JP2016188721A - Chemical heat storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical heat storage device for suppressing a decline in the heat generation performance due to the thermodecomposition of ammonia.SOLUTION: The chemical heat storage device includes: a reactor having a heat storage material 24 to generate heat by chemical reaction with reaction medium and desorbing the reaction medium by the absorption of the heat, and a container 27 storing the heat storage material 24; a reservoir for reserving the reaction medium; and a connection pipe communicating the reactor with the reservoir, for distributing the reaction medium between the reactor and the reservoir. The reaction medium is ammonia. The container 27 is formed of metallic material (for example, stainless steel). At least in an area having contact with the ammonia on the inner face of the container 27, a coating layer 28 of ceramic (for example, silicon dioxide, diamond-like carbon, or titanium nitride) is formed to cover the inner face of the container 27.SELECTED DRAWING: Figure 4

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. The apparatus described in Patent Document 1 includes a heat accumulator (reactor) that heats an oxidation catalyst provided in an exhaust system of an internal combustion engine. In this chemical heat storage device, when the oxidation catalyst is heated, ammonia as a reaction medium is supplied to the reactor, whereby the heat storage material accommodated in the reactor is chemically reacted with ammonia to generate heat. Further, in this chemical heat storage device, in order to suppress thermal decomposition of ammonia in the reactor when the oxidation catalyst is in a high temperature state, the oxidation catalyst is divided into an upstream first region and a downstream second region. The reactor is arranged around the first region where the amount of catalyst supported is smaller than that in the second region.

JP 2013-234625 A

  By the way, in a chemical heat storage device using ammonia as a reaction medium, the container constituting the reactor has excellent corrosion resistance of ammonia, and has strength to withstand the pressure of ammonia supplied from the reservoir during heating of the heating target. Is required. For this reason, the container is usually formed of a metal material (for example, stainless steel). However, metal components (for example, iron and chromium contained in stainless steel) contained in this metal material act as a catalyst that promotes thermal decomposition of ammonia at high temperatures. When ammonia as a reaction medium is thermally decomposed, nitrogen and hydrogen are generated. Part of the nitrogen generated by the thermal decomposition of ammonia diffuses and penetrates into the inside from the surface of the container, and combines with the metal component constituting the container to form a nitride compound. Further, hydrogen generated by the thermal decomposition of ammonia stays in the reactor, lowering the partial pressure of ammonia in the reactor and inhibiting the diffusion of ammonia into the heat storage material. As a result, the exothermic performance in the reactor when ammonia is supplied from the reservoir to the reactor is reduced.

  Accordingly, an object of the present invention is to propose a chemical heat storage device that suppresses a decrease in heat generation performance due to thermal decomposition of ammonia.

  A chemical heat storage device according to one aspect of the present invention includes a reactor having a heat storage material that generates heat by a chemical reaction with a reaction medium and desorbs the reaction medium by endotherm, and a container that houses the heat storage material. A reservoir for storing the medium; and a connecting pipe for connecting the reactor and the reservoir and for allowing the reaction medium to flow between the reactor and the reservoir. The reaction medium is ammonia, and the container is made of a metal material. The ceramic coating layer which coat | covers the inner surface of a container is formed in the part currently formed and the part which contacts ammonia at least in the inner surface of a container.

  In this chemical heat storage device, the metal component contained in the metal material on the container surface is not in direct contact with the ammonia introduced into the container due to the ceramic coating layer formed on the inner surface of the container. The catalytic action of thermally decomposing ammonia by the metal component is suppressed. Therefore, even when the reactor reaches a high temperature, thermal decomposition of ammonia and nitriding of the container are suppressed, and generation of hydrogen is suppressed. Thereby, in a chemical heat storage device, the fall of the heat generation performance by thermal decomposition and nitridation of ammonia can be controlled.

  In one embodiment of the chemical heat storage device, the ceramic of the coating layer may be silicon dioxide. The silicon dioxide coating layer may be formed by converting polysilazane. In this method of converting polysilazane, a dense film having high adhesion can be thinly formed on the surface of a container made of a metal material.

  In the chemical heat storage device of one embodiment, the ceramic of the coating layer may be diamond-like carbon. In the chemical heat storage device of one embodiment, the ceramic of the coating layer may be titanium nitride.

  In the chemical heat storage device of one embodiment, the metal material forming the container may be stainless steel. In this chemical heat storage device, the coating layer can suppress the catalytic action of thermally decomposing ammonia by metal components such as iron and chromium contained in stainless steel.

  According to the present invention, it is possible to suppress a decrease in heat generation performance due to thermal decomposition of ammonia.

It is a schematic block diagram of the exhaust gas purification system provided with the chemical heat storage apparatus which concerns on one Embodiment. It is a perspective view of the reactor with a heat exchange part of FIG. It is a sectional side view of the reactor with a heat exchange part of FIG. It is a partial expanded side sectional view of the reactor with a heat exchange part of FIG. FIG. 2 is a partially enlarged plan cross-sectional view of the reactor with a heat exchange unit in FIG. 1. It is a partially expanded plane sectional view of the reactor with a heat exchange part at the time of surface-modifying the container inner surface.

  Hereinafter, a chemical heat storage device according to an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the element which is the same or it corresponds in each figure, and the overlapping description is abbreviate | omitted.

  In the embodiment, the present invention is applied to a chemical heat storage device provided in an exhaust gas purification system provided in an exhaust system of a vehicle engine (internal combustion engine). An exhaust gas purification system according to an embodiment is a system that purifies harmful substances (environmental pollutants) contained in exhaust gas discharged from an engine (particularly, a diesel engine). A catalyst DOC (Diesel Oxidation Catalyst), SCR [Selective Catalytic Reduction], ASC [Ammonia Slip Catalyst], and DPF [Diesel Particulate Filter] of the filter are provided. Furthermore, the exhaust gas purification system according to the embodiment includes a chemical heat storage device for warming up the catalyst.

  With reference to FIG. 1, the whole structure of the exhaust-gas purification system 1 which concerns on one Embodiment is demonstrated. FIG. 1 is a schematic configuration diagram of an exhaust gas purification system 1 according to an embodiment.

  The exhaust gas purification system 1 includes a DOC (diesel oxidation catalyst) 4, a DPF (diesel exhaust particulate removal filter) 5, an SCR (selection) from the upstream side to the downstream side of the exhaust pipe 3 connected to the exhaust side of the engine 2. (Reduction catalyst) 6 and ASC (ammonia slip catalyst) 7 are provided. Exhaust gas discharged from the engine 2 flows through the exhaust pipe 3, DOC4, DPF5, SCR6, and ASC7. The upstream side and the downstream side are defined by the flow direction of the exhaust gas.

DOC4 is a catalyst that oxidizes HC, CO, etc. contained in exhaust gas. The DPF 5 is a filter that collects and removes PM contained in the exhaust gas. When ammonia (NH ₃ ) or urea water (hydrolyzed to generate ammonia) is supplied to the upstream side of the SCR 6 in the exhaust pipe 3, the SCR 6 chemically reacts ammonia and NOx contained in the exhaust gas. Thus, it is a catalyst that reduces and purifies NOx. The ASC 7 is a catalyst that oxidizes ammonia that has passed through the SCR 6 and has flowed downstream.

  Each of the catalysts 4, 6, and 7 has a temperature range (that is, an activation temperature) that can exhibit a purification ability against environmental pollutants. When the temperature of each catalyst 4, 6, 7 is lower than the activation temperature (for example, when the engine 2 is cold started), the catalyst 4, 6, 7 cannot exhibit a sufficient purification capacity. Further, when the catalyst is warmed up by the exhaust gas discharged from the engine 2, the temperature of the exhaust gas is relatively low immediately after the cold start of the engine 2, so that the catalyst cannot be warmed up quickly. Therefore, the exhaust gas purification system 1 includes a chemical heat storage device 10 for warming the exhaust gas upstream of the DOC 4 that is the most upstream catalyst and warming up the catalyst.

  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 stores the reaction medium that is desorbed from the heat storage material by the heat supplied from the heating target, and supplies the stored reaction medium to the heat storage material when necessary. In this device, the heat storage material and the reaction medium are chemically reacted to warm 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 this embodiment, the object to be heated is exhaust gas, and the reaction medium is ammonia.

  The chemical heat storage device 10 will be described in detail with reference to FIGS. 2 and 3 in addition to FIG. FIG. 2 is a perspective view of the reactor 11 with a heat exchanging portion in FIG. FIG. 3 is a side sectional view of the reactor 11 with a heat exchanging portion in FIG.

  The chemical heat storage device 10 includes a reactor 11 with a heat exchange unit, a reservoir 12, a connecting pipe 13, and a valve 14. The reactor 11 with a heat exchange part is arrange | positioned between the engine 2 and DOC4. The reactor 11 with a heat exchange part functions as a heater, and heats exhaust gas via a heat exchange part upstream from DOC4 which is the catalyst arrange | positioned in the uppermost stream. The exhaust gas heated by the heating flows into each downstream catalyst (DOC4, SCR6, ASC7). Thereby, each catalyst is warmed up.

  The reactor 11 with a heat exchange unit includes a pipe 20, two lid members 21 and 22, a plurality of heat exchange units 23, a plurality of heat storage materials 24, and a heat insulating material 25. As shown in FIG. 3, the plurality of heat exchange portions 23 and the plurality of heat storage materials 24 are alternately stacked to form a stacked body 26. The heat storage material 24 is disposed at both end portions (outermost portions in the stacking direction) of the stacked body 26. Therefore, the number of the heat storage materials 24 is one more than the number of the heat exchange parts 23. In FIG. 3, the number of heat exchanging parts 23 is three and the number of heat accumulating materials 24 is four. However, the present invention is not limited to this, and the number of heat exchanging parts 23 and heat accumulating materials 24 may be an appropriate number. . Further, the heat exchanging unit 23 may be disposed at the end of the stacked body 26.

  The pipe 20 is a pipe that surrounds the stacked body 26. The pipe 20 has a cylindrical shape with a circular cross section. The pipe 20 has a diameter larger than the diameter of the exhaust pipe 3. The upstream side of the pipe 20 is connected via the exhaust pipe 3 and the taper pipe 30. The downstream side of the pipe 20 is connected to the exhaust pipe 3 via the taper pipe 31. A lid member 21 is joined to the upstream end of the pipe 20. A lid member 22 is joined to the downstream end of the pipe 20. The lid members 21 and 22 are circular plate shapes corresponding to the shape of the pipe 20. The pipe 20 and the lid members 21 and 22 are made of stainless steel (SUS). Stainless steel is an alloy steel containing iron (Fe) as a main component and containing metals such as chromium (Cr), nickel (Ni), and molybdenum (Mo).

  The heat exchanging unit 23 forms a flow path through which the exhaust gas as a heating target is circulated, and performs heat exchange between the exhaust gas and the heat storage material 24. The heat exchange unit 23 is disposed between the heat storage material 24 and the heat storage material 24 adjacent to each other in the stacking direction of the stacked body 26. As shown in FIG. 3, the lengths of the plurality of heat exchange sections 23 in the width direction (the direction perpendicular to the flow direction of the exhaust gas and the direction perpendicular to the stacking direction of the stacked body 26) of the cylindrical pipe 20 Each is set along the inner peripheral surface 20a. Specifically, the length in the width direction of the plurality of heat exchanging parts 23 is shorter as the heat exchanging part 23 is arranged from the center side in the stacking direction of the stacked body 26 to the end side. The lengths of the plurality of heat exchange portions 23 in the exhaust gas flow direction are all the same length, and are substantially the same as the length of the pipe 20.

  The heat exchange unit 23 includes a metal tube 23a and metal fins 23b disposed in the tube 23a. In this embodiment, the tube 23a is formed in a flat rectangular tube shape. The upstream end and the downstream end of the tube 23a are open. Corresponding to the opening 23c of the tube 23a, the cover members 21 and 22 are formed with through holes 21a (only the through hole 21a of the upstream cover member 21 is shown in FIG. 2). The end on the upstream side and the end on the downstream side of the tube 23 a are fitted in the through hole 21 a of the lid member 21 and the through hole (not shown) of the lid member 22, respectively. Are joined to each other by welding or brazing. As a result, the exhaust gas can pass through the tube 23a. The fins 23 b are members for promoting heat exchange between the exhaust gas and the heat storage material 24. The fin 23b has, for example, a corrugated cross section. The fins 23b are joined to the inner wall surface of the tube 23a by welding or brazing. The tubes 23a and the fins 23b are made of stainless steel, for example.

  Thus, in the reactor 11 with a heat exchange part, the lid members 21 and 22 are joined to the upstream end part and the downstream end part of the pipe 20, and a plurality of heat exchange parts 23 are provided between the lid members 21 and 22. It is arranged. The plurality of heat storage materials 24 are accommodated in a space excluding a portion where the plurality of heat exchanging portions 23 are arranged in a cylindrical space formed by the pipe 20 and the lid members 21 and 22. Therefore, in the reactor 11 with a heat exchange part, the container 27 in which the some heat storage material 24 is accommodated is formed by the piping 20, the cover members 21 and 22, and the some heat exchange part 23 (especially tube 23a). ing.

  The heat storage material 24 is disposed in the heat storage material portion 24a provided between the heat exchange portion 23 and the heat exchange portion 23 adjacent to each other in the stacking direction of the stacked body 26 or the heat storage material portion 24a provided at the end portion in the stacking direction. Has been. Each length of the heat storage material 24 in the width direction is set to be along the inner peripheral surface 20a of the cylindrical pipe 20 as shown in FIG. The lengths of the plurality of heat storage materials 24 in the flow direction of the exhaust gas are all the same length and slightly shorter than the pipe 20.

The heat storage material 24 is a press-molded body obtained by press-molding a powder material into a pellet shape. Here, each heat storage material 24 is configured as press-molded into a flat, substantially rectangular parallelepiped shape. In addition, you may comprise the thermal storage material 24 from the pellet divided | segmented into plurality. When supplying ammonia as a reaction medium, the heat storage material 24 chemically reacts with ammonia (chemical adsorption) and generates heat. Further, when the heat storage material 24 chemically adsorbed with ammonia is heated via the heat exchanging portion 23 by the exhaust gas having a high temperature, the heat is absorbed and the ammonia is desorbed. As the heat storage material 24, a halogen compound represented by _a 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 or 3. The heat storage material 24 may be mixed with an additive that improves thermal conductivity. Examples of the additive include carbon fiber, carbon bead, SiC bead, metal bead, polymer bead, and polymer fiber. Examples of the metal material of the metal beads include Cu, Ag, Ni, Ci—Cr, Al, Fe, and stainless steel.

  The heat insulating material 25 is interposed between the inner peripheral surface 20 a of the pipe 20 and the laminated body 26. The heat insulating material 25 has an annular cross section. The outer peripheral surface side of the heat insulating material 25 has a shape along the inner peripheral surface 20 a of the pipe 20. The inner peripheral surface side of the heat insulating material 25 has a shape along the edge of the stacked body 26. The heat insulating material 25 is made of, for example, a hard ceramic material. By providing such a heat insulating material 25 on the outside of the heat storage material 24, the heat generated in the heat storage material 24 is difficult to escape to the outside of the pipe 20. In addition, you may make it arrange | position the heat insulating material 25 outside the reactor 11 with a heat exchange part.

  The reservoir 12 has an adsorbent 12a. The adsorbent 12a holds ammonia by physical adsorption and desorbs (separates) ammonia according to pressure. For example, activated carbon is used as the adsorbent 12a. In the storage device 12, ammonia is desorbed from the adsorbent 12 a during warm-up and supplied to the reactor 11 with a heat exchanging part (heat storage material 24). The material 12a is recovered by physical adsorption. The adsorbent 12a is not limited to activated carbon, and for example, mesoporous material having mesopores such as mesoporous silica, mesoporous carbon, and mesoporous alumina, or zeolite and silica gel may be used.

  The connection pipe 13 is a pipe that connects the reactor 11 with the heat exchange unit and the storage 12. The connecting pipe 13 serves as a flow path for ammonia to flow between the reactor 11 with a heat exchange section and the storage 12. As shown in FIG. 3, one end of the connection pipe 13 on the side of the reactor 11 with a heat exchange part is joined to the pipe 20 by welding or the like while being inserted into a through hole 20 b formed in the pipe 20. Yes. A through hole 25a is formed in the heat insulating material 25 corresponding to the position of the through hole 20b. An annular groove 25b is formed on the inner peripheral surface side of the heat insulating material 25 in order to facilitate the flow of ammonia in the circumferential direction. The groove 25b communicates with the through hole 25a.

  The valve 14 is a valve that opens and closes an ammonia flow path between the reactor 11 with a heat exchange unit and the storage 12. The valve 14 is disposed in the middle of the connecting pipe 13. When the valve 14 is opened, the reactor 11 with a heat exchanging part and the reservoir 12 communicate with each other through the connecting pipe 13 and ammonia can be moved. The opening / closing control of the valve 14 is performed by a dedicated controller of the chemical heat storage device 10 or an ECU [Electronic Control Unit] that controls the engine 2. The valve 14 is an electromagnetic normally closed valve, for example, and opens when a voltage is applied.

  In the chemical heat storage device 10, when the temperature of the exhaust gas discharged from the engine 2 is lower than a predetermined temperature (a temperature set based on the activation temperature of the catalyst) (for example, immediately after the engine 2 is started), the ECU The valve 14 is opened by the control. As a result, the high-pressure reservoir 12 filled with ammonia and the reactor 11 with the heat exchanging section having a lower pressure than the reservoir 12 are communicated with each other, and ammonia is desorbed from the adsorbent 12a of the reservoir 12. Release. Ammonia desorbed from the adsorbent 12a flows through the connecting pipe 13, moves to the reactor 11 with a heat exchange unit, and is supplied into the container 27 of the reactor 11 with a heat exchange unit. In the reactor 11 with a heat exchange section, the supplied ammonia and each heat storage material 24 chemically react to generate heat (exothermic reaction). The heat generated in each heat storage material 24 is conducted to each heat exchange unit 23. In each heat exchange part 23, the heat from the heat storage material 24 is given to the exhaust gas. That is, the heat exchange unit 23 exchanges heat between the heat storage material 24 and the exhaust gas. Thereby, the temperature of the exhaust gas is increased. As the exhaust gas heated by the chemical heat storage device 10 flows downstream, each catalyst (DOC4, SCR6, ASC7) is warmed up. Thereby, each catalyst is rapidly heated to the activation temperature or higher.

  If the operation of the engine 2 continues to some extent after the warm-up is finished, the temperature of the exhaust gas discharged from the engine 2 becomes high. The heat (exhaust heat) of the exhaust gas whose temperature has been increased is conducted to each heat exchange section 23. The heat storage material 24 is heated by each heat exchange part 23 heated by the heat of the exhaust gas. That is, the heat exchange unit 23 exchanges heat between the exhaust gas and the heat storage material 24. At this time, the heat storage material 24 that chemically adsorbs ammonia absorbs the heat of the exhaust gas and desorbs the ammonia. Thereby, ammonia is generated in the reactor 11 with a heat exchange part (regeneration reaction). Along with this regeneration reaction, the valve 14 is opened under the control of the ECU or the like. Thereby, the ammonia generated in the container 27 of the reactor 11 with the heat exchange section flows in the connecting pipe 13, moves to the storage 12 side, and is collected in the storage 12. In the reservoir 12, ammonia is adsorbed by the adsorbent 12a and stored.

Incidentally, in the container 27 of the heat exchange section with the reactor 11 is a high temperature (e.g., 400 ° C. or higher) becomes, as shown in equation (1), ammonia (NH ₃₎ is heated, the nitrogen _{(N 2)} Decomposes into hydrogen (H ₂ ). In particular, metal components such as iron (Fe) and chromium (Cr) present on the surface of the stainless steel of the container 27 (the container composed of the pipe 20, the cover members 21, 22 and the plurality of tubes 23a) are heated to a high temperature. It acts as a catalyst for thermal decomposition. Part of nitrogen generated by the thermal decomposition of ammonia diffuses and penetrates into the inside from the surface of the stainless steel and combines with the metal component contained in the stainless steel to form a nitride compound as shown in the formula (2). . M in the formula (2) is a metal such as iron (Fe) or chromium (Cr) contained in stainless steel, and MN is a nitride compound. When the formula (1) and the formula (2) are synthesized, the formula (3) is obtained.

  Further, when ammonia is thermally decomposed, hydrogen is generated together with nitrogen. In particular, as can be seen from Equation (3), when 1 mol of ammonia is decomposed by nitriding, 1.5 mol of hydrogen is generated. The generated hydrogen is not chemically adsorbed by the heat storage material 24 of the reactor 11 with the heat exchange section, and is not physically adsorbed by the adsorbent 12a of the storage device 12. Therefore, the generated hydrogen is present in a vacant space in the system through which ammonia flows, which is composed of the reactor 11 with the heat exchange section, the reservoir 12 and the connecting pipe 13. Therefore, as the ammonia is thermally decomposed, the amount of hydrogen in the system increases and the partial pressure of ammonia in the system decreases. When the partial pressure of ammonia in the system is lowered, the heat generation temperature of the heat storage material 24 is lowered when the reactor 11 with the heat exchange unit is maintained at a predetermined temperature. The generated hydrogen inhibits diffusion of ammonia into the heat storage material 24. As a result, the amount of heat generated when the reactor 11 with the heat exchange unit is warmed up is reduced, and the heat generation performance of the chemical heat storage device 10 is reduced. Therefore, in this chemical heat storage device 10, a coating layer for suppressing thermal decomposition (nitridation) of ammonia is formed on the inner surface of the container 27 of the reactor 11 with a heat exchange unit.

  A coating layer formed on the inner surface of the container 27 will be described with reference to FIGS. 4 and 5 in addition to FIGS. FIG. 4 is a partially enlarged side sectional view of the reactor 11 with a heat exchange section. FIG. 5 is a partially enlarged plan view of the reactor 11 with a heat exchange section.

  In the reactor 11 with a heat exchange part, the container 27 which accommodates the some heat storage material 24 is formed of the piping 20, the cover members 21 and 22, and the some tube 23a. The inner surface of the container 27 includes the inner peripheral surface 20a of the pipe 20, the surfaces 21b and 22b on the inner side (the heat storage material 24 side) of the lid members 21 and 22, and the outer sides (the heat storage material 24 side and the heat insulating material 25) of the plurality of tubes 23a. Side) surface 23d. Each of these surfaces 20a, 21b, 22b, and 23d is a surface with which ammonia supplied into the container 27 comes into contact.

A ceramic coating layer 28 is formed on all the surfaces 20a, 21b, 22b, and 23d, which are the inner surfaces of the container 27. The coating layer 28 is a thin film that covers the inner surface (the surface of stainless steel) of the container 27. For example, silicon dioxide (SiO ₂ , silica) is used as the ceramic of the coating layer 28.

  The surface of the stainless steel that is the base material of the container 27 is covered with the coating layer 28. The coating layer 28 prevents the stainless steel surface from coming into direct contact with the ammonia in the container 27. Therefore, the catalytic action of thermally decomposing ammonia by metal components such as iron and chromium contained in stainless steel is suppressed. Therefore, even when the inside of the container 27 of the reactor 11 with the heat exchanging portion becomes high temperature, ammonia thermal decomposition is suppressed, and accordingly, nitriding of the container 27 is also suppressed. As a result, the amount of nitrogen and hydrogen generated by the thermal decomposition of ammonia is reduced compared to a container without a coating layer. As a result, an increase in the partial pressure of hydrogen is suppressed, so that a decrease in the partial pressure of ammonia is suppressed. Further, the generated nitrogen is difficult to enter the container 27 (stainless steel) by the coating layer 28.

  In order to form the coating layer 28, a coating process is performed in the state of each member which comprises the container 27 before an assembly. When the coating process is performed in the state of each member, a coating layer may be formed only on the inner surface side of the container 27 assembled from each member, or a coating layer may be formed on the inner surface side and the outer surface side. When the entire member is coated, a coating layer is formed on the outer surface of the container 27 assembled from this member. In order to form the coating layer only on the inner surface side of the container 27, it is necessary to take a measure such as masking the portion other than the inner surface of the container 27 in the member during the coating process. In addition, as long as a coating process is possible in the state of the container 27 after an assembly, you may carry out in the state of the container 27 (The state in which the thermal storage material 24 is not accommodated).

  As a silicon dioxide coating method (film formation method), a known method is applied, for example, a sol-gel method or a method of converting polysilazane. The coating process by the sol-gel method is formed into a sol by hydrolysis and polymerization reaction in an alkoxide solution such as tetraethyl orthosilicate, and further gelled by heating to form a silicon dioxide thin film. The thickness of the silicon dioxide coating layer 28 by this sol-gel method is several tens of μm, for example, 30 μm.

Polysilazane is a high molecular compound having — (SiH ₂ NH) — as a basic unit, and is soluble in an organic solvent. As polysilazane, for example, perhydropolysilazane (PHPS) is used. Polysilazane reacts with moisture (H ₂ O) and converts to silicon dioxide while generating ammonia and hydrogen. The coating treatment using polysilazane is, for example, a conversion method by heating, applying an organic solvent solution of polysilazane to the surface of the member, and firing (heating) in the atmosphere or in an atmosphere containing water vapor to convert to silicon dioxide, A thin film of silicon dioxide is formed. The conversion method includes a conversion method by humidification and a conversion method by standing at room temperature. With this polysilazane conversion method, a dense film can be formed thin. The thickness of the coating layer 28 of silicon dioxide converted from polysilazane is 0. It is several μm to several μm, for example, 1 μm.

  As the ceramic of the coating layer 28, a ceramic other than silicon dioxide may be used, for example, diamond-like carbon (DLC [Diamond Like Carbon]) or titanium nitride (TiN) may be used. As a diamond-like carbon coating method, a known method is applied, for example, a CVD [Chemical Vapor Deposition] method or a PVD [Physical Vapor Deposition] method (sputtering method or the like). The thickness of the diamond-like carbon coating layer 28 is several tens of nanometers to several tens of micrometers. As a coating method of titanium nitride, a well-known method is applied, for example, there is a PVD method. The thickness of the titanium nitride coating layer 28 is several μm, for example, 2 to 3 μm.

  According to this chemical heat storage device 10, since the ceramic coating layer 28 is formed on the inner surface of the container 27 of the reactor 11 with a heat exchange part, the coating is performed even when the reactor 11 with a heat exchange part is in a high temperature state. The layer 28 can suppress thermal decomposition and nitridation of ammonia. Thereby, in the chemical heat storage apparatus 10, the fall of the heat generation performance by the thermal decomposition of ammonia in the reactor 11 with a heat exchange part can be suppressed. As a result, since the exhaust gas can be quickly heated, each catalyst such as DOC4 can be quickly heated to the activation temperature.

  Since the sol-gel method has a high processing temperature (for example, 800 ° C.), the silicon dioxide coating layer 28 by the sol-gel method has high heat resistance. In the case of this coating layer 28, the thermal conductivity is also relatively high. In addition, since the coating layer 28 is a film covering the surface of the stainless steel of the container 27, when the heat generated in the container 27 is transmitted to the heat exchanging portion 23, it becomes a factor that inhibits the heat conduction. Therefore, the coating layer 28 should have high thermal conductivity.

  In the case of the coating layer 28 of silicon dioxide formed by conversion of polysilazane, since it has a dense film quality, there are few defects such as pinholes. Further, since the coating layer 28 is a very thin film, its thermal conductivity is relatively high.

  Since the diamond-like carbon coating layer 28 has a hard film quality, the pressure resistance and wear resistance of the container 27 are improved. The diamond-like carbon coating process has a relatively low processing temperature (for example, room temperature to 200 ° C.) and a relatively short processing time compared with other ceramic coating processes. There are many advantages over other ceramic coating processes, such as uniform film formation.

  In the case of the coating layer 28 of titanium nitride, since it is a hard film quality, the pressure resistance, abrasion resistance, etc. of the container 27 are improved.

  As mentioned above, although embodiment of this invention was described, it is implemented in various forms, without being limited to the said embodiment.

  For example, in the above embodiment, the container of the reactor with a heat exchange part is applied to the one formed of stainless steel. However, the present invention is not limited to this, and other metal materials such as steel other than stainless steel, titanium, titanium alloy, etc. You may apply to the container formed. When the container formed of these metal materials is also in a high temperature state, thermal decomposition of ammonia is promoted when the metal contained in the metal material acts as a catalyst. Therefore, by forming a ceramic coating layer on the inner surfaces of these containers, it is possible to suppress a decrease in heat generation performance due to thermal decomposition of ammonia.

  In the above embodiment, the coating layer is formed on the surface of the stainless steel on the inner surface of the container. However, the present invention is not limited to this, and the coating layer is formed after the surface of the stainless steel on the inner surface of the container is modified. May be. Examples of the surface modification treatment include nitriding treatment and calorizing treatment.

  With reference to FIG. 6, the case where the nitriding process is performed as the surface modification process will be described. FIG. 6 is a partially enlarged plan sectional view of a reactor with a heat exchanging part when the inner surface of the container is surface-modified. When nitriding is performed as the surface modification treatment, a nitride layer 29 having a predetermined thickness is formed on the stainless steel surface on the inner surface of the container 27 by nitriding treatment, and then the coating layer 28 is formed on the nitrided surface. Form. In this case, the ammonia as a reaction medium in the container 27 is prevented from contacting the metal component such as iron or chromium contained in the stainless steel by the coating layer 28 and the nitride layer 29, so that the thermal decomposition of ammonia is further suppressed. The Rukoto. The nitriding treatment of the container 27 is performed by a known method such as a gas nitriding method, a plasma nitriding method, or a salt bath nitriding. For example, in the case of the gas nitriding method, each member is heated in ammonia using a nitriding furnace or the like, and a high temperature state (for example, 470 to 580 ° C.) is maintained for a predetermined time (for example, several tens of hours). Thus, the nitriding process is a very simple process as a surface modification process, and a nitride layer can be easily formed on the surface of a member (stainless steel material). When the time during which the high temperature state is maintained during the nitriding treatment is lengthened, the depth at which nitrogen penetrates into the stainless steel is increased, and nitriding proceeds into the stainless steel. Therefore, the thickness of the nitride layer 29 can be adjusted by adjusting the holding time in this high temperature state. The nitride layer 29 is preferably formed as a layer having a thickness (depth) from the surface of stainless steel of 20 μm or more.

A case where calorizing treatment is performed as the surface modification treatment will be described. When calorizing treatment is performed as a surface modification treatment, an aluminum diffusion and permeation layer having a predetermined thickness and an alumina coating are formed on the surface of stainless steel on the inner surface of the container by a calorizing treatment, and then coated on the calorized treatment surface. Form a layer. In this case, ammonia as a reaction medium in the container is prevented from contacting with metal components such as iron and chromium contained in the stainless steel constituting the container by the coating layer, the aluminum diffusion / permeation layer, and the alumina coating. Will be further suppressed. In the calorizing treatment, a penetrant composed of a mixed powder of FeAl alloy powder, alumina powder, and NH ₄ Cl powder and an object to be treated (container made of stainless steel) made of a metal material are contained in a sealed container, and 800 to This is a process of forming an aluminum diffusion / permeation layer (alloy layer of aluminum and a metal component contained in stainless steel) on the surface of a container which is an object to be processed by heat treatment at a high temperature of 1000 ° C. for a predetermined time. By this calorizing treatment, an alumina coating having a thickness of about several μm is also formed on the surface of the aluminum diffusion layer. The aluminum diffusion / penetration layer formed by calorizing treatment is preferably formed as a layer of 200 μm or more.

  Moreover, in the said embodiment, although it was set as the structure which arrange | positions the reactor with a heat exchange part in the upstream of DOC, and heated via a heat exchange part, you may arrange | position a reactor in another location and heat it, For example, the reactor may be disposed on the outer periphery of any one of DOC, SCR, and ASC. Moreover, in the said embodiment, it was set as the reactor with the heat exchange part of the structure which laminated | stacked the heat storage material and the heat exchange part alternately, and it was set as the container which accommodates several heat storage material on both sides of a heat exchange part, The configuration, the shape of the container, and the like are not particularly limited thereto. For example, the reactor may be a reactor in which a heat storage material is accommodated in an annular container that surrounds a substantially cylindrical heat exchange part, or a heat storage material in a rectangular parallelepiped container. May be used, and a plurality of rectangular parallelepiped reactors and a plurality of rectangular parallelepiped heat exchange units may be alternately stacked.

  In the above embodiment, the coating layer is formed on the entire inner surface of the container of the reactor with a heat exchange part, but if there is a part in the container that does not reach a high temperature enough to thermally decompose ammonia, The coating layer may not be formed. For example, in the case of a reactor that surrounds the heat exchanging part, the heat exchanging part is arranged on the inner peripheral surface side, but since the heat exchanging part is not arranged on the outer peripheral surface side, the outer peripheral surface side may not become high temperature. There is sex. Moreover, when there is a part which does not contact ammonia on the inner surface of the container, the coating layer may not be formed on the inner surface of the part.

  Further, in the above embodiment, the coating layer is formed on the inner surface of the reactor of the reactor with a heat exchange section, but when a member made of a metal material is provided inside the container, ammonia and A coating layer may also be formed on the contact surface. As a member provided inside the container, for example, there is a porous body provided for rapidly diffusing ammonia in a reactor or the like surrounding the heat exchange section, and this porous body is formed of a metal material. . By forming a coating layer on the surface of the member in contact with ammonia, it is possible to further suppress a decrease in heat generation performance due to thermal decomposition of ammonia.

  Further, in the above embodiment, a coating layer is formed on the inner surface of the reactor of the reactor with a heat exchanging part. If there is a part that becomes so hot that ammonia is thermally decomposed in addition to the reactor, the part is also coated. A layer may be formed. For example, the immediate vicinity of the reactor in the connecting pipe may become hot. The connecting pipe is also formed of a metal material such as stainless steel. Therefore, by forming a coating layer on the inner surface of the connection pipe in the immediate vicinity of the reactor, it is possible to further suppress a decrease in heat generation performance due to thermal decomposition of ammonia.

  Moreover, in the said embodiment, although it was set as the chemical thermal storage apparatus which heats (warms up) the exhaust gas discharged | emitted from a diesel engine, it is not restricted to this in particular, For the chemical thermal storage apparatus etc. which heat the exhaust gas discharged | emitted from a gasoline engine The present invention may be applied to an exhaust gas purification catalyst, a heat exchanger, or a chemical heat storage device that heats other engine components. Moreover, you may apply to the chemical thermal storage apparatus which heats gaseous or liquid fluids (for example, oil, water, air, water vapor | steam) besides exhaust gas. In addition to the engine, a chemical heat storage device may be applied to a garbage incineration plant, a power plant, various plant factories, and the like.

  DESCRIPTION OF SYMBOLS 1 ... Exhaust gas purification system, 2 ... Engine, 3 ... Exhaust pipe, 4 ... DOC, 5 ... DPF, 6 ... SCR, 7 ... ASC, 10 ... Chemical heat storage device, 11 ... Reactor with a heat exchange part, 12 ... Storage 12a ... adsorbent, 13 ... connecting pipe, 14 ... valve, 20 ... piping, 20a ... inner peripheral surface, 20b ... through hole, 21,22 ... lid member, 21a ... through hole, 21b, 22b ... surface, 23 ... heat exchange part, 23a ... tube, 23b ... fin, 23c ... opening, 23d ... surface, 24 ... heat storage material, 24a ... heat storage material part, 25 ... heat insulating material, 25a ... through hole, 25b ... groove part, 26 ... lamination Body, 27 ... container, 28 ... coating layer, 29 ... nitride layer, 30, 31 ... taper tube.

Claims (6)

A reactor having a heat storage material that generates heat by chemical reaction with the reaction medium and desorbs the reaction medium by endotherm, and a container that houses the heat storage material therein,
A reservoir for storing the reaction medium;
A connecting pipe that communicates the reactor and the reservoir and circulates the reaction medium between the reactor and the reservoir;
With
The reaction medium is ammonia;
The container is made of a metal material,
A chemical heat storage device in which a ceramic coating layer that covers the inner surface of the container is formed on at least a portion of the inner surface of the container that contacts the ammonia.   The chemical heat storage device according to claim 1, wherein the ceramic is silicon dioxide.   The chemical heat storage device according to claim 2, wherein the coating layer of silicon dioxide is formed by converting polysilazane.   The chemical heat storage device according to claim 1, wherein the ceramic is diamond-like carbon.   The chemical heat storage device according to claim 1, wherein the ceramic is titanium nitride.   The chemical heat storage device according to any one of claims 1 to 5, wherein the metal material is stainless steel.

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