Wastewater treatment system, steam recycling system, wastewater treatment method, and steam recycling method

Abstract

To provide a waste liquid treatment system capable of manufacturing a liquid fuel having a viscosity stable in an extended period from an organic solvent-containing coating.SOLUTION: A waste liquid treatment system relating to this invention is a waste liquid treatment system for manufacturing a liquid fuel by treating a coating waste liquid containing an organic solvent bearing isocyanate groups, discharged from an organic compound manufacturing facility. The system is assembled with a waste liquid container to which an aqueous alcohol solution and the organic solvent-containing coating waste liquid are supplied, an aqueous alcohol solution feed section for supplying the aqueous alcohol solution to the waste liquid container, and an agitation section for agitation of a mixed solution containing the organic solvent-containing coating waste liquid and the aqueous alcohol solution supplied to the waste liquid container from the organic compound manufacturing facility, wherein the content of the aqueous alcohol solution in the waste liquid container is 0.5-30 wt.% relative to 100 wt.% of the organic solvent-containing coating waste liquid.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present invention relates to a waste liquid treatment system, a steam recycling system, a waste liquid treatment method, and a steam recycling method.

Background Art

[0002] Resin compositions such as paints, adhesives, and adhesives (paints, etc.) are manufactured using organic solvents as raw materials, and waste liquids containing organic solvents (solvent waste liquids) are discharged from paint manufacturing facilities and the like. Such solvent waste liquids need to be treated as industrial waste. Therefore, in order to recycle solvent waste liquids and reduce the amount of industrial waste discharged, there is a waste liquid treatment system that generates liquid fuel by treating solvent waste liquids by heating or the like. <000001{0}>

[0003] As a waste liquid treatment system for treating such solvent waste liquids, for example, an emulsion generator is disclosed that generates an emulsified fuel by adding water to a liquid fuel such as heavy oil and light oil and repeatedly causing a pressurized collision between the oil and water in a storage tank (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Resin compositions such as paints often contain curing agents with isocyanate groups as organic solvents, and curing agents with isocyanate groups readily react with water and alcohol. Therefore, in conventional wastewater treatment systems such as the emulsion generator described in Patent Document 1, there was a problem in that the curing agent contained in the solvent wastewater reacted with water and alcohol and solidified, and when it adhered to the inner walls of the pipes and the pumps installed in the pipes, the transport performance of the solvent wastewater deteriorated. If the solvent wastewater solidifies in the liquid transport system such as pipes and pumps, in the worst case, the solidified solvent wastewater cannot be removed from the liquid transport system, and the entire pipe may need to be replaced.

[0006] Furthermore, even before the solvent waste liquid solidifies, the viscosity increases, which can raise the pressure inside the pipes through which the solvent waste liquid passes. This can cause detection devices such as sensors installed in the pipes to detect an abnormal condition and shut down, posing a problem.

[0007] Furthermore, if the waste welding material is transported to a combustion facility such as a boiler in a solidified state and burned, some of the waste welding material may reach high temperatures (for example, 1200°C), potentially generating flames, making it impossible to safely burn and process it in a combustion facility.

[0008] One aspect of the present invention aims to provide a wastewater treatment system capable of producing a liquid fuel having stable viscosity over a long period of time from an organic solvent-containing paint. [Means for solving the problem]

[0009] One aspect of the present invention is, A wastewater treatment system for producing liquid fuel by treating paint wastewater containing isocyanate groups and organic solvents discharged from an organic compound manufacturing facility, A waste liquid container into which an alcohol aqueous solution and the paint waste liquid containing the organic solvent are supplied, An alcohol aqueous solution supply unit that supplies the alcohol aqueous solution into the waste liquid container, A stirring unit for stirring a mixed solution containing the organic solvent-containing paint waste liquid and the alcohol aqueous solution supplied from the organic compound manufacturing equipment into the waste liquid container, Equipped with, This wastewater treatment system is characterized in that the alcohol aqueous solution content in the wastewater container is 0.5 wt% to 30 wt% relative to 100 wt% of the organic solvent-containing paint wastewater. [Effects of the Invention]

[0010] One embodiment of the wastewater treatment system according to the present invention can produce a liquid fuel having stable viscosity over a long period of time from paint containing an organic solvent. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing the configuration of a wastewater treatment system according to the first embodiment. [Figure 2] This figure shows an example of the configuration of an energy recycling system that includes a wastewater treatment system. [Figure 3] This figure shows an example of another configuration of a wastewater treatment system. [Figure 4] This figure shows an example of the configuration of a wastewater treatment system according to the second embodiment. [Figure 5] This figure shows an example of the configuration of a wastewater treatment system according to the third embodiment. [Figure 6] This figure shows an example of the configuration of a wastewater treatment system according to the fourth embodiment. [Figure 7] This figure shows an example of the configuration of a wastewater treatment system according to the fifth embodiment. [Figure 8] This figure shows the relationship between elapsed time and viscosity for Examples 1-9 and Comparative Example 1. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described in detail. For ease of understanding the description, the same reference numerals are given to the same components in each drawing, and duplicate descriptions are omitted. Also, the scales of the respective members in the drawings may be different from the actual ones. In this specification, “~” indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value, unless otherwise specified.

[0013] [First Embodiment] <Waste Liquid Treatment System> The waste liquid treatment system according to the first embodiment will be described. FIG. 1 is a diagram showing the configuration of the waste liquid treatment system according to this embodiment. As shown in FIG. 1, the waste liquid treatment system 1A according to this embodiment includes a waste liquid container 10, an alcohol aqueous solution supply unit 20A, a stirring unit 30, and a moving unit 40, and treats the organic solvent-containing paint waste liquid (paint waste liquid) discharged from the organic compound manufacturing facility 2 in the waste liquid container 10 to produce liquid fuel. The paint waste liquid may be pre-filtered by a filtration device 3 to remove impurities.

[0014] Note that the organic compound manufacturing facility 2 is, for example, a facility that discharges VOC gas and paint waste liquid using fuels, materials, paints, etc. The paint waste liquid in the organic compound manufacturing facility 2 is transported to the waste liquid container 10 through the paint waste liquid supply line 4. The amount of the paint waste liquid discharged from the organic compound manufacturing facility 2 is adjusted by an adjustment valve V1 provided in the paint waste liquid supply line 4 discharged from the organic compound manufacturing facility 2.

[0015] The paint waste liquid is a solution containing a compound having an isocyanate group. Examples of the compound having an isocyanate group include those contained in curing agents and the like.

[0016] The liquid fuel is a highly viscous gel-like fuel and can be used as fuel for external combustion engines and internal combustion engines such as boilers, regenerative thermal oxidizers (RTOs), and engines.

[0017] The waste liquid container 10 is a container that stores the alcohol aqueous solution and the paint waste liquid supplied thereto.

[0018] In this embodiment, when the alcohol aqueous solution is supplied from the alcohol aqueous solution supply unit 20A into the waste liquid container 10, the waste liquid container 10 is installed in the first arrangement area A1. When the paint waste liquid discharged from the organic compound manufacturing facility 2 is supplied into the waste liquid container 10, it is installed in the second arrangement area A2. When the stirring unit 30 is provided in the waste liquid container 10, it is installed in the third arrangement area.

[0019] The first arrangement area A1, the second arrangement area A2, and the third arrangement area may be any places where the supply of the alcohol aqueous solution, the supply of the paint waste liquid, the installation of the stirring unit 30, etc. can be carried out, and are not particularly limited.

[0020] The alcohol aqueous solution supply unit 20A includes an alcohol aqueous solution storage unit 201 for storing the alcohol aqueous solution, an alcohol aqueous solution supply pipe 202 for sending the alcohol aqueous solution to the waste liquid container 10, and an adjustment valve V11 for adjusting the supply amount of the alcohol aqueous solution. The alcohol aqueous solution supply unit 20A supplies the alcohol aqueous solution into the waste liquid container 10. The alcohol aqueous solution functions as an anti-caking agent for suppressing the solidification of the paint waste liquid.

[0021] Examples of the alcohol include methanol, ethanol, butanol, isopropyl alcohol (IPA), etc.

[0022] The content of alcohol in the alcohol aqueous solution supplied into the waste liquid container 10 is 0.5 wt% to 30 wt% with respect to 100 wt% of the paint waste liquid, preferably 3 wt% to 20 wt%, and more preferably 5 wt% to 15 wt%.

[0023] The alcohol aqueous solution supply unit 20A preferably has a molar ratio of 2 / 3 to 1.0, and more preferably 4 / 5 to 0.98, with respect to the amount of the compound having an isocyanate group contained in the paint waste liquid.

[0024] The stirring unit 30 is provided in the waste liquid container 10 and stirs the mixed solution containing the paint waste liquid and the alcohol aqueous solution.

[0025] The stirring unit 30 comprises a stirring blade 31, a stirring shaft 32, and a motor 33. A general-purpose stirring blade is used as the stirring blade 31.

[0026] The moving unit 40 sequentially moves the waste liquid container 10 to the first placement area A1, the second placement area A2, and the third placement area A3.

[0027] The moving unit 40 can be any means capable of moving the waste liquid container 10, such as a roller conveyor or a belt conveyor. Alternatively, the waste liquid container 10 may be moved by an operator instead of being moved by the moving unit 40.

[0028] The wastewater treatment method according to this embodiment will now be described. The wastewater treatment method according to this embodiment is performed using the wastewater treatment system 1A.

[0029] As shown in Figure 1, first, the waste liquid container 10 is placed in the first arrangement area A1, and an alcohol aqueous solution is supplied into the waste liquid container 10 (alcohol aqueous solution supply step).

[0030] Next, the waste liquid container 10 is moved from the first placement area A1 to the second placement area A2, and paint waste liquid is supplied into the waste liquid container 10 (paint waste liquid supply process). Specifically, the control valve V1 is opened to discharge the paint waste liquid from the organic compound manufacturing equipment 2 to the paint waste liquid supply line 4, and after impurities in the paint waste liquid are removed by the filtration device 3, the paint waste liquid is supplied into the waste liquid container 10.

[0031] By supplying paint waste liquid, the mixed solution containing the alcohol aqueous solution and the paint waste liquid may be filled to the full capacity of the waste liquid container 10.

[0032] The paint waste liquid is supplied in such a way that the alcohol content in the alcohol aqueous solution contained in the waste liquid container 10 is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid.

[0033] Next, the waste liquid container 10 is moved from the second placement area A2 to the third placement area A3, the stirring blade 31 and stirring shaft 32 are inserted into the waste liquid container 10, and then the motor 33 is driven to rotate the stirring blade 31 via the stirring shaft 32 to stir the mixed solution (stirring process).

[0034] The stirring time is not particularly limited and is appropriately selected depending on the amount of alcohol aqueous solution, the amount of paint waste liquid, the amount of mixed solution, the mixing ratio of the alcohol aqueous solution and the paint waste liquid, etc. For example, it is 60 minutes or less, and more preferably 10 seconds to 1200 seconds.

[0035] Next, after removing the stirring blade 31 from the waste liquid container 10, the lid 51 is placed on the waste liquid container 10 to preserve the mixed solution inside.

[0036] This process involves treating paint wastewater containing isocyanate groups, discharged from organic compound manufacturing facilities, to produce liquid fuel.

[0037] When using liquid fuel, the lid 51 is removed and the liquid fuel extraction pipe 52 is inserted into the waste liquid container 10. The liquid fuel in the waste liquid container 10 is extracted through the liquid fuel extraction pipe 52 to combustion equipment such as a combustion boiler and used as fuel.

[0038] Once all the liquid fuel in the waste liquid container 10 has been drained and the container is empty, the waste liquid container 10 is moved back to the first placement area A1 for recycling.

[0039] Thus, the wastewater treatment system 1A comprises a wastewater container 10, an alcohol aqueous solution supply unit 20A, and a stirring unit 30. The wastewater treatment system 1A supplies an alcohol aqueous solution and paint wastewater into the wastewater container 10 and stirs the mixed solution containing the alcohol aqueous solution and paint wastewater in the wastewater container 10, thereby suppressing the hardening and solidification of the paint contained in the mixed solution and converting the paint wastewater into liquid fuel. The paint wastewater contains a hydrophobic organic solvent that does not react with compounds having isocyanate groups, which are curing agents. The alcohol aqueous solution contains alcohol that is compatible with the organic solvent, and therefore can function as a treatment liquid that prevents the solidification of isocyanate groups. The wastewater treatment system 1A mixes paint wastewater with an alcohol aqueous solution in the wastewater container 10, causing a chemical reaction between the isocyanate groups, which are curing agents contained in the paint wastewater, and the alcohol or water. This suppresses the lengthening and three-dimensional networking of resin components in the paint wastewater, and prevents the curing agent in the paint wastewater from solidifying and increasing viscosity due to the alcohol aqueous solution. As a result, the liquid fuel can be stored for a long period of time with a stable viscosity. Therefore, the liquid fuel can be stored at room temperature for a long period of time, for example, more than one month. Thus, the wastewater treatment system 1A can produce liquid fuel with stable viscosity for a long period of time.

[0040] The viscosity of liquid fuels, which is used as an indicator of the viscosity of liquid fuels, can be measured using general measurement methods, such as measuring it using a flat-plate rotational viscometer (cone-plate viscometer) or a concentric cylindrical viscometer, in accordance with JIS K5600-2-3:2014.

[0041] Furthermore, the wastewater treatment system 1A can produce liquid fuel from paint wastewater, and since the liquid fuel can be used as auxiliary fuel for boilers and the like, it can add value to paint wastewater by giving it the potential to be used as fuel.

[0042] Furthermore, since the waste liquid treatment system 1A can recover and reuse the waste liquid container 10, it is possible to reduce the disposal of the contents contained in the waste liquid container 10.

[0043] Furthermore, the wastewater treatment system 1A suppresses the solidification of compounds containing isocyanate groups in the paint wastewater by using water in the alcohol aqueous solution, and also effectively lowers the flame temperature by removing heat of vaporization (sensible and latent heat) within the flame during the combustion of the liquid fuel. For example, it can suppress the generation of thermal NOx.

[0044] The waste liquid treatment system 1A can use its mobile unit 40 to supply an alcohol aqueous solution into the waste liquid container 10 in a first placement area A1, to supply paint waste liquid into the waste liquid container 10 in a second placement area A2, and to stir the mixed solution in the waste liquid container 10 in a third placement area A3. This allows the waste liquid treatment system 1A to supply an alcohol aqueous solution into the waste liquid container 10, to supply paint waste liquid into the waste liquid container 10, and to stir the mixed solution in the waste liquid container 10 while moving the waste liquid container 10 to the most appropriate area as needed.

[0045] The waste liquid treatment system 1A can supply paint waste liquid to the waste liquid container 10 via the paint waste liquid supply line 4. This allows the waste liquid treatment system 1A to automatically transport paint waste liquid from the organic compound manufacturing facility 2 to the waste liquid container 10 by passing it through the paint waste liquid supply line 4.

[0046] As described above, the wastewater treatment system 1A can produce liquid fuel with stable viscosity over a long period of time, making it suitable for use in energy recycling systems that generate steam and the like.

[0047] <Energy Recycling System> This section describes an energy recycling system that applies the wastewater treatment system 1A. Figure 2 shows an example of the configuration of an energy recycling system equipped with the wastewater treatment system 1A. As shown in Figure 2, the energy recycling system 100 includes a wastewater treatment system 110, a combustion boiler 120, a fuel-fired boiler 130, a liquid fuel supply line L10, a steam recycling line L20, and an energy supply line L30. Note that the wastewater treatment system 110 is the same as the wastewater treatment system 1A described above, so details are omitted.

[0048] The combustion boiler 120 generates steam using liquid fuel supplied from the wastewater treatment system 110 via the liquid fuel supply line L10. The combustion boiler 120 can be a general-purpose combustion boiler. In this embodiment, the combustion equipment is not particularly limited to the combustion boiler 120, as long as it is capable of generating steam using liquid fuel.

[0049] The fuel-fired boiler 130 generates steam using fuel supplied from an external source. The fuel-fired boiler 130 can be a general-purpose combustion boiler. In this embodiment, the combustion equipment capable of generating steam using fuel is not particularly limited to the fuel-fired boiler 130.

[0050] The liquid fuel supply line L10 is a supply pipe that connects the wastewater treatment system 110 and the combustion boiler 120, and supplies liquid fuel from the wastewater treatment system 110 to the combustion boiler 120.

[0051] The steam recycling line L20 is a supply pipe for supplying steam generated by the combustion boiler 120 to the steam transport line L30.

[0052] The energy supply line L30 is a supply pipe for transporting steam generated by the fuel-fired boiler 130 to the steam utilization equipment 140.

[0053] In the energy recycling system 100, liquid fuel is produced in the wastewater treatment system 1A (liquid fuel production process). The liquid fuel produced in the wastewater treatment system 1A is supplied to the combustion boiler 120 through the liquid fuel supply line L10, where steam is generated using the supplied liquid fuel (steam generation process). The steam generated in the combustion boiler 120 is supplied to the energy supply line L30 through the steam recycling line L20, where it is generated in the fuel-fired boiler 130 and mixed with the steam flowing through the energy supply line L30 (steam recycling process). The steam flowing through the energy supply line L30 is sent to the steam utilization equipment 140 for use.

[0054] The energy recycling system 100, equipped with a waste liquid treatment system 1A, can produce liquid fuel and store the produced liquid fuel stably for a long period of time. This reduces the amount of used paint waste liquid discharged to the outside as industrial waste, and it can also be used as fuel when generating steam in the combustion boiler 120.

[0055] In this embodiment, as shown in Figure 1, the waste liquid treatment system 1A supplies an alcohol aqueous solution into the waste liquid container 10 from an alcohol aqueous solution supply unit 20A. However, as shown in Figure 3, the waste liquid treatment system 1A may also include an alcohol aqueous solution supply unit 20B having a water supply unit 21 for supplying water into the waste liquid container 10 and an alcohol supply unit 22 for supplying alcohol. In this embodiment, water may be supplied into the waste liquid container 10 from the water supply unit 21 and alcohol from the alcohol aqueous solution supply unit 22B. The water supply unit 21 may include a water storage unit 211 for storing water, a water supply pipe 212 for sending water to the waste liquid container 10, and a control valve V12 for adjusting the amount of water supplied. The alcohol supply unit 22 may include an alcohol storage unit 221 for storing alcohol, an alcohol supply pipe 222 for sending alcohol to the waste liquid container 10, and a control valve V13 for adjusting the amount of alcohol supplied.

[0056] [Second Embodiment] A wastewater treatment system according to the second embodiment will now be described. The wastewater treatment system according to this embodiment produces liquid fuel without moving the wastewater container 10, in the same manner as the wastewater treatment system 1A according to the first embodiment described above.

[0057] Figure 4 shows an example of the configuration of the wastewater treatment system according to this embodiment. As shown in Figure 4, the wastewater treatment system 1B according to this embodiment does not have the moving part 40 of the wastewater treatment system 1A according to the first embodiment described above, and comprises a wastewater container 10, an alcohol aqueous solution supply unit 20B, a stirring unit 30, a mass measuring unit 60, and a storage tank 70. The wastewater container 10, the alcohol aqueous solution supply unit 20B, and the stirring unit 30 are the same as those of the wastewater treatment system 1A according to the first embodiment described above, so details are omitted.

[0058] The mass measuring unit 60 is a device for measuring the mass of the waste liquid container 10, and can use, for example, a load cell.

[0059] The storage tank 70 is a tank for storing the manufactured liquid fuel. The storage tank 70 is not particularly limited and can be used as long as it is a tank capable of storing the manufactured liquid fuel.

[0060] A wastewater treatment method using the wastewater treatment system 1B according to this embodiment will be described.

[0061] First, an alcohol aqueous solution is supplied into the waste liquid container 10 (alcohol aqueous solution supply process). The alcohol aqueous solution supply process includes a process of supplying water from the water supply unit 21 into the waste liquid container 10 (water supply process) and a process of supplying alcohol from the alcohol supply unit 22 into the waste liquid container 10 (alcohol supply process).

[0062] In the water supply process, the control valve V12 is opened to supply water from the water storage section 211 to the waste liquid container 10 via the water supply pipe 212.

[0063] In the alcohol supply process, the control valve V13 is opened to supply alcohol from the alcohol storage section 221 to the waste liquid container 10 via the alcohol supply pipe 222.

[0064] In the waste liquid container 10, water and alcohol are mixed to produce an alcohol aqueous solution.

[0065] The alcohol supply process may be performed before the water supply process, or it may be performed simultaneously with the water supply process.

[0066] Next, the control valve V1 is opened to discharge the paint waste liquid from the organic compound manufacturing equipment 2 to the paint waste liquid supply line 4. After removing impurities from the paint waste liquid using the filtration device 3, the paint waste liquid is supplied into the waste liquid container 10 (paint waste liquid supply process).

[0067] The amount of alcohol aqueous solution generated in the waste liquid container 10 is supplied in such a way that it is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid.

[0068] The alcohol aqueous solution content is measured to determine whether it is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid (alcohol aqueous solution content measurement step). Whether the alcohol aqueous solution content is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid is determined by measuring the weight of the waste liquid container 10 with the mass measuring unit 60. The mass measuring unit 60 can determine the alcohol aqueous solution content relative to the paint waste liquid from the increase in the mass of the waste liquid container 10 after the paint waste liquid has been supplied, using the mass of the waste liquid container 10 containing the alcohol aqueous solution as a reference.

[0069] The step of measuring the alcohol content of the aqueous solution may be performed after the paint waste liquid supply step, or it may be performed simultaneously.

[0070] Next, the motor 33 is driven into the waste liquid container 10 to rotate the stirring blade 31 and stir the mixed solution containing the alcohol aqueous solution and the paint waste liquid (stirring step).

[0071] The stirring time for the mixed solution is not particularly limited and may be set as appropriate.

[0072] Liquid fuel is produced by reacting paint waste liquid discharged from organic compound manufacturing facility 2 with an alcohol aqueous solution while stirring.

[0073] Next, the control valve V14 is opened to operate the pump 71, which extracts the mixed solution in the waste liquid container 10 to the solution storage line 72. The extracted mixed solution is then supplied to the storage tank 70 through the solution storage line 72 and stored in the storage tank 70 (storage process).

[0074] When liquid fuel is used, the pump 73 is operated to extract the liquid fuel from the storage tank 70 to the liquid fuel extraction line 74, which is then sent to combustion equipment such as a combustion boiler for use as fuel.

[0075] The wastewater treatment system 1B, comprising a wastewater container 10, an alcohol aqueous solution supply unit 20B, a stirring unit 30, a mass measuring unit 60, and a storage tank 70, can supply and mix a predetermined amount of alcohol aqueous solution into the paint wastewater, similar to the wastewater treatment system 1A. As a result, the wastewater treatment system 1B can suppress the solidification of the hardener in the paint wastewater by the alcohol aqueous solution, thereby increasing its viscosity. Therefore, the wastewater treatment system 1B can produce liquid fuel with stable viscosity over a long period of time.

[0076] Furthermore, like the wastewater treatment system 1A, the wastewater treatment system 1B can add value to paint wastewater by making it usable as fuel, and it can also recover and reuse the wastewater container 10, thus reducing the disposal of the contents contained in the wastewater container 10. In addition, like the wastewater treatment system 1A, the wastewater treatment system 1B can suppress, for example, the generation of thermal NOx.

[0077] [Third Embodiment] A wastewater treatment system according to a third embodiment will now be described. Figure 5 shows an example of the configuration of the wastewater treatment system according to this embodiment. As shown in Figure 5, the wastewater treatment system 1C according to this embodiment is the same as the wastewater treatment system 1B according to the second embodiment described above, but with a liquid level detection unit 80 instead of a mass measuring unit 60.

[0078] The liquid level detection unit 80 is installed on the wall of the waste liquid container 10 and detects the liquid level of the mixed waste liquid containing paint waste liquid and alcohol aqueous solution inside the waste liquid container 10. For example, a liquid level sensor can be used as the liquid level detection unit 80.

[0079] The liquid level detection unit 80 includes a liquid level detection unit 80A provided near the lower surface of the wall of the waste liquid container 10, and a liquid level detection unit 80B provided near the upper surface of the wall of the waste liquid container 10.

[0080] The liquid level detection unit 80A is preferably installed at a position where the amount of alcohol aqueous solution generated in the waste liquid container 10 reaches a predetermined standard amount. By detecting the presence or absence of alcohol aqueous solution using the liquid level detection unit 80A, it is possible to detect that a predetermined amount of alcohol aqueous solution has been supplied to the waste liquid container 10.

[0081] The liquid level detection unit 80B is preferably installed at a position where the content of the paint waste liquid supplied to the waste liquid container 10 is a predetermined standard amount. The predetermined standard amount is preferably, for example, a position where the alcohol content in the alcohol aqueous solution is 0.5 wt% to 30 wt% relative to 100 wt% of the paint waste liquid. By detecting the presence or absence of the mixed solution with the liquid level detection unit 80B, it is possible to detect that the amount of mixed solution in the waste liquid container 10 is sufficient to satisfy the condition where the alcohol content in the alcohol aqueous solution is 0.5 wt% to 30 wt% relative to 100 wt% of the paint waste liquid.

[0082] A wastewater treatment method using the wastewater treatment system 1C according to this embodiment will be described.

[0083] First, an alcohol aqueous solution is supplied into the waste liquid container 10 (alcohol aqueous solution supply step). The alcohol aqueous solution supply step is the same as that of the waste liquid treatment system 1B according to the second embodiment described above, so the details are omitted.

[0084] Next, the control valve V1 is opened to discharge the paint waste liquid from the organic compound manufacturing equipment 2 to the paint waste liquid supply line 4. After removing impurities from the paint waste liquid using the filtration device 3, the paint waste liquid is supplied into the waste liquid container 10 (paint waste liquid supply process).

[0085] The amount of alcohol aqueous solution generated in the waste liquid container 10 is supplied in such a way that it is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid.

[0086] The alcohol aqueous solution content is measured to determine whether it is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid (alcohol aqueous solution content measurement process). Whether the alcohol aqueous solution content is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid is determined by detecting the alcohol aqueous solution and the mixed solution with liquid level detection units 80A and 80B. Liquid level detection unit 80A detects the liquid level of the alcohol aqueous solution and detects the mass of alcohol in the alcohol aqueous solution from the mixing ratio of alcohol and water. Liquid level detection unit 80B detects the liquid level of the mixed solution and detects the mass of paint waste liquid in the mixed solution from the difference between liquid level detection unit 80A and liquid level detection unit 80B. This allows the alcohol aqueous solution content relative to 100 wt% of the paint waste liquid to be determined.

[0087] Next, the motor 33 is driven into the waste liquid container 10 to rotate the stirring blade 31, stirring the mixed solution containing the alcohol aqueous solution and the paint waste liquid (stirring step). The mixed solution in the waste liquid container 10 is then drawn out into the solution storage line 72, and the drawn-out mixed solution is stored in the storage tank 70 (storage step). The paint waste liquid supply step and the stirring step are the same as those of the waste liquid treatment system 1B according to the second embodiment described above, so details are omitted.

[0088] The wastewater treatment system 1C comprises a wastewater container 10, an alcohol aqueous solution supply unit 20B, a stirring unit 30, a liquid level detection unit 80, and a storage tank 70. Similar to the wastewater treatment system 1A, it can supply and mix a predetermined amount of alcohol aqueous solution into the paint wastewater. This allows the wastewater treatment system 1C to suppress the solidification of the hardener in the paint wastewater by the alcohol aqueous solution, thereby increasing its viscosity. Consequently, the wastewater treatment system 1C can produce liquid fuel with stable viscosity over a long period of time.

[0089] Furthermore, like the wastewater treatment system 1A, the wastewater treatment system 1C can add value to paint wastewater by making it usable as fuel, and since the wastewater container 10 can be recovered and reused, the disposal of the contents contained in the wastewater container 10 can be reduced. In addition, like the wastewater treatment system 1A, the wastewater treatment system 1B can suppress, for example, the generation of thermal NOx.

[0090] [Fourth Embodiment] A wastewater treatment system according to the fourth embodiment will now be described. Figure 6 is a diagram showing an example of the configuration of the wastewater treatment system according to this embodiment. As shown in Figure 6, the wastewater treatment system 1D according to this embodiment is equipped with an alcohol aqueous solution supply unit 20C in place of the alcohol aqueous solution supply unit 20B in the wastewater treatment system 1C according to the third embodiment described above. The wastewater container 10, alcohol aqueous solution supply unit 20C, stirring unit 30, storage tank 70, and liquid level detection unit 80 are the same as those in the wastewater treatment system 1C according to the third embodiment described above, so details will be omitted.

[0091] In addition to the alcohol aqueous solution storage unit 201, the alcohol aqueous solution supply pipe 202, and the control valve V11, the alcohol aqueous solution supply unit 20C includes a quantitative tank 23 between the waste liquid container 10 of the alcohol aqueous solution supply pipe 202 and the control valve V11 of the alcohol aqueous solution supply unit 20A, and a control valve V15 between the quantitative tank 23 of the alcohol aqueous solution supply pipe 202 and the waste liquid container 10.

[0092] The quantitative tank 23 stores a predetermined amount of alcohol aqueous solution that is supplied to the waste liquid container 10. Preferably, the capacity of the quantitative tank 23 is designed to match the supply amount of alcohol aqueous solution that is supplied to the waste liquid container 10.

[0093] A wastewater treatment method using the wastewater treatment system 1D according to this embodiment will be described.

[0094] First, an alcohol aqueous solution is supplied into the waste liquid container 10 (alcohol aqueous solution supply process). The alcohol aqueous solution supply process includes a step of supplying a predetermined amount of alcohol aqueous solution to a quantitative tank 23 (quantitative tank supply process) and a step of supplying the predetermined amount of alcohol aqueous solution supplied to the quantitative tank 23 to a waste liquid container 10 (quantitative alcohol aqueous solution supply process).

[0095] In the quantitative tank supply process, the control valve V11 is opened to store a predetermined amount of alcohol aqueous solution from the alcohol aqueous solution storage section 201 into the quantitative tank 23 via the alcohol aqueous solution supply pipe 202.

[0096] In the quantitative alcohol aqueous solution supply process, the control valve V15 is opened to supply a predetermined amount of alcohol aqueous solution from the quantitative tank 23 into the waste liquid container 10.

[0097] Next, the control valve V1 is opened to discharge the paint waste liquid from the organic compound manufacturing equipment 2 to the paint waste liquid supply line 4. After removing impurities from the paint waste liquid using the filtration device 3, the paint waste liquid is supplied to the waste liquid container 10 (paint waste liquid supply step), and the alcohol aqueous solution content is measured to determine whether it is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid (alcohol aqueous solution content measurement step). Subsequently, the motor 33 is driven into the waste liquid container 10 to rotate the stirring blade 31 and stir the mixed solution containing the alcohol aqueous solution and the paint waste liquid (stirring step). The mixed solution in the waste liquid container 10 is then drawn out to the solution storage line 72, and the drawn-out mixed solution is stored in the storage tank 70 (storage step). The paint waste liquid supply step, the alcohol aqueous solution content measurement step, the stirring step, and the storage step are the same as those of the waste liquid treatment system 1B according to the second embodiment described above, so details are omitted.

[0098] The waste liquid treatment system 1D comprises a waste liquid container 10, an alcohol aqueous solution supply unit 20C, a stirring unit 30, a liquid level detection unit 80, and a storage tank 70. Similar to the waste liquid treatment system 1A, it can supply and mix a predetermined amount of alcohol aqueous solution into the paint waste liquid. This allows the waste liquid treatment system 1D to suppress the solidification of the hardener in the paint waste liquid by the alcohol aqueous solution, thereby increasing its viscosity. Consequently, the waste liquid treatment system 1D can produce a liquid fuel with stable viscosity over a long period of time.

[0099] Furthermore, like the wastewater treatment system 1A, the wastewater treatment system 1D can add value to paint wastewater by making it usable as fuel, and it can also recover and reuse the wastewater container 10, thus reducing the disposal of the contents contained in the wastewater container 10. In addition, like the wastewater treatment system 1A, the wastewater treatment system 1D can suppress, for example, the generation of thermal NOx.

[0100] [Fifth Embodiment] A wastewater treatment system according to the fifth embodiment will now be described. Figure 7 is a diagram showing an example of the configuration of the wastewater treatment system according to this embodiment. As shown in Figure 7, the wastewater treatment system 1E according to this embodiment is the same as the wastewater treatment system 1D according to the fourth embodiment described above, but uses an alcohol aqueous solution supply unit 20A instead of an alcohol aqueous solution supply unit 20C and includes a control unit 90.

[0101] The control unit 90 detects the detection result of the liquid level detection unit 80 and controls the adjustment valves V1, V11, V14 and the pump 71. The control unit 90 controls the amount of alcohol aqueous solution supplied to the waste liquid container 10, the amount of paint waste liquid supplied to the waste liquid container 10, and the amount of the mixed solution in the waste liquid container 10 supplied to the storage tank 70.

[0102] A wastewater treatment method using the wastewater treatment system 1E according to this embodiment will be described.

[0103] The control unit 90 supplies an alcohol aqueous solution into the waste liquid container 10 (alcohol aqueous solution supply step). The step of measuring the alcohol aqueous solution content is performed in the same manner as in the waste liquid treatment system 1C according to the second embodiment described above, so details are omitted. The alcohol aqueous solution supply step performed by the control unit 90 is performed in the same manner as in the waste liquid treatment system 1A according to the first embodiment described above, so details are omitted.

[0104] Next, the control unit 90 controls and opens the regulating valve V1, discharges the paint waste liquid from the organic compound manufacturing facility 2 to the paint waste liquid supply line 4, removes impurities from the paint waste liquid using the filtration device 3, and then supplies the paint waste liquid into the waste liquid container 10 (paint waste liquid supply process). The paint waste liquid supply process performed by the control unit 90 is carried out in the same manner as the waste liquid treatment system 1A according to the first embodiment described above, so details are omitted.

[0105] Based on the detection results of the liquid level detection units 80A and 80B, the control unit 90 measures whether the alcohol aqueous solution content is between 0.5 wt% and 30 wt% relative to 100 wt% of the paint waste liquid (alcohol aqueous solution content measurement step). The alcohol aqueous solution content measurement step performed by the control unit 90 is carried out in the same manner as in the waste liquid treatment system 1C according to the second embodiment described above, so details are omitted.

[0106] Subsequently, the control unit 90 controls and drives the motor 33 inside the waste liquid container 10 to rotate the stirring blade 31, thereby stirring the mixed solution containing the alcohol aqueous solution and the paint waste liquid (stirring step). The mixed solution in the waste liquid container 10 is then drawn out to the solution storage line 72, and the drawn-out mixed solution is stored in the storage tank 70 (storage step). The stirring step and storage step performed by the control unit 90 are carried out in the same manner as in the waste liquid treatment system 1B according to the second embodiment described above, so details are omitted.

[0107] The waste liquid treatment system 1E comprises a waste liquid container 10, an alcohol aqueous solution supply unit 20C, a stirring unit 30, a liquid level detection unit 80, a storage tank 70, and a control unit 90. This allows for automatic control of the supply amounts of paint waste liquid and alcohol aqueous solution to the waste liquid container 10, enabling the supply and mixing of a predetermined amount of alcohol aqueous solution into the paint waste liquid. As a result, the waste liquid treatment system 1E can suppress the solidification of the hardener in the paint waste liquid by the alcohol aqueous solution, thereby increasing its viscosity. Consequently, the waste liquid treatment system 1E can produce liquid fuel with stable viscosity over a long period of time.

[0108] Furthermore, like the wastewater treatment system 1A, the wastewater treatment system 1E can add value to paint wastewater by giving it the potential to be used as fuel, and it can also recover and reuse the wastewater container 10, thus reducing the need to dispose of the contents of the wastewater container 10. In addition, like the wastewater treatment system 1D, the wastewater treatment system 1E can suppress, for example, the generation of thermal NOx. [Examples]

[0109] The embodiments will be described in more detail below with examples, but the embodiments are not limited to these examples.

[0110] <Example 1> [Preparation of the wastewater treatment system] A wastewater treatment system 1A according to the first embodiment shown in Figure 1 was prepared.

[0111] [Evaluation of liquid fuel stability] In the waste liquid container 10 of the fabricated waste liquid treatment system 1A, methanol aqueous solution and paint waste liquid were mixed as alcohol aqueous solutions, and methanol was added to the organic solvent-containing paint waste liquid at a ratio of 5 wt% to 100 wt% of the organic solvent-containing paint waste liquid. The mixture was then stirred at 23°C ± 2°C for 10 minutes. Subsequently, the viscosity of the liquid fuel generated in the waste liquid container 10 was measured using a concentric cylindrical viscometer in accordance with JIS K5600-2-3:2014 while the mixture was stored for 432 hours. Figure 8 shows the relationship between elapsed time and the viscosity of the liquid fuel.

[0112] <Examples 2 and 3> The procedure was the same as in Example 1, except that methanol was mixed into the organic solvent-containing paint waste liquid at concentrations of 10 wt% and 15 wt% relative to 100 wt% of the organic solvent-containing paint waste liquid. Figure 8 shows the relationship between elapsed time and the viscosity of the liquid fuel.

[0113] <Examples 4-6> In Example 1, the procedure was the same as in Example 1, except that isopropyl alcohol (IPA) was mixed with the organic solvent-containing paint waste liquid in amounts of 5 wt%, 10 wt%, and 15 wt% relative to 100 wt% of the organic solvent-containing paint waste liquid, instead of methanol. Figure 8 shows the relationship between elapsed time and the viscosity of the liquid fuel.

[0114] <Comparative Example 1> In Example 1, the procedure was the same as in Example 1, except that alcohol was not added to the paint waste liquid containing organic solvents. Figure 8 shows the relationship between elapsed time and the viscosity of the liquid fuel.

[0115] <Comparative Examples 2-4> The procedure was the same as in Example 1, except that ethyl acetate was mixed with the organic solvent-containing paint waste liquid in amounts of 5 wt%, 10 wt%, and 15 wt% relative to 100 wt% of the organic solvent-containing paint waste liquid, instead of methanol as the alcohol. Figure 8 shows the relationship between elapsed time and the viscosity of the liquid fuel.

[0116] As shown in Figure 8, Examples 1 to 9 were able to slow down the increase in viscosity of the liquid fuel and delay solidification more effectively than Comparative Example 1. In particular, Examples 1 to 6 were able to delay the solidification of the liquid fuel.

[0117] Therefore, it can be said that by adding 5 wt% to 15 wt% alcohol to waste paint containing organic solvents and stirring it, a liquid fuel with stable viscosity over a long period of time can be produced.

[0118] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0119] 1A, 1B, 1C, 1D, 1E, 110 Wastewater Treatment System 2 Organic compound manufacturing equipment 10 Waste liquid containers 20A, 20B, 20C Alcohol aqueous solution supply unit 21 Water supply section 22 Alcohol Supply Department 23 Quantitative Tank 30 Stirring section 31 Stirring blade 32 motors 40 Mobile Unit 60 Mass measurement section 70 Storage tank 80, 80A, 80B Liquid level detection unit 90 Control Unit 100 Energy Recycling Systems 201 Alcohol aqueous solution storage section 202 Alcohol aqueous solution supply pipe 211 Water Storage Section 212 Water supply pipe 221 Alcohol Storage Section 222 Alcohol supply pipe A1 First placement area A2 Second placement area A3 Third placement area

Claims

1. A wastewater treatment system for producing liquid fuel by treating paint wastewater containing isocyanate groups and organic solvents discharged from an organic compound manufacturing facility, A waste liquid container into which an alcohol aqueous solution and the paint waste liquid containing the organic solvent are supplied, An alcohol aqueous solution supply unit that supplies the alcohol aqueous solution into the waste liquid container, A stirring unit for stirring a mixed solution containing the organic solvent-containing paint waste liquid and the alcohol aqueous solution supplied from the organic compound manufacturing equipment into the waste liquid container, Equipped with, A wastewater treatment system in which the alcohol content in the alcohol aqueous solution in the wastewater container is 0.5 wt% to 30 wt% relative to 100 wt% of the organic solvent-containing paint wastewater.

2. When supplying the alcohol aqueous solution from the alcohol aqueous solution supply unit into the waste liquid container, the waste liquid container is installed in the first placement area. When supplying the organic solvent-containing paint waste liquid discharged from the organic compound manufacturing equipment into the waste liquid container, the waste liquid container is installed in the second placement area. When the stirring unit is provided in the waste liquid container, the waste liquid container is placed in the third arrangement area. A moving unit that sequentially moves the waste liquid container to the first, second, and third placement areas, A wastewater treatment system according to claim 1, comprising:

3. The aforementioned alcohol aqueous solution supply unit An alcohol supply unit that supplies alcohol into the waste liquid container, A water supply unit that supplies water into the waste liquid container, A wastewater treatment system according to claim 1 or 2, comprising:

4. The alcohol supply unit includes a quantitative tank that supplies a predetermined amount of the alcohol, The wastewater treatment system according to claim 3, wherein a predetermined amount of the alcohol supplied into the quantitative tank is supplied to the wastewater container.

5. A wastewater treatment system according to any one of claims 1 to 4, further comprising a mass measuring unit for measuring the mass of the wastewater container.

6. A wastewater treatment system according to any one of claims 2 to 4, further comprising a liquid level detection unit for detecting the liquid levels of the organic solvent-containing paint wastewater and the alcohol aqueous solution in the wastewater container.

7. A wastewater treatment system according to any one of claims 1 to 6, comprising a control unit that controls the amount of the organic solvent-containing paint wastewater and the alcohol aqueous solution supplied to the wastewater container.

8. The wastewater treatment system according to any one of claims 1 to 7, wherein the organic solvent-containing paint wastewater is supplied to the wastewater container via a paint wastewater supply line connecting the organic compound manufacturing equipment and the wastewater container.

9. A wastewater treatment system according to any one of claims 1 to 8, A combustion boiler that generates steam using the aforementioned liquid fuel, A fuel-fired boiler that generates steam using fuel, A liquid fuel supply line that supplies the liquid fuel from the wastewater treatment system to the combustion boiler, A steam recycling line supplies the steam generated in the combustion boiler to a steam transport line that transports the steam generated in the fuel-fired boiler to the outside, A steam recycling system equipped with [the following features].

10. A wastewater treatment method for producing liquid fuel by treating paint wastewater containing isocyanate groups and organic solvents discharged from an organic compound manufacturing facility, An alcohol aqueous solution supply process that supplies an alcohol aqueous solution to a waste liquid container, A paint waste liquid supply step of supplying the organic solvent-containing paint waste liquid to the waste liquid container, A stirring step involves stirring the mixed solution containing the alcohol aqueous solution and the organic solvent-containing paint waste liquid in the waste liquid container, Includes, A wastewater treatment method wherein the alcohol content in the alcohol aqueous solution in the wastewater container is 0.5 wt% to 30 wt% relative to 100 wt% of the organic solvent-containing paint wastewater.

11. The alcohol aqueous solution supply step involves placing the waste liquid container in the first placement area, The paint waste liquid supply process involves placing the waste liquid container in the second placement area, The stirring step involves placing the waste liquid container in the third placement area, The waste liquid treatment method according to claim 10, wherein the waste liquid container is sequentially moved to the first arrangement area, the second arrangement area, and the third arrangement area.

12. The aforementioned alcohol aqueous solution supply step, An alcohol supply step of supplying alcohol into the waste liquid container, A water supply step of supplying water into the waste liquid container, A wastewater treatment method according to claim 10 or 11, including the following:

13. The aforementioned alcohol aqueous solution supply step, A quantitative tank supply step of supplying a predetermined amount of the alcohol aqueous solution to a quantitative tank, A quantitative alcohol aqueous solution supply step, in which a predetermined amount of the alcohol aqueous solution supplied into the quantitative tank is supplied to the waste liquid container, A wastewater treatment method according to claim 10 or 11, including the following:

14. A wastewater treatment method according to any one of claims 10 to 13, comprising a step of measuring the content of an alcohol aqueous solution in the organic solvent-containing paint wastewater by measuring the mass of the wastewater container containing the mixed solution or by detecting the liquid level of the mixed solution.

15. A liquid fuel manufacturing step for obtaining the liquid fuel using the wastewater treatment method described in any one of claims 10 to 14, A steam generation step involves supplying the aforementioned liquid fuel to a combustion boiler to generate steam, A steam recycling process in which the steam generated in the combustion boiler is supplied to a steam transport line that transports steam generated using fuel in a fuel-fired boiler to steam utilization equipment, Includes steam recycling methods.

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