Waste acid recovery equipment and technological process

Abstract

The waste acid recovery equipment comprises a first rectifying tower, a second rectifying tower and a waste acid raw material tank, the first rectifying tower is in pipeline connection with the second rectifying tower and the waste acid raw material tank, and the first rectifying tower is connected with a first condenser and three first reboilers; the first condenser is connected with a first water segregator, the first water segregator is connected with a vacuum buffer tank and a second condenser, and the second condenser is connected with a waste liquid tank; the invention relates to the technical field of waste acid treatment, two rectifying towers are adopted to treat original acid liquor and rectified condensate respectively, nitric acid distilled out of the first rectifying tower flows back into the second rectifying tower through a first condenser and a first water segregator to continue to be heated and distilled, and after the nitric acid is distilled through the two independent rectifying towers, the nitric acid is recycled. Nitric acid and waste liquid (including fluosilicic acid, hydrofluoric acid, water and low-concentration waste acid) evaporated from the first section can be effectively and separately treated, and the nitric acid can be recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of waste acid treatment, and in particular to waste acid recovery equipment and a process flow. Background Art

[0002] The steel and metal products industries require the removal of iron oxide scale from steel surfaces during production, using hydrochloric acid for pickling. This process generates a significant amount of waste acid. Waste acid recovery is the recycling of this large amount of acidic waste liquid generated during industrial production. This not only avoids resource waste, environmental pollution, and threats to human health, but also generates economic and social benefits. Currently, two main methods are used to treat waste acid: acid-base neutralization and hydrochloric acid regeneration. During waste acid treatment, a separate distillation tower is typically used to distill the waste acid from a waste acid feed tank. The distilled nitric acid passes through a condenser, where a portion of the liquid flows back into the distillation tower for further distillation, while the remaining portion is recovered through a receiving tank into an acid recovery tank. This method is simple, practical, and effective in distilling the waste acid. However, in practice, the condensed liquid from the condenser, when it flows back into the original distillation tower, affects the temperature within the tower. Furthermore, the reflux liquid from the distillation tower mixes with the existing acid in the tower, affecting the distillation efficiency. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the present invention provides a waste acid recovery device and process flow, which solves the problem that the condensed reflux liquid in the existing waste acid treatment process using a separate distillation tower will affect the distillation effect of the original acid liquid in the distillation tower.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions: a waste acid recovery equipment and process flow, comprising a No. 1 distillation tower, a No. 2 distillation tower, and a waste acid raw material tank, wherein the No. 1 distillation tower is connected to the No. 2 distillation tower and the waste acid raw material tank through a pipeline, the No. 1 distillation tower is connected to a No. 1 condenser and three first reboilers, the No. 1 condenser is connected to a No. 1 water separator, the No. 1 water separator is connected to a vacuum buffer tank and a No. 2 condenser, and the No. 2 condenser is connected to a waste liquid tank;

[0005] The No. 2 distillation tower is connected to the No. 3 condenser and three second reboilers, the No. 3 condenser is connected to the No. 2 water separator, the No. 2 water separator is connected to the No. 4 condenser and is connected to the vacuum buffer tank, the No. 4 condenser is connected to the front fraction receiving tank and the rear fraction receiving tank, and the rear fraction receiving tank is connected to the recovery acid tank.

[0006] Preferably, the No. 1 water separator and the No. 2 water separator are both provided with bypass pipes, a pair of the bypass pipes are respectively connected to the No. 1 distillation tower and the No. 2 distillation tower, and a circulation pump is provided on the pair of bypass pipes.

[0007] Preferably, the front fraction receiving tank is connected to the No. 1 distillation tower pipeline, the liquid outlet end of the waste liquid tank is connected to a pump body, and the pump body is connected to a liquid outlet pipeline.

[0008] Preferably, the upper ends of the recovery acid tank and the waste acid raw material tank are both connected to an exhaust main pipe, one side of the recovery acid tank is connected to a recovery acid pump, and one side of the recovery acid pump is connected to an automatic filling machine.

[0009] Preferably, the waste acid recovery process comprises:

[0010] S1: First, the raw materials in the waste acid raw material tank are added to the No. 1 distillation tower, and the first reboiler and the second reboiler are started at the same time to heat the No. 1 distillation tower and the No. 2 distillation tower to a temperature of about 65°C;

[0011] S2: When the temperature in the No. 1 distillation tower reaches 65°C, the first stage of water will be evaporated, which contains fluorosilicic acid, hydrofluoric acid, water and low-concentration waste acid, and is finally discharged into the waste liquid tank through the No. 1 condenser, the No. 1 water separator and the No. 2 condenser;

[0012] S3: Nitric acid will be evaporated during the distillation process of the No. 1 distillation tower. The evaporated nitric acid will be refluxed into the No. 2 distillation tower through the No. 1 condenser and the No. 1 water separator to continue heating and distillation. The nitric acid distilled from the No. 2 distillation tower will pass through the No. 3 condenser, the No. 2 water separator, the No. 4 condenser and the rear distillate receiving tank, which is connected to the acid recovery tank.

[0013] Beneficial effects

[0014] This design uses two distillation towers to treat the original acid liquid and the condensate after distillation separately. The nitric acid evaporated from the No. 1 distillation tower will be refluxed to the No. 2 distillation tower through the No. 1 condenser and the No. 1 water separator to continue heating and distillation, while the nitric acid distilled from the No. 2 distillation tower will be recovered through the No. 3 condenser, the No. 2 water separator, the No. 4 condenser and the post-fraction receiving tank connected to the recovery acid tank. After distillation in two independent distillation towers, the nitric acid and the waste liquid evaporated from the first stage (including fluorosilicic acid, hydrofluoric acid, water and low-concentration waste acid) can be effectively separated and treated. The nitric acid can be recovered and reused, while the waste liquid evaporated from the first stage is discharged to the sewage station for treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the working section of the No. 1 distillation tower of the present invention.

[0016] Figure 2 This is a schematic diagram of the working section of the No. 2 distillation tower of the present invention.

[0017] In the figure: T-101, distillation tower No. 1; T-201, distillation tower No. 2; V-101, waste acid raw material tank; V-102, water separator No. 1; V-103, waste liquid tank; V-201, water separator No. 2; V-202A, front fraction receiving tank; V-202B, rear fraction receiving tank; V-301, recovery acid tank; V-302, vacuum buffer tank; E-101, condenser No. 1; E-102, condenser No. 2; E-201, condenser No. 3; E-202, condenser No. 4; P-301, recovery acid pump; M-301, automatic filling machine. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0019] See also Figure 1-2 A waste acid recovery device and process flow, comprising a No. 1 distillation tower T-101, a No. 2 distillation tower T-201, and a waste acid raw material tank V-101, wherein the No. 1 distillation tower T-101 is connected to the No. 2 distillation tower T-201 and the waste acid raw material tank V-101 through a pipeline, the No. 1 distillation tower T-101 is connected to a No. 1 condenser E-101 and three first reboilers, the No. 1 condenser E-101 is connected to a No. 1 water separator V-102, the No. 1 water separator V-102 is connected to a vacuum buffer tank V-302 and a No. 2 condenser E-102, and the No. 2 condenser E-102 is connected to a waste liquid tank V-103;

[0020] Described No. 2 rectifying tower T-201 is connected with No. 3 condenser E-201 and three second reboilers, described No. 3 condenser E-201 is connected with No. 2 water separator V-201, described No. 2 water separator V-201 is connected with No. 4 condenser E-202 and is connected with vacuum buffer tank V-302, described No. 4 condenser E-202 is connected with front fraction receiving tank V-202A and rear fraction receiving tank V-202B, described rear fraction receiving tank V-202B is connected with recovery acid tank V-301;

[0021] This waste acid recovery process uses negative pressure distillation. During the evaporation process, the vacuum (negative pressure) of the container is controlled to reduce the boiling point of the evaporated liquid. When the vacuum degree is 0.9-0.92kPa, HNO3 and HF are evaporated along with water using electricity or steam heating. After condensation, a mixed solution of HNO3 and HF is generated. During the evaporation and condensation process, the metal ions are deposited at the bottom of the distillation pot and do not flow out with the condensate.

[0022] The nitric acid distilled from the No. 1 distillation tower T-101 enters the No. 2 distillation tower T-201, which continues to circulate and heat it. The nitric acid is collected according to the reflux ratio. The acid recovery rate is 80%, and 20% of the waste liquid is discharged to the wastewater station for treatment.

[0023] Furthermore, the No. 1 water separator V-102 and the No. 2 water separator V-201 are both provided with bypass pipes, a pair of the bypass pipes are respectively connected to the No. 1 distillation tower T-101 and the No. 2 distillation tower T-201, and a pair of the bypass pipes are both provided with a circulation pump.

[0024] Furthermore, the front fraction receiving tank V-202A is connected to the first distillation tower T-101 via a pipeline, and the liquid outlet end of the waste liquid tank V-103 is connected to a pump body, which is connected to a liquid outlet pipeline.

[0025] Furthermore, the upper ends of the recovery acid tank V-301 and the waste acid raw material tank V-101 are both connected to the tail gas main pipe, one side of the recovery acid tank V-301 is connected to the recovery acid pump P-301, and one side of the recovery acid pump P-301 is connected to the automatic filling machine M-301.

[0026] Furthermore, the waste acid recovery process includes:

[0027] S1: First, add the raw materials in the waste acid raw material tank V-101 to the first distillation tower T-101, and simultaneously start the first reboiler and the second reboiler to heat the first distillation tower T-101 and the second distillation tower T-201 to about 65°C;

[0028] S2: When the temperature in the No. 1 distillation tower T-101 reaches 65°C, the first water will be distilled out, which contains hydrofluoric acid, hydrofluoric acid, water, and low-concentration waste acid. It will pass through the No. 1 condenser E-101, the No. 1 water separator V-102, and the No. 2 condenser E-102 and finally discharged into the waste liquid tank V-103;

[0029] S3: Nitric acid will be evaporated during the distillation process of the No. 1 distillation tower T-101. The evaporated nitric acid will be refluxed into the No. 2 distillation tower T-201 through the No. 1 condenser E-101 and the No. 1 water separator V-102 to continue heating and distillation. The nitric acid distilled from the No. 2 distillation tower T-201 will pass through the No. 3 condenser E-201, the No. 2 water separator V-201, the No. 4 condenser E-202 and the post-fraction receiving tank V-202B, which is connected to the acid recovery tank V-301.

[0030] By those skilled in the art, the components in this case are connected in sequence. The specific connection and operation sequence should refer to the following working principle. The detailed connection means are well-known technologies in this field. The following mainly introduces the working principle and process.

[0031] Example: First, the raw materials in the waste acid raw material tank V-101 are added to the first distillation tower T-101, and the first reboiler and the second reboiler are started at the same time to heat the first distillation tower T-101 and the second distillation tower T-201 to about 65°C; after the temperature in the first distillation tower T-101 reaches 65°C, the first section of water will be evaporated, which contains fluorosilicic acid, hydrofluoric acid, water and low-concentration waste acid, and then the first section of water will be evaporated through the first condenser E-101, the first water separator V-102, and the second condenser. E-102 is finally discharged into the waste liquid tank V-103; nitric acid will be evaporated during the distillation process of the No. 1 distillation tower T-101, and the evaporated nitric acid will pass through the No. 1 condenser E-101 and the No. 1 water separator V-102 and reflux into the No. 2 distillation tower T-201 to continue heating and distillation. The nitric acid distilled from the No. 2 distillation tower T-201 passes through the No. 3 condenser E-201, the No. 2 water separator V-201, the No. 4 condenser E-202 and the post-fraction receiving tank V-202B, which is connected to the acid recovery tank V-301.

[0032] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations. The phrase "includes an element defined by..." does not exclude the presence of other identical elements in the process, method, article, or device that includes the element.

[0033] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A waste acid recovery device and process flow, comprising a No. 1 distillation tower (T-101), a No. 2 distillation tower (T-201), and a waste acid raw material tank (V-101), wherein the No. 1 distillation tower (T-101) is connected to the No. 2 distillation tower (T-201) and the waste acid raw material tank (V-101) by a pipeline. It is characterized by: The first distillation tower (T-101) is connected to a first condenser (E-101) and three first reboilers, the first condenser (E-101) is connected to a first water separator (V-102), the first water separator (V-102) is connected to a vacuum buffer tank (V-302) and a second condenser (E-102), and the second condenser (E-102) is connected to a waste liquid tank (V-103); The No. 2 distillation tower (T-201) is connected to the No. 3 condenser (E-201) and three second reboilers, the No. 3 condenser (E-201) is connected to the No. 2 water separator (V-201), the No. 2 water separator (V-201) is connected to the No. 4 condenser (E-202) and is connected to the vacuum buffer tank (V-302), the No. 4 condenser (E-202) is connected to the front fraction receiving tank (V-202A) and the rear fraction receiving tank (V-202B), and the rear fraction receiving tank (V-202B) is connected to the recovery acid tank (V-301).

2. A waste acid recovery device according to claim 1, characterized in that: The first water separator (V-102) and the second water separator (V-201) are both provided with bypass pipes, and a pair of the bypass pipes are respectively connected to the first distillation tower (T-101) and the second distillation tower (T-201), and a circulation pump is provided on the pair of bypass pipes.

3. A waste acid recovery device according to claim 1, characterized in that: The front fraction receiving tank (V-202A) is connected to the No. 1 distillation tower (T-101) through a pipeline, and the liquid outlet end of the waste liquid tank (V-103) is connected to a pump body, and the pump body is connected to a liquid outlet pipeline.

4. The waste acid recovery equipment according to claim 1, characterized in that: The upper ends of the acid recovery tank (V-301) and the waste acid raw material tank (V-101) are both connected to a tail gas main pipe, one side of the acid recovery tank (V-301) is connected to a acid recovery pump (P-301), and one side of the acid recovery pump (P-301) is connected to an automatic filling machine (M-301).

5. A waste acid recovery process according to claim 1, characterized in that: The waste acid recovery process includes: S1: First, the raw materials in the waste acid raw material tank (V-101) are added to the first distillation tower (T-101), and the first reboiler and the second reboiler are started at the same time to heat the first distillation tower (T-101) and the second distillation tower (T-201) to about 65°C; S2: When the temperature in the No. 1 distillation tower (T-101) reaches 65°C, the first stage of water will be distilled out, which contains hydrofluoric acid, hydrofluoric acid, water and low-concentration waste acid. It will pass through the No. 1 condenser (E-101), the No. 1 water separator (V-102), and the No. 2 condenser (E-102) and finally discharged into the waste liquid tank (V-103); S3: Nitric acid will be evaporated during the distillation process in the No. 1 distillation tower (T-101). The evaporated nitric acid will pass through the No. 1 condenser (E-101) and the No. 1 water separator (V-102) and flow back to the No. 2 distillation tower (T-201) to continue heating and distillation. The nitric acid distilled from the No. 2 distillation tower (T-201) passes through the No. 3 condenser (E-201), the No. 2 water separator (V-201), the No. 4 condenser (E-202) and the rear fraction receiving tank (V-202B) and is connected to the acid recovery tank (V-301).

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