JPH04338207A - Separation of gaseous impurities from gaseous mixture - Google Patents

Abstract

PURPOSE:To increase the recovery rate of hydrogen and to make the manufacture and installation of equipment easy by specifying proper conditions of operation and design when separating gaseous impurities from a gaseous mixture using plural adsorption tanks and a holding tank. CONSTITUTION:When separating gaseous impurities from gaseous hydrogen by the pressure swing adsorption method using at least three adsorption tanks A, B, C,... having an adsorption bed and a holding tank R of filling order maintained type, let the content of object main impurities in gas to be treated by >=1.5atm in molar partial pressure. Further, let operating pressure in adsorption operation be >=4 times as much as the minimum one in purging and be >=6 times as much as the minimum one in desorption and removing of the components adsorbed on the adsorption bed. And activated carbon, molecular sieve, or molecular sieve carbon is used as an adsorbent for the adsorption bed. Thereby specific components can be effectively removed from a gaseous mixture without wasted effort and because of light weight, the manufacture and installation of equipment are made easy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas separation method for selectively separating specific components from a gas mixture using an adsorbent.

0002

[Prior Art] As a method for selectively separating specific components, particularly impurities, from a gas mixture, impurities are adsorbed onto an adsorbent packed in an adsorption tower, and when the adsorption capacity of the adsorbent reaches its limit, the adsorption layer is removed. Conventionally, a method has generally been used in which impurities are desorbed from the adsorbent and the adsorbent is regenerated by reducing the pressure and purging with a gas that does not contain many impurities.

Among them, as a gas separation method that can minimize the loss of clean gas after separation, the Japanese Patent Publication No. 62-4
7051, the following method is proposed.

The method involves selectively and adiabatically adsorbing impurities onto an adsorbent, followed by pressure relief and decoupling of the adsorbent at low pressures using a gas ranging from a less contaminated gas to a substantially pure gas. A process in which gaseous impurities are separated from a gas mixture by desorption of impurities by purging, regeneration of the adsorbent, repressurization, and the periodic use of alternating and cyclical use of a number of zones containing the adsorbent. , each cycle consisting of a number of stages starting from a first adsorption zone exhausted by adsorbing impurities, which absorb the gas phase present in the void space of said first adsorption zone. expanding through its outlet while its inlet is closed and transferring this expanded gas to the outlet of the regenerated adsorption zone within both said regenerated zone and said first zone. introducing the gas present in the void space of the first adsorption zone until pressure equalization is achieved; further expanding the gas present in the void space of the first adsorption zone through the outlet; and introducing the further expanded gas into a high void fraction. and introducing a second further expanded gas from a second fatigued adsorption zone into the opposite side of the packed column from a second fatigued adsorption zone. the first further expanded gas is removed from the void, and after finally depressurizing the first adsorption zone via its input to bring it to a minimum pressure, some of the removed gas is removed from the void. part or all of the removed gas is introduced into the first adsorption zone to purge the first adsorption zone, and any remaining portion of the removed gas is transferred into a second regenerated zone. introducing the expanded gas through its inlet to partially pressurize it and transferring the expanded gas from the third fatigued adsorption zone to the outlet of said first (here regenerated) adsorption zone. The inlet of the first adsorption zone
and a third adsorption zone, wherein said first adsorption zone is closed until pressure equalization in both said adsorption zones is achieved; at the outlet of the first adsorption zone while keeping the inlet of the zone closed until the pressure in the first adsorption zone is equal to the pressure of the gas stream homogeneous to the product; introducing the gas mixture through an inlet of said first adsorption zone and withdrawing said gas mixture through an outlet of said first adsorption zone.

[0005]

[Problems to be Solved by the Invention] Although the above method has the general feature of suppressing the loss of produced gas, the excellence of this method varies greatly depending on the selection of operating conditions and design conditions. It has not yet been fully clarified whether a separation effect significantly improved compared to the conventional method can be obtained by selecting such conditions.

Conditions that affect the results include: 1. Gas composition of the gas to be treated (molar partial pressure of impurities to be removed),
2. 3. adsorption equilibrium physical properties of the impurity gas to be removed of the adsorbent filled in the adsorption tank; Ratio between adsorption pressure and purge gas recovery adsorption tower co-current vacuum final pressure (degree of regeneration of adsorption tower); 4. Product purity of generated gas (leakage degree of impurities), 5. temperature of the gas to be treated, and 6. Amount of purge gas used7. There are adsorption and desorption speeds of target impurities to be removed, and the separation effect differs depending on how these conditions are selected.

[0007] An object of the present invention is to provide a more excellent gas separation method by setting operating conditions and design conditions when carrying out the above proposed method.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method for separating gaseous impurities from a gas mixture using an adsorption tank having an adsorption bed and a receiving and receiving order maintenance type holding tank, the method comprising at least three adsorption tanks. Steps a to i below: a) The gas to be treated flows into the first adsorption tank from its inlet, the produced gas is taken out from its outlet, and the first adsorption tank loses its adsorption capacity and the purity of the produced gas reaches the target value. b) the outlet of at least one other adsorption vessel in which the adsorption bed has been regenerated;
After connecting the outlet of the adsorption tank and equalizing the pressure of both adsorption tanks for the at least one other adsorption tank,
c) The exit of the first adsorption tank that has passed through process b and one end of the holding tank that maintains the receiving and receiving order (in the holding tank, processes a and b are connected to the first adsorption tank and In the same way, the gas in the first adsorption tank is flowed into the holding tank by connecting the outlet of another adsorption tank passed through the same process with the other end of the holding tank (in which the received gas is contained). let me,
During this period, the other end of the holding tank is connected to the outlet of a second adsorption tank which has undergone steps a, b, c and step e described below in the same manner as the first adsorption tank, thereby allowing the adsorbed components to break through. A process of purging the second adsorption tank with the gas in the holding tank that is pushed out by the inflowing gas (a part of the generated gas may be added to this gas if necessary) until it starts to occur in the gas,
d) If necessary, close the purge valve of the second adsorption tank and
After equalizing the pressure between the adsorption tank and the first adsorption tank, the communication is released; e) closing the outlet of the first adsorption tank; step c)
or a process of desorbing and removing the components adsorbed on the adsorption bed of the first adsorption tank by reducing the pressure of the first adsorption tank that has undergone step d to the lowest pressure from the purge valve on the inlet side; f)
By communicating the outlet of the third adsorption tank, which has undergone steps a and b in the same way as the first adsorption tank, and one end of the holding tank, the gas in the third adsorption tank is separated from the adsorbed components. The gas pushed out by the inflow gas (this gas g) purge the first adsorption tank by closing the purge valve of the first adsorption tank if necessary; 3
The process of releasing this contact after equalizing the pressure with the adsorption tank,
h) the outlet of at least one other adsorption vessel which has undergone process a or processes a and b in the same way as the first adsorption vessel and process f;
Alternatively, the outlet of the first adsorption tank via g is connected with the inlet of both tanks closed, and the gas from the at least one other adsorption tank is allowed to flow in (this gas may contain generated gas if necessary). After performing pressure equalization operation on both adsorption tanks at least once (some may be additionally allowed to flow in), the process of canceling this communication,
i) A gas of the same quality as the produced gas is allowed to flow into the first adsorption tank that has undergone process h through its outlet with its inlet closed, so that the pressure in the first adsorption tank and the gas of the same quality as the produced gas are j) A method in which adsorption and desorption are repeated alternately and periodically by equalizing the pressure of the flow and then releasing the communication, j) the gas to be treated is a mixture of hydrogen and at least one of the impurity gases to be removed. (k) the operating pressure during the adsorption operation in step a is at least 6 times the lowest pressure in step e; , at least four times the lowest pressure in step c, and l) the main adsorbent of the adsorption bed is at least one of activated carbon, molecular sieve, molecular sieve carbon. This is a method to separate the

By adopting the above-mentioned conditions, the gas separation method of the present invention can be applied to the method described in Japanese Patent Publication No. 47051/1983, or its related technology, in which the system is equipped with a holding tank of the type that maintains the order of receipt and payment. (A method in which part or all of the recovered gas obtained by inverting the cocurrent depressurized gas is used as the purge gas) can be greatly advantageous. In other words, the ratio between the maximum and minimum concentrations of impurities to be removed in the co-current depressurized gas from the adsorption tank used as purge gas becomes large (5 or more is possible), and the hydrogen recovery rate as produced gas is greatly improved. be able to. Also,
When the impurity concentration in the gas to be treated increases, the hydrogen recovery rate decreases only slightly in the method of the present invention compared to the degree of decrease in the hydrogen recovery rate when conventional methods are employed. Furthermore, surprisingly, it is possible to achieve an even higher hydrogen recovery rate by circulating and feeding a portion of the purge gas discharged from the adsorption tower into the gas to be treated at the entrance of the adsorption tower. When such circulating feed is performed in the conventional method, the hydrogen recovery rate is greatly reduced and it is not economical.

By the method of the present invention, for example, when a refinery plant off-gas having a methane gas content of 5% or more is treated, it is possible to achieve a particularly high hydrogen recovery rate compared to conventional methods.

The method of the invention is also suitable for the recovery of hydrogen from ethylene plant off-gas and steam reforming gas.

[0012] The receiving and receiving order maintaining type holding tank used in the present invention stores a gas mixture having a gas concentration distribution with respect to the flow path.
It allows for inflow, storage, and outflow while maintaining its distribution. To briefly explain its function, when the gas in the first adsorption tank is caused to flow into the holding tank in step c, the gas adsorbed by the adsorption bed in the first adsorption tank (hereinafter referred to as the first adsorption bed) is Impurities (hereinafter specific components will be explained as impurities, but are not limited to this) are desorbed, so the impurity concentration is relatively low in the initial stage, and relatively high in the latter stage, and the concentration of impurities flows into the holding tank. The gas that flows has an impurity concentration gradient (the part that flows in earlier has a lower impurity concentration). In step f, the first adsorption tank is purged by flowing the gas having this concentration gradient in the opposite direction to that at the time of inflow. This purge further removes impurities from the first adsorption bed, but the impurity concentration of the inflowing gas has a gradient that is high at first and gradually decreases, and when the first adsorption bed is heavily contaminated, As the first adsorption bed becomes clean with dirty gas, it is purged with clean gas, allowing for efficient purging.

[0013] The holding tank is at least one of the filled tanks filled with an inert non-porous filler having a high void ratio as disclosed in Japanese Patent Publication No. 62-47051, and is a series space partitioned by partition walls. at least one row of unfilled vessels, such as groups, spaces, or compartmentalized serial chambers, or a combination thereof, i.e.
A part of the holding tank may be filled with a filler, and the objective effects of the present invention can be achieved using any holding tank.

[0014] The gas to be treated which is the object of the method of the present invention is:
It is a mixture of hydrogen and at least one of impurity gases to be removed, and the impurities to be removed include methane, gaseous hydrocarbons other than methane, carbon dioxide, and carbon monoxide. When there is only one type of impurity to be removed, it is necessary that the content of that impurity in the gas to be treated is 1.5 ATM or more in terms of molar partial pressure. Further, when two or more types of impurities to be removed are included, the content of the main impurity to be removed in the gas to be removed needs to be 1.5 ATM or more in terms of molar partial pressure. In this case, the main impurity to be removed may be any of methane, C2 to C4 hydrocarbons, carbon dioxide, and carbon monoxide. The content of impurities to be removed in the gas to be treated is 1.5 AT in terms of molar partial pressure.
If it is less than M, a sufficient hydrogen recovery rate cannot be achieved, which is not preferable.

In addition, it is necessary that the operating pressure during the adsorption operation in step a be at least 6 times the lowest pressure in step e and at least 4 times the lowest pressure in step c; If the operating pressure is less than 6 times the minimum pressure in step e, the degree of regeneration after purging the adsorption tower will be insufficient, and if it is less than 4 times the minimum pressure in step c, the The concentration gradient of the target impurity to be removed becomes small, and the effect of improving the hydrogen recovery rate by reversing the purge gas almost disappears. Preferably, the operating pressure during the adsorption operation in step a is 10 to 5
0 kg-gauge, and the lowest pressure in process c is 1
．． 5 to 6.5 kg-gauge. The main adsorbent of the adsorption bed must be at least one of activated carbon, molecular sieve, and molecular sieve carbon, and activated carbon and molecular sieve carbon are particularly preferred. Adsorbents other than those mentioned above, such as silica gel, may be used in combination, but if the main adsorbent is other than those mentioned above, a sufficient hydrogen recovery rate cannot be achieved.

[0016] It is desirable that the concentration of the main impurity to be removed in the generated gas is 300 ppm or more. in this case,
The effects of the present invention can be exhibited to a greater extent.

When the partial pressure of the impurity to be removed in the gas to be treated is small, on the other hand, the effect is exhibited in a region where the product purity is high.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

Example 1 Gas separation was carried out using the gas separation apparatus shown in the flow sheet of FIG. 1 by the operation shown in FIG.

FIG. 1 is a flow sheet for explaining the case where the method of the present invention is carried out using four adsorption tanks and one holding tank. The main components included in the diagram are as follows.

[0021] A to D: Adsorption tank, R: Holding tank, A1, B1, C1, D1: Treated gas inlet valve, A2, B
2, C2, D2: Off gas purge valve, A3, B3, C3
, D3: Communication valve with holding tank, A4, B4, C4, D4:
Boosting valve, A5, B5, C5, D5: Produced gas outlet valve, R1, R2
: Holding tank inlet/outlet valve, P1: Produced gas valve for pressurization.

FIG. 2 is a time pressure diagram.

Focusing on adsorption tank B, each step will be explained using this as the first adsorption tank.

Steps 1 to 4 (process a): Introducing the gas to be treated into the first adsorption tank B through the valve B1 under high pressure,
The impurities are adsorbed and the generated gas is taken out from valve B5. Valves B1 and B5 are closed to end adsorption before the adsorption tank loses its adsorption capacity and the purity of the produced gas falls below the target value.

Step 5 (process b): The pressure in adsorption tank B is reduced through valve B4, and the gas is used to increase the pressure in another adsorption tank D.

Step 6: The pressure in the adsorption tank B is further reduced through the valve B3, and the gas is vented into the holding tank R through the valve R2. Continue until impurities begin to break through into the vacuum gas.

Step 7 (process c above): The gas stored in the holding tank R is pushed out by the reduced pressure gas of the adsorption tank B, and is then transferred to the second adsorption tank A via the valve R1 and the valve A3.
to purge impurities.

Step 8 (process d): The purge valve A2 of the second adsorption tank A is closed, and the pressures in the adsorption tanks B and A are re-equalized using the excess purge gas from the adsorption tank B.

Step 9 (process e): Close valve B3 and open valve B2 to reduce the pressure in adsorption tank B to the lowest pressure to remove impurities.

Step 10 (process f): The gas stored in the holding tank R is pushed out by the reduced pressure gas of the third adsorption tank C, and is introduced into the adsorption tank B via valve R2 and valve B3 to remove impurities. purge.

Step 11 (process g): The purge valve B2 of the adsorption tank B is closed, and the pressures in the adsorption tanks C and B are re-equalized using the excess purge gas from the third adsorption tank C.

Step 12 (process h): Fourth adsorption tank D
A portion of the decompressed gas and produced gas is received into adsorption tank B via valve B4 and pressurized.

Steps 13 to 15 (process i): A part of the generated gas is received into the adsorption tank B via the valves P1 and B4, and the pressure is increased to the adsorption pressure.

The composition of the gas to be treated (dry basis vol%) is as follows.

[0035] H2: 78.9, CH4: 15.5, C2
H6:3.9, C3H8:1.2, n-C4H10:0
．． 3, n- and i-C5H12:0.1, H2O:0
．． 1 The gas to be treated is 29 kg/cm2 (absolute) and 15
1500 Nm3/hour at a flow rate of 1500 Nm3/hour, and a product gas consisting of hydrogen with a purity of 99.9 vol% or more was obtained at a flow rate of 1019 Nm3/hour. That is, about 86% of the hydrogen in the gas to be treated was recovered as produced gas. The cycle time was 30 minutes and off-gas was released at 1.3 kg/cm2 (absolute). Table 1 shows the adsorption pressure in step a and the lowest pressure in steps c and e in this operation.

[0036]

[Table 1] Each of the four adsorption tanks has a diameter of 0.7 m and a height of 5.0 m.
0 m, activated carbon with an average particle size of 2.5 mm is in the upper 3/4 part, and an average particle size of 1 to 2 mm in the lower 1/4 part.
It was filled with silica gel. The holding tank was a packed tower with a diameter of 1 m and a height of 4 m filled with Raschig rings.

Comparative Example 1 Gas separation was carried out by the operation shown in FIG. 4 using the gas separation apparatus shown in the flow sheet of FIG. The difference from Example 1 is that the separation operation was performed without providing a holding tank.

The composition of the gas to be treated (dry basis vol%) is as follows.

[0039] H2: 79.2, CH4: 15.3, C2
H6:3.8, C3H8:1.2, n-C4H10:0
．． 3, n- and i-C5H12:0.1, H2O:0
．． 1 The gas to be treated is 29 kg/cm2 (absolute) and 15
It was introduced into the separator at a flow rate of 1500 Nm3/hour at a temperature of 1,500 Nm3/hour, and a product gas consisting of hydrogen with a purity of 99.9 vol% or more was obtained at a flow rate of 974 Nm3/hour. That is, about 82% of the hydrogen in the gas to be treated was recovered as produced gas. The cycle time was 31 minutes and the off gas was 1.
Released at 3 kg/cm2 (absolute).

Each of the four adsorption tanks has a diameter of 0.7 m and a height of 5.0 m, and the upper 3/4 part has an average particle size of 2.
．． 5 mm of activated carbon was filled in the lower 1/4 part with silica gel having an average particle size of 1 to 2 mm.

Example 2 Gas separation was carried out by the operation shown in FIG. 5 using the gas separation apparatus shown in the flow sheet of FIG. 1 except that it consisted of six adsorption tanks. To explain FIG. 5, that is, in comparison with the four-column type FIG. 1, two columns are in adsorption operation in the adsorption process. In addition, the pressure equalization operation with other adsorption towers has increased from once to twice.

The composition of the gas to be treated (dry basis vol%) is as follows.

[0043] H2: 72.3, CH4: 22.8, C2
H6:3.3, C3H8:1.1, n-C4H10:0
．． 3, n- and i-C5H12:0.1, H2O:0
．． 1 The gas to be treated is 29 kg/cm2 (absolute) and 20
C. and a flow rate of 4650 Nm3/hour was introduced into the separator, and a product gas consisting of hydrogen with a purity of 99.9 vol% or more was obtained at a flow rate of 2925 Nm3/hour. That is, about 87% of the hydrogen in the gas to be treated was recovered as produced gas. The cycle time from step 1 to step 13 is 16 minutes. Off gas is 1.4kg/cm2 (absolute)
It was released in

Each of the six adsorption tanks has a diameter of 0.9 m and a height of 5 m, and the upper 3/4th part has an average particle size of 2.5 m.
mm activated carbon, the lower 1/4 part has an average particle size of 1~
It was filled with 2 mm of silica gel. The holding tank is filled with Raschig rings and has a diameter of 0.8 m and a height of 10 m.
It was a packed tower.

Comparative Example 2 Gas separation was carried out by the operation shown in FIG. 6 using the gas separation apparatus shown in the flow sheet of FIG. 3 except that it consisted of six adsorption tanks. To explain FIG. 6, that is, in comparison with the four-column type FIG. 4, two columns are in adsorption operation in the adsorption process. In addition, the pressure equalization operation with other adsorption towers has increased from once to twice.

The composition of the gas to be treated (vol% on a dry basis) is as follows.

[0047] H2: 71.9, CH4: 23.1, C2
H6:3.4, C3H8:1.1, n-C4H10:0
．． 3, n- and i-C5H12:0.1, H2O:0
．． 1 The gas to be treated is 29 kg/cm2 (absolute) and 20
℃ and a flow rate of 4650 Nm3/hour was introduced into the separator, and a product gas consisting of hydrogen with a purity of 99.9 vol% or more was obtained at a flow rate of 2725 Nm3/hour. That is, about 81.5% of the hydrogen in the gas to be treated was recovered as produced gas. The cycle time from step 1 to step 13 is 16 minutes. Off-gas was released at 1.4 kg/cm2 (absolute).

Each of the 6 adsorption tanks has a diameter of 0.9 m and a height of 5 m, and the upper 3/4 part has an average particle size of 2.5 m.
mm activated carbon, the lower 1/4 part has an average particle size of 1~
It was filled with 2 mm of silica gel.

Example 3 Gas separation was carried out by the operation shown in FIG. 5 using the gas separation apparatus shown in the flow sheet of FIG. 1 except that it consisted of six adsorption tanks.

The composition of the gas to be treated (dry basis vol%) is as follows.

[0051] H2:89.2, CH4:4.7, C2H
6:4.3, C3H8:1.3, n-C4H10:0.
3, n- and i-C5H12:0.1, H2O:0.
1 The gas to be treated is 29 kg/cm2 (absolute) and 30°C
was introduced into the separator at a flow rate of 4650 Nm3/hour, and a product gas consisting of hydrogen with a purity of 99.9 vol% or more was obtained at a flow rate of 3095 Nm3/hour. That is, about 91% of the hydrogen in the gas to be treated was recovered as produced gas. Cycle time from step 1 to step 13 is 24 minutes. Off-gas was released at 1.4 kg/cm2 (absolute).

Each of the six adsorption tanks has a diameter of 0.9 m and a height of 5 m, and the upper 3/4 of the adsorption tank has an average particle size of 2.5 m.
mm activated carbon, the lower 1/4 part has an average particle size of 1~
It was filled with 2 mm of silica gel. The holding tank is filled with Raschig rings and has a diameter of 0.8 m and a height of 10 m.
It was a packed tower.

Comparative Example 3 Gas separation was carried out by the operation shown in FIG. 6 using the gas separation apparatus shown in the flow sheet of FIG. 3 except that it consisted of six adsorption tanks.

The composition of the gas to be treated (dry basis vol%) is as follows.

[0055] H2: 89.0, CH4: 4.8, C2H
6:4.3, C3H8:1.4, n-C4H10:0.
3, n- and i-C5H12:0.1, H2O:0.
1 The gas to be treated is 29 kg/cm2 (absolute) and 30°C
was introduced into the separation device at a flow rate of 4650 Nm3/hour, and a product gas consisting of hydrogen with a purity of 99.9 vol% or more was obtained at a flow rate of 3683 Nm3/hour. That is, about 89% of the hydrogen in the gas to be treated was recovered as produced gas. Cycle time from step 1 to step 13 is 25 minutes. Off-gas was released at 1.4 kg/cm2 (absolute).

Each of the six adsorption tanks has a diameter of 0.9 m and a height of 5 m, and the upper 3/4 of the adsorption tank has an average particle size of 2.5 m.
mm activated carbon, the lower 1/4 part has an average particle size of 1~
It was filled with 2 mm of silica gel.

Example 4 Using the gas separation apparatus shown in the flow sheet of FIG. 1, gas separation was carried out by the operation shown in FIG.

Composition of reducing gas to be treated (dry basis vol%)
is as follows.

[0059] H2: 48.7, N2: 3.2, CO: 1
9.7, CO2: 27.6, H2O: 0.1 The gas to be treated is 7 kg/cm2 (absolute) and 165 at 15°C.
Introduced into the separator with a flow rate of 0 Nm3/h, H2:6
A product gas consisting of 0, N2:6, and CO:29 (each vol%) was obtained at a flow rate of 1050 Nm3/hour. Cycle time is 26 minutes. Off-gas was released at 1.3 kg/cm2 (absolute).

Each of the four adsorption tanks has a diameter of 1.4 m and a height of 5 m, and the upper 3/4 of the adsorption tank has an average particle size of 2.5 m.
mm activated carbon, the lower 1/4 part has an average particle size of 1~
It was filled with 2 mm of silica gel. The holding tank was a packed tower with a diameter of 1 m and a height of 7 m filled with Raschig rings.

Example 5 The gas separation device shown in the flow sheet of FIG. 1 was used except that it consisted of six adsorption tanks, and a part of the purge gas discharged from the adsorption tank was transferred to the adsorption tank by the operation shown in FIG. Gas separation was performed by feeding the inlet gas to be processed after compression.

The composition of the gas to be treated (dry basis vol%) is as follows.

[0063] H2: 79.2, CH4: 14.5, C2
H6:4.6, C3H8:1.2, n-C4H10:0
．． 3, n- and i-C5H12:0.1, H2O:0
．． 1 The gas to be treated is 29 kg/cm2 (absolute) and 15
Make-up feed gas amount 4650Nm3 at °C
/hour, 120 of the purge gas discharged from the adsorption tank
4Nm3/hour was circulated into the separator, 99.9v
The generated gas consisting of hydrogen with a purity of ol% or more is 3296N
A flow rate of m3/h was obtained. That is, as a result, about 92.5% of the hydrogen in the gas to be treated was recovered as produced gas. Cycle time is minutes. Off gas is 1.5kg/cm2
(absolute) emitted.

Each of the six adsorption tanks has a diameter of 0.96 m.
The height is 5m, and the upper 3/4 part has an average grain size of 2.5m.
5mm activated carbon, the lower 1/4 part has an average particle size of 1
It was filled with ~2 mm of silica gel. The holding tank is filled with Raschig rings and has a diameter of 1 m and a height of 5.5 m.
It was a packed tower.

[0065]

[Effects of the Invention] According to the present invention, separation of a specific component from a gas mixture by adsorption can be carried out efficiently and without waste, and the equipment for this purpose is easy to manufacture and install because it is lightweight, and inspection and maintenance are also easy. Therefore, separation operations can be performed at lower cost than in the past. Furthermore, by circulating and feeding a portion of the purge gas, it is possible to further increase the recovery rate.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of an apparatus for carrying out the method of the invention.

FIG. 2 shows an example of a time-pressure diagram in one cycle when using the apparatus of FIG. 1.

FIG. 3 is a flow sheet of an apparatus for carrying out the conventional method.

FIG. 4 shows an example of a time-pressure diagram in one cycle when using the apparatus of FIG. 3;

FIG. 5 shows an example of a time-pressure diagram in one cycle when the adsorption tank shown in FIG. 1 has a six-tank configuration.

FIG. 6 shows an example of a time-pressure diagram in one cycle when the adsorption tank shown in FIG. 3 has a six-tank configuration.

FIG. 7 shows another example of a time-pressure diagram in one cycle when the apparatus of FIG. 1 is used.

[Explanation of symbols]

A to D Adsorption tank R Holding tank A1, B1, C1, D1 Treated gas inlet valve A2, B
2, C2, D2 Off gas purge valve A3, B3, C3
, D3 Communication valve with holding tank A4, B4, C4, D4
Boosting valve A5, B5, C5, D5 Produced gas outlet valve R1, R2
Holding tank inlet/outlet valve P1 Produced gas valve for boosting pressure

Claims (8)

[Claims] Claim 1: A method for separating gaseous impurities from a gas mixture using an adsorption tank having an adsorption bed and a receiving and receiving order maintenance type holding tank, the method comprising the following steps a to i for at least three adsorption tanks: a. ) The gas to be treated flows into the first adsorption tank from its inlet, and the produced gas is taken out from its outlet, and this inflow and removal are performed before the first adsorption tank loses its adsorption capacity and the purity of the produced gas falls below the target value. b) connecting the outlet of at least one other adsorption tank in which the adsorption bed has been regenerated with the outlet of the first adsorption tank that has undergone step a to equalize the pressure of both adsorption tanks; c) releasing the communication after sequentially carrying out the process for the at least one other adsorption tank; c) the first step after step b;
The outlet of the adsorption tank and one end of the holding tank that maintains the receiving and receiving order (
The holding tank contains gas received by communicating the outlet of another adsorption tank which has undergone steps a and b in the same manner as the first adsorption tank and the other end of the holding tank. The gas in the first adsorption tank was caused to flow into the holding tank by contacting the tank, while the other end of the holding tank was subjected to steps a, b, c and step e described below in the same manner as the first adsorption tank. By communicating with the outlet of the second adsorption tank, gas is introduced until breakthrough of the adsorbed components begins to occur in the gas (a portion of the product gas may be additionally introduced into this gas, if necessary). d) If necessary, close the purge valve of the second adsorption tank to equalize the pressure between the second adsorption tank and the first adsorption tank. e) closing the outlet of the first adsorption tank;
a process of desorbing and removing components adsorbed on the adsorption bed of the first adsorption tank by reducing the pressure of the first adsorption tank that has undergone step c or d to the lowest pressure from the purge valve on the inlet side; f) process; By connecting the outlet of the third adsorption tank, which has passed through a and b in the same manner as the first adsorption tank, and one end of the holding tank, the gas in the third adsorption tank is removed by the breakthrough of the adsorbed components. The gas pushed out by the inflow gas (this gas g) purge the first adsorption tank by closing the purge valve of the first adsorption tank if necessary (a part of the produced gas may be additionally introduced into the first adsorption tank) h) with the outlet of at least one other adsorption tank which has undergone step a or steps a and b in the same way as the first adsorption tank; The outlet of the first adsorption tank via f or g is connected with the inlets of both tanks closed, and gas from the at least one other adsorption tank is allowed to flow in (this gas may include produced gas if necessary). (a part of the gas may be additionally introduced into the adsorption tanks) and the pressure is equalized at least once in both adsorption tanks, and then the communication is released. 1
After the pressure in the first adsorption tank is equalized with the pressure in the flow of gas having the same quality as the generated gas, the communication is released. j) the gas to be treated is a mixture of hydrogen and at least one of the impurity gases to be removed, and the content of the main impurity to be removed in the gas to be treated is 1.5 ATM in molar partial pressure
k) the operating pressure during the adsorption operation in step a is at least 6 times the lowest pressure in step e and at least 4 times the lowest pressure in step c; and l) the main adsorbent in the adsorption bed is activated carbon. , a molecular sieve, and a molecular sieve carbon. Claim 2: The operating pressure during the adsorption operation in step a is 10
2. A method according to claim 1, wherein the pressure is between 1 and 50 kg-gauge and the minimum pressure in steps c or d is between 1 and 6.5 kg-gauge. 3. The impurity to be removed is one or more gases selected from the group consisting of methane, gaseous hydrocarbons other than methane, carbon dioxide, and carbon monoxide. Method. 4. The method according to claim 1, wherein the main impurity to be removed is methane gas. Claim 5: The main impurity to be removed is C2 or C.
4. A process according to claim 1, wherein the hydrocarbon is one of up to 4 hydrocarbons. 6. The method according to claim 1, wherein the main impurity to be removed is carbon dioxide. 7. The method according to claim 1, wherein the main impurity to be removed is carbon monoxide. 8. The method according to claim 1, wherein the concentration of the main impurity to be removed in the generated gas is 300 ppm or more.