RU2690479C1 - Zeolite regeneration method and device for its implementation - Google Patents

Abstract

FIELD: physics.SUBSTANCE: group of inventions relates to methods and apparatus for regenerating adsorbents using electromagnetic radiation of the microwave range and can be used in chemical, oil refining and other industries. Method of zeolite regeneration includes action on zeolite, located in working chamber, electromagnetic field of microwave range using source of microwave energy. UHF effect is performed in pulsed mode with energy supplied to sorbent determined from ratio, where P – power of microwave energy source, W, τ is UHF exposure time, s; wherein power P of microwave energy source for one sorbent heating cycle is determined from the ratio: 0.1≤P/c·m≤0.3, where c is heat capacity of water, m is mass of water contained in sorbent. Device for regeneration of zeolite includes a source of microwave energy, working chamber for arrangement of zeolite, waveguide with matching device, connecting source of microwave energy and working chamber.EFFECT: invention provides higher rate of regeneration of zeolite with reduction of moisture content in adsorbent to 3–4 % without its destruction and with preservation of adsorbing properties.5 cl, 2 dwg

Description

The group of inventions relates to methods and devices for the regeneration of adsorbents using electromagnetic radiation of the microwave range and can be used in chemical, petroleum refining and other industries. In particular, the invention can be used in bilge columns when drying natural gas to operate pneumatic control systems for valves and fittings.

In modern technology and technology for the removal of water from gases and vapors of organic compounds, zeolites are widely used. Zeolites are the most selective adsorbents with an ordered crystalline structure and a certain size of input windows. Currently, more than 100 types of zeolites have been synthesized, including about 25 identical to natural ones. Synthetic zeolites are mainly used as adsorbents and catalysts, they are more efficient and of higher quality than natural ones.

Due to the fact that zeolites are polar adsorbents, it is possible to carry out adsorption separation of substances on them, using not only the difference in molecular sizes, but also different degrees of unsaturation and polarity. Zeolites are good desiccants of gases and liquids, as well as good absorbers of sulfur-containing compounds, and therefore are widely used in the purification of gases and liquids from impurities.

Currently, compressed natural gas is used to operate pneumatic control systems for valves in gas processing plants. High demands are placed on gas for moisture content. Excess moisture in the gas leads to the formation of hydrates in the valves and the last failure of the system (especially at low temperatures). To reduce the moisture content in the gas sorbents are used - zeolites. Over time, the sorbents gain a lot of moisture and no longer effectively take moisture from the gas, so they need to be regularly regenerated.

Traditional methods of thermal regeneration of zeolites in the regeneration column are ineffective, require large energy consumption and time-consuming due to the low thermal conductivity of zeolites. The most promising is the use of microwave energy for the regeneration of zeolites. Microwave heating distinguishes volumetric heat dissipation, which can shorten the exposure time.

In the prior art, various solutions are known that are associated with the regeneration of adsorbents, including zeolites, using microwave irradiation.

For example, from the patent of the Russian Federation No. 2438774 a method is known for regenerating a sorbent using electromagnetic radiation of the high frequency range, according to which regeneration is carried out under conditions of resonance of the system, summing up the electromagnetic radiation that is necessary and sufficient to break the intermolecular bonds of the sorbent and sorbate during the interaction of electromagnetic radiation with these substances in the resonant chamber.

The disadvantage of this method is the lack of regeneration of the sorbent directly in the drying column with a pulsed gas supply and the need to use a resonant chamber for the microwave.

From the patent of the Russian Federation No. 2058183 a device is known for regenerating an adsorbent from gaseous impurities, which contains a vacuum heat-insulating casing filled with liquid nitrogen, inside which is placed a vessel with an adsorbent that is penetrated by a heater, and the vessel is connected to a gas mixture supply line and a vacuum pump in which a heater is a microwave source operating in the 300 MHz - 300 GHz frequency range, made in the form of a magnetron connected through a waveguide with a matched load.

The disadvantage is the complexity of the design of the adsorber, as well as the uneven distribution of the microwave electromagnetic field, which leads to large temperature and moisture gradients in the sorbent. In addition, the claimed frequency range does not comply with the permitted for use in industry.

Closest to the proposed method is a method of regeneration of the adsorbent, known from the RF patent №2168360. According to the regeneration method of adsorbent contained in the adsorber unit drying compressed gas, is carried out by heating the adsorbent microwave electromagnetic field and subsequent removal of desorbed components, the heating is performed before unloading the adsorber to a pressure of 2-5 kgf / cm ² above atmospheric pressure, the adsorbent is heated to 200-250 ° C for 1-5 minutes, the desorbed components are removed within 10-30 seconds when the adsorber communicates with the atmosphere.

The disadvantage of this method is the lack of vacuum and continuous operation of the microwave generator, which can lead to the destruction and overheating of the zeolite.

Closest to the proposed device is a zeolite regeneration device, known from the RF patent №100920, including an adsorber, comprising a housing made of metal, with inlet, outlet and cover pipes, an adsorbent, an insulating jacket, at least one microwave adsorbent heater, fixed in the lid, representing a magnetron connected through a waveguide with a matched load. In addition, a vacuum pump is installed at the outlet of the adsorber to remove the desorption products from the adsorber into the condensate collection tank. In this case, the magnetron can operate in the frequency range from 300 MHz to 300 GHz.

The disadvantage is the uneven distribution of the microwave electromagnetic field, which leads to large gradients of temperature and moisture content in the sorbent. In addition, the claimed frequency range does not comply with the permitted for use in industry.

The technical problem of the group of inventions is the creation of an effective method and device for the regeneration of zeolite.

The technical result is to increase the rate of regeneration of the zeolite while reducing the moisture content in the adsorbent to 3-4% without its destruction and while maintaining the adsorbing properties.

The technical result is achieved by the fact that in the method of regeneration of zeolite, including the effect on the zeolite, located in the working chamber, the electromagnetic field of the microwave range using a source of microwave energy, according to the proposed solution, in the process of influence, the vapor-gas mixture formed in the working chamber at microwave -the effect on the zeolite through the zeolite, and the microwave effect is carried out in a pulsed mode with the energy supplied to the sorbent, determined from the relationship:

,

,

, где с – теплоемкость воды, m – масса воды, содержащейся в сорбенте.where P is the power of the microwave energy source, W, τ is the time of microwave exposure, s; the power P of the microwave energy source for one cycle of heating the sorbent is determined from the relation:

where c is the heat capacity of water, m is the mass of water contained in the sorbent.

The technical result is also achieved by the fact that a device for regenerating a zeolite, including a source of microwave energy, a working chamber for accommodating a zeolite, a waveguide with a matching device, connecting the source of microwave energy and a working chamber, while the working chamber is equipped with an input for supplying natural gas and an output gas to valves, according to the proposed solution, contains a closed loop for circulation of the vapor-gas mixture formed in the working chamber during zeolite regeneration through the sorbent, made in the form of a pipeline connected to the upper and lower parts of the working chamber; pump and valves installed on the pipeline; a control unit connected to the source of microwave energy and ensuring its operation in a given mode; at the same time, the matching device is made in the form of a smooth transition from a rectangular section to a circular one and contains a hermetic insert made of radio transparent material to protect the source of microwave energy from pressure changes in the working chamber.

The control unit can be made in the form of a relay-regulator with a timer.

The device may contain a dew point sensor and a pressure sensor connected to a closed loop at the outlet of the vapor-gas mixture from the working chamber.

The invention is illustrated by a drawing and a graph, where figure 1 shows the functional diagram of the microwave installation for the regeneration of sorbents in the preparatory gas preparation unit GPM-BPIG, figure 2 shows examples of graphs of temperature (T, ° C) and humidity (W,%) an NaA zeolite from time to time (t, s) of its heating with a pulsed microwave heat supply, where 1-2 corresponds to the "heating" mode, 2-3 to the drying mode, 3-4 to the regeneration mode.

Positions in the drawing are indicated:

1 - microwave energy generator with a power source; 2 - working chamber (cylindrical resonator); 3 - zeolite; 4 - waveguide, 5 - matching waveguide device; 6 - control unit; 7 - gas supply pipeline to the working chamber; 8 - closed loop for circulation of the gas-vapor mixture; 9 - vacuum pump; 10 - pipeline for vapor-gas mixture discharge to a candle; 11 - sealed insert of radiotransparent material; 12 - dew point sensor; 13 - pressure sensor; 14, 15, 16, 17 - stop valves (gate valve, valve), 18 - gas supply pipe to the dew sensor and to the stop valves.

The proposed method of regeneration of zeolite is to affect the zeolite, located in the working chamber, the electromagnetic field of the microwave range using a source of microwave energy. In the process of exposure, the vapor-gas mixture formed in the working chamber during microwave exposure to the zeolite is circulated through the zeolite. Microwave exposure is carried out in a pulsed mode with the energy supplied to the sorbent, determined from the relation:

,

,

, где с – теплоемкость воды, Дж/(кг*К), m – масса воды, кг, содержащейся в сорбенте. where P is the power of the microwave energy source, W, τ is the microwave exposure time, s. The power P of the microwave energy source for one heating cycle of the sorbent is determined from the relationship:

where c is the heat capacity of water, J / (kg * K), m is the mass of water, kg contained in the sorbent.

At power values above the specified limit value, overheating of the sorbent and its rapid destruction is observed. At lower power values, the regeneration time increases significantly. Circulation of the gas-vapor mixture through the working chamber during the microwave treatment ensures temperature equalization by the volume of the zeolite in the working chamber, and the pulsed mode of the specified power effects allows the zeolite to be heated to a temperature that ensures the release of water molecules from the zeolite cells without destroying it and not overheating. .

During the processing of a zeolite in a microwave electromagnetic field, the humidity and pressure of the vapor-gas mixture are monitored by means of a dew point sensor and a pressure sensor, respectively.

The proposed method can be implemented using a device whose functional diagram is presented in FIG.

A device for zeolite regeneration includes a microwave generator 1 with a power source, a working chamber 2 filled with zeolite 3 and connected to a microwave generator through a rectangular waveguide 4 and matching waveguide device 5. At the same time, the control unit 6 is connected to the generator power supply, which provides on / off Microwave generator in a given mode.

To the working chamber 2 pipeline 7 supplying gas to the working chamber with valves 14, as well as a closed loop 8 for circulating gas-vapor mixture, made in the form of a pipeline, one end of which is connected to the upper part of the working chamber 2, and the other to its lower part . The contour 8 is equipped with a vacuum pump 9, which ensures the evaporating of the vapor-gas mixture formed in the working chamber during sorbent regeneration from the upper part of the chamber and its circulation through the closed contour 8 through the sorbent in the working chamber, which makes it possible to equalize the temperature and moisture content over the working chamber height. Such a direction of circulation allows simultaneously cooling the upper layers of the sorbent and heating the lower part of the regeneration column. The closed loop 8 is also equipped with a shut-off valve 15 located between the vacuum pump 9 and the inlet of the gas-vapor mixture into the working chamber 2. In addition, the device includes a pipeline 10 for discharging the vapor-gas mixture to the candle with the shut-off valve 16 connected to the outlet of the vacuum pump 9 and ensuring the vapor-gas discharge the mixture when disconnecting (overlapping) a closed loop by means of valves 15.

As the control unit 6, which controls the mode of operation of the generator, a relay-regulator with a timer connected to the generator power supply can be used. In this case, the microwave generator can be a magnetron, and the power source of the magnetron - a voltage converter at an increased frequency, which supplies the magnetron with high voltage, and the cathode of the magnetron - low. The magnetron can be installed in the middle of the wide wall of a rectangular waveguide 4 at a distance of at least 10 mm from the short-circuited end of the waveguide, exciting electromagnetic waves in the microwave waveguide.

Matching waveguide device 5 is designed to harmonize the microwave generator by the working chamber 2 and is a smooth transition from rectangular to round, providing a reduction in the standing wave ratio of the voltage. The length of the transition must not be less than the wavelength of the generator in free space.

Between the matching device 5 and the working chamber 2 there is an airtight insert 11 made of radio transparent material, which allows microwave electromagnetic radiation to penetrate into the working chamber 2 with zeolite. In one of the embodiments of the invention, the sealed insert is a radio transparent window of quartz glass with seals. In another embodiment, the insert may be made in the form of a conical ceramic insert soldered to the walls of the matching device. With such a sealing system with an overpressure, the junction of ceramics with metal will “work” in compression and will ensure the required tightness. Sealed insert 11 made of radio transparent material protects the magnetron from excessive gas pressure during adsorption and the inclusion of valves. In addition, the sealing protects the magnetron from low pressure in the process of regeneration and desorption of sorbents in the working chamber.

The device also contains a dew point sensor 12 connected to circuit 8, indicating the need for regeneration. In addition, the device may contain a pressure sensor 13 located at the outlet of the vapor-gas mixture from the working chamber 2.

The proposed device works as follows.

The signal from the dew point sensor 12, the operator learns about the need to regenerate the sorbent.

Before the start of regeneration, the tightness of the seals is checked, for which they shut off the valve 14, and the pressure inside the chamber should not decrease; as well as check the shut-off equipment of the installation (with the valves 15, 16 and 17 closed).

, где Р – мощность генератора СВЧ энергии, Вт, τ – время, с. To supply natural gas to the working chamber 2, open the valve 14 and fill the working chamber 2 with pressurized gas, after which the valve 14 is closed. Using a dew point sensor 9, measure the dew point temperature. Moreover, if the dew point temperature is higher than the allowable one, the regeneration process begins. To do this, relieve the pressure in the working chamber to atmospheric by opening the valve 16 (gas discharge to the candle). Next, close the valve 16 and open the valve 15, turn on the vacuum pump 12, as a result of which the vapor-gas mixture formed in the working chamber begins to circulate in a closed loop 8, and turn on the microwave generator 1 with the power source, thus performing a microwave effect on the working chamber zeolite 3 in the process of circulation of the gas mixture. At the same time through the control unit 6 set the pulse mode of the generator, in which the exposure to microwave energy is carried out in a pulsed mode with the energy supplied to the sorbent, defined by the ratio:

where P is the power of the microwave energy generator, W, τ is the time, s.

, где с – теплоемкость воды Дж/(кг*К), m – масса воды, кг, содержащейся в сорбенте. The power P of the microwave energy generator for one heating cycle of the sorbent is determined from the relationship:

where c is the heat capacity of water J / (kg * K), m is the mass of water, kg contained in the sorbent.

Using a microwave energy generator, the zeolite is heated to the temperature of water evaporation (the “heating” mode — section 1-2 in FIG. 2). As a result, the zeolite is heated to about 100 ° C. In the process of operation, the devices control the pressure in the working chamber 2 by means of the sensor 13. With the beginning of the pressure growth in the working chamber (over 1.1 atmospheres), the mode of the generator is changed to “drying”, which removes unbound water. In this case, the pulse effect is carried out with an energy that is 2 times less than in the “heating” mode. In this case, the heating rate of the zeolite decreases, since along with the heating process, the fraction of evaporation increases, which leads to the cooling of the zeolite. The temperature of the zeolite in this mode is maintained in the range of about 100 to 200 ° C (section 2-3 in Figure 2).

When the pressure in the working chamber is normalized (the pressure does not change), the gas-vapor mixture is discharged to the candle through the vacuum pump 9, opening the valve 16 and closing the valve 15 (turning off the closed loop 8). In this case, the mode of exposure to microwave energy on the working chamber is changed to the "regeneration" mode (section 3-4 in Figure 2), during which the removal of bound water occurs. The energy supplied in this mode to the working chamber is 0.3-0.4 of the energy supplied to the working chamber in the “heating” mode. The temperature of the zeolite in the “regeneration” mode can exceed 200 ° С (but not more than 350 ° С).

Switching modes is carried out according to the programmed timer, which allows you to set different modes of the generator and switch them both at the operator’s command and in automatic mode.

With the help of a timer, the operation time of the microwave energy source (magnetron) from 60 to 300 s, the pause time from 10 to 50 s can be set. In this case, the pulse effect can be carried out for 3600-7200 s. The time of pauses and the operation of the magnetron is selected on the basis of the mode (“heating”, “drying”, “regeneration”) and the grade of zeolite in the working chamber.

When the pressure reaches the minimum value, indicating evaporation of moisture and the end of the regeneration process, the microwave energy generator 1 with the power source is turned off.

Pipeline 18 dried gas is supplied to the dew point sensor. If the dew point temperature satisfies the requirements, for example, it reaches -70 ° C, then opening the valve 17, the gas is supplied, for example, to a storage bin, from which gas is supplied to open / close external valves (stop valves). This is done at the end of the regeneration to ensure that the properties of the zeolite are restored.

The programmed timer allows you to set different modes of operation of the generator and switch them both at the operator’s command and in automatic mode.

Pauses in the operation of the microwave generator are necessary to equalize the temperature and humidity in the sorbent, to prevent local overheating of the sorbent, as well as to maintain a given heating rate to reduce the internal stresses in the sorbent.

Practical implementation example

Was carried out the regeneration process of the zeolite brand NaA in the proposed device.

A magnetron with a power of 850 W was used as a source of microwave energy. The magnetron was installed in a rectangular waveguide with a cross section of 90 × 45 mm in the middle of its wide wall at a distance of 30 mm from the short-circuited end of the waveguide. The diameter of the working chamber was 149 mm, the height of the zeolite layer was 200 mm. The matching waveguide device was a smooth transition 200 mm long from a rectangular section to a circular one with a diameter of 149 mm. The working chamber was filled with a zeolite brand NaA, the diameter of the zeolite granules was 2 mm. As a control unit, a relay-controller was used with a timer brand OVEN UT-24. Pipeline into the working chamber 2 led natural gas. When the dew point temperature reached -50 ° C, the regeneration process began, having previously released pressure in the working chamber to atmospheric. With the help of a vacuum pump, the vapor-gas mixture was circulated in a closed loop through the volume of the working chamber during heating of the zeolite. With the help of a timer, the time of operation of the magnetron was set to 50 s, the pause time 10 s. Impulse exposure was carried out for 5400 s. As a result, the energy supplied to the zeolite was 1063 Wh (with a microwave generator power of 850 W).

Using a pressure gauge, the pressure in the working chamber was monitored. When the pressure reached over 1.05 atmospheres, the generator operation mode was changed to “drying”; in this mode, the pause time in the generator operation was 40% of its operating time: 25 s operation time, 10 s pause time, and the exposure was carried out during 3600 s. The input energy was 607 Wh.

When the pressure reached 1.1 atmospheric, the mode of action of microwave energy on the working chamber was changed to the “regeneration” mode, and the vacuum pump started pumping out the vapor-gas medium from the working chamber (after switching on the taps, opening 16 and closing 15). In the “regeneration” mode, the generator operating time was 20 s, the pause time was 10 s, and the effect was carried out for 1200 s. The input energy was 567 kWh. The temperature of the zeolite in this mode exceeded 200 ° C.

When the pressure reached the minimum values (-1 atm), indicating evaporation of moisture, the microwave energy generator 1 with the power source was turned off and the regeneration process was completed.

The moisture content in the zeolite was calculated by the formula:

,

,

where W is the moisture content in% mass .; m of _{water + pr} is the mass of water and impurities in the sorbent; m _total - the mass of dry sorbent.

The change in temperature and humidity of the zeolite from the time of its heating is presented in Figure 2. In accordance with Figure 2, in the area 1-2, the temperature of the zeolite grows almost linearly, there are almost no mass transfer processes, the moisture content does not change. Upon reaching a temperature of 100 ° C (point 2), evaporation of unbound water begins, and evaporation causes the zeolite to cool and the heating rate drops. During the temperature change in section 2-3, the kinetics of heating determine the heat generation processes in zeolite and water vapor, evaporation (separation of water molecules) from the zeolite surface, condensation of vapor on the “cold” surfaces of the working chamber and zeolite. Moisture content falls nonlinearly. When the temperature reaches point 3 (200 ° C), only bound water remains in the zeolite, the heating rate increases, and the mass transfer decreases. The moisture content decreases almost linearly. Above the temperature of point 4 (320 ° C) it is impractical to heat the zeolite, since it is difficult to control the heating rate and the zeolite can overheat and lose its sorption properties.

As a result of the implementation of the above-described method, during heat treatment of the zeolite in the working chamber with a microwave power supply, a dew point temperature of -70 ° C was reached, which makes it possible to safely operate the gas shut-off valve. At the same time, the regeneration time was reduced by 1.5 times relative to the drying of the zeolite by the conductive-convective method.

Thus, the invention allows to restore the adsorption properties of zeolite in the drying columns. The pulsed mode of microwave exposure in the process of circulation of the gas-vapor mixture allows you to remove water from the zeolite, without destroying it.

Claims (7)

1. Method of regeneration of zeolite, including the effect on the zeolite located in the working chamber, the electromagnetic field of the microwave range using a source of microwave energy, characterized in that during the treatment process the vapor-gas mixture formed in the working chamber during the microwave effect on the zeolite is circulated , through the zeolite, and the microwave effect is carried out in a pulsed mode with the energy supplied to the sorbent, determined from the relation:

, where P is the power of the microwave energy source, W, τ is the time of microwave exposure, s; the power P of the microwave energy source for one cycle of heating the sorbent is determined from the relation:

where c is the heat capacity of water, m is the mass of water contained in the sorbent. 2. A device for zeolite regeneration, including a source of microwave energy, a working chamber for accommodating a zeolite, a waveguide with a matching device, connecting a source of microwave energy and a working chamber, while the working chamber is equipped with an input for supplying natural gas to the working chamber and a gas outlet to stop valves, characterized in that it contains a closed loop for circulation of the vapor-gas mixture formed in the working chamber during the regeneration of the zeolite through the sorbent, made in the form of a pipeline connected to the upper and lower parts working chamber; pump and valves installed on the pipeline; a control unit connected to the source of microwave energy and ensuring its operation in a given mode; at the same time, the matching device is made in the form of a smooth transition from a rectangular section to a circular one and contains a hermetic insert made of radio transparent material to protect the source of microwave energy from pressure changes in the working chamber. 3. The device according to claim 2, characterized in that the control unit is made in the form of a relay-controller with a timer. 4. The device according to claim 2, characterized in that it contains a dew point sensor mounted in a closed loop at the outlet of the vapor-gas mixture from the working chamber. 5. The device according to claim 2, characterized in that it contains a pressure sensor connected to a closed circuit at the outlet of the vapor-gas mixture from the working chamber.

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