Method for depolymerization and synergistic treatment of polymeric oily sludge with hot washing

Abstract

The present application belongs to the technical field of sludge treatment, and particularly relates to a method for depolymerization and hot washing synergic treatment of poly-oil-containing sludge. The method comprises the following steps: (1) high-speed shearing to break the glue and depolymerize: mixing a glue-breaking agent with initial poly-oil-containing sludge and then high-speed shearing; (2) water stirring at a constant temperature: transferring the mixture after breaking the glue to a stirring pool, adding water and stirring, the water addition amount being 4-6:1 of the mass ratio of the initial poly-oil-containing sludge; (3) adding a hot washing agent under ultrasonic: adding a hot washing agent in the stirring pool, the hot washing agent being 1-3% of the mass of the oil sludge water mixture, ultrasonic auxiliary separation, ultrasonic power being 500-1000 W, and frequency being 25 kHz; (4) separation after standing and settling: standing until the mixture is divided into three layers; and (5) reprocessing of the solid bottom sludge layer: centrifugal separation of the bottom sludge. The process can improve the treatment efficiency of the poly-oil-containing sludge.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sludge treatment, and particularly relates to a method for treating poly-oil-containing sludge by depolymerization and hot washing. BACKGROUND

[0002] The tertiary oil recovery technology is an important technical means for old oil fields to greatly improve the oil recovery rate. The tertiary oil recovery technology uses polymer oil displacement. At present, the Daqing, Shengli and Bohai oil fields in China have used the technology for more than ten years. Although the tertiary oil recovery technology can greatly improve the oil recovery rate, the characteristics of the oil sludge recovered will be significantly different. First, the mud content is high. The destruction of the rock-soil structure inside the oil field due to multiple previous mining causes the mud content in the tertiary recovery liquid to increase significantly. Second, there are many additives. The use of various additives in the tertiary oil recovery results in the formation of oil-containing sludge with very complex composition, which is extremely difficult to treat. The composition of the poly-oil-containing sludge includes crude oil, solid particles, polymer thickening agents, surfactants, flocculants, etc. Typical polymer thickening agents include polyacrylamide, modified starch, xanthan gum, guar gum, etc. These polymers form a stable spatial network structure in the poly-oil-containing sludge, which wraps oil molecules, water and part of the solid particles, making it difficult to separate. The treatment of poly-oil-containing sludge is a major problem in the treatment of oil-containing sludge in the future.

[0003] Zhou Jun et al. (Treatment of Poly-oil-containing Sludge by Extraction and Recovery of Extractant [J]. Petroleum and Natural Gas Chemical Industry, 2018, v.47; No.245(03):93-98.) used a self-developed extractant to treat the poly-oil-containing sludge in Shengli Oilfield, and the oil content in the sludge was reduced to 0.66%. However, the extractant dosage is large, and better extraction effect often needs to be achieved by multiple extraction, and the extractant needs to be distilled and recovered, so the process cost is high. Su Yanhui et al. (Experimental Study on Ultrasonic Washing and Oil Removal of Poly-oil-containing Sludge in Offshore S Oilfield [J]. Applied Chemistry, 2014, 43(10):1928-1929.) used ultrasonic wave + auxiliary process to separate the poly-oil-containing sludge in offshore S oilfield. Although the oil removal efficiency is higher than that of the non-ultrasonic auxiliary treatment process, the oil removal rate is only 20%, which does not meet the relevant standards and requirements. Chen Hongshuo et al. (Process Test of Combined Treatment of High-oil and High-poly-oil-containing Sludge by Thermo-chemical Cleaning and Countercurrent Extraction [J]. Journal of Environmental Engineering and Technology, 2019, 9(03):85-92.) used a combined method of thermo-chemical cleaning and countercurrent extraction to treat high-oil and high-poly-oil-containing sludge, and the solid dry base oil content was 1.7%. However, the process is relatively complex and the cost is high.

[0004] Chinese patent document CN 110698035 A discloses a comprehensive treatment method for poly-containing oil sludge, which comprises the following steps: (1) ultrasonic and reagent synergistic depolymerization of poly-containing oil sludge, the depolymerization agent is selected from a mixture of one or more of hydrogen peroxide, ozone, potassium persulfate, sodium persulfate, potassium ferrate, sodium ferrate, ferrous sulfate, sodium hypochlorite, chlorine dioxide and sodium dithionite; (2) centrifugal separation; (3) low-temperature drying type reduction treatment or pyrolysis type harmless and resourceful treatment of dry sludge. This scheme has good treatment effect on poly-containing oil sludge with oil content of 27%-60%. Chinese patent document CN111849651A discloses a thermo-chemical cleaning agent for oilfield poly-containing oil sludge, which comprises various ionic cleaning agents and alkaline builders. The non-ionic cleaning agent is rhamnolipid, sophorolipid, AEO-9, EL100, SP169 or Tween 80; the alkaline builder is one or more of sodium silicate, sodium carbonate and sodium hydroxide. This scheme can reduce the interfacial tension of the oil sludge and change the surface wettability of the solid phase, which helps to remove residual oil from the solid phase; the alkaline builder has better dispersion effect; the interaction between the above components not only reduces the amount of cleaning agent, but also improves the recovery rate of crude oil, and can reduce the oil content in the oil sludge to 1%, meeting the national emission standard.

[0005] The technical route of depolymerization and hot washing synergistic treatment of poly-containing oil sludge has not been disclosed in the prior art. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art and provide a method for depolymerization and hot washing synergistic treatment of poly-containing oil sludge, in order to improve the treatment efficiency of poly-containing oil sludge.

[0007] The solution to the technical problem of the present application is:

[0008] The method for depolymerization and hot washing synergistic treatment of poly-containing oil sludge comprises the following steps:

[0009] (1) High-speed shearing and gel breaking depolymerization: mix gel breaking reagent with initial poly-containing oil sludge, the mass of gel breaking reagent is 0.5-3% of the mass of initial poly-containing oil sludge, heat to 50-70℃, high-speed shearing for 5-10 min;

[0010] (2) Water stirring at ambient temperature: transfer the mixture after crushing and gel breaking to a stirring tank and stir with water, the water amount is 4-6:1 of the mass of initial poly-containing oil sludge, the stirring speed is 100-500 r / min, the stirring time is 5-10 min, and the temperature of the mixture is maintained at 50-70℃ during the stirring;

[0011] (3) ultrasonic-assisted hot washing: adding hot washing reagent into the stirring tank, the mass of the hot washing reagent being 1-3% of the mass of the oil sludge water mixture, continuing to stir for 10-20 min; meanwhile, starting ultrasonic-assisted separation, ultrasonic power being 500-1000 W, frequency being 25 kHz;

[0012] (4) separation after static settling: after static settling, the mixture is separated into three layers, the upper layer being the crude oil layer, the middle layer being the water layer, and the lower layer being the solid sludge layer, collecting the crude oil in the upper layer;

[0013] (5) reprocessing of the solid sludge layer: centrifuging the sludge in the lower layer, and sending the separated oil-water layer back to the stirring tank, and directly utilizing or further processing the solid sludge according to its oil content.

[0014] As an improvement, in step (1), the components of the gel-breaking reagent include, by weight, 20-30 parts of quicklime, 30-40 parts of ammonium persulfate, 15-30 parts of 30% hydrogen peroxide solution, and 10-20 parts of sodium hypochlorite; wherein the ammonium persulfate can be replaced by potassium persulfate or sodium persulfate, and the sodium hypochlorite can be replaced by chlorine dioxide.

[0015] As an improvement, in step (1), the high-speed shearing is performed in a shearing crusher, and the rotating speed is 5000-7000 r / min.

[0016] As an improvement, in step (3), the components of the hot washing reagent include, by weight, 15-25 parts of caprylocapryl acid diethanolamide, 20-40 parts of fatty alcohol polyoxyethylene ether, 5-15 parts of n-butanol, 5-10 parts of sodium dodecyl sulfonate, and 3-5 parts of plant essential oil; wherein the caprylocapryl acid diethanolamide can be replaced by fatty acid diethanolamide or caprylic acid diethanolamide, the fatty alcohol polyoxyethylene ether can be replaced by propylene glycol monobutyl ether, and the sodium dodecyl sulfonate can be replaced by sodium dodecyl sulfate.

[0017] As an improvement, in step (4), the static settling time is 30-90 min.

[0018] As an improvement, in step (5), if the oil content is less than 1%, the solid sludge can be used as harmless solid waste in the construction industry or directly returned to the soil; otherwise, it is transferred to a pyrolysis furnace for pyrolysis to remove oil.

[0019] The beneficial effects of the present application are as follows:

[0020] 1. The present application utilizes chemical treatment and mechanical crushing to improve the treatment efficiency of the poly-containing oil sludge; on this basis, the depolymerization process and the hot washing process are separated, the specificity of the gel-breaking reagent and the hot washing reagent in their respective treatment processes is improved, the separation capacity for the poly-containing oil sludge is improved, and the present application has good treatment effect on high-poly-containing high-viscosity oil sludge.

[0021] 2. Using the agent described in the application can be good separation of oil and mud, after centrifugation, the upper oil layer containing water and less impurities such as silt content.

[0022] 3. Using the agent described in the application can make the oil content of the treated sediment to 1% or less.

[0023] 4. The process described in the application, can deal with the high polymer oil sludge, its oil content range is wide, allow oil content within 60%, pH range is 7~12. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The process flow chart of the application. EMBODIMENT EMBODIMENT

[0025] The polyacrylamide-containing oil sludge of the embodiment is from the tertiary oil recovery technology of Liaohe Oilfield, with a water content of 53.8%, an oil content of 34.5%, a solid content of 11.7%, and a polyacrylamide content of about 3.68%, and a pH of 8.

[0026] The polyacrylamide-containing oil sludge is treated by depolymerization and hot washing, and the process flow is as shown in Figure 1 The specific steps are as follows:

[0027] (1) High-speed shearing to break the glue and depolymerize: take 1 t of polyacrylamide-containing oil sludge, pour it into a shearing crusher, heat the temperature to 60℃, add 30 kg of glue-breaking agent, and stir and break at a speed of 6000 r / min for 5 min. The components of the glue-breaking agent include: lime 30 parts, ammonium persulfate 40 parts, 30% hydrogen peroxide 20 parts, and sodium hypochlorite 10 parts.

[0028] (2) Stirring with water at a constant temperature: about 1 t of the mixture after breaking the glue is pumped to a stirring tank, 4 t of water is added, and stirring is carried out at a speed of 100 r / min for 5 min, during which the temperature of the mixture is maintained at about 60℃;

[0029] (3) Hot washing with ultrasonic addition of medicine: 50 kg of hot washing agent is put into the stirring tank through the medicine inlet bin at the bottom of the stirring tank, and stirring is continued for 15 min. At the same time, ultrasonic assisted separation is started, with an ultrasonic power of 500 W and a frequency of 25 kHz. The components of the hot washing agent include: capryl capryl diethanolamide 15 parts, fatty alcohol polyoxyethylene ether 30 parts, n-butanol 10 parts, sodium dodecyl sulfonate 8 parts, and plant essential oil 5 parts.

[0030] (4) Separation after standing and settling: After standing and settling for 60 min, the mixture is divided into three layers, the upper layer is the crude oil layer, the middle layer is the water layer, and the lower layer is the solid sludge layer. The upper crude oil layer is collected by a floating oil collector and stored in an oil tank for transportation to a refinery for resource utilization.

[0031] (5) Re-processing of the solid sludge layer: A pipe is arranged at the bottom of the stirring tank, and a sand pumping pump is used to pump the sludge to a horizontal centrifuge for three-phase separation, with a centrifugation time of 40 min. After centrifugation, the oil-water layer obtained by separation is sent back to the stirring tank for reuse.

[0032] The solid sludge obtained by separation is about 0.21 t, and the oil content is detected by an infrared oil detector, which is found to be 5.7%, which is higher than the relevant standard. The next step of pyrolysis process is needed.

[0033] (6) Heating and pyrolysis

[0034] For solid sludge with oil content not meeting the requirements, first, it is dried to further reduce the mass of solid waste, which is beneficial to improve the pyrolysis efficiency and reduce the cost. Then, the reduced solid waste (about 0.15 t) is transferred to an electric pyrolysis furnace to remove oxygen and perform anaerobic pyrolysis, with a heating rate of 10℃ / min, a constant temperature interval of 550℃, and a time of 60 min. After pyrolysis, the oil content of the solid waste residue is checked, and the detection shows that the oil content of the solid residue is 0.76%, which meets the national emission standard (less than 1%).

[0035] Comparative Example 1

[0036] As a comparison with Example 1, the same amount of oil sludge is taken without the first step of breaking and depolymerizing the polymeric oil sludge, and the oil sludge is directly added to the stirring tank for ultrasonic-assisted medicament stirring and settling. After the (5) step of centrifugal separation, the solid sludge obtained by separation is about 0.45 tons, and the oil content is detected by an infrared oil detector, which is found to be 18.7%. It shows that the organic polymeric network structure in the polymeric oil sludge without breaking is not destroyed.

[0037] Comparative Example 2

[0038] As a comparison with Example 1, the same amount of oil sludge is taken, and the above depolymerizing agent and hot washing medicament are added to the stirring tank at the same amount as in Example 1, and ultrasonic-assisted stirring is performed under the same parameters, and then settling is performed. The solid sludge obtained by centrifugal separation is about 0.40 tons, with an oil content of about 14.9%, and the separation effect is also poor, with a high water content. The water network structure wrapped by polyacrylamide still exists. Example

[0039] The polyacrylamide-containing sludge of this embodiment is from Daqing Oilfield, and belongs to the polyacrylamide-containing sludge of tertiary oil recovery technology, with a water content of 38.3%, an oil content of 45.4%, a solid content of 16.3%, and a thickening agent content of about 5.5% (including polyacrylamide, guar gum, etc.), a large viscosity, and a pH of about 10.

[0040] The polyacrylamide-containing sludge is treated by the method of depolymerization and hot washing, and the specific steps are as follows:

[0041] (1) Breaking and depolymerizing under high-speed shearing: take 0.5 t of polyacrylamide-containing sludge, pour it into a shearing crusher, the heating temperature is 60℃, add 14 kg of gel breaking agent, and stir and crush at a speed of 6000 r / min for 10 min. The composition of the gel breaking agent includes: 20 parts of quicklime, 40 parts of potassium persulfate, 15 parts of 30% hydrogen peroxide, and 15 parts of chlorine dioxide.

[0042] (2) Stirring with water at a constant temperature: about 0.5 t of the mixture after breaking and gel breaking is pumped to a stirring tank, 3 t of water is added, and stirring is carried out at a speed of 200 r / min for 5 min, and the temperature of the mixture is maintained at about 60℃ during the stirring.

[0043] (3) Heating and washing with medicine under ultrasonic: 35 kg of hot washing agent is put into the stirring tank through the medicine inlet at the bottom of the stirring tank, and stirring is continued for 15 min. At the same time, ultrasonic assisted separation is started, with an ultrasonic power of 1000 W and a frequency of 25 kHz. The composition of the hot washing agent includes: 10 parts of fatty acid diethanolamide, 15 parts of coconut oil diethanolamide; 20 parts of propylene glycol monobutyl ether, 15 parts of n-butanol, 5 parts of sodium dodecyl sulfonate, 3 parts of sodium dodecyl sulfate, and 3 parts of plant essential oil.

[0044] (4) Separation after standing and settling: after standing and settling for 90 min, the mixture is divided into three layers: the upper layer is the crude oil layer, the middle layer is the water layer, and the lower layer is the solid sludge layer. The crude oil layer on the upper part is collected by a floating oil collector and stored in an oil storage tank for resource utilization in a refinery.

[0045] (5) Re-treatment of the solid sludge layer: a pipeline is arranged at the bottom of the stirring tank, and a sand pumping pump is used to pump the sludge to a horizontal screw centrifuge for three-phase separation, and the centrifugation time is 60 min. After centrifugation, the oil and water layers obtained by separation are sent to the stirring tank again for reuse.

[0046] The solid sludge obtained by separation is about 0.14 t, and the oil content is detected by an infrared oil detector, and it is found that the oil content is 8.6%, which is higher than the national emission standard (less than 1%), and needs to be treated by the next pyrolysis process.

[0047] (6) Heating and pyrolysis

[0048] The solid sludge after three-phase separation by the horizontal screw centrifuge is first subjected to drying treatment. The mass of the solid waste is reduced by 35%, about 0.09 t. Then the remaining solid is transferred to an electric pyrolysis furnace, oxygen is removed, and anaerobic pyrolysis is carried out, the heating rate is 20℃ / min, the constant temperature interval is 600℃, and the time is 60 min. After pyrolysis, the oil content of the solid waste residue is checked, and the oil content of the solid residue is 0.67%, which meets the national emission standard (less than 1%).

[0049] Comparative Example 3

[0050] As a comparison with Example 2, the same amount of oil sludge is taken, a certain type of oil sludge breaker and separator (main components are potassium permanganate, hydrogen peroxide, and sodium persulfate) is added, and then the above-mentioned (1)-(6) process is carried out, the addition ratio and process parameters are the same. After centrifugal separation, the oil content of the sample is about 2.5%, which is relatively low, but the oil content obtained by the present application is lower, which has an advantage.

[0051] Comparative Example 4

[0052] Different from Comparative Example 3, in step (3), the ultrasonic device is turned off, and the rest of the operations are the same as above. After centrifugal separation, the oil content of the sample is about 13.2%, which is slightly higher. The ultrasonic plays a good auxiliary separation effect. Example

[0053] The poly-containing oil sludge in this example comes from Shengli Oilfield and belongs to poly-containing sludge in tertiary oil recovery technology, with a water content of 43.7%, an oil content of 38.9%, a solid content of 17.4%, and a thickening agent such as polyacrylamide and guar gum of about 3.2%, a small viscosity, and a pH of about 7.0.

[0054] The poly-containing oil sludge is treated by depolymerization and hot washing, and the specific steps are as follows:

[0055] (1) High-speed shearing to break and depolymerize: take 1 t of poly-containing oil sludge, pour it into a shearing crusher, heat the temperature to 60℃, add 15 kg of breaker reagent, and stir and crush at a speed of 6000 r / min for 10 min. The composition of the breaker reagent includes: 25 parts of quicklime, 20 parts of ammonium persulfate, 20 parts of sodium persulfate, 20 parts of 30% hydrogen peroxide, and 20 parts of sodium hypochlorite. After stirring and crushing, the viscosity of the poly-containing oil sludge decreases and the fluidity improves.

[0056] (2) Stirring with water at a constant temperature: about 1 t of the mixture after breaking and depolymerization is pumped to a stirring tank, 5 t of water is added, and stirred at a speed of 150 r / min for 5 min, during which the temperature of the mixture is maintained at about 60℃.

[0057] (3) Ultrasonic-assisted hot washing: 60 kg of hot washing agent was added into the stirring tank through the medicine inlet at the bottom of the stirring tank, and stirring was continued for 15 min. At the same time, ultrasonic assisted separation was started, with ultrasonic power of 1000 W and frequency of 25 kHz. The components of the hot washing agent included: capric acid 15 parts, fatty alcohol polyoxyethylene ether 30 parts, n-butanol 15 parts, sodium dodecyl sulfonate 8 parts, and plant essential oil 3 parts.

[0058] (4) Separation after standing and sedimentation: standing and sedimentation for 90 min, the mixture was divided into three layers: the upper layer was the crude oil layer, the middle layer was the water layer, and the lower layer was the solid sludge layer. The upper crude oil layer was collected by a floating oil collector and stored in an oil storage tank for resource utilization in a refinery.

[0059] (5) Re-processing of solid sludge layer: a pipeline was set at the bottom of the stirring tank, and a sand suction pump was used to pump the sludge to a horizontal screw centrifuge for three-phase separation, with a centrifugation time of 60 min. After centrifugation, the oil-water layer obtained was sent back to the stirring tank for reuse.

[0060] The solid sludge obtained by separation was about 0.22 t, and the oil content was detected by an infrared oil detector, which was found to be 0.98%, meeting the national emission standard (less than 1%), and did not need to be pyrolyzed, and could be directly used for resource utilization or directly returned to the soil.

[0061] Comparative Example 5

[0062] As a comparison with Example 3, the same amount of oil sludge was taken, and in step (1), stirring was used instead of high-speed shearing, with a stirring speed of 150 r / min, and other process parameters were the same, and the above steps (2)-(6) were carried out. After centrifugal separation, the oil content of the sample was measured to be about 4.2%, which was relatively high. This shows that high-speed shearing crushing has good auxiliary effect.

Claims

1. A method for the depolymerization and synergistic treatment of polymeric oil sludge with hot wash, characterized in that, The method comprises the following steps: (1) high-speed shearing to break the glue and depolymerize: the glue breaker is mixed with the initial polymer-containing sludge, the mass of the glue breaker is 0.5-3% of the mass of the initial polymer-containing sludge, the mixture is heated to 50-70℃, and high-speed shearing is performed on the mixture; (2) water stirring with temperature: the mixture after breaking the glue is transferred to a stirring tank, water is added for stirring, the water addition amount is 4-6:1 of the mass of the initial polymer-containing sludge, and the temperature of the mixture is kept at 50-70℃ during the stirring; (3) hot washing with ultrasonic: hot washing agents are added to the stirring tank for continuous stirring, the mass of the hot washing agents is 1-3% of the mass of the sludge-water mixture, and ultrasonic is turned on to assist separation; (4) separation after standing and settling: the mixture is allowed to stand and settle, the mixture is divided into three layers, the upper layer is a crude oil layer, the middle layer is a water layer, and the lower layer is a solid sludge layer, and the crude oil in the upper layer is collected; (5) reprocessing of the solid sludge layer: the sludge in the lower layer is subjected to centrifugal separation, the oil-water layer obtained by the separation is sent to the stirring tank again, and the solid sludge is directly used for resource utilization or further treatment according to its oil content.

2. The method for depolymerization and hot wash synergic treatment of polymeric oily sludge according to claim 1, characterized in that: In the step (1), the components of the glue breaker include, by weight, 20-30 parts of quicklime, 30-40 parts of ammonium persulfate, 15-30 parts of 30% hydrogen peroxide solution, and 10-20 parts of sodium hypochlorite; wherein the ammonium persulfate can be replaced by potassium persulfate or sodium persulfate, and the sodium hypochlorite can be replaced by chlorine dioxide.

3. The method for depolymerization and hot wash synergic treatment of polymeric oily sludge according to claim 1, characterized in that: In the step (1), the high-speed shearing is performed in a shearing crusher, and the rotating speed is 5000-7000 r / min.

4. The method for depolymerization and hot wash synergic treatment of polymeric oily sludge according to claim 1, characterized in that: In the step (3), the components of the hot washing agents include, by weight, 15-25 parts of caprylocaproyl dihydroxyethylamide, 20-40 parts of fatty alcohol polyoxyethylene ether, 5-15 parts of n-butanol, 5-10 parts of sodium dodecyl sulfonate, and 3-5 parts of plant essential oil; wherein the caprylocaproyl dihydroxyethylamide can be replaced by fatty acid dihydroxyethylamide or cocodiethanolamide, the fatty alcohol polyoxyethylene ether can be replaced by propylene glycol monobutyl ether, and the sodium dodecyl sulfonate can be replaced by sodium dodecyl sulfate.

5. The method for depolymerization and hot wash synergic treatment of polymeric oily sludge according to claim 1, characterized in that: In the step (4), the standing time is 30-90 min.

6. The method of depolymerization and hot wash synergic treatment of polymeric oily sludge according to claim 1, characterized in that: In the step (5), if the oil content is less than 1%, the solid sludge can be used as harmless solid waste in the construction industry or directly returned to the soil; otherwise, the solid sludge is transferred to a pyrolysis furnace for pyrolysis to remove oil.

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