JP2642868B2 - Heat transfer method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transporting heat utilizing a synthesis / decomposition reaction or a decomposition / combustion reaction of alcohol.

[0002]

2. Description of the Related Art Low-temperature industrial waste heat, for example, 200
Low quality thermal energy below ℃ is abundant. However, since it is extremely difficult to efficiently transport this to a remote place, its use is limited to the vicinity of a heat source. For example, even if steam is obtained from a heat source of 200 ° C., it can be used only at a facility located at the same factory site or an adjacent facility at most.

[0003] In this regard, there is known a method of transporting heat using an alcohol synthesis / decomposition reaction. Examples of the decomposition reaction of alcohol include decomposition of methanol into carbon monoxide and hydrogen, decomposition of ethanol into acetaldehyde and hydrogen, and decomposition of isopropanol into acetone and hydrogen.

[0004] Incidentally, it is known that the decomposition of methanol into carbon monoxide and hydrogen is promoted by a noble metal catalyst such as platinum or a catalyst containing nickel. It is known that a catalyst containing copper is effective in decomposing ethanol. In the decomposition of isopropanol, it is known that nickel in the form of fine particles is effective and has a catalytic action at a reaction temperature of 100 ° C. or lower. Since these decomposition reactions are endothermic reactions, heat is chemically absorbed by heating the reactor to decompose the alcohol, resulting in a decomposition product containing hydrogen.

[0005] The energy retention of the decomposition products obtained in this way is generally higher than that of the starting materials. For example, methanol has a high energy of about 130 kJ / mol, ethanol has a high energy of about 110 kJ / mol, and isopropanol has a high energy of about 70 kJ / mol.

[0006] Therefore, if an alcohol is synthesized from a decomposition product, it is possible to obtain heat energy having a difference in the retained energy. According to the method using the above-mentioned alcohol synthesis / decomposition reaction, heat can be recovered and used in a remote place in a single closed system, and heat can be obtained without emitting carbon dioxide. It is possible to construct an ideal energy transportation system that is easy on the environment.

On the other hand, in the exothermic process by combustion, more heat energy can be obtained by burning the decomposition product than burning the starting material as it is. For example, burning the decomposition product of methanol makes it possible to obtain about 130 kJ more heat of combustion per mol than burning methanol directly.

The process of absorbing and releasing thermal energy utilizing the alcohol synthesis / decomposition reaction has been established in theory. For example, Saito et al. Have proposed high-grade heat (high temperature) using a chemical heat pump utilizing acetone hydrogenation reaction by isopropanol dehydrogenation and acetone hydrogenation (Catalyst 31, Vol. 285).
1989).

However, this method, like the technique described at the outset, merely recycles heat in the same facility, and is not practically applicable to efficient transfer of heat to a remote place. Therefore, there is still room for improvement in practical use in order to effectively use heat energy.

[0010]

Accordingly, it is a primary object of the present invention to provide a method for efficiently transporting thermal energy.

As described above, the biggest problem in the process of absorbing and releasing thermal energy lies in the transport of reaction products containing hydrogen obtained by the thermal energy absorbing process. Methods for transporting chemicals to remote locations include:
Using a pipeline is the most efficient, but using it requires transportation power.
In this method, the chemical substance is usually moved by pressurizing the starting point of transportation or reducing the pressure at the point of arrival by an electric motor.

However, if a normal electric booster is used,
There is a risk of consuming more energy than the heat energy absorbed by the chemical reaction. Even if the consumed energy does not exceed the absorbed heat energy, a considerable amount of energy will be consumed by the transportation process, and the efficiency of heat transportation will be significantly reduced.

For example, in order to boost the decomposition product of 1 mol of methanol from 1 atm to 10 atm by electric power at 25 ° C., about 20 kJ of energy is theoretically required. In practice, furthermore, a considerable part of the heat absorbed by 1 mol of methanol will be consumed by the booster, as a further energy loss of the booster and a loss for converting heat energy into electrical energy will occur.
Assuming that the compression efficiency of the pump is 0.8 and the power generation efficiency is 0.4, about 60 kJ of energy is consumed more. However, in order to synthesize methanol, the pressure is increased even at the landing point of the methanol decomposition product (synthesis unit). For example, if the pressure at the landing point becomes 5 atm and the pressure is increased to 150 atm, about 60 kJ of energy is also required for this increase. As a result, the amount of heat consumed and the amount of heat recovered in the pressure increase on the starting point side and the pressure increase on the contact point side become substantially equal, and thus the heat transport system cannot be established.

[0014]

Means for Solving the Problems As a result of diligent studies to achieve the above object, the present inventor has found that when the pressure of alcohol decomposition products is increased by using a hydrogen storage alloy,
The inventors have found that energy can be transported efficiently, and have completed the present invention.

That is, the present invention relates to the following heat transport method. (1) In a system in which thermal energy is released and absorbed by alcohol synthesis and decomposition reactions, after decomposing the alcohol by thermal energy and transporting the decomposition products by the pressurizing mechanism using the hydrogen storage function of the hydrogen storage alloy A method of transporting heat, wherein thermal energy is released by synthesizing alcohol again from the decomposition product. (2) In a system in which thermal energy is absorbed and released by the decomposition and combustion reaction of alcohol, after the alcohol is decomposed by thermal energy and the decomposition products are transported by the pressurizing mechanism using the hydrogen storage function of the hydrogen storage alloy, A method of transporting heat, characterized in that thermal energy is released by burning the decomposition product.

Hereinafter, the present invention will be described in detail with reference to FIG. 1 (an example of an alcohol synthesis / decomposition reaction) schematically showing an example of the present invention.

The alcohol that can be used in the method of the present invention is not particularly limited as long as side reactions do not easily occur in the synthesis / decomposition reaction and the product / decomposition product is constant. ethanol,
Isopropanol and the like.

First, for example, when methanol is used as the alcohol, a decomposition product () containing methanol is used.
Is cooled and condensed () if necessary, and then separated into carbon monoxide and hydrogen and methanol by gas-liquid separation (). The separated methanol undergoes a heating step, an evaporation step (), and the like, and is decomposed by the recovered heat (). On the other hand, carbon monoxide and hydrogen are subjected to a heating / evaporation step () if necessary, and then supplied again to alcohol synthesis together with decomposition products.

In alcohol decomposition (), part or all of methanol is decomposed into hydrogen and carbon monoxide. Decomposition reaction conditions vary depending on the type of alcohol used, the type of catalyst, and the like, but are usually about 150 to 300 ° C.,
It may be about 3 atm. As the catalyst to be used, a catalyst used in ordinary alcoholysis can be used as it is. For example, when decomposing methanol, nickel, platinum, palladium, rhodium, iridium, ruthenium, gold and the like are effective. In addition, these catalysts can be used alone or in combination of two or more.

Next, the decomposition product consisting of methanol, hydrogen and carbon monoxide is cooled, if necessary, via a cooling / condensing step () and sent to a pressure increasing device ().

The pressurizing device () performs pressurization by utilizing the hydrogen storage effect of the hydrogen storage alloy, and is installed at the starting point of transportation. Here, the type of hydrogen storage alloy that can be used in the present invention is not particularly limited, but one that absorbs hydrogen near room temperature and releases hydrogen absorbed at a temperature of about 100 ° C. at an equilibrium pressure of several atmospheres. Preferred such hydrogen storage alloys include, for example, ZrMn ₂ , LaNi
₅ , Mg ₂ Ni, TiMn _1.5 , TiFe and V _0.8 T
A multi-component alloy having a main composition of i _0.2 or the like can be given.

Examples of the pressure raising mechanism utilizing the hydrogen storage function of the hydrogen storage alloy include the following. In other words, when a hydrogen storage alloy and hydrogen are placed in an airtight container, the pressure in the container decreases because hydrogen is absorbed by the alloy near room temperature, and the pressure increases due to the release of hydrogen when heated. If a member such as a piston that reciprocates according to the pressure in the container is attached to the container, the member reciprocates with the heating and cooling of the airtight container.
Then, pressure is applied to the decomposition product by the reciprocating motion, and the decomposition product can be transported to the destination. In addition, it is preferable to use the industrial waste heat also from the viewpoint of thermal efficiency.

After the decomposition product is transported to the destination by the above-mentioned pressure raising mechanism, it is subjected to a cooling step / condensing step (), if necessary, and then subjected to alcohol synthesis (). By this alcohol synthesis, heat energy can be extracted and used as various energy sources.

The conditions for the synthesis of alcohol vary depending on the type of alcohol used, the type of catalyst, and the like.
C. and about 10 to 50 atm. Further, as a catalyst to be used, a catalyst used in ordinary alcohol synthesis can be used as it is. For example, when synthesizing methanol, a catalyst containing copper and zinc oxide is effective. In the synthesis of isopropanol from acetone and hydrogen, an alumina-supported fine particle nickel catalyst is effective.

In addition, since alcohol synthesis is an exothermic reaction, it is an advantageous reaction at a low temperature in terms of chemical equilibrium. However, in the present invention, a relatively high reaction temperature is required for efficient reaction. preferable. Therefore, it is desirable to pressurize the reaction system from the viewpoint of increasing the yield of alcohol. Also, by appropriately pressurizing the system, it is possible to use the pressure to transport the alcohol as a reaction product to the endothermic side. As the driving force for pressurizing the reaction system, a booster device using the same hydrogen storage alloy as described above may be used, or power or other energy sources may be used within a range that does not affect the energy balance of the entire system. The booster used can be used.

Further, as a transport pipe used for carrying out the present invention, it is preferable to use an ordinary pipeline for transporting a chemical substance, for example, a stainless steel pipe from the viewpoint of corrosion resistance. The transport pipe does not need to be kept warm.

On the other hand, in the case of the decomposition and combustion reaction of alcohol, the decomposition product transported by the above method is
Combustion is performed by the introduced oxygen or air, and the combustion heat is recovered and used. FIG. 2 shows an example of the case of alcohol decomposition / combustion reaction.

[0028]

According to the heat transporting method of the present invention, in particular, since the decomposition product of alcohol is transported by increasing the pressure by utilizing the hydrogen storage effect of the hydrogen storage alloy, the thermal energy can be efficiently transferred to a remote place. Transport becomes possible. For example, although it depends on the type of alcohol to be used, the type of the apparatus, the amount of waste heat recovered, the pressure loss in the pipeline, and the like, the heat can be normally transported up to a distance of about 50 km.

In particular, in the case of a closed heat transport system utilizing the synthesis / decomposition reaction of alcohol, no carbon dioxide is emitted and the environment is not polluted.

The transportation method of the present invention, which is excellent in heat transportation and utilization efficiency, is very effective not only for transportation and utilization of high-temperature waste heat but also low-temperature industrial waste heat of about 300 ° C. or less.

[0031]

The present invention will be described below in more detail with reference to examples.

Example 1 Using methanol CH ₃ OH as an alcohol, it was confirmed that heat transport was feasible with an alcohol synthesis / decomposition system as shown in FIG.

First, a mixture containing synthetic methanol and hydrogen and carbon monoxide (molar ratio: 1.12: 2.0: 1.0) is introduced into a gas-liquid separator () at 250 ° C. and 50 atm.
While removing methanol, a mixture containing hydrogen and carbon monoxide is removed. Then, after heating and evaporating the methanol, the recovered heat is used at 170 ° C./1 in the presence of a catalyst.
A decomposition reaction is performed at atm. The decomposition products were unreacted methanol and hydrogen and carbon monoxide (molar ratio 0.11: 2.0:
1.0).

After cooling and condensing the above decomposition product to 25 ° C. and 1 atm (), a pressurizing device equipped with a piston filled with hydrogen and a hydrogen storage alloy in an airtight container ()
Send to Next, the apparatus is heated and pressurized to 25
The decomposition product is transported to the alcohol synthesis unit at 10 ° C. and 10 atm.

Subsequently, the above decomposition product is heated to 302 ° C. and 50 atm by an electric booster, and then cooled and condensed ().
Then, the hydrogen, carbon monoxide and methanol recovered by the gas-liquid separation are introduced into the alcohol synthesis section (). Alcohol synthesis is performed at 250 ° C.
m. As a result of this synthesis, the heat of formation was 96.6 kJ.
Heat energy can be recovered.

In the above process, the heat transfer / use efficiency was determined. That is, the exhaust heat recovery amount Qr = 96.9 + 4
1.4 + 3.8 + 130.0-13.0 = 258.8,
Heat supply Qs = 96.6 + 4.6 + 11.7 + 56.0
From-(56.4 + 7.1 + 10.5) = 94.9, the heat transport / use efficiency Qs / Qr = 94.9 / 258.8 = 3.
7 (%).

Example 2 Using methanol CH ₃ OH as an alcohol, it was confirmed that heat transport was feasible with an alcohol decomposition / combustion system as shown in FIG.

First, synthetic methanol was decomposed at 170 ° C. and 1 atm using the recovered heat in the presence of a catalyst (). The decomposition products are unreacted methanol and hydrogen and carbon monoxide (molar ratio 0.1: 1.8: 0.9).

After the above decomposition product is cooled and condensed to 25 ° C. and 1 atm (), a pressure booster equipped with a piston filled with hydrogen and a hydrogen storage alloy in an airtight container ()
To be introduced. Next, the apparatus is heated and pressurized to 25
The decomposition product is transported to the alcohol combustion section at a temperature of 10 ° C. and subsequently, the decomposition product is burned together with the introduced air ().

In the above process, heat transfer / use efficiency was determined. That is, since the heat of combustion when methanol is directly combusted is 726.1 kJ, the exhaust heat recovery Qr = 87.3 + 117.1-11.7 = 192.
7, heat supply Qs = 841.7-726.1 = 115.
6, heat transfer / use efficiency Qs / Qr = 1115.6 / 1
92.7 = 60 (%).

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of the alcohol synthesis / decomposition process of the present invention.

FIG. 2 is a schematic view showing an example of the alcohol decomposition / combustion process of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F25B 17/12 F25B 17/12 Z // C07B 61/00 300 C07B 61/00 300 (72) Invention Person Yasuyuki Matsumura 1-31, Midorioka, Ikeda-shi, Osaka Prefecture Inside the Osaka Institute of Technology (72) Inventor Hiroaki Sakurai 1-31, Midorioka, Midorioka, Ikeda-shi, Osaka Inside the Osaka Institute of Technology (56 ) References JP-A-57-19314 (JP, A)

Claims (7)

(57) [Claims] In a system in which thermal energy is released and absorbed by an alcohol synthesis / decomposition reaction, alcohol is decomposed by thermal energy, and a decomposition product is transported by a pressurizing mechanism utilizing a hydrogen storage function of a hydrogen storage alloy. After that, thermal energy is released by synthesizing alcohol again from the decomposition product. 2. In a system in which heat energy is absorbed and released by the decomposition and combustion reaction of alcohol, alcohol is decomposed by heat energy, and the decomposition products are transported by a pressure increasing mechanism utilizing the hydrogen storage function of the hydrogen storage alloy. And then releasing thermal energy by burning the decomposition product. 3. The heat energy is industrial waste heat.
Or the method for transporting heat according to 2. 4. The method according to claim 1, wherein the alcohol is methanol.
Or the method for transporting heat according to 2. 5. The apparatus according to claim 5, wherein the pressure increasing mechanism includes a member in which the hydrogen storage alloy and hydrogen are sealed in the airtight container, and a member which reciprocates according to the pressure in the container is provided in the container. The heat transfer method according to claim 1 or 2, wherein the pressure is increased by reciprocating motion of the member accompanying heating of the hydrogen storage alloy. 6. The transportation method according to claim 5, wherein the heating of the hydrogen storage alloy is performed using industrial waste heat. 7. A hydrogen storage alloy comprising ZrMn ₂ , LaN
i ₅ , Mg ₂ Ni, TiMn _1.5 , TiFe or V
_6. The transport method according to claim 5, wherein the alloy is a ternary alloy mainly containing _0.8 Ti _0.2 .