A method for delaying scaling of equipment wall in wet-process phosphoric acid production process

Abstract

The present invention discloses a method for delaying scaling of equipment wall in the process of wet-process phosphoric acid production, belonging to the technical field of wet-process phosphoric acid production. The scheme of the present invention is: before the phosphoric acid slurry is transported to the filtering equipment of the first stage, super-exposure microbubbles of gas-liquid mixed phase are introduced into the phosphoric acid slurry, and the pressure of the phosphoric acid slurry gradually decreases during the rising process of the super-exposure microbubbles introduced, resulting in the super-exposure microbubbles continuously growing and polymerizing during the rising process, and breaking at the gas-liquid interface, realizing a cooling process similar to "flash evaporation", prompting the phosphoric acid slurry temperature to decrease, further prompting potassium fluorosilicate and sodium fluorosilicate in the phosphoric acid slurry to precipitate, and super-exposure microbubbles are used to separate them from the phosphoric acid slurry in advance. The present invention separates and discharges potassium fluorosilicate and sodium fluorosilicate in advance, which can well reduce the scaling amount of the equipment wall, reduce the frequency of manual descaling, improve the product yield, improve production efficiency, reduce environmental pollution, and promote production safety.

Description

Technical Field

[0001] The invention relates to the technical field of wet-process phosphoric acid production, and in particular to a method for delaying scaling of equipment wall surfaces in a wet-process phosphoric acid production process. Background Art

[0002] Phosphoric acid produced by decomposing phosphate rock with sulfuric acid, nitric acid or hydrochloric acid is collectively referred to as wet-process phosphoric acid. Taking sulfuric acid as an example, the process flow of wet-process phosphoric acid mainly includes the following steps:

[0003] Phosphate ore (mainly composed of Ca5F(PO4)3, SiO2, etc.) and sulfuric acid reaction: Phosphate ore and sulfuric acid react in a reactor to generate dilute phosphoric acid containing some suspended solid particles. This step is the most basic method in the production of wet phosphoric acid.

[0004] Solid-liquid separation: After the generated dilute phosphoric acid flows out, it is separated from the solid by sedimentation and clarification in the sedimentation tank. Then the clear flow from the upper layer overflows into the desulfurization tower, where the impurities react with the purifier in the tower to form precipitation and remove its organic matter and pigments.

[0005] Slurry treatment: The slurry is transported to the filtration equipment through the slurry delivery pump, which is the first stage of treatment. Then the phosphoric acid slurry after vacuum filtration is sent to the second stage of purification. The phosphoric acid slurry after vacuum filtration first enters the extraction tower, and the extractant TBP is added to the extraction tower in reverse. The two are dispersed, contacted and fully mixed with each other. Most of the phosphoric acid and the extractant form an organic phase, and the impurities enter the residual acid and are then discharged from the bottom of the tower.

[0006] Washing and stripping: The organic phase is pumped to the washing tower for washing, and the organic phase enters the stripping tower. Desalted water is added from the top of the stripping tower. The two are fully mixed under the stirring of the vibrating sieve plate. The phosphoric acid in the organic phase is stripped to the water phase to obtain purified phosphoric acid with a concentration of about 23% P2O5. The separated extractant enters the extraction tower for recycling.

[0007] Concentration: The remaining phosphoric acid enters the concentration chamber and is concentrated by heating to obtain the finished phosphoric acid.

[0008] The wet phosphoric acid process is not only technologically mature and stable and reliable in operation, but also has strong adaptability to ores and can produce phosphoric acid products with higher purity. It has been widely used in the fields of phosphate fertilizer, industrial-grade phosphoric acid and phosphate preparation.

[0009] In the production process of wet phosphoric acid, the following series of chemical reactions mainly occur:

[0010] Ca5F(PO4)3+7H3PO4+solution=5Ca(H2PO4)2+HF+solution

[0011] 5Ca(H2PO4)2+5H2SO4+solution=10H3PO4+5CaSO4·2H2O+solution

[0012] CaCO3+H2SO4+H2O=CaSO4·2H2O+CO2↑

[0013] MgCO3+H2SO4=MgSO4+H2O+CO2↑

[0014] MgCO3+3H3PO4=Mg(H2PO4)2+H2O+CO2↑

[0015] SiO2+6HF=H2SiF6+2H2O

[0016] 3SiF4+nH2O=2H2SiF6+SiO2·(n-2)H2O

[0017] Fe2O3+2H3PO4=2FePO4+3H2O

[0018] Al2O3+2H3PO4=2AlPO4+3H2O.

[0019] If the potassium (K) and sodium (Na) content in phosphate rock is high, the following chemical reactions will also occur:

[0020] H2SiF6+Na2O=Na2SiF6↓+H2O

[0021] H2SiF6+K2O=K2SiF6↓+H2O.

[0022] Therefore, potassium fluorosilicate (K2SiF6) and sodium fluorosilicate (Na2SiF6) are both precipitates produced during the production of phosphoric acid. Studies have shown that the solubility of both in phosphoric acid slurry is directly proportional to the temperature, that is, the lower the temperature, the lower the solubility of potassium fluorosilicate and sodium fluorosilicate.

[0023] In the first stage of the process of phosphate rock and sulfuric acid reacting to form slurry, potassium fluorosilicate and sodium fluorosilicate are already in a supersaturated state. Since the phosphoric acid slurry will be vacuum filtered under the condition of about 0.054-0.06Mpa, the liquid components will evaporate in large quantities under vacuum, resulting in a sudden drop in temperature. At this time, according to the above chemical reaction and principle, this sudden drop in temperature will cause a large amount of supersaturated potassium fluorosilicate and sodium fluorosilicate in the phosphoric acid slurry to precipitate, and adhere to the equipment wall (i.e.: the first stage of filtration equipment and pipelines) together with the filtered gypsum fine crystals and dispersed mud, and quickly form scale. If these scales are not cleaned in time, it will seriously affect the normal production of phosphoric acid (for example, the scale on the pipeline wall will cause blockage, thereby affecting the flow of phosphoric acid slurry).

[0024] Depending on the type of equipment, the cleaning cycle for the above-mentioned scale is generally once every 3 days, and no longer than once every 7 days (the main judgment criteria are: whether the scale causes pipeline blockage or whether it significantly reduces the heat exchange efficiency of the material). The existing scale cleaning method usually adopts manual processing, and the manual cleaning method has the following main defects:

[0025] 1. Since the scale is very hard and difficult to clean, the labor intensity is high. When cleaning, especially when cleaning the inner wall of the pipe, care should be taken to avoid scratching the original coating on the wall, otherwise the inner wall of the pipe will rust in subsequent use. Therefore, the entire descaling process is quite cumbersome, time-consuming, labor-intensive and inefficient.

[0026] 2. The system needs to be stopped for manual descaling. As mentioned above, the entire manual descaling process is quite cumbersome and the descaling efficiency is low. Therefore, not only the shutdown time is long, which affects the production efficiency of phosphoric acid, but also each start and stop of the equipment will cause certain damage to the system equipment (especially the moment of cold start), so it also has a great impact on the company's benefits and equipment maintenance.

[0027] Therefore, how to effectively slow down the accumulation rate of scale on the equipment wall, reduce the intensity of manual cleaning as much as possible, improve the descaling efficiency, or extend the cleaning cycle of the scale (more than 7 days) to ensure the production efficiency of phosphoric acid, reduce environmental pollution, and promote production safety has become a problem that technicians in this field need to solve urgently. Summary of the invention

[0028] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for delaying scaling of the equipment wall in the wet-process phosphoric acid production process, which can reduce the labor intensity of manual descaling, improve the descaling efficiency, and ensure the production efficiency of phosphoric acid.

[0029] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0030] A method for delaying scaling of equipment wall in a wet-process phosphoric acid production process, wherein ultra-exposure microbubbles of a gas-liquid mixed phase with pressure are continuously introduced into the phosphoric acid slurry before the phosphoric acid slurry is transported to a first-stage filtering device;

[0031] As the introduced super-exposure microbubbles rise, the pressure of the phosphoric acid slurry gradually decreases, causing the super-exposure microbubbles to continue to grow and aggregate, and then burst when reaching the gas-liquid interface and vaporize, thereby lowering the temperature of the phosphoric acid slurry and prompting the precipitation of potassium fluorosilicate and sodium fluorosilicate in the phosphoric acid slurry. The super-exposure microbubbles separate them from the phosphoric acid slurry; after separation, the phosphoric acid slurry is transported to the filtration equipment.

[0032] Furthermore, the present invention also performs wave energy treatment on the phosphoric acid slurry, which accelerates the rupture of the super-exposed microbubbles and instantly releases high-intensity energy, so that the fluorosilicic acid in the phosphoric acid slurry is decomposed into volatile silicon tetrafluoride and hydrogen fluoride under the action of high-intensity energy, and released from the phosphoric acid slurry.

[0033] Preferably, the wave energy treatment is ultrasonic treatment, and the frequency of the ultrasonic wave is 80-200 Hz.

[0034] Furthermore, the present invention also performs high-frequency oscillation on the wall of the device so as to make the bottom layer of the fluid boundary layer at the wall of the device enter a high-intensity turbulent state.

[0035] Preferably, the frequency of the high-frequency oscillation is 20-100 Hz, the oscillation interval is 10-30 min, and the oscillation time of each oscillation is 30-60 s.

[0036] Preferably, the surface finish of the equipment wall is at least level 7.

[0037] Preferably, when the phosphoric acid slurry is transported to the filtering equipment, the temperature is reduced by 8°C or more.

[0038] Preferably, the pressure of the super-exposure microbubbles is greater than 0 and less than or equal to 0.6 MPa.

[0039] Preferably, the ratio of the gas phase to the gas-liquid mixed phase is 2-6vt%, the mass ratio of the gas-liquid mixed phase to the phosphoric acid slurry is 1-10wt%, and the average diameter of the super-exposure microbubbles is 20-80um.

[0040] Furthermore, the phosphoric acid slurry is cooled by combining super-exposure microbubble bursting with flash evaporation.

[0041] The main design principles of the present invention are:

[0042] During the acid hydrolysis process, Ca5F(PO4)3 in the phosphate rock reacts to generate hydrogen fluoride (HF), and then the hydrogen fluoride reacts with silicon dioxide (SiO2) to be converted into fluorosilicic acid (H2SiF6). Since alkali metals such as potassium and sodium in the phosphate rock are also dissolved in the solution, and finally react with fluorosilicic acid to generate potassium fluorosilicate (K2SiF6) and sodium fluorosilicate (Na2SiF6), therefore, before the phosphoric acid slurry is passed into the filtering equipment, the present invention uses super aeration flotation means to stratify the phosphoric acid slurry (upper air flotation layer and lower floating residual layer) and cool it, so as to precipitate potassium fluorosilicate and sodium fluorosilicate in advance, and then bring them to the upper air flotation layer by super aeration micro bubbles, and finally separate and discharge them from the phosphoric acid slurry, so as to effectively reduce the amount of scaling on the wall of subsequent equipment.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The present invention performs a super-aeration flotation pretreatment on the phosphoric acid slurry before conveying it to the first-stage filtering equipment, wherein: 1) the continuously introduced stable super-aeration microbubbles will adhere to some impurities and a small amount of potassium fluorosilicate and sodium fluorosilicate that have been formed, causing them to rise with the super-aeration microbubbles, and eventually the phosphoric acid slurry forms an upper flotation layer and a lower flotation layer, while the impurities and potassium fluorosilicate and sodium fluorosilicate are located in the upper flotation layer; 2) the super-aeration microbubbles with pressure are gradually reduced during the rising process due to the phosphoric acid slurry pressure. The pressure inside and outside the super-exposure microbubbles gradually becomes unbalanced, and finally reaches the gas-liquid interface and breaks to produce more small bubbles. The small bubbles continue to rise and continuously absorb heat (vaporization effect), realizing a cooling process similar to "flash evaporation", so that the temperature of the phosphoric acid slurry is reduced. At this time, due to the dissolution characteristics of potassium fluorosilicate and sodium fluorosilicate in the phosphoric acid slurry, the cooling can cause potassium fluorosilicate and sodium fluorosilicate to continue to precipitate and adhere to the super-exposure microbubbles introduced subsequently, and be brought into the upper air flotation layer, and finally separated and discharged from the phosphoric acid slurry. In this way, the present invention avoids the precipitation and attachment of a large amount of supersaturated potassium fluorosilicate and sodium fluorosilicate on the wall of the equipment during the subsequent filtration of the phosphoric acid slurry, thereby reducing the amount of scaling on the wall of the equipment.

[0045] (2) The present invention also provides wave energy treatment. Since super-aeration flotation can provide a precondition for the cavitation effect, after adding wave energy treatment, a large number of super-aeration microbubbles can produce a cavitation effect, instantly releasing high-intensity energy, causing the fluorosilicic acid in the phosphoric acid slurry to decompose into volatile silicon tetrafluoride and hydrogen fluoride. Subsequently, due to the buoyancy difference between the two, hydrogen fluoride will be discharged from the phosphoric acid slurry before silicon tetrafluoride, thereby avoiding the reaction of hydrogen fluoride and silicon tetrafluoride to generate fluorosilicic acid again. That is, by separating and discharging F and Si in advance, the preconditions for the generation of potassium fluorosilicate and sodium fluorosilicate can be largely eliminated. The relevant chemical reaction formula is as follows:

[0046] H2SiF6=SiF4↑+2HF↑.

[0047] In this way, the present invention can separate and discharge K2SiF6, Na2SiF6 and a large amount of gaseous SiF4 and HF already formed in the phosphoric acid slurry in advance before filtering the phosphoric acid slurry, thereby greatly reducing the amount of scaling on the equipment wall.

[0048] If the cleaning cycle is the same as that of the prior art (for example, every 7 days is regarded as a statistical cycle), the present invention can effectively reduce the labor intensity of manual descaling, improve the efficiency of descaling, shorten the downtime in each cycle, and avoid cold start as much as possible; if the cleaning cycle is different from that of the prior art, the present invention can effectively extend the interval time of the cleaning cycle (experiments show that for substantially the same amount of scaling, the accumulation time required by the present invention can be up to 24 days, compared with the accumulation time required by the prior art of only 7 days). Therefore, the present invention well guarantees the production efficiency of phosphoric acid.

[0049] (3) The K2SiF6, Na2SiF6, SiF4, and HF separated and discharged by the present invention can be processed into fluorine, hydrogen fluoride, and silicon tetrafluoride through subsequent processing. Among them, fluorine occupies an important position in strategic industries such as high-end manufacturing, environmental protection, new energy, and new materials; hydrogen fluoride plays an important role in metallurgy and medicine; silicon tetrafluoride is widely used in the production of optical fiber, semiconductors, or solar cells, and is the foundation of the core manufacturing industry of the electronics industry. Therefore, the use of the scheme of the present invention can not only effectively reduce the amount of scaling on the equipment wall within the same cleaning cycle and reduce the labor intensity of descaling, but also increase the application value of the air flotation layer and reduce environmental pollution, which can be said to kill two birds with one stone.

[0050] (4) The present invention also performs high-frequency oscillation treatment on the equipment wall surface so that the fluid at the equipment wall surface continues to generate turbulence. The principle is that according to the boundary layer theory, the flow velocity of the fluid close to the wall surface under steady-state flow conditions is close to zero, which is not conducive to the removal of deposited scale from the equipment wall surface. The present invention adopts high-frequency oscillation means, by setting a reasonable oscillation frequency and oscillation time, so that the bottom layer of the fluid boundary layer at the equipment wall surface enters a high-intensity turbulent state. When the inner and outer zones of the boundary layer interact with each other, the boundary layer can be locally ruptured at a certain position on the wall surface space, thereby preventing the fluid flow velocity from approaching zero. In this way, within the same cleaning cycle, the present invention can further reduce the amount of scaling on the equipment wall surface and the labor intensity of manual scale removal.

[0051] (5) In the scheme of the present invention, since impurities and K2SiF6 and Na2SiF6 are separated in advance, the damage to the material grains is reduced, and the subsequent crystallization reaction is avoided from being seriously affected by "secondary nucleation", thereby ensuring the quality of the finished phosphoric acid product. Experiments show that by using the scheme of "super aeration flotation + cooling + wave energy treatment" of the present invention to treat 1 liter of phosphoric acid slurry, the amount of scaling is reduced from the original 2.97g to 0.96g, and the P2O5 concentration of phosphoric acid is also increased from 22% to 30%.

[0052] (6) The various links in the process flow of the present invention are closely linked, complementary and interrelated, which effectively slows down the scale accumulation rate on the equipment wall during the wet-process phosphoric acid production process. Therefore, it is very suitable for large-scale promotion and application in the wet-process phosphoric acid process. DETAILED DESCRIPTION

[0053] The present invention is further described below in conjunction with embodiments, and the embodiments of the present invention include but are not limited to the following embodiments.

[0054] Example 1

[0055] This embodiment provides a phosphoric acid slurry treatment solution based on the original wet phosphoric acid process, which mainly adopts super aeration flotation means, and can effectively slow down the accumulation rate of scale on the equipment wall during the wet phosphoric acid production process, as follows:

[0056] Before the phosphoric acid slurry is transported to the first-stage filtration equipment, the phosphoric acid slurry is first passed into a slurry tank (transition tank), and a super-aeration flotation device is placed in the slurry tank, and super-aeration microbubbles are continuously introduced into the phosphoric acid slurry using the super-aeration flotation device. This embodiment adopts the super-aeration flotation device recorded in the announcement number: CN117720078B. The super-aeration microbubbles are introduced in the form of a pressurized gas-liquid mixed phase. A gas-liquid mixed phase is formed by passing gas into the liquid phase to pressurize it, and then the gas-liquid mixed phase is introduced into the phosphoric acid slurry. In this embodiment, the pressure of the gas-liquid mixed phase is 0.1MPa, the proportion of the gas phase to the gas-liquid mixed phase is 2vt%, the mass ratio of the gas-liquid mixed phase to the phosphoric acid slurry is 1wt%, and the average diameter of the super-aeration microbubbles (D 50 ) is 20um.

[0057] The introduced super-exposure microbubbles will adhere to some impurities and a small amount of K2SiF6 and Na2SiF6 that have been formed, and make the phosphoric acid slurry present a distribution state of an upper air flotation layer and a lower floating residual layer, with K2SiF6, Na2SiF6 and impurities located in the upper air flotation layer; at the same time, during the rising process of the super-exposure microbubbles, the pressure of the phosphoric acid slurry gradually decreases, causing the internal and external pressures of the super-exposure microbubbles to gradually become unbalanced, and the super-exposure microbubbles will rupture to produce smaller bubbles. Since the small bubbles will continue to absorb heat during the floating process and take away part of the heat of the phosphoric acid slurry, the temperature of the phosphoric acid slurry will decrease, causing K2SiF6 and Na2SiF6 to continue to precipitate in the phosphoric acid slurry, and adhere to the subsequent super-exposure microbubbles, and finally be brought to the upper air flotation layer.

[0058] This embodiment uses the method of super-exposure micro-bubble rupture to reduce the temperature of the phosphoric acid slurry by 8°C when it is transported to the filtration equipment. Of course, the phosphoric acid slurry can also be cooled by combining the flash evaporation method on this basis. The purpose of combining the flash evaporation method is to more accurately control the temperature reduction of the phosphoric acid slurry. The use of the flash evaporation method will have certain equipment costs and energy consumption. Whether flash evaporation is needed or not, the enterprise can choose the best one according to the actual production situation and cost.

[0059] In the scheme of this embodiment, before the phosphoric acid slurry is filtered, super-exposure microbubbles are cleverly used to treat the phosphoric acid slurry, which can not only remove impurities, but also the cooling of the slurry caused by the rupture of the super-exposure microbubbles also prompts the early precipitation and separation of potassium fluorosilicate and sodium fluorosilicate, reducing the amount of scaling on the equipment wall, and can also effectively reduce the damage to the material grains, avoiding the subsequent crystallization reaction due to "secondary nucleation" seriously affecting the crystallization process, thereby ensuring the quality of the finished phosphoric acid product.

[0060] In addition, it should be noted that the filtration described in the scheme of CN117720078B belongs to the filtration after the second stage of extraction, and the purpose is to filter to obtain the filtrate, and then perform subsequent concentration. Although there are slurry stratification and cooling in the scheme of CN117720078B, since most of the K2SiF6 and Na2SiF6 have been deposited on the filter equipment and pipeline walls in the first stage, in the second stage, even if the slurry is stratified and cooled, there is basically no K2SiF6 and Na2SiF6 precipitation, so the main significance of the scheme of this embodiment is to delay the scaling rate of the filter equipment and pipeline walls in the first stage.

[0061] Example 2

[0062] On the basis of Example 1, this example combines ultrasonic means (ultrasonic wave generator is also set in the slurry tank) to treat phosphoric acid slurry with wave energy. The ultrasonic frequency set in this example is 200Hz, the purpose of which is to accelerate the rupture of super-exposure microbubbles and release high-intensity energy instantly, so that the fluorosilicic acid in the phosphoric acid slurry is decomposed into volatile silicon tetrafluoride and hydrogen fluoride before it reacts to generate K2SiF6 and Na2SiF6 (reaction formula: H2SiF6=SiF4↑+2HF↑). In addition to ultrasonic waves, other forms of energy waves can also be used to treat phosphoric acid slurry with wave energy, and the frequency setting is based on accelerating the rupture of super-exposure microbubbles and releasing high-intensity energy instantly.

[0063] In this way, before the phosphoric acid slurry is filtered, after super aeration flotation + cooling + wave energy treatment, the scale deposits on the equipment wall or in the pipeline can be greatly reduced within the same cleaning cycle.

[0064] Example 3

[0065] On the basis of Example 1, this embodiment uses a high-frequency oscillator to perform high-frequency oscillation treatment on the equipment wall surface, so as to generate turbulence in the fluid at the equipment wall surface, so that when the inner and outer zones of the boundary layer interact with each other, the boundary layer is locally broken at a certain position of the wall surface space, so as to avoid the fluid flow rate approaching zero, thereby better reducing the amount of scaling on the equipment wall surface within the same cleaning cycle. In addition, in order to better cooperate with turbulence, in this embodiment, the surface finish of the equipment wall surface is set to level 7, that is, the surface finish grade of the equipment wall surface is used as one of the acceptance criteria when the equipment leaves the factory, so as to cooperate with the process of "super aeration floating + cooling + wave energy treatment + high-frequency oscillation treatment of the equipment wall surface" in this embodiment; at the same time, the frequency of the high-frequency oscillation is set to 30Hz, the oscillation interval is 30min, and the oscillation time is 60s each time.

[0066] Example 4

[0067] The difference from Example 3 is that this embodiment is based on Example 2, and uses a high-frequency oscillator to perform high-frequency oscillation treatment on the wall surface of the equipment, and the frequency of the high-frequency oscillation is set to 80 Hz, the oscillation interval is 10 minutes, and the oscillation time each time is 30 seconds.

[0068] Example 5

[0069] The only difference from Example 1 is that in this embodiment, the ratio of gas phase to gas-liquid mixed phase is 6vt%, the mass ratio of gas-liquid mixed phase to phosphoric acid slurry is 10wt%, and the average diameter of super-exposure microbubbles is 80um.

[0070] Example 6

[0071] The only difference from Example 1 is that in this embodiment, by combining a flash evaporation device, the temperature of the phosphoric acid slurry is reduced by 14° C. when it is transported to the filtering device.

[0072] Example 7

[0073] The only difference from Example 2 is that in this embodiment, the ultrasonic frequency of the ultrasonic wave is 120 Hz.

[0074] Example 8

[0075] The only difference from Example 2 is that in this example, the pressure of the gas-liquid mixed phase is 0.6 MPa, and the other parameters are the same as those in Example 2.

[0076] Example 9

[0077] The only difference from Example 3 is that in this example, the temperature of the phosphoric acid slurry is reduced by 20° C. when it is transported to the filtering equipment.

[0078] Example 10

[0079] The only difference from Example 4 is that in this embodiment, the ultrasonic frequency of the ultrasonic wave is 80 Hz.

[0080] Embodiment 11

[0081] The difference from Example 1 is that in the super aerated flotation, the pressure of the gas-liquid mixed phase is 0.7 MPa; the other parameters are consistent with those in Example 1.

[0082] Example 12

[0083] The difference from Example 1 is that in this embodiment, the temperature of the phosphoric acid slurry is reduced by 7° C. when it is transported to the filtering equipment; the other parameters are consistent with those in Example 1.

[0084] Table 1 shows the scaling comparison results of Examples 1-12 and the traditional process (i.e., the pre-treatment of "super aeration flotation + cooling + wave energy treatment + equipment wall high-frequency oscillation treatment" is not used before the phosphoric acid slurry is transported to the filtration equipment) under the same working conditions, with 7 days as a statistical period.

[0085]

[0086]

[0087] Table 1

[0088] Scaling description:

[0089] 1. Reduction: The amount of scaling is reduced compared with the traditional process, and is reduced by less than one time (not included);

[0090] 2. Significant reduction: The amount of scaling is reduced compared with the traditional process, and is reduced by one time (inclusive) to three times (exclusive);

[0091] 3. Significant reduction: The amount of scaling is reduced compared to the traditional process, and is reduced by three times or more.

[0092] According to Table 1, we can see that:

[0093] (1) The results of Examples 1-12 and the traditional process show that in the same statistical period, the present invention can reduce the amount of scaling on the equipment wall, reduce the labor intensity of manual scaling removal, and improve the efficiency of scaling removal.

[0094] (2) The results of Examples 1 and 5 show that adjusting the ratio of the gas phase to the gas-liquid mixed phase, the mass ratio of the gas-liquid mixed phase to the phosphoric acid slurry, and the average diameter of the super-exposure microbubbles has little effect on the degree of scaling reduction.

[0095] (3) The results of Example 3 show that the scaling can be significantly reduced by adopting the means of "super aeration flotation + cooling + high-frequency oscillation treatment of the equipment wall". The results of Examples 2 and 8 show that the scaling can also be significantly reduced by adopting the means of "super aeration flotation + cooling + wave energy treatment" by adjusting the pressure of the gas-liquid mixed phase.

[0096] (4) The results of Examples 1 and 6 show that the greater the temperature reduction, the more significant the reduction in scaling. The results of Example 9 show that on the basis of "super aeration flotation + cooling + high-frequency oscillation", the greater the temperature reduction, the more significant the reduction in scaling.

[0097] (5) The results of Examples 2 and 7 show that the scaling can be significantly reduced by adjusting the ultrasonic frequency of the ultrasonic wave by adopting the means of "super aeration flotation + cooling + wave energy treatment". The results of Examples 4 and 10 show that the scaling can be significantly reduced by adopting the means of "super aeration flotation + cooling + wave energy treatment + high-frequency oscillation treatment of the equipment wall".

[0098] (6) The results of Example 11 show that when the pressure of the gas-liquid mixed phase is 0.7 MPa (exceeding 0.6 MPa), although the degree of scaling is still reduced compared with the traditional process, its effect is not as good as that of Example 1, which shows that the higher the pressure of the gas-liquid mixed phase, the better.

[0099] (7) The results of Example 12 show that when the slurry temperature is reduced by 7°C, although the degree of scaling is still reduced compared with the traditional process, its effect is not as good as that of Example 1. This means that when the slurry temperature is reduced by 7°C or below (the cooling range is greater than 0°C and less than or equal to 7°C), its applicable scenario is recommended to be scientific research in the laboratory. In actual engineering applications, the reduction range of the slurry temperature is preferably reduced to 8°C or above.

[0100] The above conclusions show that in the wet phosphoric acid production process, the scaling degree of the equipment and pipeline walls is strongly correlated with the temperature reduction of the phosphoric acid slurry, the pressure of the gas-liquid mixed phase, the ultrasonic frequency and the frequency of high-frequency oscillation. It is not very correlated with process parameters such as the proportion of gas phase in the gas-liquid mixed phase, the mass ratio of the gas-liquid mixed phase to the phosphoric acid slurry, and the average diameter of super-exposure microbubbles. However, compared with traditional processes, there is still improvement in the reduction of scaling within the same statistical period.

[0101] The scheme of the present invention seems simple, but it is actually not easy to think of. Only by conducting in-depth research on each process of the wet-process phosphoric acid process and fully understanding the mechanism and characteristics thereof can the pain points and difficulties in the production process of the enterprise be solved in the simplest and most effective way, and the relative balance between technology and cost can be achieved as much as possible. Therefore, compared with the prior art, the present invention has outstanding substantive characteristics and significant progress, and is very suitable for large-scale promotion and application in the wet-process phosphoric acid process.

[0102] The above embodiments are only preferred implementation modes of the present invention and should not be used to limit the protection scope of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention.

Claims

1. A method for delaying scaling of equipment walls in the production process of wet-process phosphoric acid. It is characterized in that Before the phosphoric acid slurry is transported to the first stage filtering equipment, ultra-exposure microbubbles with a gas-liquid mixed phase having a pressure greater than 0 and less than or equal to 0.6 MPa are continuously introduced into the phosphoric acid slurry; As the introduced super-exposure microbubbles rise, the pressure of the phosphoric acid slurry gradually decreases, causing the super-exposure microbubbles to continue to grow and aggregate, and then burst when reaching the gas-liquid interface and vaporize, thereby lowering the temperature of the phosphoric acid slurry and prompting the precipitation of potassium fluorosilicate and sodium fluorosilicate in the phosphoric acid slurry. The super-exposure microbubbles separate them from the phosphoric acid slurry; after separation, the phosphoric acid slurry is transported to the filtration equipment.

2. A method for delaying scaling of equipment wall surfaces in a wet-process phosphoric acid production process according to claim 1, It is characterized in that The phosphoric acid slurry is also subjected to wave energy treatment to accelerate the rupture of the super-exposed microbubbles and instantly release high-intensity energy, so that the fluorosilicic acid in the phosphoric acid slurry is decomposed into volatile silicon tetrafluoride and hydrogen fluoride under the action of high-intensity energy, and released from the phosphoric acid slurry.

3. A method for delaying scaling of equipment wall surfaces in a wet-process phosphoric acid production process according to claim 2, It is characterized in that The wave energy treatment is ultrasonic treatment, and the frequency of the ultrasonic wave is 80-200 Hz.

4. A method for delaying scaling of equipment wall in wet process phosphoric acid production according to any one of claims 1 to 3, It is characterized in that The device wall is also subjected to high-frequency oscillation to make the bottom layer of the fluid boundary layer at the device wall enter a high-intensity turbulent state.

5. A method for delaying scaling of equipment wall surfaces in a wet-process phosphoric acid production process according to claim 4, It is characterized in that The frequency of the high-frequency oscillation is 20-100 Hz, the oscillation interval is 10-30 minutes, and the oscillation time each time is 30-60 seconds.

6. A method for delaying scaling of equipment wall surfaces in a wet-process phosphoric acid production process according to claim 5, It is characterized in that The surface finish of the equipment wall is at least grade 7.

7. A method for delaying scaling of equipment wall surfaces in a wet-process phosphoric acid production process according to claim 1, 2, 3, 5 or 6, It is characterized in that When the phosphoric acid slurry is transported to the filtering equipment, the temperature is reduced by 8° C. or more.

8. A method for delaying scaling of equipment walls in a wet-process phosphoric acid production process according to claim 7, It is characterized in that In the super-exposure microbubbles, the ratio of gas phase to gas-liquid mixed phase is 2-6vt%, the mass ratio of gas-liquid mixed phase to phosphoric acid slurry is 1-10wt%; the average diameter of the super-exposure microbubbles is 20-80um.

9. A method for delaying scaling of equipment wall surfaces in a wet-process phosphoric acid production process according to claim 1, 2, 3, 5, 6 or 8, It is characterized in that The phosphoric acid slurry is cooled by combining super-exposure microbubble bursting with flash evaporation.

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