A method for cleaning the scabbing of a desorption device for aluminum-based lithium-containing material

Abstract

This invention discloses a method for cleaning scale in an aluminum-based lithium-containing material desorption device, which has the following advantages compared with the prior art: it can achieve efficient removal of scale without disassembling the bends of each layer of pipes, saving a lot of manpower and financial resources; it can recover alumina during the alkaline washing process; and the liquid alkali can be directly returned to the alumina production system for system replenishment. The method includes: Step 1: Pumping the liquid alkali in the liquid alkali tank, so that the alkali solution passes sequentially through the inner tube of the tubular heat exchanger and the reactor, while simultaneously heating the reactor to raise the temperature of the alkali solution; Step 2: Circulating the heated liquid alkali back to the outer tube of the tubular heat exchanger, and then back to the liquid alkali tank through the outer tube; Step 3: Maintaining the circulation of the alkali solution in the inner tube, reactor, and outer tube to gradually raise the temperature of the alkali solution until the temperature of the liquid alkali solution in the reactor reaches a predetermined temperature T, maintaining the predetermined temperature T, and continuously maintaining the circulation of the alkali solution in the inner tube, reactor, and outer tube for a predetermined time t to complete the alkaline washing process.

Description

Technical Field

[0001] This invention relates to the field of lithium salt preparation technology, and in particular to a method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device. Background Technology

[0002] In the continuous lithium carbonate removal device using lithium-containing aluminum hydroxide, the desorption unit uses cold material entering from the inner tube of the shell-and-tube preheater, then entering the reactor for steam heating. After heating, the material is circulated back to the outer tube of the shell-and-tube preheater. The material in the inner tube and the outer tube exchange heat directly. During this process, scaling will occur on the walls of both the inner and outer tubes. Some of the scaling on the inner tube contains a variety of complex components such as lithium carbonate, aluminum-based materials, and boehmite, making the scale very hard. Hydraulic cleaning cannot effectively remove it. At the same time, because the outer tube is inside the inner tube, the cleaning nozzle cannot enter the interior of the outer tube. Due to the characteristics of the scaling and the structure of the device, it is impossible to remove the scale by hydraulic cleaning. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems and provide a method for cleaning scale in aluminum-based lithium-containing material desorption devices, which can effectively clean scale.

[0004] To achieve the above objectives, the technical solution of the present invention is: a method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device, comprising the following steps:

[0005] Step 1: Pump the liquid alkali in the liquid alkali tank to apply pressure, so that the alkali solution passes through the inner tube of the tubular heat exchanger and the reaction vessel in sequence, while heating the reaction vessel and raising the temperature of the alkali solution.

[0006] Step 2: The heated liquid alkali is circulated back to the outer tube of the tubular heat exchanger and then flows back to the liquid alkali tank through the outer tube.

[0007] Step 3: Maintain the alkali solution in the inner tube, reactor and outer tube to gradually increase the temperature of the alkali solution until the temperature of the liquid alkali in the reactor reaches the predetermined temperature T. Maintain the predetermined temperature T and continue to circulate the alkali solution in the inner tube, reactor and outer tube for a predetermined time t to complete the alkali washing.

[0008] Furthermore, in step three, during the gradual heating of the alkali solution, the pressure range for delivering the liquid alkali is 5 MPa to 7.5 MPa.

[0009] Furthermore, the predetermined temperature T ranges from 140℃ to 150℃.

[0010] Furthermore, in step three, the temperature of the alkali solution is increased at a rate of 6°C-7°C per hour.

[0011] Furthermore, the range of the predetermined duration t is 4 hours to 6 hours.

[0012] Furthermore, the concentration of liquid alkali in the liquid alkali tank is 230 g / L - 250 g / L.

[0013] Furthermore, it also includes:

[0014] Step 4: After completing the alkaline washing of the device, stop pumping the alkaline solution and depressurize the inner tube, outer tube and the reactor.

[0015] Step 5: After depressurization, pump clean water into the inner and outer tubes of the tubular heat exchanger and the reactor to wash the inside of the pipeline.

[0016] Furthermore, in step four, depressurizing the inner tube, outer tube, and reactor includes:

[0017] The pumping device for pumping alkaline solution stops working. When the pressure inside the reactor drops to a second predetermined value, the vent valve of the reactor is opened to release the pressure. The range of the second predetermined value is 0.08 MPa to 0.12 MPa.

[0018] Furthermore, step five, which involves washing the inside of the pipeline with water, includes:

[0019] Open the short-circuit pipe to short-circuit the reactor, isolate the reactor, and connect the inner and outer pipes;

[0020] Pump clean water into the inner pipe, so that the clean water flows through the inner pipe and the outer pipe in sequence, pushing the alkaline solution in the inner pipe and the outer pipe back to the liquid alkali tank;

[0021] Open the discharge valve of the reactor to release the liquid alkali inside the reactor;

[0022] After the reactor is vented, the short-circuit pipe is closed, allowing clean water to flow sequentially through the inner pipe, the reactor, and the outer pipe for a third predetermined time to complete the water washing.

[0023] Furthermore, the third predetermined duration ranges from 50 minutes to 70 minutes.

[0024] This invention discloses a method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device, comprising the following steps: Step 1: Pumping liquid alkali in a liquid alkali tank under pressure, causing the alkali solution to pass sequentially through the inner tube of a tubular heat exchanger and a reaction vessel, while simultaneously heating the reaction vessel to raise the temperature of the alkali solution; Step 2: Circulating the heated liquid alkali back to the outer tube of the tubular heat exchanger, and then returning to the liquid alkali tank through the outer tube; Step 3: Maintaining the circulation of the alkali solution within the inner tube, reaction vessel, and outer tube to gradually raise the temperature of the alkali solution until the temperature of the liquid alkali solution in the reaction vessel reaches a predetermined temperature T, maintaining the predetermined temperature T, and continuously maintaining the circulation of the alkali solution within the inner tube, reaction vessel, and outer tube for a predetermined time t to complete the alkali washing. Compared with the prior art, this method has the following beneficial effects:

[0025] 1. Compared to problems that water-based cleaning cannot solve, this method achieves efficient removal of scabs.

[0026] 2. Material recovery: During the alkaline washing process, alumina in the scale is recovered on the one hand; on the other hand, liquid alkali can also be directly returned to the alumina production system for system replenishment, without causing any waste.

[0027] 3. Compared with water-based cleaning, it eliminates the need to disassemble the bends in the pipes on each floor, saving a significant amount of manpower and financial resources; it also reduces pollution to the site environment and protects the site environment. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of one embodiment of a method for cleaning scale in an aluminum-based lithium-containing material desorption device according to the present invention.

[0029] Figure 2 This is a schematic flowchart of the second embodiment of a method for cleaning scale in an aluminum-based lithium-containing material desorption device according to the present invention.

[0030] Figure 3 This is a schematic diagram of the process of washing the inside of the pipeline with water in a method for cleaning scale in an aluminum-based lithium-containing material desorption device according to the present invention.

[0031] Figure 4 This is a schematic diagram of the first embodiment of the cleaning system in the descaling method for aluminum-based lithium-containing materials desorption device of the present invention.

[0032] Figure 5 This is a schematic diagram of the second embodiment of the cleaning system in the descaling method for aluminum-based lithium-containing materials desorption device of the present invention.

[0033] In the diagram: 1. Alkali tank; 11. First control valve; 2. Booster pump; 3. Diaphragm pump; 4. Tubular heat exchanger; 41. Inner tube; 42. Outer tube; 5. Reactor; 50. Discharge valve; 51. Circulation pipeline; 52. Second control valve; 53. Third control valve; 54. Short-circuit pipeline; 55. Fourth control valve; 6. Steam transmission pipeline; 61. Fifth control valve; 7. Water tank; 71. Sixth control valve. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic diagrams, illustrating only the basic structure of the invention in a schematic manner, and therefore only show the components relevant to the invention. Example

[0035] Please refer to Figure 1 A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device includes the following steps:

[0036] Step 1: Pump the liquid alkali in the liquid alkali tank to apply pressure, so that the alkali solution passes through the inner tube of the tubular heat exchanger and the reaction vessel in sequence, while heating the reaction vessel and raising the temperature of the alkali solution.

[0037] Step 2: The heated liquid alkali is circulated back to the outer tube of the tubular heat exchanger and then flows back to the liquid alkali tank through the outer tube.

[0038] Step 3: Maintain the alkali solution in the inner tube, reactor and outer tube to gradually increase the temperature of the alkali solution until the temperature of the liquid alkali in the reactor reaches the predetermined temperature T. Maintain the predetermined temperature T and continue to circulate the alkali solution in the inner tube, reactor and outer tube for a predetermined time t to complete the alkali washing.

[0039] For details, please refer to Figure 4As one implementation method, the working process of the aluminum-based lithium-containing material desorption device is as follows: The device includes a slurry tank (not shown in the figure) connected to the feed end of the booster pump 2. During operation, the booster pump 2 and the diaphragm pump 3 pump the slurry to the inner tube 41 of the tubular heat exchanger 4. After passing through the inner tube 41, the slurry enters the reactor 5. The slurry is heated in the reactor. After flowing out of the reactor, the slurry enters the outer tube of the tubular heat exchanger 4. The high-temperature slurry exchanges heat with the low-temperature slurry in the inner tube. During this process, heat is generated on the side wall of the inner tube, inside the reactor, in the reactor inlet and outlet pipes, and on the inner wall of the outer tube. The technical solution of this application is as follows: It includes a liquid alkali tank 1 and a water tank 7 connected to a booster pump 2. The initial temperature of the liquid alkali in the liquid alkali tank is 35℃-40℃. A first control valve 11 is installed between the booster pump 2 and the liquid alkali tank 1. A sixth control valve 71 is installed between the water tank 7 and the booster pump 2. A diaphragm pump 3 is connected to the output end of the booster pump 2. The output end of the diaphragm pump 3 is connected to the inner tube of a tubular heat exchanger 4. The other end of the inner tube is connected to a reaction vessel 5. The reaction vessel 5 includes a circulation pipeline 51 connected to an outer tube 42. A fourth control valve 55 is installed on the circulation pipeline 51. A second control valve 52 is installed between the output end and the reactor. A short-circuit pipe 54 is also included. One end of the short-circuit pipe 54 is connected to the end of the second control valve 52 near the inner tube 41, and the other end of the short-circuit pipe 54 is connected to the end of the fourth control valve 55 near the outer tube. A third control valve 53 is installed on the short-circuit pipe 54. During initial operation, the second control valve 52 is open, the sixth control valve 71 is closed, the first control valve 11 and the fourth control valve 55 are open, and the third control valve 53 is closed. The booster pump and diaphragm pump operate to pump the alkali solution in the alkali tank 1 through the inner tube and into the reactor. The alkaline solution in the reactor 5 is heated and then flows into the outer pipe 42 through the circulation pipe 51. The alkaline solution in the outer pipe exchanges heat with the alkaline solution in the inner pipe, gradually raising the temperature of the alkaline solution. When the temperature of the alkaline solution reaches the predetermined temperature T, the temperature is maintained so that the alkaline solution circulates in the system for a predetermined time t. Since the main components of the crust in the system pipeline are lithium carbonate, aluminum-based materials and boehmite monohydrate, they can react with the alkaline solution, thereby achieving the purpose of removing the crust. This method uses the equipment included in the aluminum-based material desorption device to clean the crust, and the crust can be recycled after treatment.

[0040] Further, refer to Figure 4 The reactor is connected to a steam delivery pipeline 6, and a fifth control valve 61 is installed between the steam delivery pipeline and the reactor 5. The steam delivery pipeline is connected to the bottom of the reactor, and the internal materials are directly heated by high-temperature and high-pressure steam.

[0041] Further, refer to Figure 5In another implementation, the aluminum-based lithium-containing material desorption device includes multiple tubular heat exchangers 4 connected in series and five reactors 5 connected in series. Each reactor is connected to a steam delivery pipeline with a fifth control valve 61. In this implementation, the alkali solution is delivered to the inner tube 41 by a booster pump 2 and a diaphragm pump 3. The alkali solution flows through the inner tube of the tubular heat exchangers 4 in series and then through the five reactors in series. After exiting the reactors, it flows through the outer tube of the multiple tubular heat exchangers 4 in series and then flows back to the alkali solution tank 1. During this process, the initial temperature of the liquid alkali is 35℃-40℃, and the NK concentration of the liquid alkali is 230 g / L-250 g / L. Along the direction away from the tubular heat exchangers 4, the steam flow rate in the five reactors 5 decreases in sequence, and the specific flow rate ratio is 17:15:12:8:5, which gradually heats the alkali solution.

[0042] Specifically, the steam flow rate into each reactor can be controlled by the fifth control valve 61 on each reactor 5. The opening degree is directly proportional to the steam flow rate. The larger the opening degree of the fifth control valve 61, the larger the steam flow rate. Specifically, the opening degrees of the five fifth control valves are 17%, 15%, 12%, 8%, and 5% respectively. At the same time, the pressure of the steam buffer tank should be controlled to be 0.5-1.0 MPa higher than the pressure inside the reactor. Only when the steam pressure is higher than the pressure inside the reactor can the steam be guaranteed to enter the bottom of the reactor normally for continuous heating and temperature increase, and the back pressure of the material should not occur.

[0043] Furthermore, in the initial stage of alkali washing, the diaphragm pump is pre-pressurized to 0.25-0.3 MPa, and its operating frequency is 30 Hz, ensuring that the pressure of the pumped alkali solution is around 6.5 MPa. During the circulation of the alkali solution, for every 0.5 MPa decrease in the diaphragm pump pressure, the pump frequency is increased by 0.5 Hz to increase the alkali feed rate. Simultaneously, the steam valve opening is adjusted in a timely manner, controlling the temperature rise rate of the liquid alkali in the reactor at 6-7°C per hour. After 14 hours of circulation and temperature increase, when the temperature of the liquid alkali in the reactor reaches 140°C, the steam valves are gradually closed. After half an hour of adjustment, only the fifth control valve 61 of reactor #1, which is close to the tubular heat exchanger, remains open at 3%-5%, while the fifth control valve 61 of all other reactors is closed, maintaining the reactor temperature at 140°C-150°C. After stabilizing this temperature for 4-6 hours, the diaphragm pump frequency stabilizes at 42.8 Hz, and the diaphragm pump feed flow rate is controlled at 55 m³ / h. 3 / h, the working pressure of the diaphragm pump drops from 7.5 MPa to 5.1 MPa, the fifth control valve 61 on reactor #1 is closed, the liquid alkali heating is stopped, and the heating and alkali washing of the unit is completed.

[0044] Furthermore, as a specific implementation method, in step three, during the gradual heating of the alkali solution, the delivery pressure range of the liquid alkali is 5 MPa to 7.5 MPa. Controlling the delivery pressure of the liquid alkali within 5 MPa to 7.5 MPa ensures the delivery flow rate of the liquid alkali while avoiding the risks caused by excessive pressure, thus improving the alkali washing efficiency under the premise of safe construction.

[0045] Furthermore, as a specific implementation method, the predetermined temperature T is set within the range of 140℃-150℃. Specifically, according to statistics, when the concentration of the alkali solution is in the range of 230 g / L-250 g / L, and the temperature is controlled at 140℃-150℃, the cleaning efficiency for scabs is optimal.

[0046] Specifically, the relationship between the scab removal speed and the concentration and temperature of the alkali solution is shown in the table below:

[0047]

[0048] Specifically, as shown in the table above, the best effect on scab treatment is achieved when the alkali concentration is 245 g / L and the temperature is 145℃. Therefore, the preferred alkali concentration is 245 g / L and the preferred reaction temperature is 145℃.

[0049] Furthermore, in step three, the temperature rise rate of the alkali solution is 6℃-7℃ per hour. Specifically, the temperature rise rate of the liquid alkali is controlled at 6℃-7℃ per hour to ensure the safe operation of the equipment.

[0050] Furthermore, the range of the predetermined duration t is 4 hours to 6 hours.

[0051] Furthermore, the concentration of liquid alkali in the liquid alkali tank is 230 g / L - 250 g / L. Example

[0052] This application discloses a method for cleaning scale buildup in a desorption device for aluminum-based lithium-containing materials, referencing... Figure 2 This includes the following steps:

[0053] Step 1: Pump the liquid alkali in the liquid alkali tank to apply pressure, so that the alkali solution passes through the inner tube of the tubular heat exchanger and the reaction vessel in sequence, while heating the reaction vessel and raising the temperature of the alkali solution.

[0054] Step 2: The heated liquid alkali is circulated back to the outer tube of the tubular heat exchanger and then flows back to the liquid alkali tank through the outer tube.

[0055] Step 3: Maintain the alkali solution in the inner tube, reactor, and outer tube to gradually increase its temperature until the liquid alkali in the reactor reaches the predetermined temperature T. Maintain the predetermined temperature T and continue circulating the alkali solution in the inner tube, reactor, and outer tube for a predetermined time t to complete the alkali washing process. This also includes:

[0056] Step 4: After completing the alkaline washing of the device, stop pumping the alkaline solution and depressurize the inner tube, outer tube and the reactor.

[0057] Furthermore, in step four, depressurizing the inner tube, outer tube, and reactor includes:

[0058] The pumping device for pumping alkaline solution stops working. When the pressure inside the reactor drops to a second predetermined value, the vent valve of the reactor is opened to release the pressure. The second predetermined value is less than 0.05 MPa.

[0059] Specifically, in this embodiment, the alkaline washing process in steps one to three is the same as in embodiment one. After the alkaline washing process is completed, the booster pump 2 and diaphragm pump 3 are stopped from working, and the supply of liquid alkali to the entire device is stopped. Some of the liquid alkali continues to flow back to the liquid alkali tank, and the pressure of liquid alkali in the inner pipe 41, outer pipe 42 and reactor decreases. After the diaphragm pump and booster pump stop working for 55-65 minutes, when the pressure in the reactor decreases to the second predetermined value, the five vent valves (not shown in the figure) of the five reactors are opened to cool and depressurize the reactors. The opening degree of the vent valves is gradually increased according to the rate of pressure decrease, from 10% to 50%, to ensure that the vented steam is slowly and stably vented.

[0060] Step 5: After depressurization, pump clean water into the inner and outer tubes of the tubular heat exchanger and the reactor to wash the inside of the pipeline.

[0061] Furthermore, step five, which involves washing the inside of the pipeline with water, includes:

[0062] Open the short-circuit pipe to short-circuit the reactor, isolate the reactor, and connect the inner and outer pipes;

[0063] Pump clean water into the inner pipe, so that the clean water flows through the inner pipe and the outer pipe in sequence, pushing the alkaline solution in the inner pipe and the outer pipe back to the liquid alkali tank;

[0064] Open the discharge valve of the reactor to release the liquid alkali inside the reactor;

[0065] After the reactor is vented, the short-circuit pipe is closed, allowing clean water to flow sequentially through the inner pipe, the reactor, and the outer pipe for a third predetermined time to complete the water washing.

[0066] For details, please refer to Figure 4 , Figure 5After purging the reactor 5, control valves 52 and 55 are closed, and control valve 53 is opened to connect the short-circuit pipe 54 to the inner pipe 41 and the outer pipe 42. Control valve 11 is closed, and control valve 71 is opened. Then, booster pump 2 and diaphragm pump 3 are operated to pump clean water into the inner pipe. The clean water pushes out the liquid alkali in the inner and outer pipes and returns it to the liquid alkali tank. During this process, diaphragm pump 3 operates at 40 Hz. This step is continued for 1 hour to push all the liquid alkali in the inner and outer pipes back to the liquid alkali tank. The cleaning water is stored in the inner and outer pipes instead of the liquid alkali.

[0067] Furthermore, when the pressure of the reactor 5 is reduced to normal atmospheric pressure, the discharge valve 50 at the bottom of the reactor 5 is opened to release the liquid alkali in the reactor. During the release process, the released liquid alkali can be pumped back into the liquid alkali tank 1 until the liquid alkali in the reactor is completely discharged.

[0068] Furthermore, after the alkaline solution in the reactor is completely drained, the discharge valve 50 and the third control valve 53 are closed, and the second control valve 52 and the fourth control valve 55 are opened. Then, the diaphragm pump and the booster pump are controlled to pump the cleaning solution. At this time, the cleaning solution enters the reactor 5 through the inner pipe 41, flows into the outer pipe 42 after passing through the reactor, and is then discharged from the outer pipe. This process continues for a third predetermined time. The water washing is completed after 1 hour.

[0069] Furthermore, the third predetermined duration ranges from 50 minutes to 70 minutes, with 60 minutes being preferred.

[0070] Furthermore, after the water washing is completed, steam is supplied to reactor 5 to circulate water and raise the temperature, in preparation for the cutting of materials by the device.

[0071] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device, characterized in that, Includes the following steps: Step 1: Pump the liquid alkali in the liquid alkali tank to apply pressure, so that the alkali solution passes through the inner tube of the tubular heat exchanger and the reaction vessel in sequence, while heating the reaction vessel and raising the temperature of the alkali solution. Step 2: The heated liquid alkali is circulated back to the outer tube of the tubular heat exchanger and then flows back to the liquid alkali tank through the outer tube. Step 3: Maintain the alkali solution in the inner tube, reactor and outer tube to gradually increase the temperature of the alkali solution until the temperature of the liquid alkali in the reactor reaches the predetermined temperature T. Maintain the predetermined temperature T and continue to circulate the alkali solution in the inner tube, reactor and outer tube for a predetermined time t to complete the alkali washing.

2. The method for cleaning scale in a desorption device for aluminum-based lithium-containing materials according to claim 1, characterized in that, In step three, during the gradual heating of the alkali solution, the delivery pressure range of the liquid alkali is 5 MPa to 7.5 MPa.

3. The method for cleaning scale in a desorption device for aluminum-based lithium-containing materials according to claim 1, characterized in that, The predetermined temperature T ranges from 140℃ to 150℃.

4. The method for cleaning scale in a desorption device for aluminum-based lithium-containing materials according to claim 1, characterized in that, In step three, the temperature of the alkali solution is increased at a rate of 6°C-7°C per hour.

5. A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device according to claim 1, characterized in that, The range of the predetermined duration t is 4 hours to 6 hours.

6. A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device according to claim 1, characterized in that, The concentration of liquid alkali in the liquid alkali tank is 230 g / L - 250 g / L.

7. A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device according to claim 1, characterized in that, Also includes: Step 4: After completing the alkaline washing of the device, stop pumping the alkaline solution and depressurize the inner tube, outer tube and the reactor. Step 5: After depressurization, pump clean water into the inner and outer tubes of the tubular heat exchanger and the reactor to wash the inside of the pipeline.

8. A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device according to claim 7, characterized in that, Step four involves depressurizing the inner and outer tubes and the reactor, including: Stop pumping the alkaline solution. When the pressure inside the reactor drops to the second predetermined value, open the vent valve of the reactor to release the pressure. The range of the second predetermined value is 0.08 MPa to 0.12 MPa.

9. A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device according to claim 7, characterized in that, Step five, which involves washing the inside of the pipeline with water, includes: Open the short-circuit pipe to short-circuit the reactor, isolate the reactor, and connect the inner and outer pipes; Pump clean water into the inner pipe, so that the clean water flows through the inner pipe and the outer pipe in sequence, pushing the alkaline solution in the inner pipe and the outer pipe back to the liquid alkali tank; Open the discharge valve of the reactor to release the liquid alkali inside the reactor; After the reactor is vented, the short-circuit pipe is closed, allowing clean water to flow sequentially through the inner pipe, the reactor, and the outer pipe for a third predetermined time to complete the water washing.

10. A method for cleaning scale buildup in an aluminum-based lithium-containing material desorption device according to claim 7, characterized in that, The third preset duration ranges from 50 minutes to 70 minutes.

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