A method for withdrawing a decomposition groove

Abstract

The present invention discloses a method for withdrawing a decomposition tank, comprising the following steps: A. observing the height and distribution of the soft material wall of the decomposition tank to be withdrawn using a thermal imager; B. cutting off the process of the decomposition tank to be withdrawn and isolating the decomposition tank; C. opening the air valve closest to the highest point of the soft material wall, injecting decomposition mother liquor, and waiting for the soft material wall at that location to collapse; opening the remaining two air valves respectively, injecting mother liquor, and waiting for the soft material wall at that location to collapse, and closing the three air valves; D. injecting decomposition mother liquor from the wall valve of the decomposition tank to dilute the slurry around the wall valve; switching the large circulation to the previous decomposition tank, and then withdrawing the slurry in the decomposition tank to be withdrawn; E. injecting decomposition mother liquor from the three air valves and the wall valve of the decomposition tank to be withdrawn simultaneously, and then opening the large circulation pump to empty the diluted slurry, and finally emptying the remaining diluted slurry through the wall valve to complete the withdrawal. The method of the present invention can significantly improve the withdrawal effect.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum oxide production and decomposition, and particularly relates to a decomposition tank withdrawal method. Background Art

[0002] In the decomposition process of alumina production, there are generally 15 decomposition tanks in a series, and the storage capacity of a single decomposition tank is about 4800m 3 Each decomposition tank is removed and cleaned of scabs approximately once every year. Currently, the method for removing the decomposition tank is as follows:

[0003] The first step is to determine the decomposition tank to be decomposed and isolate the process of the decomposition tank to be decomposed;

[0004] The second step is to flush the wall valve of the decomposition tank with the decomposition mother liquor after isolation and change the circulation process to the decomposition tank in front of the decomposition tank to be decomposition;

[0005] The third step is to open the tank wall valve, and then turn on the circulation pump to return the slurry in the decomposition tank to the previous decomposition tank;

[0006] The fourth step is that if the slurry in the decomposition tank cannot be withdrawn, the decomposition mother liquor needs to be input from the three annular air valves of the decomposition tank 6 to 8 times for dilution, depending on the situation. The process of injecting the decomposition mother liquor for dilution each time is: input about 600 cubic meters of decomposition mother liquor each time to dilute the concentrated slurry in the tank, and after ventilation and stirring, turn on the large circulation pump to withdraw the diluted slurry.

[0007] The decomposition tank is considered complete only after the completion of these four steps. The entire process is time-consuming, typically requiring three days to decomposition a single tank. This is because the high solids content of the decomposition slurry (over 900g / L) makes it difficult to remove the concentrated material from the tank. This requires dilution with a large amount of decomposition mother liquor and aeration and stirring, which results in a large amount of decomposition mother liquor returning to the production process. This also increases the amount of slurry foam, severely impacting production. Furthermore, the high solids content of the slurry and the long decomposition time reduce the efficiency of the large circulation pump, which can easily cause blockage or "water hammer" in the large circulation pipeline, leading to pump rupture. This poses a significant safety risk and places high labor intensity on employees. Furthermore, a high soft wall forms on the walls of the decomposition tank. During the decomposition process, as the slurry level in the decomposition tank continuously drops, the soft wall around the tank wall emerges from the liquid surface. Without the buoyancy of the slurry solution, the soft wall collapses, easily damaging the decomposition tank's agitator blades or bending the agitator shaft, blocking the decomposition tank, making decomposition difficult, and causing equipment damage. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for withdrawing a decomposition tank. The method of the present invention can protect the decomposition tank stirring equipment from damage, while reducing the solid content of the decomposition tank slurry, and the withdrawal effect is significantly improved. A single decomposition tank takes at least 2 days less than before, which greatly improves work efficiency, reduces the withdrawal cost, greatly reduces the labor intensity of employees, and reduces the risk of safe operation.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] The decomposition tank withdrawal method is based on three inlets evenly arranged along the circumferential direction at the bottom of the decomposition tank wall and air valves at the inlets, and includes the following steps:

[0011] A. Use a thermal imager to observe the height and distribution of the soft material wall of the decomposition tank to be retreated;

[0012] B. Cut off the process of the decomposition tank to be degraded and isolate the decomposition tank;

[0013] C. Keep observing with the thermal imager. Based on the measured height distribution of the soft material wall, open the air valve closest to the highest point of the soft material wall, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open any one of the remaining two air valves, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open the last air valve, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed, then close all three air valves;

[0014] D. Inject decomposition mother liquor from the wall valve of the decomposition tank to dilute the slurry around the wall valve; after the dilution is completed, switch the large circulation to the decomposition tank before the decomposition tank to be withdrawn, and then withdraw the slurry in the decomposition tank to be withdrawn to the decomposition tank before it;

[0015] E. After the slurry in the decomposition tank is emptied by the large circulation pump, the decomposition mother liquor is injected simultaneously from the three air valves and the tank wall valve of the decomposition tank. The total amount of injected decomposition mother liquor is 300-600 m 3 , dilute the residual slurry, then open the large circulation pump to empty the diluted slurry, and finally empty the residual diluted slurry through the tank wall valve to complete the tank withdrawal.

[0016] In step C, the flow rate of the decomposition mother liquid injected into each air valve is 150-200m 3 / h.

[0017] In the step D, the flow rate of the decomposition mother liquor injected into the decomposition tank wall valve is 150-200m 3 / h, injection time is 15 to 25 minutes.

[0018] In the step E, after the slurry in the decomposition tank is emptied, the decomposition mother liquor is injected simultaneously from the three air valves and the tank wall valve of the decomposition tank, with a total injection flow rate of 300 to 600 m 3 / h.

[0019] The present invention has the following advantages:

[0020] The method for withdrawing the decomposition tank of the present invention does not require any additional materials or equipment. Before withdrawing the tank, it is only necessary to use a thermal imager to observe the height and distribution of the soft material wall on the wall of the decomposition tank, and then inject decomposition mother liquor from the bottom air valve to destroy the soft material wall on the wall of the decomposition tank in advance, thereby protecting the stirring of the decomposition tank and reducing the solid content of the slurry in the decomposition tank. The withdrawal effect is significantly improved.

[0021] The method of the present invention performs the trough withdrawal operation, and the trough withdrawal time of a single decomposition trough is at least 2 days less than before, which greatly improves the work efficiency, reduces the trough withdrawal cost, greatly reduces the labor intensity of employees, reduces the safety operation risk, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of thermal imaging observation in Example 1;

[0023] Figure 2 This is a schematic diagram of the large circulation flow of the decomposition tank of the present invention. DETAILED DESCRIPTION

[0024] In order to facilitate a better understanding of the present invention, the following examples are provided for illustration. These examples belong to the protection scope of the present invention, but do not limit the protection scope of the present invention. Example 1

[0025] The decomposition groove withdrawal method comprises the following steps:

[0026] The decomposition tank withdrawal method is based on three inlets evenly arranged along the circumferential direction at the bottom of the decomposition tank wall and air valves at the inlets, and includes the following steps:

[0027] A. Figure 1 As shown in the figure, the height and distribution of the soft material wall of the decomposition groove to be retreated are observed using a thermal imager;

[0028] B. Cut off the process of the decomposition tank to be degraded and isolate the decomposition tank;

[0029] C. Keep observing with the thermal imager. Based on the measured height distribution of the soft material wall, open the air valve closest to the highest point of the soft material wall, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open any one of the remaining two air valves, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open the last air valve, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed, then close all three air valves;

[0030] The flow rate of the decomposition mother liquor injected into each air valve is 150m 3 / h;

[0031] D. Inject decomposition mother liquor from the wall valve of the decomposition tank to dilute the slurry around the wall valve; after the dilution is completed, switch the large circulation to the decomposition tank before the decomposition tank to be decomposed, and then return the slurry in the decomposition tank to be decomposed to the decomposition tank before it;

[0032] The flow rate of the decomposition mother liquor injected into the decomposition tank wall valve is 150m 3 / h, injection time is 15min;

[0033] E. When the slurry in the decomposition tank is emptied, the decomposition mother liquor is injected simultaneously from the three air valves and the tank wall valve of the decomposition tank. The total injection flow rate is 300 m 3 / h, the amount of injected decomposition mother liquor is 300m 3 , dilute the residual slurry, then open the large circulation pump to empty the diluted slurry, and finally empty the residual diluted slurry through the tank wall valve to complete the tank withdrawal. Example 2

[0034] The decomposition groove withdrawal method comprises the following steps:

[0035] The decomposition tank withdrawal method is based on three inlets evenly arranged along the circumferential direction at the bottom of the decomposition tank wall and air valves at the inlets, and includes the following steps:

[0036] A. Use a thermal imager to observe the height and distribution of the soft material wall in the decomposition tank;

[0037] B. Cut off the process of the decomposition tank to be degraded and isolate the decomposition tank;

[0038] C. Keep observing with the thermal imager. Based on the measured height distribution of the soft material wall, open the air valve closest to the highest point of the soft material wall, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open any one of the remaining two air valves, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open the last air valve, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed, then close all three air valves;

[0039] The flow rate of the decomposition mother liquor injected into each air valve is 200m 3 / h;

[0040] D. Inject decomposition mother liquor from the wall valve of the decomposition tank to dilute the slurry around the wall valve; after the dilution is completed, switch the large circulation to the decomposition tank before the decomposition tank to be decomposed, and then return the slurry in the decomposition tank to be decomposed to the decomposition tank before it;

[0041] The flow rate of the decomposition mother liquor injected from the wall valve of the decomposition tank is 200m 3 / h, injection time is 25min;

[0042] E. When the slurry in the decomposition tank is emptied, the decomposition mother liquor is injected simultaneously from the three air valves and the tank wall valve of the decomposition tank. The total injection flow rate is 600 m 3 / h, the amount of injected decomposition mother liquor is 600m 3 , dilute the residual slurry, then open the large circulation pump to empty the diluted slurry, and finally empty the residual diluted slurry through the tank wall valve to complete the tank withdrawal. Example 3

[0043] The decomposition groove withdrawal method comprises the following steps:

[0044] The decomposition tank withdrawal method is based on three inlets evenly arranged along the circumferential direction at the bottom of the decomposition tank wall and air valves at the inlets, and includes the following steps:

[0045] A. Use a thermal imager to observe the height and distribution of the soft material wall in the decomposition tank;

[0046] B. Cut off the process of the decomposition tank to be degraded and isolate the decomposition tank;

[0047] C. Keep observing with the thermal imager. Based on the measured height distribution of the soft material wall, open the air valve closest to the highest point of the soft material wall, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open any one of the remaining two air valves, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open the last air valve, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed, then close all three air valves;

[0048] The flow rate of the decomposition mother liquor injected into each air valve is 170m 3 / h;

[0049] D. Inject decomposition mother liquor from the wall valve of the decomposition tank to dilute the slurry around the wall valve; after the dilution is completed, switch the large circulation to the decomposition tank before the decomposition tank to be decomposed, and then return the slurry in the decomposition tank to be decomposed to the decomposition tank before it;

[0050] The flow rate of the mother liquor injected into the wall valve of the decomposition tank is 170m 3 / h, injection time is 20min;

[0051] E. When the slurry in the decomposition tank is emptied, the decomposition mother liquor is injected simultaneously from the three air valves and the tank wall valve of the decomposition tank. The total injection flow rate is 350 m 3 / h, the amount of injected decomposition mother liquor is 400m 3 , dilute the residual slurry, then open the large circulation pump to empty the diluted slurry, and finally empty the residual diluted slurry through the tank wall valve to complete the tank withdrawal. Example 4

[0052] After the trough withdrawal operation was performed using the method of Example 3, the stirring blades and stirring shaft of the decomposition tank were almost not damaged due to the collapse of the soft material wall. It used to take more than 3 days to withdraw a decomposition tank, but now it can be withdrawn in less than 1 day. The operating time of the large circulation pump has been reduced from 48 hours to only 7 hours, and the efficiency of the decomposition tank withdrawal has been greatly improved. The cleaning time of a single decomposition tank has been reduced from about 3 days to 1 day, and the cleaning progress has also been greatly improved. At the same time, the labor intensity of employees and the safety production risks are reduced. The benefit calculation is as follows:

[0053] (1) Direct economic benefits

[0054] 1. Reduce the power consumption of large circulation pumps

[0055] Based on the calculation that 65 decomposition tanks are retired each year, after adopting the method of Example 3, the current of the large circulation pump increases from the original 260A to 300A. The power consumption of the large circulation pump is compared as follows:

[0056] The power consumption of the large circulation pump in the original operation method is:

[0057] 1.732*380*260*0.85 / 1000*48*65= 453814.5 kw.h

[0058] After adopting the method of Example 3, the power consumption of the large circulation pump is:

[0059] 1.732*380*300*0.85 / 1000*7*65=76363.0kw.h

[0060] Therefore, the power consumption saved by the large circulation pump is:

[0061] 453814.5-76363.0=377451.5 kw.h

[0062] Calculated at 0.58 yuan per kilowatt-hour, the annual electricity savings are: 377451.5*0.58 / 10000=219,000 yuan.

[0063] 2. Reduce the air volume used in the decomposition tank

[0064] The air volume of each decomposition tank is about 1200m3 / h, and the price of each cubic meter of power wind is 0.008 yuan. The original operation method requires 2 days of air blowing for each decomposition tank, so the annual air volume required is: 65*1200*2*24=3744000m3

[0065] After adopting the method of Example 3, the decomposition tank of the single decomposition tank is blown for 12 hours, and the annual air volume is: 65*1200*12=936000m3

[0066] The annual air volume savings are:

[0067] (3744000-936000)*0.08 / 10000=225,000 yuan

[0068] 3. Reduce the repair cost of stirring blades and stirring shafts

[0069] When the decomposition tanks were decomposed according to the original operating method, the stirring blades and stirring shafts of the RP100 and RP211 decomposition tanks were seriously damaged, while the stirring shafts of RP206, RP409, and RP506 were seriously deformed. The stirring blades of the other decomposition tanks were also slightly deformed.

[0070] (1) The RP100 agitator shaft was severely deformed at the top, middle and bottom, and the final cost of the repair was approximately RMB 260,000.

[0071] (2) Five RP211 agitator blades were broken, and the agitator shaft was also deformed. The final cost of repairing the blades and agitator shaft was approximately RMB 304,000.

[0072] (3) The final settlement cost of the RP206 agitator shaft overhaul was approximately RMB 125,000.

[0073] (4) The final settlement cost of the RP409 agitator shaft overhaul was approximately RMB 169,000.

[0074] (5) The final settlement cost of the RP506 agitator shaft overhaul was approximately RMB 137,000.

[0075] (6) Costs of repairing minor deformation of propeller blades

[0076] According to statistics, the rate of slight deformation of agitator blades is about 2%, and the cost of repairing each one is about 8,000 yuan. The annual cost savings are: 8,000 * (65-5) * 0.2 / 10,000 = 96,000 yuan.

[0077] The total annual economic benefits are:

[0078] 21.9+22.5+26+30.4+12.5+16.9+13.7+9.6=1.535 million yuan.

[0079] (2) Other economic benefits

[0080] 1. Reduce employees' labor intensity.

[0081] After adopting the method of Example 3, it used to take more than 3 days to complete the decomposition tank, but now it can be completed in less than 1 day, which reduces a large number of operations and significantly reduces the labor intensity of employees.

[0082] 2. Reduce security risks

[0083] After adopting the method of Example 3, the material flow in the pipeline is smooth, and the phenomenon of pump casing bursting and pipeline flange hitting the gasket caused by the "water hammer effect" is eliminated, which significantly reduces the safety risk of operation.

[0084] 3. Improve the efficiency of decomposition tank withdrawal

[0085] After adopting the method of Example 3, it used to take more than 3 days to completely withdraw a decomposition tank, but now it can be completed in less than 1 day, which greatly improves the withdrawal efficiency, reduces the withdrawal time, and plays a key role in reducing the number of off-line decomposition tank rotations, which is conducive to the healthy operation of decomposition tank production and cleaning.

[0086] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for withdrawing a decomposition tank, characterized in that: The operation is based on three inlets evenly arranged along the circumferential direction at the bottom of the decomposition tank wall and the air valves at the inlets, including the following steps: A. Use a thermal imager to observe the height and distribution of the soft material wall in the decomposition tank; B. Cut off the process of the decomposition tank to be withdrawn and isolate the decomposition tank; C. Keep observing with the thermal imager. Based on the measured height distribution of the soft material wall, open the air valve closest to the highest point of the soft material wall, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open any one of the remaining two air valves, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed; open the last air valve, inject decomposition mother liquid from this air valve, and wait until the soft material wall at that location is disintegrated and collapsed, then close all three air valves; D. Inject decomposition mother liquor from the wall valve of the decomposition tank to dilute the slurry around the wall valve; after the dilution is completed, switch the large circulation to the decomposition tank before the decomposition tank to be withdrawn, and then withdraw the slurry in the decomposition tank to be withdrawn to the decomposition tank before it; E. After the slurry in the decomposition tank to be withdrawn is emptied by the large circulation pump, the decomposition mother liquor is injected simultaneously from the three air valves and the tank wall valve of the decomposition tank. The total amount of decomposition mother liquor injected is 300 to 600 m3. The residual slurry is diluted, and then the large circulation pump is turned on to empty the diluted slurry. Finally, the residual diluted slurry is emptied through the tank wall valve to complete the withdrawal.

2. The decomposition tank withdrawal method according to claim 1, characterized in that: In step C, the flow rate of the decomposition mother liquid injected into each air valve is 150-200m 3 / h.

3. The decomposition tank withdrawal method according to claim 1, characterized in that: In the step D, the flow rate of the decomposition mother liquor injected into the decomposition tank wall valve is 150-200m 3 / h, injection time is 15 to 25 minutes.

4. The decomposition tank backing method according to claim 1, characterized in that: In the step E, after the slurry in the decomposition tank is emptied, the decomposition mother liquor is injected simultaneously from the three air valves and the tank wall valve of the decomposition tank, with a total injection flow rate of 300 to 600 m 3 / h.

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