A wet-process phosphoric acid defluorination and silica recycling production unit

Abstract

This application discloses a wet-process phosphoric acid defluorination and silica recycling production device, comprising: a phosphate rock slurry treatment component, a phosphoric acid defluorination treatment component, and a silica recycling component; the phosphate rock slurry treatment component and the phosphoric acid defluorination treatment component are connected by pipelines; the silica conveying pipe of the silica recycling component is connected to the pipelines connecting the phosphate rock slurry treatment component and the phosphoric acid defluorination treatment component; the phosphoric acid defluorination treatment component includes: a flash chamber and a multi-stage series-connected fluorine circulation absorption tower; the phosphoric acid conveying pipe of the phosphate rock slurry treatment component is connected to the inlet pipe of the flash chamber; the outlet of the flash chamber is connected to the inlet pipe of the first-stage fluorine circulation absorption tower. By connecting the by-product silica storage tank to the dilute phosphoric acid conveying pipe, and using the by-product silica as a defluorinating agent in the impurity removal process of dilute phosphoric acid, effective defluorination of phosphoric acid is achieved, while effective recycling of the by-product silica is realized, avoiding the problem of direct accumulation of solid waste.

Description

Technical Field

[0001] This application relates to the field of phosphate rock defluorination technology, and in particular to a wet-process phosphate defluorination and silica recycling production device. Background Technology

[0002] Phosphate rock slurry, a fundamental raw material in the wet-process phosphoric acid production industry, contains calcium fluorophosphate and a small amount of calcium fluorosilicate. The associated fluorine resources have wide applications in many fields. Therefore, the efficient recovery of fluorine and silicon resources from phosphate rock has become an inevitable trend. Phosphate rock slurry contains approximately 3% fluorine, and the finished phosphoric acid obtained using the dihydrate wet-process phosphoric acid production process contains more than 1.5% fluorine, requiring further defluorination to achieve fluorine recovery and utilization.

[0003] The existing method involves separately defluorinating the obtained phosphoric acid, which not only increases the processing steps but also increases costs. The defluorinating agent also needs to be purchased or prepared separately, adding to the production process and reducing efficiency. Traditional phosphoric acid defluorination requires high-quality silica (specific surface area > 150m³). 2 It is used as a defluorinating agent, but the price of high-quality silica is about 4,000 yuan / ton, and a large amount of solid waste that needs to be treated separately will be generated after treatment.

[0004] In the wet-process phosphoric acid production, fluorine recovery mainly focuses on the phosphoric acid concentration and evaporation process. However, the fluorine escape rate in this process is low (<20%), resulting in most of the fluorine remaining in the concentrated phosphoric acid. The fluorine remaining in the phosphoric acid has a serious impact on subsequent production and processing, as well as the quality of downstream products.

[0005] The production of hydrogen fluoride using fluorosilicic acid (a byproduct of wet-process phosphoric acid production) and 98% concentrated sulfuric acid as raw materials generates SiO2 (a byproduct). This silica has problems such as poor product quality, high impurity content, high moisture content, low activity, and high viscosity. In current treatment, it can only be returned to phosphogypsum for storage, which wastes resources, aggravates phosphogypsum pollution, and increases the difficulty of subsequent disposal.

[0006] The information disclosed in the background section is intended only to enhance the understanding of the overall background of this utility model and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Utility Model Content

[0007] This application addresses the aforementioned technical problems by providing a wet-process phosphoric acid defluorination and silica recycling production device. By connecting a by-product silica storage tank to a dilute phosphoric acid conveying pipe, and adding the by-product silica as a defluorinating agent to the dilute phosphoric acid during the impurity removal process, effective defluorination of phosphoric acid is achieved, while simultaneously achieving effective recycling of the by-product silica, thus avoiding the problem of direct accumulation of solid waste.

[0008] This application provides a wet-process phosphoric acid defluorination and silica recycling production device, including: a phosphate rock slurry treatment component, a phosphoric acid defluorination treatment component, and a silica recycling component;

[0009] The phosphate rock slurry treatment unit and the phosphate defluorination treatment unit are connected by pipelines;

[0010] The silica recycling unit's silica delivery pipe is connected to the pipelines that connect the phosphate rock slurry treatment unit and the phosphoric acid defluorination treatment unit.

[0011] The phosphoric acid defluorination treatment assembly includes: a flash chamber and a multi-stage series-connected fluorine circulation absorption tower; the phosphoric acid delivery pipe of the phosphate rock slurry treatment assembly is connected to the feed inlet pipe of the flash chamber; the discharge outlet of the flash chamber is connected to the feed inlet pipe of the first-stage fluorine circulation absorption tower.

[0012] The silica recycling system includes: a silicon tetrafluoride reaction and concentration unit, a silica filter press; the fluorosilicic acid conveying pipes of each stage of the fluorine circulation absorption tower are connected to the inlet pipes of the silicon tetrafluoride reaction and concentration unit; the outlet of the silicon tetrafluoride reaction and concentration unit is connected to the inlet pipe of the silica filter press.

[0013] The outlet of the silica filter press is connected to the pipeline that connects to the phosphate rock slurry treatment unit and the phosphate defluorination treatment unit.

[0014] Preferably, the silica recycling assembly includes: a reaction absorption tower, a distillation tower, and a stripping tower.

[0015] The outlet of the silica filter press is connected to the inlet of the reaction absorption tower; the outlet of the reaction absorption tower is connected to the inlet of the distillation column; the outlet of the distillation column is connected to the inlet of the stripping column; and the outlet of the stripping column is connected to the inlet of the distillation column.

[0016] The fluorosilicic acid outlet of the reaction absorption tower is connected to the feed inlet pipeline of the silicon tetrafluoride reaction concentration unit.

[0017] Preferably, it includes: a concentrated sulfuric acid storage tank; the outlet of the concentrated sulfuric acid storage tank is connected to the inlet pipeline of the reaction absorption tower.

[0018] Preferably, the silica recycling component includes: a silica storage tank and a silica transfer pump; the silica storage tank is connected to the outlet pipeline of the silica filter press; a transfer pipe is installed on the outlet of the silica storage tank, and the extension end of the transfer pipe is connected to a pipeline that connects to the phosphate rock slurry treatment component and the phosphoric acid defluorination treatment component; and a silica transfer pump is installed on the transfer pipe.

[0019] Preferably, the phosphoric acid defluorination treatment component includes: a graphite heat exchanger; the inlet of the graphite heat exchanger is connected to the outlet pipeline of the phosphate rock slurry treatment component; and the outlet of the graphite heat exchanger is connected to the inlet pipeline of a multi-stage series-connected fluorine circulation absorption tower.

[0020] Preferably, the multi-stage series-connected fluorine circulation absorption tower includes: a flash chamber, a first fluorine absorption tower, a first fluorine absorption circulation tank, a fluorosilicic acid circulation pump, a second fluorine absorption circulation tank, and a second fluorine absorption tower;

[0021] The flash chamber is connected to the outlet pipe of the graphite heat exchanger; the gas outlet of the flash chamber is connected to the inlet pipe of the first fluorine absorption tower; the liquid outlet of the first fluorine absorption tower is connected to the pipeline of the first fluorine absorption circulation tank; the circulation port of the first fluorine absorption circulation tank is connected to the circulation port of the first fluorine absorption tower through a circulation pipe.

[0022] The outlet of the first fluorine absorption tower is connected to the inlet of the second fluorine absorption tower via a pipeline; the outlet of the second fluorine absorption tower is connected to the second fluorine absorption circulation tank via a pipeline; the circulation port of the second fluorine absorption circulation tank and the circulation port of the second fluorine absorption tower are connected via a circulation pipe.

[0023] The second fluorine absorption circulation tank is connected to the first fluorine absorption circulation tank, and the first fluorine absorption circulation tank is connected to the fluorosilicic acid inlet pipeline of the silicon tetrafluoride reaction concentration device.

[0024] Preferably, the multi-stage series-connected fluorine circulation absorption tower includes: a horizontal axial flow pump, a first fluorine circulation transfer pump, a second fluorine circulation transfer pump, and a fluorosilicic acid circulation pump; the horizontal axial flow pump is installed on the pipeline connecting the flash chamber and the finished phosphoric acid tank;

[0025] The first fluorine circulation pump is installed on the circulation pipe that connects the circulation port of the first fluorine absorption circulation tank to the circulation port of the first fluorine absorption tower.

[0026] The second fluorine circulation pump is installed on the circulation pipe connecting the circulation port of the second fluorine absorption circulation tank and the circulation port of the second fluorine absorption tower.

[0027] The fluorosilicic acid circulation pump is installed on the pipeline connecting the first fluorine absorption circulation tank, the second fluorine absorption circulation tank, and the silicon tetrafluoride reaction concentration device.

[0028] Preferably, the phosphate rock slurry treatment assembly includes: a phosphate rock slurry conveying pipe, a concentrated sulfuric acid storage tank, an extraction tank, and a disc filter; the concentrated sulfuric acid storage tank is connected to the extraction tank via pipeline; the phosphate rock slurry conveying pipe is connected to the extraction tank via pipeline; the outlet of the extraction tank is connected to the inlet of the disc filter via pipeline; and the outlet of the disc filter is connected to the phosphoric acid defluorination treatment assembly via pipeline.

[0029] Preferably, the sulfuric acid delivery pipe of the stripping tower is connected to the extraction tank pipeline.

[0030] Preferably, the phosphate rock slurry treatment assembly includes: a concentrated sulfuric acid transfer pump; the concentrated sulfuric acid transfer pump is installed on the pipeline connecting the concentrated sulfuric acid storage tank and the extraction tank.

[0031] The beneficial effects that this application can produce include:

[0032] 1) The wet-process phosphoric acid defluorination and silica recycling production apparatus provided in this application allows the byproduct silica to be used as a defluorinating agent. This silica is connected to the graphite heat exchanger inlet of the phosphoric acid concentration unit via pipeline, and is added to the phosphoric acid concentration process. This results in a fluorosilicic acid yield exceeding 10 kg / t P₂O₅ and a fluorine content in the finished phosphoric acid reduced to 40%. Simultaneously, this apparatus enables the effective utilization of waste generated from different processes, combining the use of byproducts from the phosphoric and fluorochemical processes to construct a closed-loop industrial chain, achieving synergistic optimization of efficient resource utilization and pollution reduction.

[0033] 2) The wet-process phosphoric acid defluorination and silica recycling production device provided in this application realizes the transformation of fluorine and silicon resources from waste to treasure and their recycling, improves the comprehensive utilization rate of resources, reduces the amount of by-product silica stockpiled, effectively reduces the fluorine content in the finished phosphoric acid, improves the quality of phosphoric acid, provides high-quality raw materials for downstream production, reduces the consumption of liquid alkali (NaOH) in the downstream ammonium dihydrogen phosphate production, and avoids the introduction of Na+ into downstream production. + This can lead to problems such as scaling in the system. Compared with the traditional use of high-quality white carbon black as a defluorinating agent, it has advantages such as simple process, convenient operation, strong system integration and low production cost. Attached Figure Description

[0034] Figure 1 A schematic diagram of a wet phosphoric acid defluorination and silica recycling production apparatus in at least one embodiment provided in this application;

[0035] Legend:

[0036] Concentrated sulfuric acid storage tank 116, concentrated sulfuric acid transfer pump 120, extraction tank 121, disc filter 122, extraction tank 121, graphite heat exchanger 123, flash evaporation chamber 124, horizontal axial flow pump 125, first fluorine absorption tower 126, first fluorine absorption circulation tank 127, first fluorine circulation transfer pump 128, fluorosilicic acid circulation pump 129, second fluorine absorption circulation tank 131, second fluorine circulation transfer pump 132, second fluorine absorption tower 130, silicon tetrafluoride reaction concentration device 110, silica filter press 111, silica storage tank 112, silica transfer pump 113, reaction absorption tower 114, distillation and rectification tower 115, stripping tower 117. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] Technical means not detailed in this application and not used to solve the technical problems of this application are all set according to common general knowledge in the field, and multiple common general knowledge setting methods can be implemented.

[0040] See Figure 1 The wet process phosphoric acid defluorination and silica recycling production apparatus provided in this application includes: concentrated sulfuric acid storage tank 116, extraction tank 121, disc filter 122, extraction tank 121, silicon tetrafluoride reaction concentration device 110, filter press 111, silica storage tank 112, reaction absorption tower 114, distillation column 115, and phosphoric acid treatment components.

[0041] The outlet of the concentrated sulfuric acid storage tank 116 is connected to the inlet of the extraction tank 121. The extraction tank 121 is also connected to the conveying pipe of the phosphate rock slurry. After the phosphate rock slurry and 98% concentrated sulfuric acid are mixed and reacted in the extraction tank 121, a mixture of phosphogypsum and dilute phosphoric acid is obtained. This mixture is then conveyed to the disc filter 122 through a pipeline. After being filtered by the disc filter 122, the phosphogypsum residue is transported to the slag yard for storage. The filtrate, with dilute phosphoric acid as the main component, is conveyed to the phosphoric acid treatment unit through a pipeline.

[0042] The phosphoric acid treatment assembly includes: a graphite heat exchanger 123, a flash chamber 124, a horizontal axial flow pump 125, a first fluorine absorption tower 126, a first fluorine absorption circulation tank 127, and a first fluorine circulation transfer pump 128. 15-20% dilute phosphoric acid is preheated by the graphite heat exchanger 123, and the outlet of the graphite heat exchanger 123 is connected to the inlet of the flash chamber 124. After continuous heating of the dilute phosphoric acid in the flash chamber 124, the water contained in the dilute phosphoric acid evaporates to form concentrated phosphoric acid with a concentration of 40-50%. The concentrated phosphoric acid is discharged into the finished acid tank for storage via the horizontal axial flow pump 125 located at the outlet.

[0043] The outlet of the flash chamber 124 is connected to the inlet pipe of the first fluorine absorption tower 126. The fluorosilicic acid contained in the vapor is absorbed by the first fluorine absorption tower 126 to form a solution, which then flows through the pipeline into the first fluorine absorption circulation tank 127, which is connected to the drain pipe of the first fluorine absorption tower 126 for storage. To improve absorption efficiency, one end of the circulation pipeline is connected to the circulation port pipeline of the first fluorine absorption tower 126, and the other end is connected to the first fluorine absorption circulation tank 127. A first fluorine circulation transfer pump 128 is installed on the circulation pipeline. When the fluorosilicic acid in the solution circulating to the first fluorine absorption circulation tank 127 meets the requirements (set according to specific production needs), it is connected to the silicon tetrafluoride reaction concentration device 110 through the pipeline. In the silicon tetrafluoride reaction concentration device 110, after the fluorosilicic acid is concentrated and reacted, the slurry enters the silica filter press 111. After pressure filtration, the resulting silica slurry enters the silica storage tank 112 for buffering. The outlet of the silica storage tank 112 is connected to the pipeline on the outlet of the disc filter 122, thereby entering the dilute phosphoric acid solution obtained by the disc filter 122, where it acts as a defluorinating agent.

[0044] The fluorosilicic acid solution processed by the silica filter press 111 enters the reaction absorption tower 114 for the separation of fluorosilicic acid and sulfuric acid. The outlet of the fluorinated dilute sulfuric acid in the reaction absorption tower 114 is connected to the pipeline of the distillation column 115. Steam is introduced into the heat exchange jacket of the distillation column 115 to separate hydrofluoric acid, fluorinated dilute sulfuric acid, and fluorine-containing gas in the distillation column 115. The product HF (>99.8%) is discharged from the outlet of the distillation column 115 to the product hydrofluoric acid storage tank. The outlet of the distillation column 115 is connected to the inlet pipeline of the stripping tower 117, and the fluorinated dilute sulfuric acid produced in the distillation column 115 is discharged into the stripping tower 117. After heating, the fluorinated dilute sulfuric acid is partially vaporized to form fluorine-containing gas. The outlet of the stripping tower 117 is connected to the inlet pipeline of the distillation column 115. The stripping tower 117 is equipped with a heat exchange jacket, and steam is introduced into the heat exchange jacket to provide heat for vaporization.

[0045] In one specific embodiment, the sulfuric acid outlet of the stripping tower 117 is connected to the extraction tank 121 for processing phosphate rock slurry via a pipeline, enabling the reuse of the 74% concentration dilute sulfuric acid generated after processing in the treatment of phosphate rock slurry. This avoids material waste, and since this portion of sulfuric acid has already undergone defluorination treatment, it avoids the reintroduction of fluorine, and also reduces production costs and the amount of concentrated sulfuric acid used.

[0046] In one specific embodiment, the phosphoric acid treatment assembly includes: a second fluorine absorption circulation tank 131, a second fluorine circulation pump 132, a second fluorine absorption tower 130, and a circulation pipe; the outlet of the first fluorine absorption tower 126 is connected to the pipeline of the second fluorine absorption tower 130; the fluorosilicic acid gas absorbed and treated by the first fluorine absorption tower 126 enters the second fluorine absorption tower 130 for circulating defluorination treatment; the second fluorine absorption circulation tank 131 is connected to the liquid outlet pipeline of the second fluorine absorption tower 130; one end of the circulation pipe is connected to the second fluorine absorption circulation tank 131, and the other end is connected to the circulating liquid inlet of the second fluorine absorption tower 130; the second fluorine circulation pump 132 is installed on the circulation pipe to realize the circulating treatment of the fluorosilicic acid absorbed by the second fluorine absorption tower 130, and the gas outlet at the top of the second fluorine absorption tower 130 meets the requirements for direct discharge into the atmosphere.

[0047] In one specific embodiment, the second fluorine absorption circulation tank 131 is connected to the silicon tetrafluoride reaction concentration device 110 via pipeline, thereby achieving effective reuse of this portion of fluorosilicic acid.

[0048] In one specific embodiment, the system includes: a fluorosilicic acid circulation pump 129 and a main pipe; one end of the main pipe is connected to a silicon tetrafluoride reaction concentration device 110, and the other end is connected to a second fluorine absorption circulation tank 131 and a first fluorine absorption circulation tank 127 respectively; the fluorosilicic acid circulation pump 129 is mounted on the main pipe.

[0049] In one specific embodiment, it includes: a concentrated sulfuric acid transfer pump 120; the concentrated sulfuric acid transfer pump 120 is installed on the pipeline connecting the outlet of the concentrated sulfuric acid storage tank 116 and the inlet of the extraction tank 121.

[0050] In one specific embodiment, the heat exchange medium introduced into the heat exchange jacket of the graphite heat exchanger 123 is low-pressure steam.

[0051] In one specific embodiment, the system includes a silica transfer pump 113. The silica transfer pump 113 is installed on a pipeline connecting the outlet of the silica storage tank 112 and the outlet of the disc filter 122. It is used to transfer silica slurry that can be reused as a defluorinating agent.

[0052] In one specific embodiment, the inlet of the reaction absorption tower 114 is connected to the concentrated sulfuric acid storage tank 116 via a pipeline. A portion of the concentrated sulfuric acid enters the reaction absorption tower 114 to absorb the fluorosilicic acid in the filtrate. The absorbed solution is then refluxed into the silicon tetrafluoride reaction concentration device 110 for further reaction and concentration, thereby achieving effective and complete separation of fluorosilicic acid and silicon dioxide. When fluorine-containing dilute sulfuric acid is obtained, it is then concentrated in the distillation column 115 to obtain high-concentration hydrofluoric acid.

[0053] I. The reaction principle of the reaction carried out in this device is as follows:

[0054] Fluorine in phosphate rock slurry exists mainly in two forms: Ca5F(PO4)3 and fluorosilicates. During the wet-process phosphoric acid production, the fluorine content in the finished acid is 65-80%, 15-30% is carried away by phosphogypsum, and 3-5% escapes into the gas phase. The reaction principle is as follows:

[0055] Ca5F(PO4)3+5H2SO4+10H2O=5CaSO4·2H2O+3H3PO4+HF↑

[0056] HF reacts with SiO2 to form H2SiF6, and some fluorosilicic acid decomposes upon heating to form SiF4 and HF.

[0057] H₂SiF₆=SiF₄+2HF (thermal decomposition) (1)

[0058] SiF4 + 2HF = H2SiF6 (2)

[0059] 6HF + SiO2 = H2SiF6 + H2O (3)

[0060] 2H2SiF6+SiO2=3SiF4↑+2H2O (4)

[0061] 3SiF4+(n+2)H2O=2H2SiF6+SiO2.nH2O(water washing absorption) (5)

[0062] Except for small amounts of SiF4 and HF escaping, most of the fluorine remains in the phosphoric acid and is difficult to separate from it. The phosphoric acid is indirectly heated by steam in a heat exchanger and then enters the flash chamber. While a large amount of water evaporates, the fluorides in the acid also decompose and escape into the water vapor, forming fluorine-containing gas. This fluorine-containing gas is recycled using a washing liquid. When the concentration of fluorosilicic acid in the circulating washing liquid reaches the required level, a portion is removed from the circulating liquid as a fluorosilicic acid product.

[0063] When fluorosilicic acid in phosphoric acid decomposes and escapes upon heating, the ratio of HF to SiF4 in the gas changes with the concentration of phosphoric acid. Since SiF4 is more easily volatilized from the system, after adding silicon dioxide to the system, the reaction proceeds according to reaction formulas (3), (4), and (1) to increase the overflow rate of fluorosilicic acid and silicon tetrafluoride. After absorption by water, fluorosilicic acid is generated.

[0064] II. This device uses silica, a byproduct, as a defluorinating agent, which has the following advantages:

[0065] 1. Impurity synergistic effect: By-product SiO2 contains about 10% encapsulated H2SiF6, which slowly releases HF under acidic conditions, forming "in-situ fluorine replenishment" and promoting the formation of SiF4.

[0066] 2. Mass transfer advantage: 5-10μm particles form porous aggregates in phosphoric acid, and the effective mass transfer area increases under enhanced stirring, making up for insufficient specific surface area.

[0067] 3. Cost advantage: The cost of using by-product SiO2 directly is negligible, while the cost of high-quality white carbon black is 4,000 yuan / ton, showing a clear cost advantage.

[0068] The performance comparison between existing defluorinating agents and recycled by-products is shown in the table below:

[0069] Table 1

[0070] <![CDATA[Specific surface area / (m 2 / g)]]> ≤10 150-380 Hydroxyl group density (mmol / g) 0.35 4.2～5.5 Fluorine content (%) 13.36 ＜0.1 <![CDATA[Bulk density / (kg / m 3 )]]> 850 200-300 Unit price (RMB / ton) Negligible 4000

[0071] III. Product Performance Comparison Experiment

[0072] Three groups of 500g dilute acid were prepared, including a blank control group, a group with SiO2 (a byproduct of hydrogen fluoride production by Wengfu Yuntianhua), and an experimental group with high-quality silica. The amount of SiO2 added was 5kg / tP2O, and the amount of high-quality silica was 3kg / tP2O5. The dilute acid with a P2O5 concentration of approximately 26% was concentrated to over 46-48%, and defluorination experiments were conducted under these concentration conditions, ensuring sufficient reaction time (6 hours) to simulate the forced circulation effect during phosphoric acid concentration in industrial trials. The experimental results are shown in the table below.

[0073] Table 2 (Comparative Data on Different Defluorinating Agents)

[0074]

[0075] Table 3 (Comprehensive comparison data using different defluorinating agents, dosages, and reaction times)

[0076]

[0077] As can be seen from Table 2, after 6 hours of concentration, the fluorine content of dilute acid without defluorination agent decreased from 1.93% to 1.62%, a reduction of 15.5%. However, after using defluorination agent, the reduction can be increased to more than 50%, and the effect is even better when using high-quality silica.

[0078] As can be seen from Table 3, the fluorine content decreases with the increase of the amount of high-quality silica defluorinating agent. The solid content is lower than that of silica without added 5 kg / t P2O5. With the increase of the amount of SiO2 by-product from Wengfu Yuntianhua, the fluorine content decreases. However, after the amount of Wengfu silica exceeds 10 kg / t P2O5, the decrease in fluorine content slows down. At the same time, the amount of solids produced is large and the viscosity increases.

[0079] In summary, using 3.0 kg / t P2O5 of high-quality silica increases the yield of fluorosilicic acid by 14.5 kg; using 5.0 kg / t P2O5 of Wengfu by-product SiO2 increases the yield of fluorosilicic acid by 16.6 kg / t P2O5.

[0080] (1) Without adding defluorinating agent, the phosphoric acid is concentrated to 46.0-48.0%, and the fluorine content is reduced from 1.93% to 1.62%;

[0081] (2) Adding a defluorinating agent helps fluorine escape, reduces the fluorine content of the finished product, and can effectively improve the fluorine escape rate;

[0082] (3) The higher the amount of silica added, the more the fluorine content is reduced. Taking into account the fluorine overflow rate, silica gel production, phosphoric acid solid content and defluorinating agent cost, the amount of high-quality silica added is 3 kg / tP2O5, the amount of by-product SiO2 added by Wengfu Yuntianhua (dry basis) is 5-7 kg / tP2O5, and the yield of fluorosilicic acid can be increased by more than 5 kg / tP2O5.

[0083] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wet-process phosphoric acid defluorination and silica recycling production apparatus, characterized in that, include: Phosphate rock slurry treatment unit, phosphoric acid defluorination treatment unit, silica recycling unit; The phosphate rock slurry treatment unit and the phosphate defluorination treatment unit are connected by pipelines; The silica recycling unit's silica delivery pipe is connected to the pipelines that connect the phosphate rock slurry treatment unit and the phosphoric acid defluorination treatment unit. The phosphoric acid defluorination treatment assembly includes: a flash chamber (124) and a multi-stage series fluorine circulation absorption tower; the phosphoric acid delivery pipe of the phosphate rock slurry treatment assembly is connected to the feed inlet pipe of the flash chamber (124); the discharge port of the flash chamber (124) is connected to the feed inlet pipe of the first-stage fluorine circulation absorption tower. The silica recycling assembly includes: a silicon tetrafluoride reaction concentration unit (110) and a silica filter press (111); the fluorosilicic acid conveying pipes of each stage of the fluorine circulation absorption tower are connected to the inlet pipe of the silicon tetrafluoride reaction concentration unit (110); the outlet of the silicon tetrafluoride reaction concentration unit (110) is connected to the inlet pipe of the silica filter press (111); The outlet of the silica filter press (111) is connected to the pipeline connecting the phosphate rock slurry treatment component and the phosphate defluorination treatment component.

2. The wet-process phosphoric acid defluorination and silica recycling production apparatus according to claim 1, characterized in that, The silica recycling system includes: a reaction absorption tower (114), a distillation and rectification tower (115), and a stripping tower (117); The outlet of the silica filter press (111) is connected to the inlet of the reaction absorption tower (114); the outlet of the reaction absorption tower (114) is connected to the inlet of the distillation column (115); the outlet of the distillation column (115) is connected to the inlet of the stripping column (117); and the outlet of the stripping column (117) is connected to the inlet of the distillation column (115). The fluorosilicic acid outlet of the reaction absorption tower (114) is connected to the feed inlet pipeline of the silicon tetrafluoride reaction concentration device (110).

3. The wet-process phosphoric acid defluorination and silica recycling production apparatus according to claim 2, characterized in that, include: Concentrated sulfuric acid storage tank (116); the outlet of the concentrated sulfuric acid storage tank (116) is connected to the inlet pipeline of the reaction absorption tower (114).

4. The wet-process phosphoric acid defluorination and silica recycling production apparatus according to claim 1, characterized in that, The silica recycling assembly includes: a silica storage tank (112) and a silica transfer pump (113); the silica storage tank (112) is connected to the outlet pipe of the silica filter press (111); a transfer pipe is installed on the outlet of the silica storage tank (112), and the extension end of the transfer pipe is connected to the pipeline of the phosphate rock slurry treatment assembly and the phosphoric acid defluorination treatment assembly; the silica transfer pump (113) is installed on the transfer pipe.

5. The wet-process phosphoric acid defluorination and silica recycling production apparatus according to claim 1, characterized in that, The phosphoric acid defluorination treatment component includes: a graphite heat exchanger (123); the inlet of the graphite heat exchanger (123) is connected to the outlet pipeline of the phosphate rock slurry treatment component; the outlet of the graphite heat exchanger (123) is connected to the inlet pipeline of a multi-stage series fluorine circulation absorption tower.

6. The wet-process phosphoric acid defluorination and silica recycling production apparatus according to claim 5, characterized in that, The multi-stage series-connected fluorine circulation absorption tower includes: a flash chamber (124), a first fluorine absorption tower (126), a first fluorine absorption circulation tank (127), a fluorosilicic acid circulation pump (129), a second fluorine absorption circulation tank (131), and a second fluorine absorption tower (130); The outlet pipe of the flash chamber (124) is connected to the outlet pipe of the graphite heat exchanger (123); the outlet of the flash chamber (124) is connected to the inlet pipe of the first fluorine absorption tower (126); the outlet of the first fluorine absorption tower (126) is connected to the pipe of the first fluorine absorption circulation tank (127); the circulation port of the first fluorine absorption circulation tank (127) is connected to the circulation port of the first fluorine absorption tower (126) through a circulation pipe; The outlet of the first fluorine absorption tower (126) is connected to the inlet of the second fluorine absorption tower (130) via a pipeline; the outlet of the second fluorine absorption tower (130) is connected to the second fluorine absorption circulation tank (131) via a pipeline; the circulation port of the second fluorine absorption circulation tank (131) and the circulation port of the second fluorine absorption tower (130) are connected by a circulation pipe. The second fluorine absorption circulation tank (131) is connected to the first fluorine absorption circulation tank (127), and the first fluorine absorption circulation tank (127) is connected to the fluorosilicic acid inlet pipeline of the silicon tetrafluoride reaction concentration device (110).

7. The wet-process phosphoric acid defluorination and silica reuse production apparatus according to claim 6, characterized by The multi-stage series fluorine circulation absorption tower includes: a horizontal axial flow pump (125), a first fluorine circulation transfer pump (128), a second fluorine circulation transfer pump (132), and a fluorosilicic acid circulation pump (129); the horizontal axial flow pump (125) is installed on the pipeline connecting the flash chamber (124) and the finished phosphoric acid tank; The first fluorine circulation pump (128) is installed on the circulation pipe that connects the circulation port of the first fluorine absorption circulation tank (127) and the circulation port of the first fluorine absorption tower (126); The second fluorine circulation pump (132) is installed on the circulation pipe that connects the circulation port of the second fluorine absorption circulation tank (131) and the circulation port of the second fluorine absorption tower (130). A fluorosilicic acid circulation pump (129) is installed on the pipeline connecting the first fluorine absorption circulation tank (127), the second fluorine absorption circulation tank (131), and the silicon tetrafluoride reaction concentration device (110).

8. The wet-process phosphoric acid defluorination and silica reuse production apparatus according to claim 2, characterized by The phosphate rock slurry treatment assembly includes: a phosphate rock slurry conveying pipe, a concentrated sulfuric acid storage tank (116), an extraction tank (121), and a disc filter (122); the concentrated sulfuric acid storage tank (116) is connected to the extraction tank (121) by pipeline; the phosphate rock slurry conveying pipe is connected to the extraction tank (121) by pipeline; the outlet of the extraction tank (121) is connected to the inlet of the disc filter (122) by pipeline; and the outlet of the disc filter (122) is connected to the phosphate defluorination treatment assembly by pipeline.

9. The wet-process phosphoric acid defluorination and silica recycling production apparatus according to claim 8, characterized in that, The sulfuric acid delivery pipe of the stripping tower (117) is connected to the pipeline of the extraction tank (121).

10. The wet-process phosphoric acid defluorination and silica recycling production apparatus according to claim 9, characterized in that, The phosphate rock slurry processing assembly includes: a concentrated sulfuric acid transfer pump (120); the concentrated sulfuric acid transfer pump (120) is installed on the pipeline connecting the concentrated sulfuric acid storage tank (116) and the extraction tank (121).

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