Concentration process of sulfur and phosphorus mixed acid solution

Abstract

The invention relates to the technical field of phosphorus chemical industry, in particular to the field of IPC C01B25, and more particularly relates to a sulfur and phosphorus mixed acid solution concentration process. The process comprises the following steps: S1, filtering a sulfur-phosphorus mixed acid solution to remove metal ions so as to obtain a mixed solution 1; s2, preheating the mixed solution 1, and concentrating to obtain a mixed solution 2; and S3, controlling the vacuum degree, heating and concentrating the mixed solution 2, and simultaneously carrying out gas-phase washing to respectively obtain steam condensate and a concentrated sulfur-phosphorus mixed acid solution. By adding gas phase washing, the phosphorus content in condensate water is further reduced, the process efficiency is improved, and meanwhile, the harm of phosphorus-containing wastewater to the environment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphorus chemical industry, in particular to the field of IPC C01B25, and more specifically to a concentration process for a sulfur-phosphorus mixed acid solution. Background Art

[0002] A large amount of industrial waste acid is generated every year in my country's industrial production, especially the waste acid produced by bromination reaction (bromination waste acid). Bromination waste acid mainly contains sulfuric acid and phosphoric acid. This type of industrial waste acid has high acidity and is difficult to treat and utilize. The discharge of this industrial waste acid will cause environmental pollution and waste of resources.

[0003] CN115520844A discloses a phosphoric acid concentration control method and system. The phosphoric acid concentration control method is based on a first concentrating section and a second concentrating section arranged in series. The first concentrating section is provided with a flow control valve for the raw material dilute sulfuric acid, a first steam valve is provided on the first concentrating section, and a second steam valve is provided on the second concentrating section. The water evaporation rate in the first concentrating section is equal to the water evaporation rate in the second concentrating section. The method includes flow control of the raw material dilute phosphoric acid solution, steam volume control in the first concentrating section, and steam volume control in the second concentrating section. This method can efficiently produce concentrated phosphoric acid. However, in industrial production, phosphoric acid is rich in sulfuric acid, forming a mixed acid system. This increases the boiling point of the mixed acid and the relative volatility of the phosphoric acid. This method fails to solve the problem of phosphoric acid escape from the mixed acid. Summary of the Invention

[0004] The present invention provides a sulfur-phosphorus mixed acid solution concentration process. By optimizing process parameters, a low-concentration phosphoric-sulfuric acid mixed acid solution is concentrated to a mixed acid content of greater than 80wt%, while further reducing the phosphorus content in condensate to below 8ppm. This improves process efficiency while reducing the environmental harm of phosphorus-containing wastewater.

[0005] To achieve the purpose of the present invention, the present invention provides a process for concentrating a sulfuric and phosphoric acid mixed acid solution, which comprises the following steps:

[0006] S1, filtering the sulfur-phosphorus mixed acid solution to remove metal ions to obtain a mixed solution 1;

[0007] S2, preheating the mixed solution 1 and concentrating it to obtain the mixed solution 2;

[0008] S3, controlling the vacuum degree, heating and concentrating the mixed solution 2, and simultaneously performing gas phase washing to obtain steam condensate and concentrated sulfuric and phosphoric acid mixed solution.

[0009] Preferably, the phosphoric acid content in the sulfur-phosphorus mixed acid solution in step S1 is 3-8 wt %, the sulfuric acid content is 0.5-2 wt %, and the balance is water.

[0010] Further preferably, in the sulfur-phosphorus mixed acid solution in step S1, the phosphoric acid content is 5 wt %, the sulfuric acid content is 1 wt %, and the balance is water.

[0011] The applicant has discovered that diffusion dialysis can significantly remove metal ions by filtering a sulfur-phosphorus mixed acid solution, preventing clogging of equipment pipelines. Metal ions are continuously enriched as the concentration of the mixed acid increases. Furthermore, metal ions in high-concentration phosphoric and sulfuric acid solutions may form chelates or polymers, precipitating and adhering to the inner walls of pipelines. This not only poses a risk of pipeline blockage, but also affects heat conduction in the reactor to a certain extent, leading to increased energy consumption, temperature control deviations, and reduced concentration efficiency. However, the present invention, using diffusion dialysis at low concentrations, can control metal ion concentrations below 8 ppm, further reducing enrichment during the mixed acid concentration process.

[0012] The filtration method includes diffusion dialysis.

[0013] Preferably, the mold assembly brand used in the diffusion dialysis method is Spiraltec, model DS10-30, provided by Wuxi Meitaisi Applied Materials Technology Co., Ltd.

[0014] The applicant has found that a heating temperature of 130-170°C and a vacuum degree of -0.05 to -0.08 MPa can increase the content of phosphoric acid and sulfuric acid. As the temperature increases, the concentration efficiency improves, but excessively high temperatures increase energy consumption and are also prone to the risk of acidic vapor generation. A vacuum degree of -0.05 to -0.08 MPa reduces the acid saturated vapor pressure to a certain extent, controlling the concentration process to proceed smoothly. However, as the concentration of the mixed acid increases, the boiling point rises rapidly, the relative volatility of phosphoric acid increases, and the escaped phosphoric acid increases. The applicant has further found that by setting up a gas phase scrubbing process, the escape of phosphoric acid can be reduced.

[0015] Preferably, the preheating temperature is 90-110°C.

[0016] More preferably, the preheating temperature is 95-105°C.

[0017] More preferably, the preheating temperature is 105°C.

[0018] Preferably, the mixed solution 2 contains 13-18 wt % phosphoric acid, 3-7 wt % sulfuric acid, and the balance is water.

[0019] Further preferably, the mixed solution 2 contains 15 wt % phosphoric acid, 5 wt % sulfuric acid, and the balance is water.

[0020] Preferably, the vacuum degree is -0.05 to -0.08 MPa.

[0021] More preferably, the vacuum degree is -0.05 to -0.07 MPa.

[0022] More preferably, the vacuum degree is -0.065 MPa.

[0023] Preferably, the heating temperature is 130-170°C.

[0024] More preferably, the heating temperature is 140-165°C.

[0025] More preferably, the heating temperature is 155°C.

[0026] Beneficial effects

[0027] 1. Diffusion dialysis is used to filter the sulfur-phosphorus mixed acid solution, which can remove metal ions to a large extent and avoid blockage of equipment pipelines.

[0028] 2. The heating temperature is 130-170℃ and the vacuum degree is -0.05~-0.08MPa, which can increase the content of phosphoric acid and sulfuric acid.

[0029] 3. By adding gas phase scrubbing, the phosphorus content in the condensate is further reduced, which improves process efficiency while reducing the harm of phosphorus-containing wastewater to the environment.

[0030] 4. The preheating temperature is 90-110℃, which can improve the efficiency of mixed acid concentration.

[0031] 5. The phosphoric acid content in the mixed solution 2 is 13-18 wt %, the sulfuric acid content is 3-7 wt %, and the balance is water, which can reduce the escape of phosphoric acid during the concentration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a simplified process flow diagram for the concentration of the sulfur and phosphorus mixed acid solution in Example 1. DETAILED DESCRIPTION

[0033] Example 1

[0034] A process for concentrating a sulfuric and phosphoric acid mixed solution, such as Figure 1 As shown, the process is as follows:

[0035] S1, transporting the sulfur-phosphorus mixed acid solution in step S1 from the material tank to a diffusion osmosis membrane assembly for filtration to remove metal ions, thereby obtaining a mixed solution 1;

[0036] S2, the mixed liquid 1 is transferred to the preheater for preheating and concentrated to obtain the mixed liquid 2, and the primary steam condensate obtained by the concentration is simultaneously transferred to the primary condensate storage tank for storage;

[0037] S3, controlling the vacuum degree by a vacuum unit, conveying the mixed solution 2 to a single-effect evaporation chamber for heating and concentration, the concentrated sulfur-phosphorus mixed acid solution enters a finished acid storage tank, and the phosphorus and sulfur vapors generated by the concentration pass through a gas phase scrubber and a gas phase filter in sequence for gas phase scrubbing to obtain secondary steam condensate and the washed and concentrated sulfur-phosphorus mixed acid solution. The secondary steam condensate passes through a tail gas condenser and enters a secondary condensate storage tank, and the washed and concentrated sulfur-phosphorus mixed acid solution enters a finished acid storage tank.

[0038] In the step S1, the phosphoric acid content in the sulfur-phosphorus mixed acid solution is 5 wt %, the sulfuric acid content is 1 wt %, and the balance is water.

[0039] The brand of the diffusion dialysis module is Spiraltec, model DS10-30, and is provided by Wuxi Meitaisi Applied Materials Technology Co., Ltd.

[0040] The preheating temperature is 105°C.

[0041] The mixed solution 2 contains 15 wt % phosphoric acid and 5 wt % sulfuric acid, with the remainder being water.

[0042] The vacuum degree is -0.065 MPa.

[0043] The heating temperature is 155°C.

[0044] Example 2

[0045] The specific implementation is the same as that of Example 1; the difference is that the vacuum degree in Example 2 is -0.06 MPa and the heating temperature is 160°C.

[0046] Example 3

[0047] The specific implementation is the same as in Example 1; except that the preheating temperature in Example 3 is 110°C.

[0048] The specific implementation method is the same as that in Example 1; the difference is that, as described in Comparative Example 1, S3, the vacuum degree is controlled by a vacuum unit, the mixed solution 2 is transported to a single-effect evaporation chamber for heating and concentration, and the concentrated sulfur-phosphorus mixed acid solution enters the finished acid storage tank.

[0049] Performance testing methods

[0050] 1. The mixed solution 1 obtained in Example 1 was subjected to metal ion detection using inductively coupled plasma atomic emission spectrometry and an Agilent 5800 ICP-OES instrument.

[0051] 2. The phosphorus content (calculated as elemental phosphorus) in the secondary steam condensate obtained in Examples 1-3 and Comparative Examples 1-2 was detected using an EDX4500P-phosphorus element analyzer.

[0052] 3. Detect the phosphoric acid and sulfuric acid content in the concentrated sulfuric and phosphoric acid mixed acid solutions obtained in Example 1-3 and Comparative Example 1-2. Detection method: Instrument: EDX4500P-phosphorus element analyzer and acid-base titration method.

[0053] The test results are shown in Table 1, where “-” indicates that no test was performed.

[0054] Performance test data

[0055] Table 1

[0056]

[0057]

Claims

1. A process for concentrating a sulfuric and phosphoric acid mixed acid solution, characterized in that: The process includes the following steps: S1, filtering the sulfur-phosphorus mixed acid solution to remove metal ions to obtain a mixed solution 1; S2, preheating the mixed solution 1 and concentrating it to obtain the mixed solution 2; S3, controlling the vacuum degree, heating and concentrating the mixed solution 2, and simultaneously performing gas phase washing to obtain steam condensate and concentrated sulfuric and phosphoric acid mixed solution.

2. The process for concentrating a sulfur-phosphorus mixed acid solution according to claim 1, characterized in that: The steps The phosphoric acid content in the sulfur-phosphoric mixed acid solution in S1 is 3-8 wt %, and the sulfuric acid content is 0.5-2 wt %.

3. The process for concentrating a sulfur-phosphorus mixed acid solution according to claim 2, characterized in that: The filtration method used is diffusion dialysis.

4. A sulfur-phosphorus mixed acid solution concentration process according to claim 1 or 3, characterized in that: The preheating temperature is 90-110°C.

5. The process for concentrating a sulfur-phosphorus mixed acid solution according to claim 4, characterized in that: The preheating temperature is 95-105°C.

6. The process for concentrating a sulfur-phosphorus mixed acid solution according to claim 1, characterized in that: The mixed solution 2 contains 13-18 wt % phosphoric acid and 3-7 wt % sulfuric acid.

7. The process for concentrating a sulfur-phosphorus mixed acid solution according to claim 1, characterized in that: The vacuum degree is -0.05 to -0.08 MPa.

8. The process for concentrating a sulfur-phosphorus mixed acid solution according to claim 7, characterized in that: The vacuum degree is -0.05 to -0.07 MPa.

9. The process for concentrating a sulfur-phosphorus mixed acid solution according to claim 1, characterized in that: The heating temperature is 130-170°C.

10. The process for concentrating a sulfur and phosphorus mixed acid solution according to claim 9, characterized in that: The heating temperature is 140-165°C.

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