Heavy metal contaminated soil rotational flow crushing grading reduction and enhanced elution method and heavy metal contaminated soil rotational flow crushing grading reduction and enhanced elution system

Abstract

The invention relates to the field of soil remediation in environmental protection, in particular to a heavy metal contaminated soil rotational flow crushing grading reduction and enhanced elution method and system. The method comprises the following steps: carrying out first-stage rotational flow crushing pre-sequencing classification or multi-stage rotational flow crushing pre-sequencing classification on heavy metal polluted soil with the particle size of less than 0.2 mm after vibratory screening until the heavy metal content of underflow soil reaches the standard, and premixing overflow generated by all classification and leacheate in a material tank; the formed mixed material is divided into underflow and overflow after being subjected to rotational flow intensified elution, the underflow and the overflow after being subjected to rotational flow intensified elution are introduced into the material tank, and the underflow after being subjected to rotational flow intensified elution is filtered and dehydrated after the content of the heavy metal in the soil in the material tank reaches the standard, so that the soil with the heavy metal reaching the standard is obtained. Agglomerated soil particles are dispersed into coarse particles with low heavy metal content and fine particles with high heavy metal content through rotational flow crushing, pre-sequencing and grading, the amount of soil needing to be leached is reduced, and the polluted soil reaches related standards after being treated.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and relates to a treatment system for single or compound heavy metal contaminated soil, which is applicable to the reduction and enhanced elution of single or compound heavy metal contaminated soil. Specifically, a method and system for cyclone crushing, grading, reduction and enhanced elution of heavy metal contaminated soil is provided. Background Art

[0002] With the rapid development of industrialization and urbanization, soil pollution, especially heavy metal pollution, has become increasingly serious. Heavy metals such as lead, cadmium, and arsenic pose a serious threat to the ecological environment and human health due to their non-degradability, bioaccumulation, and toxicity. The long-term retention of heavy metals in the soil and their difficulty in natural degradation make the remediation of contaminated soil an urgent problem to be solved. Traditional heavy metal contaminated soil remediation technologies include physical remediation, chemical remediation, and biological remediation. Physical remediation usually involves excavation and replacement of soil, which is costly and has a large impact on the environment; biological remediation uses plants or microorganisms to absorb and transform heavy metals, with a long remediation cycle and limited effect. Therefore, the development of new remediation technologies to improve efficiency, reduce costs, and reduce secondary pollution has become a research hotspot. Soil leaching technology, as an effective chemical remediation method, transfers heavy metals in the soil to the liquid phase by using clean water or a specific eluent, and then treats the eluent containing heavy metals to achieve soil remediation. This technology has been widely used in soil remediation projects due to its relatively low cost, wide treatment range, and high remediation efficiency.

[0003] Since heavy metals are mainly concentrated in small particles with large specific surface areas, in the field of soil leaching, cyclone separation technology can be used to grade and reduce the particles of heavy metal-contaminated soil, separate coarse particles with low heavy metal content, reduce the volume of soil that needs to be leached, and reduce the cost of remediation. However, in soil leaching technology, water-stable aggregates still exist in the soil after conventional vibration screening, that is, fine particles with high heavy metal content and coarse particles with low heavy metal content are still combined together, resulting in excessive heavy metal content in the bottom flow soil after cyclone classification, as well as low efficiency of subsequent traditional stirring mass transfer, long leaching time, and poor elution effect. Ultrasonic enhancement has a good effect on the dispersion of aggregates, but it has high energy consumption, large equipment footprint, and a large number of auxiliary equipment, making it difficult to apply in engineering.

[0004] Chinese patent document CN113090244A discloses a method and device for separating hydrates by cyclone self-rotation. The technology aims to solve the problem of separating submarine hydrates. The present invention realizes the degumming and separation of sediment slurry containing hydrates by means of a specific cyclone degumming cylinder and a cyclone separation cylinder structure. During operation, the mixed slurry undergoes strong shear flow and wall collision in the cyclone degumming cylinder, generating high-speed self-rotation motion, overcoming the weak bonding force between muddy silt and gas hydrate particles, and achieving degumming of particles. The degummed mixed slurry enters the cyclone separation cylinder, and the muddy silt and gas hydrate are separated by centrifugal force, thereby achieving the crushing and separation of gas hydrates. However, the device is an integrated structure, which is not easy to disassemble, and is mainly aimed at the degumming and separation of gas hydrates. Due to the large differences in properties of different soils, the device is not suitable for particle separation of contaminated soil with excessive heavy metals. When studying soil contaminated by excessive heavy metals, the applicant found that some agglomerated particles in the contaminated soil have a higher bonding strength than natural gas hydrates, making them difficult to crush. They need to clean, repair or replace the crushing cylinder and separation cylinder more frequently, and a single cyclone crushing cannot effectively disperse the agglomerated particles, resulting in excessive heavy metals in the bottom flow. Chinese patent document CN211027503U discloses a heavy metal contaminated soil remediation device, which breaks up the soil through a rotating wheel to mix the eluent with the soil to improve the leaching effect. However, the device has deficiencies in production cost and stirring and mixing of the eluent, which affects the convenience of using the device. In addition, the prior art focuses on increasing the number of leaching times and the concentration of the eluent, but fails to substantially solve the technical problem that heavy metals in the soil are difficult to fully react with the eluent, and there is a problem of excessive eluent, which in turn affects the effect of soil leaching.

[0005] Chinese patent document CN118744152A discloses an ex situ leaching and remediation method for heavy metal contaminated soil, which aims to solve the problems of low efficiency and high cost in traditional soil leaching technology. The method includes multiple steps such as pre-screening, crushing, intensive treatment, mud making, soaking and elution, primary screening, cyclone separation, secondary screening, filtration dehydration and sewage treatment. In the intensive treatment stage, the heavy metal contaminated soil with a particle size less than 5mm is mixed with circulating water and eluent in a mass ratio of 1:0.7:0.3, and then stirred at a speed of 50-250r / min for more than 2 hours to ensure that the eluent is in full contact with the soil and improve the leaching effect. However, although this method has the effect of strengthening leaching, the stirring time is long, and the contaminated soil after pre-screening and crushing is not further reduced before leaching, and there is still room to further reduce the amount of eluent.

[0006] Therefore, the current ex situ leaching remediation technology urgently needs to reduce the amount of heavy metal contaminated soil to reduce the amount of elution agent used and improve the mass transfer efficiency to improve the elution efficiency. It is necessary to design a set of simple and efficient processes that can break up and grade the agglomerated soil and improve the elution efficiency. Summary of the invention

[0007] The purpose of the present invention is to provide a system for cyclone crushing and graded reduction and enhanced elution of heavy metal-contaminated soil by using the strong shearing effect of the cyclone field to disperse the agglomerated soil particles into coarse particles with low heavy metal content and fine particles with high heavy metal content, thereby reducing the amount of soil that needs to be eluted, and to enhance the elution efficiency by utilizing the improvement of mass transfer efficiency after the dispersion of the agglomerated particles, so as to solve the problems of unsatisfactory agglomerated particle dispersion effect, poor reduction effect, and low elution efficiency in the existing devices. To achieve the above purpose, the technical solution adopted by the present invention is:

[0008] A method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil, comprising:

[0009] S1, forming a mixed material in one of the following two ways:

[0010] (1) After vibration screening, heavy metal-contaminated soil with a particle size of less than 0.2 mm is pre-sorted and classified by primary cyclone crushing to be divided into a primary underflow with a soil heavy metal content that meets the standard and a primary overflow with a soil heavy metal content that exceeds the standard, and the primary overflow is pre-mixed with the eluent in a material tank;

[0011] (2) Heavy metal contaminated soil with a particle size of less than 0.2 mm after vibration screening is pre-sorted and classified through multi-stage cyclone crushing until the heavy metal content of the soil in the bottom flow meets the standard, and all overflows generated by the classification are pre-mixed with the eluent in the material tank;

[0012] S2, the mixed material formed in step S1 is divided into underflow and overflow after cyclone enhanced elution, and the underflow and overflow after cyclone enhanced elution are then introduced into the material tank to detect whether the heavy metal content of the soil in the material tank meets the standard. If not, the eluent is continued to be added and mixed and then cyclone enhanced elution is performed again. When the heavy metal content of the soil in the material tank meets the standard, the underflow after cyclone enhanced elution is filtered and dehydrated to obtain soil meeting the heavy metal standard.

[0013] The process of the above method (2) is as follows: after vibration screening, the heavy metal contaminated soil with a particle size of less than 0.2 mm is initially divided into a primary underflow and a primary overflow, and the primary underflow is further divided into a secondary underflow and a secondary overflow by secondary cyclone crushing pre-sorting and grading. If the heavy metal content of the soil in the secondary underflow exceeds the standard, the grading is continued until the heavy metal content of the soil in the N-level underflow obtained by N-level cyclone crushing pre-sorting and grading meets the standard, and all overflows generated during the grading process (including the primary overflow, the secondary overflow, ..., the N-level overflow) are pre-mixed with the eluent in the material tank; wherein N is an integer ≥2.

[0014] The above-mentioned heavy metal contaminated soil cyclone crushing, classification, reduction and enhanced elution method is suitable for heavy metal contaminated soil with a particle size less than 0.2 mm. The heavy metal contaminated soil is single-polluted or composite-polluted soil, and preferably the total heavy metal content is not higher than 10000 mg / kg.

[0015] In the above step S1, the pre-mixing time is usually 5-30 minutes.

[0016] Furthermore, in the material tank, the mass ratio of the eluent to other materials in the material tank is (5-25):1.

[0017] The median particle size of the underflow particles produced by the cyclone crushing pre-sorting and classification is >70 microns, and the median particle size of the overflow particles produced by the cyclone crushing pre-sorting and classification is <20 microns. The median particle size of the underflow particles after the cyclone enhanced elution is >40 microns, and the median particle size of the overflow particles after the cyclone enhanced elution is <20 microns.

[0018] Preferably, the primary cyclone crushing pre-sorting and grading and / or the multi-stage cyclone crushing pre-sorting and grading are operated continuously.

[0019] According to a specific embodiment of the present invention, the eluent is prepared by adding water to an eluent. The eluent is a single eluent or a compound eluent. Preferably, the concentration of the eluent is 0.05-0.3 mol / L. As an example, the compound eluent is compounded from at least two of an organic acid, a chelating agent, and a surfactant. As an example, the single eluent is selected from an organic acid, a chelating agent, or a surfactant. Common organic acid eluents include citric acid, oxalic acid, malic acid, etc.

[0020] Preferably, the cyclone enhanced elution is operated continuously, and the continuous operation time is 5 min-180 min.

[0021] According to a specific embodiment of the present invention, the liquid after underflow filtration and dehydration of soil with heavy metal content reaching the standard is treated as sewage and then reused for the preparation of the eluent.

[0022] A system for cyclone crushing, grading, reducing and enhanced elution of heavy metal contaminated soil, the system is used to implement the above-mentioned cyclone crushing and enhanced elution method for heavy metal contaminated soil, the system comprises a material tank, a cyclone crushing pre-sorting classifier and a cyclone enhanced elution device, wherein: the material tank is used to mix materials, the cyclone enhanced elution device is used to separate the mixed materials into underflow and overflow after cyclone enhanced elution, so as to remove heavy metals in the soil; the cyclone crushing pre-sorting classifier is a first-stage cyclone crushing pre-sorting classifier or a multi-stage cyclone crushing pre-sorting classifier, the cyclone crushing pre-sorting classifier comprises an overflow port and an underflow port, wherein the overflow port is connected to the material tank, the cyclone crushing pre-sorting classifier is used for cyclone crushing pre-sorting and grading, so as to grade and reduce the heavy metal contaminated soil with a particle size less than 0.2 mm after vibration screening, thereby reducing the soil content entering the cyclone enhanced elution device.

[0023] Furthermore, the cyclone-enhanced eluent is a single-stage cyclone-enhanced eluent or a multi-stage cyclone-enhanced eluent.

[0024] Furthermore, the cyclone enhanced elution device includes an outer frame from outside to inside, a crusher for crushing agglomerated soil particles with a particle size of less than 0.2 mm into coarse particles and fine particles, and a separator for separating the coarse particles from the fine particles. The separator includes an underflow outlet for sending out the separated coarse particles, wherein the underflow outlet is located at the bottom of the separator. The crusher includes a crusher inlet, which is located at the bottom of the crusher. The separator also includes a separator inlet, which is located at the top of the separator. The agglomerated soil particles enter the crusher through the crusher inlet, and the separator inlet is connected to the crusher.

[0025] Furthermore, the cyclone crushing pre-sorting classifier includes an outer frame from outside to inside, a crusher for crushing agglomerated soil particles with a particle size of less than 0.2 mm into coarse particles and fine particles, and a separator for separating the coarse particles from the fine particles. The separator includes an underflow outlet for sending out the separated coarse particles, wherein the underflow outlet is located at the bottom of the separator. The crusher includes a crusher inlet, which is located at the bottom of the crusher. The separator also includes a separator inlet, which is located at the top of the separator. Agglomerated soil particles enter the crusher through the crusher inlet, and the separator inlet is connected to the crusher.

[0026] The beneficial effects of the present invention are:

[0027] The agglomerated soil particles are dispersed into coarse particles with low heavy metal content and fine particles with high heavy metal content by the cyclone crushing pre-sorting classifier, so that the coarse particles and fine particles are discharged from the bottom flow and overflow respectively, reducing the amount of soil that needs to be eluted; the further dispersion of the agglomerated particles by the cyclone enhanced elution device can effectively make the eluent fully contact with the soil particles, improve the mass transfer efficiency of the eluent, and greatly improve the elution effect compared with the traditional stirring mass transfer method, solving the problems of unsatisfactory agglomerated particle dispersion effect, poor reduction effect, and low elution efficiency in the existing device. The whole treatment system has low energy consumption, small footprint, low cost, and no other waste liquid discharge. Preferably, by using a crusher and separator that are easy to disassemble and replace for multi-stage cyclone crushing, the agglomerated soil particles are dispersed into coarse particles with low heavy metal content and fine particles with high heavy metal content, thereby reducing the amount of soil that needs to be eluted. On the other hand, it can promote the full reaction of the eluent with the heavy metals in the soil, improve the elution efficiency, and reduce the amount of the eluent; it is convenient to clean, repair or replace the crusher and separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a process flow chart of a method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to one embodiment of the present invention.

[0029] Figure 2 It is a process flow chart of a method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to another embodiment of the present invention.

[0030] Figure 3 It is a schematic diagram of the structure of the cyclone enhanced eluting device used in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific examples. These examples are only used to illustrate the present invention and do not constitute a limitation of the scope of the present invention. The test methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0032] The following is a detailed description based on the accompanying drawings.

[0033] Figure 1This is a schematic diagram of a method for cyclone crushing, grading, reduction and enhanced elution of heavy metal contaminated soil according to one embodiment of the present invention. During normal operation, heavy metal contaminated soil with a particle size of less than 0.2 mm after vibration screening is first preliminarily divided into a primary underflow with low soil heavy metal content and a primary overflow with high soil heavy metal content through a primary cyclone crushing pre-sorting and grading, and then the primary underflow is divided into a secondary underflow with soil heavy metal content that meets the standard and a secondary overflow with soil heavy metal content that exceeds the standard through a secondary cyclone crushing pre-sorting and grading, and finally the overflow and the secondary overflow are subjected to cyclone enhanced elution to remove heavy metals from the soil. The secondary underflow is filtered and dehydrated to obtain soil that meets the heavy metal standard. In this embodiment, a primary cyclone crushing pre-sorting classifier is used for primary cyclone crushing pre-sorting and grading, a secondary cyclone crushing pre-sorting classifier is used for secondary cyclone crushing pre-sorting and grading, and a cyclone enhanced elution device is used for cyclone enhanced elution. Usually, the inlet flow rate of the primary cyclone crushing pre-sorting classifier is 0.4-1.2m 3 / h. Before the primary overflow and the secondary overflow enter the cyclone enhanced eluent, they are first mixed with the eluent, usually in the material tank for 5-30 minutes. The material in the material tank is then pressurized by a booster pump and enters the cyclone enhanced eluent. The underflow and overflow of the cyclone enhanced eluent are first passed into the material tank to detect whether the heavy metal content in the material tank meets the standard. If not, the eluent is continued to be added and mixed before entering the cyclone enhanced eluent. When the heavy metal content in the material tank meets the standard, the underflow of the cyclone enhanced eluent is filtered and dehydrated to obtain soil that meets the heavy metal standard. The cyclone enhanced elution is a continuous operation, and the rate (flow rate) of cyclone elution is 0.5-2m 3 / h, the cyclone enhanced elution time is 5-180min. The eluent added to the material tank depends on the condition of the heavy metal contaminated soil. The eluent is a single eluent or a compound eluent. The added eluent is pre-added with an appropriate amount of water to prepare an eluent, and then added to the material tank; or the eluent and water are added to the material tank to prepare an eluent in the material tank. The concentration of the eluent is 0.05-0.3mol / L. In the material tank, the mass ratio of the eluent to other materials in the material tank is (5-25):1. The median particle size of the underflow particles produced by the cyclone crushing pre-sorting and grading is >70 microns, and the median particle size of the overflow particles produced by the cyclone crushing pre-sorting and grading is <20 microns. The median particle size of the underflow particles after cyclone enhanced elution is >40 microns, and the median particle size of the overflow particles after cyclone enhanced elution is <20 microns. The liquid dehydrated by the secondary underflow filtration and the liquid dehydrated by the underflow filtration of the cyclone enhanced washer are reused for the preparation of the eluent after sewage treatment.

[0034] Figure 2 Schematic diagram of a method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to another embodiment of the present invention. This embodiment is suitable for heavy metal contaminated soil with heavy metal content lower than 1.5 times the standard value. Figure 1 Compared with the above, the secondary cyclone crushing pre-sorting and grading is cancelled. During normal operation, the heavy metal contaminated soil with a particle size of less than 0.2 mm after vibration screening is first divided into a primary underflow with a soil heavy metal content that meets the standard and a primary overflow with a soil heavy metal content that exceeds the standard through a primary cyclone crushing pre-sorting and grading. The primary overflow is removed from the soil by cyclone enhanced elution. The primary underflow is filtered and dehydrated to obtain soil that meets the heavy metal standard. In this embodiment, a primary cyclone crushing pre-sorting classifier is used for primary cyclone crushing pre-sorting and grading, and a cyclone enhanced elution device is used for cyclone enhanced elution. Before the primary overflow enters the cyclone enhanced elution device, it is first mixed with an eluent, usually in a material tank. The material in the material tank is then pressurized by a booster pump and then enters the cyclone enhanced elution device. The underflow and overflow of the cyclone enhanced elution device are first passed into the material tank to detect whether the heavy metal content in the material tank meets the standard. If it does not meet the standard, the eluent is continued to be added and mixed before entering the cyclone enhanced elution device. When the heavy metal content in the material tank meets the standard, the bottom flow of the cyclone enhanced elution device is filtered and dehydrated to obtain soil that meets the heavy metal standard. The cyclone enhanced elution is continuously operated, and the cyclone enhanced elution time is 5-180min. The eluent added to the material tank depends on the condition of the heavy metal contaminated soil. The eluent is a single eluent or a compound eluent. The added eluent is pre-added with an appropriate amount of water to form an eluent, which is then added to the material tank; or the eluent and water are added to the material tank to form an eluent in the material tank. The concentration of the eluent is 0.05-0.3mol / L. In the material tank, the mass ratio of the eluent to other materials in the material tank is (5-25):1. The median particle size of the bottom flow particles produced by the cyclone crushing pre-sorting and grading is >70 microns, and the median particle size of the overflow particles produced by the cyclone crushing pre-sorting and grading is <20 microns. The median particle size of the underflow particles after the cyclone enhanced elution is >40 microns, and the median particle size of the overflow particles after the cyclone enhanced elution is <20 microns. The liquid dehydrated by the primary underflow filtration and the liquid dehydrated by the underflow filtration of the cyclone enhanced elution device are reused for the preparation of the eluent after sewage treatment.

[0035] Embodiment 1:

[0036] 1. Material properties

[0037] Ex situ leaching and remediation of soil from a contaminated site in Chongqing was carried out. The heavy metal content in the soil with a particle size of less than 0.2 mm after vibration screening was measured and is shown in Table 1. According to the control values ​​of GB 36600-2018 Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial) , arsenic exceeded the control value of the first category of land use by 1.76 times, and lead, antimony and cobalt did not exceed the standard.

[0038] Table 1 Heavy metal content in soil and control values

[0039]

[0040] 2. Process

[0041] The heavy metal contaminated soil at the site is crushed to a particle size of less than 20 mm, and circulating water is added to the soil with a particle size of less than 20 mm to carry out drum mud making. The mud produced by the drum mud making is screened through a multi-stage vibrating screen to separate soils with particle sizes of 10-20 mm, 5-10 mm, 1-5 mm, 1-0.2 mm and less than 0.2 mm.

[0042] Heavy metal contaminated soil with a particle size of less than 0.2 mm is remediated by the implementation of the present invention, with the first-class land use control value as the target. The arsenic content of the heavy metal contaminated soil exceeds the standard by 1.76 times, which is suitable for Figure 1 The process flow shown in the figure. The heavy metal contaminated soil with a particle size of less than 0.2 mm is agglomerated soil particles with a particle size of less than 0.2 mm.

[0043] After vibration screening, heavy metal contaminated soil with a particle size of less than 0.2mm first enters the first-level cyclone crushing pre-sorting classifier to be initially divided into the first-level underflow with low heavy metal content and the first-level overflow with high heavy metal content. Then the first-level underflow enters the second-level cyclone crushing pre-sorting classifier to be divided into the second-level underflow with soil heavy metal content that meets the standard and the second-level overflow with soil heavy metal content that exceeds the standard. The second-level underflow is filtered and dehydrated, and the obtained soil is placed in the temporary storage area for heavy metal-compliant soil. The first-level overflow and the second-level overflow first enter the material tank, and the eluent is added to the material tank. The material in the material tank is pressurized by the booster pump and enters the cyclone enhanced elution device. The underflow and overflow of the cyclone enhanced elution device are first passed into the material tank to detect whether the heavy metal content in the material tank meets the standard. If not, the eluent is continued to be added and mixed before entering the cyclone enhanced elution device. When the heavy metal content in the material tank meets the standard, the underflow of the cyclone enhanced elution device is filtered and dehydrated, and the obtained soil is placed in the temporary storage area for heavy metal-compliant soil. The eluent added to the material tank is oxalic acid. The eluent is pre-added with an appropriate amount of water to prepare an eluent, which is then added to the material tank. The oxalic acid concentration in the eluent is 0.2 mol / L. In the material tank, the mass ratio of eluent to other materials is 20:1. The cyclone enhanced elution is continuously operated, the cyclone enhanced elution time is 20 minutes, and the cyclone elution rate (flow rate) is 1m 3 / h. The inlet flow rate of the first-stage cyclone crushing pre-sorting classifier is 1m 3 / h. The median particle size of the underflow particles produced by the cyclone crushing pre-sorting classification is >70 microns, and the median particle size of the overflow particles produced by the cyclone crushing pre-sorting classification is <20 microns. The median particle size of the underflow particles after the cyclone enhanced elution is >40 microns, and the median particle size of the overflow particles after the cyclone enhanced elution is <20 microns.

[0044] The schematic diagram of the structure of the cyclone enhanced elution device is as follows: Figure 3As shown, a double-layer nested structure is adopted, and the inner and outer layers of the double-layer nested structure are connected by flanges, which is convenient for replacing internal or external parts. The flange includes a flange gasket 8 and a flange hole 9. The cyclone enhanced elution device includes a crusher 6 for crushing agglomerated soil particles with a particle size of less than 0.2 mm into coarse particles and fine particles from the outside to the inside, and a separator 5 for separating coarse particles and fine particles. Among them, the separator 5 includes an underflow outlet 11 for sending out the separated coarse particles, wherein the underflow outlet 11 is located at the bottom of the separator 5. The crusher 6 includes a crusher inlet 7, which is located at the bottom of the crusher 6. The separator 5 also includes a separator inlet 4, which is located at the top of the separator 5. Agglomerated soil particles enter the crusher 6 through the crusher inlet 7, and the separator inlet 4 is connected to the crusher 6. The bottom of the crusher 6 and the separator 5 are connected by a flange. An overflow outlet 10 for sending out separated fine particles is fixedly installed on the top of the separator 5. The overflow outlet 10 passes through the outer shell 12 of the crusher 6 and enters the separator 5. The overflow outlet 10 is fixed to the outer shell 12 by the first gland 1, the second gland 2 and the gasket 3. The first gland 1 serves to seal the top of the equipment, the second gland 2 serves to assist in sealing and strengthen the structure, and the gasket 3 is used to improve the sealing of the equipment to prevent water leakage. The sewage treatment is to add coagulant PAC and flocculant PAM to the filtrate obtained by the filtration and dehydration. After the sludge is precipitated, the supernatant is reused as circulating water for the preparation of the eluent, and the bottom sludge is filtered twice to obtain a mud cake, which is then transported for treatment. The structure of the first-stage cyclone crushing pre-sorting classifier and the second-stage cyclone crushing pre-sorting classifier adopted in this embodiment is the same as the structure of the cyclone enhanced elution device described above.

[0045] 3. Repair results

[0046] As shown in Table 2, after adopting the implementation mode of the present invention, the arsenic content of the bottom flow soil of the secondary cyclone crushing pre-sorting classifier and the cyclone enhanced elution device both reached the first-class land control value of "GB 36600-2018 Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)", and the use of the primary cyclone crushing pre-sorting classifier and the secondary cyclone crushing pre-sorting classifier in combination can reduce the amount of contaminated soil to be eluted by 32.5%.

[0047] As shown in Table 3 below, after 20 minutes of cyclone enhanced elution, the arsenic content reached the control value of the first category of land use, and the removal rate reached 51.6%. The mixture of underflow and overflow obtained by the first-level cyclone crushing pre-sorting classifier and the second-level cyclone crushing pre-sorting classifier was passed into a material tank equipped with a stirring paddle for stirring and eluting (the mass ratio of the eluent to other materials was 20:1). The stirring paddle speed was set to 150r / min, the stirring time was 20min, and the removal rate was 29.8%. Compared with the removal rate of 29.8% after stirring (150r / min) and eluting for 20min, the elution efficiency is greatly improved. It shows that the embodiments of the present invention can improve the mass transfer efficiency, promote the full reaction of the eluent and heavy metals, and enhance the elution efficiency.

[0048] Table 2 Arsenic content in soil after underflow filtration and dehydration

[0049] project Secondary underflow soil Cyclone enhanced washer underflow soil Arsenic content (mg / kg) 107.2 102.4

[0050] Table 3 Remediation results of heavy metal contaminated soil

[0051] project Cyclone enhanced elution device (20min) Stirring paddle (150r / min×20min) Arsenic content (mg / kg) 102.4 148.8 Removal rate (%) 51.6％ 29.8％

[0052] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil, characterized in that: include: S1, forming a mixed material in one of the following two ways: (1) After vibration screening, heavy metal-contaminated soil with a particle size of less than 0.2 mm is pre-sorted and classified by primary cyclone crushing to be divided into a primary underflow with a soil heavy metal content that meets the standard and a primary overflow with a soil heavy metal content that exceeds the standard, and the primary overflow is pre-mixed with the eluent in a material tank; (2) Heavy metal contaminated soil with a particle size of less than 0.2 mm after vibration screening is pre-sorted and classified through multi-stage cyclone crushing until the heavy metal content of the soil in the bottom flow meets the standard, and all overflows generated by the classification are pre-mixed with the eluent in the material tank; S2, the mixed material formed in step S1 is divided into underflow and overflow after cyclone enhanced elution, and the underflow and overflow after cyclone enhanced elution are then introduced into the material tank to detect whether the heavy metal content of the soil in the material tank meets the standard. If not, the eluent is continued to be added and mixed and then cyclone enhanced elution is performed again. When the heavy metal content of the soil in the material tank meets the standard, the underflow after cyclone enhanced elution is filtered and dehydrated to obtain soil meeting the heavy metal standard.

2. The method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to claim 1, characterized in that: The heavy metal contaminated soil is single-polluted or composite-polluted soil, and the total heavy metal content is not higher than 10,000 mg / kg.

3. The method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to claim 1, characterized in that: The primary cyclone crushing pre-sorting and grading and / or the multi-stage cyclone crushing pre-sorting and grading are operated continuously.

4. The method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to claim 1, characterized in that: The eluent is prepared by adding water to an eluent, and the eluent is a single eluent or a compound eluent.

5. The method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to claim 4, characterized in that: The compound eluent is compounded from at least two of an organic acid, a chelating agent and a surfactant.

6. The method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to claim 1, characterized in that: The cyclone enhanced elution is a continuous operation, and the continuous operation time is 5min-180min.

7. The heavy metal contaminated soil cyclone crushing classification reduction and enhanced elution as claimed in claim 1, characterized in that: The liquid after underflow filtration and dehydration of soil with heavy metal content that meets the standard is treated as sewage and then reused for the preparation of elution liquid.

8. The method for cyclone crushing, classification, reduction and enhanced elution of heavy metal contaminated soil according to claim 1, characterized in that: In the material tank, the mass ratio of the eluent to other materials in the material tank is (5-25):

1.

9. A heavy metal contaminated soil cyclone crushing classification reduction and enhanced elution system, characterized in that: The system is used to implement the method for cyclone crushing, grading, reduction and enhanced elution of heavy metal contaminated soil as described in any one of claims 1 to 8, and the system includes a material tank, a cyclone crushing pre-sorting classifier and a cyclone enhanced elution device, wherein: the material tank is used to mix materials, and the cyclone enhanced elution device is used to separate the mixed materials into underflow and overflow after cyclone enhanced elution, thereby removing heavy metals in the soil; the cyclone crushing pre-sorting classifier is a single-stage cyclone crushing pre-sorting classifier or a multi-stage cyclone crushing pre-sorting classifier, and the cyclone crushing pre-sorting classifier is used for cyclone crushing pre-sorting and grading, so that the heavy metal contaminated soil with a particle size less than 0.2 mm after vibration screening can be graded and reduced, thereby reducing the soil content entering the cyclone enhanced elution device.

10. The heavy metal contaminated soil cyclone crushing classification reduction and enhanced elution system according to claim 9, characterized in that: The cyclone-enhanced eluent is a single-stage cyclone-enhanced eluent or a multi-stage cyclone-enhanced eluent.

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