Extraction apparatus for wet-process phosphoric acid

Abstract

This utility model discloses an extraction device for wet-process phosphoric acid, belonging to the field of phosphoric acid chemical technology. It includes an extraction tank, a flash cooling structure, and a rotary vacuum filter. The extraction tank comprises multiple reaction tanks and digestion tanks. The flash cooling structure includes a circulating cooling tower, a flash cooler, a primary precooler, a secondary precooler, a condenser, a flash vacuum pump, a hot water tank, and a neutralization return water tank. The precooler is connected to the circulating cooling tower. The flash cooler, primary precooler, secondary precooler, condenser, and flash vacuum pump are connected sequentially. The primary precooler is connected to the hot water tank. The secondary precooler has two outputs, one connected to the hot water tank and the other to the neutralization settling tank. The condenser is connected to the neutralization return water tank. The neutralization return water tank is connected to the neutralization settling tank. The neutralization return water tank has three outputs, one connected to the condenser, and the other two connected to the three washing zones of the rotary vacuum filter and the belt filter, respectively. The hot water tank is connected to the atmospheric condensers of the rotary vacuum filter and the belt filter.

Description

Technical Field

[0001] This utility model belongs to the field of phosphoric acid technology, and specifically relates to an extraction device for wet phosphoric acid, which optimizes the application of condensate while ensuring the cooling of the reaction solution. Background Technology

[0002] Wet-process phosphoric acid is one of the important methods for producing phosphoric acid and a fundamental product of the phosphorus chemical industry, widely used in the phosphate and compound fertilizer industries. In the wet-process preparation of phosphoric acid, sulfuric acid is used to decompose the slurry, obtaining a mixed slurry of phosphoric acid and calcium sulfate dihydrate crystals. During the decomposition process, reaction conditions such as SO3 concentration and temperature need to be controlled to obtain coarse, uniform, and easily filtered and washed calcium sulfate dihydrate crystals. The resulting mixed slurry of phosphoric acid and calcium sulfate dihydrate crystals is then separated into liquid and solid components using vacuum filtration (specifically, a rotary vacuum filter) to obtain dilute phosphoric acid and phosphogypsum. Side reactions also occur during the decomposition process, generating gases such as carbon dioxide, hydrogen fluoride, and silicon tetrafluoride. All of these reactions are carried out in a wet-process phosphoric acid extraction tank. The phosphogypsum can be dried by wet or dry discharge (specifically, a belt filter).

[0003] In the prior art, in order to control the temperature of the slurry in the extraction tank, a portion of the slurry in the last reaction tank is cooled by a flash cooler before being sent into the first reaction tank, so that the temperature of the slurry in the reaction tank is maintained below 90°C.

[0004] For example, patent application number CN201720683310.7 discloses a wet phosphoric acid extraction tank, including reaction tank A, reaction tank B, reaction tank C, reaction tank D, reaction tank E, reaction tank F, digestion tank A, digestion tank B, digestion tank C, and flash cooling system. The reaction tanks A, B, C, D, E, and F, as well as the digestion tanks A, B, and C, are connected in sequence. The flash cooling system is connected to reaction tanks A and F respectively. The tops of reaction tanks B, C, and D are higher than the tops of reaction tanks A, E, and F. Each of the tops of reaction tanks B, C, and D has two acid inlets.

[0005] For example, patent application number CN201921454876.8 discloses a wet-process phosphoric acid extraction tank, which consists of a reaction tank and a digestion tank. The reaction tank is composed of zones one to six, and the digestion tank is composed of zones seven to nine. An agitator is installed in each zone of the extraction tank. Zone one has a side channel for the cooling slurry to enter, and zone six has a side channel for the slurry axial flow pump interface. Zones two and three each have a mixing tee interface at the top. Zone six has an overflow port for the slurry to enter the digestion tank. Gate-type openings for the flow of the extraction reaction slurry are provided in the partition walls between zones one and two, two and three, three and four, four and five, five and six, seven and eight, and eight and nine. Each zone is lined with a rubber sheet impermeable layer, and the rubber sheet is lined with a carbon brick anti-corrosion layer. A carbon brick wear-resistant layer is placed below the agitator in each zone. Waste gas outlets are provided at the top of zones three and four. The sixth zone of the reaction tank in the wet-process phosphoric acid extraction tank is also equipped with a low-level flash cooling circulation pump.

[0006] For example, patent application number CN202010824645.2 discloses a defoaming feeding control device for wet phosphoric acid extraction reaction, including an extraction tank and a flash evaporator. The extraction tank consists of reaction tanks 1#-6# and digestion tanks 7#-9#, which are connected in sequence. The overflow from reaction tank 6# goes to digestion tank 7#, digestion tank 7# is connected to digestion tank 8#, and the overflow from digestion tank 8# goes to digestion tank 9#. A circulation pump is installed in reaction tank 6#, and the outlet of the circulation pump is connected to one end of the flash evaporator through a pipe. The other end of the flash evaporator is connected to reaction tank 1#. A phosphate rock slurry inlet is provided on reaction tank 1#, and sulfuric acid inlets are provided on reaction tanks 2# and 3#. Sulfuric acid inlets are also provided on the pipes.

[0007] For example, patent application number CN202011198890.3 discloses a method for removing sulfate from wet-process dilute phosphoric acid in phosphate rock slurry, the specific steps of which are:

[0008] (1) Phosphate slurry is pumped and metered by a flow meter from the thickening system and sent to the first chamber of the reaction tank; 93-98% concentrated sulfuric acid is also metered and sent by the sulfuric acid workshop to the mixing tee on the second and third chambers of the reaction tank and the first chamber of the digestion tank via pipeline.

[0009] (2) Phosphate slurry, sulfuric acid and phosphoric acid undergo a chemical reaction in a reaction tank to produce calcium sulfate dihydrate crystals and phosphoric acid.

[0010] (3) Phosphate rock slurry and sulfuric acid are set at a certain flow rate. After being metered, sulfuric acid is premixed with acid returned from filtration in the mixing three-way valve and added to the second and third chambers of the reaction tank.

[0011] (4) The reaction slurry is circulated by a low-level flash cooling circulation pump located in the sixth chamber of the reaction tank, and the cooled slurry returns to the first chamber of the reaction tank by gravity from the low-level flash cooler.

[0012] (5) The gas discharged from the low-level flash cooler first enters the precooler circulation tank in the precooler with return water from the gypsum slag yard. When dry slag discharge is adopted, industrial water is added to the tank and the gas is circulated and washed by the pump. Part of the steam is condensed. The excess circulating water is sent to the filter washing water tank as filter washing water. The gas enters the condenser and is further condensed with circulating cooling water from the circulating water system. The cooling water returns to the circulating cooling tower through the return water tank and the gas from the condenser is separated by the condenser demister. The non-condensable gas is extracted by the low-level flash cooler vacuum pump to keep the vacuum cooling system operating under negative pressure. The vacuum degree is controlled by the venting regulating valve. The gas extracted by the vacuum pump is discharged into the atmosphere.

[0013] (6) The phosphoric acid slurry in the sixth chamber of the reaction tank overflows into the first chamber of the digestion tank to prolong the residence time. The slurry is pumped from the third chamber of the digestion tank to the filter.

[0014] (7) Sulfuric acid can be added to the first chamber of the digester through the sulfuric acid feed pipe so as to adjust the SO3 concentration in the digester accordingly.

[0015] Existing wet-process phosphoric acid extraction equipment includes an extraction tank, a flash cooling structure, and a rotary vacuum filter. The extraction tank comprises multiple reaction tanks and multiple digestion tanks connected in sequence. The flash cooling structure includes a circulating cooling tower, a flash cooler, a precooler, a condenser, a flash vacuum pump, and a condensate tank. The flash cooler's inlet is connected to the last reaction tank, and its outlet is connected to the first reaction tank. The flash cooler, precooler, condenser, and flash vacuum pump are connected in sequence via pipelines. The cooling water inlets of the precooler and condenser are both connected to the circulating cooling tower via pipelines, and their condensate outlets are both connected to the condensate tank via pipelines. The condensate tank outputs water in two directions via pipelines: one output goes to the circulating cooling tower, and the other outputs to the rotary vacuum filter as wash water.

[0016] During actual use, the applicant found that the temperature of the slurry in the reaction tank was usually 90℃, occasionally reaching 95℃, resulting in a high temperature that affected the yield. Furthermore, the water volume, temperature, and cleanliness of the precooler and condenser were different, and both were sent to a rotary vacuum filter as wash water, which could not be completely consumed. Summary of the Invention

[0017] To address the aforementioned problems, this utility model provides a wet-process phosphoric acid extraction apparatus that can control the slurry temperature in the extraction tank to consistently remain below 85°C, thereby increasing the phosphorus yield by approximately 1%, while also optimizing the application of condensate. The technical solution is as follows:

[0018] This utility model provides an extraction device for wet-process phosphoric acid. The device includes an extraction tank, a flash cooling structure, and a rotary vacuum filter. The extraction tank comprises multiple reaction tanks and digestion tanks connected in sequence. The flash cooling structure includes a circulating cooling tower 7, a flash cooler 1, a precooler, a condenser 4, and a flash cooling vacuum pump 5. The inlet of the flash cooler 1 is connected to the last reaction tank, and its outlet is connected to the first reaction tank. The cooling water inlet of the precooler is connected to the circulating cooling tower 7 via a pipeline. There are two precoolers: a primary precooler 2 and a secondary precooler 3. The flash cooler 1, primary precooler 2, secondary precooler 3, condenser 4, and flash cooling vacuum pump 5 are connected in sequence via pipelines. The flash cooling structure also includes a hot water tank 9 and a neutralization return water tank 10. The condensate outlet of the primary precooler 2 is connected to the hot water tank 9 via a pipeline. The inlet of water tank 9 is connected; the condensate outlet of the secondary precooler 3 is split into two paths, one connected to the inlet of hot water tank 9 via a pipeline, and the other connected to the inlet of the neutralization and settling tank of the phosphogypsum drying device via a pipeline; the condensate outlet of the condenser 4 is connected to the inlet of the neutralization return water tank 10 via a pipeline; the inlet of the neutralization return water tank 10 is connected to the clean water outlet of the neutralization and settling tank via a pipeline; the neutralization return water tank 10 is split into three paths, the first connected to the cooling water inlet of the condenser 4 via a pipeline, the second connected to the third washing zone of the rotary vacuum filter via a pipeline, and the third connected to the third washing zone of the belt filter of the phosphogypsum drying device via a pipeline; the hot water tank 9 is split into two paths, one connected to the atmospheric condenser of the rotary vacuum filter via a pipeline, and the other connected to the atmospheric condenser of the belt filter via a pipeline.

[0019] Furthermore, the flash cooling structure in this embodiment of the present invention also includes a gas-liquid separator 6; the inlet of the gas-liquid separator 6 is connected to the exhaust port of the flash cooling vacuum pump 5 through a pipeline, and its liquid phase outlet is connected to the inlet of the hot water tank 9 through a pipeline.

[0020] Furthermore, in this embodiment of the present invention, the hot water tank 9 is provided with an overflow port at its upper part, and the overflow port of the hot water tank 9 is connected to the circulating cooling tower 7 through a pipeline.

[0021] Specifically, in this embodiment of the present invention, there are six reaction tanks, three digestion tanks, and the feed inlet of the flash cooler 1 is connected to the sixth reaction tank.

[0022] More specifically, in this embodiment of the present invention, the six reaction tanks and three digestion tanks are arranged in a nine-square grid. The first reaction tank is adjacent to the sixth reaction tank, the sixth reaction tank is adjacent to the first digestion tank, and the third digestion tank is connected to the inlet of the rotary vacuum filter through a pipeline.

[0023] Furthermore, in this embodiment of the present invention, the bottom of the primary precooler 2, the secondary precooler 3 and the condenser 4 are all provided with liquid seal tanks 8; the condensate outlet at the lower part of the liquid seal tank 8 of the primary precooler 2 is connected to the hot water tank 9 through a pipeline, and the overflow port at the upper part is connected to the circulating cooling tower 7 through a pipeline.

[0024] Specifically, in this embodiment of the invention, the hot water tank 9 is lower than the primary precooler 2, the secondary precooler 3, and the gas-liquid separator 6; the neutralization return water tank 10 is lower than the condenser 4; and the circulating cooling tower 7 is lower than the hot water tank 9. The condensate outlet of the secondary precooler 3 is connected to the neutralization sedimentation tank via a pipeline equipped with a first water pump 11. The hot water tank 9 is connected to the atmospheric condenser of the rotary vacuum filter via a pipeline equipped with a second water pump 12 and a valve, and is connected to the gas-liquid separator via a pipeline equipped with a third water pump 13 and a valve. The atmospheric condenser of the filter is connected; the neutralization return water tank 10 is connected to the three-wash zone of the rotary vacuum filter through a pipeline with a fourth water pump 14 and a valve, and is connected to the three-wash zone of the belt filter of the phosphogypsum drying device through a pipeline with a fifth water pump 15 and a valve, and is connected to the cooling water inlet of the condenser 4 through a pipeline with a first spray pump 16 and a valve; the circulating cooling tower 7 is connected to the cooling water inlets of the primary precooler 2 and the secondary precooler 3 through a pipeline with a second spray pump 17.

[0025] More specifically, in this embodiment of the present invention, the primary precooler 2 and the secondary precooler 3 both have a diameter of 1900mm and a height of 9200mm; the primary precooler 2 is connected to the circulating cooling tower 7 through two parallel second spray pumps 17, and the secondary precooler 3 is connected to the circulating cooling tower 7 through three parallel second spray pumps 17; the flow rate of the second spray pumps 17 is 600 cubic meters per hour.

[0026] Furthermore, in this embodiment of the invention, the water inlet of the circulating cooling tower 7 is connected to the phosphogypsum return water storage tank via a pipeline.

[0027] The beneficial effects of the technical solution provided by this utility model embodiment are as follows: This utility model embodiment provides an extraction device for wet phosphoric acid, which can control the temperature of the slurry in the extraction tank to always not exceed 85°C, and the phosphorus yield can be increased by about 1%, while optimizing the application of condensate.

[0028] Specifically, the condensate from the primary precooler has a small volume, high temperature (the hot water output from the hot water tank is 60-70℃), and high fluoride content; the condensate from the secondary precooler also has a small volume, high temperature (the hot water output from the hot water tank is 60-70℃), and lower fluoride content than the hot water output from the primary precooler. It is preferentially sent to the neutralization and settling tank as makeup water (meeting makeup water requirements and requiring relatively clean water), with any surplus sent to the atmospheric condenser (utilizing relatively clean hot water, reducing the need for condensate from the secondary precooler). After reaching the atmospheric condenser, the temperature further increases, serving as flushing water for the rotary vacuum filter and belt filter, improving flushing efficiency. The condenser has a large volume, slightly lower temperature, and is the cleanest; it mixes with clean water from the neutralization and settling tank (weakly alkaline, purifying the condensate from the secondary precooler and the first flushing wastewater; this lowers the temperature of the condensate in the condenser). The water output from the neutralization return water tank has a temperature of 30-45℃ (suitable for condenser circulation spray), is slightly alkaline, clean (low fluoride content), and has a large flow rate. Utilizing the condensate through a rotary vacuum filter and phosphogypsum drying device not only increases consumption but also offers greater flexibility (adjustable as needed). Furthermore, the load on the circulating cooling tower is reduced (the condensate from the precooler is used hot, requiring no cooling; the return water from the neutralization settling tank cools the condensate in the condenser, eliminating the need for condensate consumption). However, it consumes more phosphogypsum return water (if the circulating cooling tower has insufficient return water, it needs continuous replenishment of phosphogypsum return water). Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the existing wet-process phosphoric acid extraction device;

[0030] Figure 2 This is a schematic block diagram of the wet-process phosphoric acid extraction device provided in this embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the extraction tank;

[0032] Figure 4 This is a connection diagram of the extraction device and the phosphogypsum drying device;

[0033] Figure 5 This is a schematic diagram of the belt filter in a phosphogypsum drying device.

[0034] Figure 6 This is a schematic diagram of the atmospheric condenser in a phosphogypsum drying device.

[0035] Figure 7 This is a schematic diagram of the structure of the wet-process phosphoric acid extraction device provided in this embodiment of the present invention.

[0036] In the diagram: 1 Flash cooler, 2 First-stage precooler, 3 Second-stage precooler, 4 Condenser, 5 Flash vacuum pump, 6 Gas-liquid separator, 7 Circulating cooling tower, 8 Liquid seal tank, 9 Hot water tank, 10 Neutralization return water tank, 11 First water pump, 12 Second water pump, 13 Third water pump, 14 Fourth water pump, 15 Fifth water pump, 16 First spray pump, 17 Second spray pump;

[0037] A goes to the first reaction tank, B comes from the last reaction tank, C goes to the atmospheric condenser of the rotary vacuum filter, D goes to the atmospheric condenser of the belt filter, E goes to the neutralization and settling tank, F comes from the neutralization and settling tank, G goes to the third washing zone of the rotary vacuum filter, and H goes to the third washing zone of the belt filter. Detailed Implementation

[0038] To make the objectives, technical solutions and advantages of this utility model clearer, the utility model will be described in further detail below with reference to the accompanying drawings.

[0039] Example 1

[0040] See Figure 2-7 Example 1 provides an extraction apparatus for wet-process phosphoric acid, which includes an extraction tank, a flash cooling structure, and a rotary vacuum filter.

[0041] The extraction tank is used to react phosphate rock slurry with concentrated sulfuric acid. It includes multiple reaction tanks and multiple digestion tanks connected in sequence. The extraction tank is connected to the tail gas treatment device through pipelines. The tail gas treatment device is mainly used to treat acidic and fluorine-containing tail gas.

[0042] The rotary vacuum filter is used to filter the slurry after the reaction to obtain wet phosphoric acid and phosphogypsum. The rotary vacuum filter is equipped with an atmospheric condenser and a vacuum pump, etc. It includes a primary filtration zone, a filtration zone, a first washing zone, a second washing zone, a third washing zone and a filter cloth regeneration zone, etc. The specific structure is the same as the application number CN201921497395.5 (applied by our company in 2019).

[0043] The flash cooling structure includes a circulating cooling tower 7, a flash cooler 1, a primary precooler 2, a secondary precooler 3, a condenser 4, a flash vacuum pump 5, a gas-liquid separator 6, a hot water tank 9, and a neutralization return water tank 10. The inlet of the flash cooler 1 is connected to the last reaction tank, and its outlet is connected to the first reaction tank. The cooling water inlets of the primary precooler 2 and the secondary precooler 3 are connected to the circulating cooling tower 7 via pipelines. The flash cooler 1, primary precooler 2, secondary precooler 3, condenser 4, flash vacuum pump 5, and gas-liquid separator 6 are connected sequentially via pipelines. The liquid phase outlet of the gas-liquid separator 6 is connected to the inlet of the hot water tank 9 via a pipeline. The bottom of the primary precooler 2, secondary precooler 3, and condenser 4 are all equipped with liquid seal tanks 8 for liquid sealing and condensate collection.

[0044] In this system, the condensate outlet at the bottom of the liquid seal tank 8 of the primary precooler 2 is connected to the hot water tank 9 via a pipeline, and its overflow outlet at the top is connected to the circulating cooling tower 7 via a pipeline to send excess hot water to the circulating cooling tower 7 for cooling. The condensate outlet (located at the bottom) of the liquid seal tank 8 of the secondary precooler 3 has two outputs: one is connected to the inlet of the hot water tank 9 via a pipeline, and the other (preferred output) is connected to the inlet of the neutralization and settling tank of the phosphogypsum drying device via a pipeline. The condensate outlet of the condenser 4 is connected to the inlet of the neutralization return water tank 10 via a pipeline; the inlet of the neutralization return water tank 10 is connected to the clean water outlet of the neutralization and settling tank via a pipeline. The structure of the phosphogypsum drying device can be found in the description of application number CN202222150816.5 (applied by our company in 2022). The neutralization and settling tank replaces the filter press and the filter liquid storage tank to achieve solid-liquid separation.

[0045] The neutralization return water tank has three outputs: the first (priority output) is connected to the cooling water inlet of the condenser 4 through a pipeline; the second is connected to the three washing zones of the rotary vacuum filter (which can be sent to the corresponding washing water heating tank for heating as needed) through a pipeline; and the third is connected to the three washing zones of the belt filter of the phosphogypsum drying device through a pipeline.

[0046] The hot water tank 9 has two outputs. One output is connected via a pipeline to the atmospheric condenser of the rotary vacuum filter (spraying hot water to condense the gas, see the description in application number CN202311163129.X), and the other output is connected via a pipeline to the atmospheric condenser of the belt filter (spraying hot water to condense the gas, see the description in application number CN202311163129.X, preferably mixed with phosphogypsum return water to cool it to below 45°C). The hot water tank 9 has an overflow port at the top, which is connected via a pipeline to the circulating cooling tower 7 to send excess hot water to the circulating cooling tower 7 for cooling.

[0047] Furthermore, in this embodiment of the invention, the water inlet of the circulating cooling tower 7 is connected to the phosphogypsum return water storage tank via a pipeline to replenish water to the circulating cooling tower 7.

[0048] The temperature in each zone of the extraction tank is reduced to below 85℃, accelerating the hemihydrate to dihydrate crystallization reaction rate, improving the dihydrate crystal form, increasing the washing rate, and thus increasing the phosphorus yield, from 92% to 93%. For a wet-process phosphoric acid production line with an annual output of 300,000 tons, the annual savings in standard ore (containing 28% P2O5) from 92% to 93% is approximately 10,743 tons. Assuming a standard ore price of 1,000 yuan / ton, the annual benefit is 10,743 * 1,000 = 10,714,300 yuan.

[0049] Example 2

[0050] See Figure 3 Example 2 provides a wet-process phosphoric acid extraction device, the structure of which is basically the same as that of Example 1, except that: in this example, there are six reaction tanks (numbered 1-6), and three digestion tanks (numbered 7-9). The feed inlet of flash cooler 1 is connected to the sixth reaction tank (number 6). More specifically, the six reaction tanks and three digestion tanks are arranged in a nine-square grid. The first reaction tank (number 1) is adjacent to the sixth reaction tank (number 6), the sixth reaction tank (number 6) is adjacent to the first digestion tank (number 7), and the third digestion tank (number 9) is connected to the inlet of the rotary vacuum filter through a pipeline.

[0051] Example 3

[0052] See Figure 7 Example 3 provides a wet-process phosphoric acid extraction apparatus. The structure of this apparatus is basically the same as that of Example 1, except that: in this example, the hot water tank 9 is lower than the primary precooler 2, the secondary precooler 3, and the gas-liquid separator 6; the neutralization return water tank 10 is lower than the condenser 4; and the circulating cooling tower 7 is lower than the hot water tank 9. The condensate outlet of the secondary precooler 3 is connected to the neutralization settling tank via a pipeline with a first water pump 11. The hot water tank 9 is connected to the atmospheric condenser of the rotary vacuum filter via a pipeline with a second water pump 12 and a valve, and is connected to the atmospheric condenser of the belt filter via a pipeline with a third water pump 13 and a valve. The neutralization return water tank 10 is connected to the third washing zone of the rotary vacuum filter via a pipeline with a fourth water pump 14 and a valve, and is connected to the third washing zone of the belt filter via a pipeline with a fifth water pump 15 and a valve. It is connected to the cooling water inlet of the condenser 4 via a pipeline with a first spray pump 16 and a valve. The circulating cooling tower 7 is connected to the cooling water inlets of the primary precooler 2 and the secondary precooler 3 via a pipeline with a second spray pump 17.

[0053] Example 4

[0054] Example 4 provides a wet-process phosphoric acid extraction apparatus. The structure of this apparatus is basically the same as that of Example 3, except that the primary precooler 2 and secondary precooler 3 in this example both have a diameter of 1900 mm and a height of 9200 mm, and are made of 316L material, consistent with the specifications of precoolers in the prior art. The primary precooler 2 is connected to the circulating cooling tower 7 via two parallel second spray pumps 17, and the secondary precooler 3 is connected to the circulating cooling tower 7 via three parallel second spray pumps 17. The second spray pumps 17 have a flow rate of 600 cubic meters per hour, a head of 50 m, a power of 160 kW, and a rotation speed of 1450 rpm. The liquid seal tank 8 has a diameter of 1500 mm, a height of 2000 mm, and is made of 316L material.

[0055] In this patent, pumps, flow meters, or valves may be installed on the pipelines between the various structures as needed.

[0056] 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 extraction apparatus for wet-process phosphoric acid, comprising an extraction tank, a flash cooling structure, and a rotary vacuum filter, wherein the extraction tank comprises a plurality of reaction tanks and digestion tanks connected in sequence, and the flash cooling structure comprises a circulating cooling tower (7), a flash cooler (1), a precooler, a condenser (4), and a flash cooling vacuum pump (5); the inlet of the flash cooler (1) is connected to the last reaction tank, and its outlet is connected to the first reaction tank; the cooling water inlet of the precooler is connected to the circulating cooling tower (7) via a pipeline; characterized in that, There are two precoolers, namely a primary precooler (2) and a secondary precooler (3); the flash cooler (1), primary precooler (2), secondary precooler (3), condenser (4) and flash vacuum pump (5) are connected in sequence through pipelines; The flash cooling structure also includes a hot water tank (9) and a neutralization return water tank (10). The condensate outlet of the primary precooler (2) is connected to the inlet of the hot water tank (9) via a pipeline. The condensate outlet of the secondary precooler (3) is split into two paths: one path is connected to the inlet of the hot water tank (9) via a pipeline, and the other path is connected to the inlet of the neutralization sedimentation tank of the phosphogypsum drying device via a pipeline. The condensate outlet of the condenser (4) is connected to the inlet of the neutralization return water tank (10) via a pipeline. The neutralization return water tank (10) The inlet of the neutralization and settling tank (10) is connected to the clean water outlet of the neutralization and settling tank through a pipeline; the neutralization return water tank (10) has three outputs, the first of which is connected to the cooling water inlet of the condenser (4) through a pipeline, the second of which is connected to the three-wash zone of the rotary vacuum filter through a pipeline, and the third of which is connected to the three-wash zone of the belt filter of the phosphogypsum drying device through a pipeline; the hot water tank (9) has two outputs, one of which is connected to the atmospheric condenser of the rotary vacuum filter through a pipeline, and the other of which is connected to the atmospheric condenser of the belt filter through a pipeline.

2. The wet-process phosphoric acid extraction apparatus according to claim 1, characterized in that, The flash cooling structure also includes a gas-liquid separator (6); the inlet of the gas-liquid separator (6) is connected to the exhaust port of the flash cooling vacuum pump (5) through a pipeline, and its liquid phase outlet is connected to the inlet of the hot water tank (9) through a pipeline.

3. The wet-process phosphoric acid extraction apparatus according to claim 1, wherein The hot water tank (9) is provided with an overflow port at the top, and the overflow port of the hot water tank (9) is connected to the circulating cooling tower (7) through a pipeline.

4. The apparatus for the extraction of phosphoric acid by wet process according to claim 1, characterized in that, The number of reaction tanks is six, the number of digestion tanks is three, and the feed inlet of the flash cooler (1) is connected to the sixth reaction tank.

5. The wet-process phosphoric acid extraction apparatus according to claim 4, wherein The six reaction tanks and three digestion tanks are arranged in a nine-square grid. The first reaction tank is adjacent to the sixth reaction tank, the sixth reaction tank is adjacent to the first digestion tank, and the third digestion tank is connected to the inlet of the rotary vacuum filter through a pipeline.

6. The wet-process phosphoric acid extraction apparatus according to claim 2, wherein The bottom of the primary precooler (2), the secondary precooler (3) and the condenser (4) are all provided with liquid seal tanks (8); the condensate outlet at the bottom of the liquid seal tank (8) of the primary precooler (2) is connected to the hot water tank (9) through a pipeline, and the overflow port at the top is connected to the circulating cooling tower (7) through a pipeline.

7. The wet-process phosphoric acid extraction apparatus according to claim 6, wherein The hot water tank (9) is lower than the primary precooler (2), the secondary precooler (3), and the gas-liquid separator (6); the neutralization return water tank (10) is lower than the condenser (4); and the circulating cooling tower (7) is lower than the hot water tank (9). The condensate outlet of the secondary precooler (3) is connected to the neutralization sedimentation tank via a pipeline with a first water pump (11). The hot water tank (9) is connected to the atmospheric condenser of the rotary vacuum filter via a pipeline with a second water pump (12) and a valve, and it is connected to the belt filter via a pipeline with a third water pump (13) and a valve. The filter is connected to the atmospheric condenser; the neutralization return water tank (10) is connected to the three-wash zone of the rotary vacuum filter through a pipeline with a fourth water pump (14) and a valve, and is connected to the three-wash zone of the belt filter of the phosphogypsum drying device through a pipeline with a fifth water pump (15) and a valve, and is connected to the cooling water inlet of the condenser (4) through a pipeline with a first spray pump (16) and a valve; the circulating cooling tower (7) is connected to the cooling water inlet of the primary precooler (2) and the secondary precooler (3) through a pipeline with a second spray pump (17).

8. The wet-process phosphoric acid extraction apparatus according to claim 7, characterized in that, The primary precooler (2) and the secondary precooler (3) are both 1900mm in diameter and 9200mm in height. The primary precooler (2) is connected to the circulating cooling tower (7) via two parallel second spray pumps (17), and the secondary precooler (3) is connected to the circulating cooling tower (7) via three parallel second spray pumps (17). The flow rate of the second spray pumps (17) is 600 cubic meters per hour.

9. The apparatus for the extraction of phosphoric acid by wet process according to claim 1, characterized in that, The water inlet of the circulating cooling tower (7) is connected to the phosphogypsum return water storage tank via a pipeline.

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