Automatic control system and automatic control method for three-washing process in production of titanium dioxide by sulfuric acid method

Abstract

The invention provides an automatic control system for a three-washing process in sulfate process titanium dioxide production, which belongs to the technical field of chemical automation control, and comprises a filter press, a coated storage tank, a desalted water tank, a recycled water tank and a wastewater tank, the coated storage tank is connected with a water inlet pipe through a filter press feeding valve; the left water inlet valve and the right water inlet valve are connected with the desalted water tank; the water inlet pipe is connected with the desalted water tank through the central hole water inlet valve; the recycled water tank is connected with the water inlet pipe through a recycled water inlet valve and is connected with the water outlet pipe through a recycled water inlet valve; and the wastewater tank is connected with the water outlet pipe through the wastewater tank water inlet valve and is connected with the water outlet pipe through the sampling valve. The system is simple, convenient, high in automation degree, capable of accurately controlling the time of each process, high in safety coefficient and good in stability, realizes automatic control of the whole process of the three-washing process, realizes one-key starting of the three-washing process, realizes three-washing automatic control and circulation process, reduces the labor intensity, reduces the production cost, and improves the production efficiency.

Description

Technical Field

[0001] This invention relates to the field of chemical automation control technology, and more specifically, to an automatic control system for the three-washing process in the sulfuric acid process for titanium dioxide production. This invention also relates to an automatic control method for this automatic control system for the three-washing process in the sulfuric acid process for titanium dioxide production. Background Technology

[0002] Currently, the automation level of the conventional three-wash process in the industry is low, with control relying on manual operation on-site and partial remote manual control. The main problems with manual control of the three-wash process are as follows: 1) The three washing processes have strict requirements on the amount of feed, the washing time, and the endpoint of the water washing conductivity. There are also strict control requirements on the pressure and pressing time during the pressing process. The water washing time is controlled by manually measuring the conductivity. If the valve is not adjusted in time during manual operation, the amount of feed will be too much or too little, and the water washing time will be too long or too short, which will affect the product quality. If the valve is not closed or the pump is not stopped, it will cause the pipeline to burst and the material to be lost. In severe cases, it may cause personnel injury. 2) Manual washing is prone to flooding and material leakage, which affects production efficiency. At the same time, excessive pressing pressure poses a significant safety hazard.

[0003] Therefore, it is necessary to develop an automatic control system and automatic control method for the three washing processes in the sulfuric acid process for titanium dioxide production. Summary of the Invention

[0004] The primary objective of this invention is to overcome the shortcomings of the aforementioned background technology and to provide an automatic control system for the three-washing process in the production of titanium dioxide using the sulfuric acid process.

[0005] The second objective of this invention is to provide an automatic control method for the automatic control system of the three washing processes in the sulfuric acid process for titanium dioxide production.

[0006] To achieve the aforementioned first objective, the technical solution of the present invention is: an automatic control system for the three washing processes in the sulfuric acid process for titanium dioxide production, characterized in that it includes a filter press, a post-coating storage tank, a demineralized water tank, a recycled water tank, and a wastewater tank; The filter press has a left inlet at the upper left corner, a right inlet at the upper right corner, a center inlet in the middle, a left outlet at the lower left corner, and a right outlet at the lower right corner. The left inlet is connected to a left inlet valve, the right inlet is connected to a right inlet valve, the left outlet is connected to a left outlet valve, and the right outlet is connected to a right outlet valve. The center inlet is connected to an inlet pipe. Both the left and right outlets are connected to outlet pipes. The coated storage tank is connected to the inlet pipe via the filter press feed valve; the left and right inlet valves are connected to the demineralized water tank, and the inlet pipe is connected to the demineralized water tank via the center hole inlet valve; the recovery water tank is connected to the inlet pipe via the recovery water inlet valve, and to the outlet pipe via the recovery water tank inlet valve; the wastewater tank is connected to the outlet pipe via the wastewater tank inlet valve, and to the outlet pipe via the sampling valve.

[0007] The above technical solution also includes a compressed air tank; the compressed air tank is connected to the water inlet pipe through a compressed air valve.

[0008] The above technical solution also includes a pressing water tank; the pressing water tank is connected to the pressing water inlet valve via a pressing water pump, and the pressing water tank is connected to the pressing water return valve; the pressing water inlet valve is connected to the pressing water inlet of the filter press; and the pressing water return valve is connected to the pressing water return outlet of the filter press.

[0009] In the above technical solution, the coated storage tank is connected to the filter press feed valve via a feed pump; the demineralized water tank is connected to the left inlet valve, the right inlet valve, and the center hole inlet valve via a demineralized water pump; and the recycled water tank is connected to the recycled water inlet valve via a recycled water pump.

[0010] In the above technical solution, the wastewater tank is connected to the sampling valve via a conductivity meter; the outlet pipe is connected to the vent valve.

[0011] In the above technical solution, the coated storage tank, the demineralized water tank and the recycled water tank are all equipped with level gauges; the feed pump is connected to the filter press feed valve through a flow meter; and the press water pump is connected to the press water inlet valve through a pressure transmitter.

[0012] To achieve the second objective mentioned above, the technical solution of the present invention is: an automatic control method for the automatic control system of the three washing processes in the sulfuric acid process for titanium dioxide production, characterized by comprising the following steps: Step 1: The filter press is in pressure holding state, the pressure holding signal is closed, and the liquid level in the storage tank after coating is greater than 1.2m; Step 2: Click "Start Program" to initialize the equipment. At the same time, the filter press plate loosening signal is interlocked with the program end signal, and the program start button is locked. Step 3: Open the filter press feed valve, left outlet valve, right outlet valve and wastewater tank inlet valve; Step 4: Start the feed pump; Step 5: When the flow meter detects that the feed volume has reached the set value or the feed time has reached the set time, stop the feed pump; Step 6: After the feed pump stops, close the filter press feed valve; Step 7: After closing the filter press feed valve, open the recovery water inlet valve and the sampling valve; Step 8: After the recycling water inlet valve is opened for 5 seconds, turn on the recycling water pump and the air vent valve to start the recycling water washing process; Step 9: When the liquid level in the recovery water tank is lower than the set value, stop the recovery water pump. After the recovery water pump stops for 5 seconds, close the recovery water inlet valve to end the recovery water washing process. Step 10: After the recovery water inlet valve stops for 5 seconds, open the center hole inlet valve. After the center hole inlet valve is opened, start the demineralized water pump to perform the demineralized water center wash. Step 11: If the conductivity meter detects that the conductivity is lower than the set value for the recycled water tank, open the inlet valve of the recycled water tank and close the inlet valve of the wastewater tank to recycle wastewater. Step 12: When the conductivity meter detects that the conductivity is lower than the set value of the center wash conductivity endpoint, open the left inlet valve and close the center hole inlet valve and the left outlet valve. Step 13: When the conductivity meter detects a conductivity value lower than the set value for the end point of the left corner wash, start timing. During the timing process, if the conductivity rises above the set conductivity, the accumulated time is reset to zero. If the conductivity falls below the set value again, the timing restarts. Repeat these two processes until the conductivity falls below the set value for the end point of the left corner wash and the duration exceeds the set time. Then, the program proceeds to the next step, opening the left outlet valve and the right inlet valve, while simultaneously closing the left inlet valve and the right outlet valve, to begin the demineralized water right corner wash. Step 14: When the conductivity meter detects a conductivity value lower than the set value at the end of the right corner wash, start timing. During the timing process, if the conductivity rises above the set conductivity, the accumulated time is reset to zero. If the conductivity falls below the set value again, the timing restarts. Repeat these two processes until the conductivity falls below the set value at the end of the right corner wash and the duration exceeds the set time. The program then proceeds to the next step, stops the demineralized water pump, and closes the right inlet valve and sampling valve 5 seconds after the demineralized water pump stops. Open the right outlet valve to end the water washing process. Step 15: After the demineralized water pump stops for 10 seconds, open the press water inlet valve; confirm that the press water inlet valve is open, and after the press water inlet valve has been open for 5 seconds, close the exhaust valve, start the press water pump at the initial frequency, activate the interlock between the press water pump and the pressure transmitter, and switch to automatic control after the press water pump reaches the switching pressure. If the pressure is lower than the maintenance pressure, the frequency will be increased automatically, and if the pressure is higher than the maintenance pressure, the frequency will be decreased. Step 16: After the set time is reached, turn off the pressing water pump; 5 seconds after the pressing water pump stops, close the pressing water inlet valve to end the pressing process; Step 17: Purging the central tube of the filter press. Open the compressed air valve and introduce compressed air at 0.45MPa to purge the filter cake for 5 minutes. After the purging is completed, close the compressed air valve and open the press return water valve. Step 18: 20 seconds after the blower stops blowing, close the left water outlet valve, the right water outlet valve, and the water inlet valve of the recovery water tank to end the program; Step 19: Unlock the program start button to enter the manual board unloading procedure; Step 20: After manually unloading the board, repeat steps 2-19.

[0013] Compared with the prior art, the present invention has the following advantages: 1) This invention is simple and highly automated, can accurately control the time of each process, has a high safety factor and good stability, realizes the automated control of the entire three-wash process, realizes one-click start of the three-wash process, realizes automatic control and cyclic process of three washes, reduces labor intensity, reduces production costs and improves production efficiency.

[0014] 2) This invention designs an automatic control system, which improves control accuracy and efficiency.

[0015] 3) This invention adds automated equipment, which reduces the intensity of manual labor, reduces errors during manual operation, and improves the accuracy of execution.

[0016] 4) The control method of the present invention can detect electrical conductivity through an online conductivity meter and automatically control the washing time of each process to avoid production instability caused by parameter mismatch. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] Among them, 100-filter press, 110-left inlet, 111-left inlet valve, 120-right inlet, 121-right inlet valve, 130-center inlet, 140-left outlet, 141-left outlet valve, 150-right outlet, 151-right outlet valve, 160-inlet pipe, 170-outlet pipe, 171-vent valve, 180-press inlet, 190-press return outlet, 200-coated storage tank, 210-filter press feed valve, 220-feed pump, 300-deionized water tank, 31 0-Center hole inlet valve, 320-Demineralized water pump, 400-Recovery water tank, 410-Recovery water inlet valve, 420-Recovery water tank inlet valve, 430-Recovery water pump, 500-Wastewater tank, 510-Wastewater tank inlet valve, 520-Sampling valve, 530-Conductivity meter, 600-Compressed air tank, 610-Compressed air valve, 700-Pressed water tank, 710-Pressed water pump, 720-Pressed water inlet valve, 730-Pressed water return valve, 810-Level gauge, 820-Flow meter, 830-Pressure transmitter. Detailed Implementation

[0019] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but these descriptions are not intended to limit the invention and are merely illustrative. The advantages of the present invention will become clearer and easier to understand through this description.

[0020] Referring to the attached drawings, the automatic control system for the three washing processes in the sulfuric acid process for titanium dioxide production is characterized by including a filter press 100, a post-coating storage tank 200, a demineralized water tank 300, a recycled water tank 400, and a wastewater tank 500. The filter press 100 has a left inlet 110 at the upper left corner, a right inlet 120 at the upper right corner, a center inlet 130 in the middle, a left outlet 140 at the lower left corner, and a right outlet 150 at the lower right corner. The left inlet 110 is connected to the left inlet valve 111, the right inlet 120 is connected to the right inlet valve 121, the left outlet 140 is connected to the left outlet valve 141, the right outlet 150 is connected to the right outlet valve 151, and the center inlet 130 is connected to the inlet pipe 160. Both the left outlet 140 and the right outlet 150 are connected to the outlet pipe 170. The coated storage tank 200 is connected to the inlet pipe 160 via the filter press feed valve 210; the left inlet valve 111 and the right inlet valve 121 are connected to the demineralized water tank 300, and the inlet pipe 160 is connected to the demineralized water tank 300 via the center hole inlet valve 310; the recovery water tank 400 is connected to the inlet pipe 160 via the recovery water inlet valve 410, and to the outlet pipe 170 via the recovery water tank inlet valve 420; the wastewater tank 500 is connected to the outlet pipe 170 via the wastewater tank inlet valve 510, and to the outlet pipe 170 via the sampling valve 520.

[0021] It also includes a compressed air tank 600; the compressed air tank 600 is connected to the water inlet pipe 160 via a compressed air valve 610.

[0022] It also includes a pressing water tank 700; the pressing water tank 700 is connected to the pressing water inlet valve 720 via a pressing water pump 710, and the pressing water tank 700 is connected to the pressing water return valve 730; the pressing water inlet valve 720 is connected to the pressing water inlet 180 of the filter press 100; the pressing water return valve 730 is connected to the pressing water return outlet 190 of the filter press 100.

[0023] The coated storage tank 200 is connected to the filter press feed valve 210 via the feed pump 220; the demineralized water tank 300 is connected to the left inlet valve 111, the right inlet valve 121 and the center hole inlet valve 310 via the demineralized water pump 320; and the recovery water tank 400 is connected to the recovery water inlet valve 410 via the recovery water pump 430.

[0024] The wastewater tank 500 is connected to the sampling valve 520 via a conductivity meter 530; the outlet pipe 170 is connected to the exhaust valve 171.

[0025] The coated storage tank 200, the demineralized water tank 300, and the recovery water tank 400 are all equipped with level gauges 810; the feed pump 220 is connected to the filter press feed valve 210 through a flow meter 820; and the press water pump 710 is connected to the press water inlet valve 720 through a pressure transmitter 830.

[0026] An automatic control method for the automatic control system of the three washing processes in the sulfuric acid process for titanium dioxide production, characterized by comprising the following steps: Step 1: The filter press 100 is in the pressure holding state, the pressure holding signal is closed, and the liquid level in the storage tank 200 after coating is greater than 1.2m; Step 2: Click "Start Program" to initialize the equipment. At the same time, the filter press 100 loose plate signal is interlocked with the program end signal, and the program start button is locked. Step 3: Open the filter press feed valve 210, left outlet valve 141, right outlet valve 151 and wastewater tank inlet valve 510; Step 4: Start the feed pump 220; Step 5: When the flow meter 820 detects that the feed volume has reached the set value or the feed time has reached the set time, stop the feed pump 220; Step 6: After the feed pump 220 stops, close the filter press feed valve 210; Step 7: After the filter press feed valve 210 is closed, open the recovery water inlet valve 410 and the sampling valve 520; Step 8: After the recovery water inlet valve 410 is opened for 5 seconds, turn on the recovery water pump 430 and the air vent valve 171 to start the recovery water washing. Step 9: When the liquid level in the recovery water tank 400 is lower than the set value, stop the recovery water pump 430. After the recovery water pump 430 stops for 5 seconds, close the recovery water inlet valve 410 to end the recovery water washing. Step 10: After the recovery water inlet valve 410 stops for 5 seconds, open the center hole inlet valve 310. After the center hole inlet valve 310 is opened, start the demineralized water pump 320 to perform demineralized water center washing. Step 11: If the conductivity detected by the conductivity meter 530 is lower than the set value of the inlet water tank 400, open the inlet valve 420 of the inlet water tank and close the inlet valve 510 of the wastewater tank to recycle wastewater. Step 12: When the conductivity meter 530 detects that the conductivity is lower than the set value of the center wash conductivity endpoint, open the left inlet valve 111 and close the center hole inlet valve 310 and the left outlet valve 141. Step 13: When the conductivity meter 530 detects a conductivity value lower than the set value for the end point of the left corner wash, start timing. During the timing process, if the conductivity rises above the set conductivity, the accumulated time is reset to zero. If the conductivity falls below the set value again, the timing restarts. Repeat these two processes until the conductivity falls below the set value for the end point of the left corner wash and the duration exceeds the set time. Then, the program proceeds to the next step, opening the left outlet valve 141 and the right inlet valve 121, while simultaneously closing the left inlet valve 111 and the right outlet valve 151, and starting the demineralized water right corner wash. Step 14: When the conductivity meter 530 detects a conductivity value lower than the set value at the end of the right corner wash, start timing. During the timing process, if the conductivity rises above the set conductivity, the accumulated time is reset to zero. If the conductivity falls below the set value again, the timing restarts. Repeat these two processes until the conductivity falls below the set value at the end of the right corner wash and the duration exceeds the set time. The program then proceeds to the next step, stops the demineralized water pump 320, and closes the right inlet valve 121 and sampling valve 520 5 seconds after the demineralized water pump 320 stops. Open the right outlet valve 151 to end the water washing process. Step 15: After the demineralized water pump 320 stops for 10 seconds, open the pressing water inlet valve 720; confirm that the pressing water inlet valve 720 is open, and after the pressing water inlet valve 720 has been open for 5 seconds, close the exhaust valve 171, start the pressing water pump 710 at the initial frequency, and activate the interlock between the pressing water pump 710 and the pressure transmitter 830. After the pressing water pump 710 reaches the switching pressure, it switches to automatic control. If the pressure is lower than the maintenance pressure, the frequency will be increased automatically; if the pressure is higher than the maintenance pressure, the frequency will be decreased. Step 16: After the set time is reached, turn off the pressing water pump 710; after the pressing water pump 710 stops for 5 seconds, close the pressing water inlet valve 720 to end the pressing process; Step 17: Purging the central tube of the filter press. Open the compressed air valve 610 and introduce compressed air at 0.45MPa to purge the filter cake for 5 minutes. After the purge is completed, close the compressed air valve 610 and open the press return water valve 730. Step 18: 20 seconds after the blowing ends, close the left water outlet valve 141, the right water outlet valve 151 and the water inlet valve 420 of the recovery water tank to end the program; Step 19: Unlock the program start button to enter the manual board unloading procedure; Step 20: After manually unloading the board, repeat steps 2-19.

[0027] All other unspecified parts belong to the prior art.

Claims

1. An automatic control system for the third washing process in the production of titanium dioxide by the sulfuric acid method, characterized in that: It includes a filter press (100), a post-coating storage tank (200), a demineralized water tank (300), a recovery water tank (400), and a wastewater tank (500); The filter press (100) has a left inlet (110) at the upper left corner, a right inlet (120) at the upper right corner, a center inlet (130) in the middle, a left outlet (140) at the lower left corner, and a right outlet (150) at the lower right corner. The left inlet (110) is connected to the left inlet valve (111), the right inlet (120) is connected to the right inlet valve (121), the left outlet (140) is connected to the left outlet valve (141), the right outlet (150) is connected to the right outlet valve (151), and the center inlet (130) is connected to the inlet pipe (160). Both the left outlet (140) and the right outlet (150) are connected to the outlet pipe (170). The coated storage tank (200) is connected to the inlet pipe (160) via the filter press feed valve (210); the left inlet valve (111) and the right inlet valve (121) are connected to the demineralized water tank (300), and the inlet pipe (160) is connected to the demineralized water tank (300) via the center hole inlet valve (310); the recovery water tank (400) is connected to the inlet pipe (160) via the recovery water inlet valve (410), and to the outlet pipe (170) via the recovery water tank inlet valve (420); the wastewater tank (500) is connected to the outlet pipe (170) via the wastewater tank inlet valve (510), and to the outlet pipe (170) via the sampling valve (520).

2. The automatic control system for the third washing process in the production of titanium dioxide by the sulfuric acid method according to claim 1, characterized in that: It also includes a compressed air tank (600); the compressed air tank (600) is connected to the water inlet pipe (160) via a compressed air valve (610).

3. The automatic control system for the three washing processes in the sulfuric acid process for titanium dioxide production according to claim 2, characterized in that: It also includes a pressing water tank (700); the pressing water tank (700) is connected to the pressing water inlet valve (720) via a pressing water pump (710), and the pressing water tank (700) is connected to the pressing water return valve (730); the pressing water inlet valve (720) is connected to the pressing water inlet (180) of the filter press (100); the pressing water return valve (730) is connected to the pressing water return outlet (190) of the filter press (100).

4. The automatic control system for the three washing processes in the sulfuric acid process for titanium dioxide production according to claim 3, characterized in that: The coated storage tank (200) is connected to the filter press feed valve (210) via a feed pump (220); the demineralized water tank (300) is connected to the left inlet valve (111), the right inlet valve (121), and the center hole inlet valve (310) via a demineralized water pump (320); and the recovery water tank (400) is connected to the recovery water inlet valve (410) via a recovery water pump (430).

5. The automatic control system for the three washing processes in the sulfuric acid process for titanium dioxide production according to claim 4, characterized in that: The wastewater tank (500) is connected to the sampling valve (520) via a conductivity meter (530); the outlet pipe (170) is connected to the exhaust valve (171).

6. The automatic control system for the three washing processes in the sulfuric acid process for titanium dioxide production according to claim 5, characterized in that: The coated storage tank (200), demineralized water tank (300) and recovery water tank (400) are all equipped with level gauges (810); the feed pump (220) is connected to the filter press feed valve (210) through a flow meter (820); the press water pump (710) is connected to the press water inlet valve (720) through a pressure transmitter (830).

7. An automatic control method for the automatic control system of the three washing processes in the sulfuric acid process for titanium dioxide production, characterized in that, Includes the following steps: Step 1: The filter press (100) is in the pressure holding state, the pressure holding signal is closed, and the liquid level in the membrane storage tank (200) is greater than 1.2m; Step 2: Click to start the program, initialize the equipment, and at the same time, the filter press (100) plate loosening signal is interlocked with the program end, and the program start button is locked. Step 3: Open the filter press feed valve (210), left outlet valve (141), right outlet valve (151) and wastewater tank inlet valve (510); Step 4: Start the feed pump (220); Step 5: When the flow meter (820) detects that the feed volume has reached the set value or the feed time has reached the set time, stop the feed pump (220); Step 6: After the feed pump (220) stops, close the filter press feed valve (210); Step 7: After the filter press feed valve (210) is closed, open the recovery water inlet valve (410) and the sampling valve (520); Step 8: After the recovery water inlet valve (410) is opened for 5 seconds, turn on the recovery water pump (430) and the air vent valve (171) to start the recovery water washing. Step 9: When the liquid level in the recovery water tank (400) is lower than the set value, stop the recovery water pump (430). After the recovery water pump (430) stops for 5 seconds, close the recovery water inlet valve (410) to end the recovery water washing. Step 10: After the recovery water inlet valve (410) stops for 5 seconds, open the center hole inlet valve (310). After the center hole inlet valve (310) is opened, start the demineralized water pump (320) to perform demineralized water center washing. Step 11: If the conductivity meter (530) detects that the conductivity is lower than the set value of the inlet water tank (400), open the inlet valve (420) of the inlet water tank and close the inlet valve (510) of the wastewater tank to recycle wastewater; Step 12: When the conductivity meter (530) detects that the conductivity is lower than the set value of the center wash conductivity endpoint, open the left inlet valve (111) and close the center hole inlet valve (310) and the left outlet valve (141); Step 13: When the conductivity meter (530) detects a conductivity value lower than the set value of the left corner wash endpoint, start timing. During the timing process, if the conductivity rises above the set conductivity, the accumulated time is reset to zero. If the conductivity falls below the set value again, the timing is restarted. Repeat these two processes until the conductivity falls below the set value of the left corner wash endpoint and the holding time exceeds the set time. Then the program proceeds to the next step, opens the left outlet valve (141) and the right inlet valve (121), and closes the left inlet valve (111) and the right outlet valve (151) at the same time to start the demineralized water right corner wash. Step 14: When the conductivity meter (530) detects a conductivity value lower than the set value of the right corner wash endpoint, start timing. During the timing process, if the conductivity rises above the set conductivity, the accumulated time is reset to zero. If the conductivity falls below the set value again, the timing is restarted. Repeat these two processes until the conductivity falls below the set value of the right corner wash endpoint and the holding time exceeds the set time. The program then proceeds to the next step, stops the demineralized water pump (320), and closes the right inlet valve (121) and sampling valve (520) 5 seconds after the demineralized water pump (320) stops. Open the right outlet valve (151) to end the water washing. Step 15: After the demineralized water pump (320) stops for 10 seconds, open the press water inlet valve (720); confirm that the press water inlet valve (720) is open, and after the press water inlet valve (720) has been open for 5 seconds, close the exhaust valve (171), start the press water pump (710) at the initial frequency, and activate the interlock between the press water pump (710) and the pressure transmitter (830). After the press water pump (710) reaches the switching pressure, it switches to automatic control. If the pressure is lower than the maintenance pressure, the frequency will be increased automatically; if the pressure is higher than the maintenance pressure, the frequency will be decreased. Step 16: After the set time is reached, turn off the pressing water pump (710); after the pressing water pump (710) stops for 5 seconds, close the pressing water inlet valve (720) to end the pressing process; Step 17: Purge the central tube of the filter press. Open the compressed air valve (610) and purge the filter cake with compressed air at 0.45MPa for 5 minutes. After the purging is completed, close the compressed air valve (610) and open the press return water valve (730). Step 18: 20 seconds after the blower stops blowing, close the left water outlet valve (141), the right water outlet valve (151), and the water inlet valve (420) of the recovery water tank to end the program; Step 19: Unlock the program start button to enter the manual board unloading procedure; Step 20: After manually unloading the board, repeat steps 2-19.

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