Fenton demulsification method for oil sludge of cold rolling wastewater station

Abstract

The invention relates to the field of resource and environment protection, in particular to a Fenton demulsification method for oil sludge in a cold rolling wastewater station, which meets the conditions of Fenton reaction at 70-80 DEG C by utilizing a small amount of iron in the oil sludge and pickling waste liquid and acid-containing wastewater of a cold rolling plant and additionally adding a proper amount of hydrogen peroxide and a bidirectional additive. The method has the advantages that the Fenton reaction of the cold rolling wastewater oil sludge is realized, so that the purpose of demulsification is achieved, conditions are created for subsequent respective treatment of oil, water and sludge of the oil sludge in a cold rolling wastewater station, demulsified oil is recycled, generated precipitated sludge is subjected to coal blending treatment, demulsified wastewater directly enters the cold rolling wastewater station for treatment, and the treatment effect is good. A treatment scheme which is economical, reasonable, short in process and free of secondary pollution is provided for treating the oil sludge in a cold rolling plant, and the field environmental protection requirement is met; meanwhile, in order to solve the problem that a probe of a pH detector is easily wrapped by oil in a mixed solution, so that the pH of the mixed solution is difficult to measure, a simple mathematical model is established in combination with a material system.

Description

Technical Field

[0001] The present invention relates to the field of resource environmental protection, and particularly to a method for Fenton demulsification of oily sludge in a cold rolling wastewater station. Background Art

[0002] During the cold rolling process of cold rolled steel sheets, the raw material coil undergoes processes such as uncoiling, pickling, water washing, rolling, alkali washing, and water washing, and finally forms a cold rolled coil. In this process, emulsions are required for rolling. As the emulsions are recycled, their quality will decline to a certain extent. A portion of the emulsions needs to be discharged to the cold rolling wastewater station, and fresh emulsions are supplemented to meet the quality standards. The discharged waste emulsions are treated by methods such as demulsification, generating a portion of oily sludge in the wastewater station. Additionally, alkali oil wastewater is generated during the alkali washing process, and some oily sludge in the wastewater station is also produced during the treatment of this wastewater. Moreover, during on-site production and maintenance, the trenches and various oily sewage treatment units are cleaned out, also generating oily sludge in the wastewater station. The main components of this oily sludge are oil (30%-60%), water (10%-65%), iron (0.5%-2%), and impurities (10%-30%). Because the oily sludge in the water treatment unit is cleaned irregularly on-site, after a certain period of time, the surface layer of the oily sludge hardens, and the water content gradually increases from the surface to the oil-water separation interface. Additionally, when cleaning the pool, the impurity content of the sludge at the bottom of the pool is relatively large. Cold rolling emulsions are mainly composed of rolling oil (mainly palm oil), water, emulsifiers, antioxidants, oiliness agents, bactericides, etc., and their properties are particularly stable, resulting in the stable properties of the oily sludge in the wastewater station and making it difficult to demulsify. At the same time, at room temperature, the oily sludge in the cold rolling wastewater station will ferment under the action of bacteria, and after fermentation, the oily sludge becomes more viscous, in a paste form, and has very poor fluidity. The key to treating this oily sludge is to condition it, demulsify it, and destabilize it to achieve the three-phase separation of oil, water, and sludge (iron), and then separately dispose of the three phases. Common oily sludge treatment methods such as solvent extraction, conditioning-mechanical separation, high-temperature pyrolysis, incineration, etc. are not very adaptable to the oily sludge in the cold rolling wastewater station due to high costs and poor treatment effects.

[0003] The oxidation method uses oxidants to oxidize some macromolecules in the oily sludge into small molecules, which can achieve the demulsification and destabilization of the oily sludge. The Fenton method is a type of oxidation method. Under acidic conditions, the synergistic effect of hydrogen peroxide and ferrous ions generates ·OH to achieve the purpose of oxidation.

[0004] During the production process of cold rolled steel sheets, hydrochloric acid is generally used to pickle the steel sheets to remove the surface oxides, and at the same time, pickling waste liquid is generated. After pickling, the steel sheets need to be washed with water to remove the residual hydrochloric acid, generating acid-containing wastewater. The pickling waste liquid is generally treated by the roasting acid regeneration process to produce regenerated hydrochloric acid and iron oxide powder; the acid-containing wastewater is generally neutralized with lime or other alkaline substances, and after the pH index meets the standards, it is recycled or discharged within the factory.

[0005] The production process of the cold rolling mill includes sludge, pickling waste liquid and acid-containing wastewater, which provides convenient conditions for demulsifying the cold rolling sludge using the Fenton method.

[0006] The paper Optimization of Process Conditions for Dehydration of Refinery Wastewater Sludge - Lu Jianping, used chemical oil removal and viscosity reduction - sludge conditioning - centrifugal dehydration process to treat mixed sludge from a refinery's wastewater treatment system. It mainly used the Fenton method to reduce the viscosity of the sludge, and achieved its dehydrated oil separation by adding H2SO4, Fe2SO4, and H2O2. It did not mention the use of existing substances in the sludge to achieve in-situ oxidation reactions.

[0007] The paper Demulsifier Assisted Ultrasonic-Fenton Oxidation Treatment of Oily Scum - Dong Shaoxu, uses demulsifier to pre-demulsify the oil field floating oil scum, and then uses the Fenton method to degrade organic matter. This is different from the idea of ​​this patent that directly uses iron in the sludge to demulsify by self-Fenton method and treat the three phases separately.

[0008] Paper Research on Inorganic Salt-Electro-Fenton Treatment of Emulsified Oily Wastewater - Yin Wenbo, used inorganic salts to treat emulsified oily wastewater, and after demulsification, the oily wastewater was treated with electro-Fenton for oil removal. The treatment object was oily wastewater, and the Fenton method was not used for demulsification.

[0009] The application number is CN202110352321.8, and the patent name is "A method for detecting the oil content in cold-rolled sludge". The detection method is to first add a demulsifier to the cold-rolled sludge sample for demulsification treatment, then add a certain amount of extractant to it for extraction, and then filter the obtained extract to dehydrate and remove the extractant. Finally, the oil content in the sludge is measured by weight method to achieve rapid and accurate determination of the oil content in the cold-rolled sludge. The demulsifier used is concentrated nitric acid or concentrated sulfuric acid. This demulsification method is different from the Fenton method used in this patent.

[0010] The above-mentioned public documents all involve the treatment of oil sludge and oily wastewater, and the Fenton method used therein is obviously different from the in-situ self-Fenton demulsification of the iron contained in the oil sludge of the cold rolling wastewater station by this patent. Summary of the invention

[0011] The purpose of the present invention is to provide a method for Fenton demulsification of oil sludge in cold rolling wastewater station, so as to realize the Fenton reaction of oil sludge in cold rolling wastewater and achieve the purpose of demulsification.

[0012] To achieve the above object, the present invention is implemented through the following technical solutions:

[0013] A method for Fenton demulsification of oil sludge in a cold rolling wastewater station, comprising the following steps:

[0014] S1. Put the two-way additive into the preheating tank, and then add the sludge from the cold rolling wastewater station. The mass of the two-way additive is 6% - 8% of the mass of the sludge from the cold rolling wastewater station. When the temperature rises to 75°C, start stirring at a speed of 20 - 30 r / min for 30 - 60 min. Stop stirring when the materials in the preheating tank form a flowing phase, and adjust the end temperature to 80 - 90°C;

[0015] S2. Put the pickling waste liquid into the reaction tank and stir. The mass of the pickling waste liquid is 1% - 2% of the mass of the sludge from the cold rolling wastewater station. The stirring speed is 10 - 20 r / min, and start heating to heat the pickling waste liquid to 50 - 60°C;

[0016] S3. Put the preheated sludge from the cold rolling wastewater station in S1 into the reaction tank and stir. The heating temperature is 70 - 80°C, the stirring speed is 20 - 30 r / min, and the stirring time is 20 - 30 min;

[0017] S4. Put the cold rolling acid-containing wastewater into the reaction tank and stir. The mass ratio of the sludge from the cold rolling wastewater station to the cold rolling acid-containing wastewater is 1:(5 - 10). The stirring speed is 200 - 300 r / min, and the stirring time is 10 - 15 min;

[0018] S5. Supplement the pickling waste liquid into the reaction tank, adjust the initial pH value of the mixed liquid in the reaction tank to be between 0.9 and 2.2, and then stir for 30 min, and then adjust the stirring speed to 60 - 80 r / min;

[0019] S6. Divide the hydrogen peroxide into 10 - 12 portions, add one portion of hydrogen peroxide to the reaction tank every 5 - 10 min. The mass of the hydrogen peroxide is 0.4% - 0.6% of the mass of the sludge from the cold rolling wastewater station. Stop stirring after the addition, and let it stand for 8 - 12 h.

[0020] In S1, the two-way additive is waste glycol, and the waste glycol can be mixed with water in any proportion.

[0021] In S4, the pH value of the cold rolling acid-containing wastewater is 1 - 3;

[0022] In S2, the mass fraction of HCl in the pickling waste liquid is 8% - 12%, and the Fe 2+ concentration is 110 - 130 g / L.

[0023] In S5, for the initial pH value of the mixed liquid, the calculation formula is as follows:

[0024] It is calculated through the following mathematical model:

[0025]

[0026] In Formula ①: C is the concentration of HCl in the pickling waste liquid, with the unit of %; m1 is the mass of the pickling waste liquid, with the unit of kg; pH2 is the pH value of the cold-rolled acid-containing wastewater; m2 is the mass of the cold-rolled acid-containing wastewater, with the unit of kg.

[0027] In S6, the concentration range of hydrogen peroxide is 2.8% - 3.2%.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. By using the self-owned materials of the cold-rolling production line and the wastewater ethylene glycol from the hot-rolling mill and the coking plant, only a small amount of hydrogen peroxide needs to be purchased to realize the self-Fenton reaction of the cold-rolled magnetic filtration sludge.

[0030] 2. Make full use of the iron already existing in the sludge of the cold-rolling wastewater station for the Fenton reaction, reducing the consumption of externally added iron sources.

[0031] 3. Introduce additive wastewater ethylene glycol to achieve the dual effects of improving the fluidity of the cold-rolling wastewater station sludge and promoting its dispersion in the liquid phase.

[0032] 4. Combine with the existing process treatment units of iron and steel enterprises to realize the treatment of the cold-rolling wastewater station sludge, with a simple process and little investment.

[0033] 5. Combine with the inventive material system to establish a simple mathematical model to calculate the initial pH value of the mixed liquid, solving the problem that the pH detector probe is easily wrapped by the oil in the mixed liquid, making it difficult to measure the pH of the mixed liquid. Description of the Drawings

[0034] Figure 1 It is the process flow chart of the Fenton demulsification of the cold-rolling wastewater station sludge. Detailed Embodiments

[0035] The present invention will be described in detail below in conjunction with the drawings of the specification, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0036] A method for Fenton demulsification of oily sludge in a cold rolling wastewater station. At 70 - 80 °C, by utilizing a small amount of iron in the oily sludge, pickling waste liquid and acid-containing wastewater from the cold rolling mill, and additionally adding an appropriate amount of hydrogen peroxide and a two-way additive, the conditions for the Fenton reaction are met, realizing the Fenton reaction of the oily sludge in the cold rolling wastewater, thereby achieving the purpose of demulsification, creating conditions for the subsequent separate treatment of oil, water, and sludge in the cold rolling wastewater station. The demulsified oil is recovered, the generated precipitated sludge is treated by blending with coal, and the demulsified wastewater directly enters the cold rolling wastewater station for treatment, providing an economically reasonable, short-process, and non-secondary-pollution treatment plan for the cold rolling mill to treat such oily sludge, meeting the on-site environmental protection requirements; meanwhile, to solve the problem that the pH detector probe is easily wrapped by oil in the mixed liquid, making it difficult to measure the pH of the mixed liquid, combined with the invention's material system, a simple mathematical model is established to facilitate the determination and adjustment of the initial pH value of the mixed liquid; see Figure 1 , the steps are as follows:

[0037] S1. Put the two-way additive into the preheating tank, and then add the oily sludge from the cold rolling wastewater station. The mass of the two-way additive is 6% - 8% of the mass of the oily sludge from the cold rolling wastewater station. When the temperature rises to 75 °C, start stirring at a stirring speed of 20 - 30 r / min for 30 - 60 min. Stop stirring when the materials in the preheating tank form a flowing phase, and adjust the final temperature to 80 - 90 °C; the two-way additive is ethylene glycol wastewater. The two-way additive is wastewater ethylene glycol, which can be mixed with water in any proportion. The ethylene glycol wastewater is the hydraulic oil of the hot rolling mill and the locomotive of the coking plant. The ethylene glycol wastewater is generated from the regular replacement and external discharge of the two plants and can be mixed with water in any proportion. At the same time, it can act on the cold rolling magnetic filtration oily sludge, making the fluidity of the cold rolling magnetic filtration oily sludge better and increasing its dispersion degree in water.

[0038] S2. Put the pickling waste liquid into the reaction tank and stir. The mass of the pickling waste liquid is 1% - 2% of the mass of the oily sludge from the cold rolling wastewater station, and the stirring speed is 10 - 20 r / min. Start heating and heat the pickling waste liquid to 50 - 60 °C; the mass fraction of HCl in the pickling waste liquid is 8% - 12%, and the Fe 2+ concentration is 110 - 130 g / L.

[0039] S3. Put the preheated oily sludge from the cold rolling wastewater station in step S1 into the reaction tank and stir. The heating temperature is 70 - 80 °C, the stirring speed is 20 - 30 r / min, and the stirring time is 20 - 30 min.

[0040] S4. Put the cold rolling acid-containing wastewater into the reaction tank and stir. The mass ratio of the oily sludge from the cold rolling wastewater station to the cold rolling acid-containing wastewater is 1:(5 - 10), the stirring speed is 200 - 300 r / min, and the stirring time is 10 - 15 min; the pH value of the cold rolling acid-containing wastewater is 1 - 3.

[0041] S5. Supplementary add pickling waste liquid into the reaction tank, adjust the initial pH value of the mixed liquid in the reaction tank to be between 0.9 and 2.2, and then stir for 30 min, and then adjust the stirring speed to 60 - 80 r / min;

[0042] The mass fraction of HCl in the pickling waste liquid is 8% - 12%, and the concentration of Fe2+ is 110 - 130 g / L;

[0043] For the initial pH value of the mixed liquid, since there is a lot of oil in the mixed liquid, it is easy to wrap the pH meter probe and difficult to detect. Combining with the invention material system, it can be calculated through the following mathematical model:

[0044]

[0045] In Model ①: C is the concentration of HCl in the pickling waste liquid, with the unit of %; m1 is the mass of the pickling waste liquid, with the unit of kg; pH2 is the pH value of the cold-rolled acid-containing wastewater; m2 is the mass of the cold-rolled acid-containing wastewater, with the unit of kg.

[0046] S6. Divide the hydrogen peroxide into 10 - 12 portions, add one portion of hydrogen peroxide into the reaction tank every 5 - 10 min. The mass of the hydrogen peroxide is 0.4% - 0.6% of the mass of the oil sludge in the cold-rolled wastewater station. After the addition is completed, stop stirring and let it stand for 8 - 12 h;

[0047] The concentration range of the hydrogen peroxide is 2.8% - 3.2%.

[0048] The following examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are all conventional methods unless otherwise specified.

[0049] Example 1

[0050] A method for Fenton demulsification of oil sludge in a cold-rolled wastewater station, the steps are as follows:

[0051] Add 6 kg of a two-way additive into the preheating tank, and then add 100 kg of oil-filtered sludge from the cold-rolled wastewater station;

[0052] Turn on the heating, set the end temperature to 90 °C. When the temperature rises to 75 °C, start stirring, with the stirring speed of 20 r / min. After stirring for 60 min, the fluidity of the materials in the tank becomes better, and stop stirring;

[0053] Add 2 kg of pickling waste liquid with 12% mass fraction of HCl into the reaction tank, start stirring, with the stirring speed of 20 r / min, turn on the heating, heat the pickling waste liquid to 50 °C. At this time, add the preheated materials in the preheating tank into the reaction tank, set the heating temperature to 80 °C, start stirring, with the stirring speed of 20 r / min, and stir for 30 min;

[0054] Add 1000 kg of cold-rolled acid-containing wastewater with pH = 1 to the reaction tank, adjust the stirring speed to 200 r / min, stir for 15 min, calculate and supplement a small amount of pickling waste liquid, adjust the initial pH of the mixed liquid in the reaction tank to 0.9, continue stirring for 30 min, and then adjust the stirring speed to 60 r / min;

[0055] Add hydrogen peroxide with a mass fraction of 2.8% to the mixed liquid in 12 batches, 5 kg per batch, with an interval of 10 min each time. After the last addition of hydrogen peroxide, stir for 10 min and then stop stirring, and let it stand for 8 h.

[0056] Example 2

[0057] A method for Fenton demulsification of oil sludge in a cold-rolled wastewater treatment station, the steps are as follows:

[0058] Add 7 kg of two-way additive to the preheating tank, and then add 100 kg of oil-filtered sludge from the cold-rolled wastewater treatment station;

[0059] Turn on the heating, set the final temperature to 85 °C. When the temperature rises to 75 °C, start stirring, with a stirring speed of 25 r / min. After stirring for 45 min, the fluidity of the materials in the tank becomes better, and stop stirring;

[0060] Add 1.5 kg of pickling waste liquid with a mass fraction of 10% of HCl to the reaction tank, turn on the stirring, and the stirring speed is 15 r / min;

[0061] Turn on the heating, heat the pickling waste liquid to 55 °C. At this time, add the preheated materials in the preheating tank to the reaction tank, set the heating temperature to 75 °C, and the stirring speed to 25 r / min, and stir for 25 min;

[0062] Add 800 kg of cold-rolled acid-containing wastewater with pH = 2 to the reaction tank, adjust the stirring speed to 250 r / min, stir for 13 min, calculate and supplement a small amount of pickling waste liquid, adjust the initial pH of the mixed liquid in the reaction tank to 1.9, continue stirring for 30 min, and then adjust the stirring speed to 70 r / min;

[0063] Add hydrogen peroxide with a mass fraction of 2.8% to the mixed liquid in 10 batches, 4 kg per batch, with an interval of 8 min each time. After the last addition of hydrogen peroxide, stir for 10 min and then stop stirring, and let it stand for 10 h.

[0064] Example 3

[0065] A method for Fenton demulsification of oil sludge in a cold-rolled wastewater treatment station, the steps are as follows:

[0066] Add 8 kg of two-way additive to the preheating tank, and then add 100 kg of oil-filtered sludge from the cold-rolled wastewater treatment station;

[0067] Turn on the heating and set the final temperature to 80 °C. When the temperature rises to 75 °C, start stirring at a speed of 30 r / min. After stirring for 60 min, the fluidity of the material in the tank becomes better, and then stop stirring.

[0068] Add 1.0 kg of pickling waste liquor with 8% mass fraction of HCl to the reaction tank. Start stirring at a speed of 10 r / min and turn on the heating to heat the pickling waste liquor to 60 °C. At this time, add the preheated material in the preheating tank to the reaction tank. Set the heating temperature to 70 °C, start stirring at a speed of 30 r / min, and stir for 20 min.

[0069] Add 500 kg of cold rolling acid-containing wastewater with pH = 3 to the reaction tank, adjust the stirring speed to 300 r / min, and stir for 10 min. Calculate and supplement a small amount of pickling waste liquor to adjust the initial pH of the mixed solution in the reaction tank to 2.2. After continuing to stir for 30 min, adjust the stirring speed to 80 r / min.

[0070] Add hydrogen peroxide with a mass fraction of 2.8% to the mixed solution in 10 batches, 5 kg per batch, with an interval of 5 min between each batch. After the last addition of hydrogen peroxide, stir for 10 min and then stop stirring. Let it stand for 12 h.

Claims

1. A method for Fenton demulsification of oily sludge in a cold rolling wastewater treatment station, characterized in that, The steps are as follows: S1. Put the two-way additive into the preheating tank, and then add the sludge from the cold rolling wastewater station. The mass of the two-way additive is 6% - 8% of the mass of the sludge from the cold rolling wastewater station. When the temperature rises to 75°C, start stirring at a speed of 20 - 30 r / min for 30 - 60 min. Stop stirring when the materials in the preheating tank form a flowing phase, and adjust the end temperature to 80 - 90°C; S2. Put the pickling waste liquid into the reaction tank and stir. The mass of the pickling waste liquid is 1% - 2% of the mass of the sludge from the cold rolling wastewater station. The stirring speed is 10 - 20 r / min, and start heating to heat the pickling waste liquid to 50 - 60°C; S3. Put the preheated sludge from the cold rolling wastewater station in step S1 into the reaction tank and stir. The heating temperature is 70 - 80°C, the stirring speed is 20 - 30 r / min, and the stirring time is 20 - 30 min; S4. Put the acid-containing cold rolling wastewater into the reaction tank and stir. The mass ratio of the sludge from the cold rolling wastewater station to the acid-containing cold rolling wastewater is 1:(5 - 10). The stirring speed is 200 - 300 r / min, and the stirring time is 10 - 15 min; S5. Supplement the pickling waste liquid into the reaction tank, adjust the initial pH value of the mixed liquid in the reaction tank to be between 0.9 and 2.2, and then stir for 30 min, and then adjust the stirring speed to 60 - 80 r / min; S6. Divide the hydrogen peroxide into 10 - 12 portions, add one portion of hydrogen peroxide to the reaction tank every 5 - 10 min. The mass of the hydrogen peroxide is 0.4% - 0.6% of the mass of the sludge from the cold rolling wastewater station. Stop stirring after the addition is completed and let it stand for 8 - 12 h.

2. The method for Fenton demulsification of oily sludge in a cold rolling wastewater treatment station according to claim 1, characterized in that, In S1, the two-way additive is waste water ethylene glycol, and the waste water ethylene glycol can be mixed with water in any proportion.

3. The method for Fenton demulsification of oil sludge in a cold rolling wastewater station according to claim 1, characterized in that, In S4, the pH value of the acid-containing cold rolling wastewater is 1 - 3.

4. A method for Fenton demulsification of oily sludge in a cold rolling wastewater station according to claim 1, characterized in that, In S2, the mass fraction of HCl in the pickling waste liquid is 8% - 12%, and the Fe 2+ concentration is 110 - 130 g / L.

5. A method for Fenton demulsification of oily sludge in a cold rolling wastewater treatment station according to claim 1, characterized in that, In S5, the calculation formula for the initial pH value of the mixed liquid is as follows: It is calculated through the following mathematical model: In formula ①: C is the concentration of HCl in the pickling waste liquid, in %; m1 is the mass of the pickling waste liquid, in kg; pH2 is the pH value of the acid-containing cold rolling wastewater; m2 is the mass of the acid-containing cold rolling wastewater, in kg.

6. The method for Fenton demulsification of oily sludge in a cold rolling wastewater station according to claim 1, wherein In S6, the concentration range of the hydrogen peroxide is 2.8% - 3.2%.

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