JPS63185446A - Production of solid adsorbent - Google Patents

Abstract

PURPOSE:To enhance the thermal conductivity of single yarn grains when prepared in the form of grains by adding a heat conductive substance in the form of powder, etc., to silicon dioxide xerogel, agitating and mixing both materials, and then drying, dehydrating, and caking the mixture to obtain the yarn. CONSTITUTION:An acid 3 is added to an aq. soln. 2 of sodium silicate to neutralize the soln., and the obtained material is sufficiently washed with water to remove impurities and then dehydrated to form the xerogel of silicon dioxide 4. The xerogel of silicon dioxide 4 is also called silica gel. A requisite amt. of the powdery, granular, or acicular heat-conductive substance 5 is added to the gel, sufficiently agitated, and mixed to dispersedly mix the substance 5 into the gel of silica dioxide 4. The mixture of the silicon dioxide 4 and the substance 5 is then heated at high temp., dehydrated,dried, and caked to obtain the solid deodorant 6 of the desired shape.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for producing a solid adsorbent with increased thermal conductivity, and in particular to a method for producing a solid adsorbent that is used in an adsorption refrigerator that performs refrigeration operation by the refrigerant adsorption effect of the adsorbent. The present invention also relates to a method for producing the solid adsorbent, which is suitable for the purpose of manufacturing the solid adsorbent.

(Prior technology) Adsorption refrigerators, which generate cold heat by utilizing the refrigerant adsorption and desorption performance of solid adsorbents, not only can utilize low-temperature factory waste heat, but also require less energy from pumps and other equipment than compressor-type refrigerators. It has great advantages such as fewer moving parts, lower equipment cost, lower operating costs, and lower operating noise.

Incidentally, the solid adsorbents used in this type of conventional adsorption refrigerator are generally inorganic solid adsorbents such as natural zeolite and silica gel, but these solid adsorbents do not absorb their own heat. Because the conductivity is lower than that of metals, the rate of heat transfer between particles during refrigerant desorption is slow;
For example, when thermal desorption is performed by filling solid adsorbent into the fin gaps of a cross-fin coil or inside a holding container, the solid adsorbent itself acts as a heat insulating material, and the solid adsorbent located in the center of the filling space is heated. There was a problem that heating was inhibited and the desorption cycle time became extremely long.

In order to overcome this inconvenience, a solid adsorbent such as natural zeolite is ground into powder, mixed with powder of a metal with high thermal conductivity, such as copper powder, and stored in a storage tank.
Cooling systems have been proposed that increase the heating rate and efficiency of solid adsorbents. (Unexamined Japanese Patent Publication No. 58-190
(Refer to Publication No. 3062) (Problems to be solved by the invention) However, in the case of mixing solid adsorbent powder and copper powder as described above to improve the heat transfer of the adsorbent, the conventional particle size l Although it has superior adsorption efficiency compared to ~3m granular solid adsorbent, it has some handling issues such as difficulty in retaining the adsorbent when filling the gaps between the fins of cross-fin tubes or Elofin tubes. There are many problems.

In addition, in such a mixed solid adsorbent, the adsorbent particles and metal particles are only in point contact when observed microscopically, and the heat transfer coefficient between them is low, so metal powder It is necessary to increase the mixing ratio, and the mixing ratio of the solid adsorbent is correspondingly small, which reduces the amount of adsorption and increases manufacturing costs.There is still room for urgent improvement in these points. It had been.

The present invention was made to improve the thermal conductivity of the solid adsorbent used in such conventional adsorption refrigerators. The heating rate of the solid adsorbent can be increased by adding a small amount of the thermally conductive substance by mixing the thermally conductive substance in a dispersed mixing state and increasing the contact area between the thermally conductive substance and the solid adsorbent. , it is an attempt to solve the above-mentioned problems.

(Means for solving problems) FIG. 1 is a process explanatory diagram of the manufacturing method of the present invention.

First, as shown in Figure 1 (a), an acid (3) is added to an aqueous sodium silicate solution (2) to neutralize it, the solution is thoroughly washed with water to remove unnecessary substances, and then dehydrated to form a xerogel-like silicon dioxide. (4) is generated. The xerogel-like silicon dioxide (4) thus produced is also called silica gel, and is produced as a jelly-like precipitate. In addition to this, Figure 1 (
B) A thermally conductive substance in the form of a powder, a grain, or a needle (5
) was added in the required amount and stirred and mixed well to form the thermally conductive substance (
5) is mixed into gelled silicon dioxide (4) in a dispersed state. Next, silicon dioxide (4) and a thermally conductive substance (
The mixture of step 5) was dehydrated by heating at high temperature and dried to form the mixture shown in Figure 1 (
It is solidified and molded into a solid adsorbent (6) in the desired shape as shown in c).

Note that relatively inexpensive copper is usually used as the thermally conductive material (5). Further, the mixing ratio of the thermally conductive substance (5) to the adsorbent substance is preferably set to 8 to 15 weight percent.

(Function) The solid adsorbent (6) thus obtained has a thermally conductive substance (5) dispersed almost uniformly in an adsorbent substance (4) such as silica gel, as shown in Fig. 2. The entire surface is in contact with the adsorbent material (4), or the thermally conductive material (4)
Since a part of 5) is exposed on the surface of the solid adsorbent (6), when a large number of solid adsorbents (6) are filled in the fin gaps of a cross fin tube or an erotic fin tube or in a holding container, Due to the presence of the thermally conductive substance (5), the rate of heat conduction within the solid adsorbent (6) increases, and the rate of heat conduction between particles of the solid adsorbent (6) also increases. The heat transfer rate to the solid adsorbent (6) located in the upper part is increased, and the cycle time required for thermal desorption is greatly shortened.

(Example) Next, examples of the present invention will be described.

FIG. 1 is an explanatory diagram showing a process for producing a granular solid adsorbent by mixing a required amount of copper powder into silica gel.

First, an aqueous sodium silicate solution (2) is placed in a container (1), and sulfuric acid (3) is added to neutralize the solution to form a milky white translucent jelly-like precipitate. This is silicic acid called water glass, and has the general formula (SiOz)m (H2O
) Indicated by n.

The reaction during this time is as shown in the following equation.

NazSiOz+HzSOt=NaxSO4411zS
iOs '' (1) Next, the generated liquid is thoroughly washed with water and dehydrated at around 500°C to obtain xerogel-like silicon dioxide (4). ) was added at around 12% by weight and stirred well.

Silicon dioxide (4) and copper powder (5) thus obtained
) is heated at a high temperature of 500° C. or higher and dehydrated and dried to obtain a solid adsorbent (6) with high thermal conductivity in which copper powder (5) is mixed in a dispersed state in solid silica gel.

Incidentally, when the mixture of silicon dioxide (4) and copper powder (5) is ignited, powdered anhydrous silicon dioxide containing copper powder (5) is obtained, so if this is press-molded with a mold, Solid adsorbent (6) particles of any shape can be produced.

FIG. 3 is a graph comparing the heat transfer rates of a solid adsorbent prepared according to the present invention and a conventional solid adsorbent.

In the experiment, the granular solid adsorbent (6) was filled so as to be in contact with the heating wall (7) at <100°C, as shown in Fig. 4.
) The temperature rise at a measurement point (P) 4.5 cIm away from the point (P) was recorded.

In Fig. 3, (A) is a case where only copper powder is used, (B) is a case where 80 weight percent of copper powder is mixed with silica gel particles, and (C) is a case where 70 weight percent of copper powder is mixed with silica gel particles.
D) is when 50% by weight of copper powder is mixed, (E)
is for silica gel particles only.

As can be seen from the above graph, the solid adsorbent produced by the method of the present invention contains only 12% by weight of copper powder. It shows the heat transfer rate. Therefore, it is possible to save the amount of copper powder and reduce manufacturing costs, and since the shape of the solid adsorbent (6) can be set arbitrarily, the solid adsorbent (6) By appropriately adjusting the cross-sectional area of the refrigerant passage formed between the refrigerant and the adsorbent, it is possible to increase the contact opportunities between the refrigerant and the adsorbent, thereby improving the adsorption performance. Since the conduction and heat transfer coefficient between particles of the solid adsorbent (6) are high and heating is performed smoothly, the time required for desorption is greatly shortened.

In the above example, a case was explained in which copper powder was used as the thermally conductive material, but if necessary, copper particles with a particle size of 0.5 μ or less or a thickness of 0.1 to 1
It is also possible to produce a solid adsorbent in the form of a relatively large lump by mixing fl short needle-shaped copper wire, and then pulverize it into particles of the required size.It is also possible to use other metals as a substitute for copper. It is also possible to use

(Effects of the Invention) As explained above in detail, the manufacturing method of the present invention is to neutralize an aqueous sodium silicate solution with an acid, wash and dehydrate the resulting xerogel-like silicon dioxide, and add powder, granules, or needles to the After adding a thermally conductive substance, stirring and mixing, drying and dehydration are performed, and the thermally conductive substance is solidified and molded in a dispersed and mixed state, whereby the entire surface of the thermally conductive substance is covered with the adsorbent ( silica gel), and the heat transfer coefficient during this period increases dramatically, so when the solid adsorbent is formed into particles, the thermal conductivity of the single particle is high, and the heating rate during desorption and cooling during adsorption are high. The speed increases significantly. Therefore, when the solid adsorbent obtained by the method of the present invention is used in an adsorption refrigerator, the adsorption/desorption cycle time is greatly shortened and the output per unit time is increased, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram of the production method of the present invention, FIG. 2 is a cross-sectional view of the solid adsorbent obtained by the method of the present invention, and FIG. 3 is a diagram showing the heat transfer rate of the solid adsorbent obtained by the method of the present invention and the conventional Graph comparing heat transfer rate of solid adsorbent, 4th
The figure is a schematic diagram of the adsorbent heat transfer rate measurement model. (2)...Sodium silicate aqueous solution, (3)...Acid (sulfuric acid), (4)...Silicon dioxide, (5)...Thermal conductive material (copper powder), (6)... ...Solid adsorbent.

Claims (1)

[Claims] 1. A xerogel-like silicon dioxide obtained by neutralizing an aqueous sodium silicate solution with an acid, washing with water and dehydrating the powder,
A method for producing a solid adsorbent, which comprises adding a granular or acicular thermally conductive substance, stirring and mixing, followed by drying and dehydration, and solidifying and molding the thermally conductive substance in a dispersed and mixed state. 2. The method for producing a solid adsorbent according to claim 1, wherein the thermally conductive substance is copper. 3. The method for producing a solid adsorbent according to claim 1 or 2, wherein the thermally conductive substance is mixed in the adsorbent material in an amount of 8 to 15% by weight.