Preparation method of tank bottom oil sludge cleaning agent, cleaning agent and tank bottom oil sludge cleaning process

Abstract

The present invention discloses a method for preparing a tank bottom oil sludge cleaning agent, a cleaning agent and a tank bottom oil sludge cleaning process. The tank bottom oil sludge cleaning process comprises the following steps: S1: dispersion pretreatment of tank bottom oil sludge; S2: dissociation of oil-containing mud sand particles that are difficult to disperse; S3: micro separation of oil, water and mud based on friction assistance; S4: deep separation of oil, water and mud based on three-phase horizontal tank centrifugation; S5: recycling and reuse of the separated three phases. The cleaning process of the present invention is simple, has good treatment effect, does not introduce new pollutants, and can achieve resource recycling and reuse.

Description

Technical Field

[0001] The present application relates to the field of sludge treatment, and in particular to a method for preparing a tank bottom sludge cleaning agent, a cleaning agent and a tank bottom sludge cleaning process. Background Art

[0002] Tank bottom sludge refers to the viscous sludge with high viscosity formed at the bottom of the oil tank due to long-term natural sedimentation of mechanical impurities, soil, paraffin and other heavy components in the oil when the oil tank is storing oil. The amount of tank bottom sludge is increasing with the continuous collection and transportation of oil, which will directly affect the tank volume and the back-end collection and transportation processing. Therefore, it is necessary to invest a lot of manpower and material resources to regularly clean up this part of the tank bottom sludge.

[0003] This part of oil sludge has a large by-product in all major oil fields. Due to its high oil content, complex composition and difficulty in treatment, it has become a major problem in the current solid waste treatment. At present, both at home and abroad, research on the treatment of oil sludge with a high degree of aging, such as tank bottom sludge, is more important. Foreign countries have studied the treatment technology of tank bottom sludge earlier than my country, especially in the United States, Canada, Denmark and other European and American countries, where the technology is relatively mature.

[0004] my country started research on oily sludge treatment technology relatively late, especially for oily sludge with a high degree of aging. At present, the main treatment method adopted is centralized stacking and drying, and then centralized landfill. However, most of them have certain limitations, such as complex process, difficult management, too high construction investment and operation cost, limited treatment capacity, long treatment cycle, or the oily sludge needs further harmless treatment after treatment. Therefore, the centralized stacking and landfilling method widely used in my country cannot effectively solve the problem. The petroleum hydrocarbons contained in the oily sludge will enter the soil and groundwater, causing serious harm to the surrounding environment.

[0005] With the rapid development of my country's economy and the increasing attention to environmental protection, how to effectively solve the problem of tank bottom oil sludge discharge has always been the focus of the petroleum industry and even the country. The country has successively issued laws and regulations such as the "Land Reclamation Regulations", "National List of Hazardous Wastes", and "Hazardous Waste Storage Pollution Control Standards". According to the definition of oily sludge in the "National Hazardous Waste List", oily sludge is a hazardous waste. The "National Clean Production Promotion Law" requires that oily sludge must be harmlessly treated. According to the "Standards for Pollutant Control in Agricultural Sludge" (GB4284-1984), the maximum allowable amount of mineral oil in sludge shall not exceed 3000mg / kg. However, the maximum allowable amount of mineral oil in sludge treated by the centralized stacking and drying technology in the existing technology often exceeds the national standard.

[0006] Therefore, there is an urgent need for a treatment method that can reasonably treat the tank bottom sludge and realize resource recycling and reuse. Summary of the invention

[0007] In order to help treat the tank bottom sludge with large output, high oil content and complex composition in major oil fields, and considering that the amount of sludge in each oil transfer station and joint station is small and is cleaned regularly every year, the present invention provides a method for preparing a tank bottom sludge cleaning agent, a cleaning agent and a tank bottom sludge cleaning process which have simple treatment process, good treatment effect, will not introduce new pollutants and can achieve resource recovery and reuse.

[0008] The present invention adopts the following technical solution:

[0009] The preparation method of the tank bottom sludge cleaning agent is as follows: firstly, 20wt% of waste rubber cracking oil and 30wt% of heavy tar are mixed evenly, and then 45wt% of water glass and 5wt% of non-ionic surfactant are added, and emulsified and dispersed to form a black emulsion dispersion.

[0010] A further improvement to the above technical solution is that the nonionic surfactant is prepared by mixing fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether in a water glass solution with a modulus of 2.4±1 and a concentration of 15-25wt% in a weight ratio of 3:1, and adding cationic flocculant polyacrylamide; the amount of the cationic flocculant polyacrylamide is 1-3wt‰ of the weight of the tank bottom sludge to be treated.

[0011] The tank bottom sludge cleaning agent is prepared according to the above preparation method.

[0012] The tank bottom sludge cleaning process includes the following steps:

[0013] S1: Dispersion pretreatment of tank bottom oil sludge; S2: Dissociation of oil-containing mud and sand particles that are difficult to disperse; S3: Friction-assisted micro separation of oil, water and mud; S4: Deep separation of oil, water and mud based on three-phase horizontal tank centrifugation; S5: Recycling of the separated three phases.

[0014] A further improvement to the above technical solution is that the specific process of S1 is to input the tank bottom sludge into the cleaning kettle through a vacuum pump, add hot water into the cleaning kettle, and stir at a stirring speed of 200-400r / min and a stirring time of 5min-6min to achieve dispersed pretreatment of the tank bottom sludge.

[0015] A further improvement to the above technical solution is that the specific process of S2 is to add organic acid to the S1 system and stir it at a stirring speed of 200-400r / min and a stirring time of 5min-6min, so that some of the oil-containing mud and sand particles in S1 that are difficult to disperse and are coated in the oil mud are dispersed, thereby achieving the dissociation of the oil-containing mud and sand particles.

[0016] A further improvement to the above technical solution is that the specific process of S3 is to add the above cleaning agent into the cleaning kettle and stir for 10-15 minutes to achieve friction-assisted micro-separation of the three phases of oil, water and mud.

[0017] A further improvement to the above technical solution is that the specific process of S4 is to screen out the large muddy impurities after micro-separation through a vibrating screen, and pump the water, oil and fine mud into a three-phase horizontal tank centrifuge to achieve deep separation of the three phases of oil, water and mud.

[0018] A further improvement to the above technical solution is that the specific process of S5 is that after deep separation, the oil phase is in the top layer, the water phase is in the middle layer, and the solid phase is in the bottom layer; the separated oil phase is directly input into the oil gathering and processing system within the station, the water phase enters the sewage treatment system within the station, and the solid phase mud and sand can be directly discharged after natural drying.

[0019] A further improvement to the above technical solution is that in S2, the organic acid is gluconic acid, and the added weight is 1-5wt‰ of the weight of the tank bottom sludge.

[0020] The beneficial effects of the present invention are:

[0021] 1. The tank bottom sludge treatment of the present invention adopts an intermittent treatment process, a skid-mounted movable structure, and is moved according to the area where each station is located to treat the tank bottom sludge on site. Therefore, for the intermittent treatment of tank bottom sludge at the joint station and oil transfer station of different oil fields, the operation is convenient, the full utilization rate of the equipment is ensured, the treatment cost is saved, and it has good technical and economic benefits.

[0022] 2. The treatment process of the present invention makes full use of the hot water and oil-water treatment systems of the joint station and the oil transfer station. The oil sludge at the bottom of the tank can first be directly reduced in viscosity and dispersed using the hot water in the station. The treated oil phase can directly enter the oil gathering and transportation treatment system in the station, and the sewage enters the sewage treatment system in the station. The sludge can be discharged after natural drying.

[0023] 3. The treatment process provided by the present invention can separate the treated tank bottom sludge into water phase, oil phase and solid phase. The water phase directly enters the sewage treatment system, and the oil phase can directly enter the oil gathering and transportation treatment system in the station. It not only solves the problem of reducing the amount of sludge and meeting the discharge standards, but also recovers a large amount of oil resources contained in the sludge, creates certain economic benefits, and realizes resource recovery and reuse.

[0024] 4. The specific engineering process of the treatment process of the present invention is that, since the tank bottom sludge has a long storage time and high viscosity, the function of the treatment process S1 of the present invention is to use a certain amount of hot water (60°C) to reduce the viscosity of the sludge. The use of 60°C hot water is mainly due to the cloud point temperature (80°C) of the cleaning agent used later. If the temperature exceeds the cloud point temperature, the cleaning effect of the cleaning agent will be greatly reduced. Therefore, the hot water temperature is controlled at 60°C, and the subsequent cleaning effect is the best. After S1, since the tank bottom sludge contains various agents added during the oil collection process, the composition is complex, and after a long period of sedimentation, part of the sludge is difficult to disperse and is wrapped in the sludge to form a relatively stable colloidal system. In particular, FeS substances are formed under the action of microorganisms. It is difficult to completely separate them by ordinary cleaning methods. Therefore, S2 is used to dissociate the oil-containing mud sand particles in the tank bottom sludge that are difficult to disperse by organic acid. After dissociation, a cleaning agent is added to S3 for three-phase micro-separation. On the one hand, water glass has a certain alkalinity, which is easy to clean the oil. On the other hand, some silicate will be released after the water glass is diluted. The silica particles formed by the polymerization of silicate molecules can rub between the oil and the mud, which is easy to peel off the oil and the mud. The peeled oil is emulsified by an emulsifier and floats on the surface of the water, realizing the three-phase micro-separation of oil, water and mud. In order to precipitate the floating fine sand in the system, a small amount of cationic flocculant is usually added. In S4, the above-mentioned tank bottom sludge with uniform tempering and micro-separation is pumped to a three-phase horizontal tank centrifuge for oil, water and mud three-phase separation. The speed of the centrifuge is usually controlled at 3000r / min to achieve deep separation of the three phases, and the speed of the centrifuge is adjusted according to the viscosity of the sludge. This viscosity is mainly determined by the degree of sludge aging. In S5, after deep separation, the oil phase is in the uppermost layer, the water phase is in the middle layer, and the solid phase is in the lowermost layer; the separated oil phase is directly input into the oil gathering and transportation processing system within the station, the water phase enters the sewage treatment system within the station, and the solid mud and sand can be directly discharged after natural drying.

[0025] 5. In the S2 dissociation, the organic acid is gluconic acid, and the weight of the added gluconic acid is 1-5wt‰ of the weight of the oil sludge at the bottom of the tank. It is neither corrosive to the equipment nor toxic, and after stirring, it reacts completely with the coating in the oil sludge, and the organic acid in the system is finally consumed completely.

[0026] 6. In S3, the micro separation of oil, water and mud means that the three phases are separated internally, but due to the presence of surfactants, there is a certain emulsification force, which requires further centrifugal separation. In order to prevent the micro-separated oil, water and mud from sedimentation and to facilitate pumping into the three-phase centrifuge, the system temperature is kept above 40-80°C. The purpose of introducing the three-phase horizontal screw centrifuge is to achieve three-phase separation well. Its operating parameters vary according to the size of the processing volume, the power of the centrifuge and the viscosity of the processed sludge, and it has a wide range of applications.

[0027] 7. In S4, the liquid after the tank bottom sludge is evenly conditioned contains a large amount of recyclable crude oil, tank bottom sludge and cleaned water phase. Here, a three-phase horizontal screw centrifuge is introduced to directly separate the evenly conditioned liquid into solid-liquid-liquid three-phases, which can save separation steps and improve separation efficiency.

[0028] 8. Compared with the tank bottom oil mud and sand removal method provided by the invention patent (CN107857449A), the chemical hot washing process provided by the present invention mainly embodies the following advantages: ① Taking full account of the complex and difficult-to-handle characteristics of the tank bottom oil mud, a non-toxic and harmless agent is added to the hot water dispersion to disperse the difficult-to-disperse oil-containing mud and sand coated in the tank bottom oil mud as much as possible, so that the difficult-to-disperse oil-containing mud and sand will not be allowed to settle, resulting in a high oil content in the separated mud and sand; ② Taking full account of the environmental friendliness, cost and effect of the hot washing agent, the agent used in the present invention is non-toxic and harmless, the cost is relatively low, and the friction effect is added to the added agent, resulting in the separation effect of the tank bottom oil mud reaching the national discharge standard for mud and sand in oil mud (oil content <3‰); ③ The process provided by the present invention ultimately considers the three-phase separation of oil, water and mud. Not only does the mud and sand discharge meet the standard, but the oil can be recycled and the water can be recycled for further treatment (even recycled).

[0029] 9. The tank bottom sludge cleaning agent used in the present invention mainly comprises waste rubber cracking oil and heavy tar from a coking plant, and non-toxic and harmless water glass is used in large amounts, accounting for 45wt% of the entire cleaning agent. The emulsifier used is green and environmentally friendly non-ionic surfactants fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether, and the amount used is about 5wt% of the entire cleaning agent. The acid used is organic gluconic acid, and the flocculant used is cationic polyacrylamide, and the amount used is only 1wt‰ of the tank bottom sludge. Therefore, the entire cleaning agent has a low production cost, a simple preparation method, can realize resource recycling and reuse, and is easy to produce on a large scale.

[0030] 10. The tank bottom oil sludge cleaning agent used in the present invention also has the advantages of ① being clean and environmentally friendly, ② being used in a small amount (oil: cleaning agent = 10-5:1 (wt / wt)), ③ having high surface activity, and the use of the ratio of the present invention can greatly reduce the interfacial tension between oil and soil, so that the overall treatment time is short, generally only about 20 minutes for one treatment; ④ having high treatment efficiency (the oil content in the sludge is far lower than the national standard (<3‰)), etc.

[0031] 11. The tank bottom sludge cleaning agent used in the present invention has a flocculant content of 1wt‰ (relative to the content of the pipe bottom sludge used). According to the charge attraction, the flocculant causes the tiny mud and sand floating in the water to settle. A concentration higher than 2wt‰ will increase the viscosity of the water, and too low a sedimentation effect is not ideal. Therefore, 1wt‰ is finally selected for the best separation effect, and the mud and sand are easy to centrifuge. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0033] Example 1: Preparation method of tank bottom sludge cleaning agent and tank bottom sludge cleaning agent

[0034] The preparation method of the tank bottom sludge cleaning agent is as follows: firstly, 20wt% of waste rubber cracking oil and 30wt% of heavy tar are mixed evenly, and then 45wt% of water glass and 5wt% of non-ionic surfactant are added, and emulsified and dispersed to form a black emulsion dispersion.

[0035] The nonionic surfactant is prepared by mixing fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether in a water glass solution with a modulus of 2.4 and a concentration of 20wt% in a weight ratio of 3:1, and adding cationic flocculant polyacrylamide; the amount of cationic flocculant polyacrylamide is 1wt‰ of the weight of the tank bottom sludge to be treated.

[0036] Example 2: Tank bottom sludge cleaning agent

[0037] The tank bottom sludge cleaning agent of this embodiment is prepared by the preparation method of Example 1.

[0038] Example 3: Cleaning process of highly aged tank bottom sludge

[0039] The oily sludge at the bottom of the tank in an oil field was obtained. The characteristics of the sludge at the bottom of the tank are low water content, high oil content, high solid content, and severe emulsification. It is a relatively difficult to handle sludge at the bottom of the tank. After analysis, the sludge at the bottom of the tank has a water content of 5.4wt%, an oil content of 45.3wt%, and a solid content of 49.3%, which should be a highly aged sludge at the bottom of the tank.

[0040] S1, Dispersion pretreatment of tank bottom sludge.

[0041] Put 200g of the tank bottom sludge into a 500ml beaker, add an appropriate amount of water at a ratio of 3:1 (wt / wt) and put it into a constant temperature water bath at 60°C. After the temperature is constant, start mechanical stirring at a speed of 300r / min. After 5 minutes, the sludge is basically stirred evenly.

[0042] S2, dissociation of difficult-to-disperse oily mud and sand particles.

[0043] Add 0.5g of gluconic acid (relative to 1wt‰ of the amount of sludge) to the pretreated tank bottom sludge, and continue stirring for 5-6min. The tank bottom sludge becomes more uniform and is accompanied by a certain smell of hydrogen sulfide.

[0044] S3, friction-assisted micro separation of oil, water and mud.

[0045] Add 40g of the prepared cleaning agent containing water glass (according to the mass ratio of tank bottom sludge to cleaning agent 5:1) to the treated tank bottom sludge, add 0.2g of cationic flocculant polyacrylamide, continue to stir at a constant temperature of 60°C and a stirring speed of 400r / min. Stir for about 10 minutes, and the color of the system changes from black to khaki.

[0046] S4, deep separation of oil, water and mud based on three-phase horizontal tank centrifugation.

[0047] The treated tank bottom sludge is centrifuged in a centrifuge at a centrifugal speed of 3000r / min.

[0048] S5, the three phases after separation are recycled and reused. After centrifugation, the system obviously becomes a three-phase system, with an upper oil phase, a middle water phase, and a lower mud solid phase.

[0049] The upper and middle liquids (oil phase and water phase) were removed, and the lower mud phase was collected and dried in an oven, and then sent out for gas chromatography detection according to standard HJ 1021-2019.

[0050] Example 4: Cleaning process of oil sludge from medium aged tank bottom

[0051] The tank bottom sludge obtained from a certain oil field joint station is black, viscous, and fine-grained. After chemical analysis, the tank bottom sludge contains 52.36wt% oil, 16.26wt% water, and 31.38wt% solids, which should be medium-aged tank bottom sludge.

[0052] S1, Dispersion pretreatment of tank bottom sludge.

[0053] Put 200g of the oil sludge from the tank bottom into a 500ml beaker, add an appropriate amount of water at a ratio of 6:1 (wt / wt) and put it into a constant temperature water bath at 60°C. After the temperature is constant, start mechanical stirring at a speed of 300r / min. After about 5 minutes, the mixture is basically stirred evenly.

[0054] S2, dissociation of difficult-to-disperse oily mud and sand particles.

[0055] 0.2 g of gluconic acid (relative to 1 wt‰ of the sludge) was added to the pretreated tank bottom sludge, and stirring was continued for 5-6 minutes. The tank bottom sludge became more uniform and accompanied by a certain gas with a hydrogen sulfide smell.

[0056] S3, friction-assisted micro separation of oil, water and mud.

[0057] Add 20g of the prepared cleaning agent containing water glass (according to the mass ratio of tank bottom sludge to cleaning agent of 10:1) to the treated tank bottom sludge, add 0.2g of cationic flocculant polyacrylamide, continue to stir at a constant temperature of 60℃, stirring speed of 300r / min, stir for about 10 minutes, the color of the system changes from black to khaki

[0058] S4, deep separation of oil, water and mud based on three-phase horizontal tank centrifugation.

[0059] The treated tank bottom sludge is centrifuged in a centrifuge at a centrifugal speed of 3000r / min.

[0060] S5, the three phases after separation are recycled and reused. After centrifugation, the system obviously becomes a three-phase system, with an upper oil phase, a middle water phase, and a lower mud solid phase.

[0061] The upper and middle liquids (oil phase and water phase) were removed, and the lower mud phase was collected and dried in an oven, and then sent out for gas chromatography detection according to standard HJ 1021-2019.

[0062] The test results of the solid oil content in the tank bottom sludge of Example 3 and Example 4 are as follows:

[0063] Petroleum Hydrocarbons in Soil and Sediment (C 10 -C 40 The solids in the tank bottom sludge treated by chemical hot washing are extracted, purified, concentrated and fixed to volume, and then the solid petroleum hydrocarbons (C 10 -C 40 ) content, and its analysis results are shown in Table 1:

[0064]

[0065] The test results show that the solid oil content in the tank bottom sludge cleaned by chemical hot washing is far less than the national standard (<3‰), indicating that the intermittent process technology of the present invention for cleaning and treating tank bottom sludge by chemical hot washing has obvious cleaning and treatment effects on tank bottom sludge, showing broad market application prospects.

[0066] Therefore, the cleaning agent and cleaning process of the present invention are particularly effective for moderately aged and highly aged sludge, and can significantly reduce the content of petroleum hydrocarbons in the solid after treatment. The present invention can be widely used in occasions where the sludge has a high degree of aging, not limited to the tank bottom sludge of the present invention, but also including oil pipeline sludge, ground sludge and the like.

[0067] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Any feature disclosed in this specification, unless otherwise specified, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise specified, each feature is only an example of a series of equivalent or similar features.

Claims

1. Tank bottom sludge cleaning process, characterized by: The method comprises the following steps: S1: pre-dispersion of oil sludge at the bottom of the tank; S2: separation of oil-containing sludge particles that are difficult to disperse; S3: micro separation of oil, water and sludge three phases based on friction assistance; S4: deep separation of oil, water and sludge three phases based on three-phase horizontal screw centrifugation; S5: recycling and reuse of the separated three phases; The specific process of S3 is to add cleaning agent into the cleaning kettle and stir for 10-15 minutes to achieve the three-phase micro separation of oil, water and mud based on friction assistance; The preparation method of the cleaning agent is as follows: firstly, 20wt% of waste rubber cracking oil and 30wt% of heavy tar are mixed evenly, and then 45wt% of water glass and 5wt% of non-ionic surfactant are added, and emulsified and dispersed to form a black emulsion dispersion; The nonionic surfactant is fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether, which are mixed in a water glass solution with a modulus of 2.4±1 and a concentration of 15-25wt% in a weight ratio of 3:1, and a cationic flocculant polyacrylamide is added to the cleaning agent; the amount of the cationic flocculant polyacrylamide is 1-3wt‰ of the weight of the tank bottom sludge to be treated; The specific process of S1 is to input the tank bottom sludge into the cleaning kettle through a vacuum pump, add 60°C hot water into the cleaning kettle, stir, the stirring speed is 200-400r / min, the stirring time is 5min-6min, and the dispersion pretreatment of the tank bottom sludge is achieved; The specific process of S2 is to add organic acid to the S1 system and stir it at a stirring speed of 200-400r / min for 5min-6min, so as to disperse the oil-containing mud and sand particles in S1 that are partially covered in the oil mud and difficult to disperse, thereby achieving the dissociation of the oil-containing mud and sand particles; The specific process of S4 is to screen out the large muddy impurities after micro separation through a vibrating screen, and pump the water, oil and fine mud into a three-phase horizontal screw centrifuge to achieve deep separation of oil, water and mud. In S2, the organic acid is gluconic acid, and the added weight is 1-5wt‰ of the weight of the tank bottom sludge.

2. The tank bottom sludge cleaning process according to claim 1, characterized in that: The specific process of S5 is that after deep separation, the oil phase is in the uppermost layer, the water phase is in the middle layer, and the solid phase is in the bottom layer; the separated oil phase is directly input into the oil gathering and processing system within the station, the water phase enters the sewage treatment system within the station, and the solid phase mud and sand can be directly discharged after natural drying.

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