JPS63178811A - Process for separating solid from liquid - Google Patents

Abstract

PURPOSE:To maintain the capacity for separating solid from liquid of a filter cloth at high level for a long time by feeding a liquid to be filtered intermittently in a stage of separation of solid from liquid using a filter cloth travelling type solid/ liquid separation apparatus. CONSTITUTION:A liquid to be filtered contg. a solid component and a liquid component is fed from a solid/liquid feeding tank 13 onto a filter cloth 1 running and circulating in the arrow direction be being drive by a driving roll 2, and the liquid component in the liquid feed is allowed to pass through the filter cloth 1 and collected in a vacuum sucking tank 11. On one hand, the component which has not passed through the filter cloth 1 is scraped off as cake with a scraper 12 to the outside of a dehydrator, then the liquid feed is fed intermittently from a solid/liquid feed pipe 23 to the solid/liquid feed tank 13 when the filter cloth 1 is washed by the washing water ejected from a filter cloth washing nozzle 21. As the result, the clogging of the filter cloth 1 is restored by washing the filter cloth 1 effectively during the suspension of supply of the liquid feed, so the capacity for separating solid from liquid of the filter cloth 1 is held for long time at a level higher than the predertermined level.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a solid-liquid separation method using a filter cloth traveling type solid-liquid separator, and in particular, to a solid-liquid separation method that can maintain good solid-liquid separation performance of the filter cloth for a long period of time. About how it was done.

[Prior art] A solid-liquid as a stock solution to be treated is supplied to the surface of an endless filter cloth that can travel in one direction and rotate freely, and the solid-liquid is continuously separated into a solid component and a liquid component. So-called filter cloth running type filters and dehydrators are known. In such a filter cloth running type solid-liquid separator, in order to prevent clogging of the continuously circulating filter cloth and perform solid-liquid separation efficiently, components after filtration or dehydration are removed from the filter cloth. After removal, the filter cloth is washed to restore its function and is ready for the next solid-liquid separation. Such cleaning can be carried out by providing a cleaning nozzle on the front side and/or the back side of the filter cloth, as described in, for example, Japanese Utility Model Application Publication No. 61-44207.
This is usually done by spraying cleaning water onto the filter cloth from the cleaning nozzle.

However, although the cleaning effect of spraying cleaning water from a cleaning nozzle varies depending on the intensity, amount of cleaning water, etc., the clogging of the filter cloth cannot be completely eliminated by spraying cleaning water alone. Therefore, clogging progresses gradually with the passage of operating time. Conventionally, the stock solution is continuously supplied and the filter cloth is circulated continuously to perform solid-liquid separation, or the filter cloth gradually becomes clogged as described above as the operation time increases, and the stock solution on the filter cloth becomes clogged. When the processing capacity fell below a certain level, it was necessary to replace the filter cloth or wash the filter cloth with chemicals.

[Problems to be Solved by the Invention] The present invention is an apparatus that performs solid-liquid separation while continuously circulating an endless filter cloth. The purpose is to maintain performance at a predetermined level or higher for a long period of time.

Means for Solving Problem E] The solid-liquid separation method of the present invention in accordance with this objective involves continuously circulating an endless filter cloth on a constant orbit, supplying the stock solution to the surface side of the filter cloth, Solid-liquid separation that separates the stock solution into the residual component on the filter cloth and the liquid component that passes through the filter cloth, and then continuously washes the circulating filter cloth before the filter cloth reaches the stock solution supply section. The method comprises supplying the stock solution intermittently.

That is, the filter 15 is continuously circulated and washed, but only the stock solution is intermittently supplied.

This intermittent supply of the stock solution can be easily achieved, for example, by incorporating a 24-hour all-timer into the control circuit of the stock solution supply pump.

[Function] In such a method, solid-liquid separation is not performed during a certain period of time when the supply of the stock solution is stopped, and the filter cloth that is continuously circulated has the same strength and strength as when the stock solution is supplied. Washed with water mother. That is, during this time, only the filter cloth is regenerated, and the clogging of the filter cloth is efficiently recovered. Since this recovery is repeated at regular intervals, the speed at which the filter cloth clogs progress relative to the operating time is significantly reduced, the decline in the filter cloth's ability to handle the stock solution is suppressed, and the life of the filter cloth is greatly extended. .

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a filter cloth traveling type dehydrator used to carry out a method according to an embodiment of the present invention.

In FIG. 1, 1 is an endless filter cloth, and as shown in FIG. 2, rubber belts 1a with holes are sewn on both sides. This endless filter cloth 1 is stretched under tension between a drive roll 2 and three guide rolls 3.4.5, and a squeeze roll 6.7. .8. It travels and circles in the direction of the arrow on a fixed trajectory regulated by the transfer drum 9 and the like. The filter cloth 1 is stretched from the kite rolls 3 to 4 so as to have a slight upward angle with respect to the horizontal plane.

The base material of the filter 151 is preferably one described in Japanese Patent Application Laid-Open No. 59-1''15720.

That is, a textile base material using synthetic fiber yarn with a single yarn diameter of 0.1 to 10 μm is used for the weft yarns arranged at least in the width direction of the filter cloth, and the weft yarns of the base material are mainly run in the longitudinal direction and circulated. It is like having a raised cline layer of ultrafine fibers with a thickness of 0.1 to 10 μm on the surface. Further, a knitted raised filter cloth as described in JP-A-58-207917 may also be used. In such a corrugated cloth, the naps lie uniformly in the longitudinal direction, but when in use, the naps are stretched so as to face in the opposite direction to the direction in which the filter cloth 1 travels and revolves.

On the surface side of the filter cloth 1 and between the guide rolls 3 and 4, a solid liquid supply tank (undiluted solution supply section) 13 is installed.

However, in the present invention, the so-called solid-liquid supply part does not necessarily need to be configured as a tank, and may be a pipe or gutter that can directly discharge the solid-liquid.

The back side of the filter cloth 1 is connected to an air intake means 15 via an intake pipe 14 at a position facing the solid-liquid supply tank 13, so that the back side can be maintained in a reduced pressure state of 500 mm or more in the water column. A reduced pressure suction tank 11 is installed. This reduced pressure suction tank 11 has a discharge pipe 16 for liquid components. In addition, a plurality of filter cloth guide rolls 18 are arranged in parallel in the traveling and circumferential direction of the filter cloth 1 at the vacuum suction port 17 facing the back surface of the filter cloth 1 . The filter cloth guide roll 18 may be a roll with a smooth surface, but it may also be a so-called perforated roll in which a large number of holes are bored in a cylindrical roll, or a circumferential groove or groove on the surface of a cylindrical roll or a solid roll. It is preferable to use so-called grooved rolls having spiral grooves cut therein, since the actual opening area of the vacuum suction ports 17 does not decrease significantly even if they are arranged closely, and a large degree of vacuum can be obtained with a small amount of power.

Between the guide roll 4 and the drive roll 2, a transfer drum 9 and a pressure roll 6, 7, 8 are arranged facing each other with the filter cloth 1 in between. Further, a pattern scraper 12 made of a relatively soft material such as rubber or synthetic resin is in contact with the surface of the transfer tram 9. Furthermore, a chute 19 for discharging cake is installed directly below the scraper 12 and at a higher position than the drive roll 2.

The shooter 19 is made of a plate made of metal or synthetic resin, is inclined at an angle of 30 to 60 degrees with respect to the horizontal plane, and is installed at a distance of 0.5 to 20 mm from the surface of the transfer drum 9. ing.

Draining rolls 20a and 20b are installed between the guide rolls 5 and 3 and are in contact with the surface of the filter cloth 1. A filter cloth cleaning nozzle 21 is provided on the front side of the filter cloth between the drain roll and the guide roll 5, and a filter cloth cleaning nozzle 22 is provided on the back side of the filter cloth between the drain roll and the guide roll 3. There is.

In the filter cloth traveling type dehydrator having the above configuration, the solid liquid as the stock solution is transferred from the solid liquid supply pipe 23 to the solid liquid supply tank 13.
or this stock solution is supplied intermittently.

The intermittent supply is controlled by a 24-hour all-day timer built into the control circuit of the stock solution supply pump (not shown).
The stock solution supply pump is operated for a certain period of time, then stopped for a certain period of time, and this operation is repeated. However, the rotation of filter cloth 1,
Filter cloth cleaning by the cleaning nozzle is performed continuously.

Next, when supplying the stock solution intermittently as described above,
A case in which the process is carried out continuously as in the conventional case will be explained, but the operation of the apparatus shown in FIG. 1 will be explained in advance.

Driven by a drive roll 2, it travels in the direction of the arrow, and supplies a stock solution containing a solid component and a liquid component from a solid-liquid supply tank 13 onto the filter cloth 1 that is being circulated. The liquid component in the supplied solid-liquid passes through the filter cloth 1 and is collected in the vacuum suction tank 11 by gravity and by the vacuum suction action provided by the vacuum suction tank 11 .

The liquid components collected in the vacuum suction tank 11 are discharged to the outside of the dehydrator via the discharge pipe 16. On the other hand, the components that did not pass through the filter cloth 1 are carried between the transfer drum 9 and the squeeze roll 6.7.8 as the filter cloth 1 travels and rotates, and are squeezed to squeeze out the liquid components. It becomes what is called a cake. The cake is then transferred from the filter cloth 1 to the surface of the transfer drum 9,
Furthermore, it is scraped off by the scraper 12 and discharged to the outside of the dehydrator.

The scraped off cake is guided by the shooter 19 and does not fall or adhere to the filter cloth 1 from the kudzu.

The filter cloth 1 then reaches the position of the filter cloth cleaning nozzle 21, and is cleaned from the surface side by the cleaning water jetted from the filter cloth cleaning nozzle 21.

The filter cloth 1 is then cleaned by a draining roll 20 where liquid components from washing are removed.
After being removed by filter cloth cleaning nozzle 22
is cleaned from the back side and taken inside.
After the so-called clogging substances are removed and the direction of the fluff is aligned by the combing machine 24, it reaches the solid liquid supply tank 13 again and is subjected to the next dehydration.

Next, in the dehydrator operated as described above, the operating conditions of the stock solution supply pump are shown in Table 1.

In Table 1, condition N011.2.3 indicates intermittent operation, and condition N014 indicates conventional continuous operation. In other words, these operating conditions are shown in FIG. 3.

A running test was conducted under the above conditions and the following test conditions.

Raw solution supply pump: 0.75KW, 15-30 evenings/
Timer for intermittent operation: 24-hour all-day timer Filter cloth speed: 10 m/minute Filter cloth effective width: 1200 mm = 10- Decompression suction tank degree of decompression: 400 mm H20 surface washing water
: 60゜7 minutes Backwash water: 40A/min Raw sludge concentration: 14000 m9/ρ Raw sludge
: Food factory activated sludge As a result of excess sludge test, the degree of decrease in the amount of raw solution handled by the filter cloth with respect to the number of operating days is shown in Figure 4. Note that the undiluted solution throughput here is defined as the limit throughput at which sludge does not protrude from the transfer drum pressurizing section in the apparatus shown in FIG.

As shown in Fig. 4, operating condition N014, which is the conventional condition,
In this case, the throughput of stock solution decreased to 5.0 evening/min after 15 days, but the degree of decrease was significantly suppressed in the case of intermittent operation. In particular, it can be seen that the operating method under condition No. 1 (operating for 1 hour, stopping for 15 minutes) has the lowest rate of decrease in the amount of stock solution throughput, and that the clogging of the filter cloth is efficiently recovered.

Conventionally, when the throughput of stock solution decreases by 40%, the filter cloth is washed with chemicals and regenerated, but under the conditions of N011.2, even after 15 days, the filter cloth has not been washed with chemicals.
The lifespan of cotton cloth has been greatly improved.

Table 2 shows the amount of raw solution processed by the filter cloth per day after 15 days.

As shown in Table 2, it can be seen that even if the daily pump operation rate is lower due to intermittent operation, a large throughput can be obtained. Fig. 5 shows the relationship between the amount of stock solution processed after 15 days and the continuous operation time of the pump. In other words, it can be seen that the conditions of continuous operation for one hour show approximately the peak value and are close to the optimum conditions.

In addition, although the above description was made regarding the filter cloth traveling type dehydrator, the same operation and effect can be obtained with the filter cloth traveling type filtration machine.

[Effects of the Invention] As explained above, when using the solid-liquid separation method of the present invention, the stock solution is supplied intermittently, and the filter cloth can be efficiently washed to recover from clogging during the supply stop. Therefore, compared to conventional continuous feeding, the speed at which the filter cloth becomes clogged can be significantly reduced, the life of the cotton cloth can be greatly extended, and the raw solution processing capacity can be maintained at a predetermined level or higher for a long period of time. This effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view of a filter cloth traveling type dehydrator used in carrying out the method of the present invention, Fig. 2 is a perspective view of an endless filter cloth, Fig. 3 is a time chart showing the operating conditions of the stock solution supply pump, Figure 4 is a diagram showing the relationship between the number of operating days and the amount of undiluted solution processed under each operating condition, and Figure 5 is a characteristic diagram of the amount of undiluted solution processed per day under each operating condition after 15 days have elapsed. 1... Endless filter cloth 1a...
... Belt with holes 2 ... Drive roll 3.4.5 ... Kite roll 6.7.8 ... Press roll 9 ... Transfer drum 11...... Decompression suction tank 12... Scraper 13... Solid liquid supply tank 14... Intake pipe 15......Intake means 16...Discharge pipe 17...Reduced pressure suction port 18...Filter cloth guide Roll 19...
... Shooter 20a, 20b ... Draining roll 21.22 ... Filter cloth cleaning nozzle 23 ... Solid liquid supply pipe 24 ... Combiner time)

Claims (1)

[Claims] Continuously circulating an endless filter cloth on a constant orbit, supplying the stock solution to the surface side of the filter cloth, and separating the stock solution into solid-liquid into a residual component on the filter cloth and a liquid component passing through the filter cloth, A solid-liquid separation method in which a circulating filter cloth is continuously washed before the filter cloth reaches a stock solution supply section, characterized in that the stock solution is supplied intermittently.