A method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid

Abstract

The invention relates to the technical field of fluorine-containing waste acid treatment, and in particular to a method for comprehensively utilizing fluorine-containing waste acid to recover hydrofluoric acid, which is used to solve the problem that a large amount of fluorine resources are converted into sludge without economic utilization value in the existing fluorine-containing waste acid treatment method, which not only causes waste of fluorine resources, but also has the risk of secondary pollution. The method is to strip the fluorine-containing waste acid with ultrafine bubbles, and subject a part of the stripped gas to low-temperature water spray treatment to obtain aqueous hydrofluoric acid, and subject the other part of the stripped gas to temperature control to remove water vapor, and then subject it to chemical dehydration and condensation to obtain industrial anhydrous hydrogen fluoride, and subject residual liquid remaining after the ultrafine bubbles are stripped to reaction treatment, and acid solution and fluorosilicate are recovered. Through the reuse of the fluorine-containing waste acid, not only the resource utilization rate is improved, but also the impact on the environment is reduced. In addition, the process flow of the invention is simple and easy to implement, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine-containing waste acid treatment, and in particular to a method for comprehensively utilizing fluorine-containing waste acid to recover hydrofluoric acid. Background Art

[0002] Fluorine is an important trace element in the human body and is a necessary component of teeth and bones. However, excessive intake can cause poisoning symptoms such as skeletal fluorosis and dental fluorosis, and it is easily absorbed by the human body, animals and plants, and accumulates in organisms to cause poisoning. In the production process of the semiconductor, panel, and photovoltaic industries, it is sometimes necessary to use hydrofluoric acid or other acid mixtures for surface treatment, which discharges fluorine-containing waste acid to varying degrees. These wastewaters are highly acidic and have high fluoride concentrations. The current common treatment method is to adopt chemical precipitation, which uses various calcium sources (calcium chloride, calcium oxide, calcium hydroxide, carbide slag, etc.) as precipitants and uses F - With Ca 2+ The difficult-to-generate CaF is precipitated to remove fluoride ions. Treating fluorine-containing waste acid in this way will produce a large amount of solid wastes such as calcium fluoride, sodium fluoride and calcium sulfate. These sludges have complex components and are difficult to recycle. They are generally treated by landfill. A large amount of fluorine resources are converted into sludge with no economic value, which not only wastes fluorine resources, but also poses a risk of secondary pollution. At the same time, the use of chemical precipitation to treat photovoltaic waste acid will also cause the loss of other useful components in the waste acid. In view of the shortcomings of the prior art, the present invention proposes a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid, thereby realizing resource recovery and reuse, which is of great significance to energy conservation and environmental protection. Summary of the invention

[0003] In order to overcome the above-mentioned technical problems, the object of the present invention is to provide a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid: the fluorine-containing waste acid is stripped with ultrafine bubbles, a part of the blown-off gas is subjected to low-temperature water spray treatment to obtain aqueous hydrofluoric acid, the other part of the blown-off gas is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride, the residual liquid remaining after the ultrafine bubble stripping is subjected to reaction treatment, and the acid solution and fluorosilicate are recovered, thereby solving the problem that a large amount of fluorine resources in the existing fluorine-containing waste acid treatment method are converted into sludge with no economic utilization value, which not only causes a waste of fluorine resources, but also has the risk of secondary pollution.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid comprises the following steps:

[0006] Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles;

[0007] Step 2: spraying part of the blown-off gas with low-temperature water to obtain aqueous hydrofluoric acid;

[0008] Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride;

[0009] Step 4: The residual liquid left after the ultrafine bubbles are blown off is subjected to reaction treatment to recover the acid solution and fluorosilicate.

[0010] As a further solution of the present invention: the fluorine-containing waste acid in step 1 comes from waste acid produced by using hydrofluoric acid in the production process of semiconductor, panel and photovoltaic industries.

[0011] As a further solution of the present invention: the specific process of the ultrafine bubble stripping in step 1 is as follows:

[0012] The temperature is controlled at 20-30°C, and the pressure is controlled below 1atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultrafine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5μm. The fluorine-containing waste acid is blown off, and the hydrofluoric acid with a low boiling point is blown off with the ultrafine bubbles floating in the fluorine-containing waste acid to form hydrogen fluoride gas escaping the waste acid.

[0013] As a further solution of the present invention: the specific process of the low-temperature water spraying treatment in step 2 is as follows:

[0014] The water temperature of the spray water in the spray tower system is controlled to be less than 15°C, and the spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

[0015] As a further solution of the present invention: the specific process of temperature-controlled water vapor removal in step 3 is as follows:

[0016] The temperature of the gas transmission pipeline is controlled at 25-35°C, the water vapor condenses and refluxes, and the water vapor condenses to achieve the function of removing a large amount of water vapor, and the hydrogen fluoride gas is output to the back end.

[0017] As a further solution of the present invention: the specific process of the chemical dehydration in step 3 is as follows:

[0018] The hydrogen fluoride gas is passed through an adsorption dehydrating agent for adsorption dehydration to obtain anhydrous hydrogen fluoride gas.

[0019] As a further solution of the present invention: the adsorption dehydrating agent is one of anhydrous sodium sulfate and anhydrous magnesium sulfate.

[0020] As a further solution of the present invention: the specific process of the condensation in step 3 is as follows:

[0021] The temperature is controlled at -20 to 10°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride.

[0022] As a further solution of the present invention: the specific process of the reaction treatment in step 4 is as follows:

[0023] Add precipitated silica to the residual liquid, control the reaction temperature to 55-75°C, stir the reaction for 0.5-1.5h, then vacuum filter, add sulfate or hydrochloride to the filtrate, continue stirring the reaction for 0.5-1.5h, then vacuum filter, collect the filtrate to obtain acid solution, wash the filter cake with clean water and then dry it, control the reaction temperature to 110-120°C and dry it for 2-2.5h to obtain fluorosilicate.

[0024] As a further solution of the present invention: the amount of the precipitated silica added is 20-30 g of precipitated silica per 1 kg of residual liquid.

[0025] As a further solution of the present invention: the particle size of the precipitated silica is 2-10 μm.

[0026] As a further solution of the present invention: the amount of sulfate or hydrochloride added is 100-150g of sulfate or hydrochloride per 1kg of residual liquid.

[0027] As a further solution of the present invention: the sulfate is sodium sulfate, and the hydrochloride is potassium chloride.

[0028] As a further solution of the present invention: the acid solution is sulfuric acid or hydrochloric acid.

[0029] As a further embodiment of the present invention: the fluorosilicate is sodium fluorosilicate or potassium fluorosilicate.

[0030] Beneficial effects of the present invention:

[0031] The invention discloses a method for recycling hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid, which comprises the following steps: subjecting the fluorine-containing waste acid to ultrafine bubble stripping, subjecting a part of the stripped gas to low-temperature water spraying treatment to obtain aqueous hydrofluoric acid, subjecting the other part of the stripped gas to temperature control to remove water vapor, and then subjecting the other part of the stripped gas to chemical dehydration and condensation to obtain industrial anhydrous hydrogen fluoride, subjecting the residual liquid remaining after the ultrafine bubble stripping to reaction treatment, and recovering acid solution and fluorosilicate;

[0032] This method does not follow the traditional practice of producing a large amount of sludge. Instead, a portion of the valuable hydrofluoric acid is directly extracted by stripping to make aqueous hydrofluoric acid and industrial anhydrous hydrogen fluoride. The aqueous hydrofluoric acid and industrial anhydrous hydrogen fluoride are prepared by concentration and can be reused in the production process of semiconductor, panel and photovoltaic industries, achieving comprehensive utilization while reducing the generation of secondary pollution and creating benefits.

[0033] In the method, the residual liquid after stripping is subjected to reaction treatment, and the residual liquid still contains a large amount of hydrofluoric acid and fluorosilicic acid. By adding precipitated white carbon black, the following reaction occurs: 6HF+SiO2→H2SiF6+2H2O, thereby fully converting the hydrofluoric acid in the residual liquid into fluorosilicic acid. When sulfate or hydrochloride is added thereto, the following reaction occurs when sulfate is added: H2SiF6+Na2SO4=Na2SiF6↓+H2SO4, thereby fully converting the fluorosilicic acid into acid solution and sodium fluorosilicate for recovery. When hydrochloride is added, the following reaction occurs: H2SiF6+2KCl=K2SiF6↓+2HCl, thereby fully converting the fluorosilicic acid into acid solution and potassium fluorosilicate for recovery. The obtained product is easy to separate and has no other pollution. The recovered acid solution can be used in the field of pickling. The recovered fluorosilicate has high purity and can be directly sold or used to create economic value.

[0034] In summary, the method not only improves resource utilization and reduces environmental impact by reusing fluorine-containing waste acid, but also the obtained hydrofluoric acid, acid solution and fluorosilicate have high market value and significant economic benefits. In addition, the process flow of the present invention is simple and easy to implement, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] Figure 1 The present invention is a schematic diagram of the process flow of a method for comprehensively utilizing fluorine-containing waste acid to recover hydrofluoric acid. DETAILED DESCRIPTION

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Embodiment 1:

[0039] See also Figure 1 As shown, this embodiment is a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid, comprising the following steps:

[0040] Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles. The specific process is as follows:

[0041] The temperature is controlled at 30°C, and the pressure is controlled below 1atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultra-fine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5μm. The fluorine-containing waste acid is blown off, so that the hydrofluoric acid with a low boiling point is blown off with the ultra-fine bubbles floating in the fluorine-containing waste acid, forming hydrogen fluoride gas escaping the waste acid;

[0042] Step 2: A portion of the blown-off gas is subjected to low-temperature water spraying treatment to obtain aqueous hydrofluoric acid. The specific process is as follows:

[0043] The temperature of the spray water in the spray tower system is controlled to be less than 15°C. The spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

[0044] Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride. The specific process is as follows:

[0045] The temperature of the gas delivery pipeline is controlled at 35°C, the water vapor condenses and refluxes, and the water vapor condenses to achieve the function of removing a large amount of water vapor, and the hydrogen fluoride gas is output to the back end;

[0046] Then, the hydrogen fluoride gas is passed through an adsorption dehydrating agent for adsorption dehydration, wherein the adsorption dehydrating agent is anhydrous sodium sulfate, to obtain anhydrous hydrogen fluoride gas;

[0047] Then, the temperature is controlled at 10°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride;

[0048] Step 4: The residual liquid left after the ultrafine bubbles are blown off is subjected to reaction treatment to recover the acid and fluorosilicate. The specific process is as follows:

[0049] Add 20 g of precipitated silica with a particle size of 10 μm to every 1 kg of residual liquid, control the reaction temperature to 55°C, stir the reaction for 0.5 h, then vacuum filter, add 100 g of sulfate to the filtrate, the sulfate is sodium sulfate, continue stirring the reaction for 0.5 h, then vacuum filter, collect the filtrate to obtain acid solution, the acid solution is sulfuric acid, wash the filter cake with clean water and then dry it, control the reaction temperature to 110°C and dry it for 2 h to obtain fluorosilicate, the fluorosilicate is sodium fluorosilicate.

[0050] Embodiment 2:

[0051] See also Figure 1 As shown, this embodiment is a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid, comprising the following steps:

[0052] Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles. The specific process is as follows:

[0053] The temperature is controlled at 25°C, and the pressure is controlled below 1atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultra-fine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5μm. The fluorine-containing waste acid is blown off, so that the hydrofluoric acid with a low boiling point is blown off with the ultra-fine bubbles floating in the fluorine-containing waste acid, forming hydrogen fluoride gas escaping the waste acid;

[0054] Step 2: A portion of the blown-off gas is subjected to low-temperature water spraying treatment to obtain aqueous hydrofluoric acid. The specific process is as follows:

[0055] The temperature of the spray water in the spray tower system is controlled to be less than 15°C. The spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

[0056] Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride. The specific process is as follows:

[0057] The temperature of the gas transmission pipeline is controlled at 30°C, the water vapor condenses and refluxes, and the water vapor condenses to achieve the function of removing a large amount of water vapor, and the hydrogen fluoride gas is output to the back end;

[0058] Then, the hydrogen fluoride gas is passed through an adsorption dehydrating agent for adsorption dehydration, wherein the adsorption dehydrating agent is anhydrous sodium sulfate, to obtain anhydrous hydrogen fluoride gas;

[0059] Then the temperature is controlled at -5°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride;

[0060] Step 4: The residual liquid left after the ultrafine bubbles are blown off is subjected to reaction treatment to recover the acid and fluorosilicate. The specific process is as follows:

[0061] Add 25 g of precipitated silica with a particle size of 6 μm to every 1 kg of residual liquid, control the reaction temperature to 65°C, stir the reaction for 1 hour, then vacuum filter, add 125 g of sulfate to the filtrate, the sulfate is sodium sulfate, continue stirring the reaction for 1 hour, then vacuum filter, collect the filtrate to obtain acid solution, the acid solution is sulfuric acid, wash the filter cake with clean water and then dry it, control the reaction temperature to 115°C and dry it for 2 hours to obtain fluorosilicate, the fluorosilicate is sodium fluorosilicate.

[0062] Embodiment 3:

[0063] See also Figure 1 As shown, this embodiment is a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid, comprising the following steps:

[0064] Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles. The specific process is as follows:

[0065] The temperature is controlled at 20°C, and the pressure is controlled below 1atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultra-fine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5μm. The fluorine-containing waste acid is blown off, so that the hydrofluoric acid with a low boiling point is blown off with the ultra-fine bubbles floating in the fluorine-containing waste acid, forming hydrogen fluoride gas escaping the waste acid;

[0066] Step 2: A portion of the blown-off gas is subjected to low-temperature water spraying treatment to obtain aqueous hydrofluoric acid. The specific process is as follows:

[0067] The temperature of the spray water in the spray tower system is controlled to be less than 15°C. The spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

[0068] Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride. The specific process is as follows:

[0069] The temperature of the gas delivery pipeline is controlled at 25°C, the water vapor condenses and refluxes, and the water vapor condenses to achieve the function of removing a large amount of water vapor, and the hydrogen fluoride gas is output to the back end;

[0070] Then, the hydrogen fluoride gas is passed through an adsorption dehydrating agent for adsorption dehydration, wherein the adsorption dehydrating agent is anhydrous sodium sulfate, to obtain anhydrous hydrogen fluoride gas;

[0071] Then the temperature is controlled at -20°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride;

[0072] Step 4: The residual liquid left after the ultrafine bubbles are blown off is subjected to reaction treatment to recover the acid and fluorosilicate. The specific process is as follows:

[0073] Add 30 g of precipitated silica with a particle size of 2 μm to every 1 kg of residual liquid, control the reaction temperature to 75°C, stir the reaction for 1.5 hours, then vacuum filter, add 150 g of sulfate to the filtrate, the sulfate is sodium sulfate, continue stirring the reaction for 1.5 hours, then vacuum filter, collect the filtrate to obtain acid solution, the acid solution is sulfuric acid, wash the filter cake with clean water and then dry it, control the reaction temperature to 120°C and dry it for 2.5 hours to obtain fluorosilicate, the fluorosilicate is sodium fluorosilicate.

[0074] Embodiment 4:

[0075] See also Figure 1 As shown, this embodiment is a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid, comprising the following steps:

[0076] Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles. The specific process is as follows:

[0077] The temperature is controlled at 30°C, and the pressure is controlled below 1atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultra-fine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5μm. The fluorine-containing waste acid is blown off, so that the hydrofluoric acid with a low boiling point is blown off with the ultra-fine bubbles floating in the fluorine-containing waste acid, forming hydrogen fluoride gas escaping the waste acid;

[0078] Step 2: A portion of the blown-off gas is subjected to low-temperature water spraying treatment to obtain aqueous hydrofluoric acid. The specific process is as follows:

[0079] The temperature of the spray water in the spray tower system is controlled to be less than 15°C. The spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

[0080] Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride. The specific process is as follows:

[0081] The temperature of the gas delivery pipeline is controlled at 35°C, the water vapor condenses and refluxes, and the water vapor condenses to achieve the function of removing a large amount of water vapor, and the hydrogen fluoride gas is output to the back end;

[0082] Then, the hydrogen fluoride gas is passed through an adsorption dehydrating agent for adsorption dehydration, wherein the adsorption dehydrating agent is anhydrous magnesium sulfate, to obtain anhydrous hydrogen fluoride gas;

[0083] Then, the temperature is controlled at 10°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride;

[0084] Step 4: The residual liquid left after the ultrafine bubbles are blown off is subjected to reaction treatment to recover the acid and fluorosilicate. The specific process is as follows:

[0085] Add 20 g of precipitated silica with a particle size of 10 μm to every 1 kg of residual liquid, control the reaction temperature to 55°C, stir the reaction for 0.5 h, then vacuum filter, add 100 g of hydrochloride to the filtrate, the hydrochloride is potassium chloride, continue stirring the reaction for 0.5 h, then vacuum filter, collect the filtrate to obtain acid solution, the acid solution is hydrochloric acid, wash the filter cake with clean water and then dry it, control the reaction temperature to 110°C and dry it for 2 h to obtain fluorosilicate, the fluorosilicate is potassium fluorosilicate.

[0086] Embodiment 5:

[0087] See also Figure 1 As shown, this embodiment is a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid, comprising the following steps:

[0088] Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles. The specific process is as follows:

[0089] The temperature is controlled at 25°C, and the pressure is controlled below 1atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultra-fine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5μm. The fluorine-containing waste acid is blown off, so that the hydrofluoric acid with a low boiling point is blown off with the ultra-fine bubbles floating in the fluorine-containing waste acid, forming hydrogen fluoride gas escaping the waste acid;

[0090] Step 2: A portion of the blown-off gas is subjected to low-temperature water spraying treatment to obtain aqueous hydrofluoric acid. The specific process is as follows:

[0091] The temperature of the spray water in the spray tower system is controlled to be less than 15°C. The spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

[0092] Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride. The specific process is as follows:

[0093] The temperature of the gas transmission pipeline is controlled at 30°C, the water vapor condenses and refluxes, and the water vapor condenses to achieve the function of removing a large amount of water vapor, and the hydrogen fluoride gas is output to the back end;

[0094] Then, the hydrogen fluoride gas is passed through an adsorption dehydrating agent for adsorption dehydration, wherein the adsorption dehydrating agent is anhydrous magnesium sulfate, to obtain anhydrous hydrogen fluoride gas;

[0095] Then the temperature is controlled at -5°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride;

[0096] Step 4: The residual liquid left after the ultrafine bubbles are blown off is subjected to reaction treatment to recover the acid and fluorosilicate. The specific process is as follows:

[0097] Add 25 g of precipitated silica with a particle size of 6 μm to every 1 kg of residual liquid, control the reaction temperature to 65°C, stir the reaction for 1 hour, then vacuum filter, add 125 g of hydrochloride to the filtrate, the hydrochloride is potassium chloride, continue stirring the reaction for 1 hour, then vacuum filter, collect the filtrate to obtain acid solution, the acid solution is hydrochloric acid, wash the filter cake with clean water and then dry it, control the reaction temperature to 115°C and dry it for 2 hours to obtain fluorosilicate, the fluorosilicate is potassium fluorosilicate.

[0098] Embodiment 6:

[0099] See also Figure 1 As shown, this embodiment is a method for comprehensive utilization of fluorine-containing waste acid to recover hydrofluoric acid, comprising the following steps:

[0100] Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles. The specific process is as follows:

[0101] The temperature is controlled at 20°C, and the pressure is controlled below 1atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultra-fine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5μm. The fluorine-containing waste acid is blown off, so that the hydrofluoric acid with a low boiling point is blown off with the ultra-fine bubbles floating in the fluorine-containing waste acid, forming hydrogen fluoride gas escaping the waste acid;

[0102] Step 2: A portion of the blown-off gas is subjected to low-temperature water spraying treatment to obtain aqueous hydrofluoric acid. The specific process is as follows:

[0103] The temperature of the spray water in the spray tower system is controlled to be less than 15°C. The spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

[0104] Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride. The specific process is as follows:

[0105] The temperature of the gas delivery pipeline is controlled at 25°C, the water vapor condenses and refluxes, and the water vapor condenses to achieve the function of removing a large amount of water vapor, and the hydrogen fluoride gas is output to the back end;

[0106] Then, the hydrogen fluoride gas is passed through an adsorption dehydrating agent for adsorption dehydration, wherein the adsorption dehydrating agent is anhydrous magnesium sulfate, to obtain anhydrous hydrogen fluoride gas;

[0107] Then the temperature is controlled at -20°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride;

[0108] Step 4: The residual liquid left after the ultrafine bubbles are blown off is subjected to reaction treatment to recover the acid and fluorosilicate. The specific process is as follows:

[0109] Add 30g of precipitated silica with a particle size of 2μm to every 1kg of residual liquid, control the reaction temperature to 75°C, stir the reaction for 1.5h, then vacuum filter, add 150g of hydrochloride to the filtrate, the hydrochloride is potassium chloride, continue stirring the reaction for 1.5h, then vacuum filter, collect the filtrate to obtain acid solution, the acid solution is hydrochloric acid, wash the filter cake with clean water and then dry it, control the reaction temperature to 120°C and dry it for 2.5h to obtain fluorosilicate, the fluorosilicate is potassium fluorosilicate.

[0110] The fluorine-containing waste acid in Examples 1-6 was tested, and the test results are shown in the following table:

[0111] Appearance Acidity (HCl meter) m(HF),% <![CDATA[m(H2SiF6),%]]> <![CDATA[m(SO4 2- ),%]]> <![CDATA[m(Cl - ),%]]> Colorless and transparent 18.82 5.01 9.43 4.48 0.11

[0112] The methods of Examples 1-6 were evaluated, and the evaluation results are shown in the following table:

[0113]

[0114] Referring to the data in the above table, it can be known that the method of the present invention can fully remove fluorine in fluorine-containing wastewater and convert it into usable hydrofluoric acid and fluorosilicate, and recycle the acid, thereby reducing wastewater costs and creating economic benefits, and is suitable for promotion.

[0115] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0116] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid, characterized in that: The following steps are involved: Step 1: Blow off the fluorine-containing waste acid with ultra-fine bubbles; The specific process of the ultrafine bubble stripping is as follows: The temperature is controlled at 20-30°C, and the pressure is controlled below 1 atm by using a vacuum pump to reduce the pressure. The air is dispersed in the fluorine-containing waste acid through the ultra-fine bubble equipment to form a large number of air bubbles with a particle size of less than 0.5 μm. The fluorine-containing waste acid is blown off, so that the hydrofluoric acid with a low boiling point is blown off along with the ultra-fine bubbles floating in the fluorine-containing waste acid, forming hydrogen fluoride gas escaping the waste acid; Step 2: spraying part of the blown-off gas with low-temperature water to obtain aqueous hydrofluoric acid; Step 3: The other part of the gas blown out is temperature-controlled to remove water vapor, and then chemically dehydrated and condensed to obtain industrial anhydrous hydrogen fluoride; Step 4: Residual liquid remaining after the ultrafine bubbles are blown off is subjected to reaction treatment to recover acid and fluorosilicate; The specific process of the reaction treatment is as follows: Add precipitated silica to the residual liquid, control the reaction temperature to 55-75°C, stir the reaction for 0.5-1.5h, then vacuum filter, add sulfate or hydrochloride to the filtrate, continue stirring the reaction for 0.5-1.5h, then vacuum filter, collect the filtrate to obtain acid solution, wash the filter cake with clean water and then dry it, control the reaction temperature to 110-120°C and dry it for 2-2.5h to obtain fluorosilicate.

2. The method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid according to claim 1, characterized in that: The fluorine-containing waste acid in step one comes from the waste acid produced by using hydrofluoric acid in the production process of the semiconductor, panel and photovoltaic industries.

3. The method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid according to claim 1, characterized in that: The specific process of the low-temperature water spraying treatment in step 2 is as follows: The water temperature of the spray water in the spray tower system is controlled to be less than 15°C, and the spray water absorbs the hydrofluoric acid in the gas to form aqueous hydrofluoric acid.

4. The method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid according to claim 1, characterized in that: The specific process of temperature control and water vapor removal in step 3 is as follows: The temperature of the gas delivery pipeline is controlled at 25-35°C, the water vapor condenses and refluxes, and the hydrogen fluoride gas is output to the rear end.

5. The method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid according to claim 1, characterized in that: The specific process of the chemical dehydration in step 3 is as follows: Passing hydrogen fluoride gas through an adsorption dehydrating agent for adsorption dehydration to obtain anhydrous hydrogen fluoride gas; The adsorption dehydrating agent is one of anhydrous sodium sulfate and anhydrous magnesium sulfate.

6. The method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid according to claim 1, characterized in that: The specific process of the condensation in step 3 is as follows: The temperature is controlled at -20 to 10°C to condense the anhydrous hydrogen fluoride gas to form industrial anhydrous hydrogen fluoride.

7. The method for recovering hydrofluoric acid by comprehensive utilization of fluorine-containing waste acid according to claim 1, characterized in that: The amount of precipitated silica added is 20-30 g of precipitated silica per 1 kg of residual liquid; The particle size of the precipitated silica is 2-10 μm; The amount of sulfate or hydrochloride added is 100-150 g of sulfate or hydrochloride per 1 kg of residual liquid; The sulfate is sodium sulfate, and the hydrochloride is potassium chloride; The acid solution is sulfuric acid or hydrochloric acid; The fluorosilicate is sodium fluorosilicate or potassium fluorosilicate.

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