Cutting wastewater treatment device and method

Abstract

The invention relates to the technical field of wastewater treatment, in particular to a cutting wastewater treatment device and method. The technical problem to be solved by the invention is to provide the cutting wastewater treatment device and method capable of realizing deep purification of cutting wastewater and efficient recovery of valuable resources. The cutting wastewater treatment device comprises a pretreatment unit, an ultrafiltration unit, a nanofiltration unit and a reverse osmosis unit which are connected in sequence, and an auxiliary unit and a resource recovery unit which are arranged in a matched manner, the pretreatment unit comprises a self-cleaning filtering device, a coagulative precipitation tank, an air floatation tank and a demulsification device; the ultrafiltration unit comprises an ultrafiltration device and an ultrafiltration water producing tank; the nanofiltration unit comprises an NF security filter, an NF device and an NF water producing tank; the reverse osmosis unit comprises an RO security filter, an RO device and an RO water producing tank. The device achieves the effects of deep purification of cutting wastewater and efficient recovery of valuable resources.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more particularly to a cutting wastewater treatment device and method. Background Technology

[0002] In the field of machining, cutting is one of the core processes. During the process, cutting fluids containing components such as emulsified oil and polyethylene glycol are used for cooling and lubrication, which generates a large amount of cutting wastewater. This type of wastewater has a complex composition, containing not only solid impurities such as ferromagnetic and non-magnetic metal chips, but also pollutants such as emulsified oil, surfactants, polyethylene glycol, and salts. Direct discharge of such wastewater would cause serious environmental pollution.

[0003] Currently, the treatment of cutting wastewater mostly adopts a combination process of "pretreatment + membrane separation". However, the existing technology has obvious limitations: First, the pretreatment stage often relies on chemical demulsifiers, which not only easily produces chemical residues and has unstable demulsification effect, but also makes it difficult to effectively remove fine suspended solids and colloids. Second, the concentrate from the membrane separation unit lacks efficient treatment methods, and direct discharge can easily cause pollution. Polyethylene glycol and salts in the concentrate cannot be specifically recovered, resulting in low resource utilization. Third, there is insufficient synergy between the various treatment units. The screening and recovery of metal impurities is disconnected from the subsequent purification process, and the membrane device is prone to clogging due to incomplete pretreatment, affecting the operational stability and service life.

[0004] With increasingly stringent environmental protection requirements and the advancement of the "resource utilization and reduction" concept, traditional cutting wastewater treatment technologies can no longer meet the comprehensive needs of efficient purification, resource recovery, and stable operation. Therefore, there is an urgent need to develop a cutting wastewater treatment device and method that can achieve deep purification of cutting wastewater and efficient recovery of valuable resources. Summary of the Invention

[0005] In order to overcome the shortcomings of traditional cutting wastewater treatment technologies that are unable to meet the comprehensive requirements of efficient purification, resource recovery and stable operation, the present invention aims to provide a cutting wastewater treatment device and method that can achieve deep purification of cutting wastewater and efficient recovery of valuable resources.

[0006] This invention is achieved through the following specific technical means: A cutting wastewater treatment device includes a pretreatment unit, an ultrafiltration unit, a nanofiltration unit, and a reverse osmosis unit connected in sequence, as well as an auxiliary unit and a resource recovery unit. The pretreatment unit includes a self-cleaning filter, a coagulation sedimentation tank, an air flotation tank, and a demulsification device; the inlet of the self-cleaning filter is connected to the raw wastewater from the cutting process, and the outlet is connected to the inlet of the coagulation sedimentation tank; the outlet of the coagulation sedimentation tank is connected to the inlet of the air flotation tank, and the outlet of the air flotation tank is connected to the inlet of the demulsification device; the demulsification device is an electrode electrocatalytic demulsification device. The ultrafiltration unit includes an ultrafiltration device and an ultrafiltration product water tank. The inlet end of the ultrafiltration device is connected to the outlet end of the demulsification device; the product water end of the ultrafiltration device is connected to the ultrafiltration product water tank. The nanofiltration unit includes an NF security filter, an NF device, and an NF product water tank. The inlet of the NF security filter is connected to the outlet of the ultrafiltration product water tank, the outlet of the NF security filter is connected to the NF device, and the product water end of the NF device is connected to the NF product water tank. The reverse osmosis unit includes an RO security filter, an RO device, and an RO permeate tank. The inlet of the RO security filter is connected to the outlet of the RO permeate tank, the outlet of the RO security filter is connected to the RO device, and the permeate of the RO device is connected to the RO permeate tank. The outlet of the RO permeate tank is used for wastewater treatment and reuse. The auxiliary unit includes a sludge treatment device, a chemical dosing device, a chemical cleaning tank, and a wastewater pool. The sludge treatment device is connected to the sludge discharge outlets of the self-cleaning filter, coagulation sedimentation tank, demulsification device, and flotation tank in the pretreatment unit. The chemical dosing device is used to add scale inhibitors and bactericides to the inlet of the nanofiltration unit and the reverse osmosis unit. The chemical cleaning tank is used to provide chemical cleaning water to the ultrafiltration unit, NF unit, and RO unit. The chemical cleaning wastewater discharge outlets of the ultrafiltration unit, NF unit, and RO unit are all connected to the wastewater pool. The resource recovery unit includes a multi-stage screening device installed at the inlet of the self-cleaning filter, an ultrafiltration concentrate recovery device connected to the concentrate discharge end of the ultrafiltration device, an NF concentrate recovery device connected to the concentrate discharge end of the NF device, and an RO concentrate recovery device connected to the concentrate discharge end of the RO device. The multi-stage screening device is used to screen out and recover metal impurities in the wastewater raw water. The ultrafiltration concentrate recovery device is used to concentrate the ultrafiltration concentrate. The NF concentrate recovery device is used to adsorb and recover polyethylene glycol in the NF concentrate. The RO concentrate recovery device is used to perform low-temperature evaporation and salt separation and recovery of the RO concentrate.

[0007] Furthermore, the ultrafiltration concentrate recovery device is a tubular nanofiltration concentration device, which uses an oil-resistant nanofiltration membrane to concentrate the ultrafiltration concentrate. The concentrate enters the NF concentrate recovery device for co-recovery with the NF concentrate, and the permeate is returned to the inlet of the ultrafiltration device for repeated filtration.

[0008] Furthermore, the NF concentrate recovery device consists of a macroporous resin adsorption component and a desorption distillation component. The macroporous resin adsorption component uses XAD-7 macroporous resin to selectively adsorb polyethylene glycol in the NF concentrate. After adsorption saturation, the desorption distillation component uses ethanol to desorb the concentrate. The desorbed liquid is then distilled under reduced pressure to recover the ethanol. The remaining distillate is polyethylene glycol, which can be directly reused in the preparation of cutting fluid.

[0009] Furthermore, the RO concentrate recovery device includes an electrodialysis pre-concentration device, a heat pump low-temperature evaporation device, and a freeze crystallization device connected in sequence. The electrodialysis pre-concentration device concentrates the RO concentrate, the heat pump low-temperature evaporation device evaporates the concentrated RO concentrate, and the freeze crystallization device is used to separate sodium chloride and hazardous waste salt.

[0010] Furthermore, the electrode electrocatalytic device employs... The electrode plate serves as the anode, and activated carbon fiber serves as the particle electrode. A DC voltage is applied, and the hydroxyl radicals generated by electrolysis break the double layer of the emulsified oil, causing the oil droplets to coalesce. At the same time, hydrogen and oxygen microbubbles are generated to assist in subsequent deep purification.

[0011] Furthermore, the multi-stage screening device includes a strong magnetic drum and a stepped aperture screen. The strong magnetic drum is located at the front end of the water inlet of the self-cleaning filter device and has an automatic scraping device on its surface for adsorbing ferromagnetic metal debris. The stepped aperture screen is located after the strong magnetic drum for intercepting non-magnetic metal debris.

[0012] Furthermore, the oil-resistant nanofiltration membrane material of the tubular nanofiltration concentration unit is sulfonated polyethersulfone.

[0013] A method for treating cutting wastewater, characterized by comprising the following steps: Step 1: The raw wastewater from the cutting process enters a multi-stage screening device, where ferromagnetic metal chips are adsorbed by a strong magnetic roller and non-magnetic metal chips are intercepted by a stepped aperture screen. Step 2: The wastewater treated in Step 1 enters the self-cleaning filter to remove large suspended solids, and then enters the coagulation sedimentation tank. Coagulant is added to carry out the coagulation reaction, so that the colloids and suspended solids are coagulated into flocs and separated by sedimentation. Step 3: The wastewater after coagulation and sedimentation enters the flotation tank to remove floating oil and some flocs, and then enters the demulsification device to break the double electric layer of the emulsified oil, causing the oil droplets to coalesce, while generating microbubbles to assist in deep purification. Step 4: The water from the demulsifier enters the ultrafiltration unit for ultrafiltration treatment, which removes colloids, microorganisms and macromolecular organic matter. The ultrafiltration permeate is stored in the ultrafiltration permeate tank, and the concentrate enters the ultrafiltration concentrate recovery unit for concentration. The concentrate after treatment by the ultrafiltration concentrate recovery unit enters the NF concentrate recovery unit, and the permeate is returned to the inlet of the ultrafiltration unit for repeated filtration. Step 5: The ultrafiltration permeate enters the NF unit after being filtered by the NF security filter, which removes some divalent salts and organic matter. The NF permeate is stored in the NF permeate tank, and the concentrate enters the NF concentrate recovery unit. Step 6: The NF permeate is filtered through the RO security filter and enters the RO unit for reverse osmosis treatment to remove most of the salts, organic matter and microorganisms. The RO permeate is stored in the RO permeate tank for reuse, and the concentrate enters the RO concentrate recovery unit.

[0014] Compared with the prior art, the present invention has the following beneficial effects: Through the synergistic process of "pretreatment (screening + coagulation + flotation + electro-demulsification) and three-stage membrane separation (ultrafiltration + nanofiltration + reverse osmosis)," the cutting wastewater is purified step by step to achieve deep purification. The final RO permeate has excellent water quality and can be directly reused in production. It integrates a complete resource recycling unit; the front end uses multi-stage screening to recover metal scraps; the middle end uses macroporous resin adsorption and desorption processes to efficiently recover high-value polyethylene glycol from NF concentrate, which can be directly reused in cutting fluid formulation; the end end uses a combination of electrodialysis, low-temperature evaporation and freeze crystallization processes to separate and recover sodium chloride from RO concentrate, realizing the resource utilization and reduction of salt. Electrocatalytic demulsification using electrodes replaces traditional chemical demulsification, leaving no reagent residue, ensuring thorough demulsification, and generating microbubbles to aid purification, effectively protecting subsequent membrane systems; tubular nanofiltration further concentrates ultrafiltration water, reducing the amount of liquid entering subsequent recovery units and improving system recovery rate; centralized treatment of chemical cleaning wastewater from each membrane unit, and auxiliary units ensure long-term stable operation of the system. The device organically integrates pretreatment, membrane separation, auxiliary cleaning, sludge treatment and resource recycling, forming a closed-loop treatment system of "purification-reuse-recycling", which meets the requirements of cleaner production and circular economy. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings: Example

[0017] A cutting wastewater treatment device and method, such as Figure 1 As shown, it includes a pretreatment unit, an ultrafiltration unit, a nanofiltration unit, a reverse osmosis unit connected in sequence, as well as an auxiliary unit and a resource recovery unit. The pretreatment unit includes a self-cleaning filter, a coagulation sedimentation tank, an air flotation tank, and a demulsification device; the inlet of the self-cleaning filter is connected to the raw wastewater from the cutting process, and the outlet is connected to the inlet of the coagulation sedimentation tank; the outlet of the coagulation sedimentation tank is connected to the inlet of the air flotation tank, and the outlet of the air flotation tank is connected to the inlet of the demulsification device; the demulsification device is an electrode electrocatalytic demulsification device. The ultrafiltration unit includes an ultrafiltration device and an ultrafiltration product water tank. The inlet end of the ultrafiltration device is connected to the outlet end of the demulsification device; the product water end of the ultrafiltration device is connected to the ultrafiltration product water tank. The nanofiltration unit includes an NF security filter, an NF device, and an NF product water tank. The inlet of the NF security filter is connected to the outlet of the ultrafiltration product water tank, the outlet of the NF security filter is connected to the NF device, and the product water end of the NF device is connected to the NF product water tank. The reverse osmosis unit includes an RO security filter, an RO device, and an RO permeate tank. The inlet of the RO security filter is connected to the outlet of the RO permeate tank, the outlet of the RO security filter is connected to the RO device, and the permeate of the RO device is connected to the RO permeate tank. The outlet of the RO permeate tank is used for wastewater treatment and reuse. The auxiliary unit includes a sludge treatment device, a chemical dosing device, a chemical cleaning tank, and a wastewater pool. The sludge treatment device is connected to the sludge discharge outlets of the self-cleaning filter, coagulation sedimentation tank, demulsification device, and flotation tank in the pretreatment unit. The chemical dosing device is used to add scale inhibitors and bactericides to the inlet of the nanofiltration unit and the reverse osmosis unit. The chemical cleaning tank is used to provide chemical cleaning water to the ultrafiltration unit, NF unit, and RO unit. The chemical cleaning wastewater discharge outlets of the ultrafiltration unit, NF unit, and RO unit are all connected to the wastewater pool. The resource recovery unit includes a multi-stage screening device installed at the inlet of the self-cleaning filter, an ultrafiltration concentrate recovery device connected to the concentrate discharge end of the ultrafiltration device, an NF concentrate recovery device connected to the concentrate discharge end of the NF device, and an RO concentrate recovery device connected to the concentrate discharge end of the RO device. The multi-stage screening device is used to screen out and recover metal impurities in the wastewater raw water. The ultrafiltration concentrate recovery device is used to concentrate the ultrafiltration concentrate. The NF concentrate recovery device is used to adsorb and recover polyethylene glycol in the NF concentrate. The RO concentrate recovery device is used to perform low-temperature evaporation and salt separation and recovery of the RO concentrate.

[0018] Working principle: This cutting wastewater treatment device achieves deep purification and efficient recycling of cutting wastewater through a synergistic process of "pretreatment-membrane separation-resource recovery". The raw wastewater from the cutting process first enters the multi-stage screening device of the resource recovery unit. The front-end strong magnetic roller uses magnetism to adsorb ferromagnetic metal shavings, and the surface automatic scraper simultaneously cleans the adsorbed metal shavings. The subsequent stepped aperture screening screen intercepts non-magnetic metal shavings, thus completing the recovery of metal impurities.

[0019] After screening, the wastewater enters the pretreatment unit, where it first passes through a self-cleaning filter to remove large suspended solids. Then it flows into a coagulation sedimentation tank, where coagulants are added to cause colloids and suspended solids to coagulate and settle. The effluent from the sedimentation tank enters an air flotation tank to remove floating oil and remaining flocs. Finally, it enters an electrode electrocatalytic demulsification device, which... The electrode plate serves as the anode, and the activated carbon fiber serves as the particle electrode. When a DC voltage is applied, electrolysis generates hydroxyl radicals, which disrupt the double electric layer of the emulsified oil and promote the coalescence of oil droplets. At the same time, hydrogen and oxygen microbubbles are generated to assist in subsequent purification.

[0020] The pretreated wastewater enters the ultrafiltration unit, where the ultrafiltration device retains colloids, microorganisms, and macromolecular organic matter. The permeate is stored in the ultrafiltration permeate tank, while the concentrate enters the ultrafiltration concentrate recovery device for concentration. The concentrate is then transported to the NF concentrate recovery device, and the permeate is returned to the inlet of the ultrafiltration device for repeated filtration.

[0021] The ultrafiltration permeate then enters the nanofiltration unit, where minute impurities are removed by the NF security filter before entering the NF unit. The NF unit retains some divalent salts and organic matter, and the permeate is stored in the NF permeate tank. The concentrate is sent to the NF concentrate recovery unit, where polyethylene glycol is selectively adsorbed by the XAD-7 macroporous resin adsorption component. After adsorption saturation, the concentrate is desorbed by the desorption distillation component with ethanol. The desorbed liquid is then distilled under reduced pressure to recover ethanol, and the remaining component is polyethylene glycol that can be reused in the formulation of cutting fluids.

[0022] The NF permeate enters the reverse osmosis unit, and after further filtration by the RO security filter, it enters the RO unit. The RO unit removes most of the salts, organic matter, and microorganisms, and the permeate is stored in the RO permeate tank for wastewater reuse. The RO concentrate enters the RO concentrate recovery unit, is first pre-concentrated by electrodialysis, then evaporated by a heat pump low-temperature evaporation unit, and finally separated by a freeze crystallization unit to separate sodium chloride and hazardous waste salts.

[0023] Throughout the process, the sludge treatment device in the auxiliary unit collects the sludge discharged from each device in the pretreatment unit, the chemical dosing device adds scale inhibitors and bactericides to the inlet of the nanofiltration and reverse osmosis units, the chemical cleaning tank provides chemical cleaning water for each membrane device, and the cleaning wastewater is discharged into the wastewater pool for unified treatment, forming a closed-loop treatment system of "purification-reuse-recycling".

[0024] The control method of this invention is automatic control through a controller. The control circuit of the controller can be implemented by simple programming by those skilled in the art. The power supply is also common knowledge in the art. Furthermore, since this invention is mainly used to protect mechanical devices, the control method and circuit connection will not be explained in detail here.

[0025] Although this disclosure has been described in detail with reference to exemplary embodiments, it is not limited thereto, and it will be apparent to those skilled in the art that various modifications and changes may be made thereto without departing from the scope of this disclosure.

Claims

1. A cutting wastewater treatment device, characterized in that, It includes a pretreatment unit, an ultrafiltration unit, a nanofiltration unit, and a reverse osmosis unit connected in sequence, as well as an auxiliary unit and a resource recovery unit. The pretreatment unit includes a self-cleaning filter, a coagulation sedimentation tank, an air flotation tank, and a demulsification device; the inlet of the self-cleaning filter is connected to the raw wastewater from the cutting process, and the outlet is connected to the inlet of the coagulation sedimentation tank; the outlet of the coagulation sedimentation tank is connected to the inlet of the air flotation tank, and the outlet of the air flotation tank is connected to the inlet of the demulsification device; the demulsification device is an electrode electrocatalytic demulsification device. The ultrafiltration unit includes an ultrafiltration device and an ultrafiltration product water tank. The inlet end of the ultrafiltration device is connected to the outlet end of the demulsification device; the product water end of the ultrafiltration device is connected to the ultrafiltration product water tank. The nanofiltration unit includes an NF security filter, an NF device, and an NF product water tank. The inlet of the NF security filter is connected to the outlet of the ultrafiltration product water tank, the outlet of the NF security filter is connected to the NF device, and the product water end of the NF device is connected to the NF product water tank. The reverse osmosis unit includes an RO security filter, an RO device, and an RO product water tank. The inlet of the RO security filter is connected to the outlet of the RO product water tank, the outlet of the RO security filter is connected to the RO device, and the product water end of the RO device is connected to the RO product water tank. The outlet of the RO permeate tank is used for wastewater treatment and reuse. The auxiliary unit includes a sludge treatment device, a chemical dosing device, a chemical cleaning tank, and a wastewater pool. The sludge treatment device is connected to the sludge discharge outlets of the self-cleaning filter, coagulation sedimentation tank, demulsification device, and flotation tank in the pretreatment unit. The chemical dosing device is used to add scale inhibitors and bactericides to the inlet of the nanofiltration unit and the reverse osmosis unit. The chemical cleaning tank is used to provide chemical cleaning water to the ultrafiltration unit, NF unit, and RO unit. The chemical cleaning wastewater discharge outlets of the ultrafiltration unit, NF unit, and RO unit are all connected to the wastewater pool. The resource recovery unit includes a multi-stage screening device installed at the inlet of the self-cleaning filter, an ultrafiltration concentrate recovery device connected to the concentrate discharge end of the ultrafiltration device, an NF concentrate recovery device connected to the concentrate discharge end of the NF device, and an RO concentrate recovery device connected to the concentrate discharge end of the RO device. The multi-stage screening device is used to screen out and recover metal impurities in the wastewater raw water. The ultrafiltration concentrate recovery device is used to concentrate the ultrafiltration concentrate. The NF concentrate recovery device is used to adsorb and recover polyethylene glycol in the NF concentrate. The RO concentrate recovery device is used to perform low-temperature evaporation and salt separation and recovery of the RO concentrate.

2. The cutting wastewater treatment device according to claim 1, characterized in that, The ultrafiltration concentrate recovery device is a tubular nanofiltration concentration device that uses an oil-resistant nanofiltration membrane to concentrate the ultrafiltration concentrate. The concentrate enters the NF concentrate recovery device, and the permeate is returned to the inlet of the ultrafiltration device.

3. The cutting wastewater treatment device according to claim 1, characterized in that, The NF concentrate recovery device consists of a macroporous resin adsorption component and a desorption distillation component. The macroporous resin adsorption component uses XAD-7 macroporous resin to selectively adsorb polyethylene glycol in the NF concentrate; the desorption distillation component then desorbs and distills the concentrate.

4. The cutting wastewater treatment device according to claim 1, characterized in that, The RO concentrate recovery device includes an electrodialysis pre-concentration device, a heat pump low-temperature evaporation device, and a freeze crystallization device connected in sequence. The electrodialysis pre-concentration device concentrates the RO concentrate, the heat pump low-temperature evaporation device evaporates the concentrate, and the freeze crystallization device is used to separate sodium chloride and hazardous waste salt.

5. The cutting wastewater treatment device according to claim 1, characterized in that, The electrode electrocatalytic device adopts The electrode plate is the anode, and the activated carbon fiber is the particle electrode.

6. The cutting wastewater treatment device according to claim 1, characterized in that, The multi-stage screening device includes a strong magnetic drum and a stepped aperture screening screen. The strong magnetic drum is located at the front end of the water inlet of the self-cleaning filter device and has an automatic scraping device on its surface. The stepped aperture screening screen is located after the strong magnetic drum.

7. The cutting wastewater treatment device according to claim 2, characterized in that, The oil-resistant nanofiltration membrane material of the tubular nanofiltration concentration unit is sulfonated polyethersulfone.

8. A method for treating cutting wastewater based on the apparatus according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: The raw wastewater from the cutting process enters a multi-stage screening device, where ferromagnetic metal chips are adsorbed by a strong magnetic roller and non-magnetic metal chips are intercepted by a stepped aperture screen. Step 2: The wastewater treated in Step 1 enters the self-cleaning filter to remove large suspended solids, and then enters the coagulation sedimentation tank. Coagulant is added to carry out the coagulation reaction, so that the colloids and suspended solids are coagulated into flocs and separated by sedimentation. Step 3: The wastewater after coagulation and sedimentation enters the flotation tank to remove floating oil and some flocs, and then enters the demulsification device to break the double electric layer of the emulsified oil, causing the oil droplets to coalesce, while generating microbubbles to assist in deep purification. Step 4: The water from the demulsifier enters the ultrafiltration unit for ultrafiltration treatment, which removes colloids, microorganisms and macromolecular organic matter. The ultrafiltration permeate is stored in the ultrafiltration permeate tank, and the concentrate enters the ultrafiltration concentrate recovery unit for concentration. The concentrate after treatment by the ultrafiltration concentrate recovery unit enters the NF concentrate recovery unit, and the permeate is returned to the inlet of the ultrafiltration unit for repeated filtration. Step 5: The ultrafiltration permeate enters the NF unit after being filtered by the NF security filter, which removes some divalent salts and organic matter. The NF permeate is stored in the NF permeate tank, and the concentrate enters the NF concentrate recovery unit. Step 6: The NF permeate is filtered through the RO security filter and enters the RO unit for reverse osmosis treatment to remove most of the salts, organic matter and microorganisms. The RO permeate is stored in the RO permeate tank for reuse, and the concentrate enters the RO concentrate recovery unit.

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