JP6837813B2 - Wastewater treatment equipment, catalyst cleaning method - Google Patents

Description

The present invention relates to a wastewater treatment device for treating wastewater discharged from a factory or the like, and particularly cleans a wastewater treatment device that evaporates and concentrates water from wastewater containing a persistent substance, and a catalyst of the wastewater treatment device. Regarding catalyst cleaning method.

Conventionally, as a device for treating wastewater containing a persistent substance including water-soluble cutting oil, the wastewater stored in a storage tank is heated to evaporate the water, thereby causing the difficulty contained in the wastewater. An apparatus for separating a degradable substance as a solid is known (see Patent Document 1).

When the wastewater is heated and evaporated, not only water but also substances other than water may evaporate at the time of evaporation. If the wastewater contains a substance having a boiling point lower than that of water or a substance having a boiling point equivalent to that of water, these substances will also evaporate together with water. An example of a substance that evaporates with water is 1,4-dioxane (1,4-dioxane: C4H8O2) having a boiling point of 101.1 ° C. Since 1,4-dioxane dissolves in water or a solvent at room temperature, it has been conventionally used as a reactant or stabilizer added to an organic solvent. It should be noted that 1,4-dioxane is considered to have a carcinogenic risk to humans as an effect on health. At least, it has been found to be carcinogenic in animal experiments, and the International Agency for Research on Cancer (IARC) has confirmed that it may be carcinogenic to humans.

In the above-mentioned conventional apparatus, harmful substances such as 1,4-dioxane contained in the wastewater containing the persistent substance are discharged together with steam, so it is necessary to oxidatively decompose the exhaust gas with a catalyst before discharging. There is. It is known that 1,4-dioxane is decomposed relatively rapidly by an oxidation catalyst in the state of being present as a gas in the atmosphere. Conventionally, an oxidation catalyst is provided in an exhaust duct, the wastewater is heated to 100 ° C. or higher to evaporate 1,4-dioxane (boiling point 101.1 ° C.) together with water, and the vapor is passed through the oxidation catalyst. A method for decomposing 1,4-dioxane is known.

Japanese Unexamined Patent Publication No. 2009-220047

By the way, during heating of the wastewater containing the persistent substance, mist or bubbles (hereinafter referred to as mist or the like) of the wastewater may be generated in the storage tank. When the mist or the like flows into the exhaust duct together with steam and reaches the oxidation catalyst, the mist or the like adheres to the oxidation catalyst. In this case, when the attached water such as mist evaporates, the persistent substance adheres to the oxidation catalyst. As a result, in the oxidation catalyst, there arises a problem that the oxidation reaction is slowed down and the decomposition performance of harmful substances such as 1,4-dioxane is lowered. Further, when the attached mist or the like directly adheres to the oxidation catalyst, the amount of substances undergoing an oxidation reaction increases as compared with the case where steam flows into the oxidation catalyst, and the amount of heat generated by the oxidation reaction also increases. As a result, the steam may exceed the heat resistant temperature of the oxidation catalyst. In this case, there arises a problem that the oxidation catalyst is deteriorated or the oxidation catalyst is damaged.

An object of the present invention is to provide a wastewater treatment apparatus capable of cleaning an oxidation catalyst to which a persistent substance or the like is attached with steam, and a catalyst cleaning method in the wastewater treatment apparatus.

The wastewater treatment device according to the embodiment of the present invention is a device that evaporates water by heating wastewater containing a persistent substance stored in a storage tank to concentrate the wastewater. The waste water treatment device is provided in a first heating section for heating the liquid stored in the storage tank, a duct section for guiding the gas from the storage tank to the outside, and a guide path for the gas in the duct section. The oxidation catalyst, the water supply unit that supplies water to the storage tank, and the water supply unit that stores a certain amount of water in the storage tank in a state where the concentrated concentrated water is discharged from the storage tank are controlled. A cleaning control unit that controls the first heating unit so as to heat the water in the water tank to generate water vapor for cleaning the oxidation catalyst.

The wastewater treatment device is provided in the duct portion from the storage tank to the oxidation catalyst, and further includes a second heating portion for heating the steam in the duct portion. In this case, the cleaning control unit controls the second heating unit so that the water vapor rises to a predetermined temperature required for cleaning the oxidation catalyst.

The wastewater treatment device further includes a blower that sends out the steam generated in the storage tank to the outside through the duct portion. In this case, the cleaning control unit controls to drive the blower when cleaning the oxidation catalyst.

The wastewater treatment device further includes a wastewater supply unit that supplies the wastewater to the storage tank, and a concentration heating control unit. In the concentrated heating control acquisition, when the water level in the storage tank is reduced to a predetermined reference water level, the wastewater is stored in an amount equal to or smaller than the reduction amount of the water. The wastewater supply unit is controlled so as to supply the water to the tank, and the first heating unit is controlled so as to heat the mixed liquid of the water and the wastewater in the storage tank and concentrate the mixed liquid.

The catalyst cleaning method according to another embodiment of the present invention is applied to a wastewater treatment apparatus that evaporates water by heating wastewater containing a persistent substance stored in a storage tank to concentrate the wastewater. This is a method for cleaning an oxidation catalyst provided in a duct portion of the wastewater treatment apparatus. The catalyst cleaning method includes a water supply step of storing a certain amount of water in the storage tank in a state where the concentrated concentrated water is discharged from the storage tank, and the water stored in the storage tank by the water supply step. It comprises a first heating step of heating to generate steam for cleaning the oxidation catalyst.

The catalyst cleaning method includes a second heating step of heating the steam in the duct portion so that the steam generated by the first heating step rises to a predetermined temperature required for cleaning the oxidation catalyst. Is further included.

The catalyst cleaning method further includes a blowing step of blowing the water vapor generated by the first heating step toward the oxidation catalyst.

According to the present invention, it is possible to clean the oxidation catalyst to which a persistent substance is attached with steam. As a result, the slowdown of the oxidation reaction caused by the adhesion of the persistent substance to the oxidation catalyst is prevented, and the decomposition performance of harmful substances such as 1,4-dioxane can be restored.

FIG. 1 is a front view showing a wastewater treatment device 10 according to an embodiment of the present invention. FIG. 2 is a right side view showing the wastewater treatment device 10. FIG. 3 is a top view showing the wastewater treatment device 10. FIG. 4 is a system system diagram showing the configuration of the wastewater treatment device 10. FIG. 5 is a block diagram showing a configuration of a control system of the wastewater treatment device 10. FIG. 6 is a flowchart showing an example of the procedure of the catalyst cleaning treatment in the wastewater treatment apparatus 10.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. It should be noted that the embodiments described below are merely examples that embody the present invention, and do not limit the technical scope of the present invention.

[Wastewater treatment device 10]
1 to 3 are views showing the appearance of the wastewater treatment device 10. FIG. 4 is a system system diagram showing the configuration of the wastewater treatment device 10. FIG. 4 is a block diagram showing a configuration of a control system of the wastewater treatment device 10. The wastewater treatment device 10 according to the present embodiment is a device that evaporates water by heating wastewater containing a persistent substance to concentrate the wastewater. The persistent substance is, for example, a chain saturated hydrocarbon having 20 or more carbon elements, so-called paraffin. The target of treatment by the wastewater treatment apparatus 10 of the present embodiment is wastewater containing water-soluble cutting oil used for lubrication and cooling during metal cutting. Therefore, the wastewater includes not only the water-soluble cutting oil but also metal powder produced by cutting. This metal powder is also an example of the persistent substance.

As shown in FIGS. 1 to 4, the wastewater treatment device 10 includes a wastewater concentrator 11, a decomposition treatment device 12, and a control panel 30, which are roughly classified from the wastewater concentrator 11. The wastewater concentrator 11 and the decomposition treatment device 12 are connected by a connecting duct 14 so that a gas containing steam can be sent to the treatment device 12.

[Wastewater concentrator 11]
The waste water concentrator 11 includes a treatment tank 21 (an example of a storage tank of the present invention), a first heater 22 (an example of a first heating unit of the present invention), and a second heater 23 (an example of the second heating of the present invention). (Example of a unit), an air blower 24 (an example of a blower of the present invention), a defoaming agent supply unit 27, a water supply unit 28 (an example of a water supply unit of the present invention), and a discharge pump 29. There is.

The treatment tank 21 is for storing wastewater to be treated, and is formed in a substantially rectangular parallelepiped shape. A predetermined amount of liquid (wastewater or water) is stored inside the treatment tank 21. In the present embodiment, the wastewater stored in the treatment tank 21 and concentrated and treated contains the paraffin, the water-soluble cutting oil, the metal powder, 1,4-dioxane, and water. Of these, the paraffin, the water-soluble cutting oil, and the metal powder are persistent substances that are difficult to decompose by the oxidation catalyst 43 described later. The water content in the wastewater is about 90% to 95%, and therefore the viscosity of the wastewater is relatively low. The waste water contains substances other than the substances such as paraffin and 1,4-dioxane, such as rust preventive oil additives, refined mineral oils, surfactants, and additives for improving lubricity. May be. In this case, these substances are also examples of the persistent substances.

In the present embodiment, the wastewater to be treated is stored in a separately installed wastewater tank 81. The wastewater tank 81 is connected to the bottom of the treatment tank 21 by a pipe 81A. The pipe 81A is provided with an electric valve 81B that is opened and closed by electric drive and a supply pump 81C. The supply pump 81C is provided between the wastewater tank 81 and the electric valve 81B. The supply pump 81C is a pump for supplying wastewater from the wastewater tank 81 to the treatment tank 21 as needed. The electric valve 81B and the supply pump 81C are driven and controlled by the control unit 100 (see FIG. 5) of the control panel 30. The electric valve 81B is controlled and opened by the control unit 100, and the supply pump 81C is driven by the control unit 100 to supply wastewater from the wastewater tank 81 to the treatment tank 21. Further, when the electric valve 81B is closed and the drive of the supply pump 81C is stopped, the supply of wastewater is stopped. The wastewater supply unit of the present invention is realized by the electric valve 81B and the supply pump 81C.

The processing tank 21 is supported by a gantry 15. The gantry 15 is composed of a base frame 15A, a plurality of frame legs 15B extending upward from the base frame 15A, and an upper frame 15C supported by the frame legs 15B. The processing tank 21 is provided at a position separated by a predetermined height upward from the base frame 15A by the upper frame 15C.

The wastewater stored in the treatment tank 21 is, for example, sewage (so-called industrial wastewater) that is used for industrial production in factories and the like and is discarded after the use. If such wastewater is discharged into rivers and the sea as it is, it will pollute the natural environment, so it must be purified to the extent that it can be discharged into the natural environment before being discharged into the rivers and the sea. In particular, industrial wastewater from factories that perform metal processing may contain the paraffin, the water-soluble cutting oil, the metal powder, 1,4-dioxane, and water. Such wastewater is prohibited from being discharged into water areas (public water areas) including rivers and the sea unless it meets the wastewater standards (0.5 mg / L) stipulated by the Water Pollution Control Law. There is.

The first heater 22 heats the liquid (wastewater or water) stored in the treatment tank 21, and is provided in the treatment tank 21. The first heater 22 is a unit type in which, for example, an electric heater 22A such as a halogen heater and a first heating control unit 22B including a driver circuit for driving the electric heater 22A are integrally configured. The electric heater 22A is provided inside the processing tank 21, and the first heating control unit 22B is arranged outside the processing tank 21. The electric heater 22A is provided inside the treatment tank 21 below the intermediate position in the height direction, and all of the electric heater 22A is arranged in the liquid in a state where the liquid (wastewater or water) is stored in the treatment tank 21. To. The first heater 22 heats the liquid by being driven by the control unit 100. Specifically, when a drive signal is sent from the control unit 100 to the first heating control unit 22B, the first heating control unit 22B drives the electric heater 22A based on the drive signal to control heating. The first heater 22 may be any of a resistance heating method, an infrared heating method, a dielectric heating method, and an induction heating method as long as it heats the liquid in the processing tank 21. ..

The air blower 24 is an electrically driven blower. The air supply blower 24 sends steam generated from the liquid in the treatment tank 21 to the outside from the treatment tank 21 by heating by the first heater 22. As shown in FIG. 1, the air supply blower 24 is fixed to the upper surface of the base frame 15A below the processing tank 21, and the pipe 24A extending from the air supply blower 24 is a part of the connecting duct 14. It is connected to a certain intermediate duct 14A. The intermediate duct 14A is a duct member extending upward from the upper surface of the processing tank 21. A pipe (not shown) is connected from the air supply blower 24 to the intermediate duct 14A, and air is sent from the air supply blower 24 into the intermediate duct 14A through this pipe. In the present embodiment, the air supply blower 24 sends air into the intermediate duct 14A in a direction that creates an upward air flow. The air sent into the intermediate duct 14A enters the connecting duct 14 together with the steam existing in the intermediate duct 14A, and is discharged to the outside of the processing tank 21. The steam that has entered the connecting duct 14 is sent to the disassembly processing device 12 through the connecting duct 14.

In the present embodiment, the configuration in which the blower of the present invention is realized by the air blower 24 is illustrated, but the blower of the present invention is not limited to this configuration. For example, the same blower as the air supply blower 24 may be provided in the exhaust duct 44. Further, the blower of the present invention is not limited to the configuration such as the air blower 24. For example, instead of the air blower 24, an axial fan provided inside the intermediate duct 14A may be applied as a blower. In this case, since air is not sent from the outside, it is possible to prevent the steam in the intermediate duct 14A from becoming diluted.

The second heater 23 is provided in a duct from the processing tank 21 to the oxidation catalyst 43 of the decomposition processing apparatus 12, specifically, a connecting duct 14. The second heater 23 heats the gas (steam and air) in the connecting duct 14. The second heater 23 is a unit type in which, for example, an electric heater 23A such as a halogen heater and a second heating control unit 23B including a driver circuit for driving the electric heater 23A are integrally configured. The electric heater 23A is provided inside the connecting duct 14, and the second heating control unit 23B is arranged outside the connecting duct 14. The second heater 23 heats the gas in the connecting duct 14 by being driven by the control unit 100. Specifically, when a drive signal is sent from the control unit 100 to the second heating control unit 23B, the second heating control unit 23B drives the electric heater 23A based on the drive signal to control heating. The second heater 23 is any of a resistance heating method, an infrared heating method, a microwave heating method, a dielectric heating method, and an induction heating method as long as it heats the gas in the connecting duct 14. It may be.

The defoaming agent supply unit 27 includes a storage box 27A for storing the defoaming agent, a pipe 27B for connecting the storage box 27A and the processing tank 21, and an electric valve 27C provided in the pipe 27B. When it is determined by the foam detection sensor 33 described later that bubbles are generated in the processing tank 21, the electric valve 27C is opened, and the defoaming agent is charged into the processing tank 21 from the storage box 27A through the pipe 27B. .. As the defoaming agent, for example, a silicone-based defoaming agent, an organic-based defoaming agent, or the like can be applied.

The water supply unit 28 supplies water to the treatment tank 21 and is provided in the vicinity of the treatment tank 21. A water supply port 21C communicating with the inside of the treatment tank 21 is provided on the side wall of the treatment tank 21. The water supply unit 28 has a water supply pipe 28A extending from a water supply source 28D such as a water source or a water tank, and the water supply pipe 28A is connected to a water supply port 21C of the treatment tank 21. The water supply unit 28 supplies water from the industrial water supply to the water supply port 21C through the water supply pipe 28A. The water supplied to the water supply port 21C is stored in the treatment tank 21. The water supply pipe 28A is provided with an electric valve 28B for supplying or stopping water. The electric valve 28B is, for example, an electric ball valve. The opening and closing of the electric valve 28B is controlled by the control unit 100 of the control panel 30, and water is supplied or stopped. Further, the opening / closing angle of the electric valve 28B is controlled by the control unit 100 to adjust the amount of water flowing through the water supply pipe 28A.

The discharge pump 29 is provided on the lower side of the processing tank 21. Specifically, the discharge pump 29 is fixed to the upper surface of the base frame 15A below the processing tank 21. The discharge pump 29 is a pump for discharging the wastewater stored in the treatment tank 21 to the outside as needed. Therefore, a drain pipe 84 extending from the bottom of the treatment tank 21 is connected to the suction port of the discharge pump 29. In the present embodiment, the discharge pump 29 discharges wastewater to an external tank 82 (see FIG. 4) which is separately installed. Therefore, a drain pipe 85 leading to the external tank 82 is connected to the discharge port of the discharge pump 29. Further, the drain pipe 84 is provided with an electric valve 84A that is opened and closed by electric drive. The electric valve 84A and the discharge pump 29 are driven and controlled by the control unit 100 (see FIG. 5) of the control panel 30. The electric valve 84A is controlled and opened by the control unit 100, and the discharge pump 29 is driven by the control unit 100, so that the liquid (wastewater or water) in the treatment tank 21 is discharged to the external tank 82. Further, when the electric valve 84A is closed and the drive of the discharge pump 29 is stopped, the discharge of the liquid is stopped.

[Disassembly processing device 12]
The decomposition treatment device 12 is provided in the exhaust gas guide path from the treatment tank 21, the connecting duct 14, and the exhaust duct 44, and has a tubular housing 41, an oxidation catalyst 43, an exhaust duct 44, and an exhaust blower. A 45, a temperature sensor 46, and a temperature sensor 47 are provided.

The housing 41 is formed in a tubular shape having a circular cross section extending in the vertical direction. One side (inlet side) of the housing 41 is connected to the outlet side of the connecting duct 14, and the gas guided from the connecting duct 14 flows into the inside. An exhaust duct 44 is connected to the other side (outlet side) of the housing 41. The gas (steam) sent from the connecting duct 14 is guided upward through the inside of the housing 41 and flows into the exhaust duct 44. That is, inside the housing 41, an air flow from the lower part to the upper part is generated.

The oxidation catalyst 43 is provided inside the housing 41. The oxidation catalyst 43 is a metal catalyst containing platinum as a main component, and is a so-called metal honeycomb catalyst having a honeycomb structure. When a gas containing vapor sent from the connecting duct 14 passes through the inside of the honeycomb structure, the 1,4-dioxane contained in the gas and the oxidation catalyst 43 undergo an oxidation reaction to form 1,4-dioxane. Completely disassembled. Specifically, 1,4-dioxane is decomposed to generate water vapor (water) and carbon dioxide. When the gas contains VOC gas in addition to the vapor of 1,4-dioxane, the VOC gas and the oxidation catalyst 43 undergo an oxidation reaction to completely decompose the VOC gas.

The temperature sensor 46 detects the temperature (catalyst inlet temperature) below the oxidation catalyst 43 inside the housing 41. Further, the temperature sensor 47 detects the temperature (catalyst outlet temperature) above the oxidation catalyst 43 inside the housing 41. The temperature sensors 46 and 47 send a sensor signal corresponding to the temperature of the detection target to the control unit 100. The control unit 100 calculates the temperature of the detection target based on the sensor signal, and displays the temperature information on the liquid crystal monitor 106.

[Control panel 30]
The control panel 30 controls the heating of the liquid (wastewater or water) in the treatment tank 21 by the first heater 22, controls the water supply to the treatment tank 21 by the water supply unit 28, and the gas (steam or water) by the second heater 23. The heating of air) is controlled, and the supply of wastewater to the treatment tank 21 by the supply pump 81C or the like is controlled. As shown in FIG. 1, the control panel 30 has a self-standing box-shaped cabinet 30A installed on the upper frame 15C of the gantry 15, and further, a control unit 100 such as a sequencer is contained therein. Is provided. A door 30B that can be opened and closed is provided on the front surface of the cabinet 30A, and the door 30B is provided with a liquid crystal monitor 106, other operation units, and the like.

The control unit 100 is a computer having a CPU 101, a ROM 102, a RAM 103, an EEPROM 104 (registered trademark), and the like, and controls the wastewater treatment apparatus 10 in an integrated manner. The control program is stored in the ROM 102, and when the CPU 101 reads out the control program and executes it, the concentration heat treatment and the cleaning heat treatment described later are executed. The concentrated heat treatment and the cleaning heat treatment will be described later.

A liquid crystal monitor 106, a first heating control unit 22B, and a second heating control unit 23B are connected to the control unit 100 so that signals and data can communicate with each other.

The treatment tank 21 is provided with a temperature sensor 32, a bubble detection sensor 33, a liquid level level sensor 34, and a temperature sensor 35.

The temperature sensor 32 detects the temperature of the liquid (wastewater or water) stored in the treatment tank 21, and is composed of, for example, a resistance temperature detector, a thermocouple, a thermistor, or the like. The temperature sensor 32 sends a sensor signal corresponding to the temperature to be detected to the control unit 100 of the control panel 30. The control unit 100 calculates the temperature of the detection target based on the sensor signal, and displays the temperature information on the liquid crystal monitor 106.

Further, the first heating control unit 22B drives the electric heater 22A of the first heater 22 to control heating. The first heating control unit 22B heats and controls the electric heater 22A so that the temperature detected by the temperature sensor 32 becomes a predetermined set temperature. The information on the set temperature is stored in the EEPROM 104. In the present embodiment, the set temperature is set to a temperature at which the liquid can evaporate. For example, when the liquid is water, the temperature is set to 100 ° C., and when the liquid is wastewater, the temperature is set to 105 ° C. The first heating control unit 22B PID controls the electric heater 22A based on the detected temperature of the liquid. Specifically, the first heating control unit 22B strengthens the heating by the electric heater 22A when the detection temperature is lower than the set temperature, and heats by the electric heater 22A when the detection temperature exceeds the set temperature. Weak or pause.

The second heating control unit 23B drives the electric heater 23A of the second heater 23 to control heating. In the present embodiment, the second heating control unit 23B drives the electric heater 23A to PID control the electric heater 23A so that the inlet temperature of the oxidation catalyst 43 of the decomposition processing apparatus 12 becomes 350 ° C. The second heating control unit 23B heats and controls the electric heater 23A so that the temperature detected by the temperature sensor 46 becomes a predetermined target temperature (for example, 350 ° C.). The target temperature information is stored in the EEPROM 104.

The foam detection sensor 33 detects whether or not bubbles are generated on the liquid surface of the wastewater stored in the treatment tank 21, and is, for example, separated from the space above the treatment tank 21 at a predetermined distance. It is composed of a light emitting element and a light receiving element. The upper limit water level of the liquid to be stored is set in the treatment tank 21, and in the present embodiment, the water level is set to the water level when 100 liters of liquid is stored in the treatment tank 21. The light emitting element and the light receiving element are provided at a position slightly above the upper limit water level, specifically, at a position 150 mm higher than the upper limit water level.

The light emitting element is, for example, a light emitting diode. The light receiving element is, for example, a phototransistor. Light is emitted from the light emitting element to the light receiving element, and a voltage signal corresponding to the irradiated light is sent to the control unit 100. When bubbles are generated on the liquid surface of the wastewater, the light is blocked and the voltage level of the voltage signal is lowered. The control unit 100 determines that bubbles are generated on the liquid surface when the voltage level becomes less than the threshold value. In the present embodiment, if the generated bubbles are separated from the liquid surface and sent to the decomposition processing device 12 through the connecting duct 14, the decomposition processing device 12 may stop or break down. Therefore, when it is determined that bubbles are generated, the control unit 100 controls the electric valve 27C to supply the defoaming agent from the defoaming agent supply unit 27 to the treatment tank 21.

The liquid level sensor 34 detects the position of the liquid level of the liquid (wastewater or water) stored in the treatment tank 21, and for example, a float switch type sensor or one using capacitance is used. Conceivable. The liquid level sensor 34 detects whether or not the liquid level of the wastewater has reached the upper limit water level, the intermediate water level, or the reference water level defined in the treatment tank 21. In the present embodiment, the upper limit water level is set to the water level when 100 liters of liquid is stored in the treatment tank 21. The reference water level is set to the water level when 90 liters of liquid is stored in the treatment tank 21. This reference water level is a water level used for determining whether or not the cleaning heat treatment described later has been completed. Further, the intermediate water level is set between the upper limit water level and the reference water level, and is set, for example, the water level when 95 liters of liquid is stored in the treatment tank 21. This intermediate water level is a water level used to determine the amount of wastewater supplied when performing the concentrated heat treatment described later. The liquid level sensor 34 sends a sensor signal corresponding to the water level of the waste water to the control unit 100, and the control unit 100 has the sensor signal level corresponding to the upper limit water level, the intermediate water level, and the reference water level. Whether or not the liquid level has reached the upper limit water level, the intermediate water level, or the reference water level is determined depending on whether or not the level value is reached.

A temperature sensor 35 is provided in the connecting duct 14. The temperature sensor 35 is provided on the upper part of the side surface of the processing tank 21. The temperature sensor 35 detects the temperature of the gas in the space above the processing tank 21, and is composed of, for example, a resistance temperature detector. The temperature sensor 35 sends a sensor signal corresponding to the temperature of the detection target to the control unit 100. The control unit 100 calculates the temperature of the detection target based on the sensor signal, and displays the temperature information on the liquid crystal monitor 106.

By the way, when wastewater containing a persistent substance such as paraffin is evaporated and concentrated, mist or bubbles of wastewater (hereinafter referred to as mist or the like) may be generated in the treatment tank 21 during heating of the wastewater. .. When the mist or the like flows into the connecting duct 14 together with steam and reaches the oxidation catalyst 43, the mist or the like adheres to the oxidation catalyst 43. In this case, when the adhered water such as mist evaporates and the persistent substance adheres to the oxidation catalyst 43, the oxidation reaction is slowed down and the decomposition performance of harmful substances such as 1,4-dioxane is deteriorated. The problem arises. Further, when the attached mist or the like directly adheres to the oxidation catalyst 43, the amount of substances undergoing an oxidation reaction increases as compared with the case where steam flows into the oxidation catalyst 43, and the amount of heat generated by the oxidation reaction also increases. As a result, the steam may exceed the heat resistant temperature of the oxidation catalyst 43. In this case, there arises a problem that the oxidation catalyst 43 is deteriorated or the oxidation catalyst 43 is damaged. On the other hand, in the present embodiment, since the cleaning heat treatment described later is performed, the persistent substance is cleaned by steam to clean the oxidation catalyst 43 to which the persistent substance or the like is attached. It can be removed from 43.

[Cleaning heat treatment, concentrated heat treatment]
Next, an example of the procedure of the cleaning heat treatment and the concentrated heat treatment executed by the control unit 100 will be described with reference to the flowchart of FIG. Here, in the cleaning heat treatment, the water stored in the treatment tank 21 is evaporated to generate water vapor by performing each of the treatments of steps S11 to S16 in FIG. 6, and the oxidation catalyst 43 is cleaned by the water vapor. It is a process. The control unit 100 that performs the cleaning heat treatment is the cleaning control unit of the present invention. Further, the catalyst cleaning method of the present invention is realized by performing the cleaning heat treatment. Further, in the concentrated heat treatment, the wastewater stored in the treatment tank 21 is evaporated and concentrated by performing each of the treatments of steps S17 to S22 in FIG. 6, and 1,4-dioxane and 1,4-dioxane contained in the evaporated steam are concentrated. This is a process for decomposing VOC gas. The control unit 100 that performs the concentration heat treatment is the concentration heat control unit of the present invention. S11, S12, ... In the figure represent processing procedure (step) numbers. The processing in each step is performed by the control unit 100, more specifically by the CPU 101 executing the control program in the ROM 102. In the following, for convenience of explanation, an example in which the treatment in step S11 is started in a state where the concentrated heat treatment is performed and the concentrated water is discharged to the external tank 82 will be described.

First, in step S11, the control unit 100 determines whether or not the liquid is stored in the processing tank 21. This determination process is performed based on the sensor signal from the liquid level sensor 34.

Next, in step S12, the control unit 100 drives and controls the electric valve 28B to operate the electric valve 28B from the closed position to the open position. As a result, water such as industrial water is supplied (supplied) to the treatment tank 21 through the water supply pipe 28A.

In step S13, the control unit 100 determines whether or not a certain amount of water has been supplied to the treatment tank 21. Specifically, the control unit 100 determines whether or not water has been supplied to the upper limit water level in the treatment tank 21. This determination process is performed based on the sensor signal from the liquid level sensor 34. When the control unit 100 determines that the liquid level of water has reached the upper limit water level (YES in S13), the control unit 100 returns the electric valve 28B from the open position to the closed position and stops the water supply (S14). In step S13, the water supply is continued until it is determined that the water level has reached the upper limit water level. The step of performing the treatments of steps S12 and S13 is the water supply step of the present invention.

When the water supply is stopped, in the next step S15, the primary heating evaporation treatment is executed. In the primary heated steam treatment, the water stored in the treatment tank 21 is heated to generate steam from the water, the steam is supplied from the connecting duct 14 to the oxidation catalyst 43, and the steam is discharged to the outside from the exhaust duct 44. Is. The step of performing the primary heating evaporation treatment is the first heating step of the present invention. In the primary heating evaporation treatment in step S15, the air supply treatment (S152) in which the air supply blower 24 is driven to send the water vapor generated in the treatment tank 21 to the oxidation catalyst 43 side, the first heater 22 and the second heater 23 are subjected to. It includes a heating treatment (S152) of driving to heat the water in the treatment tank 21 and the gas in the connecting duct 14.

In step S151 (air supply processing), the control unit 100 drives the air supply blower 24 to send air into the connecting duct 14. As a result, the water vapor generated in the processing tank 21 is sucked into the connecting duct 14, and further blown to the housing 41 through the connecting duct 14. The air blowing process of the present invention is realized by performing the air blowing process in step S151.

Here, the amount of air blown by the air blower 24 is controlled by the control unit 100 so as to be the amount of air required for cleaning the oxidation catalyst 43. For example, the higher the content of the persistent substance in the wastewater to be treated, the greater the amount of the persistent substance adhering to the oxidation catalyst 43. It is conceivable to increase the amount of air blown by the air blower 24 in proportion to the content rate.

In step S152 (heat treatment), the control unit 100 sends a drive signal to the first heating control unit 22B to drive the electric heater 22A of the first heater 22. At this time, the first heating control unit 22B heats and controls the water so that it boils and evaporates by PID control. Further, the control unit 100 sends a drive signal to the second heating control unit 23B to drive the electric heater 23A of the second heater 23. At this time, the second heating control unit 23B controls the PID so that the inlet temperature of the oxidation catalyst 43 becomes the target temperature (for example, a temperature within the range of 250 ° C. to 350 ° C.) required for cleaning the oxidation catalyst 43. The electric heater 23A is heated and controlled. By this heat treatment, the steam that has entered the housing 41 is heated to the target temperature and passes through the oxidation catalyst 43, whereby the deposits such as the persistent substance adhering to the oxidation catalyst 43 are steam of steam. It is washed by being peeled off by a stream.

By performing the primary heat evaporation treatment, the amount of water stored in the treatment tank 21 gradually decreases. In the next step S16, the control unit 100 determines whether or not the water in the treatment tank 21 has decreased to the reference water level. This determination process is performed based on the sensor signal from the liquid level sensor 34. When the control unit 100 determines that the liquid level of water has decreased to the reference water level (YES in S16), the control unit 100 proceeds to the next step S17.

In the next step S17, the control unit 100 controls the electric valve 81B to operate the electric valve 81B from the closed position to the open position, and also drives the supply pump 81C. As a result, wastewater is supplied from the wastewater tank 81 to the treatment tank 21. At this time, the water stored up to the reference water level and the wastewater are mixed. The amount of wastewater supplied to the treatment tank 21 is such that the liquid level of the mixed solution of water and wastewater reaches the intermediate water level from the reference water level (5 liters in the present embodiment). When the control unit 100 determines that the liquid level of the mixed liquid has reached the intermediate water level based on the sensor signal from the liquid level sensor 34, the control unit 100 returns the electric valve 81B to the closed position and stops the supply pump 81C. And stop the supply of wastewater.

The amount of wastewater supplied in step S17 is larger than the amount of decrease in water (10 liters in the present embodiment) obtained by the primary heat evaporation treatment in step S15 so that the total amount of the mixed solution does not exceed the upper limit water level. It is set to a small amount. Of course, the amount of wastewater supplied may be the same as the amount of decrease as long as the total amount of the mixed solution does not exceed the upper limit water level.

After that, in step S18, the control unit 100 executes the secondary heat evaporation treatment having the same contents as the primary heat evaporation treatment of step S15 described above. The secondary heating / evaporation treatment is the second heating step of the present invention.

When the mixed liquid is heated by performing the secondary heating evaporation treatment in step S18, the water contained in the mixed liquid becomes steam and flows into the connecting duct 14. In addition, 1,4-dioxane, which has almost the same boiling point as water, also flows into the connecting duct 14 as steam. Further, even when the wastewater contains VOC, the VOC becomes steam (VOC gas) and flows into the connecting duct 14. After that, these vapors flow into the housing 41. The gas flowing into the housing 41 is heated to 350 ° C. by the second heater 23, and when it passes through the oxidation catalyst 43, it is decomposed into water vapor and carbon dioxide by an oxidation reaction with the oxidation catalyst 43. As described above, in step S18, a process of supplying a gas to the oxidation catalyst 43 to oxidize and decompose 1,4-dioxane and VOC gas contained in the gas is performed, and a process of concentrating the mixed solution is performed. ..

The heat generated by the oxidation reaction in the oxidation catalyst 43 raises the temperature of the gas around the oxidation catalyst 43 to about 400 ° C. to 450 ° C. That is, the temperature of the gas that has passed through the oxidation catalyst 43 rises by 50 ° C. to 100 ° C. from the catalyst inlet temperature (for example, 350 ° C.). In this state, the gas is discharged to the outside from the exhaust duct 44. The gas is not discharged at a high temperature of 400 ° C. to 450 ° C., but is cooled while being diluted by the air blown into the exhaust duct 44 by an exhaust blower (not shown) and then discharged to the atmosphere. ..

In the present embodiment, as will be described later, by repeating the steps S17 to S21, the concentration of 1,4-dioxane in the mixed solution in the treatment tank 21 becomes equal to or less than a predetermined target concentration value. Evaporation, decomposition, and concentration of the mixed solution are repeated until.

Specifically, in the next step S19, the control unit 100 determines whether or not the mixed solution in the treatment tank 21 has decreased to the reference water level. This determination process is performed based on the sensor signal from the liquid level sensor 34. When the control unit 100 determines that the liquid level of the mixed solution has decreased to the reference water level (YES in S19), the control unit 100 counts up the number of processes (concentration frequency) in which the secondary heat evaporation process is performed, and causes the RAM 103. Remember (S20).

In the next step S21, the control unit 100 determines whether or not the count-up processing number is a predetermined set number. In the present embodiment, the number of times of setting is set to 2000 times. In the configuration of the present embodiment, the number of times of setting is preferably set within the range of 2000 times to 4000 times. The set value of the set number of times is arbitrary, and is determined according to the water content in the wastewater, the volume of the treatment tank 21, the set temperature of the wastewater to be heated (for example, 105 ° C. in this embodiment), and the like. If it is determined in step S21 that the number of processes is less than the set number of times, the control unit 100 returns to step S17 and repeats the processes of each procedure after step S17. In the present embodiment, as described above, the reference water level is a water level having a liquid volume of 90 liters, and the intermediate water level is a water level having a liquid volume of 95 liters. That is, the capacity from the reference water level to the intermediate water level is 5 liters. Therefore, the treatment of each procedure of steps S17 to S21 is repeated every time the water and 1,4-dioxane contained in the mixed liquid in the treatment tank 21 evaporate and the mixed liquid is reduced by 5 liters. On the other hand, if it is determined in step S21 that the number of processes is the set number of times, the control unit 100 proceeds to step S25.

In step S25, the control unit 100 drives the discharge pump 29, opens the electric valve 84A provided in the drain pipe 84, and concentrates the concentrated water stored in the treatment tank 21 (the mixed solution is prepared. The concentrated product) is discharged to the external tank 82. As a result, the concentrated water flows from the treatment tank 21 into the external tank 82 through the drain pipe 84 and the drain pipe 85 by the discharge pump 29. Then, after the concentrated water is discharged, the electric valve 84A is returned to the closed position, the discharge pump 29 is stopped, and then the processes of each procedure after step S11 are executed again.

As described above, in the wastewater treatment apparatus 10 of the above-described embodiment, by performing the cleaning heat treatment, deposits such as the persistent substance adhering to the oxidation catalyst 43 during the concentrated heat treatment are removed. It is washed so that it can be peeled off by the steam flow of steam. As a result, the slowdown of the oxidation reaction caused by the adhesion of the persistent substance to the oxidation catalyst is prevented, and the decomposition performance of harmful substances such as 1,4-dioxane can be restored.

10: Wastewater treatment device 11: Wastewater concentrator 12: Decomposition treatment device 21: Treatment tank 22: First heating unit 23: Second heating unit 24: Air supply blower 27: Defoamer supply unit 28: Water supply unit 29: Discharge Pump 30: Control panel 43: Oxidation catalyst 44: Exhaust duct 46: Temperature sensor 47: Temperature sensor

Claims (8)

Wastewater that evaporates the water contained in the wastewater and concentrates the wastewater by heating the wastewater that contains persistent substances that are difficult to decompose by the oxidation reaction and substances that can be decomposed by the oxidation reaction stored in the storage tank. It ’s a processing device,
A first heating unit that heats the liquid stored in the water tank,
A duct portion that guides gas from the storage tank to the outside,
An oxidation catalyst provided in the gas guide path in the duct portion and
A water supply unit for supplying industrial water to the reservoir,
The so concentrated concentrated water to store a certain amount of the industrial water to the storage tank in a state of being discharged from the storage tank water supply unit to control, by heating the industrial water in the storage tank A wastewater treatment apparatus comprising: a cleaning control unit that controls the first heating unit so as to generate water vapor for cleaning the oxidation catalyst. A second heating unit provided in the duct portion from the storage tank to the oxidation catalyst and for heating the steam in the duct portion is further provided.
The wastewater treatment apparatus according to claim 1, wherein the cleaning control unit controls the second heating unit so that the water vapor generated from the industrial water rises to a predetermined temperature required for cleaning the oxidation catalyst. .. Further provided with a blower for sending the steam generated from the industrial water in the storage tank to the outside through the duct portion.
The wastewater treatment device according to claim 1 or 2, wherein the cleaning control unit controls to drive the blower when cleaning the oxidation catalyst. A wastewater supply unit that supplies the wastewater to the storage tank,
When the water level of the industrial water in the reservoir is reduced to the reference level to a predetermined, supplying the waste water decreased the same amount or the decrease amount smaller amount than the industrial water to the reservoir controlling the waste water supply unit so as to, concentrated heating control for controlling the first heating portion so as to concentrate the heat to the mixed solution a mixed solution of the waste water and the industrial water in the storage tank The wastewater treatment apparatus according to any one of claims 1 to 3, further comprising a unit. The wastewater treatment apparatus according to claim 4, wherein the reference water level is a water level used for determining whether or not cleaning of the participating catalyst by the steam generated from the industrial water is completed. Wastewater that evaporates the water contained in the wastewater and concentrates the wastewater by heating the wastewater that contains persistent substances that are difficult to decompose by the oxidation reaction and substances that can be decomposed by the oxidation reaction stored in the storage tank. A catalyst cleaning method that is applied to a treatment device and cleans an oxidation catalyst provided in a duct portion of the wastewater treatment device.
A water supply step of storing a certain amount of industrial water to the storage tank in a state of concentrated concentrated water is discharged from the reservoir,
Catalyst cleaning method characterized in that it comprises a a first heating step to produce steam for cleaning the oxidation catalyst by heating the industrial water stored in the reservoir by the water supply step. Further, a second heating step of heating the steam in the duct portion so that the steam generated from the industrial water by the first heating step rises to a predetermined temperature required for cleaning the oxidation catalyst. The catalyst cleaning method according to claim 6, which includes. The catalyst cleaning method according to claim 6 or 7 , further comprising a blowing step of blowing the steam generated from the industrial water by the first heating step toward the oxidation catalyst.

Images