CN110947746A - Ectopic cleaning method for repairing petroleum-polluted soil - Google Patents
Ectopic cleaning method for repairing petroleum-polluted soil Download PDFInfo
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- CN110947746A CN110947746A CN201911314467.2A CN201911314467A CN110947746A CN 110947746 A CN110947746 A CN 110947746A CN 201911314467 A CN201911314467 A CN 201911314467A CN 110947746 A CN110947746 A CN 110947746A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/02—Extraction using liquids, e.g. washing, leaching, flotation
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The invention relates to the technical field of petroleum-polluted soil remediation, in particular to an ex-situ cleaning method for the petroleum-polluted soil remediation. The method comprises the steps of analyzing the mechanical composition characteristics of the petroleum-polluted soil to be treated, primarily screening and analyzing the dirty oil desorption rate characteristics in a cleaning system, establishing specific two-stage cleaning flows aiming at the soil with different textures according to analysis data, determining cleaning-level replacement time nodes, realizing the cleaning process of the petroleum-polluted soil with different particle sizes, and recycling all levels of cleaning liquid. The invention realizes the high-efficiency and low-consumption cleaning treatment process of the high-concentration petroleum polluted soil.
Description
Technical Field
The invention relates to the technical field of petroleum-polluted soil remediation, in particular to an ex-situ cleaning method for the petroleum-polluted soil remediation.
Background
With the continuous advance of industrialization, the petrochemical industry develops rapidly, and the petroleum pollution problem becomes more prominent. The quantity of the petroleum-polluted soil is increased every year, and the treatment requirement is more urgent. In the prior art, various physical, chemical and biological repair methods are developed and applied, but the engineering application of each repair technology is always restricted by the treatment technical defects of high cost, low efficiency and multiple risks. The soil cleaning technology is a traditional physical remediation technology, adopts a method of applying a water phase combined medicament to enhance the hydrophilicity of the petroleum pollutants, elutes the petroleum molecules adhered to the surface of the soil colloid, and performs centralized treatment on the cleaning solution, thereby achieving the purpose of removing the petroleum pollutants from the soil environment and achieving the remediation of the petroleum-polluted soil.
At present, in the cleaning and treatment of the petroleum-polluted soil, the in-situ leaching technology has the advantage of being suitable for large-scale restoration, but is limited by the soil permeability, the leaching solution direction and the like which are difficult to control. In-situ leaching technology only faces to the hydraulic transmission coefficient>10-3The removal efficiency of consumed pollutants is achieved only when the soil is porous and permeable in cm/s, and the leaching solution flows in an indefinite direction, so that the underground water is easily polluted. The soil ex-situ cleaning technology is used for carrying out pollutant elution treatment on the excavated polluted soil by utilizing cleaning equipment and structures, and has the advantages of high treatment load, wide usability, strong normalization, short treatment period and the like. However, the existing soil ex-situ leaching technology mainly uses the integral soil cleaning with a medicament, lacks the targeted cleaning for the structural properties of soil, and most of the elution waste liquid is discharged after centralized treatment, thereby causing the waste of energy consumption and hydraulic resources, increasing the operation cost and improving the difficulty of cleaning quality guarantee.
Meanwhile, in the development of the multi-stage cleaning technology in recent years, the defects that cleaning targets of all stages of cleaning processes are not clear, the multi-stage cleaning processes are redundant, all stages of cleaning solutions are not recycled or recycled in a disordered manner, time nodes connected among all stages of cleaning processes are not clear and accurate, and separating means among all phases of all stages of cleaning systems are not clear are commonly existed, so that the adverse effects that the multi-stage cleaning implementation efficiency is not high, the effect is limited, the cleaning load of polluted soil is increased, the cleaning cost is increased and the like due to the disordered recycling of the cleaning solutions are caused. The patent aims at the problems to carry out targeted cleaning process design and realize the aim of cleaning and treating the petroleum polluted soil by high-efficiency recycling.
Disclosure of Invention
The invention aims to establish an ex-situ cleaning method for restoring petroleum-polluted soil.
In order to achieve the purpose, the invention adopts the technical scheme that:
an ex-situ cleaning method for repairing petroleum-polluted soil is characterized in that the petroleum-polluted soil to be treated is subjected to mechanical composition characteristic analysis, primary screening and dirty oil desorption rate characteristic analysis in a cleaning system, the specific two-stage cleaning process aiming at the soil with different textures and cleaning level replacement time nodes are carried out according to analysis data, the cleaning process of the petroleum-polluted soil with different particle sizes is achieved, and meanwhile, cleaning solutions at all stages are recycled.
Further, performing mechanical composition characteristic analysis on the petroleum-polluted soil to be treated, and determining a two-stage soil cleaning process; and determining a cleaning grade replacement time node according to the first-stage elution rate change characteristics of the petroleum pollutants in the cleaning system, thereby realizing the cleaning of the petroleum polluted soil under different particle sizes.
The mechanical composition characteristic of the petroleum polluted soil to be treated is that when the sand grain component (0.05-2mm) is more than or equal to 25 percent and the sticky grain component (less than 0.002mm) is less than or equal to 35 percent, the soil is defined as sandy soil, and a two-stage decrement cleaning process is selected; when the sand grain component (0.05-2mm) < 25% or the sticky grain component (<0.002mm) > 35%, the soil is defined as non-sandy soil, and a two-stage cleaning process is selected.
The cleaning grade replacement time node is determined according to the change characteristics of the elution rate of the petroleum pollutants in the cleaning system, and when the first-stage elution rate of the dirty oil in the elution system is reduced to 0-20% of the maximum elution rate, the second-stage cleaning is carried out.
In a further aspect of the present invention,
(1) and (3) analyzing the soil characteristics: analyzing the mechanical composition of the petroleum-polluted soil, judging whether the polluted soil is sandy soil or non-sandy soil, and determining the selection of a cleaning process flow;
(2) cleaning pretreatment: mixing oil-contaminated soil and first-stage cleaning solution hot-alkali water (generally mixed according to the volume ratio of 1: 5-1: 20), fully stirring and pulping, and transferring the slurry into a mechanical oscillating screen for wet oscillating screening; separating clean gravel components with the particle size of more than 5mm, and feeding the sieved slurry into a cleaning tank for primary cleaning;
(3) first-stage cleaning: performing primary cleaning according to a cleaning process route determined by the attributes (mechanical composition and cleaning level replacement time node) of the soil to be treated; the sandy soil screened slurry is stirred, mixed and cleaned in a primary cleaning tank according to set time, then a solid/liquid two-phase separation is carried out through a cyclone separator, clean soil components with the particle size of 0.2-5mm are screened out, and slurry mixture containing the soil with the particle size of less than 0.2mm enters secondary cleaning;
or, the non-sandy soil screened slurry is stirred, mixed and cleaned with hot alkaline water in a primary cleaning tank according to set time, solid/liquid three-phase separation is carried out through a horizontal spiral centrifuge, all soil solids with the particle size of less than 5mm, a cleaning liquid phase and a dirty oil phase are separated, and all soil solids with the particle size of less than 5mm enter a secondary cleaning tank for secondary cleaning; (3) secondary cleaning: when sandy soil is treated, the primary cleaning discharge slurry is continuously fully stirred, mixed and cleaned in a secondary cleaning tank through hot alkali, the discharged material enters a lamination centrifuge for solid/liquid two-phase separation, clean soil components with the grain size of 0.01-0.2mm are separated, a residual oil/water/soil mixed phase is subjected to emulsion breaking treatment and then enters a flotation machine for separating a cleaning water phase and a dirty oil phase, residual muck in the flotation machine is less than 0.01mm, the residual muck enters an acidification tank for treatment, the unearthed soil and the clean soil components with the grain size of 0.01-0.2mm separated by the lamination are combined for screw-stacking dehydration treatment, and finally the discharged material is clean soil with the grain size of less than 0.2 mm;
or, the non-sandy soil is treated, all soil solids with the particle size of less than 0.5mm are mixed with cleaning liquid added with surfactant medicaments in a secondary cleaning tank and are fully stirred and cleaned, the discharged materials enter a lamination centrifuge for solid/liquid two-phase separation, clean soil components with the particle size of 0.01-5mm are separated, a residual oil/water/soil mixed phase (the soil components with the particle size of less than 0.01 mm) enters an oil-water separation tank for oil/water separation, the residual discharged materials of the oil-water separation tank enter a flotation machine after emulsion breaking, the flotation machine obtains residual dregs, the residual dregs are treated by an acidification tank and then are combined with the clean soil components with the particle size of 0.01-5mm separated by the lamination for screw lamination dehydration, and finally the discharged materials are the soil components with the particle size of less than 5mm, namely the clean soil.
In the two-stage decrement cleaning process, respectively collecting a flotation separation water phase and a stacked spiral dehydration water phase after the second-stage cleaning, and recycling the flotation separation water phase and the stacked spiral dehydration water phase as a cleaning solution for the first-stage cleaning; in the two-stage cleaning process, the cleaning liquid phase separated by the horizontal screw after the first-stage cleaning is reused in the hot alkali cleaning liquid in the first-stage cleaning tank, the separated water phase in the oil-water separation tank after the second-stage cleaning, the separated water phase in the flotation machine and the overlapped screw dehydration water phase are recycled as the cleaning liquid components of the second-stage cleaning tank, the mode of cleaning liquid recycling is adopted, and zero emission is realized.
Furthermore, the cleaning process is designed as follows:
(1) and (3) analyzing the soil characteristics: after excavating and crushing high-concentration petroleum polluted soil, analyzing the texture of the soil, performing a soil cleaning pilot test by adopting a cleaning solution system, determining the characteristic of the elution rate of dirty oil, and determining the selection of a cleaning process;
(2) cleaning pretreatment: mixing the oil-contaminated soil and first-stage cleaning liquid hot-alkali water in a given proportion in a pulping tank, fully stirring and pulping, and transferring the pulp into a mechanical oscillating screen for wet oscillating screening; separating clean gravel components with the particle size of more than 5mm, and enabling the sieved slurry to enter a cleaning tank for further cleaning treatment;
(3) first-stage cleaning: aiming at sandy soil treatment, slurry is stirred, mixed and cleaned in a primary cleaning tank, then a solid/liquid two-phase separation is carried out through a cyclone separator, clean soil components with the grain size of 0.2-5mm are screened out, residual components are also oil/water/soil mixed phases containing a small amount of water, and the oil/water/soil mixed phases enter a secondary cleaning tank for secondary cleaning; aiming at non-sandy soil treatment, slurry is stirred and cleaned with hot alkaline water in a primary cleaning tank, solid/liquid three-phase separation is carried out through a horizontal spiral centrifuge, all soil solids with the particle size of less than 5mm, a cleaning liquid phase and a dirty oil phase are separated, cleaning liquid and hot alkaline water washing liquid are mixed and prepared and are reused for primary cleaning of a new batch of polluted soil, the dirty oil phase enters a dirty oil tank to be collected, and all soil solids with the particle size of less than 5mm enter a secondary cleaning tank to be subjected to secondary cleaning.
(4) Secondary cleaning: aiming at sandy soil treatment, the primary cleaning discharge slurry is continuously fully stirred and cleaned in a secondary cleaning tank, the discharged material enters a lamination centrifuge for solid/liquid two-phase separation, clean soil components with the grain size of 0.01-0.2mm are separated, the residual oil/water/soil mixed phase is subjected to emulsion breaking treatment and then enters a flotation machine for separating a cleaning water phase and a dirty oil phase, the dirty oil phase enters an oil storage tank for storage, the water phase is recycled in the primary cleaning tank, residual muck in the flotation machine is less than 0.01mm, the residual muck enters an acidification tank for treatment, the unearthed soil and the clean soil components with the grain size of 0.01-0.2mm separated by the lamination are combined for screw-overlapping dehydration treatment, the final discharged material is clean soil with the component of less than 0.2mm, and the cleaning liquid water phase and the effluent of the flotation machine are jointly recycled in the primary cleaning tank, so; aiming at non-sandy soil treatment, mixing and fully stirring and cleaning all soil solids with the size of less than 0.5mm in a secondary cleaning tank by a cleaning solution added with a new surfactant medicament, discharging the mixture into a lamination centrifuge for solid/liquid two-phase separation, separating clean soil components with the size of 0.01-5mm, performing oil/water separation treatment twice because the content of clay particles in the soil with the size of less than 0.01 component in the residual oil/water/soil mixed phase is higher, separating the mixture by an oil-water separation tank, feeding the oil phase into an oil storage tank, feeding the water phase into a secondary cleaning tank for recycling, feeding the residual discharge material from the oil-water separation tank into a flotation machine after demulsification, completing oil/water re-separation, feeding the oil phase into an oil storage tank, feeding the water phase into a secondary cleaning tank for recycling, combining the residual muck with the clean soil components with the size of 0.01-5mm separated from the lamination after being treated by an acidification tank for carrying out, finally discharging to obtain clean soil with components of less than 5mm, and enabling the water phase of the cleaning solution to enter a secondary cleaning tank to finish zero-emission recycling of the cleaning solution.
The invention has the following advantages and beneficial effects:
the invention discloses an ex-situ cleaning method for petroleum-contaminated soil, which is designed according to the petroleum contamination characteristics of different soil textures in a classified manner to realize targeted cleaning of the petroleum-contaminated soil, and specifically comprises the following steps:
(1) according to the invention, the petroleum polluted soil is divided into sandy soil and non-sandy soil according to the texture characteristics, wherein the sandy soil is high in sand component content ratio, low in powder and clay component content ratio, the non-sandy soil is low in sand component content, high in powder and clay component content, small in sand component specific surface area, weak in dirty oil adsorption, easy to clean and desorb, large in clay component specific surface area, high in dirty oil adsorption capacity and difficult to clean, so that the polluted soil is subjected to classification and shunt process treatment according to the texture characteristics, the pollution degree of low-pollution components is prevented from being increased, the treatment load and energy consumption are reduced, and targeted and efficient treatment is realized.
(2) The invention adopts a method of cleaning and screening sand soil, the cleaning of sand soil pollution is relatively easy, the first-stage cleaning can meet the treatment requirement, the slurry containing fine-particle soil components such as powder particles, sticky particles and the like after the screening and separation is continuously subjected to second-stage cleaning, the cleaning period is further prolonged while the cleaning reduction of the polluted soil is realized, the fine-particle soil pollution components with higher adsorption content and higher strength are promoted to desorb dirty oil, and the purposes of low consumption and high efficiency cleaning are achieved.
(3) The invention adopts an integral multi-stage cleaning method for non-sandy soil, and mainly uses powder particles and sticky particles, so that the integral two-stage cleaning process is carried out after soil gravel components with the particle size larger than 5mm are pretreated, the cleaning solution containing surfactant is replaced by a three-phase separation mode after the weak adsorption sump oil on the outer layer of the soil particles is removed by one-stage hot alkali cleaning, and the washing solution containing surfactant is continuously eluted for the soil components with the particle size smaller than 5mm, so that the energy consumption load of separation of the particle size components due to overhigh content of the fine particle size components is avoided, the targeted elution is carried out for the adsorption strength of the sump oil, and the cleaning efficiency is improved.
(4) The cleaning waste liquid generated by different cleaning processes has certain difference according to different characteristics of cleaning medicines of the components of the soil to be cleaned and the like, so that the recycling modes are different. Aiming at the multistage decrement cleaning process, after 0.2-5mm component soil particles are separated by primary cleaning, the original cleaning system is continuously subjected to secondary cleaning and separation, so that the same thermokalite cleaning solution is used for both cleaning, and the cleaning waste liquid is recycled into an initial primary cleaning tank after deoiling treatment; and aiming at the two-stage cleaning process, a horizontal centrifuge is adopted for three-phase separation after the first-stage cleaning, only soil containing a small amount of water enters a second-stage cleaning stage, a surfactant agent is injected into the second-stage cleaning, and the whole soil cleaning with the components of less than 5mm is continuously carried out under the condition of not carrying out soil reduction, so that the cleaning waste liquid of the two-stage cleaning has different components and is not suitable for cross or mixed use, and the cleaning waste liquid is recycled in the current cleaning process. The targeted reuse mode also has the targeting property of the technical process, and the increase of the cleaning load caused by cross contamination is avoided.
(5) According to the elution rate in the primary cleaning process and the secondary cleaning process, when the elution rate is reduced to 0-20% of the maximum elution rate, the primary cleaning process is stopped and the secondary cleaning process is performed, so that the cleaning energy consumption is saved, and the low-efficiency cleaning process is reduced.
(6) The ectopic cleaning process is particularly suitable for cleaning and treating the high-concentration petroleum polluted soil, and can obtain good standard-reaching treatment effect.
Drawings
FIG. 1 is a flow chart of the process for cleaning the petroleum-contaminated soil provided by the invention.
Fig. 2 is a graph showing the change of desorption rate in the cleaning test of the petroleum-contaminated sandy soil provided in example 1 of the present invention.
Fig. 3 is a diagram showing the cleaning effect of the petroleum-contaminated sandy soil provided in embodiment 1 of the present invention.
Fig. 4 is a graph showing the change of desorption rate in the cleaning test of the petroleum-contaminated non-sandy soil according to example 2 of the present invention.
Fig. 5 is a diagram illustrating the cleaning effect of the petroleum-contaminated non-sandy soil according to embodiment 2 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The established ectopic cleaning process for the petroleum-contaminated soil carries out double-flow design aiming at the texture characteristics of the contaminated soil, combines scientific linkage of a multi-stage cleaning stage and recycling of cleaning liquid, and effectively realizes a cleaning and desorption process for the petroleum-contaminated soil with high efficiency and low consumption.
The invention develops a targeted cleaning process design aiming at the property difference of the mechanical composition and the like of the polluted soil, considers the difference of the adsorption characteristics between different soil size fraction compositions and petroleum pollutants, generally speaking, the soil clay component in sandy soil is relatively low, the content of each size fraction component is relatively average, the specific surface area of the sandy component with higher content is smaller, the content of adsorbed dirty oil is not high, and the cleaning is trade-carried out, so that the treatment is suitable for respectively treating each size fraction, the loam clay component content is high, the separation of each size fraction in the cleaning is difficult, and the integral multiple cleaning efficiency is higher after the separation of the components with super-large particle size. Therefore, different process flows are designed by the invention, and the cleaning fluid is recycled in each process flow so as to achieve the aim of a targeted cleaning process and realize the ectopic cleaning process of the petroleum-polluted soil, which has the advantages of soil treatment reduction, harmless oil stain collection and recycling of the cleaning fluid.
Example 1 ectopic cleaning treatment of oil-contaminated sandy soil
Referring to fig. 1, the contaminated soil used in the test is high-concentration petroleum contaminated soil which is contaminated by petroleum in oil field for a long time, and the oil content of the soil is measured to be 15.2% (W/W, g.g.g) after the soil is crushed and impurity-removed-1). Soil is first removed by sieving>5mm fraction, then against<The soil cleaning test is carried out on 5mm components, each parameter condition of a project treatment cleaning system is simulated, the composition of soil size fractions is analyzed, hot alkaline water with the pH value of 11 and the temperature of 70 ℃ is selected as a cleaning solution, the cleaning solution is mixed with the screened polluted soil, the solid-liquid mixing ratio is 1:15(g/g), the soil is cleaned under the stirring intensity of 160r/min, the cleaning temperature is kept at 70 ℃, the cleaning period is 48min, the soil sample is cleaned every 3min, the petroleum residue rate in the soil is measured, the composition of the analyzed soil size fractions can be obtained, the soil mechanical components comprise 48.6% of sand grains, 31.6% of powder grains and 19.8% of sticky grains, the soil belongs to sandy soil, and therefore a multi-stage decrement cleaning process is selected for cleaning and treating the petroleum polluted soil. In the cleaning test process, when the cleaning time is as long as 15min, the desorption rate of the petroleum reaches 5.88 mg/kg.min at the maximum, and the desorption rate is reduced to 0.88 mg/kg.min at 30min, which is 15% of the maximum desorption rate, so that the secondary cleaning treatment needs to be carried out when the primary cleaning is carried out for 30min (see fig. 2).
A large-scale engineering treatment demonstration test (testA) is carried out by taking the petroleum polluted soil after crushing and impurity removal as a treatment object, and meanwhile, a control treatment (ckA) of single continuous cleaning of the complete soil component is set. Exemplary test group cleaning conditions were: the first-stage cleaning solution is hot alkaline solution with pH of 11, the cleaning temperature is 70 ℃, the solid-to-liquid ratio is 1:15(g/g), the cleaning mixing intensity is 150r/min, and the stirring time is 30 min. The cleaning process comprises the following steps: mixing the oil-contaminated soil and a first-stage hot alkali cleaning solution in a pulping tank, fully stirring and pulping, and transferring the pulp into a mechanical oscillating screen for wet oscillating screening; separating clean gravel components with the particle size of more than 5mm, sieving slurry, feeding the slurry into a first-stage cleaning tank, stirring and cleaning, then performing solid/liquid two-phase separation through a cyclone separator, screening out clean soil components with the particle size of 0.2-5mm, enabling residual components to be oil/water/soil mixed phases containing a small amount of water, feeding the oil/water/soil mixed phases into a second-stage cleaning tank, continuously performing full stirring and cleaning, discharging the material, feeding the material into a lamination centrifuge for solid/liquid two-phase separation, separating out clean soil components with the particle size of 0.01-0.2mm, performing emulsion breaking treatment on the residual oil/water/soil mixed phases, feeding the residual oil/water/soil mixed phases into a flotation machine for separating out a cleaning water phase and a dirty oil phase, feeding the dirty oil phase into an oil storage tank for storage, recycling the water phase into the first-stage cleaning tank, enabling residual muck in the flotation machine to be less than 0.01mm in size, feeding the acidification tank for treatment, performing stack screw, the final discharge is clean soil with the components of less than 0.2mm, and the water phase of the cleaning liquid and the effluent of the flotation machine are jointly reused in a primary cleaning tank. After the soil of each size fraction component is mixed and homogenized, the residual petroleum amount is determined to be 1.9 percent and less than 2 percent, the treatment standard aiming at the soil polluted by high-concentration petroleum is achieved, and the residual petroleum rate of the soil of a control group is up to 8.9 percent (see figure 3).
Therefore, the multistage decrement cleaning process for sandy soil effectively cleans soil components of each size fraction, has good cleaning capability particularly for fine particle (powder and clay) components with large pollution load, greatly improves the cleaning and desorption efficiency of the whole high-concentration petroleum polluted soil, and realizes standard treatment of the polluted soil.
Example 2 ectopic cleaning and treatment of non-sandy soil polluted by petroleum
The contaminated soil used in the test is high-concentration petroleum-contaminated soil which is contaminated by petroleum for a long time in an oil field and a well siteAfter the soil is broken and decontaminated, the oil content is measured to reach 16.8 percent (W/W, g.g)-1). The soil is firstly pretreated and removed by wet screening>5mm fraction, then against<The method comprises the steps of carrying out a soil cleaning test on 5mm components, simulating various parameter conditions of an engineering treatment cleaning system to analyze the composition of soil size fractions, selecting 70-DEG C hot alkaline water with pH of 10.5 as a cleaning solution, mixing the hot alkaline water with the screened contaminated soil to enable the solid-liquid mixing ratio of the mixed solution to be 1:16(g/g), cleaning under the stirring intensity of 140r/min, keeping the cleaning temperature at 70 ℃, carrying out cleaning period to be 60min, sampling a soil cleaning sample every 3min, and measuring the petroleum residue rate in the soil. The composition of the soil grain fraction can be analyzed, the mechanical components of the soil comprise 12.6 percent of sand grains, 44.6 percent of powder grains and 42.8 percent of sticky grains, and the mechanical components belong to powdery sticky loam, namely non-sandy soil, so a two-stage cleaning process is selected for cleaning and treating the petroleum-polluted soil. In the process of a small-scale cleaning test, when the cleaning time is as long as 18min, the desorption rate of petroleum reaches 6.0 mg/kg.min at the maximum, and the desorption rate is reduced to 0.61 mg/kg.min at 33min and is 10.2 percent of the maximum desorption rate (see figure 4), so that the secondary cleaning treatment needs to be carried out when the primary cleaning time is 33 min.
And (3) carrying out a large-scale engineering treatment demonstration test (testB) by taking the petroleum polluted soil after crushing and impurity removal as a treatment object, and simultaneously setting a control treatment (ckB) of continuously cleaning the whole soil component once under the same cleaning solution condition. Exemplary test group cleaning conditions were: the first-stage cleaning solution is hot alkaline solution with pH of 10.5, the cleaning temperature is 70 ℃, the solid-to-liquid ratio is 1:16(g/g), the cleaning mixing intensity is 140r/min, and the stirring time is 33 min. The cleaning process comprises the following steps: mixing the oil-contaminated soil and a first-stage hot alkali cleaning solution in a pulping tank, fully stirring and pulping, and transferring the pulp into a mechanical oscillating screen for wet oscillating screening; separating clean gravel components with the particle size of more than 5mm, enabling the sieved slurry to enter a primary cleaning tank for stirring and cleaning, then performing solid/liquid three-phase separation through a horizontal spiral centrifugal machine, separating all soil solids with the particle size of less than 5mm, a cleaning liquid phase and a dirty oil phase, mixing and modulating the cleaning liquid and a hot alkali water washing liquid, recycling the mixed soil to clean the polluted soil of a new batch at the primary stage, enabling the dirty oil phase to enter a dirty oil tank for collection, and enabling all soil solids with the particle size of less than 5mm to enter a secondary cleaning tank for secondary cleaning. Mixing all soil solids with the size of less than 0.5mm with a cleaning solution added with a new nonionic-anionic compound surfactant medicament in a secondary cleaning tank, fully stirring and cleaning, wherein the medicament usage amount reaches 0.8% (g/g), discharging, feeding into a lamination centrifuge for solid/liquid two-phase separation, separating out clean soil components with the size of 0.01-5mm, performing oil/water separation twice because the content of clay particles in the soil with the size of less than 0.01 in the residual oil/water/soil mixed phase is higher, feeding into an oil-water separation tank for separation, feeding the oil phase into an oil storage tank, feeding into a secondary cleaning tank for recycling, feeding into a flotation machine after demulsification of the residual discharge material in the oil-water separation tank, completing oil/water re-separation, feeding the oil phase into an oil storage tank, feeding into a secondary cleaning tank, processing residual muck in an acidification tank, combining with the clean soil components with the size of 0.01-5mm separated by lamination, performing overlapping and dewatering treatment, finally discharging to obtain clean soil with components of less than 5mm, and enabling the water phase of the cleaning solution to enter a secondary cleaning tank to finish zero-emission recycling of the cleaning solution. The residual quantity of petroleum in the complete discharged soil is measured to reach 1.8 percent and less than 2 percent, the treatment standard aiming at the soil polluted by high-concentration petroleum is reached, and the residual rate of the petroleum in the soil of a control group is up to 8.2 percent (see figure 5).
Therefore, the two-stage cleaning process for the non-sandy soil effectively aims at the problems of high content of fine particle components, large energy consumption load of particle size separation and the like, two different cleaning liquids are adopted for targeted cleaning, and a complete cleaning process is carried out without reduction treatment, so that a good cleaning effect is obtained, the cleaning desorption efficiency of the high-concentration petroleum polluted soil is greatly improved, and the standard treatment of the polluted soil is realized.
Claims (6)
1. An ex-situ cleaning method for restoring petroleum-polluted soil is characterized by comprising the following steps: the method comprises the steps of analyzing the mechanical composition characteristics of the petroleum-polluted soil to be treated, primarily screening and analyzing the dirty oil desorption rate characteristics in a cleaning system, establishing specific two-stage cleaning flows aiming at the soil with different textures according to analysis data, determining cleaning-level replacement time nodes, realizing the cleaning process of the petroleum-polluted soil with different particle sizes, and recycling all levels of cleaning liquid.
2. The ex-situ cleaning method for remediating petroleum-contaminated soil as recited in claim 1, wherein: performing mechanical composition characteristic analysis on the petroleum-polluted soil to be treated, and determining a two-stage soil cleaning process; and determining a cleaning grade replacement time node according to the first-stage elution rate change characteristics of the petroleum pollutants in the cleaning system, thereby realizing the cleaning of the petroleum polluted soil under different particle sizes.
3. The ex-situ cleaning method for remediating petroleum-contaminated soil as recited in claim 2, wherein: the mechanical composition characteristic of the petroleum polluted soil to be treated is that when the sand grain component (0.05-2mm) is more than or equal to 25 percent and the sticky grain component (less than 0.002mm) is less than or equal to 35 percent, the soil is defined as sandy soil, and a two-stage decrement cleaning process is selected; when the sand grain component (0.05-2mm) < 25% or the sticky grain component (<0.002mm) > 35%, the soil is defined as non-sandy soil, and a two-stage full-scale cleaning process is selected.
4. The ex-situ cleaning method for remediating petroleum-contaminated soil as recited in claim 2, wherein: the cleaning grade replacement time node is determined according to the change characteristics of the elution rate of the petroleum pollutants in the cleaning system, and when the first-stage elution rate of the dirty oil in the elution system is reduced to 0-20% of the maximum elution rate, the second-stage cleaning is carried out.
5. The ex-situ cleaning method for remediating petroleum-contaminated soil as recited in any one of claims 1 to 4, wherein:
(1) and (3) analyzing the soil characteristics: analyzing the mechanical composition of the petroleum-polluted soil, judging whether the polluted soil is sandy soil or non-sandy soil, and determining the selection of a cleaning process flow; adopting a cleaning system to carry out a soil cleaning bench test, and determining a cleaning grade replacement time node according to the change characteristic of the dirty oil elution rate;
(2) cleaning pretreatment: mixing the oil-contaminated soil with first-stage cleaning solution hot-alkali water, fully stirring and pulping, and transferring the slurry into a mechanical oscillating screen for wet oscillating screening; separating clean gravel components with the particle size of more than 5mm, and feeding the sieved slurry into a cleaning tank for primary cleaning;
(3) first-stage cleaning: according to the attribute of the soil to be treated, the sandy soil screened slurry is stirred, mixed and cleaned in a primary cleaning tank for a set time, then a cyclone separator is used for solid/liquid two-phase separation, clean soil components with the particle size of 0.2-5mm are screened out, and a slurry mixture containing the soil with the particle size of less than 0.2mm enters secondary cleaning;
or, the non-sandy soil screened slurry is stirred, mixed and cleaned with hot alkaline water in a primary cleaning tank according to set time, solid/liquid three-phase separation is carried out through a horizontal spiral centrifuge, all soil solids with the particle size of less than 5mm, a cleaning liquid phase and a dirty oil phase are separated, and all soil solids with the particle size of less than 5mm enter a secondary cleaning tank for secondary cleaning;
(4) secondary cleaning: when sandy soil is treated, the primary cleaning discharge slurry is continuously fully stirred, mixed and cleaned in a secondary cleaning tank through hot alkali, the discharged material enters a lamination centrifuge for solid/liquid two-phase separation, clean soil components with the grain size of 0.01-0.2mm are separated, a residual oil/water/soil mixed phase is subjected to emulsion breaking treatment and then enters a flotation machine for separating a cleaning water phase and a dirty oil phase, residual muck in the flotation machine is less than 0.01mm, the residual muck enters an acidification tank for treatment, the unearthed soil and the clean soil components with the grain size of 0.01-0.2mm separated by the lamination are combined for screw-stacking dehydration treatment, and finally the discharged material is clean soil with the grain size of less than 0.2 mm;
or, the non-sandy soil is treated, all soil solids with the particle size of less than 0.5mm are mixed with cleaning liquid added with surfactant medicaments in a secondary cleaning tank and are fully stirred and cleaned, the discharged materials enter a lamination centrifuge for solid/liquid two-phase separation, clean soil components with the particle size of 0.01-5mm are separated, a residual oil/water/soil mixed phase (the soil components with the particle size of less than 0.01 mm) enters an oil-water separation tank for oil/water separation, the residual discharged materials of the oil-water separation tank enter a flotation machine after emulsion breaking, the flotation machine obtains residual dregs, the residual dregs are treated by an acidification tank and then are combined with the clean soil components with the particle size of 0.01-5mm separated by the lamination for screw lamination dehydration, and finally the discharged materials are the soil components with the particle size of less than 5mm, namely the clean soil.
6. The ex-situ cleaning method for remediating petroleum-contaminated soil as recited in claim 5, wherein: in the two-stage decrement cleaning process, respectively collecting a flotation separation water phase and a stacked spiral dehydration water phase after the second-stage cleaning, and recycling the flotation separation water phase and the stacked spiral dehydration water phase as a cleaning solution for the first-stage cleaning; in the two-stage full-scale cleaning process, the cleaning liquid phase which is subjected to horizontal spiral separation after the first-stage cleaning is reused in the hot alkaline cleaning liquid of the first-stage cleaning tank, the separated water phase in the oil-water separation tank after the second-stage cleaning, the separated water phase in the flotation machine and the overlapped spiral dehydration water phase are recycled as the cleaning liquid components of the second-stage cleaning tank, the cleaning liquid is recycled, and zero emission is realized.
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