Method for removing organic solvent in raffinate acid

Abstract

The invention relates to the technical field of phosphorus chemical industry, in particular to a method for removing an organic solvent in raffinate acid, which comprises the following steps: mixing the heated raffinate acid with an oxidant, and carrying out oxidation reaction at 90-100 DEG C; the temperature of the heated raffinate acid is 60 to 120 DEG C. According to the method, the oxidizing agent is adopted to oxidize the residual organic solvent in the raffinate acid, the organic solvent in the raffinate acid is decomposed into CO2 and H2O, solvent volatilization is effectively eliminated, and no volatile solvent is generated on site in the pretreatment process; metal ions such as Fe < 2 + > in the raffinate acid are effectively utilized as an oxidation catalyst, the use amount of an oxidizing agent is reduced, the oxidation efficiency is improved, the removal rate of volatile organic solvents in the raffinate acid can reach 100%, and the total TOC removal rate can be greater than 90%.

Description

Technical Field

[0001] The invention relates to the technical field of phosphorus chemical industry, and in particular to a method for removing an organic solvent from raffinate acid. Background Art

[0002] The wet phosphoric acid solvent extraction method for purifying phosphoric acid is gradually replacing the high-energy-consuming thermal phosphoric acid due to its low energy consumption and cost. Commonly used extraction solvents include ethers, esters, fatty alcohols, organophosphorus, amines and ketones. The solvents are volatile and have a flash point of 50 to 145°C. The solvent purification extraction produces raffinate acid as a by-product, and phosphoric acid, which accounts for about half of the feed acid, is distributed to the raffinate acid. The residual organic extraction solvent in the raffinate acid is easy to corrode equipment and rubber during storage, transportation and use, resulting in reduced quality of the raffinate acid and reduced equipment service life. Due to the corrosiveness of the residual organic solvent in the raffinate acid, the equipment has safety and environmental risks such as corrosion and leakage during use.

[0003] Regarding the treatment of residual organic solvents in the raffinate, the industry generally adopts heating, boiling and distilling the raffinate to volatilize the residual organic solvents in the raffinate. However, this treatment method has high energy consumption, long process, and produces condensed water containing organic solvents; incomplete absorption of organic solvents will emit foul odors or peculiar smells; and the solvents and organic matter in the raffinate cannot be completely removed. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for removing the organic solvent in the raffinate acid, and the removal rates of the organic solvent and TOC in the raffinate acid are both high.

[0005] The present invention provides a method for removing an organic solvent from raffinate acid, comprising the following steps:

[0006] The heated raffinate is mixed with an oxidant and subjected to oxidation reaction at 90 to 100° C.;

[0007] The temperature of the heated raffinate is 60-120°C.

[0008] Preferably, the mass content of P2O5 in the raffinate is 20% to 54%, and the mass content of Mg 2+ The mass content of Fe is less than 1%, 2+ The mass content of N<3000ppm, the mass content of Al<2000ppm, the mass content of TBP>10ppm, and the mass content of TOC>50ppm;

[0009] The pH value of the raffinate acid is <1.

[0010] Preferably, the raffinate is heated to 95-100°C.

[0011] Preferably, the heating method is direct heating or using a partition heat exchange device to increase the temperature of the raffinate acid.

[0012] Preferably, the oxidant is at least one of peroxide and superoxide.

[0013] Preferably, the peroxide is hydrogen peroxide with a mass concentration of 27.5% to 70%;

[0014] The superoxide is ozone.

[0015] Preferably, the oxidant accounts for 0.5% to 5% of the mass of the heated raffinate.

[0016] Preferably, the mixing time is not less than 30 min.

[0017] Preferably, after the heated raffinate acid is mixed with the oxidant, the oxidation reaction time is not less than 30 minutes.

[0018] The present invention uses an oxidant to oxidize the residual organic solvent in the raffinate acid, decomposes the organic solvent in the raffinate acid into CO2 and H2O, effectively eliminates solvent volatilization, and no volatile solvent is generated on site during the pretreatment process; Fe in the raffinate acid is effectively utilized. 2+ Metal ions such as chlorinated metals are used as oxidation catalysts to reduce the amount of oxidants used and improve oxidation efficiency. The removal rate of volatile organic solvents in the raffinate can reach 100%, and the total TOC removal rate can reach more than 90%. The odor is effectively solved from the source. Due to the significant removal benefits of solvents and organic matter, the corrosion of equipment and rubber can be significantly improved, the service life of the equipment can be extended, and the safety and environmental risks can be reduced. Compared with the existing raffinate heating, boiling and distillation processes, the present invention does not produce solvent-containing condensed water, which is conducive to a clean environment.

[0019] Compared with the traditional method of heating and volatilizing solvents, the present invention uses an oxidation method to degrade volatile organic solvents and organic matter in the raffinate acid, which saves energy and reduces consumption, is beneficial to improving the production and operation environment, and does not generate secondary pollutants. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with 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.

[0021] The present invention provides a method for removing an organic solvent from raffinate acid, comprising the following steps:

[0022] The heated raffinate is mixed with an oxidant and subjected to oxidation reaction at 90 to 100° C.;

[0023] The temperature of the heated raffinate is 60-120°C.

[0024] In certain embodiments of the present invention, the mass content of P2O5 in the raffinate is 20% to 54%, and the mass content of Mg 2+ The mass content of Fe is less than 1%, 2+ The mass content of isocyanate is <3000ppm, the mass content of Al is <2000ppm, the mass content of organic solvent (TBP) is >10ppm, and the mass content of total organic carbon (TOC) is >50ppm.

[0025] For example, in the raffinate, the mass content of P2O5 is 20% to 30%, and the mass content of Mg 2+ The mass content of Fe is 0.3% to 1%, 2+ The mass content is 2000~3000ppm, Al 3+ The mass content of B2 is 1000-2000ppm, the mass content of TBP is 10-100ppm, and the mass content of TOC is 50-250ppm.

[0026] Specifically, in the raffinate, the mass content of P2O5 is 22.66%, and the mass content of Mg 2+ The mass content of Fe is 0.59%, 2+ The mass content of Al is 2205ppm, 3+ The mass content of is 1226ppm, the mass content of organic solvent TBP is 58ppm, and the mass content of TOC is 188ppm.

[0027] The pH value of the raffinate acid is <1.

[0028] The temperature of the heated raffinate is not higher than the boiling point of the raffinate. In certain embodiments of the present invention, the temperature of the heated raffinate is 80-100°C, 90-100°C or 95-100°C; specifically 60°C, 80°C or 100°C.

[0029] The heating method may be direct heating or using a partition heat exchange device to increase the temperature of the raffinate acid.

[0030] In certain embodiments of the present invention, the oxidant is at least one of peroxide and superoxide; the peroxide may be hydrogen peroxide with a mass concentration of 27.5% to 70%, preferably 27.5%. The superoxide may be ozone. The oxidant accounts for 0.5% to 5% of the mass of the heated raffinate. The oxidant does not introduce Cl - 、NO3 -、SO4 2- , avoid secondary contamination of the residual acid and accelerate corrosion of equipment materials.

[0031] The mixing time is not less than 30 minutes, such as 1 to 2 hours, specifically 1 hour. The mixing is carried out in a tubular mixer.

[0032] The oxidation reaction is carried out in an oxidation reaction tank.

[0033] After the heated raffinate acid is mixed with the oxidant, the oxidation reaction time is not less than 30 minutes, such as 1 to 2 hours, specifically 1.5 hours.

[0034] The present invention is based on the Fe contained in the raffinate. 2+ , in Fe 2+ Under the catalysis of Fe 2+ +H2O2→Fe 3+ +(OH) - +OH·), it is the presence of hydroxyl radicals that makes H2O2 more oxidizing. Therefore, persistent organic matter, especially aromatic compounds and some heterocyclic compounds that are difficult to oxidize with common reagents, are all degraded by non-selective oxidation. 2+ The coordinated coupling effect can oxidize and degrade alcohols, esters, ethers or mixtures of the above solvents to generate CO2 and H2O, completely remove the solvents and organic matter in the raffinate acid, effectively solve the odor in the raffinate acid, and the products will not affect the surrounding environment, keeping the operating environment clean.

[0035] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0036] In order to further illustrate the present invention, a method for removing an organic solvent from raffinate provided by the present invention is described in detail below in conjunction with examples, but it should not be construed as limiting the scope of protection of the present invention.

[0037] In the embodiments and comparative examples, the mass content of P2O5 in the raffinate is 22.66%, and the mass content of Mg 2+ The mass content of Fe is 0.59%, 2+ The mass content of Al is 2205ppm, 3+ The mass content of 1226ppm, the mass content of organic solvent (TBP) is 58ppm, and the mass content of TOC is 188ppm. The pH value of the raffinate acid is <1.

[0038] Comparative Examples 1 to 4 and Examples 1 to 9

[0039] Method for removing organic solvent from raffinate acid:

[0040] 1) The partition heat exchange equipment is used to heat the raffinate acid to the experimental set temperature (i.e., oxidation reaction temperature), the temperature range is 45-100°C (see Table 1).

[0041] 2) The heated raffinate acid and the oxidant (hydrogen peroxide, mass concentration of 27.5%) are mixed in a tubular mixer in proportion (the mixing time is 1 hour), and the percentage of the added amount of hydrogen peroxide to the mass of the heated raffinate acid is shown in Table 1; then, an oxidation reaction is carried out in an oxidation reaction tank (the reaction temperature is shown in Table 1).

[0042] The parameters and effect data of each embodiment and comparative example are shown in Table 1. In Table 1, temperature: the temperature of the raffinate after heating in step 1); hydrogen peroxide / raffinate: the percentage of the amount of hydrogen peroxide added in step 2) to the mass of the raffinate after heating; reaction time: the time of the oxidation reaction in step 2); TOC: the mass content of TOC in the oxidized raffinate obtained in step 2); TBP: the mass content of TBP in the oxidized raffinate obtained in step 2).

[0043] Table 1 Parameters and effect data of various embodiments and comparative examples

[0044]

[0045]

[0046] From Comparative Examples 1 to 2 in Table 1, it can be seen that the TOC and TBP removal by heating and boiling the raffinate acid without adding hydrogen peroxide is low in the TOC and TBP removal rate, and the TOC and TBP removal rate increases with increasing temperature.

[0047] From Comparative Examples 3 to 4 in Table 1, it can be seen that the temperature of the raffinate after heating is 45° C., the percentage of the added amount of hydrogen peroxide to the mass of the raffinate after heating is 2.02% and 3.01%, respectively, the TOC removal rates are 53.45% and 74.14%, respectively; the TBP removal rates are 54.26% and 59.04%, respectively.

[0048] From Examples 1 to 3 in Table 1, it can be seen that the temperature of the raffinate after heating is 60°C, the amount of hydrogen peroxide increases from 0.99% of the mass of the heated raffinate to 1.65% and 2.03%, and the TOC removal rates are 50%, 70.21%, and 80.85%, respectively; the TBP removal rates are 84.48%, 100%, and 100%, respectively.

[0049] From Examples 4 to 6 in Table 1, it can be seen that the temperature of the raffinate after heating is 80°C, the amount of hydrogen peroxide increases from 0.67% of the mass of the heated raffinate to 1.01% and 1.99%, and the TOC removal rates are 42.55%, 80.85%, and 84.04%, respectively; the TBP removal rates are 99.31%, 100%, and 100%, respectively.

[0050] From Examples 7 to 9 in Table 1, it can be seen that when the temperature of the raffinate after heating is 100° C., the amount of hydrogen peroxide increases from 0.49% to 1.11% and 2.01% of the mass of the raffinate after heating, and the TOC removal rates are 65.43%, 85.64% and 90.43%, respectively; the TBP removal rates are all 100%.

[0051] Comparative Example 5

[0052] The existing Fenton conditions are used to control the oxidation pH value and temperature, and an oxidant is added to degrade the organic matter in the raffinate acid.

[0053] The difference from Example 1 is:

[0054] There is no step 1);

[0055] Step 2) is:

[0056] 2-1) adjusting the pH value of the raffinate to 3-4 using sodium hydroxide; adjusting the pH value of the raffinate from less than 1 to 3-4, precipitating a neutralized precipitate, and filtering and separating;

[0057] 2-2) Hydrogen peroxide (hydrogen peroxide, mass concentration is 27.5%) is added to 0.99% of the mass of the raffinate obtained in step 2-1), and the raffinate and hydrogen peroxide are fully mixed in a tubular mixer according to the proportion, and the Fenton room temperature oxidation conditions are adopted, and the residence time in the oxidation reaction tank is 1 hour.

[0058] Due to the filtration and separation of the neutralization precipitate in step 2) of Comparative Example 5, a part of the organic solvent floating in the raffinate acid was adsorbed by the neutralization precipitate, resulting in the TOC of the raw material raffinate acid used in Comparative Example 5 being reduced from 188 to 150 ppm, and the TBP content being reduced from 58 ppm to 9 ppm.

[0059] The parameters and effect data of Example 1 and Comparative Example 5 are shown in Table 2.

[0060] Table 2 Effect data of Example 1 and Comparative Example 5

[0061]

[0062] As can be seen from Table 2, step 2) of comparative example 5 adopts traditional Feton conditions. Under the condition that other steps are the same, it can be seen that traditional Fenton conditions cannot effectively remove TOC and TBP in the raffinate acid. The TOC removal rate of the raffinate acid is 29.33%, and the TBP removal rate is 44.44%. The removal rates of TOC and TBP are lower than those in Example 1.

[0063] In Example 5 and Example 8, by increasing the oxidation temperature, the removal effect of TOC and TBP can be further improved under the condition of substantially the same amount of oxidant as that of Comparative Example 5. The comparative examples and examples fully illustrate that the present invention can significantly reduce TOC and TBP by increasing the oxidation temperature and acidity, and the removal effect is better than that of the traditional Fenton method.

[0064] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for removing an organic solvent from raffinate acid, comprising the following steps: The heated raffinate is mixed with an oxidant and subjected to oxidation reaction at 90 to 100° C.; The temperature of the heated raffinate is 60-120°C.

2. The removal method according to claim 1, characterized in that: The mass content of P2O5 in the raffinate is 20% to 54%, and the mass content of Mg 2+ The mass content of Fe is less than 1%, 2+ The mass content of N<3000ppm, the mass content of Al<2000ppm, the mass content of TBP>10ppm, and the mass content of TOC>50ppm; The pH value of the raffinate acid is <1.

3. The removal method according to claim 1, characterized in that: Heat the raffinate to 95-100°C.

4. The removal method according to claim 3, characterized in that: The heating method is direct heating or using a partition heat exchange device to increase the temperature of the raffinate acid.

5. The removal method according to claim 1, characterized in that: The oxidant is at least one of peroxide and superoxide.

6. The removal method according to claim 5, characterized in that: The peroxide is hydrogen peroxide with a mass concentration of 27.5% to 70%; The superoxide is ozone.

7. The removal method according to claim 1, characterized in that: The oxidant accounts for 0.5% to 5% of the mass of the heated raffinate.

8. The removal method according to claim 1, characterized in that: The mixing time is not less than 30 minutes.

9. The removal method according to claim 1, characterized in that: After the heated raffinate acid is mixed with the oxidant, the oxidation reaction time is not less than 30 minutes.

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