KR19990080570A - Multi-tubular catalyst tower for hydrogen isotope exchange reaction between hydrogen and water - Google Patents

Abstract

The present invention relates to a catalyst tower for separating deuterium or tritium using a hydrogen isotope exchange reaction between hydrogen and water.

Since the hydrogen isotope exchange reaction in the catalyst tower is a reaction in which both the catalyst exchange reaction and the gas-liquid exchange reaction occur simultaneously, the catalyst bed for the catalytic reaction and the absorption layer for the gas-liquid exchange reaction are appropriately disposed in the catalyst tower, The gas flows from the top of the tower to the bottom and from the bottom of the tower to the top so that the hydrogen isotope exchange reaction takes place continuously.

In the conventional catalyst tower, the catalyst layer and the absorption layer which do not act as a catalyst are alternately arranged in the height direction, and a special device (for example, a bubble cap, etc.) is installed to prevent water passing through the absorption layer from entering the catalyst layer. It is bulky and its internal structure is complicated.

In order to solve the disadvantages of the conventional catalyst tower, a space in which a catalyst layer and an absorption layer can be installed using multiple pipes having different diameters is formed, and an absorption layer is arranged in the radial direction and the catalyst layer is arranged outside. have. Compared to the conventional catalyst tower, the present invention can reduce the volume of the catalyst tower as a whole by lowering the height of the tower and increasing the space utilization. In addition, since the catalyst layer and the absorbing layer are arranged in the radial direction, water from the absorbing layer cannot enter the catalyst layer, thus eliminating the need for a separate device for preventing the inflow of water and simplifying the internal structure. .

Description

Multi-tubular catalyst tower for hydrogen isotope exchange reaction between hydrogen and water

The present invention relates to a multi-tubular catalyst tower necessary for the concentration, production of deuterium and the separation of tritium using hydrogen isotope exchange between hydrogen and water.

US Pat. No. 2,690,379, which is related to the present invention, discloses that heavy water is decomposed by the equilibrium reaction between deuterium-containing hydrogen and water on a catalyst in which platinum group elements are supported on an inert carrier. A method of making is described. The equilibrium reaction between deuterium containing hydrogen and water on the catalyst is as follows, and the two stage exchange process takes place simultaneously.

HD (gas) + H ₂ O (liquid) = H ₂ (gas) + HDO (liquid)

H ₂ O (vapor) + HD (gas) = H ₂ (gas) + HDO (vapor) ------- Step 1

HDO (vapor) + H ₂ O (liquid) = H ₂ O (vapor) + HDO (liquid) ------- Step 2

The hydrogen isotope exchange reaction between hydrogen and steam in stage 1 takes place on the catalyst, and stage 2 occurs at the contact surface of water and steam. However, although the catalyst catalyzes the hydrogen isotope exchange reaction between hydrogen and water vapor, there is a problem that the activity of the catalyst is greatly reduced when the catalyst comes in direct contact with water.

U. S. Patent No. 3,888, 974 on a hydrophobic catalyst proposed to delay the catalytic activity from contacting water with a decrease in the activity of the catalyst is disclosed in the application of a hydrophobic membrane to a hydrophilic catalyst such as a platinum-carrying carbon catalyst, or U.S. Patent No. 4,025,560. It is prepared by a method of supporting a metal on a hydrophobic carrier as in the arc. However, these hydrophobic catalysts are also used in a catalyst bed in the form of a trickle bed in which water descends from the top of the tower and hydrogen rises from the bottom of the tower to the top. Degradation of activity cannot be fundamentally avoided.

As a way to overcome these shortcomings, Nakakone (published by the Tokyo Institute of Tokyo Publication 1982, "Separation of Deuterium and Tritium", p. 7), etc., is a separated bed type catalyst. Suggested a tower. The schematic diagram is shown in FIG. 1, which is one theory that the hydrophobic platinum group catalyst layer 30 in which the hydrogen isotope exchange reaction between hydrogen and water vapor of step 1 described above occurs, and It consists of the absorption layer 20 of the hydrophilic filler in which a liquid exchange reaction takes place. This type of catalyst tower has the advantage that only hydrogen gas and water vapor pass through the hydrophobic catalyst layer 30, thereby preventing the deactivation of the catalyst due to the liquid water. According to Shimizu (1992, M. Shimizu, S. Kiyota, R. Ninimiya Bulletin of the Research Laboratory for Nuclear Reactors, "Hydrogen Isotope Enrichment by Hydrophobic Pt-Catalyst in Japan and Western Countries"), Fugen power plant (1986) was applied to heavy water upgrader, and it is reported that there is no deactivation of catalyst due to heavy water upgrader operation. However, the separation bed catalyst tower has a disadvantage that a dead space is formed around the absorbent layer because the height of one theoretical stage is 30 cm. In addition, a device such as a bubble cap 23 to prevent water from entering the catalyst layer is required, which makes the catalyst tower complicated and uneconomical.

That is, since the conventional catalyst tower as shown in FIG. 1 has a structure in which the catalyst layer and the absorption layer are arranged in the height direction, the height of one theoretical stage is large, and unnecessary space is generated by decreasing the cross-sectional area to increase the flow velocity of the reactants in the absorption layer. In actual processes requiring several tens of stages, the total height and volume of the catalyst tower is too large. In addition, since the catalyst layer and the absorber layer are arranged in the height direction, the internal structure and design of the catalyst tower are complicated due to a device that prevents water passing through the absorber layer from entering the catalyst layer.

The present invention is to provide a separation-bed catalyst tower having the same catalyst tower performance as compared to the conventional catalyst tower, but having a lower height of the catalyst tower and a simpler internal structure.

In the present invention to solve the shortcomings of the conventional catalyst tower by using a multi-tube of different diameters to create a space in which the catalyst can be installed in the radial direction and a space for installing the filler does not catalyze the absorption layer therein, The catalyst layer was arranged outside. By doing so, the height is lower than that of the conventional catalyst tower, and unnecessary space is also reduced. In addition, since the catalyst layer and the absorbing layer are arranged in the radial direction, water passing through the absorbing layer does not enter the catalyst layer, thereby eliminating the need for a separate water inflow preventing device.

According to the present invention, when the amount of the catalyst is treated in a catalyst layer having a constant product, that is, the product of the cross-sectional area and the height, the reaction time of the reactant and the catalyst is constant according to the mutual change of the cross-sectional area and the height. Performance rarely changes. Therefore, the present invention has the advantage that the height of the tower can be reduced and the internal structure can be simplified without any change in the amount of catalyst charged in the catalyst layer and the performance of the catalyst tower.

1 is a longitudinal cross-sectional view of a conventional catalyst tower in which an absorption layer and a catalyst layer are arranged in a height direction of a tower;

2 is an absorption layer, a gas flow path, and the catalyst layers are arranged in the radial direction of the tower.

Longitudinal section structure of the multi-tubular catalyst tower of the present invention having a lowered height

3 is a longitudinal cross-sectional view of a multi-tubular catalyst tower having a height lowered by absorbing layers and dual catalyst layers arranged in a radial direction of the column as another embodiment of the present invention.

<Description of the code | symbol about the main code of the drawing>

10: enclosure 11: upper guide pipe 12: lower guide pipe

13: gas passage 14: liquid outlet 20: absorber layer

21: liquid disperser 22: support 23: bubble cap

30 catalyst layer 31 first catalyst layer 32 second catalyst layer

The first catalyst tower in a specific embodiment of the present invention, as shown in Figure 2 using a triple tube tower of different diameters to create a space for the catalyst installation, gas flow space, the catalyst installation space does not catalyze, The absorption layer 20, the gas flow passage 13, and the catalyst layer 30 are arranged from the inside in the radial direction. The cross-sectional area of the gas flow path is to be 1/2 of the cross-sectional area of the catalyst bed, and is calculated by the following equation.

(One)

Where R ₁ is the radius of the absorbent layer, R ₂ is the radius of the gas flow space, and R ₃ is the radius of the catalyst bed.

The liquid disperser 21 is installed above the absorbent layer, and the support 22 is installed below the catalyst layer and the absorbent layer, respectively, and a liquid outlet 14 descending from the upper end to the lower end is provided. Hydrogen and water vapor react while going up the catalyst layer 30, descend through the gas flow passage 13, and then up through the absorbent layer 20. The gas-liquid exchange reaction occurs between the water vapor entering the absorbent layer and the water descending from the upper portion, and the water falling down the absorbent layer is designed to descend to the lower absorbent layer by gravity without entering the catalyst layer 20. Compared with the conventional catalyst tower of FIG. 1, it can be seen that the height of the catalyst tower is reduced without changing the volume of the absorber layer and the catalyst layer, and there is no need for a separate device to prevent water from flowing into the catalyst layer.

The second catalyst tower in a specific embodiment of the present invention, as shown in Figure 3 using a triple tube tower of different diameter to create a double space for the catalyst installation and the catalyst installation space without the catalytic action, the radial direction The absorber layer 20, the first catalyst layer 31, and the second catalyst layer 32 are arranged from the inside. The cross-sectional area of the first catalyst layer and the cross-sectional area of the second catalyst layer are the same, and calculated by the following equation.

(2)

Where R ₁ is the radius of the absorbent layer, R ₂ is the radius of the first catalyst layer, and R ₃ is the radius of the second catalyst layer.

The liquid disperser 21 is installed on the absorbent layer, and the support 22 is installed on the catalyst layer and the lower part of the absorbent layer, respectively, and a liquid outlet 14 descending from the upper part to the lower part is provided.

Hydrogen and water vapor are reacted while going up the second catalyst layer 32 and down the first catalyst layer 31 and then up through the absorbent layer 20. The gas-liquid exchange reaction occurs between the water vapor entering the absorbent layer and the water descending from the upper portion, and the water falling down the absorbent layer is designed to descend to the lower absorbent layer by gravity without entering the catalyst layer. Compared with the conventional catalyst tower of FIG. 1, the volume of the absorption layer and the catalyst layer is not changed, the height of the catalyst tower is reduced, and a separate water inflow prevention device is not required for the catalyst layer.

The present invention can be used not only to separate deuterium from hydrogen, but also to separate tritium from hydrogen or to separate tritium from deuterium by the following examples. In the test of the present invention, the catalyst was used by loading 0.8% platinum by weight on a styrene-divinylbenzene copolymer molded into pellets having a diameter and a height of 4 mm.

The method for producing a catalyst is as described in Korean Patent No. 59757 (Hansoo Lee, a method for preparing a pellet-type hydrophobic polymer catalyst for hydrogen isotope exchange and hydrogenation reaction). As the hydrophilic filler of the absorbent layer, a wire-mesh ring (diameter × height 3 × 3 mm) made of stainless steel (normschliff Geratebau-Wertheim, Germany) was used.

Example 1 Separation of Deuterium from Hydrogen

In order to measure the efficiency of the multi-tubular catalyst tower for the deuterium exchange reaction between hydrogen and water, hydrogen having a natural isotope amount (D / H = 1.2 × 10 ⁻⁴ ) was used after purification. Water (distilled water) and heavy water were mixed and used (D / H = 2.0 × 10 ⁻² ). Hydrogen flows from the bottom of the catalyst tower to the top and water flows from the top to the bottom. Hydrogen is passed through a humidification tower filled with uncatalyzed charge prior to entering the catalyst tower to saturate the hydrogen with water vapor so that water from the catalyst tower flows downward.

Efficiency of Catalyst Layer in Catalyst Tower η _c Is the relative difference between the concentration difference between the fluid entering and leaving the catalyst bed and the concentration difference when the reaction in Step 1 is complete and equilibrium is reached. In other words,

(3)

here x ₀ Is the deuterium atomic ratio (D / H) in hydrogen entering the catalyst layer, x Is the atomic ratio (D / H) of deuterium in hydrogen coming out of the catalyst layer.

Deuterium atomic ratio in hydrogen can be measured by gas chromatography or mass spectrometry, x _e Is the deuterium atomic ratio (D / H) in the hydrogen exiting the catalyst layer, assuming that equilibrium has been reached and the equilibrium has been reached. This is the component mass balance equation and separation coefficient for hydrogen and water vapor flow α _{g (H / D)} Obtained from Separation factor α _{g (H / D)} Is a measure of the separation of isotopes in the deuterium exchange between hydrogen and steam, and is defined as the ratio of the atomic ratio of heavy isotopes to light isotopes of hydrogen and steam at equilibrium, a function of temperature alone. In other words,

(4)

On the other hand, the hydrogen and steam mixed gas reacted in the catalyst layer flows into the liquid water and countercurrent flowing in the lower part in the absorption layer, and gas-liquid exchange occurs between the water vapor and the water in the reaction scheme of Step 2.

Efficiency of such absorption layer in catalyst tower η _p Similar to the efficiency of the catalyst bed, is the ratio of the concentration difference between the fluid entering the absorbing bed and the fluid coming out of the absorbent bed and the difference in concentration when the reaction of step 2 is complete and equilibrium is reached. In other words,

(5)

here z ₀ Is the atomic ratio (D / H) of deuterium in the water entering the absorption layer z Is the atomic ratio (D / H) of deuterium in the water coming out of the absorption layer. The atomic ratio (D / H) of deuterium in water can be measured by infrared spectroscopy. z _e Is the deuterium atomic ratio (D / H) in the water exiting the absorption layer, assuming that the isotope exchange reaction has been completed and the equilibrium has been reached. α _{l (H / D)} Available from Separation factor α _{l (H / D)} Is a measure of the separation of isotopes in the deuterium exchange between water and steam, and is defined as the ratio of the atomic ratio of heavy isotopes to light isotopes of water and steam at equilibrium, a function of temperature only.

(6)

As a result of measuring the efficiency of the catalyst layer and the absorbing layer for the multi-tubular catalyst tower of FIG. 2 and FIG. This proves that the catalyst used is useful for the separation of deuterium from hydrogen, and the height of the catalyst tower can be reduced to 2/3 of that of the conventional catalyst tower while maintaining the separation performance by the method of the present invention. .

Therefore, the multi-tubular catalyst tower of the present invention can improve the simplicity and economy of the process for separating deuterium from hydrogen.

Table 1 and the catalyst bed of a multi-tubular catalyst tower for deuterium separation from hydrogen

Efficiency of the absorbing layer (catalyst amount: 190 cm 3, temperature: 70 ° C. (343K), pressure: 1 atm)

Type of catalyst tower Hydrogen flow rate (cm 3 / s) Water flow rate (g / s) Catalyst Bed Efficiency Efficiency of Absorption Layer The multi-tube catalyst tower of FIG. 2 462 22.2 0.97 0.98 577 27.8 0.99 0.97 693 33.4 0.96 0.97 The multi-tubular catalyst tower of FIG. 3 462 22.2 0.98 0.98 577 27.8 0.98 0.98 693 33.4 0.97 0.97

Example 2 Separation of Tritium from Hydrogen

The equilibrium reaction between tritium-containing hydrogen and water on the catalyst can be expressed as

HT (gas) + H ₂ O (liquid) = H ₂ (gas) + HTO (liquid)

This equilibrium reaction takes place by simultaneously performing the catalyst phase exchange reaction in step 1 and the exchange process by gas-liquid contact in step 2.

H ₂ O (vapor) + HT (gas) = H ₂ (gas) + HTO (vapor) -------- 1st stage

HTO (vapor) + H ₂ O (liquid) = H ₂ O (vapor) + HTO (liquid) --------- 2 stage

In order to measure the efficiency of the multi-tubular catalyst tower for the tritium exchange reaction between hydrogen and water, hydrogen having a natural isotope amount (T / H = 1.75Bq / l) was purified and tritium was used. The concentration was prepared at 300 Bq / l and used.

Efficiency of Catalyst Layer in Catalyst Tower η _c ), Gas phase separation coefficient ( α _{g (H / T)} ), The efficiency of the absorber layer ( η _p ), Separation coefficient of liquid phase ( α _{l (H / T)} ) Can be expressed as in the formulas (3)-(6) of the first embodiment. The concentration of each fluid represents the atomic ratio (T / H) of tritium, and the tritium concentration can be measured with a liquid scintillation counter.

Table 2 shows the results of measuring the efficiency of the catalyst layer and the absorption layer for the tritium exchange reaction between hydrogen gas and liquid water for the multi-tubular catalyst tower of FIG. 2 and FIG. 3, and each efficiency is 0.95 or more under appropriate operating conditions. Can be. This proves that the catalyst used is useful for the separation reaction of tritium from hydrogen and the height of the catalyst tower can be reduced to 2/3 of that of the conventional catalyst tower while maintaining the separation performance by the method of the present invention. to be.

Therefore, the multi-tubular catalyst tower of the present invention greatly improves the economics of the process of separating tritium from hydrogen.

Table 2 and the catalyst bed of a multi-tubular catalyst tower for tritium separation from hydrogen

Efficiency of absorbing layer (catalyst amount: 190 cm 3, temperature: 70 ° C. (343K), pressure: 1 atm)

Type of catalyst tower Hydrogen flow rate (cm 3 / s) Water flow rate (g / s) Catalyst Bed Efficiency Efficiency of Absorption Layer Multi-tubular catalyst tower of Figure 2 462 22.2 1.0 0.97 577 27.8 0.99 0.98 693 33.4 0.97 0.97 Multi-tubular catalyst tower of Figure 3 462 22.2 0.97 0.96 577 27.8 0.99 0.97 693 33.4 0.99 0.97

The present invention can reduce the height of the tower by 33% as the performance is the same as or higher than that of the conventional catalyst tower by arranging the absorption layer inside and the catalyst layer outside in the radial direction using multiple tubes having different diameters. It is an economical catalyst tower that reduces the volume of the tower by 44% by reducing unnecessary space. In addition, since the catalyst layer and the absorber layer are arranged in the radial direction, since the water passing through the absorber layer cannot be introduced into the catalyst layer, a separate water inflow prevention device is not required, so the internal structure is simplified and is easy to design and manufacture. In addition, since the inflow of water into the catalyst layer can be prevented at the source during the operation of the catalyst tower, it is possible to provide a catalyst tower that is easy to design, manufacture and operate.

Claims (2)

In the catalyst tower in which the absorbent layer 20 and the catalyst layer 30 are continuously assembled in a stacked manner, a lower induction pipe having an upper induction pipe 11 and a liquid outlet port 14 having an open center in the enclosure 10 is formed. 12) in the assembled state to form a gas flow path (13), but the center of the upper guide pipe (11) is filled with the absorbent layer 20 and between the outer surface of the lower guide pipe 12 and the inner wall of the enclosure (10) There is a multi-tubular catalyst tower for hydrogen isotope exchange reaction between hydrogen and water, characterized in that the catalyst layer 30 is filled. The method of claim 1, The first catalyst layer 31 is formed on the vertical passage of the gas flow passage 13 formed by the upper guide pipe 11 and the lower guide pipe 12, and the outer wall of the lower guide pipe 12 and the enclosure 10. A multi-tubular catalyst tower for hydrogen isotope exchange reaction between hydrogen and water, wherein the second catalyst layer 32 is filled between inner walls to divide the catalyst layer.