Device for producing monoammonium phosphate from refined phosphoric acid tail liquid

Abstract

A device for producing monoammonium phosphate from refined phosphoric acid tail liquid comprises a stirring tank, a first filter, a stirring tank, a second filter, a stirring tank, a third filter, a concentration tank, a crystallization tank, a centrifugal machine and a fluidized bed which are sequentially connected, jackets are arranged outside the stirring tank and the crystallization tank, and the stirring tank is communicated with a fluosilicic acid pipe, an exhaust pipe, a water inlet pipe and an ammonia gas pipe. The utility model provides a method for producing monoammonium phosphate from refined phosphoric acid tail liquid in order to overcome the defects of high production cost of products and low quality and industrial added value of the products. The device disclosed by the utility model not only improves the removal rate of impurities in the raffinate acid, but also improves the content of total nitrogen in total nutrients of a product, so that the quality of the product is improved, and the additional value of the raffinate acid product is also improved.

Description

Technical Field

[0001] The utility model relates to a device for producing magnesium sulfate and industrial-grade monoammonium phosphate by refining tail liquid of wet-process phosphoric acid by solvent extraction, belonging to the technical field of phosphorus chemical production. Background Art

[0002] In the process of refining wet-process phosphoric acid, the volume of the tail liquid of the wet-process phosphoric acid will be greatly reduced after the extraction of the wet-process phosphoric acid stock solution, because the phosphoric acid and water in the wet-process phosphoric acid stock solution are extracted and taken away by the extractant; and the content of metal ions such as iron, aluminum, and magnesium that are almost not extracted and remain in the tail liquid during the extraction process will be greatly increased, resulting in a high viscosity of the tail liquid, which can only be used for the production of fertilizers. At present, the use of raffinate acid in my country is generally mainly mixed with wet-process phosphoric acid to produce fertilizer-grade ammonium phosphate. Some manufacturers have tried to use raffinate acid to produce powdered and granular MAP, but due to the high viscosity of the raffinate acid, the slurry is easy to clog the equipment; and the water content of the produced product is too high and the nitrogen content is insufficient. Therefore, many manufacturers mix raffinate acid with wet-process phosphoric acid to increase the neutralization degree during the ammoniation reaction to produce granular monoammonium phosphate, but the resulting product is easy to agglomerate. These examples show that the physical and chemical properties of raffinate acid will vary with the raw acid of the raffinate acid, the purification process and the extractant. The reuse of raffinate acid should adjust the process according to the difference of raffinate acid. Wengfu Company in Guizhou uses raffinate acid to produce DAP. The method is to mix wet-process phosphoric acid and raffinate acid in a mass ratio of 7:3, and then introduce ammonia to prepare DAP. However, this method consumes a large amount of wet-process phosphoric acid while consuming raffinate acid, and because the pH of the slurry increases during the ammonia reaction, a large amount of metal ions in the raffinate acid will form secondary precipitated salts. These secondary precipitated salts will have a great impact on the purity and appearance of the DAP product. Utility Model Content

[0003] The purpose of the utility model is to propose a method for producing monoammonium phosphate from refined phosphoric acid tail liquid in view of the defects and shortcomings of the prior art, such as low recycling rate of wet phosphoric acid tail liquid, unreasonable production process, high production cost of the obtained product, low product quality and industrial added value. The utility model not only improves the impurity removal rate in raffinate acid, but also increases the total nitrogen content in the total nutrients of the product, thereby improving the product quality and the product added value of raffinate acid.

[0004] In order to solve the above problems, the technical solution of the utility model is:

[0005] A device for producing monoammonium phosphate from refined phosphoric acid tail liquid comprises a first stirring tank, a first filter, a stirring tank, a second filter, a second stirring tank, a third filter, a concentration tank, a crystallization tank, a centrifuge and a fluidized bed which are connected in sequence, wherein the stirring tank and the crystallization tank are provided with jackets outside, and the stirring tank is connected with a fluorosilicic acid pipe, an exhaust pipe, a water inlet pipe and an ammonia pipe.

[0006] An aeration pipe is arranged at the bottom of the stirring tank, and the ammonia pipe is connected to the aeration pipe.

[0007] The exhaust pipe is connected to the ammonia recovery system.

[0008] The first filter, the second filter and the third filter are all plate and frame filters.

[0009] The beneficial effects of the utility model are: not only the removal rate of impurities in the raffinate acid is improved, but also the content of total nitrogen in the total nutrients of the product is increased, so that the product quality is improved, and the added value of the raffinate acid product is also increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The utility model is further described below in conjunction with the accompanying drawings:

[0011] Figure 1 It is a structural schematic diagram of the utility model.

[0012] In the figure: a first stirring tank 1, a first filter 2, a stirring tank 3, a second filter 4, a second stirring tank 5, a third filter 6, a concentration tank 7, a crystallization tank 8, a centrifuge 9, and a fluidized bed 10. DETAILED DESCRIPTION

[0013] like Figure 1 As shown, a device for producing monoammonium phosphate from refined phosphoric acid tail liquid includes a first stirring tank 1, a first filter 2, a stirring tank 3, a second filter 4, a second stirring tank 5, a third filter 6, a concentration tank 7, a crystallization tank 8, a centrifuge 9 and a fluidized bed 10 connected in sequence, the stirring tank 3 and the crystallization tank 8 are provided with a jacket, and a fluorosilicic acid pipe, an exhaust pipe, a water inlet pipe and an ammonia pipe are connected to the stirring tank 3. An aeration pipe is provided at the bottom of the stirring tank 3, and the ammonia pipe is connected to the aeration pipe. The exhaust pipe is connected to the ammonia recovery system. The first filter 2, the second filter 4 and the third filter 6 are all plate and frame filters. An online pH detector is installed on the stirring tank 3.

[0014] The implementation process of the utility model is:

[0015] S1: firstly, wet-process phosphoric acid tail liquid and mineral powder are added into the first stirring tank 1 for stirring and desulfurization, and then the stirred slurry is pumped into the first filter 2 for filtration by the mud pump;

[0016] S2: The tail liquid filtered out by the first filter 2 is sent to the stirring tank 3, and fluorosilicic acid is added to the stirring tank 3 through the fluorosilicic acid tube, wherein the mass ratio of fluorosilicic acid to the tail liquid is 1:4, and the fluorosilicic acid and the tail liquid react at room temperature for 45 minutes;

[0017] S3: sending water into the stirring tank 3 through the water inlet pipe for stirring and mixing, wherein the water and the tail liquid are mixed in a ratio of 1:1;

[0018] S4: hot water at a temperature of 70° C. is continuously fed into the jacket of the stirring tank 3, and ammonia is introduced into the stirring tank 3 through the ammonia pipe for bubbling and stirring reaction. The ammonia discharged from the stirring tank 3 is sent to the ammonia recovery system through the exhaust pipe. When the online pH detector detects that the pH of the tail liquid is 3.5, the stirring tank 3 stops stirring and the feeding of ammonia is stopped. Then, the stirring tank 3 is allowed to stand for sedimentation and the tail liquid is sent to the second filter 4 for filtration, wherein the filter cloth used in the second filter 4 is 100-160 mesh;

[0019] S5: The filtrate filtered out by the second filter 4 is sent to the second stirring tank 5, and ammonium fluoride solid is added to the second stirring tank 5, and the liquid-to-solid ratio of the added ammonium fluoride solid to the filtrate is 1:0.01;

[0020] S6: After the filtrate reacts with the ammonium fluoride solid to obtain a slurry, the slurry is allowed to stand and then sent to the third filter 6 for filtration, and the filter cloth used in the third filter 6 is 100-160 mesh;

[0021] S7: The filtrate filtered out by the third filter 6 is sent to the concentration tank 7. The concentration tank 7 concentrates the filtrate to a relative density of 1.38 and then sends it to the crystallization tank 8 for crystallization to obtain industrial grade monoammonium phosphate, wherein cooling water with a temperature of 40°C needs to be sent into the jacket of the crystallization tank 8.

[0022] S8: Send the crystallized monoammonium phosphate crystals to centrifuge 9 for solid-liquid separation.

[0023] S9: The centrifuged monoammonium phosphate crystals are conveyed by a screw conveyor into a fluidized bed 10 for drying to obtain industrial-grade monoammonium phosphate.

[0024] The method not only improves the removal rate of impurities in the raffinate acid, but also increases the content of total nitrogen in the total nutrients of the product, thereby improving the product quality and the added value of the raffinate acid product.

[0025] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the utility model concept. The protection scope of the utility model should not be deemed to be limited to the specific forms described in the embodiments. The protection scope of the utility model also extends to equivalent technical means that can be thought of by those skilled in the art based on the concept of the utility model.

Claims

1. A device for producing monoammonium phosphate from refined phosphoric acid tail liquid, characterized in that: The invention comprises a first stirring tank (1), a first filter (2), a stirring tank (3), a second filter (4), a second stirring tank (5), a third filter (6), a concentration tank (7), a crystallization tank (8), a centrifuge (9) and a fluidized bed (10) which are connected in sequence. The stirring tank (3) and the crystallization tank (8) are provided with jackets outside. The stirring tank (3) is connected to a fluorosilicic acid pipe, an exhaust pipe, a water inlet pipe and an ammonia pipe.

2. The device for producing monoammonium phosphate from refined phosphoric acid tail liquid according to claim 1, characterized in that: An aeration pipe is provided at the bottom of the stirring tank (3), and the ammonia pipe is connected to the aeration pipe.

3. The device for producing monoammonium phosphate from refined phosphoric acid tail liquid according to claim 1, characterized in that: The exhaust pipe is connected to the ammonia recovery system.

4. The device for producing monoammonium phosphate from refined phosphoric acid tail liquid according to claim 1, characterized in that: The first filter (2), the second filter (4) and the third filter (6) are all plate-and-frame filters.

5. The device for producing monoammonium phosphate from refined phosphoric acid tail liquid according to claim 1, characterized in that: An online pH detector is installed on the stirring tank (3).

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