Defoaming method and system for decomposing aluminum oxide slurry

Abstract

According to the defoaming method and system for decomposing the aluminum oxide slurry, by means of the method and system, before the slurry enters a first tank, primary defoaming is carried out, auxiliary defoaming is carried out on foam generated by decomposition of each middle tank, and due to the fact that the diameters of inlets of a first-stage conical channel and a second-stage conical channel are larger than those of outlets of the first-stage conical channel and the second-stage conical channel, secondary defoaming is carried out; when the slurry passes through the first-stage conical channel and the second-stage conical channel, bubbles in the slurry are broken under the action of tensile stress, so that the content of the bubbles in the slurry is reduced from the source, the influence of the bubbles in the subsequent decomposition process is reduced, and the generation of the bubbles in each decomposition tank is indirectly reduced. Secondly, during auxiliary defoaming, foam slurry of the corresponding decomposition tank can be collected through the overflow tank, foam in the slurry can be adsorbed, extruded and crushed in real time under the action of the negative pressure adsorber and the extrusion cavity and then discharged into the overflow tank again, the process can adapt to different slurry form working conditions, the defoaming efficiency is guaranteed, and the defoaming effect is good. Therefore, the product quality is improved.

Description

Technical Field

[0001] The present invention relates to the field of alumina production, and particularly relates to a defoaming method and system for alumina slurry decomposition. Background Art

[0002] The production of alumina in the world mainly adopts the Bayer process. After bauxite is mixed with recycled mother liquor, ground finely, and dissolved by heating reaction, the Bayer digestion liquor is diluted by red mud washing liquor in a dilution tank, and then transported to a separation and settling tank. After adding a flocculant, the sodium aluminate solution after separating red mud is called crude liquor. The crude liquor is refined and filtered, and the sodium aluminate solution is called semen. The process of precipitating aluminum hydroxide by seed decomposition of the sodium aluminate solution is carried out in a series of multiple decomposition tanks. Under the condition of adding aluminum hydroxide seeds to the first decomposition tank, the decomposition slurry is completed under the conditions of appropriate temperature reduction and a residence time of dozens of hours. By reducing the temperature, the sodium aluminate solution is in a supersaturated state. Under the supersaturated condition, aluminum hydroxide seeds are added, that is, the seed decomposition process is used to produce aluminum hydroxide. The decomposed aluminum hydroxide slurry needs to be subjected to liquid-solid separation. The filtrate after the decomposition slurry is solid-liquid separated is called decomposition mother liquor. The decomposition mother liquor is evaporated and concentrated and enters the next cycle, which is called recycled mother liquor. The aluminum hydroxide seeds precipitated from the sodium aluminate solution need to be filtered to reduce the sodium aluminate solution attached to its surface, otherwise it will affect the decomposition rate and the particle size of aluminum hydroxide. In the alumina production process, the decomposition process is one of the important processes.

[0003] During the decomposition process, when the sodium aluminate solution accumulates to a certain extent in the decomposition stage, due to the presence of organic matter in the bauxite and the added additives, and there is organic matter in the bauxite, mainly in the form of humic acid, which dissolves in the alkaline solution during digestion. As the organic matter accumulates in the system, during the decomposition process, due to the gradual decrease in temperature and the crystallization water carried away by the precipitated aluminum hydroxide, the solubility of sodium oxalate also becomes supersaturated, resulting in the precipitation of sodium oxalate, the appearance of a suspension layer or a large amount of foam. The traditional series of decomposition tanks consists of multiple individual decomposition tanks connected in series. Although there is a certain height difference between each decomposition tank in the design, sometimes it is necessary to introduce a certain amount of compressed air into the decomposition slurry in the lifting pipe. At this time, the air mixed into the slurry will also generate bubbles. At the same time, the solid phase in the decomposition tank foam (scum), mainly aluminum hydroxide fine particles adsorbed with sodium oxalate, and when the organic matter in the solution is high, in addition to aluminum hydroxide, there is also solid sodium oxalate. These solids adsorb on the surface of the two-phase bubbles, forming three-phase foam and improving the stability of the foam. Secondly, the stronger the hydrophobicity of the solid surface, the easier it is to adsorb on the surface of the bubbles, and the more difficult it is for the liquid in the liquid film to drain, the higher the stability of the foam. The bubbles in the liquid always rise to the liquid surface, forming a bubble polymer separated by a liquid film composed of a small amount of liquid, further improving the stability of the foam. Regardless of the form, due to the small specific gravity, the foam floats on the surface of the slurry, easily generating a false liquid level, which directly affects production. Therefore, eliminating the influence of foam is crucial for the entire process. The traditional defoaming method mainly uses defoamers for defoaming, but since the defoamers are chemical drugs, the organic matter in them enters the alumina production system after being added, which is not conducive to normal production after long-term accumulation. Summary of the Invention

[0004] To solve the above technical defects, the process of the present invention adopts the methods of primary defoaming and auxiliary defoaming, which can gradually reduce the foam generated in each decomposition tank, thereby improving production efficiency and output.

[0005] The present invention adopts the following technical solutions:

[0006] A defoaming method for alumina slurry decomposition, comprising the following steps:

[0007] S1: Obtain the seed liquor, cool the seed liquor obtained by the Bayer process through a plate heat exchanger, mix it with seeds, and send it into a high-level tank for decomposition through a seed pump;

[0008] S2: First tank decomposition, after the slurry decomposed stably in the high-level tank is subjected to primary defoaming, it is sent into the first tank for decomposition;

[0009] S3: Intermediate tank decomposition, the slurry flowing out of the first tank is sequentially decomposed through multiple intermediate tanks step by step, and the foam generated in each intermediate tank decomposition will be subjected to auxiliary defoaming through an overflow tank;

[0010] S4: The second last tank decomposition and defoaming. After the slurry is decomposed in the last intermediate tank, it is sent to the second last tank. The foam generated during the decomposition process in the second last tank will be filtered by the flat plate vacuum filter and then sent to the last tank for decomposition.

[0011] S5: The last tank decomposition. The slurry decomposed in the second last tank is sent to the last tank for decomposition through the lifting pipe. After decomposition, it is separated by the vertical disc vacuum filter to form a filter cake, which is used as seed crystals after washing or enters the product system.

[0012] Preferably, the steps of the defoaming assembly for primary defoaming are as follows:

[0013] S100: The slurry in the high-level tank is sucked out by a vacuum pump and sent into the front chamber A through the inlet of the defoaming main body.

[0014] S101: When the pressure inside the front chamber A is greater than the pressure in the middle chamber B, the slurry will enter the middle chamber B through the first-stage conical channel on the first defoaming plate. As the slurry passes through the first-stage conical channel, the foam in the slurry will be squeezed and broken.

[0015] S102: When the pressure inside the middle chamber B is greater than the pressure in the rear chamber C, the slurry that has been primarily defoamed in the middle chamber B passes through the second-stage conical channel on the second defoaming plate, continues to squeeze and break the unbroken foam and then enters the rear chamber C, and finally enters the first tank through the rear chamber C.

[0016] Preferably, during the primary defoaming process, the pressure in the front chamber A of the defoaming main body needs to be maintained at 0 to -15 kPa, and the flow rate of the slurry inlet is 0.8 - 1.2 m / s; the pressure in the middle chamber B is set at -15 kPa to -50 kPa, and the flow rate in the first-stage conical channel is maintained at 12 - 18 m / s; the pressure in the rear chamber C is set at -50 kPa to +5 kPa, and the flow rate in the second-stage conical channel is maintained at 25 - 30 m / s.

[0017] Preferably, the auxiliary defoaming mainly defoams each overflow tank through the auxiliary defoaming mechanism. The auxiliary defoaming mechanism can automatically adjust its height according to the height of the foam slurry in the overflow tank, and can adaptively adjust the adsorption force and defoaming efficiency according to the feedback information of the viscosity sensor and the flow rate sensor.

[0018] Preferably, the present invention also provides a system for the defoaming method of an alumina slurry decomposition tank, including a plate heat exchanger, a high-level tank, a first tank, intermediate tanks, a second last tank, and a last tank. The plate heat exchanger is connected to the high-level tank, the high-level tank is connected to the first tank through a defoaming assembly, the first tank is connected to the intermediate tanks through a lifting pipe, there are at least three intermediate tanks, and they are also connected to each other through a lifting pipe and an overflow tank. The second last tank is also connected to the adjacent intermediate tank through a lifting pipe, and the second last tank is also connected to the second last tank through a lifting pipe.

[0019] Preferably, the defoaming component includes a defoaming main body, a first defoaming plate and a second defoaming plate. An inlet and an outlet are respectively formed at the bottom and the top of the defoaming main body. The first defoaming plate and the second defoaming plate are sequentially arranged inside the defoaming main body from bottom to top. The inside of the defoaming main body is divided into a front chamber A, a middle chamber B and a rear chamber C by the first defoaming plate and the second defoaming plate. Each chamber is connected to an external pressure sensor and a pressure compensator. A plurality of first conical channels and second conical channels are respectively formed on the first defoaming plate and the second defoaming plate. The first conical channels and the second conical channels are staggered and corresponding to each other. Titanium nitride coatings are attached to the surfaces of the first conical channels and the second conical channels. Two groups of first grooves are further formed on the inner wall of the defoaming main body. The first defoaming plate and the second defoaming plate are both made of silicon carbide ceramics or wear-resistant alloys, and second grooves are formed at the edges. A limiting plate is movably installed inside the second grooves.

[0020] Preferably, a plurality of auxiliary defoaming mechanisms are further arranged along the length direction of the overflow tank. The auxiliary defoaming mechanism includes an adjusting bracket and an extrusion defoaming component, and the extrusion defoaming component is movably installed on the adjusting bracket.

[0021] Preferably, the extrusion defoaming component includes a connecting frame, a floating plate, a negative pressure adsorber, a protective cover, an extrusion chamber, a speed regulating motor, a rotating shaft, a connecting arm, a roller, an extrusion pipe, a discharge pipe and a controller. The connecting frame is movably installed between two adjusting brackets. A floating plate is fixed at the bottom of the connecting frame. A negative pressure adsorber is further fixedly installed on one side of the floating plate. A protective cover, a speed regulating motor, an extrusion chamber and a controller are arranged in the middle of the floating plate. A rotating shaft is installed inside the extrusion chamber, and the rotating shaft is also fixedly connected to the output end of the speed regulating motor. A plurality of connecting arms are circumferentially arranged on the rotating shaft. A roller is movably installed at the end of each connecting arm. One end of the extrusion pipe is connected to the negative pressure adsorber, and the other end extends into the discharge pipe. The extrusion pipe passes through the extrusion chamber and is located between the inner wall of the extrusion chamber and the roller.

[0022] Preferably, a viscosity sensor and a flow rate sensor are further arranged on the floating plate, and both the viscosity sensor and the flow rate sensor are in signal connection with the controller.

[0023] Preferably, a plurality of adsorption nozzles are further arranged at the adsorption end of the negative pressure adsorber. Each adsorption nozzle is connected to a delivery pump through a channel, and the output end of the delivery pump is connected to the input end of the extrusion pipe.

[0024] The beneficial effects of the present invention are as follows:

[0025] First, before the slurry enters the first tank, it undergoes primary defoaming through a defoaming component. Since the diameters of the inlets of the first-stage conical channel and the second-stage conical channel are larger than those of the outlets, when the slurry passes through the constriction ends of the first-stage conical channel and the second-stage conical channel under the action of pressure, the bubbles in the slurry are ruptured under the action of tensile stress. In this way, the bubble content in the slurry is reduced from the source, thereby reducing the influence of foam in the subsequent decomposition process and indirectly reducing the generation of foam in each decomposition tank. Secondly, the first defoaming plate and the second plate can be quickly disassembled and assembled, which is convenient for regular cleaning. The surfaces of the first-stage conical channel and the second-stage conical channel are both coated with titanium nitride wear-resistant coatings, effectively improving the wear resistance of the first-stage conical channel and the second-stage conical channel and extending their service life.

[0026] Second, during the decomposition process, the overflow tank can collect the foam slurry of the corresponding decomposition tank. And under the action of the negative pressure adsorber and the extrusion cavity, the foam in the slurry can be adsorbed and continuously broken in the extrusion cavity to form a slurry state. The process controller can adaptively adjust the adsorption capacity of the negative pressure adsorber and the rotation speed of the speed control motor according to the viscosity and flow rate of the slurry, so as to adapt to the states of different slurries, and discharge the defoamed slurry back into the overflow tank, reducing the influence of the foam in the last tank on the decomposed slurry, thus ensuring the decomposition efficiency of the last tank and improving the quality of the product. Brief Description of the Drawings

[0027] Figure 1 is the method flow chart of the present invention;

[0028] Figure 2 is the process flow chart of the present invention;

[0029] Figure 3 is the internal structure schematic diagram of the defoaming component;

[0030] Figure 4 is Figure 3 the enlarged structure schematic diagram of part E in

[0031] Figure 5 is Figure 3 the enlarged structure schematic diagram of part F in

[0032] Figure 6 is the structure schematic diagram of the auxiliary defoaming mechanism;

[0033] Figure 7 is Figure 6 the enlarged structure schematic diagram of part G in

[0034] In the figure: plate heat exchanger 1, elevated tank 2, first tank 3, intermediate tank 4, second last tank 5, last tank 6, material lifting pipe 7, overflow tank 8, horizontal disc vacuum filter 9, vertical disc vacuum filter 10, defoaming assembly 11, defoaming main body 110, first defoaming plate 111, second defoaming plate 112, primary conical channel 113, secondary conical channel 114, front chamber A, middle chamber B, rear chamber C, auxiliary defoaming mechanism 12, adjustment bracket 120, extrusion defoaming assembly 121, connecting frame 1210, floating plate 1211, negative pressure adsorber 1212, protective cover 1213, extrusion chamber 1214, speed regulating motor 1215, rotating shaft 1216, connecting arm 1217, roller 1218, extrusion pipe 1219, discharge pipe 1220, controller 1221, adsorption nozzle 13, delivery pump 14, first groove 15, second groove 16, limiting plate 17, viscosity sensor 18 and flow rate sensor 19. Detailed implementation manners

[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0037] Embodiment 1:

[0038] Please refer to Figures 1 to 2 , a defoaming method for alumina slurry decomposition, comprising the following steps:

[0039] S1: Obtain semen. The semen obtained by the Bayer process is cooled by the plate heat exchanger 1 and then mixed with seeds, and is sent into the elevated tank 2 through a seed pump for decomposition; the elevated tank 2 mainly plays a stabilizing role. After the slurry is stabilized in the elevated tank 2, the foam in the subsequent decomposition process can be reduced, ensuring that the slurry entering the first tank 3 can be fully decomposed without being affected by the foam.

[0040] S2: The first tank 3 decomposes. After the stable slurry decomposed from the high-level tank 2 is initially defoamed by the defoaming component 11, it is sent to the first tank 3 for decomposition. Among them, the initial defoaming reduces the foam at the source. The principle is to use the pressure difference generated when the foam passes through the micropores to break the liquid film, and the surface tension of the foam is destroyed through secondary step-by-step extrusion. In this way, when entering the first tank 3 for decomposition, a large number of bubbles will not be generated.

[0041] S3: The intermediate tank 4 decomposes. The slurry flowing out of the first tank 3 is successively decomposed through multiple intermediate tanks 4 step by step. The foam generated during the decomposition of each intermediate tank 4 will be assisted in defoaming through the overflow tank 8. During the assisted defoaming, mainly the foam generated during the decomposition in each intermediate tank 4 is collected through the overflow tank 8, and then the collected foam is assisted in defoaming. In this way, it is ensured that the overflowing foam in each intermediate tank 4 will not flow into the second-to-last tank 5, thereby affecting the decomposition of the second-to-last tank 5.

[0042] S4: Decomposition and defoaming of the second-to-last tank 5. After the slurry is decomposed by the last-stage intermediate tank 4, it is sent to the second-to-last tank 5. The foam generated during the decomposition of the second-to-last tank 5 will be filtered by the horizontal disk vacuum filter 9 and then sent to the last tank 6 for decomposition. The foam generated during the decomposition of the second-to-last tank 5 will be filtered by the horizontal disk vacuum filter 9, so that the foam will not be brought into the last tank 6, thereby affecting the decomposition efficiency of the last tank 6;

[0043] S5: The last tank 6 decomposes. The slurry decomposed by the second-to-last tank 5 is sent to the last tank 6 for decomposition through the lifting pipe 7. After decomposition, it is separated by the vertical disk vacuum filter 10 to form a filter cake, which is used as crystal seeds after washing or enters the product system.

[0044] Refer to Figures 3 - 4 , the steps of initial defoaming by the defoaming component 11 are as follows:

[0045] S100: The slurry in the high-level tank 2 is sucked out by a vacuum pump and sent into the front chamber A through the inlet of the defoaming main body 110;

[0046] S101: When the pressure inside the front chamber A is greater than the pressure in the middle chamber B, the slurry will pass through the first-stage conical channel 113 on the first defoaming plate 111 and enter the middle chamber B. When the slurry passes through the first-stage conical channel 113, the foam in the slurry will be squeezed and broken;

[0047] S102: When the pressure inside the middle chamber B is greater than the pressure in the rear chamber C, the slurry that has been initially defoamed in the middle chamber B passes through the second-stage conical channel 114 on the second defoaming plate 112, continues to squeeze and break the unbroken foam and then enters the rear chamber C, and finally enters the first tank 3 through the rear chamber C.

[0048] During the primary defoaming process, the pressure in the three-section chamber inside the defoaming main body 110 is mainly controlled by an external pressure regulator. The pressure regulator can automatically compensate and adjust the pressure of each chamber according to the real-time pressure information of the pressure sensors in each chamber, ensuring that the pressure remains stable during the defoaming process and avoiding the problem of inaccurate pressure control caused by slurry fluctuations, which leads to unsatisfactory defoaming.

[0049] The pressure of the A section in the front chamber of the defoaming main body 110 needs to be set between 0 and -15 kPa, and the slurry inlet flow rate is maintained at 0.8 - 1.2 m / s. This can ensure that the slurry enters the front chamber A at a certain pressure and speed. The pressure and flow rate of the feed cannot be higher than this range, otherwise new bubbles will be generated. As the slurry enters, the pressure of the middle chamber B is set between -15 kPa and -50 kPa. Due to the pressure difference, the slurry in the front chamber A will pass through the first-stage conical channel at a speed of 12 - 18 m / s. Due to the conical structure and the effect of the pressure difference, the bubbles in the slurry are broken. After the middle chamber B is filled with slurry, similarly, the slurry passes through the second-stage conical channel at a speed of 25 - 30 m / s, thereby realizing the re-breaking of the bubbles in the slurry.

[0050] Specific defoaming working principle:

[0051] First, before starting, the inside of the defoaming component 11 is under the same pressure. When defoaming is required, first, the decomposed and stable slurry in the high-level tank 2 is sucked out by a vacuum pump, and then the slurry is controlled to enter the front chamber A at a certain pressure, 0 to -15 kPa, and a flow rate of 0.8 - 1.2 m / s. As the slurry continuously and stably enters, the front chamber A will be filled with slurry. At this time, as the slurry continues to be transported, the pressure in the front chamber A will gradually be higher than the pressure in the middle chamber B. At this time, the slurry will pass through the first-stage conical channel 113. Since the inlet of the first-stage conical channel 113 is larger than the outlet, the bubbles in the slurry will be squeezed against each other, so that the bubbles inside the slurry are completely broken. Then, as the slurry accumulates in the middle chamber B, the slurry in the middle chamber B will pass through the second-stage conical channel 114. The defoaming principle is the same as that in the first-stage conical channel 113, further defoaming the unbroken bubbles in the primary slurry. In this way, through two-stage defoaming, the bubble content in the slurry is reduced, thereby reducing the influence of foam during the decomposition process.

[0052] Refer to Figure 5 The auxiliary defoaming is mainly carried out by the auxiliary defoaming mechanism 12 to defoam each overflow tank 8. The auxiliary defoaming mechanism 12 can automatically adjust its height according to the height of the foam slurry in the overflow tank 8, and can adaptively adjust the adsorption force and defoaming efficiency according to the feedback information of the viscosity sensor 18 and the flow rate sensor 19.

[0053] The present invention also provides an alumina slurry decomposition defoaming system, which includes a plate heat exchanger 1, a high-level tank 2, a first tank 3, intermediate tanks 4, a second last tank 5 and a last tank 6. The plate heat exchanger 1 is connected to the high-level tank 2. The high-level tank 2 is connected to the first tank 3 through a defoaming assembly 11. The first tank 3 is connected to the intermediate tanks 4 through a lifting pipe 7. There are at least three intermediate tanks 4, and they are also connected to each other through the lifting pipe 7 and an overflow tank 8. The second last tank 5 is also connected to an adjacent intermediate tank 4 through the lifting pipe 7, and the second last tank 5 is also connected to the last tank 6 through the lifting pipe 7. Through the above technical solution, the semen cools down in the plate heat exchanger 1 and is mixed with seeds, then enters the high-level tank 2 for stable decomposition. Then, through the secondary microporous extrusion of the defoaming assembly 11, the bubbles in the slurry are broken, thus reducing the content of bubbles in the slurry and ensuring the subsequent carbonization decomposition of the slurry. Secondly, the auxiliary defoaming mechanism 12 on the overflow tank 8 can defoam the foam generated by the decomposition of the first tank 3 and each intermediate tank 4 separately, and finally concentrate in the second last tank 5 and be filtered by a flat plate vacuum filter 9. Finally, it continues to decompose through the last tank 6. In this process, since the last tank 6 will not accumulate the foam from the upper level, the decomposition efficiency of the last tank 6 is maximized. The foam generated by the decomposition in the last tank 6 itself will be filtered under the action of a vertical plate vacuum filter 10, and then become recycled mother liquor after evaporation. The fine particles in the foam and aluminum hydroxide form a filter cake together, which is washed and returned to the first decomposition tank as seeds or enters the product system.

[0054] Refer to Figures 3 - 5, the defoaming component 11 includes a defoaming main body 110, a first defoaming plate 111 and a second defoaming plate 112. An inlet and an outlet are respectively provided at the bottom and the top of the defoaming main body 110. The stabilized slurry enters the front chamber A through the inlet. The first defoaming plate 111 and the second defoaming plate 112 are sequentially arranged in the defoaming main body 110 from bottom to top. The defoaming main body 110 is divided into a front chamber A, a middle chamber B and a rear chamber C by the first defoaming plate 111 and the second defoaming plate 112. Each chamber is connected to an external pressure sensor and a pressure compensator. A plurality of first conical channels 113 and second conical channels 114 are respectively provided on the first defoaming plate 111 and the second defoaming plate 112, and the first conical channels 113 and the second conical channels 114 are staggered and corresponding to each other. The diameter of the inlet of the first conical channel 113 and the second conical channel 114 is larger than the diameter of the outlet. In this way, when the slurry passes through the contraction ends of the first conical channel 113 and the second conical channel 114 under the action of pressure, the bubbles in the slurry are broken under the action of tensile stress. In this way, the bubble content in the slurry is reduced from the source, thereby reducing the formation of foam on the surface of the slurry. And a titanium nitride coating is attached to the surfaces of the first conical channel (113) and the second conical channel (114), so as to avoid the wear of the first conical channel (113) and the second conical channel (114). Two groups of first grooves 15 are also provided on the inner wall of the defoaming main body 110. The first defoaming plate 111 and the second defoaming plate 112 are made of silicon carbide ceramics or wear-resistant alloys, and second grooves 16 are provided on the upper sides of the edges. A limiting plate 17 is movably installed in the second groove 16. The first groove 15 and the second groove 15 can cooperate with each other to limit the first defoaming plate 111 and the second defoaming plate 112. That is, when disassembly is required, only an external ejector rod needs to be inserted, so that the limiting plate 17 can compress the spring inside the second groove 16, and the first defoaming plate 111 and the second defoaming plate 112 can be taken out as a whole. In this way, it is convenient to clean the first conical channel (113) and the second conical channel (114), prevent blockage and cause low defoaming efficiency. Secondly, modular assembly and disassembly improve work efficiency.

[0055] Refer to Figures 5 - 7, a plurality of auxiliary defoaming mechanisms 12 are further provided along the length direction of the overflow tank 8, and the auxiliary defoaming mechanisms 12 are installed at intervals, which can improve the defoaming efficiency of the foam. Secondly, a centrifugal separator or a filter screen can be provided at the front end position of each overflow tank 8. The centrifugal separator and the filter screen can remove solid particles in the slurry, avoid the influence of the solids on the auxiliary defoaming mechanism 12, and ensure the working efficiency of the subsequent auxiliary defoaming mechanism 12. The auxiliary defoaming mechanism 12 includes an adjustment bracket 120 and an extrusion defoaming assembly 121, and the extrusion defoaming assembly 121 is movably installed on the adjustment bracket 120. Among them, the adjustment bracket 120 can be automatically adjusted up and down mainly according to the liquid level of the slurry in the overflow tank 8. The principle is that the density of the material of the floating plate 1211 is less than that of the slurry, so that the floating plate 1211 will change continuously with the liquid level of the slurry.

[0056] The extrusion defoaming assembly 121 includes a connecting frame 1210, a floating plate 1211, a negative pressure adsorber 1212, a protective cover 1213, an extrusion chamber 1214, a speed regulating motor 1215, a rotating shaft 1216, a connecting arm 1217, a roller 1218, an extrusion pipe 1219, a discharge pipe 1220 and a controller 1221. The connecting frame 1210 is movably installed between two adjustment brackets 120, and the top of the connecting frame 1210 is movably installed on the adjustment bracket 120 through a rotating shaft. The bottom of the connecting frame 1210 is fixedly provided with the floating plate 1211. The floating plate 1211 is generally made of ceramic material with a hollow structure, which will make the floating plate 1211 float on the slurry, thereby improving the stability. A negative pressure adsorber 1212 is also fixedly installed on one side of the floating plate 1211. The negative pressure adsorber 1212 mainly adsorbs the foam on the surface of the slurry and sends the adsorbed foam into the extrusion chamber 1214 through the extrusion pipe 1219, so that the foam is broken and returns to the slurry in the overflow tank 8. A protective cover 1213 is installed in the middle of the floating plate 1211. A speed regulating motor 1215, an extrusion chamber 1214 and a controller 1221 are arranged in the protective cover 1213. The controller 1221 is also connected to the speed regulating motor 1215 in a signal manner. A rotating shaft 1216 is installed in the extrusion chamber 1214, and the rotating shaft 1216 is also fixedly connected to the output end of the speed regulating motor 1215. A plurality of connecting arms 1217 are arranged circumferentially on the rotating shaft 1216, and a roller 1218 is movably installed at the end of each connecting arm 1217. One end of the extrusion pipe 1219 is connected to the negative pressure adsorber 1212, and the other end extends into the discharge pipe 1220, and the extrusion pipe 1219 passes through the extrusion chamber 1214 and is located between the inner wall of the extrusion chamber 1214 and the roller 1216.

[0057] A viscosity sensor 18 and a flow rate sensor 19 are also provided on the floating plate 1211, and both the viscosity sensor 18 and the flow rate sensor 19 are signal-connected to the controller 1221. The viscosity sensor 18 and the flow rate sensor 19 can monitor the flow rate and viscosity of the slurry in the overflow tank 8 in real time. When the viscosity and flow rate change, they can transmit signals to the controller 1221 in real time, and the controller 1221 will change the adsorption capacity of the negative pressure adsorber 1212 and the rotation speed of the speed control motor 1215 in real time, so as to ensure the defoaming rate of the foam. The following table shows the defoaming data of the irradiation defoaming mechanism 12 for slurries with different viscosities and flow rates.

[0058]

[0059] According to the actual data, the controller 1221 can automatically adjust the adsorption capacity and defoaming efficiency according to the feedback information of the viscosity sensor 18 and the flow rate sensor 19, replacing the traditional method of using defoamers for defoaming.

[0060] A number of adsorption nozzles 13 are also provided at the adsorption end of the negative pressure adsorber 1212. Each adsorption nozzle 13 is coated with a polytetrafluoroethylene cleaning coating, so that foam is not easily accumulated on the adsorption nozzle 13, ensuring that the adsorption nozzle 13 will not be corroded and blocked. Each adsorption nozzle 13 is connected to the delivery pump 14 through a channel, and the output end of the delivery pump 14 is connected to the input end of the extrusion tube 1219.

[0061] Extrusion defoaming principle:

[0062] First, the negative pressure adsorber 1212 sucks the foam in the slurry through the adsorption nozzles 13 by negative pressure. Each adsorption nozzle 13 sends the foam into the delivery pump 14 through the corresponding channel. Under the action of the delivery pump 14, the foam is transported to the extrusion chamber 1214 through the extrusion tube 1219. During this process, the speed control motor 1216 is started to drive the rotating shaft 1216 to rotate in the extrusion chamber 1214. During the rotation process, the connecting arm 1217 rotates synchronously. Since the other end of each connecting arm 1217 is movably connected to the roller 1218, during the rotation process, since there is a gap between the roller 1218 and the inner wall of the extrusion chamber 1214, and the extrusion tube 1219 passes through the gap, the roller 1218 will continuously press the extrusion tube 1219, causing the foam in the extrusion tube 1219 to break, and the foam can also be discharged from the extrusion tube 1219 during the rotation process. There will be no bubbles in the discharged liquid, and it will return to the slurry through the discharge pipe 1220.

[0063] The above are only the preferred embodiments of the present invention, and do not limit the present invention in other forms. Any person skilled in the relevant art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A defoaming method for alumina slurry decomposition, characterized in that, It includes the following steps: S1: Obtain semen. Cool the semen obtained by the Bayer process through a plate heat exchanger (1), mix it with seeds, and send it into a high-level tank (2) through a seed pump for decomposition; S2: Decompose in the first tank (3). After primary defoaming of the stable slurry decomposed in the high-level tank (2), send it into the first tank (3) for decomposition; S3: Decompose in the intermediate tanks (4). Send the slurry flowing out of the first tank (3) through multiple intermediate tanks (4) for step-by-step decomposition. The foam generated during the decomposition in each intermediate tank (4) will be assisted in defoaming through an overflow tank (8); S4: Decompose and defoam in the second-to-last tank (5). After the slurry is decomposed in the last-stage intermediate tank (4), send it to the second-to-last tank (5). The foam generated during the decomposition in the second-to-last tank (5) will be filtered through a flat-plate vacuum filter (9) and then sent to the last tank (6) for decomposition; S5: Decompose in the last tank (6). Send the slurry decomposed in the second-to-last tank (5) to the last tank (6) through a lifting pipe (7) for decomposition. After decomposition, separate it through a vertical-plate vacuum filter (10) to form a filter cake, which is used as seeds after washing or enters the product system.

2. The defoaming method for alumina slurry decomposition according to claim 1, characterized in that, The steps of primary defoaming are as follows: S100: Suck out the slurry in the high-level tank (2) through a vacuum pump and send it into the front chamber A through the inlet of the defoaming main body (110); S101: When the pressure inside the front chamber A is greater than the pressure in the middle chamber B, the slurry will enter the middle chamber B through the first-stage conical channel (113) on the first defoaming plate (111). When the slurry passes through the first-stage conical channel (113), the foam in the slurry will be squeezed and broken; S102: When the pressure inside the middle chamber B is greater than the pressure in the rear chamber C, the slurry that has been defoamed at the first stage in the middle chamber B passes through the second-stage conical channel (114) on the second defoaming plate (112), continues to squeeze and break the unbroken foam and then enters the rear chamber C, and finally enters the first tank (3) through the rear chamber C.

3. The defoaming method for alumina slurry decomposition according to claim 2, wherein During the primary defoaming process, the pressure in the front chamber A of the defoaming main body (110) needs to be maintained at 0 to -15 kPa, and the flow rate of the slurry inlet is 0.8 - 1.2 m / s; the pressure in the middle chamber B is set at -15 kPa to -50 kPa, and the flow rate in the first-stage conical channel (113) is maintained at 12 - 18 m / s; the pressure in the rear chamber C is set at -50 kPa to +5 kPa, and the flow rate in the second-stage conical channel (114) is maintained at 25 - 30 m / s.

4. The defoaming method for alumina slurry decomposition according to claim 1, wherein The auxiliary defoaming mainly defoams each overflow tank (8) through an auxiliary defoaming mechanism (12). The auxiliary defoaming mechanism (12) can automatically adjust its height according to the height of the foamed slurry in the overflow tank (8), and can adaptively adjust the adsorption force and defoaming efficiency according to the feedback information of the viscosity sensor (18) and the flow rate sensor (19).

5. An antifoaming system for alumina slurry decomposition, which is used to implement the antifoaming method for alumina slurry decomposition according to any one of claims 1-4, and is characterized in that, It includes a plate heat exchanger (1), a high-level tank (2), a first tank (3), an intermediate tank (4), a second-to-last tank (5) and a last tank (6). The plate heat exchanger (1) is connected to the high-level tank (2). The high-level tank (2) is connected to the first tank (3) through an antifoaming component (11). The first tank (3) is connected to the intermediate tank (4) through a feeding pipe (7). There are no less than three intermediate tanks (4), and they are also connected to each other through the feeding pipe (7) and an overflow tank (8). The second-to-last tank (5) is also connected to an adjacent intermediate tank (4) through the feeding pipe (7). The second-to-last tank (5) is also connected to the last tank (6) through the feeding pipe (7).

6. The defoaming system for alumina slurry decomposition according to claim 5, characterized in that, The antifoaming component (11) includes an antifoaming main body (110), a first antifoaming plate (111) and a second antifoaming plate (112). An inlet and an outlet are respectively formed at the bottom and the top of the antifoaming main body (110). The first antifoaming plate (111) and the second antifoaming plate (112) are sequentially arranged inside the antifoaming main body (110) from bottom to top. The inside of the antifoaming main body (110) is divided into a front chamber A, a middle chamber B and a rear chamber C by the first antifoaming plate (111) and the second antifoaming plate (112). Each chamber is connected to an external pressure sensor and a pressure compensator. A number of first tapered channels (113) and second tapered channels (114) are respectively formed on the first antifoaming plate (111) and the second antifoaming plate (112). The first tapered channels (113) and the second tapered channels (114) are staggered and corresponding to each other. A titanium nitride coating is attached to the surfaces of the first tapered channels (113) and the second tapered channels (114). Two groups of first grooves (15) are further formed on the inner wall of the antifoaming main body (110). The first antifoaming plate (111) and the second antifoaming plate (112) are made of silicon carbide, and second grooves (16) are formed on their edges. A limiting plate (17) is movably installed inside the second grooves (16).

7. The defoaming system for alumina slurry decomposition according to claim 5, wherein, A number of auxiliary antifoaming mechanisms (12) are further arranged along the length direction of the overflow tank (8). The auxiliary antifoaming mechanisms (12) include adjusting brackets (120) and extrusion antifoaming components (121). The extrusion antifoaming components (121) are movably installed on the adjusting brackets (120).

8. The defoaming system for alumina slurry decomposition according to claim 7, wherein, The extrusion defoaming assembly (121) includes a connecting frame (1210), a floating plate (1211), a negative pressure adsorber (1212), a protective cover (1213), an extrusion chamber (1214), a speed control motor (1215), a rotating shaft (1216), a connecting arm (1217), a roller (1218), an extrusion pipe (1219), a discharge pipe (1220) and a controller (1221). The connecting frame (1210) is movably installed between two adjusting brackets (120). The bottom of the connecting frame (1210) is fixed with the floating plate (1211). One side of the floating plate (1211) is also fixedly installed with the negative pressure adsorber (1212). The protective cover (1213) is installed in the middle of the floating plate (1211). The speed control motor (1215), the extrusion chamber (1214) and the controller (1221) are arranged in the protective cover (1213). The rotating shaft (1216) is installed in the extrusion chamber (1214). The rotating shaft (1216) is also fixedly connected with the output end of the speed control motor (1215). A plurality of connecting arms (1217) are circumferentially arranged on the rotating shaft (1216). The end of each connecting arm (1217) is also movably installed with a roller (1218). One end of the extrusion pipe (1219) is connected with the negative pressure adsorber (1212), and the other end extends into the discharge pipe (1220). The extrusion pipe (1219) passes through the extrusion chamber (1214) and is located between the inner wall of the extrusion chamber (1214) and the roller (1216).

9. The defoaming system for alumina slurry decomposition according to claim 8, wherein A viscosity sensor (18) and a flow rate sensor (19) are also arranged on the floating plate (1211), and both the viscosity sensor (18) and the flow rate sensor (19) are in signal connection with the controller (1221).

10. The defoaming system for alumina slurry decomposition according to claim 8, characterized in that, A plurality of adsorption nozzles (13) are also arranged at the adsorption end of the negative pressure adsorber (1212), and each adsorption nozzle (13) is connected with a delivery pump (14) through a channel. The output end of the delivery pump (14) is connected with the input end of the extrusion pipe (1219).

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