RU88987U1 - DEVICE FOR CLEANING AND DRYING COMPRESSED GAS - Google Patents

Abstract

1. A device for drying and purifying compressed gas, comprising a piping system, an electrical equipment system, an automatic control unit, shutoff valves, an oil / water separator, a filter, at least two alternately working adsorbers in which a porous electrically conductive adsorbent (carbon material is placed for drying and purifying gas) or porous metal), characterized in that at the adsorption stage in order to enhance the adsorption of polar molecules of pollutants, the porous conductive adsorbent is polarized COROLLARY electrodes, one of which is in contact with the adsorbent, and the other adsorber to the housing, wherein the adsorbent is isolated relative to the housing adsorber and the outlet of the adsorbers mounted vacuum pump, alternately removing components desorbed from the adsorber during the regeneration. ! 2. The device according to claim 1, characterized in that an assembly for measuring the concentration of components extracted from the compressed gas connected to the automatic control unit is installed on the outlet pipe of the purified and dried gas. ! 3. The device according to claim 1, characterized in that the switching of the adsorbers is performed by the automatic control unit according to the signal of the measuring unit of the concentration of components extracted from the compressed gas. ! 4. The device according to claim 1, characterized in that a node for measuring the humidity of the compressed gas connected to the automatic control unit is installed on the outlet pipe of the purified and dried gas. ! 5. The device according to claim 4, characterized in that the adsorbers are switched by the automatic control unit according to the signal of the compressed gas humidity measuring unit.

Description

The invention relates to adsorption methods for gas purification and separation of gas mixtures, and, in particular, to methods for drying and purifying compressed gases, and can be used in the chemical, food and oil and gas industries to produce gases of the required composition with the required degree of drying and purification.

It is known that in various industries there are processes in which the use of poorly purified and dried gases is unacceptable, which can lead to accidents and a decrease in the quality of products. In this regard, it is necessary to have reliable methods and devices for the implementation of high-quality cleaning and drying of gases.

In industry, methods of adsorption drying and purification of compressed gas are widely used, in which silica gel, active alumina, porous coals, natural and synthetic molecular sieves (zeolites) are used for drying and purifying gases. Their capacity, as a rule, does not exceed 30 g of water per 100 g of adsorbent, which requires the use of a sufficiently large mass of adsorbent for cleaning and drying.

There is a method of deep comprehensive purification of air from carbon dioxide and moisture, including adsorption of the removed components by solid molecular sieves - zeolites with their subsequent regeneration (restoration of adsorption properties) by heating and gas purging. (N.V. Keltsev, Fundamentals of Adsorption Technology, 1976, p. 411).

The disadvantage of this method is that as a result of the absorption of carbon dioxide by zeolites, there is a decrease in their water absorption capacity. In addition, a significant amount of energy is required for the regeneration of zeolites. These factors reduce the effectiveness of zeolites for the comprehensive cleaning and drying of air.

Known methods for increasing the absorption efficiency of water vapor (or other substance) by saturating the adsorbent with salt solutions, thereby enhancing the contribution of chemisorption to the adsorption process.

A known method, including the impregnation of silica gel with an aqueous solution, calcium chloride and lithium bromide, as a result of which increases the capacity for water vapor and the strength of the adsorbent (RF patent No. 2274484, publ. 2006).

Also known is a method of drying air with solid porous composite moisture absorbers, which are hygroscopic inorganic substances (a mixture of lithium and calcium chlorides) located on a porous carrier. As a porous carrier in the known method, crushed silica gel is used, bonded into durable waterproof granules with various mineral binders. As a result, a sorbent with a high dynamic capacity for water vapor is obtained (RF patent No. 2174870, publ. 2001).

To improve the quality of gas cleaning and drying and to reduce the size of the device, composite sorbents are used, consisting of an open-pore matrix and an absorbent substance placed in these pores. Inorganic oxides, carbon sorbents, polymers, natural sorbents, porous metals, porous composites or their mixtures, solutions and crystalline hydrates are used as a porous matrix, and inorganic salts, their mixtures, solutions and crystalline hydrates are placed in the pores as hygroscopic substances. These materials can significantly increase the sorption capacity in water (up to 75-80 g per 100 g of dry sorbent) and lower the desorption temperature to 50-80 ° C (RF patent No. 2101423, publ. 1998).

The disadvantages of the known methods are the complexity of the production process of adsorbents and, consequently, an increase in their cost, low mechanical strength (brittleness) in difficult operating conditions (significant temperature drops, the presence of droplet moisture, high speeds of the gas to be drained). In this case, in the presence of oil vapor in compressed air, due to the small pore sizes of the adsorbents for drying the gas and the presence of chemically active centers on the surface of the adsorbent, the formation and concentration of an oil film that is practically not removed during desorption is possible.

In addition, since the adsorption process in known technical solutions occurs only due to surface attraction forces determined by the structure and size of the pores, or by the chemical properties of the compounds in the sorbent layer, adsorption of the adsorbent and destruction of the transition pores can occur during cleaning and drying, “Poisoning” of the adsorbent with undesirable chemical compounds contained in the gas to be cleaned.

It is also quite difficult to regulate the necessary degree of purification and influence the adsorption properties of the adsorbent directly during operation; the adsorption process cannot be intensified or reversed; this also complicates the organization of the regeneration process and the need for the additional cost of a large amount of energy for the desorption stage.

To regenerate zeolites, as a rule, a sufficiently large amount of energy is required (for high-quality regeneration, it is necessary to heat the adsorbent to a temperature of 300-400 °°). For the regeneration of silica gels and active alumina, a lower regeneration temperature (100-200 ° C) is required. In both cases, the adsorbent is heated either by heating the outer surface of the adsorber (RF patent No. 2106528, publ. 1999, RF patent No. 2182513, publ. 2002), or by heating the purge gas (N.V. Keltsev, Fundamentals of adsorption technology , 1976, p. 411).

Known methods for supplying heat to the adsorbent during the regeneration process have the following disadvantages.

When heating the outer surface of the adsorber, uneven heating of the adsorbent is possible, especially intensifying toward the center of the adsorber, and in addition, part of the heat, even if high-quality thermal insulation is organized, is released into the environment.

The purge gas has a sufficiently low heat capacity, therefore, for high-quality regeneration, it is necessary to increase either its flow rate or temperature, which can negatively affect the strength of the adsorbent granules and increase operating costs.

Thus, the principle of heating an adsorber body directly with an external heat source, or heating a gas with an external heat source and the subsequent use of heated gas as a heat carrier for carrying out regeneration of the adsorbent, used in many well-known gas cleaning and drying plants, has a rather low efficiency and leads to increased energy consumption to conduct regeneration.

Based on the foregoing, we can conclude that all known methods and methods for cleaning and drying gases in a stationary adsorbent layer have, in general, a single approach: widely known industrial sorbents, or combinations thereof, are used to intensify the regeneration process, as a rule, sorbents during their production, they are saturated with hydrophilic (having high solubility in water) substances that enhance the chemical component of adsorption — chemisorption and increase the specific capacity of adsorbents; sorbents are also impregnated with various chemical compounds to increase the strength of the adsorbent grains, or they are saturated with chemical catalysts that accelerate the necessary chemical reactions to recover or modify the component extracted from the gas stream.

The objective of the present invention is to expand the arsenal of technical means used in the process of cleaning and drying gases, increasing the efficiency, economy, reliability and increasing the life of existing gas treatment plants used in various industries.

The essence of the invention is as follows.

The method of drying and purification of compressed gas involves the preliminary purification of gas in an oil / water separator, followed by drying and purification in one of two alternately working adsorbers, while the second adsorber is regenerated during gas drying in one of the adsorbers. A porous electrically conductive material is used as the adsorbent placed in the adsorbers, while during the drying of the gas in one of the adsorbers, the adsorbent located in it is polarized to form an electrostatic charge on the surface that enhances the adsorption of polar molecules of gas pollutants, and at the stage of regeneration of the adsorber, the polarization of adsorbent stop or change its polarity.

At the stage of regeneration of the adsorber, the adsorbent located in it is heated by passing a constant or alternating electric current through it.

A device for drying and cleaning compressed gas contains a system

pipelines, electrical system, automatic control unit, electrically operated valves, oil and water separator, filter, at least two alternately working adsorbers in which a porous electrically conductive adsorbent (carbon material or porous metal) is placed for drying and purifying the gas. At the adsorption stage, in order to enhance the adsorption of polar molecules of gas pollutants, the porous conductive adsorbent is polarized by electrodes, one of which is in contact with the adsorbent and the other with the adsorber body, while the adsorbent is isolated relative to the adsorber body, and a vacuum pump is installed at the outlet of the adsorbers, alternately removing desorbed components from adsorbers during regeneration.

At the outlet of the purified and dried gas, a unit for measuring the concentration of components extracted from the compressed gas or a unit for measuring the humidity of the compressed gas connected to the automatic control unit can be installed.

The adsorbers are switched by the automatic control unit by the signal of the unit for measuring the concentration of components extracted from the compressed gas, or the unit for measuring the humidity of the compressed gas.

The adsorbent may additionally contain a catalyst that increases, at the stage of regeneration of the adsorbent, the rate of the oxidation (decomposition) reaction of the hydrocarbons absorbed by the adsorbent with the release of heat, which can be used to regenerate the adsorbent.

The proposed method allows you to control the adsorption process, while increasing the capacity of the adsorbent for the components extracted from the gas, and, consequently, increases the efficiency of the device, and reduces the energy consumption for regeneration of the adsorbent.

As the adsorbent in the proposed device may be

applied electrically conductive material with a highly developed surface, carbon molecular sieves, carbon fibers, carbon fabric, porous (sponge) conductive metals (iron, titanium, bronze, aluminum), composite conductive materials.

The proposed method of cleaning and drying is carried out without the use of chemical compounds and catalysts to enhance chemisorption. For cleaning and drying, the natural electrostatic effects that occur during the interaction of molecules of gas pollutants on the surface of adsorbents in the process of physical adsorption are used and enhanced, and thus the proposed method does not follow explicitly from the prior art.

The action of the proposed method and device is based on the following facts.

All adsorption interactions can be divided into two main types: physical adsorption and sorption based on the forces of chemical interaction. Physical adsorption is caused by the forces of molecular interaction. In most cases, the main contribution to the energy of interactions is made by dispersion forces. The molecules of most pollutants absorbed during adsorption have fluctuating dipoles and quadrupoles, causing “instantaneous” deviations of the electron density distribution from the average distribution. When the molecules of substances polluting the gas come closer to the atoms or molecules of the adsorbent, the motion of fluctuating dipoles and quadrupoles acquires a systematic and strictly ordered character, which causes the appearance of attraction between them. In some cases, dispersion forces are amplified by electrostatic forces.

The interaction caused by electrostatic forces depends, as a rule, on the chemical nature of the pollutant absorbed by the adsorbent and its contribution to the total interaction energy during the adsorption of polar molecules on electron-neutral carbon sorbents is practically zero. (N.V. Keltsev, Fundamentals of Adsorption Technology, 1976, pp. 27-28).

The mechanism of adsorption of polar water molecules in known sorbents (zeolite, silica gel) is determined by the interaction on the surface of the adsorbent with surface hydroxyl groups having an uncompensated electrostatic charge and the formation of hydrogen bonds. In the case when the sorbents additionally contain salts or oxides, the sorption mechanism is determined mainly by chemical interactions, as a result of which chemisorption reactions occur in the pores of the sorbent.

A feature of active carbons as an industrial sorbent is that their surface is electrically neutral, and adsorption on coals is mainly determined by the dispersion forces of interaction. (N.V. Keltsev, Fundamentals of Adsorption Technology, 1976, p. 86). If activated carbons are used for drying gases, the volume of absorbed water almost completely fills their pores, and the water adsorption isotherms are S-shaped, hysteresis is not observed, and it is not necessary to expend a large amount of energy for desorption for regeneration (ibid., P. 87 -88).

By creating an electrostatic charge on the surface of an electrically neutral sorbent, it is possible to significantly enhance the sorption of polar molecules using adsorption mechanisms that are not inherent in electrically neutral sorbents, but for other sorbents they are the main mechanism of sorption. In this case, the degree of polarization of the sorbent can

manage by actually regulating the adsorption forces.

Known methods for the extraction and concentration of substances by adsorption of solute in an electric field, and at least one electrode is an electrically conductive adsorbent (RF patent No. 2137757, publ. 1999). This method cannot be used for drying and purification of gases, since extraction and concentration in the specified method is carried out from an aqueous solution of a substance.

The proposed method is characterized in that the process of extraction of pollutants (cleaning and drying) is carried out in a gaseous medium, passing the polluted gas through a polarized adsorbent, and the rate of extraction of harmful substances from the gas is higher, since the permeability of gases to the pores of the adsorbent and the diffusion rate in the gas are greater than in a liquid.

The method differs from the known ones in that the gas cleaning and drying efficiency is achieved by polarizing the electrically conductive (carbon) adsorbent, as a result, a charge is formed on its surface. Particles (molecules) of water and polar hydrocarbon molecules contained in a gas, having an uncompensated charge, are more intensively adsorbed on the surface of the adsorbent, while one electrode is in contact with the adsorbent, and the other is in contact with the surface of the adsorber isolated from the adsorbent. The voltage applied to the adsorber should be much lower than the energy of dissociation of water into oxygen and hydrogen, but sufficient to create at least a monomolecular layer of adsorbed gas-polluting substance on the surface of the adsorbent, and the subsequent layers should be formed using a hydrogen bond (in the case of water), reinforced electrostatic component.

When saturating the adsorbent, it is necessary to regenerate it, and for the continuity of the drying process, it is advisable to use two alternately working adsorbers, while one adsorber purifies and dehydrates the gas, the other is regenerated.

When the degree of purification and drying decreases, the adsorbers are switched over, in which one adsorber that has been used for drying is switched on for regeneration. Regeneration is carried out as follows. Reverse voltage is applied to the electrodes, which repels molecules from the surface of the adsorbent. In this case, desorption of water molecules occurs and their fusion is possible due to polarization.

To remove desorption products from the adsorbers, the device may further comprise a vacuum pump installed at the outlet of the adsorbers, and pumping and dumping the desorption products into the drainage.

To regenerate a moisture-saturated electrically conductive sorbent, a method of heating the adsorbent directly can be applied by passing direct or alternating current through it, while the adsorbed harmful substances in the pores will be removed with greater efficiency compared to blowing with steam or external heating.

Figure 1 presents a schematic diagram of a device for cleaning and drying gas; figure 2 presents the design of the adsorber used to implement the proposed method of purification and drying of gas.

The device for implementing the proposed method consists of installed along the gas: water separator 1, filter 2, two adsorbers 3, 4 connected in parallel through insulating connections through non-return valves 5 and 6, respectively, to the outlet pipe, and through electrically operated valves 7 and 8 respectively, to the electric drive vacuum pump 9, which ensures the discharge of desorption products into the drainage.

The oil-water separator 1 and the filter 2 through the electrically operated valves 10 and 11, respectively, are connected to the drainage line, where periodic purging is performed. Switching of the adsorbers 3 and 4 is carried out using electric actuator valves 12 and 13, respectively. To control the quality of the exhaust gas, an assembly for measuring the concentration of the component extracted from the gas stream (in particular, a humidity measurement unit) 14 is installed at the outlet pipe; for monitoring and controlling the temperature of the adsorbers during regeneration, the thermometers 15 and 16 are provided in the adsorbers 3 and 4, respectively.

The device for drying and purifying gas is controlled in accordance with a predetermined algorithm of operation by means of an automatic control unit 17, which is connected by electric circuits to electric actuator valves 7, 8, 10, 11, 12, 13, a vacuum pump 9, and a unit for measuring the concentration extracted from the gas stream component 14 and thermometers 15 and 16.

The adsorber for implementing the proposed method of cleaning and drying gas (see figure 2) includes a housing 18 with an inlet gas pipe 19, an outlet gas pipe 20 and an outlet pipe of liquid (desorption products) 21. An electrically conductive adsorbent 22 is disposed coaxially relative to the housing and electrically isolated from the housing 18 by means of a strip 23 and rings 24. The adsorbent 22 is fixed in the cover 25. Additionally, an electrical voltage is supplied from the control unit 17 to the electrodes 26 in contact with the adsorbent 2 2 and to the electrode 27 in contact with the housing 18, in addition, through the electrodes 26, a direct or alternating current supply is provided for heating the electrically conductive adsorbent 22. To ensure an acceptable temperature on the surface of the adsorber, thermal insulation is made in the form of a heat-insulating material 28 closed by a casing 29. Additionally, a layer of adsorbent placed thermometer 30 in the insulating pocket 31 to control the temperature during regeneration. The design of the adsorber provides for its operation at high (over 10 MPa) working pressure.

The installation works as follows.

Compressed gas under operating pressure enters the water-oil separator 1, where the gas is purified from large particles of moisture, oil and mechanical particles. From the oil-water separator 1, gas enters the filter 2, in which the gas is cleaned of oil vapors that adversely affect the operation of the adsorbent. Separated in the oil-water separator 1 and the filter 2, the oil-water emulsion through the valves 10 and 11 is sent with periodic purges to the drainage. The gas purified from drip moisture and oil enters one of the adsorbers 3, 4, where the gas is dried to the specified conditions. The adsorbers 3, 4 operate alternately (one is running for drying, and the other is being regenerated at this time, while the regeneration time is much shorter than the time for the adsorber to dry). In the process of gas passing through a dry adsorber, a polarized electrically conductive adsorbent 22 in it is saturated with polar molecules of the extracted substance, and the dried and purified gas enters the outlet pipe through one of the non-return valves 5 or 6. After saturation of the adsorbent, the adsorbers switch over, and the earlier adsorbed cleaning and drying the adsorber is switched on for regeneration, during which the current source is switched off or its polarity is changed, it can additionally occur on roar adsorbent by passing a direct or alternating current. After heating the adsorbent to a predetermined temperature, evacuation (pumping out) of the desorbed extractable material and removal of the desorbed components into the drainage is performed.

After the adsorber, the dried and purified gas enters the outlet pipe to consumers. If the humidity of the gas supplied to consumers is higher than the set (control) setting, the automatic control unit 17, according to the readings of the unit for measuring the concentration of the extracted component in the gas stream (unit for measuring humidity) 14 installed on the outlet pipeline, switches the adsorbers.

The present invention improves the efficiency and reliability of the process of cleaning and drying compressed gas, reduces operating costs, and also provides control of the processes of adsorption and desorption of plants for cleaning and drying gases, and can be used in the chemical, food and oil and gas industries to produce gases of the required composition with the required degree of drying and cleaning.

Claims (5)

1. A device for drying and purifying compressed gas, comprising a piping system, an electrical equipment system, an automatic control unit, shutoff valves, an oil / water separator, a filter, at least two alternately working adsorbers in which a porous electrically conductive adsorbent (carbon material is placed for drying and purifying gas) or porous metal), characterized in that at the adsorption stage in order to enhance the adsorption of polar molecules of pollutants, the porous conductive adsorbent is polarized COROLLARY electrodes, one of which is in contact with the adsorbent, and the other adsorber to the housing, wherein the adsorbent is isolated relative to the housing adsorber and the outlet of the adsorbers mounted vacuum pump, alternately removing components desorbed from the adsorber during the regeneration. 2. The device according to claim 1, characterized in that an assembly for measuring the concentration of components extracted from the compressed gas connected to the automatic control unit is installed on the outlet pipe of the purified and dried gas. 3. The device according to claim 1, characterized in that the switching of the adsorbers is performed by the automatic control unit according to the signal of the measuring unit of the concentration of components extracted from the compressed gas. 4. The device according to claim 1, characterized in that a node for measuring the humidity of the compressed gas connected to the automatic control unit is installed on the outlet pipe of the purified and dried gas. 5. The device according to claim 4, characterized in that the adsorbers are switched by the automatic control unit according to the signal of the compressed gas humidity measuring unit.