RU170496U1 - DEVICE FOR CONTINUOUS SEPARATION OF A MIXTURE OF HYDROCARBON GASES - Google Patents

Abstract

The utility model relates to the field of chemistry, namely the separation of gas mixtures, and can be used in various industries, energy and agriculture. A device for the continuous separation of a methane-butane mixture of hydrocarbon gases includes a source of its supply under high pressure, connected in series with the supmembrane space of the 1st membrane module, then with a vacuum compressor with the possibility of pumping out permeate after the membrane from the 1st membrane module and feeding it into the supramembrane the space of the 2nd membrane module, with a vacuum pump with the possibility of pumping out permeate from the 2nd membrane module. The retentate output of the 2nd membrane module is connected through a vacuum compressor to the supmembrane space of the 3rd membrane module with the possibility of returning the retentate after the 3rd membrane module to recycling, the permeate output of the 2nd membrane module is connected to the permeate output of the 3rd membrane module. The retentate of the 1st membrane module is methane concentrate, the permeate of the 2nd and 3rd membrane modules is butane concentrate. These modules are equipped with poly-4-methyl-1-pentin membranes with variable butane / methane selectivity increasing with increasing partial pressure of butane. The technical result is to ensure the stable production of butane and methane concentrates of the required quality. 1 tablet, 2 ill., 2 ave.

Description

The utility model relates to the field of chemistry, namely the separation of gas mixtures, and can be used in various industries, energy and agriculture.

One of the processes for separating gas mixtures is membrane gas separation. A device that implements this process allows sufficiently efficient separation of various gas mixtures. For example, membrane separation of air has led to the creation of industrial plants for the production of technical nitrogen [Membrane technology and application / Richard W. Baker. - 2 ^nd ed., 538, p.cm., John Wiley & Sons, Ltd, California, USA, 2004], when the product of the membrane process is retentate (non-penetrated through the membrane stream with a nitrogen concentration> 98 vol.%). Here, the main component of the initial mixture is air nitrogen (78% vol.), And oxygen is the minor component (21% vol.). The concentration of nitrogen in the retentate is due to the higher permeability of oxygen through the membrane compared to nitrogen. The separation of mixtures of lower hydrocarbons, when C ₃₊ hydrocarbons are low-concentrated components of the mixture, requires the use of hydrocarbon-selective membranes, mainly permeable to C3-C4 hydrocarbons compared to methane. In this case, the problem is also solved with obtaining a conditioned mixture (lowering the concentration of C3 + hydrocarbons) with a methane content of> 99 vol. % in the form of retentate, which is the product (methane of technical quality). The prospects of membrane technologies are connected both with the relevance of the tasks being solved and with the high efficiency of the process compared to other separation processes, with the possibility of separation of various gas mixtures, low energy consumption (there is no energy consumption for phase transitions), reagentless and compact equipment. At the same time, in the device, the separated mixture (feed stream) is brought into contact on one side of the selectively permeable non-porous membrane at an elevated pressure, components penetrated through the membrane (permeate with an increased content of more penetrating C3 + hydrocarbons) are removed at reduced pressure from the back of the membrane, and the retentate ( non-penetrated through the membrane stream enriched with a low-penetrating component C ₁ ) is supplied as the target product. In practice, the driving force of the process is the concentration gradient (partial pressure of the components), which is achieved by increasing the pressure of the mixture at the inlet to the membrane module and artificially lowering the pressure of the mixture from the back of the membrane (for example, by vacuum evacuation). Known devices that implement the method of separation of methane / butane mixtures using hydrocarbon-selective membranes described in [US 5707423 (1998) invs. I. Pinnau, A. Morisato; Morisato A., Pinnau I. // J. Membr. Sci. 1996. V. 121. P. 243-250; J. Schultz, K.-V. Peinemann, J. Membr. Sci. 1996, 110, Matson SM, Ratzke K, Shaikh MQ, Litvinova EG, Shishatskiy SM, Peinemann K.-V., Khotimskiy VS // Polym. Sci. Ser. A. 2012. V. 54. P. 671-677, 37. Yu. Yampol'skii et al., Membrane separation of gaseous C ₁ -C ₄ alkanes, Petroleum Chemistry, December 2011, Volume 51, Issue 8. pp 585-594; Sergey Shishatskiy, Valeriy Khotimskiy, Klaus-Viktor Peinemann et al., A Novel Poly (4-methyl-2-pentyne) / TiO ₂ Hybrid Nanocomposite Membrane for Natural Gas Conditioning: Butane / Methane Separation, Macromol. Chem. Phys. 2007, 208, 2412-2418] for methane / butane mixtures with a low butane content (2-5 vol.%). The most effective membranes include high-permeability polymer glasses that demonstrate a synergistic effect for mixtures: the separation selectivity of butane / methane mixtures is always higher than the ideal selectivity published in the literature as the ratio of the permeabilities of individual butane and methane. Separation selectivity decreases with increasing process temperature. Note that the most highly permeable and hydrocarbon-selective membranes are those based on polytrimethylsilylpropine (PTMSP) (selectivity of α separation of butane / methane mixture reaches 30) and poly-4-methyl-1-pentine (PMP) (selectivity of α separation of butane / methane reaches 23 for a homopolymer and 34 for a membrane containing titanium oxide nanoparticles). Unfortunately, PTMSP membranes are not resistant to C ₅₊ aliphatic hydrocarbons, which are usually found in the main industrial sources of methane, such as natural and associated gases, while PMP is resistant to aliphatic and aromatic hydrocarbons of various structures. The known device is aimed at conditioning methane in the form of a retentate (methane content> 98 vol.%) For further transportation. Permeate containing an increased concentration of butane is sent for further processing.

In these devices, the target product is retentate. According to our estimates, for the separation of methane / butane mixtures, the device is in one stage (one membrane module) with known membranes tested for methane / butane mixtures with a butane concentration of 2-5 vol. %, provides permeate with a butane concentration in the range of 10-25% vol., which corresponds to the published selectivity of the separation of mixtures of butane / methane polymer membranes based on polydimethylsiloxane (PDMS) or poly-4-methyl-1-pentin (PMP) in the range of 7 -23.

Closest to the claimed (prototype) is a device for continuous emission of vapors of organic substances, including butane, from the air for the purpose of purification, using membranes based on polyesterimide or polydimethylsiloxane [United States Patent, 4994094, class. IPC B01D 53/02, publ. 02/19/1991]. In this case, the most effective device is three membrane modules included in the recycling.

However, this device is not used to separate a mixture of methane and butane, and the membrane used in it, as described above, does not allow for stable effective separation of methane-butane mixtures.

The objective of the utility model is to ensure the stable production of butane and methane concentrates of the required quality.

To solve this problem, a device is proposed for continuous separation of a mixture of hydrocarbon gases, including a source of supply of a mixture of hydrocarbon gases under high pressure, connected in series with the supmembrane space of the 1st membrane module, then a vacuum compressor with the ability to pump permeate after the membrane from the 1st membrane module and feeding it into the supmembrane space of the 2nd membrane module, with a vacuum pump with the possibility of pumping out permeate from the 2nd membrane module, while the reten exit ata 2nd membrane module is connected via a vacuum compressor with nadmembrannym space 3rd membrane module with the possibility of returning the retentate after the third membrane module is recycled, and the permeate outlet 2nd membrane module connected to an output of permeate third membrane module. The difference between the device and the known one from the prototype is that the mixture of hydrocarbon gases is a methane-butane mixture, the output of the retentate of the 1st membrane module is the output of methane concentrate, the outputs of the permeate of the 2nd and 3rd membrane modules are outputs of the butane concentrate, and the indicated the modules are equipped with poly-4-methyl-1-pentin membranes with variable selectivity for the butane / methane mixture, which increases with increasing partial pressure of butane.

In FIG. 1 shows a diagram of a device for the continuous separation of methane / butane mixtures to obtain methane and butane concentrates, where:

1 - feed source of the initial butane-methane mixture; 2 - 1st membrane module MM1; 3 - membrane in the module MM1; 4 - yield of methane concentrate; 5 - flow-through vacuum pump; 6 - membrane in the MM2 module; 7 - 2nd membrane module MM2; 8 - vacuum compressor; 9 - membrane in the module MM3; 10 - 3rd membrane module MM3; 11 - flow-through vacuum pump; 12 - total yield of butane concentrate; 13 - output of butane concentrate from the MM2 module; 14 - output of butane concentrate from the MM3 module; 15 - line recycling from the module MM3.

In FIG. Figure 2 shows the dependence of the selectivity of the separation of butane / methane mixtures α on the partial pressure of butane P (C ₄ H ₁₀ ) in a mixture with methane using PMP membranes. The selectivity of the separation of the butane-methane mixture increases significantly with increasing concentration of butane in the mixture (in contrast to the parameters known in the literature for other membranes).

To separate the methane-butane mixture with a stable production of methane and butane concentrates, it is proposed to equip the membrane modules MM1, MM2 and MM3 with membranes made of poly-4-methyl-1-pentin, which has a variable selectivity for the separation of butane / methane, increasing with increasing partial pressure of butane in the mixture with methane according to the graph in FIG. 2, covering a temperature range of 0-40 ° C. This device ensures the continuity of the process with simultaneous production of methane concentrate with a purity> 99% and butane concentrate with its increased content.

The device includes a source of supply of a mixture of hydrocarbon gases (butane-methane mixture) 1 under elevated pressure, connected in series with the supranembrane space of the 1st membrane module MM1 2, equipped with a membrane 3, a vacuum pump 5 for pumping permeate after the membrane and feeding it into the supramembrane space the second membrane module MM2 7, equipped with a membrane 6, a vacuum pump 11 for pumping out permeate, while the output of the retentate of the second module 7 is connected through a vacuum compressor 8 with the supmembrane space of the third membrane This module MM3 10, equipped with a membrane 9, through the compressor 8 to return the retentate after the third membrane module to recycling 15. Module MM1 has an outlet for retentate - methane concentrate 4. Outputs for permeate - butane concentrate - module MM2 and module MM3 - 13 and 14 respectively, they are connected to each other and to the common outlet of butane concentrate 12 through a flow-through vacuum pump 11. Thus, the device has one inlet for the initial binary mixture and two outlets for conditioned methane (methane concentrate) and butane concentrate. Membranes 3, 6 and 9 are made of poly-4-methyl-1-pentin with variable selectivity. The specified device provides the production of butane concentrate and the stable production of methane concentrate (methane content in the product is not less than 99% vol.).

The device operates as follows. The initial methane-butane mixture from source 1 is supplied under pressure to the membrane module MM1 2, equipped with a membrane with variable selectivity 3, and conditions (pressure drop across the membrane, degree of selection) are selected taking into account the selectivity of butane / methane according to the functions of FIG. 2, and in the form of a retentate, the desired methane concentrate 4 is obtained (methane content not less than 99% vol.). The permeate from the MM1 module is sent through a vacuum compressor 5 to the membrane module MM2 7. For the 6 MM2 membrane, conditions are selected (pressure drop across the membrane, degree of selection) taking into account the selectivity of butane / methane according to the functions of FIG. 2. The retentate from the MM2 module is fed through the compressor 8 to the MM3 membrane module 10. For the 9 MM3 membrane, the conditions (pressure drop across the membrane, degree of selection) are also selected taking into account the butane / methane selectivity for the functions of FIG. 2. The retentate from the MM3 module is fed to the recycle 15 at the entrance to the membrane module MM1, and the permeate from the outlet 14 after mixing with the permeate from the outlet 13 of the MM2 module through the vacuum pump 11 is extracted as a butane concentrate 12, thereby ensuring the continuous production of methane and butane concentrates .

Below are examples that demonstrate the useful properties of the proposed device for the continuous production of methane and butane concentrates. Note that for comparative optimization of the process, the degrees of selection θ (the ratio of permeate flux to the input flux to the membrane module) and the membrane area in the membrane modules MM1, MM2 and MM3 are varied. All other indicators (pressure of the mixture to the membrane, pressure of the mixture after the membrane) are recorded for comparison (see Table 1). In the examples, membranes with different butane / methane separation selectivity, including those with variable selectivity, were used. Membranes with variable selectivity are made of PMP, membranes with constant selectivity are made of polydimethylsiloxane. The process temperature in all examples is 40 ° C in order to guarantee no condensation of butane in the system.

Example No. 1 (comparative).

The composition of the initial butane / methane mixture 5/95 vol. % The input stream of the initial mixture of 39 m ³ (NU) / h In the membrane modules, the area of the MM1 membrane is 1.07 m ² , the area of the MM 2 membrane is 2.33 m ² and the area of the MM 3 membrane is 0.08 m ² . The pressure parameters of the butane-methane mixture in the membrane modules and the degree of selection are presented in Table 1 (No. 1 p / p). To separate the mixture using membranes with constant selectivity α (C ₄ H ₁₀ / CH ₄ ) = 10. The result is the target methane concentrate (99% vol. Methane, 1% vol. Butane). Butane concentrate consists of 49% vol. methane and 51% vol. butane.

Example No. 2.

The composition of the initial butane / methane mixture 5/95 vol. % The input stream of the initial mixture of 39 m ³ (NU) / h In the membrane modules, the membrane area of MM 1 is 1.0 m ² , the membrane area of MM 2 is 0.65 m ² and the membrane area of MM 3 is 0.02 m ² . The pressure parameters of the butane-methane mixture in the membrane modules and the degree of selection are presented in Table 1 (No. 2 p / p). To separate the mixture using membranes with variable selectivity from PMP. The functions of the dependence of separation selectivity on the partial pressure of butane in the mixture are shown in FIG. 2. The result is the target methane concentrate (99% vol. Methane, 1% vol. Butane). Butane concentrate consists of 16% vol. methane and 84% vol. butane.

Thus, the proposed device is most effective for the continuous production of concentrates of methane and butane from methane-butane mixtures.

In the examples, the selectivity parameters of the membranes at 40 ° C, which are minimal for the scope of claims of the utility model, are given. Lowering the temperature, for example to 0 ° C, improves these indicators (see Fig. 2) and, thus, the membrane separation of the binary mixture will only improve.

As can be seen from the above examples, the production of butane concentrate with its increased content is achieved only using the inventive device.

Claims (1)

A device for continuous separation of a mixture of hydrocarbon gases, including a source of supply of a mixture of hydrocarbon gases under elevated pressure, connected in series with the supmembrane space of the 1st membrane module, then with a vacuum compressor with the possibility of pumping permeate after the membrane from the 1st membrane module and feeding it into the supmembrane the space of the 2nd membrane module, with a vacuum pump with the possibility of pumping out permeate from the 2nd membrane module, while the output of the retentate of the 2nd membrane module is connected through a vacuum compressor with a supmembrane space of the 3rd membrane module with the possibility of returning the retentate after the 3rd membrane module to recycling, the permeate output of the 2nd membrane module is connected to the permeate output of the 3rd membrane module, characterized in that the mixture of hydrocarbon gases is methane butane mixture, the output of the retentate of the 1st membrane module is the output of methane concentrate, the outputs of the permeate of the 2nd and 3rd membrane modules are the outputs of the butane concentrate, and these modules are equipped with poly-4-methyl-1-pentine membranes with variable selectivity for a butane / methane mixture, increasing with increasing partial pressure of butane.

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