Pretreatment method before recycling of petrochemical sewage

Abstract

The invention relates to a pretreatment method before petrochemical sewage reuse, which comprises the following steps: mixing petrochemical sewage, a flocculating agent and an electrostatic regulator in a high-density tank, reacting for 1-10 minutes after the pH value of the petrochemical sewage obtained by mixing is 7.0-8.8, adding a softening agent, an alkaline agent and a coagulant aid to regulate the pH value of the petrochemical sewage obtained by mixing reaction to 9.5-10.6, and then adding a flocculating agent and an electrostatic regulator to react for 1-10 minutes after the pH value of the petrochemical sewage obtained by mixing reaction is 9.5-10.6. Softening, settling and carrying out solid-liquid separation; wherein the flocculant is an inorganic polymeric flocculant; the coagulant aid contains an organic polymer coagulant aid; the electrostatic conditioning agent contains a compound with a structural formula of NH-{R-NH-(CH2CH2O) n-[(CH2CH (CH3) O] m-H} 2, R is one or two of-C2H < 4 >-,-C2H < 4 > NHC < 2 > H < 4 >-,-C2H < 4 > NHC < 2 > H < 4 >-and-C2H < 4 > NHC < 2 > H < 4 >-, n is selected from integers of 0-50, m is selected from integers of 0-50, and m and n are not 0 at the same time. The method disclosed by the invention is low in treatment cost and good in treatment effect, can remove suspended matters, hard matters, part of macromolecular organic matters and water treatment agents in the petrochemical sewage under the condition of relatively low pH value, and meanwhile, reduces the problem of membrane pollution and blockage of a subsequent membrane treatment unit.

Description

Technical Field

[0001] The present application relates to a pretreatment method for petrochemical wastewater before reuse. Background Art

[0002] The use of sewage reuse technology to treat sewage and recycle it can not only save a lot of water resources, but also significantly reduce sewage discharge, thus becoming the focus of water conservation and emission reduction for industrial enterprises.

[0003] After years of efforts, sewage reuse technology has made great progress, forming two mainstream technologies: moderate sewage treatment and reuse for circulating cooling water system and deep sewage treatment for boiler feed water. Among them, deep sewage treatment technology mostly adopts double membrane treatment process with reverse osmosis as the core, such as:

[0004] A. The article "Desalination of Recycled Water from Refinery Wastewater" in the 2006 Vol. 29, No. 2 of Petrochemical Environmental Protection introduced that Yanhua Company used ultrafiltration + reverse osmosis to treat the recycled water from its refinery wastewater and then reused it in the boiler.

[0005] B. The article "Technology of Deep Treatment of Wastewater for Reuse in Medium-Pressure Boilers of Power Plants" in "Industrial Water Treatment" Vol. 25, No. 6, 2005 introduced the engineering technology of reuse of mixed wastewater from refining, chemical and domestic products in medium-pressure boilers of power plants after deep treatment.

[0006] The UF membrane + RO membrane water treatment technology has a simple process, high separation efficiency, good effluent quality, and small footprint. However, when applied to the sewage reuse pretreatment process, the biggest threat is that high concentrations of pollutants in the sewage will cause membrane fouling, resulting in membrane flux attenuation, shortened backwashing and chemical cleaning cycles, and reduced water production and service life. The pore size of the UF membrane is between 0.01-0.05μm, which separates substances such as proteins, colloids, bacteria, and macromolecular organic matter. When the concentration of suspended matter, polymer compounds, and microorganisms is high, it is easy to block the UF membrane, resulting in a sharp drop in the permeability of the UF membrane, or when there is a strong adsorption effect between the organic components in the sewage and the membrane material, an adsorption layer will also be formed on the surface of the UF membrane, causing concentration polarization. During the operation of the RO membrane, as the concentration of pollutants increases, suspended particles will precipitate on the membrane, blocking the water inlet flow channel, increasing friction resistance (pressure drop), and insoluble salts will precipitate from the concentrated water to form scale on the membrane surface. The most common insoluble salts are calcium carbonate scale, magnesium hydroxide precipitation, barium sediment, strontium sediment, etc.

[0007] Therefore, in order to ensure the long-term stable operation of the double membrane system, it is necessary to remove suspended matter, hardness and certain macromolecular organic matter (colloids) in the sewage in advance to meet the requirements of double membrane treatment and reuse.

[0008] Under the general background of water conservation and emission reduction in petrochemical enterprises, the headquarters requires that the enterprise's wastewater reuse rate be greater than 60%. After multiple cycles and concentration, the wastewater, after being treated in the sewage treatment plant, contains not only suspended matter and COD, but also relatively high calcium and magnesium ions. It also contains water treatment agents added in the early process, such as: polymer scale inhibitors and dispersants, macromolecular corrosion inhibitors, pre-filming agents, etc. The presence of these agents will stably disperse suspended matter, calcium and magnesium ions in the water, maintain the supersaturated state of the solution, make it difficult to remove hardness, and the effect of removing suspended matter and colloids is poor.

[0009] The hardness removal boundary conditions are determined according to the requirements of each enterprise's sewage entering the double membrane. Generally, the total hardness is required to be less than 80-100 mg / L. To meet this requirement, the pH value of the high-density sedimentation tank for conventional biochemical effluent is generally controlled at around 10.6-11.0, while the pH value of the high-density sedimentation tank for treating petrochemical wastewater containing water treatment agents often needs to be controlled to 11.0-11.5. The consumption of chemicals is huge, which brings great trouble to on-site operation and management.

[0010] CN 114702158A A device and method for integrated desiliconization and hardness removal introduces a method of sequentially passing high-silicon and high-hardness wastewater into a regulating tank, a hardness removal tank, a silicon removal tank, a coagulation tank, a flocculation tank and a sedimentation tank, so that the hardness removal products and desiliconization products formed after the high-silicon and high-hardness wastewater is desiliconized and removed are coagulated in the same coagulation tank and flocculated in the same flocculation tank, and then settled in the same sedimentation tank and separated from the water phase. The pH value of the regulating tank is controlled at 11-12 in this patent.

[0011] The article "Analysis on the Hardness Removal Effect of Pretreatment of Circulating Water and Wastewater from Coking Plants" published in the third issue of Resources and Environment in 2020, aimed at the high hardness and high alkalinity of circulating water and wastewater from coking plants, and adopted the method of adding double alkali "Na 2 CO 3 +NaOH" + PAM was used for pretreatment, and HCl was used for neutralization after treatment. The effluent was always hard (measured in CaCO 3 Calculation) < 80mg / L, Na 2 CO 3 The average addition amount is 432 mg / L, and the pH value needs to be adjusted to 11.0-11.5.

[0012] The article "Research on the dosage of reagents for the hardness removal process of circulating water and sewage" published in the 7th issue of "Industrial Safety and Environmental Protection" in 2023 summarizes the water hardness removal process in current water treatment technology based on the high hardness of circulating cooling water. It also conducts experimental research on the dosage of reagents for the hardness removal process of circulating water and sewage in the recycling and reuse process. The total hardness of the effluent (measured in CaCO 3 If the hardness of the effluent water is lower than 100mg / L and the dosage of sodium carbonate is 300mg / L, the pH value needs to be adjusted to 10.7-10.8. If the hardness of the effluent water is further reduced, the pH value needs to be further increased. Summary of the invention

[0013] The purpose of the present disclosure is to provide a pretreatment method for petrochemical wastewater before reuse. The method has low treatment cost and can remove suspended matter, hardness, and some macromolecular organic matter in petrochemical wastewater under relatively low pH conditions, while reducing the membrane fouling problem of subsequent membrane treatment units.

[0014] In order to achieve the above-mentioned object, the present invention provides a pretreatment method for petrochemical wastewater before reuse, which comprises: in a high-density tank, petrochemical wastewater, a flocculant and an electrostatic regulator are mixed, the pH value of the mixed petrochemical wastewater is 7.0-8.8, and after reacting for 1-10 minutes, a softener, an alkali agent and a coagulant are added to adjust the pH value of the mixed petrochemical wastewater to 9.5-10.6, and softening, sedimentation and solid-liquid separation are performed; wherein the flocculant contains an inorganic polymer flocculant; the coagulant contains an organic polymer coagulant; the electrostatic regulator contains a structural formula of NH-{R-NH-(CH 2 CH 2 O) n -[(CH 2 CH(CH 3 )O] m -H} 2 The compound, R is -C 2 H 4 -、-C 2 H 4 NHC 2 H 4 -、-C 2 H 4 NHC 2 H 4 NHC 2 H 4 -and-C 2 H 4 NHC 2 H 4 NHC 2 H 4 NHC 2 H 4 -, n is selected from an integer of 0-50, m is selected from an integer of 0-50, and m and n are not 0 at the same time.

[0015] Through the above technical solution, the method disclosed in the present invention has the following advantages:

[0016] (1) The method disclosed in the present invention can remove the hardness of sewage within a relatively low pH range of 9.5-10.6, has simple operation, good treatment effect, and low reagent cost.

[0017] (2) The method disclosed in the present invention can effectively remove suspended solids, some water treatment agents, and macromolecular COD colloids in sewage. The large number of hydrophilic ether bonds in the electrostatic regulator molecules can help macromolecular organic matter such as polyacrylamide to be carried away from the membrane surface by the shear flow of the membrane, thereby reducing pollution to the membrane.

[0018] (3) The method disclosed in the present invention can render some impurities in sewage in a non-cationic state, thereby increasing repellency with membrane materials, reducing adsorption on the membrane surface, and thereby reducing the occurrence of membrane fouling.

[0019] Other features and advantages of the present disclosure will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0020] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0021] The present invention provides a pretreatment method for petrochemical wastewater before reuse, which comprises: in a high-density tank, petrochemical wastewater, a flocculant and an electrostatic regulator are mixed, the pH value of the mixed petrochemical wastewater is 7.0-8.8, and the mixture is reacted for 1-10 minutes, a softener, an alkali agent and a coagulant are added to adjust the pH value of the mixed petrochemical wastewater to 9.5-10.6, and softening, sedimentation and solid-liquid separation are performed; wherein the flocculant contains an inorganic polymer flocculant; the coagulant contains an organic polymer coagulant; the electrostatic regulator contains a structural formula of NH-{R-NH-(CH 2 CH 2 O) n -[(CH 2 CH(CH 3 )O] m -H} 2 The compound, R is -C 2 H 4 -、-C 2 H 4 NHC 2 H 4 -、-C 2 H 4 NHC 2 H 4 NHC 2 H 4 -and-C 2 H 4 NHC 2 H 4 NHC 2 H 4 NHC 2 H 4-, n is selected from an integer of 0-50, m is selected from an integer of 0-50, and m and n are not 0 at the same time.

[0022] In the present disclosure, the pH value of the mixed petrochemical wastewater is 7.0-8.8, which is the natural pH value after the petrochemical wastewater, flocculant and electrostatic regulator are mixed, and no additional pH auxiliary adjustment step is required.

[0023] The inventors of the present disclosure have found that the method of the present disclosure can be used to treat petrochemical wastewater. Through the synergistic effect of the composite water treatment agent, on the one hand, it can produce precipitation with COD (part of the water treatment agent) in the water, and on the other hand, it can well compress the double electric layer, increase antistatic and permeability, overcome the repulsion between colloids and particles, promote the aggregation of precipitation, and the generated flocs can further adsorb and sweep macromolecular organic matter in the water. The large number of hydrophilic ether bonds in the electrostatic regulator molecules can make some impurities in the sewage in a non-cationic state, helping the pollutants in the sewage to be carried away from the membrane surface with the shear flow, thereby reducing membrane pollution.

[0024] And in actual industrial production, the hardness removal unit needs to add alkali to adjust the pH value of the sewage, usually using a double alkali method (sodium hydroxide + sodium carbonate) for hardness removal. When adjusting the pH value, the amount of alkali added needs to be increased by 10 times for every unit increase in the pH value in the alkaline aqueous solution, and the higher the pH value, the stronger the buffering capacity of the water, the greater the consumption of alkalinity by other ions in the water, and the greater the amount of alkali added, especially for sewage containing water treatment agents. After the sewage is treated for hardness removal, the pH value of the sewage needs to be adjusted to neutral with acid before the subsequent membrane treatment unit. The amount of acid and alkali consumed in this process is very large, and the cost of traditional petrochemical sewage treatment methods is relatively high. The method disclosed in the present invention is simple and low in cost, and can remove suspended matter, hardness, some macromolecular organic matter and water treatment agents in petrochemical sewage under relatively low pH conditions, while reducing the problem of membrane fouling in subsequent membrane treatment units.

[0025] In a specific embodiment of the present disclosure, the static control agent contains a multi-branched nonionic compound, which is generated by reacting polyethylene polyamine as an initiator with ethylene oxide and propylene oxide. In a preferred specific embodiment of the present disclosure, the static control agent contains polyethylene polyamine polyoxyethylene ether and / or polyethylene polyamine polyoxypropylene ether synthesized using ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, etc. as initiators.

[0026] According to the present disclosure, the softener can be a carbonate, and the alkali agent can be a hydroxide. In a specific embodiment of the present disclosure, the softener is selected from one or more of sodium carbonate, potassium carbonate and sodium bicarbonate, preferably sodium carbonate; the alkali agent is selected from one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide.

[0027] According to the present disclosure, the dosage of the softener in the method of the present disclosure can vary in a wide range according to actual water treatment needs, for example, it can be 0-800 mg / L, preferably 50-300 mg / L.

[0028] According to the present disclosure, the mass concentration of flocculant refers to the mass of flocculant added to petrochemical wastewater per unit volume, and the mass concentration of coagulant aid refers to the mass of coagulant aid added to petrochemical wastewater per unit volume. The mass concentration of flocculant and the mass concentration of coagulant aid can vary within a wide range. In one embodiment, the mass concentration of flocculant is 5-300 mg / L, preferably 20-150 mg / L, and the mass concentration of coagulant aid is 0.2-5 mg / L, preferably 0.5-2 mg / L.

[0029] According to the present disclosure, the mass concentration of the flocculant and the mass concentration of the coagulant aid can vary within a wide range. In a preferred specific embodiment of the present disclosure, the ratio of the mass concentration of the flocculant to the mass concentration of the coagulant aid is (10-400):1, preferably (30-150):1. In this embodiment, the ratio of the amount of flocculant to the coagulant aid is appropriate, which can more effectively remove suspended matter, hardness, some macromolecular organic matter and water treatment agents in petrochemical wastewater, while reducing the membrane fouling problem of subsequent membrane treatment units.

[0030] According to the present disclosure, the mass concentration of the electrostatic regulator refers to the mass of the electrostatic regulator added to the petrochemical wastewater per unit volume, and the mass concentration of the electrostatic regulator can vary within a large range. In one embodiment, the mass concentration of the electrostatic regulator is 1-30 mg / L, preferably 2-20 mg / L.

[0031] In a specific embodiment of the present disclosure, the ratio of the mass concentration of the electrostatic regulator to the mass concentration of COD in the petrochemical wastewater is (0.01-0.40):1, preferably (0.05-0.3):1; in this embodiment, the usage ratio of the electrostatic regulator to the COD in the petrochemical wastewater is appropriate, which can more effectively remove suspended matter, hardness, some macromolecular organic matter and water treatment agents in the petrochemical wastewater, while reducing the membrane fouling problem of the subsequent membrane treatment unit.

[0032] In a specific embodiment of the present disclosure, the inorganic polymer flocculant is selected from polyaluminum salts and / or polyferric salts; preferably, the inorganic polymer flocculant is selected from one or more of polyaluminum sulfate, polyaluminum chloride, polyaluminum ferric chloride, polyaluminum silicate sulfate, polyferric sulfate and polyferric chloride, preferably one or more of polyaluminum chloride, polyaluminum sulfate, polyferric chloride and polyferric sulfate.

[0033] In a specific embodiment of the present disclosure, the organic polymer coagulant is anionic polyacrylamide and / or nonionic polyacrylamide, preferably anionic polyacrylamide. Because the surface charge of the reverse osmosis membrane (RO membrane) of the membrane treatment unit is negative, in order to prevent the cationic coagulant from being strongly adsorbed and deposited on the membrane surface, anionic polyacrylamide is selected as the organic polymer coagulant. According to the present disclosure, the number average molecular weight of the organic polymer coagulant is 1 million to 50 million, preferably 3 million to 40 million.

[0034] In a specific embodiment of the present disclosure, n is selected from an integer of 0-50, preferably an integer of 5-20, m is selected from an integer of 0-50, preferably an integer of 5-20, and m and n are not 0 at the same time, and the relative molecular mass is 2000-6000.

[0035] According to the present disclosure, the high-density tank is a device for water treatment well known to those skilled in the art. In a specific embodiment of the present disclosure, the conditions for water treatment in the high-density tank include: a total residence time of 5-100 min, preferably 10-40 min.

[0036] According to the present disclosure, the method of the present disclosure can treat the effluent from a petrochemical sewage treatment plant containing one or more of the effluent from a biological secondary sedimentation tank, circulating water wastewater and double membrane backwash water. The pretreatment method of the present disclosure is particularly suitable for treating petrochemical sewage containing water treatment agents, and has a better treatment effect.

[0037] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0038] The raw materials used in the following examples and comparative examples are commercially available unless otherwise specified. The following examples and comparative examples treat wastewater from a petrochemical plant (including biochemical effluent, circulating water wastewater, backwash water and other mixed wastewater), and the water quality of the petrochemical plant wastewater is shown in Table 1.

[0039] Table 1

[0040] parameter Analyzing the values pH 8.6 Oil (mg / L) 0.3 COD(mg / L) 58.6 Conductivity / (μS / cm) 1570 <![CDATA[Total hardness (mg / L, CaCO 3 calculated)]]> 325.6 <![CDATA[Alkalinity (mg / L, CaCO 3 equivalent)]]> 149.8 Total phosphorus (mg / L) 10.9 Organic phosphorus (mg / L) 0.6 Suspended matter (mg / L) 45

[0041] Example 1

[0042] In the high-density pool, 80 mg / L of polyaluminium chloride (PAC) and 10 mg / L of tetraethylene pentamine polyoxyethylene polyoxypropylene ether (R: -C 2 H 4 NHC 2 H 4 NHC 2 H 4 NHC 2 H 4-, n is 40-50, m is 10-20), the pH value of the petrochemical wastewater obtained by mixing is 7.9, after the mixing reaction for 5 minutes, sodium carbonate with a mass concentration of 200 mg / L, anionic polyacrylamide with a mass concentration of 2 mg / L, and sodium hydroxide are added to adjust the pH value of the petrochemical wastewater to 10.3, and the total retention time of the petrochemical wastewater in the high-density tank is 30 minutes. The total hardness, COD, total phosphorus, organic phosphorus, and suspended solids content of the petrochemical wastewater after the above treatment are shown in Table 2, the same below.

[0043] Example 2

[0044] The petrochemical wastewater was treated in the same manner as in Example 1, except that the dosage of sodium carbonate was 300 mg / L.

[0045] Example 3

[0046] The petrochemical wastewater was treated in the same manner as in Example 1, except that the dosage of the flocculant PAC was 110 mg / L.

[0047] Example 4

[0048] The petrochemical wastewater was treated in the same manner as in Example 1, except that the dosage of the coagulant cationic polyacrylamide was 1 mg / L.

[0049] Example 5

[0050] The petrochemical wastewater was treated in the same manner as in Example 1, except that the dosage of the polyethylene polyamine polyoxyethylene ether was 5 mg / L.

[0051] Example 6

[0052] The petrochemical wastewater was treated in the same manner as in Example 1, except that the total residence time of the wastewater in the high-density tank was 15 minutes.

[0053] Example 7

[0054] The simulated wastewater was treated in the same manner as in Example 1, except that the total hardness of the simulated wastewater was 325 mg / L and the wastewater did not contain a water treatment agent.

[0055] Comparative Example 1

[0056] The petrochemical wastewater was treated in the same manner as in Example 1, except that polyethylene polyamine polyoxyethylene ether was not added.

[0057] Comparative Example 2

[0058] The simulated wastewater was treated in the same manner as in Example 7, except that polyethylene polyamine polyoxyethylene ether was not added.

[0059] Comparative Example 3

[0060] The petrochemical wastewater was treated in the same manner as in Example 1, except that 4.0 mg / L of sorbitan fatty acid ester polyoxyethylene ether + 6.0 mg / L of polyethylene glycol 400 was used instead of polyethylene polyamine polyoxyethylene ether.

[0061] Test Example 1

[0062] The treated sewage was subjected to a dynamic simulation of the full cycle to investigate the changes in membrane flux.

[0063] 10 L of petrochemical wastewater treated in Example 1 was added to the water tank, and the pH value was adjusted to 7.5. Under the conditions of initial water inlet flow rate of 0.7 L / min and 25°C, full circulation operation was carried out. During the operation, all concentrated drainage and clean water were returned to the water tank to keep the water quality of the water sample constant. The water production flow rate (L / min) was recorded every 4 h, and the membrane flux % was calculated. Membrane flux % = water production flux / water production flux at the start of the reverse osmosis membrane pollution test operation × 100.

[0064] Experimental results: Membrane flux decrease: 2.4% in 4h; 3.7% in 8h; 5.8% in 12h.

[0065] Test Example 2

[0066] The treated sewage was subjected to a dynamic simulation of the full cycle to investigate the changes in membrane flux.

[0067] 10L of petrochemical wastewater treated in Comparative Example 1 was added to the water tank, and the pH value was adjusted to 7.5. Under the conditions of initial water inlet flow rate of 0.7L / min and 25°C, full circulation operation was carried out. During the operation, all concentrated drainage water and clean water were returned to the water tank to keep the water quality of the water sample constant. The water production flow rate (L / min) was recorded every 4h, and the membrane flux% was calculated. Membrane flux%=water production flux / water production flux at the start of the reverse osmosis membrane pollution test operation×100.

[0068] Experimental results: Membrane flux decrease: 4h 6.7%; 8h 9.9%; 12h 15.4%.

[0069] Test Example 3

[0070] The treated sewage was subjected to a dynamic simulation of the full cycle to investigate the changes in membrane flux.

[0071] 10L of petrochemical wastewater treated in Comparative Example 3 was added to the water tank, and the pH value was adjusted to 7.5. Under the conditions of initial water inlet flow rate of 0.7L / min and 25°C, full circulation operation was carried out. During the operation, all concentrated drainage water and clean water were returned to the water tank to keep the water quality of the water sample constant. The water production flow rate (L / min) was recorded every 4h, and the membrane flux% was calculated. Membrane flux%=water production flux / water production flux at the start of the reverse osmosis membrane pollution test operation×100.

[0072] Experimental results: membrane flux decreases by 5.2% after 4 hours, 7.1% after 8 hours, and 10.2% after 12 hours.

[0073] Table 2

[0074]

[0075] From the comparison between Examples 1-6 and Comparative Examples 1 and 3, it can be seen that the methods disclosed in Examples 1-6 can effectively reduce the total hardness, COD value, total phosphorus, organic phosphorus and suspended solids of petrochemical wastewater, which is better than the treatment effect of the methods in Comparative Examples 1 and 3 on wastewater. Among them, the simulated wastewater treated in Example 7 does not contain a water treatment agent, and polyethylene polyamine polyoxyethylene ether is used in its treatment process; Comparative Example 2 treats the same simulated wastewater as Example 7, and polyethylene polyamine polyoxyethylene ether is not used in its treatment process. From the comparison of the treatment results of Example 7 and Comparative Example 2, it can be seen that polyethylene polyamine polyoxyethylene ether has an excellent effect on treating petrochemical wastewater containing a water treatment agent (such as a scale inhibitor dispersant).

[0076] Furthermore, from the comparison of test examples 1, 2, and 3, it can be seen that the method disclosed in the present invention can reduce the adsorption of solutes in sewage on the membrane surface, thereby effectively avoiding membrane fouling.

[0077] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0078] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0079] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A pretreatment method for petrochemical wastewater before reuse, the method comprising: In a high-density tank, petrochemical sewage, flocculant and electrostatic regulator are mixed, the pH value of the mixed petrochemical sewage is 7.0-8.8 and reacted for 1-10 minutes, then softener, alkali agent and coagulant are added to adjust the pH value of the mixed petrochemical sewage to 9.5-10.6, and softening, sedimentation and solid-liquid separation are performed; Wherein, the flocculant contains an inorganic polymer flocculant; the coagulant aid contains an organic polymer coagulant aid; the electrostatic regulator contains a structural formula of NH-{R-NH-(CH2CH2O) n -[(CH2CH(CH3)O] m -H}2, R is one or two of -C2H4-, -C2H4NHC2H4-, -C2H4NHC2H4NHC2H4- and -C2H4NHC2H4NHC2H4NHC2H4-, n is selected from an integer of 0-50, m is selected from an integer of 0-50, and m and n are not 0 at the same time.

2. The pretreatment method according to claim 1, wherein: The static regulator contains a multi-branched nonionic compound, which is generated by polymerization reaction of polyethylene polyamine as an initiator with ethylene oxide and / or propylene oxide; the polyethylene polyamine is selected from one or more of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

3. The pretreatment method according to claim 1, wherein: The static regulator is polyethylene polyamine polyoxyethylene ether and / or polyethylene polyamine polyoxypropylene ether.

4. The pretreatment method according to claim 1, wherein: The ratio of the mass concentration of the flocculant to the mass concentration of the coagulant aid is (10-400):1, preferably (30-150):

1.

5. The pretreatment method according to claim 4, wherein: The mass concentration of the flocculant added to the petrochemical wastewater is 5-300 mg / L, preferably 20-150 mg / L; the mass concentration of the coagulant aid is 0.2-5 mg / L, preferably 0.5-2 mg / L.

6. The pretreatment method according to claim 1, wherein: The ratio of the mass concentration of the electrostatic regulator to the mass concentration of COD in the petrochemical wastewater is (0.01-0.40):1, preferably (0.05-0.3):1; the mass concentration of the electrostatic regulator added to the petrochemical wastewater is 1-30 mg / L, preferably 2-20 mg / L.

7. The pretreatment method according to claim 1, wherein: The inorganic polymer flocculant is selected from one or more of polyaluminium sulfate, polyaluminium chloride, polyaluminium ferric chloride, polyaluminium silicate sulfate, polyferric sulfate and polyferric chloride, preferably one or more of polyaluminium chloride, polyaluminium sulfate, polyferric chloride and polyferric sulfate; The organic polymer coagulant aid is anionic polyacrylamide and / or nonionic polyacrylamide, preferably anionic polyacrylamide; the number average molecular weight of the organic polymer coagulant aid is 1 million to 50 million, preferably 3 million to 40 million.

8. The pretreatment method according to claim 1, wherein: The softener is selected from one or more of sodium carbonate, potassium carbonate and sodium bicarbonate; the alkali agent is selected from one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide.

9. The pretreatment method according to claim 1, wherein: n is selected from an integer of 5-20, m is selected from an integer of 5-20, and the relative molecular mass is 2000-6000.

10. The pretreatment method according to claim 1, wherein: The conditions for water treatment in the high-density pool include: a total residence time of 5-100 min, preferably 10-40 min.

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