A wet phosphoric acid purification and arsenic removal system, arsenic removal process and its application

Abstract

This invention discloses a wet-process phosphoric acid purification and arsenic removal system, arsenic removal process, and its application, relating to the field of wet-process phosphoric acid purification and impurity removal technology. The system includes a phosphoric acid feed tank, a Venturi jet reactor, a tubular scrubbing absorber, a reaction washing and ripening tank, and a hydrogen sulfide reactor connected in sequence. The hydrogen sulfide reactor is also connected to the Venturi jet reactor. An arsenic removal filter assembly is connected to the reaction washing and ripening tank, and this filter assembly is connected to the phosphoric acid feed tank. A purification and arsenic removal process and its application are also provided. The system has a compact design, reasonable layout, simple equipment structure, and low operation difficulty, effectively reducing the addition of sodium sulfide. The system is in a closed state, effectively controlling the safety risk of hydrogen sulfide leakage, resulting in high safety; the impurity removal efficiency is high. This solves the problem of existing arsenic removal systems having a large amount of sodium sulfide added, which easily leads to hydrogen sulfide leakage and low safety.

Description

Technical Field

[0001] This invention relates to the field of wet phosphoric acid purification and impurity removal technology, specifically a wet phosphoric acid purification and arsenic removal system, arsenic removal process, and its application. Background Technology

[0002] Solvent extraction is a common method for the purification of wet-process phosphoric acid. Fertilizer-grade wet-process phosphoric acid is purified by extraction to remove harmful impurities, yielding food-grade phosphoric acid. Food-grade phosphoric acid has strict requirements regarding the content of arsenic impurities; the current national standard (GB1886.304-2020) requires that the arsenic content in food-grade phosphoric acid be less than 0.5 ppm.

[0003] The current method for removing arsenic involves pretreatment at the front end of a wet phosphoric acid purification unit. Sodium sulfide is added to the phosphoric acid and reacts with the arsenic in the phosphoric acid to produce a precipitate. After filtration and separation, the precipitate is filtered to remove the acid and then enters the subsequent extraction and purification process, where sodium sulfide is added again for further arsenic removal.

[0004] This process involves adding sodium sulfide in the pretreatment and extraction purification stages, generating a large amount of hydrogen sulfide. This poses a risk of hydrogen sulfide leakage and poisoning in the affected area, increasing the difficulty of safety management. Furthermore, this method results in a lengthy arsenic removal process, and the inability to promptly report arsenic level control and analysis results leads to significant challenges in arsenic level control, prolonged adjustment times, and instances where food-grade phosphoric acid products fail to meet standards. Summary of the Invention

[0005] In order to overcome the deficiencies in the prior art, the present invention provides a wet phosphoric acid purification and arsenic removal system, arsenic removal process and its application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a wet phosphoric acid purification and arsenic removal system, the system comprising, in sequence, a phosphoric acid feed tank, a Venturi jet reactor, a tubular scrubbing absorber, a reaction scrubbing and ripening tank, and a hydrogen sulfide reactor, wherein the hydrogen sulfide reactor is also connected to the Venturi jet reactor; the reaction scrubbing and ripening tank is connected to an arsenic removal filter assembly, which is connected to the phosphoric acid feed tank.

[0008] Furthermore, the arsenic removal filtration assembly includes an arsenic removal filtration conveying pump, a precision filtration circulation pump, a precision filter, and a product acid clearing tank connected in sequence. The precision filter is also connected to an arsenic slag concentrate tank, and the outlet end of the arsenic slag concentrate tank is connected to a plate and frame filter press. The outlet end of the plate and frame filter press is connected to the phosphoric acid raw material tank.

[0009] Furthermore, the outlet end of the precision filter is also connected to the precision filter circulation pump.

[0010] Furthermore, an arsenic slag concentrate tank is connected to the plate and frame filter press via an arsenic slag concentrate delivery pump.

[0011] Furthermore, a phosphoric acid feedstock transfer pump is connected between the phosphoric acid feedstock tank and the Venturi jet reactor.

[0012] Furthermore, a reaction washing circulation pump is connected between the tubular washing absorber and the reaction washing maturation tank.

[0013] Secondly, the present invention provides a purification and arsenic removal process, comprising the following steps:

[0014] The raw acid from the phosphoric acid feed tank is fed into the Venturi jet reactor, and the hydrogen sulfide reactor is turned on to send hydrogen sulfide into the Venturi jet reactor for reaction.

[0015] The material after the reaction in the Venturi jet reactor is sequentially passed through a tubular washing absorber, a reaction washing and maturation tank for washing, reaction, and maturation to obtain solid arsenic sulfide precipitate. Excess unreacted hydrogen sulfide gas in the reaction washing and maturation tank is returned to the hydrogen sulfide reactor.

[0016] The phosphoric acid solution containing impurities after the reaction in the reaction washing and ripening tank is introduced into the arsenic removal and filtration assembly for arsenic removal and impurity removal. The purified phosphoric acid solution is then returned to the phosphoric acid raw material tank, and the removed impurities are discharged and collected.

[0017] Furthermore, the arsenic removal filtration assembly performs arsenic removal by including the following steps:

[0018] The phosphoric acid solution containing impurities is transported to a precision filter through an arsenic removal filtration pump for filtration. After filtration, the solution is introduced into the product acid clearing tank, and the arsenic slag concentrate obtained by filtration is discharged into the arsenic slag concentrate tank.

[0019] The arsenic slag concentrate in the arsenic slag concentrate tank is transported to a plate and frame filter press for filtration and pressing via an arsenic slag concentrate transfer pump. The filtered phosphoric acid solution is sent back to the phosphoric acid raw material tank, while the filtered solid arsenic slag is discharged and collected.

[0020] Thirdly, the present invention provides an application of a purification and arsenic removal process in the purification and impurity removal of wet phosphoric acid.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention provides a wet phosphoric acid purification and arsenic removal system. The system features a compact design, reasonable layout, simple equipment structure, and low operational difficulty. It effectively reduces the addition of sodium sulfide, and the entire system is in a closed state, effectively controlling or reducing the safety risk of hydrogen sulfide leakage, thereby greatly improving system safety. The addition of an arsenic removal reaction system and an arsenic slag filtration system results in high impurity removal efficiency. It solves the problem of existing arsenic removal systems having a large amount of sodium sulfide added, leading to easy hydrogen sulfide leakage and low safety.

[0023] 2. The purification and arsenic removal process provided by this invention eliminates and replaces the pre-process treatment in wet phosphoric acid arsenic removal, resulting in less environmental pollution, higher safety, and improved reliability and stability. Furthermore, the process flow is short, the arsenic removal reaction is efficient, process parameters can be adjusted quickly, and product quality is stable. It solves the problems of existing processes requiring the addition of sodium sulfide, which easily leads to hydrogen sulfide leakage, and the complexity and difficulty in flexibly controlling arsenic levels.

[0024] 3. The purification and arsenic removal process provided by this invention has a wide range of applications and advantages. Attached Figure Description

[0025] Figure 1 The present invention provides a schematic diagram of a wet phosphoric acid purification and arsenic removal system.

[0026] Attached diagram labels: 1-Phosphoric acid feed tank, 2-Venturi jet reactor, 3-Tube washing absorber, 4-Phosphoric acid feed transfer pump, 5-Reaction washing and maturation tank, 6-Reaction washing circulation pump, 7-Hydrogen sulfide reactor, 8-Arsenic removal filtration transfer pump, 9-Precision filter, 10-Precision filtration circulation pump, 11-Product acid clearing tank, 12-Arsenic slag concentrate tank, 13-Arsenic slag concentrate transfer pump, 14-Plate and frame filter press. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In a first aspect, the present invention provides a wet phosphoric acid purification and arsenic removal system, please refer to [reference needed]. Figure 1 The system includes a phosphoric acid feed tank 1, a Venturi jet reactor 2, a tubular washing absorber 3, a reaction washing and maturation tank 5, and a hydrogen sulfide reactor 7 connected in sequence. The hydrogen sulfide reactor 7 is also connected to the Venturi jet reactor 2. The reaction washing and maturation tank 5 is also connected to an arsenic removal filter assembly, and the outlet of the arsenic removal filter assembly is connected to the phosphoric acid feed tank 1.

[0029] In some embodiments of the present invention, please continue to refer to Figure 1 The arsenic removal filtration assembly includes an arsenic removal filtration conveying pump 8, a precision filtration circulation pump 10, a precision filter 9, and a product acid cleaning tank 11 connected in sequence. The inlet of the arsenic removal filtration conveying pump 8 is connected to the outlet of the reaction washing and maturation tank 5. The outlet of the arsenic removal filtration conveying pump 8 is connected to the inlet of the precision filtration circulation pump 10. The outlet of the precision filtration circulation pump 10 is connected to the inlet of the precision filter 9. One outlet of the precision filter 9 is connected to the inlet of the product acid cleaning tank 11. The other outlet of the precision filter 9 is also connected to the inlet of the arsenic slag concentrate tank 12. The outlet end of the arsenic slag concentrate tank 12 is connected to a plate and frame filter press 14. The outlet end of the plate and frame filter press 14 is connected to the phosphoric acid raw material tank 1.

[0030] In some embodiments of the present invention, please continue to refer to Figure 1 The other outlet of the precision filter 9 is also connected to the inlet of the precision filter circulation pump 10.

[0031] In some embodiments of the present invention, please continue to refer to Figure 1 The arsenic slag concentrate tank 12 is connected to the plate and frame filter press 14 by an arsenic slag concentrate conveying pump 13. Specifically, the outlet of the arsenic slag concentrate tank 12 is connected to the inlet of the arsenic slag concentrate conveying pump 13, and the outlet of the arsenic slag concentrate conveying pump 13 is connected to the inlet of the plate and frame filter press 14.

[0032] In some embodiments of the present invention, please continue to refer to Figure 1 A phosphoric acid feedstock tank 1 and a venturi jet reactor 2 are connected by a phosphoric acid feedstock pump 4. Specifically, the outlet of the phosphoric acid feedstock tank 1 is connected to the inlet of the phosphoric acid feedstock pump 4, and the outlet of the phosphoric acid feedstock pump 4 is connected to the inlet of the venturi jet reactor 2.

[0033] In some embodiments of the present invention, please continue to refer to Figure 1 A reaction washing circulation pump 6 is connected between the tubular washing absorber 3 and the reaction washing and maturation tank 5. Specifically, the outlet of the reaction washing and maturation tank 5 is connected to the inlet of the reaction washing circulation pump 6, and the outlet of the reaction washing circulation pump 6 is connected to the tubular washing absorber 3.

[0034] During operation, the raw acid from the phosphoric acid feed tank 1 is transported into the Venturi jet reactor 2 via the phosphoric acid feed transfer pump 4. At the same time, the hydrogen sulfide produced by the reaction in the hydrogen sulfide reactor 7 also enters the Venturi jet reactor 2. In the Venturi jet reactor 2, the hydrogen sulfide reacts with the arsenic in the phosphoric acid to form arsenic sulfide. Then, it is thoroughly reacted and matured by circulating spraying through the reaction washing and maturation tank 5, the reaction washing circulation pump 6, and the tubular washing absorber 3, so that the arsenic in the phosphoric acid is completely reacted to form solid arsenic sulfide precipitate. Excess unreacted hydrogen sulfide gas in the reaction washing and maturation tank 5 is returned to the hydrogen sulfide reactor 7 through the pipeline.

[0035] The phosphoric acid solution containing arsenic sulfide solids in the reaction washing and ripening tank 5 is transported to the circulation pipe of the precision filter 9 by the arsenic removal filtration transfer pump 8. It is circulated at a high flow rate by the precision filter circulation pump 10. The pressure difference between the inlet and outlet of the filter tube of the precision filter 9 generates the filtration driving force. The phosphoric acid solution is filtered through the filter (membrane) tube of the precision filter 9 and enters the product acid solution tank 11. The solid content of arsenic sulfide in the circulation loop of the precision filter 9 increases, forming arsenic slag concentrate. When a certain solid content value is reached, it is discharged into the arsenic slag concentrate tank 12.

[0036] In practical applications, continuous discharge is achieved by ensuring that the inflow of phosphoric acid solution containing arsenic sulfide solids is equal to the outflow of phosphoric acid clear liquid and arsenic slag concentrate, thus maintaining material balance. Precision filter 9 employs cross-flow filtration, which improves filtration capacity, reduces filtration attenuation rate, and solves the problems of easy clogging of the filter (membrane) tube and poor cleaning and regeneration effects.

[0037] The arsenic slag concentrate in the arsenic slag concentrate tank 12 is transported to the plate and frame filter press 14 by the arsenic slag concentrate transfer pump 13 for filtration and pressing. The mother liquor is returned to the phosphoric acid raw material tank 1. The solid arsenic slag that is filtered and pressed is discharged and then processed in the stockyard.

[0038] The system features a compact design, rational layout, simple equipment construction, and low operational difficulty. It effectively reduces the addition of sodium sulfide, and the entire system is in a closed state, effectively controlling or reducing the safety risk of hydrogen sulfide leakage, thus greatly improving system safety. The addition of an arsenic removal reaction system and an arsenic slag filtration system results in high impurity removal efficiency. It solves the problem of existing arsenic removal systems having a large amount of sodium sulfide added, leading to easy hydrogen sulfide leakage and low safety.

[0039] Secondly, the present invention provides a purification and arsenic removal process, comprising the following steps:

[0040] The raw acid from the phosphoric acid feed tank 1 is fed into the Venturi jet reactor 2, and the hydrogen sulfide reactor 7 is turned on to send hydrogen sulfide into the Venturi jet reactor 2 for reaction.

[0041] The material after the reaction in the Venturi jet reactor 2 is sequentially washed, reacted, and matured through the tubular washing absorber 3 and the reaction washing and maturation tank 5 to obtain solid arsenic sulfide precipitate. Excess unreacted hydrogen sulfide gas in the reaction washing and maturation tank 5 is returned to the hydrogen sulfide reactor 7.

[0042] The phosphoric acid solution containing impurities after the reaction in the reaction washing and ripening tank 5 is introduced into the arsenic removal and filtration assembly for arsenic removal and impurity removal. The purified phosphoric acid solution after impurity removal is sent back to the phosphoric acid raw material tank 1, and the removed impurities are discharged and collected.

[0043] In some embodiments of the present invention, the arsenic removal filtration assembly performs arsenic removal by including the following steps:

[0044] The phosphoric acid solution containing impurities is transported to the precision filter 9 through the arsenic removal filter transfer pump 8 for filtration. After filtration, the solution is introduced into the product acid clearing tank 11, and the arsenic slag concentrate obtained by filtration is discharged into the arsenic slag concentrate tank 12.

[0045] The arsenic slag concentrate in the arsenic slag concentrate tank 12 is transported to the plate and frame filter press 14 by the arsenic slag concentrate transfer pump 13 for filtration and pressing. The filtered phosphoric acid solution is sent back to the phosphoric acid raw material tank 1, while the filtered solid arsenic slag is discharged and collected.

[0046] Understandably, eliminating or replacing the wet phosphoric acid arsenic removal process at the front end reduces environmental pollution, increases safety, and improves reliability and stability. Furthermore, the process is shorter, the arsenic removal reaction is better, process parameters can be adjusted quickly, and product quality is more stable. It also solves the problems of existing processes requiring the addition of sodium sulfide, which can easily lead to hydrogen sulfide leakage, and the complexity and difficulty in flexibly controlling arsenic levels.

[0047] Thirdly, the present invention provides an application of a purification and arsenic removal process in the purification and impurity removal of wet phosphoric acid.

[0048] The above is a detailed description of the present invention. The following are embodiments of the present invention. Example 1

[0049] A wet phosphoric acid purification and arsenic removal system includes a phosphoric acid feed tank 1, a Venturi jet reactor 2, a tubular scrubbing absorber 3, a reaction scrubbing and ripening tank 5, and a hydrogen sulfide reactor 7 connected in sequence. The hydrogen sulfide reactor 7 is also connected to the Venturi jet reactor 2. The reaction scrubbing and ripening tank 5 is connected to an arsenic removal filter assembly, and the outlet of the arsenic removal filter assembly is connected to the phosphoric acid feed tank 1. Example 2

[0050] Based on Example 1, the arsenic removal filtration assembly includes an arsenic removal filtration conveying pump 8, a precision filtration circulation pump 10, a precision filter 9, and a product acid clearing tank 11 connected in sequence. The precision filter 9 is also connected to an arsenic slag concentrate tank 12. The outlet end of the arsenic slag concentrate tank 12 is connected to a plate and frame filter press 14. The outlet end of the plate and frame filter press 14 is connected to the phosphoric acid raw material tank 1.

[0051] The outlet of the reaction washing and ripening tank 5 is connected to the inlet of the arsenic removal filter transfer pump 8. The outlet of the arsenic removal filter transfer pump 8 is connected to the inlet of the precision filter circulation pump 10. The outlet of the precision filter circulation pump 10 is connected to the inlet of the precision filter 9. One outlet of the precision filter 9 is connected to the inlet of the product acid clearing tank 11. The other outlet of the precision filter 9 is also connected to the inlet of the filter circulation pump 10. The other outlet of the precision filter 9 is also connected to the inlet of the arsenic slag concentrate tank 12. Example 3

[0052] Based on Example 2, the outlet of the precision filter 9 is also connected to the precision filter circulation pump 10. An arsenic slag concentrate tank 12 is connected to the plate and frame filter press 14 via an arsenic slag concentrate transfer pump 13. The outlet of the arsenic slag concentrate tank 12 is connected to the inlet of the arsenic slag concentrate transfer pump 13, the outlet of the arsenic slag concentrate transfer pump 13 is connected to the plate and frame filter press 14, and the outlet of the plate and frame filter press 14 is connected to the phosphoric acid feed tank 1. Example 4

[0053] Based on Example 1, a phosphoric acid feedstock pump 4 is connected between the phosphoric acid feedstock tank 1 and the Venturi jet reactor 2. A reaction washing circulation pump 6 is connected between the tubular washing absorber 3 and the reaction washing and maturation tank 5. Specifically, the outlet of the reaction washing and maturation tank 5 is connected to the inlet of the reaction washing circulation pump 6, and the outlet of the reaction washing circulation pump 6 is connected to the tubular washing absorber 3.

[0054] The outlet of the phosphoric acid feed tank 1 is connected to the inlet of the phosphoric acid feed pump 4. The outlet of the phosphoric acid feed pump 4 is connected to the inlet of the Venturi jet reactor 2. The outlet of the Venturi jet reactor 2 is connected to the inlet of the tubular scrubbing absorber 3. The outlet of the tubular scrubbing absorber 3 is connected to the inlet of the reaction washing and maturation tank 5. The outlet of the reaction washing and maturation tank 5 is connected to the hydrogen sulfide reactor 7. The outlet of the hydrogen sulfide reactor 7 is connected to the Venturi jet reactor 2. Another outlet of the reaction washing and maturation tank 5 is also connected to an arsenic removal filter assembly, and the outlet of the arsenic removal filter assembly is connected to the phosphoric acid feed tank 1. Example 5

[0055] This invention provides a purification and arsenic removal process, comprising the following steps:

[0056] The raw acid from the phosphoric acid feed tank 1 is fed into the Venturi jet reactor 2, and the hydrogen sulfide reactor 7 is turned on to send hydrogen sulfide into the Venturi jet reactor 2 for reaction.

[0057] The material after the reaction in the Venturi jet reactor 2 is sequentially washed, reacted, and matured through the tubular washing absorber 3 and the reaction washing and maturation tank 5 to obtain solid arsenic sulfide precipitate. Excess unreacted hydrogen sulfide gas in the reaction washing and maturation tank 5 is returned to the hydrogen sulfide reactor 7.

[0058] The phosphoric acid solution containing impurities after the reaction in the reaction washing and ripening tank 5 is introduced into the arsenic removal and filtration assembly for arsenic removal and impurity removal. The purified phosphoric acid solution after impurity removal is sent back to the phosphoric acid raw material tank 1, and the removed impurities are discharged and collected. Example 6

[0059] Based on Example 5, the arsenic removal filtration assembly performs arsenic removal by including the following steps:

[0060] The phosphoric acid solution containing impurities is transported to the precision filter 9 through the arsenic removal filter transfer pump 8 for filtration. After filtration, the solution is introduced into the product acid clearing tank 11, and the arsenic slag concentrate obtained by filtration is discharged into the arsenic slag concentrate tank 12.

[0061] The arsenic slag concentrate in the arsenic slag concentrate tank 12 is transported to the plate and frame filter press 14 by the arsenic slag concentrate transfer pump 13 for filtration and pressing. The filtered phosphoric acid solution is sent back to the phosphoric acid raw material tank 1, while the filtered solid arsenic slag is discharged and collected. Example 7

[0062] In this embodiment, a purification and arsenic removal process is provided, including the following steps:

[0063] The raw acid from the phosphoric acid feed tank 1 is fed into the Venturi jet reactor 2, and the hydrogen sulfide reactor 7 is turned on to send hydrogen sulfide into the Venturi jet reactor 2 for reaction.

[0064] The material after the reaction in the Venturi jet reactor 2 is sequentially washed, reacted, and matured through the tubular washing absorber 3 and the reaction washing and maturation tank 5 to obtain solid arsenic sulfide precipitate. Excess unreacted hydrogen sulfide gas in the reaction washing and maturation tank 5 is returned to the hydrogen sulfide reactor 7.

[0065] The phosphoric acid solution containing impurities after the reaction in the reaction washing and ripening tank 5 is introduced into the arsenic removal and filtration assembly for arsenic removal and impurity removal. The purified phosphoric acid solution after impurity removal is sent back to the phosphoric acid raw material tank 1, and the removed impurities are discharged and collected.

[0066] In some embodiments of the present invention, the arsenic removal filtration assembly performs arsenic removal by including the following steps:

[0067] The phosphoric acid solution containing impurities is transported to the precision filter 9 through the arsenic removal filter transfer pump 8 for filtration. After filtration, the solution is introduced into the product acid clearing tank 11, and the arsenic slag concentrate obtained by filtration is discharged into the arsenic slag concentrate tank 12.

[0068] The arsenic slag concentrate in the arsenic slag concentrate tank 12 is transported to the plate and frame filter press 14 by the arsenic slag concentrate transfer pump 13 for filtration and pressing. The filtered phosphoric acid solution is sent back to the phosphoric acid raw material tank 1, while the filtered solid arsenic slag is discharged and collected.

[0069] The phosphoric acid solution was sampled and tested, and the arsenic content of the impurities was consistently controlled below 0.4 ppm. This demonstrates the effectiveness of the impurity removal method in this case. Example 8

[0070] A wet phosphoric acid purification and arsenic removal system includes a phosphoric acid feed tank 1, a Venturi jet reactor 2, a tubular scrubbing absorber 3, a phosphoric acid feed transfer pump 4, a reaction washing and maturation tank 5, a reaction washing circulation pump 6, a hydrogen sulfide reactor 7, an arsenic removal filtration transfer pump 8, a precision filter 9, a precision filtration circulation pump 10, a product acid clearing tank 11, an arsenic slag concentrate tank 12, an arsenic slag concentrate transfer pump 13, and a plate and frame filter press 14.

[0071] Among them, the inlet of the phosphoric acid feed pump 4 is connected to the acid outlet at the lower end of the phosphoric acid feed tank 1, and the outlet of the phosphoric acid feed pump 4 is connected to the acid inlet of the Venturi jet reactor 2.

[0072] The exhaust port of hydrogen sulfide reactor 7 is connected to the inlet of Venturi jet reactor 2;

[0073] The Venturi jet reactor 2 is connected to the tubular washing absorber 3, which is connected to the reaction washing and maturation tank 5. The insertion tube of the tubular washing absorber 3 connected to the reaction washing and maturation tank 5 is below the operating liquid level of the reaction washing and maturation tank 5.

[0074] The inlet of the reaction washing circulation pump 6 is connected to the liquid outlet at the lower end of the reaction washing and maturation tank 5, and the outlet of the reaction washing circulation pump 6 is connected to the nozzle of the tubular washing absorber 3.

[0075] The precision filter circulation pump 10 is connected to the tube side channel of the precision filter 9, forming a circulation loop;

[0076] The inlet of the arsenic removal filter transfer pump 8 is connected to the lower outlet of the reaction washing and maturation tank 5, and the outlet of the arsenic removal filter transfer pump 8 is connected to the inlet pipeline of the precision filter circulation pump 10.

[0077] The upper inlet of the arsenic slag concentrate tank 12 is connected to the inlet pipe of the precision filter circulation pump 10.

[0078] The drain port of the precision filter 9 is connected to the acid inlet of the product acid cleaning tank 11;

[0079] The inlet of the arsenic slag concentrate transfer pump 13 is connected to the lower outlet of the arsenic slag concentrate tank 12, the outlet of the arsenic slag concentrate transfer pump 13 is connected to the inlet of the plate and frame filter press 14, and the outlet of the plate and frame filter press 14 is connected to the upper pipe of the phosphoric acid raw material tank 1.

[0080] Among them, multiple precision filters 9 can be connected in parallel or in series. The filter (membrane) tube is made of ceramic or non-metallic engineering materials, and the filter pore size is 0.02 to 1.0 micrometers.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wet phosphoric acid purification and arsenic removal process, characterized in that, The process is carried out using the following system, which includes, in sequence, a phosphoric acid feed tank, a Venturi jet reactor, a tubular scrubbing absorber, a reaction scrubbing and ripening tank, and a hydrogen sulfide reactor, wherein the hydrogen sulfide reactor is also connected to the Venturi jet reactor; the reaction scrubbing and ripening tank is connected to an arsenic removal filter assembly, which is connected to the phosphoric acid feed tank. The arsenic removal filtration assembly includes an arsenic removal filtration conveying pump, a precision filtration circulation pump, a precision filter, and a product acid clearing tank connected in sequence. The precision filter is also connected to an arsenic slag concentrate tank. The outlet end of the arsenic slag concentrate tank is connected to a plate and frame filter press. The outlet end of the plate and frame filter press is connected to the phosphoric acid raw material tank. The outlet of the reaction washing and maturation tank is connected to the inlet of the arsenic removal filter transfer pump. The outlet of the arsenic removal filter transfer pump is connected to the inlet of the precision filter circulation pump. The outlet of the precision filter circulation pump is connected to the inlet of the precision filter. One outlet of the precision filter is connected to the inlet of the product acid clearing tank. The other outlet of the precision filter is also connected to the inlet of the filter circulation pump. The other outlet of the precision filter is also connected to the inlet of the arsenic slag concentrate tank. The process includes the following steps: The raw acid from the phosphoric acid feed tank is fed into the Venturi jet reactor, and the hydrogen sulfide reactor is turned on to send hydrogen sulfide into the Venturi jet reactor for reaction. The material after the reaction in the Venturi jet reactor is sequentially passed through a tubular washing absorber, a reaction washing and maturation tank for washing, reaction, and maturation to obtain solid arsenic sulfide precipitate. Excess unreacted hydrogen sulfide gas in the reaction washing and maturation tank is returned to the hydrogen sulfide reactor. The phosphoric acid solution containing impurities after the reaction in the reaction washing and ripening tank is introduced into the arsenic removal and filtration unit for arsenic removal and impurity removal. The purified phosphoric acid solution after impurity removal is sent back to the phosphoric acid raw material tank, and the removed impurities are discharged and collected. The phosphoric acid solution containing arsenic sulfide solids in the reaction washing and ripening tank is transported to the precision filter circulation pipe by the arsenic removal filtration transfer pump. The precision filter circulation pump circulates at a high flow rate, and the pressure difference between the inlet and outlet of the precision filter tube generates a filtration driving force. The phosphoric acid solution is filtered through the precision filter tube and enters the product acid solution tank. The arsenic sulfide solid content in the precision filter tube circulation loop increases, forming arsenic slag concentrate. When a certain solid content is reached, it is discharged into the arsenic slag concentrate tank. The precision filter adopts cross-flow filtration.

2. The wet phosphoric acid purification and arsenic removal process according to claim 1, characterized in that, An arsenic slag concentrate delivery pump is connected between the arsenic slag concentrate tank and the plate and frame filter press.

3. The wet phosphoric acid purification and arsenic removal process according to claim 1, characterized in that, A phosphate feedstock delivery pump is connected between the phosphate feedstock tank and the Venturi jet reactor.

4. The wet phosphoric acid purification and arsenic removal process according to claim 1, characterized in that, A reaction washing circulation pump is connected between the tubular washing absorber and the reaction washing maturation tank.

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