JPS631416A - Gas adsorbing purification method - Google Patents

Abstract

PURPOSE:To increase purging effect by storing for a while part of the gas discharged out of the parallel flow pressure reducing process in the pressure swinging method and discharging the effluent gas out, starting with the gas of higher concentration of adsorbing component, to an adsorption bed carrying out desorption process. CONSTITUTION:Raw material gas is introduced to an adsorption bed 2 to adsorb impurities, and after product gas is removed from valve 25 and adsorbed, the pressure is reduced through a valve 24 to be used for pressurizing the adsorption bed 4, and then the gas is further reduced through a valve 23 to be stored in a gas storage 5, the pressure reduced gas from the valve 23 being introduced to an adsorption bed 1 through a valve 13 to purge impurities. Then, a valve 22 is opened and the pressure is reduced to the maximum lowest, separating impurities, which are removed by the purge gas introduced from an adsorption bed 3, being pressure reduced, and the purge gas is introduced from a gas storage 5 and impurities are removed from the valve 22. Then, part of pressure reduced gas and product gas coming from the adsorption bed 4 is introduced and the pressure is raised, being pressurized up to the adsorption pressure by raw material gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pressure swing adsorption method for purifying raw material gas by adsorption.

[Prior Art] Conventionally, there is a pressure swing adsorption method as a gas purification method for selectively adsorbing and removing components to be removed in a raw material gas. This method consists of the following steps: a) High-pressure raw material gas is passed through the adsorption bed, and when the adsorption bed reaches almost saturation, b) the pressure is reduced in parallel to the gas inflow direction in step a), and the outflow The gas is allowed to flow into the adsorption bed in step e) until the pressures of both are approximately equal to each other, C) The pressure is further reduced to cocurrent flow, and the gas that flows out is allowed to flow into the adsorption bed in step d) as a barge gas, d ) further countercurrent depressurization to the lowest pressure and desorption of the adsorption bed using barge gas desorption, and e) repressurization by introducing the depressurized gas and product gas from step b). .

As a representative example of this conventional technology,
There is 082. This technique involves each of the above-mentioned steps and is the basis of the pressure swing adsorption method.

Another example is Japanese Patent Laid-Open No. 56-38121. This example is characterized in that a preferable purge gas concentration profile is obtained by once storing the reduced pressure gas used for purging in a packed column and then causing it to flow back.

[Problems to be Solved by the Invention] Among the above-mentioned conventional techniques, in the former, the gas flowing out from step C) is used as barge gas, so the adsorption front gradually advances to the adsorption bed outlet during parallel flow depressurization. Eventually, breakthrough of the adsorbed material occurs and the barge gas becomes progressively contaminated, reducing the regeneration effect.

For this reason, it is necessary to reduce the utilization efficiency of the adsorbent and operate in a state where no breakthrough occurs even during pressure distribution. This ultimately leads to a low yield of products of non-adsorbed components. Also,
Many proposals have been made to improve this shortcoming, but what about the equipment? 31E has become sloppy, leading to an increase in cost.

The latter example solves the problem of the former, and in order to obtain the highest purge efficiency, a packed column can be used to receive the purge gas and then flow it back to allow impurity breakthrough. This method attempts to obtain an optimal purge gas concentration profile, and has been successful to some extent, but this method requires a filler with a capacity that can store most of the purge gas. It requires a tower and is structurally complex, resulting in high costs.

[Means for Solving the Problems] In the present invention, a part of the gas flowing out from step C) is temporarily stored in a gas reservoir, and the purge gas flowing into the adsorption bed in step d) is a gas having a high concentration of adsorbed components. It is characterized in that the gas with a low concentration of adsorbed components is placed next.

The impurity concentration in the reduced pressure gas in step C) rises rapidly at the point where breakthrough occurs, and then becomes almost constant; a sharp change occurs, especially when impurities with larger molecular weights than the product break through. During our pilot studies, we discovered that taking advantage of this fact does not require a complete reversal of the purge order. In other words, (1) before passing through the barge gas, (2) f! Did you divide it into two parts after passing through and run (2)? It has been found that by flowing &(1), almost the same effect as the latter example of the prior art can be obtained.

In other words, using a gas reservoir, (a) store (1) in the gas reservoir and flow it after (2), (b) store <2) in the gas reservoir, and before flushing (1), (
There are two methods: 2), which allows the concentration profile of the purge gas to be easily changed to a preferable shape, thereby increasing the purge efficiency.

[Actual BE example Next, the present invention will be explained with reference to the drawings.

'f. FIG. 1 is a flowchart of an apparatus having four adsorption beds and one gas reservoir suitable for carrying out the method of the invention.

The main components are as follows.

1-4...Adsorption bed, 5...Gas reservoir, 11,21,31.41...Material gas population valve, 12,2
2, 32. 42...Off gas outlet valve, 13, 23, 33
．． 43... Purge valve, 14, 24, 34. 44... Boosting valve, 15, 25. 35. 45... Product gas outlet valve 53...
...Gas reservoir outlet valve, 55...Product gas valve for boosting pressure.

Embodiment 1, FIG. 2 is a time pressure diagram when gas before breakthrough is stored in the gas reservoir 5, and FIG. 3 is a valve switching program.

Each step will be explained focusing on the adsorption bed 2.

Steps 1 to 4 Raw material gas is introduced through valve 21 under high pressure, impurities are adsorbed, and product gas is taken out from valve 25.

5. End the adsorption, reduce the pressure via the valve 24, and use the gas to increase the pressure of the adsorption bed 4.

6. The pressure is further reduced through the valve 23 and the gas is stored in the gas reservoir 5. (At this time, a part of the gas can also be used for persiping the adsorption bed 1.) When impurities begin to break through in the reduced pressure gas, proceed to the next step.

The gas whose pressure is reduced through the valve 23 is transferred to the adsorption bed 1 through the valve 13.
to purge impurities.

The valve 23 is closed and the valve 22 is opened to reduce the pressure to the lowest level and remove impurities.

Halt (Purge can be performed using part of the gas in the gas reservoir.) Hold (Purge can be performed using part of the gas being sent from the suction bed 3 to the gas reservoir 5 during depressurization. You can also do it.

) Purge gas from the adsorption bed 3 under reduced pressure is introduced through the valve 23 and the desorbed impurities are taken out from the valve 22.

Purge gas is introduced from the gas reservoir 5 through the valves 53 and 23, and the desorbed impurities are taken out from the valve 22.

13 The depressurized gas and part of the product gas from the adsorption bed 4 are received through the valve 24 and pressurized.

14 to 16 Part of the product gas is received through valves 55 and 24 and the pressure is increased to the adsorption pressure.

Example 1-1 Supply gas composition (dry amount: .21 $vol!!) H, 63.
5, N234.7, CO0.7, CH. 1.
1 feed gas consists of 4 adsorption beds containing 0.9 m3 of calcium zeolite A and 21 kg/cm2 (
absolute) and 30°C at a flow rate of 8900 Nm 37 days, and a product gas consisting of at least 99.99% hydrogen is discharged at a flow rate of 4450 Nm 37 days]. On this basis, approximately 79% of the hydrogen in the feed gas is recovered as product gas. Cycle time 2Eim+n 6 barge gas 8.6Nm3, high purity gas 5.0Nm
Store 3 in the gas reservoir (1.Orn3) for later use. (This amount of purge gas is the amount of gas that comes out of one adsorption tower and is used for one purge, and in one cycle, this f
ix number of towers. same as below. ) Example 1-2 Supply gas composition (dry basis vol main) H, 57.5, N, : ] 0.7, CO 0.7, C
H,1.1 Feed gas consists of 6 adsorption beds containing 0.9 m3 of calcium zeolite A, 21 kg/c
m2 (absolute) and 15,400 N at 30 °C
G+ Introduced with a flow rate of 37 days, at least 99.9
Product gas consisting of 7% hydrogen is released at a flow rate of 89008 mj7d. On this basis, approximately 85% of the hydrogen in the feed gas is recovered as product gas. cycle time j
4min, off-gas is released at 1.4'Ig7cm2.

High purity gas 2.0N out of Versi gas 3.2Nm3
Store m3 in the gas reservoir (0.6 rr+3) for later use.

Example 1-3 Supply gas composition (dry basis vol%;) H2 67.5, N2 30.7. CO0.7,
The CH4 1.1 feed gas consisted of 8 adsorption beds containing 0.7 m3 of calcium theolite A and 21 kg
/cm' (absolute) and 28,800 at 30°C
Nm was introduced at a flow rate of 37 days and at least 99. '3
Product gas consisting of 9% hydrogen is released at a flow rate of 17,2008 m37 days. On this basis, approximately 88% of the hydrogen in the feed gas is recovered as product gas. Cycle time 10.5mi.

Saifugas is released into the field at 1.4 kg/cm2.

1.2N of high purity gas out of 1.8Nm3 of barge gas
Store rn3 in a gas reservoir (0.7 m3) for later use.

Embodiment 2, FIG. 4 is a time-pressure diagram when gas after breakthrough is stored in the gas reservoir 5, and FIG. 5 is a valve switching program.

Each step will be explained focusing on the adsorption bed 2.

Steps 1 to 4 Raw material gas is introduced through valve 2l under high pressure, impurities are adsorbed, and product gas is taken out from valve 25.

5. End the adsorption, reduce the pressure via the valve 24, and use the gas to increase the pressure of the adsorption bed 4.

6. The pressure is further reduced through the valve 23, and the resulting gas is introduced into the adsorption bed 1 through the valve 13 for purging. Purge ends before impurities break through into the vacuum gas.

7 The pressure is reduced through the valve 23, and the gas reservoir 5 is released through the valve 53.
to store gas. (During this time, impurity breakthrough occurs.) 8. Close valve 23 and open valve 22 to reduce the pressure to the lowest pressure to remove impurities.

9. Purge gas is received from the gas reservoir 5 through the valves 53 and 23, and the separated impurities are taken out through the valve 22.

Gas from the adsorption bed 3 under reduced pressure of 1O is received through the valve 23 and purged, and the desorbed impurities are taken out through the valve 22.

11-12 Hold 13 Receives the reduced pressure gas and part of the product gas from the adsorption bed 4 via the valve 24 and increases the pressure.

14 to 16 A part of the fi product gas is received through valves 55 and 24 and the pressure is increased to the adsorption pressure.

Example 2-1 Supply gas composition (dry basis voH;) H265.0, N232.5, COI. 2, C
H, 1. 3 The feed gas was fed to an adsorption system consisting of 4 adsorption beds containing 0.9 m3 of calcium zeolite 21 Kg 7 cm2 (absolute) at 850 °C at 30 °C.
Introduced with a flow rate of 0Nm37 ports, at least 99.9
Purified gas consisting of hydrogen with a purity of 91; is 4300Nff
Released with an iffi of I3/day. On this basis, about 78 tons of the feed gas was recovered as product gas.

Purge gas 8.68+n Gas with lower purity among 3 4.
2[03 was stored in a gas reservoir (2.1+n 3) for later use.

[Effect of the invention] By first using gas containing many impurities for purging,
Breakthrough to the purge gas can be tolerated, allowing effective use of the purge gas and adsorbent. Further, the gas tank used for this purpose may be a simple container, and since it can only receive a portion of the barge gas, the capacity can be small and the cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of an apparatus having four adsorption beds and one gas reservoir suitable for carrying out the process of the invention;
The figure shows a time-pressure diagram when gas before breakthrough is stored in gas reservoir 5, Figure 3 is the valve switching program, and Figure 4 is a time-pressure diagram when gas after breakthrough is stored in gas reservoir 5. ,
FIG. 5 shows the valve switching program. 1 to 4: Adsorption bed, 5: Gas reservoir, Patent applicant Tadashi Wakabayashi, Representative of Heavy Oil Countermeasures Technology Research Association Figure 3 Figure 5

Claims (3)

[Claims] (1) It has four or more adsorption beds that selectively adsorb components to be removed in the raw material gas, a) high-pressure raw material gas is passed through the adsorption beds, and when the adsorption beds reach almost saturation, b) step a. ), and the outflow gas is allowed to flow into the adsorption bed in step e) until the pressures of both are almost balanced, and c) the pressure is further reduced in parallel flow, and the outflow gas is used as purge gas. d) further countercurrent depressurization to a minimum pressure to desorb the adsorbent bed in combination with desorption by purge gas; e) depressurized gas and product gas from step b); In the pressure swing adsorption method, which consists of each step of introducing and repressurizing, a part of the gas flowing out from step c) is temporarily stored in a gas reservoir, and the purge gas flowing into the adsorption bed in step d) is:
A gas adsorption purification method characterized in that a gas with a high concentration of adsorbed components is processed first and a gas with a low concentration of adsorbed components is processed next. (2) All or a part of the gas initially flowing out from step c) is temporarily stored in a gas reservoir, and then the gas flowing out immediately flows into the adsorption bed in step d), and then the gas stored in the gas reservoir The gas adsorption purification method according to claim 1, wherein the gas adsorption and purification method is made to flow. (3) direct the gas initially flowing out from step c) to step d);
The gas flowing out is then temporarily stored in a gas reservoir, and this gas is then passed through the adsorption bed in step d).
A method for adsorption and purification of gas according to claim 1, in which the gas is introduced into an adsorption bed.