JPH07155511A - Method for monitoring amount of flocculant to be added and device therefor - Google Patents

Abstract

PURPOSE:To optimize the amt. of a flocculant to be added by arranging a heater and temp. sensors in a passage, detecting the temp. rise of each sensor when the heater is pulse-energized and contrasting the temp. rises. CONSTITUTION:A heater 3 is arranged in a passage 4, and two temp. sensors 1 and 2 are provided on the downstream side at a distance from each other. A flocculant is added to the excess activated sludge, and the dehydrated filtrate flows down in the passage 4. The heater 3 is pulse-energized, the heat of the heater 3 is diffused into the boundary layer by conduction, and the temps. detected by the sensors 1 and 2 are maximized. At this time, even if the amt. of flocculant added is too much or too little, the viscosity of the flocculated liq. is increased, the boundary layer develops, and hence the difference in maximum temp. between the sensors 1 and 2 is reduced. Accordingly, whether an optimum amt. of the flocculant is added or not is judged by monitoring the temp. difference.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for determining whether the amount of coagulant added is excessive or insufficient.

[0002]

2. Description of the Related Art As a method for treating water and waste water, there is a coagulation treatment method. In this aggregating method, if the amount of the aggregating agent added is excessive, the agent may be wasted and the aggregating effect may be reduced. If the amount of the aggregating agent added is too small, the aggregating effect is insufficient.

[0003]

Conventionally, whether or not the addition amount of the coagulant is appropriate is judged by collecting and observing the coagulated liquid. There was a problem such as taking time.

[0004]

According to the method for monitoring the amount of coagulant added according to the present invention, a heater is provided in the flow path of the coagulated liquid, and a plurality of temperature sensors are provided downstream of the heater in the downward direction. The temperature rise of each temperature sensor when the heater is pulsed to generate heat is detected, and the temperature rise value of each temperature sensor is compared, so that the addition amount of the coagulant is in an appropriate range. The feature is to judge whether or not.

The coagulant addition amount monitoring device of the present invention comprises a flow path for the liquid subjected to the coagulation treatment, a heater provided in the flow path,
It is provided with a plurality of temperature sensors provided downstream of the heater in the flow path at intervals in the flow-down direction, and means for comparing detected temperatures of the temperature sensors.

[0006]

If the added amount of the coagulant is excessive, the coagulant is dissolved in the liquid subjected to the coagulation treatment and the viscosity of the liquid increases. If the coagulant is too small, the concentration of the tacky microorganic substance in the liquid will be high and the viscosity will be high.

By the way, when the heater is placed in the flow of the fluid, a zone in which the flow stays, called a boundary layer, is formed on the downstream side of the heater, and a free flow region is formed outside the zone. Then, as the viscosity of the liquid increases, the boundary layer develops, that is, the boundary layer width in the direction orthogonal to the flow direction increases.

In the boundary layer, there is almost no convective heat transfer, and heat is mainly transferred by conduction. In the free flow region, heat transfer is mainly performed by convection.

In the method and apparatus of the present invention, however, a plurality of temperature sensors are provided downstream of the heater at intervals in the flow-down direction. Therefore, these temperature sensors are arranged in the boundary layer.

When the heater is made to generate heat in a pulsed manner, that is, for a short time, the heat of the heater is diffused into the boundary layer by conduction heat transfer. Therefore, the temperature detected by the temperature sensor on the most upstream side closest to the heater reaches a maximum value after a lapse of a predetermined time after the heat generation of the heater, and then when the predetermined time further elapses, the temperature detected by the second temperature sensor reaches a maximum value. Becomes (Hereinafter, the maximum value of the detected temperature may be referred to as the maximum temperature value.) As mentioned above, the more the boundary layer is developed, the larger the amount of conduction heat transfer is, so the heat is well transferred to the temperature sensor on the downstream side. The temperature maximum values of the plurality of temperature sensors are all considerably high, and the difference between the temperature maximum values of the respective sensors is small. On the contrary, when the boundary layer does not develop much, the amount of heat transfer to the temperature sensor becomes small. Almost no heat is transmitted to the temperature sensor on the most downstream side, and the maximum temperature value is also extremely small. Thus, the more the boundary layer does not develop, the larger the difference between the temperature maximum values of the temperature sensors becomes.

As described above, even if the amount of the aggregating agent added is excessive or, on the contrary, too small, the viscosity of the coagulated liquid increases and the boundary layer develops. As a result, the difference between the temperature maximum values of the plurality of temperature sensors becomes large regardless of whether the boundary layer addition amount is excessive or insufficient. Therefore, by monitoring the difference between the temperature maximum values of these temperature sensors, it is possible to determine whether the addition amount of the coagulant is an appropriate amount.

[0012]

EXAMPLE FIG. 1 is a schematic view for explaining an example method. The electric heater 3 is arranged in the flow path 4, and two temperature sensors 1 and 2 are provided on the downstream side of the electric heater 3 at intervals.

A dewatered filtrate obtained by adding a coagulant to the surplus activated sludge of the sewage and dehydrating it is flowed into the flow path 4.

The main operating conditions are as follows.

Type of flocculant: cationic polymer Amount of flocculant added: about 100 to 300 mg
/ L Cross-sectional area of flow path 4: 6 cm ² Length of heater 3: 2 cm Diameter of heater 3: 6 mm Resistance value of heater 3: 5 Ω Distance between heater 3 and temperature sensor: 5 cm Distance between temperature sensors 1 and 2: 5 cm Flow rate of liquid flowing through the flow channel: 180 l / min Flow velocity of liquid flowing through the flow channel: 0.5 cm / sec Normal temperature of liquid flowing through the flow channel: 20 ° C. When measuring, apply a current of 4 A to the heater 3. Energizing for 10 seconds, the temperature maximum values of the temperature sensors 1 and 2 are detected, and the difference ΔT between the temperature maximum value Tmax and the temperature Tstandard before the temperature rise is calculated for each sensor 1 and 2, ΔT ₁ , ΔT
₂

FIG. 2 shows the measurement results of the ratio (temperature rising value ratio) ΔT ₂ / ΔT ₁ of the temperature rising values ΔT ₁ and ΔT ₂ . As is clear from FIG. 2, when the amount of coagulant added is about 200 ppm, ΔT ₂ / ΔT ₁ becomes minimum,
It was determined that the amount of coagulant added was about the optimum amount.
(Note that this judgment result was also in agreement with the visual observation of the sample liquid separately performed.) In FIG. 2, when the amount of the coagulant added exceeds 200 ppm, ΔT ₂ / ΔT ₁ gradually increases. Further, when the added amount is less than 200 ppm, ΔT ₂ / ΔT ₁ rapidly increases.

FIG. 3 is a system diagram of a sludge flocculation / dehydration treatment facility incorporating the monitoring device shown in FIG.

A coagulant is added to the raw mud from the chemical dissolution tank 12 and the chemical injection pump 13 in the middle of the pipe 10, and the raw mud is introduced into the dehydrator 14 to form a dehydrated cake.

The dehydrated filtrate is a flow rate control valve 16 and an on-off valve 1.
It is introduced into the flow path 4 via 8. Control device 2 for heater 3
Power is supplied from 0, and the temperatures detected by the temperature sensors 1 and 2 are input to the controller 20.

Note that washing water can be supplied to the flow path 4 from a pipe 24 having an opening / closing valve 22. Valve 16,1
8, 22 and the chemical injection pump 13 are controlled by the controller 20. 26 is an inverter. In this equipment, from the detection values of the temperature sensors 1 and 2, the difference temperature ratio ΔT ₂
/ A [Delta] T ₁ is calculated, by controlling the chemical feeding, chemical dosing quantity as the [Delta] T ₂ / [Delta] T ₁ becomes minimum, can be optimized amount the amount of flocculant.

[0021]

As described above, according to the method of monitoring the coagulant addition amount of the present invention and the monitoring apparatus therefor, the coagulant addition amount can be surely made to be the optimum amount, and the cost of the medicine can be reduced and the treatment can be performed. Water quality can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a monitoring device according to an embodiment.

FIG. 2 is a graph showing experimental data.

FIG. 3 is a system diagram of coagulation processing equipment.

[Explanation of symbols]

 1, 2 Temperature sensor 3 Heater 4 Flow path

Claims (2)

[Claims] 1. When a heater is provided in the flow path of the agglomerated liquid and a plurality of temperature sensors are provided downstream of the heater at intervals in the flow-down direction to heat the heater in a pulsed manner. Monitoring the coagulant addition amount, which is characterized by detecting the temperature rise value of each temperature sensor and comparing the temperature rise value of each temperature sensor to determine whether the coagulant addition amount is within an appropriate range. Method. 2. A flow path for the agglomerated liquid, a heater provided in the flow path, and a plurality of temperatures provided downstream of the heater in the flow path at intervals in the flow-down direction. An apparatus for monitoring the amount of coagulant added, comprising a sensor and a means for comparing the temperature detected by the temperature sensor.