CN-122006635-A - Extraction system and process of semi-aqueous wet-process phosphoric acid

CN122006635ACN 122006635 ACN122006635 ACN 122006635ACN-122006635-A

Abstract

The invention discloses an extraction system and a process of semi-aqueous wet phosphoric acid, which relate to the field of wet phosphoric acid production and aim to solve the problems of unbalanced reaction heat removal, unstable crystallization control, uneven heat utilization, fluorine dissipation environmental protection risks and the like of the traditional semi-aqueous process; each unit is organically linked, and through flash evaporation cooling and steam heat supplementing cooperative temperature control, crystal slurry flows back to provide stable seed crystals, and waste gas is collected and treated in a concentrated manner, so that the heat balance of the system, the optimization of crystallization quality and the environment protection reach the standard are realized. The invention has reasonable structure, stable operation, low energy consumption, small phosphorus loss, coarse gypsum crystallization and easy filtration, and can remarkably improve the efficiency, economy and environmental protection of the semi-aqueous wet phosphoric acid production.

Inventors

Li Lvchao
LI WENCHAO
LI KAI
YAN SHIKE
LI YONGHUI

Assignees

昆明尔康科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260326

Claims (10)

1. The extraction system of the wet phosphoric acid by the semi-aqueous method is characterized by comprising a raw material pretreatment unit, a multi-stage reaction unit, a flash evaporation cooling unit, a crystallization and crystal growing unit, a crystal slurry reflux unit, a steam heat supplementing unit and an exhaust gas centralized treatment unit; The raw material pretreatment unit comprises an ore pulp tank (105), an ore pulp pump (104), an ore pulp filter press (103), a conveying belt (102), a concentrate warehouse (101), a metering belt (1) and a high-level dissolution tank (2) which are connected in sequence; the multistage reaction unit comprises a first reaction tank (3), a second reaction tank (4), a third reaction tank (5) and a fourth reaction tank (6) which are sequentially connected in series; The flash cooling unit comprises an axial flow pump (7), a high-level flash chamber (8) and a flash cooling vacuum pump (9), wherein the feeding end of the axial flow pump (7) is communicated with a fourth reaction tank (6), the discharging end of the axial flow pump is communicated with the high-level flash chamber (8), the discharging port of the high-level flash chamber (8) is communicated with a first reaction tank (3), and the flash cooling vacuum pump (9) is communicated with the high-level flash chamber (8) and is used for extracting fluorine-containing gas and heat in the high-level flash chamber; The crystallization unit of growing crystals includes crystallization tank (10) and growing crystals groove (12), the overflow mouth intercommunication of feed inlet and fourth reaction tank (6) of crystallization tank (10), and the discharge gate of crystallization tank (10) and the feed inlet intercommunication of growing crystals groove (12), inside stirring rake that all is equipped with of crystallization tank (10) and growing crystals groove (12), crystallization tank (10) are equipped with concentrated sulfuric acid and add the mouth.
2. The extraction system of wet phosphoric acid by semi-aqueous method of claim 1, wherein the high-level dissolution tank (2) is internally provided with a stirring paddle and a guide cylinder, and the high-level dissolution tank (2) is communicated with a filter of a subsequent filtering process and is used for receiving dilute phosphoric acid returned by the filter.
3. The extraction system of wet phosphoric acid by a semi-aqueous method according to claim 1, wherein the first reaction tank (3) and the third reaction tank (5) are respectively provided with a concentrated sulfuric acid inlet, the discharge port of the high-level dissolution tank (2) is communicated with the feed port of the first reaction tank (3), and stirring paddles and a baffle plate for preventing vortex are arranged inside each reaction tank.
4. The extraction system of wet phosphoric acid by semi-aqueous method according to claim 1, wherein the crystal slurry reflux unit comprises a slurry reflux pump (11), the feed end of the slurry reflux pump (11) is communicated with the crystallization tank (10), and the discharge end of the slurry reflux pump is respectively communicated with the first reaction tank (3) and the fourth reaction tank (6) and is used for refluxing crystal nucleus-containing slurry in the crystallization tank (10) to the first reaction tank (3) and the fourth reaction tank (6) to serve as seed crystals.
5. The extraction system of wet phosphoric acid by semi-aqueous method according to claim 1, wherein the steam heat supplementing unit comprises a steam adding pipeline (15) and a control valve, and the steam adding pipeline (15) is respectively communicated with the first reaction tank (3), the third reaction tank (5) and the crystallization tank (10) and is used for supplementing low-pressure steam to each tank body.
6. The extraction system of wet phosphoric acid by a semi-aqueous method according to claim 1, wherein the waste gas centralized processing unit comprises a centralized fan (13) and a tail gas washing system (14), gas phase spaces of the first reaction tank (3), the second reaction tank (4), the third reaction tank (5), the fourth reaction tank (6), the crystallization tank (10) and the crystal growth tank (12) are all communicated through pipelines, an air inlet end of the centralized fan (13) is communicated with the gas phase space of the crystallization tank (10), an air outlet end of the centralized fan is communicated with the tail gas washing system (14), and the tail gas washing system (14) is used for processing fluorine-containing waste gas and generating fluosilicic acid.
7. The extraction system of the wet-process phosphoric acid by the semi-aqueous method according to claim 1, wherein the ore pulp filter press (103) is a plate-and-frame filter press and is used for dehydrating phosphorite slurry with the solid content of about 68% conveyed by the ore pulp tank (105) to the water content of about 13%, and the metering belt (1) is used for accurately metering the feeding amount of the wet ore entering the high-level dissolving tank (2) so as to realize water balance and reaction stability of the system.
8. The extraction system of wet phosphoric acid by semi-aqueous method according to claim 1, wherein the concentration fan (13) is used for establishing a micro negative pressure environment in the whole reaction extraction system, the micro negative pressure range is-100 Pa to-300 Pa, fluorine-containing waste gas escaping from each tank body is forcedly collected, the tail gas washing system (14) is provided with a washing water circulation loop, and washing water absorbs the fluorine-containing waste gas through repeated circulation washing and gradually concentrates to form fluosilicic acid products.
9. A process for the extraction of phosphoric acid by the semi-aqueous wet process based on the system according to any one of claims 1 to 8, characterized in that it comprises the following steps: s1, raw material pretreatment and pre-dissolution, namely feeding flotation ore pulp into an ore pulp tank (105) for adjustment and concentration until the solid content is about 68%, conveying the flotation ore pulp to an ore pulp filter press (103) through an ore pulp pump (104) for deep dehydration to obtain wet ore with the water content of about 13%, feeding the wet ore into a concentrate warehouse (101) for stockpiling and homogenization through a conveying belt (102), feeding the wet ore into a high-level dissolving tank (2) after accurate metering through a metering belt (1), mixing the wet ore with dilute phosphoric acid returned by a filter, forming uniform phosphorus ore pulp under the action of a stirring paddle and a guide cylinder, completing pre-dissolution and pulp mixing, and simultaneously recycling waste heat of returned acid to improve the initial temperature of the ore pulp; S2, multistage extraction reaction, namely automatically flowing phosphorite slurry in a high-level dissolving tank (2) into a first reaction tank (3) by gravity, adding 98% of concentrated sulfuric acid into the first reaction tank (3), simultaneously introducing crystal slurry which flows back from a crystallization tank (10) by a slurry return pump (11), introducing low-pressure steam according to the reaction temperature to maintain the optimal initial reaction temperature, flowing mixed slurry out of the bottom of the first reaction tank (3), sequentially and serially flowing into a second reaction tank (4), a third reaction tank (5) and a fourth reaction tank (6), supplementing 98% of concentrated sulfuric acid and low-pressure steam into the third reaction tank (5) to maintain the reaction condition, and carrying out total reaction time for 4-6 hours until the phosphorite decomposition rate reaches more than 97%, thereby generating calcium sulfate hemihydrate slurry; S3, flash evaporation cooling and heat circulation, namely pumping high-temperature slurry in a fourth reaction tank (6) to a high-position flash evaporation chamber (8) through an axial flow pump (7), rapidly flashing water in the slurry and taking away a large amount of latent heat under a negative pressure environment formed by a flash cooling vacuum pump (9), enabling the temperature of the slurry to rapidly drop, pumping fluorine-containing water vapor generated by flash evaporation by the flash cooling vacuum pump (9), enabling the cooled slurry to automatically flow back to the first reaction tank (3) by virtue of gravity, realizing heat balance and temperature control balance of the system, and using high-temperature heat energy recovered by flash evaporation for other production procedures; S4, crystallizing, crystal growing and crystal slurry reflux, namely overflowing the slurry in the fourth reaction tank (6) from the upper part into the crystallization tank (10), accurately controlling the crystallization temperature by introducing low-pressure steam into the crystallization tank (10), controlling the supersaturation degree of the slurry through the rotating speed of a stirrer, enabling the hemihydrate gypsum to grow in a crystal mode, quantitatively refluxing the slurry containing a large amount of hemihydrate gypsum crystal nucleus in the crystallization tank (10) to the first reaction tank (3) and the fourth reaction tank (6) through a slurry return pump (11), promoting the directional growth of the crystal as a seed crystal, enabling the slurry at the bottom of the crystallization tank (10) to flow into the crystal growing tank (12), realizing the curing and coarsening of the crystal under mild stirring, and enabling the dissolution of the tiny crystal and the continuous growth of the coarse crystal through the Oswald curing effect; S5, the waste gas is intensively treated and separated from products, namely, a micro negative pressure is established in a system formed by each reaction tank, a crystallization tank (10) and a crystal growing tank (12) through a centralized fan (13), fluorine-containing waste gas escaping from each tank body is forcedly and intensively extracted to a tail gas washing system (14), the waste gas is reversely washed by adopting washing water circulation, fluoride is absorbed and concentrated to generate fluosilicic acid byproducts, purified tail gas is discharged up to standard, and slurry in the crystal growing tank (12) is conveyed to a filtering section for liquid-solid separation, so that a finished phosphoric acid product and a coarse and easy-to-filter gypsum filter cake are obtained.
10. The process for extracting phosphoric acid by a semi-aqueous wet process according to claim 9, wherein in S3, the temperature of the slurry after flash cooling is reduced from 105 ℃ to about 95 ℃, and in S4, the crystallization temperature in the crystallization tank (10) is controlled to about 105 ℃.

Description

Extraction system and process of semi-aqueous wet-process phosphoric acid Technical Field The invention relates to the field of wet-process phosphoric acid production, in particular to an extraction system and process of semi-aqueous wet-process phosphoric acid. Background The semi-aqueous wet-process phosphoric acid process can directly produce phosphoric acid with higher concentration, and gypsum crystallization property can be regulated and controlled, so that the process is widely applied to the field of wet-process phosphoric acid production. However, the conventional semi-water process has a plurality of defects in actual operation, and seriously affects the production efficiency, the product quality and the environmental protection performance: 1. The unbalance of the reaction heat removal is that the reaction of phosphorite and concentrated sulfuric acid releases heat severely, so that the system temperature is higher and difficult to control accurately, the conversion of semi-hydrated gypsum to anhydrous gypsum is easy to be caused by the excessive temperature, the scaling of equipment is caused, and the equipment corrosion and the escape of fluorine are aggravated; 2. the crystallization control is unstable, the growth and conversion of gypsum crystals are extremely sensitive to supersaturation, temperature and crystal nucleus quantity, the crystal nucleus generation and growth conditions in the traditional process are difficult to coordinate, fine and uneven crystals are easy to generate, the subsequent filtering performance is poor, the washing efficiency is low, and the phosphorus loss is larger; 3. The heat utilization of the system is unbalanced, namely, the problem of heat surplus exists in the reaction zone, and the crystallization zone needs to be supplemented with heat to maintain proper crystallization temperature, so that the overall heat utilization efficiency needs to be improved; 4. fluorine dissipation control is insufficient, namely fluorine-containing gas collection points which are escaped in the reaction and crystallization processes are dispersed, treatment is not centralized, and the environment-friendly risk of unorganized emission exists; 5. The prior art is improved aiming at a single link (such as cooling or crystallization), and lacks a solution for systematically and synergistically innovation of heat balance, crystallization control and waste gas centralized treatment, so that the comprehensive problems cannot be fundamentally solved. Therefore, we propose an extraction system and process of semi-aqueous wet phosphoric acid to solve the above problems. Disclosure of Invention Aiming at the defects of the prior art, the invention provides an extraction system and a process of semi-aqueous wet-process phosphoric acid, and solves the problems of the prior art. The extraction system of the semi-aqueous wet-process phosphoric acid comprises a raw material pretreatment unit, a multi-stage reaction unit, a flash evaporation cooling unit, a crystallization crystal growing unit, a crystal slurry reflux unit, a steam heat supplementing unit and an exhaust gas centralized treatment unit; The raw material pretreatment unit comprises an ore pulp tank, an ore pulp pump, an ore pulp filter press, a conveying belt, a concentrate warehouse, a metering belt and a high-level dissolution tank which are connected in sequence; The multistage reaction unit comprises a first reaction tank, a second reaction tank, a third reaction tank and a fourth reaction tank which are sequentially connected in series; The flash cooling unit comprises an axial flow pump, a high-level flash chamber and a flash cooling vacuum pump, wherein the feeding end of the axial flow pump is communicated with the fourth reaction tank, the discharging end of the axial flow pump is communicated with the high-level flash chamber, the discharging port of the high-level flash chamber is communicated with the first reaction tank, and the flash cooling vacuum pump is communicated with the high-level flash chamber and is used for extracting fluorine-containing gas and heat in the high-level flash chamber; the crystallization crystal growing unit comprises a crystallization tank and a crystal growing tank, wherein a feed inlet of the crystallization tank is communicated with an overflow port of a fourth reaction tank, a discharge port of the crystallization tank is communicated with a feed inlet of the crystal growing tank, stirring paddles and vortex-preventing baffle plates are arranged inside the crystallization tank and the crystal growing tank, and a concentrated sulfuric acid feeding port is arranged in the crystallization tank. As a further technical scheme of the invention, the stirring paddles and the guide cylinder are arranged in the high-level dissolution tank, and the high-level dissolution tank is communicated with the filter in the subsequent filtering process and is used for receiving dilute phosphoric acid return