JPS6246484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for separating and concentrating deuterium or tritium, which are hydrogen isotopes, using a water-hydrogen isotope exchange reaction.

It is known that the water-hydrogen isotope exchange reaction proceeds and is achieved through the following two-step reaction process.

1st reaction process: Isotope exchange reaction between hydrogen and water vapor 2nd reaction process: Isotope exchange reaction between water and water vapor So-called hydrophobic catalysts, in which platinum metal is finely dispersed and supported on a carrier made of porous Teflon or styrene/divinylbenzene copolymer to prevent deterioration, have come into widespread use. With this catalyst, deuterium or tritium in hydrogen is transferred to water vapor through an exchange reaction and concentrated. In the second reaction process, by bringing liquid water into physical contact with water vapor,
Deuterium or tritium in water vapor moves into liquid water and becomes concentrated. As a result, hydrogen isotopes are transferred sequentially from hydrogen to water vapor to liquid water, and the overall reaction is to concentrate hydrogen isotopes from hydrogen to liquid water. However, the first and second reaction processes are each governed by an equilibrium constant that is fixed at the reaction temperature, and in one reaction process, the hydrogen isotope transferred from hydrogen to water is approximately 3 times as large for deuterium and about 3 times as large for tritium. The concentration ratio is only about 5 times higher. Therefore, in order to separate and concentrate hydrogen isotopes to a desired concentration, it is necessary to sequentially repeat the reaction process many times. A multistage exchange reaction tower is an example of a conventional device for achieving this purpose (see Japanese Patent Publication No. 5691/1983). Figure 1 shows its conceptual diagram. 1 is a catalyst bed filled with a hydrophobic catalyst, where hydrogen gas and water vapor (dotted arrows) rising from the bottom of the column are brought into co-current contact with the catalyst bed, and the hydrogen-steam gap in the first reaction process is The isotope exchange reaction is carried out. 2 is a gas-liquid contact section, where the liquid water (white arrow) descending from the top of the column and the steam rising from the catalyst bed are brought into countercurrent contact, resulting in the water-steam reaction in the second reaction process. The isotope exchange reaction is carried out between Reference numeral 3 denotes a liquid water distributor, which is connected to a conduit passing through the catalyst bed so that the liquid water falling from the gas-liquid contact portion does not directly touch the catalyst bed. As shown in FIG. 1, the multi-stage exchange reaction column is constructed by stacking such units in multiple stages to superimpose exchange reactions and achieve desired hydrogen isotope separation.

However, a drawback of conventional equipment is that a mixed gas of hydrogen and water vapor rises from the bottom to the top of the catalyst bed against the direction of gravity, which may cause some of the saturated water vapor to condense or drop onto the catalyst bed due to agitation. A phenomenon was often observed in which liquid water remained in the reactor, thereby inhibiting the catalyst exchange reaction in the first reaction process. Furthermore, since the gas-liquid contact section and the catalyst bed are located one above the other, the column length becomes undesirable. This is because, especially in facilities that handle radioactive isotopes such as tritium, there are often height restrictions when constructing equipment, and it is necessary to keep the height of the equipment as low as possible.

The present inventor has conducted research on a device free from such drawbacks and has completed the present invention.

The present invention provides a gas-liquid contact method in which liquid water toward the bottom of the tower contacts hydrogen and water vapor toward the top of the tower in a multistage exchange reaction tower for carrying out a hydrogen isotope exchange reaction between water and hydrogen. part; a catalyst part disposed around the outer periphery of the gas-liquid contact part for performing a gas phase exchange reaction between hydrogen and water vapor; an upper partition member disposed outside the upper end of the gas-liquid contact part; the catalyst a lower partition member disposed inside the lower end of the section; a device disposed at the center of the lower partition member for receiving liquid water flowing down from the gas-liquid contact section and distributing it to the top of the lower gas-liquid contact section; This is a multi-stage exchange reaction tower characterized by comprising: a flow path provided around the catalyst section through which hydrogen and water vapor pass.

The present invention lowers the column length by arranging the gas-liquid contact part and the catalyst part, which were conventionally arranged vertically, on almost the same horizontal plane, and also changes the flow direction of hydrogen and steam in the catalyst part, that is, the catalyst bed, by gravity. It is characterized by preventing liquid water from staying in the catalyst bed by oriented downward. Therefore, although the multistage exchange reaction column of the present invention is not different in principle from the conventional apparatus described above,
This eliminates the drawbacks of conventional devices and further improves the separation effect.

The present invention will be explained in more detail below with reference to the drawings. As shown in FIG. 2, the exchange reaction unit of the present invention includes a gas-liquid contact section 10, a catalyst bed 11 disposed around the outer periphery of the gas-liquid contact section 10, and a catalyst bed 11 disposed at the bottom of the catalyst bed.
A distributor 12 is provided for distributing liquid water to the top of the lower gas-liquid contact section. Although the cross-sectional shapes of the gas-liquid contact portion 10 and the catalyst bed 11 are not particularly limited, it is generally convenient to make them concentric circles. An outer wall 15 of the exchange reaction unit is provided around the outer periphery of the catalyst bed 11, and the upper end of this outer wall 15 and the upper end of the gas-liquid contact section 10 are connected by a partition plate 13. On the other hand, the catalyst bed 11 and the distributor 12 are connected by a partition plate 16. Connecting means such as flanges (not shown) are attached to the upper and lower ends of such units, thereby allowing the units to be stacked in multiple stages and configured as an exchange tower.

The gas-liquid contact section 10 is composed of a regular packing or irregular packing used in ordinary industrial absorption towers, or a perforated plate tower or a bell tower consisting of a combination of several stages. It's okay. The catalyst bed 11 may be formed by using a hydrophobic catalyst, and may be constructed by stacking granular catalysts having various shapes such as spherical and cylindrical shapes, or having a regular shape such as a honeycomb shape.

The hydrogen and steam mixed gas rising from the bottom direction through the gap 17 between the catalyst bed 11 and the outer wall 15 enters the catalyst bed from the top of the catalyst bed as indicated by the dotted arrow, and moves up the catalyst bed in the direction of gravity. The exchange reaction of the first reaction step is carried out in the catalyst bed. In this case, even if liquid water were to adhere to the catalyst surface in the catalyst bed due to droplet agitation or partial condensation of water vapor, this liquid water would not be able to reach the catalyst because the gas is flowing in the direction of gravity. It is swept away to the bottom of the bed and does not remain in the catalyst bed, thereby preventing a drop in catalyst activity due to coating with liquid water. The hydrogen and water vapor mixed gas reacted in the catalyst bed is guided from the bottom of the gas-liquid contact section 10 into the interior thereof, and liquid water (white arrow) is dispersed from the upper distributor 12 in the gas-liquid contact section. come into contact with
A second reaction step, an exchange reaction, is performed. The distributor 12 not only plays the role of uniformly distributing liquid water to the top of the gas-liquid contact section 10, but also prevents the hydrogen and water vapor mixed gas from directly reaching the gas-liquid contact section 10 without passing through the catalyst bed 11. It also has the role of a water seal to ensure that. The water falling from the top of the tower passes through the thick line arrow and reaches the distributor 12.
The gas then reaches the gas-liquid contact section 10 and descends to the bottom of the column without passing through the catalyst bed 11. The entire exchange column is maintained at a predetermined temperature. For example, if the outer surface is
The reaction temperature is maintained at a constant temperature of, for example, 60° C. to 80° C. by covering it with water and flowing hot water or the like kept at a constant temperature inside the mantle.

Examples are shown above in order to prove the function of the exchange reaction column according to the present invention.

Example 1 A column with an inner diameter of 18 mm and a height of 100 mm in which 3 mm Dixon rings (trade name) were irregularly packed was used as a gas-liquid contact part, and a column with a height of 80 mm as a catalyst bed. , using a styrene-divinylbenzene copolymer-platinum catalyst formed into a honeycomb shape of concentric cylinders with an inner diameter of 20 mm and an outer diameter of 38 mm, the efficiency of the gas-liquid contact part ηb (defined as the equilibrium attainment rate of the first reaction process) ) and the efficiency ηc of the catalyst bed (defined as the rate of reaching equilibrium in the second reaction process) were measured individually at a reaction temperature of 70°C. As a result, the results shown in FIG. 3 were obtained. The vertical axis of the figure shows the efficiencies ηb and ηc, and the horizontal axis shows the gas cylinder velocity at which the hydrogen and water vapor mixed gas passes through the gas-liquid contact area and the catalyst bed.

As shown in FIG. 3, when the efficiency of the gas-liquid contact part and the catalyst bed have the same value, for example, ηb, η
For c0.92, the gas cylinder velocity is 0.4 at the gas-liquid contact area.
m/sec, and 0.8 m/sec at the catalyst bed.
This means that if the efficiency of the gas-liquid contact area and the catalyst bed are the same, the cross-sectional area of the catalyst bed will be 1/1/1 of the cross-sectional area of the gas-liquid contact area.
2 is sufficient, and there is no need to unnecessarily increase the cross-sectional area of the catalyst bed. In conclusion, compared to the conventional apparatus described above, the apparatus according to the present invention has a column inner diameter of
It is enough to make the tower about 1.3 times thicker, and about 0.6 times the tower length is sufficient.

Example 2 Using a gas-liquid contact section and catalyst bed having the same dimensions as those used in Example 1, an exchange column according to the invention as shown in FIG. 2 was constructed. The number of stages was 10. Using this exchange tower, tritium-enriched hydrogen and saturated steam were supplied from the bottom of the tower, and natural water was supplied from the top of the tower. Hydrogen flow rate is 17 moles per hour,
A tritium separation test was conducted with a water flow rate of 8.5 mol/hour and a reaction temperature of 70°C. As a result, the tritium concentration in the hydrogen gas exiting from the top of the tower was reduced to 1/150 of the tritium concentration in the hydrogen gas at the bottom of the tower. This corresponds to the reaction efficiency of each stage unit functioning at gas-liquid contact section efficiency ηb = 0.92 and catalyst bed efficiency ηc = 0.95, and it is clear that this exchange tower can maintain extremely high efficiency. Summer.

As shown in Example 1, the multistage exchange reaction tower according to the present invention can greatly reduce the tower length compared to the conventional equipment, and the hydrogen and steam mixed gas passing through the catalyst bed flows in the direction of gravity. Therefore, it is possible to prevent a decrease in the activity of the catalyst due to the accumulation of liquid water. Furthermore, as shown in Example 2, the reaction efficiency is high and the production is easy. It can be applied to various fields of hydrogen isotope separation technology, such as heavy water production and tritium separation and removal, and its effects are significant.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional multi-stage exchange column, FIG. 2 is an explanatory diagram of a multi-stage exchange reaction column according to the present invention, and FIG. It is a graph showing the relationship between the efficiency of the gas-liquid contact portion and the catalyst bed with respect to the cylinder speed. Explanation of drawing numbers, 1... Catalyst bed, 2... Gas-liquid contact section, 3... Distributor, 10... Gas-liquid contact section, 11... Catalyst bed, 12... Distributor, 13... Partition Board, 14...Hot water tank mantle, 15
...Outer wall, 16...Partition plate, 17...Gas passage.

Claims (1)

[Claims] 1. In a multi-stage exchange reaction tower for carrying out a hydrogen isotope exchange reaction between water and hydrogen, liquid water directed toward the bottom of the tower is brought into contact with hydrogen and water vapor directed toward the top of the tower. a gas-liquid contact section; a catalyst section disposed on the outer periphery of the liquid contact section for performing a gas phase exchange reaction between hydrogen and water vapor; an upper partition member disposed outside the upper end of the gas-liquid contact section; a lower partition member disposed inside the lower end of the catalyst section; a lower partition member disposed at the center of the lower partition member to receive liquid water flowing down from the gas-liquid contact section and spray it onto the top of the lower gas-liquid contact section; A multi-stage exchange reaction tower comprising: an apparatus; a flow path provided around the catalyst section through which hydrogen and water vapor pass; 2. The multistage exchange reaction tower according to claim 1, wherein the gas-liquid contact section and the catalyst section are concentric cylinders. 3. The multistage exchange reaction tower according to claim 1 or 2, wherein the cross-sectional area of the catalyst section is about 1/2 of the cross-sectional area of the gas-liquid contact section.