System for producing phosphoric acid by mixing white fertilizer and concentrate slurry

Abstract

This utility model discloses a system for producing phosphoric acid by blending white fertilizer with concentrate slurry. The outlet of the slurry mixing tank is connected to the inlet of the ball mill and the slurry tank, respectively. The outlet of the white fertilizer feeding hopper is connected to the inlet of the ball mill. The outlet of the ball mill is connected to the inlet of the slurry tank. The outlet of the slurry tank, the outlet of the sulfuric acid pipeline, and the outlet of the defoamer pipeline are all connected to the inlet of the reaction tank. The overflow outlet of the reaction tank is connected to the inlet of the digestion tank. The outlet of the digestion tank is connected to the inlet of the crystal growth tank. The outlet of the crystal growth tank is connected to the inlet of the filter press. Beneficial effects: This utility model has a simple connection structure, is easy to implement, reduces investment costs, reduces equipment investment and floor space, enhances decomposition reaction efficiency, increases the production rate of the target product phosphoric acid, eliminates the need for additional impurity removal processes, reduces production energy consumption and costs, increases resource added value, achieves water resource recycling, and meets the industry's environmental protection requirements for "phosphorus and fluorine co-recovery."

Description

Technical Field

[0001] This utility model relates to the field of white fertilizer treatment technology, and in particular to a system for producing phosphoric acid by blending white fertilizer with concentrate slurry. Background Technology

[0002] In the phosphorus chemical industry chain, wet-process phosphoric acid production uses phosphate rock as the core raw material, producing phosphoric acid through processes such as sulfuric acid decomposition and solid-liquid separation. However, the stockpiling of phosphogypsum, a byproduct, has become an environmental pain point for the industry. Meanwhile, the production of feed-grade dicalcium phosphate generates a large amount of byproduct white fertilizer (fertilizer-grade dicalcium phosphate), with a P2O5 content of 20-35% and a fluorine content of 4-12%. Direct stockpiling can easily cause groundwater pollution, while direct application can damage crops due to fluoride toxicity. Furthermore, the dicalcium-soluble phosphorus content is as high as 90%, resulting in low fertilizer efficiency. Therefore, the resource recovery of white fertilizer is not only related to environmental compliance but also a key path to improving phosphorus resource utilization. In the existing technology, CN113603070A proposes a method for producing phosphoric acid from white fertilizer. The core steps are: first, decompose white fertilizer with a moisture content of 25-30% using 18-20% recycled phosphoric acid; react at 40℃ for 2 hours to generate calcium dihydrogen phosphate dihydrate; then add sulfuric acid to generate phosphoric acid and a solid phase; and finally, react the separated filter cake with the white fertilizer to prepare superphosphate. This patent is the first to achieve the direct conversion of white fertilizer to phosphoric acid, avoiding the resource waste of traditional phosphate rock-consuming production methods. However, its technical solution still has significant limitations: 1. Raw material compatibility defects: The decomposition reaction is carried out using only white fertilizer raw material without co-processing with mainstream raw materials such as phosphate concentrate. As a result, the process cannot be directly integrated into the existing phosphoric acid production unit, and a separate reaction system needs to be built, which increases equipment investment and land area.

[0003] 2. Insufficient reaction efficiency and impurity control: The cyclic phosphoric acid decomposition stage only achieves mixing by stirring, without grinding pretreatment. The uneven particle size of the white fertilizer particles leads to a low Ca(H2PO4)2•2H2O formation rate. In addition, the precipitates such as iron phosphate and aluminum phosphate generated during the reaction directly enter the subsequent system, reducing the purity of the phosphoric acid product, requiring an additional impurity removal process.

[0004] 3. Incomplete resource recovery: The filter cake is only used to prepare low-grade superphosphate, and the calcium and phosphorus elements in the solid phase are not fully utilized. In summary, although CN113603070A pioneered a technological path for producing phosphoric acid from white fertilizer, there is still room for improvement in areas such as raw material synergy, system integration, impurity control, and comprehensive resource utilization. How to deeply integrate the white fertilizer processing technology with the existing phosphoric acid production system, while improving phosphorus recovery rates and ensuring product purity and environmental compliance, has become a pressing technical challenge for the industry. Utility Model Content The main purpose of this invention is to provide a system for producing phosphoric acid by blending white fertilizer with concentrate slurry, which reduces investment costs, equipment investment and floor space, enhances decomposition reaction efficiency, improves the production rate of the target product phosphoric acid, eliminates the need for additional impurity removal processes, reduces production energy consumption and costs, increases resource added value, realizes water resource recycling, and meets the industry's environmental protection requirements of "phosphorus and fluorine co-recovery". To achieve the above objectives, the technical solution adopted by this utility model is as follows: a system for producing phosphoric acid by blending white fertilizer with concentrate slurry, comprising a phosphate powder feeding hopper, a diatomaceous earth feeding hopper, a belt conveyor, a slurry mixing tank, a water supply pipeline, a ball mill, a slurry tank, a white fertilizer feeding hopper, a reaction tank, a sulfuric acid pipeline, a defoamer pipeline, a digestion tank, a crystal growth tank, and a filter press; the outlets of the phosphate powder feeding hopper and the diatomaceous earth feeding hopper are connected to the inlet of the slurry mixing tank via the belt conveyor, and the outlet of the water supply pipeline is connected to the inlet of the slurry mixing tank; the slurry mixing tank... The outlet of the slurry tank is connected to the inlet of the ball mill and the slurry tank, respectively. The outlet of the white fertilizer feed hopper is connected to the inlet of the ball mill. The outlet of the ball mill is connected to the inlet of the slurry tank. The outlet of the slurry tank, the outlet of the sulfuric acid pipeline, and the outlet of the defoamer pipeline are all connected to the inlet of the reaction tank. The overflow outlet of the reaction tank is connected to the inlet of the digestion tank. The outlet of the digestion tank is connected to the inlet of the crystal growth tank. The outlet of the crystal growth tank is connected to the inlet of the filter press.

[0005] Furthermore, an iron remover is installed on the belt conveyor.

[0006] Furthermore, the reaction tank is divided into six interconnected reaction chambers at the bottom. The outlet of the slurry tank and the outlet of the defoamer pipeline are both connected to the inlet of the first reaction chamber. The outlet of the sulfuric acid pipeline is connected to the inlets of the second and third reaction chambers, respectively. The outlet of the sixth reaction chamber is connected to the inlet of the low-level flash evaporator, and the outlet of the low-level flash evaporator is connected to the inlet of the first reaction chamber.

[0007] Furthermore, the low-level flash evaporator, precooler, fluorine scrubbing tower, condenser, demister, and water ring vacuum pump are connected in sequence according to the gas flow direction. The liquid outlets of the condenser and the demister are both connected to the liquid inlet of the condenser liquid seal tank, and the liquid outlet of the condenser liquid seal tank is connected to the liquid inlet of the slurry tank.

[0008] Furthermore, the digester is divided into three chambers. The overflow port of the sixth reaction chamber is connected to the liquid inlet of the first and second digestion chambers of the digester. The first and second digestion chambers of the digester are interconnected. The overflow port of the second digestion chamber is connected to the liquid inlet of the third digestion chamber of the digester. The outlet of the sulfuric acid pipeline is connected to the liquid inlet of the second digestion chamber of the digester.

[0009] This utility model has the following beneficial effects: 1. This utility model has a simple connection structure that is easy to implement, strong raw material synergy, compatibility with existing equipment, and reduced investment costs. It breaks through the limitations of the existing technology of "single white fertilizer raw material". After white fertilizer and phosphate concentrate are mixed and ground in a ball mill, they react synergistically. There is no need to build a separate white fertilizer treatment system. It can be directly embedded into existing wet phosphoric acid production equipment (such as reusing slurry tanks, reaction tanks, filter presses and other mature equipment), reducing equipment investment and land area. 2. This utility model pre-treats the "white fertilizer-concentrate slurry" by adding a ball mill, making the white fertilizer particles uniform in size and significantly increasing the formation rate of Ca(H2PO4)2•2H2O. At the same time, the reaction tank adopts a six-chamber staged reaction + low-level flash cooling design to achieve gradient addition of sulfuric acid and precise control of reaction temperature, further enhancing the decomposition reaction efficiency and increasing the formation rate of the target product phosphoric acid. 3. This utility model uses an iron remover on a belt conveyor to remove iron impurities from phosphate powder in advance, reducing the formation of precipitates such as iron phosphate and aluminum salts; the simultaneous addition of diatomaceous earth can optimize the crystal morphology of gypsum and prevent impurities from being trapped; combined with the addition of sulfuric acid to the digester to regulate the SO3 concentration, multiple measures ensure the purity of the phosphate product, eliminating the need for additional impurity removal processes and reducing production energy consumption and costs. 4. The solid material (gypsum) produced by this invention can be directly used as a building material raw material after pressure filtration and separation. Compared with the existing technology of "preparing low-grade superphosphate from filter cake", the added value of resources is improved. The fluorine-containing tail gas is treated in a closed loop through "multi-stage washing-condensation and return", which removes fluoride ions. The condensate is returned to the slurry tank, realizing the recycling of water resources, which meets the industry's environmental protection requirements of "co-recovery of phosphorus and fluorine". Attached Figure Description 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.

[0010] Figure 1 This is a schematic diagram of the overall structure of a system for producing phosphoric acid by blending white fertilizer with concentrate slurry, according to this utility model. In the diagram: 1. Phosphate concentrate feed hopper; 2. Diatomaceous earth feed hopper; 3. Belt conveyor; 4. Slurry mixing tank; 5. Water pipeline; 6. Ball mill; 7. Slurry tank; 8. White fertilizer feed hopper; 9. Reaction tank; 91. Reaction chamber; 10. Sulfuric acid pipeline; 11. Defoamer pipeline; 12. Digestion tank; 13. Crystal growth tank; 14. Filter press; 15. Iron remover; 16. Low-level flash evaporator; 17. Precooler; 18. Condenser; 19. Demister; 20. Water ring vacuum pump; 21. Condenser liquid seal tank; 22. Fluorine scrubbing tower. Detailed Implementation

[0011] The following is in conjunction with the appendix Figure 1 The principles and features of this utility model are described, making the technical means, creative features, and achieved objectives of this utility model easy to understand, and further elaborating on this utility model.

[0012] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0013] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," and "connected," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0014] like Figure 1 As shown, the technical solution adopted by this utility model is as follows: a system for producing phosphoric acid by blending white fertilizer with concentrate slurry, which includes a phosphoric acid powder feeding hopper 1, a diatomaceous earth feeding hopper 2, a belt conveyor 3, a slurry mixing tank 4, a water supply pipeline 5, a ball mill 6, a slurry tank 7, a white fertilizer feeding hopper 8, a reaction tank 9, a sulfuric acid pipeline 10, a defoamer pipeline 11, a digestion tank 12, a crystal growth tank 13, and a filter press 14; the discharge ports of the phosphoric acid powder feeding hopper 1 and the diatomaceous earth feeding hopper 2 are connected to the inlet of the slurry mixing tank 4 through the belt conveyor 3, and an iron remover 15 is installed on the belt conveyor 3.

[0015] The outlet of water pipeline 5 is connected to the inlet of slurry tank 4. The outlet of slurry tank 4 is connected to the inlets of ball mill 6 and slurry tank 7 respectively. The outlet of white fertilizer hopper 8 is connected to the inlet of ball mill 6. The outlet of ball mill 6 is connected to the inlet of slurry tank 7. The outlet of slurry tank 7, the outlet of sulfuric acid pipeline 10 and the outlet of defoamer pipeline 11 are all connected to the inlet of reaction tank 9. The overflow outlet of reaction tank 9 is connected to the inlet of digestion tank 12. The outlet of digestion tank 12 is connected to the inlet of crystal growth tank 13. The outlet of crystal growth tank 13 is connected to the inlet of filter press 14.

[0016] The reaction tank 9 is divided into six interconnected reaction chambers 91. The outlet of the slurry tank 7 and the outlet of the defoamer pipeline 11 are both connected to the inlet of the first reaction chamber. The outlet of the sulfuric acid pipeline 10 is connected to the inlet of the second and third reaction chambers respectively. The outlet of the sixth reaction chamber is connected to the inlet of the low-level flash evaporator 16, and the outlet of the low-level flash evaporator 16 is connected to the inlet of the first reaction chamber.

[0017] The low-level flash evaporator 16, precooler 17, fluorine scrubbing tower 22, condenser 18, demister 19 and water ring vacuum pump 20 are connected in sequence according to the gas flow direction. The liquid outlets of condenser 18 and demister 19 are connected to the liquid inlet of condenser liquid seal tank 21, and the liquid outlet of condenser liquid seal tank 21 is connected to the liquid inlet of slurry tank 4.

[0018] The digester 12 is divided into three chambers. The overflow port of the sixth reaction chamber 91 is connected to the liquid inlet of the first and second digestion chambers of the digester 12. The first and second digestion chambers of the digester 12 are connected to each other. The overflow port of the second digestion chamber of the digester 12 is connected to the liquid inlet of the third digestion chamber of the digester 12. The outlet of the sulfuric acid pipeline 10 is connected to the liquid inlet of the second digestion chamber of the digester 12.

[0019] Working principle: 1. Raw material co-processing stage Phosphate powder and diatomaceous earth pretreatment: Phosphate powder is output from phosphate powder feeding hopper 1, and diatomaceous earth is simultaneously fed from diatomaceous earth feeding hopper 2. Both fall into belt conveyor 3. The iron remover 15 on the conveyor adsorbs iron impurities in the phosphate powder in real time to avoid the formation of ferric phosphate in subsequent reactions, which would affect the purity of the product, and at the same time ensure the service life of equipment such as ball mill 6. Slurry preparation and white fertilizer blending and grinding: The phosphate concentrate-diatomite mixture after iron removal is transported to the slurry preparation tank 4. The water supply pipeline 5 injects process water or circulating water into the slurry preparation tank 4 according to the preset slurry concentration to complete the initial slurry preparation. The slurry after slurry preparation is transported in two ways: one way is directly sent to the slurry tank 7 for temporary storage, and the other way is sent to the ball mill 6. At the same time, white fertilizer is put into the ball mill 6 through the white fertilizer feeding hopper 8, and is fully mixed and refined with the slurry in the grinding chamber (controlling the uniformity of particle size). The ground "white fertilizer-concentrate slurry" mixture is also transported to the slurry tank 7 to achieve homogenization blending of the two raw materials. 2. Multi-stage reaction and crystal form regulation stage The reaction tank 9 is a staged reaction tank: the homogeneous slurry in the slurry tank 7, the sulfuric acid transported by the sulfuric acid pipeline 10 (dynamically adjusted according to the slurry flow ratio), and the defoamer transported by the defoamer pipeline 11 enter different reaction chambers 91 of the reaction tank 9 respectively: the slurry and defoamer preferentially enter the first reaction chamber to initially suppress the reaction foam and start the decomposition reaction; the sulfuric acid is distributed to the second and third reaction chambers to carry out a gradient reaction with the slurry (to avoid excessive local sulfuric acid concentration leading to abnormal gypsum crystallization); the six interconnected reaction chambers 91 in the lower part of the reaction tank 9 form a slurry circulation path of "1#→2#→3#→4#→5#→6#", ensuring sufficient reaction. Flash cooling and temperature control: Part of the slurry in the sixth reaction chamber is transported to the low-level flash evaporator 16, where the heat generated by the reaction is removed through flash evaporation. The cooled slurry is returned to the first reaction chamber, so that the temperature of the entire reaction system is stabilized at 75-90℃ (matching the optimal reaction activity range of phosphate rock and white fertilizer), avoiding P2O5 loss caused by high temperature or the impact of low temperature on the reaction rate. Crystal growth optimization in digestion tank 12: The remaining slurry in the sixth reaction chamber enters the first and second digestion chambers of digestion tank 12 through the overflow port (to adjust the crystal lattice morphology). The two chambers are connected to ensure uniform slurry residence time. At the same time, sulfuric acid pipeline 10 adds an appropriate amount of sulfuric acid to the second digestion chamber (adjusted according to the SO3 concentration feedback of the filtrate, controlling the SO3 content to 22-30 g / L) to further promote gypsum crystal growth. The slurry then overflows to the third digestion chamber (feed grid of crystal growth tank 13), and after completing the crystal morphology optimization, it is transported to crystal growth tank 13 to lay the foundation for subsequent filtration and separation.

[0020] 3. Product separation and exhaust gas recirculation stage Phosphoric acid and solid separation: The gypsum crystals that have grown fully in the crystal growth tank 13 are mixed with phosphoric acid and then transported to the filter press 14 for solid-liquid separation. After separation, the target product phosphoric acid (P2O5 concentration 22%-28%) is obtained. The solid (gypsum) can be directly used as a building material raw material (such as gypsum board production), realizing high value-added utilization of resources. Closed-loop treatment of fluorinated tail gas: The fluorinated vapor generated by the low-level flash evaporator 16 is treated sequentially in the following order: "precooler 17 → fluorine scrubbing tower 22 → condenser 18 → demister 19". The precooler 17 performs preliminary cooling, the fluorine scrubbing tower 22 further adsorbs fluoride ions, the condenser 18 condenses the vapor into liquid, and the demister 19 separates the residual gas and liquid. The treated non-condensable gas is discharged in compliance with standards by the water ring vacuum pump 20. The condensate is collected in the condenser liquid seal tank 21 and finally returned to the slurry tank 4 as a slurry preparation medium, realizing the recycling of water and fluorine resources and avoiding tail gas emission pollution. The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A system for producing phosphoric acid by blending white fertilizer with concentrate slurry, characterized in that, It includes a phosphate concentrate feeding hopper, a diatomaceous earth feeding hopper, a belt conveyor, a slurry mixing tank, a water pipeline, a ball mill, a slurry tank, a white fertilizer feeding hopper, a reaction tank, a sulfuric acid pipeline, a defoamer pipeline, a digestion tank, a crystal growth tank, and a filter press. The outlets of the phosphate concentrate feeding hopper and the diatomaceous earth feeding hopper are connected to the inlet of the slurry mixing tank via the belt conveyor. The outlet of the water pipeline is connected to the inlet of the slurry mixing tank. The outlet of the slurry mixing tank is connected to the ball mill and the slurry tank respectively. The inlet of the slurry tank is connected to the outlet of the white fertilizer hopper, which is connected to the inlet of the ball mill. The outlet of the ball mill is connected to the inlet of the slurry tank. The outlet of the slurry tank, the outlet of the sulfuric acid pipeline, and the outlet of the defoamer pipeline are all connected to the inlet of the reaction tank. The overflow outlet of the reaction tank is connected to the inlet of the digestion tank. The outlet of the digestion tank is connected to the inlet of the crystal growth tank. The outlet of the crystal growth tank is connected to the inlet of the filter press.

2. The system for producing phosphoric acid by blending white fertilizer with concentrate slurry according to claim 1, characterized in that, A magnetic separator is installed on the belt conveyor.

3. The system for producing phosphoric acid from a white fertilizer blended concentrate slurry according to claim 1, characterized in that, The reaction tank is divided into six interconnected reaction chambers at the bottom. The outlet of the slurry tank and the outlet of the defoamer pipeline are both connected to the inlet of the first reaction chamber. The outlet of the sulfuric acid pipeline is connected to the inlets of the second and third reaction chambers respectively. The outlet of the sixth reaction chamber is connected to the inlet of the low-level flash evaporator, and the outlet of the low-level flash evaporator is connected to the inlet of the first reaction chamber.

4. The system for producing phosphoric acid from a white fertilizer blended concentrate slurry according to claim 3, characterized in that, The low-level flash evaporator, precooler, fluorine scrubbing tower, condenser, demister, and water ring vacuum pump are connected in sequence according to the gas flow direction. The liquid outlets of the condenser and the demister are both connected to the liquid inlet of the condenser liquid seal tank, and the liquid outlet of the condenser liquid seal tank is connected to the liquid inlet of the slurry tank.

5. The system for producing phosphoric acid by blending white fertilizer with concentrate slurry according to claim 3, characterized in that, The digester is divided into three chambers. The overflow port of the sixth reaction chamber is connected to the liquid inlet of the first and second digestion chambers of the digester. The first and second digestion chambers of the digester are interconnected. The overflow port of the second digestion chamber is connected to the liquid inlet of the third digestion chamber of the digester. The outlet of the sulfuric acid pipeline is connected to the liquid inlet of the second digestion chamber of the digester.

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