JP3016327B2 - Control method of coagulation mixing tank - 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 a coagulation mixing tank used for solid-liquid separation of various sludges and slurries.

[0002]

2. Description of the Related Art Conventionally, in a process of solid-liquid separation of a suspension such as sludge or slurry, a suspension is supplied to a coagulation mixing tank, and floc is formed while stirring with a stirrer in the tank. The suspension in the mixing tank is pumped to a filter press by a pump.

[0003]

However, in the above-mentioned conventional structure, the amount of the suspension fed from the coagulation mixing tank to the filter press gradually decreases with an increase in the amount of cake in the filter press. , The residence time of the suspension gradually increases. Therefore, if the stirrer is always rotated at a constant speed in the coagulation mixing tank, proper stirring in the initial state becomes excessive in the final state, and the floc is destroyed.

For this reason, it has been proposed to detect the number of rotations of a pump for pumping to a filter press and to control the number of rotations of the stirrer according to the number of rotations. When the number is reduced, stirring is insufficient, and there is a problem that suspended substances such as sludge in the suspension (hereinafter, also simply referred to as suspension) are not sufficiently aggregated.

[0005] On the other hand, the supply of the suspension to the coagulation mixing tank is usually level-controlled. When the level in the tank is low, the suspension is supplied, and when the level is high, the suspension is stopped. However, when stirring at a constant speed, or when controlling the rotation speed of the stirrer according to the rotation speed of the pump as described above, appropriate stirring is performed because the amount of suspension in the tank is not considered. However, there is a problem that the floc is broken or unagglomerated.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method for controlling a flocculation mixing tank capable of flocculating suspended substances in a suspension without causing floc destruction or non-coagulation. It is.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method in which a suspension supplied to a flocculation and mixing tank is pumped to a filter press by a pump while being stirred by a stirrer in the tank. Detecting the water level of the suspension by the water level detection means, detecting the rotation speed of the pump by the rotation speed detection means, and controlling the rotation speed of the stirrer according to the detected water level and the rotation speed. I do.

[0008]

According to the above construction, when the suspension is supplied to the coagulation mixing tank, an increase in the water level of the suspension in the tank is detected. Therefore, the stirrer is controlled to rotate at high speed according to the water level. Thereby, the suspension and the flocculant can be sufficiently mixed to prevent the suspension from being unagglomerated.

Also, no suspension is supplied to the coagulation mixing tank,
When the rotation speed of the pump is low, the rotation speed of the stirrer is reduced to prevent over-coagulation or destruction of flocs, and when the rotation speed of the pump is high, the rotation speed of the stirrer is increased to prevent non-coagulation. Even when the pump rotation speed is the same, when the water level of the suspension in the tank is high, the suspension and the flocculant are sufficiently mixed by increasing the rotation speed of the stirrer to prevent unagglomeration and prevent the water level. When is low, excessive coagulation or destruction of flocs can be prevented by lowering the rotation speed of the stirrer.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a flocculation mixing tank 1 has a stirrer 2. A suspension supply pipe 3 is provided at the top of the flocculation mixing tank 1, and a liquid feed pipe 4 is provided at a bottom thereof. ing. A pump 5 is interposed in the middle of the liquid feed pipe 4, and the tip side of the liquid feed pipe 4 communicates with a filter press 6. The drive 7 of the pump 5 is provided with a tachometer 8 as rotation speed detecting means.
Are connected to the control device 9 via a signal line, and the driving device 10 of the stirrer 2 is connected to the control device 9 via the control line. Further, a differential pressure type liquid level gauge 12 as a water level detecting means is provided below the coagulation mixing tank 1, and this liquid level gauge 12 is also connected to the control device 9 via a signal line.
It is connected to the.

The operation of the above configuration will be described below.
The suspension 11 supplied to the coagulation mixing tank 1 from the suspension supply pipe 3 under level control conditions is mixed with the coagulant while being stirred by the stirrer 2 in the tank, and the suspended substance in the suspension 11 is mixed. Undergo flocculation to form flocs. Then, the suspension 11 containing the floc is supplied to the filter press 6 through the liquid feed pipe 4 by the pump 5. While the treatment is continued in this manner, the rotation speed of the pump 5 gradually decreases due to the load resistance that increases with the gradual increase in the cake amount in the filter press 6, and the amount of the suspension 11 flowing out to the filter press 6 decreases. Then, the suspension 11 stays in the coagulation mixing tank 1. At this time, the number of revolutions of the driving device 7 of the pump 5 is detected by the tachometer 8, and the water level of the suspension 11 in the coagulation mixing tank 1 is detected by the differential pressure level gauge 12 and transmitted to the controller 9. Is done. Then, in response to the decrease in the rotation speed of the pump 5, the control device 9 controls the driving device 10 of the agitator 2.
Is controlled, excessive agitation of the suspension 11 is suppressed, and excessive aggregation of the suspension 11 or breakage of flocs is prevented. Even if the decrease in the rotation speed of the pump 5 is similar to this, when the water level of the suspension 11 in the tank 1 is higher, the rotation speed of the stirrer 2 is controlled to be higher, and the unagglomerated suspension 11 Is prevented.

When the suspension 11 is supplied to the flocculation / mixing tank 1, a rise in the water level in the flocculation / mixing tank 1 is detected with almost no change in the rotation speed of the pump 5 being detected. In response to the rise in the water level, the rotation speed of the stirrer 2 is increased by the control device 9, and the suspension 11 and the coagulant are sufficiently mixed in the tank, so that the suspension 11 is prevented from being non-agglomerated.

[0013]

As described above, according to the present invention, the rotation speed of the stirrer is controlled according to the water level of the suspension in the tank and the rotation speed of the pump for pumping the suspension. Since the appropriate agitation can be performed on the suspension, the destruction of flocs in the suspension and the non-aggregation of the suspension, especially when the suspension is supplied, are prevented. can do.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coagulation mixing tank 2 Stirrer 5 Pump 6 Filter press 8 Tachometer (rotation speed detection means) 11 Suspension 12 Differential pressure level gauge (water level detection means)

Claims (1)

(57) [Claims] When the suspension supplied to the coagulation mixing tank is pumped to a filter press by a pump while being stirred by a stirrer in the tank, a water level of the suspension in the tank is detected by water level detection means, A method for controlling a flocculation and mixing tank, wherein the number of revolutions of a pump is detected by a number of revolutions detecting means, and the number of revolutions of the stirrer is controlled according to the detected water level and the number of revolutions.