JP2017096537A - Chemical heat storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of heat generation performance in a chemical heat storage device.SOLUTION: A chemical heat storage device 10 includes: a storage 11 for storing NH; and a heater 12 having a particulate reaction material 14 for generating heat by a chemical reaction with NHand for desorbing NHwhen heated. The material of the reaction material 14 is metal halide, and at least at one part on the surface of particles 19 of the reaction material 14, a metal oxide 17 of the same kind of metal as the metal contained in the metal halide is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a chemical heat storage device.

As a conventional chemical heat storage device that heats a warm-up target, for example, a chemical heat storage device that is applied to an exhaust purification system that purifies exhaust discharged from an internal combustion engine of a vehicle is known (see, for example, Patent Document 1). . In the chemical heat storage device applied to the exhaust gas purification system, when the temperature of the exhaust gas discharged from the internal combustion engine becomes lower than the warm-up start temperature, NH ₃ which is a reaction medium stored in the reservoir reacts through the supply pipe. Supplied to the vessel. As a result, the supplied NH ₃ and the reaction material in the reactor chemically react to generate heat. That is, an exothermic reaction occurs. Exhaust as a heating target is heated via a heat exchanger or the like by heat generated by the exothermic reaction. Further, when the temperature of the exhaust discharged from the internal combustion engine becomes higher than the reaction medium regeneration temperature, the heat of the exhaust is given to the reaction material in the reactor, and NH ₃ is desorbed from the reaction material in the reactor. That is, a regeneration reaction occurs. Then, the desorbed NH ₃ is collected in the reservoir through the supply pipe.

JP 2013-72558 A

When the reaction material and NH ₃ react and NH ₃ is taken into the crystal of the reaction material, the melting point of the reaction material falls below the original melting point of the reaction material. For this reason, in the conventional chemical heat storage device, when the reaction material in the reactor is exposed to a high temperature state for a long time during the regeneration reaction after the exothermic reaction is completed, a part of the particles of the reaction material is melted, There is a possibility that the number of pores constituting the NH ₃ diffusion channel existing on the surface of the reaction material particles may be reduced. Here, the term “melting” includes not only a flow phenomenon that occurs when the melting point is reached but also a particle enlargement phenomenon (sintering) at a temperature lower than the melting point. When the pores present on the surface of the reaction material particles are reduced, the diffusion rate of NH ₃ supplied to the reactor into the reaction material becomes slow. That is, the reaction rate between the reaction material and NH ₃ decreases. As a result, there is a problem that heat generation performance in the chemical heat storage device is lowered.

  An object of this invention is to provide the chemical thermal storage apparatus which can suppress the fall of exothermic performance.

Chemical heat storage device according to the present invention includes a reservoir for storing NH _3, when heated together generates heat by chemical reaction between NH ₃ and reactor with a particulate reactive material capable of leaving the NH _3, the The material of the reaction material is a metal halide, and an oxide of the same type of metal as the metal contained in the metal halide is formed on at least a part of the surface of the particles of the reaction material.

In the chemical heat storage device according to the present invention, the material of the reaction material is a metal halide, and an oxide of the same type of metal as the metal contained in the metal halide is at least part of the surface of the particles of the reaction material. Is formed. The metal halide used in the reaction material has a melting point lower than the original melting point of the metal halide when NH ₃ is incorporated. In contrast, oxides of the same kind of metal as the metal contained in the metal halide is inert to NH _3, has a higher melting point than the metal halide is NH ₃ was incorporated. For this reason, even when the reaction material becomes high temperature during the regeneration reaction and the reaction material melts, the metal oxide formed on the surface of the particles of the reaction material is hardly melted. Since the reactant particles are adjacent to each other through such a metal oxide, a NH ₃ diffusion channel can be secured by a gap between the reactant particles. Then, during the exothermic reaction after the regeneration reaction, NH ₃ can be reliably supplied to the reaction material by the secured NH ₃ diffusion channel, and a decrease in the reaction rate can be suppressed. As a result, it is possible to suppress a decrease in heat generation performance in the chemical heat storage device.

  In the chemical heat storage device according to the present invention, the oxide may be an oxide in a state where at least a part of the reaction material is oxidized. In this case, it is possible to easily realize a configuration in which an oxide of the same type of metal as the metal contained in the metal halide is formed on at least a part of the surface of the reactant particle.

In the chemical heat storage device according to the present invention, the oxide may cover the entire surface of the particles of the reaction material. In this case, since the metal oxide is reliably interposed between the particles of the reaction material, the NH ₃ diffusion channel can be more sufficiently secured by the gap between the particles of the reaction material.

  ADVANTAGE OF THE INVENTION According to this invention, the chemical thermal storage apparatus which can suppress the fall of heat_generation | fever performance is provided.

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 of this invention. It is a schematic sectional drawing which shows the state in which the metal oxide is formed on the surface of the particle | grains of a reaction material. It is a conceptual diagram which shows a mode that the particle | grains of a reaction material fuse | melt at the time of regeneration reaction in the conventional chemical heat storage apparatus. Is a graph showing the temperature change during the exothermic reaction of MgBr ₂ in the case of non-oxidized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  With reference to FIG. 1, the exhaust gas purification system provided with the chemical heat storage apparatus which concerns on one Embodiment of this invention is demonstrated. FIG. 1 is a schematic configuration diagram illustrating an exhaust purification system including a chemical heat storage device according to an embodiment of the present invention.

  The exhaust purification system 1 is disposed in an exhaust system of a diesel engine 2 (hereinafter simply referred to as an engine 2) that is an internal combustion engine of a vehicle, and removes harmful substances (environmental pollutants) contained in exhaust discharged from the engine 2. Purify. The exhaust purification system 1 includes a heat exchanger 4, an oxidation catalyst (DOC: Diesel Oxidation Catalyst) 5, which are arranged in order from an upstream side to a downstream side in an exhaust pipe 3 which is an exhaust passage connected to an engine 2. A diesel exhaust particulate filter (DPF) 6, a selective catalytic reduction (SCR) 7, and an oxidation catalyst (ASC: Ammonia Slip Catalyst) 8 are provided.

The heat exchanger 4 transfers heat between the exhaust from the engine 2 and a reaction material 14 described later. The heat exchanger 4 has a honeycomb structure, for example. The DOC 5 oxidizes and purifies HC and CO contained in the exhaust. The DPF 6 collects and removes particulate matter (PM) contained in the exhaust gas. The SCR 7 reduces and purifies NOx contained in the exhaust with urea or ammonia (NH ₃ ). The ASC 8 oxidizes and purifies NH ₃ that has passed through the SCR 7 and has flowed downstream of the SCR 7.

  Each catalyst of DOC5, SCR7, and ASC8 has a temperature range that can exhibit the ability to purify environmental pollutants, that is, an activation temperature. However, immediately after the engine 2 is started, the temperature of the exhaust gas immediately after being discharged from the engine 2 is as low as about 100 ° C., and may be lower than the activation temperature of each catalyst. Even in such a case, it is necessary to quickly bring the temperature of each catalyst to the activation temperature in order to exhibit the purification ability of each catalyst.

  Therefore, the exhaust gas purification system 1 according to the present embodiment includes a chemical heat storage device 10 that heats the exhaust gas via the heat exchanger 4 arranged on the most upstream side of the exhaust pipe 3. When the chemical heat storage device 10 heats the exhaust gas via the heat exchanger 4, the exhaust gas whose temperature is higher than that of the upstream side flows on the downstream side of the heat exchanger 4, and the catalyst is activated early. Can do.

The chemical heat storage device 10 uses the NH ₃ as a reaction medium and utilizes a reversible chemical reaction to heat the exhaust gas to be heated via the heat exchanger 4 without any external energy. In other words, the chemical heat storage device 10 is typically leave accumulated heat by the state to separate the reaction member 14 and the NH ₃ to be described later, when the heating of the heat exchanger 4 is required, reacting the NH ₃ By supplying to the material 14, heat is generated from the reaction material 14 and the exhaust gas is heated through the heat exchanger 4.

  The chemical heat storage device 10 includes a storage 11 (reservoir), a heater 12 (reactor), a supply pipe 15, and a valve 16.

Storage 11 includes an adsorbent 13 capable of leaving the holding and NH ₃ by physical adsorption of NH _3. As the adsorbent 13, activated carbon, carbon black, mesoporous carbon, nanocarbon, zeolite, or the like is used. Storage 11, by physically adsorbed NH ₃ to the adsorbent 13, for storing NH _3.

  The heater 12 is disposed around the exhaust pipe 3 so as to correspond to the heat exchanger 4 in the exhaust pipe 3. That is, the heater 12 is disposed so as to heat the heat exchanger 4. The heater 12 has, for example, an annular cross section surrounding the exhaust pipe 3. The cross-section of the annular cross section is a surface obtained by cutting the heater 12 perpendicular to the exhaust flow direction in the exhaust pipe 3.

The heater 12 has an oxide-containing reaction material 18. The oxide-containing reaction material 18 includes a particulate reaction material 14. That is, the heater 12 has a reaction material 14. In the present embodiment, the particulate form includes a powder form constituted by fine particles such as powder. The reaction member 14, together with NH ₃ and then a chemical reaction to generate heat, and desorbs NH ₃ by being heated by the exhaust of the heat to a high temperature. Therefore, in the heater 12, when NH ₃ is supplied from the storage 11, the NH ₃ and the reaction material 14 chemically react to generate heat. In the heater 12, when heat equal to or higher than the desorption start temperature is applied, NH ₃ is desorbed from the reaction material 14 and begins to release NH ₃ . Since the exothermic temperature and the desorption start temperature differ depending on the combination of NH _{3 as the} reaction medium and the reaction material 14, the reaction material 14 is appropriately selected according to the target heating temperature to be heated.

  As the reaction material 14, a metal halide represented by a composition formula MXa is used. That is, the material of the reaction material 14 is a metal halide. 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 a number specified by the valence of M, and is 2-3.

  Furthermore, in this embodiment, the oxide containing reaction material 18 contains the metal oxide 17 as shown in FIG. That is, the oxide-containing reaction material 18 includes a particulate reaction material 14 and a metal oxide 17 formed on the surface of the particles 19 of the reaction material 14. FIG. 2 is a schematic cross-sectional view showing a state in which the metal oxide 17 is formed on the surface of the particles 19 of the reaction material 14. The metal oxide 17 is formed on at least a part of the surface of the particle 19 of the reaction material 14. In the present embodiment, the metal oxide 17 covers the entire surface of the particles 19 of the reaction material 14.

The metal oxide 17 is an oxide of the same type of metal as the metal contained in the metal halide used in the reaction material 14. The same type of metal is a metal having the same characteristics as each other, for example, metals having the same atomic number. For example, when the reaction material 14 is MgBr ₂ , the metal oxide 17 is MgO.

  The oxide-containing reaction material 18 is press-molded with the metal oxide 17 formed on the surfaces of the particles 19 of the particulate reaction material 14. By this press molding, the oxide-containing reaction material 18 is molded into a molded body such as a plate shape, a pellet shape, or a tablet shape. For example, the oxide-containing reaction material 18 is obtained by uniformly mixing the particulate reaction material 14 in which the metal oxide 17 is formed on the surface of the particles 19 with a powder mixer or the like, and placing the mixture in a mold. For example, it is formed by being pressed and pressed at a pressure of 20 to 100 MPa.

In the present embodiment, the metal oxide 17 is formed by oxidizing the reaction material 14. For example, the metal oxide 17 is formed by heat-treating the reaction material 14 in a dry oxygen atmosphere. For example, when MgBr ₂ is used as the reaction material 14, the heat treatment is performed in a tubular furnace under conditions where the heating temperature is about 650 ° C. or higher and the heating time is about 1 hour. When the reaction material 14 is heat-treated in a dry oxygen atmosphere, at least a part of the metal contained in the metal halide used in the reaction material 14 is oxidized. Thereby, the metal oxide 17 is formed on at least a part of the surface of the particle 19 of the reaction material 14. That is, the metal oxide 17 is an oxide in a state where at least a part of the reaction material 14 is oxidized. Further, the metal oxide 17 is not limited to the heat treatment, and may be formed, for example, by performing a vacuum film forming process on the reaction material 14.

The formation of the metal oxide 17 on the surface of the particles 19 of the reaction material 14 is confirmed by using an X-ray diffraction method (XRD) or the like. For example, when the reaction material 14 is MgBr ₂ , it can be confirmed that a peak indicating MgO appears in the X-ray diffraction pattern measured by the X-ray diffraction method for the reaction material 14 after the oxidation treatment. it can.

  The oxidation treatment of the reaction material 14 may be performed after the above press molding. That is, the oxide-containing reaction material 18 may be configured by press-molding the particulate reaction material 14 and then oxidizing the reaction material 14 to form the metal oxide 17 on the surfaces of the particles 19. .

The particles 19 of the reaction material 14 are adjacent to each other through the metal oxide 17. The metal oxide 17 has a rough structure, and NH ₃ can pass therethrough. The metal oxide 17 is inactive to the reactant 14 and NH ₃ during the regeneration reaction in which NH ₃ is desorbed from the reactant 14, and has a melting point higher than the temperature of the reactant 14 during the regeneration reaction. Have. Inactive means that it is chemically stable and difficult to react chemically. The regeneration reaction is a reaction in which heated heat of exhaust gas is applied to the reaction material 14 of the heater 12 and NH ₃ is desorbed from the reaction material 14, and the reaction from the right side to the left side in the reaction formula (A) described later is performed. It is a reaction. The temperature of the reaction material 14 at the time of the regeneration reaction is, for example, the peak temperature (for example, about 400) of the reaction material 14 that becomes the highest temperature during the regeneration reaction. Therefore, the metal oxide 17 does not chemically react with the reactant 14 or NH ₃ during the regeneration reaction. In addition, the metal oxide 17 itself does not melt during the regeneration reaction. In the present embodiment, melting includes not only a flow phenomenon that occurs when the melting point is reached but also a particle enlargement phenomenon (sintering) at a temperature lower than the melting point. When the temperature of the reaction material 14 at the time of the regeneration reaction is, for example, about 400 ° C., the metal oxide 17 can react to both the reaction material 14 and NH ₃ in a temperature environment of about 400 ° C., for example. It does not react chemically and does not melt itself.

  The reaction material 14 disposed in the heater 12 has a heat conductivity higher than that of the reaction material 14, and serves as a heat conduction path that efficiently transfers heat generated in the reaction material 14 to the heat exchanger 4. Materials may be mixed. For example, when forming the reaction material 14 into a plate-shaped, pellet-shaped, or tablet-shaped molded body, the powdered reaction material 14 and the heat conducting material are uniformly mixed with a powder mixer or the like, and the mixture is molded. It is also possible to press and harden it into As the heat conducting material, for example, carbon fiber, carbon bead, SiC bead, metal bead, polymer bead, polymer fiber, or the like is used. As the metal beads, for example, metal beads such as Cu, Ag, Ni, Ci—Cr, Al, Fe, or stainless steel are used. Moreover, you may use the material which processed metal sheets, such as a graphite sheet or aluminum, as a heat conductive material.

The supply pipe 15 connects the storage 11 and the heater 12, and distributes NH ₃ between the storage 11 and the heater 12. That is, the supply pipe 15 forms a supply flow path in which NH ₃ moves between the storage 11 and the heater 12. The valve 16 is disposed in the supply pipe 15. That is, the valve 16 is disposed between the storage 11 and the heater 12. The valve 16 opens and closes the NH ₃ flow path between the storage 11 and the heater 12. For example, the valve 16 is an electromagnetic on-off valve. Opening control and closing control of the valve 16 are performed by a controller (not shown).

In the chemical heat storage device 10 as described above, when the temperature of the exhaust is lower than the warm-up start temperature, the valve 16 is opened, so that NH ₃ accommodated in the storage 11 is supplied to the heater 12 through the supply pipe 15, The reaction material 14 (for example, MgBr ₂ ) of the heater 12 chemically reacts with NH _3, and heat is generated from the reaction material 14. That is, a reaction from the left side to the right side (exothermic reaction) in the following reaction formula (A) occurs. The heat exchanger 4 is heated by the heat generated by the heater 12, and the exhaust gas is heated via the heat exchanger 4.
Mg (NH ₃ ) _X Br ₂ + YNH ₃ ＭｇMg (NH ₃ ) _{x + Y} Br ₂ (A)

When a predetermined time elapses after the valve 16 is opened, or when the temperature of the exhaust gas from the engine 2 becomes equal to or higher than the predetermined temperature, the valve 16 is closed, and the warm-up during the operation of the engine 2 ends. After the warm-up, when the engine 2 enters a steady operation state and the temperature of the exhaust gas discharged from the engine 2 becomes sufficiently high, the heat of the exhaust gas reacts with the heater 12 via the heat exchanger 4 this time. It will be given to the material 14. That is, the reaction material 14 is heated by the exhaust gas through the heat exchanger 4. When the temperature of the exhaust gas becomes equal to or higher than a predetermined recovery temperature, a regeneration reaction in which NH ₃ is desorbed from the reaction material 14 in a state where NH ₃ is chemically adsorbed inside the heater 12 (from the right side in the above reaction formula (A)). Reaction to the left side) occurs. Here, the predetermined recovery temperature is the temperature of the exhaust gas that can give the reaction material 14 heat sufficient to desorb NH ₃ from the reaction material 14. When the NH ₃ from the reaction member 14 detached, the valve 16 is opened, the NH ₃ desorbed from the reaction member 14 is movable from the heater 12 to the storage 11 through the supply pipe 15. When NH ₃ returns to the storage 11, NH ₃ is physically adsorbed by the adsorbent 13 in the storage 11 and collected.

In general, in order to desorb all NH ₃ from the reactant 14 in which NH ₃ is most coordinated (for example, hexahydrate in MgBr ₂ ) to make the NH ₃ non-coordinated reactant 14, NH ₃ must be Compared with the case where NH ₃ is partially desorbed from the maximum coordinated reaction material 14 (eg, hexahydrate in MgBr ₂ ) and NH ₃ becomes a low-coordinate reaction material 14, the energy is very high. Necessary. That is, a high temperature heat source is required to desorb NH ₃ from the reaction material 14. Therefore, normally, the reaction material 14 in which NH ₃ is coordinated to the maximum by causing NH ₃ to be supplied to the reaction material 14 having low NH ₃ coordination (for example, a hydrate in MgBr ₂ ) causes an exothermic reaction. For example, in the case of MgBr ₂ , a hexahydrate), and a reaction material 14 in which NH ₃ is coordinated to the maximum (for example, MgBr ₂ is a hexahydrate) causes heat to cause an elimination reaction, thereby reducing NH _3. coordination of the reaction member 14 (e.g., MgBr in ₂ 2 dihydrate) so as to, and controls the reaction. However, the low-coordinating reaction material 14 has a problem that its melting point is lower than that of the unnatural product due to coordination of NH ₃ . For example, in the case of MgBr ₂ , the melting point of the unnatural product is 700 ° C. or more, whereas in the case of MgBr ₂ , the melting point is lowered to about 400 ° C.

  Next, with reference to FIG. 3, the problem of the deterioration of the heat generation performance in the conventional chemical heat storage device will be described. FIG. 3 is a conceptual diagram showing how particles 19 of the reaction material 14 are melted during a regeneration reaction in a conventional chemical heat storage device. 3A shows the particles 19 of the reaction material 14 at a low temperature, and FIGS. 3B to 3D show how the particles 19 of the reaction material 14 melt at a high temperature.

At a low temperature, as shown in FIG. 3A, the particles 19 of the reaction material 14 are not melted, but the movement of atoms constituting the particles 19 is activated by heat and starts to soften. When heat is applied to the reaction material 14 during the regeneration reaction and the reaction material 14 reaches a high temperature (for example, about 400 ° C.), the particles 19 of the reaction material 14 begin to melt, as shown in FIG. This is because the reaction material 14 is made of a low-coordination (for example, MgBr ₂ dihydrate) material, so that the reaction material 14 has a melting point that is the original melting point of the reaction material 14 (that is, the unnatural reaction material 14). This is because it is lower than the melting point). And when predetermined time passes in such a high temperature state, as shown to (c) of FIG. 3, the contact surface of adjacent particle | grains 19 will join. As a result, the surface area of the bonded surface of each particle 19 is reduced, and the pores serving as NH ₃ diffusion channels are reduced due to blockage or the like. When the time further elapses, as shown in FIG. 3D, the melting of each particle 19 progresses, the joint surface of each particle 19 becomes larger, and the reduction of the pores further proceeds. As described above, when the pores serving as the NH ₃ diffusion flow path decrease due to the melting of the particles 19 of the reaction material 14, the diffusion speed of the NH ₃ supplied to the heater 12 into the reaction material 14 becomes slow. That is, the reaction rate between the reaction material 14 and NH ₃ decreases. As a result, there is a problem that the heat generation performance is lowered.

In response to this problem, according to the chemical heat storage device 10 according to the present embodiment, the material of the reaction material 14 is a metal halide (for example, MgBr ₂ ), and the same kind of metal as the metal contained in the metal halide. A metal metal oxide 17 (for example, MgO) is formed on at least a part of the surface of the particle 19 of the reaction material 14. When the metal halide is incorporated with NH ₃ , the melting point thereof is lower than the original melting point of the metal halide. In contrast, metal oxide 17 is inert with respect to NH _3, has a higher melting point than the metal halide is NH ₃ was incorporated. For this reason, even when the reaction material 14 becomes high temperature during the regeneration reaction and the reaction material 14 is melted, the metal oxide 17 formed on the surface of the particles 19 of the reaction material 14 is hardly melted. Since the particles 19 of the reaction material 14 are adjacent to each other through such a metal oxide 17, a NH ₃ diffusion channel can be secured by a gap between the particles 19 of the reaction material 14. In the exothermic reaction after the regeneration reaction, NH ₃ can be reliably supplied to the reaction material 14 through the secured NH ₃ diffusion flow path, and a decrease in the reaction rate can be suppressed. As a result, it is possible to suppress a decrease in heat generation performance in the chemical heat storage device 10.

  Further, since the metal oxide 17 is an oxide in which at least a part of the reaction material 14 is oxidized, the above-described configuration, that is, the metal oxide 17 is formed on at least a part of the surface of the particle 19 of the reaction material 14. The configured configuration can be easily realized.

In addition to this, the metal oxide 17 covers the entire surface of the particles 19 of the reaction material 14, so that the metal oxide 17 is reliably interposed between the particles 19 of the reaction material 14. Therefore, the NH ₃ diffusion channel can be more sufficiently secured by the gap between the particles 19 of the reaction material 14.

Next, with reference to FIG. 4 and Table 1, an example of an effect of suppressing a decrease in heat generation performance due to the metal oxide 17 being formed on the surface of the particles 19 of the reaction material 14 will be described. In this example, MgBr ₂ was used as the reaction material 14. In this example, an experiment on heat generation performance was performed as follows.

First, MgBr ₂ was filled in a bottomed rectangular tube-shaped stainless steel reaction vessel, and a lid with an NH ₃ introduction hole was attached to the opening of the reaction vessel and sealed. Subsequently, after the gas remaining in the internal space of the reaction vessel was removed with a vacuum pump, NH ₃ was introduced to cause an exothermic reaction. After completion of the exothermic reaction, a ceramic heater was brought into close contact with the outside of the reaction vessel, heated to a MgBr ₂ temperature of about 400 ° C., and allowed to stand for 3 hours to cause a regeneration reaction. Note that the emission destination NH ₃ during regeneration reaction of NH ₃ with an empty vessel, was as NH ₃ in a predetermined amount is not too high system pressure even by detachment. Thereafter, NH ₃ was again introduced into the reaction vessel to cause an exothermic reaction, and the exothermic performance was evaluated. The exothermic performance is calculated by measuring the MgBr ₂ temperature with a thermocouple previously installed in the reaction vessel to calculate the peak value of MgBr ₂ temperature during the exothermic reaction (hereinafter also referred to as “exothermic temperature”). The exothermic temperature was used for evaluation. Hereinafter, the exothermic reaction after the regeneration reaction is performed at a high temperature of about 400 ° C. is also referred to as “exothermic reaction after the heat history”.

As a comparative example, without the first particular oxidation treatment MgBr ₂ was directly subjected to the experiments described above. The result is shown in FIG. FIG. 4 is a graph showing a temperature change during an exothermic reaction of MgBr ₂ when not oxidized. The horizontal axis of FIG. 4 shows elapsed time [s], and the vertical axis of FIG. 4 shows the temperature of MgBr ₂ . The graph 20b of FIG. 4 shows the temperature change of MgBr ₂ during the exothermic reaction when there is no thermal history as a reference value. The case where there is no thermal history is a case where the regeneration reaction of NH ₃ is caused not in a high temperature state of about 400 ° C. but in a low temperature vacuum. For example, the vacuum is performed so that the temperature of MgBr ₂ becomes a low temperature of about 180 ° C. This is the case where the NH ₃ regeneration reaction is carried out. In this case, since MgBr ₂ is not at a high temperature during the regeneration reaction, the melting of MgBr ₂ does not occur, and as a result, the heat generation performance does not deteriorate due to the melting of MgBr ₂ . As shown in the graph 20b, the heat generation temperature of MgBr ₂ in this case was 260 ° C.

On the other hand, the graph 20a of FIG. 4 shows the temperature change of MgBr ₂ during the exothermic reaction after the thermal history. As shown in the graph 20a, the exothermic temperature of MgBr ₂ was about 237 ° C. In the case of the graph 20a, the response of the exothermic reaction was worse and the exothermic performance was worse than in the case of the graph 20b. This is because the MgBr ₂ melted due to the high temperature of 400 ° C. during the regeneration reaction, the pores serving as the NH ₃ diffusion channel were blocked, and the NH ₃ supply rate during the exothermic reaction was slow. As a result, it has shown that the heat-generation performance fell.

Next, as an example, the above-described experiment was performed using MgBr ₂ after the oxidation treatment. As the oxidation treatment, heat treatment was performed in a dry oxygen atmosphere. In Example 1, the heat treatment was performed under conditions where the heating temperature was about 650 ° C. and the heating time was about 10 minutes. In Example 2, the heat treatment was performed under conditions where the heating temperature was about 650 ° C. and the heating time was about 30 minutes. In Example 3, the heat treatment was performed under conditions where the heating temperature was about 500 ° C. and the heating time was about 10 minutes. In Example 4, the heat treatment was performed under conditions where the heating temperature was about 500 ° C. and the heating time was about 30 minutes. In addition, the temperature increase rate in each said Example was 10 degrees C / min. The results of Examples 1 to 4 are shown in Table 1 below. Table 1 is a table showing the heat generation performance for each heat treatment condition (heating temperature and heating time). In Table 1, the exothermic temperature of MgBr ₂ during the exothermic reaction after the thermal history is shown as the exothermic performance. In any of Examples 1 to 4, it was confirmed by X-ray diffraction that MgO was formed on at least a part of the surface of the MgBr ₂ particles after the heat treatment.

As shown in Table 1, in Example 1, the exothermic temperature of MgBr ₂ during the exothermic reaction after the thermal history was 259 ° C. In Example 2, the exothermic temperature of MgBr ₂ during the exothermic reaction after the heat history was 259 ° C. In Example 3, the exothermic temperature of MgBr ₂ during the exothermic reaction after the heat history was 241 ° C. In Example 4, the exothermic temperature of MgBr ₂ during the exothermic reaction after the heat history was 242 ° C. Therefore, in any of Examples 1 to 4, the exothermic temperature of MgBr ₂ during the exothermic reaction after the thermal history was higher than 237 ° C. in the comparative example and approached the reference value of 260 ° C.

As described above, it has been shown that by using MgBr ₂ in which MgO is formed on at least a part of the surface of the particle by oxidation treatment, it is possible to suppress a decrease in exothermic performance during an exothermic reaction after the thermal history.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, You may change in the range which does not change the summary described in each claim, or may apply to others.

  In the above embodiment, the metal oxide 17 is an oxide in which at least a part of the reaction material 14 is oxidized, but is not limited thereto. For example, the metal oxide 17 is not an oxide of the metal itself contained in the metal halide used in the reaction material 14, but is another type that is the same type as the metal and not contained in the reaction material 14. It may be a metal oxide.

  In the said embodiment, although the heater 12 was arrange | positioned around the exhaust pipe 3 so as to correspond to the heat exchanger 4, and it had a cross-sectional annular shape, it is not restricted to this. For example, you may arrange | position a heater so that it may correspond only to a part of heating object. Further, the heater may be arranged at a place other than the outside of the exhaust pipe, for example, may be arranged inside the exhaust pipe in order to heat the exhaust. When a heater is arranged inside the exhaust pipe, for example, a configuration in which a plurality of heaters and a heat exchange unit are alternately stacked, the heat exchange unit is integrated with the heater, and the exhaust is heated by the heater through the heat exchange unit. May be.

  A catalyst coat layer may be formed on part or all of the surface of the heat exchanger 4. In the above embodiment, the heating object is the heat exchanger 4, but the heating object may be another catalyst such as DOC 5 or exhaust gas flowing through the exhaust pipe 3.

  In the said embodiment, although the chemical thermal storage apparatus was applied to the diesel engine 2 which is an internal combustion engine of a vehicle, it is not restricted to this. For example, the chemical heat storage device may be applied to a gasoline engine or the like.

  Further, the chemical heat storage device may be a device that heats a heating target provided other than the exhaust system of the engine. Such a heating target may be various heat media such as engine oil, cooling water, or air. At this time, a heat exchanger may be disposed on the path through which the heat medium flows, and the heat exchanger may be heated by the chemical heat storage device. Further, the chemical heat storage device may be applied to other than the engine.

  DESCRIPTION OF SYMBOLS 10 ... Chemical thermal storage apparatus, 11 ... Storage (reservoir), 12 ... Heater (reactor), 14 ... Reactant, 17 ... Metal oxide (oxide), 19 ... Particles.

Claims (3)

A reservoir for storing NH ₃ ;
When heated with heat is generated by a chemical reaction between NH ₃ and reactor with a particulate reactive material desorbed NH _3, and
With
The material of the reaction material is a metal halide,
A chemical heat storage device in which an oxide of the same type of metal as that contained in the metal halide is formed on at least a part of the surface of the particles of the reaction material.   The chemical heat storage device according to claim 1, wherein the oxide is an oxide in a state where at least a part of the reaction material is oxidized.   The chemical heat storage device according to claim 1 or 2, wherein the oxide covers the entire surface of the particles of the reaction material.