CN112845554A

CN112845554A - Method and device for reducing polluted soil

Info

Publication number: CN112845554A
Application number: CN202011576657.4A
Authority: CN
Inventors: 刘毅; 马凯; 韩雅芳; 徐博文; 程婷婷; 许威南
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2020-12-28
Filing date: 2020-12-28
Publication date: 2021-05-28

Abstract

The disclosure relates to a method and a device for reducing contaminated soil, and provides a method for reducing contaminated soil, which comprises the following steps: (1) fully stirring and mixing the screened polluted soil and water, and then carrying out cyclone particle size classification so as to discharge large-particle-size soil with pollutants not exceeding the standard through outer cyclone underflow for solid-liquid separation and landfill, and discharge small-particle-size soil with pollutants exceeding the standard through inner cyclone overflow; and (2) carrying out cyclone concentration on the mud-water mixture overflowing and discharged in the step (1), discharging the obtained water overflow for circulation, and feeding the obtained high-concentration polluted soil into the next stage of treatment. Also provides a device for reducing the polluted soil.

Description

Method and device for reducing polluted soil

Technical Field

The utility model belongs to the field of waste electrical appliance disassembly and environmental protection, and relates to a novel method for sorting organic matters and heavy metals in contaminated site soil by adopting a cyclone field for classification. The complete equipment for realizing the pretreatment method is also provided, wherein the rotational flow equipment can be connected in series with multiple stages according to actual conditions, and the efficient and low-cost reduction treatment of the site polluted soil is realized.

Background

Soil pollution has serious influence on sustainable utilization of land resources and health development of human beings, the total point standard exceeding rate of the soil in China reaches 16.1%, and the proportion of slight, mild, moderate and severe pollution point positions is 11.2%, 2.3%, 1.5% and 1.1%, respectively, and the data is continuously rising. The pollution type is mainly inorganic type, the organic type is secondary, the specific gravity of the composite type pollution is small, and the number of the superstandard points of the inorganic pollutants accounts for 82.8 percent of the total superstandard points. At present, the soil treatment means mainly comprise a physical method, a chemical method and a biological method. These methods generally have long processing periods and high costs. Researches find that the particle size of the soil is inversely proportional to the pollution degree of the soil, the content of large-particle soil pollutants is low, and the soil quality reaches the standard. If large particles can be separated from the soil, the highly polluted parts of the small particles can be treated in a centralized way, so that the cost can be greatly reduced.

Based on the above principle and the concept of cost reduction, researchers and engineers at home and abroad have conducted technical exploration widely.

The utility model CN202824100U discloses a contaminated soil heat treatment system, which comprises a conveying device, a first section of middle storage barrel, a crushing device, a screening device, a second section of middle storage barrel, a first section of heat treatment unit, a third section of middle storage barrel, a second section of heat treatment unit, a fourth section of middle storage barrel, a cooling device and a conveying device; the two-section heat treatment unit forms a two-section heat treatment device, and in the heat treatment process of the two units, the inclusion of pollutant components and content in treatment is realized in the form of low temperature at the front section and high temperature at the rear section. The prior art realizes the screening treatment and recycling of the polluted soil in the repeated procedures of crushing, screening and heating, but the system is complex to operate, the heating temperature is overhigh, the energy consumption is high, pollutants are released into tail gas, and the tail gas treatment cost is high.

The invention patent application CN201721888114.X provides a soil grading structure, which is divided into a vertical material guide pipe, wherein a screening disc with a double-layer spiral structure is wound on the material guide pipe along the vertical direction, the screening disc comprises an upper screening net and a lower material receiving plate, and outward spiral side lines of the screening net and outward spiral side lines of the material receiving plates are fixedly connected through a connecting plate; carry out classification work to soil through the screening dish, soil falls into behind the screening net, and thinner soil passes through the material receiving plate behind the screening net, finally falls out from the passage, and thicker soil then always slides down along the screening net and finally from the landing on the screening net, but this processing apparatus only is fit for handling dry and particle size dispersion's soil, and is not good to the clay of the fine grain diameter of cladding on large granule soil and the great soil classification effect of humidity, and causes the jam of screen cloth easily.

The invention patent application CN201821306443.3 discloses an automatic soil screening device, which comprises a soil screening box elastically supported by a plurality of elastic supporting devices, wherein a feeding cover is arranged at the top of the soil screening box, and a vibrating motor is arranged at the bottom of the soil screening box; still include multistage soil screening collection device, multistage soil screening collection device can be with screening and collecting through pan feeding cover water conservancy diversion to the soil classification of soil screening incasement, but the device adopts the screen cloth screening, and the size of screening particle size has been decided to the size of screen cloth, and is relatively poor to the screening effect of micron order particle size, and has soil viscosity and the phenomenon that the water content disturbed the screening effect simultaneously.

Some current soil screening plant structures are complicated, complex operation, and hierarchical effect is poor, and is efficient. Therefore, there is a need in the art to develop a convenient and fast soil screening method for separating contaminated soil from standard soil to reduce the treatment cost, which overcomes the above-mentioned drawbacks of the prior art.

Disclosure of Invention

The present disclosure provides a novel method and apparatus for reducing contaminated soil by using a cyclone method to achieve grading of soil particle size to improve treatment efficiency and reduce removal cost of contaminants, thereby solving the problems of the prior art.

In one aspect, the present disclosure provides a method for reducing contaminated soil, the method comprising the steps of:

(1) fully stirring and mixing the screened polluted soil and water, and then carrying out cyclone particle size classification so as to discharge large-particle-size soil with pollutants not exceeding the standard through outer cyclone underflow for solid-liquid separation and landfill, and discharge small-particle-size soil with pollutants exceeding the standard through inner cyclone overflow; and

(2) and (3) carrying out cyclone concentration on the mud-water mixture overflowing and discharged in the step (1), discharging the obtained water overflow for circulation, and treating the obtained high-concentration polluted soil in the next stage.

In a preferred embodiment, in step (1), the contaminated soil and water are mixed thoroughly in a ratio of 1:50 to 1:10 for a mixing time of 10 to 30 min.

In another preferred embodiment, in step (1), the difference in median particle size of the underflow and overflow streams after cyclone size classification is in the range of 40 to 60 microns.

In another preferred embodiment, in step (1), the inlet velocity for the cyclonic size classification is from 2 to 5 m/s.

In another preferred embodiment, the soil content of contaminants in the sludge-water mixture discharged in the overflow in step (1) is not exceeded > 96%.

In another preferred embodiment, in the step (2), the recovery rate of water after the mixture of muddy water is subjected to cyclone concentration reaches 50-70%.

In another preferred embodiment, in steps (1) and (2), the split ratio for performing the cyclone size classification and the cyclone concentration is 1 to 20%.

In another aspect, the present disclosure provides a contaminated soil reduction apparatus, comprising:

the stirring tank and the particle size grading cyclone connected with the stirring tank are used for fully stirring and mixing the polluted soil screened in the step (1) with water and then carrying out cyclone particle size grading so as to discharge large-particle-size soil with pollutants not exceeding the standard through outer cyclone underflow for solid-liquid separation and landfill, and discharge small-particle-size soil with pollutants exceeding the standard through inner cyclone overflow; and

and (3) the solid-liquid separation cyclone connected with the particle size grading cyclone is used for performing step (2) to perform cyclone concentration on the mud-water mixture overflowing and discharged in the step (1), the obtained water overflows and is discharged for circulation, and the obtained high-concentration polluted soil enters the next stage of treatment.

In a preferred embodiment, the top of the stirring tank is covered with a screen of 10-30 mesh.

In another preferred embodiment, the particle size classification cyclone and the solid-liquid separation cyclone can adopt a multi-stage cyclone series connection mode according to specific requirements, and the nominal diameter of the cyclone series connection mode is 20-50 mm; the particle size grading cyclone is made of wear-resistant and acid and alkali-resistant materials, and the overflow pressure drop of the cyclone is not more than 0.10 MPa.

Has the advantages that:

the invention realizes the classified treatment of the soil with different particle sizes, greatly reduces the total treatment amount of the subsequent polluted soil, has simple and convenient method and improves the treatment efficiency.

Drawings

The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification to further illustrate the disclosure and not limit the disclosure.

Fig. 1 is a schematic view of a contaminated soil reduction process according to a preferred embodiment of the present disclosure.

Fig. 2 is a soil particle size distribution diagram according to example 1 of the present application.

Detailed Description

After extensive and intensive research, the inventor of the application finds that for a soil system, pollutants adsorbed on large-particle-size soil pore channels and surfaces can be removed up to the standard after being simply washed; the soil with small particle size is attached with a large amount of pollutants because of large specific surface area and narrow pore canal, so that the most effective and cheapest mode for the polluted soil is to grade the polluted soil firstly and process the polluted soil with small particle size and high particle size emphatically; and the solid-liquid separation and landfill of the soil are carried out by applying the cyclone, so that the reduction of the polluted soil can be realized, and the treatment cost is reduced. Based on the above findings, the present invention has been completed.

In a first aspect of the disclosure, there is provided a method of reducing contaminated soil, the method comprising the steps of:

(1) after fully mixing the screened soil with water in a stirring tank, entering a cyclone field of a particle size grading cyclone for particle size grading, discharging the large-particle-size soil with pollutants not exceeding the standard from a underflow port through an outer cyclone for solid-liquid separation and landfill, and discharging the small-particle-size soil with pollutants exceeding the standard from an overflow port through an inner cyclone; and

(2) and (2) feeding the mud-water mixture discharged from the overflow port in the step (1) into the next group of solid-liquid separation cyclones, concentrating the polluted mud-water mixture by using the characteristics of the cyclone field again, returning the obtained water into the stirring tank from the overflow port, and feeding the high-concentration polluted soil into a next-stage treatment device.

In the present disclosure, the water-soil heterogeneous mixture in the cyclone for particle size classification is converted from linear motion to rotary motion at the inlet of the cyclone under the pushing of pressure difference, the soil with smaller particle size moves to the axis along with water and is discharged from the overflow port, the soil component with larger particle size moves to the side wall and is discharged from the underflow port, and the separation between the light phase and the heavy phase is realized.

In the present disclosure, the ratio of soil and water in the stirring tank is 1:50-1:10, preferably 1:50, and the mixing time is 10-30 min.

In the present disclosure, after the particle size classification is performed by the particle size classification cyclone, the median particle size difference between the underflow port and the overflow port is in the range of 40 to 60 micrometers.

In the present disclosure, the solid-liquid separation cyclone is used for the concentration of the turbid soil solution, and the recovery rate of water reaches 50-70%.

In the present disclosure, the inlet velocity at the time of particle size classification by the particle size classifying cyclone is 2 to 5m/s, preferably 4 m/s.

In the present disclosure, the split ratio when the particle size classification and the turbid liquid concentration are performed by the particle size classification cyclone and the solid-liquid separation cyclone is 1 to 20%.

In the present disclosure, the cyclone overflow in the soil particle size cyclone separation process flows into the stirring tank as a subsequent treatment part, and the underflow split ratio is 6%.

In the present disclosure, the soil proportion of the contaminants in the overflow slurry-water mixed liquor of the particle size classification cyclone is not over-standard is > 96%.

In the present disclosure, the efficiency of the particle size classification cyclone to separate soil having a particle size of less than 20 microns is 99%.

In the present disclosure, the particle size classification cyclone and the solid-liquid separation cyclone may adopt a multi-stage cyclone series form according to specific requirements.

In a second aspect of the present disclosure, there is provided an apparatus for reducing contaminated soil, the apparatus comprising:

the agitator tank that the top covers has the screen cloth and the particle size classification swirler of being connected with the agitator tank delivery port, large granule soil and water that do not reach the pollution concentration are discharged from particle size classification swirler underflow opening, the surplus water soil mixture passes through particle size classification swirler overflow mouth and gets into next grade device, the solid-liquid separation swirler makes most water retrieval and utilization through the solid-liquid separation swirler, high concentration pollutes soil and discharges from solid-liquid separation swirler underflow opening, wherein, the flow and the pressure of particle size classification swirler and solid-liquid separation swirler detect through the electromagnetic flowmeter and the manometer of inserting.

In the present disclosure, the agitation tank is covered with a sieve of 10-30 mesh.

In the present disclosure, the overflow pressure drop for soil size classification with a size classification cyclone does not exceed 0.10MPa, preferably 0.05 MPa.

In the present disclosure, the particle size classification cyclone is made of wear-resistant, acid-and alkali-resistant materials.

In the disclosure, the particle size classification cyclone and the solid-liquid separation cyclone both adopt micro-cyclones with nominal diameters of 20-50 mm.

Reference is made to the accompanying drawings.

Fig. 1 is a schematic view of a contaminated soil reduction process according to a preferred embodiment of the present disclosure. As shown in fig. 1, after passing through a screen, the contaminated soil is mixed with water in a soil mixing and stirring tank 1-1, and a valve is opened to carry out back mixing so as to ensure that the two phases are uniformly mixed; opening a particle size grading cyclone 2-1 (which can be connected in parallel with multiple stages), grading the particle size of the soil, and directly discharging large-particle pollution-free soil (up-to-standard soil) from a underflow port and then locally burying the soil; the small-particle-size high-pollution soil enters a solid-liquid separation cyclone 2-2 (multiple stages can be connected in parallel), water collected by an overflow port of the solid-liquid separation cyclone enters a soil mixing and stirring tank 1-1 for recycling, a underflow port is the high-pollution soil after preliminary solid-liquid separation, the part enters a next-stage treatment device for advanced treatment, and the operation of the whole set of equipment can be controlled by an automatic control cabinet.

Examples

The invention is further illustrated below with reference to specific examples. It is to be understood, however, that these examples are illustrative only and are not to be construed as limiting the scope of the present invention. Test methods in which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under conditions recommended by the manufacturer. All percentages and parts are by weight unless otherwise indicated.

Example 1:

the method is used for reducing the polluted soil.

1. Particle size distribution of contaminated soil and operating conditions

The experimental soil is taken from Taizhou Wenling Wenzhu 23780 and a town electric appliance dismantling field, the particle size range of the soil is 0-1000 microns, the median particle size is 37.7 microns, and the main pollutants are organic polychlorinated biphenyl, polybrominated diphenyl ether and heavy metal pollutants Cu, Ni and Pb. Fig. 2 shows the particle size distribution of the underflow port and the overflow port after classification, and the following table 1 shows the specific concentration values of the pollutants:

table 1 contaminant concentration values

The ratio of contaminated soil to water for the experiment was 1:50, and the throughput of the apparatus was 0.8m³The inlet flow rate was 4m/s and the operating split ratio was 15%.

2. Detailed description of the preferred embodiments

As shown in fig. 1. After passing through a screen, the polluted soil is mixed in a soil mixing and stirring tank, a valve is opened for back mixing, the mixing time is controlled to be 5-10min, and the two phases are uniformly mixed; opening a particle size grading cyclone unit to grade the particle size of the soil, directly discharging large-particle pollution-free soil from a underflow port of the particle size grading cyclone unit, performing solid-liquid separation and landfill, feeding small-particle size high-pollution soil into the solid-liquid separation cyclone unit, feeding water collected by an overflow port of the solid-liquid separation cyclone unit into a soil mixing and stirring tank for recycling, wherein the underflow port is high-concentration polluted soil after preliminary solid-liquid separation, and feeding the part into a next-stage device for deep treatment; the operation of the whole set of equipment can be controlled by an automatic control cabinet.

3. Results of the experiment

After soil is sorted by using a soil rotational flow reduction device, the soil particle size of the overflow port of the particle size grading cyclone is not more than 27.3 micrometers, and the residual soil with large particle size is completely discharged from the underflow port of the cyclone; after the solid-liquid separation is carried out by the solid-liquid separation cyclone, the soil with large particle size is collected for pollutant detection, and the detection result is shown in the following table 2:

TABLE 2 concentration of large particle size soil contaminants after sorting

The content of each pollutant is within the content required by the soil standard of the first building site.

The above-listed embodiments are merely preferred embodiments of the present disclosure, and are not intended to limit the scope of the present disclosure. That is, all equivalent changes and modifications made according to the contents of the claims of the present application should be considered to be within the technical scope of the present disclosure.

All documents referred to in this disclosure are incorporated by reference into this application as if each were individually incorporated by reference. Furthermore, it should be understood that various changes or modifications to the disclosure may be made by those skilled in the art after reading the above teachings of the disclosure, and such equivalents may fall within the scope of the disclosure as defined by the appended claims.

Claims

1. A method for reducing contaminated soil, the method comprising the steps of:

2. The method according to claim 1, wherein in the step (1), the contaminated soil is sufficiently mixed with water in a ratio of 1:50 to 1:10 with stirring for 10 to 30 min.

3. The method of claim 1 or 2, wherein in step (1), the difference in median particle size of the underflow and overflow streams after the cyclonic size classification is performed is in the range of 40 to 60 microns.

4. The method according to claim 1 or 2, wherein in step (1), the inlet velocity for the cyclone size classification is 2 to 5 m/s.

5. A method according to claim 1 or 2, wherein the soil content of the effluent sludge-water mixture from step (1) is > 96% without exceeding the contaminant level.

6. The method as claimed in claim 1 or 2, wherein in the step (2), the recovery rate of water after the mixture of muddy water is subjected to the cyclone concentration is 50-70%.

7. The method according to claim 1 or 2, wherein in steps (1) and (2), the flow-division ratio for performing the cyclone size classification and the cyclone concentration is 1 to 20%.

8. An apparatus for reducing contaminated soil, the apparatus comprising:

the stirring tank (1-1) and the particle size grading cyclone (2-1) connected with the stirring tank (1-1) are used for fully stirring and mixing the polluted soil sieved in the step (1) with water and then carrying out cyclone particle size grading, so that large-particle-size soil with pollutants not exceeding the standard is discharged through outer cyclone underflow to carry out solid-liquid separation and landfill, and small-particle-size soil with pollutants exceeding the standard is discharged through inner cyclone overflow; and

and the solid-liquid separation cyclone (2-2) is connected with the particle size grading cyclone (2-1) and is used for performing cyclone concentration on the mud-water mixture overflowing and discharged in the step (1) in the step (2), the obtained water overflows and is discharged for circulation, and the obtained high-concentration polluted soil enters the next stage of treatment.

9. The apparatus as claimed in claim 8, wherein the top of the stirring tank (1-1) is covered with a 10-30 mesh screen.

10. The device according to claim 8, characterized in that the particle size classification cyclone (2-1) and the solid-liquid separation cyclone (2-2) can adopt a multi-stage cyclone series connection mode according to specific requirements, and the nominal diameter of the cyclone series connection mode is 20-50 mm; the particle size grading cyclone (2-1) is made of wear-resistant and acid-base-resistant materials, and the overflow pressure drop of the cyclone is not more than 0.10 MPa.