JPH09168710A - Regenerating method for filter cloth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform regeneration of used filter cloth and also to enhance the life of the filter cloth by washing the filter cloth in which filtration performance is lowered with an alkali solution in the case of regenerating the filter cloth used for filtration of an alkali silicate aqueous solution obtained by dissolving alkali silicate glass cullet into water. SOLUTION: In the case of producing an alkali silicate aqueous solution by dissolving alkali silicate glass cullet into water, regeneration treatment is performed for filter cloth used in a filtration process for clarifying the alkali silicate aqueous solution and the filter cloth is reused. In this case, the filter cloth in which filtration performance is lowered is treated so as to wash it by an alkali solution. An alkali metal hydroxide such as sodium hydroxide and potassium hydroxide and amines such as methyl amine and ethyl amine are cited as the alkali solution. The solution of alkali metal hydroxide is desirably used from the aspect of handling and waste liquid treatment. Alkali washing is performed in the temperature range of 0-100 deg.C, desirably 20-80 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating a filter cloth used for producing an aqueous solution of alkali silicate. Specifically, when an alkali silicate glass cullet is dissolved in water to produce an alkali silicate aqueous solution, the filter cloth used in the filtration step for clarifying the alkali silicate aqueous solution is subjected to a regeneration treatment, and the filter cloth is removed. It is a method for reuse.

[0002]

2. Description of the Related Art An aqueous solution of alkali silicate has the general formula M ₂ O.
nSiO ₂ · xH ₂ O (M = Na, K and n = 2 to
It is generally about 3.5). Civil engineering fields such as soil hardening stabilizers and cement quick-setting agents; for molding sand molds for casting; bleaching agents for pulp and deinking of waste paper. It is used in a wide range of applications such as papermaking fields such as chemicals; raw materials such as white carbon, silica gel, silica carriers for catalysts; cleaning agents, adhesives, raw materials for fire-resistant paints, chemicals for the electronic industry, etc.

In the above-mentioned applications, it is desired that the aqueous solution of alkali silicate be clear and substantially free from turbidity in quality.

The aqueous solution of alkali silicate is obtained by mixing silica sand with alkali carbonate or alkali hydroxide, heating and melting at about 1300 ° C. to form a homogeneous melt, and then cooling and solidifying to obtain alkali silicate glass cullet (hereinafter, simply (Also referred to as cullet), the cullet is obtained by dissolving it with water in an autoclave under pressure at 150 to 180 ° C., and the aqueous alkali silicate solution is a solid product that is considered to be derived from impurities in the cullet. It is generally cloudy because it exists.

In order to remove the solid matter that causes turbidity,
Generally, a filter aid such as diatomaceous earth is mixed with the aqueous solution of alkali silicate and filtered with a filter such as a filter press.

However, even when a filter aid is used during repeated filtration of the aqueous solution of alkali silicate, the filtration resistance of the filter cloth itself is gradually increased, and the filtration performance such as filtration speed is deteriorated. It was That is, the filter cloth usually needs to be replaced when used for several times of filtration, and the used filter cloth has been discarded.

[0007]

Therefore, when the alkali silicate glass cullet is dissolved in water to produce an alkali silicate aqueous solution, the filter cloth used in the filtering step and discarded if the filtration resistance increases is efficiently used. It was desired to develop a method of recycling and reusing.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to solve the above problems, and as a result, by treating a filter cloth whose filtration performance has been lowered by filtration with an alkaline solution. It has been found that the filtration resistance of the filter cloth itself is reduced and the filter cloth can be reused, and the present invention has been completed.

That is, according to the present invention, a method of regenerating a filter cloth is characterized in that an alkali silicate aqueous solution obtained by dissolving alkali silicate glass cullet in water is filtered and washed with a filter cloth alkaline solution having a lowered filtration performance. Is.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the alkali silicate glass cullet for preparing the aqueous alkali silicate solution to be filtered is not particularly limited. In particular,
Examples include sodium silicate glass cullet and potassium silicate glass cullet. The alkali silicate aqueous solution is prepared by dissolving the alkali silicate glass cullet in an autoclave together with water under pressure at a temperature of about 150 to 180 ° C.

The filter cloth to which the present invention is applied is not particularly limited in its material as long as it is a filter cloth generally used for filtering the above-mentioned alkaline silicate aqueous solution. For example, a filter cloth made of synthetic resin fibers such as polyethylene, polypropylene, nylon, polyester, polyacrylonitrile, and polyfluoroethylene is common and can be preferably used. Further, natural fibers such as cotton and wool, alkali resistant metal fibers such as stainless fibers, glass fibers, ceramic fibers and carbon fibers can also be used. Furthermore, the weaving method of the filter cloth is not particularly limited. Plain weave, twill weave, twill weave, satin weave, etc. are not limited in any way.

The filter used for filtering the aqueous solution of alkali silicate is not particularly limited as long as it uses the above filter cloth. For example, a pressure filter such as a filter press or a pressure nutche is generally used, but a vacuum filter such as a rotary cylinder type vacuum filter or a horizontal belt type vacuum filter can be used without any limitation.

A feature of the present invention resides in that the above-mentioned alkaline silicate aqueous solution is filtered to wash the filter cloth having deteriorated filtering performance with the alkaline solution.

As the alkaline solution, a known alkaline solution can be used without particular limitation. Examples of typical alkaline solutions include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; amines such as methylamine and ethylamine; anilines such as aniline and methylaniline; pyridines such as pyridine and methylpyridine. Examples: solutions of organic ammonium hydroxide compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and the like. Among them, in terms of handling and waste liquid treatment,
Preference is given to using solutions of alkali metal hydroxides. Water is generally used as the solvent of the above solution.

The concentration of the alkali solution used in the present invention varies depending on the type of alkali used and the material of the filter cloth used, and cannot be specified unconditionally, but it is approximately 0.01 to 18 N, preferably , 0.1
Within the specified range of 15 to 15, the viscosity is not large and the handling is easy, so that it can be suitably used.

The means for washing with the alkaline solution in the present invention is not particularly limited, but means for circulating the alkaline solution while holding the filter cloth in a filter such as a filter press used for filtering the aqueous solution of alkaline silicate, or A means of directly immersing a used filter cloth in an alkaline solution can be implemented. The former method of washing while maintaining the filter cloth in the filter while allowing the alkali to flow is preferable from the viewpoint of easy implementation.

The temperature of the alkali cleaning of the present invention is 0-10.
0 ° C, preferably 10 to 90 ° C, more preferably 2
It is necessary to be 0 to 80 ° C. If the temperature of the alkali washing is lower than 0 ° C., the substance causing the filtration resistance cannot be sufficiently dissolved and the regeneration effect becomes insufficient, which is not preferable. Further, if the temperature exceeds 100 ° C., it becomes difficult to handle due to the volatilization of water, and the cleaning cannot be performed efficiently, which is not preferable.

[0018]

The action of the alkaline solution in the regeneration method of the present invention is not clear, but the present inventors presume as follows. One of them is considered to have an effect of dissolving and removing amorphous and crystalline silica, which is one of the substances causing the filtration resistance of the filter cloth. In addition, the addition of alkali acts to decrease the SiO ₂ / M ₂ O molar ratio (the value of n in the above general formula) of the aqueous solution of alkaline silicate remaining on the filter cloth, which reduces the viscosity of the residual aqueous solution of alkaline silicate. Then, it may be easily removed.

By such an action, the filter cloth is efficiently regenerated and the filter cloth having a low filtration resistance can be reused in the step of filtering the aqueous solution of alkali silicate.

[0020]

As can be understood from the above description, according to the present invention, since the filtration resistance of the filter cloth having the lowered filtration performance can be reduced, the alkali silicate aqueous solution obtained by dissolving the alkali silicate glass cullet is obtained. Since the filtration time is shortened and the used filter cloth can be regenerated, the life of the filter cloth can be greatly extended.

[0021]

EXAMPLES The features of the present invention will be specifically described with reference to the following examples. However, the present invention is not limited to the following examples.

Example 1 A circular sample filter cloth having a diameter of 9 cm was cut out from a used filter cloth (made of polypropylene) having a lowered filtration performance.
The filter cloth was attached to the end of a pipe equipped with a gas meter, a pressure reducing pump, and a pressure control valve, and the amount of air flowing through the filter cloth from the outside when the pipe was in a reduced pressure state was measured. The pressure difference with the outside is kept constant at 7.4 Torr, and air 1
As a result of evaluating the clogging state of the filter cloth at the time required for 0 liter to pass, it was 120 seconds.

Next, the above filter cloth was kept warm at 50 ° C. in 3N.
It was immersed in a (normal) sodium hydroxide aqueous solution and stirred for 1 hour for washing.

The time required for 10 liters of air to pass through the filter cloth washed with the alkaline solution after the above washing was measured under the same conditions as above, and it was 64 seconds.

When the same operation was carried out in this measuring device without attaching the filter cloth, the time required for 10 liters of air to pass was 51 seconds.

Comparative Example 1 A sample filter cloth, which was similarly cut out from the used filter cloth of Example 1, was washed in the same manner except that water was used as a cleaning liquid. The time required for 10 liters of air to pass through the filter cloth thus washed under the same conditions as above was measured and found to be 115 seconds.

Claims (2)

[Claims] 1. A method for regenerating a filter cloth, which comprises filtering an aqueous solution of an alkali silicate obtained by dissolving alkali silicate glass cullet in water and washing the filter cloth having deteriorated filtration performance with an alkaline solution. 2. The cleaning temperature with an alkaline solution is 0-10.
The method for recycling a filter cloth according to claim 1, wherein the temperature is 0 ° C.