JP2009148680A - Method for recovering stock solution in filtration apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering a residual liquid in a casing as a stock solution without cake for the purpose of avoiding discarding the residual liquid as waste and avoiding leaving the stock solution in the casing. <P>SOLUTION: A filtration apparatus has a filtration filter constructed by covering the surface of a built-in filtration element 8 included in the casing 1 with a filter aid M, and extracts a filtrate F through the filtration filter from the stock solution U supplied into the casing 1. In the filtration apparatus, the method is carried out such that after finishing normal filtering processing for supplying the stock solution U into the casing 1, the inside of the casing 1 is pressurized, and the stock solution U (remaining liquid R) remaining in the casing 1 is directly extracted to the outside and recovered from the casing 1 without being passed through the filtration filter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for recovering a stock solution in a filtration device in which a filter aid is formed by coating a filter aid on the surface of a filter element incorporated in a casing and recovers all the stock solution remaining inside the casing.

  In the present invention, the liquid before being filtered is called a stock solution, and the liquid taken out by filtering is called a filtrate. Hence, “stock solution supplied to the inside of the casing” means the stock solution supplied to the inside of the casing and the outside of the filter before the normal filtration process. The “stock solution remaining inside the casing” means a stock solution remaining inside the casing and outside the filter after the normal filtration treatment or forced filtration treatment, and the “stock solution supplied to the inside of the casing”. "Is particularly called" residual liquid ".

  A filtration device that coats a filter aid (for example, diatomaceous earth) on the surface of a filtration element incorporated in a casing to constitute a filtration filter, and takes out the filtrate from the stock solution supplied into the casing through the filtration filter, In a normal filtration process, the supply of the stock solution is stopped when the supply of a predetermined amount of the stock solution is finished, the filtration resistance of the filtration filter increases with the progress of the filtration process, or the internal pressure of the casing increases. At this time, a stock solution that remains in the casing without being filtered, that is, a residual solution is generated. If it is abandoned to take out the filtrate from the residual liquid, the waste becomes excessive, and various means for taking out the filtrate from the residual liquid have been proposed.

  In Patent Document 1, in addition to a normal filter element, a dedicated filter element for filtering residual liquid is provided, and after the normal filtration process is finished for the stock solution supplied to the inside of the casing, pressurized air is supplied into the casing. A filtration method is proposed in which the residual liquid is filtered by a filtration filter comprising the dedicated filtration element. Patent Document 2 also proposes a filtration device that removes the filtrate from the residual liquid by separately filtering the residual liquid, although the configuration of a dedicated filter for filtering the residual liquid is different from that of Patent Document 1.

Japanese Unexamined Patent Publication No. 06-015115 JP 05-076710 A

  In the filtration process of the residual liquid disclosed in Patent Document 1 and Patent Document 2, the filtrate is taken out by forced filtration from the residual liquid that can no longer be taken out by the normal filtration process. However, for example, when the filtration resistance of the filter is increased due to clogging due to impurities contained in the stock solution or when the stock solution has a very high viscosity, it is difficult to practically filter the entire remaining solution. For this reason, the residual liquid is discarded as waste together with a cake mainly composed of the filter aid peeled from the filter element (the impurities contained in the stock solution adhered to the filter aid by filtering the stock solution). However, in the case of a stock solution with a high unit price, throwing away the remaining liquid as waste causes a problem of increasing the unit price of the filtrate.

  In addition, the forced filtration of the residual liquid tends to clog the cake with respect to the filter element because the residual liquid is pressed against the filter by the pressurized air. In particular, in the filtration method of Patent Document 1 in which the filtration treatment is performed in a state where the cake is mixed in the residual liquid, the clogging tends to be severe. The clogging of the cake with respect to the filter element leads to problems that increase the time and labor required for the washing process, lengthen the time required for the entire filtration process, and reduce the processing efficiency. Further, the forced filtration of the residual liquid with pressurized air is not preferable because the taken-out filtrate may involve the pressurized air and deteriorate the quality of the filtrate.

  Here, even if the residual liquid remaining without being forcedly filtered can be recovered without including the cake, it can be filtered as a new stock solution in the next filtering step without being discarded as waste. Because, in the next filtration step, the cake is peeled off from the surface of the filter element, and a filtration filter is newly coated on the surface with a filter aid. This is because the filtrate can be easily taken out. In addition, if it is necessary to finish the filtration process immediately due to operating time or production plan, etc., if the residual liquid can be recovered, the filtrate can be filtered by the normal filtration process or the forced filtration process in the next filtration process as described above. Can be taken out. Therefore, a method for recovering all remaining liquid (raw liquid remaining in the casing) without discarding the cake and containing the cake was examined.

  As a result of the study, in the filtration device that covers the surface of the filtration element built in the casing to form a filtration filter, and extracts the filtrate from the stock solution supplied to the inside of the casing through the filtration filter, After the normal filtration process has been completed for the stock solution supplied to the inside of the casing, the stock solution (residual solution) remaining inside the casing is directly discharged from the casing without passing through the filtration filter with the inside of the casing being pressurized. We have developed a method for collecting stock solutions in filtration devices that are extruded and collected. The remaining liquid can be easily pushed out of the casing and recovered by providing a recovery port at the bottom of the casing and putting the inside of the casing in a pressurized state. The recovered residual liquid can be filtered as a stock solution for the next filtration step or mixed with a new stock solution, and as a result, the filtrate can be taken out without throwing away the stock solution as waste.

  In the present invention, the residual liquid is once recovered and used as a stock solution to be filtered next, or mixed with the stock solution to be filtered next, and filtered again together with the stock solution to take out the filtrate. As described above, a stock solution containing a large amount of impurities or a high-viscosity stock solution is liable to generate a residual solution.However, since the present invention recovers the residual solution and performs filtration treatment, Even if it is a stock solution of viscosity, efficient filtration can be performed.

  In addition, after the normal filtration process is finished for the stock solution supplied to the inside of the casing, the stock solution remaining inside the casing is forcibly filtered through a filtration filter while the inside of the casing is in a pressurized state. The stock solution remaining inside may be recovered by pressing the inside of the casing in a pressurized state and directly extruding the casing without passing through the filter. In the present invention, the pressurized state in the casing follows the pressurized state due to the supply of the stock solution in the normal filtration process or the pressurized state in the forced filtration process after the filtration process. Since the pressure applied in the direction of pressing against the filter element is continuous, the cake does not peel off, and there is no possibility that the cake is mixed into the remaining liquid.

  The pressurized state inside the casing may be formed by supplying gas to the inside of the casing. The gas can be supplied into the casing from a gas supply port provided above the casing. The type of gas is not limited as long as it does not denature the stock solution, but air (including pressurized air) is preferable from the viewpoint of harmlessness and easy availability. The pressure state when the residual liquid is forcibly filtered and the pressure state when the residual liquid is pushed out and recovered may be the same or different. It is necessary to be in a pressurized state in which pressure is applied in the direction of pressing against the element. Here, if the recovery port provided at the bottom of the casing can be freely opened and closed, if the recovery port is closed and the inside of the casing is in a pressurized state, the residual liquid can be forcibly filtered and the cake does not peel off. When the recovery port is opened while maintaining the pressurized state, the remaining liquid is pushed out from the recovery port and can be recovered.

  According to the present invention, a situation in which the residual liquid is discarded as waste is avoided, and not only the residual liquid does not remain in the casing, but also the filtrate can be taken out from the recovered residual liquid. In principle, the residual liquid that cannot be filtered and remains in the casing is collected and mixed as a stock solution for the next filtration step or into a new stock solution, and then filtered again. This means that the efficiency of the filtration treatment is extremely high compared to Patent Document 1 and Patent Document 2 in which the necessity of discarding the residual liquid as waste, and particularly when the unit price of the stock solution is high, the casing according to the present invention. A method for recovering the stock solution (residual solution) remaining inside the container is suitable.

  In addition, the present invention does not need to discard the residual liquid as waste, and therefore has the effect of reducing labor, labor, and cost required for waste disposal. Furthermore, not only when the stock solution contains a lot of impurities or when it has a high viscosity, but also when the filtration process needs to be completed immediately for the convenience of operating time, production plan, etc., the filtration process is terminated at an arbitrary timing. Even in this case, there is an advantage that all the remaining liquid can be recovered. In addition, the present invention provides a filtration device that covers the filtration element with a filter aid and performs a filtration treatment, for example, a filtration device in which a tubular filtration element is erected from the bottom surface, or the tubular filtration element is suspended from the ceiling. In addition to the filter device, the present invention is excellent in that it has versatility that can be used for a filter device (leaf type) that covers the surface of the disk to be laminated with a filter aid.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the main part of the filtration apparatus of this example to which the present invention is applied, and FIGS. 2 to 5 show the flow of a series of processes from the precoat process to the residual liquid recovery process in the filtration apparatus of this example. 2 is a block diagram corresponding to FIG. 1. FIG. 2 shows a pre-coating process, FIG. 3 shows a normal filtration process for the stock solution, FIG. 4 shows a filtration process for the residual liquid, and FIG. 5 shows a residual liquid recovery process. 2 to 5, for convenience of explanation, a portion where the valve and the lid are open and in a circulation state is indicated by a thick line, and a portion where the valve and the lid are closed and a cutoff state is indicated by a broken line.

  As shown in FIG. 1, the filtration device of this example has a pressurized air supply port 3 on the top surface of the casing 1, a stock solution supply port 2 on the side surface, a waste liquid discharge port 5 and a residual liquid recovery port 7 on the bottom surface, and a bottom surface. The basic structure is such that the filter element 8 is erected from the bottom surface of the casing 1 provided with the filtrate discharge port 6. The residual liquid recovery port 7 may be used as the waste liquid discharge port 5 or may be provided along the lower end of the side surface of the casing. When the waste liquid discharge port 5 and the residual liquid recovery port 7 are used together, an open / close valve is provided for each of the discharge path leading to the discharge destination (the waste liquid tank etc. described later) and the recovery path leading to the collection destination (the stock liquid supply tank etc. described later). Alternatively, a switching valve may be provided at a branch point between the discharge path and the recovery path.

  The stock solution supply port 2 is supplied with a stock solution supply tank (not shown) through a stock solution supply valve 21, a cleaning solution supply tank (not shown) through a cleaning solution supply valve 22, and a filter aid through a filter aid supply valve 23. Tanks (not shown) are connected to each other. When the stock solution supply valve 21 is opened and the cleaning solution supply valve 22 and the filter aid supply valve 23 are closed, the stock solution U is obtained. When the wash solution supply valve 22 is opened and the stock solution supply valve 21 and the filter aid supply valve 23 are closed, the wash solution WL However, if the filter aid supply valve 23 is opened and the stock solution supply valve 21 and the cleaning solution supply valve 22 are closed, the precoat liquid PC in which the filter aid M is mixed with water is introduced into the casing 1 by a pump (not shown). Supplied. The filter aid M may be mixed with the stock solution U.

  The pressurized air supply port 3 is connected to a pressurized air supply source (not shown) via a pressurized air supply valve 31. From this point, when the pressurized air supply valve 31 is opened, the pressurized air A is supplied from the pressurized air supply port 3 into the casing 1. The pressurized air A is used for forcibly filtering the residual liquid R and for bringing the inside of the casing 1 into a pressurized state when collecting the residual liquid R, which is a feature of the present invention. The residual liquid recovery port 7 is provided with a residual liquid recovery port lid 71 at the opening end with respect to the bottom surface, and is connected to a stock liquid supply tank (not shown). From this, when the residual liquid recovery port lid 71 opens the opening end, the residual liquid R stored in the casing 1 can be recovered in the stock liquid supply tank.

  The waste liquid discharge port 5 is provided with a waste liquid discharge port lid 51 at an opening end with respect to the bottom surface, and is connected to a waste liquid tank (not shown). From this, when the waste liquid discharge port lid 51 opens the opening end, the waste liquid WF stored in the casing 1 can be discharged to the waste liquid tank. Since the waste liquid discharge port 5 communicates with the outside of the filtration element 8, it can discharge other than the filtrate. The filtrate outlet 6 is connected to a filtrate tank (not shown) via a filtrate discharge valve 61 and to the waste liquid tank via a waste liquid discharge valve 62. From this, the filtrate F can be taken out from the filtrate outlet 6 to the filtrate tank by opening the filtrate discharge valve 61 and closing the waste liquid discharge valve 62. Further, if the waste liquid discharge valve 62 is opened and the filtrate discharge valve 61 is closed, the waste liquid WF can be discharged from the filtrate discharge port 6 to the waste liquid tank. Since the filtrate outlet 6 communicates with the inside of the filter element 8, in addition to the filtrate F, waste liquid that enters the inside of the filter element 8 during the cleaning process is discharged. And switching with the waste liquid discharge valve 62.

  The filtration apparatus of this example repeats the precoat process, the normal filtration process, the filtration process with respect to the residual liquid, the residual liquid recovery process, and the washing process to filter the stock solution U. In the pre-coating process, as shown in FIG. 2, the filter aid supply valve 23 is opened, and the precoat liquid PC in which the filter aid M is mixed with water is supplied to the inside of the casing 1. The filter aid M is coated. The precoat liquid PC entering the inside of the filter element 8 is returned to the filter aid supply tank from the filtrate discharge port 6 by opening the filtrate discharge valve 61.

  In the normal filtration process, as shown in FIG. 3, the stock solution supply valve 21 and the filtrate discharge valve 61 are opened, the stock solution U is supplied into the casing 1, and the filtrate F is taken out. In this filtration step, impurities contained in the stock solution U adhere to the filter aid M coated on the surface of the filter element 8, and a cake is formed. For this reason, after filtering all the undiluted | stock solutions U, the internal pressure of the casing 1 rises.

  In the filtration process for the residual liquid, as shown in FIG. 4, the pressurized air supply valve 31 is opened to supply the pressurized air A to the inside of the casing 1, the supply of the raw liquid U is stopped, and the residual liquid R The filter is forcibly filtered by pressing it against the filter. However, even if the residual liquid R is forcibly filtered by supplying the pressurized air A to the inside of the casing 1 in a pressurized state, it is difficult to filter all the residual liquid R. Remains in the casing 1. In particular, when the stock solution U contains a large amount of impurities or has a high viscosity, the residual liquid R remaining inside the casing 1 also increases.

  Therefore, the present invention implements a residual liquid recovery step as seen in FIG. That is, while the pressurized air supply valve 31 is opened and the pressurized air A is continuously supplied to the inside of the casing 1, the residual liquid recovery port lid 71 is opened to push the residual liquid R out of the casing 1 to the stock liquid supply tank. Collect and mix with stock solution U in the next filtration step. Supplying the pressurized air A into the casing 1 not only pushes out the residual liquid R, but also presses the cake against the filter element 8 to eliminate the risk of the cake peeling off.

  Thereby, the recovered residual liquid R is not mixed with the cake, and can be mixed again with the stock solution U in the next filtration step and filtered again. Here, in order to move to the next filtration step, the cake is peeled off from the filter element 8 by the washing step and discharged to the outside of the casing 1, and then back washing or the like for supplying the washing liquid from the inside of the filtration element 8 is performed. A new pre-coating process is performed. In addition, the residual liquid recovery process may be performed immediately after the normal filtration process is completed without passing through the filtration process (forced filtration of the residual liquid). In this case, all the residual liquid R inside the casing 1 is recovered, mixed with the stock solution U in the next filtration step, and filtered again.

[Filter device configuration]
The filtration device used in the example has a configuration according to the block diagram shown in FIG. 1 described above. In other words, the filtration device used in the example has a configuration in which a candle-type filtration element 8 is built in a stainless-steel cylindrical casing 1, and the total filtration area of the filtration element 8 is 3 m ² .

[Pre-coating process]
Diatomaceous earth was used as the filter aid M covering the surface of the filter element 8. Specifically, water suspended by adding 3 kg of diatomaceous earth, that is, the precoat liquid PC300L, was supplied to the inside of the casing 1 from the stock liquid supply port 2 by opening the filter aid supply valve 23. The flow rate of the diatomaceous earth precoat liquid PC passing through the filter element 8 was set to 180 L / min. Ten minutes after the start of supply of the diatomaceous earth precoat liquid PC, it is confirmed that the surface of the filter element 8 is coated with diatomaceous earth and the diatomaceous earth precoat liquid PC stored in the casing 1 is transparent, and the precoating process is performed. finished.

[Normal filtration process]
In this example, a high-viscosity solution (viscosity 100 cps) was filtered as stock solution U. The high-viscosity solution was supplied to the inside of the casing 1 from the stock solution supply port 2 by closing the filter aid supply valve 23 and opening the stock solution supply valve 21 after the precoat process. The water stored in the casing 1 after the pre-coating process passes through the filter (filter element 8 whose surface is coated with the filter aid M) with the newly supplied high-viscosity solution with the waste liquid discharge valve 62 opened. Can be discharged. After a few minutes from the start of the supply of the high-viscosity solution, confirm that all the water stored in the casing 1 has been replaced with the high-viscosity solution, close the waste liquid discharge valve 62, and open the filtrate discharge valve 61 this time. The high-viscosity filtrate F was taken out. At this time, the flow rate of the high-viscosity solution passing through the filter element 8 was 18 L / min, and the internal pressure of the casing 1 was 230 kPa.

[Filtering process for residual liquid]
Several hours after the start of filtration, the internal pressure of the casing 1 reached 350 kPa. In the embodiment, when the internal pressure of the casing 1 reaches 350 kPa, the pressurized air supply valve 31 is opened and pressurized air A (pressure 250 kPa) is supplied into the casing 1 from the pressurized air supply port 3. The stock solution supply valve 21 was closed to stop the supply of the high viscosity solution. Thereby, the residual liquid R of the high-viscosity solution stored inside the casing 1 is pushed by the pressurized air A, forcibly filtered through the filtration filter, and the filtrate F is continuously taken out from the filtrate outlet 6. It was. In the example, the forced filtration treatment for the residual liquid R was continued for ten or more minutes, and about 20% of the residual liquid R could be taken out as the filtrate F.

[Residual liquid recovery process]
The residual liquid R remaining inside the casing 1 even after the forced filtration process by supplying the pressurized air A is continued while the pressurized air A is continuously supplied and the pressurized state inside the casing 1 is maintained. The liquid recovery lid 71 was opened slightly to recover from the residual liquid recovery port 7. The recovered residual liquid R was recovered while being pressed against the internal pressure (100 kPa) while maintaining the internal pressure of the casing 1 at an internal pressure (100 kPa) that does not cause the cake to peel from the filter element 8, so that the cake may be mixed in. However, it was usable by being mixed in the stock solution U in the next filtration step. In the examples, the total amount of the filtrate F taken out by the normal filtration process and the forced filtration process was 1220 L, and the recovered residual liquid R was 168 L. And since the whole quantity of the said residual liquid R mixed in the undiluted | stock solution U in the next filtration process and was again filtered, the filtrate F was able to be taken out from the total quantity of the residual liquid R substantially.

It is a block diagram showing the principal part of the filtration apparatus of this example to which this invention is applied. It is a block diagram equivalent to FIG. 1 showing the precoat process in this example. It is a block diagram equivalent to FIG. 1 showing the normal filtration process with respect to stock solution in the filtration apparatus of this example. It is a block diagram equivalent to FIG. 1 showing the filtration process with respect to residual liquid in the filtration apparatus of this example. It is a block diagram equivalent to FIG. 1 showing the residual liquid collection process in the filtration apparatus of this example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Raw solution supply port 3 Pressurized air supply port 5 Waste liquid discharge port 6 Filtrate discharge port 7 Residual liquid collection port 8 Filtration element U Stock solution R Residual solution M Filter aid
PC precoat solution
WL Cleaning fluid A Pressurized air F Filtrate
WF waste liquid

Claims (3)

In the filtration device for covering the surface of the filtration element built in the casing with a filter aid to constitute a filtration filter, and taking out the filtrate through the filtration filter from the stock solution supplied to the inside of the casing,
After the normal filtration process has been completed for the stock solution supplied to the inside of the casing, the stock solution remaining inside the casing is recovered by pushing the inside of the casing into a pressurized state and directly pushing it out of the casing without passing through the filter. A method for recovering a stock solution in a filtration device. After the normal filtration process for the stock solution supplied to the inside of the casing is completed, the stock solution remaining inside the casing is filtered through a filtration filter while the inside of the casing is pressurized, and the stock solution remaining inside the casing is removed. 2. The method for recovering a stock solution in a filtration apparatus according to claim 1, wherein the inside of the casing is pressurized and then directly pushed out of the casing without passing through the filter and recovered. The method for recovering a stock solution in a filtration device according to claim 1 or 2, wherein a gas is supplied to the inside of the casing to bring the inside of the casing into a pressurized state.

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