CN111170320A - Device and method for recycling waste acid solution for polycrystalline silicon texturing - Google Patents
Device and method for recycling waste acid solution for polycrystalline silicon texturing Download PDFInfo
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- CN111170320A CN111170320A CN201911377570.1A CN201911377570A CN111170320A CN 111170320 A CN111170320 A CN 111170320A CN 201911377570 A CN201911377570 A CN 201911377570A CN 111170320 A CN111170320 A CN 111170320A
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/08—Compounds containing halogen
- C01B33/10—Compounds containing silicon, fluorine, and other elements
- C01B33/103—Fluosilicic acid; Salts thereof
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/38—Nitric acid
- C01B21/44—Concentration
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/38—Nitric acid
- C01B21/46—Purification; Separation ; Stabilisation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
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- C30B33/10—Etching in solutions or melts
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
- C02F2101/14—Fluorine or fluorine-containing compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
- C02F2101/163—Nitrates
Abstract
The invention relates to a device and a method for recycling waste acid liquor used for polycrystalline silicon texturing, wherein, a secondary chemical reaction precipitation section is used for neutralizing hydrofluoric acid through a primary reaction, and a secondary reaction generates a precipitate of fluosilicate, and the precipitate can be sold; the rectification purification section can rectify and purify the dilute nitric acid in the dilute nitric acid to generate concentrated nitric acid, and in the method, the dilute nitric acid with the concentration of about 65 percent is obtained by evaporating and concentrating the nitric acid through a dehydrating agent reduced pressure rectification process and can be directly reused in a wool making solution system, so that the cyclic utilization of the nitric acid is realized, and the medicament cost is reduced; the dehydrating agent regeneration section is to add certain content of magnesium oxide into a solution containing a small amount of dilute magnesium nitrate for neutralization, evaporate the magnesium nitrate to obtain the high-concentration concentrated magnesium nitrate, and directly use the concentrated magnesium nitrate as the dehydrating agent to be applied to the rectification purification section. The invention achieves the resource and recycling of waste water and solid waste, further reduces the operation cost and production cost of enterprises, and meets the requirements of energy conservation, high efficiency and environmental protection.
Description
Technical Field
The invention relates to the technical field of environmental protection treatment, in particular to the technical field of waste liquid recycling, and specifically relates to a device and a method for recycling waste acid liquid for polycrystalline silicon texturing.
Background
During the polysilicon texturing treatment, a large amount of waste acid liquid is generated, wherein the waste acid liquid comprises nitric acid, hydrofluoric acid and fluosilicic acid. At present, five methods are mainly used for treating the waste mixed acid: neutralization method, evaporation process, direct incineration, membrane separation and resin adsorption technology.
The five methods all have certain defects:
the first is a neutralization method, which not only needs to consume a large amount of alkaline substances, but also wastes nitric acid and hydrofluoric acid which can be recycled and reused in waste acid. In addition, because the waste acid contains heavy metal ions, nitrate ions and fluoride ions can not be treated, and the standard of environmental protection and standard emission can not be met.
The second is an evaporation process which is divided into a neutralization-displacement-evaporation process and a displacement-evaporation process. The neutralization-displacement-evaporation process comprises the steps of carrying out waste acid neutralization reaction by using lime emulsion, filtering to remove fluoride ions to obtain a calcium nitrate solution, carrying out sulfuric acid displacement reaction on the calcium nitrate solution to obtain calcium sulfate precipitate and nitric acid, and finally filtering, evaporating, concentrating and recovering to obtain the nitric acid. The process technology recovers a certain amount of nitric acid, reduces nitrate ions in the discharged water, is beneficial to environmental protection, and simultaneously reduces the discharge of fluorine ions, but has the defect that the equipment is frequently scaled in the evaporation process; the introduction of sulfuric acid increases the equipment investment and has complex operation; calcium nitrate is contained in the recovered nitric acid, which influences the recycling of the nitric acid returned to the pickling line. The replacement-evaporation process is to directly carry out sulfuric acid replacement reaction in order to save alkali consumption, and finally recover nitric acid and hydrofluoric acid through negative pressure evaporation to obtain metal sulfate, but has the defects of incomplete reaction and high energy consumption. Also, sulfuric acid is required, which increases the equipment investment and complicates the operation.
Thirdly, direct incineration, wherein the direct incineration process is that nitric acid, hydrofluoric acid and water in the waste mixed acid are separated through incineration; on the other hand, the nitrate in the waste mixed acid is thermally decomposed to obtain a metal oxide. However, nitric acid and nitrate are heated and decomposed into nitrogen oxides, so that a tail gas nitrogen oxide purification system is required to be added, and the investment is increased. Meanwhile, the recovery rate of nitric acid is only about 30%, and the corrosion resistance of equipment is serious.
And fourthly, membrane method separation has the advantages of small investment, simpler device structure and the defects of generating dilute waste acid with equal volume quantity, having poor separation effect on low-concentration metal ions and immature technology.
And fifthly, resin adsorption, namely, special resin is adopted for adsorption treatment of waste acid, and although the special resin adsorption process can achieve the purpose of recovering the waste acid without consuming heat energy, the adsorption process has the defect that after the resin adsorption treatment is saturated, at least the same amount of pure water is consumed for regeneration of the resin. The result is an increase in investment in the pure water system and in the wastewater treatment system, and the residual metal ions in the recovered acid is still around 20%.
Disclosure of Invention
The invention aims to provide a device for recycling waste acid solution for polycrystalline silicon texturing, which has a simple overall structure, can effectively recycle waste acid, and has better environmental protection property because a dehydrating agent, reclaimed water and the like can be recycled.
Furthermore, the invention also provides a method for recycling the waste acid solution for polysilicon texturing, which can effectively recycle nitric acid in the waste acid solution to form concentrated nitric acid, and hydrofluoric acid and fluosilicic acid to form solid precipitates for recycling, wherein the dehydrating agent and the reclaimed water can be recycled, thereby greatly improving the purification efficiency, simultaneously reducing the purification cost and meeting the requirements of stable product index, energy conservation, high efficiency and environmental protection.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a device for recycling waste acid liquor generated in polycrystalline silicon texturing, which comprises a silicon dioxide reaction kettle, a nitrate reaction kettle, a bag filter, a rectifying tower, a second condenser, a vacuum buffer tank and a concentrated nitric acid storage tank, wherein the silicon dioxide reaction kettle, the nitrate reaction kettle, the bag filter, the rectifying tower, the second condenser, the vacuum buffer tank and the concentrated nitric acid storage tank are sequentially connected through pipelines.
For the above technical solution, the applicant has further optimization measures.
Optionally, the device still includes rare magnesium nitrate storage tank, evaporimeter, first condenser, well water buffer tank and concentrated magnesium nitrate storage tank, rare magnesium nitrate storage tank connects the rectifying column for collect remaining rare magnesium nitrate in rectifying column bottom, rare magnesium nitrate storage tank and evaporimeter, first condenser, well water buffer tank connect gradually, evaporimeter lower part export with the import of concentrated magnesium nitrate storage tank links to each other.
Further, the bottom of the rectifying tower is connected with a reboiler, a liquid outlet of the reboiler is connected with the dilute magnesium nitrate storage tank, a liquid inlet and a steam outlet of the reboiler are respectively connected with the rectifying tower, and the reboiler and the bottom liquid in the rectifying tower carry out interphase mass transfer.
Furthermore, a security filter and an intermediate storage tank are arranged between the bag filter and the rectifying tower, the bag filter is connected with the security filter, the outlet of the security filter is connected with the intermediate storage tank, and the intermediate storage tank is connected with the rectifying tower and used for supplying materials to the rectifying tower.
Particularly, the invention also provides a method for recycling the waste acid solution for polycrystalline silicon texturing, which comprises the following steps:
step 1: determining the contents of nitric acid, hydrofluoric acid and fluosilicic acid in the wool making waste acid solution;
step 2: after the content of each acid solution is measured, mixing and adding silicon dioxide into the wool making waste acid solution, and reacting hydrofluoric acid in the silicon dioxide to generate fluosilicic acid;
and step 3: adding nitrate into the mixed acid solution after the reaction of adding silicon dioxide, reacting to generate fluorosilicate precipitate, and filtering to remove the fluorosilicate precipitate to obtain filtrate, namely dilute nitric acid;
and 4, step 4: and (3) mixing the dehydrating agent with the dilute nitric acid obtained in the step (3), then carrying out reduced pressure rectification treatment, and condensing the concentrated nitric acid steam generated by rectification to form concentrated nitric acid.
Optionally, the dehydrating agent is concentrated magnesium nitrate, and a dilute magnesium nitrate solution containing a small amount of nitric acid is left after rectification treatment in the step 4.
Still further, the method may further comprise,
and 5: and (3) after the content of nitric acid in the dilute magnesium nitrate solution generated in the step (4) is measured, adding magnesium oxide to neutralize the dilute nitric acid, evaporating the neutralized dilute magnesium nitrate solution, and obtaining a concentrated magnesium nitrate solution after part of water is removed by evaporation, wherein the concentrated magnesium nitrate solution can be used as the dehydrating agent in the step (4).
Further, the dilute magnesium nitrate solution left in the step 4 is firstly treated by a reboiler, the gas-phase product of the reboiler and the descending liquid of the rectifying section carry out interphase mass transfer, and the liquid-phase product is the dilute magnesium nitrate solution containing dilute nitric acid after primary purification.
Further, the relation ratio of the molar quantity of the silicon dioxide added in the step 2 to the molar quantity of the hydrofluoric acid is 1: 1.
Further, the nitrate added in the step 3 is potassium nitrate or sodium nitrate.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:
the device and the method for recycling the waste acid solution for the polycrystalline silicon texturing have a three-section structure, and comprise a secondary chemical reaction precipitation section, a rectification purification section and a dehydrating agent regeneration section. Specifically, the secondary chemical reaction precipitation section is to neutralize hydrofluoric acid through a primary reaction, generate a precipitate of fluorosilicate through a secondary reaction, and recycle and clean the precipitate to obtain economic benefits; the rectification purification section can rectify and purify the dilute nitric acid to generate concentrated nitric acid, and in the method, the dilute nitric acid with the concentration of about 65 percent is obtained by evaporating and concentrating the nitric acid through a dehydrating agent reduced pressure rectification process, wherein the content of metal ions and impurities reaches the level of electronic grade, and the nitric acid can be directly recycled in a wool making liquid system, so that the recycling of the nitric acid is realized, and the cost of a medicament is reduced; the dehydrating agent regeneration section is that after a certain content of magnesium oxide is added into a dilute magnesium nitrate solution containing a small amount of dilute nitric acid for neutralization, the steam generated in an evaporator does not contain acid any more, so that the condensed magnesium nitrate can be directly used as reclaimed water for reuse, and the rest is high-concentration concentrated magnesium nitrate which can be directly used as a dehydrating agent to be applied to the rectification purification section. Therefore, in the whole recycling process, the recycling and the recycling of the waste water and the solid waste are realized, the operation cost and the production cost of enterprises are further reduced, and the requirements of energy conservation, high efficiency and environmental protection are met.
Drawings
Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:
fig. 1 is a schematic overall structure diagram of a waste acid liquor recycling device for polycrystalline silicon texturing according to an embodiment of the invention.
Wherein the reference numerals are as follows:
1-a silica reaction kettle; 2-a nitrate reaction kettle; 3-bag filter; 4-cartridge filter; 5-gear pump; 6, 7-intermediate storage tank; 8-dilute nitric acid delivery pump; 9-a static mixer; 10-a rectifying tower; 11-a first condenser; 12-a reboiler; 13-vacuum buffer tank; 14-concentrated nitric acid storage tank; 15-a first vacuum pump; 16-dilute magnesium nitrate pump; 17, 18-dilute magnesium nitrate storage tank; 19-evaporator, 20-second condenser; 21-a reclaimed water buffer tank; 22-a second vacuum pump; 23-concentrated magnesium nitrate recycling pump; 24-concentrated magnesium nitrate storage tank.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first", "second", "third" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance, such as the first, second and third heating tubes, in order to be able to describe the product structure more clearly, without limiting its importance.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1:
the embodiment describes a device for recycling waste acid liquor in polycrystalline silicon texturing, as shown in fig. 1, the device mainly comprises a silicon dioxide reaction kettle 1, a nitrate reaction kettle 2, a bag filter 3, a rectifying tower 10, a first condenser 11, a vacuum buffer tank 13, a concentrated nitric acid storage tank 14, dilute magnesium nitrate storage tanks 17 and 18, an evaporator 19, a second condenser 20, a reclaimed water buffer tank 21 and a concentrated magnesium nitrate storage tank 24, and some pump valves and the like for pumping transmission liquid or gas and the like. The silicon dioxide reaction kettle 1, the nitrate reaction kettle 2, the bag filter 3, the rectifying tower 10, the first condenser 11, the vacuum buffer tank 13 and the concentrated nitric acid storage tank 14 are sequentially connected through pipelines, the dilute magnesium nitrate storage tanks 17 and 18 are connected with the rectifying tower 10 and used for collecting the residual dilute magnesium nitrate at the bottom of the rectifying tower 10, the dilute magnesium nitrate storage tanks 17 and 18 are sequentially connected with the evaporator 19, the second condenser 20 and the reclaimed water buffer tank 21, and the outlet at the lower part of the evaporator 19 is connected with the inlet of the concentrated magnesium nitrate storage tank 24.
The bottom of the rectifying tower 10 is connected with a reboiler 12, a liquid outlet of the reboiler 12 is connected with the dilute magnesium nitrate storage tanks 17 and 18, a liquid inlet and a steam outlet of the reboiler 12 are respectively connected with the rectifying tower 10, and the reboiler 12 and the bottom liquid in the rectifying tower 10 perform interphase mass transfer.
In order to further filter impurities in the acid liquor and ensure the purity of the nitric acid solution sent to the rectification and purification section, a security filter 4 and intermediate storage tanks 6 and 7 are arranged between the bag filter 3 and the rectification tower 10, the bag filter 3 is connected with the security filter 4, the outlet of the security filter 4 is connected with the intermediate storage tanks 6 and 7, and the intermediate storage tanks 6 and 7 are connected with the rectification tower 10 and used for feeding the rectification tower 10.
The connection relation of all the components is introduced according to the flow direction and the processing relation of the fluid, specifically, waste acid liquid firstly enters a silicon dioxide reaction kettle 1 to react with silicon dioxide to neutralize hydrofluoric acid, and then enters a nitrate reaction kettle 2 from the silicon dioxide reaction kettle 1, in the embodiment, potassium nitrate is added into the nitrate reaction kettle 2, so that potassium fluosilicate precipitate is generated in the nitrate reaction kettle 2, then the precipitate is filtered out through a bag filter 3, and acid liquid essential oil gear pump 5 after secondary filtration through a protective filter is conveyed to intermediate storage tanks 6 and 7. The intermediate tanks 6, 7 function as intermediate storage, and the intermediate tanks 6, 7 in this embodiment are arranged one by one, and therefore have two intermediate tanks 6, 7.
The middle storage tanks 6 and 7 are introduced into the static mixer 9 through the dilute nitric acid delivery pump 8, dilute nitric acid and a dehydrating agent are mixed in the static mixer 9 and then enter the rectifying tower 10, the vacuum rectification is carried out in the rectifying tower 10, the nitric acid steam with high concentration is output from the upper end of the rectifying tower 10, the nitric acid steam is condensed in the first condenser 11 to obtain concentrated nitric acid, wherein one part of the nitric acid steam is condensed and then is refluxed by the top sprayer of the rectifying tower 10 as reflux, the other part of the nitric acid steam enters the concentrated nitric acid storage tank 14, in order to be capable of delivering the nitric acid steam more smoothly, a vacuum buffer tank 13 is further arranged between the concentrated nitric acid storage tank 14 and the condenser, and the vacuum buffer tank 13 is connected with an external first vacuum pump 15.
The tower bottom of the rectifying tower 10 is dilute magnesium nitrate containing a small amount of nitric acid, the solution enters a reboiler 12, then a small amount of the solution is evaporated into steam, the steam enters the rectifying tower 10 in the rectifying and purifying section and carries out mass transfer with descending liquid in the rectifying tower 10, a large amount of the liquid is purified and then conveyed to dilute magnesium nitrate storage tanks 17 and 18 in the dehydrating agent regeneration section through a dilute magnesium nitrate pump 16, and the dilute magnesium nitrate storage tanks 17 and 18 are one-used one-standby one and have two functions.
The amount of dilute nitric acid in dilute magnesium nitrate storage tanks 17 and 18 is measured, and a complete dilute magnesium nitrate solution can be obtained by adding magnesium oxide into the dilute magnesium nitrate storage tanks for neutralization, then the dilute magnesium nitrate solution after the reaction is completely led into an evaporator 19, wherein a falling film evaporator 19 is adopted, after the evaporator 19 evaporates the dilute magnesium nitrate solution, the steam is water without acid, after being condensed, the water can be stored in a reclaimed water buffer tank 21 to be used as reclaimed water, the reclaimed water buffer tank 21 is connected with an external second vacuum pump 22 through a water pipe, and the concentrated magnesium nitrate at the bottom of the evaporator 19 is stored in the concentrated magnesium nitrate storage tank 24, and when needed, a concentrated magnesium nitrate recycling pump 23 connected with the concentrated magnesium nitrate is opened to be used as a dehydrating agent to be sent out of the static mixer 9 for recycling, and the dehydrated magnesium nitrate recycling and the diluted nitric acid enter the rectifying tower 10 again.
Example 2:
in particular, the embodiment describes a method for recycling waste acid solution for polycrystalline silicon texturing, which comprises the following steps:
step 1: determining the contents of nitric acid, hydrofluoric acid and fluosilicic acid in the wool making waste acid solution;
step 2: after the content of each acid solution is measured, mixing and adding silicon dioxide into the wool making waste acid solution, wherein the relation ratio of the molar weight of the added silicon dioxide to the molar weight of hydrofluoric acid is 1:1, stirring and reacting for 30 minutes, reacting the hydrofluoric acid to generate fluosilicic acid and silicon tetrafluoride, and allowing the silicon tetrafluoride as a gas to pass through an exhaust passage to a waste gas treatment device;
and step 3: adding potassium nitrate into the mixed acid liquid after the reaction of adding the silicon dioxide, wherein the molar ratio of the added potassium nitrate to the fluosilicic acid is 2: 1, stirring for 30 minutes, then reducing the temperature of a reaction kettle after reaction to achieve the purpose of cold crystallization, reducing the solubility of potassium fluosilicate to convert the potassium fluosilicate to the maximum extent to generate potassium fluosilicate precipitate, cleaning, evaporating and drying the potassium fluosilicate precipitate to obtain a product for sale, and filtering to remove the potassium fluosilicate precipitate to obtain filtrate, namely dilute nitric acid;
and 4, step 4: and (3) mixing concentrated magnesium nitrate (dehydrating agent) with the dilute nitric acid obtained in the step (3) and then carrying out vacuum rectification, wherein the vacuum rectification is carried out by using a vacuum circulating pump to form a condition of-0.01 MPa in a rectifying tower 10 and the temperature is 85-95 ℃. Condensing the concentrated nitric acid steam generated by rectification to form concentrated nitric acid;
and 5: and (4) after the rectification treatment in the step 4, reserving a dilute magnesium nitrate solution containing a small amount of nitric acid, adding magnesium oxide to neutralize the dilute nitric acid in the dilute magnesium nitrate solution generated in the step 4 after the nitric acid content in the dilute magnesium nitrate solution is measured, evaporating the neutralized dilute magnesium nitrate solution, removing part of water by evaporation, and then obtaining a residual solution which is a concentrated magnesium nitrate solution, wherein the concentrated magnesium nitrate solution can be used as the dehydrating agent in the step 4.
In order to realize the primary purification of the dilute magnesium nitrate solution, the dilute magnesium nitrate solution left in the step 4 is firstly treated by a reboiler 12, the gas-phase product of the reboiler 12 and the descending liquid of the rectifying section carry out interphase mass transfer, and the liquid-phase product is the dilute magnesium nitrate solution containing the dilute nitric acid after the primary purification.
Example 3:
the waste acid from the polysilicon texturing production line is adopted in the embodiment, the content of the waste acid is about 30% of nitric acid, about 3% of hydrofluoric acid and about 5% of fluosilicic acid, the content of metal ions such as silver ions, aluminum ions, calcium ions, potassium ions, sodium ions, zinc ions and the like is from hundreds of ppb to tens of thousands of ppb, and the treatment capacity is 1 ton/day. The waste acid liquor is collected in batches and sent to a silicon dioxide reaction kettle 1 (1 cubic meter), 24.8 kilograms of silicon dioxide is added, after stirring and reacting for 30 minutes, sending the mixture to a potassium nitrate reaction kettle (1 cubic meter), adding 116.4 kilograms of potassium nitrate, stirring and reacting for 30 minutes, the potassium nitrate reaction kettle is a jacket type reaction kettle with stirring, cooling water with the temperature of 5-7 ℃ is introduced into a jacket for precipitation for half an hour after the reaction is finished, and then filtering the obtained product by a bag filter 3 and a cartridge filter 4, wherein filter residues are potassium fluosilicate precipitate, washing the product for 3-5 times by using deionized water, measuring the pH value of the washing water to be about 6-7 (the washing water is dilute acid liquid and can be introduced into a potassium nitrate reaction kettle for subsequent treatment, so that the discharge of acidic wastewater is reduced), drying the obtained potassium fluosilicate at the temperature of 120 ℃, and obtaining a byproduct potassium fluosilicate after two hours, so that the potassium fluosilicate reaches the industrial grade sale standard. The filtrate from the cartridge filter 4 is dilute nitric acid and enters the intermediate storage tanks 6 and 7.
Under the initial condition, 150Kg of magnesium nitrate is added into a concentrated magnesium nitrate storage tank 24, 50Kg of deionized water is added to prepare a concentrated magnesium nitrate solution, and the mass ratio of the concentrated magnesium nitrate solution to the dilute nitric acid by a concentrated magnesium nitrate pump is 2.1: the flow ratio of 1 is mixed by a static mixer 9 and then enters a rectifying tower 10, the height of the rectifying tower 10 is 3m, the diameter of the tower is 200mm, the height of a packing layer is 2.5 m, and 5 kg of saturated steam is adopted for heating. The operation temperature is 85-95 ℃, the reflux ratio is 0.25, and the operation pressure is-0.01 MPa. The nitric acid steam at the tower top is condensed by a condenser to obtain about 65 percent of dilute nitric acid, wherein the content of metal ions reaches the electronic grade standard, and the dilute nitric acid can be directly recycled to a polysilicon wool making production line. The dilute magnesium nitrate solution containing metal ions at the bottom of the tower bottom of the rectifying tower 10 is conveyed to a dilute magnesium nitrate buffer tank (one is used for spare) through a conveying pump, the dilute magnesium nitrate buffer tank is kept for three hours in each tank, 0.35 Kg of magnesium oxide is added for stirring reaction for 15 minutes, then the dilute magnesium nitrate solution is conveyed to a falling film evaporator 19 for dehydration, the height of the tower is 2 meters, the diameter of the tower is 200mm, the temperature of the evaporator 19 is 120 ℃, the operating pressure is-0.01 MPa, 5 kilograms of saturated steam is adopted for heating, the water vapor at the top of the evaporator 19 can be directly recycled as reclaimed water after being condensed by a condenser, and the concentrated magnesium nitrate solution at the bottom of the evaporator 19 is conveyed to the rectifying tower 10 through the conveying.
In the whole process flow, the recovery rate of the nitric acid is as high as 98%, the concentration is about 65%, the content of metal ions is in the standard of an electronic-grade reagent, and the nitric acid can be directly recycled to a production line. The comprehensive utilization rate of hydrofluoric acid and fluosilicic acid is up to above 90%, basically no acidic waste water is produced, and the by-product potassium fluosilicate can be sold as an industrial product.
In summary, the device and the method for recycling the waste acid solution for the polycrystalline silicon texturing have a three-section structure, and comprise a secondary chemical reaction precipitation section, a rectification purification section and a dehydrating agent regeneration section. Specifically, the secondary chemical reaction precipitation section is to neutralize hydrofluoric acid through a primary reaction, generate a precipitate of potassium fluosilicate through a secondary reaction, and recycle and clean the precipitate to obtain economic benefits; the rectification purification section can rectify and purify the dilute nitric acid to generate concentrated nitric acid, and in the method, the dilute nitric acid with the concentration of about 65 percent is obtained by evaporating and concentrating the nitric acid through a dehydrating agent reduced pressure rectification process, wherein the content of metal ions and impurities reaches the level of electronic grade, and the nitric acid can be directly recycled in a wool making liquid system, so that the recycling of the nitric acid is realized, and the cost of a medicament is reduced; the dehydrating agent regeneration section is that after a certain content of magnesium oxide is added into a solution containing a small amount of dilute magnesium nitrate for neutralization, the steam generated in the evaporator 19 does not contain acid any more, so that the condensed magnesium nitrate can be directly used as reclaimed water for reuse, and the rest is high-concentration concentrated magnesium nitrate which can be directly used as the dehydrating agent to be applied to the rectification purification section. Thereby, in the whole recycling process, the reclamation and the recycling of the waste water and the solid waste are achieved, the operation cost and the production cost of enterprises are further reduced, and the requirements of energy conservation, high efficiency and environmental protection are met
The above embodiments are merely illustrative of the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and implement the invention, and not to limit the scope of the invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered by the scope of the present invention.
Claims (10)
1. The utility model provides a be used for polycrystalline silicon making herbs into wool acid pickle recycle device, its characterized in that, includes silica reation kettle, nitrate reation kettle, bag filter, rectifying column, first condenser, vacuum buffer tank and concentrated nitric acid storage tank, wherein, connect gradually through the pipeline between silica reation kettle, nitrate reation kettle, bag filter, rectifying column, first condenser, vacuum buffer tank, concentrated nitric acid storage tank.
2. The device for recycling the waste acid liquor generated in the texturing of the polycrystalline silicon according to claim 1, further comprising a dilute magnesium nitrate storage tank, an evaporator, a second condenser, a reclaimed water buffer tank and a concentrated magnesium nitrate storage tank, wherein the dilute magnesium nitrate storage tank is connected with the rectifying tower and is used for collecting the dilute magnesium nitrate remained at the bottom of the rectifying tower, the dilute magnesium nitrate storage tank is sequentially connected with the evaporator, the second condenser and the reclaimed water buffer tank, and an outlet at the lower part of the evaporator is connected with an inlet of the concentrated magnesium nitrate storage tank.
3. The device for recycling the spent acid solution for polysilicon etching according to claim 2, wherein the bottom of the rectifying tower is connected with a reboiler, a liquid outlet of the reboiler is connected with the dilute magnesium nitrate storage tank, a liquid inlet and a steam outlet of the reboiler are respectively connected with the rectifying tower, and the reboiler performs phase-to-phase mass transfer with the bottom liquid in the rectifying tower.
4. The recycling device of waste acid liquor generated in polysilicon etching according to any one of claims 1 to 3, wherein a security filter and an intermediate storage tank are arranged between the bag filter and the rectifying tower, the bag filter is connected with the security filter, the outlet of the security filter is further connected with the intermediate storage tank, and the intermediate storage tank is further connected with the rectifying tower for supplying the rectifying tower.
5. A method for recycling waste acid liquor in polycrystalline silicon texturing is characterized by comprising the following steps:
step 1: determining the contents of nitric acid, hydrofluoric acid and fluosilicic acid in the wool making waste acid solution;
step 2: after the content of each acid solution is measured, mixing and adding silicon dioxide into the wool making waste acid solution, and reacting hydrofluoric acid in the silicon dioxide to generate fluosilicic acid;
and step 3: adding nitrate into the mixed acid solution after the reaction of adding silicon dioxide, reacting to generate fluorosilicate precipitate, and filtering to remove the fluorosilicate precipitate to obtain filtrate, namely dilute nitric acid;
and 4, step 4: and (3) mixing the dehydrating agent with the dilute nitric acid obtained in the step (3), then carrying out reduced pressure rectification treatment, and condensing the concentrated nitric acid steam generated by rectification to form concentrated nitric acid.
6. The device for recycling the waste acid solution for polycrystalline silicon texturing according to claim 5, wherein the dehydrating agent is concentrated magnesium nitrate, and a dilute magnesium nitrate solution containing a small amount of nitric acid is left after the rectification treatment in the step 4.
7. The recycling device of acid pickle for polysilicon texturing according to claim 6, further comprising,
and 5: and (3) after the content of nitric acid in the dilute magnesium nitrate solution generated in the step (4) is measured, adding magnesium oxide to neutralize the dilute nitric acid, evaporating the neutralized dilute magnesium nitrate solution, and obtaining a concentrated magnesium nitrate solution after part of water is removed by evaporation, wherein the concentrated magnesium nitrate solution can be used as the dehydrating agent in the step (4).
8. The device for recycling the spent acid solution for polycrystalline silicon texturing according to claim 6 or 7, wherein the dilute magnesium nitrate solution left in the step 4 is treated by a reboiler, the gas-phase product of the reboiler and the descending liquid of the rectifying section perform phase-to-phase mass transfer, and the liquid-phase product is the dilute magnesium nitrate solution containing the dilute nitric acid after primary purification.
9. The recycling device of the acid pickle for polysilicon texturing according to claim 5, wherein the ratio of the molar amount of silicon dioxide added in the step 2 to the molar amount of hydrofluoric acid is 1: 1.
10. The device for recycling the acid pickle produced in polycrystalline silicon texturing according to any one of claims 5 to 9, wherein the nitrate added in the step 3 is potassium nitrate or sodium nitrate.
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| CN201911377570.1A CN111170320B (en) | 2019-12-27 | 2019-12-27 | Device and method for recycling waste acid solution for polycrystalline silicon texturing |
| PCT/CN2020/135166 WO2021129404A1 (en) | 2019-12-27 | 2020-12-10 | Device and method for recycling waste acid liquid for polycrystalline silicon texturing |
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| CN201911377570.1A CN111170320B (en) | 2019-12-27 | 2019-12-27 | Device and method for recycling waste acid solution for polycrystalline silicon texturing |
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| CN112573751A (en) * | 2020-12-11 | 2021-03-30 | 广州科城环保科技有限公司 | Recycling treatment device and treatment process for waste tin stripping liquid |
| WO2021129404A1 (en) * | 2019-12-27 | 2021-07-01 | 苏州晶洲装备科技有限公司 | Device and method for recycling waste acid liquid for polycrystalline silicon texturing |
| CN113816405A (en) * | 2021-11-08 | 2021-12-21 | 湖北九宁化学科技有限公司 | Method for recycling fluorine-containing waste acid in photovoltaic industry |
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| CN111170320B (en) | 2021-01-19 |
| WO2021129404A1 (en) | 2021-07-01 |
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