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CN-122007142-A - Micro-foam restoration system and method for organic contaminated soil

CN122007142ACN 122007142 ACN122007142 ACN 122007142ACN-122007142-A

Abstract

The invention discloses a micro-foam restoration system and method for organic contaminated soil, which belong to the technical field of soil pollution restoration, wherein a micro-foam generation unit consists of a micro-foam matrix and a column type gas stone device which are connected in series, an outlet of the micro-foam matrix is divided into two paths through a second two-position three-way electromagnetic valve, and liquid is alternately supplied to different groups of gas stone devices, so that a liquid pump and the micro-foam generation unit continuously operate, the downtime waiting time of a traditional intermittent pump is eliminated, and the restoration efficiency is remarkably improved. In the soil remediation process, two-way alternate injection is performed to generate boiling micro-foam, and a foam pump is controlled to continuously convey clear water and combine with compressed air to perform intermittent purging and final drying. The micro-foam generated by the invention has uniform particle size and high stability, can obviously improve the desorption efficiency of organic pollutants such as polycyclic aromatic hydrocarbon, has the self-cleaning capability of a system, has no secondary pollution, and is particularly suitable for repairing complex organic polluted soil such as coking sites.

Inventors

  • LI HUA
  • ZHU YUEN
  • ZHAO WENJING
  • ZHANG YAXIN
  • ZHANG QICHUAN

Assignees

  • 山西大学
  • 山西省安装集团股份有限公司

Dates

Publication Date
20260512
Application Date
20260409

Claims (10)

  1. 1.A microfoam restoration system and method for organically contaminated soil, comprising: the medicament supply unit comprises a high-concentration rhamnolipid solution tank (1), a clear water solution tank (2), a diluted rhamnolipid solution tank (3) and a liquid distribution pipeline connected with the tank body; The power transmission unit comprises a liquid pump (4) and a multi-channel selection electromagnetic valve (6), wherein the liquid pump (4) is selectively communicated with the high-concentration rhamnolipid solution tank (1), the clear water solution tank (2) or the diluted rhamnolipid solution tank (3) through the multi-channel selection electromagnetic valve (6); the micro-foam generating unit comprises a rhamnolipid micro-foam matrix (5) and a column type air stone device (10) arranged in a soil remediation pool (8), wherein an inlet of the rhamnolipid micro-foam matrix (5) is communicated with an outlet of a liquid drawing pump (4) through a first two-position three-way electromagnetic valve (7), and an outlet of the rhamnolipid micro-foam matrix is communicated with the soil remediation pool (8); The air source supply unit comprises a compressed air source (9), wherein an air outlet pipeline of the compressed air source (9) is divided into at least two branches, one branch is communicated with an inlet of the rhamnolipid micro-foaming matrix (5), and the other branch is communicated with a column type air stone device (10) in the soil remediation pool (8); the control unit is configured with double-flow automatic control logic and is used for switching and executing a soil remediation process and an equipment cleaning process; In the soil remediation process, the liquid pump (4) is configured to continuously work or work according to a preset time sequence, the diluted rhamnolipid solution is pumped into the rhamnolipid micro-foaming matrix (5) and mixed with compressed air to form primary micro-foam, and the primary micro-foam enters the soil remediation pool (8) and is subjected to secondary foaming through the upright column type gas stone device (10); the outlet pipeline of the rhamnolipid micro-foaming matrix (5) is connected with a second two-position three-way electromagnetic valve (11), the second two-position three-way electromagnetic valve (11) divides micro-foam fluid into at least two independent branches, namely a branch A and a branch B, which are respectively connected to upright column type air stone device groups with different spatial distributions in a soil remediation pool (8), and are respectively arranged into a group A and a group B; In the soil remediation process, the control unit is configured to execute two-way alternate fluid replacement logic, namely, the second two-position three-way electromagnetic valve (11) is controlled to perform seamless switching between the branch A and the branch B, so that the liquid pump (4) and the rhamnolipid micro-foaming matrix (5) continuously run, micro-foaming fluid is alternately injected into the group A and the group B gas stone devices, and intermittent waiting time caused by starting and stopping of a pump body is eliminated.
  2. 2. The microfoam restoration system and method for organic contaminated soil as recited in claim 1, wherein a plurality of foam generating devices distributed in an array are provided in said rhamnolipid microfoam matrix (5), and a distance between adjacent foam generating devices is 10 micrometers for achieving preliminary thorough mixing of gas-liquid two phases and generation of micro bubble nuclei under high pressure.
  3. 3. The microfoam restoration system and method for organic contaminated soil according to claim 1, wherein the pillar type gas stone device (10) has a cylindrical porous structure with a pore size ranging from 40 to 60 mesh, and is used for cutting and secondarily refining a gas-liquid mixture from the rhamnolipid microfoam matrix (5) to generate main microfoam with a particle size ranging from 50 to 200 μm.
  4. 4. The micro-foam restoration system and method for organic contaminated soil according to claim 1, wherein a third two-position three-way electromagnetic valve (92) and a one-way valve (91) are arranged on a branch of the compressed air source (9) communicated to the column type air stone device (10); In the soil remediation process, the branch is opened to assist secondary foaming, and a third two-position three-way electromagnetic valve (92) is linked with a second two-position three-way electromagnetic valve (11), and is mainly used for supplying air to the group A when supplying liquid to the group A and is mainly used for supplying air to the group B when supplying liquid to the group B; in the equipment cleaning process, the branch is used for blowing the column type air stone device (10) by introducing compressed air.
  5. 5. The micro-foam restoration system and method for organically-polluted soil as set forth in claim 1, wherein said dual-flow automated control logic specifically includes: The soil remediation process comprises the steps of controlling a liquid pump (4) to continuously run, controlling a second two-position three-way electromagnetic valve (11) to switch between a branch A and a branch B according to a preset time interval, and simultaneously controlling a compressed air source (9) to provide a constant-pressure air source; The equipment cleaning process comprises the steps of controlling a multi-channel selection electromagnetic valve (6) to be switched to a clear water solution tank (2), controlling a liquid pump (4) to continuously run to pump clear water into the system, then controlling a compressed air source (9) to work in a purging-stopping intermittent mode, and finally continuously introducing compressed air to purge a system pipeline from a wet state to a dry state.
  6. 6. The micro-foam restoration system and method for organic contaminated soil according to claim 5, wherein in the soil restoration process, when the soil area pressure corresponding to a certain branch reaches a preset upper limit, the control unit triggers the second two-position three-way electromagnetic valve (11) in advance to switch.
  7. 7. The microfoam restoration system and method for organic contaminated soil as recited in claim 5, wherein in said apparatus cleaning process, the intermittent purge mode of compressed air is set to be operated for 8-12 minutes, stopped for 3-5 minutes, and the total cleaning time is not less than 2 hours, and the final stage of the cleaning process includes a continuous aeration-drying process having a duration of not less than 30 minutes.
  8. 8. The micro-foam restoration system and method for organic contaminated soil according to claim 1, wherein an adjustable float flowmeter (93) is arranged on both branches of the air outlet pipeline of the compressed air source (9) for respectively adjusting the air flow rate entering the rhamnolipid micro-foaming matrix (5) and the column type air stone device (10).
  9. 9. The micro-foam restoration system and method for organic contaminated soil according to claim 1, further comprising a distributed sensor network, wherein the distributed sensor network comprises a pore water pressure sensor, an oxidation-reduction potential probe, a temperature sensor and a volatile organic compound on-line monitor, and the sensor network is connected with a control unit and is used for monitoring the restoration process in real time and feeding back and adjusting operation parameters.
  10. 10. A method for repairing a micro-foam for organically-polluted soil using the method as claimed in any one of claims 1 to 9, comprising the steps of, in order: S1, preprocessing and arranging a system, namely configuring diluted rhamnolipid solution with set concentration, finishing arrangement of injection wells and monitoring sensors, dividing the injection wells into at least two groups, and arranging the injection wells into a group A and a group B; S2, starting a double-path alternate repair process, namely starting a liquid pump (4) and a compressed air source (9) through a control unit to generate micro-foam, and controlling a second two-position three-way electromagnetic valve (11) to firstly guide the micro-foam into the group A air stone device for injection; S3, seamless switching, namely controlling a second two-position three-way electromagnetic valve (11) to rapidly switch to a group B gas stone device for injection under the condition of not stopping a liquid pump (4) when the preset time or pressure threshold is reached, and enabling a group A to enter a relaxation reaction period; s4, circularly running, namely repeating the step S3, and alternately injecting micro-foam into the group A and the group B until the repair is completed; S5, executing a device cleaning flow, namely switching to a cleaning mode after repairing, flushing a system pipeline and components by using clear water circulation, and then carrying out intermittent purging and final drying by using compressed air until no medicament residue exists in the system and the system is in a dry state.

Description

Micro-foam restoration system and method for organic contaminated soil Technical Field The invention relates to the technical field of soil pollution remediation, in particular to a micro-foam remediation system and method for organic polluted soil, which are particularly suitable for in-situ or ex-situ remediation of organic polluted soil difficult to degrade such as Polycyclic Aromatic Hydrocarbons (PAHs), petroleum hydrocarbons, phenols and the like, and are particularly suitable for the fine treatment of heavy pollution sites such as coking plants, chemical plants and the like. Background With the acceleration of global industrialization progress, the problem of soil pollution of the left-over industrial site is increasingly serious, and the soil pollution becomes a key factor for restricting the sustainable development of cities and threatening the health of human bodies. Wherein, the soil of the sites such as coking plants, petrochemical plants, gas plants and the like is rich in toxic and harmful substances such as Polycyclic Aromatic Hydrocarbons (PAHs), benzene series (BTEX), phenols, cyanide and the like. The organic pollutants have the characteristics of strong hydrophobicity, high octanol-water distribution coefficient (Kow), easiness in being adsorbed in soil organic matters and micropores, difficulty in biodegradation and the like, and are called as refractory pollutants. Conventional soil remediation techniques have significant limitations in facing such complex contaminations: 1. The thermal desorption method has high removal efficiency, but has huge energy consumption (generally needs to be heated to 300-500 ℃), high operation cost, and high temperature can damage the soil aggregate structure and microbial community, so that the ecological function of the soil is lost, and the restored soil can be utilized only by re-improvement. 2. And (3) leaching the soil by injecting a chemical agent solution. However, most conventional leaches are macroscopic fluids and are difficult to access soil micropores (< 50 microns), resulting in insufficient contact of the agent with the contaminants and limited removal rates. In addition, the use of large amounts of chemical agents may change the pH of the soil, cause secondary pollution, and make the waste liquid treatment difficult. 3. The bioremediation method utilizes microorganisms to degrade pollutants, has low cost and environmental friendliness, but has extremely long reaction period (often needs years), and high-concentration toxic pollutants can inhibit the activity of microorganisms, so that the requirement of urgent site redevelopment is difficult to meet. 4. The common aeration method is to introduce air or oxygen into the soil, but the formed bubbles have large particle size (millimeter level), the rising speed is high, the specific surface area is small, the gas-liquid mass transfer efficiency is low, the carrying capacity of the medicament is poor, and the strongly adsorbed organic pollutants are difficult to effectively emulsify and strip. In recent years, the micro-nano bubble technology has been used in the field of environmental control for its unique physicochemical properties (such as large specific surface area, long residence time, high negative potential on the surface, free radical generation, etc.). The micro-foam repair technology uses micro-bubbles as a carrier, carries a surfactant (such as biosurfactant rhamnolipid) into soil micropores, and removes pollutants through solubilization, emulsification, desorption and other actions. However, the existing micro-foam generating devices and processes still have the following key bottlenecks: 1. the bubbles have uneven particle size distribution, and it is difficult to achieve both miniaturization and uniformity of bubbles by a single foaming device. The generated bubbles are often mixed in size, and large bubbles quickly escape, so that the utilization rate of the medicament is reduced, and the soil structure is possibly damaged (air channeling). 2. The system pipeline is remained and blocked, and biosurfactants such as rhamnolipid and the like have certain viscosity and colloid characteristics and are easy to adhere to the inner wall of the pipeline, the valve and the surface of a precise foaming element (such as microporous ceramic). The existing system lacks an efficient and automatic online cleaning mechanism, is easy to cause micropore blockage, flow reduction and even cross-pollutes repair sites of different batches after long-term operation. 3. The operation mode is stiff, the efficiency is low, and the traditional system mostly adopts a continuous constant current injection mode and cannot adapt to resistance change caused by soil heterogeneity. Part of the intermittent system adopts a mode of 'pump stop-wait-pump start', and during the period of pump stop, the whole system is in a static state, so that equipment is idle and time is wasted (the intermittent waiting time is 15-2