A universal method for ultrasonic treatment of oily sludge

Abstract

The application discloses a universal method for treating oily sludge by ultrasonic waves. The method comprises the following steps: firstly, determining the water content, solid content and oil content of the oily sludge; secondly, screening the optimal parameters for treating the oily sludge by ultrasonic waves through orthogonal test; thirdly, adding quartz sand with a particle size of 200-300 meshes into the oily sludge to adjust the solid content of the oily sludge to 41.6 %; and finally, treating the oily sludge by ultrasonic waves according to the optimal ultrasonic power and ultrasonic treatment time to realize the recovery of crude oil and three-phase separation. The method can change the properties of the oily sludge by adding quartz sand to adjust the solid content of the oily sludge, and the formed ultrasonic treatment method is not limited to a certain specific oily sludge, and is universal for all oily sludge with a solid content of less than 41.6 %.

Description

Technical Field

[0001] This invention belongs to the field of oily sludge treatment technology, and relates to a universal method for ultrasonic treatment of oily sludge. Background Technology

[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 in it makes it biotoxic. Depending on its origin, the oil content of oily sludge ranges from 30 wt% to 80 wt%. Therefore, improper disposal of oily sludge can lead to resource waste and pose risks to the ecological environment.

[0003] Currently, the main technologies for treating oily sludge include solvent extraction, high-temperature pyrolysis, incineration, and landfill. However, these technologies generally suffer from low crude oil recovery rates, poor stability, and the risk of secondary pollution. Some researchers have used ultrasound to treat oily sludge, but these methods are mainly for specific types of oily sludge and lack universality and vary considerably. 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 a study on the ultrasonic treatment of oily sludge from the Shengli Oilfield. The results showed that the optimal parameters for ultrasonic treatment of this specific type of oily sludge were an ultrasonic frequency of 15kHz, an ultrasonic treatment time of 30min, and an 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: 123-137.) conducted ultrasonic treatment on oily sludge from Changqing Oilfield. The results showed that for this specific oily sludge, the optimal ultrasonic frequency was 21.7 kHz, the treatment time was 10-20 min, and the ultrasonic intensity was 0.28 W / cm². 2 At this time, crude oil recovery is most effective. Therefore, it is essential to develop a universally applicable ultrasonic treatment method for oily sludge. Summary of the Invention

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

[0005] The technical solution for achieving the objective of this invention is as follows:

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

[0007] Step 1: Determine the moisture content, solids content, and oil content of the oily sludge;

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

[0009] With a fixed sample size and ultrasonic frequency, an orthogonal experiment was conducted to determine the ultrasonic power and ultrasonic treatment time with the highest recovery rate as the optimal ultrasonic power and ultrasonic treatment time.

[0010] Step 3: Add quartz sand with a particle size of 200-300 mesh to the oily sludge to adjust the solid content of the oily sludge to 41.6%. After mixing evenly, perform ultrasonic treatment on the sludge according to the optimal ultrasonic power and ultrasonic treatment time selected 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 acid-washed with 20% HCl solution, washed with water, dried at 65°C, cleaned with 10% H2O2 solution, washed with water, and dried at 65°C.

[0012] Further, 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 sample size is fixed at 10g, the ultrasonic frequency is 25KHz, the optimal ultrasonic power is 130W, and the ultrasonic treatment time is 25min; in step 3, the amount of quartz sand added is 40% (based on the weight of the oily sludge being 100%).

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

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

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

[0016] (3) No chemical agents are added during the ultrasound process, so there is no risk of secondary pollution to the environment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a general method for ultrasonic treatment of oily sludge.

[0018] Figure 2 The crude oil recovery rate of oily sludge treated with ultrasound under different ultrasonic power and ultrasonic treatment time conditions was determined.

[0019] Figure 3 To measure the crude oil recovery rate of simulated oily sludge containing different mass fractions of quartz sand with a particle size of 70-110 mesh after ultrasonic treatment for different times at an ultrasonic power of 130W, the following study was conducted.

[0020] Figure 4 To measure the crude oil recovery rate of simulated oily sludge containing different mass fractions of quartz sand with a particle size of 200-300 mesh after ultrasonic treatment for different times at an ultrasonic power of 130W, the following study was conducted.

[0021] Figure 5 To measure the crude oil recovery rate of simulated oily sludge containing different mass fractions of quartz sand after ultrasonic treatment for different times at an ultrasonic power of 130W, with 600 mesh quartz sand added. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0023] This invention employs ultrasonic technology to treat oily sludge. The stability of the oily sludge is a key factor affecting the efficiency of ultrasonic treatment. The particle size and content of particulate matter in the oily sludge greatly affect the interaction strength with crude oil, thus altering the stability of the oily sludge. The cavitation, thermal, and mechanical effects generated by ultrasound can break the chemical bonds between the particulate matter and the crude oil, causing the crude oil to desorb from the sludge. Due to density differences, the crude oil floats at the top of the system, the particulate matter settles at the bottom, and the aqueous phase is located in the middle, thereby achieving crude oil recovery and three-phase separation.

[0024] This invention determines the optimal parameters for ultrasonic treatment using oily sludge taken from actual oilfields. Different simulated oily sludges are prepared by mixing oily sludge from the actual site with treated quartz sand. By changing the particle size and content of the quartz sand, the interaction strength between the particles and the crude oil is altered. Under the same ultrasonic conditions, the applicable range for ultrasonic treatment of oily sludge is determined using the crude oil recovery rate as an indicator.

[0025] Example 1

[0026] The oily sludge from the bottom of the tank was taken from an oilfield in North China. The oily sludge was relatively viscous and had poor flowability, with a viscosity of 11203 mPa·s. Experiments showed that the water content of the oily sludge was 11.17%, the solids content was 2.67%, and the oil content was 86.16%. With a fixed ultrasonic frequency of 25 kHz, orthogonal experiments and significance analysis were used to screen the main factors affecting the efficiency of ultrasonic treatment of the oily sludge. The orthogonal experiments and significance analysis are shown in Tables 1 and 2, respectively.

[0027] Table 1. Orthogonal experimental table for ultrasonic treatment

[0028] 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. Analysis of Variance Table of Orthogonal Experiment Results

[0030] 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] Table 2 shows that sample size is the main factor affecting the ultrasonic treatment of oily sludge. Under the condition of a limited sample size of 10g, the ultrasonic power and ultrasonic treatment time were further screened, and the results are shown in [Table 2]. Figure 2 As can be seen from the figure, the crude oil recovery effect is best when the ultrasonic power is 130W and the ultrasonic treatment time is 25min.

[0032] Therefore, the ultrasonic treatment parameters for the oily sludge in subsequent experiments were determined to be: ultrasonic frequency 25 kHz, sample size 10 g, ultrasonic power 130 W, and ultrasonic treatment time 25 min. Next, the properties of the oily sludge were altered 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) Take 200g of quartz sand in a 500ml beaker, add 100ml of 20% HCl solution and mix with the quartz sand. After stirring, soak for 2 hours, let it stand to precipitate, pour off the upper acid liquid, and wash the acid-washed quartz sand repeatedly with deionized water until the deionized water is clear. Stirring is required during this period. (2) After filtering out the deionized water, place the quartz sand in a 65℃ constant temperature drying oven to dry for 24 hours. After drying, take it out. (3) Add 100ml of 10% H2O2 solution, stir and soak for 0.5 hours. Pour off the upper liquid, wash repeatedly with deionized water until the deionized water is clear, filter out the deionized water, and place the quartz sand in a 65℃ constant temperature drying oven to dry for later use.

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

[0035]

[0036] The above nine simulated oily sludge samples with added quartz sand were subjected to ultrasonic treatment under the same ultrasonic conditions. The appropriate particle size and content of the added quartz sand were determined based on the crude oil recovery rate. The results are as follows: Figures 3-5 As shown in the figure, the amount of quartz sand added is 40% of the oily sludge. When the solid content of the simulated oily sludge is 41.6% and the particle size of the quartz sand is 200-300 mesh, the ultrasonic treatment effect is the best. After ultrasonic treatment for 25 minutes, the crude oil recovery rate is 34.23%. In summary, the ultrasonic treatment method of the present invention has universality and is applicable to any oily sludge with a solid content ≤41.6%.

Claims

1. A universal method for ultrasonic treatment of oily sludge, characterized in that, Includes the following steps: Step 1: Determine the moisture content, solids content, and oil content of the oily sludge; Step 2, Screening the optimal parameters for ultrasonic treatment of oily sludge: With a fixed sample size and ultrasonic frequency, an orthogonal experiment was conducted to determine the ultrasonic power and ultrasonic treatment time that yielded the highest crude oil recovery rate. Step 3: Add quartz sand with a particle size of 200-300 mesh to the oily sludge to adjust the solid content of the oily sludge to 41.6%. After mixing evenly, perform ultrasonic treatment on the sludge according to the optimal ultrasonic power and ultrasonic treatment time selected 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 ℃, cleaned with 10% H2O2 solution, washed with water, and dried at 65 ℃.

3. The universal method according to claim 1, characterized in that, In step 1, the water content of the oily sludge was 11.17%, the solid content was 2.67%, and the oil content was 86.16%. In step 2, the sample size was fixed at 10g, the ultrasonic frequency was 25KHz, the optimal ultrasonic power was 130W, and the ultrasonic treatment time was 25min. In step 3, based on the weight of the oily sludge as 100%, the amount of quartz sand added was 40%.

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