JP7536286B2 - Waste liquid treatment device, heating adjustment method - Google Patents

Description

The present invention relates to a waste liquid treatment device that heats waste liquid contained in a treatment tank to evaporate the water content and thereby concentrates the waste liquid, and a heating adjustment method that is applied to the waste liquid treatment device.

Conventionally, there is known a treatment device that concentrates wastewater by repeatedly performing an evaporation process in which the wastewater contained in a treatment tank is heated to evaporate the water, and a supply process in which untreated wastewater is supplied (replenished) to the treatment tank when the level of the wastewater drops to a predetermined level due to evaporation (see Patent Document 1). In the supply process, the level of the wastewater is detected by a water level sensor (water level gauge) installed in the treatment tank, and the wastewater is supplied based on the detection result.

JP 2018-044752 A

In conventional waste liquid treatment devices that treat waste liquids to be disposed of, such as wastewater and waste oil, when foam generation in the treatment tank is detected, an antifoaming agent is supplied to the treatment tank. However, if the viscosity of the waste liquid increases as a result of the waste liquid being replenished (replenished) to the treatment tank, foam generation may not be sufficiently suppressed even if an antifoaming agent is supplied. If foam generation is frequently detected, the operation of the waste liquid treatment device is abnormally stopped, and the waste liquid in the treatment tank must be discharged as industrial waste. In this case, there is a risk that waste liquid that is not sufficiently concentrated will be discharged.

The object of the present invention is to provide a waste liquid treatment device and a heating adjustment method that can reliably concentrate the waste liquid in the treatment tank.

(1) A waste liquid treatment device according to one embodiment of the present invention is a waste liquid treatment device that heats the waste liquid contained in a treatment tank and evaporates the water contained therein to concentrate the waste liquid. The waste liquid treatment device includes a heating unit that heats the waste liquid in the treatment tank, a foam detection unit that detects foam generated in the treatment tank, an antifoaming agent supply unit that supplies an antifoaming agent to the treatment tank when the foam is detected by the foam detection unit, and a heating control unit that suppresses heating by the heating unit when the foam is detected again by the foam detection unit before a first predetermined set time has elapsed since the antifoaming agent was supplied.

Because of this configuration, the strength of the heating by the heating unit can be suppressed to a level where bubbles do not form in the treatment tank. As a result, the waste liquid treatment device can be operated continuously without being shut down immediately due to the formation of bubbles. In addition, although the heating power is suppressed, by operating the waste liquid treatment device continuously, the waste liquid can be concentrated until the desired concentrated water is obtained without stopping halfway through the concentration of the waste liquid.

(2) The heating control unit is characterized in that the shorter the first set time is, the greater the amount of heating suppression by the heating unit.

This allows the heating strength from the heating section to be gradually reduced until bubbles are no longer easily generated.

(3) A waste liquid treatment device according to another embodiment of the present invention is a waste liquid treatment device that heats the waste liquid contained in a treatment tank and evaporates the water content to concentrate the waste liquid. The waste liquid treatment device includes a heating unit that heats the waste liquid in the treatment tank, a foam detection unit that detects bubbles generated in the treatment tank, a waste liquid supply unit that supplies the waste liquid to the treatment tank when the liquid level of the waste liquid in the treatment tank drops to the make-up water level due to evaporation of the water content, and a heating control unit that suppresses heating by the heating unit when the foam detection unit detects the foam before a second predetermined set time has elapsed since the waste liquid was supplied by the waste liquid supply unit.

Because of this configuration, the intensity of heating by the heating unit can be reduced by the low combustion process to a level that does not generate bubbles in the treatment tank without waiting for the first set time to elapse. Here, it is preferable that the second set time is shorter than the first set time.

(4) A heat adjustment method according to another embodiment of the present invention is a heat adjustment method applied to a waste liquid treatment device that heats waste liquid contained in a treatment tank to evaporate the water content, thereby concentrating the waste liquid. The waste liquid treatment device includes a heating unit that heats the waste liquid in the treatment tank, and a foam detection unit that detects foam generated in the treatment tank. The heat adjustment method includes an antifoaming agent supplying step of supplying an antifoaming agent to the treatment tank when foam is detected by the foam detection unit, and a heating suppressing step of suppressing heating by the heating unit when foam is detected again by the foam detection unit before a first predetermined set time has elapsed since the antifoaming agent was supplied.

(5) A heat adjustment method according to another embodiment of the present invention is a heat adjustment method applied to a waste liquid treatment device that heats waste liquid contained in a treatment tank to evaporate the contained moisture and thereby concentrate the waste liquid. The waste liquid treatment device includes a heating unit that heats the waste liquid in the treatment tank and a foam detection unit that detects foam generated in the treatment tank. The heat adjustment method includes a waste liquid supplying step of supplying the waste liquid to the treatment tank when the liquid level of the waste liquid in the treatment tank drops to a make-up water level due to evaporation of the contained moisture, and a heat suppressing step of suppressing heating by the heating unit when foam is detected by the foam detection unit before a second predetermined set time has elapsed since the waste liquid was supplied by the waste liquid supplying step.

According to the present invention, it is possible to reliably concentrate the waste liquid in the treatment tank.

FIG. 1 is a diagram showing the configuration of a wastewater treatment system 10 including a wastewater concentrating device 11 according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the wastewater concentrating device 11. FIG. 3 is a flow chart showing an example of a procedure of the concentration process executed in the wastewater concentrating device 11. FIG. 4 is a flow chart showing an example of a procedure of the concentration process executed in the wastewater concentrating device 11. FIG. 5 is a flow chart showing an example of a procedure of the low combustion process included in the concentration process. FIG. 6 is a flow chart showing another example of the procedure of the concentration treatment carried out in the wastewater concentrating device 11. In FIG.

Below, an embodiment of the present invention will be described with reference to the drawings as appropriate. Note that the embodiment described below is merely an example of the present invention and does not limit the technical scope of the present invention.

[Wastewater treatment system 10]
The wastewater treatment system 10 shown in FIG. 1 treats wastewater (waste liquid) discharged from a factory or the like, and specifically, it evaporates water from the wastewater to concentrate the wastewater, and decomposes and purifies persistent substances contained in gas generated from the wastewater.

In the following, the wastewater treatment system 10 will exemplify wastewater contaminated by impurities and harmful substances, which is a liquid that is discarded after use in a factory or business establishment. A specific example of the wastewater is used cutting oil (an example of a difficult-to-decompose substance) for lubrication and cooling during metal cutting. Here, the cutting oil is a water-soluble cutting oil of type A1 as specified in JIS K 2241, which has a lower density than water. The wastewater also includes metal powder generated by cutting. The wastewater to be treated by the wastewater treatment system 10 is not limited to wastewater containing a water-soluble cutting oil of type A1, but may also include wastewater containing other water-soluble cutting oils (types A2 and A3) or water-insoluble cutting oils (types N1 to N4) as specified in JIS K 2241. The wastewater also includes waste liquids used in various fields or industries, such as organic wastewater, oil-containing wastewater, pharmaceutical and food wastewater, plating wastewater, and painting wastewater.

As shown in FIG. 1, the wastewater treatment system 10 is broadly divided into a wastewater concentrator 11 (one example of a wastewater treatment device of the present invention), a decomposition treatment device 12, and a control device 13 (see FIG. 2) that controls the operation of the wastewater treatment system 10. The wastewater concentrator 11 and the decomposition treatment device 12 are connected to each other by a connecting duct 14 so that gas containing steam is sent from the wastewater concentrator 11 to the decomposition treatment device 12.

In this embodiment, the wastewater concentrator 11 of the wastewater treatment system 10 is described as an example of the wastewater treatment device of the present invention, but for example, the wastewater treatment device of the present invention may be a waste oil treatment device that treats waste oil (waste liquid) containing water discharged from a factory, etc.

[Wastewater concentrator 11]
The wastewater concentrating apparatus 11 heats the wastewater contained in a treatment tank 16 to evaporate water therefrom, thereby concentrating the wastewater. As shown in Fig. 1, the wastewater concentrating apparatus 11 mainly includes a treatment tank 16 (an example of a treatment tank of the present invention), a water level tank 18, a first heating device 22 (an example of a heating section of the present invention), a second heating device 23, an air blower 24, various sensors 32 to 35, a defoaming agent supplying section 27 (an example of a defoaming agent supplying section of the present invention), a supply pump 61, and a discharge pump 62.

The treatment tank 16 is for containing the wastewater to be treated. A predetermined amount of wastewater is stored inside the treatment tank 16. In the process of concentrating the wastewater, the wastewater is supplied to the treatment tank 16 so that the water level of the wastewater becomes the upper water level H1 described below. In other words, the upper water level H1 is the upper water level at which the wastewater is stored in the treatment tank 16 in the process of concentrating the wastewater.

In this embodiment, the wastewater stored in the treatment tank 16 and concentrated is, for example, wastewater (so-called industrial wastewater) that is used in industrial production in a factory or the like and then discarded after use. As described above, the wastewater contains a water-soluble cutting oil of type A1 as defined in JIS K 2241 (hereinafter, sometimes simply referred to as "water-soluble cutting oil"), the metal powder, and water. The water-soluble cutting oil of type A1 contains an oil component (such as mineral oil or fatty oil) that is an example of a hydrophobic substance that is poorly soluble in water, and a surfactant as an emulsifier, and is emulsified by dilution with water to form a milky emulsion. The wastewater may contain substances such as paraffin and 1,4-dioxane, rust-preventive oil additives, refined mineral oil, surfactants, additives for improving lubricity, and the like. All of these are difficult-to-decompose substances.

The wastewater to be treated is stored in a separately installed wastewater tank 81. The content of water-soluble cutting oil and the content of water in the wastewater vary depending on the factory or business from which the wastewater is collected. Therefore, the viscosity of the wastewater to be concentrated and brought from the factory or business to the wastewater treatment plant in which the wastewater treatment system 10 is installed varies depending on the source of collection, and sometimes high-viscosity wastewater is brought in, and sometimes low-viscosity wastewater is brought in. Therefore, the state of the wastewater stored in the wastewater tank 81 (degree of viscosity, content of persistent substances, etc.) changes every time wastewater is added to the wastewater tank 81.

The wastewater tank 81 is connected to the treatment tank 16 by a pipe 51. The pipe 51 is provided with an electric valve 51A that is opened and closed by electric drive, and a supply pump 61. The supply pump 61 is provided between the wastewater tank 81 and the electric valve 51A. The supply pump 61 is an electric pump for supplying wastewater from the wastewater tank 81 to the treatment tank 16 as necessary. The electric valve 51A and the supply pump 61 are driven and controlled by the control unit 100 (see FIG. 2) of the control device 13. The electric valve 51A is opened under the control of the control unit 100, and the supply pump 61 is driven by the control unit 100, thereby supplying wastewater from the wastewater tank 81 to the treatment tank 16. When the electric valve 51A is closed and the drive of the supply pump 61 is stopped, the supply of wastewater is stopped. The electric valve 51A and the supply pump 61 realize the wastewater supply unit of the present invention that supplies wastewater from the wastewater tank 81 to the treatment tank 16.

A bubbling pipe 26 with many small holes is provided at the bottom of the treatment tank 16. The bubbling pipe 26 is connected to an air tank 37 (compressed air supply unit) as an externally installed compressed air source by an air pipe 55. When an electromagnetic valve 55A provided in the air pipe 55 is operated to supply compressed air to the air pipe 55, countless air bubbles are generated from the bubbling pipe 26, and the wastewater in the treatment tank 16 is agitated by the upward flow of the air bubbles. The compressed air source may be an air compressor.

The first heating device 22 heats the wastewater stored in the treatment tank 16. The first heating device 22 includes, for example, a combustion furnace 221 disposed in the treatment tank 16, a burner 222 that radiates heat to the combustion furnace 221, a pressure equalizing valve 223 that adjusts the amount of fuel gas, a blower 224 that supplies air to the burner 222, and an electric valve 225 that adjusts the amount of air supplied to the burner 222. The combustion furnace 221 is formed in a pipe shape and is provided inside the treatment tank 16. The combustion furnace 221 is provided inside the treatment tank 16 below the middle position in the height direction, and with a predetermined amount of wastewater stored in the treatment tank 16, the entire wastewater is placed in the liquid. The burner 222 supplies heat by burning the fuel gas in the combustion furnace 221. The exhaust gas after combustion is sent from the combustion furnace 221 to an exhaust pipe 31 connected to the treatment tank 16 and discharged to the outside from the exhaust pipe 31.

A pipe 56 for supplying fuel gas is connected to the burner 222, and a pipe 57 for supplying air from the blower 224 is connected separately from the pipe 56. The motor-operated valve 225 is provided on the pipe 57. The motor-operated valve 225 is driven and controlled by the control unit 100 (see FIG. 2) of the control device 13. Specifically, when the control unit 100 outputs a drive signal to the motor-operated valve 225, the motor-operated valve 225 is opened, and when the output of the drive signal is stopped, the motor-operated valve 225 is closed.

The pressure equalizing valve 223 is provided in the pipe 56. In addition, the pressure equalizing valve 223 is connected to a branch pipe 58 that branches off from the secondary side of the motor-operated valve 225 in the pipe 57. The pressure equalizing valve 223 adjusts the gas pressure in the pipe 56 so that it is approximately the same as the air pressure in the branch pipe 58.

The blower 224 is an electrically driven air blower. The first heating device 22 has a blower control unit 226 that controls the drive of the blower 224. The blower control unit 226 drives the blower 224 by inverter control. When the control unit 100 outputs a drive signal corresponding to a predetermined air volume to the blower control unit 226, the blower control unit 226 outputs a frequency signal corresponding to the predetermined air volume to the blower 224 to control the drive of the blower 224. Note that by changing the output level of the drive signal, the frequency of the frequency signal is changed, and the air volume of the blower 224 is adjusted.

The first heating device 22 controls the heating of the wastewater by controlling the combustion using a so-called pressure equalizing valve method. In the first heating device 22, when the blower control unit 226 outputs the frequency signal to the blower 224 so as to achieve a predetermined air volume, air is supplied from the blower 224 to the pipe 57. When the air volume of the blower 224 is adjusted, the air pressure in the pipes 57 and 58 fluctuates, and the pressure equalizing valve 223 is adjusted to an opening degree according to the air pressure in the pipes 57 and 58. As a result, by adjusting the air volume supplied from the blower 224, it is possible to adjust the combustion amount of the burner 222 while maintaining the air-fuel ratio of the air and fuel gas supplied to the burner 222 at an appropriate value. In other words, the first heating device 22 can control the heating of the wastewater stored in the treatment tank 16 by controlling the air volume of the blower 224.

The first heating device 22 is not limited to a configuration that heats using the pressure equalizing valve method. For example, the first heating device 22 may be configured to heat using a method in which an electric valve is provided in the pipe 56 instead of the pressure equalizing valve 223, and the opening degree of this electric valve is controlled according to the air volume of the blower 224.

The first heating device 22 may be of any configuration as long as it heats the wastewater in the treatment tank 16, and may be an electric heater instead of the burner 222 or the combustion furnace 221. In this case, a drive signal for driving the electric heater is output from the control unit 100, and the first heating device 22 controls the heating of the wastewater stored in the treatment tank 16 by adjusting the level of this drive signal.

The air blower 24 (see FIG. 1) is an electrically driven blower. The air blower 24 blows steam generated from the wastewater in the treatment tank 16 by heating with the first heating device 22 from the treatment tank 16 to the outside. The air blower 24 is connected to the intermediate duct 14A, which is a part of the connecting duct 14, by a pipe 25. The intermediate duct 14A is a duct member extending upward from the upper surface of the treatment tank 16. The air blown out from the air blower 24 is sent into the intermediate duct 14A through the pipe 25. In this embodiment, the air blown out by the air blower 24 is sent by the pipe 25 in a direction that generates an upward airflow inside the intermediate duct 14A. The airflow of the air sent into the intermediate duct 14A guides gas containing steam generated in the treatment tank 16 to the connecting duct 14, thereby discharging the gas to the outside of the treatment tank 16. The gas that has entered the connecting duct 14 is sent through the connecting duct 14 to the decomposition treatment device 12.

The second heating device 23 is provided in the connecting duct 14. The second heating device 23 heats the gas (steam and air) passing through the connecting duct 14. The second heating device 23 is a unit type in which 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 disposed outside the connecting duct 14. The second heating device 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 the heating. The second heating device 23 may use any of the following heating methods as long as it heats the gas in the connecting duct 14: resistance heating, infrared heating, microwave heating, dielectric heating, and induction heating.

The defoaming agent supplying section 27 includes a storage box 30 that stores the defoaming agent, and an electric valve 29A provided on a pipe 29 that connects the storage box 30 and the treatment tank 16. When the foam sensor 33 described later detects the generation of foam in the treatment tank 16, the electric valve 29A is opened, and the defoaming agent is introduced (supplied) from the storage box 30 through the pipe 29 into the treatment tank 16. As the defoaming agent, for example, a silicone-based defoaming agent or an organic-based defoaming agent can be used. However, in terms of cost, it is preferable to use water supplied from a water source or a water tank or other water supply source as the defoaming agent. When water is used as the defoaming agent, a spray nozzle is provided at the end of the pipe 29, and mist-like water is sprayed from the spray nozzle toward the liquid surface in the treatment tank 16.

A water supply pipe 28 extending from a water supply source (not shown), such as a water source or a water tank, is connected to the treatment tank 16. The water supply pipe 28 is provided with an electric valve 28A for starting and stopping the supply of water. The electric valve 28A is, for example, an electric ball valve. The opening and closing of the electric valve 28A is controlled by the control unit 100 of the control device 13, so that water is supplied from the water supply pipe 28 to the treatment tank 16 as needed.

The discharge pump 62 is an electric pump. The discharge pump 62 discharges wastewater stored in the treatment tank 16 to the outside of the treatment tank 16 as necessary. In this embodiment, the discharge pump 62 is used to send concentrated water in the treatment tank 16 after concentration processing to the external tank 36. A pipe 54 is connected to the bottom of the treatment tank 16, and this pipe 54 is connected to the external tank 36. The discharge pump 62 is provided on the pipe 54.

In addition, an electrically operated valve 54A that is electrically opened and closed is provided upstream of the discharge pump 62 in the piping 54. The electric valve 54A is opened under the control of the control unit 100, and the discharge pump 62 is driven by the control unit 100, thereby discharging the wastewater (concentrated water) in the treatment tank 16 into the external tank 36. When the electric valve 54A is closed and the drive of the discharge pump 62 is stopped, the discharge of the wastewater stops.

The water level tank 18 is provided alongside the treatment tank 16, and like the treatment tank 16, is formed to be capable of storing wastewater therein. The water level tank 18 does not have any openings or ducts communicating with the atmosphere, and is formed as a sealed type. As will be described later, the water level tank 18 is used to store wastewater therein and measure the level of the wastewater. The water level tank 18 has the same height as the treatment tank 16, and is installed at the same height as the treatment tank 16. It is sufficient for the water level tank 18 to have a capacity that is applicable to such uses, and in this embodiment, the capacity is smaller than that of the treatment tank 16.

As shown in FIG. 1, the lower part of the treatment tank 16 and the lower part of the water level tank 18 are connected by a connecting pipe 52 so that wastewater can flow between the two tanks. In this way, because the treatment tank 16 and the water level tank 18 are connected by the connecting pipe 52, when wastewater is supplied to the treatment tank 16, the wastewater spreads throughout the water level tank 18, and the position of the liquid surface (water level) of the wastewater in the water level tank 18 becomes the same height as the position of the liquid surface of the wastewater in the treatment tank 16.

The upper part of the treatment tank 16 and the upper part of the water level tank 18 are connected by a connecting pipe 53, and the air layer at the upper part of the treatment tank 16 and the air layer at the upper part of the water level tank 18 are connected by a connecting pipe 52. Therefore, the water level tank 18 can be connected to the atmosphere via the connecting pipe 53 and the treatment tank 16.

The water level tank 18 is provided with a liquid level sensor 34. The liquid level sensor 34 detects the position (water level) of the liquid level of the wastewater stored in the water level tank 18. Specifically, it is a guided pulse type sensor that detects the position (water level) of the liquid level by sending a pulse signal toward the liquid level and receiving a pulse signal reflected by the liquid level. The liquid level sensor 34 is used to detect whether the liquid level of the wastewater has reached the upper limit water level H1 set in the water level tank 18, a make-up water level H2 lower than the upper limit water level H1, or a lower limit water level H3 even lower than the make-up water level H2. The liquid level sensor 34 may be, for example, a float switch type or a capacitance type.

In this embodiment, the upper limit water level H1 is set to the water level when a specified amount (e.g., 500 liters) of wastewater is stored in the treatment tank 16. The make-up water level H2 is set to the water level when 90% of the specified amount of wastewater is stored in the treatment tank 16. The make-up water level H2 is a water level used to determine whether or not the wastewater in the treatment tank 16 needs to be replenished due to evaporation and reduction. The lower limit water level H3 is a water level used to determine whether or not the treatment tank 16 is empty after the concentrated water in the treatment tank 16 has been discharged.

The liquid level sensor 34 sends a detection signal corresponding to the position of the wastewater liquid level to the control unit 100, and the control unit 100 determines whether the liquid level has reached the upper limit water level H1 or the make-up water level H2 depending on whether the level of the detection signal is a level value corresponding to the upper limit water level H1 or the make-up water level H2.

The treatment tank 16 is equipped with a temperature sensor 32, a foam sensor 33 (an example of the foam detection unit of the present invention), and a temperature sensor 35.

The temperature sensor 32 detects the temperature of the wastewater contained in the treatment tank 16, and is composed of, for example, a resistance temperature detector, a thermocouple, or a thermistor. The temperature sensor 32 sends a sensor signal corresponding to the temperature of the object to be detected to the control unit 100 of the control device 13. The control unit 100 calculates the temperature of the object to be detected based on the sensor signal, and displays the temperature information on the LCD monitor 106.

The first heating device 22 also stops heating when the temperature detected by the temperature sensor 32 exceeds a predetermined set temperature. Information on the set temperature is stored in the EEPROM 104. In this embodiment, the set temperature is set to 105°C. When the detected temperature exceeds 105°C, it means that the wastewater has become more concentrated and has risen to an abnormal temperature. Therefore, in this case, the first heating device 22 stops heating to stop further concentration processing.

The foam sensor 33 detects the presence or absence of bubbles on the surface of the wastewater stored in the treatment tank 16. When the wastewater in the treatment tank 16 is heated, bubbles generated by the heating may cause the surface of the wastewater to foam. The higher the viscosity of the wastewater, the more likely it is that bubbles will form. The foam sensor 33 detects the presence or absence of bubbles thus generated. The foam sensor 33 is composed of, for example, a light-emitting element and a light-receiving element spaced a predetermined distance apart in the space above the treatment tank 16. The light-emitting element and the light-receiving element are located slightly above the upper water level H1, specifically, at a position 150 mm higher than the upper water level H1.

The light-emitting element is, for example, a light-emitting diode. The light-receiving element is, for example, a phototransistor. Light is irradiated 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 generated on the liquid surface of the wastewater increase and reach the light path from the light-emitting element to the light-receiving element, the light passing through the light path is blocked and the voltage level of the voltage signal decreases. The control unit 100 determines that bubbles are generated on the liquid surface when the voltage level becomes less than a predetermined threshold value. In this embodiment, if the generated bubbles leave the liquid surface and are sent to the decomposition treatment device 12 through the connecting duct 14, there is a risk that the decomposition treatment device 12 will stop or break down. Therefore, when the control unit 100 determines that bubbles are generated, it controls the motor valve 29A to supply defoaming agent from the defoaming agent supply unit 27 to the treatment tank 16.

The temperature sensor 35 is provided on the upper surface of the treatment tank 16. The temperature sensor 35 detects the temperature inside the treatment tank 16, specifically, the temperature of the gas in the space above the treatment tank 16. The temperature sensor 35 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 LCD monitor 106.

[Decomposition treatment device 12]
The decomposition treatment device 12 is provided downstream of the connecting duct 14. The decomposition treatment device 12 includes a cylindrical housing 41, an oxidation catalyst 43, and an exhaust duct 44.

The housing 41 is formed in a cylindrical shape that extends vertically and has a circular cross section. One side (the inlet side) of the housing 41 is connected to the outlet side of the connecting duct 14, and gas guided from the connecting duct 14 flows into the inside. The other side (the outlet side) of the housing 41 is connected to the exhaust duct 44. 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. In other words, an airflow is generated inside the housing 41 that flows from the bottom to the top.

The oxidation catalyst 43 is provided inside the housing 41. The oxidation catalyst 43 is a metal catalyst whose main component is platinum, and is a so-called metal honeycomb catalyst having a honeycomb structure. When the gas containing steam sent from the connecting duct 14 passes through the inside of the honeycomb structure, an oxidation reaction occurs between the oxidation catalyst 43 and the difficult-to-decompose substances contained in the gas, and the substances are decomposed.

[Control device 13]
The control device 13 controls the heating of the wastewater in the treatment tank 16 by the first heating device 22, the heating of the gas (steam or air) by the second heating device 23, the supply or replenishment of wastewater to the treatment tank 16 by the supply pump 61 or the like, the discharge of the concentrated wastewater (concentrated water) by the discharge pump 62 or the like, the supply of defoaming agent by the motor-operated valve 29A of the defoaming agent supply section 27, and the supply of water by the motor-operated valve 28A.

As shown in FIG. 2, the control device 13 includes a control unit 100 such as a sequencer. The housing of the control device 13 also includes an LCD monitor 106 and an operation unit 107 for inputting operation instructions.

The control unit 100 is connected to a memory unit 105, an LCD monitor 106, an operation unit 107, various sensors 32 to 35, various pumps 61, 62, various motor-operated valves 28A, 29A, 51A, 54A, a first heating device 22, and a second heating device 23, and is configured to be capable of mutual communication of signals and data. The LCD monitor 106 displays the wastewater level in the treatment tank 16 based on the output of the liquid level sensor 34.

The control unit 100 is a computer having a CPU 101, a ROM 102, a RAM 103, an EEPROM 104 (registered trademark), etc., and controls the wastewater treatment system 10. A control program is stored in the ROM 102, and the CPU 101 reads and executes the control program to perform the concentration process and low combustion process described below.

In the wastewater concentrator 11, which concentrates wastewater, when foam generated in the treatment tank 16 is detected by the foam sensor 33, an antifoaming agent is supplied from the antifoaming agent supply section 27 to the treatment tank 16. However, if the viscosity of the wastewater increases as a result of the wastewater being replenished from the wastewater tank 81 to the treatment tank 16, the generation of foam may not be sufficiently suppressed even if an antifoaming agent is supplied. In the wastewater concentrator 11, when foam generation is detected multiple times in succession, operation is abnormally stopped, the concentration process is stopped, and the wastewater in the treatment tank 16 must be discharged as industrial waste. In this case, there is a risk that wastewater that is not sufficiently concentrated will be discharged.

In contrast, in this embodiment, the wastewater concentrator 11 performs the concentration process and low combustion process described below so that the wastewater in the treatment tank 16 can be reliably concentrated.

[Concentration process]
Next, an example of the procedure of the concentration process executed by the control unit 100 of the wastewater concentrating apparatus 11 will be described with reference to the flowcharts of Figures 3 and 4, and the heating adjustment method of the present invention will be described. Here, Figures 3 and 4 are flowcharts showing an example of the procedure of the concentration process executed by the control unit 100 of the wastewater concentrating apparatus 11. In the figures, S11, S12, ... represent the numbers of the processing procedures (steps). 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.

For ease of explanation, the following describes an example in which the processing from step S11 onwards is performed when the treatment tank 16 and the water level tank 18 are both empty, the motor-operated valves 28A, 29A, 51A, 54A and 225 are closed, and the solenoid valve 55A is in the closed position.

In step S11, the control unit 100 performs a wastewater supply process (wastewater supply step) to supply wastewater to the treatment tank 16. Specifically, the control unit 100 controls the motor-operated valve 51A to operate the motor-operated valve 51A from the closed position to the open position, and also drives the supply pump 61. This starts the supply of wastewater from the wastewater tank 81 to the treatment tank 16.

When wastewater is supplied to the treatment tank 16 by the supply pump 61, the wastewater flows from the bottom of the treatment tank 16 through the connecting pipe 52 into the water level tank 18. When the wastewater is then stored up to the upper water level H1, the control unit 100 stops the supply of wastewater. Specifically, when the control unit 100 determines that the liquid level of the wastewater has reached the upper water level H1 based on the detection signal from the liquid level sensor 34, it returns the motor-operated valve 51A to the closed position and stops the supply pump 61, thereby stopping the supply of wastewater.

In the next step S12, the control unit 100 starts a heating process (heating step) to heat the wastewater stored in the treatment tank 16. Specifically, the control unit 100 operates the motor-operated valve 225 of the first heating device 22 from the closed position to the open position, and also drives the blower 224 to supply air to the piping 57, and then ignites the fuel gas in the burner 222 to burn the fuel gas. At this time, the first heating device 22 controls the heating so as to achieve a predetermined heating power. Specifically, the blower control unit 226, which has received a drive signal from the control unit 100, outputs a frequency signal of a predetermined reference frequency (e.g., 60 Hz) to the blower 224, and drives the blower 224 so as to achieve a predetermined rated air volume.

In step S12, the control unit 100 outputs a drive signal to the second heating control unit 23B of the second heating device 23 to drive the electric heater 23A of the second heating device 23. At this time, the second heating control unit 23B controls the heating of the electric heater 23A by PID control so that the inlet temperature of the oxidation catalyst 43 becomes a temperature at which the persistent substances can be oxidized. The control unit 100 also drives the air blower 24 to send air into the connecting duct 14. As a result, the water vapor generated in the treatment tank 16 is sucked into the connecting duct 14, and is further blown through the connecting duct 14 to the housing 41 and sent to the oxidation catalyst 43 side.

When the heating process of step S12 begins, the amount of wastewater stored in the treatment tank 16 gradually decreases due to the evaporation of the water content, and the wastewater becomes more concentrated.

In step S13, the control unit 100 determines whether the wastewater temperature has risen to an abnormal temperature (set temperature 105°C) based on the sensor signal from the temperature sensor 32. If it is determined that the wastewater temperature has risen to the set temperature, the control unit 100 outputs an error indicating an abnormal wastewater temperature to the LCD monitor 106, and performs error processing to stop the heating process by the first heating device 22 and the second heating device 23 (S131). After that, the series of processes ends.

If it is determined in step S13 that the wastewater is not at an abnormal temperature, the control unit 100 determines whether the wastewater in the treatment tank 16 has decreased to the make-up water level H2 (S14). This determination process is performed based on a detection signal from the liquid level sensor 34. If the control unit 100 determines that the liquid level of the wastewater has decreased to the make-up water level H2 (YES in S14), the process proceeds to the next step S15.

In step S15, it is determined whether the number of times the wastewater has been replenished has reached a predetermined set number N1. If it is determined that the number of times the wastewater has been replenished has not reached the set number N1, the control unit 100 proceeds to the next step S16.

The set number of times N1 is set to the number of times that will produce the desired concentrated water (e.g., wastewater with a water content of about 30%). In this embodiment, the set number of times N1 is set to 2000 times. Note that the value of this set number of times N1 is arbitrary and is determined according to the water content of the wastewater, the volume of the treatment tank 16, the set temperature of the wastewater to be heated (e.g., 105°C in this embodiment), etc.

In step S16, the control unit 100 performs a wastewater supply process (wastewater supply step) to supply wastewater to the treatment tank 16. This wastewater supply process is the same as the process in step S11 described above, so a detailed description will be omitted here. After that, the process returns to step S13, and the processes from step S13 onwards are performed. Note that step S16 is an example of the wastewater supply step of the present invention.

On the other hand, if it is determined in step S15 that the number of replenishments has reached the set number N1, the control unit 100 proceeds to step S17 and stops the heating process by the first heating device 22 and the second heating device 23 (S17).

Then, in step S18, the control unit 100 performs a concentrated water discharge process (concentrated water discharge step) to discharge the concentrated water accumulated in the treatment tank 16 after the concentration process. Specifically, the control unit 100 operates the motor-operated valve 54A from the closed position to the open position, and drives the discharge pump 62. The concentrated water is discharged from the bottom of the treatment tank 16, passes through the pipe 54, and is stored in the external tank 36.

If it is determined in step S14 that the wastewater level has not dropped to the make-up water level H2 (NO in S14), the control unit 100 determines in the next step S19 whether foam has been generated in the treatment tank 16 based on the sensor signal from the foam sensor 33. If it is determined that foam has been generated, the control unit 100 proceeds to step S23 in FIG. 4. On the other hand, if foam has not been detected, the control unit 100 proceeds to step S20.

In step S20, the control unit 100 judges whether the time elapsed since the last time bubbles were detected, that is, the time during which bubbles were not detected (hereinafter referred to as non-detection time), is equal to or longer than a predetermined set time T1. If the detected time is equal to or longer than the set time T1, it is judged whether or not the low combustion state described below is in progress (S21), and if the low combustion state is in progress, a combustion increase process is performed (S22). Here, the low combustion state is a state in which heating by the first heating device 22 is suppressed by the low combustion process (S25 in FIG. 4) described below, and the combustion of the burner 222 is suppressed. If bubbles have not been detected in the treatment tank 16 for the set time T1 or longer, it is not necessary to keep the low combustion state, so the control unit 100 increases the heating from the low combustion state and performs a process to increase the amount of combustion. Specifically, the control unit 100 increases the frequency of the frequency signal to the blower control unit 226 so as to increase the current air volume of the blower 224 by 10% of the rated air volume.

If it is determined in step S20 that the non-detection time is less than the set time T1, or if it is determined in step S21 that the low combustion state is not present, the control unit 100 returns to step S13 and performs the process of transitioning to step S13.

As shown in FIG. 4, when the process proceeds to step S23, the control unit 100 controls the motor valve 29A to supply defoaming agent from the defoaming agent supply unit 27 to the treatment tank 16 in order to eliminate the bubbles that have been generated in the treatment tank 16. Note that step S23 is an example of the defoaming agent supply process of the present invention.

In the next step S24, the control unit 100 judges whether or not foam is detected again before a predetermined set time T10 (an example of the first set time of the present invention) has elapsed. In other words, the control unit 100 judges whether or not foam is detected again by the foam sensor 33 before the set time T10 has elapsed since the defoaming agent was supplied. Here, the set time T10 is a reference time for judging whether or not to execute the low combustion process described below, and in this embodiment, the set time T10 is set to 60 seconds. The set time T10 may be counted from the time when the supply of the defoaming agent is started (the time when the motor valve 29A is opened) or from the time when the supply of the defoaming agent is completed (the time when the motor valve 29A is closed).

If bubbles are detected again before the set time T10 has elapsed in step S24, the control unit 100 performs a low-burn process in the next step S25 to suppress heating by the first heating device 22. The low-burn process is, for example, a process of reducing the frequency of the frequency signal to the blower control unit 226 so as to reduce the current air volume of the blower 224 by 10% of the rated air volume. The control unit 100 performing such a process is an example of a heating control unit of the present invention. Step S25 is also an example of a heating suppression step of the present invention. On the other hand, if bubbles are not detected again before the set time T10 has elapsed in step S24, the control unit 100 does not perform the low-burn process, but returns to step S13 and performs the processes from step S13 onwards.

As described above, in this embodiment, in the wastewater concentrating device 11, when the liquid level of the wastewater in the treatment tank 16 drops to the refill water level H2 due to evaporation of the water contained in the wastewater, the wastewater is replenished to the treatment tank 16, and when foam is detected by the foam sensor 33 before the predetermined set time T10 has elapsed since the end of the refill of the wastewater, a low combustion process is performed to suppress heating by the first heating device 22. This makes it possible to suppress heating by the first heating device 22 to a level where foam is not generated in the treatment tank 16. As a result, the wastewater concentrating device 11 can be operated continuously without immediately stopping abnormally when foam is generated. In addition, by operating continuously although the heating power is suppressed, the wastewater concentration can be concentrated until the desired concentrated water (for example, wastewater with a water content of about 30%) is obtained without stopping halfway.

The low combustion process (S25) shown in FIG. 4 may be executed, for example, according to the flowchart shown in FIG. 5. Here, FIG. 5 is a flowchart showing another example of the procedure of the low combustion process.

As shown in FIG. 5, the low combustion process is a process in which the shorter the time Tr from when the defoaming agent is supplied until foam is detected again (hereinafter referred to as the redetection time Tr), the greater the amount of heating suppression by the first heating device 22, i.e., the smaller the amount of fuel.

Specifically, first, in step S251, the control unit 100 determines whether the redetection time Tr is equal to or greater than the preset time T11. The preset time T11 is, for example, 30 seconds. That is, the control unit 100 determines whether the redetection time Tr is equal to or greater than the preset time T11 and less than the preset time T10. Here, when it is determined that the redetection time Tr is equal to or greater than the preset time T11, the control unit 100 reduces the frequency of the frequency signal to the blower control unit 226 so as to reduce the air volume supplied by the blower 224 by 15% of the rated air volume (S252). Specifically, the blower control unit 226 outputs a frequency signal whose frequency is 15% lower than the reference frequency (for example, 60 Hz) to the blower 224. Then, the process returns to step S13.

If it is determined in step S251 that the redetection time Tr is less than the set time T11, the control unit 100 determines in the next step S253 whether the redetection time Tr is equal to or greater than a predetermined set time T12. The set time T12 is, for example, 10 seconds. That is, the control unit 100 determines whether the redetection time Tr is equal to or greater than the set time T12 and less than the set time T11. Here, if it is determined that the redetection time Tr is equal to or greater than the set time T12, the control unit 100 reduces the frequency of the frequency signal to the blower control unit 226 so as to reduce the air volume supplied by the blower 224 by 30% of the rated air volume (S254). Specifically, the blower control unit 226 outputs a frequency signal whose frequency is 30% lower than the reference frequency (for example, 60 Hz) to the blower 224. Then, the process returns to step S13.

If it is determined in step S253 that the redetection time Tr is less than the set time T12, the control unit 100 determines in the next step S255 whether the redetection time Tr is equal to or greater than a predetermined set time T13. The set time T13 is, for example, 3 seconds. That is, the control unit 100 determines whether the redetection time Tr is equal to or greater than the set time T13 and less than the set time T12. Here, if it is determined that the redetection time Tr is equal to or greater than the set time T13, the control unit 100 reduces the frequency of the frequency signal to the blower control unit 226 so as to reduce the air volume supplied by the blower 224 by 45% of the rated air volume (S256). Specifically, the blower control unit 226 outputs a frequency signal whose frequency is 45% lower than the reference frequency (for example, 60 Hz) to the blower 224. Then, the process returns to step S13.

Also, when it is determined in step S255 that the redetection time Tr is less than the predetermined set time T13, the control unit 100 reduces the frequency of the frequency signal to the blower control unit 226 so as to reduce the air volume supplied by the blower 224 by 60% of the rated air volume (S257). Specifically, the blower control unit 226 outputs a frequency signal whose frequency is 60% lower than the reference frequency (e.g., 60 Hz) to the blower 224. Then, the process returns to step S13.

By performing this low combustion process, the heating strength of the first heating device 22 can be gradually reduced until bubbles are no longer easily generated.

In this embodiment, as shown in FIG. 4, a processing example in which the determination process of step S24 is performed after the defoaming agent is supplied has been described, but the present invention is not limited to such a processing example. For example, as shown in FIG. 6, when foam is detected by the foam sensor 33 before a predetermined set time T20 (an example of the second set time of the present invention) has elapsed since wastewater was replenished into the treatment tank 16, a low combustion process that suppresses heating by the first heating device 22 may be performed. Here, the set time T20 is set to a time shorter than the set time T10. The set time T20 is a reference time for determining whether foam is detected immediately after the replenishment of wastewater in step S16, and is set to, for example, 5 seconds in this embodiment. In other words, when foam is detected within the set time T2 after the wastewater is replenished and the replenishment is completed, the control unit 100 operates the motor valve 28A to perform a water addition process (S232) in which water is supplied to the treatment tank 16, and then performs a low combustion process (S25).

For example, when highly viscous wastewater is replenished into the treatment tank 16, bubbles are likely to form. By carrying out this type of treatment, the intensity of heating by the first heating device 22 can be reduced by the low combustion treatment to a level at which bubbles do not form in the treatment tank 16, without waiting for the set time T10 to elapse.

10: Wastewater treatment system, 11: Wastewater concentrator, 12: Decomposition treatment device,
13: control device, 16: treatment tank, 18: water level tank,
22: first heating device, 23: second heating device, 27: defoamer supplying section,
32: temperature sensor, 33: bubble sensor, 34: liquid level sensor,
35: temperature sensor, 37: air tank, 51A: motor valve,
54A: Motor valve, 55: Air pipe, 55A: Solenoid valve,
61: supply pump, 62: discharge pump, 81: wastewater tank,
100: control unit, 221: combustion furnace, 222: burner,
223: pressure equalizing valve, 224: blower, 225: motor valve,
226: Blower control unit

Claims (5)

A waste liquid treatment apparatus for concentrating waste liquid by heating the waste liquid contained in a treatment tank and evaporating the water contained therein,
a heating unit for heating the waste liquid in the treatment tank;
A foam detection unit that detects foam generated in the treatment tank;
a defoaming agent supplying unit that supplies a defoaming agent to the treatment tank when the foam is detected by the foam detecting unit;
a heating control unit that suppresses heating by the heating unit when the foam is detected again by the foam detection unit before a predetermined first set time has elapsed since the defoaming agent was supplied. The waste liquid treatment device according to claim 1, wherein the heating control unit increases the amount of heating suppression by the heating unit as the first set time becomes shorter. A waste liquid treatment apparatus for concentrating waste liquid by heating the waste liquid contained in a treatment tank and evaporating the water contained therein,
a heating unit for heating the waste liquid in the treatment tank;
A foam detection unit that detects foam generated in the treatment tank;
a waste liquid supply unit that supplies the waste liquid to the treatment tank when the liquid level of the waste liquid in the treatment tank drops to a make-up water level due to evaporation of the contained moisture;
a heating control unit that suppresses heating by the heating unit when the bubble detection unit detects a bubble before a predetermined second set time has elapsed since the waste liquid supply unit supplies the waste liquid. A heating and adjusting method applied to a waste liquid treatment apparatus for concentrating a waste liquid by heating the waste liquid contained in a treatment tank and evaporating the water contained therein, comprising:
The waste liquid treatment device includes a heating unit that heats the waste liquid in the treatment tank, and a foam detection unit that detects foam generated in the treatment tank,
a defoaming agent supplying step of supplying a defoaming agent to the treatment tank when the foam is detected by the foam detection unit;
a heating suppression process for suppressing heating by the heating unit if the foam is detected again by the foam detection unit before a predetermined first set time has elapsed since the defoaming agent was supplied. A heating and adjusting method applied to a waste liquid treatment apparatus for concentrating a waste liquid by heating the waste liquid contained in a treatment tank and evaporating the water contained therein, comprising:
The waste liquid treatment device includes a heating unit that heats the waste liquid in the treatment tank, and a foam detection unit that detects foam generated in the treatment tank,
a waste liquid supplying step of supplying the waste liquid to the treatment tank when the liquid level of the waste liquid in the treatment tank drops to a make-up water level due to evaporation of the contained moisture;
and a heating suppression process for suppressing heating by the heating section when the bubble is detected by the bubble detection section before a predetermined second set time has elapsed since the waste liquid is supplied by the waste liquid supply process.