A rinsing system of a strip steel pickling line and a method of operation thereof

Abstract

This invention relates to a rinsing system and its operating method for a steel strip pickling unit. The rinsing system includes a rinsing tank, a rinsing water spraying device, a purging device, and a drying device. The bottom of the rinsing tank is equipped with an inclined surface and a drainage channel to quickly discharge the rinsing water, ensuring no water remains in the tank and eliminating the conditions for generating high-temperature steam, thus preventing water rust caused by shutdown. When the pickling unit malfunctions and shuts down, the rinsing water from the final-stage rinsing tank is introduced into each subsequent rinsing tank to perform a short-term rinsing of the steel strip within the rinsing section, removing residual acid from the surface of the steel strip and eliminating water rust caused by excessively acidic rinsing water. Purging is performed during and after the short-term rinsing process, followed by drying to prevent water rust caused by residual rinsing water.

Description

Technical Field

[0001] This invention relates to the field of strip steel production technology, and in particular to a rinsing system and its working method for a strip steel pickling unit. Background Technology

[0002] Before cold rolling, the iron oxide scale on the surface of hot-rolled strip coils must be removed to prevent it from being pressed into the surface of the rolled piece during cold rolling, thus affecting the surface quality. Common methods for removing iron oxide scale include mechanical descaling and chemical descaling, with chemical descaling involving pickling with sulfuric acid or hydrochloric acid. Currently, there are three main methods for pickling strip steel used worldwide: single-coil pickling, continuous pickling, and semi-continuous pickling, all achieved through different pickling units. In continuous pickling units, after the strip steel passes through the pickling tank and rinsing tank, residual moisture on the surface of the strip steel must be removed to ensure good surface quality of the pickled strip steel.

[0003] like Figure 1 The diagram shows a structural schematic of a strip steel pickling unit. After uncoiling, the hot-rolled strip steel continuously passes through three pickling tanks (tank SX1, tank SX2, and tank SX3), where the acid in each tank removes the iron oxide scale. It then passes through four rinsing tanks (tank PX1, tank PX2, tank PX3, and tank PX4) to remove residual acid from the surface. The pickling solution in each tank circulates independently through corresponding circulation tanks (external circulation tanks 1, 2, and 3). Rinse water at approximately 70°C in each rinsing tank is pumped to the spray beam and sprayed onto the upper and lower surfaces of the strip steel by the corresponding circulation pump. Fresh demineralized water in the demineralized water tank TY overflows sequentially from tank PX4 (tank PX4) against the direction of the strip steel's movement into tanks PX3 (tank PX3), PX2 (tank PX2), PX1 (tank PX1), and the rinsing water tank CX. The rinsing water in rinsing tank #4 (PX4) is the cleanest, and its pH value is greater than 3.8.

[0004] During the pickling process, if the pickling unit malfunctions and stops for more than 5 minutes, approximately 20 meters of strip steel in the rinsing section will develop black rust (known as shutdown rust) under the influence of residual acid and water vapor in the rinsing tank, rendering it unusable. Currently, the method for handling shutdown rust is to reverse the strip steel moving mechanism before restarting the pickling unit, moving the strip steel with shutdown rust back into the pickling tank. The acid in the pickling tank then removes the rust, and the pickling unit can then resume normal production. This method has two problems: first, the reverse movement of the strip steel carries acid from the No. 1 pickling tank towards the inlet, corroding the equipment and polluting the environment; second, the strip steel retraction speed is low, requiring more than 2.5 minutes for one retraction, directly affecting the production efficiency of the pickling unit.

[0005] Chinese patent application CN 115074741 A discloses a "pickled rust removal process", which includes the following steps: S1, adding a secondary pickling tank after the No. 4 rinsing tank and connecting it to the exhaust system; S2, adding a secondary rinsing tank after the secondary pickling tank; S3, installing an air purging duct in the secondary rinsing tank; S4, installing a control valve Vg and connecting it to the acid supply pipeline of the secondary pickling tank; S5, installing control valves V1, V2, V3, and V4; S6, installing a return acid pipe for the secondary pickling tank; S7, installing a water supply pipeline for the secondary rinsing; S8, connecting the pipeline from the secondary rinsing to the rinsing water tank. This pickling rust removal process adds a secondary pickling tank and a secondary rinsing tank after the original rinsing tank, which can completely eliminate rust defects during shutdown. The rust removal process is fully included in the normal start-up and shutdown process, without the need for additional manual operation and time to stop the equipment, thus improving the production efficiency of the equipment. Summary of the Invention

[0006] This invention provides a rinsing system and its operating method for a steel strip pickling unit. The bottom of the rinsing tank is equipped with an inclined surface and a drainage trough to quickly discharge the rinsing water, ensuring that no water remains in the rinsing tank and eliminating the conditions for generating high-temperature water vapor, thus preventing water rust caused by shutdown. When the pickling unit fails and shuts down, the rinsing water in the final rinsing tank is introduced into each subsequent rinsing tank to perform a short-term rinsing of the steel strip in the rinsing section, removing residual acid from the surface of the steel strip and eliminating water rust caused by excessive acidity of the rinsing water. During and after the short-term rinsing, purging is performed, followed by drying to prevent water rust caused by residual rinsing water.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A rinsing system for a steel strip pickling unit includes several rinsing tanks arranged sequentially along the moving direction of the steel strip. Each rinsing tank is equipped with several sets of blow nozzles and rinsing water nozzles. Each rinsing tank is equipped with an external circulation tank, forming a rinsing water circulation loop through corresponding circulation pipelines. A circulation pump is installed on the rinsing water circulation loop, and control valves are installed on the upstream and downstream rinsing water circulation loops of the circulation pump. The external circulation tank corresponding to the last rinsing tank near the exit end of the steel strip is connected to the rinsing water circulation loops corresponding to the other rinsing tanks through return pipelines, and each return pipeline is equipped with a control valve. The rinsing system also includes a drying device.

[0009] Furthermore, there are four rinsing tanks, sequentially named rinsing tank #1, rinsing tank #2, rinsing tank #3, and rinsing tank #4 along the direction of strip movement. Rinsing tank #1 is equipped with an external circulation tank #1, forming a rinsing water circulation loop one via corresponding circulation pipes. This loop one is equipped with a circulation pump #1 and a control valve. Rinsing tank #2 is equipped with an external circulation tank #2, forming a rinsing water circulation loop two via corresponding circulation pipes. This loop two is equipped with a circulation pump #2 and a control valve. Rinsing tank #3 is equipped with an external circulation tank #3, forming a rinsing water circulation loop three via corresponding circulation pipes. The third circulation loop is equipped with a #3 circulation pump and a control valve; the #4 rinsing tank is equipped with a #4 external circulation tank, forming a fourth rinsing water circulation loop through corresponding circulation pipelines. The fourth rinsing water circulation loop is equipped with a #4 circulation pump and a control valve; the #4 external circulation tank is connected to the first rinsing water circulation loop through a return pipeline, which is equipped with a control valve; the #4 external circulation tank is connected to the second rinsing water circulation loop through a return pipeline, which is equipped with a control valve; the #4 external circulation tank is connected to the third rinsing water circulation loop through a return pipeline, which is equipped with a control valve; the #4 external circulation tank is equipped with a pH value detection device.

[0010] Furthermore, the bottom surface of the rinsing tank is inclined, and the end near the transmission side is higher than the end near the operation side. The angle between the inclined surface and the horizontal plane is 10° to 15°. A drainage trough is provided at the bottom of the rinsing tank, and the drainage trough has multiple drainage outlets, which are connected to the corresponding external circulation tank through drainage pipes.

[0011] Furthermore, the length direction of the rinsing tank is parallel to the strip moving direction, and the length of a single rinsing tank is 4 to 5 m; the width direction of the rinsing tank is perpendicular to the strip moving direction, and the internal width of a single rinsing tank is 2.5 to 3 m; the height of the rinsing tank is 1.2 to 1.5 m.

[0012] Furthermore, the rinsing water nozzles are located on the rinsing water spray beams; along the moving direction of the strip, 3 to 4 rinsing water spray beams are respectively arranged above and below the strip; each rinsing water spray beam is equipped with 30 to 50 rinsing water nozzles.

[0013] Furthermore, both the rinse water spray beam and the rinse water nozzle are made of acid-resistant PP material, and the working pressure of the rinse water nozzle is 0.25-0.3 MPa.

[0014] Furthermore, the purge nozzles are located on the air purging beams; along the direction of strip movement, the air purging beams are arranged in 3 to 4 rows above and below the strip; each air purging beam is equipped with 30 to 50 purge nozzles.

[0015] 8. The rinsing system of a steel strip pickling unit according to claim 1, characterized in that the air blowing beam and the blowing nozzle are both made of PP acid-resistant material, and the working pressure of the blowing nozzle is ≥0.4MPa.

[0016] Furthermore, the rinsing tank has several dryers installed on the outer side of the tank wall near the operating side, with several sets of hot air inlets correspondingly opened on the upper part of the tank wall; the dryer consists of a shell and a heat exchanger, heat sink, and fan installed inside the shell, with one side of the shell tightly attached to the tank wall, and an air outlet opened at the position corresponding to the hot air inlet; the heat exchanger is located below the air outlet, with heat sink installed on the outer side of the heat exchanger, and a fan installed below the heat exchanger; the dryers are installed one-to-one with the pickling tank heaters; the heat exchanger has a steam inlet connected to the steam outlet of the corresponding pickling tank heater, and the steam inlet of the pickling tank heater is connected to the external steam main pipe; the steam outlet of the heat exchanger is connected to the demineralized water tank.

[0017] A method for operating a rinsing system of a steel strip pickling unit includes:

[0018] 1) When the pickling unit is operating normally, fresh demineralized water is continuously injected into external circulation tank #4; when the rinsing water in external circulation tank #4 exceeds the set capacity, it overflows into external circulation tank #3; when the rinsing water in external circulation tank #3 exceeds the set capacity, it overflows into external circulation tank #2; when the rinsing water in external circulation tank #2 exceeds the set capacity, it overflows into external circulation tank #1; and when the rinsing water in external circulation tank #1 exceeds the set capacity, it overflows into the rinsing water tank, thus ensuring a continuous renewal of the rinsing water in the four external circulation tanks; external circulation tank #4 is equipped with a pH detection device, which detects pH changes when the pH value is high. When the measured pH value is greater than the upper limit of the set value, the flow rate of the replenished demineralized water is increased; the strip steel is rinsed sequentially through the rinsing water of rinsing tanks 1# to 4#, and the pH value of the rinsing water in the external circulation tank 4# is >3.8; each rinsing tank rinses the upper and lower surfaces of the strip steel through the corresponding rinsing water nozzles, and the rinse water after rinsing is collected in the drainage tank through the bottom slope and quickly discharged into the corresponding external circulation tank through each drain outlet to ensure that no rinsing water accumulates in the rinsing tank; while rinsing with water spray, compressed air is introduced into the blower nozzles to blow the upper and lower surfaces of the strip steel.

[0019] 2) When the pickling unit is shut down due to a malfunction, the following measures shall be taken to prevent rust from forming on the strip:

[0020] a. Use the rinsing water in the No. 4 external circulation tank to rinse all the strip steel remaining in the rinsing section for a short time; at this time, close the control valve upstream of the circulation pump on the rinsing water circulation loop corresponding to the No. 1 to No. 3 rinsing tanks, and at the same time open the control valves on the 3 return pipelines, so that the rinsing water in the No. 4 external circulation tank is simultaneously introduced into the 3 return pipelines, that is, all the strip steel in the No. 1 to No. 4 rinsing tanks are rinsed with the rinsing water in the No. 4 external circulation tank;

[0021] b. While rinsing briefly, compressed air is introduced into the blow nozzle to blow the upper and lower surfaces of the strip.

[0022] c. After a short rinsing lasts for at least 10 seconds, all circulating pumps stop running. The control valves downstream of the circulating pumps in each rinsing water circulation loop and the control valve upstream of the corresponding circulating pump in the No. 4 rinsing tank remain open. The control valves upstream of the circulating pumps in each rinsing water circulation loop are opened. The control valves on all return pipelines are closed. Each blower nozzle continues to blow for at least 10 seconds to dry the surface moisture of the strip steel.

[0023] d. Steam from the pickling tank heater is introduced into the heat exchangers of each dryer in the rinsing section. After purging is completed, the dryer fan is started, and the hot air generated by the heat exchanger is blown into the rinsing tank through the hot air outlet to dry the surface of the strip steel.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1) The bottom of the rinsing tank is equipped with a slope and a drainage trough to quickly drain the rinsing water from the rinsing tank, so that no water remains in the rinsing tank, eliminating the conditions for the generation of high temperature water vapor in the rinsing tank and preventing water rust caused by shutdown.

[0026] 2) When the pickling unit fails and stops, the rinsing water in the final rinsing tank is introduced into each rinsing tank to rinse the strip steel in the rinsing section for a short time to remove the residual acid on the surface of the strip steel and eliminate the rust caused by the shutdown water due to the excessive acidity of the rinsing water.

[0027] 3) The strip surface is blown during and after short-time rinsing, and then dried to prevent water rust caused by residual rinsing water during shutdown.

[0028] 4) Completely eliminate the conditions that cause rust in parking spaces, effectively reducing the scrap rate caused by rust in parking spaces;

[0029] 5) By using the method described in this invention, it is no longer necessary to reverse the strip to remove water rust from the shutdown, thus avoiding downtime caused by reversing the strip and improving the production efficiency of the pickling unit;

[0030] 6) The steam from the outlet of the pickling tank heater is used as the heat source for the dryer to realize the utilization of waste heat, while reducing the consumption of demineralized water and saving energy. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the existing pickling unit.

[0032] Figure 2 This is a schematic diagram of the rinsing system described in this invention.

[0033] Figure 3This is a schematic diagram of the structure of a single rinsing tank according to the present invention.

[0034] Figure 4 This is a rinsing flow chart of the pickling unit under normal operation as described in this invention.

[0035] Figure 5 This is a schematic diagram of the dryer described in this invention.

[0036] Figure 1 In the middle section: SX1.1# pickling tank, SX2.2# pickling tank, SX3.3# pickling tank, PX1.1# rinsing tank, PX2.2# rinsing tank, PX3.3# rinsing tank, PX4.4# rinsing tank, XH1.1# external circulation tank, XH2.2# external circulation tank, XH3.3# external circulation tank, CX. rinsing water tank, TY. demineralized water tank.

[0037] Figures 2-5 In the middle section: 1R.1# Rinse Tank 2R.2# Rinse Tank 3R.3# Rinse Tank 4R.4# Rinse Tank R1. Rinse Water Nozzle R2. Air Purging Beam R3. Circulation Pump R4. External Circulation Tank R5, R6. Control Valve R7. Drain 1T.1# External Circulation Tank 2T.2# External Circulation Tank 3T.3# External Circulation Tank 4T.4# External Circulation Tank P1.1# Circulation Pump P1.1# Circulation Pump P2.2# Circulation Pump P3.3# Circulation Pump P4.4# Circulation Pump V1~V13. Control Valve G1. Demineralized Water Tank G2. Rinse Water Tank PHC. pH Value Detection Device B. (Rinse Tank) Tank Wall K. Hot Air Outlet H1.1# Pickling Tank Heater H2.2# Pickling Tank Heater H3.3# Pickling Tank Heater W. Dryer Detailed Implementation

[0038] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0039] like Figure 2 As shown, the rinsing system of the strip pickling unit of the present invention includes several rinsing tanks arranged sequentially along the strip moving direction. Each rinsing tank is equipped with several sets of blowing nozzles and rinsing water nozzles R1 above it. Each rinsing tank is equipped with an external circulation tank R4, which forms a rinsing water circulation loop through corresponding circulation pipelines. A circulation pump R3 is provided on the rinsing water circulation loop. Control valves R5 and R6 are respectively provided on the rinsing water circulation loops upstream and downstream of the circulation pump R3. The external circulation tank corresponding to the last rinsing tank near the strip exit end is connected to the rinsing water circulation loops corresponding to the other rinsing tanks through return pipelines, and each return pipeline is equipped with a control valve. The rinsing system also includes a drying device.

[0040] Furthermore, there are four rinsing tanks, arranged sequentially along the moving direction of the strip as rinsing tank 1R, rinsing tank 2R, rinsing tank 3R, and rinsing tank 4R. Rinsing tank 1R is equipped with an external circulation tank 1T, forming a first rinsing water circulation loop through corresponding circulation pipes. This loop includes a circulation pump P1 and control valves V1 and V2. Rinsing tank 2R is equipped with an external circulation tank 2T, forming a second rinsing water circulation loop through corresponding circulation pipes. This loop includes a circulation pump P2 and control valves V3 and V4. Rinsing tank 3R is equipped with an external circulation tank 3T, forming a third rinsing water circulation loop through corresponding circulation pipes. Loop 3 is equipped with a #3 circulating pump P3 and control valves V5 and V6; Rinse tank 4R is equipped with an external circulating tank 4T, forming rinse water circulation loop 4 through corresponding circulation pipelines. Rinse water circulation loop 4 is equipped with a #4 circulating pump P4 and control valves V7 and V8; External circulating tank 4T is connected to rinse water circulation loop 1 through return pipeline 1, and control valve V9 is installed on return pipeline 1; External circulating tank 4T is connected to rinse water circulation loop 2 through return pipeline 2, and control valve V10 is installed on return pipeline 2; External circulating tank 4T is connected to rinse water circulation loop 3 through return pipeline 3, and control valve V11 is installed on return pipeline 3; External circulating tank 4T is equipped with a pH value detection device PHC.

[0041] Furthermore, such as Figure 3 As shown, the bottom surface of the rinsing tank is inclined, and the end near the transmission side is higher than the end near the operation side. The angle between the inclined surface and the horizontal plane is 10° to 15°. A drainage trough is provided at the bottom of the rinsing tank, and the drainage trough has multiple drainage outlets R7, which are connected to the corresponding external circulation tanks R4 through drainage pipes.

[0042] Furthermore, the length direction of the rinsing tank is parallel to the strip moving direction, and the length of a single rinsing tank is 4 to 5 m; the width direction of the rinsing tank is perpendicular to the strip moving direction, and the internal width of a single rinsing tank is 2.5 to 3 m; the height of the rinsing tank is 1.2 to 1.5 m.

[0043] Furthermore, the rinse water nozzles R1 are located on the rinse water spray beams; along the moving direction of the strip, the rinse water spray beams are arranged in 3 to 4 rows above and below the strip; each rinse water spray beam is equipped with 30 to 50 rinse water nozzles R1.

[0044] Furthermore, both the rinse water spray beam and the rinse water nozzle R1 are made of acid-resistant PP material, and the working pressure of the rinse water nozzle R1 is 0.25-0.3 MPa.

[0045] Furthermore, the purge nozzles are disposed on the air purging beam R2; along the moving direction of the strip, the air purging beam R2 is provided with 3 to 4 rows above and below the strip; each air purging beam R2 is provided with 30 to 50 purge nozzles.

[0046] Furthermore, both the air purging beam R2 and the purging nozzle are made of acid-resistant PP material, and the working pressure of the purging nozzle is ≥0.4MPa.

[0047] Furthermore, such as Figure 5 As shown, the rinsing tank has several dryers W on the outer side of the tank wall B near the operation side, and several sets of hot air inlets K are correspondingly opened on the upper part of the tank wall B. The dryer W consists of a shell and a heat exchanger, heat sink, and fan installed inside the shell. One side of the shell is in close contact with the tank wall B, and an air outlet is opened at the position corresponding to the hot air inlet K. The heat exchanger is located below the air outlet, and heat sink is installed on the outer side of the heat exchanger. The fan is located below the heat exchanger. The dryers W are arranged one-to-one with the pickling tank heaters. The heat exchanger has a steam inlet connected to the steam outlet of the corresponding pickling tank heater. The steam inlet of the pickling tank heater is connected to the external steam main pipe. The steam outlet of the heat exchanger is connected to the demineralized water tank G1.

[0048] The present invention discloses a method for operating a rinsing system of a steel strip pickling unit, comprising:

[0049] 1) such as Figure 4 As shown, during normal operation of the pickling unit, fresh demineralized water is continuously injected into external circulation tank 4T (4#). When the rinsing water in external circulation tank 4T exceeds the set capacity, it overflows into external circulation tank 3T (3#). When the rinsing water in external circulation tank 3T exceeds the set capacity, it overflows into external circulation tank 2T (2#). When the rinsing water in external circulation tank 2T exceeds the set capacity, it overflows into external circulation tank 1T (1#). When the rinsing water in external circulation tank 1T exceeds the set capacity, it overflows into rinsing water tank G2, thus ensuring a continuous renewal of the rinsing water in the four external circulation tanks. External circulation tank 4T (4#) is equipped with a pH value detection device. Set the pH value to PHC. When the detected pH value is greater than the upper limit of the set value, increase the flow rate of the replenished demineralized water. The strip steel is rinsed sequentially through the rinsing water in rinsing tanks 1# to 4# (1R to 4R). The pH value of the rinsing water in the external circulation tank 4T (4T) is >3.8. Each rinsing tank rinses the upper and lower surfaces of the strip steel through the corresponding rinsing water nozzle R1. The rinsed rinsing water is collected in the drainage tank through the bottom slope and quickly discharged into the corresponding external circulation tank through each drainage port R7 to ensure that no rinsing water accumulates in the rinsing tank. While rinsing with water spray, compressed air is introduced into the blower nozzle to blow the upper and lower surfaces of the strip steel.

[0050] 2) When the pickling unit is shut down due to a malfunction, the following measures shall be taken to prevent rust from forming on the strip:

[0051] a. Use the rinsing water in the 4T external circulation tank #4 to rinse all the strip steel remaining in the rinsing section for a short time; at this time, close the control valve upstream of the circulation pump on the rinsing water circulation loop corresponding to the rinsing water circulation loop of the rinsing tanks 1R to 3R of the 1# to 3# rinsing tanks, and at the same time open the control valves on the 3 return pipelines, so that the rinsing water in the 4T external circulation tank #4 is simultaneously introduced into the 3 return pipelines, that is, all the strip steel in the 1R to 4R rinsing tanks 1# to 4# rinsing tanks 1R to 4R is rinsed with the rinsing water in the 4T external circulation tank #4;

[0052] b. While rinsing briefly, compressed air is introduced into the blow nozzle to blow the upper and lower surfaces of the strip.

[0053] c. After a short rinsing lasts for at least 10 seconds, all circulating pumps stop running. The control valves downstream of the circulating pumps in each rinsing water circulation loop and the control valves upstream of the corresponding circulating pumps in rinsing tank 4R remain open. The control valves upstream of the circulating pumps in each rinsing water circulation loop are opened. All control valves on the return pipelines are closed. Each blower nozzle continues to blow for at least 10 seconds to dry the surface moisture of the strip steel.

[0054] d. Steam from the pickling tank heater is introduced into the heat exchangers of each dryer W in the rinsing section. After purging is completed, the fan of dryer W is started, and the hot air generated by the heat exchanger is blown into the rinsing tank through the hot air outlet K to dry the surface of the strip steel.

[0055] Existing pickling units typically have flat bottoms in their rinsing tanks without drainage channels, leading to the accumulation of rinsing water inside. This invention designs the bottom of the rinsing tank as a slope with a drainage channel. The purpose is to ensure that the rinsing water sprayed from the nozzles quickly enters the drainage channel along the slope and is rapidly discharged from the rinsing tank through the drain pipe. This ensures that the rinsing tank is never filled with water, thus eliminating the conditions for rust formation during shutdowns caused by high-temperature steam generated from accumulated rinsing water.

[0056] During normal operation of the pickling unit, the rinsing water nozzles are used to rinse the upper and lower surfaces of the strip steel. In this invention, the rinsing water nozzles are also used to rinse the strip steel briefly after the pickling unit fails and stops, in order to remove residual acid from the surface of the strip steel and eliminate the conditions for water rust caused by residual acid on the surface of the strip steel during shutdown.

[0057] During normal operation of the pickling unit, the blow nozzles are used to blow the upper and lower surfaces of the strip steel. In this invention, the blow nozzles are also used to blow the surface of the strip steel after a short rinsing following a malfunction shutdown of the pickling unit, in order to remove most of the rinsing water from the surface of the strip steel and eliminate the conditions for water rust caused by residual rinsing water on the surface of the strip steel during shutdown.

[0058] After the pickling unit stops, not all the strip steel remaining in the rinsing section has been rinsed in all four rinsing tanks. Since the acid value of the rinsing water in the final stage, namely the rinsing water in external circulation tank #4, is the lowest, this invention uses the rinsing water from external circulation tank #4 (4T) to rinse all the strip steel remaining in the rinsing section. To ensure sufficient power for jet rinsing, all four circulation pumps are engaged. External circulation tank #4 is connected to the rinsing water circulation loops corresponding to rinsing tanks #1 to #3 via three return pipes. Return pipe one is connected to the inlet of circulation pump #1 (P1), and a control valve V9 is installed on return pipe one; return pipe two is connected to the inlet of circulation pump #2 (P2), and a control valve V10 is installed on return pipe two; return pipe three is connected to the inlet of circulation pump #3 (P3), and a control valve V11 is installed on return pipe three. The function of control valves V9, V10 and V11 is to ensure that when the pickling unit fails and stops, all the rinsing water used for short-term rinsing of rinsing tanks 1# to 3# is supplied by external circulation tank 4T 4#.

[0059] This invention uses an external circulation tank to control the cascade overflow of rinsing water, so the overflow baffle in a conventional pickling tank no longer serves its purpose.

[0060] The following embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0061]

Example

[0062] like Figures 2-5 As shown, in this embodiment, the rinsing system of the steel strip pickling unit includes four rinsing tanks, namely rinsing tanks 1# to 4# (1R to 4R), and also includes a rinsing water spraying device, a purging device, and a drying device; wherein:

[0063] 1. The structure of the rinsing tank;

[0064] In this embodiment, the four rinsing tanks have basically the same structure, and the structure of a single rinsing tank will be described. The running direction of the strip steel is the length direction of the rinsing tank, and the length of a single rinsing tank is 4.5m. The direction perpendicular to the running direction of the strip steel is the width direction of the rinsing tank, and the internal width of the rinsing tank is 3m. The height of the rinsing tank is 1.5m.

[0065] The bottom of the rinsing tank is sloped, with the higher end of the slope located on the drive side and the lower end on the operating side. The slope angle is 10°. A drainage trough is located at the lower end of the slope, with four drain outlets (R7) at its bottom, providing a total drainage capacity of ≥50m³. 3 / h.

[0066] 2. Structure of the rinsing water spraying device;

[0067] In this embodiment, each rinsing tank has four rinsing water spray beams arranged above and below the corresponding strip steel, and each rinsing water spray beam is equipped with 40 rinsing water nozzles R1. Both the rinsing water spray beams and the rinsing water nozzles R1 are made of acid-resistant PP material, and the working pressure of the rinsing water nozzles R1 is 0.3 MPa.

[0068] 3. The structure of the purging device;

[0069] In this embodiment, each rinsing tank has four air purging beams R2 arranged above and below the corresponding strip steel, and each air purging beam R2 is equipped with 40 purging nozzles. Both the air purging beams R2 and the purging nozzles are made of acid-resistant PP material, and the working pressure of the purging nozzles is 0.4 MPa.

[0070] 4. External circulation structure of the rinsing tank;

[0071] 1) Function of the external circulation tanks; This embodiment has a total of 4 external circulation tanks, that is, one external circulation tank is located below each rinsing tank, and the volume of the external circulation tanks is 6m³. 3 It is used to store and circulate rinsing water, ensuring that no water remains in the rinsing tank and preventing high-temperature water vapor from forming due to water in the rinsing tank, which could cause rust during shutdown.

[0072] 2) The drain pipe of the rinsing tank is located at the bottom of the rinsing tank. Each drain outlet is connected to the main drain pipe through a corresponding branch pipe, with a drainage capacity of ≥50m³. 3 / h. The other end of the main drain pipe connects to the corresponding external circulation tank. The function of the drain pipe is to quickly guide the rinse water in the rinsing tank into the external circulation tank.

[0073] 3) Circulation pumps and control valves; each external circulation pipeline is equipped with a circulation pump, with a pumping capacity ≥ 50m³. 3 The pump operates at a rate of [number] / h, providing power for the spraying of rinse water. One control valve is installed upstream and downstream of the circulation pump to control the flow rate of the rinse water and to switch pipelines.

[0074] 4) The rinse water in the external circulation tanks is cascaded and refreshed; during normal rinsing, in order to control the acid value of the rinse water in the four external circulation tanks within the set range, fresh demineralized water needs to be continuously injected into external circulation tank #4 (4T). In this embodiment, the rinse water in external circulation tank #4 (4T) is greater than 5 ml. 3 At that time, overflow occurs into external circulation tank #3 (3T); the rinsing water level in external circulation tank #3 (3T) exceeds 4.5 m³. 3 At that time, overflow occurs into external circulation tank #2 (2T); the rinsing water in external circulation tank #2 (2T) exceeds 4m³. 3 At that time, overflow occurred into the 1T external circulation tank #1, and the rinsing water volume in the 1T external circulation tank #1 exceeded 3.5m³. 3During this process, water overflows into the rinsing tank G2 to continuously refresh the rinsing water in the four external circulation tanks. External circulation tank #4 (4T) is equipped with a pH detection device (PHC). When the detected pH value exceeds the upper limit of the set value, the flow rate of the supplemental demineralized water is increased via an interlock in the control system. As the strip steel passes through rinsing tanks #1 to #4 (1R to 4R), it is rinsed using the rinsing water from the corresponding external circulation tanks #1 to #4 (1T to 4T). The rinsing water in external circulation tank #4 (4T) is the cleanest, with a pH value > 3.8.

[0075] 5. Structure of the drying device;

[0076] 1) Dryer Setup. In this embodiment, three dryers W are installed on the outer side of the operating tank wall of the rinsing section to dry the strip steel in the rinsing section after the pickling unit fails and shuts down, preventing the strip steel from developing rust due to shutdown water. The flow velocity of the fan in the dryer W is 6000 m / s. 3 / h, air pressure is 100mmWC.

[0077] 2) Setting of hot air inlets. In this embodiment, three sets of hot air inlets are opened on the upper part of the tank wall on the operating side of the rinsing section. Each set of hot air inlets consists of two hot air inlets K set at the top and bottom. The hot air inlets K are set one-to-one with the air outlets on the corresponding dryers W and are sealed and connected to each other, and are used to introduce hot air into the rinsing tank to dry the strip steel.

[0078] 3) Waste Heat Utilization. In this embodiment, the pickling unit is equipped with pickling tank #1, pickling tank #2, and pickling tank #3. Each pickling tank has two pickling tank heaters at its bottom. The steam outlet of heater H1 in pickling tank #1 is connected in parallel via pipeline to the steam inlet of the heat exchanger in the first dryer. The steam outlet of heater H2 in pickling tank #2 is connected in parallel via pipeline to the steam inlet of the heat exchanger in the second dryer. The steam outlet of heater H3 in pickling tank #3 is connected in parallel via pipeline to the steam inlet of the heat exchanger in the third dryer. The steam outlets of the heat exchangers in the three dryers are connected in parallel via pipeline to the demineralized water tank G1 to recover condensate.

[0079] In this embodiment, the operation process of the pickling unit after a malfunction and shutdown is as follows:

[0080] 1. Short rinse;

[0081] After the pickling unit malfunctions and shuts down, circulating pumps P1-P4 (1#-4#) continue to operate; control valves V1, V3, V5, V7, and V8 remain open; control valves V2, V4, and V6 are closed, stopping the flow of 1T-3T of rinsing water from external circulating tanks 1#-3# into the rinsing water spray beams of rinsing tanks 1R-3R. Control valves V9, V10, and V11 are opened, allowing 4T of rinsing water from external circulating tank 4# to enter the rinsing water spray beams of all rinsing tanks, providing short-term spray rinsing to the upper and lower surfaces of all strip steel in the rinsing section through rinsing water nozzles R1.

[0082] 2. Rinse water circulation;

[0083] Rinse water in external circulation tank 4T (4T) is sprayed onto the upper and lower surfaces of the strip through rinse water nozzles in rinse tank 1R (1R). The rinse water falls to the bottom of rinse tank 1R, enters the drainage trough along the slope, and enters external circulation tank 1T (1T) through the drain outlet and drain pipe. Rinse water in external circulation tank 4T (4T) is sprayed onto the upper and lower surfaces of the strip through rinse water nozzles in rinse tank 2R (2R). The rinse water falls to the bottom of rinse tank 2R, enters the drainage trough along the slope, and enters external circulation tank 2T (2T) through the drain outlet and drain pipe. The rinsing water in external circulation tank 4T is sprayed onto the upper and lower surfaces of the strip steel through the rinsing water nozzles in rinsing tank 3R. The rinsing water falls to the bottom of rinsing tank 3R, enters the drainage trough along the slope, and enters external circulation tank 3T through the drain outlet and drain pipe. The rinsing water in external circulation tank 4T is sprayed onto the upper and lower surfaces of the strip steel through the rinsing water nozzles in rinsing tank 4R. The rinsing water falls to the bottom of rinsing tank 4R, enters the drainage trough along the slope, and enters external circulation tank 4T through the drain outlet and drain pipe.

[0084] 3. Blowing during the short rinsing process;

[0085] During the short-term rinsing, compressed air is introduced into all the blow nozzles to blow the upper and lower surfaces of the strip steel, blowing the rinsing water off the surface of the strip steel, accelerating the renewal of the rinsing water on the surface of the strip steel, and increasing the rinsing area of ​​the strip steel by the rinsing water, thereby strengthening the rinsing effect.

[0086] 4. Blowing after a short rinse;

[0087] After a short rinse lasting 10 seconds, all circulation pumps stop, and control valves V1, V3, V5, V7, and V8 remain open; control valves V2, V4, and V6 are open; and control valves V9, V10, and V11 are closed. After the short rinse ends, the blow nozzles continue blowing for another 10 seconds to thoroughly remove the rinse water from the strip surface.

[0088] 5. Drying;

[0089] Steam from the outlet of each pickling tank heater is fed into the heat exchangers of the three dryers in the rinsing section. After purging is completed, the fans of the three dryers are started to send hot air into the rinsing tank to dry the surface of the strip steel.

[0090] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A rinsing system of a pickling line of a strip steel, comprising a plurality of rinsing tanks arranged in sequence along the moving direction of the strip steel, and a plurality of groups of blowing nozzles and rinsing water nozzles are arranged above each of the rinsing tanks; characterized in that, The rinsing tank is provided with an external circulating tank in one-to-one correspondence, a rinsing water circulating loop is formed through the corresponding circulating pipeline, a circulating pump is arranged on the rinsing water circulating loop, and control valves are arranged on the upstream and downstream of the circulating pump respectively; the external circulating tank corresponding to the last rinsing tank near the strip steel moving-out end is connected to the rinsing water circulating loops corresponding to the remaining rinsing tanks through return pipelines respectively, and control valves are arranged on the return pipelines respectively; the rinsing system is further provided with a drying device; The rinsing tank is provided with an external circulating tank in one-to-one correspondence, a rinsing water circulating loop is formed through the corresponding circulating pipeline, a circulating pump is arranged on the rinsing water circulating loop, and control valves are arranged on the upstream and downstream of the circulating pump respectively; the external circulating tank corresponding to the last rinsing tank near the strip steel moving-out end is connected to the rinsing water circulating loops corresponding to the remaining rinsing tanks through return pipelines respectively, and control valves are arranged on the return pipelines respectively; the rinsing system is further provided with a drying device; The rinsing tank is provided with an external circulating tank in one-to-one correspondence, a rinsing water circulating loop is formed through the corresponding circulating pipeline, a circulating pump is arranged on the rinsing water circulating loop, and control valves are arranged on the upstream and downstream of the circulating pump respectively; the external circulating tank corresponding to the last rinsing tank near the strip steel moving-out end is connected to the rinsing water circulating loops corresponding to the remaining rinsing tanks through return pipelines respectively, and control valves are arranged on the return pipelines respectively; the rinsing system is further provided with a drying device; 2. A pickling line according to claim 1, characterized in that The rinsing tank is provided with an external circulating tank in one-to-one correspondence, a rinsing water circulating loop is formed through the corresponding circulating pipeline, a circulating pump is arranged on the rinsing water circulating loop, and control valves are arranged on the upstream and downstream of the circulating pump respectively; the external circulating tank corresponding to the last rinsing tank near the strip steel moving-out end is connected to the rinsing water circulating loops corresponding to the remaining rinsing tanks through return pipelines respectively, and control valves are arranged on the return pipelines respectively; the rinsing system is further provided with a drying device; 3. A pickling line according to claim 1, characterized in that The bottom surface of the rinsing tank is a slope, and the end near the driving side is higher than the end near the operating side, the included angle between the slope and the horizontal plane is 10°-15°; a drain groove is arranged at the low end of the bottom of the rinsing tank, the drain groove is provided with a plurality of drain openings, and the drain openings are connected to the corresponding external circulating tanks through a drain pipeline. The length direction of the rinsing tank is parallel to the strip steel moving direction, and the length of a single rinsing tank is 4-5 m; the width direction of the rinsing tank is perpendicular to the strip steel moving direction, and the internal width of a single rinsing tank is 2.5-3 m; the height of the rinsing tank is 1.2-1.5 m.

4. A pickling line according to claim 1, characterized in that The rinsing water nozzles are arranged on the rinsing water spraying beams; along the moving direction of the strip, the rinsing water spraying beams are arranged in 3-4 rows above and below the strip; and each row of the rinsing water spraying beams is provided with 30-50 rinsing water nozzles.

5. A pickling line according to claim 4, characterized in that The rinsing water spraying beams and the rinsing water nozzles are made of PP acid-resistant material, and the working pressure of the rinsing water nozzles is 0.25-0.3 MPa.

6. A pickling line according to claim 1, characterized in that The blowing air nozzles are arranged on the air blowing beams; along the moving direction of the strip, the air blowing beams are arranged in 3-4 rows above and below the strip; and each row of the air blowing beams is provided with 30-50 blowing air nozzles.

7. A pickling line according to claim 6, characterized in that The air blowing beams and the blowing air nozzles are made of PP acid-resistant material, and the working pressure of the blowing air nozzles is ≥0.4 MPa.

8. A method of operating a rinsing system of a pickling line for strip steel as claimed in claim 1, characterized in that It comprises: 1) When the pickling unit is working normally, fresh desalted water is continuously injected into the 4# external circulating tank; when the rinsing water in the 4# external circulating tank is more than the set capacity, it overflows into the 3# external circulating tank; when the rinsing water in the 3# external circulating tank is more than the set capacity, it overflows into the 2# external circulating tank; when the rinsing water in the 2# external circulating tank is more than the set capacity, it overflows into the 1# external circulating tank; and when the rinsing water in the 1# external circulating tank is more than the set capacity, it overflows into the rinsing water tank, so as to keep the rinsing water in the four external circulating tanks being continuously updated; the 4# external circulating tank is provided with a pH value detection device, and when the detected pH value is greater than the upper limit of the set value, the flow of the supplemented desalted water is increased; the strip is rinsed by the rinsing water of the 1#-4# rinsing tanks in turn, and the pH value of the rinsing water in the 4# external circulating tank is >3.8; the upper and lower surfaces of the strip are rinsed by the corresponding rinsing water nozzles of the rinsing tanks, and the rinsed rinsing water is collected on the bottom slope and discharged into the corresponding external circulating tank through the drainage openings, so as to ensure that the rinsing tanks are not accumulated with rinsing water; while the water rinsing is performed, compressed air is introduced into the blowing air nozzles to blow the upper and lower surfaces of the strip; 2) When the pickling unit is stopped due to failure, the following method is adopted to prevent the strip from being rusted due to stoppage: a. The rinsing water in the 4# external circulating tank is used to rinse the strip in the rinsing section for a short time; at this time, the control valves on the upstream of the circulating pumps in the rinsing water circulating loops corresponding to the 1#-3# rinsing tanks are closed, and the control valves on the three backflow pipelines are opened, so that the rinsing water in the 4# external circulating tank is introduced into the three backflow pipelines, i.e. the 1#-4# rinsing tanks all use the rinsing water in the 4# external circulating tank to rinse the strip; b. While the short-time rinsing is performed, compressed air is introduced into the blowing air nozzles to blow the upper and lower surfaces of the strip; c. After the short-time rinsing lasts for at least 10 s, all the circulating pumps are stopped, the control valves on the downstream of the circulating pumps in the rinsing water circulating loops and the control valve on the upstream of the circulating pump corresponding to the 4# rinsing tank are kept open, the control valves on the upstream of the circulating pumps in the rinsing water circulating loops are opened, all the control valves on the backflow pipelines are closed, and the blowing air nozzles continue to blow for at least 10 s to dry the water on the surface of the strip. d. The steam in the pickling tank heater is introduced into the heat exchanger of each dryer in the rinsing section. When the blowing is finished, the fan of the dryer is started, the hot air produced by the heat exchanger is blown into the rinsing tank through the hot air port to dry the surface of the strip.

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