JPS5926117A - Filtering method - Google Patents

Abstract

PURPOSE:To prevent a short-pass phenomenon at the time of air blow, by a method wherein a fibrous material is adhered to the surface of the cake on a filtering surface directly before air blow is carried out from the upper part of a filter tank. CONSTITUTION:Directly before air blow is carried out, a filter aid 12 containing a fiber introduced into a raw liquid tank 3 to be mixed in a raw liquid and the filter aid-containing raw liquid is introduced into a filter tank 1 by a pipe 9 to carry out filtering. Therefore, the fiber material is adhered to the surface of the cake on each filtering surface. In the next step, a valve 10 is closed while a valve 5 is opened to perform air blow from the upper part in the filter tank 1 and the filtering of the residual liquid in the tank 1 is promoted while the release of the cake is carried out after liquid removal is performed. In this case, because the fiber material is adhered to the surface of the cake, cracks are not generated to the cake even if air blow is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of filtering a raw solution by passing it through the filter surfaces of a series of filter members installed in a filtration tank. The present invention relates to an improvement of a filtration method in which residual liquid is discharged by pushing down the liquid level in a tank.

When the stock solution is filtered using this type of filtration method, over time, 411 pieces of cake adhere to the filtration surface of each filtration member.
Since this will result in a decrease in filtration performance, after a predetermined period of filtration work, the remaining liquid in the filtration tank is drained and the cake is peeled off. In the process of discharging the residual liquid, pressurized gas is introduced into the upper part of the tank to perform air blowing, since the tank is still full of liquid even after filtration is completed through the gas introduction pipe installed at the top of the tank. depressing the liquid level to facilitate filtration, or in conjunction with
The residual liquid is quickly discharged from the discharge pipe attached to the residual liquid treatment plate at the bottom 1 of the tank.However, in conventional filtration methods, when such air blowing is performed, cake on the filter surface is removed. Cracks may occur in the air, and air leaks from the cracks, resulting in the so-called Noyoto bath phenomenon, which has the disadvantage that the air blowing effect is not sufficiently exerted.

An object of the present invention is to solve the above-mentioned problems of the prior art, and therefore, to provide a filtration method that can prevent the short-pass phenomenon during air blowing.

A feature of the present invention is that in order to prevent cracks from occurring in the cake during air blowing, immediately before the end of filtration, a stock solution or filtrate mixed with a filter aid containing a fibrous material is introduced into a filtration tank, and the fibrous material is is to adhere to the cake on the filter surface.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 somewhat schematically shows an apparatus for carrying out an embodiment of the present invention, in which (1) is a filtration tank, (2)
is a series of filtration elements installed therein, in this example vertically arranged filter leaves, and (3) is a stock tank. An air introduction pipe (4) for blowing air is installed at the top VC of the filter tank (1), and (5) and (6) are associated valves. The lower part of the filtration tank (1) is equipped with a manifold (7) that communicates with the bottom of each filter leaf (2), and the manifold is connected to a filtrate outlet pipe (8). The stock solution tank (3) and the filtration tank (1) are connected by a pipe (9), to which a valve 00) is attached.

During operation, the air blow valve (5) is closed and the pipe (9
) valve (10) is opened, and the pipe (9) is opened from the stock tank (3).
The stock solution is introduced from the lower part of the filtration tank (1) through the filtration tank (1), and the stock solution is filtered by the filter surface of each filter leaf (2).The filtered solution is collected in the manifold (7) and sent to the outlet pipe (8).
). When the filtration performance deteriorates due to cake adhesion on the filter surface as the filtration time passes, air blowing is performed, but just before that, filter aid f121 containing fibers is placed in the stock solution tank (3) and mixed with the stock solution. Similarly, the stock solution containing the filter aid is introduced into the filter tank (1) through the pipe (9) rc,
Perform filtration. Thus, fibrous material adheres to the cake surface of each filter surface. The fibrous material may be any fibrous material that can prevent cracks in the cake, for example, natural fibers, artificial fibers, or other fibrous materials.

Next, the valve (10) is closed and the valve (5) is opened to blow air from the upper part of the filtration tank (1) to promote filtration of the remaining liquid in the tank (1) and remove the liquid. , peeling of the cake is performed. In this case, since fibrous material is attached to the surface of the cake, even if air blowing is performed,
No cracks will occur in the cake.

FIG. 2 shows another embodiment of the present invention, in which horizontally stacked horizontal filter plates are used as the filter member (2), and the outlet pipe (8) is located at the bottom of the filter tank ill. installed on. In this example, the filter aid (llll
It includes a mixing tank (+12) for mixing the water, its take-out pipe (131) is connected to the pipe (9), and its take-out pipe (+3
Valves 141 and (+5+) are attached to the pipe (9) near the stock solution tank (3) and the valve (+5+), respectively.As in the above embodiment, the filtration work is performed with the valve -(+4) closed. Immediately before stopping the filtration work, a filter aid (Ill) containing a fibrous material is mixed into the stock solution in advance in the mixing tank (02), and the valve (15) is closed and the valve 141 is opened. The stock solution mixed with the filter aid is passed through the filter tank (ll
17, and filtration is performed. Therefore, the fibrous material adheres to the surface of the cake on the filtration surface of each filter plate 12) and prevents cracks from forming in the cake, so that the liquid in the filtration tank (1) can be effectively removed by air blowing. I can do it.

In the above embodiment, the filter aid is mixed with the stock solution and introduced into the filtration tank, but as shown in FIG.
If 1 is provided, the filter aid can be mixed into the filtrate after filtration and then introduced into the filtration tank (1). The liquid mixed with this filter aid is introduced into the filtration tank just before the end of filtration, and at that time there is a considerable amount of cake adhering to the filter surface, so if the filter aid is introduced together with the filtrate, the filtration will be completed. Since this process is carried out quickly, the efficiency of the filtration work can be improved. In some cases, other liquids can be used instead of the filtrate.

As described above, according to the present invention, the fibrous material is attached to the surface of the cake on the filtration surface immediately before air blowing from the top of the filtration tank, so even if air blowing is performed, the occurrence of cracks in the cake is prevented. Therefore, the air short-pass phenomenon does not occur, the air blowing effect can be fully exhibited, and the remaining liquid in the filtration tank can be appropriately discharged.

[Brief explanation of the drawing]

FIG. 1 is a somewhat diagrammatic elevational view of an apparatus for carrying out one embodiment of the invention, and FIG. 2 is a similar view showing an apparatus for carrying out another embodiment.

Claims (4)

[Claims] (1) Filter the raw solution by passing it through the filtration surfaces of a series of filtration members installed in the filtration tank, and after an appropriate filtration time [Air blow is performed from the upper part of the filtration tank to lower the liquid level in the filtration tank. In a filtration method in which residual liquid is discharged by pressing down, a filter aid containing a fibrous material is applied immediately before the end of filtration to prevent cracks from forming on the cake adhering to the filtration surface of each filtration member during the air blowing process. A filtration method characterized by introducing the mixed stock solution or filtrate into the filtration tank and causing the fibrous material to adhere to the cake on the filtration surface. (2) The filtration method according to claim 1, wherein the filter aid is mixed in the stock solution tank. (3) The filtration method according to claim 1, wherein the filter aid is mixed into the stock solution in a mixing tank different from the stock solution tank. (4) The filtration method according to claim 1, wherein the filter aid is mixed into the filtrate in a mixing tank different from the stock solution tank.