JP2012035163A - Pretreatment apparatus for membrane separation, and membrane separation method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pretreatment apparatus for membrane separation having zeolite membranes with an elongated service life, and a membrane separation method using the same.SOLUTION: There is provided a membrane separation method for separating a treating object consisting of a liquid mixture or a gaseous mixture by bringing the treating object into contact with the zeolite membranes. Prior to bringing the treating object into contact with the zeolite membranes, the zeolite particles filled in the pretreatment apparatus 3 independent from membrane separation apparatuses 11-16 having the zeolite membranes are brought into contact with the treating object.

Description

  The present invention relates to a pretreatment device for membrane separation that extends the life of a zeolite membrane and a membrane separation method using the same.

  In recent years, membrane separation methods have been actively adopted as a method for separating water from bioethanol containing impurities such as water and purifying high-purity ethanol, and a method for separating and removing harmful substances such as PCBs from contaminated liquids. ing. As a membrane separation method for treating a liquid mixture or a gas mixture, the liquid mixture is brought into contact with one side (supply side) of the separation membrane, and the opposite side (permeation side) is decompressed, whereby a specific liquid (permeation substance) is obtained. Vapor permeation method that vaporizes and separates (pervaporation method), vapor permeation method that supplies a gas mixture or liquid mixture in vapor state, contacts the separation membrane, depressurizes the permeate side and separates specific vapor (See, for example, Patent Document 1).

  In commercial plants for these membrane separation methods, zeolite membranes excellent in heat resistance and chemical resistance are formed in a cylindrical shape, and a membrane module in which a large number of them are arranged is a unit device for membrane separation means. Are connected in series to increase the treatment capacity (permeation flux) while maintaining the selective permeation performance (permeate concentration) extremely high. Thus, in a membrane separation apparatus in which a plurality of membrane modules are connected in series, the brown coloration due to the adhesion of impurities is more conspicuous in the zeolite membrane arranged in the leading membrane module. It was found for the first time by the present invention that the pressure loss finally increases and the zeolite membrane is easily broken. The number of zeolite membranes arranged in one membrane module is about 38 to 2250, and exchanging a large number of expensive zeolite membranes in a relatively short period of time is costly and requires a lot of labor. There is concern about an increase in processing costs.

  Note that, as a pretreatment of the membrane separation operation, the life of the zeolite membrane could not be extended even if the object to be treated was filtered with a prefilter or subjected to an ion exchange treatment.

JP 2006-263561 A

  An object of the present invention is to provide a pretreatment device for membrane separation that extends the life of a zeolite membrane and a membrane separation method using the same.

  The membrane separation method of the present invention that achieves the above object is a membrane separation method in which an object to be treated consisting of a liquid mixture or a gas mixture is brought into contact with a zeolite membrane for separation, before the object to be treated is brought into contact with the zeolite membrane. Furthermore, the zeolite particles filled in the pretreatment device independent of the membrane separation device having the zeolite membrane are brought into contact with the object to be treated.

  The pretreatment device for membrane separation of the present invention is a pretreatment device that is independently arranged upstream of a membrane separation device that separates an object to be treated comprising a liquid mixture or a gas mixture by contacting the zeolite membrane. The pretreatment apparatus has a main body filled with an inlet and an outlet of the object to be processed and zeolite particles, so that the object to be processed supplied from the inlet to the main body comes into contact with the zeolite particles. And a control means for adjusting the residence time of the object to be processed in the main body.

  In the membrane separation method of the present invention, before the object to be treated such as a liquid mixture is brought into contact with the zeolite membrane and separated, the zeolite particles which are inexpensive and easy to exchange are brought into contact with the object to be treated. A component capable of adhering to the existing zeolite or a component that causes damage such as dealumination is caused to act on the zeolite particles and consumed. As a result, there is no trace component affecting the zeolite in the object to be treated, or the content thereof is reduced, so that the trace component is prevented from adhering to the zeolite membrane in the membrane module and dealumination is caused, The life of the film can be extended.

The zeolite particles are preferably zeolites having at least one cation selected from Na, K, Ca, Ba, and Mn. The zeolite particles have high durability, and the zeolite particles have Na ⁺ , K ⁺ Etc. can flow into the membrane module together with the object to be treated to protect the zeolite membrane.

  When the membrane separator is configured by connecting a plurality of membrane modules having zeolite membranes in series, the time during which the object to be in contact with the zeolite particles is the object to be treated in the membrane module arranged first. The residence time is preferably set to be longer than the above, and the components affecting the zeolite in the object to be treated can be sufficiently reduced.

  When the object to be treated is heated or vaporized by the heating means and then supplied to the membrane separation apparatus, the object to be treated is transferred to the inside of the heating means or from the heating means to the membrane separation apparatus before entering the heating means. The object to be treated can be brought into contact with the zeolite particles at any position during the period.

  The pretreatment device for membrane separation according to the present invention is disposed independently upstream of a membrane separation device for bringing a target object such as a liquid mixture into contact with a zeolite membrane and separating the target, and an inlet, an outlet and an outlet of the target object, and It has a main body filled with zeolite particles, and is configured so that the object to be processed supplied from the inflow port to the main body contacts the zeolite particles, and adjusts the residence time of the object to be processed in the main body. Because it has a control means, the components that can adhere to the zeolite present in the object to be treated and the components that cause damage such as dealumination are acted on and consumed by the zeolite particles, so there are no trace components affecting the zeolite. Alternatively, the content can be sufficiently reduced. Thereby, it can suppress that a trace component adheres to dealt with in the zeolite membrane in the membrane module arrange | positioned downstream, or dealumination takes place, and can extend a lifetime of a zeolite membrane.

  The zeolite particles filled in the pretreatment device for membrane separation may be zeolite having at least one cation selected from Na, K, Ca, Ba, and Mn.

It is explanatory drawing of the process flow which shows an example of embodiment of the membrane separation method of this invention. It is a cross-sectional schematic diagram which illustrates the membrane module which comprises the membrane separation method of this invention. It is a cross-sectional schematic diagram which illustrates the mixing means which comprises the pre-processing apparatus of this invention. It is a cross-sectional schematic diagram which illustrates the other mixing means which comprises the pre-processing apparatus of this invention.

  The present invention is described in detail below.

  FIG. 1 is an explanatory diagram of a process flow showing an example of an embodiment when the membrane separation method of the present invention is applied to a vapor permeation method. Hereinafter, as an example, a case where water is selectively removed from a liquid mixture of an ethanol / water mixture system will be described. However, the membrane separation method of the present invention is not limited by the process flow, and other than the ethanol / water mixture system. The present invention can be effectively applied to a liquid mixture and a pervaporation method.

  In FIG. 1, a vapor permeation membrane separation system to which the membrane separation method of the present invention is applied mainly comprises heating means comprising an evaporator 2, pretreatment means comprising a pretreatment device 3, membrane modules 11-16, and It includes a membrane separation means comprising a condenser 4. The object to be processed is supplied from the supply tank 1 to the evaporator 2 through the plurality of heat exchangers 8 by the supply pump unit 7. The object to be processed is heated and vaporized by heating means represented by the evaporator 2. In addition to the evaporator, examples of the heating means include a distillation tower, a vapor compressor, an infrared heater, a dielectric heating device, and the like, and any of them may be arranged. In the case of a membrane separation system by a pervaporation method, a heat exchanger, a heater, a dielectric heater, a laser heater, or the like can be used instead of the evaporator.

  The to-be-processed object vaporized with the evaporator 2 is supplied to the pre-processing apparatus 3 independent from the membrane separator, and the trace component which affects a zeolite is removed by contact with a zeolite particle. The to-be-processed object processed with the pre-processing apparatus 3 is supplied to the membrane separator with which the membrane modules 11-16 were connected in series. In the illustrated example, six membrane modules 11 to 16 are connected in series, but the number of membrane modules is not limited to this, and can be increased or decreased according to required performance. The membrane modules 11 to 16 can have the same structure.

  FIG. 2 is a cross-sectional view schematically illustrating the structure of the membrane modules 11 to 16. The membrane module 11 includes a steam supply chamber 21 and permeate steam chambers 22 arranged on both sides, and the steam supply chamber 21 and the permeate steam chamber 22 are supported by a tube plate 26 and a tube plate 26 on both sides. The structure is separated by a long cylindrical zeolite membrane 25. An object to be processed that has been processed by the pretreatment device 3 is supplied as supply steam 20 to one end of the steam supply chamber 21. The supply steam 20 is induced by a baffle 27 and contacts a large number of zeolite membranes 25 as indicated by white arrows in the figure. The zeolite membrane 25 is designed to be selectively permeable to water, and only water vapor passes through the zeolite membrane 25 and is separated from the supply vapor 20. The supply steam 20 flows outside the zeolite membrane 25, flows out from the other end as non-permeate steam 24, and is supplied to the downstream membrane module 12. This is repeated a plurality of times, and the non-permeated vapor flowing out from the most downstream membrane module 12 is high-purity ethanol vapor from which water vapor has been separated and removed. This high purity ethanol is stored in the product tank 5 through the heat exchanger 8 and the pressure control valve 9.

  On the other hand, the inside of the permeate vapor chamber 22 and the long cylindrical zeolite membrane 25 communicating therewith is decompressed. As a result, among the ethanol / water mixed system vapors in contact with the outside of the zeolite membrane 25, only water vapor permeates into the inside of the zeolite membrane 25, thereby being separated as the permeated vapor 23. The permeated steam 23 is condensed into water by the condenser 4 and collected in the condensed water tank 6. In FIG. 2, the permeate vapor chambers 22 are installed at both ends of the membrane module 11, but both the permeate vapor chambers 22 communicate with the condenser 4 as shown in FIG. 1.

  In recent years, in a membrane separation system in which a plurality of membrane modules are connected in series, an upstream membrane module, in particular, the first membrane module 11 is more likely to turn brown due to the small amount of trace components in the non-treated material adhering to the zeolite membrane. It was found. In the first membrane module 11 as well, it can be seen that the zeolite membrane disposed near the inlet of the supply steam 20 has more deposits and is more strongly colored to brown. When these deposits were analyzed, it was confirmed that they contained trace amounts of sulfate ions, nitrate ions, chloride ions, sodium, iron and the like. The fact that such a trace component adheres to the zeolite membrane is likely to cause dealumination of the zeolite due to the presence of both protons (hydrogen ions) and water on the surface of the zeolite membrane. It is considered that the dealumination of crystals occurs due to the dealumination of zeolite, the pores of the zeolite membrane are blocked, and the pressure loss increases. Further, when the crystal collapses, the zeolite membrane is destroyed, and a hole penetrating the membrane is formed, and there is a concern that the membrane separation performance is significantly lowered. For this reason, the lifetime of the zeolite membrane is shortened, and an expensive zeolite membrane must be replaced in a short period of time, and the number of zeolite membranes arranged in one membrane module is as large as about 38 to 2250. Therefore, since much time and labor are required for the replacement work, there is a concern that the processing cost of the membrane separation operation becomes high.

  In addition, as a pretreatment of the membrane separation operation, the object to be treated was filtered with a prefilter or subjected to an ion exchange treatment to remove trace impurity parts in the object to be treated. The pretreatment could not extend the life of the zeolite membrane.

  On the other hand, in the present invention, before the object to be treated is brought into contact with the zeolite membrane, it is brought into contact with inexpensive and easily exchangeable zeolite particles. That is, the pretreatment device 3 is filled with zeolite particles so that a trace component affecting the zeolite contained in the object to be treated acts on the zeolite particles in advance. As a result, trace components that affect the zeolite are consumed and are no longer present in the object to be treated, or the amount thereof is greatly reduced. In other words, the object to be treated discharged from the pretreatment device 3 has a reduced content of trace components that affect the zeolite as much as possible. Therefore, it adheres to the zeolite membrane or is damaged by dealumination. The life of the zeolite membrane can be extended without being affected.

  Here, the residence time of the object to be treated in the pretreatment device 3 should be made sufficiently long, and preferably the object to be treated is in contact with the zeolite particles during the residence time of the object to be treated in the first arranged membrane module. Like that. Thereby, the quantity of the trace component which affects the zeolite which exists in a to-be-processed object can be decreased as much as possible. In addition, the lifetime of the zeolite membrane in the membrane module arranged at least first can be extended to the same level or more as the lifetime of the zeolite membrane in the second membrane module of the membrane separation apparatus without the pretreatment device.

  The position where the pretreatment device 3 is arranged is not particularly limited as long as the above-described effects can be obtained. In FIG. 1, it arrange | positions between the heating means which consists of the evaporator 2, and the 1st membrane module 11, However, It is not limited to this, You may arrange | position in the upstream of a heating means or the inside of a heating means.

The zeolite particles filled in the pretreatment device 3 may be any zeolite that is usually used in membrane separation methods, and the zeolite structure and composition are not limited. The zeolite particles are preferably those formed of zeolite having at least one cation selected from Na, K, Ca, Ba, and Mn in the lattice. In particular, zeolite particles containing at least one cation selected from Na ⁺ and K ⁺ are preferred, and particles made of NaA-type zeolite containing Na ⁺ are particularly preferred. By having cations such as Na ^+, durability against a small amount of protons contained in the object to be treated is increased. Further, when dealumination progresses and the zeolite crystal collapses, cations such as Na ⁺ are released and supplied to the membrane module along with the object to be treated. It is expected to play a role in inhibiting and protecting the zeolite membrane.

  The pretreatment device of the present invention is independently arranged upstream of a membrane separation device that separates an object to be treated comprising a liquid mixture or a gas mixture by contacting the zeolite membrane. This pretreatment apparatus has an inlet, an outlet, and a main body part of an object to be processed, and the main body part is configured to fill the zeolite particles and to distribute the object to be processed. As a result, the to-be-treated material introduced into the pretreatment apparatus is consumed by the trace components that come into contact with the zeolite particles and affect the zeolite present in the to-be-treated material while flowing through the main body from the inflow port and discharging from the outflow port. Is done.

  The pretreatment apparatus of the present invention has a control means for adjusting the residence time of the object to be processed in the main body. The control means for adjusting the residence time is not particularly limited, and examples thereof include a flow control valve, a baffle, a workpiece circulation pump, a simulated moving bed, and a stirring means. The control means for adjusting the residence time can sufficiently lengthen the residence time of the object to be processed in the pretreatment device, preferably during the residence time of the object to be processed in the membrane module arranged first, It can adjust so that a to-be-processed object may contact a zeolite particle. Thereby, the quantity of the trace component which affects the zeolite which exists in a to-be-processed object is made as small as possible.

  The zeolite particles to be filled in the pretreatment device are preferably formed of zeolite having at least one cation selected from Na, K, Ca, Ba, and Mn in the lattice. The form of the zeolite particles is not particularly limited as long as it is inexpensive and can be easily exchanged. For example, zeolite seed crystals, zeolite powder, molecular sieves (pellets), NaA-type zeolite membranes broken pieces or pulverized products thereof, etc. It can be illustrated.

  In the present invention, a normal adsorption device, ion exchange device, cation supply device or the like can be used as the pretreatment device. As an adsorption device, a zeolite mixture is mixed with a liquid mixture to remove a trace component affecting the zeolite, and a zeolite particle is filled into the device, and the liquid mixture or gas mixture is passed through the device. Examples include a fixed bed type adsorption device, a moving bed type adsorption device, and a fluidized bed type adsorption device that perform adsorption. Moreover, when using an ion exchange apparatus and a cation supply apparatus, the zeolite particle is filled in the space where the liquid mixture or gas mixture in these apparatuses flows, and the object to be treated can be brought into contact with the zeolite particles.

  In this invention, when a to-be-processed object is a gas mixture, it can be used combining a mixing means and a gas-solid separation means as a pre-processing apparatus. As the mixing means, for example, a gas-solid mixing apparatus as shown in FIGS.

  In FIG. 3, the mixing means 31 has an inlet 32 and an outlet 33, and zeolite particles 35 are accommodated between the porous bodies 34 arranged at the upper part and the lower part of the main body part. The gas mixture is introduced from the inflow port 32 and is mixed with and contacted with the zeolite particles 35 in the main body, so that trace components that affect the zeolite present in the gas mixture are consumed and removed. The gas mixture thus pretreated is discharged from the outlet 33 and supplied to the downstream gas-solid separation means. Note that a door 36 that can be opened and closed is provided in the main body, and the zeolite particles 35 can be easily exchanged.

  In FIG. 4, the mixing means 41 has an inflow port 42, an outflow port 43 and a zeolite particle supply port 44 in a substantially cylindrical main body. The gas mixture is introduced from the inflow port 42 which is eccentric from the center line of the cross section and is directed in the tangential direction so as to form a swirl flow v toward the main body, and flows in a spiral manner in the main body. The zeolite particles 45 are supplied from the zeolite particle supply port 44 to the swirl flow v of the gas mixture, and are mixed and contacted. Thereby, trace components that affect the zeolite present in the gas mixture are consumed and removed. The gas mixture thus pretreated is discharged from the outlet 43 along with the zeolite particles, and is supplied to the downstream gas-solid separation means to separate the zeolite particles. Note that the zeolite particle supply port 44 may be configured by a diffuser to promote mixing of the zeolite particles.

  Moreover, as a gas-solid separation means, a bag filter, a cyclone, a sedimentation tank etc. can be illustrated, for example.

  The pretreatment apparatus of the present invention is used for pretreatment of any membrane separation operation of a pervaporation method, a vapor permeation method and a gas phase separation method using a zeolite membrane for a liquid mixture or a gas mixture. Can do. By using this pretreatment device, the life of the zeolite membrane can be extended.

  The liquid mixture or gas mixture to be separated in the present invention is not particularly limited. For example, water and a mixture of alcohols such as methanol, ethanol, and propanol or carboxylic acids such as acetic acid, propionic acid, and butyric acid, acetone, and methyl ethyl ketone Such as ketones, carbon tetrachloride, halogenated hydrocarbons such as trichloroethylene, or organic solutions such as the carboxylic acids, and mixtures of the alcohols, the alcohols or carboxylic acids, and aromatics such as benzene and cyclohexane And a mixture thereof. In particular, in the dehydration separation of water-ethanol, water-propanol, water-acetic acid and the like, the treatment capacity, that is, the total permeation amount and the separation factor is high, and high separation performance can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited by these Examples.

Example 1
An isopropanol solution containing 10% by weight of water was prepared as a liquid mixture. Dichloroethane was added to the isopropanol solution as a trace component affecting the zeolite so as to have a concentration of 200 ppm. This was heated to 135 ° C. to decompose dichloroethane, and then cooled to room temperature. The pH of the liquid mixture before heating was pH 7.5 at room temperature, and the pH of the object heated to 135 ° C. was lowered to about pH 4.7.

  A 200 mesh under NaA-type zeolite seed crystal (zeolite particles) was added in an equal weight to dichloroethane and stirred at room temperature for 8 hours. The pH of the object to be treated after stirring rose to about pH 7.8 at room temperature. The NaA-type zeolite particles and the object to be treated were subjected to dehydration purification by a vapor permeation method using a zeolite membrane. As the zeolite membrane, a membrane separation apparatus using one cylindrical type made of NaA-type zeolite having an outer diameter of 12 mm and a length of 200 mm was used. At this time, the water concentration, water flux, and isopropanol (IPA) flux of the permeate permeated through the zeolite membrane were measured, and the changes with time were evaluated and shown as “Example 1” in Table 1.

Comparative Example 1
Except that the seed crystals of NaA-type zeolite were not added, the change in membrane performance over time was evaluated when dehydrated and purified by the same vapor permeation method using the workpiece prepared in the same manner as in Example 1. The results are shown in “Comparative Example 1” in Table 1.

  From these results, in the membrane separation method of Example 1, no change in the appearance of the zeolite membrane was observed, the flux of the permeate was ensured until 297 hours, and no decrease in the water concentration in the permeate was observed. On the other hand, in the membrane separation method of Comparative Example 1 in which the object to be treated was not previously contacted with the zeolite particles, the appearance of the zeolite membrane was changed from brown to brown with the passage of time from the initial white color, and the flux of the permeate was changed over time. It decreased with progress, and it was confirmed that the water concentration in the permeate decreases significantly after 154 hours. As a result, it was confirmed that the membrane separation method of Comparative Example 1 was mixed with isopropanol (IPA) in the permeate as time passed, and the membrane separation performance deteriorated.

DESCRIPTION OF SYMBOLS 1 Supply tank 2 Evaporator 3 Pretreatment apparatus 4 Condenser 5 Product tank 6 Condensed water tank 7 Supply pump 7 Regenerator 8 Heat exchanger 9 Pressure control valve 11-16 Membrane module 20 Supply steam 21 Steam supply chamber 22 Permeation steam chamber 23 Permeated vapor 24 Non-permeated vapor 25 Zeolite membrane 26 Tube plate 27 Baffle

Claims (8)

  A membrane separation method for separating an object to be treated comprising a liquid mixture or a gas mixture in contact with a zeolite membrane, and before the object to be treated is brought into contact with the zeolite membrane, independent of the membrane separation apparatus having the zeolite membrane. A membrane separation method characterized in that the zeolite particles filled in a pretreatment device are brought into contact with the object to be treated.   The membrane separation method according to claim 1, wherein the zeolite particles are made of zeolite having at least one kind of cation selected from Na, K, Ca, Ba, and Mn.   When the membrane separation device is configured by connecting a plurality of membrane modules having a zeolite membrane in series, the object to be treated is longer than the residence time of the object to be treated in the first arranged membrane module. 3. The membrane separation method according to claim 1, wherein the membrane separation method is in contact with zeolite particles.   When the object to be treated is heated or vaporized by the heating means and then supplied to the membrane separation apparatus, the object to be treated comes into contact with the zeolite particles while being transferred from the heating means to the membrane separation apparatus. The membrane separation method according to claim 1, 2, or 3.   The object to be treated comes into contact with the zeolite particles inside the heating means when the object to be treated is heated or vaporized by a heating means and then supplied to the membrane separation device. The membrane separation method according to 1, 2 or 3.   When the object to be treated is heated or vaporized by a heating means and then supplied to the membrane separation device, the object to be treated comes into contact with the zeolite particles before entering the heating means. Item 4. The membrane separation method according to Item 1, 2 or 3.   A pretreatment device that is independently disposed upstream of a membrane separation device that separates a treatment object made of a liquid mixture or a gas mixture into contact with a zeolite membrane, the pretreatment device comprising a flow of the treatment object An inlet, an outlet, and a main body filled with zeolite particles, and the target object supplied from the inlet to the main body is configured to come into contact with the zeolite particles; A pretreatment device for membrane separation, comprising control means for adjusting the residence time.   The pretreatment apparatus for membrane separation according to claim 7, wherein the zeolite particles are made of zeolite having at least one cation selected from Na, K, Ca, Ba, and Mn.

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