WO2004089518A1

WO2004089518A1 - Filtration method using cross-flow film and producing method of acrylamide using the same

Info

Publication number: WO2004089518A1
Application number: PCT/JP2004/004534
Authority: WO
Inventors: Hiroyasu Banba; Kozo Murao; Katsuo Ishii
Original assignee: Dia-Nitrix Co., Ltd.
Priority date: 2003-04-04
Filing date: 2004-03-30
Publication date: 2004-10-21
Also published as: JPWO2004089518A1

Abstract

A filtration method using a cross-flow film has a storage vessel and a circulation pump that are used for circulating and feeding a raw material liquid or a concentrate liquid that is obtained by concentrating the raw material liquid. The method has a step of continuously filtering the raw material liquid or the concentrate liquid by the cross-flow film while additionally feeding the raw material liquid into the storage vessel so as to maintain the level of the liquid in the vessel constant, a step of concentrating a liquid while further continuing the filtration to lower the liquid level with the additional feeding of the raw material liquid to the storage vessel stopped, and a step of discharging a remaining concentrate liquid after the concentration step.

Description

Description Filtration method using cross-flow type membrane and method for producing acrylamide using the same

The present invention relates to a filtration method using a cross-floor type single membrane apparatus having a storage tank for circulating and supplying a concentrate or a concentrated solution containing a suspension, and a method for producing acrylamide using the same. About the method.

Priority is claimed on Japanese Patent Application No. 2003-108183, filed on April 4, 2003, the content of which is incorporated herein by reference. Background art

In a cross-flow type membrane, the raw material liquid is continuously supplied in parallel with the membrane, and the pressure difference between the primary side of the membrane (the side to which the raw material liquid is supplied) and the secondary side (the opposite side of the primary side) is measured. It is used for filtration. In such a filtration, the cake deposited on the membrane surface can be peeled off by the action of the shear force generated by flowing the raw material liquid in parallel with the membrane, so that the thickness of the deposited cake can be reduced, Blockage of the membrane can be suppressed. Therefore, it has a feature that a high filtration rate can be obtained for a long time.

The filtration by cross-flow type membrane takes advantage of the above-mentioned characteristics, such as final filtration of drinking water in the food field, filtration and purification in the chemical industry field, and separation and concentration of microorganisms and culture fluid in the biochemical field. Very widely used.

FIG. 1 is a diagram schematically showing a filtration device provided with a cross-flow type membrane.

The filtration device 1 includes a storage tank 3 to which a raw material liquid containing a suspension is supplied via a supply pump 2, a cross-flow type membrane 4 for filtering the raw material liquid, and a raw material liquid from the storage tank 3 to the cross-flow type membrane 4. A feed pipe 5 for transferring the liquid, a return pipe 6 for transferring the concentrated liquid discharged from the primary side of the cross opening type membrane 4 to the storage tank 3, and a circulation pump 7 provided in the feed pipe 5. And a filtrate transfer pipe 8 for transferring the filtrate filtered by the cross-flow type membrane 4.

In the filtration device 1, the supply pump 2 is connected to a liquid level controller 9 provided in the storage tank 3. More controllable. The feed pipe 5 is provided with a flow meter 10 and a circulating pressure regulator 11 for controlling the circulating pump 7 according to the pressure. The filtrate transfer pipe 8 is provided with a filtrate outlet pressure gauge 12, and the filtrate transfer pipe 8 is further provided with a withdrawal pump 15 controlled by a first filtrate outlet valve 13 and a flow rate indication controller 14. And a second filtrate discharge pipe 18 provided with a second filtrate outlet valve 17.

As a conventional filtration method using the filtration device 1, a patch process and a continuous process are known. In the batch process, the concentrated solution is supplied from the storage tank 3 to the cross opening type membrane 4 by the circulation pump 7 and continuously filtered, and the filtrate filtered by the cross opening type 4 membrane is passed through the filtrate transfer pipe 8. to recover. At the same time, the concentrated liquid in which the suspension is concentrated through the primary side of the cross-flow type membrane 4 is returned to the storage tank 3 via the return pipe 6 and circulated. That is, the patch process is a method in which these operations are performed until the amount of liquid in the storage tank 3 decreases to an arbitrary amount to obtain a filtrate and a concentrated solution.

In the continuous process, as in the patch process, the concentrated solution is supplied from the storage tank 3 to the cross opening type membrane 4 by the circulation pump 7 and continuously filtered, and the filtrate filtered through the cross opening type 1 membrane 4 is filtered. Collect via transfer tube 8. At the same time, the concentrated liquid, in which the suspension is concentrated by passing through the primary side of the cross flow type membrane 4, is returned to the storage tank 3 via the return pipe 6 and circulated. At that time, the continuous process is performed by operating the liquid level controller 9 installed in the storage tank 3 to control the supply pump 2 and supplying new raw material liquid so that the liquid level in the storage tank 3 becomes constant. This is a method of obtaining a filtrate and a concentrated solution.

Until now, no attempt has been made to attempt a combined filtration method that combines a continuous process followed by a patching process.

In such a filtration device, pores formed in the cross-flow type membrane are closed as the filtration time becomes longer. The degree of pore blockage varies depending on characteristics such as the particle size and molecular weight distribution of the suspension. Therefore, usually, the pore size suitable for the suspension or the raw material liquid is used for the purpose of suppressing blockage. Is selected. Furthermore, as a filtration method for suppressing the clogging of the filtration membrane pores at the initial stage of filtration and obtaining a high filtration rate, for example, Japanese Patent No. 3129644 discloses a method in which the secondary side of the membrane is started before the filtration step is started. A method of sealing with a liquid is shown. Regarding a method for removing microbial cells from a reaction solution produced by using a microbial catalyst, Japanese Patent Publication No. 05-49273 discloses a dead-end filtration method. Japanese Patent Publication No. 0 0 1—7 8 7 49 discloses a removal method using bubbles.

By the way, as in the prior art, in a method in which the raw material liquid or the concentrated liquid is simply circulated and the filtration is continued through a mouth-and-mouth type one membrane, the concentration of the suspended solids in the concentrated liquid is greatly increased as the filtration proceeds. To rise. Here, as the concentration of the suspension increases, the viscosity of the circulating concentrate increases, and as a result, the pressure loss when circulating the concentrate increases. In order to keep the circulation speed constant when the pressure loss increases, it is necessary to increase the discharge pressure of the circulating pump. Pressure is limited. Therefore, when the pressure loss increases, the circulation speed of the concentrated liquid decreases and the filtration time becomes longer. When the circulation speed decreases, the flow speed of the concentrate on the membrane becomes slower, and the effect of preventing the accumulation of suspended particles on the membrane surface, which is a characteristic of the cross-flow type membrane, cannot be utilized. Into a vicious circle. Therefore, it is difficult to obtain a high filtration rate for a long time.

Therefore, in the above-mentioned filtration method, when the concentration of the suspension in the concentrate reaches a predetermined condition, the exhaust valve 19 of FIG. After discharging from the discharge pipe 20 and then regenerating by washing the membrane, the filtration operation is restarted again. Here, the discharged concentrated liquid with a high concentration of suspended solids is collected and reused or discarded.However, in the case of energy consumption, the amount of suspended solids is reduced in order to reduce the amount of waste. It has been demanded that the amount of discharged liquid be reduced by concentrating the solution as high as possible. In order to increase the concentration of the suspension to the required concentration, it is conceivable to further increase the continuous filtration time, but in that case, the filtration speed becomes extremely slow, which is an economic efficiency problem. There is a point. In addition, suspensions are susceptible to physical disruption and chemical or biological metamorphosis, such as microbial cells! In the case of /, in the case of the concentrate, the concentrated liquid or the filtrate may be mixed with crushed substances or denatured substances, and may cause quality problems such as coloring and reduced purity. W

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Also, from the environmental point of view, the amount of concentrated solution to be discarded, the amount of washing solution and replacement solution used when washing or replacing the inside of the filter, and the amount of concentrated solution with a high concentration of suspended solids after solution replacement It is required to reduce such factors. For this reason, it is necessary to reduce the amount of waste concentrate by increasing the concentration of the suspension in the concentrate to be discarded as much as possible. However, until now, as disclosed in Japanese Patent No. 3312964, a method for increasing the filtration rate has been disclosed, but the required filtrate can be obtained without reducing the filtration rate during continuous filtration. No filtration method has been disclosed for increasing the concentration of the suspension in the concentrated solution after filtration without increasing the time for obtaining the same. Disclosure of the invention

The present invention has been made in view of the above circumstances, and provides a method of filtering with a cross-type mouth-type membrane which increases the concentration of a suspension in a concentrated solution after filtration without increasing the filtration time, and a method for filtering the same. An object of the present invention is to provide a method for producing acrylamide used. The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, the filtration step of circulating filtration while continuously supplying the raw material liquid and the supply of the raw material liquid were stopped, and the suspension in the concentrated liquid after the filtration step was stopped. The present inventors have found that the separation from the concentration step of further concentrating the turbid matter is very effective in solving the above-mentioned problems, and have reached the present invention.

A first aspect of the present invention is a method for filtering a raw material liquid or a concentrated liquid obtained by concentrating the raw material liquid by a cross-type opening type membrane provided with a storage tank and a circulation pump, the method comprising: A filtration step of continuously filtering the raw material liquid or the concentrated liquid by the cross opening type membrane while supplying a new raw material liquid to the storage tank so that the liquid level in the storage tank is constant; In the state where supply of the new raw material liquid to the storage tank is stopped, filtration is further continued to concentrate while lowering the level of the liquid level in the storage tank, and after the concentration step, the remaining concentrated liquid is removed. And a discharging step for discharging.

According to this aspect, the concentration of the concentrated liquid after filtration can be increased while shortening the filtration time. Furthermore, since the concentration of the concentrated solution can be increased, continuous filtration can be performed for a long time using a smaller filtration device.

In the filtration method using a cross mouth type membrane according to the present invention, the concentration step and the drainage step are performed. A liquid replacement step of supplying a replacement liquid to the storage tank and filtering the replacement liquid may be provided between the discharge step and the storage tank so as to keep the level of the storage tank constant.

In the filtration method using a cross-flow type membrane of the present invention, the cross-flow type membrane is preferably a hollow fiber membrane.

In the filtration method using a cross mouth type membrane according to the present invention, when the suspension in the raw material solution filtered by the cross mouth type membrane is a microorganism, the raw material liquid is an aqueous acrylamide solution containing microbial cells. Especially suitable in cases.

A second aspect of the present invention is a method for producing acrylamide, which has a separation step including the above-mentioned filtration method using a cross-over type one membrane. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram schematically illustrating an example of a filtration device provided with a cross-flow type membrane. BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of a filtration method (hereinafter, abbreviated as a filtration method) using a cross-flow type membrane of the present invention will be described with reference to the drawings. The filtering device used in this embodiment is shown in FIG. 1 described above, and the description thereof is omitted here. Here, the “raw material liquid” is a liquid containing a suspension, and the “concentrated liquid” is a liquid in which the concentration of the suspension is higher than that of the raw material liquid by a filtration operation. The term “filtrate” refers to a liquid that does not contain suspended matter that has flowed out of a crossflow membrane.

In this filtration method, first, in the filtration step, the supply pump 2 is operated so that the level of the storage tank 3 for circulating and supplying the raw material liquid or the concentrated liquid to the cross-flow type membrane 4 becomes constant. Supply new raw material liquid to 3. At the same time, the circulating pump 7 installed in the feed pipe 5 is operated to supply the raw material solution or the concentrated solution to the cross-flow type membrane 4, and the first filtrate outlet valve 13 is opened and the withdrawal pump 15 is made. And continuously filter. Further, the concentrated liquid discharged from the cross-flow type membrane 4 is returned to the storage tank 3 via the return pipe 6, and the concentrated liquid is circulated.

Next, in the concentration step, the supply pump 2 is stopped and the supply of the new raw material liquid to the storage tank 3 is stopped. Then, with the supply stopped, circulate the concentrate further. The suspension in the concentrated solution is further concentrated by lowering the level of the storage tank 3 by filtration through a cross-over type membrane 4.

Next, in the discharging step, the discharging valve 19 is opened, and the remaining concentrated liquid in which the suspended matter is concentrated is discharged through the discharging pipe 20.

After discharging the concentrated liquid, the cross-flow type membrane 4 is washed and regenerated. By regenerating the membrane in this way, a high filtration rate can be maintained continuously.

In the filtration step, the operation of the supply pump 2 is controlled by a liquid level controller 9 in order to keep the liquid level in the storage tank 3 constant. Specifically, when the storage tank 3 is at the predetermined liquid level, the operation of the supply pump 2 is stopped by the liquid level controller 9 installed at a predetermined level of the storage tank 3, and the level of the liquid is controlled from the predetermined liquid level. When it becomes low, the supply pump 2 is operated to supply a new raw material liquid.

The liquid level in the storage tank 3 is preferably determined from the filtration time and the characteristics of the filtration device in consideration of a decrease in filtration speed due to an increase in the concentration of suspended solids in the storage tank 3 over time. In the concentration step, the viscosity of the concentrated solution increases with the concentration, and the discharge pressure of the circulation pump 7 rises. The flow rate may be adjusted.

The cross-flow type membrane 4 of the filtration device 1 that performs this filtration method may be any type such as a flat membrane, a spiral membrane, and a hollow fiber membrane, but is large in filtration area as compared with the size of the device. Hollow fiber membranes are preferred. When a hollow fiber membrane is used, the pressure loss due to circulation is large.To increase the concentration of suspended solids in the concentrated liquid finally discharged, a hollow fiber membrane with a large inner diameter or a hollow fiber with a short length is required. It is preferable to select a thread membrane.

Examples of the raw material liquid that can be filtered by this filtration method include drinking water in the food field, industrial products in the chemical industry field, culture liquid in the biochemical field, and reaction liquid in a bioreactor. Among these, non-Newtonian fluids whose physical properties such as viscosity change greatly with concentration and in which the suspension to be filtered is a microorganism, specifically, a reaction solution using a microbial catalyst are particularly suitable. ing. Among them, it is suitable for an acrylamide aqueous solution produced by a microbial catalyst.

In particular, aqueous acrylamide solutions produced using unimmobilized microbial catalysts Contains microorganisms that are not immobilized, that is, suspensions on the order of microns, and it is preferable to use a cross-flow membrane as a method for separating the microorganisms. Therefore, the method of the present invention is useful.

Here, the term “unimmobilized microbial catalyst” refers to a catalyst in which the microbial cell membrane comes into direct contact with the reaction solution, and includes comprehensive immobilization, that is, polyacrylamide, polyvinyl alcohol, carrageenan, agar, gelatin, and alginic acid. These catalysts are high molecular substances, etc., which have not been subjected to the method of entrapping and immobilizing the cells.

That is, a microorganism method in which the microorganisms are cultured and, if necessary, washed, etc., or the microbial cells are crosslinked or aggregated with a substance having a polyfunctional group such as daltalaldehyde, It includes those immobilized by non-inclusive methods such as the carrier binding method in which the body is chemically bonded to glass beads, resin, silica gel, etc.

There are various types of microbial catalysts capable of producing acrylamide. For example, Bacillus, Bacteridium, Micrococcus, and Brevibacterimn (Japanese Patent Publication 62) — 21519), the genus Corynebacterium Nocardia (see JP-B-56-17918), the genus Pseudomonas (see JP-B-59-37951) Genus, Microbacterium (see JP-B-4-1873), Rhodococcus (see JP-B-4-14873, JP-B-6-55148, JP-B-7-40948), acromopac Microbial species such as genus Achromobacter (see JP-A-6-225780) and genus Pseudonocardia (see JP-A-9-175978) are preferred. Furthermore, bacteria belonging to the genus Rhodococcus are more preferred.

Alternatively, the nitrile hydratase gene derived from the microorganism described above may be obtained, and the gene may be introduced into any host as it is or artificially improved.

For example, Escherichia coli MT 10770 (FERM P-14756) transformed with nitroni rehydratase of the genus Achromobacter (see Japanese Patent Application Laid-Open No. 8-266277), and nitrino rehydraters of the genus Pseudonocardia Escherichia coli MT 10822 (FERM BP-5785) transformed with W

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Microorganisms transformed with nitrile hydratase of the species Rhodococcus rhodochrous (see Japanese Patent Application Laid-Open No. 411,739) can be used. .

Various methods for producing acrylamide using a microbial catalyst are also conceivable, but acrylonitrile, which is a raw material, is dissolved in an aqueous solvent, and the microbial catalyst may be added. The reaction method, mode, etc. may be performed under conditions that are optimized for the purpose of production and for each microbial catalyst!

In the filtration method described above, a concentration step is provided after the filtration step. In this concentration step, filtration is performed without supplying a new raw material liquid, so that the suspension in the concentrated liquid can be concentrated in a short time. Can be concentrated. Therefore, the concentration of the concentrated solution after filtration can be increased while shortening the filtration time. Here, the filtration time in the present invention is the total time required for the filtration step and the concentration step.

Note that the present invention is not limited to the above embodiment. For example, a liquid replacement step may be provided between the concentration step and the discharge step, in which a replacement liquid such as pure water is supplied to the storage tank and filtered to keep the level of the storage tank constant. If there is a liquid replacement step between the concentration step and the discharge step, reduce the amount of components in the concentrated liquid discharged in the discharge step, that is, the amount of acrylamide when the raw material liquid is an aqueous acrylamide solution As a result, the amount of waste can be reduced and the yield of acrylamide recovered in the filtrate can be increased. In the present invention, when the liquid is replaced, the amount of the replacement liquid can be reduced because the amount of the concentrated liquid is reduced by the concentration step.

When a liquid replacement step is provided, the concentrated liquid after the liquid replacement can be further concentrated before the discharge step.

As the replacement liquid, a liquid containing no or very few suspensions is used.In consideration of post-treatment, etc., one of the solvents constituting the raw material liquid, a mixture thereof, or a solution is usually used. Used. If water is available, it is more economical and safer.

Also, in the filtration process, when new raw material liquid is supplied to the storage tank at a constant rate, the filtrate is adjusted by adjusting the valve provided in the filtrate transfer pipe without using a liquid level controller. The level of the reservoir may be kept constant by adjusting the discharge rate. Further, in the specific example of the above-mentioned filtration method, the filtration device has a single mouth-and-mouth type one membrane, but two or more cross-flow type membranes may be installed in parallel. If two or more cross-flow type membranes are installed in parallel, it is possible to switch between a cross-flow type membrane that performs a filtration step and a concentration step and a cross-flow type membrane that performs a membrane regeneration step. Continuous filtration becomes possible.

Furthermore, when the present invention is used, continuous filtration can be performed in a short time at a lower suspension concentration, so that when the suspension is a microbial catalyst, the stress applied to the microbes is reduced, and as a result, the microbes are generated from the microbes. The remarkable result that the amount of impurities mixed in the filtrate was reduced and the quality of the obtained filtrate was improved was obtained.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)

(1) Preparation of raw material liquid

As a microbial catalyst, Rhodococcus rhodochrous Jl (F ERM BP-1478) (described in Japanese Patent Publication No. 6-55148) having nitrile hydratase activity was used as the raw material water. Was reacted with acrylonitrile to prepare 500 kg of a 50% by mass aqueous solution of acrylamide, which was used as a raw material liquid.

The amount of the microbial catalyst used at that time was 50 g in terms of the dry cell mass, and the concentration of the microbial catalyst in the 50% by mass acrylamide aqueous solution was 0.01 mass% (100 p. pm).

(2) Cross-flow type membrane

The cross opening type membrane used in this example has the following specifications.

Internal pressure type hollow fiber membrane module (lab module) manufactured by Kuraray Co., Ltd.

Element type: MLE 7101

Hollow fiber inside diameter outside diameter: 1. OmmZO. 6mm

Separation characteristics (90% cut): 0.02 μm

Maximum transmembrane pressure difference (operating maximum pressure difference): 294 kPa

Hollow fiber length: 1m Number of hollow fibers (module): 126

Effective membrane area: 0.24 m2

(3) Filtration process

First, 5 kg of the raw material liquid is introduced into the storage tank 3 using the filtration device 1 shown in FIG. 1 equipped with the cross-flow type membrane described above, and then, while circulating the raw material liquid, the circulation flow rate becomes 100 kg / hour. The flow rate of the circulation pump 7 was adjusted as described above. During this adjustment, the first filtrate outlet valve 13 and the second filtrate outlet valve 17 were closed to prevent the filtrate from being discharged. In addition, the liquid level controller 9 was set to the liquid level of the storage tank 3 at this time.

Next, the first filtrate outlet valve 13 was opened, the extraction pump 15 was operated, and the flow rate of the filtrate was adjusted so as to be 10 kgZ hours, and filtration was started. At the same time, the liquid level controller 9 of the storage tank 3 was activated to control the supply pump 2, and the raw material liquid was supplied so that the liquid level of the storage tank 3 was constant.

Then, after 480 kg of the raw material liquid was filtered in 48 hours, the filtration was temporarily stopped. By this filtration, the concentration of the microbial catalyst in the storage tank 3 was reduced to 1% by mass. The circulating pressure (the pressure indicated by the circulating pressure controller 11) was about 0.14 MPa immediately after the start of the filtration, and increased to about 0.23 MPa at the end of the filtration. The filtrate outlet pressure (the pressure indicated by the filtrate outlet pressure gauge 12) is changing from 0.03MPa to 0.02MPa, and is hardly sucked by the withdrawal pump 15, and there is still room for the filtration speed. Was.

(4) Concentration process, discharge process

Stop the liquid level controller 9 in the storage tank 3 to stop supplying new raw material liquid, and use the circulation pressure controller 11 to adjust the flow rate of the circulation pump 7 so that the circulation pressure does not exceed 0.25 MPa. Was automatically adjusted to start the concentration step. At this time, the second filtration outlet valve 17 was fully opened to discharge the furnace liquid.

After 20 minutes, the circulation pump 7 was stopped, and the concentrated liquid concentrated through the discharge pipe 20 was discarded. The amount of discarded concentrate is 1.7 kg, and the concentration of microbial catalyst in the concentrate is about 2.9 mass. /. Met. The circulation flow rate in the concentration step was 100 kgZ hours immediately after the start of concentration, but dropped to about 30 kgZ hours immediately before the end of concentration. In this example, the microbial catalyst concentration could be increased to about 2.9% by mass in 48 hours and 20 minutes.

Further, the obtained filtrate was colorless and transparent.

Table 1 shows a comparison between Example 1 and Example 2 and Comparative Examples shown below. In the table, “〇” is attached to each of the preferred values of Example 1 and Example 2, and “X” is compared to the corresponding example in each comparative example. Each is attached to an inappropriate value.

(Comparative Example 1)

The raw material liquid was filtered in the same manner as in Example 1 except that the concentration step of (4) was not performed.

(4 ') Discharge process The liquid level controller 9 of the storage tank 3 was stopped to stop supplying new raw material liquid, the circulation pump 7 was stopped, and the concentrated liquid concentrated through the discharge pipe 20 was discarded. The amount of the discarded concentrate was 5.0 kg, and the concentration of the microbial catalyst in the concentrate was about 1.0% by mass.

In addition, the obtained filtrate was colorless and transparent.

(Comparative Example 2)

(3) The raw material liquid was filtered in the same manner as in Example 1 except that the filtration step was as follows, and the concentration step was omitted.

(3 ') Filtration process

First, 1.7 kg of the raw material liquid was charged into the storage tank 3, and then the flow rate of the circulation pump 7 was adjusted while circulating the raw material liquid so that the circulation flow rate became 100 kgZ hours. During this adjustment, the first filtrate outlet valve 13 and the second filtrate outlet valve 17 were closed so that the filtrate was not discharged. At this time, the liquid level in the storage tank 3 內 was set in the liquid level controller 9.

Next, the first filtrate outlet valve 13 was opened, and the extraction pump 15 was operated to adjust the flow rate of the filtrate to 10 kg / hour, and filtration was started. At the same time, the liquid level controller 9 of the storage tank 3 was activated, and the raw material liquid was supplied so that the liquid level of the storage tank 3 was constant.

After about 20 hours, the filtrate outlet pressure was almost atmospheric pressure (less than 0.1 MPa), so the second filtrate outlet valve 17 was fully opened, and the subsequent filtration speed was achieved. Next, the concentrated liquid was circulated by automatically adjusting the flow rate of the circulating pump 7 using the circulating pressure controller 11 so that the circulating pressure did not exceed 0.25 MPa. After about 85 hours, the filtration of the 480 kg raw material liquid was completed.

In this filtration step, the filtration rate after 20 hours from the start of filtration gradually decreased from 10 kgZ hours, and decreased to about 3 kgZ hours immediately before the end of filtration.

The concentration of the microbial catalyst in the storage tank 3 was concentrated to 2.9% by mass as in Example 1, but the filtration time was significantly longer.

The filtrate obtained was transparent but slightly reddish.

(Example 2) After further concentrating the concentrated solution in the same manner as in Example i, the solution was replaced with pure water, and the concentrated solution 'was discarded.

In the liquid replacement at that time, first, after the concentration is stopped, the set level of the liquid level controller 9 is set to the level after the concentration, and the liquid level controller 9 controls the pure water supply pump (not shown). Switched to Next, the second filtrate outlet valve 17 is fully opened, and the flow rate of the circulation pump 7 is automatically adjusted using the circulation pressure controller 11 so that the circulation pressure does not exceed 0.25 MPa. The liquid replacement was started.

Then, when 5 kg of pure water was supplied to the storage tank 3, the liquid replacement was terminated, and subsequently, the concentrated liquid after the liquid replacement was discarded. The amount of the concentrate was 1.7 kg, and the concentration of the microbial catalyst in the suspension was about 2.9% by mass. The acrylamide concentration in the concentrate was about 3% by mass.

In addition, the obtained filtrate was colorless and transparent.

(Comparative Example 3)

The raw material liquid was filtered in the same manner as in Example 2 except that the concentrated liquid obtained in the same manner as in Comparative Example 1 was subjected to liquid replacement as described below.

In the liquid replacement at that time, first, after the filtration was completed, the liquid level controller 9 was switched to control the pure water supply pump while the set level of the liquid level controller 9 was kept as it was. Next, the first filtrate outlet valve 13 was fully opened, and the liquid was replaced by adjusting the flow rate of the filtrate to be 10 kg Z hours using the withdrawal pump 15.

The solution was replaced with 5 kg of pure water, and the concentrated solution was discarded. The amount of the concentrate was 5.0 kg, and the concentration of the microbial catalyst in the suspension was about 1.0% by mass. The acrylamide concentration in the concentrate was about 19% by mass.

In addition, the obtained filtrate was colorless and transparent.

(Comparative Example 4)

The concentrated liquid obtained in the same manner as in Comparative Example 2 was filtered from the raw material liquid in the same manner as in Example 2.

Then, when 5 kg of pure water was supplied to the storage tank 3, the liquid replacement was terminated, and subsequently, the concentrated liquid after the liquid replacement was discarded. The amount of the concentrate was 1.7 kg, and the concentration of the microbial catalyst in the concentrate was about 2.9% by mass. Also, the concentration of acrylamide in the concentrate It was about 3% by mass. '

The filtrate obtained was transparent but slightly reddish.

Since Examples 1 and 2 had a concentration step, the concentrated solution could be concentrated to a high concentration in a short time. Furthermore, in Example 2, the liquid was replaced, so that the acrylamide concentration in the discarded concentrated solution was low, the burden on waste disposal was small, and the acrylamide loss was small, resulting in a very economically efficient process. .

On the other hand, since Comparative Example 1 did not have a concentration step, the amount of concentrated liquid discarded was large, the concentration of microorganisms therein was low, and the acrylamide content was high. In other words, the burden on waste disposal is large, and the loss of acrylamide is also large. In Comparative Example 2, although the amount of waste disposal was kept low, the filtration time required to reach the concentrated liquid amount as in Example 1 was long, and the filtrate was slightly colored, and the quality of acrylamide was deteriorated.

In Comparative Example 3, since the liquid was replaced without having a concentration step, the amount of the concentrated liquid discarded was large, and the concentration of the microbial catalyst therein was low. Furthermore, the concentration of acrylamide in the discarded concentrate was high, which resulted in economically unfavorable results. In Comparative Example 4, the filtration time required to reach the concentration of the concentrated solution as in Example 1 was long, and the filtrate was slightly colored, and the quality of acrylamide was deteriorated. Industrial potential

The filtration method using a cross-flow type membrane of the present invention is a filtration method using a cross-flow type membrane provided with a storage tank and a circulation pump for circulating and supplying a raw material liquid or a concentrated liquid obtained by concentrating the raw material liquid, A filtration step of continuously filtering the raw material liquid or the concentrated liquid by the cross-flow type membrane while supplying new raw material liquid to the storage tank so that the liquid level in the storage tank is constant. A concentration step in which, while the supply of the new raw material liquid to the storage tank is stopped, the filtration is further continued to concentrate while lowering the liquid level in the storage tank; and a concentration remaining after the concentration step Since it has a discharge step of discharging the liquid, the concentration of the concentrated liquid after the filtration can be increased while shortening the filtration time. Furthermore, since the concentration of the concentrated solution can be increased, continuous filtration can be performed for a long time using a smaller filtration device.

Claims

The scope of the claims

1. A filtration method using a cross-floor type membrane provided with a storage tank and a circulation pump for circulating and supplying a raw material liquid or a concentrated liquid obtained by concentrating the raw material liquid,

A filtration step of continuously filtering the raw material liquid or the concentrated liquid through the cross opening type membrane while supplying new raw material liquid to the storage tank so that the liquid level in the storage tank becomes constant. ,

A state in which the supply of the new raw material liquid to the storage tank is stopped, and further, a concentration step of continuing filtration to concentrate while lowering a liquid level in the storage tank;

Discharging the remaining concentrated liquid after the concentration step.

2. The method for filtration using a cross-flow type membrane according to claim 1, further comprising:

A liquid replacement step is provided between the concentration step and the discharge step, in which the replacement liquid is supplied to the storage tank and filtered so as to keep the liquid level in the storage tank constant.

3. A method for filtration using a cross mouth type membrane according to claim 1,

The cross-flow type membrane is a hollow fiber membrane.

4. A filtration method using a cross mouth type membrane according to claim 1,

The suspension in the raw material liquid filtered by the cross-flow type membrane is a microorganism.

5. A method for filtration with a cross mouth type membrane according to claim 1,

The raw material liquid is an aqueous acrylamide solution containing microbial cells.

6. A method for producing acrylamide,

A separation step including a filtration method using a cross opening type membrane according to claim 5 is provided. al

Processing liquid storage tank

Filtrate