WO2013021966A1 - Dehydration system and dehydration method - Google Patents

Abstract

Provided are a dehydration system and dehydration method, said dehydration system carrying out regeneration of water separation membranes while the system as a whole is in operation and being made such that the number of water separation membranes required is reduced. The dehydration system has at least one water separation membrane unit (10) in operation and is configured such that for the at least one water separation membrane unit (10) in operation, there can be at least one water separation membrane unit (20) not in operation. Heated gas for regeneration is supplied to a flow path (22) for a fluid to be treated with a water separation membrane (21) of the water separation membrane unit (20) not in operation, and in a state in which the dehydration system is in operation, the water separation membrane (21) can be regenerated by the heated gas for regeneration passing through the water separation membrane (21).

Description

Dehydration system and method

The present invention relates to a dehydration system and a dehydration method. More specifically, the present invention relates to a dehydration system and a dehydration method capable of efficiently dehydrating a mixture of ethanol, propanol, and water having an azeotropic composition with water, or a mixture of acid and water.

Ethanol is attracting attention as a fuel source to replace petroleum fuel, and its market size is predicted to be 115 million kiloliters in 2015. However, in order to employ ethanol as a fuel, a crude product obtained from a bio raw material such as corn must be purified by distillation and dehydrated to at least 99.5 wt% or more.
Conventionally, in dehydration, a dilute ethanol aqueous solution is concentrated in the distillation column to near the azeotropic point of the ethanol / water system and then dehydrated.

As a method for dehydrating, there is a method of adding an entrainer and dehydrating by azeotropic distillation. However, this method has a drawback in that it requires a step of azeotropic distillation of the ternary system and further recovery of the entrainer, which requires a large amount of heat energy.

There is also a method in which a plurality of molecular sieve tanks are juxtaposed and dewatered while switching batches. However, even with this method, there is a problem that a great amount of energy is consumed for the regeneration of the molecular sieve layer.

Therefore, it has been devised to use elements that do not have the above disadvantages, such as a water separation membrane (Patent Document 1: Japanese Patent Laid-Open No. 58-21629).

However, when PV (pervaporation) using a water separation membrane unit equipped with a water separation membrane is adopted, the water separation membrane deteriorates, so the replacement frequency is high, and the plant is frequently stopped along with the replacement. There was an inconvenience of having to.

Also, such deterioration of the water separation membrane is predicted, and an allowable deterioration ratio in the later period of use is set. For example, assuming that 200 water separation membranes are used, the initial deterioration ratio in the usage period is set to 1, and the limit of the allowable deterioration ratio is set to 0.4. Then, the required number at the beginning of the usage period is 200 / 0.4 = 500 (books). Therefore, in general, the number of water separation membranes to be equipped tends to be excessive.

JP 58-21629 A

The present invention has been made in view of the above circumstances, and provides a dehydration system and a dehydration method in which the water separation membrane is regenerated and the required number of water separation membranes is reduced while the entire system is in operation. The purpose is to provide.

In order to achieve the above object, a dehydration system according to the present invention is a dehydration system for separating water from a fluid to be treated, comprising at least one water separation membrane unit in operation, and the at least one water separation The membrane unit is configured such that at least one non-operating water separation membrane unit can be installed, and the flow path of the fluid to be treated of the water separation membrane constituting the non-operating water separation membrane unit is heat for regeneration. The water separation membrane can be regenerated by allowing the regeneration hot gas to permeate the water separation membrane in a state where the gas supply path is operated and the dehydration system is in operation. .

In one embodiment, the dehydration system according to the present invention includes a line for separating water from a fluid to be processed that is processed by the water separation membrane unit in operation, and a water separation membrane unit that is not in operation. The regeneration hot gas can be sucked at an operating pressure for separating water by joining a line for sucking the regeneration hot gas.

The present invention is a dehydration method in another aspect, and in the dehydration method of separating water from a fluid to be treated, the dehydration method includes at least one water separation membrane unit in operation, and the at least one water separation membrane unit A dehydration system in which at least one non-operating water separation membrane unit is installed, supplying regeneration hot gas to the flow path of the fluid to be treated of the water separation membrane constituting the non-operating water separation membrane unit; The regeneration hot gas permeates through the water separation membrane and the water separation membrane is regenerated while the dehydration system is in operation.

In one embodiment, the dehydration method according to the present invention includes a line for separating water from a fluid to be treated that is processed by the water separation membrane unit in operation, and a water separation membrane unit that is not in operation. The regeneration hot gas can be sucked at an operating pressure for separating water by joining a line for sucking the regeneration hot gas.

In the present invention, the fluid to be treated is generally an organic aqueous solution.
Organic components of the organic aqueous solution include alcohols such as ethanol, propanol, isopropanol and glycol, carboxylic acids such as acetic acid, ethers such as dimethyl ether and diethyl ether, aldehydes such as acetaldehyde, ketones such as acetone and methyl ethyl ketone, and ethyl acetate. One organic component selected from the group consisting of esters, which is soluble in water, can be mentioned.

An inert gas is suitable as the regeneration hot gas that can be employed in the present invention.
Examples of the inert gas include the following.
(1) Nitrogen gas If the oxygen concentration increases to the air level, the separation membrane is modified by oxidation, which is not preferable. Accordingly, the oxygen content is preferably less than 10%. In addition, if it is a small amount, the removal by partial combustion of ethanol is advantageous on the contrary, and when aiming at such an effect, oxygen may be contained up to about 5%.
(2) Carbon dioxide Nitrogen can be used instead. Carbon dioxide produced as a by-product in the production of ethanol can also be used.
(3) Other inert gases It should be noted that an inert gas on the periodic table such as Ar can be used instead of nitrogen.
(4) Mixture Further, instead of nitrogen, a mixture of the inert gases mentioned above can also be adopted.
The temperature of the regenerating hot gas is preferably 78 ° C. to 300 ° C., which is an intermediate region between the boiling point of ethanol of 78.3 ° C. and the temperature exceeding 300 ° C. at which carbon starts to precipitate on the film from ethanol. . As a gas heating method, in addition to the actual heating, the heat of the product fluid obtained from the fluid to be treated can be recovered by a heat exchanger.

According to the present invention, there are provided a dehydration system and a dehydration method in which the water separation membrane is regenerated and the required number of water separation membranes is reduced while the entire system is in operation.

BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram explaining the embodiment about the dehydration system for implementing the dehydration method which concerns on this invention. FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along the line BB of FIG. 2A regarding one embodiment of a water separation membrane that can be employed in the present invention. FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along the line CC of FIG. 3A for one embodiment of a water separation membrane that can be employed in the present invention.

Hereinafter, the dehydration system and the dehydration method according to the present invention will be described in more detail with reference to embodiments thereof. In the following embodiments, a dehydration system including a specific number of water separation membrane units will be exemplified, but the present invention is not limited to a specific number of water separation membrane units.
A description will be given of a form in which the fluid to be treated is crude ethanol containing water and the regenerating hot gas is a heated nitrogen gas. However, it does not preclude that the present invention is applied based on the technical common sense of those skilled in the art even in the case of using other types of fluids to be treated or hot gas for regeneration.

FIG. 1 shows an embodiment of a dehydrating system according to the present invention.
The dehydration system according to the present embodiment includes an operating water separation membrane unit 10 and a water separation membrane unit 20 being regenerated.
These water separation membrane units 10 and 20 are devices for separating water from the crude ethanol using the water separation membranes 11 and 21 by the pervaporation method.
The water separation membrane units 10 and 20 are provided with water separation membranes 11 and 21 having one or more flow paths 12 and 22 extending in the left and right directions through which crude ethanol passes in the main body. A crude ethanol inlet is provided on the left side of the water separation membranes 11 and 21, and a crude ethanol outlet is provided on the right side.
Shell portions 13 and 23 are defined on the water permeation side by the outer peripheral surfaces of the water separation membranes 11 and 21 and the inner wall of the unit main body.

In the illustrated state, in the raw material (crude ethanol) supply lines 14 and 24, the valve 15 on the water separation membrane unit 10 side is opened, and the valve 25 on the water separation membrane unit 20 side is closed. In the product discharge lines 18 and 28, the valve 19 on the water separation membrane unit 10 side is opened, and the valve 29 on the water separation membrane unit 20 side is closed.
On the other hand, in the nitrogen gas supply lines 16 and 26, the valve 17 on the water separation membrane unit 10 side is closed, and the valve 27 on the water separation membrane unit 20 side is opened.

One Embodiment of the Dehydration Method According to the Present Invention Next, one embodiment of the dehydration method according to the present invention using the dehydration system according to the embodiment of FIG. 1 will be described.
In the state shown in the figure, the crude ethanol is supplied only to the water separation membrane unit 10, and the water that has permeated the water separation membrane 11 from the flow path 12 is sucked by the decompression action by the decompression pump 30 and is discharged from the shell portion 13. 31 to separate. Ethanol separated from water is recovered as a product.

On the other hand, nitrogen gas heated to 78 ° C. to 300 ° C. is supplied to the water separation membrane unit 20 from the line 26 as a regenerating hot gas via the heat exchanger 32. Nitrogen gas is supplied to the flow path 22 and pushes out the ethanol accumulated in the water separation membrane 21. The extruded nitrogen gas containing ethanol is sucked from the line 33. The water separation membrane 21 is porous, and ethanol molecules are accumulated in the pores.

Then, as shown in the figure, a line 31 for separating water from the crude ethanol treated in the water separation membrane unit 10 and a line 33 for sucking nitrogen gas from the water separation membrane unit 20 are merged to form water. Nitrogen gas is also sucked at an operating pressure [133.22 to 13332.2 Pa (10 to 100 torr)] for reducing the pressure.

In the form of FIG. 1, it is possible to regenerate the deteriorated water separation membrane unit without stopping the operation of the entire dehydration system. Moreover, the water separation membrane unit 20 can be regenerated at an operating pressure for reducing the pressure of the water separation membrane unit 10 in operation. For this reason, another decompression device is not required. In addition, the discharge lines 31 and 33 from the shell portions 13 and 23 can be commonly used in both the operation and regeneration states of the water separation membranes 10 and 20, and the number of parts can be reduced. *

The sucked nitrogen gas contains extruded ethanol. Also, ethanol may be contained in the water that is suction-separated from the water separation membrane unit 10. Therefore, a recovery device for recovering ethanol from the mixture that is joined and discharged by the pump 30 can be provided, and this can be returned to the water separation membrane unit 10 that is operating.

Other Forms of Dehydration System According to the Present Invention FIG. 1 is a simplified conceptual diagram for explanation, and an apparatus not shown can be implemented as a form provided without departing from the spirit of the present invention. . Moreover, it can also implement as a form provided with two or more water separation membrane units in operation. Such a form group is also included in the concept of the present invention, and will be described below as an example.

When water is separated from the raw raw ethanol, the higher the temperature of the crude ethanol, the more advantageous. Therefore, for example, crude ethanol is preferably heated to about 100 to 150 ° C. Therefore, it is general to provide a heater in the lines 14 and 24 in the upstream of the water separation membrane units 10 and 20.
As a result, the resulting product ethanol will have heat. This heat can also be imparted to the supplied crude ethanol using a heat exchanger.
Furthermore, a part of ethanol obtained from the line 18 can be returned to the line 14 again to separate the water that has not been removed.

Also, a plurality of water separation membrane units 10 in operation can be provided in parallel. In this case, when the water separation membrane units are arranged in series with respect to the flow direction of the crude ethanol, for example, when three stages are provided, the ethanol that has passed through the first stage water separation membrane unit is sent to the second stage water separation membrane unit. It is also possible to send ethanol that has passed through the water separation membrane unit at the stage to the water separation membrane unit at the third stage, and finally recover the product ethanol.
In this form, the water collected from all the water separation membrane units in operation and the water separation membrane unit being regenerated can be collected, and ethanol leaking into the water can be collected by the collection device.

Further, here, it is possible to distribute the first to third stages in order from the lowest deterioration ratio, stop the operation in the order in which the deterioration ratio reaches the set value, and perform the regeneration process. By operating in this way, the overall processing capacity from the first stage to the third stage can be kept constant. That is, a regeneration cycle can be constructed.

In the present specification, the deterioration ratio is a ratio between a water permeation rate at the beginning of the use period and a water permeation rate at that time. Here, for example, assume that the deterioration ratio is set to 0.8. In the actual machine, a plurality of dehydration systems described with reference to FIG. Assuming such a situation, for example, when 200 water separation membranes are always operated, the required number in the initial period of use is 200 / 0.8 = 250 (pieces). That is, the required number of water separation membranes can be reduced by setting the deterioration ratio.
The reason why the deterioration ratio can be set as high as 0.8 is that the water separation membrane unit can be simultaneously regenerated in the operating state.

In the operation of the dehydration system according to the present invention and the execution of the dehydration method according to the present invention including the execution of such a regeneration cycle, processor control according to the common general technical knowledge of those skilled in the art can be performed.

As long as the purpose is not hindered, the dehydration system according to the present invention can be realized as a multistage dehydration system having more than three stages, and the number of water separation membrane units to be regenerated is limited to one. is not.

Further, a concentration meter for monitoring the concentration of ethanol taken out from each water separation membrane unit can be installed in each water separation membrane unit. As a result, the deterioration ratio can be monitored.
Furthermore, a thermometer for monitoring the temperature of the product fluid taken out from each water separation membrane unit may be provided.

Further, an alternative form that is possible in the form of employing one operating water separation membrane unit as shown in FIG. 1 is also adopted in a form having two or more working water separation membrane units unless contrary to the object of the present invention. can do.

Water Separation Membrane that can be Employed in the Present Invention Water separation membranes used in water separation membrane units such as the water separation membrane units 10, 20 etc. separate crude ethanol into anhydride and water. Such water separation membranes are known in various forms and are commercially available. In the present invention, for example, a monolith type and a tubular type water separation membrane can be used.

An example of the monolith type water separation membrane 110 will be described with reference to FIGS. 2A and 2B. FIG. 2B is a cross section taken along line BB of FIG. 2A. The monolith-type water separation membrane 110 is provided with a plurality of crude ethanol flow paths 110 that are one or more hollow portions extending vertically to pass crude ethanol through a cylindrical water separation membrane 110. Usually, in such a form of water separation membrane, the crude ethanol flow path 110c inside the water separation membrane is called the primary side or supply side of the membrane, and the outside of the water separation membrane 110 is the secondary side of the membrane, or It is called the transmission side.

In such a pervaporation membrane separation using the water separation membrane 110, unlike the embodiment shown in FIG. 1, the water separation membrane 110 is arranged such that the flow path direction is parallel to the vertical direction as shown in FIG. It can also be installed.
Then, while reducing the permeation side of the water separation membrane 110, the crude ethanol is supplied from the inlet 110a on the lower side in the vertical direction, flows in the direction opposite to the gravity, and is discharged from the outlet 110b on the upper side in the vertical direction. By this operation, the water in the crude ethanol becomes water vapor and is extracted from the side surface of the cylindrical water separation membrane 110 to the permeate side. As a result, the crude ethanol recovered from the water separation membrane part outlet 110b is dehydrated.

The illustrated monolith-type water separation membrane 110 is schematic, but as an example, a columnar water separation membrane with a diameter of 30 mm is provided with 30 holes with a diameter of 3 mm. Can do. As another example, a water separation membrane having a diameter of 150 to 200 mm and having 200 holes having a diameter of 2 mm can be used. The length of the water separation membrane can be appropriately determined by those skilled in the art according to the desired membrane performance, but as an example, a length of 150 mm to 1 m can be used.

As another example, a tubular type will be described with reference to FIGS. 3A and 3B. 3B is a cross-sectional view taken along the line CC of FIG. 3A. The tubular water separation membrane 210 has a tubular shape in which only one crude ethanol passage 210c is provided. The tubular-type water separation membrane 210 has the same installation mode and effect as the monolith-type water separation membrane. As an example of the tubular water separation membrane, one having an outer diameter of 10 mm and an inner diameter of 7 mm can be used, and as another example, one having an outer diameter of 30 mm and an inner diameter of 22 mm can be used. As an example, a length of 150 mm to 1 m can be used.

As a material for the water separation membrane, a microporous membrane having a nano-order or smaller pore size precisely controlled with an inorganic material can be used. The microporous membrane exhibits a molecular sieving effect that allows a gas with a small molecular diameter to pass through and excludes a gas with a large molecular diameter, and shows a behavior of activated diffusion in which the permeability coefficient increases with increasing temperature. Examples of the microporous membrane include a carbon membrane, a silica membrane, and a zeolite membrane. In the present embodiment, a carbon-based inorganic water separation membrane having a pore diameter of 10 angstroms or less is suitable as the water separation membrane.

Also, an inorganic water separation membrane described in Japanese Patent No. 2808479 can be applied. The inorganic water separation membrane of Patent No. 2808479 is an acid-resistant composite separation obtained by supporting silica gel obtained through hydrolysis of an alkoxysilane containing an ethoxy group or a methoxy group in the pores of an inorganic porous body. It is a membrane.

It should be noted that the form, size, and material of the water separation membrane can be appropriately selected by those skilled in the art according to the purpose of use.

10, 20 Water separation membrane unit 11, 21 Water separation membrane 12, 22 Flow path 13, 23 Shell portion 14, 24, 16, 26, 18, 28, 31 Line 15, 25, 17, 27, 19, 29 Valve 30 Pressure reduction pump 32 Heat exchanger 110, 210 Water separation membrane 110a, 210a Crude ethanol inlet 110b, 210b Crude ethanol outlet 110c, 210c Flow path

Claims (8)

1. A dehydration system for separating water from a fluid to be treated, comprising at least one active water separation membrane unit, and at least one non-operating water separation for the at least one water separation membrane unit In a state where the membrane unit can be installed, the flow path of the fluid to be treated of the water separation membrane constituting the non-operating water separation membrane unit is the supply path for the regenerating hot gas, and the dehydration system is in operation. A dehydration system characterized in that the water separation membrane can be regenerated by allowing the regeneration hot gas to permeate the water separation membrane.
2. A line for separating water from the fluid to be treated that is processed by the water separation membrane unit in operation and a line for sucking the regeneration hot gas from the non-operating water separation membrane unit, 2. The dehydration system according to claim 1, wherein the regeneration hot gas is sucked at an operating pressure for separating water.
3. The dehydration system according to claim 1 or 2, wherein the fluid to be treated is an organic aqueous solution.
4. The organic components of the organic aqueous solution include alcohols such as ethanol, propanol, isopropanol and glycol, carboxylic acids such as acetic acid, ethers such as dimethyl ether and diethyl ether, aldehydes such as acetaldehyde, ketones such as acetone and methyl ethyl ketone, and ethyl acetate. The dehydration system according to any one of claims 1 to 3, wherein the organic component is one organic component selected from the group consisting of esters and is soluble in water.
5. In a dehydration method for separating water from a fluid to be treated, at least one water separation membrane unit in operation is provided, and at least one non-operational water separation membrane unit is provided for the at least one water separation membrane unit. In the dehydration system installed, the regeneration hot gas is supplied to the flow path of the fluid to be treated of the water separation membrane constituting the non-operating water separation membrane unit, and the regeneration A dehydration method, wherein hot water is permeated through the water separation membrane to regenerate the water separation membrane.
6. A line for separating water from the fluid to be treated that is processed by the water separation membrane unit in operation and a line for sucking the regeneration hot gas from the non-operating water separation membrane unit, 6. The dehydrating method according to claim 5, wherein the regeneration hot gas is sucked at an operating pressure for separating water.
7. The dehydration method according to claim 5 or 6, wherein the fluid to be treated is an organic aqueous solution.
8. The organic components of the organic aqueous solution include alcohols such as ethanol, propanol, isopropanol and glycol, carboxylic acids such as acetic acid, ethers such as dimethyl ether and diethyl ether, aldehydes such as acetaldehyde, ketones such as acetone and methyl ethyl ketone, and ethyl acetate. The dehydration method according to any one of claims 5 to 7, wherein the organic component is one organic component selected from the group consisting of esters and is soluble in water.

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