Multi-stage active switch type in-situ soil pollution gas heating device and heating method

Abstract

The application discloses a multi-section active switch type in-situ soil pollution gas heating device and a heating method, which comprises a flue gas generation and discharge system and a heating system; the flue gas generation and discharge system comprises a gas supply device, a burner, a burner nozzle, a flue gas concentration discharge device and a pneumatic valve control box; the burner nozzle is connected with a flue gas introduction pipe; the flue gas introduction pipe is connected to the pneumatic valve control box; the flue gas concentration discharge device is connected with the pneumatic valve control box through a flue gas discharge pipe; the heating system comprises a heating well, a spiral flue gas inner pipe and a plurality of flue gas pipes, and different flue gas pipes are connected to different depths of the spiral flue gas inner pipe; the opening and closing of different pneumatic valves are controlled to realize the connection of the flue gas introduction pipe and the flue gas discharge pipe with any two flue gas pipes, and the heating of the spiral flue gas inner pipe at different depths is realized. The application can flexibly and specifically realize the differentiated heating requirement of different depth soil layers, realizes accurate heating, and saves energy.

Description

Technical Field

[0001] The present invention belongs to the field of contaminated soil and groundwater remediation, and specifically relates to a multi-stage active switch type contaminated soil in-situ gas heating device and a heating method. Background Art

[0002] For organically contaminated soils, especially those contaminated by polycyclic aromatic hydrocarbons, pesticides, and petroleum hydrocarbons, which are difficult to treat with traditional remediation processes, in-situ thermal desorption (ITD) is widely used due to its excellent treatment results and strong site adaptability. Currently, the mainstream ISD technologies on the market include in-situ resistance heating, in-situ heat conduction-electric heating, in-situ heat conduction-gas heating, and in-situ steam heating.

[0003] In-situ resistance heating and in-situ steam heating are limited by factors such as soil moisture content, electrical conductivity, soil homogeneity, and soil permeability. They are applicable to a limited number of sites and have a low application rate. In-situ thermal conduction heating is currently the mainstream in-situ heating technology.

[0004] In-situ heat conduction heating involves building a heating well in the soil, arranging electric heating rods in the heating well, or introducing combustion flue gas to heat the casing of the heating well. The heated casing continuously transmits heat to the surrounding soil through thermal radiation, thereby heating the surrounding soil. According to the different energy supply situations, it can be divided into two methods: in-situ heat conduction - electric heating and in-situ heat conduction - gas heating. In-situ heat conduction heating is less affected by the physical and chemical properties of the soil and has a wider adaptability. However, due to the influence of the arrangement of the heating rods or flue gas heating channels in the heating well, there are also some problems in in-situ heat conduction heating:

[0005] The heating well used in the in-situ heat conduction-gas heating process consists of two layers of casing, inner and outer. The flue gas after combustion is input through the inner casing and drawn out by the induced draft fan from the interlayer between the inner and outer casings. The flue gas heats the inner and outer casings, thereby heating the surrounding soil. In the current process, the inner and outer casings are arranged vertically and parallel, resulting in the flow path of the flue gas in the casing being limited only by the depth of the heating well or the length of the inner casing. If the heating power needs to be increased, it can only be done by increasing the amount of hot gas and the gas temperature, resulting in a low heat utilization rate of the flue gas after combustion and increased costs. In addition, this arrangement has basically the same path for the flue gas in the inner and outer casings vertically along the heating well, and it is also impossible to meet the differentiated heating needs of soil layers at different depths. Summary of the Invention

[0006] In response to the above problems, the present invention aims to provide a multi-stage active switching contaminated soil in-situ gas heating device and heating method, which can flexibly and specifically meet the differentiated heating requirements of soil layers at different depths, achieve precise heating, and save energy. This objective of the present invention is achieved through the following technical solutions:

[0007] A multi-stage active switching type contaminated soil in-situ gas heating device, comprising a flue gas generating and exhausting system arranged above the ground and a heating system deep underground; the flue gas generating and exhausting system comprises a gas supply device, a burner, a burner nozzle, a flue gas centralized exhausting device and a pneumatic valve control box; the gas supply device is connected to the burner through a gas supply pipeline, the burner is connected to the burner nozzle below, and the outlet of the burner nozzle is connected to a flue gas inlet pipe; the outlet of the flue gas inlet pipe is connected to the pneumatic valve control box; the flue gas centralized exhausting device is connected to the pneumatic valve control box through a flue gas exhaust pipe; the heating system comprises a heating well, a spiral flue gas inner tube arranged in the heating well and a plurality of flue gas ducts, different flue gas ducts are connected to different depths of the spiral flue gas inner tube; the pneumatic valve control box controls the opening and closing of different pneumatic valves therein to realize the connection of the flue gas inlet tube and the flue gas exhaust tube with any two flue gas ducts, thereby forming different closed-loop flue gas passages to realize the heating of the spiral flue gas inner tube at different depths.

[0008] For further optimization, the spiral flue gas inner tube is a connected whole or divided into multiple sections; the spiral pitches of the spiral flue gas inner tube are equal, or the spiral pitches of each section are unequal.

[0009] In one of the optimization solutions, the spiral smoke inner tube is a connected whole, and the smoke duct includes a main smoke duct and multiple auxiliary smoke ducts. The spiral smoke inner tube surrounds the main smoke duct, the main smoke duct is connected to the bottom end of the spiral smoke inner tube, and the multiple auxiliary smoke ducts are connected to the spiral smoke inner tube at different depths. The spiral spacing of the spiral smoke inner tube is equal.

[0010] Another optimized solution is that the spiral inner smoke tube is divided into at least two unconnected sections, and the sections are arranged in sequence up and down, and the upper and lower ends of any section of the spiral inner smoke tube are respectively connected to a smoke duct.

[0011] Another optimization solution is that the spiral smoke inner tube is divided into at least two sections, and the sections are arranged in sequence up and down. The smoke duct includes a main smoke duct and multiple auxiliary smoke ducts. Each section of the spiral smoke inner tube surrounds the main smoke duct and the bottom end is connected to the main smoke duct at different depths. The upper end of each section of the spiral smoke inner tube is connected to an auxiliary smoke duct.

[0012] Furthermore, the flue gas generation and emission system also includes a temperature control system, which is connected to temperature sensors set in contaminated soil at different depths and set at different depth sections of the spiral flue gas inner tube. The temperature control system receives signals from the temperature sensors and sends signals to the gas supply device to control the delivery of the gas.

[0013] The heating device is used for auxiliary heating of pollutant extraction in organic contaminated soil, and different vertical horizontal layers in the contaminated soil require different heating temperatures and times.

[0014] A heating method based on the multi-stage active switch type contaminated soil in-situ gas heating device comprises the following steps:

[0015] Step 1: Determine the land characteristics of the area to be heated: the land characteristics include land pollution characteristics, soil characteristics and hydrogeological characteristics;

[0016] Step 2: Based on the characteristics of the land, the land to be heated is generalized and layered along the vertical direction;

[0017] Step 3: Determine the heating target temperature of each layer of soil based on the characteristics of each layer of land;

[0018] Step 4: Install the heating device in the area to be heated, and determine the heating time required to heat each layer of soil based on the output power of the heating device and the characteristics of each layer of soil;

[0019] Step 5: Heating the spiral flue gas inner tube in the soil layer at different depths is achieved by controlling the opening and closing of different pneumatic valves;

[0020] When the final temperature of soil heating is set to T c When the temperature is greater than 100℃, the power input per unit depth of soil is calculated using the formula:

[0021]

[0022] Where: β represents the average power input per unit depth of a single heating device, W·m -1 ;t b Indicates the time required for the water in the soil to completely evaporate, day; t c2 represents the time required to heat the soil from 100℃ to the target temperature, day; A represents the range of influence of heat radiation of a single heating device, m 2 ρ s represents the soil particle density, g·m -3 ; C s represents the heat capacity of soil particles, W·day·g -1 ℃ -1 ; θ represents soil porosity; ρ w represents the density of water, g·m-3 ; C w represents the heat capacity of water, W·day·g -1 ℃ -1 ; δ represents the water saturation in the soil; T b Indicates the boiling point of water, ℃; T a Indicates the temperature of the soil before heating, ℃; T c Indicates the final temperature in the soil, °C; h w Represents the heat of vaporization of water, unit is W·day·g –1 .

[0023] When the final temperature of soil heating is set to T c When the temperature is less than or equal to 100℃, the power input in each soil layer is calculated using the formula:

[0024]

[0025] Where: σ is a value between 0 and 1, representing the proportion of water evaporation under the condition of heating temperature below 100℃, t c1 Indicates the time required for the soil to heat to the target temperature.

[0026] When the power is fixed, the heating time of each layer can be inferred by combining the plot characteristics of each layer through formula (1) or formula (2).

[0027] In step one, the land pollution characteristics include the type of pollutants, the saturated vapor pressure of pollutants, the boiling point of pollutants, the spatial distribution range of pollutants and the concentration of pollutants; the soil characteristics of the stratum include soil type, soil moisture content, soil particle density, soil porosity, heat capacity of soil particles, soil initial temperature, soil permeability, soil thermal conductivity and soil thermal conductivity coefficient; the hydrogeological characteristics include groundwater depth, aquifer thickness, hydraulic gradient, soil permeability and groundwater flow rate.

[0028] The advantages and beneficial effects of the present invention are:

[0029] The present invention can adopt targeted differential heating schemes based on the differences in pollutant types, spatial distribution, soil quality, and hydrogeological conditions in contaminated soil remediation, thereby achieving differentiated heating temperatures at different depths. This is conducive to the implementation of precise depth and timed heating, and can effectively save energy and reduce carbon emissions while ensuring the heating effect.

[0030] This invention uses temperature sensors embedded at varying depths in the soil surrounding the heating well to detect the heating temperature of soil in different strata, enabling precise heating at a specific depth, time, and power. This significantly improves the accuracy of heating duration and temperature measurements at different depths and strata, and also enhances construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below with reference to the accompanying drawings and examples.

[0032] Figure 1 This is a schematic diagram of the heating system structure of Example 1;

[0033] Figure 2 This is a schematic diagram of the usage status of the heating device of Example 1.

[0034] Figure 3 This is a schematic diagram of the pneumatic valve control in Example 1;

[0035] Figure 4 This is a schematic diagram of the heating system structure of Example 2;

[0036] Figure 5 This is a schematic diagram of the heating system structure of Example 3;

[0037] Figure 6 Schematic diagram of the heating cycle in the embodiment.

[0038] 11. Burner; 12. Burner nozzle; 13. Spiral flue gas inner pipe; 141. Flue gas inlet pipe; 143. Main flue gas duct; 142, 144, 145. Auxiliary flue gas duct; 146. Flue gas discharge pipe; 15. Heating well outer casing; 16. Heating well flange cover; 21. In-situ multiphase extraction well; 22. Screening section; 23. Solid pipe section; 24. Multiphase extraction wellhead; 25. Liquid extraction pipeline; 26. Submersible pump; 31. Gas supply device; 32. Centralized flue gas discharge device; 33. Temperature control system; 34. Gas supply pipeline; 35. Temperature sensor; 36. Thermocouple; 37. Temperature sensor wire; 38. Pneumatic valve control box; 4. Tailwater and exhaust gas treatment system; 51. Horizontal barrier layer; 52. Vertical barrier wall. J11-J13 represent the heating section, and S1-S6 represent pneumatic valves. DETAILED DESCRIPTION

[0039] Example 1

[0040] A multi-stage active switch type contaminated soil in-situ gas heating device, such as Figure 1 As shown, it includes a flue gas generation and exhaust system installed above the ground and a heating system deep underground. The flue gas generation and exhaust system includes a gas supply device 31, a burner 11, a burner nozzle 12, a flue gas centralized exhaust device 32, and a pneumatic valve control box 38. The gas supply device 31 is connected to the burner 11 via a gas supply pipeline 34. The burner 11 is connected to the burner nozzle 12 below. The outlet of the burner nozzle 12 is connected to a flue gas introduction pipe 141. The outlet of the flue gas introduction pipe 141 is connected to the pneumatic valve control box 38. The flue gas centralized exhaust device 32 is connected to the pneumatic valve control box 38 via a flue gas exhaust pipe 146.

[0041] The heating system includes a heating well, a spiral flue gas inner tube 13 arranged in the heating well, and multiple flue gas ducts, and different flue gas ducts are connected to different depths of the spiral flue gas inner tube 13; the spiral flue gas inner tube 13 is a connected whole, and the spacing between each spiral is the same. The flue gas duct includes a main flue gas duct 143 and multiple auxiliary flue gas ducts 143, 144, and 145. The spiral flue gas inner tube 13 surrounds the main flue gas duct 143, and the main flue gas duct 143 is connected to the bottom end of the spiral flue gas inner tube 13. Multiple auxiliary flue gas ducts 142, 144, and 145 are connected to the spiral flue gas inner tube 13 at different depths.

[0042] The pneumatic valve control box 38 controls the opening and closing of different pneumatic valves to connect the smoke inlet pipe 141 and the smoke exhaust pipe 146 to any two smoke ducts, thereby forming different closed-loop smoke passages to achieve heating of the spiral smoke inner pipe 13 at different depths. Figure 3 shown.

[0043] like Figure 2 As shown, the flue gas generation and emission system also includes a temperature control system 33. This temperature control system 33 is connected to temperature sensors 35 located at different depths in the contaminated soil and at different depths within the spiral flue gas inner tube 13. The temperature control system 33 receives signals from the temperature sensors 35 and sends them to the gas supply device 31 to control the delivery of the gas. The temperature sensors 35 include thermocouples 36 and temperature sensor wires 37.

[0044] The heating well includes a heating well outer casing 15 at the bottom and around the well and a heating well flange cover 16 arranged at the top.

[0045] Example 2

[0046] A multi-stage active switch type contaminated soil in-situ gas heating device, such as Figure 4 As shown, in this embodiment, the spiral inner flue gas tube 13 is divided into two unconnected sections, which are arranged in sequence up and down. The upper and lower ends of any section of the spiral inner flue gas tube 13 are respectively connected to a flue gas duct.

[0047] Other settings are the same as those in Example 1.

[0048] Example 3

[0049] A multi-stage active switch type contaminated soil in-situ gas heating device, such as Figure 5As shown, in this embodiment, the spiral smoke inner tube 13 is a connected whole, and the smoke duct includes a main smoke duct 143 and multiple auxiliary smoke ducts 142, 144, and 145. The spiral smoke inner tube 13 surrounds the main smoke duct 143, and the main smoke duct 143 is connected to the bottom end of the spiral smoke inner tube 13. The multiple auxiliary smoke ducts are connected to the top end of the spiral smoke inner tube 13 at different depths, and the spiral spacing of the spiral smoke inner tube 13 is different.

[0050] Other settings are the same as those in Example 1.

[0051] Example 4

[0052] The heating method of the heating device in Example 1 comprises the following steps:

[0053] Step 1: Determine the plot characteristics of the area to be heated: The plot characteristics include plot pollution characteristics, soil layer characteristics, and hydrogeological characteristics; the plot pollution characteristics include pollutant type, pollutant saturated vapor pressure, pollutant boiling point, pollutant spatial distribution range, and pollutant concentration; the stratum soil characteristics include soil type, soil moisture content, soil particle density, soil porosity, soil particle heat capacity, soil initial temperature, soil permeability, soil thermal conductivity, and soil thermal conductivity; the hydrogeological characteristics include groundwater depth, aquifer thickness, hydraulic gradient, soil permeability, and groundwater flow rate. In this embodiment, the vertical distribution of pollutants is divided into three parts. The upper layer mainly consists of VOCs such as benzene series and chlorinated hydrocarbons, which are volatile; petroleum hydrocarbons and some PAHs with boiling points below 250°C, which are semi-volatile; and the lower layer mainly consists of pesticides with boiling points above 250°C, which are difficult to volatilize. The soil properties are evenly distributed vertically.

[0054] Step 2: Based on the characteristics of the land, the land to be heated is generally layered along the vertical direction; in this embodiment, it is divided into 3 layers.

[0055] Step 3: Determine the heating target temperature of each layer of soil based on the characteristics of each layer of land.

[0056] Step 4: Set up the heating device in the area to be heated, and determine the heating time required to heat each layer of soil based on the power of the heating device and the characteristics of each layer of soil; the heating time for each layer is lower layer > middle layer > upper layer.

[0057] Based on the maximum fixed power, the heating time can be inferred by formula (1) or formula (2), and the constant temperature time can be determined based on the pollution characteristics of the plot and experience. In some cases, the constant temperature time can also be 0, which is more convenient for calculation.

[0058] Step 5: Heating of the spiral flue gas inner tube in soil layers at different depths is achieved by controlling the opening and closing of different pneumatic valves.

[0059] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and is not limiting. Although the present invention is described in detail with reference to the preferred arrangement scheme, ordinary technicians in this field should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A heating method based on a multi-stage active switching contaminated soil in-situ gas heating device, characterized by: The heating device includes a smoke generation and exhaust system arranged above the ground and a heating system deep underground; The flue gas generation and emission system comprises a gas supply device (31), a burner (11), a burner nozzle (12), a flue gas centralized emission device (32), a pneumatic valve control box (38) and a temperature control system (33); the gas supply device (31) is connected to the burner (11) through a gas supply pipeline (34); the burner (11) is connected to the burner nozzle (12) below, and the outlet of the burner nozzle (12) is connected to a flue gas inlet pipe (141); the outlet of the flue gas inlet pipe (141) is connected to the pneumatic valve control box (38); the flue gas centralized emission device (32) and the pneumatic valve control box (38) are connected through a flue gas emission pipe (146); the temperature control system (33) is connected to temperature sensors (35) arranged in contaminated soil at different depths and at different depth sections of the spiral flue gas inner tube (13); the temperature control system (33) receives signals from the temperature sensors (35) and sends signals to the gas supply device (31) to control the delivery of gas; The heating system comprises a heating well, a spiral flue gas inner tube (13) arranged in the heating well, and a plurality of flue gas ducts, wherein different flue gas ducts are connected to different depths of the spiral flue gas inner tube (13); The pneumatic valve control box (38) controls the opening and closing of different pneumatic valves therein to connect the smoke inlet pipe (141) and the smoke exhaust pipe (146) to any two smoke ducts, thereby forming different closed-loop smoke passages to achieve heating of the spiral smoke inner pipe (13) at different depths; The following steps are involved: Step 1: Determine the land characteristics of the area to be heated: the land characteristics include land pollution characteristics, soil characteristics and hydrogeological characteristics; Step 2: Based on the characteristics of the land, the land to be heated is generalized and layered along the vertical direction; Step 3: Determine the heating target temperature of each layer of soil based on the characteristics of each layer of land; Step 4: Install the heating device in the area to be heated, and determine the heating time required to heat each layer of soil based on the output power of the heating device and the characteristics of each layer of soil; and inversely deduce the heating time based on the maximum fixed power using formula (1) or formula (2); When setting the final temperature of soil heating When the temperature is greater than 100℃, use formula (1): （1） Where: Represents the average power input per unit depth of a single heating device, W⋅m -1 ; Indicates the time required for the water in the soil to completely evaporate, day; Indicates the time required for the soil to heat from 100℃ to the target temperature, day; Indicates the influence range of heat radiation of a single heating device, m 2 ; represents the soil particle density, g⋅m -3 ; represents the heat capacity of soil particles, W⋅day⋅g -1 ⋅℃ -1 ; Indicates soil porosity; represents the density of water, g⋅m -3 ; represents the heat capacity of water, W⋅day⋅g -1 ⋅℃ -1 ; Indicates the water saturation in the soil; Indicates the boiling point of water, ℃; Indicates the temperature of the soil before heating, °C; represents the final temperature in the soil, °C; h w Represents the heat of vaporization of water, the unit is W⋅day⋅g –1 ; When setting the final temperature of soil heating When the temperature is less than or equal to 100℃, use formula (2): （2） Where: It is a value between 0 and 1, representing the percentage of water evaporation when the heating temperature is below 100°C. Indicates the time required for the soil to heat to the target temperature; Step 5: Heating of the spiral flue gas inner tube in the soil layer at different depths is achieved by controlling the opening and closing of different pneumatic valves; in step 1, the land pollution characteristics include the type of pollutants, the saturated vapor pressure of pollutants, the boiling point of pollutants, the spatial distribution range of pollutants and the concentration of pollutants; the soil characteristics of the soil layer include soil type, soil moisture content, soil particle density, soil porosity, heat capacity of soil particles, soil initial temperature, soil permeability, soil thermal conductivity and soil thermal conductivity coefficient; the hydrogeological characteristics include groundwater depth, aquifer thickness, hydraulic gradient, soil permeability and groundwater flow rate.

2. The heating method according to claim 1, wherein: The spiral flue gas inner tube (13) is a connected whole or is divided into multiple sections; the spiral pitches of the spiral flue gas inner tube (13) are equal, or the spiral pitches of the sections are unequal.

3. The heating method according to claim 2, wherein: The spiral smoke inner tube (13) is a connected whole, and the smoke duct includes a main smoke duct (143) and a plurality of auxiliary smoke ducts. The spiral smoke inner tube (13) surrounds the main smoke duct (143), and the main smoke duct (143) is connected to the bottom end of the spiral smoke inner tube (13). The plurality of auxiliary smoke ducts are connected to the spiral smoke inner tube (13) at different depths, and the pitch of the spirals of the spiral smoke inner tube (13) is equal.

4. The heating method according to claim 2, wherein: The spiral flue gas inner tube (13) is divided into at least two unconnected sections, and each section is arranged in sequence up and down, and the upper and lower ends of any section of the spiral flue gas inner tube (13) are respectively connected to a flue gas duct.

5. The heating method according to claim 2, wherein: The spiral inner smoke tube (13) is divided into at least two sections, and the sections are arranged in sequence up and down. The smoke duct includes a main smoke duct (143) and a plurality of auxiliary smoke ducts. Each section of the spiral inner smoke tube (13) surrounds the main smoke duct (143) and the bottom end is connected to the main smoke duct (143) at different depths. The upper end of each section of the spiral inner smoke tube (13) is connected to an auxiliary smoke duct.

6. The heating method according to claim 1, wherein: The invention is applied to auxiliary heating for extracting pollutants from organic contaminated soil, wherein different vertical horizontal layers in the contaminated soil require different heating temperatures and times.

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