JPS5879600A - Controller for feeding chemical - Google Patents

Abstract

PURPOSE:To minimize the total sum of the costs of flocculating agents and the costs of auxiliary fuel by providing a device for operating the feeding rate of a chemical at which the total sum of the costs of the auxiliary fuel in an incineration stage and the costs of chemicals in a chemical feed stage is minimized and a control section for the amts. of the chemicals to be added. CONSTITUTION:The outputs of a sludge concn. meter 9 and a measuring device 10 for capillary suction time are supplied to the 1st arithmetic device 11. The relations between the rate of chemical feeding and the moisture contents of dehydrated sludge are beforehand inputted to the 2nd arithmetic device 14, which receives the output from the device 11 and calculates the relations between the rate of chemical feed and the moisture contents of the dehydrated sludge of that time. Further, said device calculates the relations between the rate of chemical feeding and the moisture contents of the dehydrated sludge and the relations between the rate of chemical feeding and the costs of auxiliary fuel in an incinerating stage. Said device calculates the relations between the rate of chemical feeding and the costs of chemicals as well and determines the rate of chemical feeding at which the total sum of the costs of the auxiliary fuel and the costs of chemicals in that time is minimized. The outputs of the device 12 are supplied to a controller 13 which controls a control valve 14.

Description

Detailed Description of the Invention (a) Description of the Technical Field The present invention relates to a chemical injection control device C for concentrating and dewatering organic sludge generated in sewage treatment, and more specifically to an auxiliary device for incineration step 1. Kuwano control system that can minimize the sum of fuel costs and chemical costs in the collection process.

(4) Description of Prior Art In the sludge treatment process, organic sludge generated in the sewage water treatment process is first sent to a thickening cypress and concentrated. III/a
The sludge is then sent to a chemical-mixing hinoki, where a coagulant is added and dewatered. Furthermore, the dehydrated sludge is sent to an incinerator and incinerated.

In such a sludge treatment process (-), the chemical injection control of the flocculant in the chemical injection process is carried out in advance by Leaf Test Town's dewatering test C.
-, the chemical injection rate at which the water content of the dehydrated sludge is the minimum I: was determined, and the amount of added flocculant was adjusted by measuring the flow rate and concentration of the sludge fed into the dehydrator. However, this concentration control method has the following drawbacks. If the dewatering characteristics of the sludge change during wholesale, the chemical injection rate that keeps the water content of the dehydrated sludge to a minimum of 1-1 will change;
It was necessary to carry out manual labor and re-determine the drug injection rate, which required a considerable amount of effort. Recently, as a method to overcome the shortcomings of these chemical injection control methods, the capillary suction time of the sludge introduced into the dehydrator is also measured at the same time, and the set value of the chemical injection rate can be determined without performing frequent C-nileaf tests. Some methods are being used to change the appropriateness.

Capillary suction time Fi is the time it takes for water in sludge to permeate a certain distance in a piece of paper by capillary force, and is one index expressing the dewatering characteristics of sludge.

The conventional control method described above minimizes the moisture content of dewatered sludge.
This has the advantage that the volume of dewatered sludge can be minimized. For this reason, I: was an effective control method in cases where dehydrated sludge was disposed of directly in a room. However, it became difficult to secure land for a room in a nearby metropolitan area.
The number of cases in which dehydrated sludge is incinerated and prepared as incinerated ash for disposal is increasing (Dehydrated sludge 1: On the other hand, incinerated ash is Ko −
In such a sludge treatment process that incorporates an incineration process after the dewatering process, a chemical injection control method that reduces the water content of dehydrated sludge to a minimum of 52 is not necessarily optimal. From a cost perspective, a chemical injection control method that minimizes the sum of the flocculant cost in the chemical injection process and the cost of auxiliary fuel (usually heavy oil) in the incineration process is recommended. Considering that it is synthesized from

(C) Purpose of the Invention The present invention is a book based on the above-mentioned idea, so
0(d) The purpose of the invention is to provide a chemical injection control device that can easily minimize the sum of the flocculant cost in the chemical injection process and the auxiliary fuel cost in the incineration process, namely: A chemical injection control device Fi of the present invention, a mixing device that adds and mixes chemicals to sludge generated from a sewage treatment process, etc.;
# In the sludge treatment process I2, which is composed of at least a dehydrator for dewatering the chemical-added sludge flowing out from the mixing device, and an incinerator for incinerating the dehydrated sludge carried out from the dehydrator, 6. No. 1, 2 and 3 measurements for measuring the chain degree (X) flow rate' (Q)% and capillary suction time (OEIT) of the inflowing sludge; A first arithmetic device that divides the output of the third measuring device to calculate 08T/X, and receives the output from the first arithmetic device and calculates a predetermined value (08T/X) as a parameter. From the relationship between the chemical injection rate and the water content of dehydrated sludge, it is determined that the sum of the auxiliary fuel cost for the incineration process and the chemical cost for the chemical injection process ≦2 is the minimum. The device is characterized in that it comprises an adjusting section that adjusts the amount of added chemicals as the target value of the chemical injection rate output from the second calculation scissors device.

Normally, the relationship between the collection rate of flocculant and the water content of dehydrated sludge is as follows:
There is a downwardly convex curved relationship, and there is a chemical dosing rate that can minimize the water content of dehydrated sludge.

It is well known that the dewatering characteristics of sludge can be improved using the index Fi(08T/X). That is, the first &
As shown in At2, if the relationship between the flocculant injection rate and the water content of dehydrated sludge is determined in advance by minimizing the parameter 82 (OBT/x), 08'! To measure ' and X;
Therefore, the relationship between the chemical injection rate for the sludge with the dewatering characteristics at that time and the water content of the dehydrated sludge can be determined.

The auxiliary fuel cost in the incineration process can be determined, for example, by the following formula.

η ; Efficiency (1) Equation 1: s Q (II 61/I A eη
Fill can be regarded as a constant. Therefore, (1)
If we rearrange the equation, we get 32 as shown in equation (2).

f = Kl・−−Kl −−−−−−−−(2)xl
, Kl; Constant As is clear from equation (2), Lid 2, 1i! There is a proportional relationship between the auxiliary fuel cost and the water content of dehydrated sludge. Therefore, the relationship between the collection rate and the auxiliary fuel cost is the same as the relationship between the chemical injection rate and the water content of dehydrated sludge. Convex curve relationship feeling - becomes.

On the other hand, the relationship between collection rate and drug cost is naturally proportional to g2.

Second, the relationship between the lIk efficiency, the fuel cost, the chemical cost, and the sum of these costs is shown. 21st
At Wl2, point B indicates the injection rate that indicates the minimum water content, and point B indicates the chemical injection rate that minimizes the sum of auxiliary fuel cost and chemical cost. The sludge that has been concentrated in the condensing tank is introduced into the chemical mixture through the water pipe 1 and mixed with the flocculant added through the flocculant injection pipe 3. Thereafter, it is sent to a dehydrator 5 through a water conduit 4. In dehydrator 5, it is separated into r liquid and dehydrated sludge, and %P liquid is f
It is discharged through the liquid pipe 6. On the other hand, the dehydrated sludge is transported to the incinerator No. 8 by the belt conveyor and is incinerated.

(-) Function of the Invention In such a sludge treatment process, a water conduit IC is installed, a sludge concentration meter 9 such as an ultrasonic type, and a capillary suction time shelf fItlO! 2, the sludge flk degree X and the capillary suction time 08T are measured, respectively. The outputs of the sludge conversion rate meter 9 and the capillary suction time measuring device 1110 are supplied to the first calculation device 11, where 087/X is calculated. 12
The second calculation device number = has previously input the relationship between the chemical injection rate and the dehydrated sludge water content with 08T/z as a parameter (-), and after receiving the output from the first calculation device 11, the current 08T Calculate the relationship between the collection rate and the water content of dehydrated sludge at Calculate the relationship with fuel cost. Also calculate the relationship between collection rate and drug cost, and calculate the 08T/Xi at that time.
Find the collection rate (target value) that minimizes the sum of the auxiliary fuel cost and drug cost in both cases. The output of the second arithmetic unit 112 is supplied to the regulator 13, which adjusts the control valve 14 so that the drug injection rate reaches the target value.

(a) Detailed explanation of the invention I: Even if the dehydration properties of sludge change, the cost of auxiliary fuel in the incineration plant and the chemicals in the incineration plant will vary accordingly. Since the chemical injection rate 42 is adjusted so that the total sum with the cost is the minimum, the processing cost can be reduced.

[Brief explanation of the drawing]

The first factor is a diagram showing the relationship between collection rate and water content of dehydrated sludge by dividing 087/X into a parameter basket, and Figure 2 shows the collection rate, chemical cost, auxiliary fuel cost for the incineration process, and these costs. FIG. 3 is a block diagram schematically representing an embodiment of the present invention. 1.3, 4.6... Water pipe 2... Mixing tank 5...
Dehydrator 7...Sludge transporter 8...Incinerator 9...Sludge concentration meter lO...Capillary suction time -j constant device 11.12...Calculation device 13...Adjustment rod 14.
... Control valve 35.16 ... Flow meter 1st section 1st rate flexibility] 2 years

Claims (1)

[Claims] A mixing device that adds and mixes chemicals to sludge generated from sewage treatment processes, a dehydrator that dewaters the IIk-added sludge that flows out from the mixing device, and an incinerator that incinerates the dehydrated sludge discharged from the dehydrator. In the sludge treatment process, the mixing device 1: measures the l1f(x) and flow rate (Q) of the sludge, and the capillary suction time (aSte). Standard and wrinkled silver 1. A first arithmetic device that divides the output of the third measurement instrument to calculate 08〒/X; A second calculation device that calculates a chemical injection rate at which the sum of the auxiliary fuel cost in the incineration process and the chemical cost in the chemical injection process is at least 1 U based on the relationship with the water content of dehydrated sludge, and # an output from the second calculation device. 1. A chemical injection control device comprising: a joint section that sets the target value of the chemical injection rate at the sardine quantity V*.