heat generated in the heat storage material 17 by the chemical reaction between the reaction medium and the heat storage material 17 is effectively transmitted through the heat transfer material 18 in the reaction section 16. Since the heat transfer material 18 passes the reaction medium, the heat transfer material 18 does not inhibit the chemical reaction between the heat storage material 17 and the reaction medium. As a result, the thermal conductivity in the reaction section 16 is improved.

In this aspect, the reaction part 16 may be formed by compacting particles having a surface coated with the heat transfer material 18. If a gap is formed inside the reaction unit 16, the gap may be a factor that hinders transmission of heat generated in the heat storage material 17. When the reaction part 16 is formed by compacting particles having the surface coated with the heat transfer material 18, the reaction part 16 has sufficient particles coated with the heat transfer material 18. It is arranged in a dense state. For this reason, while the some heat transfer material 18 connects reliably inside the reaction part 16, formation of a clearance gap inside the reaction part 16 is suppressed. Thereby, the thermal conductivity of the reaction part 16 further improves.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the reaction part 16 is formed by coating the surface of the secondary particles of the heat storage material 17 with the heat transfer material 18 and compacting the secondary particles coated with the heat transfer material 18. However, it is not limited to this. After the surface of the secondary particles of the heat storage material 17 is coated with the heat transfer material 18, the reaction particles 16 are formed by enclosing the secondary particles coated with the heat transfer material 18 in the ring case 15 in a dense state. May be. In this case, the reaction part 16 exhibits a shape corresponding to the shape of the space formed in the ring case 15. The spatial volume of the secondary particles coated with the heat transfer material 18 and the amount enclosed in the ring case 15 are such that the heat storage material 17 expands due to the coordination bond between the NH ₃ and the heat storage material 17. You may determine based on the volume at the time. In this case, when the heat storage material 17 expands, the reaction part 16 can be configured without a gap.

In the above embodiment, the reactor 11 is disposed around the oxidation catalyst 4, but is not limited thereto. The reactor 11 may be disposed in the oxidation catalyst 4.

In the said embodiment, the halide shown by the compositional formula MXa is used as the heat storage material 17 and the heat storage material 17 generates heat by a chemical reaction with NH ₃ , but is not limited thereto. The gaseous reaction medium is not limited to NH _3, and may be, for example, H ₂ O (water vapor). In this case, CaO, MnO, CuO, Al ₂ O ₃ or the like is used as a heat storage material that chemically reacts with H ₂ O.

In the above embodiment, the chemical heat storage device 10 heats the oxidation catalyst 4 disposed in the exhaust system of the diesel engine 2, but is not limited thereto. The chemical heat storage device 10 may heat other catalyst disposed in the exhaust system of the diesel engine 2 or a member such as a place where the exhaust catalyst is not located in the exhaust pipe 9. In addition to the diesel engine 2, the present invention can also be applied to a catalyst disposed in an exhaust system of a gasoline engine or a chemical heat storage device that heats a member such as a portion where the catalyst is not located in an exhaust pipe. The present invention is also applicable to a chemical heat storage device that heats an object to be heated other than the engine exhaust system.

The present invention can be used for a chemical heat storage device for warming up a catalyst disposed in an exhaust system of an internal combustion engine (for example, a diesel engine).

4 ... oxidation catalyst (object to be heated), 10 ... chemical heat storage device, 11 ... reactor, 13 ... reservoir, 16 ... reaction section, 17 ... heat storage material, 18 ... heat transfer material.

Claims

A chemical heat storage device for heating an object to be heated,
A reactor having a reaction part disposed around or inside the heating object and including a heat storage material that chemically reacts with a gaseous reaction medium to generate heat;
A reservoir connected to the reactor and storing the reaction medium;
The reaction part is configured to be in a state in which the surface of particles of the heat storage material is coated with a non-metallic heat transfer material having a higher thermal conductivity than the heat storage material and capable of passing the reaction medium. Yes.
The chemical heat storage device according to claim 1,
The reaction part is formed by compacting the heat storage material in a state where the surfaces of the particles of the heat storage material are coated with the heat transfer material.
The chemical heat storage device according to claim 1 or 2,
The heat transfer material is a carbon-based material.