JP2014234950A - Chemical heat accumulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical heat accumulating device capable of recovering a reaction medium surely at proper timing.SOLUTION: A chemical heat accumulating device 10 has: a ring-shaped reactor 11 arranged around an oxidation catalyst 4 and including a reaction material for generating heat by chemically reacting with NH; a heat accumulator 12 for performing heat accumulation by adsorbing and storing NH; a medium supply passage 13 for connecting the reactor 11 and the heat accumulator 12 and for supplying NHto the reactor 11 from the heat accumulator 12; and a medium supply passage 14 for connecting the reactor 11 and the heat accumulator 12 so as to be parallel with the medium supply passage 13 and for supplying NHto the heat accumulator 12 from the reactor 11. The medium supply passage 14 is provided with a suction pump 16. The suction pump 16 forcibly lowers pressure inside the reactor 11 by forcibly sucking the inside of the reactor 11, and forcibly recovers NHfrom the reactor 11 to the heat accumulator 12.

Description

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

  Conventionally, as a chemical heat storage device provided in an exhaust system of an engine, for example, a device described in Patent Document 1 is known. The chemical heat storage device described in Patent Document 1 is disposed in a gas passage tube that houses a catalyst body, and includes a first container that contains an adsorbent that generates heat and absorbs heat due to adsorption and desorption of a medium to be adsorbed, and a gas passage tube. And a second container that is disposed outside and is connected to the first container via a communication pipe and stores the adsorbed medium. When the catalyst body is heated, the medium to be adsorbed in the second container is supplied to the first container through the communication pipe, the medium to be adsorbed is adsorbed by the adsorbent, and the adsorbent generates heat. The medium is heated. Thereafter, when the exhaust gas temperature from the engine becomes high and the temperature of the catalyst body becomes sufficiently high, the heat is transferred to the first container, so that the adsorbent is heated and the adsorbed medium is desorbed from the adsorbent. The adsorbed medium returns to the second container through the communication pipe and is collected.

JP-A-11-3111117

  However, in the above prior art, if the exhaust gas temperature in the gas passage tube does not become sufficiently high, the adsorbent in the first container is not heated, and in some cases, the adsorbed medium (reaction medium) is not collected in the second container. there is a possibility. If the adsorbed medium is not collected in the second container, the adsorbed medium is not supplied from the second container to the first container at the next engine start, so the adsorbent does not generate heat, and as a result, the catalyst body is heated. I can't do that.

  An object of the present invention is to provide a chemical heat storage device that can reliably recover a reaction medium at an appropriate time.

  The present invention relates to a chemical heat storage device that heats an object to be heated provided in an exhaust system of an engine, and includes a reaction material that is disposed around or inside the object to be heated and that chemically reacts with a reaction medium to generate heat. A heat storage device that stores heat by storing the reaction medium, a first supply passage that is connected to the reaction device and the heat storage device, and that supplies the reaction medium from the heat storage device to the reaction device; A second supply passage connected in parallel to the reactor to supply the reaction medium from the reactor to the heat accumulator, and provided in the second supply passage, by forcibly lowering the pressure in the reactor, The heat storage device is provided with a forced recovery means for forcibly recovering the reaction medium.

  As described above, in the chemical heat storage device of the present invention, when the heating object is heated, the reaction medium stored in the heat storage device is supplied to the reactor through the first supply passage, and is included in the reaction material. And the reaction medium chemically react to generate heat, and the object to be heated is heated by the heat. When recovering the reaction medium to the heat accumulator, the temperature at which the reaction medium is desorbed from the reaction material is lowered by forcibly reducing the pressure in the reactor by the forced recovery means, and the reaction medium is transferred from the reactor to the heat accumulator. It becomes easy to be collected. By using the forced recovery means in this way, the reaction medium can be reliably recovered to the heat accumulator at an appropriate time. Further, by forcibly lowering the pressure in the reactor, the reaction medium can be recovered even at a temperature lower than the ambient temperature, so that the reaction medium can be efficiently recovered in the heat accumulator.

  Preferably, the apparatus further includes temperature detection means for detecting the temperature of the heating object, and control means for controlling the forced recovery means to operate based on the temperature of the heating object detected by the temperature detection means.

  In this case, for example, even if the temperature of the exhaust gas flowing through the object to be heated is not sufficiently high, the forced recovery means is activated when the temperature detected by the temperature detection means reaches a predetermined temperature. The medium can be reliably collected in the heat accumulator.

  Also, a determination unit that determines whether or not the filter disposed downstream of the heating target is before the time for regenerating PM contained in the exhaust gas, and the filter performs regeneration of PM by the determination unit. Control means for controlling the forced recovery means to operate when it is determined that it is before the time to perform may be further provided.

  Thus, when the filter is before the time to regenerate PM, the forced recovery means is activated to prevent the reaction medium in the reactor from being thermally decomposed due to an increase in exhaust temperature during PM regeneration. Is done.

  According to the present invention, the reaction medium can be reliably recovered at an appropriate time. Thereby, it becomes possible to heat a heating target object using a reaction medium also at the time of the next engine starting.

It is a schematic block diagram which shows the exhaust gas purification system provided with one Embodiment of the chemical heat storage apparatus which concerns on this invention. It is a graph which shows the equilibrium pressure characteristic of a reactor. It is a schematic block diagram which shows the exhaust gas purification system provided with other embodiment of the chemical heat storage apparatus which concerns on this invention.

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

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

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

The oxidation catalyst 4 is a catalyst that oxidizes and purifies HC, CO, etc. contained in the exhaust gas. The DPF 5 is a filter that collects and removes PM contained in the exhaust gas. The SCR 6 is a catalyst that reduces and purifies NOx contained in exhaust gas using ammonia (NH ₃ ) generated from urea water supplied by the addition valve 8. The addition valve 8 is connected to the urea water tank 9. The oxidation catalyst 7 is a catalyst that oxidizes NH ₃ that has flowed downstream of the SCR 6.

  Such an exhaust catalyst such as the oxidation catalyst 4 has a temperature range (activation temperature) that exhibits its ability to purify environmental pollutants. Therefore, in order to set the temperature of the oxidation catalyst 4 to the activation temperature, it is necessary to heat the oxidation catalyst 4.

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

The chemical heat storage device 10 is a ring-shaped reactor 11 disposed around the oxidation catalyst 4 and a heat storage device that is connected to the reactor 11 and stores heat by adsorbing and storing NH ₃ as a reaction medium. 12.

The reactor 11 contains a reaction material that chemically reacts with NH ₃ to generate heat. As the reaction material, for example, MgCl ₂ , CaCl ₂ , NiCl ₂ , ZnCl ₂ , SrCl ₂ , MnCl ₂ , CoCl ₂ or the like is used.

The regenerator 12 contains activated carbon that physically adsorbs NH ₃ . As NH ₃ is physically adsorbed on the activated carbon, NH ₃ is stored in the heat accumulator 12 in a high pressure state. In addition, as an adsorbent that adsorbs NH ₃ , zeolite may be used instead of activated carbon.

The chemical heat storage device 10 connects the reactor 11 and the heat storage 12, and a medium supply passage 13 for supplying NH ₃ from the heat storage 12 to the reactor 11, and the medium supply passage 13 in parallel. The reactor 11 and the regenerator 12 are connected so as to have a medium supply passage 14 for supplying NH ₃ from the reactor 11 to the regenerator 12. The medium supply passage 13 is provided with an electromagnetic on-off valve 15.

The medium supply passage 14 is provided with a suction pump 16 that forcibly sucks the inside of the reactor 11. The suction pump 16 forcibly lowers the pressure in the reactor 11 and creates a pressure difference between the reactor 11 and the heat accumulator 12, thereby forcing NH ₃ from the reactor 11 to the heat accumulator 12. It is a forced collection means to collect.

  Furthermore, the chemical heat storage device 10 includes a temperature sensor 17 and a controller 18. The temperature sensor 17 is a temperature detection unit that detects the temperature of the oxidation catalyst 4, and may directly detect the temperature of the oxidation catalyst 4 itself, or the temperature of the exhaust gas flowing through the oxidation catalyst 4 may be used as the temperature of the oxidation catalyst 4. It may be detected.

  The controller 18 is a control means for controlling the on-off valve 15 and the suction pump 16 based on the detection value of the temperature sensor 17. Specifically, the controller 18 controls the opening / closing valve 15 to open when the oxidation catalyst 4 is heated, and closes the opening / closing valve 15 when the oxidation catalyst 4 is not heated, and operates the suction pump 16. If so, control is performed so that the on-off valve 15 is closed.

Further, the controller 18 controls the suction pump 16 to operate when the detection value of the temperature sensor 17 reaches a specified temperature. Here, the specified temperature is set to a temperature higher than the activation temperature of the oxidation catalyst 4 and lower than the temperature at which NH ₃ is desorbed from the reaction material when exhaust heat is given to the reaction material in the reactor 11. Yes.

In the exhaust purification system 1 configured as described above, when the temperature of the exhaust gas from the engine 2 is low, the on-off valve 15 is opened so that the NH ₃ stored in the heat accumulator 12 is transferred to the medium supply passage. 13, the reaction material (for example, MgCl ₂ ) and NH ₃ in the reaction device 11 are chemically reacted and chemisorbed (coordinated bond), and heat is generated from the reaction material. That is, the reaction from the left side to the right side (exothermic reaction) occurs in the following reaction formula. The oxidation catalyst 4 is heated to the activation temperature by the heat generated in the reactor 11. When the oxidation catalyst 4 is heated to the activation temperature, the on-off valve 15 is closed so that the NH ₃ stored in the heat accumulator 12 is not excessively supplied to the reactor 11.
MgCl ₂ + _x NH ₃ Ｍｇ Mg (NH ₃ ) _x Cl ₂ + heat

On the other hand, when the temperature of the exhaust gas from the engine 2 becomes high, the heat of the exhaust gas is given to the reactor 11 through the oxidation catalyst 4, so that the reactant (for example, MgCl ₂ ) and NH ₃ are separated. . That is, a reaction (regeneration reaction) from the right side to the left side in the above reaction formula occurs. Then, NH ₃ separated from the MgCl ₂ is collected in the heat accumulator 12 by moving from the reactor 11 to the heat accumulator 12 by pressure difference. Thus, in the chemical heat storage device 10 using the pressure difference between the reactor 11 and the heat storage device 12, it is necessary to raise the temperature of the reactor 11 to a temperature at which NH ₃ is separated from MgCl ₂ .

Therefore, in the present embodiment, the pressure inside the reactor 11 is reduced by sucking the inside of the reactor 11 by the suction pump 16, and NH ₃ is separated from MgCl _{2 while} the temperature of the reactor 11 is lower. Like that. Specifically, when the temperature of the oxidation catalyst 4 rises to a preset specified temperature (described above), the inside of the reactor 11 is forcibly sucked by the suction pump 16. Thus, the pressure in the reactor 11 is lowered, also the temperature in the reactor 11 in an ordinary pressure even before rising to a temperature at which the NH ₃ from MgCl ₂ are separated, the NH ₃ from MgCl ₂ separation Will come to do. Then, the separated NH ₃ is forcibly returned to the heat accumulator 12 through the medium supply passage 14 and recovered by the action of the suction pump 16. Thereby, heat storage is performed in the heat accumulator 12.

Here, the equilibrium pressure characteristic of the reactor 11 is shown in FIG. In FIG. 2, the equilibrium pressure characteristic is a characteristic representing the relationship between temperature and pressure when NH ₃ is separated from MgCl ₂ , and as the pressure increases, the temperature required to separate NH ₃ increases. As the pressure decreases, the temperature required to separate NH ₃ decreases. When the pressure inside the reactor 11 is lowered by forcibly sucking the inside of the reactor 11 with the suction pump 16, NH ₃ can be separated from MgCl ₂ at a lower temperature. Further, the temperature at which NH ₃ is separated from MgCl _{2 is set} to a temperature t lower than the ambient temperature (atmosphere temperature) t ₀ by forcibly sucking the reactor 11 with the suction pump 16 and lowering the pressure in the reactor 11. In this case, NH ₃ is recovered to the heat accumulator 12 by an extra temperature range Δt between the temperature t and the ambient temperature t ₀ without applying heat from the outside.

As described above, in the present embodiment, the suction pump 16 is provided in the medium supply passage 14, and when the temperature of the oxidation catalyst 4 reaches the specified temperature, the inside of the reactor 11 is forcibly sucked by the suction pump 16, Since NH ₃ is forcibly recovered from the reactor 11 to the heat accumulator 12, even if the temperature of the reactor 11 does not reach the temperature at which NH ₃ is separated from MgCl ₂ by exhaust heat, the NH ₃ is stored. The container 12 can be reliably recovered. Thereby, since NH ₃ can be supplied from the heat accumulator 12 to the reactor 11 at the next startup of the engine 2, the oxidation catalyst 4 can be reliably heated by the reactor 11.

Further, forcibly sucking the inside of the reactor 11 by the suction pump 16 increases the recovery rate of NH ₃ from the reactor 11 to the heat accumulator 12, so that the oxidation catalyst 4 is sufficiently heated, for example, at the time of PM regeneration. When NH ₃ is recovered in such a state, thermal decomposition of NH ₃ can be prevented.

Further, the pressure inside the reactor 11 is forcibly reduced by forcibly sucking the inside of the reactor 11 with the suction pump 16, so that, for example, the temperature at which NH ₃ is separated from MgCl ₂ becomes lower than the ambient temperature. Thus, when the pressure is reduced, NH ₃ can be recovered in the regenerator 12 without heating the reactor 11. Therefore, for example, the efficiency of recovering NH ₃ can be improved as compared with the case of recovering NH ₃ by heating the reactor 11 with a heater.

  FIG. 3 is a schematic configuration diagram showing an exhaust purification system including another embodiment of the chemical heat storage device according to the present invention. In the figure, the same reference numerals are given to the same elements as those in the above-described embodiment, and the description thereof is omitted.

  In the figure, the chemical heat storage device 10 of this embodiment includes a differential pressure sensor 21 and a controller 22. The differential pressure sensor 21 detects a differential pressure between the upstream pressure of the DPF 5 and the downstream pressure of the DPF 5.

  The controller 22 controls the suction pump 16 based on the detection value of the differential pressure sensor 21. Specifically, the controller 22 immediately before the time when PM should be removed (regenerated) because PM is accumulated in the DPF 5 when the detection value of the differential pressure sensor 21 is higher than a preset specified differential pressure. Then, the suction pump 16 is controlled to operate.

  Here, the differential pressure sensor 21 and the controller 22 constitute determination means for determining whether or not the DPF 5 is before the timing for regenerating PM contained in the exhaust gas. The controller 22 constitutes control means for controlling the suction pump 16 to operate when it is determined by the determination means that the DPF 5 is before the time for performing PM regeneration.

  In addition, regeneration of PM is implemented as follows. That is, fuel is added into the exhaust passage 3 from a fuel addition means (not shown) arranged upstream of the oxidation catalyst 4, and the fuel is oxidized by the oxidation catalyst 4, so that the temperature of the exhaust gas is changed to PM. To a temperature where it burns. Then, the exhaust gas having a high temperature in the oxidation catalyst 4 flows into the DPF 5 and the PM deposited on the DPF 5 is burned and removed.

Thus, in the present embodiment, NH ₃ is forcibly recovered from the reactor 11 to the heat accumulator 12 by forcibly sucking the inside of the reactor 11 by the suction pump 16 immediately before the time to regenerate PM. Is done. Therefore, when the oxidation catalyst 4 is at a sufficiently high temperature, NH ₃ is recovered, so that thermal decomposition of NH ₃ in the reactor 11 can be prevented.

  Note that the determination means for determining whether it is before the time to regenerate PM is not particularly limited to the determination based on the detection value of the differential pressure sensor 21, but from the operation time of the vehicle (operation time of the engine 2). You may judge.

  As mentioned above, although several suitable embodiment of the chemical heat storage apparatus which concerns on this invention has been described, this invention is not limited to the said embodiment.

For example, in the above embodiment, the medium supply passage 13 for supplying NH ₃ from the regenerator 12 to the reactor 11 is directly connected to the reactor 11 and the regenerator 12, but the configuration is not particularly limited, and suction The medium supply passage 13 may be connected in parallel to the medium supply passage 14 so as to bypass the pump 16.

In the above embodiment, by force sucking the reactor 11, as a forced recovery means for forcibly recovering NH ₃ from the reactor 11 to the heat accumulator 12 has been used the suction pump 16, otherwise A compressor may be used.

  Furthermore, in the above embodiment, the reactor 11 is arranged around the oxidation catalyst 4, but the configuration is not particularly limited, and the reactor may be arranged inside the oxidation catalyst 4.

In the above-described embodiment, the suction pump 16 is controlled to operate when the detected value of the temperature sensor 17 reaches the specified temperature or before the time for regenerating PM. The time is not particularly limited. For example, the heat accumulator 12 is provided with a temperature sensor and a pressure sensor, and when the engine 2 is stopped, the suction pump 16 is operated when it is determined that NH ₃ cannot be recovered from the detected values of the temperature sensor and the pressure sensor. Alternatively, the suction pump 16 may be controlled to operate when a predetermined time elapses after the oxidation catalyst 4 is heated.

In the above embodiment, the reaction medium NH ₃ and a reaction material such as MgCl ₂ and CaCl ₂ are chemically reacted to generate heat. However, the reaction medium is not limited to NH ₃ in particular. For example, it may be H ₂ O or CO ₂ . When using of _{H 2} O as the reaction medium, using CaO, SrO, BaO, or the like as a reaction material to _{between H 2} O and chemical reactions, when using CO ₂ as the reaction medium, to CO ₂ and chemistry reactions MgO, CaO, BaO or the like is used as the material.

  Furthermore, the chemical heat storage device 10 of the above embodiment heats the oxidation catalyst 4, but the present invention provides other exhaust catalysts such as the selective reduction catalyst 6 and the oxidation catalyst 7, and urea water supplied by the addition valve 8. The present invention can also be applied to a disperser that disperses and diffuses water or a device that heats the exhaust passage 3 itself. The present invention is not limited to the diesel engine 2 but can be applied to one that heats an exhaust catalyst or the like provided in an exhaust system of a gasoline engine.

  DESCRIPTION OF SYMBOLS 2 ... Diesel engine, 3 ... Exhaust passage (exhaust system), 4 ... Oxidation catalyst (object to be heated), 11 ... Reactor, 12 ... Regenerator, 13 ... Medium supply passage (first supply passage), 14 ... Medium supply Passage (second supply passage), 16 ... suction pump (forced recovery means), 17 ... temperature sensor (temperature detection means), 18 ... controller (control means), 21 ... differential pressure sensor (determination means), 22 ... controller ( Determination means, control means).

Claims (3)

In a chemical heat storage device for heating a heating object provided in an exhaust system of an engine,
A reactor including a reaction material disposed around or inside the heating object and generating heat by chemically reacting with a reaction medium;
A heat accumulator for storing heat by storing the reaction medium;
A first supply passage connected to the reactor and the regenerator, for supplying the reaction medium from the regenerator to the reactor;
A second supply passage connected in parallel to the first supply passage for supplying the reaction medium from the reactor to the heat accumulator;
And a forcible recovery means for forcibly recovering the reaction medium from the reactor to the heat accumulator by forcibly lowering the pressure in the reactor. A chemical heat storage device. Temperature detecting means for detecting the temperature of the heating object;
The chemical heat storage device according to claim 1, further comprising a control unit configured to control the forced recovery unit to operate based on the temperature of the heating object detected by the temperature detection unit. Determination means for determining whether or not the filter disposed downstream of the heating object is before the timing for regenerating PM contained in the exhaust gas;
And a control unit that controls the forced recovery unit to operate when the determination unit determines that the filter is before the time to regenerate the PM. The chemical heat storage device according to 1.

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