Sodium phenolate phenol extraction sewage treatment process

Abstract

The invention relates to a phenol sodium salt phenol extraction sewage treatment process. The process comprises the following steps: removing oil stains and solid impurities in sewage; extracting and separating by using an extracting agent, and cooling a water phase at the temperature of-5 DEG C to 5 DEG C to separate out Na2SO4 crystals in the water phase, so as to obtain a suspension; centrifugally separating the obtained suspension, heating and dissolving the obtained solid-phase crude salt, evaporating and crystallizing, centrifugally dewatering, and drying to obtain a Na2SO4 salt product; and mixing salt wastewater obtained by centrifugal separation and evaporation, and carrying out biochemical treatment. According to the treatment process provided by the invention, the salt with economic value in the phenol extraction sewage is recovered, the obtained Na2SO4 salt can reach the commercial standard of third level or above, meanwhile, harmful substances such as phenol and heavy metals in the wastewater are separated, and the phenol content in the finally discharged sewage can be as low as 0.05 mg / L.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a wastewater treatment process for extracting phenol from sodium phenol salt. Background Art

[0002] Industrial tar is washed with NaOH aqueous solution during deep processing, and an aqueous solution containing sodium phenolate is produced after washing, commonly known as "sodium phenolate". This type of wastewater mainly contains high concentrations of sodium sulfate salts, various types of tar, pyridine alkali, cyanide, phenol and other heterocyclic and polycyclic compounds. Among them, the main components of phenolic compounds are phenol, o-cresol, m-cresol, p-cresol, xylenol, catechol and its homologues; heterocyclic compounds include: pyridine, quinoline, imidazole, indole, diazine, azabiphenyl, etc.; polycyclic aromatic hydrocarbon compounds include: naphthalene, anthracene, phenanthrene, acenaphthene, benzopyrene, etc.

[0003] Sodium phenol salt is usually used to extract crude phenol products. The current typical process includes sulfuric acid phenollysis, that is, adding dilute sulfuric acid to sodium phenol salt to react sulfuric acid and alkali to obtain an aqueous sodium sulfate solution, and phenol floats on the sodium sulfate solution. The saline wastewater produced after extracting crude phenol contains Na2SO4 salt, phenol and tar, of which the Na2SO4 salt content is about 10%~25% and the phenol concentration is about 0.5~5g / L. It is a difficult-to-degrade saline wastewater. How to treat such wastewater at low cost is an industry problem. Summary of the invention

[0004] The purpose of the present invention is to provide a wastewater treatment process for extracting phenol from sodium phenol salt.

[0005] The solution adopted by the present invention to solve the above technical problems is: A process for treating wastewater by extracting phenol from sodium phenol salt comprises the following steps: (1) Pretreatment to remove oil and solid impurities in the wastewater to be treated; (2) Extraction and removal of phenol: adding the extractant to the wastewater to be treated, extracting and separating, regenerating the extract phase, and sending the aqueous phase to the next step of treatment; (3) Cooling crystallization: the wastewater is cooled at -5°C to 5°C to precipitate Na2SO4 crystals to obtain a suspension; (4) Centrifugal separation: the obtained suspension is centrifuged to obtain a liquid phase, which is salt wastewater A, and the obtained solid phase crude salt enters the next step of treatment; (5) Evaporation and crystallization: the obtained solid phase crude salt is heated to dissolve, evaporated and crystallized, the evaporating liquid is salt wastewater B, the solid phase is centrifuged and dehydrated, and dried to obtain Na2SO4 salt product; (6) Biochemical treatment of wastewater: Salt wastewater A and salt wastewater B are mixed and then biochemically treated.

[0006] Furthermore, in step (1), a flocculant is used for pretreatment.

[0007] Furthermore, the flocculant is selected from one or more components of polyaluminium chloride, polyaluminium sulfate, polyferric chloride, polyferric sulfate, polysilicic acid and polyacrylamide.

[0008] Furthermore, the amount of flocculant added is 0.01% to 0.1% of the sewage mass.

[0009] The flocculation method is to add flocculants to the sewage to be treated, stir evenly, let it stand and settle, and separate the precipitate. The oil and solid impurities in the sewage are entrained and precipitated by the flocculants to achieve separation.

[0010] Through pretreatment, all solid particles in the sewage are removed, the heavy metal content does not exceed 0.01 mg / L, and the oil content is less than 20 ppm.

[0011] Furthermore, the extractant comprises sulfonated kerosene, N503, and tributyl phosphate, and the volume ratio of the three is 1: (0.1~2): (0.1~1); the volume ratio of the three is, for example, 1:0.1:1, 1:0.2:0.9, 1:0.4:0.8, 1:0.6:0.7, 1:0.8:0.6, 1:1:0.5, 1:1.2:0.4, 1:1.4:0.3, 1:1.6:0.2, 1:1.8:0.1, and 1:2:0.1.

[0012] Furthermore, after the solid phase is heated and dissolved in step (5), porous microspheres with a mass of 5% to 20% of the mass of the solution and a particle size of 0.5 to 5 mm are added to the solution, mixed and stirred for 0.1 to 2 hours, and then filtered to separate the solid and liquid phases, and the obtained liquid phase is further evaporated and crystallized.

[0013] Furthermore, the porous microspheres are selected from any one of porous ceramics, activated carbon, porous silica gel, and macroporous adsorption resin.

[0014] Furthermore, the phenol content in the salt wastewater A and the salt wastewater B does not exceed 200 mg / L.

[0015] Furthermore, it also includes an oxidation step, during the solid phase heating and dissolution process in step (5), hydrogen peroxide is added to the solution for oxidation treatment.

[0016] Furthermore, the oxidant is selected from any one of hydrogen peroxide and ozone.

[0017] Furthermore, in step (6), activated sludge is used for biochemical treatment. The phenol content in the discharged water after biochemical treatment is less than 0.5 mg / L.

[0018] The present invention provides a treatment process for extracting phenol from sodium phenol salt wastewater, which recovers salt with economic value in wastewater, and the obtained Na2SO4 salt can meet the market standard of grade three or above. Meanwhile, harmful substances such as phenol and heavy metals in the wastewater are separated, and the phenol content in the wastewater finally discharged can be as low as 0.05 mg / L. DETAILED DESCRIPTION

[0019] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0020] The embodiment of the present invention uses phenol extraction wastewater produced by a coking plant, wherein the Na2SO4 content is 210 g / L and the total phenol content is 3.6 g / L. Example

[0021] A process for treating wastewater by extracting phenol from sodium phenol salt comprises the following steps: (1) Add 0.01% polyacrylamide flocculant to the phenol extraction wastewater, stir evenly, let it settle, separate the precipitate, and extract the supernatant for the next step of treatment. The heavy metal content in the supernatant was measured to be 5μg / L, and the oil content was <8ppm.

[0022] (2) Sulfonated kerosene, N503 and tributyl phosphate in a volume ratio of 1:0.1:1 are mixed as an extractant and added to the supernatant obtained in step (1), and the extract phase is regenerated and the aqueous phase is treated in the next step.

[0023] (3) The aqueous phase obtained in step (2) was cooled to -5°C to precipitate Na2SO4 crystals therein, and the obtained suspension was centrifuged to separate the separated liquid phase into salt wastewater A. The obtained solid phase crude salt was processed in the next step. The total phenol content in the waste brine A was 187 mg / L.

[0024] (4) The solid crude salt obtained in step (3) is heated, the solid phase is dissolved, evaporated and crystallized, and the evaporated liquid is collected to obtain salt wastewater B. The crystallized solid phase is centrifuged and dehydrated and dried to obtain a Na2SO4 salt product. The purity of the Na2SO4 salt is measured to be 95.4%, which meets the requirements of the third-grade anhydrous sodium sulfate product.

[0025] (5) Biochemical treatment of wastewater: Salt wastewater A and salt wastewater B are mixed and biochemically treated using activated sludge. The phenol content in the treated effluent is less than 0.5 mg / L. Example

[0026] A process for treating wastewater by extracting phenol from sodium phenol salt comprises the following steps: (1) Add 0.01% polyacrylamide flocculant to the phenol extraction wastewater, stir evenly, let it settle, separate the precipitate, and extract the supernatant for the next step of treatment. The heavy metal content in the supernatant was measured to be 5 μg / L, and the oil content was <8 ppm.

[0027] (2) Sulfonated kerosene, N503 and tributyl phosphate in a volume ratio of 1:1:0.5 are mixed as an extractant and added to the supernatant obtained in step (1), and the extract phase is regenerated and the aqueous phase is treated in the next step.

[0028] (3) The aqueous phase obtained in step (2) was cooled to -5°C to precipitate Na2SO4 crystals therein, and the obtained suspension was centrifuged to separate the separated liquid phase into salt wastewater A. The obtained solid phase crude salt was processed in the next step. The total phenol content in the waste brine A was 114 mg / L.

[0029] (4) The solid crude salt obtained in step (3) is heated, the solid phase is dissolved, evaporated and crystallized, and the evaporated liquid is collected to obtain salt wastewater B. The crystallized solid phase is centrifuged and dehydrated and dried to obtain a Na2SO4 salt product. The purity of the Na2SO4 salt is measured to be 97.4%, which meets the requirements of the third-grade anhydrous sodium sulfate product.

[0030] (5) Biochemical treatment of wastewater: Salt wastewater A and salt wastewater B are mixed and biochemically treated using activated sludge. The phenol content in the treated effluent is less than 0.5 mg / L. Example

[0031] A process for treating wastewater by extracting phenol from sodium phenol salt comprises the following steps: (1) Add 0.01% polyacrylamide flocculant to the phenol extraction wastewater, stir evenly, let it settle, separate the precipitate, and extract the supernatant for the next step of treatment. The heavy metal content in the supernatant was measured to be 5 μg / L, and the oil content was <8 ppm.

[0032] (2) Sulfonated kerosene, N503 and tributyl phosphate in a volume ratio of 1:2:0.1 are mixed as an extractant and added to the supernatant obtained in step (1), and the extract phase is regenerated and the aqueous phase is treated in the next step.

[0033] (3) The aqueous phase obtained in step (2) was cooled to -5°C to precipitate Na2SO4 crystals therein, and the obtained suspension was centrifuged to separate the separated liquid phase into salt wastewater A. The obtained solid phase crude salt was processed in the next step. The total phenol content in the waste brine A was 173 mg / L.

[0034] (4) The solid crude salt obtained in step (3) is heated, the solid phase is dissolved, evaporated and crystallized, and the evaporated liquid is collected to obtain salt wastewater B. The crystallized solid phase is centrifuged and dehydrated and dried to obtain a Na2SO4 salt product. The purity of the Na2SO4 salt is measured to be 96.2%, which meets the requirements of the third-grade anhydrous sodium sulfate product.

[0035] (5) Salt wastewater A and salt wastewater B are mixed and biochemically treated using activated sludge. The phenol content in the treated effluent is less than 0.5 mg / L. Example

[0036] A process for treating wastewater by extracting phenol from sodium phenol salt comprises the following steps: (1)~(3): Same as Example 2.

[0037] (4) The solid phase crude salt obtained in step (3) is heated. After the solid phase is dissolved, a porous ceramic having a mass of 5% of the solution mass and a particle size of 3±2 mm is added to the solution, and the mixture is stirred for 1 hour under heat preservation. The solid and liquid phases are then separated by filtration. The obtained liquid phase is further evaporated and crystallized. The evaporated liquid is collected to obtain salt wastewater B. The crystallized solid phase is centrifugally dehydrated and dried to obtain a Na2SO4 salt product. The purity of the Na2SO4 salt is measured to be 98.4%, which meets the requirements of anhydrous sodium sulfate secondary product.

[0038] (5) Biochemical treatment of wastewater: Salt wastewater A and salt wastewater B are mixed and biochemically treated using activated sludge. The phenol content in the treated effluent is less than 0.5 mg / L. Example

[0039] A process for treating wastewater by extracting phenol from sodium phenol salt comprises the following steps: (1)~(3): Same as Example 2.

[0040] (4) The solid phase crude salt obtained in step (3) is heated. After the solid phase is dissolved, hydrogen peroxide is added to the solution for oxidation treatment. After the oxidation is completed, evaporation and crystallization are continued. The evaporated liquid is collected to obtain salt wastewater B. The crystallized solid phase is centrifuged and dehydrated and dried to obtain a Na2SO4 salt product. The purity of the Na2SO4 salt is measured to be 97.9%, which meets the requirements of the third-grade anhydrous sodium sulfate product.

[0041] (5) Biochemical treatment of wastewater: Salt wastewater A and salt wastewater B are mixed and biochemically treated using activated sludge. The phenol content in the treated effluent is less than 0.5 mg / L.

[0042] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A process for treating wastewater by extracting phenol from sodium phenol salt, characterized in that: The steps include: (1) Pretreatment to remove oil and solid impurities in the wastewater to be treated; (2) Extraction and removal of phenol: adding the extractant to the wastewater to be treated, extracting and separating, regenerating the extract phase, and sending the aqueous phase to the next step of treatment; (3) Cooling crystallization: the wastewater is cooled at -5°C to 5°C to precipitate Na2SO4 crystals to obtain a suspension; (4) Centrifugal separation: the obtained suspension is centrifuged to obtain a liquid phase, which is salt wastewater A, and the obtained solid phase crude salt enters the next step of treatment; (5) Evaporation and crystallization: the obtained solid crude salt is heated to dissolve, evaporated and crystallized, the evaporating liquid is salt wastewater B, the solid phase is centrifuged and dehydrated, and dried to obtain Na2SO4 salt product; (6) Biochemical treatment of wastewater: Salt wastewater A and salt wastewater B are mixed and then biochemically treated.

2. The process for treating wastewater by extracting phenol from sodium phenol salt according to claim 1, characterized in that: Step (1) uses a flocculant for pretreatment.

3. The process for treating wastewater by extracting phenol from sodium phenol salt according to claim 2, characterized in that: The flocculant is selected from one or more components of polyaluminium chloride, polyaluminium sulfate, polyferric chloride, polyferric sulfate, polysilicic acid and polyacrylamide.

4. The process for treating wastewater by extracting phenol from sodium phenol according to claim 1, characterized in that: The extractant comprises sulfonated kerosene, N503 and tributyl phosphate, and the volume ratio of the three is 1: (0.1-2): (0.1-1).

5. The process for treating wastewater by extracting phenol from sodium phenol salt according to claim 1, characterized in that: After the solid phase is heated and dissolved in step (5), porous microspheres with a mass of 5% to 20% of the solution mass and a particle size of 0.5 to 5 mm are added to the solution, mixed and stirred for 0.1 to 2 hours, and then filtered to separate the solid and liquid phases, and the resulting liquid phase is further evaporated and crystallized.

6. The process for treating wastewater by extracting phenol from sodium phenol salt according to claim 5, characterized in that: The porous microspheres are selected from any one of porous ceramics, activated carbon, porous silica gel, and macroporous adsorption resin.

7. The process for treating wastewater by extracting phenol from sodium phenol salt according to claim 1, characterized in that: The method further comprises an oxidation step, wherein during the solid phase heating and dissolution process in step (5), an oxidant is added to the solution for oxidation treatment.

8. The process for treating wastewater by extracting phenol from sodium phenol salt according to claim 7, characterized in that: The oxidant is selected from any one of hydrogen peroxide and ozone.

9. The process for treating wastewater from phenol by extracting phenol from sodium phenol salt according to claim 1, characterized in that: Step (6) uses activated sludge for biochemical treatment.