JPS59229000A - Control device for chemical injecting quantity of sludge treating apparatus - Google Patents

Abstract

PURPOSE:To perform satisfactory adjustment of sludge by comparing values of pH measured for an FeCl3 injecting tank and a Ca(OH)2 injecting tank with predetermined values of pH and controlling the quantities of FeCl3 and Ca(OH)2 to be injected in accordance with the difference of pH between the measured values and the predetermined values. CONSTITUTION:Comparison of pH measured in an FeCl3 injecting tank 1 and preset value therefor, for example 3.5-5.5 is performed by a pH controller 8, and the control of the quantity of FeCl3 to be injected is done by controlling a motor valve 11a in accordance with the difference between both values. The control of the quantity of Ca(OH)2 to be injected is performed by controlling a motor valve 16 basing on the difference between the value of pH in a Ca(OH)2 injecting tank and a preset value, for example 11-12. The quantity of Ca(OH)2 to be injected is obtd. as an output of a pH controller 14 which is used as an input of set value to a Ca(OH)2 injection controller 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for controlling the injection amount of these chemicals in a sludge treatment facility in which sludge is tempered by introducing ferric chloride and then adding slaked lime. This invention relates to a chemical injection amount control device.

Conventionally, there has been a device of this type as shown in FIG.

In the figure, 24 is a chemical injection tank consisting of a ferric chloride injection tank 1 and a slaked lime injection tank 2.

The sludge first enters the ferric chloride injection tank 1 through the input sludge pipe 3, and is mixed with the NFC ferric chloride injected into the ferric chloride injection pipe 5 by the action of the stirring device 18. The sludge then enters the slaked lime injection tank 2 and is mixed with the slaked lime injected into the slaked lime injection pipe 6 by the action of the stirring device 18. This 1
The sludge is refined by The tempered sludge is sent to the dewatering process through a feed sludge line 4 to the dewatering all (not shown).

19 is an input sludge flow meter, and 20 is an input sludge concentration meter, both of which are installed in the input sludge pipe line 3.

Reference numeral 21 denotes a computing unit, which inputs the measured values of the input sludge flow meter 19 and the input sludge concentration meter 20. 22 and 23 are ratio setters, both of which are connected as inputs from the arithmetic unit 21. lla is an electric valve, and 12 is a ferric chloride flowmeter, both of which are installed in the ferric chloride injection pipe 5. 9 is a ferric chloride injection amount controller, to which the outputs of the ratio setter 22 and the ferric chloride flowmeter 12 are connected as inputs.
The output is connected to the electric valve 11a. 11b is an electric valve, and 17 is a slaked lime flow meter, both of which are installed in the slaked lime injection pipe 6. Reference numeral 15 denotes a slaked lime purchase amount controller, to which the output of the ratio setter 23 and the slaked lime flowmeter 17 is connected as an input, and the output is connected to the electric valve 11b.

Next, the operation will be explained. The amount of ferric chloride and slaked lime to be injected is proportional to the solid content in the input sludge, and is the amount fC, and by injecting this amount, the sludge is tempered in a predetermined manner.

QF6”kl・Ci @Qi ・= 1
llQca=ni, ・Ci −Q i −+
21 Where, QFe: Ferric chloride injection amount Qc&': Slaked lime injection amount Qi: Input sludge flow rate C11L Input sludge concentration The concentration (Ci) is -'f-n-t'', obtained as the output signal of the input sludge flow meter 19 and the input sludge concentration meter 20, and the calculation of tl, (C1-Qi), in other words, the concentration of the input sludge in the input sludge. The calculation of the amount of solid matter (dry matter) is performed by the calculator 21. In equation (1), the proportionality constant (kl) is determined by the ratio setter 22, and the calculation on the right side is determined by the ratio setter 22. 1. Therefore, (QFf, ) is obtained as the output of the ratio setter 22, and nl is the setting input for the ferric chloride injection amount controller 9. In the ferric chloride injection amount controller 9, Output of ratio setting device 22 and ferric chloride flow meter 1
With the output of 2.

An operation is performed to set the opening degree of the electric valve 11a.

This adjusts the injection amount of ferric chloride to a predetermined value.
Ru. 'In the formula F7t+21, the proportionality constant (k2) is set in advance in the ratio setter 23, and the calculation on the right side is performed in the ratio setter 23, so (Q(3a) is the output of the ratio setter 23. The obtained n and n become the settings for the slaked lime injection amount regulator 15.

In the slaked lime injection amount adjustment t+15, the electric valve 1 is
The operation to set the opening degree of 1b is performed.

At this time, the amount of slaked lime injected is adjusted to a predetermined value.

Since the conventional chemical injection amount control device for sludge treatment equipment is configured as described above, the amount of chemical injection is only adjusted according to the amount of solid matter in the sludge, and the amount of sludge that is related to the amount of chemical consumption is adjusted. No consideration was given to the alkalinity of the sludge, and as a result, the ever-changing alkalinity of the sludge caused an insufficient loading of chemicals, making it difficult to obtain a good sludge conditioning effect.
do not have. Furthermore, if the amount of chemicals injected becomes excessive, the amount of sludge to be treated will increase, resulting in the disadvantage that stable operation cannot be achieved.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it measures the pH value of the ferric chloride injection tank and the slaked lime injection tank, and compares the measured values of n et al.
n+t''n compared with predetermined t'1cpH,
We provide a chemical injection amount control device that controls the injection amount of ferric chloride and slaked lime according to the difference in the amount of sludge, and enables good sludge conditioning without causing excess or deficiency in the amount of chemicals used. It is intended to.

An embodiment of the present invention will be described below with reference to the drawings. Second
In the figure, 24 is a chemical injection tank consisting of a ferric chloride injection tank 1 and a slaked lime injection tank 2η), 3 is an input sludge pipe, 4 is a supply sludge pipe, 5 is a ferric chloride injection pipe, 6 is a slaked lime injection pipe, 11a and Ilb are electric valves, 12 is a ferric chloride flow meter, 17 is a slaked lime flow needle, and 1B is a stirring device. These elements are equivalent to those shown in FIG.

7. 13 is 7 n (''n ferric chloride injection tank 1 is installed in slaked lime injection ia 2.
is a manual setting device. 8 is the pH for ferric chloride injection tank 1
The controller receives signals from the pHHI 3 and the manual setting device 10 as inputs, and its output is connected to the injection amount controller 9. Further, 14 is a pH controller for the slaked lime injection tank 2, which inputs signals from the pH meter 13 and the manual setting device 16, and whose output is connected to the injection amount controller 15.

Next, the operation will be explained. In fig.

The amount of ferric chloride injected is controlled based on the pH value of 1 yen of the ferric chloride injection tank measured by pHHI3, and the fc value of 3.5 to 5.
The pH controller 8 compares the value f'l'fc set in advance to the value 1. Electric valve 1 according to the difference of 7
Eri is achieved by adjusting 1&.

QF6=G□(p)l 1- pH1) -tal
where pH□: ferric chloride injection PapI (senp H1
”: Ferric chloride injection tank pH setting piece G□: pH controller 8
The gain of ferric chloride injection tank pH setting @ (pH,'') is set in the manual setting device 10. Ferric chloride injection amount (Q?
, ) is obtained as the output of the pH controller 8.

This serves as a set value input for the ferric chloride injection amount controller 9.

In this controller 9, the signal from the ferric chloride flowmeter 7 and (
QFe) is used to adjust the electric valve 11a.

'F7 (The amount of slaked lime injection is controlled by the slaked lime injection tank 2
The electric valve 16 is activated according to the difference between the H number and the fcpH setting, which is set in the range of π, for example, 11 to 12.
It is achieved by adjusting the

Qoa=Q2(pH2-pI(2”)...(4
1 where pH2=slaked lime injection tank phi pH,”: slaked lime injection tank pE setting Tsukuda G2: gain of pH controller 14 (calculation of formula 41 is performed by pH controller 14. Slaked lime injection tank pH setting Tsukuda (pH 2 The pH value (P) of the slaked lime injection tank is set using the manual setting device 16, and the pH value (P) of the slaked lime injection tank is set using the pH meter 13.
n is obtained as the output of n. The amount of slaked lime injection (Qc) is
The output of the pH controller 14 becomes the set value input of the slaked lime injection amount controller 15. This controller 15
Then, an operation is performed to adjust the electric valve 11b using the signal from the slaked lime injection unit 12 and (Qaa).

The 7'C chemical injection amount control device shown in FIG. 2 was used.

Refining experiments were conducted on several sludges with different sludge properties by injecting ferric chloride and slaked lime, and the results were evaluated from the viewpoints of filtration performance, sludge compressibility, and dehydration cake removability from the dehydrator cloth surface. A comprehensive evaluation of the tempering effect was performed. Figure 3 shows the relationship between the sludge pH value after ferric chloride injection and C8T, and Figure 4 shows the sludge control in the relationship between the sludge pl (PL) after ferric chloride injection and the sludge pH value after slaked lime injection. The suitable area for young buds is shown.

As is clear from Figures 3 and 4, the pH value at which a good tempering effect can be obtained is 3.5 to 5 after ferric chloride injection.
．． 5. Although the pH value is limited to a narrow range of 11 to 12 after injecting slaked lime, according to the present invention, the pH value can be accurately maintained within the desired range, so that stable tempered young buds can always be obtained.

In the above embodiment, the instrumentation circuit is constructed of a time-continuous analog type, but the same effect can be obtained with a time-discontinuous analog type (sampling type) or digital type instrumentation circuit.

As described above, according to the present invention, the pH values of the ferric chloride injection tank and the slaked lime injection tank are measured, and the amount of chemical injection is controlled according to the difference from the predetermined set value. It can fully respond to fluctuations in the alkalinity of input sludge, ensuring good sludge conditioning without causing excess or deficiency in the amount of chemicals used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional chemical injection amount control device, FIG. 2 is a block diagram showing the configuration of a chemical injection amount control device according to an embodiment of the present invention, and FIG. 3 is ferric chloride. The graph showing the relationship between the sludge OpH value after injection and CTS, Figure 4, shows the preferred range for the conditioning effect in the relationship between the sludge pH value after ferric chloride injection and the sludge pH value after slaked lime injection. This is a graph showing. 1... Ferric chloride injection tank, 2... Slaked lime injection tank, 3
... Input sludge pipe line, 4... Supply sludge pipe line, 5...
Ferric chloride injection pipe line, 6... Slaked lime injection line, 7, 1
3...pH meter, 8,14...pH controller, 9.15
...Injection amount controller, 10.16-...Manual setting device, 1
1a, 11b... Electric valve, 12... Ferric chloride flow meter, 17... Slaked lime flow meter, 24... Chemical injection tank. Note that the same cylinder numbers in Figure 1 indicate the same or equivalent parts. π3 Figure 4 Figure 2 Chloride fang

Claims (1)

[Claims] (1) In a chemical injection amount control device for controlling the injection amounts of ferric chloride and slaked lime when sludge is tempered by injecting ferric chloride into sludge and then injecting slaked lime, The first pH meter measures the pH of the sludge after ferric chloride is injected, and the measured pH is compared with the fcpH set value, and the amount of ferric chloride to be injected is determined according to the difference. a ferric chloride injection amount controller to adjust the amount of ferric chloride, a second pH meter to measure the pH of the sludge after slaked lime is injected, and a pH setting that predetermines n'fcpH measured by this second pH meter. 1. A chemical injection amount control device for sludge treatment equipment, comprising: a slaked lime injection amount controller that adjusts the amount of slaked lime injection in accordance with the difference in slaked lime value. (21 pH setting value after ferric chloride injection is 3.5 to 5.5
2. The chemical injection amount control device for sludge treatment equipment according to claim 1, wherein the pH setting value after injection of slaked lime is 11 to 12.