JP3101027B2 - Regeneration method of ceramic filter - Google Patents

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 ceramic filter, and more particularly to a method for regenerating a filter used for purifying tap water.

[0002]

2. Description of the Related Art In recent years, it has been strongly pointed out that tap water has become bad. The causes include chlorine, rust, odor, bacteria, and the like. Furthermore, it has recently been pointed out that there is a carcinogen, trihalomethane. Under these circumstances, household water purifiers that remove harmful substances for the human body are attracting attention. Many of the water purifiers known at present have a type in which activated carbon and a hollow fiber membrane filter are used in combination, and rust and bacteria that cannot be completely removed by activated carbon can be removed by the microfiltration action of the hollow fiber membrane. An example is disclosed in JP-A-2-198684.

[0003]

However, the type using the hollow fiber membrane filter has the following problems. If the hollow fiber membrane also becomes clogged with time, it must be periodically eliminated to maintain the filter function. In order to remove the clogging, it is conceivable to perform a chemical cleaning or to remove the organic component causing the clogging by incineration. However, since the hollow fiber membrane is an organic membrane formed of a polymer material and has poor chemical resistance and heat resistance, such a method cannot be adopted at all.

[0004] Therefore, it is conceivable to pass the washing water. In this case, however, a pressure higher than that during the filtration operation is applied, so that such a high pressure is applied to the hollow fiber which is an organic membrane. Doing so results in the pores of the membrane being widened and impairing the filter function. In this regard, the same result can be obtained by employing a method in which the filter is washed by applying a counter pressure to the filter.

[0005] After all, although the hollow fiber membrane filter has a high purification function, it cannot be reused when clogged, and must be discarded, which is a serious problem in terms of economic efficiency. . In that regard, if you incorporate a ceramic filter with excellent chemical resistance and heat resistance into the water purifier,
What is clogged and collected can be washed and reused, so that the economic burden can be reduced.

The present invention has been developed in view of such circumstances, and an object of the present invention is to provide a method of reproducing a ceramic filter appropriately.

[0007]

[MEANS FOR SOLVING THE PROBLEMS] The reproducing method of the present invention comprises:
In a method of regenerating a formed ceramic filter incorporated in a tap water purifier, a cleaning step using an alkaline cleaning liquid, a subsequent cleaning step using an acidic cleaning liquid, and further performing ultrasonic cleaning in pure water. The cleaning step includes a cleaning step using an alkaline cleaning liquid and a subsequent cleaning step using an acidic cleaning liquid.

In the alkaline cleaning step, when the ceramic filter after filtering the tap water is immersed in the alkaline cleaning liquid under predetermined conditions, the organic substances causing clogging and the silicon, albeit in trace amounts, are eluted, respectively. . Examples of the alkaline cleaning liquid include NaOH, N
Each aqueous solution of H4OH and NaOCl can be used.
Even if these are used alone, a predetermined cleaning effect can be obtained, but a higher cleaning effect can be obtained by using a mixture of two or more types.

[0009] In the alkaline cleaning step, 400
The incineration step using a heating temperature of from 1 to 1200 ° C may be used instead. By exposing the entire ceramic filter to a temperature in this range, organic substances can be incinerated and eliminated.

As the acidic cleaning liquid, for example, HNO3, H
Cl can be used, and the same cleaning effect can be obtained by using any of them. When the ceramic filter that has undergone the alkali cleaning step is immersed in this cleaning solution under predetermined conditions, metal ion compounds such as Ca, Mg, and Fe are eluted.

Further, in order to effectively recover the cleaning function, it is necessary to perform the alkali cleaning in the order prior to the acid cleaning. Although the reason for this has not been elucidated in detail, it is considered that the organic substance is transformed into a state in which the organic substance cannot be effectively removed by the alkali cleaning due to the acid cleaning.

Further, after the acid cleaning, the ultrasonic cleaning is performed by immersing the ceramic filter in pure water to further enhance the cleaning effect.

[0013]

【Example】

(Ceramic Filter) The ceramic filter 1 to be cleaned is a round bar having an outer diameter of 30 mm and a total length of 250 mm containing an Al2 O3 component of 95% or more. As shown in FIG. A plurality of inflow water holes 2 (hole diameter 3 mm, 37 holes) penetrate in the axial direction. For this filter, a so-called monolith type having a membrane structure formed by coating a fine-grain layer on a support layer to form an asymmetric structure was used, and a filter having an average pore diameter of about 0.5 μm was selected. . Example 1 FIG. 1 shows a regeneration process including a plurality of processes performed on a ceramic filter 1 having clogged. First, an appropriate number of ceramic filters 1 are put into a number of buckets 4 suspended from a circulation line 3.

After that, it is transferred to an alkali cleaning step.
0.5% by weight of NaOH as the alkaline cleaning solution,
An aqueous solution containing 0.2% by weight of NaOCl (PH1
2) is used, and the ceramic filter 1 is a bucket 4
Together with the cleaning solution. At this time, the temperature in the cleaning tank was kept at 50 ° C., and the immersion time was about 1 hour. According to an experiment performed by the present inventors, the liquid temperature was 1%.
When the temperature exceeds 00 ° C., the cleaning tank and the ceramic filter 1 are corroded. Conversely, it is found that an effective cleaning effect cannot be obtained at a temperature lower than 10 ° C., and the cleaning time (immersion time)
It is preferable to perform the operation in the range of 5 minutes to 60 minutes from the viewpoint of work efficiency.

The alkali-cleaned ceramic filter 1 is immersed in hot water at 50 ° C. for about one hour to wash off the alkaline cleaning liquid, and then transferred to an acid cleaning step.

In this step, the acidic cleaning solution is H
A 10% (wt%) aqueous solution of Cl is used (PH 0.
2), the ceramic filter 1 is immersed in this liquid. At this time, the temperature in the cleaning tank was room temperature (about 20 ° C.), and the immersion time was about 1 hour. As in the case of the alkali cleaning, it has been confirmed that the liquid temperature is suitably in the range of 10 to 100 ° C., and the cleaning time is at least 30 minutes.

The acid-washed ceramic filter 1 is poured into hot water at 30 to 50 ° C. for about 1 hour, and then subjected to 1 hour of water washing (water temperature about 20 ° C.). After that, ultrasonic cleaning is performed for about 3 minutes while immersed in ultrapure water,
Let stand for about 1 hour. Ceramic filter 1
Is then taken out of the bucket 4 through a drying process (drying temperature 100 ° C.) for about 3 hours.

Here, P is a circulation pump, and 6 is a filter device. (Confirmation test of cleaning effect) Tap water is supplied to an unused ceramic filter 1 from the opposite end face while one end face is closed. In this case, the filtration pressure (differential pressure between the inlet side and the outlet side of the ceramic filter 1) is 1 kg.
/ cm2 and the water temperature is kept at about 30 ° C. Under these conditions, the amount of purified water obtained per unit time when tap water is supplied to the ceramic filter 1 is measured. Further, after continuing to pass about 600 liters of water, the purified water amount per unit time is measured again.

As a result of this water flow, the clogged ceramic filter 1 is washed through the above-described washing step, and the amount of purified water is measured again under the same conditions. For Example 1, this was repeated six times.

The results of the measurement are as shown in Table 1. However, in the table, the transmittance is an unused ceramic filter 1
It shows the ratio of each measured water purification amount when the water purification amount per unit time measured at the time of the first water passage is set to 100. The number in parentheses is about 60 for each batch.
It shows the transmittance before washing when water is passed through 0 liter.

As shown in Table 1, the filter of Example 1 has a high transmittance after cleaning, and has a very high cleaning effect. Also, even after the repetition of six times, the transmittance was hardly reduced, and it can be seen that the cleaning function was maintained as it was. Example 2 In Example 2, only one kind of an aqueous NaOH solution was used as the alkaline cleaning liquid. In the alkaline cleaning step, the ceramic filter 1 is made of 0.1% NaOH.
The weight% aqueous solution was immersed for about 1 hour while maintaining the liquid temperature at about 50 ° C. In the acid washing step, as in Example 1, an aqueous solution of HCl was used, and immersed in a 1% by weight aqueous solution of HCl at about 20 ° C. for the same time. The other conditions were the same as in Example 1.

According to the measurement results of the second embodiment, although the effect of washing and regenerating is slightly inferior to that of the first embodiment, there is no problem in practical use, and it is possible to use a single kind of alkaline cleaning liquid. Was confirmed. Example 3 In Example 3, cleaning was performed by using NH4 OH instead of NaOH in the alkaline cleaning liquid used in Example 1. The specific conditions are as follows.
An aqueous solution containing 0.5% by weight of NaOCl and 0.5% by weight of NaOCl was immersed for 1 hour while maintaining the solution temperature at about 50 ° C. The acid washing step and other steps were all performed under the same conditions as in Example 1.

As a result, it was confirmed that the use of NH4 OH as an alkaline cleaning solution provided a practically sufficient cleaning effect, although the effect was slightly inferior to that of Example 1. Example 4 In Example 4, HNO3 was used as the acidic cleaning solution instead of HCl.
In the acid washing step, the ceramic filter 1 is made of a 10% aqueous solution of HNO3 at a liquid temperature of about 2%.
It was immersed for 1 hour while being kept at 0 ° C. In the alkaline washing step, as in Example 1, NaOH and NaOCl were used and immersed in an aqueous solution in which 1% by weight and 0.5% by weight were mixed under the same conditions. Other conditions are also in Example 1.
Is the same as

According to the measurement result of the fourth embodiment, there is almost no difference in the cleaning effect from the case of the first embodiment. Therefore, either of HCl and HNO3 can be selectively used for the acidic cleaning solution. -Example 5-In Example 5, an incineration step was performed instead of the alkali cleaning step, and organic substances attached to the ceramic filter 1 were removed by incineration. That is, the ceramic filter 1 was placed in an electric furnace in which the inside of the refrigerator was kept at about 500 ° C., and heated for about 1 hour.
Then, it is left as it is and cooled to room temperature, and then transferred to an acidic washing step. The acidic cleaning solution is 10% by weight of HCl.
An aqueous solution is used, and the solution temperature is maintained
Soaked for hours.

The results were slightly, but slightly inferior, to any of the examples from Example 1 to Example 4. The reason that the regenerating effect is lower than that of other examples is that it is possible to elute silicon in a small amount when performing alkali cleaning, but silicon is not removed simply by incineration, but rather its oxide. May be in a form that is not eluted by subsequent acid washing. However, it is apparent from the results shown in Table 1 that the regeneration step after the incineration step has a sufficient regeneration effect in practical use.

[0026]

(Comparative Example 1) Comparative Example 1 examines the change in the cleaning effect when the concentration of the alkaline cleaning liquid is reduced from the case of Example 2. Here, in the alkaline cleaning step, N
A 0.05% by weight aqueous solution of aOH was used, and a 0.5% by weight aqueous solution of HCl was used in the acid washing step. All other steps were prepared under the same conditions as in Example 2.

As shown in Table 2, the results showed that the transmittance was reduced to about half that of Example 2 and the cleaning effect was insufficient. From this, it is considered necessary that the concentration of the alkaline cleaning liquid contains at least 0.1% by weight of an alkali component. (Comparative Example 2) In Comparative Example 2, the steps of the alkali cleaning and the acid cleaning were reversed, and the alkali cleaning was performed after the ceramic filter 1 was subjected to the acid cleaning. As a specific condition, in the acid washing step, HCl is used.
10% by weight of an aqueous solution kept at 20 ° C. for 1 hour, and in an alkaline washing step, an aqueous solution containing 1% by weight of NaOH and 0.5% by weight of NaOCl was kept at about 50 ° C. Soaked for 1 hour. All other steps and conditions were performed as in the other examples.

As shown in Table 2, no sufficient cleaning effect was obtained. Comparative Example 3 In this example, the alkali cleaning step was omitted, that is, the cleaning was started from the acid cleaning step. As the acidic cleaning liquid, a 10% by weight aqueous solution of HCl was used, and was immersed at a liquid temperature of 20 ° C. for 1 hour. Other steps are the same as those described above.

As a result, only an inadequate cleaning effect was obtained only by acid cleaning. Comparative Example 4 In this example, the acid washing step and the subsequent hot water washing step were omitted. The alkaline cleaning solution used was 1% by weight of NaOH, and was immersed at a solution temperature of 50 ° C. for 1 hour. As a result, similarly to Comparative Example 3, the result of the cleaning was clearly insufficient even with the alkali cleaning alone. (Comparative Example 5) In this example, the incineration temperature condition when the incineration step was replaced with the incineration step in Example 5 was changed, whereas the incineration temperature in Example 5 was 500 ° C. In Comparative Example 5, the temperature was set to 300 ° C. The test was performed under the same other conditions as in Example 5.

As a result, as shown in Table 2, the incineration of organic matter was clearly considered to be insufficient. As a result of the additional tests performed by the inventors, in order to obtain an effective regenerating effect, the ceramic filter 1 should be heated at a heating temperature of at least about 400 ° C. and at a heating temperature of about 1200 ° C. or less as the upper limit of the heat resistance. It was found to be necessary.

[0031]

[Table 2]

[0032]

According to the present invention, the economical efficiency of the water purifier can be improved because the ceramic filter which has been clogged by the flow of tap water can be effectively regenerated and reused.

[Brief description of the drawings]

FIG. 1 is a diagram of a cleaning process according to the cleaning method of the present invention.

FIG. 2 is a perspective view of a ceramic filter.

[Explanation of symbols]

 1. Ceramic filter

Continuation of front page (56) References JP-A-63-72320 (JP, A) JP-A-63-310604 (JP, A) JP-A-2-157086 (JP, A) JP-A-64-30603 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 41/04 B01D 65/02

Claims (2)

(57) [Claims] 1. A method for regenerating a formed ceramic filter incorporated in a tap water purifier, comprising: a cleaning step using an alkaline cleaning liquid, a subsequent cleaning step using an acidic cleaning liquid, and ultrasonic cleaning in pure water. A method for regenerating a ceramic filter. 2. A method for regenerating a ceramic filter after filtering tap water, the method comprising: 400 ° C. to 1200 ° C.
A method for regenerating a ceramic filter, comprising: an incineration step of heating in the range described above; and a subsequent washing step using an acidic washing solution.