CN117862205A - Tower plate type leaching repair system suitable for low-permeability soil heavy metal pollution - Google Patents

Abstract

The invention relates to the field of soil heavy metal remediation, in particular to a tray type leaching remediation system suitable for low-permeability soil heavy metal pollution. The system comprises a soil particle feeding unit, a sieve plate, a leaching solution spraying unit, a negative pressure suction filtration unit and a waste liquid treatment and circulation unit, wherein the soil particle feeding unit is used for feeding by adopting a soil particle powder spraying mode, so that the soil void ratio is increased, and the soil permeability is enhanced; the leaching solution is sprayed and soaked to effectively transfer heavy metals from soil to water phase; performing negative pressure suction filtration to complete solid-liquid separation; the waste liquid is treated and recycled, so that water is saved; the tray type design is flexible and efficient, and the occupied area is saved. The method can be used for leaching and repairing the heavy metal pollution of the sand soil and also can be used for leaching and repairing the low-permeability soil, so that the heavy metal pollution in the low-permeability soil is effectively repaired and removed.

Description

A tray-type leaching and remediation system suitable for heavy metal contamination of low-permeability soil

Technical Field

The invention relates to the field of soil heavy metal remediation, in particular to a tray-type elution remediation system suitable for low-permeability soil heavy metal pollution.

Background technique

The threat posed by heavy metal pollution in soil to the environment and human health has attracted the attention of scholars at home and abroad, and its governance has become a hot topic of research recently.

Heavy metal pollution in soil is non-degradable and highly mobile. At the same time, the natural purification of heavy metal soil pollution takes a long time and is prone to cause environmental chain reactions, which not only affects plant growth, but may also affect the quality of the atmosphere and water environment. Heavy metal pollution in soil may also cause food chain pollution and endanger human health. Soil leaching is an effective method for soil heavy metal remediation. Soil leaching can not only quickly remove pollutants from the soil, but also complete the treatment of high-concentration contaminated soil in a short period of time. It has a simple process and high remediation efficiency, and the investment consumption and treatment costs are relatively low. It is especially suitable for the treatment of small areas of heavily contaminated soil. It has now become one of the main means of rapid remediation technology for contaminated soil. The traditional stirring soil leaching remediation (device) system has poor treatment effect on low permeability soil (silt/clay) and is not very applicable. The cost of treating the mud produced by leaching is high.

Summary of the invention

In view of the problems that traditional stirring soil leaching and remediation systems have poor treatment effects on low-permeability soils (silt/clay), are not very applicable, and have high costs for treating the mud produced by leaching, the present invention proposes a tower plate leaching and remediation system suitable for heavy metal pollution in low-permeability soils, which can effectively repair and remove heavy metal pollution in low-permeability soils.

In order to solve the above technical problems, the present invention is solved by the following technical solutions:

A tray-type elution remediation system suitable for low-permeability soil heavy metal contamination, the remediation system comprising a plurality of remediation units, each of which comprises a soil particle feeding unit, a sieve plate, an eluent spraying unit, a negative pressure filtration unit and a waste liquid treatment circulation unit;

Furthermore, the soil particle feeding unit comprises a pneumatic conveyor and a soil feeding nozzle, wherein the pneumatic conveyor can convey particles with a particle size of 2 mm or less and has an adjustable flow rate, which is proportional to the soil particle size. The soil feeding nozzle is movable and can evenly spray the soil particles onto the sieve plate.

Furthermore, the sieve plate comprises a lower microporous ceramic filter plate and an upper nylon filter screen, the pore size of the ceramic filter plate is not larger than the soil particle size, preferably the pore size of the ceramic filter plate is 0.05 mm, and the nylon filter screen is a 1000 mesh filter screen. The soil material thickness on the sieve plate is proportional to the soil particle size.

Furthermore, the eluent spray unit is equipped with multiple nozzles, the spraying range can evenly cover the sieve plate, the atomization degree is high, the water droplets are small, the impact strength on the soil below is small, and the spraying speed is proportional to the thickness of the soil. The eluent has a good wettability to the soil. The eluent immerses the soil and stands for a period of time, and the standing time is inversely proportional to the soil particle size.

Furthermore, the negative pressure filtration unit includes a vacuum pump and an air suction port. The vacuum pump can produce a higher vacuum degree. Multi-stage vacuum pumps are used in series. The air suction port has a baffle protection device to prevent the eluent from entering. The negative pressure filtration unit has good sealing performance, and the discharge port is in a sealed state during filtration.

Furthermore, the waste liquid treatment circulation unit includes a leaching waste liquid treatment tank and a leaching liquid preparation tank.

Furthermore, the repair unit adopts a modular design and can be combined in a tower plate manner according to site conditions.

The plate elution remediation system for heavy metal pollution in low permeability soil includes the following remediation steps:

(1) Arranging the soil particle feeding unit, sieve plate, eluent spraying unit, negative pressure filtration unit and waste liquid treatment circulation unit according to the heavy metal pollution characteristics, soil type and site conditions;

(2) evenly spreading the pre-screened contaminated soil (particle size ≤ 2 mm) onto the sieve plate through the soil particle feeding unit;

(3) spraying the eluent onto the contaminated soil particles on the sieve plate through the eluent spraying unit, stopping the spraying when the eluent submerges the soil particles, letting it stand for a period of time, and extracting the eluent to the drain port under the sieve plate through the negative pressure filtration unit until it is drained;

(4) the elution waste liquid is treated and recycled by the waste liquid treatment circulation unit;

(5) Repeating steps (2) to (4) to dissolve and treat heavy metals in a cyclic manner;

(6) After a batch of soil is processed, it is taken out through the discharge port and a new batch of soil is loaded for processing.

Compared with the traditional soil leaching and remediation system, the present invention has the following advantages:

(1) High degree of automation, uniform powder feeding by pneumatic conveyor: By adopting pneumatic conveyor and movable soil feeding nozzle, automatic conveying of particles with a particle size of 2mm and below is achieved, and the flow rate is adjustable. This makes the soil particles evenly distributed on the sieve plate, creating gaps, thereby increasing soil permeability.

(2) Spraying method wets soil particles, and immersion method increases contact time: The eluent spray unit is equipped with multiple nozzles, which can evenly cover the sieve plate, highly atomize, and produce small water droplets, thereby evenly and fully wetting the soil particles. Through the immersion method, the contact time between the eluent and the soil particles is increased, which helps the heavy metals transfer to the liquid phase and improves the elution effect.

(3) Use negative pressure filtration to complete solid-liquid separation and reduce mud treatment costs: The negative pressure filtration unit generates a high vacuum degree through a vacuum pump, and multiple vacuum pumps are used in series to achieve solid-liquid separation. Compared with the traditional stirring system, this design is less likely to produce mud, greatly reducing the cost of mud treatment.

(4) Modular design, flexible assembly, and space saving: The repair unit adopts a modular design, and the tower plate system can be freely built according to the site conditions and assembled flexibly. Each repair unit can be controlled individually, which is convenient to operate, and the design saves site space.

(5) Recycling of leaching waste liquid to save water: The waste liquid treatment circulation unit includes a leaching waste liquid treatment pool and a leaching liquid preparation pool, which realizes the recycling of leaching waste liquid, saves water, and complies with the concept of environmental protection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of an overall system of a specific embodiment of the present invention;

FIG2 is an overall process flow chart of a specific embodiment of the present invention;

The numbers in the figure are: 1. Pneumatic conveyor; 2. Soil feeding nozzle; 3. Sieve plate; 4. Eluent nozzle; 5. Centrifugal pump; 6. Eluent waste treatment tank; 7. Vacuum pump; 8. Vacuum port; 9. Drain port; 10. Discharge port; 11. Valve; 12. Contaminated soil; 13. Eluent preparation tank.

Detailed ways

The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and the features in the embodiments can be combined with each other without conflict.

With reference to Figures 1 and 2 and the embodiments, the present invention is further described in detail:

In a specific embodiment, the pneumatic conveyor 1 of the soil particle feeding unit is a positive pressure dense phase pneumatic conveyor, which can convey particles with a particle size of 2 mm or less and has an adjustable flow rate, which is proportional to the soil particle size. The nozzle aperture of the soil feeding nozzle 2 is 3 mm, and it can be moved to evenly spray the soil particles onto the screen plate. In a specific embodiment, the feeding thickness is 20 cm. The powder spraying feeding is mainly to create gaps between soil particles and increase soil permeability.

The sieve plate 3 mainly plays the role of filtering the eluent. In a specific embodiment, the sieve plate 3 uses a 5m×5m×0.06m ceramic filter plate with a pore size of 0.05mm. The bottom and surrounding of the filter plate are supported by stainless steel reinforcing ribs. A 5m×5m nylon filter screen with a sieve hole of 1000 mesh is attached to the filter plate to facilitate material discharge.

In a specific embodiment, the eluent spraying unit eluent nozzle 4 uses a diffuse stainless steel nozzle with high atomization degree, small water droplets, low impact strength on the soil below, and the eluent soaking time is 20 minutes. The centrifugal pump 5 uses a 10-stage centrifugal pump with a rated power of 1000kw and a rated head of 2953m.

In a specific embodiment, the vacuum pump 7 of the negative pressure filtration unit uses a three-stage vacuum pump connected in series to produce a high vacuum degree. A 20 cm PVC arc baffle is used above the suction port 8 to protect it from the eluent being drawn out.

In a specific embodiment, the waste liquid treatment circulation unit elution waste liquid treatment tank 6 adjusts the waste liquid pH value by adding sodium hydroxide to generate lead hydroxide precipitate. Then, the lead hydroxide precipitate is flocculated into a mass by flocculation and flotation, and scraped away by a scraper. The elution liquid preparation tank 13 adds citric acid and a surfactant to prepare the elution liquid, which is filtered through the filter screen at the bottom of the preparation tank and then sucked into the spray system through a centrifugal pump.

In a specific embodiment, 5 layers of repair units are selected for tower plate type erection.

A tray-type leaching and remediation system for heavy metal pollution in low-permeability soil of the present invention comprises the following steps:

(1) Arranging the soil particle feeding unit, the sieve plate 3, the eluent spraying unit, the negative pressure filtration unit and the waste liquid treatment circulation unit according to the heavy metal pollution characteristics, soil type and site conditions;

(2) evenly spreading the pre-screened contaminated soil onto the sieve plate through the soil particle feeding unit;

(3) spraying the eluent onto the contaminated soil particles on the sieve plate through the eluent spraying unit, stopping the spraying when the eluent submerges the soil particles, letting it stand for a period of time, and extracting the eluent to the drain port under the sieve plate through the negative pressure filtration unit until it is drained;

(4) the elution waste liquid is treated and recycled by the waste liquid treatment circulation unit;

(5) Repeating steps (2) to (4) to dissolve and treat heavy metals in a cyclic manner;

(6) After a batch of soil is processed, it is taken out through the discharge port and a new batch of soil is loaded for processing.

In summary, the tower plate elution remediation system suitable for heavy metal pollution in low permeability soil of the present invention has a high degree of automation in the pneumatic conveying of soil particles, and the powder spraying type feeding is uniform, which can easily produce soil particle gaps and increase soil permeability. The addition of elution liquid by spraying can evenly and fully wet the soil particles; increasing the contact time between the elution liquid and the soil by immersion helps to transfer heavy metals to the liquid phase. The solid-liquid separation is completed by negative pressure filtration, which is not easy to produce mud and greatly reduces the cost of mud treatment. The sieve plate elution can be eluted in small amounts and multiple times, and the elution is more thorough. The tower plate modular design is flexible in assembly and can be freely built according to project requirements, saving site space. Each remediation unit can be controlled individually and is easy to operate. The elution waste liquid is recycled to save water.

Claims (7)

1. A tray-type elution and remediation system suitable for low-permeability soil heavy metal pollution, characterized by: The remediation system comprises a plurality of remediation units, each of which comprises a soil particle feeding unit, a sieve plate (3), a washing liquid spraying unit, a negative pressure filtration unit and a waste liquid treatment circulation unit; The following steps are involved in the leaching repair process: The soil particle feeding unit, the sieve plate (3), the eluent spraying unit, the negative pressure filtration unit and the waste liquid treatment circulation unit are arranged according to the heavy metal pollution characteristics, the soil type and the site conditions; Evenly spreading the pre-screened contaminated soil onto the sieve plate (3) through the soil particle feeding unit; The eluent spraying unit sprays the contaminated soil particles on the sieve plate (3) with the eluent spraying unit, stops spraying when the eluent submerges the soil particles, leaves the eluent to stand for a period of time, and then extracts the eluent to the drain port under the sieve plate through the negative pressure filtration unit until it is drained; The elution waste liquid is treated and recycled by the waste liquid treatment circulation unit; Repeat the above steps to dissolve and treat heavy metals repeatedly; After one batch of soil is processed, it is taken out through the discharge port and a new batch is loaded for processing. 2. According to claim 1, the tower plate elution remediation system suitable for heavy metal pollution in low permeability soil is characterized in that: the soil particle feeding unit includes a pneumatic conveyor (1) and a soil feeding nozzle (2), the pneumatic conveyor (1) can transport particles with a particle size of 2 mm or less and the flow rate is adjustable; the soil feeding nozzle (2) is movable and can evenly spray soil particles onto the screen plate. 3. According to claim 1, the tower plate elution remediation system suitable for low permeability soil heavy metal pollution is characterized in that: the sieve plate (3) includes a lower microporous ceramic filter plate and an upper nylon filter screen, the pore size of the lower microporous ceramic filter plate is not larger than the soil particle size, and the soil loading thickness on the sieve plate is proportional to the soil particle size. 4. According to claim 1, the tower plate elution remediation system suitable for low permeability soil heavy metal pollution is characterized in that: the eluent spray unit is equipped with multiple eluent nozzles (4), the spraying range evenly covers the sieve plate (3), and the spraying speed is proportional to the soil loading thickness; the eluent immerses the soil and stands for a period of time, and the standing time is inversely proportional to the soil particle size. 5. According to claim 1, the tower plate elution remediation system suitable for low permeability soil heavy metal pollution is characterized in that: the negative pressure filtration unit includes a vacuum pump (7) and an air suction port (8), and multiple vacuum pumps are used in series. The air suction port (8) has a baffle protection device to prevent the elution liquid from entering; the negative pressure filtration unit has good sealing performance, and the discharge port (9) is in a sealed state during filtration. 6. The tray-type elution remediation system for heavy metal pollution in low-permeability soil according to claim 1 is characterized in that the waste liquid treatment circulation unit comprises an elution waste liquid treatment tank (6) and an elution liquid preparation tank (13). 7. The tray-type elution remediation system for heavy metal pollution in low-permeability soil according to claim 1 is characterized in that the remediation unit adopts a modular design and can be combined in tray-type according to site conditions.