Coating pretreatment low-temperature degreasing system and method

Abstract

The invention discloses a low-temperature degreasing system for coating pretreatment, and belongs to the field of purification and reutilization of degreasing fluid for automobile coating pretreatment. The coating pretreatment low-temperature degreasing system comprises a degreasing tank provided with a workpiece inlet end A and a workpiece outlet end B; the heating module is arranged at the bottom of the degreasing tank and is used for heating the degreasing fluid in the degreasing tank; the first hydrodynamic cavitation module is connected with the degreasing tank; the heating demulsification oil-water separator is connected with the degreasing tank; and the second hydrodynamic cavitation module is connected with the heating demulsification oil-water separator. According to the coating pretreatment low-temperature degreasing system and method, the heating demulsification technology and the hydrodynamic cavitation technology are combined for use, and the better degreasing and oil removing effect can be achieved under the condition that the temperature is lower than the temperature of traditional high-temperature heating demulsification; under the condition that the working temperature of the degreasing tank is reduced, the degreasing fluid can keep the same cleaning capacity; therefore, energy consumption is saved, and the degreasing tank liquid replacement period is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of purification and reuse of degreasing liquid for automotive painting pretreatment, specifically to the field of low-temperature degreasing system for painting pretreatment. Background Art

[0002] Degreasing is an important process in the pretreatment line of an automotive painting workshop. The function of degreasing and oil removal is to clean the grease, dirt, dust, etc. on the surface of the welded workpieces, providing a clean and well-contact surface with the workpieces for phosphating (or silanization) to ensure the formation of a complete phosphating film (or silane film). Incomplete degreasing in the pretreatment not only hinders the formation of the phosphating film (or silane film), but also affects the adhesion, decorative performance, and corrosion resistance of the coating during painting after phosphating (or silanization). Degreasing relies on the dissolution and saponification of the degreasing agent on the dirt and the physical effects of surfactants on the dirt such as wetting, penetration, and dispersion, so that the dirt leaves the metal surface and the clean cleaning agent occupies the surface of the vehicle body, thus achieving the purpose of cleaning the metal surface.

[0003] Automotive painting production lines are highly automated and use medium-high temperature degreasing processes, that is, the degreasing working temperature is maintained at 50 - 60 °C during production. To maintain this process temperature for degreasing, the workshop needs to consume a large amount of heat energy.

[0004] Along with the continuous mixing of the oil carried by the vehicle body during the production process into the degreasing system, the oil content in the degreasing liquid gradually increases, and the degreasing effect is severely affected, which in turn leads to poor painting quality of the vehicle body. How to separate the oil and dirt in the degreasing bath from the bath liquid and maintain the cleanliness and degreasing ability of the bath liquid is an important topic studied by automotive painting factories and painting equipment manufacturers. The requirements for oil removal in the degreasing system are to ensure that the oil in the bath liquid can be promptly treated and centrally recovered and treated to maintain the cleaning ability of the degreasing liquid, and at the same time, reduce the amount of degreasing waste liquid brought to the sewage treatment station to relieve the pressure on the sewage treatment station.

[0005] The current existing solution is to install a high-temperature demulsifying oil-water separator for degreasing the degreasing bath. Its principle is to heat the bath liquid to a certain temperature (80 - 90 °C) to make the oil particles in the emulsion aggregate and accelerate their floating or sedimentation. Although heating can accelerate the oil-water separation, in some cases, especially when the emulsion is very stable, it may take a long time and a higher temperature to achieve an ideal separation effect, accompanied by a large amount of energy support during the heating process, especially when the processing volume is large, the energy consumption cost is extremely high. At the same time, during the heating process, strict safety measures are required to prevent fire and explosion accidents.

[0006] Traditional degreasing and oil removal technologies and processes all use high-temperature heating for demulsification and combine chemical agents for degreasing and oil removal, which have the following disadvantages: (1) High energy consumption. The degreasing bath liquid needs to be maintained at 50 - 60 °C for cleaning the vehicle body through a circulating heating method, and the floating oil on the surface of the bath liquid overflows to the traditional oil-water separator, which works at a high temperature of 70 - 90 °C for demulsification and oil-water separation; (2) Low oil removal efficiency. Due to process and technical limitations, the traditional high-temperature heating demulsification oil-water separator can only solve the oil in a small part of the bath liquid that overflows on the surface, and the oil in the bath liquid in the degreasing tank cannot be solved. In addition, the high temperature of 70 - 90 °C will also damage the performance of the degreasing agent and increase the consumption of the degreasing agent; (3) Large discharge of degreasing wastewater. As the number of vehicles being cleaned increases, the oil content in the degreasing bath liquid becomes higher and higher, making the performance of degreasing and oil removal unable to meet the process quality requirements, and the production line must stop production to replace the degreasing bath liquid. A car painting workshop will generate hundreds to thousands of tons of degreasing oily wastewater in a year. Degreasing wastewater belongs to hazardous waste and cannot be treated by traditional water treatment processes, and enterprises need to spend expensive costs to treat degreasing wastewater. Summary of the Invention

[0007] To solve the above problems of degreasing liquid treatment before painting, the present invention provides a low-temperature degreasing system and method for pretreatment before painting, which combines heating demulsification with hydrodynamic cavitation technology, can have a better degreasing and oil removal effect under the condition of a temperature lower than that of traditional high-temperature heating demulsification, and can keep the degreasing liquid having the same cleaning ability under the condition of reducing the working temperature of the degreasing tank, thereby saving energy consumption and extending the replacement cycle of the degreasing bath liquid.

[0008] The low-temperature degreasing system for pretreatment before painting includes:

[0009] A degreasing tank, provided with an inlet end A for workpieces and an outlet end B for workpieces;

[0010] A heating module, arranged at the bottom of the degreasing tank, for heating the degreasing liquid in the degreasing tank;

[0011] A first hydrodynamic cavitation module, connected to the degreasing tank;

[0012] A temperature-raising demulsification oil-water separator, connected to the degreasing tank;

[0013] A second hydrodynamic cavitation module, connected to the temperature-raising demulsification oil-water separator.

[0014] Preferably, the first hydrodynamic cavitation module includes a first high-pressure pump and a first cavitation generator connected in sequence; the first high-pressure pump is connected to the inlet end A, the first cavitation generator is connected to the outlet end B; a positive pressure gauge is connected between the first high-pressure pump and the first cavitation generator; the first cavitation generator is provided with a negative pressure port, and the negative pressure port is connected to a negative pressure gauge.

[0015] Preferably, a liquid extraction port of the first hydrodynamic cavitation module is provided at the workpiece inlet end A, and the liquid extraction port is located in the middle and lower layers of the degreasing tank; a first liquid outlet manifold of the first hydrodynamic cavitation module is provided at the workpiece outlet end B; the first liquid outlet manifold is close to the liquid level of the degreasing tank.

[0016] Preferably, second liquid outlet manifolds are respectively provided on both sides in the width direction of the degreasing tank, and the liquid outlet of the second liquid outlet manifold forms a certain inclination angle with the length direction of the degreasing tank and faces the workpiece inlet end A.

[0017] Preferably, the temperature-raising demulsifying oil-water separator is connected to an oil liquid collector, and the oil liquid collector is arranged on the liquid surface at the workpiece inlet end A; the temperature-raising demulsifying oil-water separator is provided with a liquid return end, and the liquid return end is connected to the degreasing tank.

[0018] Preferably, the temperature-raising demulsifying oil-water separator includes:

[0019] a heating tank, in which a heater is arranged, and the heating tank is connected to the degreasing tank;

[0020] a cavitation tank, which is connected to the second hydrodynamic cavitation module, and the second hydrodynamic cavitation module includes a second high-pressure pump and a second cavitation generator arranged in sequence;

[0021] a static tank, which is provided with a second oil collecting tank and a liquid return tank;

[0022] The heating tank communicates with the cavitation tank.

[0023] Preferably, a partition is arranged in the middle of the heating tank, and the partition divides the heating tank into a first tank and a second tank. The heater is arranged in the first tank. The partition is provided with a through hole for communicating the first tank and the first tank. A first oil collecting tank is arranged in the second tank; a U-shaped pipe for connecting the cavitation tank is arranged in the second tank.

[0024] Preferably, a baffle is arranged in the cavitation tank, and the baffle divides the cavitation tank into a first chamber and a second chamber; the distance between the baffle and the bottom of the cavitation tank is greater than zero, and the U-shaped pipe extends to the second chamber.

[0025] Preferably, the second chamber is connected to the second high-pressure pump; the first chamber is connected to the second cavitation generator; a positive pressure gauge is connected between the second high-pressure pump and the second cavitation generator, and the second cavitation generator is provided with a negative pressure port, and the negative pressure port is connected to a negative pressure gauge.

[0026] Preferably, an overflow port is arranged between the cavitation tank and the static tank; the static tank is provided with a lead-out pipe, the lead-out pipe communicates with the liquid return tank, and an adjusting pipe is arranged at the upper end of the lead-out pipe.

[0027] Preferably, an oil skimming device is further connected to the liquid surface at the workpiece inlet end A of the degreasing tank.

[0028] The low-temperature degreasing method for pretreatment of painting using the low-temperature degreasing system for pretreatment of painting described above includes:

[0029] S1. The degreasing tank heating module heats the degreasing tank liquid to maintain the working temperature of the degreasing tank; the degreasing tank liquid is subjected to hydrodynamic cavitation treatment, and the oil-water interface of the emulsified oil is broken through hydrodynamic cavitation to promote the conversion of emulsified oil into floating oil.

[0030] S2. The liquid outlet manifold of the hydrodynamic cavitation module pushes the oil floating on the liquid surface from the workpiece outlet end B to the workpiece inlet end A. An oil collector is provided at the workpiece inlet end A. Using the oil collector, the oil with a high oil content on the surface of the degreasing tank liquid is pumped to the temperature-raising demulsifying oil-water separator by a pump.

[0031] S3. Inside the temperature-raising demulsifying oil-water separator, first through heating and preliminary skimming, and then the liquid after preliminary skimming is introduced into the cavitation tank through a U-shaped pipe, and hydrodynamic cavitation treatment is carried out again in the cavitation tank. The cavitation treatment liquid overflows to the settling tank; in the settling tank, further oil separation is carried out; the oil enters the oil collecting tank and is introduced into an oil barrel; the purified liquid enters the return liquid tank and is introduced into the degreasing tank.

[0032] Further, the low-temperature degreasing method for pretreatment of painting further includes S4. After the oil with a very high oil content on the surface of the degreasing tank liquid is separated by the temperature-raising demulsifying oil-water separator, the remaining floating oil is further collected and subjected to oil-water separation by the oil skimming device.

[0033] Compared with the prior art, the beneficial technical effects of the present invention are:

[0034] 1. By adding the technology of hydrodynamic cavitation to the original process flow, the mechanical effects of friction and shear generated by cavitation change the molecular cluster form of the multiphase mixture in the solution, turn the large molecular clusters into small molecular clusters, enhance the activity of the solution molecules, reduce the viscosity and surface tension of the solution system, improve the solubility and penetration of the solution system, and enhance the wettability of the solution system, thereby enhancing the degreasing ability of the solution.

[0035] 2. The instantaneous local high temperature and high pressure generated by hydrodynamic cavitation are also accompanied by strong shock waves and microjets with a speed of more than 1400 m / s and other mechanical effects, during which a large amount of energy is released; these effects can all cause the oil-water interface of the emulsified oil to be squeezed or impacted and damaged, the emulsified oil is broken up into fine oil droplets, and quickly float up with microbubbles. Due to the sufficient number of bubbles, the collision coefficient increases, and the small oil droplets quickly collide and aggregate into large oil droplets, completing the transformation into floating oil. At this time, the removal of floating oil is accelerated through the floating oil collection and separation technology, significantly improving the oil removal and purification ability.

[0036] 3. The system combines heating demulsification and hydrodynamic cavitation technology, which can achieve better degreasing and oil removal effects under the condition of lower temperature than the traditional high-temperature heating demulsification temperature; it can keep the same cleaning ability of the degreasing solution under the condition of reducing the working temperature of the degreasing tank; thus, it can save energy consumption and extend the replacement cycle of the degreasing tank solution.

[0037] 4. The liquid intake port of the first hydrodynamic cavitation module is located in the middle and lower layers of the degreasing tank, which can carry out cavitation treatment on the degreasing solution in the middle and lower layers of the degreasing tank. It can not only remove the floating oil on the surface but also remove the emulsified oil in the degreasing tank solution, ensuring good cleaning effect of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the system flow of the treatment system of the present invention.

[0039] Figure 2 It is a schematic diagram of the system flow structure of the treatment system of the present invention.

[0040] Figure 3 It is a schematic diagram of the structure of the low-temperature demulsification oil-water separator.

[0041] Figure 4 It is a top view of the degreasing tank.

[0042] Figure 5 It is a top view of the degreasing tank in another way.

[0043] In the figure: degreasing tank 1, first cavitation generator 2, first liquid outlet manifold 20, second liquid outlet manifold 21, first high-pressure pump 3, temperature-rising demulsification oil-water separator 4, heating tank 40, heater 401, partition 402, through hole 4020, first tank 403, second tank 404, first oil collecting tank 4040, cavitation tank 41, U-shaped pipe 410, baffle 411, first chamber 412, second chamber 413, overflow port 414, static tank 42, return liquid tank 420, lead-out pipe 421, regulating pipe 4210, second oil collecting tank 422, second high-pressure pump 5, second cavitation generator 6, positive pressure gauge 60, negative pressure gauge 61, floating oil separation device 7, oil liquid collector 70, degreasing agent feeding area 8, heating module 9, filter 90, heat exchanger 91. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The present invention will be further described below in conjunction with the drawings and specific embodiments:

[0045] Embodiment 1

[0046] As Figure 1 , the low-temperature degreasing system for pre-treatment of painting includes a degreasing tank, which is respectively connected to a heating module, a first hydrodynamic cavitation module, and a temperature-rising demulsification oil-water separator; the temperature-rising demulsification oil-water separator is connected to a second hydrodynamic cavitation module, and the temperature-rising demulsification oil-water separator is also connected to an oil barrel.

[0047] As shown in Figure 2 , the low-temperature degreasing system for pre-treatment before painting includes a degreasing tank 1, the degreasing tank 1 is provided with a workpiece inlet end A and a workpiece outlet end B; a heating module 9, which is arranged at the bottom of the degreasing tank 1 to heat the degreasing liquid in the degreasing tank 1; a first hydraulic cavitation module, which is connected to the degreasing tank 1; a temperature-rising demulsification oil-water separator 4, which is connected to the degreasing tank 1; the temperature-rising demulsification oil-water separator 1 is connected to a second hydraulic cavitation module.

[0048] As shown in Figure 2 , the degreasing tank 1 is also provided with a degreasing agent feeding port, and the degreasing agent feeding port is connected to a degreasing agent feeding area 8. The heating module 9 includes a pump, a filter 90, and a heat exchanger 91 arranged in sequence. The heat exchanger continuously exchanges heat for the degreasing liquid in the degreasing tank through steam or hot water to raise the temperature of the degreasing liquid.

[0049] In this embodiment, the workpiece is an automotive sheet metal part. As shown in Figure 2 , the automotive sheet metal part enters from the A side of the degreasing tank 1 in the workpiece feeding direction and is immersed in the degreasing tank 1. The grease and dirt on the surface of the automotive sheet metal part are cleaned and the part exits the degreasing tank 1 from the B side.

[0050] As shown in Figure 2 , the first hydraulic cavitation module includes a first high-pressure pump 3 and a first cavitation generator 2 connected in sequence; the first high-pressure pump 3 is connected to the workpiece inlet end A, and the first cavitation generator 2 is connected to the workpiece outlet end B; a positive pressure gauge is connected between the first high-pressure pump 3 and the first cavitation generator 2, and the first cavitation generator is provided with a negative pressure port, and the negative pressure port is connected to a negative pressure gauge.

[0051] As shown in Figure 2 , the degreasing tank 1 is provided with a liquid extraction port of the first hydraulic cavitation module at the workpiece inlet end A, and the liquid extraction port is located in the middle and lower layers of the degreasing tank 1. As shown in Figure 4 , the workpiece outlet end B is provided with a first liquid outlet manifold 20 communicating with the first cavitation generator 2; the first liquid outlet manifold 20 is a row of pipes provided with a plurality of liquid outlet ports, and the first liquid outlet manifold 20 pushes the oil liquid with a high oil content in the upper layer of the degreasing tank from the workpiece outlet end B to the workpiece inlet end A. As shown in Figure 2 , the liquid outlet ports of the first liquid outlet manifold 20 maintain a certain inclination angle with the liquid level. The first liquid outlet manifold 20 is arranged at the upper end of the degreasing tank 1 close to the liquid level and sprays liquid obliquely towards the liquid level, which is beneficial to pushing the upper layer oil liquid of the degreasing tank 1 to the workpiece inlet end A.

[0052] As shown in Figure 5, in the case where the degreasing tank has a large volume and a large length dimension, second liquid outlet manifolds 21 are respectively provided on both sides in the width direction of the degreasing tank 1. The liquid outlet of the second liquid outlet manifold 21 forms a certain inclination angle with the length direction of the degreasing tank 1 and faces the workpiece inlet end A. The position of the oil collector 70 is on one side of the workpiece inlet end A, and the liquid outlet of the temperature-raising demulsifying oil-water separator is on the other side of the workpiece inlet end A; so that the floating oil gathers and is collected at the position of the oil collector 70.

[0053] Such as Figure 2 , the temperature-raising demulsifying oil-water separator 4 is connected to the oil collector 70, and the oil collector 70 is arranged on the liquid surface of the workpiece inlet end A; the temperature-raising demulsifying oil-water separator 4 is provided with a liquid return end, and the liquid return end is connected to the degreasing tank 1.

[0054] In this embodiment, the oil collector 70 is a floating floating oil liquid suction device.

[0055] Such as Figure 3 , the temperature-raising demulsifying oil-water separator includes: a heating tank 40, a heater 401 is arranged in the heating tank 40, and the heating tank 40 is connected to the oil collector 70; a cavitation tank 41, the cavitation tank 41 is connected to a second hydraulic cavitation module, and the second hydraulic cavitation module includes a second high-pressure pump 5 and a second cavitation generator 6 arranged in sequence. A positive pressure gauge 60 is arranged between the high-pressure pump 5 and the second cavitation generator 6. The second cavitation generator 6 is provided with a negative pressure port, and the negative pressure port is connected to a negative pressure gauge 61, a check valve; a 42 static tank, which is provided with a second oil collecting tank 422 and a liquid return tank 420; the heating tank 41 is communicated with the cavitation tank 42.

[0056] As another implementation manner.

[0057] A partition plate 402 is arranged in the middle of the heating tank 41. The partition plate 402 divides the heating tank 1 into a first tank 403 and a second tank 404. The heater 401 is arranged in the first tank 403. A through hole 4020 for communicating the first tank and the first tank is arranged on the partition plate 402. A first oil collecting tank 4040 is arranged in the second tank 404; a U-shaped pipe 410 connecting the cavitation tank is arranged in the second tank 404.

[0058] The heating tank 41 is arranged into two tanks, and the heater is placed in a separate space, so that the heating efficiency is improved. And the heated liquid is introduced into the second tank through the through hole 4020, and oil-water separation is carried out through the first oil collecting tank 4040, so that the heated liquid can be preliminarily skimmed.

[0059] A baffle plate 411 is provided in the cavitation tank 41. The baffle plate 411 divides the cavitation tank 41 into a first chamber 412 and a second chamber 413. The distance between the baffle plate 411 and the bottom of the cavitation tank 41 is greater than zero. The U-shaped tube 410 extends into the second chamber 413, and the outlet of the U-shaped tube is arranged in the second chamber 413. The second chamber 413 is connected to the second high-pressure pump 5. The high-pressure pump 5 is connected to the second cavitation generator 6, and the first chamber 412 is connected to the second cavitation generator.

[0060] An overflow port 414 is provided between the cavitation tank 41 and the static tank 42. The liquid after cavitation treatment in the cavitation tank overflows to the static tank 42 through the overflow port 414. A lead-out pipe 421 is provided in the static tank 42. The lead-out pipe 421 communicates with the liquid return tank 420, and an adjusting pipe 4210 is provided at the upper end of the lead-out pipe 421.

[0061] The cavitation treatment liquid in the cavitation tank is introduced into the static tank through overflow. By changing the height of the adjusting pipe 4210, the floating oil overflowing to the second oil collecting tank 422 is adjusted. When the outlet height of the adjusting pipe 4210 is higher than the notch of the second oil collecting tank 422, the floating oil after standing overflows to the second oil collecting tank 422. When the outlet height of the adjusting pipe is lower than the notch of the second oil collecting tank 422, the second oil collecting tank 422 is drained of oil. The net liquid at the lower layer of the static tank is introduced into the liquid return tank 420 through the lead-out pipe 421, so that the degreasing liquid is further separated from oil and water, and the oil content of the liquid returning to the degreasing tank is greatly reduced.

[0062] The first cavitation generator and the second cavitation generator. The cavitation generator includes a container with a decreasing inner diameter from top to bottom. A liquid inlet pipe with a tangential introduction is provided on the container. An outlet pipe is provided in the middle of the container. A Venturi tube structure is provided inside the outlet pipe, and a flow guiding member is provided under the outlet pipe. The liquid is sent into the hydraulic cavitation generator at a certain pressure by a high-pressure pump. After the liquid enters the hydraulic cavitation generator, a swirling flow similar to a hurricane shape is formed in the cavity of the container, and the laminar flows will rub and shear against each other. During the process of the swirling flow rotating from top to bottom in the cavity, it accelerates, and the speed becomes faster and faster. Passing through the throat of the Venturi tube, a negative pressure environment is formed when the flow rate is the largest, and passive air dissolution generates air bubbles. Then the pressure quickly recovers, the air bubbles burst and release energy, generating a hydraulic cavitation effect.

[0063] The working mode of the pre-coating treatment low-temperature degreasing system of Embodiment 1:

[0064] The workpiece is immersed in the degreasing tank 1 along the workpiece inlet direction. After cleaning and degreasing, the grease, dirt, dust, etc. on the surface of the workpiece are cleaned, and the oil stains and dirt are left in the degreasing tank. The heating module continuously exchanges heat and heats the degreasing liquid in the degreasing tank 1. The purpose of heating is to maintain the working temperature of the degreasing tank liquid; at the same time, hydraulic cavitation treatment is carried out on the degreasing liquid to further demulsify the water-in-oil in the emulsified state, so that the miscellaneous oil and fine particles float further. The first liquid outlet manifold 20 of the first cavitation generator 2 pushes the degreasing liquid with floating oil on the liquid surface of the degreasing tank towards the workpiece inlet end A. An oil collector 70 is provided on the liquid surface at the workpiece end A. The oil collector 70 collects the floating oil with part of the liquid and fine particles, and pumps it to the temperature-raising demulsifying oil-water separator 4 through a pump. In the temperature-raising demulsifying oil-water separator 4, preliminary oil skimming is first carried out through heating, and then through the second cavitation generator, hydraulic cavitation treatment is carried out to further carry out cavitation demulsification on the preliminarily skimmed liquid. After the demulsified liquid overflows to the static tank 42 and stands, oil-water separation is carried out again. The floating oil enters the second oil collecting tank 422, and the purified liquid enters the return liquid tank 420; the return liquid tank 420 is the return liquid end of the temperature-raising demulsifying oil-water separator, and the return liquid end sends the purified liquid to the degreasing liquid tank.

[0065] Embodiment 2:

[0066] Different from Embodiment 1, on the basis of Embodiment 1, an oil separation device 7 is also provided on the liquid surface at the workpiece inlet end A of the degreasing tank. The oil separation device 7 is connected to the oil collector 70. The structure of the oil separation device 7 is the prior art, and its technical information can be obtained from the oil skimmer in Patent CN201921892786.7. This oil separation device can collect a small amount of floating oil on the surface of the degreasing tank and further separate oil and water, keeping the liquid surface clean so that when the automotive sheet metal part enters from the workpiece inlet end A, it does not stick to grease.

[0067] For the pre-coating treatment low-temperature degreasing method using the pre-coating treatment low-temperature degreasing system described above, the method includes:

[0068] S1. Use the heating module of the degreasing tank to heat the degreasing tank liquid to maintain the working temperature of the degreasing tank; carry out hydraulic cavitation treatment on the degreasing tank liquid, and break the oil-water interface of the emulsified oil through hydraulic cavitation to convert the emulsified oil into floating oil.

[0069] S2. The liquid outlet manifold of the hydraulic cavitation module pushes the oil liquid floating on the liquid surface from the workpiece outlet end B towards the workpiece inlet end A. An oil collector is provided at the workpiece inlet end A. Using the oil collector, the floating oil with part of the liquid on the liquid surface is pumped to the temperature-raising demulsifying oil-water separator through a pump.

[0070] S3. In the temperature-raising demulsifying oil-water separator, preliminary oil skimming is first carried out through heating, and then the liquid after preliminary oil skimming is introduced into the cavitation tank through a U-shaped pipe, and hydraulic cavitation treatment is carried out on the cavitation tank. The liquid after cavitation overflows into the static tank; in the static tank, further oil-liquid separation is carried out; the oil enters the oil collection tank and is introduced into the oil barrel; the purified liquid enters the return liquid tank and is introduced into the degreasing tank.

[0071] The pre-treatment low-temperature degreasing method for painting further includes S4. After the oil-liquid separation of the oil liquid with a very high oil content on the surface of the degreasing tank liquid by the temperature-raising demulsifying oil-water separator, the floating oil separation device is used to further collect the remaining floating oil and carry out oil-water separation.

[0072] The technical solution of the present invention is further described below in conjunction with experimental data:

[0073] Cleaning up to standard: The degreasing liquid is operated in accordance with QB / T 2117-1995 "General Water-based Metal Detergent", and the oil removal rate is not less than 90% to meet the standard.

[0074] As the liquid temperature rises, the surface tension of the liquid will decrease. In order to obtain a better cleaning effect, the traditional process of pre-treatment before painting in a conventional workshop must raise the temperature of the degreasing liquid to 60 °C.

[0075] According to the authoritative third-party inspection report.

[0076] (1) The degreasing liquid will gradually reach a saturated state after cleaning a certain amount of oil-containing metal, resulting in a decline in the cleaning effect. The low-temperature degreasing and oil removal system treatment can restore the cleaning ability of the saturated degreasing liquid. The total number of test pieces that can be cleaned up to standard by the degreasing liquid after repeated treatment by this system is 28 pieces, which is equal to 2 times the number of test pieces that can be cleaned up to standard by the original degreasing liquid. It can be considered that this system can reduce the usage amount of the degreasing liquid by more than half.

[0077] Cleaning temperature / °C Total number of qualified test pieces after cleaning / piece Original degreasing solution 60 14 Degreasing solution after treatment with saturated degreasing solution 60 28

[0078] (2) Compare the surface tension of the original degreasing liquid at 60 °C with the surface tension of the degreasing liquid after treatment by this system at 30 °C, 40 °C, 45 °C, and 48 °C. The measured value of the surface tension at 45 °C after treatment by this system is less than the surface tension at 60 °C before treatment, that is, the degreasing temperature of the degreasing liquid after treatment is reduced by 15 °C and still maintains the same cleaning power as the degreasing liquid before treatment.

[0079] Test temperature / °C Surface tension / mN / m Degreasing solution before treatment 60 29.6 55 29.9 48 30.4 45 29.4 Degreasing solution after treatment 48 29.2 45 29.5 40 29.8 30 30.8

[0080] (3)The number of cleaned qualified test pieces that the degreasing solution treated by hydrodynamic cavitation can clean at 46 °C is equal to or greater than the number of cleaned qualified test pieces that the degreasing solution before treatment can clean at 60 °C, that is, the degreasing solution treated by hydrodynamic cavitation has the same cleaning power as the degreasing solution at 60 °C at 46 °C. 14 °C can be considered as the degreasing temperature that can be reduced by the treatment of this system.

[0081] Cleaning temperature / °C Total number of qualified test pieces after cleaning / piece Degreasing solution before treatment 60 12 Degreasing solution after treatment 46 12

[0082] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are all covered by the protection scope of the present invention.

Claims

1. Low temperature degreasing system before painting, characterized by: include: The degreasing tank is provided with a workpiece inlet end A and a workpiece outlet end B; A heating module is disposed at the bottom of the degreasing tank to heat the degreasing liquid in the degreasing tank; A first hydrodynamic cavitation module connected to the degreasing tank; A heating demulsification oil-water separator connected to the degreasing tank; The second hydraulic cavitation module is connected to the temperature-raising emulsion-breaking oil-water separator.

2. The low-temperature degreasing system for pre-coating treatment according to claim 1 is characterized in that: The first hydraulic cavitation module includes a first high-pressure pump and a first cavitation generator which are connected in sequence; the first high-pressure pump is connected to the workpiece inlet end A, and the first cavitation generator is connected to the workpiece outlet end B; a positive pressure gauge is connected between the first high-pressure pump and the first cavitation generator; the first cavitation generator is provided with a negative pressure port, and the negative pressure port is connected to a negative pressure gauge.

3. The low-temperature degreasing system for pre-coating treatment according to claim 1 is characterized in that: The workpiece inlet end A is provided with a liquid intake port of the first hydraulic cavitation module, and the liquid intake port is located in the middle and lower layers of the degreasing tank; the workpiece outlet end B is provided with a first liquid outlet bus connected to the first hydraulic cavitation module; the first liquid outlet bus is close to the liquid surface of the degreasing tank.

4. The low-temperature degreasing system for pre-coating treatment according to claim 3 is characterized in that: Second liquid outlet busbars are respectively provided on both sides of the degreasing tank in the width direction. The liquid outlets of the second liquid outlet busbars are inclined at a certain angle to the length direction of the degreasing tank and face the workpiece inlet end A.

5. The low-temperature degreasing system for pre-coating treatment according to claim 1 is characterized in that: The temperature-rising demulsification oil-water separator is connected to an oil collector, and the oil collector is arranged on the liquid surface of the workpiece inlet end A; the temperature-rising demulsification oil-water separator is provided with a liquid return end, and the liquid return end is connected to the degreasing tank.

6. The low-temperature degreasing system for pre-painting treatment according to claim 1 is characterized in that: The temperature-raising emulsion-breaking oil-water separator comprises: A heating tank, wherein a heater is provided in the heating tank, and the heating tank is connected to the degreasing tank; A cavitation tank, wherein the cavitation tank is connected to the second hydraulic cavitation module, and the second hydraulic cavitation module includes a second high-pressure pump and a second cavitation generator which are arranged in sequence; The static tank is provided with a second oil collecting tank and a liquid return tank; The heating tank is communicated with the cavitation tank.

7. The low-temperature degreasing system for pre-coating treatment according to claim 6, characterized in that: A partition is provided in the heating tank, which divides the heating tank into a first tank and a second tank. The heater is arranged in the first tank. The partition is provided with a through hole connecting the first tank and the second tank. A first oil collecting tank is provided in the second tank.

8. The low-temperature degreasing system for pre-coating treatment according to claim 6 or 7, characterized in that: A baffle is provided in the cavitation tank, which divides the cavitation tank into a first cavity and a second cavity, and the distance between the baffle and the bottom of the cavitation tank is greater than zero; the heating tank is provided with a U-shaped tube connected to the cavitation tank, and the U-shaped tube extends to the second cavity.

9. The low-temperature degreasing system for pre-coating treatment according to claim 8, characterized in that: The second cavity is connected to a second high-pressure pump; the first cavity is connected to a second cavitation generator; a positive pressure gauge is connected between the second high-pressure pump and the second cavitation generator, the second cavitation generator is provided with a negative pressure port, and the negative pressure port is connected to a negative pressure gauge.

10. The low-temperature degreasing system for pre-painting treatment according to claim 6, characterized in that: An overflow port is provided between the cavitation tank and the static tank; the static tank is provided with an outlet pipe, the outlet pipe is connected to the liquid return tank, and a regulating pipe is provided at the upper end of the outlet pipe.

11. The low-temperature degreasing system for pre-painting treatment according to claim 1, characterized in that: A floating oil separation device is also connected to the liquid surface at the workpiece inlet end A of the degreasing tank.

12. A method for low-temperature degreasing before painting using the low-temperature degreasing system before painting according to any one of claims 1 to 11, characterized in that: The method comprises: S1, the degreasing tank heating module heats the degreasing tank liquid to maintain the working temperature of the degreasing tank; the degreasing tank liquid is subjected to hydraulic cavitation treatment to break the oil-water interface of the emulsified oil through hydraulic cavitation, so that the emulsified oil is transformed into floating oil; S2. The outlet bus of the hydraulic cavitation module pushes the oil floating on the liquid surface from the workpiece outlet end B to the workpiece inlet end A. An oil collector is provided at the workpiece inlet end A. The oil with high oil content on the surface of the degreasing tank liquid is pumped to the temperature-raising demulsification oil-water separator by using the oil collector; S3. The interior of the heating demulsification oil-water separator is first heated and preliminarily skimmed, and then the preliminarily skimmed liquid is introduced into the cavitation tank through a U-shaped tube, and then hydraulic cavitation treatment is performed in the cavitation tank, and oil-liquid separation is performed again.

13. The low-temperature degreasing method before painting according to claim 12, characterized in that: In the S3, the cavitation treatment liquid overflows to the static tank; in the static tank, the oil and liquid are further separated; the oil enters the oil collecting tank and is introduced into the oil barrel; the clean liquid enters the liquid return tank and is introduced into the degreasing tank.

14. The low-temperature degreasing method before painting according to claim 12, characterized in that: The low-temperature degreasing method before painting further comprises: S4. After the oil with high oil content on the surface of the degreasing tank liquid is separated by the heating demulsification oil-water separator, the remaining floating oil is further collected and separated by the floating oil separation device.

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