阅读说明：本技术 一种连续化生产十八水合硫酸铝的装置及工艺 (Device and process for continuously producing aluminum sulfate octadecahydrate ) 是由 李琰君 杨阿三 屠美玲 贾继宁 于 2019-10-09 设计创作，主要内容包括：本发明公开了一种连续化生产十八水合硫酸铝的装置及工艺,本发明的装置包括内部盛有稀相废硫酸的第一储罐、内部盛有浓相硫酸的第二储罐、连续釜式反应器、梯度结晶器、固液分离器；第一储罐和第二储罐分别通过输送泵与连续釜式反应器由管路连接,连续釜式反应器通过螺旋进料机与储料仓相通接,储料仓内添加有氢氧化铝。连续釜式反应器的出液口通过梯度结晶器与固液分离器由管路连接,反应液在梯度结晶器内结晶出十八水合硫酸铝反应产物后,送入到固液分离器内分离得到十八水合硫酸铝晶体和母液,母液可作为稀相废硫酸重新利用。本发明生产十八水合硫酸铝的过程中对硫酸的质量要求不高,可将废硫酸资源化利用,并降低废硫酸的处理成本。(The invention discloses a device and a process for continuously producing aluminum sulfate octadecahydrate, wherein the device comprises a first storage tank, a second storage tank, a continuous kettle type reactor, a gradient crystallizer and a solid-liquid separator, wherein dilute-phase waste sulfuric acid is contained in the first storage tank; the first storage tank and the second storage tank are respectively connected with the continuous kettle type reactor through pipelines through a delivery pump, the continuous kettle type reactor is communicated with the storage bin through a spiral feeder, and aluminum hydroxide is added into the storage bin. The liquid outlet of the continuous kettle type reactor is connected with a solid-liquid separator through a gradient crystallizer by a pipeline, reaction liquid is sent into the solid-liquid separator for separation after crystallization of an aluminum sulfate octadecahydrate reaction product in the gradient crystallizer, and the aluminum sulfate octadecahydrate crystal and mother liquid are obtained, and the mother liquid can be reused as dilute phase waste sulfuric acid. The method has low requirement on the quality of sulfuric acid in the production process of the aluminum sulfate octadecahydrate, can utilize the waste sulfuric acid as resources, and reduces the treatment cost of the waste sulfuric acid.)

1. The device for continuously producing the aluminum sulfate octadecahydrate is characterized by comprising a first storage tank (11) filled with dilute-phase waste sulfuric acid, a second storage tank (12) filled with concentrated-phase sulfuric acid, a continuous kettle type reactor (1), a gradient crystallizer (2), a solid-liquid separator (3), a spiral feeder and a storage bin filled with aluminum hydroxide powder; a sulfuric acid feeding pipe is arranged on the continuous kettle type reactor (1), the first storage tank (11) and the second storage tank (12) are respectively connected with the sulfuric acid feeding pipe on the continuous kettle type reactor (1) through pipelines by a delivery pump, and the storage bin is communicated with the continuous kettle type reactor (1) through a spiral feeder;

dilute phase waste sulfuric acid in the first storage tank (11), concentrated phase sulfuric acid in the second storage tank (12) and aluminum hydroxide in the storage bin are fed into the continuous kettle type reactor (1) together for continuous production of aluminum sulfate octadecahydrate; the liquid outlet of the continuous kettle type reactor (1) is connected with the solid-liquid separator (3) through a gradient crystallizer (2) by a pipeline, reaction liquid is sent into the solid-liquid separator (3) to be separated into octadeca-hydrated aluminum sulfate crystals and mother liquid after crystallizing octadeca-hydrated aluminum sulfate reaction products in the gradient crystallizer (2), the octadeca-hydrated aluminum sulfate crystals are discharged from a solid outlet of the solid-liquid separator (3), the mother liquid separated in the solid-liquid separator (3) is divided into two paths to be discharged, one path is discharged into the first storage tank (11) to be reused as dilute-phase waste sulfuric acid, and the other path is returned back to the gradient crystallizer (2) again to adjust the solid-liquid ratio of the octadeca-hydrated aluminum sulfate crystals in the gradient crystallizer (2) to the reaction liquid mother liquid.

2. An apparatus for continuously producing aluminum sulfate octadecahydrate according to claim 1, wherein the gradient crystallizer (2) comprises a top heating chamber (201) with a heating jacket (204) on the outside, a middle crystallization chamber (202) and a bottom crystal collecting chamber (203) with a condensing jacket (206) on the outside; a liquid outlet of the continuous kettle type reactor (1) is connected with a top heating chamber (201) of the gradient crystallizer (2) through a pipeline, and a gradient cooling device is arranged on the outer side of the middle crystallization chamber (202) so that the temperature of the solution in the middle crystallization chamber (202) is reduced in a gradient manner from top to bottom; the bottom of bottom crystal collection room (203) is close to one end edge and is provided with brilliant liquid discharging pipe (25) and is connected with solid-liquid separator (3) through brilliant liquid discharging pipe (25), still be equipped with first material harrow (24) on bottom crystal collection room (203), the crystal of deposit bottom crystal collection room (203) is held back to send towards brilliant liquid discharging pipe (25) through first material harrow (24) to finally discharge through brilliant liquid discharging pipe (25).

3. The device for continuously producing the aluminum sulfate octadecahydrate according to claim 2, wherein the gradient cooling device comprises a plurality of heat exchange interlayers (205) which are arranged at intervals from top to bottom outside the middle crystallization chamber (202), a heat exchange medium is respectively introduced into each heat exchange interlayer (205), the temperature of the heat exchange medium introduced into the heat exchange interlayers (205) is sequentially reduced from top to bottom, a stirring device (21) for stirring the liquid in the top heating chamber (201) is arranged on the top heating chamber (201), the heating jacket (204) is used for heating to control the temperature of the solution in the top heating chamber (201) to be 90-105 ℃, and the condensing jacket (206) is used for cooling to control the temperature of the solution in the bottom crystal collecting chamber (203) to be 25 ~ 35 ℃.

4. The apparatus for continuously producing aluminum sulfate octadecahydrate according to claim 2, further comprising a mother liquor return pipe (23), wherein the middle crystallization chamber (202) is fixedly provided with a flow guide pipe (22) having openings at the upper and lower ends thereof at the inner center thereof, the length of the flow guide pipe (22) is the same as that of the middle crystallization chamber (202), and the annular wall of the flow guide pipe (22) is uniformly provided with a plurality of through holes;

an opening at one end of the mother liquor return pipe (23) penetrates through the upper part of the crystal collecting chamber (203) at the bottom, and vertically extends into the guide pipe (22) from an opening at the lower end of the guide pipe (22) upwards; the other end opening of the mother liquor return pipe (23) is communicated with the liquid outlet of the solid-liquid separator (3), so that one path of mother liquor discharged from the solid-liquid separator (3) is discharged into the guide pipe (22) through the mother liquor return pipe (23).

5. The apparatus for continuously producing aluminum sulfate octadecahydrate according to claim 4, further comprising a mother liquor impurity removal apparatus, wherein the mother liquor impurity removal apparatus comprises a sedimentation tank (8) and a first adsorption tower (9) filled with an adsorbent, the liquid outlet of the solid-liquid separator (3) is connected with the liquid inlet of the first adsorption tower (9) through the sedimentation tank (8) by a pipeline, the liquid outlet of the first adsorption tower (9) is divided into two paths, one path is connected with the first storage tank (11) by a pipeline, and the other path is communicated with the draft tube (22) in the gradient crystallizer (2) through a mother liquor return tube (23); and a metal precipitator is added into the sedimentation tank (8) to perform flocculation sedimentation on heavy metal ions in the mother liquor flowing through the sedimentation tank (8).

6. The device for continuously producing aluminum sulfate octadecahydrate according to claim 1, which is characterized by further comprising a crystal impurity removing device, wherein the crystal impurity removing device comprises a crystal washing device (4), a crystal washing liquid storage tank (10) filled with a crystal washing solution, a filtering separator, a second adsorption tower (7) filled with an adsorbent and a drying box (6), both the solid outlet of the solid-liquid separator (3) and the liquid outlet of the crystal washing liquid storage tank (10) are connected with the crystal washing device (4) through pipelines, the aluminum sulfate octadecahydrate crystal discharged from the solid outlet of the solid-liquid separator (3) and the crystal washing solution in the crystal washing liquid storage tank (10) are introduced into the crystal washing device (4) together for crystal washing treatment, the mixture after crystal washing is subjected to solid-liquid separation through the filtering separator, the obtained solid enters the drying box (6) for drying, and an aluminum sulfate octadecahydrate product is obtained, and the obtained liquid is subjected to adsorption and impurity removal through a second adsorption tower (7), and then reflows to a crystal washing liquid storage tank (10) to be used as a crystal washing solution for repeated use.

7. The apparatus for continuously producing aluminum sulfate octadecahydrate according to claim 6, wherein the crystal-washing solution contained in the crystal-washing liquid storage tank (10) is saturated aluminum sulfate octadecahydrate aqueous solution, and the adsorbent is activated carbon or activated carbon fiber.

8. The apparatus for continuously producing aluminum sulfate octadecahydrate according to claim 1, wherein the first storage tank (11) and the second storage tank (12) are each provided with an online sulfuric acid concentration detector, and the pipelines between the first storage tank (11) and the continuous tank reactor (1) and between the second storage tank (12) and the continuous tank reactor (1) are each provided with a flow meter.

9. A process for continuously producing aluminum sulfate octadecahydrate is characterized by comprising the following steps:

s1, preliminarily mixing dilute-phase waste sulfuric acid with the mass concentration of 20 ~ 40% and concentrated-phase sulfuric acid with the mass concentration of 50 ~ 85%, then feeding the mixture and aluminum hydroxide powder into a continuous kettle-type reactor (1), carrying out continuous stirring reaction at the temperature of 75 ~ 95 ℃ and under the normal pressure condition, and continuously discharging the reacted reaction liquid from a liquid outlet of the continuous kettle-type reactor (1);

s2: crystallizing the reacted reaction liquid in a gradient crystallizer (2) to obtain an aluminum sulfate octadecahydrate reaction product, and then sending the reaction product into a solid-liquid separator (3) for separation to obtain aluminum sulfate octadecahydrate crystals and mother liquor, wherein the obtained mother liquor can be used as dilute-phase waste sulfuric acid to be repeatedly used in the process of continuously producing the aluminum sulfate octadecahydrate; washing the obtained aluminum sulfate octadecahydrate crystal with saturated aluminum sulfate octadecahydrate water solution, and drying to obtain the target product of aluminum sulfate octadecahydrate.

10. The process for continuously producing aluminum sulfate octadecahydrate according to claim 9, wherein the concentration of sulfuric acid in the mixed solution formed by the preliminary mixing of dilute-phase waste sulfuric acid and concentrated-phase sulfuric acid is within 30 ~ 60wt%, the molar ratio of sulfuric acid to aluminum hydroxide in the mixed solution formed by the preliminary mixing of dilute-phase waste sulfuric acid and concentrated-phase sulfuric acid is 1.5 ~ 5:1, and the residence time of the reaction in the continuous tank reactor (1) is 30-480 minutes.

Technical Field

The invention relates to a device and a process for continuously producing aluminum sulfate octadecahydrate.

Background

The sulfuric acid is applied to the aspects of industrial production, and a large amount of waste sulfuric acid is produced while the sulfuric acid is utilized. Compared with industrial solid waste and industrial waste gas, the waste sulfuric acid is a liquid, and the waste sulfuric acid or sulfuric acid-containing wastewater discharged from production cannot be directly used in the original process; unreasonable treatment can acidify the water body or soil, harm the ecological environment and waste a large amount of resources.

The method needs a large amount of energy consumption, has certain rationality for the waste sulfuric acid with the concentration of more than 60 percent, but is not suitable for recycling the low-concentration waste sulfuric acid, and the concentration of the waste sulfuric acid produced by the industry is between 20 ~ 85 percent, so the method can be considered to be used in other production processes with low requirements on the quality of the sulfuric acid, thereby saving resources and reducing the discharge amount of the waste sulfuric acid.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention aims to provide a device and a process for continuously producing aluminum sulfate octadecahydrate. In the process for continuously producing the aluminum sulfate octadecahydrate, the invention has low quality requirement on sulfuric acid in the process of producing the aluminum sulfate octadecahydrate, so that the waste sulfuric acid can be recycled, the treatment cost of the waste sulfuric acid can be reduced, and the aluminum sulfate octadecahydrate product with industrial raw material value can be produced.

The device for continuously producing the aluminum sulfate octadecahydrate is characterized by comprising a first storage tank, a second storage tank, a continuous kettle type reactor, a gradient crystallizer, a solid-liquid separator, a spiral feeder and a storage bin, wherein dilute-phase waste sulfuric acid is contained in the first storage tank, concentrated-phase sulfuric acid is contained in the second storage tank, and aluminum hydroxide powder is added in the storage bin; the continuous kettle type reactor is provided with a sulfuric acid feeding pipe, the first storage tank and the second storage tank are respectively connected with the sulfuric acid feeding pipe on the continuous kettle type reactor through pipelines by a delivery pump, and the storage bin is communicated with the continuous kettle type reactor through a spiral feeder; dilute phase waste sulfuric acid in the first storage tank, concentrated phase sulfuric acid in the second storage tank and aluminum hydroxide in the storage bin are fed into the continuous kettle type reactor together for reaction for continuously producing aluminum sulfate octadecahydrate; the liquid outlet of the continuous kettle type reactor is connected with the solid-liquid separator through a pipeline through a gradient crystallizer, reaction liquid is crystallized in the gradient crystallizer to obtain an aluminum sulfate octadecahydrate reaction product, the reaction liquid is sent into the solid-liquid separator to be separated to obtain aluminum sulfate octadecahydrate crystals and mother liquid, the aluminum sulfate octadecahydrate crystals are discharged from a solid outlet of the solid-liquid separator, the mother liquid separated in the solid-liquid separator is discharged in two ways, one way of the mother liquid is discharged into a first storage tank to be reused as dilute phase waste sulfuric acid, the other way of the mother liquid reflows into the gradient crystallizer 2 again to adjust the concentration of the aluminum sulfate octadecahydrate crystals in the reaction liquid (namely, the solid-liquid ratio of the aluminum sulfate octadecahydrate crystals to the reaction liquid mother liquid is adjusted, and the purpose that the mother liquid reflows into the gradient crystallizer 2 is that the concentration of the aluminum sulfate octadecahydrate crystals in the reaction liquid in the middle lower part of the gradient crystallizer 2 is higher, and the, therefore, partial mother liquor flows back to the gradient crystallizer 2 again, aluminum sulfate octadecahydrate crystals in the reaction liquid are diluted to a certain degree, the fluidity of the reaction liquid is increased, and the blockage in the gradient crystallizer 2 is prevented).

The device for continuously producing the aluminum sulfate octadecahydrate is characterized in that the gradient crystallizer comprises a top heating chamber, a middle crystallization chamber and a bottom crystal collecting chamber, wherein the outer side of the top heating chamber is provided with a heating jacket; the liquid outlet of the continuous kettle type reactor is connected with a top heating chamber of the gradient crystallizer through a pipeline, and a gradient cooling device is arranged on the outer side of the middle crystallization chamber, so that the temperature of the solution in the middle crystallization chamber is reduced in a gradient manner from top to bottom; the bottom of bottom crystal collection room is close to one end edge and is provided with the brilliant liquid discharging pipe and is connected with solid-liquid separator through the brilliant liquid discharging pipe, still be equipped with first material harrow on the bottom crystal collection room, the crystal of deposit bottom the bottom crystal collection room is raked towards the brilliant liquid discharging pipe through first material harrow and is sent to finally discharge through the brilliant liquid discharging pipe.

The device for continuously producing the aluminum sulfate octadecahydrate is characterized in that the gradient cooling device comprises a plurality of heat exchange interlayers which are arranged outside the middle crystallization chamber at intervals from top to bottom, a heat exchange medium is respectively introduced into each heat exchange interlayer, the temperature of the heat exchange medium introduced into the heat exchange interlayers is sequentially reduced from top to bottom, a stirring device for stirring the liquid in the top heating chamber is arranged on the top heating chamber, the heating sleeve is used for heating to control the temperature of the solution in the top heating chamber to be 90-105 ℃, and the condensing jacket is used for cooling to control the temperature of the solution in the bottom crystal collecting chamber to be 25 ~ 35 ℃.

The device for continuously producing the aluminum sulfate octadecahydrate is characterized by also comprising a mother liquor return pipe, wherein the center inside the middle crystallization chamber is fixedly provided with a guide pipe with openings at the upper end and the lower end, the length of the guide pipe is the same as that of the middle crystallization chamber, and the annular wall of the guide pipe is uniformly provided with a plurality of through holes; an opening at one end of the mother liquor return pipe penetrates through the upper part of the crystal collecting chamber at the bottom, and vertically extends upwards into the guide pipe from an opening at the lower end of the guide pipe; the other end opening of the mother liquid return pipe is communicated with the liquid outlet of the solid-liquid separator, so that one path of mother liquid discharged from the solid-liquid separator is discharged into the guide pipe through the mother liquid return pipe.

The device for continuously producing the aluminum sulfate octadecahydrate is characterized by further comprising a mother liquor impurity removal device, wherein the mother liquor impurity removal device comprises a sedimentation tank and a first adsorption tower filled with an adsorbent, a liquid outlet of a solid-liquid separator is connected with a liquid inlet of the first adsorption tower through the sedimentation tank by a pipeline, a liquid outlet of the first adsorption tower is divided into two paths, one path is connected with a first storage tank by a pipeline, and the other path is communicated with a guide pipe in the gradient crystallizer through a mother liquor return pipe; and a metal precipitator is added in the sedimentation tank to carry out slow coagulation sedimentation flocculation sedimentation on heavy metal ions in the mother liquor flowing through the sedimentation tank.

The device for continuously producing the aluminum sulfate octadecahydrate is characterized by also comprising a crystal impurity removal device, the crystal impurity removing device comprises a crystal washing device, a crystal washing liquid storage tank filled with crystal washing solution, a filtering separator, a second adsorption tower filled with adsorbent and a drying box, wherein a solid outlet of the solid-liquid separator and a liquid outlet of the crystal washing liquid storage tank are both connected with the crystal washing device through pipelines, the aluminum sulfate octadecahydrate crystal discharged from the solid outlet of the solid-liquid separator and the crystal washing solution in the crystal washing liquid storage tank are introduced into the crystal washing device together for crystal washing treatment, and the mixture after crystal washing is subjected to solid-liquid separation through the filtering separator, and drying the obtained solid in a drying box to obtain an aluminum sulfate octadecahydrate product, adsorbing and removing impurities from the obtained liquid through a second adsorption tower, and refluxing the obtained liquid into a crystal washing liquid storage tank to be used as a crystal washing solution for recycling.

The device for continuously producing the aluminum sulfate octadecahydrate is characterized in that the crystal washing solution contained in the crystal washing liquid storage tank is saturated aluminum sulfate aqueous solution, and the adsorbent is activated carbon or activated carbon fiber.

The device for continuously producing the aluminum sulfate octadecahydrate is characterized in that the first storage tank and the second storage tank are both provided with online sulfuric acid concentration detectors, and flow measuring instruments are arranged on a pipeline between the first storage tank and the continuous kettle-type reactor and a pipeline between the second storage tank and the continuous kettle-type reactor.

The continuous production process of the aluminum sulfate octadecahydrate is characterized by comprising the following steps of:

s1, preliminarily mixing dilute-phase waste sulfuric acid with the mass concentration of 20 ~ 40% and concentrated-phase sulfuric acid with the mass concentration of 50 ~ 85%, feeding the mixture and aluminum hydroxide powder into a continuous kettle-type reactor, carrying out continuous stirring reaction at the temperature of 75 ~ 95 ℃ under normal pressure, and continuously discharging the reaction liquid after the reaction from a liquid outlet of the continuous kettle-type reactor;

s2: crystallizing the reacted reaction liquid in a gradient crystallizer to obtain an aluminum sulfate octadecahydrate reaction product, sending the reaction product into a solid-liquid separator, and separating to obtain aluminum sulfate octadecahydrate crystals and mother liquor, wherein the obtained mother liquor can be used as dilute-phase waste sulfuric acid to be repeatedly used in the process of continuously producing the aluminum sulfate octadecahydrate; washing the obtained aluminum sulfate octadecahydrate crystal with saturated aluminum sulfate water solution, and drying to obtain the target product of aluminum sulfate octadecahydrate.

The process for continuously producing the aluminum sulfate octadecahydrate is characterized in that the concentration of sulfuric acid in mixed liquid formed by primarily mixing dilute-phase waste sulfuric acid and concentrated-phase sulfuric acid is within the range of 30 ~ 60wt%, the feeding molar ratio of sulfuric acid to aluminum hydroxide in the mixed liquid formed by primarily mixing the dilute-phase waste sulfuric acid and the concentrated-phase sulfuric acid is 1.5 ~ 5:1, and the reaction residence time in a continuous kettle type reactor is 30-480 minutes.

Compared with the prior art, the invention has the following beneficial effects:

1) the method takes the two waste sulfuric acids with the mass concentration of 50 ~ 85% and 20 ~ 40% as raw materials to prepare the aluminum sulfate octadecahydrate, can effectively utilize the low-concentration waste sulfuric acid, has little influence on the continuous production of the aluminum sulfate octadecahydrate even if the raw materials of the waste sulfuric acid contain heavy metal ion impurities such as Fe ions and Cr ions, reduces the discharge of sulfuric acid, improves the resource utilization rate, and can utilize the waste sulfuric acid with the concentration of 20 ~ 40% to reduce the discharge of waste acid.

2) In the process for continuously producing the aluminum sulfate octadecahydrate, the two waste sulfuric acids with the mass concentration of 50 ~ 85% and 20 ~ 40% are preliminarily mixed to form a sulfuric acid solution with the medium concentration, the reaction solution after the sulfuric acid solution with the medium concentration reacts with the aluminum hydroxide is subjected to crystallization and solid-liquid separation in sequence, the obtained mother solution forms waste sulfuric acid with the lower concentration, the mother solution is mixed with the waste sulfuric acid with the mass concentration of 50 ~ 85% and can be repeatedly used in the process for producing the aluminum sulfate octadecahydrate, the resource utilization rate of the sulfuric acid is high, the product generated by the reaction is the aluminum sulfate octadecahydrate, a large amount of moisture in the reaction solution can be absorbed in the production process of the aluminum sulfate octadecahydrate, so that the sulfuric acid and free moisture in the reaction solution are reduced simultaneously, the higher sulfuric acid concentration is kept in the mother solution obtained by crystallization and solid-liquid separation of the reaction solution, the obtained mother solution can be recycled in a system after impurities are removed, wastewater is not generated basically in the treatment process, and the whole process for producing the octadecahydrate aluminum sulfate hydrate is environment-friendly.

3) Compared with the pressurized reaction for producing the aluminum sulfate octadecahydrate in the prior art, the reaction for continuously producing the aluminum sulfate octadecahydrate is carried out under normal pressure, so that the requirement on equipment can be reduced, and the operation safety is improved; the reaction heat is released in the reaction process of the aluminum hydroxide and the waste sulfuric acid, and the required reaction temperature is 75-95 ℃, so that the energy consumption requirement for maintaining the reaction is low, and a low-grade heat source in a factory can be utilized. Within the reaction temperature range, the aluminum hydroxide and the waste sulfuric acid can react at a proper reaction rate, materials can keep fluidity in the reaction process, the materials can be uniformly mixed under stirring, and the materials can be conveyed.

4) The device for continuously producing the aluminum sulfate octadecahydrate has reasonable structural design, the reacted reaction liquid is subjected to gradient crystallization in the gradient crystallizer, explosive crystallization is avoided, and the crystallization efficiency of the aluminum sulfate octadecahydrate product in the reaction liquid is high. The whole process for continuously producing the aluminum sulfate octadecahydrate rarely generates waste water, and the production process is environment-friendly. In the device for continuously producing the aluminum sulfate octadecahydrate, the first storage tank and the second storage tank are respectively provided with the sulfuric acid concentration online detector, the pipelines between the first storage tank and the continuous kettle type reactor and the pipelines between the second storage tank and the continuous kettle type reactor are respectively provided with the flow measuring instruments, and the sulfuric acid concentration in the mixed liquid formed by primarily mixing the dilute-phase waste sulfuric acid and the concentrated-phase sulfuric acid is controlled to keep a stable level by monitoring the concentrations of the dilute-phase waste sulfuric acid and the concentrated-phase sulfuric acid and the conveying flow of the dilute-phase waste sulfuric acid and the concentrated-phase sulfuric acid, so that the aluminum sulfate octadecahydrate product is efficiently produced.

Drawings

FIG. 1 is a schematic structural diagram of an apparatus for continuously producing aluminum sulfate octadecahydrate according to the present invention;

FIG. 2 is a schematic structural view of a gradient crystallizer of the present invention;

in the figure: 1-a continuous kettle type reactor, 11-a first storage tank, 12-a second storage tank, 2-a gradient crystallizer, 201-a top heating chamber, 202-a middle crystallization chamber, 203-a bottom crystal collecting chamber, 204-a heating sleeve, 205-a heat exchange interlayer, 206-a condensation jacket, 21-a stirring device, 22-a guide pipe, 23-a mother liquid return pipe, 24-a first material rake, 25-a crystal liquid discharge pipe, 3-a solid-liquid separator, 4-a crystal washing device, 5-a filtering separator, 6-a drying box, 7-a second adsorption tower, 8-a settling pond, 9-a first adsorption tower and 10-a crystal washing liquid storage tank.

Detailed Description

The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.