JP2004121961A - Membrane separation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent the clogging of a film with suspended solids (SS) in a liquid to be treated and to recover valuables in a high recovery ratio in a method in which, after the valuables are recovered on the filtrate side by concentrating the liquid to be treated containing the valuables and SS by membrane separation, the valuable left on the concentrated liquid side are further recovered by diafiltration. <P>SOLUTION: Large-size SS in the treatment liquid is removed by a SS separation means 1. The separated liquid is concentrated by membrane-separated by a membrane separation device. After that, when the concentrated is added with water to be subjected to the diafiltration, the separated large-size SS are mixed with water for the diafiltration and added. The valuables contained in the large-size SS can be recovered by the diafiltration. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a membrane separation method suitable for recovering valuable resources from a fermentation solution or a saccharified solution.
[0002]
[Prior art]
When commercializing valuable products such as enzymes produced by a fermentation method, for example, enzymes such as lipase, cellulase, and xylase, bioactive peptides, proteins, etc., the production bacteria and the fermentation products are separated to collect valuable products. There is a need.
[0003]
2. Description of the Related Art Conventionally, as a method for recovering valuable resources from a fermentation liquid and separating cells, there is a membrane separation method using an MF (microfiltration) membrane or a UF (ultrafiltration) membrane.
[0004]
Cell separation from the fermentation liquor and recovery of the target organic matter by membrane separation consist of membrane separation of the fermentation liquor (permeation of valuables and concentration of the cells) and diafiltration (hydrolysis treatment, which remains on the concentrated liquid side). Recovery of valuables to the permeate side). That is, first, the fermented liquor is subjected to membrane separation treatment, valuable resources are collected on the permeate side, and the cells are concentrated. After the cells have been concentrated to some extent, water is added to the concentrate side (water treatment). To facilitate recovery of valuables remaining on the concentrate side to the permeate side.
[0005]
The recovery of valuable substances on the permeate side by the membrane separation method is also applied to the purification of a saccharified solution obtained by saccharifying starch such as corn starch with an enzyme.
[0006]
The fermented solution used for membrane separation contains a large amount of SS such as bacterial cells and fermentation products. The saccharified solution also contains a large amount of SS such as oil, protein, and fiber. As described above, in the membrane separation treatment of a liquid containing a large amount of SS, a membrane having a large primary-side channel diameter such as a tubular type membrane is used to prevent the membrane from being clogged. However, even if such a membrane is used, it is difficult to reliably prevent the membrane from being clogged.In addition, this type of membrane has a small membrane area with respect to the module capacity, the apparatus becomes excessively large, and cross-flow occurs. The disadvantage is that the required power costs are enormous.
[0007]
Japanese Patent Publication No. 1-12478 proposes a method of separating the SS content in the saccharified solution by centrifugation prior to the membrane separation of the saccharified solution. By removing a part of the SS in advance prior to the membrane separation treatment, the membrane can be prevented from being clogged, and a spiral membrane or a hollow fiber membrane having a high membrane packing density can be applied.
[0008]
However, if the SS component is separated prior to the membrane separation treatment, the SS component is separated as a wet cake, and the valuables contained in the liquid in this cake will be discarded together with the SS component. Recovery rate decreases. That is, in general, the SS content in the fermented liquor or saccharified liquor is about 0.1 to 5% by weight on a dry weight basis, but 5 to 30% by weight on a wet basis. Valuables contained in the weight percent liquid are discarded.
[0009]
In order to recover the valuables in the separated SS, there is a method of washing the cake of the separated SS and subjecting the cleaning water to membrane separation to recover valuables from the cleaning water. However, there is a disadvantage that the membrane separation device in the subsequent stage becomes large due to an increase in the amount of the liquid to be treated due to water washing.
[0010]
[Patent Document 1]
Japanese Patent Publication No. 1-1478 / 0011
[Problems to be solved by the invention]
The present invention solves the above-mentioned conventional problems, concentrates a liquid to be treated containing valuables and SS components by membrane separation treatment, collects valuables on a permeate side, and removes valuables remaining on the concentrate side. In a method of further recovering materials by diafiltration, to provide a membrane separation method capable of effectively preventing clogging of a membrane due to SS content in a liquid to be treated and recovering valuable materials at a high recovery rate. With the goal.
[0012]
[Means for Solving the Problems]
The membrane separation method of the present invention is a method in which a liquid to be treated containing a valuable material and an SS component is subjected to membrane separation treatment and a valuable material is collected on a permeate side, and a coarse SS component in the liquid to be treated is removed. A pretreatment step, a concentration step of subjecting the separated solution obtained in the pretreatment step to membrane separation and concentration, and a water treatment step of adding water to the concentrated solution obtained in the concentration step and membrane separation. Wherein the coarse SS separated in the pretreatment step is added to the concentrated solution to be hydrolyzed.
[0013]
In the present invention, valuable substances contained in the coarse SS separated in the pretreatment step can be recovered by diafiltration (hydrolysis treatment).
[0014]
The separated coarse SS is preferably mixed with water to be added to the concentrate for diafiltration and added.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the membrane separation method of the present invention will be described in detail with reference to the drawings.
[0016]
1 and 2 are system diagrams each showing an embodiment of the membrane separation method of the present invention. In FIGS. 1 and 2, members having the same function are denoted by the same reference numerals.
[0017]
In the method of FIG. 1, the valves V ₁ and V ₂ are closed, and first, the liquid to be treated is introduced into the SS separation means 1 through the pipe 11 to remove coarse SS in the liquid to be treated. The SS separation means 1 is not particularly limited as long as it can remove coarse SS in the liquid to be treated, and a decanter, a centrifuge, an inclined screen, a wedge wire screen, or the like is used. Can be.
[0018]
The separated liquid from which the coarse SS component has been removed by the SS separating means 1 is then introduced into the membrane separation device 2 through a pipe 12 and circulated through a circulating line 13 of the concentrated liquid to perform a membrane separation treatment in a cross-flow manner, thereby obtaining valuable resources. The substance is recovered in the permeate, and the SS and the like are concentrated in the concentrate. The permeate is taken out from the pipe 14. On the other hand, the coarse SS fraction separated by the SS separation means 1 is sent from the pipe 15 to the mixing tank 3 and mixed with water from the pipe 16.
[0019]
In the membrane separation device 2, after the concentration has progressed to a predetermined magnification, water is added to further collect valuable resources remaining on the concentrate side, and diafiltration is performed.
[0020]
In other words, the water for diafiltration the valve V ₁ is opened (hereinafter sometimes referred to as "DF for added water".) As a pipe the water separated coarse SS component is mixed with SS separator 1 From 17, the concentrate is added to the circulation line 13 of the concentrate, and the membrane is further subjected to membrane separation treatment, and valuable resources are collected on the permeate side. The amount of water and the method of water necessary for the diafiltration are appropriately selected depending on the concentration of valuables in the concentrated solution, the rejection of valuables by the membrane, the target recovery of valuables, and the like. The method of water addition may be continuous water supply or intermittent water supply.
[0021]
After sufficient recovering valuable material in the concentrate by diafiltration discharges the valve V ₁ is closed, to the outside of the system the concentrate from the pipe 18 a valve V ₂ is opened.
[0022]
In FIG. 1, concentration and diafiltration are performed by one membrane separation device. In FIG. 2, two membrane separation devices are connected in series, and concentration is performed by the first membrane separation device 4 in the preceding stage. Then, diafiltration by a water treatment is performed in the second membrane separation device 5 at the subsequent stage.
[0023]
In the method of FIG. 2 as well, coarse SS in the liquid to be treated is separated and removed by the SS separation means 1 in the same manner as in FIG. 1, and the separated liquid is supplied to the concentrated liquid circulation line 13 of the first membrane separation device 4. And concentrate. The concentrated liquid of the first membrane separation device 4 is supplied from a pipe 19 to a second membrane separation device 5 into which DF-added water from the mixing tank 3 is introduced. Perform filtration.
[0024]
The permeate containing valuables obtained from the first membrane separation device 4 and the second membrane separation device 5 is taken out from the pipes 14 and 21. On the other hand, the concentrated liquid in the second membrane separation device 4 is discharged from the pipe 18 to the outside of the system.
[0025]
1 and 2 show an example of an embodiment of the membrane separation method of the present invention, and the present invention is not limited to the illustrated ones as long as the gist is not exceeded.
[0026]
For example, in FIG. 2, a membrane separation device for concentration may be further provided, the concentration may be performed by the first and second membrane separation devices, and the diafiltration may be performed by the third membrane separation device.
[0027]
In any method, the coarse SS component is separated and removed from the liquid to be treated in advance, and the valuable material can be recovered by diafiltration from the separated and removed coarse SS component, so that the recovery efficiency of the valuable material is high. . In recovering valuable resources from the coarse SS, the coarse SS is supplied to the diafiltration step, so that blockage of the membrane and the like can be prevented, and a stable membrane separation process can be performed. That is, in the diafiltration process, the recovery of the valuables in the liquid to be treated progresses to some extent, and the concentration of the valuables in the concentrated solution is low. Is hardly blocked. For this reason, even if the separated coarse SS component is added to the diafiltration step, the blocking of the film is prevented from being promoted by the SS component. In particular, by mixing the coarse SS component with water for diafiltration and supplying it, the coarse SS component can be gradually supplied as a uniform aqueous dispersion, so that stable operation of diafiltration can be achieved. This is preferable because valuable resources can be efficiently collected without any loss.
[0028]
In the present invention, in order to effectively prevent blockage of the membrane of the subsequent-stage membrane separation device without excessively increasing the load of the preceding-stage SS separation unit, the pretreatment SS separation unit uses It is preferable to separate and remove about 20 to 70% of SS.
[0029]
When the separated coarse SS is mixed with water and added as DF-added water, the SS concentration in the DF-added water is not particularly limited. However, if the SS concentration is excessively high, the DF-added water is added. Since the stable operation of the membrane separation device is impaired, the SS concentration in the DF-added water is preferably 8% by weight or less as a dry concentration. However, if the SS concentration is reduced, the amount of DF-added water increases and the treatment efficiency deteriorates. Therefore, the SS concentration in the DF-added water is determined by the SS concentration in the liquid to be treated, the performance of the membrane separation device used, and the membrane separation conditions (diafiltration). It is preferable to set the amount of water added with DF so as not to be excessively large according to the amount of water necessary for torsion). In the normal case, the SS concentration in the DF-added water is preferably 1 to 8% by weight in dry concentration.
[0030]
The SS concentration in the DF-added water is not necessarily required to be constant during the diafiltration step, but may be gradually increased. That is, at the initial stage of diafiltration, water containing no coarse SS is added, diafiltration is performed to some extent, and when the concentration of valuable substances in the concentrated solution is reduced and its viscosity is reduced, the coarse SS is removed. DF-containing water containing water may be added.
[0031]
In the present invention, an MF or UF membrane is preferably used as a membrane used for the membrane separation treatment. There is no limitation on the film material, and a metal film, a polyolefin film, a polysulfone film, a Teflon film, a ceramic film, or the like is used. The selection of the MF or UF film and the selection of the film material are performed in consideration of the molecular weight of the valuable material, the properties of the liquid to be treated, and the like. Although there is no particular limitation on the membrane type, a hollow fiber, a tubular, a spiral, a plate and frame type membrane module or the like is generally used.
[0032]
In particular, as shown in FIG. 2, when the treatment is performed by arranging membrane separators in multiple stages in series, an organic membrane is used for the former membrane separator for concentration and the latter is used for diafiltration. It is preferable to use an inorganic membrane for the membrane separation device.
[0033]
That is, the organic film is economically advantageous because the device is small in size and inexpensive as compared with the inorganic film, but the chemical and mechanical strength is inferior to the inorganic film, and operation under severe conditions cannot be performed. There is a disadvantage that the concentration rate cannot be increased and the concentration is limited to about 10 to 20 times. On the other hand, inorganic membranes have higher chemical and mechanical strength than organic membranes, can be operated under higher conditions than organic membranes, and can be concentrated up to about 50 times, but are expensive and require a larger apparatus. , Economically disadvantageous.
[0034]
Therefore, by utilizing such characteristics of the organic membrane and the inorganic membrane, the organic membrane is used at the time of low concentration by the first-stage membrane separation device, and the inorganic membrane is used at the time of high concentration by the second-stage membrane separation device. It is possible to efficiently collect valuable resources while preventing an increase in the size of equipment and a rise in equipment costs.
[0035]
In this case, as the organic membrane of the former-stage membrane separation device, a hollow-type or spiral-type polytetrafluoroethylene membrane, a PVDF (polyvinylidene fluoride) membrane, a polyolefin membrane, a polysulfone membrane, or the like can be used. As the inorganic film on the side, a tubular stainless titanium film (an MF film having a titanium active layer formed by sintering titanium powder on the surface of a stainless steel support obtained by sintering a uniform stainless powder) or the like is used. be able to.
[0036]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0037]
Example 1
According to the method of the present invention, a membrane separation treatment was carried out on a glucose solution (glucose concentration: 300 g / L, SS dry concentration: 0.3% by weight) which had been saccharified by enzyme. 500 L of this glucose solution was treated with a wedge wire screen (aperture: 0.3 mm) to separate and remove coarse SS (pretreatment step). Thereby, the SS dry concentration of the liquid passing through the screen became 0.2% by weight. 490 L of this screen passing liquid was subjected to a membrane separation treatment using a first membrane separation apparatus (a tubular membrane having a pore diameter of 0.1 μm, a membrane area of 0.5 m ² ). On the other hand, the coarse SS component on the screen was mixed with 60 L of water to form a slurry. This slurry had a glucose concentration of 50 g / L and an SS dry concentration of 0.7% by weight.
[0038]
After concentrating the 490 L screen-passed liquid to 24.5 L using a membrane separation device (concentration step), the SS for the coarse SS is divided into 10 L portions and added to the concentrate side to perform diafiltration (hydrolysis treatment). Step) to obtain a permeate.
[0039]
When 465.5 L of the permeate in the concentration step and 70 L of the permeate in diafiltration were combined, the recovery of glucose was determined to be 98.6%.
[0040]
Comparative Example 1
In Example 1, when the treatment was carried out in the same manner except that the coarse SS component on the screen was not supplied to the water treatment step, the recovery rate of glucose was 97.4%.
[0041]
From this result, it can be seen that by supplying the coarse SS separated in the pretreatment step to the water treatment step and performing diafiltration, the recovery efficiency of valuable resources can be increased.
[0042]
【The invention's effect】
As described above in detail, according to the membrane separation method of the present invention, in the pretreatment step, in order to remove the coarse SS content contained in the liquid to be treated such as a fermentation solution or a saccharification solution in advance, in the subsequent membrane separation step The treatment can be stably performed over a long period of time by preventing the film from being blocked. In addition, by recovering valuable resources contained in the separated coarse SS components by diafiltration, valuable resources can be recovered at a high recovery rate.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a membrane separation method of the present invention.
FIG. 2 is a system diagram showing another embodiment of the membrane separation method of the present invention.
[Explanation of symbols]
1 SS separation means 2, 4, 5 Membrane separation device 3 Mixing tank

Claims (2)

A method in which a liquid to be treated containing a valuable material and an SS component is subjected to membrane separation treatment to collect a valuable material on a permeate side,
A pretreatment step of removing a coarse SS component in the liquid to be treated;
A concentration step of subjecting the separated solution obtained in the pretreatment step to membrane separation treatment and concentration,
A water treatment step of adding water to the concentrated solution obtained in the concentration step and performing a membrane separation treatment,
A membrane separation method comprising adding the coarse SS separated in the pretreatment step to the concentrated solution to be hydrolyzed. 2. The membrane separation method according to claim 1, wherein the coarse SS separated in the pretreatment step is mixed with water for the water treatment and added to the concentrated solution.

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