KR100218917B1 - Non-uniform high thermal conductivity reaction block and manufacturing method - Google Patents

Abstract

The present invention comprises the steps of: a) preparing a reaction mixture of a metal halide and a carbon-based support; b) the reaction mixture is composed of a cylindrical outer frame and a plurality of cylinders having a predetermined thickness and having different inner diameters and movable up and down, and the height of the lower end of each cylinder from the bottom surface of the outer frame is outside of the outer frame. Injecting into a forming mold having an inner frame installed to increase or decrease in a stepwise manner and a cylindrical rod provided on the innermost side of the inner frame to contact the bottom surface of the outer frame; And c) compressing the reaction mixture in the mold by pushing the inner mold of the mold downward for a predetermined distance so that the height of the lower end of each cylinder from the bottom of the outer frame is the same. Provided are a method for producing a reaction block having excellent heat transfer and mass transfer characteristics for use in a chemical heat pump whose apparent density distribution is not overall uniform but which gradually increases or decreases toward the edge, and a reaction block produced accordingly.

Description

Non-cracked high thermal conductivity reaction block and its manufacturing method

The present invention relates to a reaction block used in a chemical heat pump using a high-reaction reaction of a metal halide / ammonia or water vapor system, and more particularly, in order to improve heat transfer and mass transfer characteristics in a chemical reactor, The present invention relates to a reaction block and a method of manufacturing the same, which increase or decrease in steps toward the edge of the block and are not overall uniform.

Chemical heat pump is a type of heat pump that uses reversible chemical reactions involving reaction heat to perform the functions of heat storage, heat storage, freezing, and temperature raising. It is a heating / cooling device, a late night electric heat storage system, or a building refrigeration air conditioning system. Used for

On the other hand, CFC-based refrigerants used in refrigeration and refrigeration systems have a problem of destroying the stratospheric ozone layer, and the Montreal Protocol on the Restriction of Refrigerant Use has banned the use of such refrigerants after a certain period of time. Therefore, there is an urgent need for development of alternative refrigeration and refrigeration systems that do not use CFC-based refrigerants, and chemical heat pump technology is expected to satisfy these requirements.

However, high-reaction reactions such as metal halide / ammonia or water vapor systems, such as NaBr-NH ₃ , NiCl ₂ -H ₂ O or NiCl ₂ -NH ₃ , which occur in a reactor of a conventional chemical heat pump As this progresses, mass transfer of the reaction gas, that is, gas diffusion, is not performed smoothly due to the volume swelling phenomenon of the solid reaction layer. In addition, due to the low thermal conductivity of the solid salt used as the reaction layer in the reactor, since the reaction heat is not easily released, reverse reaction may occur, thereby lowering the overall reaction conversion rate. In order to improve this problem, for example, by using a carbon-based material such as spherical carbon particles, expanded graphite or carbon fiber mixed with a solid salt to increase the porosity of the reaction layer and facilitate the mass transfer of the reaction gas. In addition, the carbon-based material has a high thermal conductivity, so the heat removal and supply rate for the high-gas reversible reaction is fast. The reaction mixture of the solid salt and the carbon-based support is generally prepared by impregnation or solid phase mixing, and the like, and the final molded block is usually cylindrical.

However, the reaction blocks thus prepared have a uniform mixing ratio, apparent density and porosity as a whole. Therefore, the volume expansion phenomenon seen when the carbonaceous support is not used is still seen, which in turn causes the problem of worsened mass transfer of the reaction gas. In addition, before the reaction block reacts with the reaction gas, the properties of the respective positions in the reaction block are uniform, but the reaction product is generated and the material transfer and heat transfer characteristics are changed, so the reaction conversion rate is changed according to the position and temperature and pressure gradients are generated. . In addition, in order to improve mass transfer, the apparent density of the reaction block must be made small. In order to do so, the total volume per fixed mass of the solid salt becomes large, and thus, the chemical heat pump system becomes large in volume. In addition, if the temperature gradient in the reaction block is large during the reaction, control of the reaction conditions is not easy, and if the heat in the reaction block cannot be removed quickly during the reaction for a predetermined time, there is a problem that the reaction rate is lowered due to the reverse reaction caused by the heat. .

In addition, the pores become larger than before the reaction due to the gas desorption during the desorption reaction of the gas, which is a reverse reaction of the high-gas reaction, and the pores are a barrier to heat transfer. There is also a problem that the conversion rate of the desorption reaction is not achieved as much as desired within a predetermined time. This conventional homogeneous reaction block was still limited and not satisfactory.

Accordingly, the present invention has been made to solve the above problems, the object of which is to increase the step by step toward the edge of the block without uniform density in the method for producing a reaction block of a solid salt-carbon-based support By manufacturing so that the reaction gas is adsorbed to the solid salt, even if the reaction proceeds, the gas permeability in the reaction block can be kept constant regardless of volume expansion, and the reaction heat generated by the reaction can be more smoothly transferred to the reactor heat exchange wall, It is to provide a reaction block having improved conversion rate of gas desorption reaction and a method for producing the same.

Figure 1a is a perspective view of a mold for producing a non-uniform high thermal conductivity reaction block in accordance with the present invention.

FIG. 1B is a sectional view of the forming die shown in FIG. 1A.

2 is a graph comparing the reaction rates of the homogeneous thermally conductive block and the non-uniform thermally conductive block in which NiCl ₂ is used as the reaction salt.

The present invention to achieve the above object is a) preparing a reaction mixture of a metal halide and a carbon-based support; b) the reaction mixture is composed of a cylindrical outer frame and a plurality of cylinders having a predetermined thickness and having different inner diameters and movable up and down, the height of the lower end of each cylinder from the bottom surface of the outer frame toward the outside of the outer frame; Inserting into a forming mold having an inner frame installed to increase or decrease in stages and a cylindrical rod provided on the innermost side of the inner frame to contact the bottom surface of the outer frame; And c) compressing the reaction mixture in the mold by pushing the inner mold of the mold downward for a predetermined distance so that the height of the lower end of each cylinder from the bottom of the outer frame is the same. Provided are a process for producing a reaction block for use in a chemical heat pump in which the apparent density distribution is not overall uniform but gradually increases toward the edge, and the reaction block produced accordingly.

1A and 1B are respectively a perspective view and a cross-sectional view of a forming mold for producing a non-uniform high thermal conductivity reaction block according to the present invention. The structure of the mold of FIG. 1A and a method of manufacturing a non-uniform reaction block using the mold will be described in more detail as follows.

The mold has a cylindrical outer frame, inner frame and cylindrical rod (A). The inner frame is formed of a plurality of cylinders having a predetermined thickness and inner diameters (W ₀ , W ₁ , W ₂ , W ₃ , W ₄ , W ₅ ) that are different from each other and move up and down, respectively, and have a height difference (D ₁ , D). ₂ , D ₃ , D ₄ ) so that the height (h ₁ , h ₂ , h ₃ , h ₄ , h ₅ ) of the lower end of each cylinder from the bottom face of the outer frame is stepped outward of the outer frame. Installed to increase. In addition, the cylindrical rod is for forming a hole that serves as a movement path of the reaction gas, and is provided on the innermost side of the inner frame so as to contact the bottom surface of the outer frame. The holes are formed in the same direction as the inflow direction of the reaction gas, and may be formed during molding as in the above method, or may be separately formed after molding. Also here a reaction block with one hole is produced, but more than two are possible if heat transfer is considered.

Before molding, the block molding conditions of the volume of the mold and the apparent density after compression are determined, and the amount of the reaction mixture to be compressed is calculated accordingly, and a predetermined amount is weighed into the mold. Subsequently, when the lower end of each cylinder is pushed downward by a predetermined distance downward to lower the inner frame of the mold to a portion indicated by the dotted line under the mold, the apparent density distribution is not uniform as a whole. A non-uniform reaction block increasing step by step is prepared, which is preferably used in close contact with the reaction blocks in the reactor and in close contact with the reactor walls for efficient heat transfer.

The functional effects of the reaction block of the present invention as described above will be described with reference to the adsorption reaction and the desorption reaction, which are important reactions related to the use of the reaction block.

A) adsorption reaction

Teq)를 균일 열전도성 반응 블록(이하 균일 블록이라 한다)보다 크게 하여 속도가 향상되는 효과를 얻을 수 있다. 또한 반응 블록내의 안쪽과 반응기 벽쪽의 온도차이를 줄임으로서 실제 공정에서 용이성을 얻을 수 있을 것으로 기대된다.The non-uniform high thermal conductivity reaction block (hereinafter referred to as non-uniform block) smoothly transfers the reaction heat generated during the synthesis reaction with the reaction gas to the outside direction, that is, to the reactor wall, thereby suppressing the temperature rise inside the reaction block due to the exothermic reaction. This also improves the removal of heat through the reactor walls and increases the reaction rate with the thermodynamic equilibrium temperature (

It is possible to obtain an effect of increasing the speed by making Teq larger than the uniform thermally conductive reaction block (hereinafter referred to as uniform block). It is also expected that ease of use in the actual process will be achieved by reducing the temperature difference between the inside of the reaction block and the reactor wall.

B) desorption reaction

Non-uniform blocks made so that the outer portion of the block has a high amount of salt, that is, the apparent density is increased toward the outside of the block, utilize a heat transferred from the reactor wall to produce a decomposition reaction, ie, a gas desorption reaction. It is expected that the reaction rate and the desorption reaction conversion rate at the initial stage of the reaction will be improved because the amount is relatively higher than that of the uniform block and the thermal conductivity is high on the reactor wall.

Prior to the embodiment described as an example of the production method of the reaction mixture of the general metal halide and carbon-based support used in the present invention as follows.

First expandable graphite (aka graphite interlayer compound) is expanded for 10 minutes at 800 to 850 ℃, then washed with distilled water and then dried at 800 ℃ again for 30 minutes. Subsequently, the expanded graphite is mixed with a metal salt, for example NiCl ₂ , in a predetermined mixing ratio. The mixing method is to make a desired amount of NiCl ₂ into an aqueous solution and then impregnate the expanded graphite. The impregnated mixture is maintained for 4 to 6 hours to remove moisture under the conditions of 65 to 105 ° C and -700 to -650 mmHg to prepare a reaction mixture.

The present invention is now described in more detail with reference to the following examples. However, this embodiment is exemplary and can be modified and changed within the scope of the present invention without limiting the present invention.

Examples 1 and 2 are tests for determining the best conditions for the production of non-uniform reaction blocks. The reactions with ammonia varying by making different apparent densities and mixing ratios for reaction blocks with an overall uniform density distribution. I observed the speed.

Example 1

Comparison of Reaction Rate of Ammonia Gas for Each Homogeneous Reaction Block with Different Apparent Density

The compared reaction block has a mixing weight ratio of NiCl ₂ to Pangfang graphite of 4: 6, and according to the preparation method of the reaction mixture, the outer diameter is 4.1 cm, the inside diameter 0.5 cm and the height 1.0 cm, the cylindrical density of 300, respectively. There were three types of homogeneous blocks molded differently at 400 and 500 kg / m ³ , and the homogeneous blocks were reacted with ammonia gas, respectively.

Reactor as the following stylized outside and sealed, 1kg / cm ² pressure of ammonia gas from the NH ₃ gas cylinder was inserted to the reaction block can be brought into close contact with the reactor wall connected to the NH ₃ gas cylinder as a cylindrical reactor of stainless steel or carbon steel Injected. Ammonia gas was introduced into the reactor and diffused into the block through the inner hole of the reaction block to react with a salt, that is, NiCl ₂ , where the weight loss of the bomb was weighed with an electronic balance. Since the amount of salt in the block is already known, the theoretical amount of adsorption of the total ammonia gas reacted with the salt can be known, and the loss of NH ₃ bombe over time means the actual amount of reacted ammonia gas. At the end of the reaction, the NH ₃ bomb was no longer lost. The ratio of the actual adsorption amount to the theoretical adsorption amount of the ammonia gas reacted with the three types of homogeneous reaction blocks was calculated by the reaction conversion rate, and the results are shown differently according to the reaction time.

When the apparent densities were 300, 400, and 500 kg / m ³ , the porosities in the blocks were 0.52, 0.35, and 0.2, respectively, and as the apparent density increased, the mass transfer of ammonia gas became more difficult. Therefore, the smaller the apparent density, the larger the conversion rate and the faster the reaction rate.

Example 2

Reaction Conversion Rate of Ammonia Gas for Each Homogeneous Reaction Block with Different Mixing Ratio of Metal Halide and Carbon Support

All three uniform blocks prepared as in Example 1 except that the apparent density was the same at 350 kg / m ³ and the mixing weight ratio of NiCl ₂ to expanded graphite was 4: 6, 5: 5 and 6: 4. Was tested in the same manner as in Example 1, the ratio of the actual adsorption amount to the theoretical adsorption amount of ammonia reacted for each reaction block was calculated as the reaction conversion rate, and the results are shown differently according to the reaction time. It was.

As shown in Table 2, as the mixing ratio of the expanded graphite increases, the impregnation amount of NiCl ₂ in the reaction block decreases, but the effective thermal conductivity in the reaction block increases, so that the heat generated in the reaction can be easily removed. It's faster.

Subsequently, Example 3 is to show that the heat transfer characteristics of the present invention are excellent by comparing the performance of the non-uniform reaction block prepared according to the present invention with the conventional homogeneous reaction block.

Example 3

Performance Improvement Comparison of Uniform and Non-Uniform Blocks

To compare the heat transfer characteristics of the uniform and non-uniform blocks, first push the cylindrical rod with a diameter of 1.5 cm to the bottom of the mold of Figure 1 to the bottom and set the height difference (D) of the five cylindrical frames to 5 cm each. , The weight ratio of NiCl ₂ to expanded graphite is 4: 6, and the apparent density is increased to 160, 220, 280, 340, 400kg / m ³ from the inside of the reaction block with an outer diameter of 1.5 cm, inner diameter of 1.5 cm and height of 1 cm. Non-uniform blocks were prepared. In addition, a uniform density of 320 kg / m ³ was obtained using the same amount of reaction mixture with a weight ratio of NiCl ₂ and expanded graphite as 4: 6 with non-uniform blocks of 15cm outside diameter, 1.5cm inside diameter and 0.5cm height. The block was prepared.

As a preliminary test before direct reaction with ammonia, the temperature was measured at various locations within the reaction block by applying heat from the outside of the reactor, and the non-uniform block had a temperature difference of 10 ° C./5.4 cm between the inside and the outside of the reactor after 7 minutes of heating time. In contrast, the temperature difference of the uniform block was found to be 19 ° C / 5.4 cm. This is because the heat transfer characteristics of the non-uniform block are good to transfer heat supplied from the reactor wall to the inside.

FIG. 2 shows the results of a reaction test with ammonia gas for each of the non-uniform blocks and the uniform blocks. As shown in FIG. 2, the reaction rate of the non-uniform block appeared quickly, which overcomes the limitation of mass transfer due to the volume expansion of the reaction block. In other words, the apparent density in the reaction block becomes larger, so that the thermal conductivity is improved, thereby improving the diffusion of ammonia gas.

In addition, although the reaction block is a cylindrical block, the shape is not limited, and for example, the height can be lowered to produce a flat block, and in addition, various types of pillars such as polygonal columns such as triangles and squares. Non-uniform blocks of type are also possible.

As such, the non-uniform reaction block prepared to increase the apparent density step by step from the inside to the outside can effectively transfer the reaction heat to the reactor wall, and also has excellent material transfer characteristics. In the above, the mass transfer and heat transfer effects of the non-uniform block in which the apparent density increases from the inside of the reaction block toward the edge have been mainly described. However, on the contrary, it can be made to reduce the apparent density, and these can be used in various applications such as when the reaction rate is to be suppressed for a special purpose.

Claims (2)

a) preparing a reaction mixture of a metal halide and a carbon-based support; b) the reaction mixture is composed of a cylindrical outer frame and a plurality of cylinders having a predetermined thickness and different in inner diameter and movable up and down, the height of the lower end of each cylinder from the bottom surface of the outer frame toward the outer side of the outer frame; Inserting into a forming mold having an inner frame installed to increase or decrease in stages and a cylindrical rod provided on the innermost side of the inner frame to contact the bottom surface of the outer frame; And c) compressing the reaction mixture in the mold by pushing the inner mold of the mold downward a predetermined distance so that the height of the lower end of each cylinder from the bottom surface of the outer frame is the same. A method for producing a reaction block for use in a chemical heat pump, in which the density distribution is not uniform throughout and increases or decreases in steps toward the edges. A reaction block prepared by the method according to claim 1.

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