Method for purifying water by additionally arranging magnetic precipitation device on balance valve water return pipeline

Abstract

The invention discloses a method for purifying water by additionally arranging a magnetic precipitation device on a water return pipeline of a balance valve, and aims to solve the problems. The method for purifying water by adding the magnetic precipitation device to the water return pipeline of the balance valve is suitable for a closed cooling water system for purifying raw water to obtain 2 megohms of high-purity water, at least 90% of the cooling water pipeline is made of 304 stainless steel pipes (5-10% of the cooling water pipeline is locally scattered and cannot be completely made of 304 stainless steel; and a closed cooling water system of a high-precision filter which is less than or equal to 10-20 microns is arranged at the cooling water inlet end of high-end equipment of a production process line. The service life of a high-precision equipment filter of a process production line can be effectively prolonged, the problem of high cost of replacing 2 megohms of high-purity cooling water per week can be solved, and the frequency of disassembling and cleaning the plate heat exchanger during production halt can be reduced.

Description

Technical Field

[0001] The present invention relates to a cooling water system for high-precision equipment in a process production line of a high-end integrated circuit manufacturing industry, and more specifically, to a cost reduction method for the demand for cooling water quality of high-precision equipment in a process production line and high reliability assurance. Background Art

[0002] The domestic manufacturing industry is constantly upgrading and transforming from low-end to high-end manufacturing. The high-precision equipment of process production lines is becoming more and more expensive, and the supporting constant temperature and humidity purification plants are becoming more and more popular. The water quality requirements of process cooling water required by high-precision equipment are also getting higher and higher. However, the materials of heat exchangers, pipes, valves and other materials of domestic general refrigeration equipment cannot meet the high-precision equipment of the production line. As a result, there are always inferior pipe parts with excessive iron content being corroded in the circulating cooling water system, releasing iron oxide particles and polluting the entire circulating cooling water system. At present, the source of iron oxide microparticle pollution in the process cooling water system of the high-end manufacturing industry of integrated circuits is mainly at the refrigeration end and substandard stainless steel pipes and valve accessories.

[0003] In order to protect the internal part of the equipment from being polluted by impurity particles in the cooling water, integrated circuit equipment manufacturers often install 10-50um precision filters at the water inlet of the equipment. When high-end manufacturing companies design and install process cooling water systems when building factories, they will also use plate heat exchangers to divide the cooling end of the circulating cooling water system, which is prone to iron oxide particle pollution, and the cooling water of the high-precision equipment of the terminal production line into two independent internal and external circulating cooling water systems, thereby isolating the iron oxide particle pollution generated by the cooling end from the external cooling water circulation system. The plate heat exchanger, circulating water pump and pipelines of the internal cooling water circulation system for high-precision equipment on the production line are all made of 100% stainless steel to ensure that no iron oxide particles are generated in the fully enclosed internal circulation cooling water system. However, the installation of a plate heat exchanger process cooling water system also has great disadvantages. After all, there are still iron oxide particles constantly generated in the external cooling water circulation system. After adsorption and scaling on the exchange surface of the external circulation side of the plate heat exchanger, the heat exchange efficiency is seriously affected. In severe cases, it even blocks the internal water flow channel of the plate heat exchanger and corrodes the inner wall. It is necessary to stop production and disassemble the plate heat exchanger regularly, which seriously affects the continuous production guarantee of the enterprise. And every time you disassemble and clean the plate heat exchanger, you need to be extremely careful. The stacked stainless steel metal sheets for heat exchange must not be bumped or bent. In order to ensure that the plate heat exchanger does not leak after reinstallation, you have to buy a new sealing gasket from the plate heat exchanger manufacturer at a high price every time. The plate heat exchanger has high heat exchange efficiency and is easy to disassemble and clean, but only those who have used it know it, just like the business story of giving away kerosene lamps for free. Each subsequent disassembly and replacement of the sealing gasket can only be purchased from the original manufacturer. The total price of replacing the sealing gasket several times is equivalent to buying another plate heat exchanger.

[0004] After experiencing the pain of being able to afford plate heat exchangers but not being able to use them, some high-end manufacturing companies have adopted the solution of replacing plate heat exchangers with water tanks. The internal and external circulating hot and cold water are compatible in the water tank, which can also meet the water temperature control requirements of the high-precision equipment process cooling water on the production line. However, a 10-50um precision filter must be installed on the water inlet of the high-precision equipment on the production line. Otherwise, pollutants such as iron oxide particles on the refrigeration end will enter the terminal high-precision equipment. If it causes failure of the high-precision process production equipment, it will cause huge economic losses.

[0005] In view of the above problems, improving the stainless steel material of cooling water pipelines is the most fundamental solution. However, the current domestic general refrigeration equipment water circulation system cannot use 100% qualified stainless steel materials, so it is particularly important to reduce system pipeline corrosion and remove iron oxide particles from pollution sources. The present invention utilizes the original balance valve return pipeline of the process cooling water system without adding power energy consumption, and utilizes the characteristics of strong floatation and weak magnetic conductivity of iron oxide particles. It uses NdFeB strong magnetic strips and double-layer non-woven filter cotton to adsorb and fix 10-100um iron oxide particles in the cooling water. It only needs to regularly clean and clean the non-woven filter cotton of the balance valve return pipeline to achieve energy-free and continuous purification of iron oxide particle pollution in the process cooling water, solving the problem of iron oxide impurities in domestic stainless steel pipelines contaminating the cooling water quality of high-end manufacturing process production equipment.

[0006] 1. The problem of iron oxide particles in the process cooling water of high-end integrated circuit manufacturing industry affecting terminal equipment; 2. Solve the problem of high energy consumption, large water flow / pressure fluctuations and poor reliability of installing in-line filters for process cooling water. 3. Solve the problem of micron-sized iron oxide particles in cooling water pipelines being difficult to capture and clean, requiring regular shutdown of terminal production line equipment to replace filters, or stopping the entire cooling water system to disassemble the plate heat exchanger to clean the internal iron oxide scaling, which is costly. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for purifying water by installing a magnetic precipitation device in the return pipe of a balancing valve, so as to remove the iron oxide pollution problem in the process cooling water.

[0008] The above technical purpose of the present invention is achieved through the following technical solution: the method comprises the following steps:

[0009] 1) The original pipeline of process cooling water is fully utilized, and only the magnetic precipitation water purification device is installed at the interface between the return pipe of the balancing valve and the water tank, without increasing additional energy consumption;

[0010] 2) The water purification device uses conventional inclined tube precipitation + NdFeB strong magnetic adsorption and non-woven fiber fixation to firmly adsorb the iron oxide microparticles with magnetic conductivity flowing through the surface of the non-woven fabric, and the clean water slowly rises from the inclined tube. The water purification device is simple and efficient;

[0011] 3) The non-woven fabric inside the water purification device mainly assists the NdFeB strong magnetic absorption and fixation of iron oxide particles. No matter how dirty it is, it will not block the water flow channel and the process cooling water will not overflow, ensuring that the process cooling water system is absolutely safe and reliable;

[0012] 4) It is necessary to clarify the water quality requirements of the production line precision equipment and the main function of this device is to remove and purify the iron oxide microparticle pollution problem in the high-standard process cooling water that meets the national standard (total iron content less than 1PPM).

[0013] By adopting the above technical scheme, 1. A strong magnetic precipitation water purification device is installed according to the return water pipeline of the balancing valve in the process cooling water system, and the bypass (balancing valve) return water in the continuous circulation of process cooling water is used to continuously circulate and purify the water quality, so as to ensure reliable, efficient and energy-saving effects.

[0014] 2. It is necessary to verify the water quality standard requirements of high-end production line equipment, especially the accuracy of the filter at the water inlet. The present invention is only applicable to process cooling water that meets the GB / T50050-2017 industrial closed-loop cooling water quality standard and the solid particle grade (GB13277.1-2016) standard. The high-end manufacturing cooling water system is trapped in the stainless steel pipe material iron oxide particle pollution system. For open cooling water systems with a large amount of algae and dust pollution, the invention is not recommended.

[0015] In summary, the present invention has the following beneficial effects: the return water enters the magnetic precipitation water purification device through the process cooling water balance valve, and the iron oxide microparticles are drawn into the non-woven fabric fibers for adsorption and fixation due to gravity and the strong magnetic attraction of the neodymium iron boron at the bottom of the device, and can no longer be washed away by the water flow, and are separated from the clean water flow that slowly rises through the inclined tube, thereby achieving the purpose of water purification. As long as the process cooling water circulation system operates normally, the magnetic precipitation water purification device can continuously circulate and remove the iron oxide particles in the water, thereby achieving the purpose of purifying the water quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram of a universal closed process cooling water system of the present invention;

[0017] Figure 2 This is a diagram of a closed process cooling water system of a plateless heat exchanger of the present invention;

[0018] Figure 3 It is a schematic structural diagram of the magnetic precipitation water purification device of the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. It should be noted that the embodiments of the present application and the features therein may be combined with each other without conflict.

[0020] The following is a specific implementation example of our company: In order to alleviate the weekly shutdown of production line equipment personnel to replace the process cooling water inlet high-precision filter, the power guarantee department needs to continuously replace the 2MΩ pure water in the water tank every day. Taking our company's 8 cubic water tank as an example, the cost of replacing pure water can save more than 100,000 yuan each year.

[0021] Table 1: GB / T50050-2017 Closed Industrial Circulating Cooling Water Quality Standard

[0022]

[0023] Table 2: Solid particle grade of process cooling water (GB13277.1-2016)

[0024]

[0025] General closed process cooling water system diagram (see Figure 1 ), generally including internal circulation process cooling water (pump) circulation system and external circulation process chilled water (pump) circulation system, plus refrigerator, plate heat exchanger, water tank, filter, bypass balancing valve, etc.;

[0026] The internal circulation process cooling water transfers the heat of the production line process equipment in the workshop to the plate heat exchanger, and then exchanges it to the external circulation process chilled water through the plate heat exchanger. Finally, the heat generated by the production line equipment is discharged to the outside by the refrigerator. The high-end production line process equipment in the integrated circuit purification workshop has extremely high requirements for the water quality, temperature and reliability of the process cooling water. Therefore, the internal circulation cooling water system that is in direct contact with the high-end production line equipment is isolated from the external circulation chilled water by a plate heat exchanger, and a bag filter is also installed in series in the internal circulation cooling water system to purify and filter particles larger than 50 microns in the internal circulation cooling water system. Multiple parallel refrigeration units, high-efficiency plate heat exchangers, large-capacity water tanks and one-in-one cooling water pump can ensure that the cooling water supplied to the production line process equipment is constant and uninterrupted, and the bypass balancing valve can control the cooling water pressure supplied to the production line process equipment to be basically stable.

[0027] The biggest disadvantages of this system:

[0028] 1.50um series bag filter accuracy cannot filter 20-30um iron oxide particles in cooling water. If the accuracy of the series filter is improved, the flow and pressure of the entire circulating water system will be affected;

[0029] 2. The plate heat exchanger can isolate the external circulating chilled water from polluting the production line process equipment, but it cannot avoid polluting the outer heat exchange surface of the plate heat exchanger, resulting in a decrease in heat transfer efficiency, and it needs to be regularly shut down for disassembly and cleaning;

[0030] 3. Investment cost and use cost. During the design and installation, the internal circulation process cooling water pipeline system connected to the production line process equipment is all made of domestic high-quality 304 stainless steel, and the external circulation chilled water system is made of low-cost carbon steel. It seems that the investment cost is saved in one investment, but the domestic high-quality 304 stainless steel pipe has a high impurity content and is still prone to electrochemical corrosion during use, and will continuously release impurities such as iron oxide ions into the circulating cooling water. The fundamental reason is that the domestic high-quality 304 stainless steel material cannot be consistent with the material of the production line process equipment, especially the reality that the materials of imported high-end integrated circuit production line equipment are several grades higher than domestic high-quality 304 stainless steel. Therefore, imported high-end integrated circuit equipment has to add high-precision filters in the process cooling water inlet pipeline to protect itself.

[0031] Closed process cooling water system diagram without plate heat exchanger (see Figure 2 ),and Figure 1 Compared with the general closed process cooling water system diagram, the plate heat exchanger is missing to isolate the internal and external circulating water systems. The external circulating process chilled water is directly mixed into the internal circulating process cooling water tank, which also meets the requirements of heat exchange and temperature control. Because our company's high-end integrated circuit production line equipment has a high demand for process cooling water, we adopt an internal and external circulation fully closed system to prevent external dust and algae from entering the water system and causing pollution. The one-time investment cost is high. The internal and external circulating cooling water pipelines are basically made of domestic high-quality 304 stainless steel. The high cost investment in the early stage avoids the problem of carbon steel pipe valves being easily rusted and polluting the water quality in the later stage. Eliminating the plate heat exchanger also avoids the problem of the plate heat exchanger needing to be shut down and disassembled for cleaning regularly. However, in actual use, it was found that the 10um precision filter of the production line process equipment is still easy to be blocked. In severe cases, it must be replaced within a period of no more than 1 week. Before the particulate matter and source of the 10um precision filter of the production line process equipment are found to be blocked, it can only be alleviated by continuously replacing the process cooling water.

[0032] The requirements for process cooling water quality of integrated circuit high-end process production line equipment are much higher than the national cooling GB / T50050-2017 industrial circulating cooling water quality index (see attached for details). Figure 1 ) and GB-5750 Water Treatment Water Quality Index Test Standard (see Appendix for details) Figure 2) standard, our company has repeatedly inspected the process cooling water externally and all of them meet the above national standards, including the total iron content is <1ppm. However, in actual use, there is still a problem of clogging the high-precision filter of the process production equipment. In addition, the raw water of our process cooling water is 2MΩ pure water, and the contaminated SS particles and content in the water quality are less than the test range of the detection instrument, resulting in the inability to identify the pollutants through standard detection. After repeatedly hanging NdFeB strong magnets in the cooling water tank, a trace amount of black particles were finally captured in the middle gap of the strong magnetic block. The color is consistent with the micro-particles that contaminate and clog the 10um precision filter, and it is basically determined to be black iron oxide micro-particles, which have the characteristics of being adsorbed by NdFeB strong magnets, but are different from the common reddish-brown iron oxide rust. Due to the weak magnetic adsorption capacity of the tiny particles, the outside of the NdFeB strong magnetic block can adsorb particles in the water, but it will also be washed away by the water flow. After determining that the process cooling water pollutants are iron oxide particles, the problem of iron impurities in domestic stainless steel pipes, valves and other materials was also exposed.

[0033] Magnetic Sedimentation Water Purification Device (See Figure 3 ), mainly referring to the principle of sewage treatment sedimentation tank, raw water with microparticles enters the bottom of magnetic precipitation water purification device, and the purified water slowly rises through the inclined tube. The iron oxide microparticles are precipitated downward under the action of gravity and the attraction of the strong magnetic NdFeB at the bottom, and are captured and fixed when adsorbed on the non-woven fabric, so as to achieve the purpose of separating and purifying water. The purified water enters the water outlet from the upper overflow tank and returns to the process cooling water tank. Together with the main process cooling water, it continuously circulates and separates the iron oxide microparticles to achieve the purpose of purifying the entire circulating water system. When cleaning, just open the drain valve and flush the inclined tube and non-woven fabric in the device with water. The impact force of the water flow can flush out the iron oxide adsorbed on the surface of the non-woven fabric and discharge it through the drain valve pipeline. Because the drain valve designed and installed by the magnetic precipitation water purification device is lower than the outlet pipe, the switch can be completed by simply opening the drain valve when flushing and discharging regularly. Moreover, the non-woven fabric in the magnetic precipitation water purification device mainly serves to capture and fix iron oxide microparticles. The purified water flow does not pass through the non-woven fabric, so there are no problems such as clogging and overflow of the filter water purifier, which can ensure the safety and reliability of the process cooling water system.

[0034] The present invention is suitable for a closed cooling water system in which the raw water reaches 2MΩ high-purity water after purification, and at least 90% of the cooling water pipeline material is 304 stainless steel pipe (5-10% is the cooling water pipeline is partially scattered and cannot be fully made of 304 stainless steel, such as the iron shell, end cover, and other pipe accessories of the refrigerator heat exchanger), and the high-end equipment cooling water inlet of the production process line is installed with a ≤10-20um high-precision filter. It can effectively extend the service life of the filter of the high-precision equipment of the process production line, reduce the high cost of replacing 2MΩ high-purity cooling water every week, and reduce the number of shutdowns to disassemble and clean the plate heat exchanger.

[0035] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for purifying water by installing a magnetic precipitation device on the return pipe of a balancing valve, characterized in that: The method comprises the following steps: 1) The original pipeline of process cooling water is fully utilized, and only the magnetic precipitation water purification device is installed at the interface between the return pipe of the balancing valve and the water tank, without increasing additional energy consumption; 2) The water purification device uses conventional inclined tube precipitation + NdFeB strong magnetic adsorption and non-woven fiber fixation to firmly adsorb the iron oxide microparticles with magnetic conductivity flowing through the surface of the non-woven fabric, and the clean water slowly rises from the inclined tube. The water purification device is simple and efficient; 3) The non-woven fabric inside the water purification device mainly assists the NdFeB strong magnetic absorption and fixation of iron oxide particles. No matter how dirty it is, it will not block the water flow channel and the process cooling water will not overflow, ensuring that the process cooling water system is absolutely safe and reliable; 4) It is necessary to clarify the water quality requirements of the production line precision equipment and the main function of this device is to remove and purify the iron oxide microparticle pollution problem in the high-standard process cooling water that meets the national standard (total iron content less than 1PPM).

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