RU2625983C1 - Ejector membrane-sorption device for separation of gas mixtures - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: ejector membrane-sorption device for separating gas mixtures contains a compressor to which an ejection mixer outlet is connected, at least two adsorbers filled with solid adsorbent through a gas pressure regulator and a desorption ejector inlet through a gas pressure regulator. The oulet of the ejection mixer through the gas flow regulator is connected to the first distribution valve. The adsorber inlets are connected to the first distribution valve to switch the flow of compressed gas from the compressor between the adsorbers. The outlets of the adsorbers are provided with control valves for withdrawing the gas from the adsorbers to the discharge pipeline and connected through a second distribution valve to the membrane filter, one of the withdrawal tubes is connected to the consumer and the second to the ejection mixer.

EFFECT: provide stationary operation mode for the membrane filter with continious feed and product flows and continious flow of displacement from the adsorbers to ensure the maximum separation characteristics of the device as a whole.

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Description

An ejector membrane-sorption device for separating gas mixtures refers to the technology of separating gas mixtures by membrane and adsorption methods in order to obtain enriched components.

The invention relates to membrane adsorption devices using a gas ejector to separate gas mixtures and can be used to obtain enriched components in binary and multicomponent gas mixtures, in particular in the production of oxygen from atmospheric air in various fields.

Gas mixtures are separated by various physicochemical methods, including membrane and adsorption ones. The adsorption method of air separation is based on the principle of selective absorption of the components of the gas mixture. Absorption is carried out by special molecular sieves under conditions of short-cycle adsorption. The process is based on the dependence of gas absorption by an adsorbent on pressure: the ability of an adsorbent to absorb gas is directly proportional to pressure. Thus, adsorption occurs at elevated pressure, and the desorption process is carried out by depressurization. Typically, the sorption and desorption cycles of certain gas components (for example, in the enrichment of oxygen from air - nitrogen sorption) alternate in at least two parallel adsorption columns on adsorbent beds.

Since the degree of extraction of the final product is defined as the ratio of the amount of product to the initial feed stream of the device, the criterion for increasing the degree of extraction at a given amount of product enrichment is the so-called relative selection, which is the ratio of the product stream to the stream at the compressor inlet.

A distinctive feature of the ejector membrane-sorption installation is the combination of the sorption unit operating in non-stationary mode and the membrane operating essentially in stationary mode. The combination of these two blocks is possible only if a constant flow from the adsorbers at the stage of displacement. In this case, a constant product flow can be provided on the membrane unit. This condition can only be fulfilled if a constant load on the compressor is ensured, so that it operates at a constant pressure and gas flow.

The membrane air separation method is based on the principle of selective membrane permeability. The principle of operation of membrane gas separation units consists in different rates of gas penetration through the polymer membrane under the action of a pressure drop across the membrane.

The frequency of the compressor leads to cyclic pressure loading of the membrane apparatus. A known decrease in the mechanical strength of a membrane made of polymeric materials in the presence of droplet moisture in combination with cyclic loading leads to a loss in the reliability of the apparatus, up to its premature failure.

The prior art METHOD AND INSTALLATION FOR SEPARATION AND / OR DRYING GAS MIXTURES USING MEMBRANE DEVICES (patent for invention RU No. 2233698, publ. 10.08.2004, Bull. No. 22). A known method of separation and / or drying of gas mixtures consists in the fact that a stream of compressed gas is fed to a membrane gas separation device in an apparatus for separating and / or drying gas mixtures, in which it is divided into two streams, while controlling the pressure and / or flow dried gas at the outlet of the installation by changing the operating pressure in the membrane device using a pressure reducer-regulator installed in front of the membrane device, together with a throttle installed at the outlet of the membranes th device, which is used for initial setup of the degree of dry gas selection.

Recently, combined plants have been used, in which adsorption columns and membrane blocks are used, which provides increased energy efficiency at specified enrichment values of the final product of the gas mixture. Thus, the prior art adsorption-membrane installation described in patent EPO No. 266884. The known installation comprises a compressor for supplying the initial gas mixture (air), two parallel adsorption columns filled with a solid adsorbent, a membrane unit installed at the outlet of the adsorption columns, and an additional membrane unit into which a gas stream is formed, which is formed at the stages of pressure relief and purge adsorbers. Despite all the advantages of plants of this type, they have a significant drawback - it is necessary to use a compressor at each stage of separation, which a priori makes the process economically unprofitable.

There are installations with one compressor. So, the prior art membrane adsorption installation (patent for utility model RU No. 955547, publ. 07/10/2010, Bull. No. 19), consisting of a combination of membrane and adsorption separation blocks, is characterized in that it is equipped with an additional membrane block, installed on the first degree of separation, the input of which is connected to the pipe outlet of the separation product of the sorption block. In plants of this type, the recycle stream is compressed along with the power stream, which also leads to an increase in energy costs.

The prior art also known adsorption-membrane installation described in the patent of Russian Federation No. 4223461. The known installation also contains a compressor for supplying the initial gas mixture (air), two parallel adsorption columns filled with a solid adsorbent, and a membrane unit installed at the outlet of the adsorption columns and providing additional enrichment of the final product. This unit also uses only one compressor. A distinctive feature of the proposed scheme is that the residual stream purges the adsorber under reduced pressure, which is an ineffective way to increase the degree of extraction of the final product.

The prior art ejector membrane sorption device for separating gas mixtures (utility model patent RU No. 139877, publ. 04/27/2014, Bull. No. 12), which is the closest analogue of the claimed invention.

Known ejector membrane sorption device for separating gas mixtures, contains a compressor, at least two adsorbers filled with adsorbent, having inlet nozzles that are connected through the first valve for switching the gas flow between the adsorbers to the outlet of the ejector mixer, which is connected to the compressor outlet, and outlet nozzles of adsorbers, which are equipped with valves for venting gas from the adsorbers to the waste pipe and are connected through a second distribution valve to the membrane filter, pat which is connected to the consumer to drain the fraction of the gas mixture that has penetrated through the membrane from the low pressure cavity and is connected to the ejector mixer to drain the gas mixture that has not penetrated through the membrane and is connected to the ejector mixer. The device has an increased degree of product extraction due to the use of ejector mixing recirculation flow and power flow at the compressor outlet, as a result of which the composition of the mixture at the inlets of the adsorbers changes with a small change in pressure and the outlet of the ejector. An additional ejection mixer with a receiver can be installed on the discharge pipe, which allows increasing energy efficiency by reducing the desorption pressure.

The disadvantage of the prototype is the lack of active control elements of the separation process in a device containing a recirculation loop that combines a stationary separation element (membrane module or membrane filter) and non-stationary separation elements (adsorbers filled with sorbent). Without controlling the compressor operating mode and flows in the device, the declared result cannot be achieved in principle, since the displacement mode in the adsorption column will not be stationary (gas pressure and flow rate increase sharply), which will lead to erosion of the adsorption front and, as a result, to loss of separation work . In addition, pressure and flow surges in the adsorption column inevitably lead to unsteady operation of the membrane filter (membrane module), and, as a result, pressure and flow surges in the recirculation loop.

The technical result is achieved by the implementation of the claimed invention and is to provide a stationary mode of operation of the membrane filter with constant power and product flows and a constant flow of displacement from adsorbers to ensure maximum separation characteristics of the device as a whole.

An ejector membrane-sorption device for separating gas mixtures, containing at least two adsorbers filled with a solid adsorbent, a compressor, the outlet pipe of which is connected to the adsorbers through adjustable valves and with an inlet to the ejector mixer, the outlet of which is connected through the first distribution valve to the inlet adsorbers nozzles, and the outputs of the adsorbers are equipped with control valves for venting gas from the adsorbers to the discharge pipe and are connected via a second distribution valve to the membrane filter, one of the outlet pipes of which is connected to the consumer, and the second to the ejector mixer, while the gas flow regulator is installed at the outlet of the ejection mixer, a gas pressure regulator is installed on the pipeline connecting the compressor to the adjustable valves, and a distribution valve with two outlets, the first outlet is connected to the atmosphere, the second to the desorption ejector, which is also connected to the compressor through a pressure regulator.

In a particular case, the ejector membrane-sorption device for separating gas mixtures may contain auxiliary equipment for gas preparation at the compressor outlet (cleaning, drying, heating).

In addition, an ejector membrane-sorption device for separating gas mixtures at the inlet of the membrane filter on the pipeline connecting the adsorbers to the membrane filter may include auxiliary equipment for averaging the gas composition at the inlet of the membrane filter (for example, a receiver).

In FIG. 1 presents a diagram of the inventive device.

The device includes a compressor 1, parallel adsorbers 2 and 3 filled with a solid adsorbent. The inputs of the adsorbers 2 and 3 are connected through a three-way control valve 4 and through the gas flow regulator 5 to the ejection mixer 6, which in turn is connected to the compressor 1. The inputs of the adsorbers 2 and 3 are also connected to the control valves 7 and 8, which are connected to the compressor 1 through the gas pressure regulator 9.

The outputs of the adsorbers 2 and 3 are connected through a three-way control valve 9 and a receiver for averaging the gas concentration 10 to the membrane filter 11. The membrane filter 11 has high and low pressure cavities separated by a selective membrane element and provides both an increase in the concentration of the target component and gas purification flow from organic pollutants and solid particles, including sorbent nanoparticles. The outlet pipe from the low-pressure cavity of the membrane filter 11 is connected to the consumer, and the outlet pipe from the high-pressure cavity is connected to the ejection mixer 6.

The outputs of the adsorbers 2 and 3 are connected through control valves 12, 13 to the distribution valve 14, which is connected to the desorption ejector 15 and a discharge pipe for exhausting gas, characterized by a higher adsorption value, from the adsorbers 2 and 3. The desorption ejector 15 is also connected to the compressor 1 through gas pressure regulator 16.

The ejector membrane-sorption device for separating gas mixtures works as follows.

It is assumed that the separation process in the stage of short-cycle adsorption (CCA) contains the following working stages: desorption due to depressurization, filling the adsorber with a stream from the compressor and / or stream from the outlet of the ejector mixer, adsorption and displacement of the product by the stream from the outlet of the ejector mixer. Since the pressure loss in the CCA stage at the stage of displacement in the high-pressure cavity of the membrane stage is small, the pressure loss in the ejector due to the correct choice of its parameters can also be made quite small.

The source gas mixture (air) is compressed using compressor 1 and pressurized through a pipe to an ejection mixer 6, where the concentration of the target component is increased by mixing the flow from the high-pressure cavity of the membrane filter.

Compressed air from the compressor 1 through the gas pressure regulator 9 enters the control valve 7 (the control valves 8 and 12 are closed) and through it enters the adsorber 2, filling the adsorber 2 is carried out to a pressure of 4-10 atm. After that, the valve 7 closes and the compressed and additionally enriched target component air stream, the value of which is set by the gas flow regulator 5 under a pressure of 4 ÷ 10 atmospheres, passes through the electromagnetic control valve 9, open towards the adsorber 2 and enters the inlet of the adsorber 2. When air passes through the adsorbent layer, the more adsorbed component is easily absorbed by it, while the less adsorbed component, which has a lower adsorption value and, accordingly, is absorbed at a lower rate, skips t at the end of the layer and enters through a switching electromagnetic distribution valve 9 open for it into a membrane filter 11, in front of which a receiver can be installed to average the concentration of gas 10, the stream enriched in the sorbent from impurities and products of abrasion of sorbents, penetrated through the membrane filter 11, enters the consumer, and not flowing through the membrane, the stream exits through the pipe and is fed into the ejection mixer 2.

During the filling of adsorber 2 in adsorber 3, pressure is released and gas is desorbed from the adsorbent through a control valve 13 (control valve 12 is closed at this time). From the control valve 13, gas enters the distribution valve 14, with which gas is directed into the atmosphere until the pressure in the adsorber reaches a pressure of 1-3 ata, after which the distribution valve 14 switches the flow to the desorption ejector 15, which works as a jet pump i.e. using a high-pressure gas stream from the compressor 1, which is supplied to the desorption ejector 15, the desorption ejector pumps gas from the adsorber 3 to a pressure of 0.1-0.5 atm.

After a half-cycle, adsorbers 2 and 3 exchange their functions. Such a cycle is repeated many times. Thus, the described embodiment of the installation provides a stable mode of operation of the installation with maximum separation characteristics.

Implementation examples

Example 1

The goal is to obtain air enriched with oxygen up to a predetermined concentration of 50% (vol.) At given parameters of the membrane stage.

The set parameters of the membrane stage include: the value is the ratio of the pressure in the low cavity to the pressure in the high pressure cavity; the selectivity value (the ratio of the permeability of the components) is equal to 7.

When using the proposed device, the oxygen-rich product stream enters the consumer in an amount of 0.6 m 3 / h at a pressure of 6 atmospheres and a pressure ratio in the membrane stage of 6/8. Desorption pressure 0.3 at.

The constant flow at the outlet of the TA-100K Durr Technik compressor is 3.6 m3 / h at a pressure of 8 atm. The displacement flow at the outlet of the adsorber is 1.5 m3 / h. When the ratio of the pressure in the low-pressure cavity to the pressure in the high-pressure cavity is 6/8 and the selectivity is 6.3, a product stream of 0.975 m3 / h is supplied to the consumer at a pressure of 6 atm. Moreover, the relative selection of product oxygen is 0.27. The remaining flow from the compressor outlet is directed to the filling of the adsorbers and to the desorption ejector. The oxygen concentration in the product stream is 50%. This mode in the absence of new features of the invention is fundamentally impossible to implement. The oxygen concentration in the product stream is 50%.

Example 2

When using the proposed device with the parameters of example 1 while reducing the desorption pressure to 0.1 atm. Due to the ejector blown by the stream from the compressor, it is possible to obtain a product stream with a product purity of up to 65%. In this case, the stationary mode of operation of the stream entering the membrane filter and product stream is maintained. In the examples, an AirLiquide membrane module was used as a membrane filter. Zeolite HF-5120 (Hong Kong Chemical Corp.) was used as a sorbent. A DurrTechnik compressor model TA-100K Durr Technik was used as a compressor.

Claims (3)

1. An ejector membrane-sorption device for separating gas mixtures, containing at least two adsorbers filled with a solid adsorbent, a compressor, the outlet pipe of which is connected to the adsorbers through adjustable valves and with an inlet to the ejector mixer, the outlet of which is connected through the first distribution valve to the inlet nozzles of the adsorbers, and the outputs of the adsorbers are equipped with control valves for venting gas from the adsorbers to the waste pipe and are connected through the second distribution valve to the membranes one filter, one of the branch pipes of the outlet which is connected to the consumer, and the second to the ejector mixer, characterized in that a gas flow regulator is installed at the outlet of the ejector mixer, a gas pressure regulator is installed on the pipeline connecting the compressor with adjustable valves, and is installed on the discharge pipe control valve with two outlets, the first outlet is connected to the atmosphere, the second to the desorption ejector, which is also connected to the compressor through a pressure regulator. 2. An ejector membrane-sorption device for separating gas mixtures according to claim 1, characterized in that at the compressor output auxiliary equipment for gas treatment is installed (cleaning, drying, heating). 3. The ejector membrane-sorption device for separating gas mixtures according to claim 2, characterized in that at the inlet of the membrane filter on the pipeline connecting the adsorbers to the membrane filter, auxiliary equipment is installed to average the gas composition at the inlet of the membrane filter.

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