Solar-assisted soil organic pollutant in-situ pyrolysis desorption system

Abstract

The invention discloses a solar-assisted in-situ pyrolysis desorption system for soil organic pollutants. The solar-assisted in-situ pyrolysis desorption system comprises a solar heat collection device, a pyrolysis system for heating soil, an extraction system and a tail gas emission treatment system, the solar heat collection device is connected with the pyrolysis system and provides heat energy for the pyrolysis system, the pyrolysis system is connected with the extraction system, and the tail gas emission treatment system is connected with the extraction system. According to the system, a three-layer soil covering system is arranged to replace a traditional cement layer, excavation and transportation are not needed, leakage of polluted soil is avoided, the engineering earthwork volume is reduced, and low carbon and environmental protection are achieved; solar energy is used for providing a heat source for soil in-situ pyrolysis desorption, a tail gas treatment system is arranged, the structure and the working principle are simple, the heat exchange efficiency is high, pollutant desorption is fast, and good popularization value is achieved; the device has the advantages of simple structure, safety and reliability in use, low energy consumption and no tail gas emission, and provides a new scheme for energy conservation and emission reduction of a soil pyrolysis desorption technology.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation equipment, and particularly to a solar-assisted in-situ thermal desorption system for soil organic pollutants. Background Art

[0002] With the adjustment of the urban economic structure, the relocation of a large number of chemical industrial sites out of the urban area, the excavation and reuse of landfills, etc. have all caused varying degrees of pollution of land resources. Due to the wide variety of organic pollutants left in the polluted sites, and the redevelopment is often for commercial purposes (such as housing, school, hospital land, etc.), with heavy tasks and short cycles, it is not suitable to adopt biochemical remediation technologies with long remediation times and strong pertinence. Instead, more efficient methods should be sought to address the problem of soil complex organic pollution. The thermal desorption technology is an important method to evaporate organic pollutants through thermochemical means and separate them from the soil medium, thereby achieving the efficient and rapid removal of various organic pollutants. In-situ thermal desorption, due to its advantages of facilitating pollution control, eliminating the need for transportation and disposal, short construction period, high removal rate, etc., has significant repair effects on organic polluted soils such as polycyclic aromatic hydrocarbons, pesticides, petroleum, polychlorinated biphenyls, polybrominated diphenyl ethers, etc., and has become a soil remediation technology with broad prospects.

[0003] The current main in-situ thermal desorption technologies mainly include resistance thermal desorption technology, heat conduction thermal desorption technology, and steam thermal desorption technology. However, these thermal desorption technologies themselves still have problems of high energy consumption and high carbon emissions. Currently, it is known that the electricity cost input of electrothermal desorption accounts for about 50% of the total production input. The main reasons restricting their popularization and application are various difficulties such as the difficulty in obtaining large-scale temporary electricity in some sites, the steam injection heating desorption technology being easily restricted by the site geological conditions and the upper limit of the target temperature, and the soil gas desorbed being not easily effectively captured and escaping to pollute the environment. Solar energy is a clean energy source that is inexhaustible and has a huge resource volume. The total amount of solar radiation energy on the earth's surface per year is 1×10 18 kW·h, which is more than ten thousand times the total annual energy consumption of the world. Developing solar thermal utilization technology and applying it to in-situ soil thermal desorption is one of the effective ways to reduce the energy consumption of this technology and promote its clean thermal substitution and low-carbon transformation. In addition, developing the treatment technology for the tail gas after thermal desorption has a great promoting effect on promoting the application of thermal desorption technology. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned deficiencies of the prior art, solve the problems of high energy consumption and high carbon emissions in the prior art, and provide a solar-assisted in-situ thermal desorption system for soil organic pollutants that makes full use of resources, has less pollution, broad application prospects, and can use solar energy as a heat source.

[0005] The present invention is realized through the following technical solutions: A solar-assisted in-situ thermal desorption system for soil organic pollutants, comprising a solar heat collection device, a pyrolysis system for heating the soil, an extraction system, and an exhaust gas emission treatment system; the solar heat collection device is connected to the pyrolysis system and provides heat energy for it, the pyrolysis system is connected to the extraction system, and the exhaust gas emission treatment system is connected to the extraction system.

[0006] In this system, the heat energy collected by the solar heat collection device is directly provided to the pyrolysis system. The organic pollution gas generated by the pyrolysis system heating the soil is extracted from the soil through the extraction system and finally transported to the exhaust gas emission treatment system.

[0007] The solar heat collection system includes a heat absorption plate, a heat storage device, a controller, and a heating chamber; the heat absorption plate is respectively connected to the heat storage device and the controller, the heating chamber is respectively connected to the heat storage device and the controller, and the heat storage device is connected to the controller; the heating chamber is connected to the pyrolysis system. The connection mode of each component of the solar heat collection system can ensure that the absorbed solar heat energy is not wasted. When heating the gas in the heating chamber, the heating temperature can be adjusted according to the type of soil organic pollutants. The heat storage device is mainly used to temporarily store the unused heat absorbed by the heat absorption plate. It is directly connected to the heat absorption plate to reduce the loss caused during the heat transportation process. The controller is used to monitor the operation of the entire solar heat collection device and can also adjust relevant parameters. The heating chamber is used to heat the gas and adjust the temperature of the heated gas, so that the high-temperature gas is transported to the soil through the pipeline, thereby achieving the purpose of heating the soil.

[0008] The pyrolysis system device includes heating rods, a conveying pipeline, temperature measuring holes, pressure measuring holes, and a soil covering layer; the temperature measuring holes and pressure measuring holes are mainly concentrated in the lower layer of the soil covering layer contaminated by organic pollutants to ensure that the deep soil is fully heated and the purpose of repairing the deep soil is achieved; there are two thin pipes inside the conveying pipeline, and the internal structure of the heating rod consists of a circulating U-shaped pipeline. The two ends of the U-shaped pipeline are respectively connected to the two thin pipes inside the conveying pipeline through a first flange and a second flange; the conveying pipeline is connected to the solar heat collection device. The structural setting of the U-shaped pipeline and the thin pipes can ensure the recycling of the heat conduction gas used.

[0009] The soil covering layer is composed of a water storage layer, a drainage layer, and a low-permeability layer from top to bottom. The water storage layer is mainly composed of fine soil particles with a particle size less than 5 mm, the drainage layer is mainly composed of coarse soil particles with a particle size of 10 - 40 mm, and the low-permeability layer is mainly composed of soil powder with a particle size less than 2 mm. The soil covering layer is composed of three different particle sizes of soil particles, replacing the traditional cement layer to achieve the function of preventing seepage and closing air.

[0010] The compactness of the low-permeability layer is above 95%.

[0011] The extraction system includes an extraction pipeline, a vacuum pump, and a vacuum extraction well with a sealed bottom end; the vacuum extraction well is inserted into the soil covering layer of the pyrolysis system, the vacuum extraction well is connected to the extraction pipeline, and the end of the extraction pipeline is connected to the vacuum pump; the vacuum pump is connected to the tail gas emission treatment system. The connection between the vacuum extraction well and the extraction pipeline can transport the extracted gas.

[0012] A number of air channels are provided on the circumferential direction of the pipe wall of the vacuum extraction well from bottom to top, and the arc length of each air channel is one-fourth of the circumference of the vacuum extraction well; a number of heating rods are provided, and the number of heating rods are connected in parallel on the conveying pipeline; a number of vacuum extraction wells are provided, and the number of heating rods and the number of vacuum extraction wells are distributed at intervals alternately. The lengths of the heating rods and the vacuum extraction wells are determined by the depth of the contaminated soil.

[0013] The tail gas treatment system includes a gas-liquid separator, a fan, a granular biochar tank, and a bag filter; the gas-liquid separator is respectively connected to the fan and the bag filter, and the fan is connected to the granular biochar tank; the gas-liquid separator is connected to the extraction system. The gas-liquid separator separates the mixture of gas and liquid extracted from the extraction system, the fan transports the gas separated by the separation device to the granular biochar tank, the granular biochar tank adsorbs the harmful substances in the gas and then discharges it, and the bag filter is used to treat the liquid discharged from the gas-liquid separator.

[0014] The heat absorption plate adopts a heat pipe type vacuum tube heat collection plate.

[0015] The surface of the conveying pipeline is provided with a heat preservation material layer. The setting of the heat preservation material layer can reduce the heat loss and realize the maximum utilization of heat.

[0016] Compared with the prior art, the advantages of the present invention are as follows: This system uses a three-layer soil covering system to replace the traditional cement layer, without excavation and transportation, avoiding the spillage of contaminated soil, reducing the engineering earthwork volume, and being low-carbon and environmentally friendly; using solar energy as the heat source for in-situ soil thermal desorption, and equipped with a tail gas treatment system, its structure and working principle are simple, the heat exchange efficiency is high, and the pollutant desorption is fast, having good popularization value; having the advantages of safe and reliable use, low energy consumption, and no tail gas emission, providing a new solution for the energy conservation and emission reduction of the soil thermal desorption technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of an embodiment of the present invention;

[0018] Figure 2Schematic diagram of the internal structure of the heating rod according to an embodiment of the present invention;

[0019] Figure 3 Schematic diagram of the internal structure of the conveying pipeline according to an embodiment of the present invention.

[0020] Meanings of the reference numerals in the figure: 1, heat absorption plate; 2, heat storage device; 3, controller; 4, heating chamber; 51, temperature measuring hole; 52, pressure measuring hole; 6, heating rod; 7, vacuum extraction well; 8, low permeability layer; 9, drainage layer; 10, water storage layer; 11, conveying pipeline; 12, extraction pipeline; 13, vacuum pump; 14, gas-liquid separator; 15, fan; 16, granular biochar tank; 17, bag filter. Detailed implementation manners

[0021] The content of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0022] Embodiment

[0023] Refer to Figures 1 to 3 , which is a solar-assisted in-situ thermal desorption system for soil organic pollutants, including a solar heat collection device, a pyrolysis system for heating the soil, an extraction system, and a tail gas emission treatment system; the solar heat collection device is connected to the pyrolysis system and provides heat energy for it, the pyrolysis system is connected to the extraction system, and the tail gas emission treatment system is connected to the extraction system. Figure 1 The wavy area in is the location of the pollutants.

[0024] In this system, the heat energy collected by the solar heat collection device is directly provided to the pyrolysis system. The organic pollution gas generated by the pyrolysis system heating the soil is extracted from the soil through the extraction system and finally transported to the tail gas emission treatment system. This system provides a new way to transport the heating gas to the soil, achieving the purpose of soil remediation. Since the treatment is carried out in-situ in the soil, there is no excavation or transportation, avoiding the spillage and large-scale transfer of polluted soil and reducing the engineering earthwork volume. At the same time, the use of solar energy saves the utilization of resources and solves the problem that it is difficult to obtain large-scale temporary electricity in some sites.

[0025] The solar heat collection system includes a heat absorption plate 1, a heat storage device 2, a controller 3, and a heating chamber 4; the heat absorption plate 1 is respectively connected to the heat storage device 2 and the controller 3, the heating chamber 4 is respectively connected to the heat storage device 2 and the controller 3, and the heat storage device 2 is connected to the controller 3; the heating chamber 4 is connected to the pyrolysis system. The connection mode of each component of the solar heat collection system can ensure that the absorbed solar heat energy is not wasted, and the heating temperature can be adjusted according to the type of organic pollutants in the soil when heating the air in the heating chamber 4. The heat storage device 2 is mainly used to temporarily store the unused heat absorbed by the heat absorption plate 1. It is directly connected to the heat absorption plate 1 to reduce the loss caused during the heat transportation process. The controller 3 is used to monitor the operation of the entire solar heat collection device and can adjust relevant parameters at the same time. The heating chamber 4 is used to heat the gas and adjust the temperature of the heated gas, so that the high-temperature gas is transported to the soil through the pipeline, thereby achieving the purpose of heating the soil. The heat absorbed by the solar energy is transported to the heating chamber 4 through the controller 3, and after heating the gas, it is transported to the heating rod 6, while the excess solar heat energy is stored in the heat storage device 2.

[0026] The pyrolysis system device includes a heating rod 6, a conveying pipeline 11, a temperature measuring hole 51, a pressure measuring hole 52, and a soil covering layer; the temperature measuring hole 51 and the pressure measuring hole 52 are mainly concentrated in the lower layer of the soil covering layer contaminated by organic pollutants to ensure that the deep soil is fully heated to achieve the purpose of repairing the deep soil; there are two thin pipes inside the conveying pipeline 11, and the internal structure of the heating rod 6 is composed of a circulating U-shaped pipeline. The two ends of the U-shaped pipeline are respectively connected to the two thin pipes inside the conveying pipeline 11 through the first flange and the second flange; the conveying pipeline 11 is connected to the solar heat collection device. The structural settings of the U-shaped pipeline and the thin pipes can ensure the recycling of the heat conduction gas used.

[0027] The structure of the heating rod 6 is as Figure 2 shown. The heated gas is input from end A, flows through the U-shaped pipeline, and is output from end B. Flanges (the first flange and the second flange respectively) are installed at both ends A and B to facilitate connection with the conveying pipeline 11. In addition, two thin pipes are arranged inside the conveying pipeline 11. One is specially used to convey the heated gas, and the other is used to recover the gas that has released heat. The two thin pipes are respectively connected to the heating chamber 4 to form a circulation path to ensure the recycling of resources. Flange connection ports are respectively arranged on the two thin pipes to facilitate connection with the pipeline (U-shaped pipeline) inside the heating rod 6. The heating rod 6 heats the contaminated soil layer by layer horizontally and vertically. After entering through one end of the heating pipe in the heating rod 6, it starts to heat as the depth of the soil increases, and gradually spreads to the surrounding of the soil, and then heats layer by layer upward. This heating method can achieve the highest heat utilization efficiency and repair rate. The gas that has lost heat is re-transported back to the heating chamber 4 through the pipeline to achieve the purpose of recycling.

[0028] The soil covering layer from top to bottom is respectively a water storage layer 10, a drainage layer 9 and a low permeability layer 8. The water storage layer 10 is mainly composed of fine soil particles with a particle size less than 5 mm. The drainage layer 9 is mainly composed of coarse soil particles with a particle size of 10 - 40 mm. The low permeability layer 8 is mainly composed of soil powder with a particle size less than 2 mm. The soil covering layer is composed of soil particles with three different particle sizes, replacing the traditional cement layer, achieving the function of preventing seepage and closing air.

[0029] The compaction degree of the low permeability layer 8 is above 95%.

[0030] The extraction system includes an extraction pipeline 12, a vacuum pump 13 and a vacuum extraction well 7 with a sealed bottom end; the vacuum extraction well 7 is inserted into the soil covering layer of the pyrolysis system, the vacuum extraction well 7 is connected to the extraction pipeline 12, and the end of the extraction pipeline 12 is connected to the vacuum pump 13; the vacuum pump 13 is connected to the tail gas emission treatment system. The vacuum extraction well 7 is connected to the extraction pipeline 12, which can transport the extracted gas out.

[0031] A number of air channels are arranged circumferentially and upward along the pipe wall of the vacuum extraction well 7, and the arc length of each air channel is one - quarter of the circumference of the vacuum extraction well 7; a number of heating rods 6 are provided, and a number of heating rods 6 are connected in parallel on the conveying pipeline 11; a number of vacuum extraction wells 7 are provided, and a number of heating rods 6 and a number of vacuum extraction wells 7 are arranged at intervals and alternately; a spacing of 5 cm - 15 cm is set between the vacuum extraction well 7 and the heating rod 6. Setting a spacing of 5 cm - 15 cm between the vacuum extraction well 7 and the heating rod 6 can ensure that the organic pollution gas can be quickly extracted after the soil is heated. The lengths of the heating rod 6 and the vacuum extraction well 7 are determined by the depth of the contaminated soil.

[0032] The tail gas treatment system includes a gas - liquid separator 14, a fan 15, a granular biochar tank 16 and a bag - type filter 17; the gas - liquid separator 14 is respectively connected to the fan 15 and the bag - type filter 17, and the fan 15 is connected to the granular biochar tank 16; the gas - liquid separator 14 is connected to the vacuum pump 13 of the extraction system. The gas - liquid separator 14 separates the mixture of gas and liquid extracted from the extraction system. The fan 15 transports the gas separated by the separation device to the granular biochar tank 16. The granular biochar tank 16 adsorbs the harmful substances (organic pollutants) in the gas using the multi - pore structure of the biochar and then discharges it into the atmosphere. The bag - type filter 17 is used to treat the liquid coming out of the gas - liquid separator 14.

[0033] The heat absorption plate 1 adopts a heat - pipe vacuum tube solar collector plate.

[0034] The surface of the conveying pipeline 11 is provided with a heat - insulating material layer. The setting of the heat - insulating material layer can reduce the heat loss and achieve the maximum utilization of heat.

[0035] The above detailed description is a specific description of the feasible embodiments of the present invention, and such embodiments are not intended to limit the patent scope of the present invention. Any equivalent implementation or modification without departing from the present invention shall be included in the patent scope of this case.

Claims

1. A solar-assisted in-situ thermal desorption system for soil organic pollutants, characterized in that: it includes a solar heat collection device, a pyrolysis system for heating the soil, an extraction system, and a tail gas emission treatment system; the solar heat collection device is connected to the pyrolysis system and provides heat energy for it, the pyrolysis system is connected to the extraction system, and the tail gas emission treatment system is connected to the extraction system.

2. The solar-assisted in-situ thermal desorption system for soil organic pollutants according to claim 1, characterized in that: the solar heat collection system includes a heat absorption plate, a heat storage device, a controller, and a heating chamber; the heat absorption plate is respectively connected to the heat storage device and the controller, the heating chamber is respectively connected to the heat storage device and the controller, and the heat storage device is connected to the controller; the heating chamber is connected to the pyrolysis system.

3. The solar-assisted in-situ thermal desorption system for soil organic pollutants according to claim 1, characterized in that: the pyrolysis system device includes heating rods, a conveying pipeline, temperature measuring holes, pressure measuring holes, and a soil covering layer; the temperature measuring holes and pressure measuring holes are mainly concentrated in the lower layer of the soil covering layer contaminated by organic matter; two thin pipes are arranged inside the conveying pipeline, and the internal structure of the heating rod is composed of a circulating U-shaped pipeline. The two ends of the U-shaped pipeline are respectively connected to the two thin pipes inside the conveying pipeline through a first flange and a second flange; the conveying pipeline is connected to the solar heat collection device.

4. The solar-assisted in-situ thermal desorption system for soil organic pollutants according to claim 3, characterized in that: the soil covering layer is composed of a water storage layer, a drainage layer, and a low permeability layer from top to bottom. The water storage layer is mainly composed of fine soil particles with a particle size less than 5 mm, the drainage layer is mainly composed of coarse soil particles with a particle size of 10 - 40 mm, and the low permeability layer is mainly composed of soil powder with a particle size less than 2 mm.

5. The solar-assisted in-situ thermal desorption system for soil organic pollutants according to claim 4, characterized in that: the compactness of the low permeability layer is above 95%.

6. The solar-assisted in-situ thermal desorption system for soil organic pollutants according to claim 3, characterized in that: the extraction system includes an extraction pipeline, a vacuum pump, and a vacuum extraction well with a sealed bottom end; the vacuum extraction well is inserted into the soil covering layer of the pyrolysis system, the vacuum extraction well is connected to the extraction pipeline, and the end of the extraction pipeline is connected to the vacuum pump; the vacuum pump is connected to the tail gas emission treatment system.

7. The solar-assisted in-situ thermal desorption system for soil organic pollutants according to claim 6, characterized in that: a number of air channels are provided along the circumferential direction of the wall of the vacuum extraction well from bottom to top, and the arc length of each air channel is one-fourth of the circumference of the vacuum extraction well; a number of heating rods are provided, and a number of the heating rods are connected in parallel on the conveying pipeline; a number of vacuum extraction wells are provided, and a number of the heating rods and a number of the vacuum extraction wells are arranged at intervals and alternately.

8. The in-situ thermal desorption system for soil organic pollutants assisted by solar energy according to claim 1, characterized in that: the tail gas treatment system includes a gas-liquid separator, a fan, a granular biochar tank and a bag filter; the gas-liquid separator is respectively connected to the fan and the bag filter, and the fan is connected to the granular biochar tank; the gas-liquid separator is connected to the extraction system.

9. The in-situ thermal desorption system for soil organic pollutants assisted by solar energy according to claim 2, characterized in that: the heat absorption plate adopts a heat pipe type vacuum tube heat collecting plate.

10. The in-situ thermal desorption system for soil organic pollutants assisted by solar energy according to claim 3, characterized in that: a heat preservation material layer is provided on the surface of the conveying pipeline.

Images