Air knife blow-off drying system and method for cold-rolled stainless steel strip production line

Abstract

This invention discloses an air knife purging and drying system and method for a cold-rolled stainless steel strip production line, belonging to the field of metal material processing. The air knife purging and drying system of this invention includes an edge purging unit, a plate surface purging unit, and an air supply unit. The edge purging unit is located after the squeeze roller at the outlet of the pickling and rinsing section, and includes several sets of air knives symmetrically arranged on the upper and lower surfaces of the strip edge for directional purging to remove residual liquid from the strip edge. The plate surface purging unit is located after the edge purging unit, and includes several sets of air knives symmetrically arranged on the upper and lower surfaces of the strip for full-coverage purging along the entire width of the strip to remove residual liquid from the strip surface. The air supply unit consists of four independent fans. This invention achieves energy saving and consumption reduction, lowers operating costs, and simultaneously meets the high-efficiency drying requirements of strips of different specifications at different operating speeds, while also featuring low noise, easy installation, and easy maintenance.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, and relates to an air knife blowing and drying system and method for cold-rolled stainless steel strip production line. Background Technology

[0002] In the production process of cold-rolled stainless steel strip, after pickling and rinsing, a large amount of liquid will remain on the surface of the strip. If the residual liquid is not effectively removed, it will directly affect the surface quality of the strip in subsequent processes, and may even cause defects such as rust and oxidation. The pickling and rinsing section of the cold rolling mill currently uses a combination of steam heating and drying to dry the surface of the strip. Its drying box fan has a power of 37kW. It draws ambient air and exchanges heat with saturated steam to about 120°C to dry the surface of the strip. Although the system can meet the basic production needs, it has the following shortcomings: (1) High energy consumption: The system needs to consume electricity and steam at the same time. The steam consumption can reach 1t / h, and the overall operating cost remains high; (2) Complex equipment: It involves equipment such as steam heat exchange, fan, and pipeline, which occupies a large area and is inconvenient to maintain and repair; (3) Limited efficiency: For thin strips running at high speed, the traditional drying method is difficult to completely remove the residual liquid on the surface in a short time.

[0003] Therefore, there is an urgent need to develop a new type of strip steel surface drying system that is compact, energy-efficient, and has excellent drying effect. Summary of the Invention

[0004] To address the problems of high energy consumption, complex equipment, and limited drying efficiency in the traditional "steam + fan" drying method of cold-rolled stainless steel strip pickling lines, this invention proposes a combined air knife purging drying system and method. This system adopts a two-stage collaborative structure of edge purging and plate surface purging, and significantly improves purging efficiency by optimizing airflow angle and distance parameters.

[0005] This invention provides an air knife purging and drying system for a cold-rolled stainless steel strip production line, suitable for the high-efficiency drying requirements of strips of different specifications at different operating speeds. The strips have a thickness of 0.3-3.0 mm, a width of 600-1300 mm, and an operating speed of 10-140 m / min. The air knife purging and drying system includes an edge purging unit, a plate surface purging unit, and an air supply unit. The edge blowing unit is located after the squeeze roller at the outlet of the pickling and rinsing section. It includes several sets of air knives symmetrically arranged on the upper and lower surfaces of the strip edge to perform directional blowing on the strip edge and remove residual liquid from the strip edge. The plate surface purging unit is located after the edge purging unit and includes several sets of air knives symmetrically arranged on the upper and lower surfaces of the strip steel. It is used to perform full-coverage purging of the entire strip steel width direction to remove residual liquid from the strip steel plate surface. The air supply unit consists of four independent fans, which are respectively connected to the edge purging unit and the panel purging unit. The air knife is connected to the fans through pipes.

[0006] Furthermore, the edge purging unit comprises 8-16 air knives, symmetrically arranged on the upper and lower surfaces of the strip, with 4-8 knives on each side. A segmented control method is adopted, with the 8-16 air knives divided into two groups, front and rear. Each group contains 2-4 air knives on the upper and lower sides. The two groups are supplied with air by two independent fans. The front group (2-4 upper and 2-4 lower) is closer to the centerline of the strip channel and is suitable for edge purging of narrow strips; the rear group (2-4 upper and 2-4 lower) is farther from the centerline of the strip channel and is suitable for edge purging of wide strips. Segmented control is implemented according to strip width: when operating narrow strips, only the front group of air knives is activated; when operating wide strips, both groups of air knives are activated simultaneously. The airflow regulating valve can adjust the airflow in segments according to the strip width and operating speed to achieve energy-saving operation. Each air knife is 250mm long and has a blade width of 1.5mm. The angle between the air knife and the strip width direction is 35°, and the angle between the blowing direction and the strip running direction is 45°. The vertical distance between the air knife outlet and the strip surface is 30~80mm, with the optimal distance being 50mm.

[0007] Furthermore, the number of air knives in the plate surface purging unit is 4 to 6, symmetrically arranged on the upper and lower surfaces of the strip, with 2 to 3 on each side. Each air knife is 1300mm long and has a blade width of 1.5mm. The angle between the purging direction and the running direction of the strip is 45°. The vertical distance between the air knife outlet and the strip surface is 30 to 80mm, with the optimal distance being 50mm.

[0008] Furthermore, the fan is a ring blower with a single motor power of 22kW and a total power of 88kW; the fan outlet and the air knife are connected by a flexible hose, and the flexible hose is equipped with an air volume regulating valve for adjusting the air volume in stages according to the strip steel specifications and operating speed.

[0009] The air knife, pipe, and fan of this invention are installed on a steel structure support and fixed at a preset angle to the running direction of the strip steel; the electrical control system adopts a PLC controller, and the control components are industrial-grade components, which have functions such as manual / automatic switching, segmented air volume adjustment, and fault alarm.

[0010] This invention provides a method for air knife purging and drying in a cold-rolled stainless steel strip production line, comprising the following steps: Step S1: System Startup When the production line receives the start signal, the fan of the air supply unit is started first; the fan corresponding to the panel purging unit is started first, and the fan corresponding to the edge purging unit is started after the fan is running stably. Step S2: Width detection and air knife segmentation selection After being squeezed dry by the squeezing rollers at the outlet of the pickling and rinsing section, the strip steel enters the air knife purging area. The width sensor located at the entrance of the edge purging unit detects the strip steel width in real time and transmits the detection signal to the PLC controller. The PLC automatically selects the edge air knives within the corresponding width range based on the strip steel width value. When the strip steel width is ≤1000mm, only the first group of air knives closest to the center line of the strip steel channel is activated. When the width is >1000mm, all 8 to 16 air knives are activated. The solenoid valves corresponding to the unselected air knives are closed, and the blower outputs the corresponding air volume through frequency conversion regulation to achieve on-demand air supply and energy-saving operation.

[0011] Step S3: Speed ​​detection and airflow adjustment A speed sensor monitors the strip's running speed in real time and feeds it back to the PLC controller. The PLC automatically adjusts the fan's output airflow based on the strip speed: when the strip speed is ≤50m / min, the airflow regulating valve opening is set to 40%~50%; when the speed is ≤100m / min, the opening is set to 60%~80%; and when the speed is >100m / min, the opening is set to 90%~100%. Through dual control of frequency conversion regulation and valve opening, optimal purging effect is ensured at different operating speeds.

[0012] Step S4: Two-stage coordinated purging The strip first enters the edge cleaning unit: the high-speed airflow from the air knife forms a 35° angle with the width direction of the strip and a 45° angle with the running direction of the strip, concentrating on the edge area of ​​the strip to quickly blow away the residual liquid at the edge of the squeeze roll gap. After edge cleaning, the strip enters the surface cleaning unit: the high-speed airflow from the air knife forms a 45° angle with the running direction of the strip, providing full coverage cleaning across the entire width direction to further remove residual liquid from the surface; the two cleaning units work in sequence to achieve efficient removal of residual liquid from the strip surface.

[0013] Step S5: Purge complete and system standby. When the production line stops or the strip steel stops running, the PLC controller first shuts down the fan corresponding to the edge blowing unit, and then shuts down the fan corresponding to the plate blowing unit after a 10-second delay, ensuring that all air knives stop emitting air. The system then enters standby mode, waiting for the next production instruction.

[0014] The beneficial effects of this invention are: (1) This invention achieves energy saving and consumption reduction, reduces operating costs, meets the high-efficiency drying requirements of strip steel of different specifications at different operating speeds, and has the characteristics of low noise, easy installation and easy maintenance.

[0015] (2) Excellent drying effect: Through the synergistic effect of the two-stage blowing units at the edge and the plate surface, combined with the optimized air knife angle and distance parameters, the strip steel surface and edge residual liquid are fully covered and efficiently blown away; the drying effect is better than the traditional drying method.

[0016] (3) Compact structure and easy maintenance: The system occupies a small area, and the air knife and fan are modularly designed for easy installation; it adopts a low-noise fan and flexible connection, with operating noise ≤85dB, and is easy to maintain and repair.

[0017] (4) Stable and reliable operation: the fan operating amplitude is ≤4mm / s and the bearing temperature is ≤ambient temperature +40℃, which ensures the long-term stable operation of the equipment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall layout of the air knife blowing and drying system of the present invention; Figure 2 Schematic diagram of the air knife arrangement for the edge purging unit; Figure 3 This is a schematic diagram of the air knife arrangement in the panel purging unit.

[0019] In the diagram: 1 is the strip steel, 2 is the edge blowing unit, 3 is the plate blowing unit, 4 is the air knife, 5 is the annular blower, and 6 is the flexible hose. Detailed Implementation

[0020] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments.

[0021] Example 1: like Figures 1-3 As shown, this embodiment takes the No. 3 cold line unit of the cold rolling mill as an example. The specifications of strip steel 1 are 0.3-3.0mm in thickness and 600-1300mm in width. The production line running speed is 10-140m / min.

[0022] Following the squeeze rollers at the outlet of the pickling and rinsing section, the edge blowing unit 2 and the surface blowing unit 3 are installed sequentially. The edge blowing unit contains 16 air knives 4, each 450mm long. Figure 2 The air purifiers are symmetrically arranged on the upper and lower surfaces of the strip, with 8 on each side and 8 in a single operation. They are at a 35° angle to the width direction of the strip and at a 45° angle to the running direction of the strip. The vertical distance between the air outlet and the strip is 50mm. They are used for directional purging of residual liquid on the edge of the strip.

[0023] The panel purging unit consists of six air knives, each 2000mm in length. Figure 3 The air outlets are symmetrically arranged on the upper and lower surfaces of the strip, with three on each side. The blowing direction is at a 45° angle to the running direction of the strip, and the vertical distance between the outlet and the strip is 50mm. They are used to fully cover the surface of the strip.

[0024] The air supply unit uses four independently operating ring blowers, each with a motor power of 22kW, for a total power of 88kW. The blower outlets are connected to each air knife via flexible hoses and are equipped with airflow regulating valves. The electrical control system uses a PLC controller to adjust the airflow of the edge blowing unit and the surface blowing unit in stages based on the strip's running speed and width signals, achieving energy-saving operation.

[0025] The PLC controller can be a Siemens S7-1200 or S7-1500 series PLC (such as CPU 1214C or CPU 1512SP), possessing high-speed processing capabilities and industrial-grade reliability. The control components are industrial-grade parts, featuring manual / automatic switching, segmented airflow adjustment, and fault alarm functions. The PLC receives signals from the strip width and speed sensors, and, combined with a preset control algorithm, automatically determines the number of air blades to be activated and the fan power level, achieving intelligent segmented adjustment control. The control signals for the fan and air blades communicate with the PLC in real time via the PROFINET industrial Ethernet bus, ensuring timely and accurate control response. The control system should also have remote monitoring capabilities, displaying system operating parameters, historical data storage, and fault diagnosis alarms in real time on the host computer interface in the control room.

[0026] During system operation, the strip steel passes sequentially through the edge blowing unit and the surface blowing unit. Under the action of high-speed airflow, residual liquid on the surface and edges is quickly blown away, resulting in a drying effect superior to that before the modification. Actual testing showed that, at a maximum operating speed of 140 m / min, the surface dryness of the strip steel met the production process requirements, the system operating noise was ≤85 dB, the fan amplitude was ≤4 mm / s, and the bearing temperature was ≤ ambient temperature +40℃.

[0027] When the strip width is ≥1200mm and the running speed is ≥100m / min, the PLC controller executes the high-speed wide strip purging mode: (1) Edge purging unit: All 16 air knives (8 on top and 8 on the bottom) are activated, the blower is running at full power, and the air volume regulating valve is set to 100%. The first 8 air knives (4 on top and 4 on the bottom) and the last 8 air knives (4 on top and 4 on the bottom) are used simultaneously. The first 8 air knives are suitable for edge purging of narrow strip steel, which is closer to the center line of the strip steel channel; the last 8 air knives are suitable for edge purging of wide strip steel, which is farther from the center line of the strip steel channel. The two-stage air knives work together to purge and concentrate on removing residual liquid at the edge of the squeeze roll gap.

[0028] (2) Strip surface purging unit: All 6 air knives (3 on top and 3 on the bottom) are activated, the fan is running at full power, and the air volume regulating valve is set to 100%. The purging direction is at a 45° angle to the strip running direction, achieving full coverage purging across the entire strip width, ensuring sufficient airflow impact force on the strip surface under high-speed operation. The air knives symmetrically arranged on the upper and lower surfaces form a high-speed air curtain, quickly blowing away residual liquid on the strip surface and diverting it to both sides to prevent liquid accumulation or backflow.

[0029] (3) Purging process timing control: After the system detects that the strip steel has entered the purging area, it first starts the corresponding fan of the plate surface purging unit. After the fan runs stably (about 5 to 8 seconds), it starts the corresponding fan of the edge purging unit. After the strip steel has completely passed through, the edge purging unit fan is turned off first, and the plate surface purging unit fan is turned off after a delay of 10 seconds to ensure that the entire strip steel surface is effectively purged.

[0030] Actual testing showed that, under extreme conditions of a strip width of 1300mm and an operating speed of 140m / min, this system could completely remove residual liquid from the surface and edges of the strip, achieving a drying effect that met production process requirements, with no visible residual liquid or water stains on the strip surface. Continuous operation testing showed that the system's operating noise was ≤85dB, fan amplitude was ≤4mm / s, and bearing temperature was ≤ambient temperature +40℃. All operating indicators met design expectations, and the equipment has demonstrated stable and reliable long-term operation.

[0031] Compared to traditional steam heating and drying methods (steam consumption of approximately 1 t / h and electric power of 37 kW), this system consumes only 88 kW of electricity, which is equivalent to a reduction of approximately 45% in standard coal consumption compared to traditional methods, achieving significant energy savings. Simultaneously, this system avoids the complex maintenance and heat loss issues associated with steam pipelines, reduces the system footprint by approximately 60%, and extends the equipment maintenance cycle to more than twice that of traditional methods, effectively solving the technical challenge of drying thin-gauge wide strip steel at high speeds.

[0032] Example 2 Taking the No. 4 finished product pickling line of the cold rolling mill as an example, the technical solution of the present invention is further verified under the harsh working conditions of wide strip steel (width 1200~1300mm) and high-speed operation (100~140m / min).

[0033] Under this operating condition, the edge purging unit is equipped with 16 air knives (8 at the top and 8 at the bottom), the plate surface purging unit is equipped with 6 air knives (3 at the top and 3 at the bottom), and the air supply unit is equipped with 4 22kW ring blowers, for a total power of 88kW. The vertical distance between the air knife outlet and the strip surface is adjusted to 30mm under high-speed conditions to minimize airflow diffusion loss and improve purging force. The angle between the air knife purging direction and the strip width direction is maintained at 35°, and the angle with the strip running direction is maintained at 45°.

[0034] This embodiment provides a drying method for the above-mentioned air knife blowing and drying system, including the following steps: Step S1: System Startup When the production line receives the start-up signal, it first starts the fans of the air supply unit. First, start the fans corresponding to the panel purging unit (2 units). After the fans are running stably (about 5 to 10 seconds), start the fans corresponding to the side purging unit (2 units).

[0035] Step S2: Width detection and air knife segmentation selection After being squeezed dry by the squeeze rollers at the outlet of the pickling and rinsing section, the strip steel enters the air knife purging area. A width sensor located at the inlet of the edge purging unit detects the strip steel width in real time and transmits the detection signal to the PLC controller. Based on the strip steel width value, the PLC automatically selects the edge air knives within the corresponding width range; in this embodiment, if the strip steel width is >1000mm, all 16 air knives are activated. The blower outputs the corresponding air volume through frequency conversion regulation, achieving on-demand air supply and energy-saving operation.

[0036] Step S3: Speed ​​detection and airflow adjustment A speed sensor detects the running speed of the strip in real time and feeds it back to the PLC controller. The PLC automatically adjusts the output air volume of the blower according to the strip speed: in this example, the strip speed is >100m / min, and the air volume regulating valve opening is set to 90%~100%. Through dual control of frequency conversion regulation and valve opening, the best purging effect is ensured at different running speeds.

[0037] Step S4: Two-stage coordinated purging The strip first enters the edge cleaning unit: the high-speed airflow from the air knife forms a 35° angle with the width direction of the strip and a 45° angle with the running direction of the strip, concentrating on the edge area of ​​the strip to quickly blow away the residual liquid at the edge squeeze roll gap. After edge cleaning, the strip enters the surface cleaning unit: the high-speed airflow from the air knife forms a 45° angle with the running direction of the strip, providing full coverage cleaning across the entire width direction, further removing residual liquid from the surface. The two-stage cleaning units work in sequence to achieve efficient removal of residual liquid from the strip surface.

[0038] Step S5: Purge complete and system standby. When the production line stops or the strip steel stops running, the PLC controller first shuts down the fan corresponding to the edge blowing unit, and then shuts down the fan corresponding to the plate blowing unit after a 10-second delay, ensuring that all air knives stop emitting air. The system then enters standby mode, waiting for the next production instruction.

Claims

1. An air knife blow drying system for a cold rolled stainless steel strip production line, characterized in that, This system is suitable for high-efficiency drying of strip steel of different specifications at different operating speeds. The strip steel has a thickness of 0.3-3.0 mm, a width of 600-1300 mm, and an operating speed of 10-140 m / min. The air knife blowing drying system includes an edge blowing unit, a plate blowing unit, and an air supply unit. The edge blowing unit is located after the squeeze roller at the outlet of the pickling and rinsing section. It includes several sets of air knives symmetrically arranged on the upper and lower surfaces of the strip edge to perform directional blowing on the strip edge and remove residual liquid from the strip edge. The plate surface purging unit is located after the edge purging unit and includes several sets of air knives symmetrically arranged on the upper and lower surfaces of the strip steel. It is used to perform full-coverage purging of the entire strip steel width direction to remove residual liquid from the strip steel plate surface. The air supply unit consists of four independent fans, which are respectively connected to the edge purging unit and the panel purging unit. The air knife is connected to the fans through pipes, and an air volume regulating valve is installed on the pipes.

2. The air knife blow-off drying system for a cold-rolled stainless steel strip production line according to claim 1, characterized in that, The edge purging unit has 8-16 air knives, symmetrically arranged on the upper and lower surfaces of the strip, with 4-8 knives on each side. It adopts a segmented control method, with the 8-16 air knives divided into front and rear groups. Each group contains 2-4 air knives on the upper and lower sides. The front and rear groups are supplied with air by two independent fans. The control is segmented according to the strip width: when operating narrow strip, only the front group of air knives is activated; when operating wide strip, both the front and rear groups of air knives are activated simultaneously. The air volume regulating valve adjusts the air supply in segments according to the strip width and operating speed to achieve energy-saving operation.

3. The air knife blow-off drying system for a cold-rolled stainless steel strip production line according to claim 2, characterized in that, Each air knife is 250mm long and has a blade width of 1.5mm; the angle between the air knife and the strip width direction is 35°, and the angle between the blowing direction and the strip running direction is 45°; the vertical distance between the air knife outlet and the strip surface is 30~80mm.

4. The air knife blow-off drying system for a cold rolled stainless steel strip production line of claim 1, characterized in that, The plate surface purging unit has 4 to 6 air knives, symmetrically arranged on the upper and lower surfaces of the strip, with 2 to 3 air knives on each side. Each air knife is 1300mm long and has a blade width of 1.5mm. The angle between the purging direction and the running direction of the strip is 45°. The vertical distance between the air knife outlet and the strip surface is 30 to 80mm.

5. The air knife blowing and drying system for a cold-rolled stainless steel strip production line according to claim 1, characterized in that, The fan is a ring blower with a single motor power of 22kW and a total power of 88kW. The fan outlet and the air knife are connected by a flexible hose, and the flexible hose is equipped with an air volume regulating valve to adjust the air volume in stages according to the strip steel specifications and operating speed.

6. A method for air knife purging and drying in a cold-rolled stainless steel strip production line, comprising the air knife purging and drying system for a cold-rolled stainless steel strip production line as described in any one of claims 1 to 5, characterized in that... Includes the following steps: Step S1: System Startup When the production line receives the start signal, it first starts the fan of the air supply unit; First, start the fan corresponding to the panel purging unit. After the fan is running stably, start the fan corresponding to the edge purging unit. Step S2: Width detection and air knife segmentation selection After being squeezed dry by the squeezing rollers at the outlet of the pickling and rinsing section, the strip steel enters the air knife purging area. The width sensor located at the entrance of the edge purging unit detects the strip steel width in real time and transmits the detection signal to the PLC controller. The PLC automatically selects the edge air knives within the corresponding width range based on the strip steel width value. When the strip steel width is ≤1000mm, only the first group of air knives closest to the center line of the strip steel passage is activated. When the width is >1000mm, all air knives are activated. The solenoid valves corresponding to the unselected air knives are closed, and the blower outputs the corresponding air volume through frequency conversion regulation to achieve on-demand air supply and energy-saving operation. Step S3: Speed ​​detection and airflow adjustment The speed sensor detects the running speed of the strip in real time and feeds it back to the PLC controller. The PLC automatically adjusts the output air volume of the blower according to the strip speed: when the strip speed is ≤50m / min, the opening of the air volume regulating valve is set to 40%~50%; when the speed is ≤100m / min, the opening is set to 60%~80%; when the speed is >100m / min, the opening is set to 90%~100%. Through the dual control of frequency conversion regulation and valve opening, the best purging effect can be obtained at different running speeds. Step S4: Two-stage coordinated purging The strip first enters the edge cleaning unit: the high-speed airflow from the air knife forms a 35° angle with the width direction of the strip and a 45° angle with the running direction of the strip, concentrating on the edge area of ​​the strip to quickly blow away the liquid remaining in the squeeze roll gap at the edge; after edge cleaning, the strip enters the plate cleaning unit: the high-speed airflow from the air knife forms a 45° angle with the running direction of the strip, providing full coverage cleaning across the entire width direction to further remove residual liquid from the plate surface; the two cleaning units work in sequence; Step S5: Purge complete and system standby. When the production line stops or the strip stops running, the PLC controller first shuts down the fan corresponding to the edge blowing unit, and then shuts down the fan corresponding to the plate blowing unit after a 10-second delay, ensuring that all air knives stop blowing air; the system enters standby mode, waiting for the next production instruction.

7. The air knife blow-drying method for a cold-rolled stainless steel strip production line according to claim 6, characterized in that, The PLC controller is a Siemens S7-1200 series or S7-1500 series PLC. The PLC receives signals from the strip width sensor and speed sensor to determine the number of air knives to be activated and the power level of the fan, thereby realizing intelligent segmented adjustment and control.

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