JP2010242989A - Heat storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a heating efficiency in a heat storage device in which a plurality of alkaline earth metallic oxides are mixed and housed in a reactor. <P>SOLUTION: This heat storage device includes a water chamber 10, a reactor 20 housing first alkaline earth metallic oxide and second alkaline earth metallic oxide, a passage 40 connecting the water chamber 10 and the reactor 20, and circulating water, a control valve 42 opening/closing the passage, and a control means 60 controlling opening/closing of the control valve 42. The substance quantity of the first alkaline earth metallic oxide is set so that the temperature in the reactor 20 rises to a temperature greater than or equal to a second temperature activating a second hydration reaction, which is the reaction between the second alkaline earth metallic oxide and water, from a first temperature, which is the temperature before the occurrence of a first hydration reaction, which is the reaction between the first alkaline earth metallic oxide and water, when the first hydration reaction occurs. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat storage device.

  Alkaline earth metal oxides react with water (hydration reaction) to generate heat and form hydroxides. Conversely, when heat is applied to the produced hydroxide, it is decomposed into the original oxide and water. That is, these chemical reactions can be performed reversibly. Therefore, by heating the alkaline earth metal hydroxide, an oxide is generated and heat can be stored (endothermic reaction). Moreover, the stored heat can be taken out by adding water to the decomposed oxide (exothermic reaction).

  Patent Document 1 discloses a heat generating device using such an alkaline earth metal oxide. In the heat generating device described in Patent Document 1, the circulation path of water passing through the reactor filled with the alkaline earth metal oxide has a sealed structure, and the binding between the alkaline earth metal and carbon dioxide gas is suppressed. Thereby, the heat generating apparatus described in Patent Literature 1 protects the heat storage ability due to the above reversible reaction that disappears when the alkaline earth metal is changed to the carbonate compound, and maintains the heat storage ability for a long time.

JP 07-180539 A

  However, in the heat generating device described in Patent Document 1, when a plurality of alkaline earth metal oxides are mixed and accommodated in a reactor, there is a problem that the efficiency of heat generation is not sufficient.

  This invention is made | formed in view of the said problem, and makes it a subject to improve the efficiency of heat_generation | fever in the heat storage apparatus which mixed the some alkaline-earth metal oxide and accommodated in the reactor.

  The heat storage device according to the present invention includes a water chamber storing water, a reactor containing a first alkaline earth metal oxide and a second alkaline earth metal oxide, the water chamber and the reactor. A passage through which the water flows, a control valve that is disposed in the passage and that opens and closes the passage, and a control means that controls the opening and closing of the control valve, and is opened by the control means A first hydration reaction which is a hydration reaction of the first alkaline earth metal oxide and the water when the water is circulated from the water chamber into the reactor via the control valve. When this occurs, the temperature in the reactor is changed from the first temperature, which is the temperature before the first hydration reaction, to the hydration reaction between the second alkaline earth metal oxide and the water. Before the second hydration reaction is activated, the temperature rises to a temperature equal to or higher than the second temperature. Materials of the first alkaline earth metal oxide, characterized in that it is set.

  According to the heat storage device according to the present invention, the second hydration reaction by the second alkaline earth metal oxide is efficiently caused by the heat of the first hydration reaction by the first alkaline earth metal oxide. be able to. Therefore, the heat generation efficiency of the heat storage device can be improved.

  In the above configuration, a heat source for applying heat to the water chamber and the reactor is provided, and the hydroxide generated by the first hydration reaction is converted to the first alkaline earth by the heat applied from the heat source. When the first hydration reaction is caused again after being decomposed into the metal oxide and the water, the control means has a heat quantity based on the substance amount of the first alkaline earth metal oxide by the heat source. After being applied to the water chamber and the reactor, the control valve is opened to allow the water to flow from the water chamber into the reactor.

  According to the above configuration, even if the amount of the first alkaline earth metal oxide to be decomposed is reduced, the first hydration reaction is caused after heat is applied to the water chamber and the reactor. Can do. Therefore, the heat generation efficiency of the heat storage device can be improved.

  In the above structure, the first alkaline earth metal oxide is calcium oxide, the second alkaline earth metal oxide is magnesium oxide, and the second temperature is 100 ° C. can do.

  According to the above configuration, the heat in the hydration reaction of calcium oxide can raise the temperature in the reactor to 100 ° C. at which the hydration reaction of magnesium oxide is activated. Can efficiently cause the hydration reaction of magnesium oxide. Therefore, the heat generation efficiency of the heat storage device can be improved.

  According to this configuration, in the heat storage device in which a plurality of alkaline earth metal oxides are mixed and filled in the reactor, the efficiency of heat generation can be improved.

FIG. 1 is a schematic diagram illustrating a configuration of a heat storage device 100 according to the first embodiment. FIG. 2 is a flowchart of control processing during heat generation in the heat storage device 100 according to the first embodiment. FIG. 3 is a flowchart of control processing during heat generation in the heat storage device 100 according to the second embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a configuration of a heat storage device 100 according to the first embodiment.

  The heat storage device 100 includes a heat storage device 110 and an engine exhaust pipe 120. The heat accumulator 110 is assembled on the downstream side of the catalyst device 130 disposed on the exhaust pipe 120 of the engine.

  The heat accumulator 110 includes a water chamber 10 in which water is stored, and a reactor 20 that contains a first alkaline earth metal oxide and a second alkaline earth metal oxide. In this example, the first alkaline earth metal oxide is calcium oxide (CaO), and the second alkaline earth metal oxide is magnesium oxide (MgO).

The heat storage device 100 includes a pipe 30. The pipe 30 is a passage through which oil passes. The pipe 30 includes a plurality of heat exchanging parts 32 that are branched into the water chamber 10 and the reactor 20. In the heat exchange unit 32, heat generated by the hydration reaction of CaO and MgO in the reactor 20 is transferred to the oil flowing through the pipe 30 and collected. Thus, the heat recovered in the oil can be used to warm up each part of the engine. The hydration reaction of CaO and MgO is represented by the following formulas (1) and (2), respectively. Hereinafter, the reactions represented by (1) and (2) are referred to as a first hydration reaction and a second hydration reaction, respectively.
CaO + H ₂ O → Ca (OH) ₂ + Q ₁ (exothermic reaction) (1)
MgO + H ₂ O → Mg (OH) ₂ + Q ₂ (exothermic reaction) (2)
The temperature at which the second hydration reaction is activated is higher than the temperature at which the first hydration reaction is activated. For this reason, in order to cause the second hydration reaction, the temperature in the reactor 20 needs to be higher than when the first hydration reaction is caused.

The bottoms of the water chamber 10 and the reactor 20 are disposed in contact with the exhaust pipe 120. Therefore, the water in the water chamber 10 and the Ca (OH) ₂ and Mg (OH) ₂ generated by the hydration reaction in the reactor 20 are exhausted through the exhaust pipe 120 via the exhaust pipe 120. Receives heat from gas. That is, the exhaust pipe 120 functions as a heat source that applies heat to the water chamber 10 and the reactor 20. In the reactor 20, the decomposition reaction of Ca (OH) ₂ and Mg (OH) ₂ represented by the following formulas (3) and (4) occurs. Hereinafter, the reactions represented by (3) and (4) are referred to as a first decomposition reaction and a second decomposition reaction, respectively.
Ca (OH) ₂ → CaO + H ₂ O − Q ₁ (endothermic reaction) (3)
Mg (OH) ₂ → MgO + H ₂ O-Q ₂ (endothermic reaction) (4)

  The heat accumulator 110 connects the water chamber 10 and the reactor 20, and includes a passage 40 through which water flows and a control valve 42 that is disposed in the passage 40 and supplies or shuts off water. The passage 40 is formed to circulate the water in the water chamber 10 into the reactor 20. The control valve 42 is an electromagnetic valve and is opened and closed under the control of a C / U 60 described later.

The heat accumulator 110 includes a steam pipe 50 that connects the water chamber 10 and the reactor 20. The steam pipe 50 is a passage through which water vapor generated by the thermal reaction of Ca (OH) _{2 and} the thermal reaction of Mg (OH) ₂ in the reactor 20 flows to the water chamber 10. The steam pipe 50 is provided with a check valve 52 that closes the steam pipe 50 and blocks the flow of water vapor from the water chamber 10 into the reactor 20.

  The heat accumulator 110 includes a control unit (C / U) 60 that is a control means. Furthermore, the heat accumulator 110 includes a temperature sensor 12 that detects the water temperature in the water chamber 10, a water level sensor 14 that detects the water level in the water chamber 10, and a temperature sensor 22 that detects the temperature in the reactor 20. The C / U 60 is electrically connected to the control valve 42, the check valve 52, the temperature sensor 12, the water level sensor 14, and the temperature sensor 22, respectively. The C / U 60 determines the open / close state of the control valve 42 based on the water temperature in the water chamber 10 acquired by the temperature sensor 22, and sends an open / close signal to the control valve 42.

Next, a method for setting the amount of CaO in the reactor 20 will be described. The substance amount of CaO is the second temperature at which the second hydration reaction is activated from the first temperature, which is the temperature before the first hydration reaction occurs, in the reactor 20. The temperature is set to rise to the above temperature. Here, the first temperature is a temperature at a cold start, for example, 25 ° C. The second temperature is 100 ° C., which is a temperature at which the hydration reaction of MgO is activated. In order to increase the temperature in the reactor 20 from 25 ° C. to a temperature of 100 ° C. or higher, it is necessary to satisfy the following formula (5).
_{Q × n 1 ≧ (C 1} × n 1 + C 2 × n 2 + C 3 × n 3) × (100-25) (5)
In the formula (5), Q represents the theoretical reaction heat amount [kJ / mol] of the first hydration reaction, n represents the substance amount [mol], and C represents the molar specific heat [kJ / mol · ° C.]. Subscript 1 indicates a value related to CaO, subscript 2 indicates a value related to MgO, and subscript 3 indicates a value related to water. When the equation (5) is transformed, the condition of the CaO substance amount n ₁ can be obtained as in the following equation (6).
n ₁ ≧ (C ₂ × n ₂ + C ₃ × n ₃ ) × 75 / (Q−75 × C ₁ × n ₁ ) (6)
From the above, based on the amount of MgO and water, the amount of CaO can be set so that the temperature in the reactor 20 rises from 25 ° C. to a temperature of 100 ° C. or higher. Thus, by setting the amount of CaO, the second hydration reaction can be efficiently caused only by the heat of the first hydration reaction. Therefore, the heat generation efficiency of the heat storage device can be improved.

  With reference to FIG. 2, the control process at the time of heat_generation | fever in the thermal storage apparatus 100 is demonstrated. FIG. 2 is a flowchart of control processing by the C / U 60.

Before starting the processing of the flowchart, it is assumed that the substance amount n ₁ of CaO in the reactor 20 is set to satisfy the formula (6), and the temperature in the reactor 20 is 25 ° C.

First, the C / U 60 checks whether or not there is a warm-up request for each part of the engine (step S10). If there is no warm-up request (No in step S10), the process ends. When the C / U 60 confirms that there is a warm-up request (Yes in step S10), the control valve 42 is opened to supply water from the water chamber 10 into the reactor 20 (step S20). As a result, a first hydration reaction occurs in the reactor 20. Further, since the substance amount n ₁ of CaO in the reactor 20 is set so as to satisfy the formula (6), the temperature in the reactor 20 rises to a temperature of 100 ° C. or higher. Therefore, the second hydration reaction occurs due to the heat of the first hydration reaction.

  The C / U 60 determines whether or not the supply of water from the water chamber 10 to the reactor 20 has been completed (step S30). For example, when the temperature in the reactor 20 is detected by the temperature sensor 22 and the temperature in the reactor 20 becomes equal to or higher than a predetermined temperature, it is determined that the supply of water has ended. When the C / U 60 determines that the supply of water has not ended (No in step S30), the process returns to step S30 and the supply of water is continued. When the C / U 60 determines that the supply of water has ended (Yes in step S30), the control valve 42 is closed to interrupt the supply of water from the water chamber 10 to the reactor 20 (step S40). ). Thus, the process ends.

  According to Example 1, water is circulated from the water chamber 10 into the reactor 20 through the control valve 42 opened by the C / U 60, and the first alkaline earth metal oxide CaO and water When the first hydration reaction is performed, the temperature in the reactor 20 is changed from the first temperature, which is the temperature before the first hydration reaction occurs, to the second alkaline earth metal. The substance amount of CaO is set so that the temperature rises to a temperature equal to or higher than the second temperature, which is a temperature at which the second hydration reaction, which is a hydration reaction between MgO as an oxide and water, is activated. Thereby, the 2nd hydration reaction by MgO can be efficiently caused by the heat by the 1st hydration reaction by CaO. Therefore, the heat generation efficiency of the heat storage device 100 can be improved.

  In Example 1, the example which accommodates CaO and MgO in the reactor 20 was demonstrated. The example in which the first temperature is 25 ° C. at the cold start has been described. An example in which the second temperature is 100 ° C., which is the activation temperature of the MgO hydration reaction, has been described. The first temperature may be another temperature. Further, one of CaO and MgO may be another alkaline earth metal oxide, or the other two alkaline earth metal oxides may be used. In that case, the alkaline earth metal oxide having the lower activation temperature of the hydration reaction is the first alkaline earth metal oxide, and the alkaline earth metal oxide having the higher activation temperature of the hydration reaction is the second. As the alkaline earth metal oxide, the first temperature, the second temperature, the substance amount of the second alkaline earth metal oxide, and the substance amount of water supplied into the reactor 20, What is necessary is just to set the substance amount of alkaline-earth metal oxide.

  In Example 1, the example arrange | positioned so that the bottom face of the water chamber 10 and the reactor 20 might contact the exhaust pipe 120 was demonstrated. In addition, for example, the water chamber 10 and the reactor 20 and the exhaust pipe 120 may be integrated. By configuring the water chamber 10 and the reactor 20 and the exhaust pipe 120 in this way, even when the temperature in the reactor 20 is lower than 25 ° C. at the time of cold start, heat from the exhaust gas flowing in the exhaust pipe 120 is obtained. Thus, the temperature in the reactor 20 can be quickly raised.

  In the first embodiment, an example in which oil passes through the inside of the pipe 30 has been described. For example, cooling water may be used instead of oil.

  In the first embodiment, the example in which the heat accumulator 110 is assembled on the downstream side of the catalyst device 130 disposed on the exhaust pipe 120 of the engine has been described. The heat accumulator 110 may be assembled on the upstream side of the catalyst device 130.

  A second embodiment of the present invention will be described. The heat storage device according to the second embodiment has the same configuration as the heat storage device 100 according to the first embodiment, and thus the description thereof is omitted. The second embodiment is different from the first embodiment in the control method during heat generation. With reference to FIG. 3, the control method during heat generation according to the second embodiment will be described. FIG. 3 is a flowchart of control processing by the C / U 60. The same processes as those shown in FIG. 2 are given the same numbers.

In the following description, before starting the process of the flowchart, the amount of CaO substance in the reactor 20 is assumed to be n ₁ ′, which is a value larger than n ₁ that satisfies Equation (6) of Example 1. The temperature in the reactor 20 is 25 ° C. as in Example 1.

With reference to FIG. 3, the processing in step S <b> 10 is the same as that in the first embodiment, and thus description thereof is omitted. When the C / U 60 confirms that there is a warm-up request (Yes in step S10), it determines whether or not the decomposition rate is equal to or higher than the target value. Here, the decomposition rate (hereinafter referred to as R ₁ ) is generated by the first decomposition reaction after the first hydration reaction with respect to the substance amount n ₁ ′ of CaO before the first hydration reaction occurs. It is a ratio of the amount of CaO substance to be made. Target value (hereinafter, _{R 2)} and the first hydration reaction occurs before the CaO amount of material _{n 1} 'for a ratio of amount of substance _{n 1} of _CaO, R _{2 =} n 1 / _{n 1'} It can be expressed as. When the first hydration reaction and the first decomposition reaction are alternately repeated, the substance amount of CaO gradually decreases due to, for example, the fact that CaO is carbonated. Therefore, the decomposition rate R ₁ is equal to the initial target value R ₂ , but gradually decreases from the target value R ₂ as the first hydration reaction and the first decomposition reaction are alternately repeated. In addition, the heat generated by the first hydration reaction also gradually decreases as the CaO substance amount decreases.

If the decomposition rate _{R 1} is not the target value _{R 2} or more (No in step S12), C / U60 temperature of the temperature and the reactor 20 in the water chamber 10 detected by the temperature sensor 12 and 22, the reactor 20 It is determined whether or not the temperature is a temperature T necessary for the temperature to rise from 25 ° C. to a temperature of 100 ° C. or higher (step S14). The temperature T can be obtained by the following equation (7).
T = 100 × (C ₁ × n ₁ + C ₂ × n ₂ + C ₃ × n ₃ )
_{-R 1 × Q × n 1 /} (C 1 × n 1 + C 2 × n 2 + C 3 × n 3) (7)
In Expression (7), Q, n, C, and subscripts 1, 2, and 3 are the same as those described in the first embodiment, and thus the description thereof is omitted. When the temperature in the water chamber 10 and the temperature in the reactor 20 are not equal to or higher than T ° C. (No in step S14), the water chamber 10 and the reactor 20 are heated by the exhaust gas flowing in the exhaust pipe 120 that is a heat source. (Step S16), the temperature in the water chamber 10 and the temperature in the reactor 20 are increased, and the process returns to Step S14. When step S14 is Yes, it progresses to step S20. Since the process after step S20 is the same as that of Example 1, description is abbreviate | omitted. Thus, the process ends.

  According to Example 2, the heat source 120 for applying heat to the water chamber 10 and the reactor 20 is provided, and the hydroxide generated by the first hydration reaction is converted into CaO by the heat applied from the heat source 120. When the first hydration reaction is caused again after being decomposed into water, the C / U 60 as the control means imparts heat quantity based on the amount of CaO substance into the water chamber 10 and the reactor 20 by the heat source 120. Then, the control valve 42 is opened to allow water to flow from the water chamber 10 into the reactor 20. Thereby, even if the substance amount of the first alkaline earth metal oxide to be decomposed is reduced, the first hydration reaction can be caused after the heat amount is applied to the water chamber and the reactor. Therefore, the heat generation efficiency of the heat storage device can be improved.

In Example 2, the decomposition rate R ₁ was described. The decomposition rate R ₁ may be estimated from the heat of reaction. That is, the ratio of the amount of heat transferred from the exhaust gas flowing through the exhaust pipe 120 to the Ca (OH) ₂ via the exhaust pipe 120 to the theoretical amount of heat absorbed in the first decomposition reaction is represented by the decomposition rate R. ₁ may be considered. The amount of heat transferred to Ca (OH) ₂ can be determined from the amount of Ca (OH) ₂ substance, the temperature detected by the temperature sensor 22, and the molar specific heat of Ca (OH) ₂ . Further, the decomposition rate R ₁ may be estimated from the amount of water generated in the first decomposition reaction. That is, relative to the amount of water theoretically generated in the first decomposition reaction, the ratio of the amount of water detected at a first decomposition reaction, may be regarded as a decomposition rate R _1. The amount of water detected during the first decomposition reaction can be detected by the water level sensor 14.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims.・ Change is possible.

10 Water chamber 20 Reactor 30 Piping 32 Heat exchange section 40 Passage 42 Control valve 50 Steam piping 52 Check valve 60 C / U
100 heat storage device 110 heat storage device 120 exhaust pipe 130 catalyst device

Claims (3)

A water chamber that stores water,
A reactor containing a first alkaline earth metal oxide and a second alkaline earth metal oxide;
A passage for connecting the water chamber and the reactor and through which the water flows;
A control valve disposed in the passage to open and close the passage;
Control means for controlling opening and closing of the control valve;
The water is circulated from the water chamber into the reactor through the control valve opened by the control means, and the hydration reaction of the first alkaline earth metal oxide and the water When the first hydration reaction is, the temperature in the reactor is changed from the first temperature, which is the temperature before the first hydration reaction, to the second alkaline earth metal oxide. The amount of the first alkaline earth metal oxide is increased so that the second hydration reaction, which is a hydration reaction between water and the water, rises to a temperature equal to or higher than a second temperature that is a temperature at which the second hydration reaction is activated. A heat storage device characterized by being set. A heat source for applying heat to the water chamber and the reactor;
The first hydration reaction is performed again after the hydroxide generated by the first hydration reaction is decomposed into the first alkaline earth metal oxide and the water by the heat applied from the heat source. The control means opens the control valve after a heat quantity based on the substance amount of the first alkaline earth metal oxide is applied to the water chamber and the reactor by the heat source. The heat storage device according to claim 1, wherein the water is circulated from the water chamber into the reactor. The first alkaline earth metal oxide is calcium oxide;
The second alkaline earth metal oxide is magnesium oxide;
The heat storage device according to claim 1 or 2, wherein the second temperature is 100 ° C.

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