阅读说明：本技术 一种含氟浓硫酸分离回收的方法 (Method for separating and recovering fluorine-containing concentrated sulfuric acid ) 是由 何睿鸣 张月娥 彭丽华 于 2021-10-26 设计创作，主要内容包括：本发明公开了一种含氟浓硫酸分离回收的方法,包括将用脱盐水两级循环、HF分离、HF吸收、HF尾气吸收等四个部分,该方法将含氟浓硫酸中的HF分离,并分离回收满足生产要求的氢氟酸产品以及获得纯度满足要求的稀硫酸产品,实现了含氟废浓硫酸的综合资源再生与利用。(The invention discloses a method for separating and recycling fluorine-containing concentrated sulfuric acid, which comprises four parts of desalted water two-stage circulation, HF separation, HF absorption, HF tail gas absorption and the like.)

1. A method for separating and recovering concentrated sulfuric acid containing fluorine comprises two-stage circulating dilution of concentrated sulfuric acid by desalted water, HF separation, HF absorption and HF tail gas absorption, separation of hydrofluoric acid from sulfuric acid, and recovery of hydrofluoric acid and dilute sulfuric acid products.

2. The method of claim 1, comprising the steps of,

1) pumping desalted water into a primary circulating tank V1 at about 30% of liquid level, circulating through a primary circulating pump P1, slowly introducing fluorine-containing concentrated sulfuric acid into the primary circulating tank V1 to be mixed and circulated with the desalted water, overflowing the circulating liquid to a secondary circulating tank V2 pre-injected with 30% of desalted water, and continuously circulating through a secondary circulating pump P2, wherein the temperature of the circulating tank V1 and the temperature of the circulating tank V2 are 70-140 ℃, and the pressure is 5 kpa;

2) HF circularly separated from the circulating tanks V1 and V2 is sent to a first-stage absorption tower T2;

3) pumping the liquid part in the secondary circulating tank V2 into the top of a separation tower T1, introducing low-pressure steam into the bottom of the separation tower T1, separating HF in the liquid out of the top of the separation tower in a gas mode, and extracting dilute sulfuric acid in the bottom of the separation tower T1, wherein the pressure of the separation tower T1 is 0.3mPa, and the temperature is 70-140 ℃;

4) sending the HF gas separated from the top of the separation tower T1 into a primary absorption tower T2, absorbing the HF gas by adopting desalted water as absorption liquid, and extracting a hydrofluoric acid product from a tower kettle of the primary absorption tower T2;

5) delivering the gas separated from the top of the first-stage absorption tower T2 into a second-stage absorption tower T3, absorbing HF gas by using desalted water as absorption liquid, and pumping hydrofluoric acid solution in the tower kettle of the second-stage absorption tower T3 into the first-stage absorption tower T2;

6) and (3) delivering the gas separated from the tower top of the secondary absorption tower T3 into a tertiary absorption tower T4, and taking KOH solution as absorption liquid to ensure that the tail gas reaches the standard and is discharged.

3. The method as claimed in claim 2, step 6), KF waste liquid in tower bottom of the three-stage absorption tower T4 is extracted from bottom, one part is pumped into the three-stage absorption tower T4, and the other part is discharged.

4. The process as claimed in claim 2, wherein a reboiler E2 is provided in the bottom of the separation column T1 as a supplementary heat source, and the reboiler adopts low-pressure saturated steam of 0.5mpa as a heat source.

5. The process of claim 4, wherein the reboiler E2 is in the form of a thermosiphon.

6. The method of claim 2, wherein the hydrofluoric acid product produced by the first-stage absorption tower T2 has a hydrofluoric acid purity of 58-60%.

7. The method of claim 2, wherein the absorption liquid used in the three-stage absorption tower T4 is 10% KOH solution.

8. The method of claim 2, wherein the weight ratio of desalted water to fluorine-containing concentrated sulfuric acid in the primary circulation V1 in the step 1) is controlled to be 1 (3.0-3.5).

9. The method of claim 2, wherein the temperature of the circulation tank V1 and the circulation tank V2 in the step 1) is 120-140 ℃.

Technical Field

The invention belongs to the field of fine chemistry and chemical engineering, in particular to a method for separating and recovering fluorine-containing concentrated sulfuric acid, and particularly relates to a continuous production process and a method for regenerating and utilizing fluorine-containing concentrated sulfuric acid comprehensive resources.

Background

With the development of fluorine chemical industry in recent years, hydrofluoric acid is widely applied to lithium battery industry, electronic industry, photovoltaic industry and traditional fluorine chemical downstream industry, and when the hydrofluoric acid is used in a HF gas mode, HF gas purification is inevitably involved, concentrated sulfuric acid is mostly adopted for purification, so that waste acid containing fluorine concentrated sulfuric acid is inevitably generated, and the amount of the generated waste acid containing fluorine concentrated sulfuric acid is also increased sharply along with the popularization of the fluorine chemical application field and the expansion of market yield.

The existing fluorine-containing waste acid recovery technology is few, the recovery technology is still incomplete, and the recovery technology mainly comprises the technologies of evaporation concentration, pyrolysis, reaction preparation of byproducts and the like, but most of the methods are in a test or technical research and development state, the implementation process is difficult, and the defects of incomplete HF recovery, abnormal use of byproducts, high production energy consumption, kettle type reaction and the like exist.

CN112047303A discloses a recovery processing method of mixed waste acid containing fluorine and nitric acid, which adopts concentrated sulfuric acid to dilute and heat the mixed acid, so that the mixed acid escapes from a waste acid system in a gas mode to obtain a mixed acid product, and simultaneously adopts heat conducting oil as a heat source to concentrate the waste sulfuric acid for recycling. The method does not separate the mixed acid, cannot be used in a large area as a single product, and meanwhile, the waste sulfuric acid is concentrated by adopting the heat conduction oil, so that the energy consumption is high, the requirement on equipment materials is high, and the production risk is high.

CN110155956A discloses a fluoride-containing waste acid treatment device and a treatment method thereof, wherein HF is obtained by adopting a high-temperature cracking mode, and the fluoride-containing waste acid is treated in a sodium fluosilicate product mode through water glass absorption. The method adopts a high-temperature cracking furnace, the operating temperature is up to 1050 ℃, HF in waste acid is mixed with water to greatly damage the fire material and the furnace body material in the high-temperature cracking furnace, and the actual production has great difficulty; meanwhile, a large amount of fluorine-containing waste residues are generated by the high-temperature cracking furnace, further treatment cost is also increased, and the method does not thoroughly treat the fluorine-containing waste acid.

CN110590013A discloses a method and a system for treating fluorine-containing waste sulfuric acid, wherein the method adopts a four-stage chemical reaction mode and an electrochemical separation mode to prepare the fluorine-containing waste sulfuric acid into different components of derivative chemicals, thereby realizing the treatment of the fluorine-containing waste sulfuric acid. The method has complicated flow, the grading chemical reaction can not be thoroughly divided, and the actual control difficulty is higher; meanwhile, the products are separated by adopting electrochemistry with great energy consumption, and a single pure product is difficult to obtain.

CN1180043A discloses a process for extracting hydrofluoric acid from sulfuric acid containing fluorine, wherein the equipment used in the process consists of a distillation tower kettle, a reflux condenser, a pipeline and an absorption tower. The specific production process is as follows: the fluorine-containing sulfuric acid introduced into the distillation tower kettle is heated to evaporate, and the evaporated hydrogen fluoride gas is introduced into the absorption tower and absorbed by pure water in the tower to become hydrofluoric acid. The method can separate fluorine from sulfuric acid in the fluorine-containing sulfuric acid, so that fluorine resources are fully utilized, and the pollution of fluorine to the environment is eliminated. However, the method disclosed by the patent adopts intermittent operation, so that the intermittent time of batch preparation is inevitable and the efficiency is low. The hydrofluoric acid recovery rate is low, the concentration is 55%, the heat energy and the energy consumption of distillation are provided in the form of a heat exchanger, the separated HF is absorbed in a bubbling mode and is intermittently operated, the efficiency is low, and the tail gas is difficult to ensure to reach the environmental protection standard.

Through comparative analysis and actual production experience, the following problems are found in the prior art:

1. HF is not completely recovered, byproducts cannot be used normally, and tail gas emission reaches the standard difficultly;

2. the recovery process of the waste acid containing fluorine does not completely generate new pollution sources such as secondary fluorine-containing waste residue and the like;

3. high treatment cost, high energy consumption, and high requirements on equipment material and type selection.

Disclosure of Invention

The invention aims to provide a method for separating and recovering fluorine-containing concentrated sulfuric acid, which can continuously separate HF in the fluorine-containing concentrated sulfuric acid and recover and obtain a hydrofluoric acid product and a dilute sulfuric acid product meeting the production purity requirement. The method realizes the regeneration and utilization of fluorine-containing concentrated sulfuric acid comprehensive resources. Not only solves the problem of difficult treatment of fluorine-containing concentrated sulfuric acid, but also respectively obtains hydrofluoric acid products and dilute sulfuric acid products which can meet the requirement of production purity, thereby really realizing changing waste into valuable.

The invention relates to a method for separating and recovering fluorine-containing concentrated sulfuric acid, which comprises the steps of using desalted water for two-stage circulating dilution of concentrated sulfuric acid, HF separation, HF absorption and HF tail gas absorption, separating hydrofluoric acid from sulfuric acid, and recovering hydrofluoric acid and dilute sulfuric acid products.

The method of the present invention specifically comprises the following steps,

1) pumping desalted water into a primary circulating tank V1 at about 30% of liquid level, circulating through a primary circulating pump P1, slowly introducing fluorine-containing concentrated sulfuric acid into the primary circulating tank V1 to be mixed and circulated with the desalted water, overflowing the circulating liquid to a secondary circulating tank V2 pre-injected with 30% of desalted water, and continuously circulating through a secondary circulating pump P2, wherein the temperature of the circulating tank V1 and the temperature of the circulating tank V2 are 70-140 ℃, preferably 120-140 ℃, and the pressure is 5 kpa;

2) HF circularly separated from the circulating tanks V1 and V2 is sent to an absorption tower T2;

3) pumping the liquid part in the secondary circulating tank V2 into the top of a separation tower T1, introducing low-pressure steam into the bottom of the separation tower T1, separating HF in the liquid out of the top of the separation tower in a gas mode, and extracting dilute sulfuric acid in the kettle of the separation tower T1, wherein the pressure of the separation tower T1 is 0.3mPa, the temperature is 70-140 ℃, and the preferable temperature is 120-140 ℃;

4) sending the HF gas separated from the top of the separation tower T1 into a primary absorption tower T2, absorbing the HF gas by adopting desalted water as absorption liquid, and extracting a hydrofluoric acid product from a tower kettle of the primary absorption tower T2;

5) delivering the gas separated from the top of the first-stage absorption tower T2 into a second-stage absorption tower T3, absorbing HF gas by using desalted water as absorption liquid, and pumping hydrofluoric acid solution in the tower kettle of the second-stage absorption tower T3 into the first-stage absorption tower T2;

6) and (3) delivering the gas separated from the tower top of the secondary absorption tower T3 into a tertiary absorption tower T4, and taking KOH solution as absorption liquid to ensure that the tail gas reaches the standard and is discharged.

In the method of the invention, in the step 6), the KF waste liquid in the tower bottom of the three-stage absorption tower T4 is extracted from the bottom, one part of the KF waste liquid is pumped into the three-stage absorption tower T4, and the other part of the KF waste liquid is discharged.

In the method of the invention, a reboiler E2 is arranged at the bottom of the separation tower T1 to serve as a supplementary heat source, the reboiler adopts low-pressure saturated steam of 0.5mpa to serve as a heat source, and the reboiler E2 adopts a thermosiphon mode.

In the method, the hydrofluoric acid product extracted from the first-stage absorption tower T2 has the hydrofluoric acid concentration of 60%.

In the method of the present invention, the absorption liquid used in the third absorption tower T4 is a 10% KOH solution.

In the method of the invention, the weight ratio of the desalted water to the fluorine-containing concentrated sulfuric acid in the first-stage circulation V1 in the step 1) is controlled to be 1: (3.0-3.5).

In a specific embodiment, the method for separating and recovering the fluorine-containing concentrated sulfuric acid comprises the following steps,

1) firstly, 30% of desalted water is injected into a secondary circulating tank V2, a secondary circulating pump P2 is started for circulation, meanwhile, part of desalted water is pumped into a primary circulating tank V1 to 30% of liquid level, and a primary circulating pump P1 is started for circulation;

2) controlling fluorine-containing concentrated sulfuric acid by a flow meter and an adjusting valve, slowly connecting the fluorine-containing concentrated sulfuric acid into a primary circulating tank V1, overflowing the fluorine-containing concentrated sulfuric acid into a secondary circulating tank V2 for continuous circulation after the liquid level reaches the height, wherein the temperature of a circulating tank V1 and the temperature of a circulating tank V2 are 70-140 ℃ (preferably 120-140 ℃), the pressure is 5kpa, and HF generated in the circulating process of the circulating tank V1 and the circulating tank V2 is separated out of the top of the circulating tank in a gas mode;

3) pumping part of the circulating liquid in the secondary circulating tank V2 into the top of a separation tower T1 through a secondary circulating pump P2, pumping part of the circulating liquid into a secondary circulating tank V2 for continuous circulation, introducing low-pressure steam into the bottom of the separation tower T1, separating HF in the circulating liquid (waste acid) out of the top of the separation tower in a gas mode by using the direct heat of the steam, and arranging a siphon reboiler E2 at the tower kettle of the separation tower T1 to supplement the heat source for separation, wherein the pressure of the separation tower T1 is 0.3mPa, the temperature is 70-140 ℃, and the preferable temperature is 120-140 ℃;

4) extracting dilute sulfuric acid in a tower kettle of a separation tower T1, and cooling by a cooler to obtain a dilute sulfuric acid product;

5) conveying the HF gas separated from the top of the towers in the steps 2 and 3 into a primary absorption tower T2 through a pipeline for absorption, conveying the unabsorbed gas into a secondary absorption tower T3 for absorption, and taking absorption liquid as desalted water;

6) one part of the absorption liquid of the secondary absorption tower T3 for absorbing HF is pumped into the primary absorption tower T2, the other part of the absorption liquid is pumped into the secondary absorption tower T3 for continuous absorption, and a hydrofluoric acid product is extracted from a tower kettle of the primary absorption tower T2;

7) and the tail gas which is not absorbed by the second-stage absorption tower T3 is sent into a third-stage absorption tower T4 for absorption, the absorption liquid is KOH solution, the tail gas is ensured to be discharged after reaching the standard, and the absorption liquid is discharged by KF waste liquid.

In the above embodiments, the first-stage recycle tank V1 and the second-stage recycle tank V2 of the method of the present invention fully utilize the dilution heat of sulfuric acid to remove HF from waste concentrated sulfuric acid (or waste acid).

In the above embodiment, most of the HF in the spent acid is separated in the separation column T1.

In the above embodiment, the separation column T1 used 0.3mpa saturated low pressure steam as a direct heat source, with a thermosiphon reboiler E2 in the column bottom to supplement the heat source.

In the above embodiment, the apparatus and the pipeline in contact with the concentrated sulfuric acid containing fluorine and the hydrofluoric acid according to the method of the present invention employ PTFE lining in the lower temperature part and PFA lining in the higher temperature part.

According to the method, the concentration of the separated and recovered dilute sulfuric acid product is 56-60%, and the concentration of the recovered hydrofluoric acid product is 58-60%.

The method of the invention has the advantages of

The method for separating and recovering the fluorine-containing concentrated sulfuric acid realizes the regeneration and utilization of comprehensive resources by separating and recovering sulfuric acid and hydrofluoric acid through a continuous production process. The invention has the advantages that:

1. the method can obtain a dilute sulfuric acid product with the purity of 56-60%, and can meet the requirements of production users;

2. the hydrofluoric acid product with the purity of 58-60% can be obtained by the method, and the requirements of production users can be met;

3. the method adopts a continuous separation technology, and the equipment utilization rate is greatly improved compared with the traditional technology;

4. the method of the invention utilizes the fluorine-containing concentrated sulfuric acid as a resource, not only solves the problem of difficult treatment of the fluorine-containing concentrated sulfuric acid, but also is respectively worth of hydrofluoric acid products and dilute sulfuric acid products meeting the production purity requirements, thereby really realizing the purpose of changing waste into valuable.

In conclusion, the method of the invention adopts continuous operation and has higher efficiency. The hydrofluoric acid recovery rate is high, and the absorption limit value can reach 60%. The invention fully utilizes the dilution heat of the sulfuric acid as a heat source for distillation, adopts a small amount of steam to be directly introduced into the material for supplement, and can save the whole heat energy by 80-85 percent on the basis of the previous patent. The invention adopts two-stage circulating absorption and one-stage tail gas alkali absorption, both are continuously operated, the absorption efficiency is high, and simultaneously the tail gas is ensured to reach the standard (environmental protection) and be discharged.

Drawings

FIG. 1 is a schematic process flow diagram of the process of the present invention.

Detailed Description

The invention is further described below with reference to examples: but are representative. To aid in understanding the spirit of the invention and not to limit the scope of the invention in any way.

The reaction process flow employed in the method of the following example is shown in FIG. 1, in which V1 represents a primary circulation tank, V2 represents a secondary circulation tank, P1 represents a primary circulation pump, P2 represents a secondary circulation pump, P3 represents a sulfuric acid pump, P4 represents a primary absorption pump, P5 represents a secondary absorption pump, P6 represents a tertiary absorption pump, T1 represents a separation column, T2 represents a primary absorption column, T3 represents a secondary absorption column, T4 represents a tertiary absorption column, E1 represents a sulfuric acid cooler, and E2 represents a reboiler.

Example 1 separation of concentrated sulfuric acid containing fluorine and recovery of sulfuric acid and hydrofluoric acid

Referring to fig. 1, the process flow comprises the following specific steps:

1) firstly, 30% of desalted water is injected into a secondary circulating tank V2, a secondary circulating pump P2 is started for circulation, meanwhile, part of desalted water is pumped into a primary circulating tank V1 to 30% of liquid level, and a primary circulating pump P1 is started for circulation;

2) fluorine-containing concentrated sulfuric acid is controlled by a flow meter and a regulating valve, and is slowly connected into a primary circulating tank V1, the fluorine-containing concentrated sulfuric acid is circulated by a circulating pump, the fluorine-containing concentrated sulfuric acid overflows to a secondary circulating tank V2 to continue circulation after the liquid level of circulating liquid reaches a certain height, the temperature of the circulating process is controlled to be 120-140 ℃, the pressure is 5kpa, HF generated in the circulating process of the circulating tank V1 and the circulating tank V2 is separated from the top of the circulating tank in a gas mode, and the HF is sent to a primary absorption tower to be absorbed by desalted water, wherein the desalted water: the weight ratio of the fluorine-containing concentrated sulfuric acid (waste liquid) is 1: 3-3.5.

3) Pumping part of circulating liquid in a circulating tank V2 into a circulating tank V2 by a secondary circulating pump P2 connected by a secondary circulating tank V2 for continuous circulation, and pumping part of the circulating liquid into a separating tower T1 from the top of the separating tower T1, meanwhile, introducing low-pressure steam into the bottom of the separating tower T1, separating HF in circulating liquid waste acid out of the top of the tower in a gas mode by utilizing direct heat of the steam, and arranging a siphon reboiler E2 at the tower bottom of the separating tower T1 for supplement as a separating heat source; meanwhile, a dilute sulfuric acid product pump is arranged at the bottom of the separation tower T1, a dilute sulfuric acid product is extracted through the pump, and is cooled by a cooler and then recovered to obtain a dilute sulfuric acid product with the purity of 56-60%, the pressure of the separation tower T1 is 0.3mPa, and the temperature of the separation tower T1 is controlled at 120-140 ℃.

4) And (3) conveying the HF gas separated from the circulating tower and the separating tower in the steps 2 and 3 into a first-stage absorption tower T2 through a pipeline, absorbing by using desalted water as absorption liquid, conveying the unabsorbed HF gas to a second-stage absorption tower T3 through a pipeline, absorbing by using desalted water as absorption liquid, conveying the unabsorbed tail gas to a third-stage absorption tower T4 through a pipeline, and absorbing by using 10% KOH solution to ensure that the tail gas reaches the standard and is discharged. Wherein the pressure of the absorption towers T2, T3 and T4 is 5kPa, and the temperature is controlled to be 50-70 ℃.

5) Pumping part of absorption liquid of the second-stage absorption tower T3 for absorbing HF into an absorption tower T3 for continuous absorption, pumping part of absorption liquid into a first-stage absorption tower T2, pumping out hydrofluoric acid in the tower kettle of the absorption tower T2, and recovering to obtain a hydrofluoric acid product meeting the production requirement, wherein the purity of the hydrofluoric acid product is 58-60%.

The above examples are representative only, and any simple modifications and variations made within the spirit of the present invention are within the scope of the present invention.