MXPA97006200A - Va permeation system - Google Patents

Abstract

The present invention relates to: A process for the removal of a first vapor from a fluid feed stream containing a mixture of vapors, the process comprising the steps of: (a) Providing a membrane having a feed side and a side of permeation material, and which is selectively permeable to the first vapor, (b) directing the fluid feed stream to the feed side of the membrane and withdrawing a stream of the spent retention material in the first vapor and withdrawing a stream of the permeation material enriched in the first vapor from the side of the permeation material enriched in the first vapor from the side of the permeation material of the membrane, and (c) directing a gas phase sweep current to the side of the permeation material of the membrane, the sweep current flowing in countercurrent with respect to the flow of the fluid feed stream, wherein the pressure ratio Partially of the first vapor in the sweep stream in relation to the partial pressure of the first vapor in the holding material stream is less than 0.9, wherein steam and the vapor mixture comprise compounds with boiling points above 0 ° C, but lower at 200 ° C at an atmosphere of pressure

Description

"STEAM PERMEATION SYSTEM" BACKGROUND OF THE INVENTION Steam permeation is a membrane-based process that can be used to separate mixtures of vapors. In one example of this process, a vaporous mixture of Vapor A and Vapor B is fed to the supply side of a membrane, while a vacuum pump or a gaseous sweep current, usually in combination with a condenser, maintains a pressure Partially low of Vapor B on the side of the membrane permeation material to provide a chemical potential gradient of Vapor B through the membrane. Primarily, Vapor B and a certain amount of Vapor A are transported to the side of the permeation material of the membrane to form a vapor phase permeation material. The key to the development of the efficient low-cost steam permeation process is the method used to maintain a low partial pressure of Vapor B on the side of the membrane permeation material. The prior art describes the application of a vacuum to the side of the permeation material of the membrane, reducing the total pressure of the permeation material, thereby reducing the partial pressure of Steam B on the side of the permeation material of the membrane. However, in many cases, the cost and complexity of the vacuum system makes this impractical. Also, the vacuum-driven system often has a leak, allowing air to enter the system. For many separations, especially those with oxygen-sensitive compounds or highly flammable compounds, the presence of oxygen is undesirable or dangerous. Therefore, alternative methods are desirable. U.S. Patent No. 4,978,430 discloses a steam permeation process for dehydrating and concentrating an aqueous solution containing an organic compound, whereby the permeation material is maintained under reduced pressure or a "dry inert gas" can be used to reduce the partial pressure. U.S. Patent No. 5,226,932 discloses a membrane process for drying non-condensable gases such as air, nitrogen, carbon dioxide or ammonia using low vacuum levels and a dry countercurrent sweep gas on the permeation material side of the membrane. U.S. Patent No. 5,108,464 also discloses a membrane process for drying non-condensable gases such as air, lower hydrocarbons and acid gases using a countercurrent sweep gas, wherein the sweep gas can be introduced into the gas. side of the permeation material of a hollow fiber membrane module at the end of the retention material, such that it mixes with the permeation material as it passes along the membrane and then exits at the end of the membrane. the power of the module. U.S. Patent No. 5,034,025 discloses a membrane process for drying non-condensable gases containing water vapor, such as air, carbon dioxide or natural gas, which includes maintaining a partial pressure differential of water vapor through the membrane, contacting the lower pressure side and the permeation material of the membrane with a dry organic condensable scavenging gas which is immiscible with water, preferably in a countercurrent flow mode, collecting and condensing the scavenging gas which contains the permeated water, thus forming a two-phase aqueous-organic liquid condensate, and then separating the organic and aqueous phases. As is evident from what has been mentioned above, the prior art has suggested the use of a gaseous sweep current in countercurrent on the permeation side of the separation membrane. However, guidelines have not been suggested regarding the properties that this sweeping gas should have. It has been found that, in order to use a gas sweeping current in countercurrent on the permeation side which is practical, it must have a low concentration or a low partial pressure of Vapor B on the permeation side of the membrane. In addition, the method of generating the sweep gas containing low concentration of Vapor B must be carefully selected in order to maintain a high-performance, efficient, low-cost system.

COMPENDIUM OF THE INVENTION The present invention comprises a vapor permeation process for the selective removal of a first motor from a feed stream containing a mixture of vapors, comprising the steps of: (a) providing a membrane having feed and material sides permeation feed; (b) directing the feed stream to the feed side of the membrane and removing a current of the spent retention material in the first steam from the feed side of the membrane and removing a stream of permeation material enriched in the first steam from the side of the permeation material of the membrane; and (c) directing a gas phase sweep current to the side of the membrane permeation material the sweep current flows countercurrent with respect to the flow of the feed stream, wherein the partial pressure of the first vapor in the stream The sweep is low enough so that the ratio of the partial pressure of the first vapor in the sweep current to the partial pressure of the first vapor in the holding stream is less than 0.9. An aspect closely related to the invention is the method used to generate the sweep current. The invention includes methods selected for membrane separation, absorption, condensation, bottled purified gases, and gas produced by the evaporation of a liquefied gas. Another closely related aspect of the invention is the use of a vapor removal process in the permeation material stream that is enriched in the first vapor. The steam removal process is selected from condensation, absorption and membrane separation. The steam removal process can also be used to produce an exhausted gas phase stream that can be recycled back to the steam permeation process, which is introduced as the scavenging gas in step (c).

BRIEF DESCRIPTION OF THE DIFFERENT VIEWS OF THE DRAWINGS Figures 1 to 10 are schematic showing alternative embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION For purposes of the present invention, the following definitions are used. Vapors: fluids in the gas phase lower than their critical temperatures and which have a boiling temperature higher than -100 ° C. Sweeping: gas phase fluid, that is, not a liquid at operating conditions of the process; it can be a vapor, as long as it has a low concentration or a partial pressure of steam B. Steam-rich permeation material B: the partial pressure of Steam B in the permeation material stream divided by the sum of the partial pressure of the Steam B and the partial pressure of Vapor A in the permeation material stream is greater than the same ratio in the feed stream. This term does not necessarily mean that the partial pressure of the Vapor B in the permeation material is greater than the partial pressure of the Vapor B in the feed, since the permeation material also contains the gas of sweep of the gas phase. For illustrative purposes, it is assumed that the feed stream contains two vapors: Vapor A and Vapor B. It is further assumed that the membrane is more permeable to Vapor B than Vapor A. Figure 1 shows the basic process using a membrane to produce a stream of permeation material rich in Vapor B, and a stream of retention material exhausted from Steam B, using a countercurrent sweep current to maintain a low partial pressure in Vapor B on the side of the permeation material of the membrane . Figure 2 shows a process similar to that shown in Figure 1, with the exception of the sweep current being produced by a membrane-based unit. Figure 3 shows a process similar to that shown in Figure 1 with the exception that the sweep current is produced by a hybrid compression / condensation process. Figure 4 shows a process similar to that shown in Figure 1 with the exception that the sweep current is produced by an absorption process. Figure 5 shows a process similar to that shown in Figure 1 with the exception that the sweep current is obtained from bottled purified gas. Figure 6 shows a process similar to that shown in Figure 1, with the exception that the sweep current is produced by the evaporation of a liquefied gas. Figure 7 shows a process similar to that shown in Figure 1, except that the sweep current is produced by directing the vapor permeation material stream rich in Vapor B to a second membrane-based process, producing a stream of material of spent steam retention B that is used as the sweep stream, thereby recycling the gas used for the sweep current. A replenishing gas stream is used to counteract any of the gas losses of the second membrane.

Figure 8 shows a process similar to that shown in Figure 1 with the exception that the sweep current is produced by directing the steam-rich permeation material stream to a compression / condensation process, which produces a non-condensable stream exhausted from Vapor B that is used as the sweep current, thus recycling the gas used for the sweep current. Figure 9 shows a process similar to that shown in Figure 1 with the exception that the sweep current is produced by directing the steam-rich permeation material stream to the absorption process, which produces a depleted steam stream. which is used as the sweep current, thus recycling the gas used for the sweep current. Figure 10 shows a process similar to that shown in Figure 1, with the exception that the sweep current is a gas and a vacuum pump is used in the permeation material streams rich in Vapor B to improve efficiency. It has been found that for the use of a countercurrent sweep current to be effective in the removal of steam, the ratio of the partial pressure of the most permeable vapor in the sweep, with respect to that of the same component in the retention material, must be less than 0.9, preferably less than 0.5. If this partial pressure ratio is greater than 0.9, the driving force for transporting the vapor from the feed side of the membrane to the permeation / sweeping material stream becomes unacceptably low, which in turn leads to regimes of low feed flow to achieve a certain level of purity of the retention material stream. Low feed flow rates mean higher system costs because the increased membrane area is required to treat a given feed rate regime. However, when the partial pressure ratio of the permeation material is less than 0.9, the driving force is high enough to allow reasonable feed flow rates that are used to obtain a purity of the acceptably high retention material, leading to efficient low-cost systems. The temperature of the feed must be greater than its condensation temperature at one atmosphere, which in turn must be higher than the ambient temperature, and especially preferably greater than 40 ° C, while the total feed pressure must be greater than the ambient pressure, and preferably less than 10 atmospheres.

The separation to be achieved by the vapor permeation process of the present invention is especially preferred the removal of water vapor from organic vapors, but can also be applied to the removal of volatile compounds from water, or the separation of organic and inorganic vapor mixtures. In general, the membrane used is selected so that the small component of the feed stream is selectively removed by the membrane; however, the invention need not be limited to this. The volumetric flow of the sweep current in the sweep inlet can be adjusted to provide the desired efficiency. Preferably, the volumetric flow of the sweep current is sufficient to reduce the partial pressure of the most permeable component on the side of the permeation material of the membrane, at the end of the retaining material of the module to less than about 90 percent or lower than the value on the feed side of the membrane, at the end of the module holding material. The amount of sweeping that is used will therefore depend on the operating conditions and the desired concentration of the most permeable component in the stream of the holding material. Generally, the volumetric flow of the sweep current must be at least 0.5 percent of the volumetric flow of the combined mixture on the side of the permeation material. In cases where the desired concentration in the retentate stream is very low and the membrane selectivity is high, the volumetric flow of the sweep current can be 99 percent or more of the volumetric flow of the combined mixture on the side of the permeation material. The sweep current used can be any condensable gas or vapor containing a low concentration of the steam to be removed from the feed stream. For example, in applications where inert gas nitrogen is used to protect a flammable solvent, nitrogen can be used as the sweep stream. Other examples of fluids that can be used as the sweep current include the inert gases argon and helium; hydrogen; air; steam; carbon dioxide; and carbon monoxide. The vaporous mixture comprising the feed stream to the membrane selected for the vapor permeation process can be derived from a variety of sources including, but not limited to, vent streams from the industrial process, the vaporous upper material of a process of distillation, the upper material of a reflow process, the vaporized liquids of the industrial processes, the ventilation currents of the vaporized industrial process, the liquids of the chemical process, the production of fine chemical substances, the production of pharmaceutical materials, the recovery or purification of flavors and fragrances from natural products, and fermentation processes. The vapors comprising the vaporous feed mixture can be virtually any of the compounds with sufficient volatility to be present in the vapor phase. Typically, this includes compounds with boiling temperatures that are less than about 200 ° C at one atmosphere, preferably greater than room temperature but less than 180 ° C, and more preferably greater than 40 ° C but less than 150 ° C. ° C. Examples of the compounds that can be removed from the vaporous feed mixture by the process of the present invention include, but are not limited to: water, chlorofluorocarbons such as Freons and Halons; chlorinated hydrocarbons, such as methylene chloride, trichlorethylene, trichloroethanes, carbon tetrachloride, and chlorobenzene; non-chlorinated hydrophobic organic compounds such as benzene, toluene, xylene, ethylbenzene, cyclohexane, hexane and octane; non-chlorinated hydrophilic organics, such as methanol, ethanol, isopropyl alcohol and other alcohols; acetone, ethyl acetate, methylethyl ketone, tertiary methylbutyl ketone and other ketones; nitrobenzene, phenols and cresols; formic acid, acetic acid and other organic acids, amines, including triethylamine and pyridine; acetonitrile; dimethylformamide, dimethylacetamide, and N-methylpyrolidinone; and volatile inorganic compounds such as ammonia, bromine, iodine, sulfur dioxide and thionyl chloride. The types of membranes suitable for use in the present invention can be broadly described as separation membranes which are used due to their selectively permeable nature and more specifically those which are relatively vapor permeable relative to other vapors in the feed stream, and that they are "non-reactive" with vapors of interest in the sense of not contributing without causing any reaction and chemical conversion of the vapor that is to be removed. The membrane can also be manufactured entirely from a perm-selective material or the perm-selective material can be supported on a porous membrane, cloth or screen. Examples of these perm-selective materials useful for these separations include but are not limited to hydrophilic materials, including polyvinyl alcohol, cellulosic materials, chitin and derivatives thereof; polyurethanes, polyamides, polyamines, poly (acrylic acids), poly (acrylates), poly (vinyl acetates), and polyethers; hydrophobic materials such as natural rubber, nitrile rubber, polystyrene-butadiene copolymers, poly (butadiene-acrylonitrile) rubber; polyurethanes; polyamides; polyacetylenes; poly (trimethylsilylpropino); fluoroelastomers; poly (vinylchlorides); poly (phosphazenes), particularly those with organic substituents; halogenated polymers such as poly (vinylidene fluoride) and poly (tetrafluoroethylene); and polysiloxanes, including silicone rubber. Ion exchange membranes can also be used for some applications. Mixtures, copolymers, and crosslinked versions of these materials are also useful. The crosslinking of the polymers is preferred in most cases to provide sufficient resistance to swelling or dissolution by components of the feed stream. The membrane can also be isotropic or asymmetric. further, the membrane can be homogeneous or a multi-layer composite. In most cases, it is preferred that the membrane material be crosslinked to provide sufficient resistance to swelling or dissolution by the components in the feed stream. The membrane can be manufactured by a solvent phase inversion process, a thermally induced phase inversion process, a melt extrusion process, or by a wet or dry solvent molding process. In the case of multilayer composites, the selective layer may be formed by dip coating, painting, spray coating, solution coating or interfacial polymerization. In multilayer composites, the support layers that provide mechanical strength to the compound (as opposed to the perm-selective layer) should provide as little resistance as technically possible for the transport of the permeation species through the selective layer. . In addition, the support membrane must be chemically and thermally resistant, allowing operation in hot feed streams containing different chemical constituents. Suitable materials for the support membrane include, but are not limited to: organic polymers such as polypropylene, polyacrylonitrile, poly (vinylidene fluorides), poly (etherimides), polyimides, polysulfones, poly (ether sulfones), poly (arylsulfones), poly ( phenylquinoxalines), polybenzimidazoles, and copolymers and mixtures of these materials; and inorganic materials such as porous glass, carbon, ceramics and metals. The membrane can be used in the form of a flat sheet or a hollow fiber or tube. For the membrane in planar form, the membrane can be placed in the plate module and the frame designed to allow the countercurrent flow of the permeation material stream relative to the feed stream. Spirally wound modules are not suitable, since they do not allow countercurrent flow. For fibers and hollow tubes, the flow of food can be outside (side of the helmet) or inside (tube side) of the fibers. A hollow fiber membrane membrane feed module on the tube side is especially preferred. The materials used in the membrane module must have sufficient chemical and thermal resistance to allow long-term operation.

EXAMPLE 1 Using a system essentially of the same configuration as that shown in Figure 2, a vaporous feed solution comprising 4.8 weight percent water in isopropyl alcohol (IPA) at a pressure of 0.1 bar (gauge) and a temperature of 95 ° C, was fed at a rate of 7.8 kilograms per hour towards the openings of hollow fiber membranes in a module having an effective membrane area of 2.8 square meters. The internal surfaces of the hollow fibers were coated with a selective layer of a hydrophilic crosslinked polyamide blended with polyvinyl alcohol. A sweep current comprising dry air at 95 ° C and having a condensation temperature of -29 ° C to 6.9 bar (gauge), was generated by passing compressed air at 6.9 bar (gauge) through a dehydration module Air (ADU) manufactured by AquaAir, Inc. of Bend, Oregon. The pressure of this sweep stream was reduced to ambient pressure using a throttle valve and introduced to the side of the permeation material of the membrane in an inlet placed near the end of the module holding material to flow essentially countercurrently. to the flow of the feed at 280 liters (STP) per minute. Under the described operating conditions, the holding material stream had a water partial pressure of 0.00338 bar (absolute), while the sweep current input had a partial water pressure of 0.0005 bar (absolute), so that the ratio of the partial pressure of water in the sweeping current to the partial pressure of water in the holding material stream was 0.015. This yielded a water concentration of the retention material stream of 0.1 percent by weight which corresponds to a water removal rate of 97.9 percent.

EXAMPLE 2 Using a system essentially of the same configuration as that shown in Figure 5, a vaporous feed solution comprising 5.9 weight percent water in (IPA), at a pressure of 0.05 bar (gauge) and a temperature of 90 ° C, was fed at a rate of 4.4 kilograms per hour towards the openings of the hollow fiber membranes in a module having an effective membrane area of 2.8 square meters. The internal surfaces of the hollow fibers were coated with a selective layer of the crosslinked hydrophilic polymer of Example 1. A scavenging stream comprising nitrogen from a gas cylinder at essentially ambient pressure and 90 ° C was introduced on the side of the permeation material of the membrane in an inlet placed near the end of the module holding material to flow essentially countercurrent with respect to the flow of the feed at 136 liters (STP) / minute . Under these operating conditions, the stream of the retention material had a partial water pressure of 0.00048 bar (absolute), while the entrainment of the sweep current had a partial water pressure of 0.00002 (absolute) so that the ratio of the partial pressure of water in the sweep current with respect to the partial pressure in the holding material stream was 0.032. This yielded a water concentration of the retention material stream of 0.01 percent by weight that corresponds to a water removal rate of 99.8 percent.

EXAMPLE 3 Using a system essentially of the same configuration as shown in Figure 10, a vaporous feed solution comprising 7.6 weight percent water in (IPA) at a pressure of 0.3 bar (gauge) and a temperature of 91 ° C, was fed at a rate of 8.5 kilograms per hour towards the openings of the hollow fiber membranes in a module having an effective membrane area of 2.8 square meters. The internal surfaces of the hollow fibers were coated with a selective layer of the crosslinked hydrophilic polymer of Example 1. A scavenging stream comprising dry air at 91 ° C and 0.3 bar (absolute) and a condensation temperature -30 ° C to 6.9 bar (gauge) was generated by passing compressed air at 6.9 bar (gauge) through the same ADU module used in Example 1. The dry air sweep current produced by this module was introduced to the permeation side of the membrane in an orifice of input placed near the end of the module holding material so as to flow essentially countercurrent with respect to the feed flow to 127 liters (STP) / minute.A vacuum pump was used to reduce the pressure of the flow of the permeability up to 0.3 bar (absolute). Under these conditions, the stream of the retention material had a partial water pressure of 0.00203 bar (absolute) while the The input of the sweep current had a partial water pressure of 0.00005 bar (absolute) so that the ratio of the partial pressure of the water in the sweep current to the partial pressure of water in the flow of the holding material was of 0.024. This yielded a water concentration of the retention material stream of 0.1 weight percent corresponding to a 99.2 percent water removal rate.

EXAMPLE 4 Example 3 was essentially repeated with the following exceptions: the vaporous feed solution contained 9.4 weight percent water at a pressure of 0.1 bar (namometric) and was fed at a rate of 6.0 kilograms per hour towards the fiber membrane module hollow the sweep current was nitrogen from a gas cylinder at 91 ° C and 0.3 bar (absolute) flowing at 57 liters (STP) / minute. Under these conditions, the stream of the retention material had a partial water pressure of 0.00008 bar (absolute), while the sweep current input had a partial water pressure of 0.00002 bar. (absolute), so that the ratio of the partial pressure of water in the sweep current to the partial pressure of water in the stream of the holding material was 0.2. This yielded a water concentration of the retention stream of 0.002 weight percent which corresponds to a water removal rate of 99.9 percent.

EXAMPLE 5 Using a system essentially of the same configuration as that shown in Figure 10, a vaporous feed solution comprising 3.3 weight percent water in ethyl acetate at a pressure of 0.3 bar (gauge) and a temperature of 95 ° C, it was fed at a rate of 0.14 kilogram per hour towards the openings of the hollow fiber membranes in a module having an effective membrane area of 232 square centimeters. The internal surfaces of the hollow figures were coated with a selective layer as in Example 1. A scavenging stream comprising nitrogen from a gas cylinder at 95 ° C and 0.3 bar (absolute) was introduced to the side of the permeation material of the membrane in an inlet hole placed near the end of the module retainer material in order to flow almost countercurrent to the feed flow to 0.6 liter (STP) / minute. A vacuum pump was used to reduce the pressure of the penetration material stream to 0.3 bar (absolute). Under these operating conditions, the current of the holding material had a partial water pressure of 0.01524 bar (absolute), while the sweep current input had a partial water pressure of 0.00002 bar (absolute), so that the retention of the partial pressure of water in the sweeping current with respect to the partial pressure of water in the stream of the holding material was 0.001. This yielded a water concentration of the retention material stream of 0.1 percent by weight which corresponds to a water removal rate of 89.9 percent.

EXAMPLE 6 Using a system essentially of the same configuration as that shown in Figure 10, a vaporous feed solution comprising 12.2 weight percent water in ethanol at a pressure of 0.2 bar (gauge) and a temperature of 91 ° C, was fed at a rate of 0.07 kilogram per hour towards the openings of the hollow fiber membranes in a module having an effective membrane area of 232 square centimeters. The internal surfaces of the hollow fibers were coated with a selective layer as in Example 1. A scavenging stream comprising nitrogen from a gas cylinder at 91 ° C and 0.3 bar (absolute) was introduced on the side of the permeation material of the membrane in an inlet hole placed near the end of the module holding material in order to flow almost countercurrent with respect to the flow of the feed at 0.6 liter (STP) / minute. A vacuum pump was used to reduce the pressure of the penetration material stream to 0.3 bar (absolute). Under the described operating conditions, the holding material stream had a partial water pressure of 0.00460 bar (absolute), while the sweep current input had a partial water pressure of 0.00002 bar (absolute), so that the ratio of the partial pressure of water in the sweeping current to the partial pressure of water in the stream of the holding material was 0.003. This yielded a water concentration of the retention material stream of 0.2 percent by weight which corresponds to a water removal rate of 98.7 percent.

EXAMPLE 7 Using a system essentially of the same configuration as that shown in Figure 10, a vaporous feed solution comprising 7.5 percent water in tetrahydrofuran at a pressure of 0.1 bar (gauge) and at a temperature of 80 ° C was fed at a rate of 1.8 kilograms per hour to the openings of the hollow fiber membranes in a module that has an effective membrane area of 1.4 square meters. The internal surfaces of the hollow figures were coated with a selective layer as in Example 1. A scavenging stream comprising nitrogen from a gas cylinder at 80 ° C and 0.3 bar absolute was introduced to the side of the permeation material of the membrane in an inlet hole placed near the end of the module holding material in order to flow almost countercurrent with respect to the flow of the feed at 85 liters (STP) / minute. A vacuum pump was used to reduce the pressure of the permeation material stream to 0.3 bar (absolute). Under the described operating conditions, the holding material stream had a water partial pressure of 0.00686 bar (absolute), while the sweep current input had a partial water pressure of 0.00002 bar (absolute) so that the ratio of the partial pressure of water in the sweeping current to the partial pressure of water in the stream of the holding material was 0.002. This yielded a water concentration of the retention material stream of 0.001 weight percent which corresponds to a water removal rate of 99.9 percent.

EXAMPLE 8 Example 3 was repeated essentially with the following exceptions: the vaporous feed solution contained 12.7 percent of water at a pressure of 0.1 bar (namometric) and a temperature of 95 ° C, the sweep current was nitrogen from a gas cylinder to 95 ° C and 0.3 bar (absolute) and flowed at 57 liters (STP) / minute. Under these operating conditions, the current of the holding material had a partial water pressure of 0.00047 bar (absolute), while the sweep current input had a partial water pressure of 0.00002 bar (absolute), so that the ratio of the partial pressure of water in the sweeping current to the partial pressure of water in the stream of the holding material was 0.32. This yielded a water concentration of the retention material stream of 0.014 percent by weight, which corresponds to a water removal rate of 99.9 percent.

COMPARATIVE EXAMPLE 1 For comparison purposes, the system and the module described in Example 8 were operated under identical operating conditions, with a countercurrent flow of the permeation material, but with the nitrogen sweep flux adjusted to zero so that nitrogen was not introduced as a scavenging gas to the membrane module. Under these conditions the stream of the retention material had a water concentration of 5.2 weight percent which corresponds to a water removal rate of only 60 percent.

EXAMPLE 9 A computerized mathematical model of the system shown in Figure 8 was prepared and used to predict system performance using different parameters. A vaporous feed solution comprising 18 weight percent water in IPA at a pressure of 0.1 bar (gauge) and a temperature of 95 ° C, was fed at 8.9 kilograms per hour to the openings of the fiber membrane hollow in a module that has an effective membrane area of 2.8 square meters.

The internal surfaces of the hollow fibers of which were coated with the same type of selective layer that was used in the previous Examples.

A sweeping nitrogen stream at 95 ° C and an essentially ambient pressure and having a partial pressure of water vapor of 0.0007 bar (absolute) was introduced to the side of the permeation material of the membrane in an inlet orifice placed near from the end of the module holding material in order to flow almost countercurrent with respect to the flow of the feed at 516 liters (STP) / minute. Under these conditions, the permeation material exiting the module had a water vapor partial pressure calculated of 0.047 bar (absolute). This current is fed to a compressor, where the pressure is increased to 0.9 bar (gauge). The resulting high pressure current is sent to a condenser operating at a temperature of 0 ° C where the water vapor condenses. The non-condensable stream leaving the condenser is reduced to an essentially ambient pressure using a throttle valve. The resulting ambient pressure stream is assumed to have a partial water vapor pressure of 0.0005 bar (absolute). The current is then heated to 95 ° C and introduced into the module as a countercurrent sweep current. Under these operating conditions, the stream of the retention material had a calculated water concentration of 0.05 weight percent which corresponds to a partial water vapor pressure of 0.00014 bar (absolute). Therefore, the module has a calculated water removal rate of 99.7 percent and the ratio of the partial pressure of the water vapor in the sweep current to that of the current of the retention material is calculated as being of 0.36.

EXAMPLE 10 A model of the computerized mathematical system shown in Figure 7 was prepared and used to predict the operation of the system using different parameters. The same vaporous feed solution as in Example 9 was fed in the same manner and at the same rate to the same hypothetical hollow fiber membrane module and using the same sweep current of Example 9, to produce a permeation material leaving the module having a partial pressure of water vapor calculated from 0.047 bar (absolute). This current is fed to a compressor, where the pressure is increased to 6.9 bar (gauge). The resulting high pressure current is calculated to have a condensation temperature (at 6.9 bar (gauge)) of 74 ° C. This current is then directed to a membrane gas drying module to reduce the condensing temperature of the gas to 0 ° C (to 6.9 bar (gauge).) The pressure of this current is then reduced to essentially ambient pressure using a gas valve. throttle and spare nitrogen from a gas cylinder at a flow rate of 103 liters (STP) / minute is mixed with this stream., which has a partial pressure of water vapor calculated from 0.0005 bar (absolute) is then heated to 95 ° C and introduced into the module as a sweep current. Under these operating conditions, the stream of the retention material has a calculated water concentration of 0.05 weight percent which corresponds to a partial pressure of water vapor of 0.00014 bar (absolute). Therefore, the module has a water removal rate of 99.7 percent and the ratio of the partial pressure of water vapor in the sweep current to that of the current of the retention material is 0.36.

EXAMPLE 11 A computerized mathematical model of the system shown in Figure 9 was prepared and used to predict the operation of the system using the different parameters. The same vaporous feed solution was fed in the same manner and at the same rate to the same module and using the same sweep current of Example 9, to produce a permeation material leaving the module having a partial pressure of water vapor calculated from 0.047 bar (absolute). This current is fed to a compressor, where the pressure is increased to 6.9 bar (gauge). The resulting high pressure stream is sent to a desiccant bed where the water is removed to a condensation temperature of 0 ° C. The pressure of the drying drying nitrogen is then reduced to essentially ambient pressure using a throttle valve. The resulting ambient pressure current has a water vapor partial pressure calculated of 0.005 bar (absolute). The current is then heated to 95 ° C and introduced into the module as a sweep current. Under these operating conditions, the stream of the retention material has a calculated water concentration of 0.05 weight percent which corresponds to a partial pressure of water vapor of 0.00014 bar (absolute). Therefore, the module has a calculated water removal rate of 99.7 percent and the ratio of the partial pressure of water vapor in the sweep current to that of the current of the retention material is 0.36.

EXAMPLES 12 to 17 A computerized mathematical model of the system shown in Figure 10 was prepared and used to predict the operation of the system, using different parameters. A vaporous feed solution comprising 10 weight percent water in IPA at a pressure of 0.1 bar (gauge) and a temperature of 95 ° C, is fed into the openings of the hollow fiber membranes in a module having a Effective membrane area of 2.8 square meters, the internal surfaces of the hollow fibers of which are coated with the same type of selective layer as in the previous Examples. The flow regime of this feed stream was varied as shown in Table 1 and as will be discussed below. A current of sweeping nitrogen at 95 ° C and at a pressure of 0.2 bar (absolute) and having the different partial pressures of water vapor shown in Table 1, was introduced on the side of the permeation material of the membrane in an inlet hole positioned near the end of the module holding material in order to flow almost countercurrent with respect to the flow of the 57 liter (STP) / minute feed. The flow regime of the vaporous feed solution was varied as shown in Table 1 so that under the specified operating conditions, the stream of the retention material had a water partial pressure of 0.0039 bar (absolute), which corresponds to a water concentration of the retention material stream of 0.1 percent by weight of water, corresponding to a water removal rate of 99 percent. The results in Table 1 show that when the ratio of the partial pressure of the water in the sweep current to the partial pressure of water in the stream of the retention material is greater than about 0.9, the rate of feed flow to the module must be very low to obtain the desired concentration of water from the retention material resulting in a high cost and inefficient system. The reason why the rate of feed flow to the module must be very low to obtain the water concentration of the desired retention material, is because when the ratio is greater than 0.9, the partial pressure driving force for the Water vapor transport through the membrane also becomes low. Therefore, to achieve a certain concentration of the water in the retention material, the flow rate of the feed solution to the module must be reduced to allow sufficient time for the water to be removed from the feed solution. The reason why an >ratio results0.9 in an inefficient high cost system is because when the ratio is greater than 0.9, the feed flow rate towards the module will be low in comparison as when the ratio is less than 0.9. As a result, to treat a given volume of feed solution, a larger membrane area will be required which is less efficient, and a requirement for a larger membrane surface area leads to higher membrane costs and ultimately to a higher cost system .

Table 1 Example Water Vapor Partial Pressure Rate Ratio bar [absolute] Sweep to Flow Partial Pressure of Ali¬ Sweep Material of the Reference Material Retention Retention (kg / hour) 12 0.0013 0.0039 0.33 6.8 13 0.0021 0.0039 0.55 6.4 14 0.0027 0.0039 0.70 6.0 0.0036 0.0039 0.94 5.0 16 0.0038 0.0039 0.97 4.6 17 0.0039 0.0039 1.00 4.2 Terms and expressions that have been used in the foregoing specification are used here as terms of description and not limitation, and there is no intent, in the use of these terms and expressions, to exclude equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only or the claims that will be given below.

Claims (20)

CLAIMS:

1. A process for the removal of a first vapor from a fluid feed stream containing a mixture of vapors, the process comprises the steps of: (a) providing a membrane having feed and permeation material sides and which is selectively permeable to the first steam; (b) directing the fluid feed stream to the feed side of the membrane and removing a stream of spent retention material in the first steam and removing a stream of the permeation material enriched in the first vapor from the side of the permeation material of the membrane; and (c) directing a gas phase fluid sweep current to the side of the membrane permeation material, the sweep current flows countercurrent to the flow of the fluid feed stream, where the partial pressure of the first The vapor in the sweep current is low enough that the ratio of the partial pressure of the first vapor in the sweep current to the partial pressure of the first vapor in the flow of the retention material is less than 0.9.

2. The process according to claim 1, wherein the gas phase sweep current is generated by a process that is selected from membrane separation, absorption and condensation.

3. The process according to claim 1, wherein the gas phase sweep current is obtained from bottled purified gases.

4. The process according to claim 1, wherein the gas phase sweep current is obtained by evaporation of liquid gas.

The process according to claim 1, which includes the additional step (d) of directing the flow of the permeation material enriched in the first vapor to the steam removal process.

6. The process according to claim 1 O 2 O 3 O 4 O 5, wherein a vacuum is applied to the side downstream of the sweep stream.

The process according to claim 5, wherein the vapor removal process of step (d) is selected from condensation, absorption and membrane separation.

8. The process according to claim 5, wherein the vapor removal process of step (d) produces a spent gas phase stream that is exhausted in the first vapor, wherein the concentration of the first vapor in the phase stream of spent gas is sufficiently low such that the ratio of the partial pressure of the first vapor in the spent gas phase stream to the partial pressure of the first vapor in the stream of the holding material is less than 0.9.

9. The process according to claim 8, wherein the spent gas phase current is used as the sweep current in step (c), thereby recycling the gas phase sweep current.

10. The process according to claim 1, wherein the membrane is a membrane composed of hollow fiber.

11. The process according to claim 1, wherein the first steam is water vapor.

12. The process according to claim 1, wherein the vapor mixture comprises water vapor and at least one organic vapor.

13. The process according to claim 12, wherein at least one organic vapor consists predominantly of organic compounds having boiling temperatures greater than 0 ° C, but less than 200 ° C.

The process according to claim 13, wherein at least one organic vapor is selected from the group consisting of isopropyl alcohol, ethanol, ethyl acetate and tetrahydrofuran.

15. The process according to claim 1, wherein the feed stream has a condensation temperature greater than 40 ° C at 1 atmosphere.

16. The process according to claim 15, wherein the temperature of the feed stream is maintained at a temperature that is greater than or equal to the condensation temperature of the feed stream at 1 atmosphere.

17. The process according to claim 1, where the feed current is maintained at a pressure greater than 0 bar (gauge) and less than 10 bar (gauge).

18. The process according to claim 17, wherein the feed stream is maintained at a pressure less than 4 bar (gauge).

19. The process according to claim 1, wherein the ratio of the partial pressure of the first vapor in the scavenging current to the partial pressure of the first vapor in the stream of the retention material is less than 0.5.

20. A process for the removal of water vapor from a gas phase feed stream containing a mixture consisting of water and organic vapors, where the organic vapors predominantly comprise organic compounds with boiling temperatures greater than 0 ° C but below 200 ° C, and where the feed stream has a condensation temperature greater than 40 ° C at 1 atmosphere, and the feed stream is maintained at a temperature higher than the condensation temperature, and where the pressure of the feed stream is greater than 0 bar (gauge) and less than 10 bar (gauge) the process comprises the steps of: (a) providing a hollow fiber module having feed ends in the retention material and holes of retaining material and at least two holes of the penetrating material, the hollow fiber module comprises a plurality of hollow fiber membranes positioned with so parallel to each other and sealed inside a chamber, the hollow fiber membranes comprise a selective layer on a supporting layer; (b) directing the gas phase feed stream to the feed hole of the hollow fiber module, removing a stream of spent steam retention material from the retention material hole and removing a stream of the penetration material enriched in water vapor from an orifice of permeation material placed near the module feed end; and (c) directing a gas phase fluid sweep stream to an orifice of permeation material placed near the end of the module holding material, the sweep current flows countercurrent to the flow of the flow of the gas stream. phase feed of gs, where the partial pressure of the water vapor in the sweep current is low enough so that the ratio of the partial pressure of the water vapor in the sweep current to the partial pressure of the steam of water in the stream of the retention material is less than 0.9.