JP3159353B2 - Control method of sludge supply pressure in screw press - 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 controlling sludge supply pressure when dewatering sludge using a screw press. Conventionally, the performance of a dehydrator is generally expressed and evaluated in terms of filtration speed, cake moisture content, and SS recovery rate. The present invention is intended to control the supply pressure of sludge based on the SS recovery rate in this, and to operate the screw press efficiently.

[0002]

2. Description of the Related Art Conventionally, a filtrate concentration meter for determining the recovery rate of SS is well known. That is, if the concentration of the filtrate is known, it is possible to determine how much solids have been separated from the stock solution whose concentration is known. The measurement accuracy is as high as 10 to 1000 mg-SS / l.

[0003]

However, in the above-described densitometer, in which a filter cloth is used as a filter medium such as a filter press or a belt press, the SS in the filtrate contains fine particles passing through the filter cloth. It is possible to measure with high accuracy because it is uniform.However, in the case of using a mesh filter medium, such as a screw press, and using a flocculant immediately before dehydration, the SS particles in the filtrate are non-uniform. In some cases, flocculants aggregate in the filtrate due to the action of the added flocculant. As described above, when large and small SS particles are mixed in the filtrate, the large particles become an obstacle, and the optical sensor cannot accurately measure the SS amount. Therefore, the supply pressure cannot be controlled based on the unstable SS amount.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a technique which is effective when used in a screw press or the like in which large and small SS particles are mixed in a filtrate as described above. The filtrate at the inlet of the outer cylindrical screen of the screw press is intermittently collected, the SS particles in the collected filtrate are crushed to uniform size, and the turbidity of the filtrate is measured by an optical sensor. In this method, the supply pressure of the sludge supply pump to the screw press is controlled based on the measured turbidity to maintain the SS concentration in the filtrate at a certain level or less.

[0005]

According to the present invention, the S of the sampled filtrate is
Since the size of the S particles is made uniform and then the light sensor is applied, the amount of the SS particles in the filtrate can be accurately measured. Therefore, if the pushing pressure of the supply pump is controlled based on the measured value, a proper dewatering operation can be performed.

That is, in a screw press,
Since the filter medium is coarse using a wire mesh or punching metal, if it is pushed in at high pressure, it will pass through, and large SS particles will enter the filtrate. However, according to the present invention, if the allowable SS amount in the filtrate is set, the indentation pressure can be selected based on that. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0007]

FIG. 1 is a flow sheet diagram of a method for controlling a supply pressure according to the present invention.
Reference numeral 2 denotes a mixing tank for a flocculant, 3 a supply pump for a flocculant, and 4 a supply pump for sludge.

Reference numeral 5 denotes a filtrate receiver provided below the outer cylindrical screen 1a of the screw press 1, which is divided into front and rear parts. Reference numeral 5a denotes a filtrate receiver provided on the inlet side of the sludge to the outer cylindrical screen 1a.
It is connected to the measuring device 6 for SS in the filtrate so that a sampling filtrate is collected from the filtrate receiver 5a.
5b is a filtrate receiver provided in the latter half of the outer cylindrical screen 1a.
It is.

Reference numeral 7 denotes a control panel of the supply pump 4, which receives the measured value information of the SS amount of the measuring device 6, controls the supply pump 4 based on the measured value, and sends the information to the screw press 1. The sludge supply pressure is adjusted.

Next, the configuration of the measuring device 6 will be specifically described with reference to FIG. In FIG. 2, reference numeral 6a denotes a measuring cell made of transparent glass, 6b denotes a reciprocating piston for supplying and discharging a filtrate for measurement provided therein, and 6c denotes a reciprocating piston.
This is a filtrate supply / discharge port opened opposite to the reciprocating piston 6b, and a homogenizer 6d that can rotate at high speed and stir the filtrate is provided in the supply / discharge path. The supply / discharge path is connected to the filtrate receiver 5a.

Further, in FIG. 2, reference numeral 6e is light sensors provided relative to both sides of the measuring cell 6a, the
A measuring cell 6a of the light projected from the light sensors 6e hit is are subjected chamfered. A wiper 6f is provided on the outer edge of the front end of the reciprocating piston 6b.

In order to adjust the supply pressure of the sludge to the screw press 1 with the control device configured as described above, the following operation is performed. First, by the reciprocating piston 6b,
The filtrate in the filtrate receiver 5a is sucked into the measuring cell 6a, and at the same time, the filtrate aspirated by the homogenizer 6d is stirred and stirred.
S is made uniform.

Next, the optical sensor 6e detects the SS.
The filtrate having a uniform content is irradiated, and the amount of contained SS is measured. When measuring this SS amount, in the present invention,
Since the filtrate is agitated by the homogenizer 6d and the SS component is crushed and uniformized, the light projected from the optical sensor 6e uniformly transmits through the filtrate, and the SS amount can be accurately measured.

The filtrate whose measurement has been completed in this way is extruded by the reciprocating piston 6b into another filtrate discharge path 5c, while the measured value of the measuring device 6 is sent to the control panel 7 as information. The control panel 7 can adjust the supply pressure of the supply pump 4 in light of a preset reference value of the SS amount in the filtrate, thereby adjusting the amount of missing from the outer cylinder screen 1a.

Further, the measuring device 6 used in the present invention, the wiper 6f reciprocating piston 6b provided within the measurement cell 6a is, since in sliding contact with the inner surface of the measuring cell 6a in each reciprocating clean it, light sensor 6e is good and stable, and the error of the measured value of SS is small.
It can measure accurately.

Further, in the present invention, the filtrate is sampled at the inlet of the outer cylinder screen 1a for sampling the filtrate. The outer cylinder screen
Rather than mixing and sampling the entire filtrate of 1a ,
Separating and collecting the filtrate immediately after the inlet and measuring it has a higher rate of change in the concentration (SS amount), which facilitates the measurement, and the corresponding adjustment of the supply pump 4 based on the result is easy and matches the actual situation. It is.

In this embodiment, the homogenizer 6d is used to crush and equalize SS in the sampled filtrate, but other means such as an ultrasonic device may be used. Further, a photoelectric switch may be used as the optical sensor. In short, the feature of the present invention is that the sampled filtrate is crushed and homogenized, the amount of transmitted light is made uniform to obtain an accurate measurement value, and the supply pressure of the supply pump 4 is controlled based on this. There is something.

[0018]

As described above, the present invention can accurately measure the amount of SS in a filtrate when a filter medium such as a screw press has a coarse mesh and SS particles are mixed in a large or small amount in the filtrate. The measured value information is fed back to the stock solution supply pump so that the dehydration operation can be performed under optimum conditions. Conventionally, the concentration was not useful for controlling the supply pressure while having precise measurement accuracy. Is a control method that replaces the
The benefits gained from sludge dewatering operations are significant.

[Brief description of the drawings]

FIG. 1 is a schematic flow sheet diagram of a control method according to the present invention.

FIG. 2 is also a vertical sectional view of a measuring instrument used for the control method.

[Explanation of symbols]

 Reference Signs List 1 screw press 1a outer cylinder screen 6e optical sensor 4 supply pump

Continued on the front page (51) Int.Cl. ⁷ Identification code FI B01D 33/80 B01D 33/34 B30B 11/24

Claims (1)

(57) [Claims] 1. An outer cylindrical screen 1 of a screw press 1.
The filtrate at the inlet of a was intermittently collected, and after crushing the SS particles in the collected filtrate to make the size uniform, the turbidity of the filtrate was measured using the optical sensor 6e. ,
Controlling the supply pressure of the sludge supply pump 4 to the screw press 1 based on the measured turbidity to maintain the SS concentration in the filtrate at a certain level or less, and controlling the supply pressure of the sludge in the screw press. Method.