JPH0125612B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixed gas permeation separator comprising a membrane of porous material with reinforced mechanical strength.

Membranes used in gas separators using permeable membranes are broadly classified into non-porous polymer membranes and porous membranes such as porous glass, alumina, and porous carbon. Non-porous polymer membranes have been put into practical use for industrial gas separation because they can yield products with fairly high purity, but their permeability coefficients are very small compared to porous membranes, so they have large permeability. Due to the area requirements, a type of separator in which fine hollow fibers are bundled has been developed. However, polymer membranes have low heat resistance and cannot be used at temperatures above 200°C, so in order to use them in combination with high-temperature reaction systems, cooling and reheating processes are required, which requires a large amount of cost. . Further, ultrafine hollow fibers are easily clogged and deteriorated by dust, tar, etc. contained in the gas, and a purification process is required to remove these substances, which also requires a large amount of cost.

On the other hand, porous membranes typified by ceramic membranes are quite promising for industrial gas separation due to their physical properties. In other words, the separation mechanism of porous membranes is mainly based on Knudsen's theory. When gas passes through pores that are much smaller than the mean free path of the gas, the separation coefficient α of the two gas components is calculated as follows: It is expressed as the square root of the ratio of molecular weight m ₁ and m ₂ , With this level of separation coefficient, it is not possible to purify each component gas to high purity in a single separation operation, but since the amount of permeation per unit area is large and the material is generally heat resistant, When obtaining a product or adjusting the composition of a mixed gas, the purpose can be achieved with a relatively small device using this porous membrane, and the high temperature reaction gas can be kept at a high temperature without being cooled to room temperature. Since it can be introduced into the separator, it is economical in terms of both equipment costs and energy costs. A specific example of such a case is to use a mixed gas of hydrogen and carbon monoxide generated by partial oxidation of heavy oil, coal, etc. for chemical synthesis, and adjust the mixing ratio according to the synthesis reaction. This is the case when hydrogen is separated from other gases at high temperatures.
Gas separation using a porous membrane is a method suitable for the purpose in such cases, but in general, there are few membrane materials with reliable mechanical strength, making it difficult to implement into practical equipment. For example, porous membranes such as porous carbon are brittle and have poor mechanical strength, so they cannot be used in industrial equipment that operates under severe conditions, such as those that separate high-pressure gases at tens of atmospheres by applying a large pressure difference. In view of these points, the present invention has made gas separation under high pressure possible by using a porous membrane as a component that has mechanical strength by reinforcing both sides of the porous membrane as described above with metal plates. This invention relates to a gas separator using membrane permeation. The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view of an embodiment of a membrane gas separator according to the present invention, FIG. 2 is a cross-sectional view of the part shown in FIG. 1, and FIG. 3 is a vertical cross-sectional view of a permeable membrane element. . In FIG. 1, reference numeral 1 denotes a transmission membrane element, and a plurality of transmission membrane elements 1 are arranged in parallel as shown in the figure and with their cross sections as shown in FIG. 2, forming a transmission membrane element group. 2. The permeable membrane element 1 includes a metal outer tube 3 having a large number of small holes 3a in the tube wall, and a metal inner tube 4 having a large number of small holes 4a in the tube wall, each having a ring 5 at each end. The gap between the outer tube 3 and the inner tube 4 is filled with a porous membrane 6, and the contact surface 7 between the ring 5 and the outer tube 3, and the contact surface 8 between the outer tube 3 and the inner tube 4 are brazed, etc. It is configured by sealing it. The porous substance used as the porous membrane 6 is porous carbon or the like, and the diameter of the pores is generally about 100 Å to 200 Å. This carbon-based porous membrane is manufactured by, for example, filling the above-mentioned gap in advance with a mixture of pulverized coal and a binder, and then heating and sintering it after assembly. Although these porous membranes are suitable for the purpose of gas separation in specific cases as described above, they all have low mechanical strength. Therefore, in order to reinforce this, the outer tube 3 and inner tube 4 sandwiching the porous membrane 6 from both sides in a sandwich-like manner are preferably made of stainless steel or the like having high mechanical strength and high corrosion resistance.

Diameter, length, plate thickness, small hole 3 of outer tube 3 and inner tube 4
Specifications such as the diameter, number, and arrangement of a and 4a, and the type and thickness of the porous membrane 6 are arbitrarily selected depending on the type of mixed gas to be separated and the conditions to be provided. Next, a transmission membrane element group 2 in which a plurality of transmission membrane elements 1 configured in this manner are arranged in parallel is housed in the body 9. Furthermore, the lower and upper ends of the transmission membrane element group 2 are attached to the tube sheets 10a and 10b, respectively, as shown in FIG. 3, and the outer tube 3 is opened in the tube sheets 10a and 10b.
A contact surface 11a between the outer tube 3 and a hole having approximately the same diameter as the outer diameter of the
and 11b are welded by brazing or the like. Similarly, the upper and lower ends of the body 9 are also connected to the tube plates 10a and 1.
0b by brazing or welding. tube plate 1
End plates 13a and 13b having gas inlets and outlets 12a and 12b are attached to 0a and 10b. The tube plate 10a and the end plate 13a and the tube sheet 10b and the end plate 13b are fixed by the flange portions 14a and 14b.
This is done using bolts and nuts through the packing. Incidentally, gas outlet pipes 15a and 15b are attached to the upper and lower parts of the body 9. The body 9, tube plates 10a, 10b, end plates 13a, 13b, and gas inlet/outlet tubes 12a, 12b, 15a, 15b are all made of stainless steel, which has high mechanical strength and is corrosion resistant.

The structure of the membrane permeable gas separator according to the present invention is as described above. Next, an embodiment of this gas separator will be described together with an example of its operation. First, the specifications of the transmission membrane element 1 are as follows. The inner diameter of the outer tube 3 is 26 mm, the outer diameter of the inner tube 4 is 20 mm, each length is 3000 mm, and both the outer tube 3 and the inner tube 4 are made of stainless steel with a plate thickness of 2 mm.
In both cases, small holes with a diameter of 1 mm were made at equal intervals at a rate of 0.7 holes/cm ² . The porous membrane is a carbon-based porous membrane with a thickness of 3 mm. After kneading pulverized coal with tar pitch as a binder and filling it into the gap between the outer tube 3 and the inner tube 4, it is heated to about 800℃. and sintered. A transmission membrane element group 2 was constructed by housing 1,500 such transmission membrane elements 1 in a body 9 having a cross-sectional area of 15,000 cm ² . Further, the body 9, tube plates 10a, 10b, end plates 13a, 13b, etc. were all made of stainless steel.

Next, an example of operation in which a mixed gas of hydrogen and carbon monoxide is separated using this gas separator will be described with reference to FIGS. 1 and 3. Hydrogen 50% by volume, carbon monoxide 50%
A mixed gas 1000Nm ³ /h with a composition of volume%
Gas inlet pipe 12 at 50ata (absolute atmospheric pressure) and 500℃
a, the liquid is distributed in the small chamber 16a formed by the tube plate 10a and the end plate 13c, and flows into the inner tube 4 of each permeable membrane element 1. This mixed gas flow flows through the inner tube 4 of each permeable membrane element, passes through the small holes 4a distributed on the wall surface, and comes into contact with the carbon-based porous membrane 6 filled in the gap between the inner and outer tubes, and the mixed gas flows through the inner tube 4 of each permeable membrane element. Hydrogen gas molecules in the constituent molecules preferentially form the porous membrane 6
It diffuses inside and reaches the outer tube 3, and then reaches the space 17 in the body 9 through the small holes 3a distributed on the wall surface of the outer tube 3. Next, carbon monoxide molecules also diffuse and permeate through the porous membrane 6 at a slow speed, reaching the space 17. As a result, the composition of the gas that has passed through each permeable membrane element 1 and reached the space 17 is 80% by volume of hydrogen and 20% by volume of carbon monoxide. The mixed gas of 500 Nm ³ /h thus obtained in the space 17 drops to 10 ata during this time and is taken out from the gas outlet pipes 15a, 15b. On the other hand, carbon monoxide of the gas flowing through the inner tube 4 that does not pass through the inner porous membrane is concentrated, and the carbon monoxide is concentrated on the tube plate 10b and the end plate 13b.
500 Nm ³ /h is taken out from the gas outlet pipe 12b at a pressure of 49.8 ata with a composition of 20% by volume hydrogen and 80% by volume carbon monoxide.

In this example, the separation efficiency is at this level, but if a separated gas with even higher purity is required, the purpose can be achieved by providing one or more stages of the same gas separator and passing it through. Needless to say.

The present invention is configured and implemented as described above, and its features and effects are as follows. First, by filling a porous permeable membrane between a metal outer tube and an inner tube, it has become possible to obtain a strong permeable membrane element that can withstand stress such as high pressure applied to the membrane surface. As a result, when the amount of permeation per unit area is large and heat resistance is required, a suitable permeable membrane such as porous carbon can be used to achieve membrane permeation type gas separation that overcomes the mechanical strength that these permeable membranes have. I became able to make utensils. In other words, it has become possible to produce a membrane-permeable gas separator that has a large permeation rate, is heat resistant, and has mechanical strength. In addition, the structure including the attachment of the permeable membrane element to the tube plate, the permeable membrane element group, the body, the tube plate, the head plate, etc. is similar to the structure of a shell-and-tube heat exchanger, and the structure of this shell-and-tube heat exchanger is It can be easily manufactured using the following manufacturing technology.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of a gas separator using membrane permeation according to the present invention, FIG. 2 is a cross-sectional view of FIG. 1, and FIG. 3 is a vertical cross-sectional view of a permeable membrane element. 1 is a permeable membrane element, 2 is a group of permeable membrane elements, 3 is a metal outer tube, 4 is a metal inner tube, 3a and 4a are small holes, 6
1 is a porous membrane, 9 is a body, 10a and 10b are tube plates, 1
2a, 12b are gas inlet pipes or outlet pipes, 13a,
13b is an end plate, and 15a, 15b are gas outlet pipes.

Claims (1)

[Claims] 1. Between a metal outer tube having a plurality of small holes in the tube wall and a metal inner tube having a plurality of small holes in the tube wall,
A permeable membrane of carbonaceous porous material is formed by mixing and filling pulverized coal and a binder in advance and sintering the mixture. A permeable membrane element group is constituted by a plurality of sealed permeable membrane elements, and the permeable membrane element group is housed in a body having a gas outlet pipe, and each of the permeable membrane elements and each upper end and each lower end of the body are connected to each other. 1. A gas separator using a permeable membrane, characterized in that it has a structure in which an end plate having a gas inlet pipe or an outlet pipe is fixed to each tube sheet by welding to each tube sheet.