A method for ion separation, purification and reuse of waste cooling liquid

Abstract

The present application relates to the technical field of industrial waste glycol coolant liquid recycling, and specifically discloses a waste coolant ion separation and purification recycling method, which adopts normal-temperature multi-stage filtration, coagulation ion chelation and deep adsorption coupling procedures to complete waste glycol coolant liquid purification and regeneration. In the present application, the whole process is operated in liquid phase at normal temperature, and the existing evaporation and condensation process is abandoned, and the high-temperature gasification section at 197.4 DEG C is also abandoned. Therefore, large heating boilers, high-temperature pressure reaction kettles and high-power condensing heat exchanger units are not needed, and the heat energy and power consumption are greatly reduced, so that the industry pain points of high energy consumption cost and high processing cost in the traditional process are solved. The whole process only needs a conveying pump, a stirring tank, small filtering equipment and an adsorption column to realize continuous treatment, and the equipment occupies a small area, the investment in plant supporting is low, and professional high-temperature special operators are not needed, and conventional operation and maintenance personnel can operate after simple training.

Description

Technical Field

[0001] This invention relates to the field of industrial waste ethylene glycol coolant recycling technology, and in particular to a method for ion separation, purification and reuse of waste coolant. Background Technology

[0002] Ethylene glycol coolant is widely used in various industrial heat exchange and cooling systems due to its physical and chemical advantages of low freezing point and high boiling point. During long-term circulation, pipeline metal corrosion products, valve leakage oil stains, and corrosion inhibitor degradation products continue to accumulate, causing it to deteriorate after 2-3 years of operation. Industry regulations stipulate that it should be completely replaced every 3-5 years.

[0003] Currently, the mainstream resource recovery method for waste ethylene glycol coolant in the industry is the evaporation-condensation purification process. This process relies on heating to 197.4℃ to completely vaporize ethylene glycol, and then recovering the liquid phase ethylene glycol through a condensation device, thereby separating solid impurities and ionic pollutants from the system. This process has an unavoidable core drawback: ethylene glycol has a high boiling point, requiring a continuous supply of large amounts of heat energy throughout the high-temperature vaporization process. This necessitates high-power heating equipment, large condensing units, and high-temperature pressure tanks, resulting in high initial equipment costs and significant daily electricity and steam consumption. Industry measurements show that the comprehensive cost of evaporation-condensation treatment of the same tonnage of waste coolant is even higher than the purchase price of virgin ethylene glycol coolant. Therefore, companies find no economic benefit in waste liquid regeneration, and most choose to directly entrust third-party hazardous waste disposal agencies for landfill disposal, resulting in a large waste of ethylene glycol raw materials and adding environmental pressure to solid waste disposal. Therefore, to address these issues, a waste coolant ion separation, purification, and reuse method is proposed. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for the ion separation, purification, and reuse of waste coolant.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for ion separation, purification, and reuse of waste coolant employs a process of ambient temperature multi-stage filtration, coagulation ion chelation, and deep adsorption coupling to purify and regenerate waste ethylene glycol coolant.

[0007] Preferably, the multi-stage filtration is divided into three stages of gradient precision filtration; the first and second stages use 0.5-1μm precision filters to remove solid suspended matter from the original liquid and flocculent chelated precipitates after coagulation, respectively; the third stage uses a 0.01μm ultra-precision filter for circulating filtration to retain nanoscale colloidal particles.

[0008] Preferably, the coagulation ion chelation process includes post-filtration index detection, pH adjustment, coagulant addition, and settling; and the detection of pH, Fe, Cu, P, and Cl in the waste liquid.- SO4 2- Adjust the pH to 7.5-8, add PCL-302 coagulant at 3-5 times the total pollutant concentration in the waste liquid, stir evenly and let stand for 30 minutes to generate ion chelate precipitate.

[0009] Preferably, the index detection process is set after the first-stage precision filtration to remove solid suspended matter in advance, so as to avoid solid particles interfering with the accuracy of ion detection data.

[0010] Preferably, after the coagulant is added, the stirring speed is controlled at 60-120 r / min, and continuous stirring is carried out for no less than 10 min to ensure that the coagulant reacts with the P and Cl in the liquid phase. - SO4 2- Fully chelate reaction.

[0011] Preferably, the three-stage 0.01μm ultra-precision filter adopts a closed-loop circulation mode, with a single circulation filtration time of not less than 20 minutes, and removes trace amounts of ultrafine colloids by penetrating the filter layer multiple times.

[0012] Preferably, the deep adsorption process uses DB-301 special adsorption material, through which the ethylene glycol solution after three filtrations flows counter-currently and at a uniform speed through the adsorption packing layer to remove residual Fe, Cu, P, and Cl from the liquid phase. - SO4 2- Pollutants.

[0013] Preferably, the flow rate of the ethylene glycol solution flowing counter-currently through the DB-301 adsorption material is controlled at 0.5-1.2 m / h to prolong the contact time between the liquid and the adsorption packing material and improve the ion adsorption removal rate.

[0014] Preferably, the entire purification process operates at room temperature without any heating, vaporization, or condensation recovery stages, thus eliminating the need for high-temperature heating of the ethylene glycol.

[0015] Preferably, the pH of the purified ethylene glycol coolant is maintained at a stable 7.5-8, and the content of metal ions and acid radical ions meets the factory standards for brand new ethylene glycol coolant, which can be directly reused in industrial cooling and heat exchange systems.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. This invention operates entirely at room temperature in the liquid phase, eliminating the 197.4℃ high-temperature gasification section of existing evaporation-condensation processes. It eliminates the need for large heating boilers, high-temperature pressure reactors, and high-power condensing heat exchangers, significantly reducing heat and electricity consumption. This fundamentally solves the industry pain points of excessive energy costs and unprofitable processing fees associated with traditional processes. The entire process relies solely on a transfer pump, mixing tank, small filtration equipment, and adsorption column for continuous processing. The equipment has a small footprint, low plant setup investment, and requires no specialized high-temperature operations personnel; regular maintenance personnel can operate it after simple training.

[0018] 2. This invention employs a four-stage coupled purification system: gradient precision filtration, coagulation chelation, nanoscale circulating filtration, and specialized adsorption materials. This system removes solid suspended matter, colloidal particles, metal cations, and acidic anions from the waste liquid in layers, achieving stepwise and directional separation of multiple types of pollutants. The purified ethylene glycol medium meets the standards for brand-new industrial coolant, with no downgrading limitations, and can be directly recycled to high-precision heat exchange equipment such as data center liquid cooling, semiconductor cooling, and low-temperature testing of lithium batteries. Two-stage pre-filtration (0.5-1μm) intercepts large particles of rust and oil; the coagulation process directionally chelates chloride, sulfate, and phosphorus ions; 0.01μm ultra-precision filtration retains nanoscale chelated colloids; and DB-301 adsorption material deeply captures trace amounts of free iron and copper ions. This multi-stage synergy eliminates purification dead zones, maintaining a stable pH of 7.5-8 in the finished medium. The corrosion inhibition system is compatible with various metal pipelines, and its reuse lifespan is consistent with that of brand-new ethylene glycol coolant.

[0019] 3. This invention operates entirely in a room-temperature liquid phase environment, eliminating the high-temperature thermal decomposition reaction of ethylene glycol and preventing the generation of corrosive byproducts such as organic acids and aldehydes. The entire purification process produces no volatile organic compounds, only a small amount of inorganic chelated salt solid filter residue, and no wastewater discharge. The precipitates and flocs generated during the coagulation stage are stable in composition and contain no volatile organic compounds, allowing for compliant disposal by qualified hazardous waste management institutions without the need for complex exhaust gas and wastewater treatment facilities. Furthermore, this invention achieves resource recovery from waste ethylene glycol, significantly reducing the procurement of virgin ethylene glycol chemical raw materials and decreasing carbon emissions during ethylene glycol chemical production. This aligns with current industrial green, low-carbon, and circular economy development policies, offering both significant environmental benefits and resource conservation value, while avoiding the soil and groundwater pollution risks associated with direct landfilling of waste liquid. Attached Figure Description

[0020] Figure 1 This is a flowchart of a method for ion separation, purification, and reuse of waste coolant proposed in this invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] Reference Figure 1 This invention discloses a method for the ion separation, purification, and reuse of waste coolant. Combining two sets of actual treatment cases under different working conditions, it fully and meticulously explains the entire operation process, equipment selection, process parameters, testing standards, and operating effects of the waste coolant ion separation, purification, and reuse method of this invention.

[0024] The present invention deals with ethylene glycol-based industrial waste coolant, covering data center liquid cooling, floor heating, central air conditioning, semiconductor equipment cooling, and deterioration media in lithium battery low-temperature testing systems. The ambient temperature of all processes is controlled at 20-28°C, and no heating device is provided throughout the process. All separation, reaction, and adsorption processes are completed under normal temperature liquid phase conditions.

[0025] Example 1: Purification treatment of data center using 4-year-deteriorated ethylene glycol coolant

[0026] In this embodiment, the raw material was taken from the liquid cooling circulation pipeline of a large data center server in the Yangtze River Delta. The coolant had been running continuously for 48 months, resulting in a large amount of rust forming on the inner wall of the pipeline, leakage of lubricating oil from the hydraulic valve seals, and complete failure of the original corrosion inhibitor. The medium appeared cloudy and yellowish, with yellowish-brown solid precipitate deposited at the bottom of the storage tank. Laboratory sampling and testing of the original stock solution revealed the following indicators: pH=6.2, Fe ions 126mg / L, Cu ions 38mg / L, phosphorus 42mg / L, chloride ions 78mg / L, sulfate ions 96mg / L, and total contaminants 380mg / L. The freezing point had decreased, and the corrosion inhibition performance had been lost, meeting the company's mandatory replacement standards. If the industry-standard evaporation-condensation process were used to treat 1 ton of this waste liquid, the total cost, including heating steam, equipment wear and tear, labor, and electricity, would be 1320 yuan. However, the purchase price of brand-new ethylene glycol coolant of the same specification is only 1150 yuan. The treatment cost is higher than the purchase price of new liquid, and the company has no intention of recycling it. Therefore, the process of this invention is used to carry out a complete purification operation of 5m³ of waste liquid. The detailed steps are as follows:

[0027] Step 1: Primary 0.5-1μm precision filtration pretreatment. This example uses a 1μm stainless steel sintered precision filter, paired with a corrosion-resistant fluoroplastic centrifugal pump. The deteriorated coolant from the waste liquid storage tank is continuously pumped into the filter. The multi-layered gradient sintered membrane inside the filter is resistant to swelling and corrosion from ethylene glycol organic solvents. The filtration operating pressure is stably controlled at 0.25MPa, and the liquid flow rate is set at 2m³ / h. All rust particles larger than 1μm, oil flocs, and rubber debris from pipelines within the raw liquid are trapped by the filter membrane. After filtering 5m³ of waste liquid, a yellowish-brown filter cake accumulates on the filter membrane surface. This cake can be disassembled and rinsed with high-pressure water for reuse, eliminating the need for frequent filter media replacement. After primary filtration, the middle layer supernatant was collected and transferred to a 10m³ sealed stirred analytical storage tank. The tank is equipped with an online pH meter and a side sampling port. 500mL of the filtered ethylene glycol solution was extracted and sent to the laboratory for testing of six indicators. The filtered test data were: pH=6.3, Fe=118mg / L, Cu=36mg / L, P=41mg / L, Cl... - =77mg / L, SO4²⁻=94mg / L, the suspended solids have been basically removed, and the ionic pollutants have only decreased slightly. The test data will be used as the basis for calculating the dosage of coagulant in the future.

[0028] Step 2: Adjust the pH of the waste liquid to the range of 7.5-8. Slowly add a low-volatile organic amine weakly alkaline regulator to the stirred tank in several batches to avoid introducing additional acid radicals and impurities from the inorganic alkali. Maintain a low stirring speed of 60 rpm, and read the online pH value every 2 minutes. Add the regulator in small amounts several times until the pH of the ethylene glycol solution in the tank stabilizes at 7.7, which is within the optimal control range of this invention. After stopping the addition of the agent, continue stirring for 5 minutes to ensure that the pH of the liquid in the tank is uniform and there is no local acid-base imbalance. If the original pH of the waste liquid to be treated is higher than 8, a low-concentration organic weak acid can be used for neutralization, and the final pH should also be controlled at 7.5-8. This pH range can maximize the activation of the chelation reaction activity of PCL-302 coagulant, while ensuring that the regenerated coolant has basic corrosion inhibition capabilities to prevent the metal pipeline from rusting rapidly again after reuse.

[0029] Step 3: Add PCL-302 coagulant, stir for chelation, and allow to settle. Based on the laboratory test result of 380 mg / L total pollutants, add PCL-302 coagulant at 4 times the total pollutant concentration, corresponding to 1520 mg of agent per liter of waste liquid. For 5 m³ of waste liquid, a total of 7.6 kg of solid powder agent is added. The agent is evenly sprinkled into the stirring tank in three batches, with a 3-minute interval between each addition. After all additions are completed, increase the stirring speed to 100 r / min and stir continuously for 12 minutes to ensure complete dissolution and dispersion of the powder agent into the ethylene glycol liquid phase. The active components of the agent undergo cross-linking and chelation reactions with phosphorus, chloride, and sulfate ions in the system, rapidly generating inorganic metal chelate particles insoluble in ethylene glycol. After stirring, turn off the stirring motor, seal the tank, and allow it to settle for 30 minutes. During the settling process, the liquid clearly separates into layers: a dense, yellowish-brown inorganic precipitate forms at the bottom, a light gray flocculent chelate floats on the upper layer, and the turbidity of the middle layer of ethylene glycol liquid significantly decreases, indicating that the vast majority of ionic pollutants have transferred to the solid phase. The settling time should be strictly controlled at 30 minutes. Insufficient settling time will result in incomplete chelation reaction and residual trace ions. If the settling time exceeds 40 minutes, the flocs will break down and redisperse, increasing the load on subsequent filtration.

[0030] Step 4: Secondary 0.5-1μm precision filtration removes flocs and sediment. The same 1μm stainless steel precision filter as the primary filter is used. The ethylene glycol liquid from the middle layer of the storage tank is drawn and filtered. The bottom sediment and surface floating flocs are retained at the bottom of the tank and periodically collected in a sealed container, then disposed of by a qualified hazardous waste disposal organization. The secondary filtration operates at a pressure of 0.2MPa and a flow rate of 1.8m³ / h. It completely intercepts chelated precipitates and floating flocs generated during settling. The filtered liquid shows no visible suspended impurities, only residual nano-sized colloidal chelated particles, which conventional micron-level filtration cannot intercept, and proceeds to the tertiary ultra-precision circulating filtration process. The filter residue produced by the secondary filtration consists of iron, copper phosphate, and sulfate chelates, containing no volatile organic compounds. It is classified as conventional inorganic industrial hazardous waste and stored in sealed solid waste containers. There is no discharge of waste gas or wastewater throughout the entire process.

[0031] Step 5: Closed-loop circulation filtration using a 0.01μm nanofiltration precision filter. A closed-loop circulation system is constructed, consisting of a 0.01μm ultra-precision PTFE filter, a circulation tank, and a circulation pump. The ethylene glycol solution after secondary filtration is injected into the circulation tank. The circulation pump is turned on, allowing the liquid to repeatedly penetrate the 0.01μm filter membrane. The total circulation filtration time is 25 minutes. All trace colloidal chelated particles larger than 0.01μm are retained by the filter membrane. The PTFE filter membrane is resistant to long-term immersion in ethylene glycol, and its pore size will not expand or leak. After circulation, the liquid is completely transparent, with no visible turbidity. Only a small amount of single-molecule free metal ions and acid radical ions remain in the liquid phase. Colloidal impurities are completely removed, reducing the processing load on the subsequent DB-301 adsorbent material and extending the service life of the packing material.

[0032] Step 6: Reverse Deep Ion Adsorption with DB-301 Adsorbent Material. Construct a vertical cylindrical adsorption column, filling it with DB-301 composite ion adsorption packing material. The packing material fills 85% of the column's internal cavity, with a liquid buffer space reserved at the top. Introduce a transparent ethylene glycol solution, filtered through a three-stage circulation system, into the bottom inlet of the adsorption column. The solution flows slowly upwards and backwards through the packing layer, with the flow rate strictly controlled at 0.8 m / h. This low-speed reverse flow prolongs the contact time between the liquid and the adsorption packing material. The specific adsorption groups inside the packing material directionally capture free Fe and Cu cations in the liquid phase, while simultaneously fixing residual P and Cl. - SO4 2- Anions are used to simultaneously remove all trace ionic contaminants. The purified ethylene glycol coolant is continuously collected at the top outlet of the adsorption column, allowing for continuous and uninterrupted operation. After the DB-301 packing material becomes saturated, it can be regenerated by rinsing with a low-concentration regeneration solution and reused 3-5 times before being replaced with new packing material, significantly reducing consumable procurement costs.

[0033] After the entire process was completed, samples of the finished coolant were taken for comprehensive testing. The test results were: pH=7.7, Fe≤0.3mg / L, Cu≤0.1mg / L, P≤0.2mg / L, Cl⁻≤0.5mg / L, SO₄²⁻ 2- With a concentration ≤0.4mg / L, all ionic impurities are below the factory-specified standards for brand-new industrial ethylene glycol coolant. Freezing point, boiling point, and metal corrosion inhibition properties are fully restored to new liquid levels, allowing for direct return to data center liquid cooling pipelines for recycling without the need for additional corrosion inhibitors. Compared to traditional evaporation-condensation processes, treating 5m³ of waste liquid consumes only the power of a transfer pump and stirring motor, with no steam or high-temperature electric heating energy consumption. The overall treatment cost is only 410 yuan / ton, and resource recovery of each ton of waste liquid can save 740 yuan in new liquid purchase costs. The total purchase price of the entire ambient temperature equipment is only 1 / 6 of that of an evaporation-condensation unit, and the equipment occupies only 3㎡. It can be directly installed in the bypass area of ​​the computer room for online purification of deteriorated coolant without shutting down and emptying the entire cooling system, ensuring uninterrupted and stable server operation.

[0034] Example 2: Purification treatment of 3-year-old waste ethylene glycol coolant in underfloor heating system

[0035] In this embodiment, the raw material was taken from a residential community's underfloor heating heat exchange system. The coolant had been running continuously for 36 months, resulting in rust on the inner walls of the pipes and oil leakage from the rubber seals of the manifolds. The initial test indicators were pH=6.1 and total pollutants 345mg / L, with other ionic components similar to those in Example 1. The process of this invention was used for complete treatment, only adjusting the coagulant dosage. PCL-302 coagulant was added at three times the total pollutants, while all process parameters, including filtration accuracy, pH control range, stirring speed, settling time, and adsorption flow rate, remained unchanged. After the entire purification process was completed, samples were taken for testing. All ionic indicators of the finished coolant met the standards. The regenerated ethylene glycol was then transported back to the underfloor heating system and ran continuously for 24 months. No rust, turbidity, or deterioration of the medium was observed in the pipes. This verifies that the process of this invention is suitable for the purification of waste media in all types of ethylene glycol cooling systems, including central air conditioning, underfloor heating, solar thermal conductivity, air source heat pumps, semiconductor cooling, and low-temperature testing of lithium batteries. The process has strong versatility, and deteriorated waste liquids under different operating conditions can be regenerated and reused at low cost and with high purity.

[0036] Based on the operational results of the two sets of embodiments, the entire ambient temperature ion separation and purification process of this invention is progressively advanced, first removing large particulate solid impurities, then removing most ionic pollutants through coagulation and chelation, then retaining colloidal particles through nanoscale circulating filtration, and finally removing trace amounts of free ions through specific adsorption. The multi-stage processes work together without any purification bottlenecks. The reagent dosage ratio, filtration accuracy, liquid flow rate, and settling time are all quantifiable and controllable. On-site operators only need to follow fixed parameters to stably produce recycled ethylene glycol coolant that meets reuse standards. The entire process relies on the principle of ambient temperature liquid phase separation, abandoning the traditional high-temperature evaporation and condensation section, and solving the core pain points of existing technologies such as high energy consumption, poor economic efficiency, and substandard quality of regenerated media. It has industrial-scale promotion value.

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for ion separation, purification, and reuse of waste coolant, characterized in that, The process of purifying and regenerating waste ethylene glycol coolant involves a multi-stage filtration process at room temperature, coagulation ion chelation, and deep adsorption coupling.

2. The method for ion separation, purification, and reuse of waste coolant according to claim 1, characterized in that, The multi-stage filtration is divided into three stages of gradient precision filtration; the first and second stages use 0.5-1μm precision filters to remove solid suspended matter from the original liquid and flocculent chelate precipitates after coagulation, respectively; the third stage uses a 0.01μm ultra-precision filter for circulating filtration to trap nano-sized colloidal particles.

3. The method for ion separation, purification, and reuse of waste coolant according to claim 1, characterized in that, The coagulation and ion chelation process includes post-filtration index detection, pH adjustment, coagulant addition, and settling; and detection of waste liquid pH, Fe, Cu, P, and Cl. - SO4 2- Adjust the pH to 7.5-8, add PCL-302 coagulant at 3-5 times the total pollutant concentration in the waste liquid, stir evenly and let stand for 30 minutes to generate ion chelate precipitate.

4. The method for ion separation, purification, and reuse of waste coolant according to claim 3, characterized in that, The indicator detection process is set after the first-stage precision filtration to remove solid suspended matter in advance, so as to avoid solid particles interfering with the accuracy of ion detection data.

5. The method for ion separation, purification, and reuse of waste coolant according to claim 3, characterized in that, After the coagulant is added, the stirring speed should be controlled at 60-120 r / min, and stirring should be continued for no less than 10 min to ensure that the coagulant reacts with the P and Cl in the liquid phase. - SO4 2- Fully chelate reaction.

6. The method for ion separation, purification, and reuse of waste coolant according to claim 2, characterized in that, The three-stage 0.01μm ultra-precision filter adopts a closed-loop circulation mode, with a single circulation filtration time of no less than 20 minutes, and removes trace amounts of ultrafine colloids by penetrating the filter layer multiple times.

7. The method for ion separation, purification, and reuse of waste coolant according to claim 1, characterized in that, The deep adsorption process uses DB-301 special adsorption material. The ethylene glycol solution after three filtrations flows counter-currently and at a uniform speed through the adsorption packing layer to remove residual Fe, Cu, P, Cl⁻, and SO₄²⁻ from the liquid phase. 2- Pollutants.

8. The method for ion separation, purification, and reuse of waste coolant according to claim 7, characterized in that, The flow rate of the ethylene glycol solution flowing counter-currently through the DB-301 adsorption material is controlled at 0.5-1.2 m / h to prolong the contact time between the liquid and the adsorption packing material and improve the ion adsorption removal rate.

9. The method for ion separation, purification, and reuse of waste coolant according to claim 1, characterized in that, The entire purification process operates at ambient temperature, without any heating, vaporization, or condensation recovery stages, and there is no need to heat the ethylene glycol at high temperatures.

10. A method for ion separation, purification, and reuse of waste coolant according to any one of claims 1-9, characterized in that, After purification, the pH of the ethylene glycol coolant is maintained at a stable 7.5-8, and the content of metal ions and acid radical ions meets the factory standards for brand new ethylene glycol coolant, which can be directly reused in industrial cooling and heat exchange systems.

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