Rapid fluoride salt removal system based on sodium aluminate solution evaporation

Abstract

The utility model discloses a quick fluoride salt removal system based on sodium aluminate solution evaporation, which belongs to the technical field of aluminum oxide production and comprises evaporators, seven evaporators are sequentially connected together to form a seven-effect evaporator group, II-V-effect evaporators are respectively connected with I-IV-stage flash evaporators, a fluoride salt washing device comprises a switching pipeline, and the switching pipeline is communicated with the flash evaporators. A discharging port of the VII-effect evaporator is connected with a feeding port of the VI-effect evaporator, a discharging port of the VI-effect evaporator is connected with a six-effect discharging pipeline, two four-flash discharging pumps are arranged at the outlet end of the six-effect discharging pipeline in parallel, a seven-effect discharging pipe is connected between a discharging port of the VII-effect evaporator and a feeding port of the VI-effect evaporator, the middle of the seven-effect discharging pipe and the middle of the six-effect discharging pipeline are connected with a switching pipeline, and switching control valves are arranged at the two ends of the switching pipeline. The self-circulation evaporation station has the advantages that the switching pipeline is arranged for washing when the effective temperature difference of fluoride salt separated out due to long-term use of the VI-effect evaporator exceeds 10 DEG C, high-efficiency operation of the self-circulation evaporation station is guaranteed, and operation and maintenance work intensity is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of alumina production, and particularly relates to a rapid defluorination salt system based on evaporation of sodium aluminate solution. BACKGROUND

[0002] In the process of producing alumina by the Bayer method, the temperature of evaporated water is relatively high, reaches above 120 DEG C, and if the evaporated water is directly discharged, great waste is caused, and in order to improve the utilization rate, the existing process is to generate evaporated water by heat exchange of new steam through an evaporator, discharge the evaporated water into a later-stage condensate flash evaporator, generate low-pressure exhaust steam by multiple flash evaporation, use the low-pressure exhaust steam for heating of a later-stage evaporator, and finally use the low-pressure exhaust steam for heating of a heat-electricity deoxidizer.

[0003] However, in the process of evaporating sodium aluminate, fluorinated salt is precipitated in the running process of the six-effect evaporator, and more fluorinated salt is precipitated in the inner wall of the heating pipe along with the increase of the running time, the fluorinated salt crystalline layer formed in the inner wall of the heating pipe continuously increases the effective temperature difference of the six-effect evaporator, and the serious decline of the heat transfer efficiency of the heating pipe will affect the running efficiency and index control of the evaporator system. But the discharge of the seven-effect evaporator can only enter the six-effect evaporator, the production of the seven-effect liquid cannot be stopped, and therefore the six-effect evaporator cannot be isolated for removal of fluorine ion water washing operation, and the long-term accumulation of fluorine ions will seriously affect the running efficiency of the evaporator. If fluorine ion removal water washing operation is performed, the entire evaporator system must be stopped, a large amount of manpower is required, the operation workload is increased, and the production economic benefit is seriously affected due to the stoppage of the system.

[0004] Patents of part seven-effect evaporation system are disclosed in the prior art, wherein the utility model patent with publication number CN216259139U discloses a seven-effect evaporation system, which is characterized by comprising a raw liquid tank, a raw liquid flash evaporator, a blending tank and I-effect evaporator-VII-effect evaporator, I-stage flash evaporator-V-stage flash evaporator, I-stage condensate tank-VII-stage condensate tank, the discharge end of the raw liquid tank is divided into two branches, one branch is sequentially conveyed to the raw liquid flash evaporator, VII-effect evaporator, VI-effect evaporator, blending tank, and the other branch is sequentially conveyed to V-effect evaporator, IV-effect evaporator, III-effect evaporator, II-effect evaporator, I-effect evaporator, I-stage flash evaporator, II-stage flash evaporator, III-stage flash evaporator, IV-stage flash evaporator, V-stage flash evaporator and blending tank; the I-effect evaporator-VI-effect evaporator is heated by countercurrently inputting new steam to evaporate the material, and the condensate of the I-effect evaporator-VII-effect evaporator is cooled by the I-stage condensate tank-VII-stage condensate tank and then discharged. Although the problem of further reducing the steam consumption of the evaporator and improving the efficiency of the evaporator is solved, there is still the problem that fluorinated salt is precipitated in the six-effect evaporator, and the operation of the unit is affected when cleaning the fluorinated salt.

[0005] In view of this, the inventors have conducted in-depth research on this demand, and thus the present case has been produced. Utility model content

[0006] In order to overcome the problem that fluorinated salt is precipitated in the six-effect evaporator in the prior art, and the operation of the unit is affected when cleaning the fluorinated salt, the present utility model provides a rapid fluorinated salt removal system based on sodium aluminate solution evaporation, which comprises an evaporator composed of a heating chamber and a vapor-liquid separation chamber, seven evaporators are sequentially connected together to form a seven-effect evaporator group, the II-effect, III-effect and IV-effect evaporators are respectively connected with the I-stage flash evaporator, II-stage flash evaporator, III-stage flash evaporator and IV-stage flash evaporator, and the seven-effect evaporator group and the I-stage to IV-stage flash evaporators are connected with each other to form a solution concentration loop and a steam circulation loop, and a fluorinated salt water washing device is arranged on the VI-effect evaporator.

[0007] The fluorinated salt water washing device comprises a switching pipeline, the discharge port of the VI-effect evaporator is connected with a six-effect discharge pipeline, two four-flash discharge pumps are arranged in parallel at the outlet end of the six-effect discharge pipeline, a seven-effect discharge pipe is connected between the discharge port of the VII-effect evaporator and the feed port of the VI-effect evaporator, the seven-effect discharge pipe is connected with the switching pipeline at the middle part of the six-effect discharge pipeline, and switching control valves are arranged at both ends of the switching pipeline.

[0008] The fluorinated salt water washing is arranged between the VI-effect evaporator and the VII-effect evaporator, the switching pipeline is connected in the middle of the VI-effect evaporator discharge pipeline and the VI-effect evaporator discharge pipeline, the VI-effect evaporator can be switched for water washing at any time when the VI-effect evaporator effective temperature difference exceeds 10℃ due to long-term use, the high efficiency operation of the self-circulation evaporation station is ensured, and the operation and maintenance work intensity is greatly reduced, and the operation is safer and more effective.

[0009] Preferably, the material enters the flash device from the I-effect evaporator, the material enters the first-stage flash evaporator for cooling first, and then enters the II-effect evaporator, the III-effect evaporator and the IV-effect evaporator for cooling in sequence, and then is discharged to obtain the evaporation mother liquor; the new steam is added from the I-effect evaporator, and the generated secondary steam enters the next-stage evaporator in sequence.

[0010] Preferably, the VI-effect evaporator is connected with the VI-effect circulating pipeline, the VI-effect circulating pipeline is connected with the secondary steam condensate inlet pipeline near the VI-effect evaporator, and the VI-effect circulating pipeline is provided with the VI-effect circulating pump.

[0011] Preferably, the VI-effect discharge pipeline is provided with the forced-effect feeding pipeline near the VI-effect pump outlet valve, the forced-effect feeding pipeline is connected with the dissolution tank at the end, the forced-effect feeding pipeline is provided with the forced-effect feeding pump, and the outlet end of the forced-effect feeding pump is provided with the forced-effect feeding pump outlet valve.

[0012] Preferably, the VI-effect evaporator is connected with the VI-effect circulating pipeline, the VI-effect circulating pipeline is connected with the secondary steam condensate inlet pipeline near the VI-effect evaporator, and the VI-effect circulating pipeline is provided with the VI-effect circulating pump.

[0013] Preferably, the end of the VI-effect discharge pipeline is connected with the self-circulation evaporation station, the unqualified water tank, the raw liquid tank and the mother liquid tank through pipelines.

[0014] Preferably, the VI-effect discharge pipeline is provided with the VI-effect circulating pipeline, the VI-effect circulating pipeline is connected with the secondary steam condensate inlet pipeline near the VI-effect evaporator, and the VI-effect circulating pipeline is provided with the VI-effect circulating pump.

[0015] Preferably, the I-effect evaporator, the II-effect evaporator, the III-effect evaporator, the IV-effect evaporator, the V-effect evaporator, the VI-effect evaporator and the VII-effect evaporator all adopt falling film evaporators for evaporation, and each-stage evaporator adopts a split type or an integrated type process.

[0016] Preferably, the temperature of the secondary steam condensate water when the VI-effect evaporator is washed is 70-75℃.

[0017] Preferably, the absolute pressure of the new steam added into the Ith evaporator is 0.8-0.9 MPa, corresponding to the saturated steam temperature of 171-176 DEG C, and the temperature of the material discharged from the fourth flash evaporator is 86-92 DEG C.

[0018] The technical scheme of the present application has the following beneficial effects:

[0019] (1) The fluorinated salt water washing is arranged between the VIth evaporator and the VIIth evaporator, the switching pipeline is connected in the middle of the seventh-effect discharge pipeline and the sixth-effect discharge pipeline, the water washing can be switched at any time when the effective temperature difference of the VIth evaporator exceeds 10 DEG C due to long-term use, the high-efficiency operation of the self-circulation evaporation station is ensured, the operation and maintenance work intensity is greatly reduced, and the operation is safer and more effective.

[0020] (2) The water washing arrangement eliminates the traditional complicated links of shutdown-discharge-measures-addition of blind plate-isolation-starting-up-water washing-shutdown-discharge-measures-removal of blind plate-restoration of process-restarting, the working capacity of about 15 persons for 24 hours of maintenance personnel and operators can be saved, and the influence of the shutdown of the self-circulation evaporation station on the alumina output is reduced.

[0021] (3) The fluorinated salt causticization process after water boiling is added, the operation efficiency of the evaporator is improved, the steam consumption is reduced, the production liquid volume can be better controlled, and the output affected by the shutdown is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the present application, and should not be regarded as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of the drawings.

[0023] Figure 1 is a schematic diagram of a rapid fluorinated salt removal system based on sodium aluminate solution evaporation of the present application;

[0024] In the figure, 1 is a switching pipeline, 2 is a sixth-effect discharge pipeline, 3 is a fourth-flash discharge pump, 4 is a seventh-effect discharge pipe, 5 is a switching control valve, 6 is a sixth-effect material pump, 7 is a sixth-effect pump inlet valve, 8 is a sixth-effect pump outlet valve, 9 is a forced-effect feed pipe, 10 is a post-dissolution tank, 11 is a forced-effect feed pump, 12 is a forced-effect feed pump outlet valve, 13 is a sixth-effect circulation pipeline, 14 is a secondary steam condensate inlet pipeline, 15 is a sixth-effect circulation pump, 16 is a seventh-effect material pump, 17 is a seventh-effect pump inlet valve, and 18 is an isolation valve. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present application.

[0026] The present embodiment adopts fluorinated salt water washing arranged between the VI-effect evaporator and the VII-effect evaporator, and when the VI-effect evaporator effective temperature difference exceeds 10 DEG C due to long-term use of precipitated fluorinated salt, the VI-effect evaporator can be switched for water washing at any time, so as to ensure high efficiency operation of the self-circulation evaporation station, and also greatly reduce operation and maintenance work intensity, and be more safe and effective.

[0027] As shown in the drawings, Figure 1 A rapid fluorinated salt removing system based on sodium aluminate solution evaporation includes an evaporator composed of a heating chamber and a vapor-liquid separation chamber, seven evaporators are sequentially connected together to form a seven-effect evaporator group, the II-effect, III-effect, IV-effect and V-effect evaporators are respectively connected with a first-stage flash evaporator, a second-stage flash evaporator, a third-stage flash evaporator and a fourth-stage flash evaporator, the seven-effect evaporator group and the first-stage to fourth-stage flash evaporators are connected with each other to form a solution concentration loop and a steam circulation loop, and the VI-effect evaporator is provided with a fluorinated salt water washing.

[0028] The fluorinated salt water washing includes a switching pipeline 1, a discharge outlet of the VI-effect evaporator is connected with a six-effect discharge pipeline 2, two fourth-stage flash discharge pumps 3 are arranged in parallel at an outlet end of the six-effect discharge pipeline 2, a seven-effect discharge pipeline 4 is connected between a discharge outlet of the VII-effect evaporator and a feed inlet of the VI-effect evaporator, the seven-effect discharge pipeline 4 is connected with the switching pipeline 1 at a middle part of the six-effect discharge pipeline 2, and switching control valves 5 are arranged at both ends of the switching pipeline 1.

[0029] Here, the fluorinated salt water washing is arranged between the VI-effect evaporator and the VII-effect evaporator, the seven-effect discharge pipeline 4 is connected with the switching pipeline 1 at the middle part of the six-effect discharge pipeline 2, and when the VI-effect evaporator effective temperature difference exceeds 10 DEG C due to long-term use of precipitated fluorinated salt, the VI-effect evaporator can be switched for water washing at any time, so as to ensure high efficiency operation of the self-circulation evaporation station, and also greatly reduce operation and maintenance work intensity, and be more safe and effective.

[0030] As a preferred embodiment, the material from the I-effect evaporator enters the flash device, and the material first enters the first-stage flash evaporator for cooling, and then enters the second-stage flash evaporator, the third-stage flash evaporator, and the fourth-stage flash evaporator for cooling before being discharged to obtain the evaporated mother liquor; the new steam is added from the I-effect evaporator, and the generated secondary steam enters the next-stage evaporator.

[0031] As a preferred embodiment, the six-effect discharge pipeline 2 is connected with a six-effect material passing pump 6 at one end close to the VI-effect evaporator, a six-effect pump inlet valve 7 is installed at the inlet of the six-effect material passing pump 6, and a six-effect pump outlet valve 8 is installed at the outlet of the six-effect material passing pump 6.

[0032] As a preferred embodiment, the six-effect discharge pipeline 2 is provided with a forced-effect feeding pipe 9 close to the six-effect pump outlet valve 8, a post-dissolution tank 10 is connected at the end of the forced-effect feeding pipe 9, a forced-effect feeding pump 11 is installed on the forced-effect feeding pipe 9, and a forced-effect feeding pump outlet valve 12 is installed at the outlet end of the forced-effect feeding pump 11.

[0033] Here, the recycled water is pumped into the post-dissolution tank 10 by the forced-effect discharge pump to add lime for causticization.

[0034] As a preferred embodiment, the feeding inlet of the VI-effect evaporator is connected with a six-effect circulating pipeline 13, the six-effect circulating pipeline 13 is connected with a secondary steam condensate inlet pipeline 14 close to the VI-effect evaporator, and a six-effect circulating pump 15 is installed on the six-effect circulating pipeline 13.

[0035] As a preferred embodiment, the end of the six-effect discharge pipeline 2 is connected with the self-circulation evaporation station, the unqualified water tank, the raw liquid tank, and the mother liquor tank through pipelines, respectively.

[0036] As a preferred embodiment, the seven-effect discharge pipeline 4 is provided with a seven-effect material passing pump 16 at one end close to the VII-effect evaporator, a seven-effect pump inlet valve 17 is installed at the inlet end of the seven-effect material passing pump 16, and an isolation valve 18 is installed on the seven-effect discharge pipeline 4 close to the switching pipeline 1 and away from the VII-effect evaporator, the switching pipeline 1 is of a DN250 type, and the isolation valve 18 is a Y-type slurry valve.

[0037] As a preferred embodiment, the I-effect evaporator, the II-effect evaporator, the III-effect evaporator, the IV-effect evaporator, the V-effect evaporator, the VI-effect evaporator, and the VII-effect evaporator all adopt falling film evaporators for evaporation, and each stage of the evaporators adopts a split type or an integrated type process.

[0038] As a preferred embodiment, the temperature of the secondary steam condensate water when washing the VI-effect evaporator is 70-75°C.

[0039] As a preferred embodiment, the absolute pressure of the new steam added into the I-effect evaporator is 0.8-0.9 MPa, corresponding to a saturated steam temperature of 171-176 DEG C, and the temperature of the material discharged from the fourth flash evaporator is 86-92 DEG C.

[0040] The preferred embodiments of the present application have been described above with the preferred embodiments, but are not intended to limit the present application, and various modifications and changes can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A rapid defluoridation salt system based on evaporation of sodium aluminate solution characterized in that, The seven-effect evaporator group comprises a I-effect evaporator, a II-effect evaporator, a III-effect evaporator, a IV-effect evaporator, a V-effect evaporator, a VI-effect evaporator and a VII-effect evaporator, the II-effect evaporator, the III-effect evaporator, the IV-effect evaporator and the V-effect evaporator are respectively connected with a I-stage flash evaporator, a II-stage flash evaporator, a III-stage flash evaporator and a IV-stage flash evaporator, the seven-effect evaporator group and the I-stage to IV-stage flash evaporators are connected to form a solution concentration loop and a steam circulation loop, and the VI-effect evaporator is provided with a fluorinated salt water washing device. The fluorinated salt water washing device comprises a switching pipeline (1), an outlet of the VI-effect evaporator is connected with a six-effect outlet pipeline (2), two four-stage flash outlet pumps (3) are arranged in parallel at an outlet end of the six-effect outlet pipeline (2), a seven-effect outlet pipe (4) is connected between an outlet of the VII-effect evaporator and an inlet of the VI-effect evaporator, the seven-effect outlet pipe (4) is connected with the switching pipeline (1) at a middle part of the six-effect outlet pipeline (2), and switching control valves (5) are arranged at both ends of the switching pipeline (1).

2. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1, wherein, Material enters the flash evaporator from the I-effect evaporator, is cooled in the I-stage flash evaporator, and is sequentially cooled in the II-stage flash evaporator, the III-stage flash evaporator and the IV-stage flash evaporator, and then is discharged to obtain evaporated mother liquor; new steam is added from the I-effect evaporator, and generated secondary steam is sequentially introduced into the next stage evaporator.

3. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1, wherein, The six-effect outlet pipeline (2) is connected with a six-effect material pump (6) at one end close to the VI-effect evaporator, a six-effect pump inlet valve (7) is arranged at an inlet of the six-effect material pump (6), and a six-effect pump outlet valve (8) is arranged at an outlet of the six-effect material pump (6).

4. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 3, wherein, The six-effect outlet pipeline (2) is provided with a forced-effect feeding pipe (9) close to the six-effect pump outlet valve (8), the forced-effect feeding pipe (9) is connected with a dissolution tank (10) at a tail end, a forced-effect feeding pump (11) is arranged on the forced-effect feeding pipe (9), and a forced-effect feeding pump outlet valve (12) is arranged at an outlet end of the forced-effect feeding pump (11).

5. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1, wherein, The VI-effect evaporator is connected with a six-effect circulation pipeline (13), the six-effect circulation pipeline (13) is connected with a secondary steam condensate inlet pipeline (14) close to the VI-effect evaporator, and a six-effect circulation pump (15) is arranged on the six-effect circulation pipeline (13).

6. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1 wherein, The tail end of the six-effect outlet pipeline (2) is connected with a self-circulation evaporation station, an unqualified water tank, a raw liquid tank and a mother liquid tank through pipelines.

7. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1 wherein, The seven-effect outlet pipe (4) is provided with a seven-effect material pump (16) at one end close to the VII-effect evaporator, a seven-effect pump inlet valve (17) is arranged at an inlet end of the seven-effect material pump (16), an isolation valve (18) is arranged on the seven-effect outlet pipe (4) close to the switching pipeline (1) and away from the VII-effect evaporator, the switching pipeline (1) is a DN250 type, and the isolation valve (18) is a Y type slurry valve.

8. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1 wherein, The I-effect evaporator, II-effect evaporator, III-effect evaporator, IV-effect evaporator, V-effect evaporator, VI-effect evaporator and VII-effect evaporator all adopt falling film evaporators for evaporation, and each stage of evaporator adopts a split type or an integrated type structure.

9. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1, wherein, The temperature of the secondary steam condensate water when washing the VI-effect evaporator is 70-75℃.

10. The rapid defluoridation salt system based on evaporation of sodium aluminate solution as claimed in claim 1, wherein, The absolute pressure of the new steam added into the I-effect evaporator is 0.8-0.9Mpa, corresponding to a saturated steam temperature of 171-176℃, and the temperature of the material discharged from the fourth stage flash evaporator is 86-92℃.

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