Universal method for ultrasonic treatment of oily sludge

Abstract

The invention discloses a universal method for ultrasonic treatment of oily sludge. The method comprises the following steps: measuring the water content, solid content and oil content of the oily sludge, screening optimal parameters of the oily sludge subjected to ultrasonic treatment through an orthogonal test, adding quartz sand with the particle size of 200-300 meshes into the oily sludge, adjusting the solid content of the oily sludge to 41.6%, and carrying out ultrasonic treatment to obtain the oily sludge. And carrying out ultrasonic treatment on the crude oil according to the screened optimal ultrasonic power and ultrasonic treatment time to realize recovery and three-phase separation of the crude oil. According to the method, the property of the oil-containing sludge is changed by additionally adding the quartz sand and regulating and controlling the solid content of the oil-containing sludge, and the formed ultrasonic treatment method is not limited to certain specific oil-containing sludge and has universality for all oil-containing sludge with the solid content smaller than or equal to 41.6%.

Description

Technical Field

[0001] The invention belongs to the technical field of oily sludge treatment, and relates to a universal method for ultrasonically treating oily sludge. Background Art

[0002] Oily sludge is an industrial solid waste generated during the extraction, refining, storage and transportation of crude oil. The presence of organic pollutants and heavy metals makes oily sludge biologically toxic. Due to different sources, the oil content of oily sludge ranges from 30wt% to 80wt%. Therefore, improper treatment of oily sludge may cause waste of resources and pose risks to the ecological environment.

[0003] At present, the main treatment technologies for oily sludge include solvent extraction, high-temperature pyrolysis, incineration and landfill, but there are generally problems such as low crude oil recovery rate, poor stability, and risk of secondary pollution. Some researchers have used ultrasound to treat oily sludge, but they are mainly used for specific oily sludge. Their methods are not universal and vary greatly. For example, Liu et al. (Liu J, Yang F, Xia J, et al. Mechanism of ultrasonic physical-chemical viscosity reduction for different heavy oils [J]. ACS omega, 2021, 6 (3): 2276-2283.) conducted relevant research on ultrasonic treatment of oily sludge in Shengli Oilfield. The results showed that the optimal parameters for ultrasonic treatment of this specific oily sludge are ultrasonic frequency of 15kHz, ultrasonic treatment time of 30min, and ultrasonic power of 500W / h. Luo et al. (Luo X, Gong H, He Z, et al. Research on mechanism and characteristics of oil recovery from oily sludge in ultrasonic fields[J]. Journal of Hazardous Materials, 2020, 399: 123137.) conducted ultrasonic treatment on oily sludge from Changqing Oilfield. The results showed that for this specific oily sludge, the ultrasonic frequency was 21.7 kHz, the treatment time was 10 to 20 min, and the ultrasonic intensity was 0.28 W / cm 2 Therefore, it is necessary to develop a universal ultrasonic treatment method for oily sludge. Summary of the invention

[0004] The purpose of the present invention is to provide a universal method for ultrasonic treatment of oily sludge.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] A universal method for ultrasonic treatment of oily sludge comprises the following steps:

[0007] Step 1, determining the water content, solid content and oil content of the oily sludge;

[0008] Step 2, screening the optimal parameters for ultrasonic treatment of oily sludge:

[0009] The sample size and ultrasonic frequency were fixed, and an orthogonal test of ultrasonic power and ultrasonic treatment time was set. The ultrasonic power and ultrasonic treatment time with the highest recovery rate were determined as the optimal ultrasonic power and ultrasonic treatment time.

[0010] Step 3, adding quartz sand with a particle size of 200-300 mesh to the oily sludge, adjusting the solid content in the oily sludge to 41.6%, mixing evenly, and subjecting it to ultrasonic treatment according to the optimal ultrasonic power and ultrasonic treatment time screened in step 2 to achieve crude oil recovery and three-phase separation.

[0011] Preferably, in step 3, the quartz sand is pretreated as follows before being added: the quartz sand is sequentially pickled with 20% HCl solution, washed with water, dried at 65°C, washed with 10% H2O2 solution, washed with water, and dried at 65°C.

[0012] Furthermore, in step 1, the water content of the oily sludge is 11.17%, the solid content is 2.67%, and the oil content is 86.16%; in step 2, the fixed sample size is 10 g and the ultrasonic frequency is 25 KHz, the optimal ultrasonic power is 130 W and the ultrasonic treatment time is 25 min; in step 3, the amount of quartz sand added is 40% (based on the weight of the oily sludge as 100%).

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] (1) The present invention adjusts the solid content of the oily sludge by adding quartz sand in a specific particle size range, thereby changing the properties of the oily sludge. The resulting ultrasonic treatment method is not limited to a specific oily sludge, but is universally applicable to all oily sludges with a solid content of ≤41.6%.

[0015] (2) Since frequency-modulated ultrasonic equipment is expensive, the present invention provides a method for determining whether the optimal effect is achieved under a specific ultrasonic frequency based on the characteristics of the oily sludge, thereby guiding actual projects to screen treatment process routes and technologies based on the properties of the oily sludge.

[0016] (3) The present invention does not add chemical agents during the ultrasonic process, and there is no risk of secondary pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the universal method for ultrasonic treatment of oily sludge.

[0018] Figure 2 The crude oil recovery rate of oily sludge treated with ultrasound under different ultrasonic powers and ultrasonic treatment times.

[0019] Figure 3 The crude oil recovery rate of simulated oily sludge containing different mass fractions of quartz sand after ultrasonic treatment for different times when the ultrasonic power was 130W was used to add quartz sand with a particle size of 70-110 mesh.

[0020] Figure 4 The crude oil recovery rate of simulated oily sludge containing different mass fractions of quartz sand after ultrasonic treatment for different times when the ultrasonic power was 130W was used to add quartz sand with a particle size of 200-300 mesh.

[0021] Figure 5 The crude oil recovery rate of simulated oily sludge containing different mass fractions of quartz sand after ultrasonic treatment for different times when the ultrasonic power was 130W was used to add quartz sand with a particle size of 600 mesh. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0023] The present invention adopts ultrasonic technology to treat oily sludge. The stability of oily sludge is a key factor affecting the efficiency of ultrasonic treatment. The particle size and content of particulate matter in oily sludge will greatly affect the intensity of interaction with crude oil, thereby changing the stability of oily sludge. The cavitation effect, thermal effect and mechanical effect generated by ultrasonic wave can destroy the chemical bond between particulate matter and crude oil, so that crude oil can be desorbed from sludge. Due to the density difference, crude oil will float on the upper part of the system, particulate matter will be deposited on the lower part, and water phase will be located in the middle part, so as to realize crude oil recovery and three-phase separation.

[0024] The present invention determines the optimal parameters of ultrasonic treatment by taking oily sludge from actual oil fields. The oily sludge from actual sites is mixed with treated quartz sand to prepare different simulated sludges, and the particle size and content of quartz sand are changed to change the interaction intensity between particles and crude oil. Under the same ultrasonic conditions, the application range of ultrasonic treatment of oily sludge is determined with crude oil recovery rate as an indicator.

[0025] Example 1

[0026] The oily sludge at the bottom of the tank was taken from an oil field in North China. The oily sludge is relatively viscous and has poor fluidity. Its viscosity is 11203mPa·s. The experimental results show that the water content of the oily sludge is 11.17%, the solid content is 2.67%, and the oil content is 86.16%. The ultrasonic frequency is fixed at 25kHz, and the main factors affecting the efficiency of ultrasonic treatment of oily sludge are screened by orthogonal test and significance analysis. The orthogonal test and significance analysis are shown in Tables 1 and 2 respectively.

[0027] Table 1 Ultrasonic treatment orthogonal experiment table

[0028] serial number Sample size (g) Ultrasonic power (W) Ultrasonic time (min) Recovery rate 1 10 65 5 57.22％ 2 10 195 30 42.13％ 3 10 325 15 26.65％ 4 30 65 30 77.31％ 5 30 195 15 74.30％ 6 30 325 5 31.91％ 7 50 65 15 69.38％ 8 50 195 5 71.39％ 9 50 325 30 84.16％

[0029] Table 2. ANOVA table of orthogonal experiment results

[0030] factor Sum of Squares of Variance Degrees of Freedom Mean Square F-number Significance Sample size 0.170 2 0.085 21.036 * Ultrasonic power 0.004 2 0.002 0.538 Ultrasound time 0.004 2 0.002 0.464

[0031] As can be seen from Table 2, sample size is the main factor affecting ultrasonic treatment of oily sludge. Under the condition of limiting the sample size to 10 g, the ultrasonic power and ultrasonic treatment time were further screened. The results are shown in Figure 2 As can be seen from the figure, when the ultrasonic power is 130W and the ultrasonic treatment is 25min, the crude oil recovery effect is the best.

[0032] Therefore, the ultrasonic treatment parameters of oily sludge in subsequent experiments were determined as ultrasonic frequency 25kHz, sample size 10g, ultrasonic power 130W, and ultrasonic treatment time 25min. Then, the properties of oily sludge were changed by adding quartz sand of different particle sizes and contents to determine the optimal quartz sand addition parameters. The quartz sand addition information is shown in Table 3.

[0033] Before adding quartz sand, the quartz sand is treated as follows to remove impurities: (1) 200 g of quartz sand is put into a 500 ml beaker, 100 ml of 20% HCl solution is added to the quartz sand and mixed, the mixture is stirred and then soaked for 2 h, and the mixture is allowed to settle. The upper acid solution is poured out, and the acid-washed quartz sand is repeatedly washed with deionized water until the deionized water is clear, and stirring is required during the process; (2) After filtering out the deionized water, the quartz sand is placed in a 65°C constant temperature drying oven for drying for 24 h, and then taken out after drying; (3) 100 ml of 10% H2O2 solution is added, stirred, and then soaked for 0.5 h, the upper liquid is poured out, and the mixture is repeatedly washed with deionized water until the deionized water is clear, the deionized water is filtered out, and the quartz sand is placed in a 65°C constant temperature drying oven for drying for use.

[0034] Table 3 Detailed list of quartz sand particle size and addition amount

[0035]

[0036] The above nine simulated oily sludges with quartz sand added were ultrasonically treated under the same ultrasonic conditions. The particle size and content of the appropriate quartz sand to be added were determined according to the crude oil recovery rate. The results are as follows: Figures 3 to 5 As shown. The amount of quartz sand added is 40% of the oily sludge, so that when the solid content of the simulated oily sludge is 41.6%, the ultrasonic treatment effect is best when the quartz sand particle size is 200-300 mesh. After 25 minutes of ultrasonic treatment, the crude oil recovery rate is 34.23%. In summary, the ultrasonic treatment method of the present invention is universal and is applicable to any oily sludge with a solid content of ≤41.6%.

Claims

1. A universal method for ultrasonic treatment of oily sludge, characterized in that: The following steps are involved: Step 1, determining the water content, solid content and oil content of the oily sludge; Step 2, screening the optimal parameters for ultrasonic treatment of oily sludge: The sample size and ultrasonic frequency were fixed, and an orthogonal test of ultrasonic power and ultrasonic treatment time was set. The ultrasonic power and ultrasonic treatment time with the highest recovery rate were determined as the optimal ultrasonic power and ultrasonic treatment time. Step 3, adding quartz sand with a particle size of 200-300 mesh to the oily sludge, adjusting the solid content in the oily sludge to 41.6%, mixing evenly, and subjecting it to ultrasonic treatment according to the optimal ultrasonic power and ultrasonic treatment time screened in step 2 to achieve crude oil recovery and three-phase separation.

2. The universal method according to claim 1, characterized in that: In step 3, the quartz sand is pretreated as follows before being added: the quartz sand is sequentially acid-washed with 20% HCl solution, washed with water, dried at 65°C, washed with 10% H2O2 solution, washed with water, and dried at 65°C.

3. The universal method according to claim 1, characterized in that: In step 1, the water content of the oily sludge is 11.17%, the solid content is 2.67%, and the oil content is 86.16%; in step 2, the fixed sample size is 10 g and the ultrasonic frequency is 25 KHz, the optimal ultrasonic power is 130 W and the ultrasonic treatment time is 25 min; in step 3, the amount of quartz sand added is 40%.

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