PCW 40% process cooling water system key technology research and industrial application

I. Introduction

  • Operating mechanism: The operation of the PCW system follows the core principles of closed-loop circulation and precise temperature control. The specific operating process is as follows: first, the chiller cools the chilled water to the set temperature of 7 ± 0.2 ℃, and then the chilled water enters one side of the plate heat exchanger flow channel; At the same time, the cooling water flowing out of the production equipment jacket or cooling pipeline absorbs the heat generated by the operation of the equipment, and the temperature rises to 20 ± 0.3 ℃. The cooling water enters the other side channel of the plate heat exchanger. Inside the plate heat exchanger, through the heat conduction of metal plates, following the second law of thermodynamics, heat spontaneously transfers from high-temperature cooling water to low-temperature chilled water, reducing the temperature of the cooling water to the set value of 17 ± 0.3 ℃, completing the cooling process. After cooling, the cooling water is pressurized by a variable frequency pump and then transported back to the cooling pipelines of various production equipment to achieve continuous cooling of the equipment. The chilled water that has absorbed heat returns to the freezer and is cooled again, forming a complete dual circulation loop. This closed loop design ensures that there is almost no material exchange between the circulating water and the external environment, effectively preventing pollutants such as dust and carbon dioxide from entering the water, ensuring long-term stability of water quality, and reducing the loss of water resources. The precise control of pressure and temperature is the key to ensuring the stable operation of the PCW system. In terms of pressure control, the system installs high-precision pressure sensors at key pipeline nodes to monitor system pressure in real time. When the pressure exceeds the set upper limit (such as 0.8MPa), the PLC will automatically reduce the operating frequency of the variable frequency pump, reduce water flow, and thus reduce system pressure; When the pressure is lower than the set lower limit (such as 0.6MPa), increase the frequency of the variable frequency pump, increase the flow rate, and ensure that the system pressure is stable within the range of 0.7 ± 0.05MPa. In terms of temperature regulation, high-precision temperature sensors are installed in the pipelines of the cooling water entering and leaving the plate heat exchanger, as well as at the cooling water outlet of the production equipment. The PLC adjusts the opening of the electric regulating valve on the chilled water side based on the deviation between the cooling water outlet temperature and the set value (17 ± 0.3 ℃) to accurately control the flow of chilled water entering the plate heat exchanger, thereby achieving precise control of the cooling water temperature and ensuring that the production equipment always operates in the optimal temperature environment.

    • (II) Functional positioning of 40% paper-based materials

    1. Core role: In multiple key links of the PCW system, 40% paper-based materials play various key roles such as filtration and purification, sealing and protection, and heat conduction enhancement due to their unique structural and performance advantages. They are one of the core functional materials that ensure the efficient and stable operation of the system.
      2. . In the water quality filtration process, 40% paper-based material is used as the core substrate of the filter element. Its unique fiber interweaving structure forms a complex three-dimensional microporous network, like a fine filter with both depth and accuracy. It can not only efficiently intercept small impurities and suspended particles in water, but also capture some colloidal particles and microorganisms, significantly improving the cleanliness of circulating water. In the field testing of a PCW system in an electronic chip manufacturing enterprise, a filter with a 40% paper-based material filter element was used. Compared with traditional stainless steel metal filter elements, the filtration efficiency of key harmful particles and impurities with a particle size less than 10 μ m in water increased from 70% to over 90%. The turbidity of circulating water decreased from 0.5NTU to below 0.1NTU, significantly improving the cleanliness of circulating water and effectively reducing photolithography defects and etching deviations caused by impurity adhesion in the chip manufacturing process, resulting in a 1.2 percentage point increase in chip yield. In the sealing and protection process, 40% paper-based material can be specially modified to make sealing gaskets. With its good flexibility, compression resilience, and water resistance, it can tightly adhere to equipment interfaces, pipeline flanges, and other sealing surfaces, fill the small gaps and roughness defects of the sealing surfaces, form a reliable sealing barrier, and effectively prevent circulating water leakage. Compared to traditional rubber sealing gaskets, paper-based sealing gaskets have lower creep rates and better sealing performance stability under long-term compression and immersion in circulating water environments. In the heat exchange enhancement stage, 40% paper-based material can be used as an auxiliary heat dissipation material for the heat exchanger. By adhering to the heat exchange surface, its fiber porous structure can increase the heat exchange area, promote fluid turbulence, enhance convective heat transfer effect, thereby improving overall heat exchange efficiency, helping to reduce equipment operating temperature, and reduce energy consumption of the freezer.
    2. Performance requirements: To ensure that 40% paper-based materials can stably adapt to the core working conditions of PCW system at 17 ± 0.3 ℃ water temperature and 0.7MPa pressure for a long time, while meeting the functional requirements of different application scenarios, they must have excellent performance in multiple aspects.
      3. . Firstly, high water resistance is a core basic requirement. In environments that are continuously exposed to circulating water for a long time, the material should have extremely low hydrophilicity, not be excessively soaked by water, and should not undergo dissolution, swelling, or structural degradation. It is necessary to maintain structural integrity and performance stability for a long time. To achieve this requirement, special waterproof modification processes are usually required, such as coating the material surface with organic silicon waterproof coatings, adding fluorine based hydrophobic agents, or changing the surface chemical structure of the material through plasma treatment to reduce surface energy and endow the material with excellent hydrophobic properties. Secondly, the low solubility property is crucial. During long-term use, materials must not release harmful impurities such as heavy metal ions and organic pollutants into the circulating water, otherwise it will lead to an increase in the conductivity of the circulating water, deterioration of water quality, and corrosion of equipment pipelines or pollution of the production process. Therefore, the raw materials selected for the material must have extremely high chemical stability, and the preparation process must strictly control the impurity content. Thirdly, good mechanical strength is the key to ensuring the service life of materials. Under a working pressure of 0.7 MPa in the system, the material needs to have sufficient tensile strength, compressive strength, and tear resistance, and must not undergo cracking, deformation, or delamination. Especially when used as a filter material, it also needs to withstand the impact pressure of fluids. Fourthly, excellent thermal stability is indispensable. Within the temperature fluctuation range (10-30 ℃) that may occur in the PCW system, the various performance indicators of the material should remain stable without significant changes, ensuring reliable operation of the system under different working conditions. In addition, depending on the specific application scenario, the material may also need to have specific functional properties, such as precise porosity and filtration accuracy when used as a filtering material, and long-term antibacterial performance when used as an antibacterial material.

    III. Preparation and Performance Analysis of 40% Paper based Materials

    (1) Material Formula and Preparation Process

    1. Raw Material Screening: Based on the functional positioning and performance requirements of 40% paper based materials, this study conducted a large number of raw material screening experiments and ultimately determined to use wood pulp fibers (40% mass fraction), polymer resins (30% mass fraction), and functional fillers (30% mass fraction) as the core raw material system. The synergistic effect of each component ensures that the comprehensive performance of the material meets the standard. Among them, wood pulp fibers are used as the skeleton support component of the material, and high-quality coniferous wood pulp imported from Canada is selected. The average length of this type of wood pulp fibers can reach 2.5-3.0mm, with an aspect ratio greater than 80. The fiber surface has abundant hydroxyl groups, which can form good fiber bonding strength through hydrogen bonding, providing excellent mechanical support for paper-based materials. To further enhance the bonding performance of fibers, a systematic pretreatment of wood pulp fibers is required: firstly, the pulp board is dissociated into individual fibers by a hydraulic pulper at room temperature and low speed (300r/min), and 0.1% dispersant is added to prevent fiber aggregation; Subsequently, the PFI pulping machine is used for pulping treatment, with strict control of the pulping degree between 30-35 ° SR. Through fiber refinement and fiber separation, the specific surface area and active sites of the fibers are increased, and the binding force between fibers is optimized. Polymer resin is used as a bonding and modifying component, using independently developed modified polypropylene resin. The resin is modified by grafting acrylic ester groups, with a glass transition temperature as low as -10 ℃ and a fracture elongation of up to 300%. It not only has excellent chemical stability, corrosion resistance, and flexibility, but also forms chemical bonds with hydroxyl groups on the surface of wood pulp fibers, significantly improving the bonding strength between fibers. Functional fillers are selected from surface modified nano silica particles with a particle size controlled between 20-50nm and a specific surface area greater than 200m ²/g. After treatment with silane coupling agents, amino groups are introduced into the surface, which can form a good interfacial bond with wood pulp fibers and polymer resins, effectively filling the pores between fibers and improving the density, hardness, and wear resistance of the material. The specific preparation process of the material is as follows: First, add the pre treated wood pulp fibers to deionized water to prepare a fiber suspension with a mass fraction of 5%. Stir at a high-speed stirrer (800r/min) for 30 minutes to ensure uniform dispersion of the fibers; Step 2: Mix the polymer resin with functional nano silica in proportion, add an appropriate amount of ethanol as the dispersion medium, and prepare a uniform modifier dispersion by combining ultrasonic dispersion (power 500W, time 30min) with mechanical stirring (1500r/min, time 60min); Step three, slowly add the modifier dispersion to the fiber suspension and continue stirring for 120 minutes to ensure that each component fully contacts the reaction; The fourth step is to use a long web paper machine for papermaking, with a controlled speed of 1.5m/min and a vacuum degree of 0.06MPa, to form uniform wet paper sheets; Step 5: Place the wet paper sheet into a hot press machine for hot pressing, strictly control the hot pressing temperature of 150-180 ℃, hot pressing pressure of 5-8MPa, and hot pressing time of 30 minutes, so that the polymer resin melts and tightly binds with the fibers, forming a paper-based material blank with certain strength and structure; Step 6: Perform plasma surface modification treatment on the blank, using argon gas as the plasma gas source, with a treatment power of 300W and a treatment time of 5 minutes. Introduce active groups on the material surface to enhance its surface adhesion and the bonding performance of subsequent functional coatings.
    2. Key process parameters: Through single factor variable experiments and orthogonal experiments, the influence of three key process parameters, fiber beating degree, resin cross-linking degree, and forming pressure, on the properties of 40% paper-based materials was systematically explored, and the optimal control range of each parameter was clarified.
      3. . The fiber beating degree has a significant impact on the mechanical properties and pore structure of materials: when the beating degree increases from 25 ° SR to 35 ° SR, the degree of fiber refinement continuously increases, the specific surface area gradually increases, the hydrogen bonding points between fibers increase, the tensile strength of the material steadily increases from 30MPa to 45MPa, and the elongation at break increases from 5% to 8%; But when the beating degree exceeds 35 ° SR, the fibers will undergo excessive cutting, and the average length will be shortened to below 2.0mm, resulting in a decrease in the bonding force between fibers and a decrease in the tensile strength of the material. At the same time, the pore size distribution of the material shifts towards smaller pores, with the average pore size decreasing from 8 μ m to 3 μ m and the air permeability sharply decreasing from 80mL/(m ² · s) to 30mL/(m ² · s), which is not conducive to the application of the material in the filtration field. The crosslinking degree of resin is a core parameter that affects the chemical stability and water resistance of materials. By adjusting the dosage of curing agent (diisopropylbenzene peroxide) (0.5% -2.0%) and curing temperature (120-180 ℃), the crosslinking degree can be precisely controlled. When the crosslinking degree is increased from 60% to 80%, the chemical stability of the material is significantly enhanced. After soaking in 80 ℃ hot water for 24 hours, the water absorption rate decreases from 15% to 8%, and the swelling rate decreases from 10% to 4%; But when the crosslinking degree exceeds 80%, the rigidity of the resin molecular chains significantly increases, the flexibility of the material decreases, the elongation at break decreases from 8% to 3%, and the brittleness increases. When subjected to impact or vibration