JPS59207827A - Method for separating gas from gas mixture - Google Patents

Abstract

PURPOSE:To separate CO of high purity from a mixed gas consisting essentially of H2 and CO at a low cost, by using membrane modules having different separation degrees of H2/CO in combination. CONSTITUTION:CO of high purity is separated from a mixed gas, consisting essentially of H2, and obtained by decomposing heavy oil or coal, etc. using gas separation membranes. In the method, membrane modules having different separation degrees of H2/CO are used in combination. In the stage of a raw gas, i.e. a mixed gas consisting essentially of H2 and CO in a high H2 concentration, a membrane having a high separation degree of a rapidly permeating component gas (H2) from a slowly permeating component gas (CO) is used. After using the membrane, a membrane having a low separation degree of H2/CO is used in the stage of reduced H2 concentration. Thus, the aimed CO of high purity can be separated without requiring means of boosting the pressure of the raw gas side, reducing the pressure on the permeation side nor purging with the gas (CO) other than the component gas for permeation, etc.

Description

[Detailed description of the invention] The present invention provides 7 heavy oils, 1 coal, etc., obtained by cracking 82,
From a Go-based mixed gas, using a gas separation membrane,
First, it relates to a method for separating high-purity CO. In particular, high-purity CO is extracted from the mixed gas mainly composed of H2 and Go, and this CO is mixed with methanol, acetic acid,
Or when used in the production of oxalic acid, etc. + 'Bl) 11
The aim is to provide a method for

Separation of gas from a mixed gas using a gas separation membrane is already known and is also used industrially. (
Bunnan+: CEP, oat 1982, p.
(age 27-32) However, all of these techniques are mainly based on the separation of easily permeable components (in the case of the present invention, H2), and the separation of components that are difficult to permeate (in the case of the present invention, such as CO), as in the method of the present invention. ) There were no good proposals for separation.

Generally, when a gas separation membrane is used, the overspeed of gas in the membrane follows the following equation (1) for each component gas.

% formula % (1 Q, gas permeation rate (crrl (STP) /se
c) pl: Partial pressure of permeated component on raw gas side (c1nH?) p
2: Permeation law 〃(Il)K, permeability of permeable component to membrane (7(STP)/LJA, ``CC+ On Hj
? )S゛Membrane area (c17b) As is clear from equation (1), in the process of separation on the membrane.

As the component gas that permeates quickly (H2 in the case of the present invention) is lost from the raw gas side, p decreases. On the other hand, on the transparent side,
Conversely, the component gas that permeates faster (in the case of the present invention, ■(2
) increases, so p2 is close to the total pressure on the permeate side.
'4.

Therefore, as the concentration of the component gas that permeates slowly (in the case of the present invention, CO) increases on the raw gas side, the value of pl-J)2 decreases, and the value of pl-J)2 decreases, and the component gas that permeates faster than the raw gas (in the present invention, In the case of (2), the removal of ■(2) will be difficult to proceed.To solve this problem, in addition to raising +p+f, that is, boosting the pressure.
Measures such as reducing the pressure on the permeation side or purging the permeation side with a gas other than the component gas to be permeated (in the case of the present invention, purging with Co or the like) are taken. However, the former requires extra power and increases the cost due to the high pressure of the process.

In the latter case, the concentration of the permeate component gas (H2 in the case of the present invention) on the permeate side decreases, and additional gas is added, which increases costs.

The present invention is a method devised to solve these problems, and is performed at the stage where the component gas (H2 in the present invention) to be permeated is released on the raw gas side.

The solution is to use a membrane with a low separation (in the case of the present invention, H2/Co separation). That is, two or more membrane modules are used, and a membrane with a high degree of H2/Co separation is used at a stage when the H2 concentration in the raw gas (mixed gas mainly consisting of H2 and co) is high.
When the H2 concentration is low, a membrane with low H2/Go separation is used.

The details of the present invention will be further explained using Examples and Comparative Examples.

Example 1 Case 1 In the case of carrying out the method of the present invention using a mixed gas of H2 and Co with a relatively high concentration of C011 among cracked gases such as heavy oil, the comparatively soft Example 1 and 2 are known methods, In the case of comparative example 1 (
is an example in which a membrane with a high degree of H2/Co separation (a membrane with the same degree of separation as the one used in the third module in Example 1) is used, whereas in the case of Comparative Example 2, the degree of H2/CO separation is low! ie5. (
An example in which a membrane with the same resolution as the membrane used in the second and third stage modules in Example 1 was used is shown.

From these results, it can be seen that when trying to obtain gas with a purity of 98% CO, Example 1 using the method of the present invention obtained the maximum amount of gas. In other words, 9 of the same amount of gas
When trying to obtain a gas having a concentration of s% co, the method of the present invention has the minimum area. still.

In the case of Comparative Example 2, it is quite close to Example 1 of the method of the present invention (i
? 4 was obtained, but the H2 concentration on the permeation side was low.

Furthermore, the amount of permeation is large, which is disadvantageous compared to the method of the present invention.

Example 2 is a case in which the method of the present invention is implemented using a mixed gas of H2 and Co with a relatively low CO concentration in a minute gas such as heavy oil, and Comparative Examples 3 and 4 are conventional methods. In case 3, a membrane with high H2/Co separation (M with the same separation as the membrane used for the first stage module in Example 2) was used.
In the case of Comparative Example 4, a membrane with low H2/CO separation (Example 2
An example using a membrane with the same resolution as the membrane used in the second stage module is shown below. In these cases as well, the above-mentioned Example 1
It can be seen that Example 2 of the present invention method is the most excellent as in the case of [Example].

This example shows the case where the method of the present invention is carried out using a mixed gas of H2 and Co having a relatively high OO concentration among cracked gases such as heavy oil.

] - Figure 114 is a flow sheet in which the method of the present invention was implemented.
Show the diagram.

A, B, and C indicate lamentations, and are published in Japanese Unexamined Patent Application Publication No. 1989-57, respectively.
It is filled with 3,000 hollow fibrous polyimide membranes prepared by the method described in Japanese Patent Application Laid-open No. 157435 or Japanese Patent Application Laid-open No. 57-15819. The size of the module is 2φ×20αL.

The A module has a separation membrane with a H2/co separation degree of 120.

That is, H2 permeability (KH2) 9.0X10-6. Co
A polyimide separation membrane with a permeability (KCO) 'i' of 5 x 10-8 was used. B.

The C module has a H2/Co separation membrane with a separation degree of 15.

νIJchi H2 transparency 1lAi degree (KH2) 9. OX 1O
A polyimide separation membrane with -6Co permeability (KCO) of 6.0 x 10-7 was used.

The H2, Co mixed gas is sent to the A module from the conduit l after passing through the injection gas removal device. At this time, the pressure was 3''9/cni (gauge) and the temperature was room temperature.

In the A module, the permeate gas exits through the flow conduit 3 from the outside to the inside of the hollow fiber membrane. The pressure at this time was 11"-910i (gauge). The non-permeable gas flows along the outside of the hollow fiber membrane and exits through conduit 2.
It is sent to the B module. In the B module, as in the A module, the permeated gas flows from the outside of the hollow fiber membrane toward the inside and flows out from the conduit 5. C
It is sent to the module. In the C module, as in the A and B modules, the permeate gas flows out from the flow conduit 8 from the outside to the inside of the hollow fiber membrane.

The rare gas flows along the outside of the hollow fiber membrane and exits through the conduit 7.

Flow at the entrance] C, exit and other places, H2, C
! 0 composition is shown in Table 1.

Comparative Example 1 In this example, the H2/CO content in all modules A, B, and C was 120 degrees, that is, the H2 concentration was excessive (Kn2) 9
．． OX10.

The same procedure as in Example 1 was carried out except that a polyimide separation membrane having a CO permeability (Kco) of 7.5 x 10-8 was used. The results are shown in Table 1.

Comparative Example 2゜In this example, A, B, (both modules have a H2/C0 separation degree of 15, that is, a H2 permeability (KH2) of 9.0XIC1'
, c.

Transparency (Kco) 6. The same procedure as in Example 1 was carried out except that a polyimide separation membrane of OX 10-7 was used. The results are shown in Table 1.

First Fitting Example 2 This example shows the case of implementing the present invention using a +(2,Co) mixed gas with a relatively low CO concentration among cracked gases such as 1 heavy oil.

FIG. 2 shows a schematic diagram of a flow sheet implementing the method of the invention. A and B indicate membrane modules, respectively, published in Japanese Patent Application Laid-Open No. 1983-
It is filled with 3,000 hollow fiber polyimide membranes prepared by the method described in Japanese Patent Application Laid-open No. 1.57435 or Japanese Patent Application Laid-open No. 15819/1983.

The size of the module is 2 onφX 20 on,i.

The A module has H2/Co separation degree of 12 as in Example 1.
0 separation membrane, i.e. H2 permeability (KH2) 9. Ox
10-6゜co 7 excess (Kco) 7.5 X 10
-8 polyimide separation membrane was used. B module has H
2/CO separation degree 20, that is, H2i1j excess (K
H2) 9. OX 10-6. Go transparency (Kco)
A 4.5 x 10-' polyamide separation membrane was used.

The gas introduction method, pressure, temperature, etc. were all the same as in Example 1.

The results are shown in Table 2.

Comparative Example 3 In this example, the H2/CO separation degree was 120, that is, the H2 permeability (Kl(,,) 9.0X10-
6. CO permeability (KCO) 7.5 x 10-”
Example 2 was carried out in the same manner as in Example 2, except that a polyimide separation membrane was used. The results are shown in Table 2.

Comparative Example 4 In this example, both the A and B modules had a H2/OO separation degree of 20, that is, a H2 permeability (Kl(2) 9.0X10-6
The same procedure as in Example 2 was conducted except that a polyimide separation membrane with a co-permeability (KCO) of 4.5XlO-' was used. The results are shown in Table 2.

Table 217

[Brief explanation of drawings]

Figures 1 and 2 each represent a schematic diagram of a gas separation flow sheet, where A, B, and O are modules. 1.2, 3, 4.5, 6, 7, 8.9 are conduits Patent applicant: Ube Industries, Ltd.

Claims (1)

[Claims] H2. obtained by decomposing coal, etc. When separating sieved pure adsorbed CO from a C:O-based mixed gas using a gas separation membrane, two or more 1-module modules are used, and at a stage where the 82 concentration in the raw gas is high, it takes 82,700 minutes: 'i11 using a high membrane + H2f! At a lower stage, ++,
/ co The feature is that it uses a membrane with a low temperature of 1 degree. A method of producing one portion of high-purity C○ from a mixed gas consisting mainly of H,..., GO.