JP2016223761A - Chemical heat storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical heat storage device capable of alleviating temperature change of a reservoir while achieving downsizing of the reservoir.SOLUTION: A chemical heat storage device 10 includes: a reactor 11 having a reaction material 15 which generates heat by a chemical reaction with a reaction medium and in which, when heat is imparted, the reaction medium is desorbed and heat is stored; and an adsorber 13 connected to the reactor 11. The adsorber 13 includes: an adsorbent 16 in which the reaction medium is adsorbed and also the reaction medium is desorbed; and a container 17 for accommodating the adsorbent 16. In the container 17 of the adsorber 13, a heat transfer material 18 whose thermal conductivity is higher than that of the adsorbent 16 and whose thermal capacity is larger than that of the adsorbent 16 exists together with the adsorbent 16.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a chemical heat storage device.

As a conventional chemical heat storage device, for example, a device described in Patent Document 1 is known. A chemical heat storage device described in Patent Document 1 includes a reactor including a reaction material that chemically reacts with ammonia (NH ₃ ), and ammonia including an adsorbent that is physically connected to the reactor via a pipe line and physically adsorbs ammonia. And a reservoir. The ammonia store has a structure in which flat containers filled with an adsorbent material and heat exchange fins are alternately arranged.

JP 2013-242053 A

In general, an adsorbent that physically adsorbs NH ₃ as a reaction gas generates heat when adsorbing NH ₃ and absorbs heat when desorbing NH ₃ . In order to efficiently perform the adsorption and desorption of NH _{3 on} the adsorbent, it is desirable to keep the temperature of the ammonia reservoir constant by performing heat exchange between the adsorbent and the outside air. However, since the heat conductivity of the adsorbent itself filled in the ammonia reservoir is poor, in order to sufficiently suppress the temperature change of the ammonia reservoir, it is necessary to increase the heat exchange area with the outside air in the ammonia reservoir. There is. In the ammonia storage device described in Patent Document 1, the container filled with the adsorbent is divided into a plurality of flat portions, and the heat exchange fins are arranged between the flat containers, so that the adsorbent and the outside air are arranged. Heat exchange with the other. However, if the temperature change of the ammonia storage device is sufficiently suppressed with such a configuration, there arises a problem that the structure of the ammonia storage device becomes complicated and the ammonia storage device becomes large.

  The objective of this invention is providing the chemical thermal storage apparatus which can relieve | moderate the temperature change of a storage device, aiming at size reduction of a storage device.

  A chemical heat storage device according to one embodiment of the present invention includes a reactor having a reaction material that generates heat by being subjected to a chemical reaction with a reaction medium and desorbs the reaction medium when heat is applied thereto, and a reservoir connected to the reactor. The storage device has an adsorbent from which the reaction medium is adsorbed and from which the reaction medium is desorbed, and a container for containing the adsorbent, and the thermal conductivity is adsorbed in the container of the reservoir. A heat transfer material having a higher heat capacity than that of the adsorbent is mixed with the adsorbent.

  In such a chemical heat storage device, a heat transfer material having a thermal conductivity higher than that of the adsorbent and a heat capacity larger than that of the adsorbent is mixed with the adsorbent in the container of the reservoir. Therefore, when the reaction medium is desorbed from the adsorbent in the reservoir, the adsorbent absorbs heat, so that heat is transferred from the heat transfer material to the adsorbent. For this reason, the temperature fall of a store is suppressed. On the other hand, when the reaction medium is adsorbed on the adsorbent of the reservoir, the adsorbent generates heat, and heat moves from the adsorbent to the heat transfer material. For this reason, the temperature rise of the reservoir is suppressed. Therefore, it is not necessary to increase the size of the reservoir in order to suppress the temperature change of the reservoir by exchanging heat between the adsorbent and the outside air. Thereby, the temperature change of a reservoir can be relieved, aiming at size reduction of a reservoir.

  The adsorbent and the heat transfer material are composed of a plurality of particles. When the mode diameter of the particles of the adsorbent is Ra and the mode diameter of the particles of the heat transfer material is Rm, 0.1 ≦ Rm / Ra ≦ 10.0 may be sufficient. In this case, the gap between the adsorbent particles and the heat transfer material particles is reduced, and a sufficient contact area between the adsorbent material and the heat transfer material is ensured. Heat becomes easy to move. Thereby, when the reaction medium is desorbed from the adsorbent, the temperature drop of the reservoir is further suppressed, and when the reaction medium is adsorbed to the adsorbent, the temperature rise of the reservoir is further suppressed.

  The adsorbent and the heat transfer material are composed of a plurality of particles. When the total volume of the adsorbent particles in the container is Va and the total volume of the heat transfer material particles in the container is Vm, 0. It may be 1 ≦ Vm / Va ≦ 5.0. In this case, it is possible to suppress an increase in the size of the reservoir due to an increase in the total volume of the heat transfer material particles while relaxing the temperature change of the reservoir.

  The heat transfer material has a plate shape and may be in contact with the inner wall surface of the container. In this way, when the heat transfer material contacts the inner wall surface of the container, heat exchange between the heat transfer material and the outside air is performed through the container in addition to heat transfer between the adsorbent and the heat transfer material. Become. Thereby, the temperature change of a reservoir | reserver can be relieve | moderated further.

  The container may be formed in a cylindrical shape. In this case, since the strength of the container is higher than when the container is formed in a rectangular parallelepiped shape or a cubic shape, the thickness of the container can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the chemical heat storage apparatus which can relieve | moderate the temperature change of a storage device is achieved, aiming at size reduction of a storage device.

It is a schematic block diagram which shows the exhaust gas purification system provided with the chemical heat storage apparatus which concerns on one Embodiment. It is sectional drawing of the adsorption device shown by FIG. It is a graph which shows the particle size distribution of the adsorbent and heat transfer material shown in FIG. Is a graph comparing the temperature change of the adsorber during desorption time and adsorption of NH ₃ for the adsorbent. It is sectional drawing which shows the modification of the adsorption device shown by FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

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

  The exhaust purification system 1 includes a heat exchanger 3, a diesel oxidation catalyst (DOC) 4, a diesel exhaust particulate removal filter (DPF) 5, a selective catalytic reduction (SCR) 6, and an ammonia slip. A catalyst (ASC: Ammonia Slip Catalyst) 7 is provided. The heat exchanger 3, the DOC 4, the DPF 5, the SCR 6, and the ASC 7 are sequentially disposed in the exhaust passage 8 connected to the engine 2 from the upstream side to the downstream side.

The heat exchanger 3 exchanges heat between the exhaust gas discharged from the engine 2 and the reactor 11 of the chemical heat storage device 10 described later. The DOC 4 oxidizes and purifies HC and CO contained in the exhaust gas. The DPF 5 removes PM from the exhaust gas by collecting particulate matter (PM) contained in the exhaust gas. The SCR 6 reduces and purifies NOx contained in the exhaust gas with urea or ammonia (NH ₃ ). ASC7 oxidizes NH ₃ passing through the SCR6.

Further, the exhaust purification system 1 includes a chemical heat storage device 10 that heats the exhaust gas to be heated via the heat exchanger 3 without requiring external energy such as electric power. The chemical heat storage device 10 is a device that uses a reversible chemical reaction to heat (warm up) a heating target without external energy. Specifically, the chemical heat storage device 10 desorbs the reaction medium from the reaction material 15 by the heat supplied from the heating target, stores the desorbed reaction medium, and stores the stored reaction medium in the reaction material 15. Is a device that causes the reaction material 15 and the reaction medium to chemically react with each other and warms the object to be heated using reaction heat (heat radiation) during the chemical reaction. That is, the chemical heat storage device 10 is a device that stores heat from a heating target and supplies heat to the heating target by using a reversible chemical reaction. In the present embodiment, the object to be heated is exhaust gas, and the reaction medium is ammonia (NH ₃ ).

The chemical heat storage device 10 includes a reactor 11 disposed so as to be capable of exchanging heat with respect to the heat exchanger ₃ , and an adsorber 13 that is a reservoir connected to the reactor 11 via an NH ₃ supply pipe 12. I have. The NH ₃ supply pipe 12 constitutes an NH ₃ flow path through which NH ₃ flows between the reactor 11 and the adsorber 13. An open / close valve 14 is disposed in the NH ₃ supply pipe 12.

The reactor 11 has a reaction material 15 that generates heat due to a chemical reaction with NH ₃ and stores heat by desorbing NH ₃ when heat of exhaust gas is applied. As the reaction material 15, 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 2-3.

FIG. 2 is a cross-sectional view of the adsorber 13. In FIG. 2, the adsorber 13 includes an adsorbent 16 from which NH ₃ is physically adsorbed and from which NH ₃ is desorbed, and a container 17 that accommodates the adsorbent 16.

  As the adsorbent 16, activated carbon, carbon black, mesoporous carbon, nanocarbon, zeolite, or the like is used. The adsorbent 16 is composed of a plurality of particles. The plurality of particles constituting the adsorbent 16 have a certain degree of distribution in size.

In the container 17 of the adsorber 13, a heat transfer material 18 that transfers heat to and from the adsorbent 16 by absorbing or releasing heat is mixed with the adsorbent 16. The heat transfer material 18 is a highly heat conductive material having a higher thermal conductivity than the adsorbent 16 and a material having a larger heat capacity than the adsorbent 16. The heat transfer material 18 is made of a material that is chemically inert with respect to the reaction medium (NH _{3 in} this embodiment). That is, the heat transfer material 18 is a material that does not chemically react with NH ₃ . As such heat transfer material 18, a metal such as stainless steel, iron, copper, silver, nickel or aluminum, or a ceramic such as glass, alumina, zirconia, SiC or SiO ₂ is used. Specifically, as the heat transfer material 18, for example, a material having a thermal conductivity of 1 W / m · K or more is used.

  Similarly to the adsorbent 16, the heat transfer material 18 is composed of a plurality of particles. The plurality of particles constituting the heat transfer material 18 also have a certain distribution in size. The heat transfer material 18 and the adsorbent 16 are filled in the container 17 by a known stirring method. In the container 17, the heat transfer material 18 is randomly and uniformly mixed with the adsorbent 16.

  At this time, when the mode diameter of the particles of the adsorbent 16 is Ra and the mode diameter of the particles of the heat transfer material 18 is Rm, preferably 0.1 ≦ Rm / Ra ≦ 10.0, It is particularly preferable that ≦ Rm / Ra ≦ 1.0. As shown in FIG. 3, the mode diameter of a particle is a particle diameter having the highest frequency in the particle size distribution.

  Note that the particle diameter shown here is the equivalent diameter of a particle calculated from geometric characteristics, or the effective diameter of a particle calculated from dynamic characteristics or optical characteristics. For example, the effective diameter of the particle calculated from the optical characteristics is a particle diameter (D50) at which the cumulative volume in the particle size distribution measured by a laser diffraction / scattering particle diameter measuring apparatus is 50%. The particle diameters of the adsorbent 16 and the heat transfer material 18 are, for example, about several μm.

  Further, when the total volume of the particles of the adsorbent 16 in the container 17 is Va and the total volume of the particles of the heat transfer material 18 in the container 17 is Vm, 0.1 ≦ Vm / Va ≦ 5.0. It is particularly preferable that 0.1 ≦ Vm / Va ≦ 1.0. The total volume of the particles is expressed as the true volume excluding the space between the particles.

A container 17 that is a pressure container filled with NH ₃ as a reaction medium is formed in a cylindrical shape. One end of the NH ₃ supply pipe 12 is fixed to the upper flat surface of the container 17. The container 17 is made of a material (for example, stainless steel) having high corrosion resistance with respect to NH ₃ .

In the exhaust purification system 1 provided with the chemical heat storage device 10 as described above, when the temperature of the exhaust gas discharged from the engine 2 is lower than the warm air temperature at which the exhaust gas purification catalyst such as DOC4 can be activated, it is opened and closed. The valve 14 is opened. Then, due to the pressure difference between the adsorber 13 and the reactor 11, NH ₃ is desorbed from the adsorbent 16 of the adsorber 13, and the desorbed NH ₃ is supplied to the reactor 11 through the NH ₃ supply pipe 12. The Then, the reaction material 15 of the reactor 11 (e.g. MgBr ₂₎ and the NH ₃ is the chemical reaction (chemical adsorption) and heat is generated. That is, a reaction from the left side to the right side (exothermic reaction) in the following reaction formula (A) occurs. The heat generated in the reactor 11 is transmitted to the heat exchanger 3, and the exhaust gas is heated (warmed up) through the heat exchanger 3. Then, the heated exhaust gas raises the DOC 4 to an activation temperature suitable for purification of pollutants.
_{MgBr 2 + x NH 3 ⇔ Mg} (NH 3) x Br 2 + heat ... (A)

On the other hand, when the temperature of the exhaust gas discharged from the engine 2 becomes equal to or higher than the regeneration temperature, the heat of the exhaust gas is given to the reaction material 15 of the reactor 11 through the heat exchanger 3, so that the reaction material 15 absorbs the heat. Then, NH ₃ is desorbed from the reaction material 15. That is, a reaction (regeneration reaction) from the right side to the left side in the above reaction formula (A) occurs. Then, due to the pressure difference between the reactor 11 and the adsorber 13, NH ₃ desorbed from the reaction material 15 returns to the adsorber 13 through the NH ₃ supply pipe 12 and is accommodated in the container 17 of the adsorber 13. The NH ₃ returning to the adsorbent 16 is physically adsorbed. Thereby, NH ₃ is recovered in the adsorber 13.

Here, when NH ₃ is desorbed from the adsorbent 16, the adsorbent 16 absorbs the ambient heat, so that the temperature of the adsorber 13 decreases. When the temperature of the adsorber 13 decreases, the NH ₃ becomes difficult to desorb from the adsorbent 16 thereafter. On the other hand, when NH ₃ is physically adsorbed on the adsorbent 16, the adsorbent 16 generates heat, so that the temperature of the adsorber 13 increases. When the temperature of the adsorber 13 increases, NH ₃ becomes difficult to be physically adsorbed by the adsorbent 16 thereafter.

For this reason, conventionally, an adsorber is configured by alternately stacking tubes and heat exchange fins containing adsorbents, and heat exchange between the adsorber and the outside air makes it possible to change the temperature of the adsorber. Had eased. However, in order to relieve the temperature change of the adsorber using heat exchange fins as in the past, the structure for heat exchange becomes complicated and the adsorber becomes large in size. It was. On the other hand, when the chemical heat storage device 10 is to be mounted on a vehicle or the like, it is necessary to reduce the size of the adsorber in terms of mountability. Therefore, when the adsorber is downsized with the conventional structure, the heat exchange performance with air is lowered, and the following problems occur. That is, when NH ₃ is desorbed from the adsorbent, the adsorbent absorbs heat, and as shown by the broken line P in FIG. 4A, the temperature of the adsorbent rapidly decreases immediately after the desorption of NH ₃ . On the other hand, when NH ₃ is adsorbed on the adsorbent, the adsorbent generates heat, and as shown by the broken line P in FIG. 4B, the temperature of the adsorbent rapidly increases immediately after the desorption of NH ₃ .

On the other hand, in the present embodiment, in the container 17 of the adsorber 13, a heat transfer material 18 having a higher thermal conductivity than the adsorbent 16 and a larger heat capacity than the adsorbent 16 is mixed together with the adsorbent 16. . Therefore, when NH ₃ is desorbed from the adsorbent 16, the adsorbent 16 absorbs ambient heat, but a heat transfer material 18 having a large heat capacity and good thermal conductivity is disposed around the adsorbent 16. Therefore, the adsorbent 16 does not take heat away from the surrounding adsorbents 16, but heat mainly moves from the heat transfer material 18 to the adsorbents 16. For this reason, as shown by the solid line Q in FIG. 4A, a decrease in the temperature of the adsorber 13 during the desorption of NH ₃ is suppressed. On the other hand, when NH ₃ is adsorbed on the adsorbent 16, the adsorbent 16 generates heat. At this time, heat moves from the adsorbent 16 to the heat transfer material 18 arranged in contact with the periphery of the adsorbent 16. As indicated by the solid line Q in FIG. 4B, the temperature rise of the adsorber 13 during the adsorption of NH ₃ is suppressed. Therefore, it is not necessary to increase the size of the adsorber 13 in order to suppress the temperature change of the adsorber 13 by exchanging heat between the adsorbent 16 and the outside air.

Thus, according to this embodiment, the temperature change of the adsorber 13 during the adsorption and desorption of NH ₃ with respect to the adsorbent 16 can be mitigated. By relaxing the temperature change of the adsorber 13, the desorption of NH ₃ from the adsorbent 16 and the adsorption of NH ₃ to the adsorbent 16 are performed quickly. Therefore, the heat output of the reactor 11 can be increased, and the recovery time of NH ₃ in the adsorber 13 can be shortened.

  The adsorber 13 has a structure in which an adsorbent 16 mixed with a heat transfer material 18 is accommodated in a container 17. Therefore, the structure of the adsorber 13 can be simplified and the physique of the adsorber 13 can be simplified as compared with the adsorber provided with a plurality of heat exchange fins that exchange heat between the adsorbent and the outside air. It can be downsized.

Further, when the mode diameter of the particles of the adsorbent 16 is Ra and the mode diameter of the particles of the heat transfer material 18 is Rm, the particles of the adsorbent 16 are satisfied by satisfying 0.1 ≦ Rm / Ra ≦ 10.0. And the gap between the particles of the heat transfer material 18 are reduced, and the adsorbent 16 and the heat transfer material 18 are finely filled. Accordingly, a sufficient contact area between the adsorbent 16 and the heat transfer material 18 is ensured, so that heat easily moves between the adsorbent 16 and the heat transfer material 18. Thereby, when NH ₃ is desorbed from the adsorbent 16, the temperature decrease of the adsorbent 16 is further suppressed, and when the NH ₃ is adsorbed onto the adsorbent 16, the temperature increase of the adsorbent 16 is further suppressed. .

  Further, when the total volume of the particles of the adsorbent 16 in the container 17 is Va and the total volume of the particles of the heat transfer material 18 in the container 17 is Vm, 0.1 ≦ Vm / Va ≦ 5.0 is satisfied. Thus, an increase in the size of the adsorber 13 due to an increase in the total volume of the particles of the heat transfer material 18 can be suppressed while relaxing the temperature change of the adsorbent 16.

Further, since the container 17 as a pressure container for storing high-pressure NH ₃ is formed in a cylindrical shape, the strength of the container 17 is higher than when the container 17 is formed in a rectangular parallelepiped shape or a cubic shape. Therefore, the thickness of the container 17 can be reduced.

FIG. 5 is a cross-sectional view showing a modification of the adsorber 13 shown in FIG. In FIG. 5, the adsorber 13 has a heat transfer material 20 instead of the heat transfer material 18. That is, in the container 17 of the adsorber 13, a plurality of (here, six) heat transfer materials 20 are mixed together with the adsorbent 16. The heat transfer material 20 has a thin flat plate shape. The heat transfer material 20 is formed of the same material as the heat transfer material 18 described above. The heat transfer material 20 is provided with a hole (not shown) through which NH ₃ can pass. Each heat transfer material 20 is arranged in parallel with each other at equal intervals. The peripheral edge of each heat transfer material 20 is in contact with the inner wall surface of the container 17.

  When the heat transfer material 20 contacts the inner wall surface of the container 17, heat exchange between the heat transfer material 20 and the outside air is performed via the container 17 in addition to heat transfer between the adsorbent 16 and the heat transfer material 20. Will come to be. Thereby, the temperature change of the adsorption device 13 can be relieved further.

  Further, by making the shape of the heat transfer material 20 flat, the adsorber 13 can be easily manufactured as compared to the case where the particle heat transfer material 18 is evenly mixed with the particle adsorbent 16. Can do.

  In the modification, the heat transfer material 20 has a flat plate shape, but the heat transfer material 20 may be a curved plate or the like as long as it has a plate shape.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the container 17 has a cylindrical shape, but the container 17 is not particularly limited thereto, and may have a rectangular tube shape or the like.

In the above embodiment, the reaction medium NH ₃ and the reaction material 15 represented by the composition formula MXa are chemically reacted to generate heat. However, the reaction medium is not particularly limited to NH _3. , CO ₂ or the like may be used. When CO ₂ is used as the reaction medium, the reactants to be chemically reacted with CO ₂ include MgO, CaO, BaO, Ca (OH) ₂ , Mg (OH) ₂ , Fe (OH) ₂ , and Fe (OH) _3. FeO, Fe ₂ O _3, Fe ₃ O ₄ or the like is used.

  Furthermore, in the said embodiment, although exhaust gas is heated via the heat exchanger 3 by the chemical heat storage apparatus 10, this invention is applicable also to the chemical heat storage apparatus which heats catalysts, such as DOC4 directly. Further, the present invention is not limited to the exhaust system of the diesel engine 2 but can be applied to a chemical heat storage device disposed in the exhaust system of the gasoline engine.

  Moreover, in the said embodiment, although exhaust gas is heated via the heat exchanger 3 by the chemical heat storage apparatus 10, this invention is applicable also to the chemical heat storage apparatus which heats heating objects other than an engine exhaust system. It is. Such a heating target may be various heat media such as engine oil, cooling water or air. At this time, the reactor 11 of the chemical heat storage device 10 is disposed on the outer periphery (a part of the outer periphery or the entire outer periphery) of the heat medium flow path through which the heat medium flows, and the heat medium flow path itself is heated. Also good. Further, a heat exchanger may be disposed in the heat medium flow path through which the heat medium flows, and the heat medium may be heated via the heat exchanger. In addition, a heat exchanger integrated heater in which a plurality of reactors with reaction materials and heat exchangers such as heat exchange fins are alternately arranged is configured, and the heat medium is stored in the heat exchanger integrated heater. You may arrange | position in the heat-medium storage part currently carried out, or on the heat-medium flow path through which a heat-medium flows. Furthermore, the present invention can also be applied to a chemical heat storage device arranged other than the engine.

  DESCRIPTION OF SYMBOLS 10 ... Chemical thermal storage apparatus, 11 ... Reactor, 13 ... Adsorber (reservoir), 15 ... Reactant, 16 ... Adsorbent, 17 ... Container, 18 ... Heat transfer material, 20 ... Heat transfer material

Claims (5)

A reactor having a reaction material that generates heat by being subjected to a chemical reaction with the reaction medium and desorbs the heat when the heat is applied;
A reservoir connected to the reactor,
The reservoir includes an adsorbent from which the reaction medium is adsorbed and from which the reaction medium is desorbed, and a container for storing the adsorbent.
A chemical heat storage device, wherein a heat transfer material having a thermal conductivity higher than that of the adsorbent and a heat capacity larger than that of the adsorbent is mixed with the adsorbent in the container of the reservoir. The adsorbent and the heat transfer material are composed of a plurality of particles,
2. The condition according to claim 1, wherein when the mode diameter of the particles of the adsorbent is Ra and the mode diameter of the particles of the heat transfer material is Rm, 0.1 ≦ Rm / Ra ≦ 10.0. Chemical heat storage device. The adsorbent and the heat transfer material are composed of a plurality of particles,
When the total volume of the adsorbent particles in the container is Va and the total volume of the heat transfer material particles in the container is Vm, 0.1 ≦ Vm / Va ≦ 5.0. The chemical heat storage device according to claim 1 or 2, characterized in that   The chemical heat storage device according to claim 1, wherein the heat transfer material has a plate shape and is in contact with an inner wall surface of the container.   The chemical heat storage device according to any one of claims 1 to 4, wherein the container is formed in a cylindrical shape.

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