JPH08197097A - Treatment of analytic output device in anaerobic digestion monitoring device - Google Patents

Abstract

PURPOSE: To easily change the analytic condition of an analytic output device by setting an expected value from the parameters required by an analytic output device having received a 1 pH measured value, indicating past data on a trend graph, computing the measured data in a specified manner and indicating the result on the trend graph. CONSTITUTION: A liq. in a settling and clarifying tank 25 treated in a flocculation tank 24 and the settling and clarifying tank 25 is injected into a titration tank 26, and the titration on the acid side and that on the alkali side are respectively conducted. Reagents 33 (hydrochloric acid and sodium hydroxide) are injected from dispensers 31 and 32, the pH is measured by a pH meter 27, and the titration data (injection, pH and temp.) are inputted to an analytic output device 30. The parameters necessary to analysis are read out by the output device 30 from a file and initialized, and then the past data are indicated on the trend graph. Meanwhile, reverse regression analysis and optimization are applied to the titration data in a specified manner, and the data are indicated on the trend graph. Consequently, the measured data are confirmed even in the computation, errors are confirmed, and the measured data are preserved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing an analysis output device in an anaerobic digestion tank monitoring device for continuously monitoring changes in the state of an anaerobic digestion tank for treating sludge.

[0002]

2. Description of the Related Art Generally, biological anaerobic sludge digestion is 2
It progresses in stages depending on the type of bacterial group. The first stage is called “acid production stage”, and sludge introduced into the digestion tank is decomposed into intermediate products such as organic acids by the action of hydrolyzing bacteria or acid producing bacteria. The second stage is called the "methane production stage", in which the intermediate products such as organic acids produced in the above acid production stage are decomposed into the final products such as methane gas, carbon dioxide and ammonia by the action of methanogens. It

Ammonia produced in the second step is
It has the function of neutralizing the organic acid generated in the first step and the pH buffering ability (ability to resist pH change) together with the bicarbonate generated by dissolution of carbon dioxide, which is good for methanogens. It helps to create a weak alkaline environment inside the tank.

Since the growth rate of methanogenic bacteria is slower than that of acid-producing bacteria and they are more sensitive to environmental changes, it is generally said that the methanogenic stage determines the rate of digestion. Therefore, it is important to maintain an in-tank environment suitable for survival of methanogens in order for the digestion tank to operate properly.

From this point of view, it is extremely important to continuously monitor the state change in the digestion tank in order to achieve and maintain good digestion of anaerobic sludge. If the condition becomes defective, it takes a long time to recover, so it is the most important task in operation management to promptly detect that the condition inside the tank is abnormal. The following four items are known as operation management indexes for digestion tanks that have been conventionally known. (1) pH control (2) Organic acid concentration control (3) Alkalinity control (4) Methane gas production rate control Regarding the pH control in (1) above, the digestion tank that is normally operating well is described. In some cases, the pH in the tank is maintained near neutral. However, when an abnormality occurs in the digestive tank, it first appears as a pH abnormality, that is, a phenomenon in which the pH deviates from around neutral. For example, when the activity of the methanogen in the second step is weakened, the organic acid produced in the first step of anaerobic digestion is accumulated without being decomposed, and a pH lowering (acidification) phenomenon occurs. If the ammonia production in the second stage is excessive compared to the acid production in the first stage,
Ascending phenomenon occurs.

[0006] Regarding the control of the organic acid concentration of the above (2), this organic acid is a substrate for methanogenic bacteria, but when the organic acid concentration becomes high or the pH decreases, the organic acid is a weak acid. Therefore, non-ionized non-ionized organic acid increases. It is known that this non-ionized organic acid becomes a suppressive toxic substance for methanogens when the concentration exceeds a certain level, and the rancid phenomenon caused by the overload of organic substances on the digestive tank is caused by the non-ionized organic acid. It is said to be the result of the suppressive toxicity effect. The non-ionized organic acid concentration can be determined from the organic acid concentration as a function of pH.

Next, regarding the above-mentioned (3) control of alkalinity, since the sludge in the digestion tank has a high pH buffering ability, the abnormality in the digestion tank is prominently manifested as pH abnormality.
In many cases, the terminal stage is in a state where the trouble has progressed considerably. However, the precursor of abnormal pH in the digestive tank can be understood as a change in the buffering ability of pH. The alkalinity is an index showing the buffering ability of this pH. The alkalinity of anaerobic sludge is mainly due to soluble inorganic carbon. Soluble inorganic carbon buffers changes in the pH of the solution by changing the form of carbon dioxide, bicarbonate, and carbonic acid as the ionic charge in the solution changes. The molar ratio of these three forms of inorganic carbon can be obtained by theoretical calculation as a function of pH from the concentration of soluble inorganic carbon as the sum of the three forms.

Further, regarding the control of the methane gas production rate (4), abnormalities in activity due to environmental changes of methanogens or inflow of inhibitory toxic substances (sulfides and heavy metals) appear as a decrease in methane gas production rate. The generation rate of methane gas is obtained by multiplying the gas generation rate by the partial pressure (concentration) of methane gas in the gas.

In addition to the above monitor items, nutrient salt balance (C / N ratio, trace amount of essential heavy metal) and control of tank temperature can be mentioned. However, the nutrient salt balance does not need to be monitored frequently and continuously unless the composition of the input sludge changes suddenly, and the temperature inside the tank has been conventionally well monitored and controlled.

[0010]

As an apparatus for continuously monitoring the above-mentioned state change in the digestion tank, the overall configuration of the apparatus will be described with reference to the schematic diagram shown in FIG. That is, the digestion tank sludge is sampled in the mud receiving tank 1 and the coagulating tank 2
Polymer coagulant 2a is added to agglomerate the fine particle component,
Next, after coagulating and precipitating in the settling tank 3 for solid-liquid separation, the supernatant of this settling tank 3 is filtered using a filter 4 to obtain a filtrate having a target ss concentration or less, and a fixed amount of this filtrate. (For example, 100 ml) is weighed and sent to the acid titration tank 5 and the alkali titration tank 6. The excess amount of the filtrate is stored in each titration tank 5,
It is discharged from 6 by an air pump (not shown). There is also a method of using a centrifuge instead of the above coagulation and precipitation.

HCl and NaOH as titration reagents were sequentially added to the acid titration tank 5 and the alkali titration tank 6 at a pitch amount of 0.05-0.10 ml using dispensers 8 and 9 and an electric buret. , Titration was carried out until the pH reached 2.0 and 10.0 respectively, and this titration amount and the pH measured by the pH meter 10
Sequence controller 1 whose value constitutes the control unit 13
1 and the personal computer 12 send the acid
The treatment based on the alkali equilibrium theory is performed, and in addition to the total organic acid concentration (A), the ammonia concentration (N), the total inorganic carbon concentration (T), etc. are monitored. It should be noted that the processing can be performed only by the personal computer 12 without the sequence controller 11.

In the apparatus shown in FIG. 3, when performing continuous monitoring for an anaerobic digestion tank based on the above-mentioned acid-alkali equilibrium theory, a sequence controller 11 or a personal computer 12 in which all steps constitute a control unit 13 is performed.
It is characterized in that it can be automatically measured based on a program that is installed in advance.

An example of this program will be described using the algorithm shown in FIG. In FIG. 4, all the items to be continuously monitored as a digestion tank monitor can be measured from the pH-titration data pair as a digestion tank monitor. Here, the algorithm of FIG. 4 will be described. The process in the main routine indicated by this control is a constant time interrupt process driven at a predetermined cycle (for example, 20 msec) by an operating system (not shown).

When the control starts in the figure, first, in step 101, setting data such as initial data is input,
After the array declaration of each data and the interrupt condition are set in step 102, each variable is initialized in step 103,
The required system state is set. Next step
At 104, the pH value and temperature at the 0th time are measured for each of the acid and alkali sides, and the initialization of the automatic dispenser and the error check are performed.

Next, in step 105, the timer 1 for measuring the acid side is set, and in step 106, the dispensed amount 1 of the acid is calculated based on the setting data. Based on the calculation result, in step 107, the chemical is dispensed into the acid titration tank by the automatic dispenser. And by step 108,
Immediately, the pH 1 and temperature T1 of the acid titration tank are measured.

Next, in step 109, timer> TM
1, that is, the time T set in the timer 1 during the above measurement
When the time has passed since M1, the process proceeds to step 111 and the last data is forcibly set as the measurement data. The above-mentioned time TM1 does not greatly affect the entire measurement time,
And it is desirable that the time is sufficient to stabilize the pH.

In step 109 above, the timer <TM
1, that is, the measurement time T set in the timer 1
If it does not reach M1, in other words, if the timer 1 is not counted up, in step 110, pH1-pH
1 ', that is, the rate of change of pH is calculated, and when the value does not exceed the initial value DpH input in the setting data,
Returning to step 106, the dispensing amount 1 is calculated again, and the next dispensing amount is calculated based on the set dispensing amount range. In step 110, pH1-pH1 '> DpH, that is, if the rate of change of pH exceeds the pH input based on the setting data, in step 111 the final pH, dispenser and temperature data are set. It The temperature data is used as a correction signal for improving accuracy.

When the pH of the sample gradually decreases due to the dispensing of the chemicals and the pH becomes equal to or lower than pHDN (lower limit) in step 112, an end flag is set in step 113, and the measurement on the acid side ends and step 114 In the personal computer 12, data processing for monitoring is performed.

On the other hand, the measurement on the alkali side is performed alternately with the above steps 105 to 114 at a constant time interval. For this measurement on the alkaline side, first, in step 115, the timer 2 for measuring the alkaline side is set, and
The dispensed amount 2 of alkali is calculated by 116 based on the setting data. Based on this calculation result, step 117
Causes the chemical to be dispensed into the alkali titration tank. Then, in step 118, the pH 2 and the temperature T2 of the alkali titration tank are immediately measured.

Hereinafter, steps 119 to 121, which are substantially the same as the steps described in steps 109 to 111 on the acid side, are carried out to perform the data set on the alkali side. Then, the pH of the sample gradually increases due to the dispensing of the chemicals, and the pH of the sample is increased in step 122.
Becomes pHUP (upper limit), the end flag is set in step 123, and the measurement on the alkali side ends
At 124, data processing for monitoring is performed in the personal computer 12. The steps on the acid side and the steps on the alkali side are alternately performed at a certain time, but the acid side is measured first, or the alkali side is measured first or alternately. Whether to measure is freely selectable.

As described above, since continuous monitoring of the anaerobic digestion tank is performed by a program installed in the sequence controller 11 or the personal computer 12 in advance, it is not easy to change the analysis conditions.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a processing method of an analysis output device in an anaerobic digestion tank monitoring device in which analysis conditions can be easily changed.

[0023]

Means and Actions for Solving the Problems
In order to achieve the above object, the first aspect of the invention is to sample digested sludge and introduce it into a titration tank, and to dispense the amount of reagent corresponding to the value previously obtained by the control unit into this sampling liquid while When the pH value is measured and the digestion state is continuously monitored by the liquid pH value and the amount of reagent dispensed, after the liquid pH value is measured, when the measurement is completed, the measurement data is output to an analysis output device. When transmitted, the analysis output device first reads the parameters required for analysis from the file and sets the initial values, then inputs the past data and displays the past data in the trend graph, and at the same time, transmits the measured data. Is calculated and the calculation result is displayed on the trend graph.

A second aspect of the present invention is characterized in that the analysis output device is in a measurement data interrupt waiting state before the measurement data is transmitted.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an anaerobic digestion tank monitoring device applied to an embodiment of the present invention. In FIG. 1, a motor operated valve 21 samples sludge from the digestion tank and stores it in a mud receiving tank 22. P of the sludge stored in this mud receiving tank 22
H is measured by the pH meter 23. When the pH measurement is completed, the sludge is sent to the coagulation tank 24 and at the same time, the coagulant 24a is injected. After that, the aggregating agent 24a and the sludge are sufficiently stirred by the stirrer 24b, and when the stirring is completed, only the separated liquid is drawn into the clarification tank 25 at an extremely slow speed (a speed at which the sludge is not sucked). Suction is stopped when the amount of the liquid in the sedimentation tank 25 becomes sufficient for titration.

Next, the liquid is injected from the precipitation tank 25 into the titration tank 26, and the titration tank 26 performs titration on the acid side and the alkali side, respectively. During the titration, the reagent product 33 (hydrochloric acid, sodium hydroxide) is injected by the dispensers 31 and 32, and the pH value at that time is measured by the pH meter 27. 28 is a thermometer and 29 is a calibration liquid. When the titration on the acid side and the titration on the alkali side are completed, the titration data (injection amount, pH, temperature) is transmitted to the analysis output device 30. After that, each tank enters a cleaning process, and when cleaning is completed, it goes into a standby state. The above operation is controlled by a control unit (not shown) (the control unit shown in FIG. 3 is used).

Next, the processing of the analysis output device 30 will be described with reference to the flowchart of FIG. First, after the program A is started, initialization and declaration, variables, arrays, and interruption are performed in step S1, and then initial values are set in step S2. With this initial value setting, the parameters required for analysis are read from the parameter file and set. After setting, after inputting the titration data in the past in step S3, the titration data is displayed in a trend graph in step S4, and the process waits for the titration data interrupt in step S5. The interrupt waiting process in step S5 is configured to operate when titration data is transmitted from the data transmission in step S12 of program B.

In step S5, when an error signal is transmitted from a control unit (not shown), an error message is displayed on the CRT screen and the state is maintained until the error is released. When the error disappears, the transmitted titration data is received.

On the other hand, after the program B is started, initialization and declaration, variables, arrays and interruption are performed in step S6, and then initial values are set in step S7. After setting the initial value, the analysis signal is waited in step S8, and titration data is input in step S9. After the titration data is obtained by the method shown in FIG. 4, multiple regression analysis is performed in step S10, and then the optimization process is performed in step S11 to determine each substance concentration obtained as a measured value. The result thus measured is transmitted to the interrupt waiting process of step S5 via the data transmission of step S12. In the interrupt process, when data is received, it is plotted on the trend screen (the trend screen is displayed even during data measurement or calculation). The above processing may be repeated during measurement, and the calculation result may be transmitted and output to a higher-level computer.

By controlling the processing of the analysis output device as described above, the program A can be used even when the parameter file is changed.
The analysis conditions can be easily changed only by changing the initial value setting of.

[0031]

As described above, according to the present invention,
In the processing of the analysis output device, the analysis condition can be easily changed by changing the parameter file. Further, there is an advantage that the measured data can be confirmed by the trend graph even during the calculation, the error can be confirmed, and the measured data can be saved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an anaerobic digestion tank monitoring device applied to an embodiment of the present invention.

FIG. 2 is a flowchart showing an embodiment of the present invention.

FIG. 3 is a schematic diagram showing an example of a conventional acid-alkali titrator.

FIG. 4 is a flowchart of a conventional digestion tank monitoring method.

[Explanation of symbols]

 21 ... Motorized valve 22 ... Mud receiving tank 24 ... Flocculating tank 25 ... Sedimenting tank 26 ... Titrating tank 30 ... Analysis output device S2 ... Initial value setting step S3 ... Past data input step S4 ... Trend graph display step S5 ... Interrupt waiting step

Claims (2)

[Claims] 1. A digested sludge is sampled and introduced into a titration tank, and a liquid pH value is measured while dispensing an amount of a reagent corresponding to a value previously determined by a control unit into this sampling liquid, and measuring this liquid. In what continuously monitors the digestion state by pH value and reagent dispensing amount, after measuring the liquid pH value, if the measurement is completed, the measurement data is transmitted to the analysis output device, First, after reading the parameters necessary for analysis from the file and setting the initial values, input the past data and display the past data on the trend graph, and at the same time, calculate the transmitted measurement data and trend the calculation results. A method for processing an analysis output device in an anaerobic digestion tank monitoring device, characterized in that it is displayed in a graph. 2. The analysis output device according to claim 1, wherein the analysis output device is in a measurement data interrupt waiting state before the measurement data is transmitted. Processing method.