JPS6071017A - Dehydration filtering method - Google Patents

Abstract

PURPOSE:To lower the moisture content of a cake comprising a powder for a ceramic stock material or other powder, by introducing a predetermined amount of the next slurry prior to generating blow pass, and performing dehydration filtering plural times without taking out the cake. CONSTITUTION:At first, a proper amount of a slurry corresponding to the volume of a tank is introduced onto the filter plate in the tank from an introducing pipe and filtered while compressed air is introduced into the tank from an air pipe. In this case, air blow is performed by compressed air until a predetermined time is elapsed and stopped before a crack is generated. Hereinafter, the slurry is similarily introduced only over scheduled times to repeatedly perform dehydration filtering. Air blow in the final dehydration of the slurry is succeeded over a predetermined time without generating the crack of a cake or succeeded without exerting influence upon dehydration efficiency even if a crack is generated in a part of the cake layer at an upper layer position.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention preferably relates to a method for dehydrating and filtering a slurry containing powder for ceramic raw materials such as silicon or alumina, or other powders, and in particular, the present invention relates to a method for dehydrating and filtering a slurry containing powder for ceramic raw materials such as silicon or alumina, or other powders. The present invention relates to a filtration method in which slurry is introduced and dehydrated by pressurizing it with pressurized air introduced into a tank.

In the conventional filtration method of this kind, the maximum amount of slurry is introduced into the tank, and the slurry is dehydrated and filtered until the maximum amount of water is removed.Therefore, when the dehydration filtration reaches the final stage, the amount of water generated on the filter plate is removed. Cracks form in the cake, resulting in a so-called blow bath condition in which the introduced pressurized air blows through the cracks. In this blow bath state, the air introduced into the tank simply blows through, so there is no further reduction in the moisture content, and therefore, this state was the limit. For example, dehydration filtration of a slurry containing ceramic raw material powder is one step in the ceramic manufacturing process, and in order to suitably perform the next steps such as chemical treatment and drying after dehydration filtration, it is necessary to remove the cake in the dehydration filtration step. It is desirable to reduce the water content to 10-15%, more preferably 10% or less, but in the conventional method, the water content is limited to 20-30%, which significantly reduces the efficiency of the next step. This had become a bottleneck in the ceramic manufacturing process.

In addition, in order to reduce the moisture content of the cake, a method was also seen in which a rotating cake push-down plate was installed and used to push down the cake, but even then the moisture content did not decrease that much. As the plates wear out, impurities get mixed into the cake, reducing the purity of the ceramic raw material powder.

Second, it had the disadvantage of complicating the mechanism of the filter.

An object of the present invention is to provide a dehydration filtration method that can significantly reduce the moisture content of a cake made of powder for ceramic raw materials or other powders.

The filtration method according to the present invention is characterized by placing a filter medium support member such as a punched metal horizontally in a tank and placing the slurry on the filter plate. The introduction of pressurized air is stopped before the resulting cake cracks, and then the slurry is introduced again from -1- and dehydrated and filtered. The idea is to introduce the slurry and thus perform multiple dehydration filtrations without removing the cake.

An example of an apparatus for carrying out the filtration method of the present invention includes a tank, a filter plate including a filter cloth placed horizontally at the bottom thereof, a drain pipe under the filter plate, and a cake removal pipe. The second part of the tank is equipped with an inlet pipe for introducing the slurry to be filtered and an air pipe for introducing pressurized air. After the filtration is completed, the cake formed on the filter plate is taken out from the cake removal tube.

The filtration method according to the present invention uses silicon (Sl) and alumina (
This is applied to the filtration of slurry containing fine particles that are non-plastic and have low activity or adhesion, such as powder for ceramic raw materials such as A1203), and first, an appropriate amount of slurry is introduced according to the capacity of the tank. The air is introduced from the tube onto the filter plate in the tank, and pressurized air is introduced from the air tube for filtration. Typically, pressurized air is at a pressure of about 2 kg/cm2. As dehydration progresses, the filtered water is discharged from the drain pipe, and the powder or particles in the slurry remain on the filter plate and begin to form a cake. Even after a certain amount of time has passed, the cake still contains a considerable amount of moisture. After that, air blowing is performed using pressurized air until a predetermined period of time has elapsed to further remove the moisture in the cake, but if air blowing is performed any longer than that, cracks will occur in the cake. Stop air blowing before this occurs.

In the next step, a predetermined amount of slurry is again introduced from the introduction pipe onto the cake obtained in the previous step, pressurized air is introduced from the air pipe to perform air blowing, and dehydration and filtration are performed in the same manner as before. As a result, a new cake is formed on top of the previous cake, but the air blowing is stopped after the cake has been filtered to the extent that no cracks are formed.

Furthermore, if desired, a predetermined amount of slurry is further introduced into the tank from above the cake, filtered by air blowing, and the air blowing is stopped before the third slurry causes cracks in the cake. Thereafter, slurry is introduced in the same manner for a predetermined number of books and dehydration and filtration are repeated.

In this way, by introducing the slurry multiple times without removing the cake and performing dehydration filtration, a plurality of layers of cake are formed on the second part of the filter plate in the tank. and,
Air blowing in the final slurry dewatering process is continued for a predetermined time without cracking the cake, or even if cracks occur in a portion of the upper cake layer, the air blowing process continues with almost no effect on the dewatering efficiency. The advantage of the present invention is that air blowing can be carried out effectively, and by air blowing at this final stage, a desired reduction in moisture content can be achieved.

That is, even if cracks occur in the cake due to air blowing in the final stage, in most cases only the uppermost cake layer will have cracks, and the next layer will not have cracks. Cracks occur in the top layer of cake because it has a higher dewatering efficiency than the cake layers below it. The reason why cracks occur only in the uppermost layer of cake and does not progress to the next layer of cake or even to the cakes in the lower layers is thought to be because the moisture content of each layer is slightly different.

Therefore, even if a crack occurs in the cake with the lowest layer, there is no blow bath condition in which pressurized air can blow through without resistance.
Air blowing can be performed effectively and the moisture content of the cake can be further reduced. The figure shows a case where the slurry is introduced three times, resulting in a three-layered cake, but even if the slurry is introduced two times or more than four times, it will not work. It is clear that almost the same effect can be obtained. If the slurry is introduced too many times, the operation becomes complicated and the operation time becomes longer, so it is preferable to limit the number of times the slurry is introduced to a few times.

Next, examples of the present invention will be shown.

Example (1) 450 g of Si with a particle size of 10-20 μm, 270 g of Al203 with a particle size of 3-5 μm, 180 g of A1203 with a particle size of 1-2 μm
was mixed into 3,000 cc of aqueous solution to form a slurry, and then filtered through a horizontal filter plate type filtration device using an air blower with 1.9 kg/cm 2'J of pressurized air over the course of the process shown in the table below. As a result of dehydration and filtration, and finally air blowing for a relatively long time, the top part of the cake was 7% and the bottom part was 9%.
A cake with a moisture content of .

1 1,. 500 1,000 250゜2 1.00
0 800 590 3 500 400 425 4 300 800 1.580 Example (2) Using the same slurry as in Example (1) above, it was filtered under the same conditions as shown in the table below, and finally After performing two air blows for 20 minutes, a cake with a moisture content of 11% in the upper part and 16% in the lower part was obtained.

l 1. ．． 500 1.000 1802 300 3
．． 00 120 3 300 200 1.45 4 300 200] 50 5 450 920 1,. As is clear from the example described in "365", according to the present invention, dehydration can be effectively carried out by air blowing in the final stage, so excellent dehydration filtration of powders for ceramic raw materials, etc. is possible. becomes.

Claims (1)

[Claims] (1) A filtration method in which a slurry containing a non-plastic ceramic raw material powder is introduced onto a filter plate placed horizontally in a tank, and the slurry is dehydrated by pressurizing with pressurized air introduced into the tank. An appropriate amount of slurry is introduced onto the plate, dehydrated and filtered using pressurized air, and dehydrated and filtered to such an extent that no cracks occur in the cake formed on the filter plate, and then the introduction of pressurized air is stopped. A predetermined amount of slurry is introduced onto the cake, and pressurized air is introduced again to repeat the same dehydration filtration, thereby forming a plurality of layers of cake on the filter plate, and a final dehydration filtration step. A dehydration filtration method characterized in that the air blowing using the pressurized air is sometimes carried out for a predetermined period of time.