阅读说明：本技术 一种半水-二水法磷酸快速萃取结晶生产系统及工艺 (Semi-water-dihydrate phosphoric acid rapid extraction crystallization production system and process ) 是由 冯克敏 文慧 姜伟 姚石林 李占荣 张森林 于 2020-05-07 设计创作，主要内容包括：本发明公开了一种半水-二水法磷酸快速萃取结晶生产系统及工艺,包括溶解槽和结晶槽,溶解槽的容积为结晶槽的2～4倍,结晶槽上连接有闪蒸分离器,闪蒸分离器底端的液相出口连接有闪蒸分离液封槽,闪蒸分离液封槽的上部通过管道与结晶槽连通；闪蒸分离液封槽的下部通过半水给料泵连接有半水过滤装置,半水过滤装置上连接有转化槽,转化槽通过二水给料泵连接有二水过滤装置；闪蒸分离器顶端的气相出口连通有雾沫分离器,雾沫分离器下端的液相出口连通闪蒸分离液封槽,雾沫分离器上端的气相出口连接有闪蒸洗涤系统。该系统和工艺可大幅缩短全系统物料停留时间,缩减幅度高达50%,有助于增加产量,降低能耗和生产成本,适用于连续大规模生产。(The invention discloses a system and a process for producing phosphoric acid by a semi-water-dihydrate method through rapid extraction crystallization, which comprises a dissolving tank and a crystallization tank, wherein the volume of the dissolving tank is 2-4 times that of the crystallization tank, the crystallization tank is connected with a flash separator, a liquid phase outlet at the bottom end of the flash separator is connected with a flash separation liquid seal tank, and the upper part of the flash separation liquid seal tank is communicated with the crystallization tank through a pipeline; the lower part of the flash separation liquid seal tank is connected with a semi-water filtering device through a semi-water feeding pump, the semi-water filtering device is connected with a conversion tank, and the conversion tank is connected with a secondary water filtering device through a secondary water feeding pump; the gas phase outlet at the top end of the flash separator is communicated with an entrainment separator, the liquid phase outlet at the lower end of the entrainment separator is communicated with the flash separation liquid seal tank, and the gas phase outlet at the upper end of the entrainment separator is connected with a flash washing system. The system and the process can greatly shorten the material retention time of the whole system, reduce the material retention time by 50 percent, are beneficial to increasing the yield and reducing the energy consumption and the production cost, and are suitable for continuous large-scale production.)

1. A semi-water-dihydrate phosphoric acid rapid extraction crystallization production system is characterized in that: the device comprises a dissolving tank, a crystallization tank, a semi-water slurry pump, a flash separator and a mist separator, wherein the volume of the dissolving tank is 2-4 times of that of the crystallization tank, the crystallization tank is connected with the dissolving tank through an overflow pipe, a return pipe and a semi-water slurry circulating pump are connected between the crystallization tank and the dissolving tank, and stirring devices are arranged in the dissolving tank and the crystallization tank;

the top of the flash separator is provided with a gas phase outlet, the upper part of the flash separator is provided with a feed inlet, the bottom of the flash separator is provided with a liquid phase outlet, one end of the semi-aqueous slurry pump is connected with the crystallization tank through a pipeline, the other end of the semi-aqueous slurry pump is connected with the feed inlet of the flash separator, and a slurry injection device is arranged at the feed inlet of the flash separator; a gas phase outlet of the flash separator is connected with the mist separator, a liquid phase outlet of the flash separator is connected with a flash separation liquid seal tank, one part of slurry in the flash separation liquid seal tank is introduced into the crystallization tank through a pipeline, and one part of slurry is sent into the semi-water filtering device through a semi-water feed pump; the semi-water filtering device is connected with a conversion tank, and the conversion tank is connected with a secondary water filtering device through a secondary water feeding pump;

the side part of the mist separator is provided with an air inlet, the top part of the mist separator is provided with a gas phase outlet, the bottom part of the mist separator is provided with a liquid phase outlet, and the liquid phase outlet of the mist separator is connected with a flash separation liquid seal tank and a gas phase outlet which are connected with a flash washing system.

2. The system for producing phosphoric acid by semi-hydrated-dihydrate method through rapid extraction and crystallization as claimed in claim 1, wherein a flue gas recovery pipe is connected above the dissolving tank and the crystallization tank, and the other end of the flue gas recovery pipe is connected with a flue gas washing system.

3. The system for producing phosphoric acid by semi-hydrated-dihydrate through rapid extraction and crystallization as claimed in claim 1, wherein a stirring device is arranged in the conversion tank.

4. A semi-water-dihydrate phosphoric acid rapid extraction crystallization production process is characterized in that the semi-water-dihydrate phosphoric acid rapid extraction crystallization production system of any one of claims 1 to 3 is adopted, and the specific process is as follows:

adding the crushed phosphorite raw material and concentrated sulfuric acid into a dissolving tank, fully stirring to enable the materials to circularly react, and reacting the phosphorite under the decomposition action of the concentrated sulfuric acid to generate calcium sulfate hemihydrate; after the reaction, the slurry overflows into a crystallization tank, excessive concentrated sulfuric acid is added into the crystallization tank, and the slurry promotes the calcium sulfate hemihydrate crystal to grow continuously under the action of the excessive concentrated sulfuric acid and active silicon dioxide; controlling the retention time of the materials in the dissolving tank to be 2-2.5 h, and controlling the retention time in the crystallization tank to be 1-1.5 h;

the slurry in the crystallization tank enters a flash separator through a semi-aqueous slurry pump for cooling, the pressure of the flash separator is controlled to be 10-15 KPa, and the temperature difference between an inlet and an outlet is controlled to be 10-25 ℃; the slurry is sprayed into the flash separator through a spraying device, the cooled fluorine-containing gas enters the mist separator through a gas phase outlet for further gas-liquid separation, and the separated gas enters a tail gas washing system; the cooled slurry flows into a flash separation liquid seal tank from a liquid phase outlet under the action of gravity, one part of the slurry in the flash separation liquid seal tank flows back to a crystallization tank, the other part of the slurry is sent into a semi-water filtering device through a semi-water feeding pump for filtering, semi-water gypsum and filtered acid are obtained after filtering, the filtered acid is the product phosphoric acid, and the semi-water gypsum enters a conversion tank; in the conversion tank, semi-hydrated gypsum is subjected to a dihydrate reaction under the action of concentrated sulfuric acid, slurry after the reaction is sent to a dihydrate filtering device through a dihydrate feeding pump for filtering, dihydrate gypsum is obtained through separation, the reaction time of materials in the conversion tank is controlled to be 1.5-2 hours, and the total residence time of the materials in the system is controlled to be 5.5-6 hours.

5. The process for producing phosphoric acid by a semi-water-dihydrate method through rapid extraction and crystallization as claimed in claim 4, wherein the solid-to-liquid ratio of the semi-water slurry in the dissolving tank to the semi-water slurry in the crystallization tank is 2: 1-3: 1.

Technical Field

The invention belongs to the technical field of phosphoric acid production, and particularly relates to a semi-water-dihydrate phosphoric acid rapid extraction crystallization production system and a semi-water-dihydrate phosphoric acid rapid extraction crystallization production process.

Background

The industrial production of phosphoric acid can be divided into two major categories, one is thermal production and the other is wet production. The wet production is to decompose phosphate rock with strong inorganic acid (such as sulfuric acid, hydrochloric acid, nitric acid, fluosilicic acid, etc.). The wet method has low production cost, but the product contains certain impurities, so the wet method is mainly used for producing phosphate fertilizer at present and partially replaces the raw material of medium-end and low-end phosphorus products produced by a thermal method.

When the conditions such as reaction temperature, the addition amount of sulfuric acid and the like are different, the crystalline form of calcium sulfate usually contains dihydrate CaSO₄·2H₂O, hemihydrate α -CaSO₄·1/2H₂O and anhydrate CaSO₄And (4) three types. The semi-hydrated-dihydrate production process mainly controls reaction conditions to crystallize materials into calcium sulfate hemihydrate firstly, then changes the reaction conditions along with high-concentration phosphoric acid to recrystallize the calcium sulfate hemihydrate into calcium sulfate dihydrate, and the semi-hydrated-dihydrate production process is the semi-hydrated-dihydrate production process.

As is well known, in the domestic wet-process phosphoric acid semi-water-dihydrate production device, the residence time of the whole system materials is mostly controlled to be 9.5-14 h, so that the semi-water-dihydrate extraction tank for large-scale energy production occupies a large area, the device is high in operation energy consumption, and no method for well solving the problem exists at present.

Disclosure of Invention

The invention provides a semi-water-dihydrate phosphoric acid rapid extraction crystallization production system and a semi-water-dihydrate phosphoric acid rapid extraction crystallization production process, and aims to solve the problems of long retention time and low production speed of the existing phosphoric acid production materials.

Therefore, the invention adopts the following technical scheme:

a quick extraction and crystallization production system for phosphoric acid by a semi-water-dihydrate method comprises a dissolving tank, a crystallization tank, a semi-water slurry pump, a flash separator and a mist separator, wherein the volume of the dissolving tank is 2-4 times of that of the crystallization tank, the crystallization tank is connected with the dissolving tank through an overflow pipe, a return pipe and a semi-water slurry circulating pump are connected between the crystallization tank and the dissolving tank, and stirring devices are arranged in the dissolving tank and the crystallization tank;

the top of the flash separator is provided with a gas phase outlet, the upper part of the flash separator is provided with a feed inlet, the bottom of the flash separator is provided with a liquid phase outlet, one end of the semi-aqueous slurry pump is connected with the crystallization tank through a pipeline, the other end of the semi-aqueous slurry pump is connected with the feed inlet of the flash separator, and a slurry injection device is arranged at the feed inlet of the flash separator; a gas phase outlet of the flash separator is connected with the mist separator, a liquid phase outlet of the flash separator is connected with a flash separation liquid seal tank, one part of slurry in the flash separation liquid seal tank is introduced into the crystallization tank through a pipeline, and one part of slurry is sent into the semi-water filtering device through a semi-water feed pump; the semi-water filtering device is connected with a conversion tank, and the conversion tank is connected with a secondary water filtering device through a secondary water feeding pump;

the side part of the mist separator is provided with an air inlet, the top part of the mist separator is provided with a gas phase outlet, the bottom part of the mist separator is provided with a liquid phase outlet, and the liquid phase outlet of the mist separator is connected with a flash separation liquid seal tank and a gas phase outlet which are connected with a flash washing system.

Furthermore, a flue gas recovery pipe is connected above the dissolving tank and the crystallization tank, and the other end of the flue gas recovery pipe is connected with a flue gas washing system.

Further, a stirring device is arranged in the conversion tank.

The semi-water-dihydrate phosphoric acid rapid extraction and crystallization production process adopts the semi-water-dihydrate phosphoric acid rapid extraction and crystallization production system, and comprises the following specific processes:

adding the crushed phosphorite raw material and concentrated sulfuric acid into a dissolving tank, fully stirring to enable the materials to circularly react, and reacting the phosphorite under the decomposition action of the concentrated sulfuric acid to generate calcium sulfate hemihydrate; after the reaction, the slurry overflows into a crystallization tank, excessive concentrated sulfuric acid is added into the crystallization tank, and the slurry promotes the calcium sulfate hemihydrate crystal to grow continuously under the action of the excessive concentrated sulfuric acid and active silicon dioxide; controlling the retention time of the materials in the dissolving tank to be 2-2.5 h, and controlling the retention time in the crystallization tank to be 1-1.5 h;

the slurry in the crystallization tank enters a flash separator through a semi-aqueous slurry pump for cooling, the pressure of the flash separator is controlled to be 10-15 KPa, and the temperature difference between an inlet and an outlet is controlled to be 10-25 ℃; the slurry is sprayed into the flash separator through a spraying device, the cooled fluorine-containing gas enters the mist separator through a gas phase outlet for further gas-liquid separation, and the separated gas enters a tail gas washing system; the cooled slurry flows into a flash separation liquid seal tank from a liquid phase outlet under the action of gravity, one part of the slurry in the flash separation liquid seal tank flows back to a crystallization tank, the other part of the slurry is sent into a semi-water filtering device through a semi-water feeding pump for filtering, semi-water gypsum and filtered acid are obtained after filtering, the filtered acid is the product phosphoric acid, and the semi-water gypsum enters a conversion tank; in the conversion tank, semi-hydrated gypsum is subjected to a dihydrate reaction under the action of concentrated sulfuric acid, slurry after the reaction is sent to a dihydrate filtering device through a dihydrate feeding pump for filtering, dihydrate gypsum is obtained through separation, the reaction time of materials in the conversion tank is controlled to be 1.5-2 hours, and the total residence time of the materials in the system is controlled to be 5.5-6 hours.

Further, the solid-to-liquid ratio of the semi-aqueous slurry in the dissolving tank and the crystallizing tank is 2: 1-3: 1.

the invention has the beneficial effects that:

1. the system and the process can greatly shorten the material retention time of the whole system, reduce the material retention time by 50 percent, are beneficial to increasing the yield and reducing the energy consumption and the production cost, and are suitable for continuous large-scale production;

2. the process can greatly reduce the slurry content in the finished phosphoric acid, effectively improve the quality of the phosphoric acid and replace part of low-grade thermal phosphoric acid products;

3. the water in the process is recycled, the emission is reduced, and the consumption of water resources is reduced.

Drawings

FIG. 1 is a system schematic of the present invention;

in the figure: 1-a dissolving tank, 2-a crystallizing tank, 3-a semi-water slurry pump, 4-a flash separator, 5-an entrainment separator, 6-a flash separation liquid seal tank, 7-a semi-water feed pump, 8-a semi-water slurry circulating pump, 9-a semi-water filtering device, 10-a converting tank, 11-a semi-water feed pump and 12-a semi-water filtering device.

Detailed Description

The invention will be further described with reference to the accompanying drawings in which:

as shown in the figure, the semi-water-dihydrate phosphoric acid rapid extraction crystallization production system comprises a dissolving tank 1 and a crystallization tank 2, wherein the volume of the dissolving tank 1 is 2-3 times that of the crystallization tank 2, and the crystallization tank 2 is connected with the dissolving tank 1 through an overflow pipe. Since the semi-water reaction is carried out in the dissolution tank 1, P of the semi-water slurry in the dissolution tank 1₂O₅The concentration is as high as more than 38%, and the influence of impurity ions causes large viscosity, high saturation, poor stirring effect and slow reaction speed of the reaction slurry. After increasing the volume of the dissolving tank 1, the reaction time can be prolonged, higher extraction rate can be obtained, and the semi-water crystal in the crystallizing tank 2 can grow further under the condition of proper excess SO3, SO that the semi-water crystal can be converted into semi-water crystal which is easy to filter.

A return pipe and a semi-water slurry circulating pump 8 are connected between the crystallization tank 2 and the dissolving tank 1, and the semi-water slurry circulating pump 8 can convey slurry in the crystallization tank 2 to the dissolving tank 1 through the return pipe. All be equipped with agitating unit in dissolving tank 1 and the crystallizer 2, the top of dissolving tank 1 and crystallizer 2 still is connected with flue gas recovery pipeline, and flue gas recovery pipeline's the other end is connected with flue gas tail-washing system.

The top of the flash separator 4 is provided with a gas phase outlet, the upper part of the flash separator 4 is provided with a feed inlet, the bottom of the flash separator 4 is provided with a liquid phase outlet, one end of the semi-water slurry pump 3 is connected with the crystallization tank 2 through a pipeline, the other end of the semi-water slurry pump is connected with the feed inlet of the flash separator 4, and a slurry injection device is arranged at the feed inlet of the flash separator 4; a gas phase outlet of the flash separator 4 is connected with the mist separator 5, a liquid phase outlet of the flash separator 4 is connected with the flash separation liquid seal tank 6, one part of slurry in the flash separation liquid seal tank 6 is introduced into the crystallization tank 2 through a pipeline, and one part of slurry is sent into the semi-water filtering device through the semi-water feeding pump 7; the semi-water filtering device is connected with a conversion tank 10, a stirring device is arranged in the conversion tank 10, and the conversion tank 10 is connected with a secondary water filtering device 12 through a secondary water feeding pump 11.

The side part of the mist separator 5 is provided with an air inlet, the top part is provided with a gas phase outlet, the bottom part is provided with a liquid phase outlet, the liquid phase outlet of the mist separator 5 is connected with a flash separation liquid seal tank 6, and the gas phase outlet is connected with a flash washing system.

A semi-water-dihydrate phosphoric acid rapid extraction crystallization production process is carried out by the equipment, and comprises the following steps and principles: adding the crushed phosphorite raw material and concentrated sulfuric acid into the dissolving tank 1, fully stirring to enable the material to circularly react, and reacting the phosphorite under the decomposition action of the concentrated sulfuric acid to generate calcium sulfate hemihydrate. The reaction formula is as follows:

Ca₅F(PO₄)₃+5H₂SO₄+2*1/2H₂O＝3H₃PO₄+5CaSO₄·1/2H₂O ↓+HF↑

after the reaction, the slurry overflows into a crystallization tank 2, excessive concentrated sulfuric acid is added into the crystallization tank 2, and the slurry promotes the calcium sulfate hemihydrate crystal to grow continuously under the action of the excessive concentrated sulfuric acid and active silica; the residence time of the materials in the dissolving tank is controlled to be 2-2.5 h, and the residence time in the crystallization tank is controlled to be 1-1.5 h.

The slurry in the crystallization tank 2 enters a flash separator 4 through a semi-water slurry pump 3 for cooling, and the pressure of the flash separator 4 is controlled to be 10-15 KPa; the slurry is sprayed into the flash separator 4 by means of a spraying device. The slurry forms liquid film double effect evaporation in the flash separator 4, which not only increases the slurry evaporation area, but also eliminates the bumping phenomenon caused by rapid slurry evaporation and temperature reduction; meanwhile, the vacuum degree is reduced, and the entrainment accompanying the evaporation gas is reduced. After passing through the flash separator 4, the temperature difference of the semi-water slurry is reduced from more than 95 ℃ to less than 70 ℃, and the temperature difference of the semi-water slurry can be controlled within 25 ℃. The cooled fluorine-containing gas enters a mist separator 5 through a gas phase outlet for further gas-liquid separation, and the separated gas enters a tail gas washing system; the cooled slurry flows into a flash separation liquid seal tank 6 from a liquid phase outlet under the action of gravity, one part of the slurry in the flash separation liquid seal tank 6 flows back to a crystallization tank, the other part of the slurry is sent into a semi-water filtering device for filtering through a semi-water feeding pump 7, semi-water gypsum and filtered acid are obtained after filtering, the filtered acid is the product phosphoric acid, and the semi-water gypsum enters a conversion tank 10; in the conversion tank 10, the hemihydrate gypsum is subjected to a dihydrate reaction under the action of concentrated sulfuric acid. The reaction formula is as follows:

CaSO₄·1/2H₂O+1/2H₂O＝CaSO₄·2H₂O↓+Q

and (3) feeding the reacted slurry into a dihydrate filtering device through a dihydrate feeding pump for filtering, separating to obtain dihydrate gypsum, controlling the reaction time of the materials in the conversion tank to be 1.5-2 h, and controlling the total retention time of the materials in the system to be 5.5-6 h.

Compared with the conventional process, the inlet of the flash separator 4 is positioned at the upper part, and slurry moves from top to bottom after entering, so that gas-liquid separation is facilitated, and the separation speed and the separation effect can be greatly improved. The concentrated sulfuric acid in the system is 98.5 wt% of concentrated sulfuric acid, the concentration of the phosphoric acid produced by adopting the process is more than 45 wt%, and the gypsum dry basis P is produced₂O₅The content of (A) is less than 0.25 wt%, the total reaction time is shortened to 5.5-6 h, and the technical effect is very obvious.

It should be noted that the above are only some embodiments of the present invention, and it should be noted that, for those skilled in the art, many modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.