Industrial grade phosphoric acid post-treatment device

Abstract

The utility model provides a kind of industrial grade phosphoric acid post-treatment device, the device includes by pipeline sequentially communicating back extraction acid preheater, pre-concentration I effect component, pre-concentration II effect component, pre-concentration acid preheater, decoloring bleaching tower, defluorination tower, defluorination acid pump, final concentration component and product acid cooler;The defluorination tower top is communicated with pre-concentration I effect component, and defluorination steam from defluorination tower enters pre-concentration I effect component, provides heat source for pre-concentration;The defluorination tower bottom is equipped with steam air inlet, and bleaching acid after being handled by decoloring bleaching tower is sent to defluorination tower upper portion feed, and low-pressure steam entered in tower bottom in defluorination tower is fully contacted in tower, stripping removes fluorine in bleaching acid.The device can solve the existing purification phosphoric acid post-treatment concentration steam consumption, product fluorine content is slightly high, product acid concentration fluctuation is larger production system problem.

Description

Technical Field

[0001] This utility model relates to the field of phosphoric acid post-processing technology, and in particular to an industrial-grade phosphoric acid post-processing device. Background Technology

[0002] Phosphoric acid has a wide range of applications, spanning chemical, agricultural, food, pharmaceutical, and new energy fields. Based on raw material sources, process conditions, and product quality, phosphoric acid is mainly produced through two processes: thermal and wet processes. Thermal phosphoric acid produces higher purity and is an important raw material for the preparation of fine phosphates; however, its high input costs and energy consumption make it unaffordable for most companies. In contrast, wet-process phosphoric acid, with its advantages of low energy consumption and low cost, has gradually replaced the thermal process. By 2024, the capacity share of wet-process phosphoric acid had reached 76.5% (3.48 million tons / total capacity 4.55 million tons); this proportion is expected to further increase in 2025. Currently, energy consumption optimization in the wet-process phosphoric acid mainly focuses on the post-concentration processing stage.

[0003] Currently, energy consumption optimization in wet-process phosphoric acid mainly focuses on the post-concentration treatment stage. However, existing wet-process phosphoric acid post-treatment processes still have three shortcomings: firstly, the single-effect pre-concentration efficiency is low; secondly, the secondary steam generated during defluorination is only condensed through cooling circulating water, without coupling and reuse, resulting in energy waste; and thirdly, the bleaching unit is located at the end of the post-treatment process, making it difficult to stably control the product acid concentration. To address these issues, this application proposes a wet-process purified phosphoric acid post-treatment device. This device, by fully utilizing secondary steam, optimizing the bleaching unit layout, and improving the deep purification capacity for impurities such as fluorine, significantly reduces energy consumption while ensuring product quality. This will contribute to the long-term stable development of my country's phosphoric acid chemical industry. Utility Model Content

[0004] In view of this, this utility model proposes an industrial-grade phosphoric acid post-treatment device and method to solve the problems of existing purified phosphoric acid post-treatment concentration steam consumption, high product fluorine content, and large fluctuations in product acid concentration in production systems.

[0005] The technical solution of this utility model is implemented as follows: This utility model provides an industrial-grade phosphoric acid post-processing device, including a back-extraction acid preheater 1, a pre-concentration I-effect component 2, a pre-concentration II-effect component 3, a pre-concentration acid preheater 4, a decolorization and bleaching tower 5, a defluorination tower 6, a defluorination acid pump 7, a final concentration component 8, and a product acid cooler 9, which are connected in sequence by pipelines. The bottom of the defluorination tower 6 is provided with a steam inlet 61. The bleaching acid treated by the decolorization and bleaching tower 5 is fed to the upper part of the defluorination tower 6 and fully contacts the low-pressure steam entering from the bottom of the defluorination tower 6 to strip and remove fluorides from the bleaching acid. The top of the defluorination tower 6 is connected to the pre-concentration I-effect component 2. The defluorination secondary steam from the defluorination tower 6 enters the pre-concentration I-effect component 2 to provide a heat source for pre-concentration.

[0006] 35% back-extraction acid (containing 25% P2O5) from the outside is heated by back-extraction acid preheater 1 and then enters pre-concentration I-effect component 2 and pre-concentration II-effect component 3 for double-effect pre-concentration treatment. After treatment, the acid is preheated to a certain temperature by pre-concentration acid preheater 4 and then enters decolorization and bleaching tower 5 for decolorization and bleaching treatment. Then it enters defluorination tower 6 for defluorination treatment. After treatment, the acid is transported to final concentration component 8 by defluorination acid pump 7 for final concentration treatment. The final concentrated acid is cooled by product acid cooler 9 to obtain the final product.

[0007] The defluorinated secondary steam generated by the defluorination tower 6 enters the pre-concentration I-efficiency component 2 to provide a heat source for pre-concentration, which can reduce energy consumption.

[0008] Based on the above technical solutions, preferably, the pre-concentration first-effect component 2 includes a pre-concentration first-effect heater 201, a pre-concentration first-effect flash chamber 202, and a pre-concentration first-effect circulation pump 203 connected in sequence by circulation pipelines; the back-extraction acid preheater 1 is connected to the pre-concentration first-effect flash chamber 202 and the pre-concentration first-effect circulation pump 203 by pipelines; the pre-concentration first-effect flash chamber 202 is connected to the pre-concentration second-effect component 3; and the defluorination tower 6 is connected to the pre-concentration first-effect heater 201.

[0009] The pre-concentration first-effect flash evaporator 202, pre-concentration first-effect circulating pump 203, and pre-concentration first-effect heater 201 are circulated in that order. After the raw material back-extracted acid is pre-concentrated to a certain concentration, it enters the pre-concentration second-effect component 3.

[0010] Based on the above technical solutions, preferably, the pre-concentration II effect component 3 includes a pre-concentration II effect heater 301, a pre-concentration II effect flash chamber 302 and a pre-concentration II effect circulation pump 303 connected in sequence by circulation pipelines. The pipelines between the pre-concentration I effect flash chamber 202 and the pre-concentration II effect flash chamber 302 and the pre-concentration II effect circulation pump 303 are connected, and the pre-concentration II effect flash chamber 302 is connected to the pre-concentration acid preheater 4.

[0011] The pre-concentrated second-effect flash evaporation chamber 302, the pre-concentrated second-effect circulating pump 303, and the pre-concentrated second-effect heater 301 are circulated in sequence. After the acid concentration of the pre-concentrated acid reaches a certain level, the next step of decolorization treatment is carried out.

[0012] Based on the above technical solutions, preferably, the top of the pre-concentration I-effect flash evaporation chamber 202 is also connected to the pre-concentration II-effect heater 301 to provide a heat source for the pre-concentration II-effect component 3; the pre-concentration I-effect heater 201 is connected to the back-extraction acid preheater 1 to provide a heat source for the back-extraction acid preheater 1.

[0013] Based on the above technical solutions, preferably, it also includes a pre-concentrated acid tank 10 and a pre-concentrated acid pump 11, wherein the pre-concentrated acid tank 10 and the pre-concentrated acid pump 11 are sequentially arranged on the pipeline between the pre-concentrated II-effect flash evaporation chamber 302 and the pre-concentrated acid preheater 4.

[0014] The pre-concentrated acid pump 11 can control the acid flow rate entering the decolorization and bleaching tower 5, thereby achieving precise control of the reaction.

[0015] Based on the above technical solutions, preferably, the final concentration component 8 includes a final concentration heater 81, a final concentration flash chamber 82, and a final concentration circulation pump 83 connected in sequence by circulation pipelines; the final concentration flash chamber 82 is connected to the product acid cooler 9; and the defluorinated acid pump 7 is connected to the pipeline between the final concentration heater 81 and the final concentration flash chamber 82.

[0016] The acid is circulated in the order of final concentration flash chamber 82, final concentration circulation pump 83 and final concentration heater 81. After the acid concentration reaches a certain concentration, the next operation is carried out.

[0017] Based on the above technical solutions, preferably, it also includes a hydrogen peroxide tank 12 and a hydrogen peroxide metering pump 13. The hydrogen peroxide tank 12 and the hydrogen peroxide metering pump 13 are connected in sequence to the decolorization and bleaching tower 5 to provide the decolorization medium hydrogen peroxide to the decolorization and bleaching tower 5.

[0018] Based on the above technical solutions, preferably, a bleaching acid tank 14 and a bleaching acid pump 15 are sequentially provided on the pipeline between the decolorization and bleaching tower 5 and the defluorination tower 6. A bleaching gas-liquid separator 16 is provided at the top of the decolorization and bleaching tower 5. The bottom of the bleaching gas-liquid separator 16 is connected to the bleaching acid tank 14. A bleaching exhaust gas fan 17 is provided at the top of the bleaching gas-liquid separator 16.

[0019] The bleaching acid pump 15 can control the flow rate of bleaching acid entering the defluorination tower 6, and achieve flow ratio control with the low-pressure steam 61 entering from the bottom of the defluorination tower 6, thereby achieving precise control of the stripping defluorination effect. The tail gas at the top of the decolorizing bleaching tower 5 enters the bleaching gas-liquid separator 16. After gas-liquid separation, the gas is discharged through the bleaching tail gas fan 17, and the liquid flows into the bleaching acid tank 14.

[0020] Based on the above technical solutions, preferably, it also includes a pre-concentration condenser 18, a final concentration condenser 19, and a vacuum air-liquid separator 20; the pre-concentration condenser 18 is located at the top of the pre-concentration II-effect flash chamber 302, the final concentration condenser 19 is located at the top of the final concentration flash chamber 82, and the pre-concentration condenser 18, the final concentration condenser 19, and the vacuum air-liquid separator 20 are connected in sequence; the vacuum air-liquid separator 20 is equipped with a vacuum pump 21 at the top and an acidic condensate tank 22 at the bottom.

[0021] The back-extraction acid preheater 1 and the pre-concentration II effect heater 301 are both connected to the acidic condensate tank 22. The acidic condensate discharged from the back-extraction acid preheater 1 and the pre-concentration II effect heater 301 enters the acidic condensate tank 22 for buffering and is then pumped to the outside for recycling as washing water.

[0022] Based on the above technical solutions, preferably, it also includes a final concentrated acid tank 23 and a final concentrated acid pump 24, which are sequentially arranged on the pipeline between the final concentrated flash evaporation chamber 82 and the product acid cooler 9.

[0023] The industrial-grade phosphoric acid post-processing device of this invention has the following advantages over the prior art:

[0024] (1) This utility model improves the efficiency of pre-concentration by setting up a pre-concentration I-effect component and a pre-concentration II-effect component for double-effect concentration, and uses the secondary steam generated in defluorination as the heat source for pre-concentration, thus realizing the recovery and utilization of secondary steam; in addition, bleaching is set before defluorination, making full use of the high temperature heat source of bleaching acid itself. The bleaching acid after decolorization and bleaching is fed to the upper part of the defluorination tower, and fully contacts the low-pressure steam entering from the bottom of the defluorination tower in the tower, stripping and removing the fluoride in the bleaching acid, thus achieving the expected defluorination effect. The defluorinated acid is finally sent to the final concentration, and by controlling the system vacuum degree and flash chamber acid temperature, 85% phosphoric acid product is obtained.

[0025] (2) The device of this utility model has the characteristics of low energy consumption, high product quality, and stable and controllable product acid concentration, and has the advantages of energy saving and high efficiency. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a structural diagram of the industrial-grade phosphoric acid post-treatment device of this utility model.

[0028] In the diagram, 1-back-extraction acid preheater, 2-pre-concentration I-effect assembly (201-pre-concentration I-effect heater, 202-pre-concentration I-effect flash chamber, 203-pre-concentration I-effect circulation pump), 3-pre-concentration II-effect assembly (301-pre-concentration II-effect heater, 302-pre-concentration II-effect flash chamber, 303-pre-concentration II-effect circulation pump), 4-pre-concentrated acid preheater, 5-decolorization and bleaching tower, 6-defluorination tower, 61-steam inlet, 7-defluorination acid pump, 8-final concentration assembly (81-final concentration heater, 8...). 2-Final Concentration Flash Chamber, 83-Final Concentration Circulation Pump, 9-Product Acid Cooler, 10-Pre-Concentrated Acid Tank, 11-Pre-Concentrated Acid Pump, 12-Hydrogen Peroxide Tank, 13-Hydrogen Peroxide Metering Pump, 14-Bleaching Acid Tank, 15-Bleaching Acid Pump, 16-Bleaching Gas-Liquid Separator, 17-Bleaching Tail Gas Fan, 18-Pre-Concentration Condenser, 19-Final Concentration Condenser, 20-Vacuum Gas-Liquid Separator, 21-Vacuum Pump, 22-Acidic Condensate Tank, 23-Final Concentrated Acid Tank, 24-Final Concentrated Acid Pump. Detailed Implementation

[0029] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0030] In the description of this utility model, it should be understood that the orientation or positional relationship indicated by terms such as "top" and "bottom" is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of description, and does not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation.

[0031] As shown in the figure, this utility model provides an industrial-grade phosphoric acid post-processing device, which includes a back-extraction acid preheater 1, a pre-concentration I-effect component 2, a pre-concentration II-effect component 3, a pre-concentration acid preheater 4, a decolorization and bleaching tower 5, a defluorination tower 6, a defluorination acid pump 7, a final concentration component 8, and a product acid cooler 9. The bottom of the defluorination tower 6 is provided with a steam inlet 61.

[0032] The back-extraction acid preheater 1, pre-concentration I-effect component 2, pre-concentration II-effect component 3, pre-concentrated acid preheater 4, decolorization and bleaching tower 5, defluorination tower 6, defluorinated acid pump 7, final concentration component 8, and product acid cooler 9 are connected sequentially via pipelines. The top of the defluorination tower 6 is connected to the pre-concentration I-effect component 2, and the defluorination secondary steam from the defluorination tower 6 enters the pre-concentration I-effect component 2 to provide a heat source for the pre-concentration I-effect.

[0033] The 35% phosphoric acid back-extraction acid is heated to a certain temperature by the back-extraction acid preheater 1, and then pre-concentrated by the pre-concentration I-effect component 2. After the acid concentration reaches a certain level, it enters the pre-concentration II-effect component 3 for secondary pre-concentration. After the acid concentration reaches a certain level, it is heated by the pre-concentration acid preheater 4 and enters from the bottom of the decolorization and bleaching tower 5. It is fully mixed with the hydrogen peroxide entering from the bottom of the decolorization and bleaching tower 5 and then overflows from the upper side of the decolorization and bleaching tower 5. It is then pumped to the upper part of the defluorination tower 6. The incoming material and the low-pressure steam entering from the bottom of the defluorination tower 6 are fully contacted and stripped to remove the fluoride from the bleaching acid. Then it is discharged from the bottom of the defluorination tower 6 and transported to the final concentration component 8 by the defluorination acid pump 7 for final concentration. The treated acid is cooled by the product acid cooler 9 and then discharged.

[0034] Specifically, the components of the pre-concentration I-effect component 2, the pre-concentration II-effect component 3, and the final concentration component 8 are the same, all including a heater, a flash chamber, and a circulation pump.

[0035] The pre-concentration first-effect component 2 includes a pre-concentration first-effect heater 201, a pre-concentration first-effect flash chamber 202, and a pre-concentration first-effect circulation pump 203. The inlet of the pre-concentration first-effect heater 201 is connected to the outlet of the pre-concentration first-effect circulation pump 203, the outlet of the pre-concentration first-effect heater 201 is connected to the inlet of the pre-concentration first-effect flash chamber 202, and the bottom outlet of the pre-concentration first-effect flash chamber 202 is connected to the inlet of the pre-concentration first-effect circulation pump 203.

[0036] Specifically, the pre-concentration II effect component 3 includes a pre-concentration II effect heater 301, a pre-concentration II effect flash chamber 302, and a pre-concentration II effect circulating pump 303. The inlet of the pre-concentration II effect heater 301 is connected to the outlet of the pre-concentration II effect circulating pump 303, the outlet of the pre-concentration II effect heater 301 is connected to the inlet of the pre-concentration II effect flash chamber 302, and the bottom outlet of the pre-concentration II effect flash chamber 302 is connected to the inlet of the pre-concentration II effect circulating pump 303.

[0037] Specifically, the discharge port on the side of the pre-concentration I-effect flash chamber 202 is connected to the pipeline between the pre-concentration II-effect flash chamber 302 and the pre-concentration II-effect circulating pump 303, thereby connecting the pre-concentration I-effect component 2 and the pre-concentration II-effect component 3.

[0038] Specifically, the side outlet of the pre-concentration II flash evaporation chamber 302 is connected to the inlet of the pre-concentration acid preheater 4, and the outlet of the pre-concentration acid preheater 4 is connected to the inlet at the bottom of the decolorization and bleaching tower 5.

[0039] Specifically, a pre-concentrated acid tank 10 and a pre-concentrated acid pump 11 are sequentially installed on the pipeline between the pre-concentrated second-effect flash evaporation chamber 302 and the pre-concentrated acid preheater 4. The treated acid is first injected into the pre-concentrated acid tank 10, and then transported to the pre-concentrated acid preheater 4 by the pre-concentrated acid pump 11. The purpose of setting up the pre-concentrated acid pump 11 is to control the acid flow rate.

[0040] Specifically, the bottom of the decolorizing and bleaching tower 5 is connected in sequence to a hydrogen peroxide metering pump 13 and a hydrogen peroxide tank 12. The hydrogen peroxide metering pump 13 pumps the hydrogen peroxide in the hydrogen peroxide tank 12 to the decolorizing and bleaching tower 5 in a quantitative control, so as to provide the decolorizing medium hydrogen peroxide for the decolorizing and bleaching tower 5.

[0041] Specifically, a bleaching acid tank 14 and a bleaching acid pump 15 are sequentially installed on the pipeline between the decolorization and bleaching tower 5 and the defluorination tower 6. The acid that has undergone decolorization and bleaching treatment is discharged from the top of the decolorization and bleaching tower 5 and enters the bleaching acid tank 14. Then, under the action of the bleaching acid pump 15, it enters the top of the defluorination tower 6.

[0042] Specifically, the top of the decolorization and bleaching tower 5 is connected to the bleaching gas-liquid separator 16, the bottom of the bleaching gas-liquid separator 16 is connected to the bleaching acid tank 14, and the top of the bleaching gas-liquid separator 16 is equipped with a bleaching exhaust gas fan 17 for discharging exhaust gas.

[0043] Specifically, the top of the defluorination tower 6 is connected to the pre-concentration first-effect heater 201, providing a heat source for the pre-concentration first-effect assembly 2. The top of the pre-concentration first-effect flash chamber 202 is also connected to the pre-concentration second-effect heater 301, providing a heat source for the pre-concentration second-effect assembly 3. The pre-concentration first-effect heater 201 is connected to the back-extraction acid preheater 1, thereby providing a heat source for the back-extraction acid preheater 1. The above connections / connections achieve the effect of saving energy consumption.

[0044] Specifically, the outlet of the defluorinated acid pump 7 is connected to the pipeline between the final concentration heater 81 and the final concentration flash chamber 82. The defluorinated acid enters the final concentration assembly 8. The final concentration assembly 8 includes the final concentration heater 81, the final concentration flash chamber 82, and the final concentration circulation pump 83. The inlet of the final concentration heater 81 is connected to the outlet of the final concentration circulation pump 83, and the outlet of the final concentration heater 81 is connected to the inlet of the final concentration flash chamber 82. The bottom outlet of the final concentration flash chamber 82 is connected to the inlet of the final concentration circulation pump 83. The side outlet of the final concentration flash chamber 82 is connected to the inlet of the product acid cooler 9. After final concentration, when the acidity reaches a certain range, it flows through the final concentration flash chamber 82 into the product acid cooler 9 for cooling.

[0045] Specifically, a final concentrated acid tank 23 and a final concentrated acid pump 24 are sequentially installed on the pipeline between the final concentrated flash evaporation chamber 82 and the product acid cooler 9. The acid after final concentration first flows into the final concentrated acid tank 23 and is then pumped to the product acid cooler 9 by the final concentrated acid pump 24 at a certain flow rate.

[0046] Specifically, it also includes a vacuum air-liquid separator 20, a pre-concentration condenser 18 connected to the top of the pre-concentration II-effect flash chamber 302, and a final concentration condenser 19 connected to the top of the final concentration flash chamber 82. The pre-concentration condenser 18, the final concentration condenser 19, and the vacuum air-liquid separator 20 are connected in sequence. The vacuum air-liquid separator 20 is equipped with a vacuum pump 21 at the top and an acidic condensate tank 22 at the bottom. The acidic water separated by the above-mentioned gas-liquid separation is recycled and reused. The vacuum non-condensable gas is transported to the exhaust gas scrubbing system for further treatment via the vacuum pump 21.

[0047] The back-extraction acid preheater 1 and the pre-concentration II effect heater 301 are both connected to the acidic condensate tank 22. The acidic condensate discharged from the back-extraction acid preheater 1 and the pre-concentration II effect heater 301 enters the acidic condensate tank 22 for buffering and is then pumped to the outside for recycling as washing water.

[0048] The apparatus of this invention is used for the post-processing of industrial-grade phosphoric acid: Back-extracted acid with a phosphoric acid concentration of 35% is used as raw material. Using defluorination secondary steam as a heat source, it is pre-concentrated to 75% through a double-effect process. The 75% pre-concentrated acid is then decolorized and bleached before entering a defluorination tower for defluorination. The defluorinated acid is then finally concentrated to 85% of the final product acid. The fluorine content, TOC, and color of the final product acid meet the requirements for food-grade phosphoric acid. The specific process flow is as follows:

[0049] (1) Dual-effect pre-concentration

[0050] The 50°C back-extraction acid (35% H3PO4, all acid concentrations below are calculated as H3PO4) from outside the boundary is heated to 65°C through heat exchange between the back-extraction acid preheater 1 and the defluorinated acidic condensate from the pre-concentration I-effect heater 201. It then enters the pre-concentration I-effect circulating pump 203 inlet of the pre-concentration I-effect component 2, where it is forcibly circulated and heated by the external heater of the pre-concentration I-effect flash chamber 202 (the heat source for the pre-concentration I-effect heater 201 comes from the secondary defluorination steam at the top of defluorination tower 6) and concentrated. The concentrated 47% back-extraction acid overflows from the pre-concentration I-effect flash chamber 202 to the pre-concentration II-effect circulating pump 203 inlet of the pre-concentration II-effect component 3, where it is forcibly circulated and heated by the external heater of the pre-concentration II-effect flash chamber 302. (The heat source for the pre-concentration II effect heater 301 comes from the secondary steam in the pre-concentration I effect flash chamber 202.) Evaporation and concentration are performed, and the concentration of the pre-concentrated acid reaches 75%. The acid overflows from the pre-concentration II effect flash chamber 302 to the pre-concentration acid tank 10 for buffering. The vacuum degree of the pre-concentration II effect flash chamber 302 is controlled at 90 kPa. The secondary steam from the pre-concentration II effect flash chamber 302 undergoes direct heat exchange and condensation with the acidic circulating water in the pre-concentration condenser 18. The vacuum non-condensable gas exiting from the top of the pre-concentration condenser 18 is separated from the entrained acidic water by the vacuum air-liquid separator 16. The vacuum non-condensable gas is then evacuated by the vacuum pump 17 and discharged to the external tail gas scrubbing system for washing and compliant discharge. The acidic circulating water return from the bottom of the pre-concentration condenser 18 flows by gravity to the external acidic circulating water station for cooling and recycling.

[0051] (2) Decolorization and bleaching

[0052] The pre-concentrated acid from the pre-concentrated acid tank 10 is pumped by the pre-concentrated acid pump 11 to the pre-concentrated acid preheater 4. After being heated to 125°C by low-pressure steam, it enters the decolorization and bleaching tower 5. At this time, 27.5% hydrogen peroxide from the hydrogen peroxide tank 12 enters the decolorization and bleaching tower 5 through the hydrogen peroxide metering pump 13 with proportional control of the hydrogen peroxide flow rate. The organic matter in the pre-concentrated acid is removed by the quantitative addition of hydrogen peroxide. The tail gas from the top of the decolorization and bleaching tower 5 enters the bleaching gas-liquid separator 16, where the acidic liquid entrained in the bleaching tail gas is separated. Then, it is transported by the bleaching tail gas fan 17 to the external tail gas scrubbing system for washing and discharge after meeting emission standards. The pre-concentrated acid after decolorization and bleaching overflows from the top of the decolorization and bleaching tower 5 into the bleaching acid tank 14 for buffering. By adjusting the amount of hydrogen peroxide added to the bleaching tower, the total organic carbon (TOC) in the bleaching acid is controlled below 50 ppm, and the color is less than 16 black.

[0053] (3) Defluorination

[0054] Bleaching acid from bleaching acid tank 14 is fed to the upper part of defluorination tower 6 via bleaching acid pump 15. It comes into full contact with the low-pressure steam entering from the bottom of defluorination tower 6 and strips off the fluorides in the bleaching acid. The defluorination secondary steam from the top of defluorination tower 6 is connected to the pre-concentration first-effect heater 201 as the heat source for heating, evaporating and concentrating the pre-concentration first-effect flash chamber 202, so as to realize the recovery and utilization of defluorination secondary steam. The fluorine content (calculated as F) in the defluorinated acid after stripping at the bottom of defluorination tower 6 is controlled below 8 ppm.

[0055] (4) Final concentration

[0056] The defluorinated acid at the bottom of the defluorination tower 6 is pumped by the defluorinated acid pump 7 to the outlet of the final concentration heater 81 and enters the final concentration assembly 8. It then enters the final concentration flash chamber 82, where it is circulated and heated by the final concentration circulation pump 83 and the final concentration heater 81, resulting in 85% final concentrated acid. The acid overflows from the final concentration flash chamber 82 to the final concentrated acid tank 23 for buffering, and is then pumped by the final concentrated acid pump 24 to the product acid cooler 9 for cooling before being stored in the off-site product acid tank area. The vacuum degree of the final concentration flash chamber 82 is controlled at 90 kPa. The secondary steam at the top of its evaporation chamber is condensed by direct heat exchange with the acidic circulating water in the final concentration condenser 19. The vacuum non-condensable gas exiting the top of the condenser is separated from the entrained acidic water by the vacuum air-liquid separator 20. The vacuum non-condensable gas is then evacuated by the vacuum pump 21 and discharged to the off-site tail gas scrubbing system for washing and compliant discharge. The acidic circulating water at the bottom of the final concentration condenser 19 flows by gravity to the off-site acidic circulating water station for cooling and recycling. The acidic condensate discharged from the vacuum air-liquid separator 20, the back-extraction acid preheater 201, and the pre-concentration II-effect heater 301 enters the acidic condensate tank 22 for buffering and is then pumped to the outside for recycling as washing water.

[0057] This invention employs a double-effect pre-concentration process using defluorination secondary steam, hydrogen peroxide decolorization and bleaching, steam stripping defluorination, and final concentration to obtain a phosphoric acid product with a fluorine content (calculated as F) of 5-9 ppm, a total organic carbon (TOC) of 30-55 ppm, and a color of 15-20 black. The three post-processing indicators meet the standard requirements of GB1886.304-2020, "Food Additive Phosphoric Acid (Wet Process)".

[0058] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An industrial-grade phosphoric acid post-processing device, characterized in that: It includes a back-extraction acid preheater (1), a pre-concentration I-effect component (2), a pre-concentration II-effect component (3), a pre-concentration acid preheater (4), a decolorization and bleaching tower (5), a defluorination tower (6), a defluorination acid pump (7), a final concentration component (8), and a product acid cooler (9) connected in sequence by pipelines. The top of the defluorination tower (6) is connected to the pre-concentration I-effect component (2), and the defluorination steam from the defluorination tower (6) enters the pre-concentration I-effect component (2) to provide a heat source for pre-concentration; The bottom of the defluorination tower (6) is provided with a steam inlet (61). The bleaching acid treated by the decolorization and bleaching tower (5) is fed to the upper part of the defluorination tower (6) and fully contacts the low-pressure steam entering from the bottom of the defluorination tower (6) to strip and remove the fluoride in the bleaching acid.

2. The industrial-grade phosphoric acid post-processing device as described in claim 1, characterized in that: The pre-concentration I-effect component (2) includes a pre-concentration I-effect heater (201), a pre-concentration I-effect flash chamber (202), and a pre-concentration I-effect circulation pump (203) connected in sequence by circulation pipelines. The pipeline connecting the back-extraction acid preheater (1) with the pre-concentration I-effect flash evaporation chamber (202) and the pre-concentration I-effect circulating pump (203) is connected; The pre-concentration I-effect flash evaporation chamber (202) is connected to the pre-concentration II-effect component (3); The defluorination tower (6) is connected to the pre-concentration I-efficiency heater (201).

3. The industrial-grade phosphoric acid post-processing device as described in claim 2, characterized in that: The pre-concentration II effect component (3) includes a pre-concentration II effect heater (301), a pre-concentration II effect flash chamber (302), and a pre-concentration II effect circulation pump (303) connected in sequence by circulation pipelines. The pipelines connecting the pre-concentration I-effect flash evaporation chamber (202) with the pre-concentration II-effect flash evaporation chamber (302) and the pre-concentration II-effect circulating pump (303) are connected; The pre-concentration II-effect flash evaporation chamber (302) is connected to the pre-concentration acid preheater (4).

4. The industrial-grade phosphoric acid post-processing device as described in claim 3, characterized in that: The pre-concentration I-effect flash chamber (202) is also connected to the pre-concentration II-effect heater (301) to provide a heat source for the pre-concentration II-effect component (3); The pre-concentration I-effect heater (201) is connected to the back-extraction acid preheater (1).

5. The industrial-grade phosphoric acid post-processing device as described in claim 3, characterized in that: It also includes a pre-concentrated acid tank (10) and a pre-concentrated acid pump (11). The pre-concentrated acid tank (10) and the pre-concentrated acid pump (11) are sequentially installed on the pipeline between the pre-concentrated II-effect flash evaporation chamber (302) and the pre-concentrated acid preheater (4).

6. The industrial-grade phosphoric acid post-processing device as described in claim 3, characterized in that: The final concentration assembly (8) includes a final concentration heater (81), a final concentration flash chamber (82), and a final concentration circulation pump (83) connected in sequence by circulation pipelines. The final concentration flash chamber (82) is connected to the product acid cooler (9); The defluorinated acid pump (7) is connected to the pipeline between the final concentration heater (81) and the final concentration flash chamber (82).

7. An industrial-grade phosphoric acid post-processing device as described in claim 6, characterized in that: It also includes a hydrogen peroxide tank (12) and a hydrogen peroxide metering pump (13). The hydrogen peroxide tank (12), the hydrogen peroxide metering pump (13) and the decolorizing and bleaching tower (5) are connected in sequence to provide the decolorizing medium hydrogen peroxide to the decolorizing and bleaching tower (5).

8. An industrial-grade phosphoric acid post-processing device as described in claim 6, characterized in that: The pipeline between the decolorization bleaching tower (5) and the defluorination tower (6) is provided with a bleaching acid tank (14) and a bleaching acid pump (15) in sequence. The bleaching tower (5) is equipped with a bleaching gas-liquid separator (16) at the top. The bottom of the bleaching gas-liquid separator (16) is connected to the bleaching acid tank (14). The top of the bleaching gas-liquid separator (16) is equipped with a bleaching exhaust gas fan (17).

9. An industrial-grade phosphoric acid post-processing device as described in claim 6, characterized in that: It also includes a pre-concentration condenser (18), a final concentration condenser (19), and a vacuum air-liquid separator (20). The pre-concentration condenser (18) is located at the top of the pre-concentration II-effect flash chamber (302), and the final concentration condenser (19) is located at the top of the final concentration flash chamber (82); the pre-concentration condenser (18), the final concentration condenser (19), and the vacuum air-liquid separator (20) are connected in sequence. The vacuum air-liquid separator (20) is equipped with a vacuum pump (21) at the top and an acidic condensate tank (22) at the bottom.

10. An industrial-grade phosphoric acid post-processing device as described in claim 6, characterized in that: It also includes a final concentrated acid tank (23) and a final concentrated acid pump (24), which are sequentially arranged on the pipeline between the final concentrated flash chamber (82) and the product acid cooler (9).

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