Method for treating oil production wastewater based on solvent extraction

Abstract

The invention discloses an oil production wastewater treatment method based on solvent extraction, and belongs to the technical field of oil production wastewater treatment. The method comprises the following steps: step 1, adding an adsorption material into an adsorption device to perform adsorption treatment on the oil extraction wastewater to obtain pretreated oil extraction wastewater; 2, adding an acid regulator into the pretreated oil extraction wastewater obtained in the step 1, and regulating the pH value to obtain the oil extraction wastewater with the pH value of 0-6; 3, mixing the phosphorus-oxygen neutral extraction agent, an amide compound and alcohol to form an extraction agent; step 4, mixing the oil-producing wastewater with the pH value of 0-6 obtained in the step 2 with the extracting agent obtained in the step 3, carrying out countercurrent six-stage extraction, combining oil organic matters in the oil-producing wastewater with the extracting agent to form an extraction compound, and separating the extraction compound from a water phase; and step 5, using a stripping agent to react with the extraction compound, and recycling the organic matters in the oil production wastewater. The tertiary oil recovery wastewater is treated through a solvent extraction method, and COD in the tertiary oil recovery wastewater is reduced to be below the relevant national standard for emission.

Description

Technical Field

[0001] The present application relates to the technical field of oil production wastewater treatment, and in particular to a method for treating oil production wastewater based on solvent extraction. Background Art

[0002] With the continuous development of domestic oil fields, the oil extraction technology has gradually improved, the development level has become higher and higher, and the recoverable oil and gas reserves of oil fields have gradually decreased. Most domestic oil fields have entered the tertiary oil recovery stage, mainly using polymer flooding and ternary composite flooding as the main oil recovery technologies. The large-scale application of tertiary oil recovery has increased the output of oil, but it has also brought many new technical problems: the water content in the middle and late production process of the oil field is high, and a large amount of oil production wastewater will be generated during the oil production process, which is more troublesome in the treatment process.

[0003] At present, tertiary oil recovery is mainly based on chemical flooding such as ASP flooding, foam flooding, and polymer flooding, which increases the oil field recovery rate by improving the sweep coefficient. After the application of chemical flooding, the tertiary oil recovery wastewater will contain polymers, alkaline compounds, various inorganic salts, crude oil, surfactants, ammonia nitrogen and other substances. The composition is particularly complex, which increases the difficulty of treating tertiary oil recovery wastewater. Compared with conventional water flooding wastewater, tertiary oil recovery wastewater has the following characteristics: (1) High viscosity. The presence of residual high molecular polymers makes the oil recovery wastewater difficult to degrade; (2) High emulsification degree. The residual polymer will form a highly elastic film with the surfactant in the water at the oil-water interface. The emulsified oil droplets in the tertiary oil recovery wastewater are particularly stable, and conventional demulsifiers are difficult to destroy them and aggregate them together; (3) The particle size of the oil droplets in the wastewater is small, most of which are below 10μm, with a high degree of dispersion. The oil-water separation technology is difficult to treat and the treatment efficiency is extremely low.

[0004] In the current tertiary oil recovery wastewater treatment process, inorganic salt colloid adsorption and polyacrylamide adsorption are usually used in combination for wastewater treatment. However, such operation still has many disadvantages. Specifically, a large amount of inorganic coagulants are used in the wastewater treatment process, and the amount of reagents used is large and the cost is high. At the same time, the added inorganic coagulants will be completely converted into chemical sludge, thereby increasing the sludge treatment cost and seriously affecting the effect of wastewater treatment. The polyacrylamide containing oil residues in tertiary oil recovery wastewater has a much higher viscosity than general wastewater. If high molecular weight components such as polyacrylamide are not specially treated, it will lead to slow sedimentation of suspended particles or flocs, low treatment efficiency, and cannot meet production needs.

[0005] Providing a method for treating tertiary oil recovery wastewater that can efficiently treat tertiary oil recovery wastewater, use less chemicals and have excellent treatment effects has become a difficult problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] The purpose of the present application is to provide a method for treating oil production wastewater based on solvent extraction, which treats tertiary oil production wastewater by solvent extraction and reduces the COD therein to below the relevant national standards for discharge.

[0007] Based on the above purpose, the present application provides a method for treating oil production wastewater based on solvent extraction, comprising the following steps: Step 1: Add adsorption material into the adsorption device to adsorb the oil production wastewater, remove the floating oil and dispersed oil in the oil production wastewater, and obtain pre-treated oil production wastewater; Step 2: Add an acid regulator to the pretreated oil production wastewater obtained in step 1 to adjust the pH to obtain oil production wastewater with a pH of 0-6; Step 3, mixing a phosphorus-oxygen neutral extractant, an amide compound and an alcohol in proportion to form an extractant; Step 4: Mix the oil production wastewater with a pH value of 0-6 obtained in step 2 with the extractant obtained in step 3, and perform 6-stage countercurrent extraction to combine the oil organic matter in the oil production wastewater with the extractant to form an extractant, and then separate it from the water phase; Step 5: using a stripping agent to react with the extractant to recycle the organic matter in the oil production wastewater encapsulated in the extractant; Step 6: Recycle the extractant after stripping.

[0008] Preferably, in step one, the adsorption material includes, by weight, 10-15 parts of quartz sand, 25-45 parts of activated carbon, 15-30 parts of perlite and 5-20 parts of gelling agent fly ash; and the mixture is mixed by particle grading.

[0009] Preferably, in step 2, the acid regulator is hydrochloric acid or sulfuric acid with a concentration of 0.1 mol / L-1 mol / L.

[0010] Preferably, in step three, the phosphorus-oxygen neutral extractant is mainly composed of one or two of phosphate esters, monoalkyl phosphoric acid diesters, dialkyl phosphoric acid monoesters, trialkyl phosphorus oxides, etc.; the amide is one or two of N,N-di(dodecyl)propionamide, N,N-di(hexadecyl)acetamide, N,N-di(octadecyl)formamide, N,N-dodecyl(tetradecyl)acetamide, N,N-hexadecyl(octadecyl)formamide, etc.; the number of carbon atoms of the alcohol is 3-12, containing straight chain or branched chain; the volume ratio of the phosphorus-oxygen neutral extractant, amide, and alcohol is 15-35:20-30:25-45.

[0011] Preferably, in step 4, when using an extractant to extract organic matter from oil production wastewater, the pH value is 0-6; the temperature is 30-80°C; the ratio is 1:10-10:1; and the extraction time is 5 minutes.

[0012] Preferably, the stripping agent in step five is an alkaline solution, the stripping temperature is 20-50° C.; the stripping volume ratio is 2-10:1, and the stripping time is 3-10 min.

[0013] Preferably, before extraction, the COD content in the oil production wastewater is 100-2000 mg / L, and after treatment, the COD content is below 75 mg / L.

[0014] Therefore, the present application provides a method for treating oil production wastewater based on solvent extraction, which has the following beneficial effects: 1. The oil production wastewater treatment method of the present invention uses less reagents, has low wastewater treatment costs, does not generate sludge, and ensures the wastewater treatment effect; the present invention can effectively reduce the COD of the wastewater, shorten the wastewater treatment time, and improve the overall treatment efficiency.

[0015] 2. In the present application, the phosphorus-oxygen neutral extractant and the amide extractant work synergistically so that the organic matter in the oil recovery wastewater forms an extractant with the extractant and then transfers it to the organic phase, and then a suitable stripping agent is selected to destroy the structure of the extractant formed by the organic matter in the oil recovery wastewater under certain conditions, so as to achieve effective separation of the extractant from the organic matter in the tertiary oil recovery wastewater; the alcohol diluent plays the role of diluting the extractant and adsorbing the emulsified oil in the polymerized oil recovery wastewater; after adsorption pretreatment and extraction, the COD of the tertiary oil recovery wastewater can be reduced to below 100 mg / L, meeting the national emission standards; DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further illustrated by the following embodiments.

[0017] Example 1 Taking 500 ml of tertiary oil recovery wastewater from the isolated island of Shengli Oilfield as the sample to be treated, the treatment method of oil recovery wastewater based on solvent extraction includes the following steps: Step 1: First, 200g of 140-mesh quartz sand, 80-mesh perlite, 100-mesh activated carbon, and 600-mesh fly ash as a gelling agent are graded according to the weight ratio of 15 parts, 35 parts, 30 parts, and 20 parts, mix them evenly, fill them into the adsorption device, and compact them.

[0018] Step 2: Pass the water sample to be treated through an adsorption device to remove floating oil and dispersed oil in the oil production wastewater, and then adjust the pH value of the treated oil production wastewater to 2.0 with 60 ml of 0.1 mol / L hydrochloric acid; Step 3, tributyl phosphate: N, N-di(hexadecyl)acetamide: octanol are prepared as an extractant in a volume ratio of 30 parts, 25 parts, and 45 parts, and the ratio is 1:2. Single-stage extraction is performed at 60°C for 5 minutes. After phase separation, the COD in the residual water is determined, and then after 6-stage countercurrent extraction, the COD of the oil production wastewater after the extraction is determined. The results of the oil production wastewater after single-stage extraction and 6-stage extraction are as follows: the COD of the untreated tertiary oil production wastewater is 2000 mg / L, after single-stage extraction, the COD in the residual water is 750 mg / L, and after 6-stage countercurrent extraction, the COD is 75 mg / L, which is lower than the national emission standard.

[0019] Step 4: Use 0.02 mol / L sodium hydroxide solution as stripping agent to destroy the structure of the extractant formed by the organic matter and the extractant in the oil production wastewater, and recycle the dissolved oil and emulsified oil in the oil production wastewater. The stripping agent is 250 ml; the stripping ratio is 2:1, the stripping temperature is 50°C, the single-stage stripping rate is 60%, and after 6 stages of countercurrent stripping, the stripping rate can reach more than 98%, and the extractant can be returned to the extraction section for normal use.

[0020] Example 2 Taking 500 ml of tertiary oil recovery wastewater from the isolated island of Shengli Oilfield as the sample to be treated, the treatment method of oil recovery wastewater based on solvent extraction includes the following steps: Step 1: First, 200g of 140-mesh quartz sand, 80-mesh perlite, 100-mesh activated carbon, and 600-mesh fly ash as a gelling agent are graded according to the weight ratio of 15 parts, 40 parts, 25 parts, and 20 parts, mixed evenly, filled into the adsorption device, and compacted.

[0021] Step 2: Pass the water sample to be treated through an adsorption device to remove floating oil and dispersed oil in the oil production wastewater, and then adjust the pH value of the treated oil production wastewater to 3.0 with 30 ml of 0.2 mol / L hydrochloric acid; Step 3, trialkylphosphine oxide: N, N-di(hexadecyl)acetamide: n-decanol prepared as an extractant in a volume ratio of 15 parts, 45 parts, and 40 parts, take 500 ml of the extractant and the pretreated oil production wastewater, according to a ratio of 1:1, single-stage extraction at 80°C for 5 minutes, after phase separation, determine the COD in the residual water, and then after 6-stage countercurrent extraction, take the residual oil production wastewater to determine the COD, the results of single-stage extraction and 6-stage extraction of oil production wastewater are as follows: the COD of untreated tertiary oil production wastewater is 2000 mg / L, after single-stage extraction, the COD in the residual water is 1000 mg / L, after 6-stage countercurrent extraction, the COD is 80 mg / L, which is lower than the national emission standard.

[0022] Step 4: Use 0.015 mol / L sodium hydroxide solution as stripping agent to destroy the structure of the extractant formed by the organic matter and the extractant in the oil production wastewater, and recycle the dissolved oil and emulsified oil in the oil production wastewater. The stripping agent is 250 ml; the stripping ratio is 2:1, the stripping temperature is 45°C, the single-stage stripping rate is 65%, and after 6 stages of countercurrent stripping, the stripping rate can reach more than 99%, and the extractant can be returned to the extraction section for normal use.

[0023] Example 3 Taking 500 ml of tertiary oil recovery wastewater from the isolated island of Shengli Oilfield as the sample to be treated, the treatment method of oil recovery wastewater based on solvent extraction includes the following steps: Step 1: First, 200g of 140-mesh quartz sand, 80-mesh perlite, 100-mesh activated carbon, and 600-mesh fly ash as a gelling agent are graded according to the weight ratio of 10 parts, 45 parts, 30 parts, and 15 parts, mix them evenly, fill them into the adsorption device, and compact them.

[0024] Step 2: Pass the water sample to be treated through an adsorption device to remove floating oil and dispersed oil in the oil production wastewater, and then adjust the pH value of the treated oil production wastewater to 1.5 with 65 ml of 0.1 mol / L hydrochloric acid; Step 3, triisobutyl phosphate: N, N-di(dodecyl)acetamide: isoamyl alcohol are prepared as an extractant in a volume ratio of 40 parts, 15 parts, and 45 parts, and the ratio is 1:2. Single-stage extraction is performed at 60°C for 5 minutes. After phase separation, the COD in the residual water is determined, and then after 6-stage countercurrent extraction, the COD of the oil production wastewater after the extraction is determined. The results of the oil production wastewater after single-stage extraction and 6-stage extraction are as follows: the COD of the untreated tertiary oil production wastewater is 2000 mg / L, the COD in the residual water after single-stage extraction is 1000 mg / L, and the COD after 6-stage countercurrent extraction is 80 mg / L, which is lower than the national emission standard.

[0025] Step 4: Use 0.01 mol / L sodium hydroxide solution as stripping agent to destroy the structure of the extractant formed by the organic matter and the extractant in the oil production wastewater, and recycle the dissolved oil and emulsified oil in the oil production wastewater. The stripping agent is 250 ml; the stripping ratio is 2:1, the stripping temperature is 40°C, the single-stage stripping rate is 66%, and after 6 stages of countercurrent stripping, the stripping rate can reach more than 99%, and the extractant can be returned to the extraction section for normal use.

[0026] Comparative Example 1: Taking 500 ml of tertiary oil recovery wastewater from the isolated island of Shengli Oilfield as the sample to be treated, the treatment method of oil recovery wastewater based on solvent extraction includes the following steps: Step 1: First, 200g of 140-mesh quartz sand, 80-mesh perlite, 100-mesh activated carbon, and 600-mesh fly ash as a gelling agent are graded according to the weight ratio of 15 parts, 35 parts, 30 parts, and 20 parts, mix them evenly, fill them into the adsorption device, and compact them.

[0027] Step 2: Pass the water sample to be treated through an adsorption device to remove floating oil and dispersed oil in the oil production wastewater, and then adjust the pH value of the treated oil production wastewater to 2.0 with 60 ml of 0.1 mol / L hydrochloric acid; Step 3: Use extractants composed of tributyl phosphate, N,N-di(hexadecyl)acetamide, and decanol in different volume ratios, respectively, at a ratio of 1:2 between the extractant and the oil production wastewater, perform single-stage extraction at 60°C for 5 minutes, and after phase separation, determine the COD in the raffinate after extraction. The test results are shown in Table 1.

[0028] Table 1. Comparison of extraction effects of different extractant compositions

[0029] Untreated tertiary oil recovery wastewater, COD at 2000mg / L, using phosphorus oxygen neutral extractant (tributyl phosphate), amide extractant (N, N-di(hexadecyl)acetamide 55%) and diluent (n-decanol) to extract oil recovery wastewater, the single-stage extraction efficiency is low and cannot be industrialized. The combination of phosphorus oxygen neutral extractant and amide extractant has a good synergistic extraction effect and can greatly improve the extraction efficiency.

[0030] Comparative Example 2: Taking 500 ml of tertiary oil recovery wastewater from the isolated island of Shengli Oilfield as the sample to be treated, the treatment method of oil recovery wastewater based on solvent extraction includes the following steps: Step 1: First, 200g of 140-mesh quartz sand, 80-mesh perlite, 100-mesh activated carbon, and 600-mesh fly ash as a gelling agent are graded according to the weight ratio of 15 parts, 40 parts, 25 parts, and 20 parts, mixed evenly, filled into the adsorption device, and compacted.

[0031] Step 2: Pass the water sample to be treated through an adsorption device to remove floating oil and dispersed oil in the oil production wastewater, and then adjust the pH value of the treated oil production wastewater to 3.0 with 30 ml of 0.2 mol / L hydrochloric acid; Step 3: prepare an extractant prepared by trialkylphosphine oxide: N,N-di(hexadecyl)acetamide: decanol in different volume ratios, take 500 ml of the extractant and mix it with the pretreated oil production wastewater in a ratio of 1:1, perform single-stage extraction at 80°C for 5 minutes, and after phase separation, determine the COD in the residual water to evaluate the single-stage extraction effect.

[0032] Table 2. Comparison of extraction effects of different extractant compositions

[0033] Through comparative cases, it can be seen that the extraction effect of organic matter in oil production wastewater using phosphorus oxygen neutral extractant and amide mixed extractant alone is not obvious. Through the coordinated use of phosphorus oxygen neutral extractant and amide mixed extractant, the COD in tertiary oil production wastewater is significantly reduced after single-stage extraction. Through theoretical calculation, it can be seen that after 6 countercurrent extractions, the COD index of oil production wastewater can meet national requirements.

[0034] Therefore, the present application provides a method for treating oil production wastewater based on solvent extraction, which treats tertiary oil production wastewater by solvent extraction and reduces the COD therein to below the relevant national standards for discharge.

[0035] In the description of this specification, the description with reference to the terms "an experimental example", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the experimental example or example are included in at least one experimental example or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same experimental example or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more experimental examples or examples in a suitable manner.

[0036] Finally, it should be noted that the above experimental examples are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred experimental examples, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for treating oil production wastewater based on solvent extraction, characterized in that: The following steps are involved: Step 1: Adding adsorption material into the adsorption device to perform adsorption treatment on the oil production wastewater, removing floating oil and dispersed oil in the oil production wastewater, and obtaining pretreated oil production wastewater; Step 2: Add an acid regulator to the pretreated oil production wastewater obtained in step 1 to adjust the pH to obtain oil production wastewater with a pH of 0-6; Step 3, mixing a phosphorus-oxygen neutral extractant, an amide compound and an alcohol to form an extractant; Step 4: Mix the oil production wastewater with a pH of 0-6 obtained in step 2 with the extractant obtained in step 3 and subject it to multi-stage countercurrent extraction, so that the organic matter in the oil production wastewater is combined with the extractant to form an extractant, which is separated from the water phase; Step 5: using a stripping agent to react with the extractant to recycle the organic matter in the oil production wastewater; Step 6: Recycle the extractant after stripping.

2. The method for treating oil production wastewater based on solvent extraction according to claim 1, characterized in that: In step 1, the adsorption material includes 10-15 parts of quartz sand, 25-45 parts of activated carbon, 15-30 parts of perlite and 5-20 parts of fly ash as a gelling agent, and is mixed by particle grading.

3. The method for treating oil production wastewater based on solvent extraction according to claim 1, characterized in that: In step 2, the acid regulator is hydrochloric acid or sulfuric acid with a concentration of 0.1 mol / L-1 mol / L.

4. The method for treating oil production wastewater based on solvent extraction according to claim 1, characterized in that: In step 3, the phosphorus-oxygen neutral extractant is mainly composed of one or two of phosphate esters, monoalkyl phosphoric acid diesters, dialkyl phosphoric acid monoesters, trialkyl phosphorus oxides, etc.; the amide is one or two of N,N-di(dodecyl)propionamide, N,N-di(hexadecyl)acetamide, N,N-di(octadecyl)formamide, N,N-dodecyl(tetradecyl)acetamide, N,N-hexadecyl(octadecyl)formamide, etc.; the number of carbon atoms of the alcohol is 3-12, containing straight chain or branched chain; the volume ratio of the phosphorus-oxygen neutral extractant, amide, and alcohol is 15-35:20-30:25-45.

5. The method for treating oil production wastewater based on solvent extraction according to claim 1, characterized in that: In step 4, when the extractant is used to extract organic matter in the oil production wastewater, the pH value is 0-6; the temperature is 30-80°C; the phase ratio is 1:10-10:1; and the extraction time is 5 minutes.

6. The method for treating oil production wastewater based on solvent extraction according to claim 1, characterized in that: The stripping agent in step five is an alkaline solution, the stripping temperature is 20-50° C., the stripping volume ratio is 2-10:1, and the stripping time is 3-10 min.

7. The method for treating oil production wastewater based on solvent extraction according to claim 1, characterized in that: Before extraction, the COD content in the oil production wastewater was 100-2000 mg / L, and after treatment, the COD content was below 75 mg / L.

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