Cleaning-low-temperature pyrolysis combined remediation method suitable for high-concentration petroleum contaminated soil treatment

Abstract

The invention belongs to the field of petrochemical environmental protection, and relates to a cleaning-low-temperature pyrolysis combined remediation method for high-concentration petroleum contaminated soil. The problems of long oily soil treatment period, low efficiency, high cost and the like in an existing repairing process are solved. The method comprises the following steps: step 1, pretreating the petroleum-contaminated soil; 2, cleaning treatment is conducted on the contaminated soil, specifically, the prepared cleaning solution is added into a cleaning tank containing oily soil, after heating and stirring are conducted, the mixed solution in the cleaning tank is subjected to centrifugal treatment, and the centrifuged mixed solution is divided into three layers including an upper layer oil phase, a middle mixed solution and a bottom layer eluted soil; recovering an upper-layer oil phase and a middle-layer cleaning solution, and collecting lower-layer eluted soil; and 3, the lower-layer eluted soil is placed in a pyrolyzing furnace for low-temperature pyrolysis treatment. Petroleum pollutants in the soil are greatly recycled through the cleaning process under the optimal condition, the contaminated soil can be treated to reach the national construction land standard through the subsequent low-temperature pyrolysis process, economic benefits are created while hazardous waste is treated, the cost is reduced, the efficiency is improved, and the environmental protection pressure is relieved.

Description

Technical field:

[0001] The invention relates to the field of petrochemical environmental protection, and in particular to a cleaning-low-temperature pyrolysis combined repair method suitable for treating high-concentration petroleum-contaminated soil. Background technology:

[0002] Petroleum is a dark brown, viscous liquid and an extremely important industrial energy source. The main components are a mixture of alkanes, cycloalkanes, aromatic hydrocarbons and non-hydrocarbon compounds. With the development of the world's petroleum industry, oil spills have occurred frequently during oil extraction and transportation, with about 40-90 million liters of petroleum products leaking each year. Oil-contaminated soil has a large output and a high content of contaminated oil. The PAH compounds contained in it have toxicological effect characteristics. The physical and chemical properties of soil contaminated by high concentrations of petroleum hydrocarbons will change greatly, the soil porosity will decrease, the microbial community structure will be destroyed, and plants will not be able to grow. Petroleum hydrocarbon-contaminated soil has the characteristics of slow migration and degradation of pollutants, difficulty in pollution control, and long control cycle. If it is not treated, it can cause serious damage to the soil ecological environment and even endanger the health of living organisms. The green treatment of petroleum-contaminated soil has always attracted much attention.

[0003] At present, the mainstream methods for treating oil-contaminated soil at home and abroad are physical remediation, chemical remediation, and biological remediation. Physical remediation technology has high energy consumption, high cost, and large workload, and is not suitable for treating large amounts of oil-contaminated soil; chemical treatment is efficient, but costly, and the wastewater and waste liquid produced will cause secondary pollution if not properly treated; biological methods are only suitable for treating low-concentration oil-contaminated soil, and have high technical requirements and long remediation time. At present, the use of combined remediation processes can effectively solve the above problems.

[0004] Chinese invention patent 201310077643.1 discloses a method for cleaning petroleum pollutants and sludge. In circulating water at a temperature of 35°C to 45°C, the matured cleaning composition is fully mixed with the oily sludge in the crude oil tank, and the petroleum pollutants are separated through degassing and oxidation steps. The temperature of the circulating water is raised to 100 to 110°C and circulated, thereby separating the combustible gas in the device and oxidizing the harmful substances and pollutants. The invention can effectively separate and recover crude oil from oily sludge, and the oil content of the separated mud and sand meets the national stacking standard. The washing water can be recycled after heating treatment without causing secondary pollution. However, the energy consumption of this technology is high, the maturation time of the cleaning composition is long, the enzyme activity has high requirements for temperature and pH, the treatment process is complex, and the water consumption is large.

[0005] Chinese invention patent 201310077643.1 discloses a method for cleaning petroleum pollutants and sludge. In circulating water at a temperature of 35°C to 45°C, the matured cleaning composition is fully mixed with the oily sludge in the crude oil tank, and the petroleum pollutants are separated through degassing and oxidation steps. The temperature of the circulating water is raised to 100 to 110°C and circulated, thereby separating the combustible gas in the device and oxidizing the harmful substances and pollutants. The invention can effectively separate and recover crude oil from oily sludge, and the oil content of the separated mud and sand meets the national stacking standard. The washing water can be recycled after heating treatment without causing secondary pollution. However, the energy consumption of this technology is high, the maturation time of the cleaning composition is long, the enzyme activity has high requirements for temperature and pH, the treatment process is complex, and the water consumption is large.

[0006] China's public patent CN118268361A discloses a method for the coordinated restoration of petroleum-contaminated soil by strengthening electric elution and gas phase extraction with fluorocarbon surfactants. After eluting the petroleum-contaminated soil with a DC electric elution system, the desorption of petroleum pollutants in the soil is enhanced by fluorocarbon surfactants. The soil solution after elution is transported to the cathode chamber through electroosmosis. The extraction system transfers and extracts the elution waste liquid in the cathode chamber to the electrolyte recovery tank for treatment. After the volatile pollutants are extracted, they pass through a post-exhaust treatment device and meet the emission standards. This method can promote the rapid analysis, desorption and removal of petroleum pollutants in contaminated soil through a combined restoration method of surfactant desorption, electric elution and gas phase extraction, breaking through the problems of complex traditional contaminated soil elution operations and unsatisfactory restoration effects. However, this method has strict technical requirements and produces a large amount of waste electrolyte during the restoration process, which is not suitable for widespread promotion and use. Summary of the invention:

[0007] The present invention aims to solve the problems of poor remediation effect and high remediation cost of the three types of processes mentioned in the background of the invention, and provide a cleaning-low temperature pyrolysis combined remediation method for high-concentration petroleum contaminated soil. The present invention rationally combines two types of commonly used remediation processes, strictly controls the process conditions, and achieves high-efficiency remediation of high-concentration petroleum contaminated soil while recovering the petroleum in the soil to obtain economic benefits.

[0008] The present invention solves the problem through the following technical solution: A cleaning-low temperature pyrolysis combined remediation method for treating high-concentration petroleum contaminated soil, comprising the following steps:

[0009] Step 1: pre-treating petroleum contaminated soil to obtain treated material M1;

[0010] Step 2, preparing a cleaning solution for petroleum-contaminated soil; adding the prepared soil cleaning solution to a cleaning tank containing the soil M1 to be repaired in proportion, heating and stirring the cleaning tank to obtain a mixed solution, centrifuging the obtained mixed solution to separate the mixed solution into three layers, an upper oil phase, a middle cleaning mixed solution, and a bottom contaminated soil; recovering the upper oil phase and the middle cleaning solution, and separating and collecting the lower contaminated soil M2;

[0011] Step 3: subjecting the contaminated soil M2 separated from the lower layer to low-temperature pyrolysis treatment: adding the cleaned petroleum-contaminated soil to the pyrolysis reactor, setting a temperature rise program for pyrolysis treatment, and obtaining the final treated soil M3;

[0012] Step 4. Preferably, the soil pretreatment method in step 1 is as follows: collecting soil contaminated with high concentrations of petroleum hydrocarbons, crushing the collected soil contaminated with high concentrations of petroleum hydrocarbons, removing impurities, mixing the soil, and placing it in a soil cleaning tank.

[0013] Step 5: Preferably, in step 2, the compounded surfactant is dissolved in water and a certain amount of auxiliary agent is added to obtain a petroleum-contaminated soil cleaning solution.

[0014] Step 6. Preferably, the selected surfactant is a combination of sodium dodecylbenzene sulfonate (SDBS) and SYO, and the auxiliary agent is one of Na2CO3, Na2SO3, and Na2SiO3. The ratio of sodium dodecylbenzene sulfonate (SDBS) and SYO composite surfactant is 1:1 to 1:3, the surfactant concentration is 3.0 to 5.0 wt%, the auxiliary agent addition amount is 1.0 to 2.0 wt%, and the liquid-solid ratio of the cleaning solution to the soil mixture is 7:1 to 3:1.

[0015] Step 7: Preferably, the cleaning temperature is 50-60°C, the cleaning time is 3-5 hours, and the cleaning intensity is 300-400 r·min -1 .

[0016] Step 8. Preferably, the pyrolysis temperature is set to 420°C to 440°C, the heating rate is 15°C / min, and the pyrolysis time is 30 to 60 min;

[0017] Step 9. Preferably, the petroleum hydrocarbon content of the soil contaminated with high concentration of petroleum hydrocarbons is ≥ 10000 mg / kg; and the petroleum hydrocarbon content of the soil contaminated with high concentration of petroleum hydrocarbons after restoration is ≤ 826 mg / kg.

[0018] The overall process flow is as follows Figure 1 shown.

[0019] Compared with the prior art, the technical solution of the present invention has the following advantages and progress:

[0021] (1) During the cleaning process, the surfactants selected are two types of anionic surfactants, whose hydrophilic groups are all sulfonates. The water solubility of sulfonates is greater than that of other sulfate types, which increases the solubility of oil in water. After the SDBS surfactant and SYO surfactant are compounded with the auxiliary agent sodium silicate, sodium ions are introduced in the process, which can increase the number of surfactant micelles and increase the solubility of oil in the micelles. The addition of sodium ions will compress the diffuse electron layer of the aggregates, weaken the repulsive effect between the surfactant "ion heads", and allow more surfactant particles to enter the micelles without increasing the free energy of the system, and aggregate into larger micelles to provide more space for coating the oil pollution, increase the solubility of oil in water, and take it away from the soil phase. The solubilization effect is used to increase the elution rate of soil pollutants and improve the remediation effect. Because of the addition of sodium ions, the two surfactants have better cleaning effects on the light components and heavy components of the four components of oil.

[0022] (2) The cleaning process can wash away a large amount of oil from the petroleum-contaminated soil, and the washed oil can be recovered later through certain means, creating economic benefits while treating hazardous waste and reducing treatment costs. Compared with directly performing high-temperature pyrolysis on the petroleum-contaminated soil, the low-temperature pyrolysis process of the oil-contaminated soil after cleaning saves more energy and produces less gaseous pollutants, and the environmental pressure of subsequent treatment is smaller. In addition, the treated soil can meet the national construction land standards and can be used for resource-related purposes. Figure 1 Cleaning-pyrolysis combined process flow chart Figure 2 Soxhlet extraction device for determining oil content in petroleum-contaminated soil Figure 3 Fluorescence irradiation of oil-contaminated soil Figure 4 Fluorescence image of oil-contaminated soil after cleaning Figure 5 Fluorescence irradiation of petroleum contaminated soil after pyrolysis Specific implementation method:

[0023] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, an actual case analysis under the guidance of the invention technology is carried out below. In the detailed description of each case below, some specific details are described in detail, but are not limited to these embodiments. For the parts that are not described in detail, those skilled in the art can also fully understand the present invention.

[0024] Embodiment 1:

[0025] The high-concentration oil-contaminated soil comes from the Zhuanxi Oil Production Plant of Shengli Oilfield. The soil is dark brown and has a pungent odor. The oil content of the oil-contaminated soil to be repaired is 12984 mg / kg as measured by experiments.

[0026] (1) Soil pretreatment: 50 g of petroleum-contaminated soil from Shengli Oilfield was taken, crushed, impurities were removed, mixed evenly, and placed in a cleaning tank;

[0027] (2) Cleaning process: Prepare a cleaning solution by dissolving 1.0 g of sodium dodecylbenzene sulfonate (SDBS), 2.0 g of SYO surfactant, and 1.0 g of an auxiliary agent (one of Na2CO3, Na2SO3, and Na2SiO3) in water to prepare a petroleum-contaminated soil cleaning solution. Take 150 ml of the prepared soil cleaning solution and add it to a cleaning tank. Heat the cleaning solution to 50°C and stir and mix it at a rate of 400 r / min to form a mixed solution. The stirring and mixing time is 5 h. Then, the obtained mixed solution is centrifuged at a speed of 8000 r / min for 5 min. After centrifugation, the mixed solution is separated into three layers, an upper oil phase, a middle water phase, and a bottom soil phase. Recover the upper oil phase and the middle layer cleaning solution, and separate and collect the lower layer of cleaned contaminated soil.

[0028] (3) Low-temperature pyrolysis process: The separated lower layer of cleaned contaminated soil is simply dried and placed in a pyrolysis device. The setting conditions are a heating rate of 15°C / min, a pyrolysis temperature of 420°C, and a pyrolysis time of 30 minutes. After the pyrolysis is completed, the repaired soil can be obtained. The oil content of the treated oily soil is 578 mg / kg.

[0029] Embodiment 2:

[0030] The high-concentration oil-contaminated soil comes from Xinjiang Oilfield. The soil is dark brown and has a pungent smell. The oil content of the oil-contaminated soil to be repaired is 16787 mg / kg as measured by experiments.

[0031] (1) Soil pretreatment: 50 g of petroleum-contaminated soil from Xinjiang Oilfield was taken, crushed, impurities were removed, mixed evenly, and placed in a cleaning tank;

[0032] (2) Cleaning process: prepare a cleaning solution, dissolve 2.0g of sodium dodecylbenzene sulfonate (SDBS), 2.0g of SYO surfactant, and 1.5g of an auxiliary agent (one of Na2CO3, Na2SO3, and Na2SiO3) in water to prepare a petroleum-contaminated soil cleaning solution, take 200ml of the prepared soil cleaning solution and add it to a cleaning tank, heat the cleaning solution to 55°C, stir and mix at a rate of 400r / min to form a mixed solution, stir and mix for 5h, and then centrifuge the obtained mixed solution at a speed of 8000r / min for 5min. After centrifugation, the mixed solution is divided into three layers, an upper oil phase, a middle water phase, and a bottom soil phase; recover the upper oil phase and the middle layer cleaning solution, and separate and collect the lower layer of cleaned contaminated soil;

[0033] (3) Low-temperature pyrolysis process: The separated lower layer of cleaned contaminated soil is simply dried and placed in a pyrolysis device. The setting conditions are a heating rate of 15°C / min, a pyrolysis temperature of 430°C, and a pyrolysis time of 40 minutes. After the pyrolysis is completed, the repaired soil can be obtained. The oil content of the treated oily soil is 609 mg / kg.

[0034] Embodiment 3:

[0035] The high-concentration oil-contaminated soil comes from Daqing Oilfield. The soil is black and has a pungent smell. The oil content of the oil-contaminated soil to be repaired is 20432 mg / kg through experiments.

[0036] (1) Soil pretreatment: 50 g of Daqing oilfield petroleum-contaminated soil was taken, crushed, impurities were removed, mixed evenly, and placed in a cleaning tank;

[0037] (2) Cleaning process: Prepare a cleaning solution by dissolving 1.0 g of sodium dodecylbenzene sulfonate (SDBS), 3.0 g of SYO surfactant, and 1.5 g of an auxiliary agent (one of Na2CO3, Na2SO3, and Na2SiO3) in water to prepare a petroleum-contaminated soil cleaning solution. Take 300 ml of the prepared soil cleaning solution and add it to a cleaning tank. Heat the cleaning solution to 55°C and stir and mix it at a rate of 400 r / min to form a mixed solution. The stirring and mixing time is 5 h. Then, the obtained mixed solution is centrifuged at a speed of 8000 r / min for 5 min. After centrifugation, the mixed solution is divided into three layers, an upper oil phase, a middle water phase, and a bottom soil phase. Recover the upper oil phase and the middle layer cleaning solution, and separate and collect the lower layer of cleaned contaminated soil.

[0038] (3) Low-temperature pyrolysis process: The separated lower layer of cleaned contaminated soil is simply dried and placed in a pyrolysis device. The setting conditions are a heating rate of 15°C / min, a pyrolysis temperature of 430°C, and a pyrolysis time of 50 min. After the pyrolysis is completed, the repaired soil can be obtained. The oil content of the treated oily soil is 655 mg / kg.

[0039] Embodiment 4:

[0040] The high-concentration oil-contaminated soil comes from Liaohe Oilfield. The soil is black and has a pungent smell. The oil content of the oil-contaminated soil to be repaired is 21458 mg / kg through experiments.

[0041] (1) Soil pretreatment: 50 g of petroleum-contaminated soil from Liaohe Oilfield was taken, crushed, impurities were removed, mixed evenly, and placed in a cleaning tank;

[0042] (2) Cleaning process: Prepare a cleaning solution by dissolving 1.0 g of sodium dodecylbenzene sulfonate (SDBS), 4.0 g of SYO surfactant, and 2.0 g of an auxiliary agent (one of Na2CO3, Na2SO3, and Na2SiO3) in water to prepare a petroleum-contaminated soil cleaning solution. Take 350 ml of the prepared soil cleaning solution and add it to a cleaning tank. Heat the cleaning solution to 60°C and stir and mix it at a rate of 400 r / min to form a mixed solution. The stirring and mixing time is 5 h. Then, the obtained mixed solution is centrifuged at a speed of 8000 r / min for 5 min. After centrifugation, the mixed solution is separated into three layers, an upper oil phase, a middle water phase, and a bottom soil phase. Recover the upper oil phase and the middle layer cleaning solution, and separate and collect the lower layer of cleaned contaminated soil.

[0043] (3) Low-temperature pyrolysis process: The separated lower layer of cleaned contaminated soil is simply dried and placed in a pyrolysis device. The setting conditions are a heating rate of 15°C / min, a pyrolysis temperature of 440°C, and a pyrolysis time of 60 min. After the pyrolysis is completed, the repaired soil can be obtained. The oil content of the treated oily soil is 734 mg / kg.

[0044] Attached Figure 2 The device for determining the oil content of petroleum-contaminated soil is shown, that is, using a Soxhlet extraction device to determine the petroleum hydrocarbon content. The determination process and device are shown in the attached figure. The results of the petroleum hydrocarbon content of the high-concentration petroleum hydrocarbon-contaminated soil after remediation in Examples 1 to 4 are shown in Table 1 below:

[0047] Table 1:

[0048]

[0049] During the implementation of the embodiment, based on the characteristic that oil will appear red when exposed to green fluorescence, the oil content in oil-contaminated soil, soil after cleaning, and soil after pyrolysis was characterized by fluorescence microscopy, as shown in the attached drawings of the specification. It was found that the oil in the oil-contaminated soil was largely removed after cleaning and was completely removed after the pyrolysis process was completed.

[0050] The above description does not limit the present invention in any form. Although the present invention has been disclosed as above through the embodiments, the above does not limit the present invention. Any technician familiar with the profession can make some changes or modify the technical contents disclosed above into equivalent embodiments with equivalent changes without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A cleaning-low temperature pyrolysis combined remediation method suitable for treating high concentration petroleum contaminated soil, characterized in that: The following steps are involved: Step 1: Pretreatment of petroleum contaminated soil; Step 2, preparing a cleaning solution for petroleum-contaminated soil; adding the prepared soil cleaning solution to a cleaning tank containing contaminated soil, heating and stirring to obtain a mixed solution, and centrifuging the mixed solution to separate it into three layers, an upper oil phase, a middle cleaning solution, and a bottom eluted soil; separating the upper oil phase, recovering the middle cleaning solution, and collecting the bottom eluted soil; Step 3: subjecting the contaminated soil separated from the lower layer to low-temperature pyrolysis treatment: the cleaned petroleum-contaminated soil is put into the pyrolysis reactor, and a temperature rising program is set to perform pyrolysis treatment, so as to obtain pyrolysis-treated soil.

2. The cleaning-low temperature pyrolysis combined remediation method suitable for treating high concentration petroleum contaminated soil according to claim 1, characterized in that: The soil pretreatment method in step 1 comprises collecting soil contaminated with high concentration of petroleum hydrocarbons, crushing the collected soil contaminated with high concentration of petroleum hydrocarbons, removing impurities, mixing the soil, and placing the soil in a soil cleaning tank.

3. The cleaning-low temperature pyrolysis combined remediation method suitable for treating high concentration petroleum contaminated soil according to claim 1, characterized in that: The step 2 is to prepare the cleaning solution for petroleum-contaminated soil: the surfactant is compounded, and an auxiliary agent is added and dissolved in water to form a cleaning solution.

4. The cleaning-low temperature pyrolysis combined remediation method for high concentration petroleum contaminated soil according to claim 1, characterized in that: In step 2, the mass ratio of the cleaning solution added to the contaminated soil is 7:1 to 3:

1.

5. The cleaning-low temperature pyrolysis combined remediation method for treating high concentration petroleum contaminated soil according to claim 3, characterized in that: In the combination of sodium dodecylbenzene sulfonate (SDBS) and SYO in step 2, the auxiliary agent type is one of Na2CO3, Na2SO3, and Na2SiO3.

6. The cleaning-low temperature pyrolysis combined remediation method for treating high concentration petroleum contaminated soil according to claim 5, characterized in that: The ratio of sodium dodecylbenzene sulfonate (SDBS) and SYO compound surfactant is 1:1-1:3, the surfactant concentration is 3.0-5.0wt%, and the additive amount is 1.0-2.0wt%.

7. The cleaning-low temperature pyrolysis combined remediation method for treating high concentration petroleum contaminated soil according to claim 1, characterized in that: In step 2, the cleaning temperature is 50-60°C, the cleaning time is 3-5 hours, and the cleaning intensity is 300-400 r·min -1 The obtained mixed solution was centrifuged at a speed of 8000 r / min and the centrifugation time was 5 min.

8. The cleaning-low temperature pyrolysis combined remediation method for high concentration petroleum contaminated soil according to claim 1, characterized in that: In step 3, the pyrolysis temperature is set to 420-440° C., the heating rate is 15° C. / min, and the pyrolysis time is 30-60 min.

9. The cleaning-low temperature pyrolysis combined remediation method suitable for treating high concentration petroleum contaminated soil according to claim 1, characterized in that: The petroleum hydrocarbon content in soil contaminated with high concentrations of petroleum hydrocarbons is ≥10,000 mg / kg; the petroleum hydrocarbon content in soil contaminated with high concentrations of petroleum hydrocarbons after remediation is ≤826 mg / kg.

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