JP2004017003A - Catalytic wet oxidation apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize a COD (chemical oxygen demand) concentration of oxidation treated waste water and to reduce wasteful driving power relating to the intrusion of oxygen-containing gas into waste water by suppressing the fluctuation of the amount of intrusion of the oxygen-containing gas from its optimum value. <P>SOLUTION: The catalytic wet oxidation apparatus for subjecting the waste water X to be treated to oxidation treatment by a catalyst in the state of mixing a prescribed amount of the oxygen-containing gas with the waste water X is equipped with a COD measuring means 1 for measuring the COD concentration of the oxygen-containing gas, an oxygen-containing gas adjusting means 7 for adjusting the supply amount of the oxygen-containing gas to be mixed with the waste water X, and a control means 14 for optimally controlling the oxygen-containing gas adjusting means 7 so as to maximize the reduction rate of the COD of the oxidation treated waste water X' with respect to the waste water X on the basis of the COD concentration of the COD measuring means 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a catalytic wet oxidation apparatus and method for oxidizing an object using a catalyst.
[0002]
[Prior art]
As is well known, a catalytic wet oxidizing apparatus is an apparatus in which an object is mixed with an oxygen-containing gas such as air and oxidized by a catalyst. Such a catalytic wet oxidation device is used for an oxidation treatment of wastewater as an object.
[0003]
For example, Japanese Patent Application Laid-Open No. 6-277680 discloses, as one of the oxidation treatment techniques for wastewater using such a catalytic wet oxidation apparatus, the optimal amount of oxygen-containing gas mixed into the wastewater based on the treatment result of the wastewater. Discloses a control technique. That is, this technique focuses on the point that when excess oxygen-containing gas is mixed into wastewater, oxygen (excess oxygen) that did not contribute to the oxidation reaction is contained in the gas generated by the oxidation treatment of the wastewater. By controlling the mixing amount of the oxygen-containing gas based on the amount of the excess oxygen, the minimum amount of the oxygen-containing gas necessary for the oxidation treatment of the wastewater is mixed into the wastewater.
[0004]
[Problems to be solved by the invention]
By the way, the technique disclosed in Japanese Patent Application Laid-Open No. 6-277680 is for optimally controlling the amount of oxygen-containing gas mixed into wastewater based on the treatment result of wastewater. I can't. That is, since the oxidation reaction requires a certain amount of time, if the mixed amount of the oxygen-containing gas is controlled based on the detection result of the excess oxygen, a so-called “control delay” occurs, and the mixed amount of the oxygen-containing gas becomes the original amount. It fluctuates greatly from the optimal value. As a result, there arises a problem that wasteful power must be given to a supply device for mixing the oxygen-containing gas into the wastewater, or that the COD concentration of the wastewater after the oxidation treatment (oxidized wastewater) fluctuates.
[0005]
The present invention has been made in view of the above problems, and has the following objects.
(1) The fluctuation of the mixed amount of the oxygen-containing gas from the optimum value is suppressed.
(2) Reduce wasteful power involved in mixing oxygen-containing gas into wastewater.
(3) Stabilize the COD concentration of the oxidized wastewater.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a COD measurement for measuring the COD concentration of the above-mentioned wastewater to be treated is performed in a catalytic wet oxidizing apparatus in which a predetermined amount of an oxygen-containing gas is mixed with the wastewater to be treated by a catalyst. Means, oxygen-containing gas adjusting means for adjusting the supply amount of the oxygen-containing gas mixed with the wastewater to be treated, and COD reduction of the oxidized wastewater with respect to the wastewater to be treated based on the COD concentration of the COD measuring means. Control means for optimally controlling the oxygen-containing gas adjusting means so as to maximize the rate.
That is, according to the first means, the supply amount of the oxygen-containing gas to be mixed with the wastewater to be treated is feedforward controlled based on the COD concentration of the wastewater before the oxidation treatment.
[0007]
As a second means relating to the catalytic wet oxidizing apparatus, the first means further comprises an oxygen detecting means for detecting an excess amount of oxygen contained in the oxidized wastewater, and the control means detects the surplus oxygen amount by the oxygen detecting means. A means for optimally controlling the oxygen-containing gas adjusting means based on the surplus oxygen amount obtained and the COD concentration is employed.
That is, according to the second means, the supply amount of the oxygen-containing gas to be mixed with the wastewater to be treated is feed-forward controlled based on the COD concentration of the wastewater to be treated before the oxidation treatment, and the wastewater having been subjected to the oxidation treatment is controlled. Feedback control is performed based on the surplus oxygen amount.
[0008]
As third means relating to the catalytic wet oxidation apparatus, in the first or second means, the control means stores in advance a relationship between a COD concentration and a unit oxygen-containing gas amount that maximizes a COD reduction rate, When the COD concentration is input from the COD measuring means, a means for calculating the amount of the oxygen-containing gas by applying the COD concentration to the relationship is adopted.
That is, according to the third means, by applying the relationship between the COD concentration and the unit oxygen-containing gas amount stored in advance in the control means, that is, the actually measured COD concentration to the control data for feedforward, the oxygen-containing gas is applied. Is calculated.
[0009]
As a fourth means relating to the catalytic wet oxidation apparatus, in any one of the first to third means, the COD measuring means measures a COD concentration based on a transmission amount of ultraviolet light applied to the wastewater to be treated. Adopt means.
That is, according to the fourth means, the COD concentration of the wastewater to be treated is measured by measuring the amount of transmitted ultraviolet light emitted from the COD measuring means.
[0010]
As a first means related to the catalytic wet oxidation method, in a catalytic wet oxidation method in which a predetermined amount of an oxygen-containing gas is mixed with a wastewater to be treated by a catalyst, the COD concentration measured for the wastewater to be treated is reduced. On the basis of this, means for setting the amount of the oxygen-containing gas so as to maximize the COD reduction rate of the oxidized wastewater with respect to the wastewater to be treated is adopted.
[0011]
As a second means related to the catalytic wet oxidation method, in the first means, the wastewater to be treated is based on the amount of excess oxygen detected in the wastewater subjected to oxidation treatment and the COD concentration measured in the wastewater to be treated. The amount of the oxygen-containing gas is set so that the COD reduction rate of the oxidized wastewater with respect to the maximum is reduced.
[0012]
As a third means relating to the catalytic wet oxidation method, in the first or second means, the COD concentration is applied to the relationship between the COD concentration and the unit oxygen-containing gas amount that maximizes the COD reduction rate. Means of calculating the amount of the oxygen-containing gas is employed.
[0013]
As a fourth means related to the catalytic wet oxidation method, in any one of the first to third means, the treatment target wastewater is irradiated with ultraviolet rays, and the COD concentration is measured based on the amount of transmitted ultraviolet rays. Is adopted.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a catalytic wet oxidation apparatus and method according to the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a processing system diagram of the catalytic wet oxidation apparatus in the present embodiment. In this figure, the symbol X is the wastewater to be treated, 1 is a COD measuring device (COD measuring means), 2 is a flow meter, 3 is a pump, 4 is a heat exchanger, 5 is a reactor, 6 is a compressor, and 7 is an air control valve. (Oxygen-containing gas adjusting means), 8 is a gas-liquid separator, 9 is a pressure indicating controller, 10 is a liquid level indicating controller, 11 is a liquid discharge control valve, 12 is a gas discharge control valve, and 13 is an oxygen concentration meter ( Reference numeral 14 denotes a control device (control means).
[0016]
The wastewater X to be treated is general wastewater containing various organic substances and inorganic substances, and is supplied to the reactor 5 via the COD measuring device 1, the flow meter 2, the pump 3, and the heat exchanger 4. The COD measuring device 1 continuously measures the COD concentration of the wastewater X to be treated (the amount of the oxidation treatment target contained in the wastewater X to be treated per unit volume) at a constant time interval and sequentially outputs the COD concentration to the control device 14. I do. The COD measuring device 1 measures the COD concentration by detecting, for example, the amount of transmitted ultraviolet light applied to the wastewater X to be treated, and as an example, “UV400G type organic pollutant measuring device” manufactured by Yokogawa Electric Corporation. There is.
[0017]
The flow meter 2 measures the flow rate of the wastewater X to be treated, which is supplied to the reactor 5, and sequentially outputs the measured flow rate to the control device 14. The pump 3 is for feeding wastewater X to be treated into the reactor 5 and regulates the flow rate. The heat exchanger 4 is provided for heat exchange between the wastewater X to be treated and the oxidized liquid X ′ discharged from the reactor 5.
[0018]
As shown in the drawing, between the heat exchanger 4 and the pump 3, compressed air pressurized by the compressor 6 into the wastewater X to be treated is mixed via the air control valve 7. . That is, a mixture of the wastewater X to be treated and the air containing oxygen as the oxygen-containing gas at a predetermined ratio is sequentially supplied to the reactor 5. The air control valve 7 adjusts the amount of air mixed with the wastewater X to be treated, that is, the air mixing amount, based on a control signal input from the control device 14. The reactor 5 is filled with a catalyst for oxidative decomposition, and oxidatively decomposes the gas-liquid mixed water of the wastewater X to be treated and air by the action of the catalyst.
[0019]
The oxidized wastewater X ′ oxidized and decomposed by the reactor 5 is supplied to the gas-liquid separator 8 via the heat exchanger 4. The gas-liquid separator 8 separates the oxidized wastewater X ′ into a liquid component and a gas component. The liquid component is discharged to the outside from the gas-liquid separator 8 via the liquid discharge control valve 11, and the gas component is discharged to the outside from the gas-liquid separator 8 via the gas discharge control valve 12.
[0020]
A pressure indicating controller 9 is provided between the gas-liquid separator 8 and the heat exchanger 4. The pressure indicating controller 9 detects the pressure of the oxidized wastewater X ′, and automatically adjusts the opening of the liquid discharge valve 11 based on the detected value. The gas-liquid separator 8 is provided with a liquid level indicating controller 10. The liquid level indicating controller 10 detects the liquid level of the oxidized wastewater X ′ in the gas-liquid separator 8 and automatically adjusts the opening of the liquid discharge control valve 11 based on the detected value. Further, an oxygen concentration meter 13 is provided in a discharge path of the gas component. The oxygen concentration meter 13 continuously measures the concentration of oxygen (excess oxygen amount) contained in the gas component and outputs the result to the control device 14.
[0021]
The control device 14 is based on the COD concentration of the wastewater X to be treated inputted from the COD measuring device 1, the flow rate of the wastewater X to be treated inputted from the flow meter 2, and the excess oxygen amount inputted from the oximeter 13. The opening degree of the air control valve 7, which is an oxygen-containing gas adjusting means, that is, the amount of air mixed with the wastewater X to be treated is controlled. Although the detailed control operation of the control device 14 will be described later, the wastewater X to be treated is oxidatively decomposed in the reactor 5 by oxygen in the air, and the COD value (the amount of the wastewater X to be treated) decreases. The oxidized wastewater X ′ in the state as described above is discharged from the reactor 5. The controller 14 optimally controls the air control valve 7, that is, the air mixing amount, so that the COD reduction rate (COD reduction rate) is maximized.
[0022]
In such a control device 14, the relationship between the COD concentration and the unit air amount (unit oxygen-containing gas amount) that maximizes the COD reduction rate (the relationship between the COD concentration and the unit air amount) is stored as control data. Have been. Here, the COD concentration represents a COD value per unit volume of the wastewater X to be treated, and the unit air amount represents an amount of air mixed with the wastewater X to be treated per unit volume. FIG. 2A is a graph showing the relationship between the COD concentration and the unit air amount. The range of the COD concentration in FIG. 2A is a range in which the COD concentration of the wastewater X to be treated can be taken. As shown in this figure, the unit air amount is determined for an arbitrary COD concentration. The controller 14 calculates the amount of air contained in the wastewater X to be treated per unit volume by applying the COD concentration input from the COD measuring device 1 to the relationship between the COD concentration and the unit air amount.
[0023]
The relationship between the COD concentration and the unit air amount shown in FIG. 2A is derived from the graph shown in FIG. 2B, that is, the experimental result showing the relationship between the air ratio and the COD reduction rate. is there. The air ratio is the ratio between the theoretical amount of air required to completely oxidize the wastewater X to be treated and the amount of air actually mixed with the wastewater X to be treated. In FIG. 2B, graph A shows the relationship between the air ratio and the COD reduction rate when the COD concentration of the wastewater X to be treated is 3760 ppm, and graph B shows the relationship when the COD concentration of the wastewater X to be treated is 5780 ppm. The relationship between the air ratio and the COD reduction rate is shown. Further, the graph C shows the relationship between the air ratio and the COD reduction rate when the COD concentration of the wastewater X to be treated is 9500 ppm.
[0024]
As can be easily understood from the intercomparison of these graphs A to C, the air ratio that maximizes the COD reduction rate does not change linearly in proportion to the change in the COD concentration of the wastewater X to be treated, but rather does not change linearly. There is a non-linear relationship with COD concentration. Further, since the unit air amount has a relationship linearly proportional to the air ratio, the unit air amount has a non-linear relationship with the COD concentration of the wastewater X to be treated as shown in FIG. is there. Therefore, in order to determine the unit air amount that maximizes the COD reduction rate based on the COD concentration of the wastewater X to be treated, the relationship (non-linear relationship) between the unit air amount and the COD concentration is determined in advance by an experiment. It is necessary to determine the unit air amount by applying the actually measured COD concentration of the wastewater X to be treated to a non-linear relationship. The graph shown in FIG. 2A, that is, the control data, is derived based on the results of such an experiment.
[0025]
Next, the operation of the catalytic wet oxidation apparatus according to the present embodiment will be described.
[0026]
As understood from the above-described configuration, the present catalytic wet oxidizing apparatus includes a feedforward control system and a feedback control system. That is, the opening degree (that is, the amount of mixed air) of the air control valve 7 is adjusted based on the COD concentration of the wastewater X to be treated input from the COD measuring device 1 and the flow rate of the wastewater X to be treated inputted from the flow meter 2. Is a feedforward control system, and a system that adjusts the degree of opening of the air control valve 7 based on the amount of excess oxygen input from the oximeter 13 is a feedback control system.
[0027]
Here, when only the feedforward control system is operated, the COD concentration and the flow rate are accurately measured, and the relationship between the COD concentration and the unit air amount stored in advance in the control device 14 becomes an accurate experimental result. Based on this, it is possible to optimally control the air mixing amount so as to maintain the COD reduction rate at the maximum with respect to the COD concentration of the wastewater X to be treated, which changes every moment. However, in the present catalytic wet oxidizer, a control system that uses both a feedforward control system and a feedback control system was adopted as a result of taking into account ensuring reliability against control system abnormalities.
[0028]
The individual roles of the feedforward control system and the feedback control system are mainly to optimally control the air mixing amount by the feedback control system, and to determine the deviation from the optimum value of the air mixing amount due to the “control delay” of the feedback control system. The correction is supplementarily performed by a feedforward control system having a higher response speed than the feedback control system. As a result, the air mixing amount actually mixed with the wastewater X to be treated maintains the minimum air amount that maximizes the COD reduction rate more faithfully.
[0029]
That is, the control device 14 maximizes the COD reduction rate with respect to the oxygen concentration input from the oximeter 13 so that the oxygen concentration maintains “zero”, that is, the minimum necessary air mixing amount. Thus, the opening degree of the air control valve 7 is feedback-controlled. On the other hand, the control device 14 applies the COD concentration of the wastewater X to be treated inputted from the COD measuring device 1 to the relationship between the previously stored COD concentration and the unit air amount to thereby increase the COD reduction rate to the maximum unit air amount. Is calculated by multiplying the unit air amount by the flow rate of the wastewater X to be treated, which is input from the flowmeter 2, to calculate an air mixing amount corresponding to the flow rate. This air mixing amount is an operation amount in the feedforward control system and follows the actual COD concentration of the wastewater X to be treated with good responsiveness, so that the deviation of the air mixing amount from the optimum value is effectively reduced and corrected.
[0030]
The pressure indicating controller 9 and the liquid level indicating controller 10 stabilize the inside of the gas-liquid separator 8. Specifically, the pressure indicating controller 9 sets the pressure value in the reactor 5 to a predetermined value. The opening of the gas discharge control valve 13 is adjusted so as to match, and the liquid level indicating controller 10 adjusts the opening of the liquid discharge control valve 11 so that the liquid level in the gas-liquid separator 8 is adjusted to a predetermined position.
[0031]
Note that the present invention is not limited to the above embodiment, and the following modified examples can be considered.
(1) In the above embodiment, the feedback control system is configured to control the air mixing amount based on the surplus oxygen amount. However, instead of this surplus oxygen amount, it is conceivable to perform feedback control of the air mixing amount based on the COD concentration of the oxidized wastewater X '. That is, a second measuring means for measuring the COD concentration of the liquid component of the oxidized wastewater X 'is prepared, and the air mixing amount is fed back based on the COD concentration of the liquid component output from the second COD measuring device. Control.
[0032]
(2) In the above embodiment, the COD measuring apparatus 1 is used to measure the COD concentration by detecting the amount of transmitted ultraviolet light irradiated to the wastewater X to be treated, but the COD concentration may be measured by ultrasonic waves. .
[0033]
(3) Although air is used as the oxygen-containing gas in the above embodiment, for example, ozone gas may be used.
[0034]
【The invention's effect】
As described above, according to the present invention, in a catalytic wet oxidizing apparatus that oxidizes with a catalyst in a state where a predetermined amount of oxygen-containing gas is mixed with wastewater to be treated, a COD measuring unit that measures the COD concentration of the wastewater to be treated And an oxygen-containing gas adjusting means for adjusting the supply amount of the oxygen-containing gas supplied to the wastewater to be treated, and a COD reduction rate of the oxidized wastewater with respect to the wastewater to be treated being maximum based on the COD concentration of the COD measuring means. And control means for optimally controlling the oxygen-containing gas adjusting means. That is, since the oxygen-containing gas adjusting means is feedforward-controlled based on the COD concentration of the wastewater to be treated, even if the COD concentration of the wastewater to be treated changes every moment due to the change in the generation state of the wastewater to be treated, the wastewater to be treated is treated as the wastewater. An optimal oxygen-containing gas amount can be mixed. Therefore, it is possible to stabilize the COD concentration of the wastewater to be subjected to the oxidation treatment, and it is possible to reduce unnecessary power related to the mixing of the oxygen-containing gas into the wastewater to be treated.
[Brief description of the drawings]
FIG. 1 is a processing system diagram of a catalytic wet oxidation apparatus according to an embodiment of the present invention.
FIG. 2 shows control data according to an embodiment of the present invention and experimental results which are the basis of the control data. (A) is a graph showing the relationship between the COD concentration and the unit air amount, and (b) is a graph showing the relationship between the air ratio and the COD reduction rate.
[Explanation of symbols]
1. COD measuring device (COD measuring means)
2 ... Flow meter 3 ... Pump 4 ... Heat exchanger 5 ... Reactor 6 ... Air compressor 7 ... Air regulating valve (oxygen-containing gas regulating means)
8 ... gas-liquid separator 9 ... pressure indicating controller 10 ... liquid level indicating controller 11 ... liquid discharge control valve 12 ... gas discharge control valve 13 ... oxygen concentration meter (oxygen detecting means)
14 Control device (control means)
X: Wastewater to be treated X ': Oxidized wastewater

Claims (8)

In a catalytic wet oxidizing apparatus in which a predetermined amount of an oxygen-containing gas is mixed with a wastewater to be treated (X) by a catalyst,
COD measuring means (1) for measuring the COD concentration of the wastewater to be treated (X);
Oxygen-containing gas adjusting means (7) for adjusting the supply amount of the oxygen-containing gas to be mixed with the wastewater (X) to be treated;
Based on the COD concentration of the COD measuring means (1), the oxygen-containing gas adjusting means (7) is controlled so that the COD reduction rate of the oxidized wastewater (X ') with respect to the wastewater (X) to be treated is maximized. A catalytic wet oxidation apparatus comprising: a control unit (14) for performing optimal control. The apparatus further comprises oxygen detection means (13) for detecting the amount of excess oxygen contained in the oxidized wastewater (X '), and the control means (14) controls the amount of excess oxygen detected by the oxygen detection means (13). The catalytic wet oxidation apparatus according to claim 1, wherein the oxygen-containing gas adjusting means (7) is optimally controlled based on the COD concentration. The control means (14) stores in advance the relationship between the COD concentration and the unit oxygen-containing gas amount which maximizes the COD reduction rate, and when the COD concentration is input from the COD measurement means (1), the COD concentration is stored. 3. The catalytic wet oxidation apparatus according to claim 1, wherein the amount of the oxygen-containing gas is calculated by applying the following formula to the relationship. The catalytic wet oxidizer according to any one of claims 1 to 3, wherein the COD measuring means (1) measures a COD concentration based on an amount of transmitted ultraviolet light applied to the wastewater (X) to be treated. . In a catalytic wet oxidation method in which a predetermined amount of an oxygen-containing gas is mixed with a wastewater to be treated (X) by a catalyst in a wet state,
The amount of the oxygen-containing gas is set based on the COD concentration measured for the wastewater to be treated (X) so that the COD reduction rate of the oxidized wastewater (X ′) with respect to the wastewater to be treated (X) is maximized. A catalytic wet method, comprising: Oxidized wastewater (X ') for the wastewater (X) based on the amount of excess oxygen detected for the oxidized wastewater (X') and the COD concentration measured for the wastewater (X). The catalytic wet oxidation method according to claim 5, wherein the amount of the oxygen-containing gas is set so that the COD reduction rate of the catalyst becomes maximum. The catalytic wet method according to claim 5 or 6, wherein the amount of the oxygen-containing gas is calculated by applying the COD concentration to the relationship between the COD concentration and the unit oxygen-containing gas amount that maximizes the COD reduction rate. Oxidation method. The catalyst wet oxidation method according to any one of claims 5 to 7, wherein the treatment target wastewater (X) is irradiated with ultraviolet rays, and the COD concentration is measured based on the transmission amount of the ultraviolet rays.

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