JPH0432685B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas that removes impurity gases such as nitrogen gas, carbon monoxide gas, and methane gas contained in hydrogen gas or helium gas by cryogenic adsorption. The present invention relates to a purification device, and more particularly to a gas purification device in which adsorbent is regenerated by direct heating by a sheathed heater built into an adsorption cylinder.

In recent years, the demand for hydrogen gas, helium gas, etc. in the semiconductor industry, nuclear industry, etc. has increased, and the gases used in these fields are required to have extremely high purity.

[Prior art]

For this reason, various gas purification devices using cryogenic adsorption are used as a means of purifying hydrogen gas or helium gas containing impurity gases such as nitrogen gas, carbon monoxide gas, and methane gas to obtain high-purity gas. are used, for example, JP-A-54-42370,
Examples include JP-A-55-7565. These devices mainly consist of an adsorption cylinder, a liquid nitrogen container, a heat insulating container, a heat exchanger, and the like, and adsorption purification of gas by deep cooling and regeneration of adsorbent by heating are repeatedly performed alternately. That is, during gas purification, by flowing hydrogen gas or helium gas containing impure gas into an adsorption column cooled with liquid nitrogen, the impure gas is adsorbed by the adsorbent and highly purified purified gas is extracted. In addition, when regenerating the adsorbent, after extracting the liquid nitrogen, the regeneration gas (purified gas) is flowed into the adsorption column while heating the adsorption column from the outside with heated air, nitrogen, etc. Impure gases are desorbed and removed.

[Problem to be solved]

However, in conventional equipment that uses such heated gas during remanufacturing, the heating efficiency when heating the gas is extremely low, the heat transfer efficiency is low because the adsorption column is heated from the outside by the heated gas, and the heating gas There were various drawbacks, such as the need for blower piping to circulate the water and heat insulation. In addition, directly heating the adsorbent with an electric heater using exposed nichrome wire may cause local heating of the adsorbent, and if the adsorbent cylinder is housed in a vacuum insulated container, There are various problems such as difficulty in taking out the lead wire outside and selecting the material for it because it penetrates the vacuum layer and is exposed to extremely low temperatures, and the insulation of the heater is poor and its lifespan is short. I couldn't convert it.

[Means for solving problems]

The present inventors have aimed to improve the shortcomings of conventional devices and to obtain a gas purification device that can significantly reduce the energy losses required for cooling and heating in the gas purification and adsorbent regeneration cycles, and that is also miniaturized. Focusing on the regeneration of adsorbent by electrical heating, the present invention was achieved as a result of intensive research.

That is, the present invention provides a gas purification apparatus using a cryogenic adsorption method, which has a double structure including an outer cylindrical container and an inner cylindrical container, one or more adsorption cylinders are housed in the inner cylindrical container, and the adsorption cylinder The gas purification device is characterized in that at least one of the gas purifiers has a built-in sheathed heater.

The shape of the adsorption cylinder used in the present invention is not particularly limited, but it is preferably cylindrical. These adsorption cylinders may be used alone, or a plurality of adsorption cylinders may be connected in series through piping.

In the present invention, the adsorbent to be filled in the adsorption cylinder includes activated carbon, molecular sieve, and zeolite, but activated carbon is particularly preferred because of its good adsorption performance for impure gases.

In the present invention, the heater built into the adsorption cylinder may be a so-called sheathed heater, for example, a heating wire such as a nickel chrome wire is housed in a metal sheath, and a space inside the sheath is filled with a high-purity magnesium oxide or the like. The heater is tightly filled with inorganic insulating powder and the terminal portion is completely sealed with a silicone sealant or epoxy resin (this also includes a so-called micro-heater, hereinafter the same). With electric heaters other than such sheathed heaters, local heating of the adsorbent, vacuum discharge, poor insulation, disconnection of heating wires, etc. are likely to occur, and it is impossible to obtain a device that can withstand practical use.

In addition, the lead wires leading from the terminals of the sheathed heater to the outside of the device are fixed in the metal tube with inorganic insulating powder similar to that used in the sheathed heater.
In addition, a material having flexibility that can be bent together with the metal thin tube is used.

The number of sheathed heaters built into an adsorption cylinder varies depending on the size of the adsorption cylinder, the amount of heating required, etc., and cannot be determined unconditionally, but if the inner diameter of a cylindrical adsorption cylinder is 100 mm or less, the number is 1 to 1. 3
It's a book. In addition, when a plurality of adsorption cylinders are connected in series by piping, a sheathed heater is usually built in the adsorption cylinder located at least on the most upstream side of the regeneration gas. Of course, it is also possible to incorporate a sheathed heater in other adsorption cylinders. Further, in order to further prevent local heating of the adsorbent and increase heat transfer efficiency to the entire adsorbent, it is preferable to provide a heat sink inside the adsorption cylinder. There are no particular restrictions on the shape or number of heat sinks as long as they can efficiently transmit the heat from the sheathed heater to the adsorbent, but for example, if multiple rectangular metal plates are used, one long side of each is connected to the sheath heater. Alternatively, the heat sinks may be provided radially in contact with the heater sheath. In addition, in addition to holes for passing the sheathed heater or heater sheath through the center, multiple metal disks with an appropriate number of holes for freely passing gas are placed horizontally and placed vertically inside the adsorption cylinder. They may be provided at intervals.

In the present invention, the adsorption cylinder is isolated from the outside world by vacuum insulation, but it has a double structure with an outer cylinder container and an inner cylinder container, and the inner peripheral surface of the outer cylinder container and the outer peripheral surface of the inner cylinder container There is a space around the entire circumference between
This space has an airtight structure to maintain a vacuum state. There is no particular restriction on the shape of the outer cylindrical container and the inner cylindrical container as long as they are cylindrical, but cylindrical shapes are preferred. The space sandwiched between the inner circumferential surface of the outer cylindrical container and the outer circumferential surface of the inner cylindrical container is always kept in a vacuum state during operation of the apparatus. One or more adsorption cylinders are housed in the inner cylinder container, and during gas purification, the adsorption cylinders are cooled from the outside by liquid nitrogen (hereinafter referred to as LN ₂ ) supplied into the inner cylinder container. .
In addition, when regenerating the adsorbent, LN ₂ is extracted from the inner cylinder container, and while the regeneration gas is flowing into the adsorption cylinder,
By heating the adsorbent with a sheathed heater built into the adsorption cylinder, the adsorbed impurity gas is desorbed and removed, but during this regeneration, it is preferable to also maintain the inside of the inner cylinder container in a vacuum state.

In the present invention, it is preferable to provide a heat exchanger between the gas supplied to the adsorption column and the gas exiting from the adsorption column in order to further improve thermal efficiency during purification and regeneration. There is no particular restriction on the location where the heat exchanger is installed; for example, (1) the space above the _LN2 liquid level in the inner cylindrical container, (2) the space between the inner peripheral surface of the outer cylindrical container and the outer peripheral surface of the inner cylindrical container. and (3) the outside of the outer cylindrical container. Among these, (2) is preferred. Furthermore, in order to improve the cooling efficiency of the raw material gas in the inner cylinder container, a part of the raw material gas supply pipe to the adsorption cylinder can be made into a pre-cooling pipe such as a serpentine pipe or a pipe with cooling fins.

Next, the present invention will be explained in more detail with reference to the drawings.

Figures 1A and 2B are a vertical cross-sectional view and a cross-sectional end view of an adsorption cylinder with a built-in sheathed heater, respectively, and Figures 2A and 2B are longitudinal sectional views of an adsorption cylinder in a different manner from that in Figure 1. and a cross-sectional end view.

In FIG. 1, inside a cylindrical container body 3 having a gas inlet 1 and an outlet 2, there is a rod-shaped sheathed heater 5 connected to a lead wire 4 protected by a metal capillary tube. The sheathed heater 5 is provided concentrically with the container body 3 so as to be buried in the filling layer, and is airtightly fixed to the container body 3 at the upper end 7 of the container body 3 by welding. Around the side surface of the sheathed heater 5, a plurality of rectangular heat dissipation plates 8,..., 8 each have one long side in contact with the sheathed heater 5, and the other long side radially toward the inner peripheral surface of the container body. The remaining space is filled with adsorbent 6 to form an adsorption column.

In Fig. 2, instead of providing the sheathed heater 5 directly inside the cylindrical container body 3 having the gas inlet 1 and outlet 2, the sheathed heater 5 is removably housed and a cylindrical heater with one end closed is used. A sheath 10 is provided concentrically with the container body 3,
The heater sheath 10 is airtightly fixed to the container body 3 at the upper end 7 of the container body 3 by welding, and heat dissipation plates 8, . . . , 8 are arranged radially around the side surfaces of the heater sheath 10. This is an adsorption cylinder similar to the one shown.

FIG. 3 is a longitudinal cross-sectional view showing the principle of the gas purification apparatus of the present invention using a single adsorption cylinder,
FIG. 4 is a longitudinal cross-sectional view showing the principle of the gas purification apparatus of the present invention in which a plurality of adsorption cylinders are used, and FIG. FIG.

In FIG. 3, an adsorption tube 9 similar to that shown in FIG. 1 or 2 is housed inside the inner tube container 11, the inner tube container 11 is housed in the outer tube container 12, and the inner tube container 11 is housed inside the inner tube container 11. A cylindrical heat exchanger 13 is located in the space sandwiched between the outer peripheral surface of the container 11 and the inner peripheral surface of the outer cylindrical container 12.
is provided. The raw material gas supply pipe 14 and the purified gas extraction pipe 15 each penetrate the wall of the outer cylinder container 12 from the outside of the apparatus, pass through the heat exchanger 13, and further penetrate the wall of the inner cylinder container 11 to reach the entrance of the adsorption cylinder 9. 1
and outlet 2. Also LN ₂
The supply pipe 16 and the LN ₂ extraction pipe 17 each penetrate the wall of the outer cylindrical container 12 and are connected to the inner cylindrical container 11. All of these pipes are airtightly fixed at the penetrating portions by welding and pipe joints. Note that the raw material gas supply pipe 14 is connected to the inner cylinder container 1.
1, a part of which is made into a flexible pipe 18.
The lead wire 4 protected by a metal thin tube is connected to the inner cylinder container 11
and the outer cylindrical container 12, and are guided to the outside through the respective walls of the outer cylindrical container 12, and the joint 1
9 and 20 in an airtight manner. When refining gas, the _LN2 supply pipe 16 is connected to the inner cylinder container 11.
LN ₂ is supplied into the interior of the adsorption cylinder 9, and the adsorption cylinder 9 is immersed in this LN ₂ and cooled from the outside. The raw material gas is passed through the raw material gas supply pipe 14 to the heat exchanger 13 and the flexible pipe 18.
The purified gas is sequentially cooled and supplied to the interior of the adsorption column 9, where impurity gas is adsorbed and removed, and exits as purified gas from the purified gas extraction pipe 15 via the heat exchanger 13. When regenerating the adsorbent, LN ₂ is extracted from the inner cylinder container 11 by the LN ₂ extraction pipe 17, and the inside of the inner cylinder container 11 is evacuated by a vacuum pump (not shown), and the sheathed heater 5 The impurity gas adsorbed is desorbed and removed by passing the regeneration gas (purified gas) in the opposite path to that used during purification while heating the adsorbent by applying electricity to the adsorbent.

In Fig. 4, four adsorption cylinders 9 with built-in sheathed heaters 5 and three adsorption cylinders 9' without built-in sheathed heaters 5 are alternately connected in series through connecting pipes 21, . . . , 21. A gas purification apparatus having a structure similar to that shown in FIG. 3 was used except that.

During gas purification, LN ₂ is supplied from the LN ₂ supply pipe 16 into the inner cylinder container 11, and the adsorption cylinders 9, 9',
..., 9', 9 are each immersed in this LN ₂ and cooled from the outside. The raw material gas is supplied through the raw material gas supply pipe 14
The purified gas is cooled through the heat exchanger 13 and the corrugated pipe 18, and is passed through the adsorption cylinders 9, 9', ..., 9, 9 in the order of connection, so that impurity gas is adsorbed and removed. The purified gas is discharged to the outside from the purified gas extraction pipe 15 via the heat exchanger 13. When regenerating the adsorbent, LN ₂ is extracted from the inner cylinder container 11 through the LN ₂ extraction pipe 17,
Additionally, a vacuum pump (not shown)
The inside of the inner cylindrical container 11 is evacuated and the sheathed heaters 5,..., 5 are energized to flow the regeneration gas (purified gas) in the opposite path to that used during purification, thereby desorbing and removing the adsorbed impurity gas. .

In FIG. 5, a cylindrical outer container 12 and a cylindrical inner container 11 are provided concentrically with each other, and adsorption cylinders 9, 9', . . . , 9', 9 are accommodated therein. The adsorption cylinders 9, 9', ..., 9', 9 are connected in series by connecting pipes 21, ..., 21, respectively, and the gap between the outer peripheral surface of the inner cylinder container 11 and the inner peripheral surface of the outer cylinder container 12 is A cylindrical heat exchanger 13 is disposed in the space, and the gas purification device has a substantially cylindrical appearance.

〔Effect of the invention〕

The gas purification device of the present invention has the following superior features compared to conventional devices.

1. When regenerating the adsorbent, heating efficiency is extremely high, unlike indirect heating using heated gas.

2. When regenerating the adsorbent, the inside of the inner cylindrical container can also be evacuated, reducing thermal energy loss due to gas conduction.

3. There is no need for a heating furnace, blower, piping, or insulation for heating gas externally,
Therefore, the device can be made smaller, and the heat resistance specifications for sealing materials, valves, etc. can be relaxed, and equipment costs can be reduced.

Example device: In a device similar to that shown in Figs. 4 and 5, there were seven adsorption cylinders, the material of each container body was SUS304, the dimensions were 89.1 mmφ x 1000 mmH x 2 mmt, and a sheathed heater was built in. Each of the four cylinders used had a structure similar to that shown in FIG. In other words, the heater sheath for each of the four cylinders is made of SUS304, and the dimensions are 19mmφ x 1000mmH.
×1.2mmt, 200V, 500W as a sheathed heater,
Dimensions: 16mmφ x 1050mm, heat generating part length: 800mm, heat sink made of SUS304, dimensions: 30mm x 200mm x 1
16 mmt plates were used. Further, each of the seven adsorption cylinders was filled with five pieces of coconut shell activated carbon. The inner cylindrical container has dimensions of 318.5mmφ x 1400mmH x 4mmt, and the outer cylindrical container has dimensions of 600mmφ x 1600mmH x 4mmt.
A lead wire protected by a thin metal tube was passed through the walls of the inner and outer containers and connected to the slider, and each penetrating portion was fixed with a Swagelok joint (manufactured by Swagelok, USA).

This equipment was used to purify gas and regenerate adsorbent.

Purification of gas: The space between the outer circumferential surface of the inner cylinder container and the inner circumferential surface of the outer cylinder container is kept in a vacuum state (0.1 Torr), and
While LN ₂ was supplied and the adsorption cylinder was cooled to -196°C, raw hydrogen gas containing 330 ppm nitrogen gas, 70 ppm carbon monoxide gas, and 70 ppm methane gas was supplied from the raw gas supply pipe at a flow rate of 20 Nm ³ /hr to perform purification. It continued for 10 days. The purified hydrogen gas obtained during this period was analyzed by TCD and FID type gas chromatography, and as a result, no nitrogen gas, carbon monoxide gas, or methane gas was detected. The detection limits for these impurity gases are nitrogen gas 1ppm, carbon monoxide 0.1ppm,
Methane gas is 0.05ppm.

Regeneration of adsorbent: Next, the supply of raw hydrogen gas was stopped and the adsorbent was regenerated. After extracting the LN ₂ from the inner cylinder container, dry nitrogen gas at room temperature was flowed into the inner cylinder container to raise the temperature.
When the temperature inside the inner tube rose to -50°C, the nitrogen gas was stopped, and the inside of the inner tube was made into a vacuum of 0.1 Torr. Operate the slider to start applying a current of 0.5A to each sheathed heater in each adsorption tube, and gradually increase the current value to 2.0A. At the same time, purified hydrogen gas is extracted at normal pressure as gas for regenerating the adsorbent. From the tube, add 1N for the first 1 hr in the reverse direction of purification.
^m3 flowed. The temperature inside the adsorption cylinder containing the sheath heater was further increased, and when it reached 10°C, purified hydrogen gas was flowed at a flow rate of 3 Nm ³ /hr for 2 hours.
After that, the temperature inside the adsorption cylinder continues to rise.
The temperature reached 180℃. Here, turn on the current of the sheathed heater.
Although the temperature was lowered to 1.8A, the temperature inside the adsorption cylinder was 210℃ after 0.5hr.
reached and became almost constant. At this time, the temperature inside the adsorption cylinder without a built-in sheathed heater is 190.
It was warm at ℃. In this state, the flow rate of the regeneration gas is set to 1N.
m ³ /hr and continued regeneration for 3.5hr. During this time, the temperature inside the adsorption cylinder without a built-in sheath heater will be
It showed a nearly constant value at 205℃.

At this point, regeneration was terminated, the electric current was cut off, the vacuum inside the inner container was broken, and nitrogen gas at room temperature was flowed for cooling, and the temperature inside the adsorption column dropped to 120°C after 2 hours. The total electricity consumption during this period was 7KWH, and the consumption of purified hydrogen gas was ^12Nm3 . As a result of subsequent purification of hydrogen gas, the same results as above were obtained.

Comparative Example After hydrogen gas was adsorbed and purified in the same manner as in the example, the adsorbent was regenerated by changing the conditions as follows.

In other words, instead of having a sheathed heater built into the adsorption cylinder, an electric furnace and a blower are installed outside the outer cylinder, and nitrogen gas is heated in the electric furnace heated to 420°C and circulated between the inner cylinder and the adsorption cylinder. The cylinder was heated. In addition, purified hydrogen gas was heated in a separate heating furnace heated to 500°C as a regeneration gas and flowed into the adsorption cylinder.

[Regeneration of adsorbent]

First, after extracting the LN ₂ in the inner cylinder container, dry nitrogen gas at room temperature is flowed into the inner cylinder container until the inner cylinder is 0.
When the temperature was raised to 100°C, it was connected to the heated nitrogen gas circulation system described above, and the temperature inside the adsorption column was raised to 100°C in 1 hour. Purified hydrogen gas heated in an electric furnace adjusted to 500℃ while continuing to circulate nitrogen gas was flowed into the adsorption column at a flow rate of 1.5Nm ³ /hr through the same route as in the example, and the temperature reached 200℃ in 4 hours. Reached. The temperature control of the electric furnace for nitrogen gas heating was lowered to 400°C and continued for an additional 3.5 hours.

The power consumption required for regenerating the adsorbent was 38 KWH, excluding the driving power of the circulation blower, and the consumption of purified hydrogen gas was 12 Nm ³ . Subsequently, the hydrogen gas was purified, and the same results as in the example were obtained.

[Brief explanation of drawings]

Figures 1A and 2B are a vertical cross-sectional view and a cross-sectional end view, respectively, of an adsorption cylinder with a built-in sheathed heater, and Figures 2A and 2B are longitudinal cross-sections of an adsorption cylinder in a different form from that in Figure 1. FIG. 3 is a vertical sectional view showing the principle of the gas purification apparatus of the present invention using a single adsorption cylinder, and FIG. FIG. 5 is a longitudinal sectional view showing the principle of the gas purification apparatus of the present invention, and FIG. 5 is a cross-sectional end view of the cylindrical gas purification apparatus in FIG. 4. In the figure, 1...inlet, 2...exit, 3...
Container body, 4...Lead wire protected by metal thin tube, 5...Sheathed heater, 6...Adsorbent, 7...
...Top end, 8...Radiation plate, 9 and 9'...Adsorption cylinder,
10... Heater sheath, 11... Inner cylinder container, 12...
... Outer cylinder container, 13 ... Heat exchanger, 14 ... Raw material gas supply pipe, 15 ... Purified gas extraction pipe, 16 ...
LN ₂ supply pipe, 17... LN ₂ extraction pipe, 18... serpentine pipe, 19 and 20 joints, and 21... connection piping.

Claims (1)

[Claims] 1. In a gas purification device using the cryogenic adsorption method, it has a double structure with an outer cylindrical container and an inner cylindrical container,
A gas purification device characterized in that one or more adsorption cylinders are housed in the inner cylinder container, and at least one of the adsorption cylinders has a sheathed heater built therein.