KR100845518B1 - Method and apparatus for separating Krypton gas and Xenon gas - Google Patents

Abstract

The present invention is a method and apparatus for separating krypton gas and xenon gas from a krypton / xenon mixed gas.

This method passes a krypton / xenon mixed gas through a heat exchanger that is maintained above the vaporization temperature of krypton and below the freezing temperature of xenon to make xenon freeze, krypton to gaseous state, and then adsorb freeze xenon The krypton and xenon are separated from the krypton / xenon mixed gas, which is characterized by separating the krypton gas by passing the xenon adsorption and desorber passing through the gas krypton and adsorbing the zenon in the frozen state and passing the krypton gas. .

The apparatus includes a heat exchanger for introducing krypton / xenon mixed gas to freeze and discharging the xenon contained therein, and a xenon adsorption and desorption unit for adsorbing xenon which is combined with the heat exchanger and passing krypton in gas state. To control the flow of the krypton / xenon mixed gas through the heat exchanger and the xenon adsorption desorber, and to control the temperature of the heat exchanger and the xenon adsorption desorber to discharge only krypton gas or only xenon gas. It is a device for separating krypton and xenon from krypton / xenon mixed gas characterized in that it comprises a program controller.

Krypton, Xenon, Xenon, Gas Separation, Gas Adsorption, Gas Desorption, Mole Cool, Moisture Adsorption

Description

Krypton gas and xenon gas separation method and apparatus therefor {Method and apparatus for separating Krypton gas and Xenon gas}

1 is a schematic diagram for explaining the entire system of the present invention.

Figure 2 is a schematic cross-sectional view of the moisture adsorber of the present invention.

3 is a schematic cross-sectional view of the xenon adsorption and desorber of the present invention.

The present invention relates to a method and apparatus for separating krypton gas and xenon gas from a Krypton / Xenon mixed gas.

Methods and apparatus for obtaining krypton / xenon mixed gas (sometimes referred to simply as 'mixed gas' in the future) have been disclosed in the patent publication.

Publication No. 2003-0041780 (Application No. 10-2002-0071108, filed November 15, 2002), published May 27, 2003, discloses a method for recovering a krypton / xenon mixed gas. These include, by selective adsorption in lithium and silver exchange zeolites having a silver exchange capacity of 5 to 40% on an equivalent basis, accompanied by periodic thermal regeneration of the adsorbent, usually from xenon and from the bottom liquid oxygen in cryogenic air separation processes. Methods for recovering krypton are disclosed.

In addition, a method and apparatus for recovering krypton and / or xenon are disclosed in Publication No. 10-2004-0051543 (Application No. 10-2003-0090029, filed December 11, 2003) published on June 18, 2004. Here, krypton and / or xenon are supplied to the rare gas recovery system a mixture comprising at least one rare gas and oxygen selected from krypton and xenon or a mixture derived from the mixture to the rare gas recovery system, The mixed feed is crudely separated from the mixture in a method comprising separating the rare gas lean gas phase oxygen (GOX) and the rare gas rich product. The method further provides that when the mixed feed is separated by selective adsorption, at least about 50 mol% of the mixed feed is at least gaseous if the xenon concentration in the mixed feed is no more than 50 times greater than the xenon concentration in air. It is characterized in that the supply to the recovery system. One advantage of the preferred embodiment of the present invention is that it can be easily retrofitted into existing pumped LOX cycle ASUs.

Known krypton / xenon mixed gas as described above is a method and apparatus for obtaining krypton or xenon gas from a mixture of various gases.

Krypton / Xenon mixed gas is concentrated from an oxygen stream of a very large air separation plant, and is a rare gas in which krypton is mixed in a composition ratio of about 9: 1.

The present invention seeks to provide a method and apparatus for separating krypton and xenon from a mixed gas in which krypton and xenon are mixed about 9: 1.

This method configuration allows a xenon to freeze and a krypton to a gaseous state by passing a krypton / xenon mixed gas through a heat exchanger maintained at temperatures above the freezing point (freezing temperature) of the krypton and below the freezing point of xenon. The second step of separating the krypton gas by passing the xenon adsorption desorber which adsorbs the xenon in the frozen state and passes the krypton in the gas state and passes the krypton gas in the frozen state, and adsorbs the xenon adsorption desorber And a third step of recovering the xenon gas by heating the xenon adsorption-and-desorption unit above the vaporization point of the xenon so that the xenon becomes a gas state.

The structure of the apparatus is a heat exchanger for introducing krypton / xenon mixed gas into a frozen state and discharging the xenon contained therein, and a xenon adsorption coupled to the heat exchanger to adsorb the frozen xenon and pass the gaseous krypton Control valves to control the flow of the desorber and the krypton / xenon mixed gas passing through the heat exchanger and the xenon adsorption desorption unit, and control the temperature of the heat exchanger and the xenon adsorption desorption machine to discharge only krypton gas or only xenon gas. It includes a program controller for controlling. In addition, the heat exchanger is combined with a dioxo unit for converting the hydrogen in the krypton / xenon mixed gas to be converted into water vapor and a water adsorption unit adsorbed to the gas outlet of the dioxo unit to adsorb water vapor in the mixed gas. And a gas compressor coupled to the gas inlet and vacuum-substituted from the xenon adsorption and desorber, and a gas compressor coupled to the outlet of the vacuum pump to compress the gas.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1,2 and 3.

As shown in FIG. 1, the mixed gas separation system includes a dioxo unit (oxygen removal unit: Deoxo unit: 10), a moisture adsorber (20, 21), and the like in a tank 1 in which a krypton / xenon mixed gas is stored, as shown in FIG. Cryogenic Separator (100, 101), the low temperature heat exchanger 130, the xenon adsorption and desorption unit 140, the vacuum pump 150, and the compressor 160 in the low temperature separator in turn combined with the pipeline and control valves A program controller for controlling the control valves and controlling the temperature of each part is combined with each of the above elements.

First, an oxygen removal unit (Deoxo unit: 10) is for removing impurity oxygen contained in Kr / Xe mixed gas supplied from the storage tank 1, and oxygen and hydrogen are added to the mixed gas by adding hydrogen to the catalyst. When the water is changed into water vapor by the reaction, it is passed through a water absorber (for example, silica gel) to allow moisture to be adsorbed, thereby removing oxygen.

Moisture adsorber (20, 21) is combined by placing the control valves in the outlet pipeline of the oxygen removal unit 10, respectively, two sets are installed in parallel, the operation bed (A) by a switching valve (181: switching valve) And regeneration bed (B) can be separated into two sets to operate. The moisture adsorber 20 is regenerated by high temperature nitrogen at low pressure. As shown in FIG. 2, the moisture absorber is provided with filters 52 and 53 at the input end 55 and the discharge end 54 in the case 50, respectively, and is filled with activated alumina 51 to increase adsorption efficiency. .                     

Cryogenic Separator (100, 101) is a pipe connected to the outlet of the water adsorber (20, 21), respectively, is a device for separating them from each other using the difference between the freezing point of Krypton Kr and Xenon Xe. From this, and with a liquid nitrogen container 110 therein, the low temperature heat exchanger 130 to that in the liquid nitrogen container 110 while passing the gas mixture of liquid nitrogen and indirect heat exchange, heat exchange the gas mixture A xenon adsorption and desorption unit 140 for adsorbing the frozen xenon and detaching the heated xenon is installed. In addition, temperature sensors are installed in the liquid nitrogen container to control the temperature, and liquid level sensors are provided to control the liquid nitrogen liquid level. Temperature control means for receiving the signals of these sensors and maintaining the temperature at a predetermined temperature is also provided.

Xenon adsorption and desorption unit 140 has an adsorbent therein, which is to pass the krypton in the gas state, so that the xenon below the freezing point (-112 degrees Celsius) is frozen and can not pass through. The liquid level (104, 105) of the liquid nitrogen is controlled, and the high temperature desorption action by freezing adsorption and regeneration nitrogen gas is switched to operate the A and B systems by a predetermined cycle.

Meanwhile, as shown in FIG. 3, the xenon adsorption and detachment unit 140 includes filters 71 and 74 at the input end 75 and the discharge end 76, respectively, in order to prevent the debris from being damaged inside the case 70. Activated carbon (73: Activated Carbon) in the lower layer and Molecular Sieve (72: Molecular Sieve) layer in the upper layer is filled with porous specifications and frozen xenon specifications to maximize the adsorption efficiency. The adsorbent has a sufficient effective area and the surface velocity through the bed of adsorbent belongs to the 0.2 m / sec series, which is equivalent to 65% of the minimum fluidized bed velocity.

In order to recover xenon, the xenon adsorption desorption unit is heated to room temperature or higher by regeneration nitrogen gas so that when the adsorbent is raised to a temperature higher than the vaporization point, the adsorbed xenon becomes a gas state and can be recovered. The freeze-adsorbed xenon is desorbed from the xenon adsorption desorption unit during regeneration and is recovered and stored by the vacuum pump 150 and the compressor 160. It can be purified up to 99.995%.

At the time of desorption of the xenon adsorption and desorption unit, two control valves 142 and 143 provided at the inlet of the low temperature heat exchanger and the discharge side of the desorption unit are operated to isolate the desorption unit, and the krypton vacuum pump 151 is first cooled. Open the connecting valve 157 and close the xenon suction valve 145 to recover the residual krypton, and if the next adsorption / desorption is heated, the vacuum pump connection valve 157 for krypton is closed and then the xenon vacuum pump 150 and The xenon suction valve 145 is opened to recover and compress the xenon vaporized. The thickness of the adsorption-and-desorption vessel 70 and the filter 75 of the suction stage 75 have a rigid structure for safety and prevention of damage to the adsorbent. The vacuum pump may be installed at a power of -2 torr of 10.

The liquid nitrogen container 110 is supplied with liquid nitrogen under the control of the control valve 146 to control the liquid levels 104 and 105. When nitrogen is evaporated, the liquid nitrogen container 110 is exhausted to the atmosphere through the valve 147 of the vent line. The low temperature heat exchanger 130 and the xenon adsorption and desorption unit 140 inside the vessel are maintained at around -135 degrees Celsius, which is an intermediate temperature while the liquid nitrogen liquid level is controlled by the temperature control means. Since liquid nitrogen is -196 degrees Celsius at the feed end and the temperature near the liquid level inside the liquid nitrogen container is -155 degrees Celsius or lower, temperature control is performed by controlling the liquid level of liquid nitrogen in contact with the heat exchanger.

The temperature control means has a temperature sensor and a liquid level sensor in the liquid nitrogen container 110, and compares the temperature state obtained from these sensors with a set temperature and generates a control amount to control the control valves for adjusting the level of the liquid nitrogen. . The recovery of krypton gas is controlled to -135 degrees Celsius. At this time, the vaporized nitrogen is vented to the atmosphere through the nitrogen gas exhaust valve (147).

The structure of the container of the low temperature separator is divided into oil container and liquid nitrogen inner container. Insulation parts 120 and 121 made of pearlite or vacuum are formed between inner and outer tanks to increase thermal efficiency and to facilitate maintenance. It uses a heat exchanger and has an assembled cap that can be disassembled and assembled in an inner and outer tank.

It includes a temperature control means, it is provided with a process controller for controlling the entire system process, such as controlling the flow of the mixed gas by controlling the respective control valves, selecting the operation bed. This process controller is supplied with water adsorber (20, 21), low temperature separator (100, 101), liquid nitrogen supply valve (146), vacuum pump (150, 151), krypton and xenon compressor (160,161), nitrogen gas heater (170), nitrogen gas supply. Valves 171, 172, and the like. This process controller includes a computer system, receives signals from sensors installed in each part by a preset program, generates control signals for operating each valve or electric heater, monitors operation status, and two sets alternately with each other. The overall control of the processor to separate and recover the krypton gas and xenon gas is optimal.                     

Reference numerals 142, 143, 145, 146, 147, 157, 171, 172, 181, 182, 183, 184, 185, etc. refer to valves, and these valves are for controlling the opening or closing of a pipeline, and the same functions are assigned with the same reference numerals, and some of the valves are not given the same reference numerals. It is necessary for the selection and progress of the process. As an example, it is used to connect or operate a moisture absorber and a cryogenic separator set. These valves are those operated manually or automatically.

The water adsorption and desorption unit shown in FIG. 2 and the xenon adsorption and desorption unit shown in FIG. 3 are one example of the above description, and of course, various commercially available structures can be used. In addition, the configuration shown in the overall system diagram shown in FIG. 1 is just one example, and arrangement of components for realizing the technical idea of the present invention can be realized in various ways in addition to the present embodiment, and the present invention can be realized in various ways. It is a technical idea that includes the change of branch.

The following describes a process for separating krypton and xenon using such a system.

<Crypton recovery process>

The Krypton / Xenon mixed gas used as the starting material in this process is concentrated from the oxygen stream of the ultra-large air separation plant, and has a composition ratio of approximately Krypton 92.3% and Xenon 7.7% and recovers up to 99.9% purity Rare Gas. Use

First, in the Kr / Xe mixed gas storage device, the Kr / Xe mixed gas is decompressed to an appropriate pressure and supplied to the oxygen removal unit. Then, the impurity oxygen contained in the mixed gas is converted into water vapor by the reaction of hydrogen added to the oxygen removing unit and the catalyst (Catalyst) and adsorbed to the water absorber to remove oxygen from the mixed gas.

Next, the oxygen-free mixed gas is passed through a cryogenic separator, for example, the first set of water adsorber 20 and the cold separator 100, and has a high freezing point of Kr / Xe mixed gas (Centigrade Celsius). -112 degrees) is frozen and adsorbed onto the Xenon Absorber / Desorber, while Krypton (-157 degrees Celsius) with a low freezing point passes through the xenon desorber in gaseous form and is stored in storage. While the mixed gas of krypton / xenon passes through the heat exchanger 130 of the low-temperature separator A, the mixed gas is cooled to around -135 degrees Celsius according to the flow rate of the liquid nitrogen supplied into the liquid nitrogen container, but the krypton is xenon adsorption and desorption Passed through group A and recovered to the xenon storage tank in a purified state. However, the xenon and residual impurity gases are frozen while passing through the low temperature heat exchanger (indirect) and adsorbed by the adsorbents of the activated carbon layer and the molecular sieve layer in the xenon adsorption and desorber A. In this way krypton can be purified to 99.995%.

At this time, the Kr / Xe mixed gas is cooled by heat exchange with an indirect contact method with a heat exchanger in a liquid nitrogen (vaporization point -196 degrees Celsius) container, and the liquid nitrogen liquid level is controlled to be maintained at around -135 degrees Celsius. The first set of operations continues until xenon is adsorbed by a sufficient amount.

<Recovery process of xenon>

When the xenon is sufficiently adsorbed on the xenon adsorption desorption unit, the krypton / xenon mixed gas supplied to the low temperature separator A (100), which is supplied to the first set, is operated by an automatic switching valve, and the second set low temperature separator (B). Separation and recovery of krypton continues with operation, with the flow switched to (101).

However, the xenon and residual impurity gas adsorbed in the xenon adsorption desorption unit A (140) is isolated from each mixed gas and purified krypton by closing the control valves (142, 143) installed at the inlet of the low temperature heat exchanger and the outlet of the xenon adsorption desorption unit. Residual krypton in the xenon adsorption desorption unit A (140) and the low temperature heat exchanger are recovered through a krypton vacuum pump 151 in a cooled state and then boosted by a separate compressor 161 and then stored in a krypton reservoir tank.

After doing so, when the nitrogen regeneration heater 170 is operated to regenerate the xenon adsorption desorber at high temperature, freeze adsorption of the adsorbent regeneration and the xenon adsorption desorption and vaporization of xenon, which is freeze-attached inside some heat exchangers, occurs simultaneously. It is recovered and stored by vacuum pump and compressor. Purified up to 99.995%

When the xenon recovery is completed in the low temperature separator A (100), the AB switching cycle operation is performed by switching to the low temperature separator B (101).

According to the method and apparatus of the present invention, krypton and xenon (xenon), which are rare gases, can be easily obtained in a continuous process, and high-purity products can be produced at low cost.

Claims (8)

The first step is to pass the krypton / xenon mixed gas through the cryogenic heat exchanger, which is kept above the freezing point of krypton and below the freezing point of xenon, so that the xenon is frozen and the krypton is in a gaseous state. A krypton / xenon comprising a second step of separating the krypton gas by passing the xenon adsorption and desorption unit which adsorbs the freeze xenon and passes the gaseous krypton, adsorbs the freeze xenon and passes the krypton gas, Separation of krypton and xenon from mixed gas The method according to claim 1, After the second step, a third step of recovering the xenon gas by heating the xenon adsorber desorber above the vaporization point of the xenon so that the xenon adsorbed to the xenon adsorbent desorber is in a gas state from the krypton / xenon mixed gas How to separate krypton and xenon The method according to claim 1 or 2, Before the first step, the krypton / xenon mixed gas and krypton / xenon mixed gas characterized in that it passes through the dioxo unit for converting oxygen into water vapor, and then through the water adsorber adsorbing water vapor How to separate xenon The method according to claim 1, In the process of recovering krypton gas, the temperature of the low temperature heat exchanger and the xenon adsorption and desorption unit is cooled to about -135 degrees Celsius, Separation of krypton and xenon from krypton / xenon mixed gas characterized in that the xenon adsorption desorption unit is heated to 15 degrees Celsius or more in the process of recovering xenon gas The method according to any one of claims 1,2 and 4, Installed in parallel with the first set and the second set combining the low temperature heat exchanger and the xenon adsorption and desorber, If either one of the first set or the second set is in use for the process for recovering krypton gas, the other set is used for the process for recovering the xenon gas, which separates krypton and xenon from the krypton / xenon mixed gas. Way A heat exchanger for introducing a krypton / xenon mixed gas and discharging the xenon contained therein into a freezing state; A xenon adsorption and desorption unit coupled to the heat exchanger to adsorb the xenon in the freezing state and pass the krypton in the gas state; Control valves to control the flow of krypton / xenon mixed gas through the heat exchanger and xenon adsorption desorption unit, and control the temperature of the heat exchanger and xenon adsorption desorption unit to discharge only krypton gas or only xenon gas Separating krypton and xenon from krypton / xenon mixed gas characterized by comprising a program controller The method according to claim 6, A dioxo unit which combines hydrogen which is separately supplied with oxygen in the krypton / xenon mixed gas and converts it into water vapor, A device for separating krypton and xenon from a krypton / xenon mixed gas characterized in that the water adsorber coupled to the gas outlet of the dioxo unit adsorbs water vapor in the mixed gas to the heat exchanger gas inlet. The method according to claim 6, A vacuum pump for vacuum replacing the gas from the xenon adsorption and desorption unit, An apparatus for separating krypton and xenon from krypton / xenon mixed gas further comprising a gas compressor coupled to the outlet of the vacuum pump to compress the gas.

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