CN115818598A - System and method for concentrating phosphoric acid by using low-level heat energy - Google Patents
System and method for concentrating phosphoric acid by using low-level heat energy Download PDFInfo
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- CN115818598A CN115818598A CN202211180036.3A CN202211180036A CN115818598A CN 115818598 A CN115818598 A CN 115818598A CN 202211180036 A CN202211180036 A CN 202211180036A CN 115818598 A CN115818598 A CN 115818598A
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- phosphoric acid
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- fluosilicic
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- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 title claims abstract description 338
- 229910000147 aluminium phosphate Inorganic materials 0.000 title claims abstract description 169
- 238000000034 method Methods 0.000 title claims abstract description 28
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 177
- 239000002253 acid Substances 0.000 claims abstract description 148
- 238000005406 washing Methods 0.000 claims abstract description 110
- 238000004519 manufacturing process Methods 0.000 claims abstract description 15
- 238000002425 crystallisation Methods 0.000 claims abstract description 10
- 230000008025 crystallization Effects 0.000 claims abstract description 10
- 239000007788 liquid Substances 0.000 claims description 82
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 72
- 238000001704 evaporation Methods 0.000 claims description 28
- 230000008020 evaporation Effects 0.000 claims description 27
- 239000000498 cooling water Substances 0.000 claims description 14
- 238000010521 absorption reaction Methods 0.000 claims description 13
- 238000001816 cooling Methods 0.000 claims description 9
- 239000013078 crystal Substances 0.000 claims description 9
- 239000000243 solution Substances 0.000 claims description 7
- 239000000872 buffer Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000003595 mist Substances 0.000 claims description 6
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 4
- 229910052731 fluorine Inorganic materials 0.000 claims description 4
- 239000011737 fluorine Substances 0.000 claims description 4
- 230000008676 import Effects 0.000 abstract description 8
- 238000007701 flash-distillation Methods 0.000 abstract description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 5
- 229910000851 Alloy steel Inorganic materials 0.000 abstract description 4
- 229910052799 carbon Inorganic materials 0.000 abstract description 3
- 239000006227 byproduct Substances 0.000 abstract description 2
- 239000010439 graphite Substances 0.000 abstract description 2
- 229910002804 graphite Inorganic materials 0.000 abstract description 2
- 238000012423 maintenance Methods 0.000 abstract description 2
- 238000005260 corrosion Methods 0.000 abstract 1
- 230000007797 corrosion Effects 0.000 abstract 1
- 239000000047 product Substances 0.000 description 13
- 238000012546 transfer Methods 0.000 description 3
- 239000003337 fertilizer Substances 0.000 description 2
- AKEJUJNQAAGONA-UHFFFAOYSA-N sulfur trioxide Chemical compound O=S(=O)=O AKEJUJNQAAGONA-UHFFFAOYSA-N 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 238000010793 Steam injection (oil industry) Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 239000013461 intermediate chemical Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The application discloses concentrated phosphoric acid's of low-order heat energy system and method, this system include sulfuric acid cooler, phosphoric acid heater, concentrated demister of flash distillation, crystallization separator, sulfuric acid cooler shell side export link to each other with phosphoric acid heater shell side import, sulfuric acid cooler shell side import passes through the pipeline and links to each other with phosphoric acid heater shell side export, phosphoric acid heater tube side export links to each other with crystallization separator top import through concentrated demister of flash distillation, crystallization separator bottom export passes through phosphoric acid concentration circulating pump and links to each other with phosphoric acid heater tube side import. Because the phosphoric acid heater is produced and operated at a lower temperature, the phosphoric acid has low corrosion rate, and the phosphoric acid heater can be made of alloy steel instead of graphite. Flash distillation tail gas adopts the level four washing, and each level washing all is equipped with solitary circulation tank, improves byproduct fluosilicic acid concentration, ensures that non-condensable gas emission up to standard. The patent aims at saving energy, reducing consumption, reducing carbon emission of a production device and the cost of operation and maintenance.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a system and a method for concentrating phosphoric acid by using low-level heat energy, and specifically relates to a new process for heating circulating hot water by using hot sulfuric acid generated in a sulfur trioxide absorption tower of a sulfuric acid production device, circularly heating phosphoric acid by using the circulating hot water, performing flash evaporation concentration on the phosphoric acid to obtain a target product, namely concentrated phosphoric acid, washing flash evaporation tail gas, circularly concentrating a fluosilicic acid solution to obtain a high-concentration fluosilicic acid solution, producing a fluorine-containing product, and cooling non-condensable gas to reach the standard and discharging.
Background
Phosphoric acid is an important intermediate chemical product, and the application of phosphoric acid is summarized in two aspects, namely fertilizer production and industrial phosphate production, while wet-process phosphoric acid is mainly used for fertilizer production.
The production process of wet-process phosphoric acid mainly adopts a two-water method, the production process accounts for more than 80 percent, the mass concentration of the two-water method phosphoric acid product is 24 to 26 percent 2 O 5 Since the concentration is too low to be used as it is, it is necessary to concentrate the solution to a mass concentration of 40% or more. Domestic phosphoric acid (100% by weight P) in 2021 2 O 5 ) Yield approximately 1700 ten thousand tons, low mass concentration 24% -26% 2 O 5 Phosphoric acid (100% by volume P) 2 O 5 ) Nearly 1360 ten thousand tons, 5440 ten thousand tons of material objects, and 2040 ten thousand tons of water which needs to be evaporated and concentrated every year. At present, dilute phosphoric acid with low concentration is concentrated by low-pressure steam with about 0.3MPa (absolute pressure), 1.25 tons of steam are consumed for evaporating one ton of water, and 2550 million tons of low-pressure steam are consumed every year.
The domestic sulfuric acid yield is 8556 ten thousand tons in 2021 year, wherein most sulfuric acid is used for producing phosphoric acid, nearly 1 hundred million tons of steam is produced at the same time, about one fourth of the steam is used for concentrating phosphoric acid, the low-level heat energy which accounts for about 39% of the total heat generated by the production of the sulfuric acid is not completely utilized, most of the low-level heat energy is sent to a cooling tower, the heat energy of the part of the heat energy is equivalent to the heat energy of about 6000 ten thousand tons of steam, and the requirement of the concentration of the phosphoric acid can be completely met.
The low-level heat energy of the sulfuric acid production device is utilized, the energy is saved, the consumption is reduced, the carbon emission of the production device is reduced, and the operation and maintenance cost is necessary and practical.
Disclosure of Invention
The invention aims to provide a system and a method for concentrating phosphoric acid by using low-level heat energy, which can recycle the energy of the low-level heat energy, save steam and reduce carbon emission. Hot water which is circularly heated is obtained by cooling hot sulfuric acid, concentrated phosphoric acid which is a target product is obtained by circularly heating, flashing and concentrating phosphoric acid, high-concentration fluorosilicic acid solution is obtained by washing multistage flash evaporation tail gas, and non-condensable gas is discharged after being washed and cooled in multistage and reaching the standard. The invention optimizes the process operation, increases the operating rate, reduces the production cost and makes the non-condensable gas cleaner.
The purpose of the invention can be realized by the following technical scheme:
the utility model provides a system for concentrated phosphoric acid of low-order heat energy, this system includes sulfuric acid cooler, phosphoric acid heater, the concentrated demister of flash distillation, crystal separator, sulfuric acid cooler shell side export link to each other with phosphoric acid heater shell side import, the import of sulfuric acid cooler shell side is passed through the pipeline and is linked to each other with phosphoric acid heater shell side export, phosphoric acid heater tube side export is passed through the concentrated demister of flash distillation and is linked to each other with crystal separator top import, the export of crystal separator bottom is passed through the concentrated circulating pump of phosphoric acid and is linked to each other with phosphoric acid heater tube side import.
In the above system: the inlet of the tube pass of the sulfuric acid cooler is connected with a hot sulfuric acid conveying pipeline from the sulfuric acid absorption tower, the outlet of the tube pass of the sulfuric acid cooler is connected with a sulfuric acid buffer tank through a pipeline, and the outlet of the sulfuric acid conveying pump is connected with a sulfuric acid conveying pipeline of the sulfuric acid removal absorption tower.
In the above system: a pipeline connected between the phosphoric acid concentration circulating pump and the phosphoric acid heater is provided with a concentrated phosphoric acid pipeline for removing the boundary region and a dilute phosphoric acid pipeline from the boundary region; the concentrated phosphoric acid pipeline of the boundary removal zone is close to the outlet of the phosphoric acid concentration circulating pump, and the dilute phosphoric acid pipeline from the boundary zone is as close as possible to the inlet of the phosphoric acid heater tube pass.
In the above system: the outlet at the top end of the flash evaporation concentration demister is connected with a primary washing tower through a primary tubular washer, the primary washing tower is connected with a secondary washing tower through a secondary tubular washer, and the washer at the uppermost layer of the secondary washing tower is connected with a process water pipeline from a boundary region.
In the above system: an outlet of the first-stage fluosilicic acid circulating tank is connected with a liquid inlet of the first-stage tubular washer through a first-stage fluosilicic acid circulating pump, and a pipeline for removing the concentrated fluosilicic acid in the boundary area is arranged on a pipeline connecting the first-stage fluosilicic acid circulating pump and the first-stage tubular washer;
one inlet of the first-stage fluosilicic acid circulating tank is connected with a liquid outlet of the first-stage tubular washer through a pipeline, and the other inlet of the first-stage fluosilicic acid circulating tank is connected with a liquid outlet of the second-stage fluosilicic acid circulating tank through a second-stage fluosilicic acid circulating pump; an outlet of the second-stage fluosilicic acid circulating tank is connected with a liquid inlet of the first-stage washing tower through a second-stage fluosilicic acid circulating pump, one inlet of the second-stage fluosilicic acid circulating tank is connected with a liquid outlet of the first-stage washing tower through a pipeline, and the other inlet of the second-stage fluosilicic acid circulating tank is connected with a liquid outlet of the third-stage fluosilicic acid circulating tank through a third-stage fluosilicic acid circulating pump;
an outlet of the tertiary fluosilicic acid circulating tank is connected with a liquid inlet of the secondary pipe type washer through a tertiary fluosilicic acid circulating pump, one inlet of the tertiary fluosilicic acid circulating tank is connected with a liquid outlet of the secondary pipe type washer through a pipeline, and the other inlet of the tertiary fluosilicic acid circulating tank is connected with a liquid outlet of the quaternary fluosilicic acid circulating tank through a quaternary fluosilicic acid circulating pump; an outlet of the four-stage fluosilicic acid circulating tank is connected with a liquid inlet of the second-stage washing tower through a four-stage fluosilicic acid circulating pump, and an inlet of the four-stage fluosilicic acid circulating tank is connected with a liquid outlet of the second-stage washing tower through a pipeline.
In the above system: one-level fluosilicic acid circulation tank is provided with a one-level fluosilicic acid circulation tank stirrer, the second-level fluosilicic acid circulation tank is provided with a second-level fluosilicic acid circulation tank stirrer, the third-level fluosilicic acid circulation tank is provided with a third-level fluosilicic acid circulation tank stirrer, and the fourth-level fluosilicic acid circulation tank is provided with a fourth-level fluosilicic acid circulation tank stirrer.
In the above system: the outlet at the top end of the secondary washing tower is connected with a vacuum pump through a demister and a gas condenser; the liquid outlet at the bottom end of the demister is connected with a liquid outlet pipe at the bottom end of the secondary washing tower; the liquid inlet of the gas condenser is connected with the circulating cooling water upper water pipeline, and the liquid outlet at the bottom end is connected with the water return tank.
The production method for concentrating phosphoric acid by using the system to realize low-level heat energy comprises the following steps:
(1) A hot sulfuric acid cooling section: the temperature of hot concentrated sulfuric acid from a sulfuric acid absorption tower is more than or equal to 108 ℃, the hot concentrated sulfuric acid enters a tube pass inlet of a sulfuric acid cooler, heat exchange is carried out between the hot concentrated sulfuric acid and water in a shell pass in the sulfuric acid cooler, the hot sulfuric acid is cooled to be less than or equal to 95 ℃, the cooled sulfuric acid is removed from a tube pass outlet of the sulfuric acid cooler to a sulfuric acid buffer tank, and the cooled sulfuric acid is conveyed to the sulfuric acid absorption tower by a sulfuric acid conveying pump;
water from a shell pass outlet of the phosphoric acid heater enters a shell pass inlet of the sulfuric acid cooler at the temperature of more than or equal to 85 ℃, is heated to the temperature of less than or equal to 98 ℃ in the shell pass of the sulfuric acid cooler, and is conveyed to the shell pass inlet of the phosphoric acid heater by a hot water conveying pump;
(2) Heating, flashing and concentrating the phosphoric acid: the hot water from the hot water delivery pump enters the shell pass of the phosphoric acid heater at the temperature of less than or equal to 98 ℃, exchanges heat with the circulating concentrated phosphoric acid in the tube pass, is cooled to the temperature of more than or equal to 85 ℃, and is discharged from the shell pass outlet of the phosphoric acid heater to the sulfuric acid cooler; circulating concentrated phosphoric acid is from a phosphoric acid concentration circulating pump, dilute phosphoric acid is from a boundary area, two phosphoric acid streams are mixed and then enter a phosphoric acid heater tube pass inlet, the circulating phosphoric acid is heated in a phosphoric acid heater, the temperature is increased from being less than or equal to 76 ℃ to being more than or equal to 78 ℃, then the circulating concentrated phosphoric acid enters a flash evaporation concentration demister, part of moisture of the circulating concentrated phosphoric acid is removed by flash evaporation under the condition of vacuum negative pressure, the concentration of the circulating concentrated phosphoric acid is improved, the temperature is reduced to be less than or equal to 76 ℃, the circulating concentrated phosphoric acid out of the flash evaporation concentration demister is filtered, crushed and separated out of crystals by a crystal separator, then enters a phosphoric acid concentration circulating pump, part of the concentrated phosphoric acid out of the phosphoric acid concentration circulating pump is used as a circulating concentrated phosphoric acid removal heater for next circulation, the other part of the concentrated phosphoric acid is used as a target product phosphoric acid removal boundary area, and the target product phosphoric acid contains P 2 O 5 The mass concentration is 42-44%.
The method comprises the following steps: the method further comprises the following steps:
flash evaporation tail gas washing section: the temperature of the gas from the top outlet of the flash evaporation concentration demister is less than or equal to 76 ℃, the gas firstly passes through a primary tubular washer, then passes through a primary washing tower, then passes through a secondary tubular washer, and finally passes through a secondary washing tower, the washing temperature is reduced to be less than or equal to 40 ℃, and the washer at the uppermost layer of the secondary washing tower is washed by process water from a boundary area;
production of fluosilicic acidA solution section; process water from a battery compartment firstly enters a washer at the uppermost layer of a second-stage washing tower to wash gas, then enters a fourth-stage fluosilicic acid circulating tank, and washing liquid in the fourth-stage fluosilicic acid circulating tank is conveyed by a fourth-stage fluosilicic acid circulating pump to one part of the washing liquid to be circularly washed in the second-stage washing tower and the other part of the washing liquid to be washed in a third-stage fluosilicic acid circulating tank; conveying one part of the washing liquid in the third-stage fluosilicic acid circulating tank to a second-stage tubular washer for circulating washing by a third-stage fluosilicic acid circulating pump, and conveying the other part of the washing liquid to a second-stage fluosilicic acid circulating tank; conveying one part of the washing liquid in the secondary fluosilicic acid circulating tank to a primary washing tower by a secondary fluosilicic acid circulating pump for circulating washing, and conveying the other part of the washing liquid to a primary fluosilicic acid circulating tank; the washing liquid in the first-stage fluosilicic acid circulating tank is conveyed by the first-stage fluosilicic acid circulating pump, one part of the washing liquid is conveyed to a first-stage tubular washer for circular washing, the other part of the washing liquid is used as concentrated fluosilicic acid to produce fluorine-containing products, and the fluosilicic acid contains H 2 SiF 6 The mass concentration is 18-20%, and the temperature is less than or equal to 40 ℃;
a non-condensable gas cooling and discharging section; the non-condensable gas from the outlet at the top end of the secondary washing tower enters a demister to remove mist, and liquid drops condensed from the mist are discharged from the outlet at the bottom end of the demister to a liquid outlet pipe at the bottom end of the secondary washing tower; non-condensable gas is discharged from an outlet at the top end of a demister, the temperature of circulating cooling water from a circulating water station is higher than or equal to 26 ℃, the circulating cooling water enters the upper part of a gas condenser, the temperature of the non-condensable gas is completely reduced to be lower than or equal to 36 ℃, water in the non-condensable gas is removed, circulating cooling water return water and condensate in the non-condensable gas are discharged from an outlet at the bottom end of the gas condenser to a water return tank, the circulating cooling water return water is discharged from the water return tank to the circulating water station, and the return water temperature is lower than or equal to 34 ℃; and the clean non-condensable gas discharged from the top outlet of the gas condenser is pumped to a vacuum pump and is discharged by the vacuum pump after reaching the standard.
In the technical scheme of the invention: the sulfuric acid cooler is made of alloy steel, and the phosphoric acid heater is made of alloy steel or graphite.
The technical scheme of the invention is as follows: the sulfuric acid delivery pump adopts a submerged pump.
The technical scheme of the invention is as follows: the first-stage fluosilicic acid circulating pump, the second-stage fluosilicic acid circulating pump, the third-stage fluosilicic acid circulating pump and the fourth-stage fluosilicic acid circulating pump all adopt engineering plastic pumps.
The technical scheme of the invention is as follows: the vacuum pump adopts a water ring vacuum pump.
The invention has the beneficial effects that:
the invention provides a system and a method for concentrating phosphoric acid by low-level heat energy, and 1.25 tons of steam can be saved in each ton of water evaporated by the method. The phosphoric acid heater is made of alloy steel, the flow velocity of the phosphoric acid in the pipe pass of the phosphoric acid heater can adopt high flow velocity (the flow velocity can be more than 2.3 m/s), the scale formation and frequent washing in the phosphoric acid heater can be prevented, and the phosphoric acid heater is suitable for high-solid-content phosphoric acid and is not easy to abrade. The phosphoric acid is heated by hot water, so that quite stable operation conditions are provided for an evaporation system, the change of the dilute phosphoric acid feeding concentration can be balanced by adopting a process mechanism, when the concentration is low, the boiling point is reduced, the corresponding temperature difference is increased, the heat transfer rate is increased as a result, and the concentration of the target product phosphoric acid is not influenced by the feeding conditions; at high concentrations, the change is reversed. Flash distillation tail gas adopts the level four washing, and every level washing all is equipped with solitary circulation tank, improves byproduct fluosilicic acid finished product concentration, ensures that noncondensable gas emission to reach standard. And the vacuum pump is adopted to replace a steam injection unit, so that the energy consumption is reduced.
Drawings
FIG. 1 is a schematic diagram of the process flow in this patent
Wherein, sulfuric acid cooler 1, hot water transfer pump 2, phosphoric acid heater 3, sulfuric acid transfer pump 4, sulfuric acid buffer tank 5, flash evaporation concentration demister 6, crystallization separator 7, phosphoric acid concentration circulating pump 8, one-level tubular scrubber 9, one-level washing tower 10, two-level tubular scrubber 11, two-level washing tower 12, demister 13, gas condenser 14, vacuum pump 15, return water tank 16, one-level fluosilicic acid circulating pump 17, one-level fluosilicic acid circulating tank 18, one-level fluosilicic acid circulating tank stirrer 19, two-level fluosilicic acid circulating pump 20, two-level fluosilicic acid circulating tank 21, two-level fluosilicic acid circulating tank stirrer 22, three-level fluosilicic acid circulating pump 23, three-level fluosilicic acid circulating tank 24, three-level fluosilicic acid circulating tank stirrer 25, four-level fluosilicic acid circulating pump 26, four-level fluosilicic acid circulating tank 27, four-level fluosilicic acid circulating tank stirrer 28.
Detailed Description
The invention is further illustrated by the following examples, without limiting the scope of the invention:
the system for concentrating phosphoric acid by low-level heat energy comprises a sulfuric acid cooler 1, a phosphoric acid heater 3, a flash evaporation concentration demister 6 and a crystallization separator 7, wherein a shell pass outlet of the sulfuric acid cooler 1 is connected with a shell pass inlet of the phosphoric acid heater 3 through a hot water delivery pump 2, the shell pass inlet of the sulfuric acid cooler 1 is connected with a shell pass outlet of the phosphoric acid heater 3 through a pipeline, a tube pass outlet of the phosphoric acid heater 3 is connected with a top end inlet of the crystallization separator 7 through the flash evaporation concentration demister 6, and a bottom end outlet of the crystallization separator 7 is connected with a tube pass inlet of the phosphoric acid heater 3 through a phosphoric acid concentration circulating pump 8.
The inlet of the 1 tube pass of the sulfuric acid cooler is connected with a hot sulfuric acid conveying pipeline from the sulfuric acid absorption tower, the outlet of the 1 tube pass of the sulfuric acid cooler is connected with a sulfuric acid buffer tank 5 through a pipeline, and the outlet of a sulfuric acid conveying pump 4 is connected with a sulfuric acid conveying pipeline of the sulfuric acid absorption tower.
The concentrated phosphoric acid pipeline going to the boundary area and the dilute phosphoric acid pipeline coming from the boundary area are connected with a connecting pipeline from the outlet of the phosphoric acid concentration circulating pump 8 to the pipe pass inlet of the phosphoric acid heater 3, the concentrated phosphoric acid pipeline going to the boundary area is as close as possible to the outlet of the phosphoric acid concentration circulating pump 8, and the dilute phosphoric acid pipeline coming from the boundary area is as close as possible to the pipe pass inlet of the phosphoric acid heater 3.
The outlet at the top end of the flash evaporation concentration demister 6 is connected with a primary washing tower 10 through a primary tubular washer 9, the primary washing tower 10 is connected with a secondary washing tower 12 through a secondary tubular washer 11, and the washer at the uppermost layer of the secondary washing tower 12 is connected with a process water pipeline from a boundary area.
An outlet of a first-stage fluosilicic acid circulating tank 18 is connected with a liquid inlet of a first-stage tubular washer 9 through a first-stage fluosilicic acid circulating pump 17, a concentrated fluosilicic acid pipeline for removing a boundary region is connected with a connecting pipeline from the outlet of the first-stage fluosilicic acid circulating pump 17 to an inlet of the first-stage tubular washer 9, one inlet of the first-stage fluosilicic acid circulating tank 18 is connected with a liquid outlet of the first-stage tubular washer 9 through a pipeline, and the other inlet is connected with a liquid outlet of a second-stage fluosilicic acid circulating tank 21 through a second-stage fluosilicic acid circulating pump 20; an outlet of the second-stage fluosilicic acid circulating tank 21 is connected with a liquid inlet of the first-stage washing tower 10 through a second-stage fluosilicic acid circulating pump 20, one inlet of the second-stage fluosilicic acid circulating tank 21 is connected with a liquid outlet of the first-stage washing tower 10 through a pipeline, and the other inlet of the second-stage fluosilicic acid circulating tank 21 is connected with a liquid outlet of the third-stage fluosilicic acid circulating tank 24 through a third-stage fluosilicic acid circulating pump 23; an outlet of the third-stage fluosilicic acid circulating tank 24 is connected with a liquid inlet of the second-stage tubular washer 11 through a third-stage fluosilicic acid circulating pump 23, one inlet of the third-stage fluosilicic acid circulating tank 24 is connected with a liquid outlet of the second-stage tubular washer 11 through a pipeline, and the other inlet of the third-stage fluosilicic acid circulating tank 24 is connected with a liquid outlet of the fourth-stage fluosilicic acid circulating tank 27 through a fourth-stage fluosilicic acid circulating pump 26; an outlet of the fourth-stage fluosilicic acid circulating tank 27 is connected with a liquid inlet of the second-stage washing tower 12 through a fourth-stage fluosilicic acid circulating pump 26, and an inlet of the fourth-stage fluosilicic acid circulating tank 27 is connected with a liquid outlet of the second-stage washing tower 12 through a pipeline.
The outlet at the top end of the secondary washing tower 12 is connected with a vacuum pump 15 through a demister 13 and a gas condenser 14; a liquid outlet at the bottom end of the demister 13 is connected with a liquid outlet pipe at the bottom end of the secondary washing tower 12; the liquid inlet of the gas condenser 14 is connected with a circulating cooling water upper water pipeline, and the liquid outlet at the bottom end is connected with a water return tank 16.
The production method for realizing low-level heat energy concentrated phosphoric acid by utilizing the system comprises the following steps:
(1) A hot sulfuric acid cooling section: hot concentrated sulfuric acid from a sulfuric acid absorption tower has the mass concentration of 96.5-98.5% and the temperature of 108-110 ℃, enters a tube pass inlet of a sulfuric acid cooler 1, exchanges heat with water in a shell pass in the sulfuric acid cooler 1, is cooled to 93-95 ℃, and is sent to the sulfuric acid absorption tower from a tube pass outlet of the sulfuric acid cooler 1; water from a shell pass outlet of the phosphoric acid heater 3 enters a shell pass inlet of the sulfuric acid cooler 1 at 85-87 ℃, the water in the shell pass of the sulfuric acid cooler 1 is heated to 96-98 ℃, and the water is conveyed to the shell pass inlet of the phosphoric acid heater 3 by a hot water conveying pump 2.
(2) Heating, flashing and concentrating working section of phosphoric acid: the hot water from the hot water delivery pump 2 enters the shell pass of the phosphoric acid heater 3 at the temperature of 96-98 ℃, exchanges heat with the circulating concentrated phosphoric acid in the tube pass, is cooled to 85-87 ℃, and is discharged from the outlet of the shell pass of the phosphoric acid heater 3 to the sulfuric acid cooler 1; the circulating concentrated phosphoric acid comes from a phosphoric acid concentration circulating pump 8, and the mass concentration of the normal-temperature dilute phosphoric acid contains P 2 O 5 24～26 percent of phosphoric acid comes from a boundary area, two phosphoric acid streams are mixed and then enter a pipe pass inlet of a phosphoric acid heater 3, circulating phosphoric acid in the phosphoric acid heater 3 is heated, the temperature is increased to 78-80 ℃ from 74-76 ℃, then circulating concentrated phosphoric acid enters a flash evaporation concentration demister 6, part of water in the circulating concentrated phosphoric acid is removed by flash evaporation under the condition of vacuum negative pressure, the concentration of the circulating concentrated phosphoric acid is increased, the temperature is reduced to 74-76 ℃, the circulating concentrated phosphoric acid discharged from the flash evaporation concentration demister 6 is filtered, crushed and separated out crystals by a crystal separator 7, then the circulating concentrated phosphoric acid enters a phosphoric acid concentration circulating pump 8, one part of the concentrated phosphoric acid discharged from the phosphoric acid concentration circulating pump 8 is used as the circulating concentrated phosphoric acid removing heater 3 for next circulation, the other part of the circulating concentrated phosphoric acid is used as a target product to be removed from the boundary area, and the mass concentration of the target product phosphoric acid contains P 2 O 5 42-44% and 74-76 deg.C.
(3) Flash evaporation tail gas washing section: the temperature of the gas from the top outlet of the flash evaporation concentration demister 6 is 74-76 ℃, the gas firstly passes through a primary tubular washer 9, then passes through a primary washing tower 10, then passes through a secondary tubular washer 11, and finally passes through a secondary washing tower 12, the washing temperature is reduced to 38-40 ℃, and the washer at the uppermost layer of the secondary washing tower 12 is washed by process water from a battery compartment.
(4) A working section for producing fluosilicic acid solution; the process water from the battery limits firstly enters a scrubber at the uppermost layer of the second-stage washing tower 12 to wash gas, then enters a fourth-stage fluosilicic acid circulating tank 27, washing liquid in the fourth-stage fluosilicic acid circulating tank 27 is conveyed by a fourth-stage fluosilicic acid circulating pump 26 to be partially washed in the second-stage washing tower 12 in a circulating manner, and the other part of the washing liquid is conveyed to a third-stage fluosilicic acid circulating tank 24; a part of the washing liquid in the third-stage fluosilicic acid circulating tank 24 is conveyed to the second-stage tubular washer 11 by the third-stage fluosilicic acid circulating pump 23 for circulating washing, and the other part of the washing liquid is conveyed to the second-stage fluosilicic acid circulating tank 21; the washing liquid in the secondary fluosilicic acid circulating tank 21 is conveyed by a secondary fluosilicic acid circulating pump 20, one part of the washing liquid is sent to a primary washing tower 10 for circulating washing, and the other part of the washing liquid is sent to a primary fluosilicic acid circulating tank 18; the washing liquid in the first-stage fluosilicic acid circulating tank 18 is conveyed by a first-stage fluosilicic acid circulating pump 17, one part of the washing liquid is sent to a first-stage tubular washer 9 for circular washing, the other part of the washing liquid is used as concentrated fluosilicic acid to produce fluorine-containing products, and the fluosilicic acid contains H 2 SiF 6 Mass concentration is 18-20%,The temperature is 38-40 ℃.
(5) A non-condensable gas cooling and discharging section; the non-condensable gas from the outlet at the top end of the secondary washing tower 12 firstly enters a demister 13 to remove mist, and liquid drops condensed from the mist are discharged from the outlet at the bottom end of the demister 13 to a liquid outlet pipe at the bottom end of the secondary washing tower 12; non-condensable gas is discharged from an outlet at the top end of a demister 13 to a gas condenser 14, the temperature of circulating cooling water from a circulating water station is 24-26 ℃, the circulating cooling water enters the upper part of the gas condenser 14, the non-condensable gas is completely cooled to 34-36 ℃, water in the non-condensable gas is removed, circulating cooling water return water and condensate in the non-condensable gas are discharged from an outlet at the bottom end of the gas condenser 14 to a water return tank 16, the circulating cooling water return water is discharged from the water return tank 16 to the circulating water station, and the return water temperature is 32-34 ℃; the clean non-condensable gas from the top outlet of the gas condenser 14 is sent to a vacuum pump 15 and is discharged by the vacuum pump 15 after reaching the standard.
The results of the runs using the invention are shown in Table 1
TABLE 1 Performance test results table for ten thousand ton/year low-grade heat energy phosphoric acid concentration device
Claims (9)
1. A system for concentrating phosphoric acid by low-level heat energy is characterized in that: the system comprises a sulfuric acid cooler (1), a phosphoric acid heater (3), a flash evaporation concentration demister (6) and a crystallization separator (7), wherein a shell pass outlet of the sulfuric acid cooler (1) is connected with a shell pass inlet of the phosphoric acid heater (3), the shell pass inlet of the sulfuric acid cooler (1) is connected with a shell pass outlet of the phosphoric acid heater (3) through a pipeline, a tube pass outlet of the phosphoric acid heater (3) is connected with a top end inlet of the crystallization separator (7) through the flash evaporation concentration demister (6), and a bottom end outlet of the crystallization separator (7) is connected with a tube pass inlet of the phosphoric acid heater (3) through a phosphoric acid concentration circulating pump (8).
2. The system for concentrating phosphoric acid with low thermal energy according to claim 1, wherein: the inlet of the tube side of the sulfuric acid cooler (1) is connected with a hot sulfuric acid conveying pipeline from the sulfuric acid absorption tower, the outlet of the tube side of the sulfuric acid cooler (1) is connected with a sulfuric acid buffer tank (5) through a pipeline, and the outlet of a sulfuric acid conveying pump (4) is connected with a sulfuric acid conveying pipeline of a sulfuric acid removal absorption tower.
3. The system for concentrating phosphoric acid with low thermal energy according to claim 1, wherein: a pipeline connected between the phosphoric acid concentration circulating pump (8) and the phosphoric acid heater (3) is provided with a concentrated phosphoric acid pipeline for removing the boundary region and a dilute phosphoric acid pipeline from the boundary region; the concentrated phosphoric acid pipeline from the boundary region is close to the outlet of the phosphoric acid concentration circulating pump (8), and the dilute phosphoric acid pipeline from the boundary region is as close as possible to the inlet of the pipe pass of the phosphoric acid heater (3).
4. The system for concentrating phosphoric acid with low thermal energy according to claim 1, wherein: the top outlet of the flash evaporation concentration demister (6) is connected with a primary washing tower (10) through a primary tubular washer (9), the primary washing tower (10) is connected with a secondary washing tower (12) through a secondary tubular washer (11), and the uppermost layer washer of the secondary washing tower (12) is connected with a process water pipeline from a battery limits.
5. The system for concentrating phosphoric acid with low thermal energy according to claim 1, wherein: an outlet of the first-stage fluosilicic acid circulating tank (18) is connected with a liquid inlet of the first-stage tubular washer (9) through a first-stage fluosilicic acid circulating pump (17), and a pipeline for removing the concentrated fluosilicic acid in a boundary area is arranged on a pipeline for connecting the first-stage fluosilicic acid circulating pump (17) and the first-stage tubular washer (9);
one inlet of the primary fluosilicic acid circulating tank (18) is connected with a liquid outlet of the primary tubular washer (9) through a pipeline, and the other inlet is connected with a liquid outlet of the secondary fluosilicic acid circulating tank (21) through a secondary fluosilicic acid circulating pump (20); an outlet of the second-stage fluosilicic acid circulating tank (21) is connected with a liquid inlet of the first-stage washing tower (10) through a second-stage fluosilicic acid circulating pump (20), one inlet of the second-stage fluosilicic acid circulating tank (21) is connected with a liquid outlet of the first-stage washing tower (10) through a pipeline, and the other inlet of the second-stage fluosilicic acid circulating tank is connected with a liquid outlet of the third-stage fluosilicic acid circulating tank (24) through a third-stage fluosilicic acid circulating pump (23);
an outlet of the third-stage fluosilicic acid circulating tank (24) is connected with a liquid inlet of the second-stage tubular washer (11) through a third-stage fluosilicic acid circulating pump (23), one inlet of the third-stage fluosilicic acid circulating tank (24) is connected with a liquid outlet of the second-stage tubular washer (11) through a pipeline, and the other inlet of the third-stage fluosilicic acid circulating tank is connected with a liquid outlet of the fourth-stage fluosilicic acid circulating tank (27) through a fourth-stage fluosilicic acid circulating pump (26); an outlet of the four-stage fluosilicic acid circulating tank (27) is connected with a liquid inlet of the second-stage washing tower (12) through a four-stage fluosilicic acid circulating pump (26), and an inlet of the four-stage fluosilicic acid circulating tank (27) is connected with a liquid outlet of the second-stage washing tower (12) through a pipeline.
6. The system for concentrating phosphoric acid with low thermal energy according to claim 5, wherein: one-level fluosilicic acid circulation tank (18) is provided with one-level fluosilicic acid circulation tank stirrer (19), second-level fluosilicic acid circulation tank (21) is provided with second-level fluosilicic acid circulation tank stirrer (22), third-level fluosilicic acid circulation tank (24) is provided with third-level fluosilicic acid circulation tank stirrer (25), and fourth-level fluosilicic acid circulation tank (27) is provided with fourth-level fluosilicic acid circulation tank stirrer (28).
7. The system for concentrating phosphoric acid with low thermal energy according to claim 1, wherein: the top outlet of the secondary washing tower (12) is connected with a vacuum pump (15) through a demister (13) and a gas condenser (14); a liquid outlet at the bottom end of the demister (13) is connected with a liquid outlet pipe at the bottom end of the secondary washing tower (12); the liquid inlet of the gas condenser (14) is connected with a circulating cooling water upper water pipeline, and the liquid outlet at the bottom end is connected with a water return tank (16).
8. A method for producing low-grade thermal concentrated phosphoric acid by using the system of claim 1, which is characterized in that: the method comprises the following steps:
(1) A hot sulfuric acid cooling section: the temperature of hot concentrated sulfuric acid from a sulfuric acid absorption tower is more than or equal to 108 ℃, the hot concentrated sulfuric acid enters a tube pass inlet of a sulfuric acid cooler (1), heat exchange is carried out between the hot concentrated sulfuric acid and water in a shell pass in the sulfuric acid cooler (1), the hot sulfuric acid is cooled to be less than or equal to 95 ℃, the cooled sulfuric acid is removed from a tube pass outlet of the sulfuric acid cooler (1) to a sulfuric acid buffer tank (5), and the cooled sulfuric acid is conveyed to the sulfuric acid absorption tower by a sulfuric acid conveying pump (4);
water from a shell pass outlet of the phosphoric acid heater (3) enters a shell pass inlet of the sulfuric acid cooler (1) at the temperature of more than or equal to 85 ℃, the water in the shell pass of the sulfuric acid cooler (1) is heated to the temperature of less than or equal to 98 ℃, and the water is conveyed to the shell pass inlet of the phosphoric acid heater (3) by a hot water conveying pump (2);
(2) Heating, flashing and concentrating the phosphoric acid: hot water from the hot water delivery pump (2) enters the shell pass of the phosphoric acid heater (3) at the temperature of less than or equal to 98 ℃, exchanges heat with circulating concentrated phosphoric acid in the tube pass, is cooled to the temperature of more than or equal to 85 ℃, and is removed from the sulfuric acid cooler (1) from the shell pass outlet of the phosphoric acid heater (3); the circulating concentrated phosphoric acid is from a phosphoric acid concentration circulating pump (8), the dilute phosphoric acid is from a boundary region, two phosphoric acid streams are mixed and then enter a pipe pass inlet of a phosphoric acid heater (3), the circulating phosphoric acid is heated in the phosphoric acid heater (3), the temperature is increased to be more than or equal to 78 ℃ from being less than or equal to 76 ℃, then the circulating concentrated phosphoric acid enters a flash evaporation concentration demister (6), part of water in the circulating concentrated phosphoric acid is removed by flash evaporation under the condition of vacuum negative pressure, the concentration of the circulating concentrated phosphoric acid is improved, the temperature is reduced to be less than or equal to 76 ℃, the circulating concentrated phosphoric acid discharged from the flash evaporation concentration demister (6) is filtered, crushed and separated out crystals by a crystal separator (7), then the circulating concentrated phosphoric acid discharged from the phosphoric acid concentration circulating pump (8) is used as a circulating concentrated phosphoric acid removing heater (3) for next circulation, the other part of the target product phosphoric acid is used as a boundary region, and the target product phosphoric acid contains P 2 O 5 The mass concentration is 42 to 44 percent.
9. The method of claim 8, wherein: the method further comprises the following steps:
flash evaporation tail gas washing section: the temperature of the gas discharged from the top outlet of the flash evaporation concentration demister (6) is less than or equal to 76 ℃, the gas firstly passes through a primary tubular washer (9), then passes through a primary washing tower (10), then passes through a secondary tubular washer (11), and finally passes through a secondary washing tower (12), the washing temperature is reduced to be less than or equal to 40 ℃, and the uppermost layer of the secondary washing tower (12) is washed by process water from a battery boundary;
a working section for producing fluosilicic acid solution; process water from a battery compartment enters a scrubber at the uppermost layer of a second-stage washing tower (12) to wash gas, then enters a fourth-stage fluosilicic acid circulating tank (27), washing liquid in the fourth-stage fluosilicic acid circulating tank (27) is conveyed by a fourth-stage fluosilicic acid circulating pump (26), one part of the washing liquid is conveyed to the second-stage washing tower (12) for circulating washing, and the other part of the washing liquid is conveyed to a third-stage fluosilicic acid circulating tank (24); a part of the washing liquid in the third-stage fluosilicic acid circulating tank (24) is conveyed to a second-stage tubular washer (11) by a third-stage fluosilicic acid circulating pump (23) for circulating washing, and the other part of the washing liquid is conveyed to a second-stage fluosilicic acid circulating tank (21); the washing liquid in the secondary fluosilicic acid circulating tank (21) is conveyed by a secondary fluosilicic acid circulating pump (20), one part of the washing liquid is sent to a primary washing tower (10) for circulating washing, and the other part of the washing liquid is sent to a primary fluosilicic acid circulating tank (18); the washing liquid in the first-stage fluosilicic acid circulating tank (18) is conveyed by a first-stage fluosilicic acid circulating pump (17), one part of the washing liquid is sent to a first-stage tubular washer (9) for circulating washing, the other part of the washing liquid is used as concentrated fluosilicic acid to produce fluorine-containing products, and the fluosilicic acid contains H 2 SiF 6 The mass concentration is 18 to 20 percent, and the temperature is less than or equal to 40 ℃;
a non-condensable gas cooling and discharging section; non-condensable gas from an outlet at the top end of the secondary washing tower (12) firstly enters a demister (13) to remove mist, and liquid drops condensed from the mist are discharged from an outlet at the bottom end of the demister (13) to a liquid outlet pipe at the bottom end of the secondary washing tower (12); non-condensable gas is discharged from an outlet at the top end of a demister (13) to a gas condenser (14), the temperature of circulating cooling water from a circulating water station is higher than or equal to 26 ℃, the circulating cooling water enters the upper part of the gas condenser (14), the non-condensable gas is completely cooled to be lower than or equal to 36 ℃ and the water in the non-condensable gas is removed, circulating cooling water return water and condensate in the non-condensable gas are discharged from an outlet at the bottom end of the gas condenser (14) to a water return tank (16) and are discharged from the water return tank (16) to the circulating water station, and the return water temperature is lower than or equal to 34 ℃; the clean non-condensable gas from the top outlet of the gas condenser (14) is sent to a vacuum pump (15) and is discharged by the vacuum pump (15) after reaching the standard.
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