CN115304120A - Salt separation process for wastewater generated in iron phosphate production - Google Patents
Salt separation process for wastewater generated in iron phosphate production Download PDFInfo
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Abstract
The invention belongs to the field of wastewater treatment, and discloses a salt separation process for wastewater generated in iron phosphate production. Utilize iron phosphate waste water to divide salt system, iron phosphate waste water divides salt system including the preheating unit, falling film evaporation unit, forced circulation evaporation crystallization unit, continuous vacuum flash distillation crystallization unit, miscellaneous salt evaporation unit and the insoluble substance discharge unit that connect gradually, iron phosphate waste water divides salt technology to use iron phosphate waste water to divide salt system, can realize ammonium sulfate, monoammonium phosphate, miscellaneous salt and the collection of insoluble substance in the iron phosphate waste water in proper order, and the heat of the distilled water, tail gas, the steam that produce in the system obtains fine utilization, realizes zero release and energy recuperation and utilizes, possesses fine industrial application prospect.
Description
Technical Field
The invention belongs to the field of wastewater treatment, and relates to a salt separation process for wastewater generated in iron phosphate production.
Background
In recent years, the market capacity of lithium iron phosphate positive electrode battery materials is increased year by year, and the demand of iron phosphate as a precursor for producing the lithium iron phosphate positive electrode material is also increasing. The iron phosphate production process can be carried out through the processes of synthesis, water washing, precipitation, evaporation, drying and the like, the produced wastewater is mainly washing water and mother liquor, and pollutant components comprise a large amount of phosphate radicals, sulfate radicals, ammonium radicals, fluoride ions, calcium ions, magnesium ions, manganese ions and other metal ions.
At present, the patented technology about the wastewater in the iron phosphate production is mainly embodied in the pretreatment process section of iron phosphate washing water and mother liquor, different medicaments and proportions are adopted to carry out two-section PH regulation, two-section heat exchange, coagulation, precipitation and a plate-and-frame filter, and then the wastewater enters an evaporator for salt separation after ultrafiltration and reverse osmosis for further concentration.
The salt separation products of the wastewater from the iron phosphate production comprise ammonium sulfate, monoammonium phosphate, miscellaneous salts, insoluble substances, non-condensable gas and the like. At present, a complete process for separating salt from wastewater generated in the production of iron phosphate is not disclosed, and particularly, the process is suitable for properly treating non-condensable gas and insoluble substances in the wastewater generated in the production of iron phosphate.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a salt separation process for iron phosphate production wastewater.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
the utility model provides an iron phosphate waste water divides salt technology utilizes iron phosphate waste water to divide salt system, iron phosphate waste water divides salt system including the preheating unit, falling liquid film evaporation unit, forced circulation evaporation crystallization unit, continuous vacuum flash distillation crystallization unit, miscellaneous salt evaporation unit and the insoluble substance discharge unit that connect gradually, wherein:
the forced circulation evaporation crystallization unit comprises a first forced circulation evaporation assembly, a first swirler, a first thickener and a first centrifuge which are sequentially communicated with the falling film evaporation unit, and the first centrifuge is respectively communicated with a first mother liquor tank and an ammonium sulfate collection assembly; the continuous flash evaporation crystallization unit comprises a flash evaporation crystallizer, a crystallization discharge pump, a second thickener and a second centrifuge which are sequentially communicated with a first mother liquor tank, and the second centrifuge is respectively communicated with the second mother liquor tank and a monoammonium phosphate collecting component; the mixed salt evaporation unit comprises a mother liquor preheater, a second forced circulation evaporation assembly, a third swirler, a third thickener and a third centrifuge which are sequentially communicated with a second mother liquor tank, and the third centrifuge is respectively communicated with a mixed salt storage tank and the third mother liquor tank; the insoluble matter discharge unit is communicated with a third mother liquor tank;
ferric phosphate waste water divides salt process to use ferric phosphate waste water to divide salt system, including following step:
(1) Introducing the iron phosphate production wastewater into a preheating unit, preheating the wastewater by the preheating unit to 95-100 ℃, and entering a falling film evaporation unit;
(2) Concentrating the preheated iron phosphate production wastewater in a falling film evaporation unit until the mass percentage concentration of ammonium sulfate in the solution reaches 30-35%, and then entering a forced circulation evaporation crystallization unit;
(3) In a forced circulation evaporation crystallization unit, enabling a solution to enter a first forced circulation evaporation assembly for evaporation concentration to form a crystallization feed liquid until the mass percentage concentration of ammonium sulfate in the crystallization feed liquid is 50-60%, enabling the crystallization feed liquid to enter a first cyclone for preliminary separation, returning a clarified liquid to the first forced circulation evaporation assembly for re-concentration, transferring a crystal slurry to a first thickener, further concentrating the crystal slurry by the first thickener, transferring the crystal slurry to a first centrifugal machine for centrifugal separation, enabling ammonium sulfate crystals after centrifugal separation to enter an ammonium sulfate collection assembly for collection, and enabling a mother liquid after centrifugal separation to enter a vacuum flash evaporation cooling continuous crystallization unit;
(4) The mother liquor obtained after the centrifugal separation in the step (3) is placed in a vacuum flash evaporation cooling continuous crystallizer, monoammonium phosphate in the mother liquor is crystallized in the flash evaporation crystallizer until the crystallization amount of the monoammonium phosphate is 25-30%, the monoammonium phosphate is conveyed to a second thickener through a crystallization discharge pump to form crystal slurry, the obtained crystal slurry is centrifugally separated in a second centrifuge, the obtained solid phase enters a monoammonium phosphate collecting component, and the mother liquor obtained after the centrifugal separation enters a mixed salt evaporation unit;
(5) In the mixed salt evaporation unit, the mother liquor of the flash evaporation crystallization unit obtained in the step (4) is preheated by a mother liquor preheater and then enters a second forced circulation evaporator component for evaporation crystallization, and finally, the mixed salt is separated by a third centrifugal machine and is discharged by an insoluble substance discharge unit.
Further, the preheating unit comprises a distilled water preheater, a noncondensable gas preheater and a steam preheater which are sequentially connected, and the distilled water preheater is communicated with each distilled water outlet of the system; the non-condensable gas preheater is communicated with each tail gas outlet of the system; the steam preheater is provided with a steam inlet;
further preferably, in a distilled water preheater, the heat exchange between the iron phosphate production wastewater and distilled water generated by the system is carried out, and the temperature is increased from 30-35 ℃ to 80-90 ℃; in a noncondensable gas preheater, exchanging heat between the iron phosphate production wastewater and noncondensable gas generated by a system, and raising the temperature from 80-90 ℃ to 90-95 ℃; in a steam preheater, the iron phosphate production wastewater exchanges heat with fresh steam introduced from a steam port, and the temperature rises to 95-100 ℃.
Further, the falling film evaporation unit comprises a first-effect falling film evaporator, a first-effect falling film separator, a second-effect falling film evaporator, a second-effect falling film separator and a second-effect transfer pump which are sequentially communicated.
Further preferably, a first circulation pipeline is arranged between the first-effect falling-film evaporator and the first-effect falling-film separator, a second circulation pipeline is arranged between the second-effect falling-film evaporator and the second-effect falling-film separator, a third circulation pipeline is arranged between the second-effect falling-film separator and the first-effect falling-film evaporator, a first-effect falling-film circulation pump is arranged on the first circulation pipeline, a second-effect falling-film circulation pump is arranged on the second circulation pipeline, and a first scrubbing tower and a first steam compressor are arranged on the third circulation pipeline.
Further, the ammonium sulfate collecting assembly comprises a first dryer and a first packing machine which are sequentially connected with the first centrifugal machine; the monoammonium phosphate collecting component comprises a second dryer and a second packing machine which are sequentially communicated with a second centrifugal machine.
Further, the first forced circulation component comprises a first forced circulation separator, a first forced circulation evaporator component and a first crystal slurry transfer pump which are sequentially communicated, a fourth circulation pipeline is arranged between the first forced circulation separator and the first forced circulation evaporator component, and a second scrubbing tower and a second vapor compressor are arranged on the fourth circulation pipeline;
the first forced circulation evaporator assembly comprises a first forced circulation evaporator, a first forced circulation pump and a second forced circulation evaporator which are sequentially communicated with the first forced circulation separator, and the first forced circulation evaporator and the second forced circulation evaporator are communicated with the second scrubbing tower.
Further, the continuous vacuum flash evaporation crystallization unit also comprises a cooler, a condensed water tank, a vacuum pump and a non-condensable gas discharging assembly which are communicated with the flash evaporation crystallizer.
Furthermore, a fifth circulating pipeline is arranged in the flash evaporation crystallizer, and a cooling circulating pump is arranged on the fifth circulating pipeline.
Further, the second forced circulation component comprises a second forced circulation separator, a second forced circulation evaporator component and a second crystal slurry transfer pump which are sequentially communicated, a sixth circulation pipeline is arranged between the second forced circulation separator and the second forced circulation evaporator component, and a third scrubbing tower and a third vapor compressor are arranged on the sixth circulation pipeline;
the second forced circulation evaporator assembly comprises a third forced circulation evaporator, a second forced circulation pump and a fourth forced circulation evaporator which are sequentially communicated with the second forced circulation separator, and the third forced circulation evaporator and the fourth forced circulation evaporator are communicated with a third scrubbing tower.
Further, the insoluble matter discharge unit includes a drum drying module communicated with a third mother liquor tank through a third mother liquor pump.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the preheating unit, the falling film evaporation unit, the forced circulation evaporation crystallization unit, the continuous vacuum flash evaporation crystallization unit, the miscellaneous salt evaporation unit and the insoluble substance discharge unit are adopted, so that the collection of ammonium sulfate, monoammonium phosphate, miscellaneous salts and insoluble substances in the iron phosphate wastewater can be sequentially realized, the heat of distilled water, tail gas and steam generated in the system can be well utilized, the zero emission and the energy recycling are realized, and the industrial application prospect is good.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of a waste water desalting system for iron phosphate production according to the present invention.
In the figure: 1-distilled water preheater, 2-noncondensable gas preheater, 3-steam preheater, 4-one-effect falling film evaporator, 5-one-effect falling film separator, 6-one-effect falling film circulating pump, 7-two-effect falling film evaporator, 8-two-effect falling film circulating pump, 9-two-effect falling film separator, 10-first steam compressor, 11-first scrubbing tower, 12-two-effect material transfer pump, 13-second scrubbing tower, 14-first forced circulation evaporator, 15-second forced circulation evaporator, 16-first forced circulation pump, 17-first crystal pulp material transfer pump, 18-first forced circulation separator, 19-second steam compressor, 20-first swirler, 21-first thickener, 22-first centrifuge, 23-first drier, 24-first packing machine, 25-first mother liquor tank 26-a first mother liquor pump, 27-a cooling circulating pump, 28-a flash evaporation crystallizer, 29-a cooler, 30-a condensate tank, 31-a condensate pump, 32-a vacuum pump, 33-a crystallization discharge pump, 34-a second thickener, 35-a second centrifuge, 36-a second mother liquor tank, 37-a second mother liquor pump, 38-a mother liquor preheater, 39-a third scrubbing tower, 40-a third forced circulation evaporator, 41-a second forced circulation pump, 42-a fourth forced circulation evaporator, 43-a second forced circulation separator, 44-a third steam compressor, 45-a second crystal paddle material transfer pump, 46-a third cyclone, 47-a third thickener, 48-a third centrifuge, 49-a third mother liquor tank, 50-a third mother liquor pump, 51-a roller drying component, 52-a second dryer and 53-a second packing machine.
Detailed Description
In order to facilitate an understanding of the invention, reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings, and the scope of the invention is not limited to the specific embodiments described below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1
As shown in fig. 1, the embodiment discloses a salt separating system for wastewater from iron phosphate production, which comprises a preheating unit, a double-effect falling film evaporation unit, a forced circulation evaporation crystallization unit, a continuous vacuum flash evaporation crystallization unit, a mixed salt evaporation unit and an insoluble substance discharge unit, which are sequentially communicated.
The preheating unit comprises a distilled water preheater 1, a noncondensable gas preheater 2 and a steam preheater 3 which are connected in sequence, wherein the distilled water preheater 1 is communicated with a distilled water storage tank; the noncondensable gas preheater 2 is communicated with the tail gas outlets of the falling film evaporation unit and the forced circulation crystallization unit; the steam preheater 3 is provided with a steam inlet which is communicated with an external steam source.
The falling film evaporation unit comprises a first-effect falling film evaporator 4, a first-effect falling film separator 5, a second-effect falling film evaporator 7, a second-effect falling film separator 9 and a second-effect material transfer pump 12 which are sequentially communicated. A first circulation pipeline is arranged between the first-effect falling film evaporator 4 and the first-effect falling film separator 5, a second circulation pipeline is arranged between the second-effect falling film evaporator 7 and the second-effect falling film separator 9, a third circulation pipeline is arranged between the second-effect falling film separator 9 and the first-effect falling film evaporator 4, a first-effect falling film circulation pump 6 is arranged on the first circulation pipeline, a second-effect falling film circulation pump 8 is arranged on the second circulation pipeline, and a first scrubbing tower 11 and a first steam compressor 10 are arranged on the third circulation pipeline.
In the embodiment, the feeding of the falling film evaporation unit is the discharging through the steam preheating unit, the feed liquid enters the first-effect falling film evaporator 4 and the first-effect falling film circulating pump 6, after the first-effect falling film separator 5 is circularly concentrated, the concentrated liquid at the bottom of the evaporator of the first-effect falling film evaporator 4 is directly pressed into the second-effect falling film evaporator 7, and is circularly further concentrated through the second-effect falling film circulating pump 8 and the second-effect falling film separator 9. Steam at the upper part of the first-effect falling film separator 5 enters the second-effect falling film evaporator 7 and is supplied. The steam at the upper part of the two-effect falling film separator 9 enters the first vapor compressor 10 after passing through the first scrubbing tower 11, and the pressurized steam is supplied to the one-effect falling film evaporator 4. The concentrated solution at the bottom of the dual-effect falling film separator 9 enters a forced circulation evaporation crystallization unit through a dual-effect material transfer pump 12.
The forced circulation evaporation crystallization unit comprises a first forced circulation evaporation assembly, a first swirler 20, a first thickener 21 and a first centrifuge 22 which are sequentially communicated with the falling film evaporation unit, wherein the first centrifuge 22 is respectively communicated with a first mother liquor tank 25 and an ammonium sulfate collection assembly; the first forced circulation component comprises a first forced circulation separator 18, a first forced circulation evaporator component and a first crystal slurry transfer pump 17 which are sequentially communicated, a fourth circulation pipeline is arranged between the first forced circulation separator 18 and the first forced circulation evaporator component, and a second scrubber tower 13 and a second vapor compressor 19 are arranged on the fourth circulation pipeline; the first forced circulation evaporator assembly comprises a first forced circulation evaporator 14, a first forced circulation pump 16 and a second forced circulation evaporator 15 which are sequentially communicated with a first forced circulation separator 18, and the first forced circulation evaporator 14 and the second forced circulation evaporator 15 are both communicated with the second scrubbing tower 13. The steam of the first forced circulation separator 18 enters the second steam compressor 19 after being subjected to gas washing by the second gas washing tower 13, and the pressurized steam enters the first forced circulation evaporator 14 and the second forced circulation evaporator 15 to form circulation.
In this embodiment, the feed liquid concentrated by the falling film evaporation unit is pumped by the two-effect material transfer pump 12 into the first forced circulation separator 18 of the forced circulation evaporation crystallization unit, and the feed liquid is circulated by the first forced circulation pump 16 between the first forced circulation evaporator 14 and the second forced circulation evaporator 15 and between the first forced circulation separator 18 for further evaporation and concentration. Concentrated feed liquid is pumped into a first cyclone 20 through a first crystal paddle material transfer pump 17, clear liquid of the first cyclone 20 returns to a first forced circulation separator 18 for re-concentration, thick liquid at the bottom of the first cyclone 20 enters a first thickener 21, clear liquid at the upper layer of the first thickener 21 enters a first mother liquid tank 25, the thick liquid at the bottom enters a first centrifugal machine 22, ammonium sulfate salt is separated out by the first centrifugal machine 22 and enters a first drying machine 23 of an ammonium sulfate collecting system, the dried ammonium sulfate salt enters a first packing machine 24, and the ammonium sulfate product is packed and sold.
The continuous flash evaporation crystallization unit comprises a flash evaporation crystallizer 28, a crystallization discharge pump 33, a second thickener 34 and a second centrifuge 35 which are sequentially communicated with a first mother liquor tank 25 through a first mother liquor pump 26, wherein the second centrifuge 35 is respectively communicated with a second mother liquor tank 36 and a monoammonium phosphate collecting component; the continuous vacuum flash evaporation crystallization unit further comprises a cooler 29, a condensate tank 30, a vacuum pump 32 and a non-condensable gas discharging component which are communicated with the flash evaporation crystallizer 28; a fifth circulation pipeline is arranged in the flash crystallizer 28, and a cooling circulation pump 27 is arranged on the fifth circulation pipeline. The second centrifuge 35 separates out the monoammonium phosphate salt, and the monoammonium phosphate salt enters a second dryer 52 of the monoammonium phosphate collection component, and the dried monoammonium phosphate salt enters a second packing machine 53, and the ammonium sulfate product is packed and sold.
And pumping the mother liquor of the forced circulation evaporation crystallization unit into a flash evaporation crystallizer 28 through a mother liquor pump first mother liquor pump 26, pumping the crystal pulp subjected to flash evaporation crystallization into a second thickener 34 and a second centrifuge 35 through a crystallization discharge pump 33, separating salt by using the second centrifuge 35, feeding the crystal pulp into a second dryer 52 of a monoammonium phosphate collection component, drying and dehydrating, and packaging to obtain the monoammonium phosphate. The purity of the monoammonium phosphate is controlled mainly by the temperature rise of the continuous flash evaporation crystallizer 28, and the temperature rise is controlled to be 30-55 ℃. The vacuum pump 32 ensures the vacuum of the continuous flash crystallizer 28 and the non-condensable gases are discharged irregularly.
The miscellaneous salt evaporation unit comprises a second forced circulation evaporation component, a third cyclone 46, a third thickener 47 and a third centrifuge 48 which are sequentially communicated with a second mother liquor tank 36 through a second mother liquor pump 37; the second forced circulation component comprises a mother liquor preheater 38, a second forced circulation separator 43, a second forced circulation evaporator component and a second crystal pulp transfer pump 45 which are sequentially communicated, a sixth circulation pipeline is arranged between the second forced circulation separator 43 and the second forced circulation evaporator component, and a third scrubbing tower 39 and a third steam compressor 44 are arranged on the sixth circulation pipeline; the second forced circulation evaporator assembly comprises a third forced circulation evaporator 40, a second forced circulation pump 41 and a fourth forced circulation evaporator 42 which are sequentially communicated with a second forced circulation separator 43, and the third forced circulation evaporator 40 and the fourth forced circulation evaporator 42 are communicated with the third scrubbing tower 39.
The insoluble matter discharge unit includes a drum drying module 51 communicating with the third mother liquor tank 49 via a third mother liquor pump 50.
The mother liquor of the flash evaporation crystallization unit enters the second forced circulation evaporator component after being preheated by the mother liquor preheater 38, and is subjected to double-effect forced circulation evaporation and a third centrifuge 48 to separate out miscellaneous salts. Insoluble substances and other substances in the system can not form salt, and the insoluble substances and other substances are periodically discharged into the drum drying component 51 and discharged out of the system.
Example 2
The embodiment provides a method for separating salt from waste water in iron phosphate production by using the production system in embodiment 1, which specifically comprises the following steps:
(1) Introducing iron phosphate production wastewater with the temperature of 35-40 ℃ into a preheating unit, sequentially preheating by three stages of the preheating unit to reach 95-100 ℃, and introducing into a forced circulation evaporation unit, wherein the method specifically comprises the following steps:
in a first-stage distilled water preheater 1, waste water exchanges heat with distilled water generated by a system, and the temperature of the waste water is increased from 30-35 ℃ to 80-90 ℃;
in the second-stage non-condensable gas preheater 2, waste water exchanges heat with non-condensable gas generated by the system, and the temperature of the waste water is increased from 80-90 ℃ to 90-95 ℃;
in a third-stage steam preheater 3, the waste water exchanges heat with fresh steam introduced from a steam port, and the temperature is 95-100 ℃;
and the wastewater after the three-stage preheating enters a falling film evaporation unit.
(2) In a falling film evaporation unit:
the feed is discharged through a steam preheating unit, enters the first-effect falling film evaporator 4, the first-effect falling film circulating pump 6 and the first-effect falling film separator 5, is circularly concentrated, and then the concentrated solution at the bottom of the first-effect falling film evaporator 4 is directly pressed into the second-effect falling film evaporator 7 and is circularly further concentrated through the second-effect falling film evaporator 7, the second-effect falling film circulating pump 8 and the second-effect falling film separator 9; wherein, the steam at the upper part of the first-effect falling film separator 5 enters the second-effect falling film evaporator 7 to supply steam.
The steam at the upper part of the two-effect falling film separator 9 enters the first vapor compressor 10 after passing through the first scrubbing tower 11, and the pressurized steam is supplied to the one-effect falling film evaporator 4. The concentrated solution at the bottom of the dual-effect falling film separator 9 enters a forced circulation evaporation crystallization unit through a dual-effect material transfer pump 12.
(3) In a forced circulation evaporative crystallization unit:
entering a first forced circulation separator 18, forming circulation through a first forced circulation pump 16, communicating the first forced circulation evaporator 14 with a second forced circulation evaporator 15, continuously evaporating and concentrating materials in the first forced circulation evaporator 14 and the second forced circulation evaporator 15 until the mass percentage concentration of ammonium sulfate in the crystallization material liquid is 50-60%, circulating the material liquid in the first forced circulation evaporator 14 and the second forced circulation evaporator 15 through the first forced circulation pump 16, enabling the material liquid to flow at high speed in heat exchanger tubes of the first forced circulation evaporator 14 and the second forced circulation evaporator 15, setting the specific flow speed in the tubes to be 1.5-2 m/s, exchanging heat with steam in a shell pass through forced circulation heat exchange, increasing the temperature of the material liquid, enabling the temperature of the material liquid after heat exchange to be higher than the flash evaporation temperature of the material liquid in the first forced circulation separator 18, starting flash evaporation when the concentration of ammonium sulfate in the continuous evaporation and concentration process of the material liquid, and enabling the concentration of ammonium sulfate to be gradually increased when the concentration of the tube wall reaches supersaturation, and starting flash evaporation in the first forced circulation evaporator 14 and the second forced circulation evaporator 15. The crystallization feed liquid is conveyed to the first cyclone 20 through the crystallization discharge pump 33 for preliminary separation, the clarified liquid returns to the first forced circulation separator 18 for re-concentration, the crystal slurry is transferred to the first thickener 21, and after further concentration through the first thickener 21, the crystal slurry is transferred to the first centrifuge 22 for centrifugal separation. And the ammonium sulfate crystals after centrifugal separation enter an ammonium sulfate collection component for collection. And the mother liquor after centrifugal separation enters a vacuum flash evaporation cooling continuous crystallization unit.
(4) In a vacuum flash cooling continuous crystallizer:
the continuous vacuum flash crystallizer 28 is a slurry internal circulation crystallizer. The power that continuous vacuum flash evaporation crystallizer 28 supersaturation produced is that the boiling takes away the heat and the temperature that produces reduces under the material negative pressure condition, adopts frequency conversion regulation and control simultaneously, and the degree of supersaturation of regulation and control solution that can be convenient makes in the continuous vacuum flash evaporation crystallizer 28 solution supersaturation be in the crystallization metastable zone within range all the time, and the evaporating temperature in the system is low, and monoammonium phosphate's solubility is little, therefore the boiling point rises lowly, and monoammonium phosphate can crystallize in flash evaporation crystallizer 28. When the crystallization amount of the monoammonium phosphate is 25-30%, the monoammonium phosphate is conveyed to a second thickener 34 through a crystallization discharge pump 33, and the crystal slurry enters a second centrifuge 35 for centrifugal separation. After the salt is separated by the second centrifuge 35, the mixture enters a second dryer 52 of the monoammonium phosphate collection component, and after drying and dehydration, the mixture is packaged to obtain monoammonium phosphate. The purity of the monoammonium phosphate is controlled mainly by the temperature rise of the continuous flash evaporation crystallizer 28, and the temperature rise is controlled to be 30-55 ℃. The vacuum pump 32 ensures the vacuum of the continuous flash crystallizer 28 and the non-condensable gases are discharged irregularly.
(5) Miscellaneous salt evaporation unit
The mother liquor of the flash evaporation crystallization unit enters the second forced circulation evaporator component after being preheated by the mother liquor preheater 38, and is subjected to double-effect forced circulation evaporation, and the miscellaneous salt is separated by the third centrifuge 48. Insoluble substances and other substances in the system can not form salt, and are periodically discharged into the drum drying component 51 and discharged out of the system.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. The utility model provides a ferric phosphate waste water divides salt technology, its characterized in that utilizes ferric phosphate waste water to divide the salt system, ferric phosphate waste water divides the salt system including preheating unit, falling liquid film evaporation unit, forced circulation evaporation crystallization unit, continuous vacuum flash evaporation crystallization unit, miscellaneous salt evaporation unit and the insoluble substance discharge unit that connects gradually, wherein:
the forced circulation evaporation crystallization unit comprises a first forced circulation evaporation assembly, a first swirler, a first thickener and a first centrifuge which are sequentially communicated with the falling film evaporation unit, and the first centrifuge is respectively communicated with a first mother liquor tank and an ammonium sulfate collection assembly; the continuous flash evaporation crystallization unit comprises a flash evaporation crystallizer, a crystallization discharge pump, a second thickener and a second centrifuge which are sequentially communicated with a first mother liquid tank, and the second centrifuge is respectively communicated with the second mother liquid tank and a monoammonium phosphate collecting component; the mixed salt evaporation unit comprises a mother liquor preheater, a second forced circulation evaporation assembly, a third swirler, a third thickener and a third centrifuge which are sequentially communicated with a second mother liquor tank, and the third centrifuge is respectively communicated with a mixed salt storage tank and the third mother liquor tank; the insoluble matter discharge unit is communicated with a third mother liquor tank;
the salt separating system for the ferric phosphate production wastewater used in the ferric phosphate production wastewater salt separating process comprises the following steps:
(1) Introducing the iron phosphate production wastewater into a preheating unit, preheating by the preheating unit to 95-100 ℃, and entering a falling film evaporation unit;
(2) Concentrating the preheated iron phosphate production wastewater in a falling film evaporation unit until the mass percentage concentration of ammonium sulfate in the solution reaches 30-35%, and then entering a forced circulation evaporation crystallization unit;
(3) In a forced circulation evaporation crystallization unit, a solution enters a first forced circulation evaporation assembly to be evaporated and concentrated to form a crystallization feed liquid until the mass percentage concentration of ammonium sulfate in the crystallization feed liquid is 50-60%, the crystallization feed liquid enters a first cyclone to be primarily separated, a clarified liquid returns to the first forced circulation evaporation assembly to be re-concentrated, a crystal slurry is transferred to a first thickener, the crystal slurry is further concentrated by the first thickener and then transferred to a first centrifugal machine for centrifugal separation, ammonium sulfate crystals after centrifugal separation enter an ammonium sulfate collection assembly to be collected, and a mother liquid after centrifugal separation enters a vacuum flash evaporation cooling continuous crystallization unit;
(4) The centrifugally separated mother liquor obtained in the step (3) is placed in a vacuum flash evaporation cooling continuous crystallizer, monoammonium phosphate in the mother liquor is crystallized in the flash evaporation crystallizer until the crystallization amount of the monoammonium phosphate is 25-30%, the monoammonium phosphate is conveyed to a second thickener through a crystallization discharge pump to form crystal slurry, the obtained crystal slurry is centrifugally separated in a second centrifuge, the obtained solid phase enters a monoammonium phosphate collecting component, and the centrifugally separated mother liquor enters a mixed salt evaporation unit;
(5) In the miscellaneous salt evaporation unit, preheating the mother liquor of the flash evaporation crystallization unit obtained in the step (4) by a mother liquor preheater, then entering a second forced circulation evaporator component for evaporation crystallization, finally separating miscellaneous salt by a third centrifuge, and discharging by an insoluble substance discharge unit.
2. The iron phosphate production wastewater salt separation process according to claim 1, wherein the preheating unit comprises a distilled water preheater, a noncondensable gas preheater and a steam preheater which are connected in sequence, and the distilled water preheater is communicated with each distilled water outlet of the system; the non-condensable gas preheater is communicated with each tail gas outlet of the system; the steam preheater is provided with a steam inlet;
in a distilled water preheater, the heat exchange is carried out between the iron phosphate production wastewater and the distilled water generated by the system, and the temperature is increased from 30-35 ℃ to 80-90 ℃; in a noncondensable gas preheater, exchanging heat between the iron phosphate production wastewater and noncondensable gas generated by a system, and raising the temperature from 80-90 ℃ to 90-95 ℃; in a steam preheater, the iron phosphate production wastewater exchanges heat with fresh steam introduced from a steam port, and the temperature rises to 95-100 ℃.
3. The iron phosphate production wastewater salt separation process according to claim 1, wherein the falling film evaporation unit comprises a single-effect falling film evaporator, a single-effect falling film separator, a double-effect falling film evaporator, a double-effect falling film separator and a double-effect material transfer pump which are sequentially communicated.
4. The iron phosphate production wastewater salt separation process according to claim 3, wherein a first circulation pipeline is arranged between the first-effect falling film evaporator and the first-effect falling film separator, a second circulation pipeline is arranged between the second-effect falling film evaporator and the second-effect falling film separator, a third circulation pipeline is arranged between the second-effect falling film separator and the first-effect falling film evaporator, a first-effect falling film circulation pump is arranged on the first circulation pipeline, a second-effect falling film circulation pump is arranged on the second circulation pipeline, and a first scrubbing tower and a first vapor compressor are arranged on the third circulation pipeline.
5. The iron phosphate production wastewater salt separation process according to claim 1, wherein the ammonium sulfate collection assembly comprises a first dryer and a first packing machine which are sequentially connected with a first centrifuge; the monoammonium phosphate collecting component comprises a second dryer and a second packing machine which are sequentially communicated with a second centrifugal machine.
6. The iron phosphate production wastewater salt separation process according to claim 1, wherein the first forced circulation component comprises a first forced circulation separator, a first forced circulation evaporator component and a first crystal slurry transfer pump which are sequentially communicated, a fourth circulation pipeline is arranged between the first forced circulation separator and the first forced circulation evaporator component, and a second gas washing tower and a second vapor compressor are arranged on the fourth circulation pipeline;
the first forced circulation evaporator assembly comprises a first forced circulation evaporator, a first forced circulation pump and a second forced circulation evaporator which are sequentially communicated with the first forced circulation separator, and the first forced circulation evaporator and the second forced circulation evaporator are both communicated with the second scrubbing tower.
7. The iron phosphate production wastewater salt separation process according to claim 1, wherein the continuous vacuum flash crystallization unit further comprises a cooler, a condensate tank, a vacuum pump and a non-condensable gas discharge assembly which are communicated with the flash crystallizer.
8. The iron phosphate production wastewater salt separation process according to claim 1, wherein a fifth circulation pipeline is arranged in the flash evaporation crystallizer, and a cooling circulation pump is arranged on the fifth circulation pipeline.
9. The iron phosphate production wastewater salt separation process according to claim 1, wherein the second forced circulation component comprises a second forced circulation separator, a second forced circulation evaporator component and a second crystal slurry transfer pump which are sequentially communicated, a sixth circulation pipeline is arranged between the second forced circulation separator and the second forced circulation evaporator component, and a third scrubbing tower and a third steam compressor are arranged on the sixth circulation pipeline;
the second forced circulation evaporator assembly comprises a third forced circulation evaporator, a second forced circulation pump and a fourth forced circulation evaporator which are sequentially communicated with the second forced circulation separator, and the third forced circulation evaporator and the fourth forced circulation evaporator are communicated with a third scrubbing tower.
10. The iron phosphate production wastewater salt separation process according to claim 1, wherein the insoluble material discharge unit comprises a drum drying assembly communicated with a third mother liquor tank through a third mother liquor pump.
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