Full-automatic unattended processing and recycling system for silicon wafer cutting fluid in photovoltaic industry

Abstract

The utility model relates to the technical field of wastewater recycling treatment, in particular to a full-automatic unattended treatment and recycling system for silicon wafer cutting fluid in the photovoltaic industry. Comprising a waste liquid collecting pool, a waste liquid feeding tank, tubular membrane equipment, a concentrated liquid tank, a clear liquid collecting tank and a blending tank. An existing production system and an existing technological process are improved, the tubular membrane concentration system and the centrifugal separation system are additionally arranged in an original solid-liquid separation link in the production system and used for replacing a filter press for solid-liquid separation, automatic continuous production of the system can be achieved, unattended full-automatic operation can be achieved, and the production efficiency is improved. The field operation and production environment can be greatly improved, the efficiency of the device is improved, and the labor cost and the operation cost are saved. In addition, a concentrated liquid supply circulating water pool and related pipeline equipment are further designed, one more operation mode is provided for a producer to select and switch, concentrated liquid supply and circulating liquid supply can also be used, and the purposes that the system is more energy-saving and stable, the redundancy is higher, and the liquid supply consistency is better are achieved.

Description

Technical Field

[0001] This utility model relates to the field of wastewater reuse and treatment technology, and in particular to a fully automated unattended treatment and reuse system for silicon wafer cutting fluid in the photovoltaic industry. Background Technology

[0002] Currently, in the solar photovoltaic or semiconductor silicon wafer manufacturing industry, silicon wafer production and processing generally uses diamond wire cutting technology. This process uses a large amount of cutting fluid and generates a large amount of waste liquid, which contains silicon powder chips and other impurities. The common practice in the industry, both in the past and present, is to collect the waste liquid, pump it to a filter press for solid-liquid separation, and then manually test the separated clear liquid, add some effective components, and reuse it (this is a general overview; see the appendix for the detailed process flow). Figure 2 The system currently suffers from low automation, with many processes requiring manual operation. This leads to high labor costs and hinders standardization and process control. Particularly problematic is the filter press, a core component of the solid-liquid separation process. Its inability to operate continuously and requiring regular sludge unloading necessitates several manual unloading operations daily. This unloading process is prone to material spillage, creating a messy and difficult-to-manage environment. Consequently, the system struggles to achieve continuous automated production, requires significant manual labor, and lacks standardized process control. In the current context of industry upgrades, automation, and intelligent manufacturing, this system represents a bottleneck and a major pain point in the upgrading of silicon wafer wire cutting fluid recovery and treatment systems. Utility Model Content

[0003] The purpose of this invention is to provide a fully automated, unattended system for the processing and reuse of silicon wafer cutting fluid in the photovoltaic industry, solving the problems of automation, reduced manpower, and standardization in actual production processes.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This utility model provides a fully automated, unattended system for the treatment and reuse of silicon wafer cutting fluid in the photovoltaic industry. The system includes a waste fluid collection tank for receiving cutting waste fluid, a waste fluid feed tank connected to the waste fluid collection tank and used for buffering the waste fluid, a tubular membrane device connected to the waste fluid feed tank and used for concentrating the buffered waste fluid, a concentrate tank connected to the concentrate outlet of the tubular membrane device, a centrifuge or filter press connected to the concentrate tank and used for separating silicon sludge, a clear liquid collection tank connected to the clear liquid outlet of the tubular membrane device, and a mixing tank connected to the clear liquid collection tank and used for mixing cutting fluid.

[0006] The mixing liquid in the mixing tank is transported to the wire cutting workshop cutting machine through pipelines and a transfer pump for recycling; and a first fine filter is installed on the pipeline.

[0007] The clarified liquid obtained from the centrifuge or filter press is collected and then transported to the waste liquid feed tank by a transfer pump;

[0008] Some of the waste liquid in the wastewater collection tank is also transported by a water pump and filtered through parallel or series filters before entering the centralized liquid supply circulation tank.

[0009] The cutting fluid prepared in the mixing tank is also partially returned to the centralized fluid supply circulating water tank through the liquid mixing pipeline. A second fine filter is installed on the liquid mixing pipeline.

[0010] The solution in the centralized liquid supply circulating water tank is stirred and then transported by the liquid supply water pump. After being finely filtered by the third fine filter, it is sent to the cutting machine for cutting and reuse.

[0011] In this embodiment, the waste liquid in the waste liquid collection tank is further transported to the waste liquid feed tank by a centrifugal pump, and a filter is provided between the waste liquid collection tank and the waste liquid feed tank.

[0012] Furthermore in this embodiment, the waste liquid buffered in the waste liquid feed tank is transported to the tubular membrane device by a centrifugal pump.

[0013] Furthermore in this embodiment, the clarified liquid outlet end of the tubular membrane device is transported to the clarified liquid collection tank through a delivery pipe; an online automatic sampling and automatic analysis and detection device is installed on the inlet pipe of the clarified liquid collection tank.

[0014] Furthermore, in this embodiment, a stirring device is provided inside the mixing tank, and an automatic dispensing device for replenishing new cutting fluid and RO water is also provided on the mixing tank.

[0015] Furthermore, in this embodiment, temperature sensors, pH meters, turbidity sensors, level sensors, and online concentration meters are installed in the waste liquid collection tank, waste liquid feed tank, clear liquid collection tank, mixing tank, and concentrate tank for sampling and detection. The relevant data detected by each sensor are controlled by the PLC system logic. Pressure sensors and flow sensors are installed on the delivery pipe.

[0016] Compared with the prior art, the beneficial technical effects of this utility model are as follows:

[0017] This invention improves existing production systems and processes by adding a tubular membrane concentration system and a centrifugal separation system to the original solid-liquid separation stage. These systems replace filter presses for solid-liquid separation, enabling automated and continuous production. The entire process can be operated fully automatically without human intervention, significantly improving the on-site operation and production environment, increasing equipment efficiency, and saving labor and operating costs. The system also includes a centralized liquid supply circulating water tank and related piping, providing an additional operating mode for the production team to choose and switch between. It can also utilize centralized liquid supply and circulating supply, achieving a more energy-efficient, stable, and redundant system with better liquid supply consistency. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 This utility model presents a process flow diagram of a fully automated, unattended treatment and reuse system for silicon wafer cutting fluid in the photovoltaic industry.

[0020] Figure 2 This is a flowchart of the existing process. Detailed Implementation

[0021] This embodiment discloses a fully automated, unattended system for the treatment and reuse of silicon wafer cutting fluid in the photovoltaic industry. It improves the existing production system and process flow by adding a tubular membrane concentration system and a centrifugal separation system to the original solid-liquid separation stage of the production system. These systems replace the filter press for solid-liquid separation, enabling automated and continuous production. The entire process can be operated fully automatically without human intervention, which can greatly improve the on-site operation and production environment, increase equipment efficiency, and save labor costs and operating costs.

[0022] In actual production, the entire cycle from waste liquid recovery, solid-liquid separation, clear liquid preparation to reuse cutting is fully controlled by electronic instruments to collect various indicators such as liquid level, temperature, flow rate, pressure, turbidity, pH, and concentration. The system establishes relevant indicator logic control and action interlocks, and is controlled by a PLC system to run automatically (it can be switched to manual operation in special cases). This achieves automatic detection, automatic analysis, and automatic control of the entire system, and the operation is completely unattended.

[0023] In silicon wafer slicing plants, dozens or even hundreds of diamond wire cutting machines are often distributed within a single production workshop or unit to achieve the plant's specific production scale and equipment capacity. This article takes a typical configuration of a solar silicon wafer slicing system, with 30-60 wire cutting machines on a single production line, as an example to provide a detailed introduction to the system's technical advantages and processes.

[0024] As attached Figure 1As shown, multiple wire cutting machines 1 (specifically, 30-60 machines) generate cutting wastewater during the cutting process. After being discharged through drainage pipes, the wastewater flows by gravity into a wastewater collection tank 2 for unified collection, taking advantage of the terrain's elevation difference. The collected wastewater is then pumped by a centrifugal pump to a wastewater feed tank 7 for buffering. A filter is installed before the wastewater feed tank 7 to ensure that foreign objects such as broken silicon wafers and wire ends generated during wire cutting are removed before entering the tank. The filtered buffered wastewater in the wastewater feed tank 7 is then pumped by a centrifugal pump into a tubular membrane device 8.

[0025] The tubular membrane device 8 is a tubular membrane separation device. Its tubular membrane filtration system includes membrane modules, pump sets, automatic control instruments (including sensors for detecting differential pressure), and a cleaning unit. Its specific function is to concentrate the delivered waste liquid. The system will automatically adjust and control the ratio of feed rate and water production, as well as the backwashing time and frequency, according to the settings to ensure maximum efficiency. Under normal circumstances, the concentration ratio can be no less than 10 times. Assuming that the waste liquid generated by the system is 500 tons / hour, after concentration by the tubular membrane device 8, 450 tons / hour of clear liquid can be separated in this stage. The subsequent system only needs to process 50 tons of concentrated waste liquid, which greatly reduces the processing load of the subsequent system and the investment in equipment configuration.

[0026] Compared to tubular membrane systems, traditional filter presses offer no advantage in this stage in terms of effluent quality, output volume, automation, or labor efficiency. Tubular membrane equipment was designed to replace filter presses in this stage, and its operating performance and performance data have been verified by our company in actual production.

[0027] The concentrate (approximately 10%) after concentration treatment by the tubular membrane equipment 8 enters the concentrate tank 13, while the clarified liquid (approximately 90%) enters the clarified liquid collection tank 9. The inlet of the clarified liquid collection tank 9 is equipped with an online automatic sampling and analysis device (specifically used to detect pH, turbidity, and concentration). If the sample passes the automatic sampling and analysis, it enters the clarified liquid collection tank 9. If the sample fails the analysis, the inlet valve of the clarified liquid collection tank 9 automatically closes, and the clarified liquid is transported back to the waste liquid feed tank at the front end of the tubular membrane equipment 8 via a transfer pump and a three-way pipeline for further processing (this situation is generally unlikely; this backflow design is only for emergency use in extreme circumstances).

[0028] The qualified clear liquid in the collection tank 9 is pumped to the mixing tank 10. Near the mixing tank 10, an automatic batching and adding device for new cutting fluid, RO water, and other auxiliary materials is installed (specifically, a delivery pipeline consisting of a flow sensor and a solenoid valve). The mixing tank itself is equipped with a stirring device (including a stirrer and a stirring motor) and an automatic detection device (detecting temperature, pH, turbidity, concentration, and liquid level). Based on the data detected by the automatic detection device, the mixing process is interlocked, adding new cutting fluid, RO water, and other auxiliary materials and thoroughly mixing them. After the adjustment and secondary confirmation that the indicators are qualified (these indicators can be set according to production conditions), the liquid is pumped to the fine filter 11 for filtration and then sent to the wire cutting workshop cutting machine 1 for recycling.

[0029] The concentrate entering the concentrate tank 13 is pumped to the centrifuge 14 for processing. The clear liquid obtained after processing is collected and pumped to the waste liquid feed tank 7 for further processing. The resulting silica sludge 16 can be packaged in ton bags and sold as a by-product.

[0030] In the concentrated liquid treatment stage of this system, two parallel processing lines can be designed, with centrifuge 14 and filter press 15 serving as backups for each other. Alternatively, a separate concentrated liquid treatment line can be designed, equipped only with centrifuge 14 or only with filter press 15. The advantages of the dual-line design of centrifuge 14 and filter press 15 are high system redundancy, high reliability, and automatic continuous processing, meeting the downstream customers' needs for treating low-moisture silica sludge. In addition, there is a backup option in case of centrifuge failure or unsatisfactory results. The disadvantages are the need for related equipment and facilities, resulting in a large footprint and investment.

[0031] The advantages of using only centrifuges are low investment and space requirements, low operating costs, minimal consumption of filter cloth and other auxiliary materials during the processing, continuous feeding and discharging of centrifuges, automatic operation without manual unloading, high degree of automation, and unattended operation after interlocking and automatic control of relevant equipment and operating indicators. The disadvantages are that the silica sludge produced by centrifuges currently has a 10-20 percentage point higher moisture content than that of filter presses, and the failure rate is higher than that of filter presses. Routine maintenance and planned inspections must be carried out regularly.

[0032] The inclusion of a filter press is not part of the advanced features of this utility model, and therefore will not be described or compared.

[0033] Thus, the entire system can achieve a fully closed-loop, fully cyclical recycling and processing mode. Various automated instruments such as temperature, pressure, flow rate, pH, turbidity, concentration, differential pressure, and liquid level are set up in the conveying, sampling, detection, and blending links for sampling and detection. The relevant data are controlled by the PLC system logic to achieve a fully automatic unattended operation mode.

[0034] Furthermore, considering the need for daily adjustments, verification of changes in raw materials and methods during actual production, and the requirement to ensure consistent and uniform liquid supply quality when adjusting and improving the wire cutting process, the system also includes a centralized liquid supply circulating water tank 4 and related piping equipment. This provides an additional operating mode for the production team to choose and switch between, allowing for centralized liquid supply and circulating supply as well. This achieves the goal of making the system more energy-efficient, stable, more redundant, and with better liquid supply consistency. This is also one of the novelty, innovation, and practicality aspects of this system.

[0035] The specific process is as follows: During the cutting process of the wire cutting machine 1, the cutting fluid is continuously supplied while meeting the flow rate and pressure requirements of the wire cutting machine. The cutting fluid used by the machine (for ease of understanding and consistency, it is temporarily referred to as waste fluid) continuously flows by gravity into the wastewater collection tank 2. Considering that the effective components of the waste fluid in the wastewater collection tank 2 are not completely depleted, it can still be used for cutting. However, considering that it contains a lot of silicon powder, debris, etc., it will affect the cutting yield and defect rate. Therefore, the system design pumps a portion of the waste fluid in the wastewater collection tank 2 to the waste fluid collection tank 7 for solid-liquid separation and subsequent blending treatment (as described in the above process description). After the blending treatment is qualified, the clear liquid is filtered by the second fine filter 12 and then sent to the centralized liquid supply circulation water tank 4. Part of the waste liquid in the remaining wastewater collection tank 2 is pumped through parallel or series filters 3 and then enters the centralized liquid supply circulation tank 4. In other words, the centralized liquid supply circulation tank 4 contains two streams of liquid: one is the filtered waste liquid, and the other is a prepared clear liquid that has undergone solid-liquid separation and has been mixed with added active ingredients to meet the qualified cutting fluid standards. These two streams are thoroughly mixed in the centralized liquid supply circulation tank and then pumped by the supply water pump 5. After being finely filtered by the fine filter 6, they are sent to the cutting machine for reuse. The concentration, solid content, pH, and other process parameters in the centralized liquid supply circulation tank 4 are generally controlled by adjusting the amount of the added prepared clear liquid. The entire process control uses automated instrument sampling, analysis, and interlocking control, and the data is uniformly processed by the PLC control system to achieve automated, unattended operation of the equipment.

[0036] The design and integration of a centralized fluid supply circulation tank 4 and related piping systems further reduces the input of new cutting fluid and various auxiliary additives, more effectively utilizes the equipment's capacity, and further reduces the amount of waste liquid requiring solid-liquid separation. This saves on labor, production capacity, and raw materials needed for waste liquid treatment, achieving cost reduction and efficiency improvement. Furthermore, the system offers an additional operating mode that can be selected and switched, facilitating the improvement and enhancement of the wire cutting process as the main production step. This improves the consistency of fluid supply and provides a prerequisite and guarantee for exploring and accumulating cutting process experience and data based on consistent cutting fluid.

[0037] It can realize automated and continuous production operation of the system, and the whole process can be fully automated without human intervention, while saving labor costs and operating expenses.

[0038] Currently, the solid content of waste cutting fluid from silicon wafer dicing machines ranges from 0.7% to 2.2%, depending on the number of machines in operation and the cutting load. After collection, this fluid is directly pumped into a filter press, which suffers from problems such as low solid content, long filtration time, inefficient utilization of filter press capacity due to large throughput, and long manual unloading time. Adding a tubular membrane system to the system can concentrate the waste fluid with a solid content of 0.7%–2.2% multiple times. After tubular membrane treatment, the concentrated liquid is conservatively estimated to be only about 1 / 10 of the original influent. This reduces the amount of waste fluid to be treated by 10 times, significantly lowering the system's processing load.

[0039] In the past, due to the large volume of waste liquid that needed to be treated, the industry could only choose to use filter presses to treat such a large amount of waste liquid, considering factors such as investment costs and land occupation. It was not possible to consider solid-liquid separation equipment such as high-efficiency centrifuges with low processing capacity and high degree of automation. After effective separation by membrane equipment, such equipment meets the application conditions and scenarios.

[0040] High-efficiency centrifuges are highly automated and can continuously feed, discharge, and produce. Compared with filter presses, which have intermittent production, they have operational advantages. The operation process can be automatically or remotely controlled. By processing the concentrate through a high-efficiency centrifuge, a silica mud with a water content of about 60% can be obtained. Silica mud is a valuable by-product. After recycling, it can be purified to extract silicon for reuse. Currently, the industry generally sells it directly to external customers.

[0041] In summary, the key solid-liquid separation process in the system, through the introduction of tubular membrane separation equipment and centrifugal separation equipment, and the design of staged filtration and staged treatment, improves efficiency while greatly reducing the processing load. In addition, these two types of equipment can carry out continuous automated production, so automated unattended operation can be achieved, realizing the management and economic objectives of reducing manpower and increasing efficiency.

[0042] The technical solution of this utility model is that the entire system is almost completely enclosed, which reduces the risk of material leakage and spillage, and can greatly improve the on-site operating environment and production environment.

[0043] Currently, all companies in the industry use filter presses for solid-liquid separation. During the filtration process, the amount of water discharged from the filter press continuously decreases, while the filter cake thickness accumulates within the filter chamber. Once the water discharge decreases or the filter cake thickness reaches a certain level, unloading begins. During the feeding, effluent discharge, and sludge unloading processes, varying degrees of leakage, spillage, dust, and other contamination can occur. After system improvements, the addition of tubular membrane equipment and centrifuges can achieve closed-loop operation, significantly improving and ensuring a better on-site operating environment and hygiene management.

[0044] Production process control has been further standardized, and process indicators have become more controllable.

[0045] In the previous system, the solid-liquid separation process could not be automated and operated continuously. Both water production and unloading were intermittent, affected by factors such as feed pressure, filter cloth material specifications, filter aids, and flocculant additions. The immediate output was unstable, and the initial effluent from the filter press was black liquid with insufficient turbidity for reuse. The filter press capacity could not be fully utilized, and the output of clear liquid decreased over time, introducing many unstable and uncertain factors into production and operation. Because there were no standards and automation was impossible, it relied entirely on worker experience, with some indicators only controllable afterward. The process required significant operational and management effort.

[0046] The tubular membrane within this system enables stable effluent flow and quality indicators. The effluent flow rate is automatically adjusted according to settings, achieving zero turbidity and eliminating black liquor. The concentrate is centrifuged, and the silica slag can be packaged in ton bags for sale. The permeate is returned to the tubular membrane inlet, ensuring no unqualified indicators after treatment. Therefore, under automated continuous operation, all system indicators will be more stable than before. Production process control will significantly reduce the impact of human factors and individual differences on operational techniques and on-site judgment. Further standardization ensures complete process control and higher efficiency.

[0047] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A fully automated, unattended system for the treatment and reuse of silicon wafer cutting fluid in the photovoltaic industry, characterized in that: The system includes a waste liquid collection tank (2) for receiving cutting waste liquid, a waste liquid feed tank (7) connected to the waste liquid collection tank (2) and used for buffering waste liquid, a tubular membrane device (8) connected to the waste liquid feed tank (7) and used for concentrating the buffered waste liquid, a concentrate tank (13) connected to the concentrate outlet of the tubular membrane device (8), a centrifuge (14) or filter press (15) connected to the concentrate tank (13) and used for separating silica mud (16), a clear liquid collection tank (9) connected to the clear liquid outlet of the tubular membrane device (8), and a mixing tank (10) connected to the clear liquid collection tank (9) and used for mixing cutting fluid. The mixing liquid in the mixing tank (10) is transported to the wire cutting workshop cutting machine (1) through pipelines and a transfer pump for recycling; and a first fine filter (11) is installed on the pipeline; The clear liquid obtained from the centrifuge (14) or filter press (15) is collected and then transported to the waste liquid feed tank (7) by a transfer pump; In the waste liquid collection tank (2), some waste liquid is also transported by a water pump and filtered by parallel or series filters (3) before entering the centralized liquid supply circulation tank (4). The cutting fluid prepared in the mixing tank (10) is also partially returned to the centralized fluid supply circulating water tank (4) through the liquid mixing pipeline. A second fine filter (12) is installed on the liquid mixing pipeline. The solution in the centralized liquid supply circulating water tank (4) is stirred and then transported by the liquid supply water pump (5), and after being finely filtered by the third fine filter (6), it is sent to the cutting machine for cutting and reuse.

2. The fully automated unattended processing and reuse system for silicon wafer cutting fluid in the photovoltaic industry according to claim 1, characterized in that: The waste liquid in the waste liquid collection tank (2) is transported to the waste liquid feed tank (7) by a centrifugal pump, and a filter is provided between the waste liquid collection tank (2) and the waste liquid feed tank (7).

3. The fully automated unattended processing and reuse system for silicon wafer cutting fluid in the photovoltaic industry according to claim 1, characterized in that: The waste liquid buffered in the waste liquid feed tank (7) is transported to the tubular membrane device (8) by a centrifugal pump.

4. The fully automated unattended processing and reuse system for silicon wafer cutting fluid in the photovoltaic industry according to claim 1, characterized in that: The clear liquid outlet of the tubular membrane device (8) is transported to the clear liquid collection tank (9) through a delivery pipe; an online automatic sampling and automatic analysis and detection device is installed on the inlet pipe of the clear liquid collection tank (9).

5. The fully automated unattended processing and reuse system for silicon wafer cutting fluid in the photovoltaic industry according to claim 1, characterized in that: A stirring device is provided inside the mixing tank (10), and an automatic dispensing device for replenishing new cutting fluid and RO water is also provided on the mixing tank (10).

6. The fully automated unattended processing and reuse system for silicon wafer cutting fluid in the photovoltaic industry according to claim 1, characterized in that: Temperature sensors, pH meters, turbidity sensors, liquid level sensors, and online concentration meters are installed in the waste liquid collection tank (2), the waste liquid feed tank (7), the clear liquid collection tank (9), the mixing tank (10), and the concentrate tank (13) for sampling and detection. Pressure sensors and flow sensors are installed on each delivery pipe. The relevant data detected by each sensor are controlled by the PLC system logic.

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