Gas thermal desorption energy-saving structure based on energy optimization and its use method

Abstract

The present invention provides a gas thermal desorption energy-saving structure and a method of using the same, including a gas thermal desorption system, an exhaust gas treatment system, a groundwater extraction treatment system, and a normal temperature analysis or thermal desorption pretreatment system; when the exhaust gas temperature is 300-500°C, the exhaust gas is connected to the exhaust gas treatment system; when the exhaust gas temperature is less than 300°C, the exhaust gas is connected to the groundwater extraction treatment system and the normal temperature analysis or thermal desorption pretreatment system; when the exhaust gas temperature is greater than 500°C, the exhaust gas is firstly reinjected through a secondary heating well, and the exhaust gas after reinjection and cooling is then selected to be connected to a subsequent system according to its temperature. The present invention can set a reasonable heat energy recycling process according to the exhaust gas temperature, recover the thermal desorption exhaust heat energy, improve the overall thermal energy utilization rate of the system, and reduce energy consumption.

Description

Technical Field

[0001] The present invention relates to the field of contaminated soil remediation, and in particular to a multi-stage utilization process of thermal energy of fuel gas thermal desorption and a method for using the same. Background Art

[0002] In-situ soil thermal desorption remediation technology can be implemented in-situ at the contaminated site. It can remove organic pollutants in the contaminated soil by heating and extraction without excavating the contaminated soil, thereby purifying the soil. The in-situ heating unit is the core of the in-situ soil thermal desorption technology. Common technologies include in-situ resistance heating, in-situ steam injection heating, and gas heating. The in-situ gas thermal desorption technology generates high-temperature gas through the combustion of natural gas or liquefied petroleum gas, which flows in the heating well to increase the temperature of the pollutant area, change the physical and chemical properties of the pollutants, and promote the desorption of soil pollutants into the gas phase and water phase, which are then extracted from the underground environment and transferred to the ground for tail gas treatment.

[0003] A utility model patent document with publication number CN211694888U discloses a gas thermal desorption combustion device, which ignites and burns with the help of a flame tube in a heating well. The combustion heat is absorbed by the heat transfer oil through the wall of the heat transfer cylinder and conducted to the entire cylinder. The heat is rapidly conducted from the inside to the outside, and a relatively uniform and stable temperature is formed on the surface of the cylinder. Synchronous heating of strata at different depths is achieved, thereby achieving uniform and synchronous heating of strata at different depths. However, the overall structure lacks a link for recovering and utilizing the heat energy of high-temperature flue gas, resulting in the loss of exhaust heat and low thermal energy utilization.

[0004] The invention patent document with publication number CN111203432A discloses an efficient, energy-saving and clean in-situ gas thermal desorption device and method. The invention uses a perforated plate to enhance airflow disturbance to make combustion more complete and uniform. The generated high-temperature gas is directed to the shallow pile soil after heating the soil; groundwater and steam containing pollutants are extracted to the surface by a two-phase extraction well, and the condensed water is subjected to conventional water treatment; the polluted gas is directed to a subsequent valve-switched three-bed regenerative thermal oxidation furnace for disposal. The utilization rate of thermal energy is improved by heating the shallow pile soil and the regenerative thermal oxidation furnace with high-temperature flue gas. However, the burner needs to be modified and a regenerative thermal oxidation furnace needs to be installed, which results in high equipment costs and poor economic efficiency.

[0005] In summary, the current gas thermal desorption technology has problems such as high equipment modification cost, large heat loss in flue gas, low thermal utilization rate, and poor integration with other soil treatment technologies. Summary of the invention

[0006] To solve the above problems, the present invention has developed a gas thermal desorption energy-saving structure based on energy optimization and its use method for gas thermal desorption technology, combined the gas thermal desorption technology with other on-site treatment processes, recovered and utilized the flue gas thermal energy, and effectively solved the problems of high equipment modification cost, low thermal utilization rate and poor integration with other soil treatment technologies.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A gas thermal desorption energy-saving structure, characterized by comprising a gas thermal desorption system, an exhaust gas treatment system and a groundwater extraction treatment system, and also comprising a normal temperature analysis or thermal desorption pretreatment system;

[0009] The gas thermal desorption system can selectively connect to the tail gas treatment system and heat the extracted tail gas of the tail gas treatment system and the combustion air of the secondary combustion chamber through the heat exchange system;

[0010] The gas thermal desorption system can selectively connect to the groundwater extraction and treatment system, and recycle the heat energy of the groundwater extraction and treatment system through the heating pipe;

[0011] The gas thermal desorption system can be selectively connected to a normal temperature analysis system or a thermal desorption pretreatment system, and heat energy of the normal temperature analysis system or the thermal desorption pretreatment system can be recycled through a heating pipe.

[0012] The gas thermal desorption energy-saving structure, wherein: the gas thermal desorption system includes a burner, a primary heating well and an extraction well, the primary heating well is composed of an inner tube and an outer tube, the inner tube allows high-temperature flue gas to flow downward to the bottom and then flow out from the outer tube, and the outer tube wall can exchange heat with the surrounding soil; the burner can spray the high-temperature flame generated by the combustion of liquefied petroleum gas or natural gas into the inner tube of the primary heating well; the extraction well wall is provided with a slit as a channel for soil gas to enter the extraction pipe.

[0013] The gas thermal desorption energy-saving structure, wherein: the gas thermal desorption system also includes a burner secondary heating well, the secondary heating well is connected in series downstream of the primary heating well, and is also composed of an inner tube and an outer tube.

[0014] The fuel gas thermal desorption energy-saving structure, wherein: the exhaust gas treatment system includes a first heat exchanger, a second heat exchanger, a blower, a secondary combustion chamber and a chimney, the first heat exchanger is used to transfer the heat of the high-temperature flue gas to the extracted exhaust gas; the second heat exchanger is used to transfer the heat of the high-temperature flue gas to the combustion-supporting air; the secondary combustion chamber is used to purify and burn the extracted exhaust gas and then discharge it into the atmosphere; the chimney is used to discharge the low-temperature flue gas after two-stage heat exchange.

[0015] The gas thermal desorption energy-saving structure, wherein: the groundwater extraction and treatment system includes an aeration tank, a heat exchange pipe and an aeration pipe, the aeration tank stores the extracted contaminated groundwater, the heat exchange pipe is composed of a plurality of branch pipes arranged side by side, and is spirally arranged from bottom to top inside the aeration tank, and a flow regulating valve is provided on the branch pipe to adjust the flue gas flow in each branch pipe; the aeration pipe can aerate the inside of the aeration tank.

[0016] The gas thermal desorption energy-saving structure, wherein: the room temperature analysis system or thermal desorption pretreatment system includes a floor heating system, a turning equipment and a greenhouse.

[0017] The gas thermal desorption energy-saving structure, wherein: a temperature sensor is arranged at the smoke exhaust position of the gas thermal desorption system, the temperature sensor signal is connected to the controller, and the controller can select the connection direction of the smoke exhaust according to the temperature signal.

[0018] A method for using a gas thermal desorption energy-saving structure, characterized in that: using the gas thermal desorption energy-saving structure, wherein:

[0019] When the exhaust gas temperature of the fuel gas thermal desorption system is 300-500°C, the exhaust gas is connected to the tail gas treatment system;

[0020] When the exhaust gas temperature of the gas thermal desorption system is less than 300° C., the exhaust gas is connected to the groundwater extraction and treatment system and is also connected to the room temperature analysis or thermal desorption pretreatment system.

[0021] The method for using the gas thermal desorption energy-saving structure, wherein: when the exhaust temperature of the gas thermal desorption system is greater than 500°C, the exhaust gas is first reinjected through a secondary heating well, and the exhaust gas after reinjection and cooling is then connected to a tail gas treatment system, or to a groundwater extraction treatment system and a normal temperature analysis or thermal desorption pretreatment system according to its temperature.

[0022] The present invention provides a fuel gas thermal desorption energy-saving structure and a method for using the structure, thereby recovering and utilizing the exhaust heat energy of the fuel gas thermal desorption technology in multiple stages, thereby improving the overall thermal energy utilization rate of the fuel gas thermal desorption technology.

[0023] The present invention can improve the overall thermal energy utilization rate of the site by combining the gas thermal desorption technology with other technologies. The equipment of the present invention is a large-scale engineering application technology, suitable for the restoration of large, medium and small sites, with a wide range of applications, and has the characteristics of combining multiple technologies and processes, which can greatly improve the overall thermal energy utilization rate of the site. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the high smoke exhaust temperature energy-saving structure provided by the present invention.

[0025] Figure 2 It is a schematic diagram of the low smoke exhaust temperature energy-saving structure provided by the present invention.

[0026] Figure 3 This is a schematic diagram of the aeration tank piping layout.

[0027] Figure 4 It is a schematic diagram of the arrangement of series heating wells.

[0028] Explanation of the reference numerals: gas thermal desorption system 1; tail gas treatment system 2; groundwater extraction and treatment system 3; normal temperature analysis system or thermal desorption pretreatment system 4; burner 11; primary heating well 12; secondary heating well 13; extraction well 14; first heat exchanger 21; blower 22; second heat exchanger 23; secondary combustion chamber 24; chimney 25; aeration tank 31; heat exchange main pipe 32; flow valve 33; heat exchange branch pipe 34; aeration pipe 35; floor heating system 41; turning equipment 42; greenhouse 43. DETAILED DESCRIPTION

[0029] like Figure 1 , Figure 2 As shown, the present invention provides a gas thermal desorption energy-saving structure, including a gas thermal desorption system 1, an exhaust gas treatment system 2, a groundwater extraction and treatment system 3, and a room temperature analysis or thermal desorption pretreatment system 4. Several sets of gas thermal desorption energy-saving structures can be used individually or in combination in series or parallel.

[0030] When the exhaust temperature of the gas thermal desorption system 1 is between 300°C and 500°C, the exhaust is directly connected to the tail gas treatment system 2; when the exhaust temperature of the gas thermal desorption system 1 is less than 300°C, the exhaust is connected to the groundwater extraction treatment system 3 and the room temperature analysis or thermal desorption pretreatment system 4; when the exhaust temperature of the gas thermal desorption system 1 is greater than 500°C, a secondary heating well 13 can be set up first for flue gas reinjection, and the reinjected and cooled exhaust is then connected to the tail gas treatment system 2 according to its temperature, or connected to the groundwater extraction treatment system 3 and the room temperature analysis or thermal desorption pretreatment system 4.

[0031] The present invention can realize automatic control by arranging a temperature sensor at the smoke exhaust position of the fuel gas thermal desorption system 1, and the temperature sensor signal is connected to the controller, and the controller selects the connection direction of the smoke exhaust according to the temperature signal.

[0032] The gas thermal desorption system 1 includes a burner 11, a primary heating well 12, a secondary heating well 13 and an extraction well 14 connected in sequence. The burner 11 compresses the combustion-supporting air and the gas and sprays them into the inner tube of the primary heating well 12. After the high-temperature flue gas reaches the bottom, it flows back upward from the outer tube of the primary heating well 12, passes through the connecting pipe and enters the inner tube of the secondary heating well 13. After the high-temperature flue gas reaches the bottom, it flows back upward from the outer tube of the secondary heating well 13, and is finally discharged to the flue gas heat energy recovery system; the extraction well 14 extracts the contaminated soil to the tail gas treatment system 2.

[0033] The exhaust gas treatment system 2 includes a first heat exchanger 21, a blower 22, a second heat exchanger 23, a secondary combustion chamber 24 and a chimney 25. The first heat exchanger 21 performs heat exchange between the high-temperature flue gas and the contaminated soil gas extracted from the extraction well 14, transfers the heat of the high-temperature flue gas to the contaminated soil gas, increases the temperature of the contaminated soil gas, and reduces the temperature of the high-temperature flue gas. The cooled high-temperature flue gas enters the second heat exchanger 23; the blower 22 blows the combustion air into the second heat exchanger 23, the combustion air and the high-temperature flue gas perform heat exchange, transfers the heat of the high-temperature flue gas to the combustion air, increases the temperature of the combustion air, and reduces the temperature of the high-temperature flue gas. The cooled high-temperature flue gas is directly discharged through the chimney; the contaminated soil gas and the combustion air are oxidized and burned in the secondary combustion chamber 24, and the heated contaminated soil gas and the combustion air can effectively reduce the fuel consumption of the secondary combustion chamber 24.

[0034] The groundwater extraction and treatment system 3 (such as Figure 3 The aeration tank 31 includes an aeration tank 31, a heat exchange main pipe 32, a flow valve 33, a heat exchange branch pipe 34, and an aeration pipe 35. The aeration tank 31 stores the extracted contaminated groundwater. The heat exchange main pipe 32 is connected to the gas thermal desorption system 1. The heat exchange branch pipe 34 is connected to the heat exchange main pipe 32 through a flow valve 33. The flow valve 33 can adjust the temperature of the corresponding branch pipe 34 by adjusting the flue gas flow rate. The heat exchange branch pipe 34 is spirally arranged inside the aeration tank from bottom to top. Multiple groups are set according to the size of the aeration tank 31. The high-temperature flue gas exchanges heat with the contaminated groundwater in the aeration tank 31 through the heat exchange branch pipe 34, thereby increasing the temperature of the contaminated groundwater in the aeration tank 31 and thereby increasing the treatment speed of the contaminated groundwater. The aeration pipe 35 aerates the bottom of the aeration tank 31. On the one hand, it introduces oxygen into the aeration tank. On the other hand, it can be used as a gas source for stripping treatment. At the same time, it can stir the contaminated groundwater in the aeration tank to ensure the heating uniformity of the aeration tank.

[0035] In addition to the aeration process, the aeration tubes can also be replaced with injection tubes to purify groundwater through chemical oxidation, and the heat exchange tubes can increase the temperature of the water pool to play a role in thermal enhancement.

[0036] The room temperature analysis or thermal desorption pretreatment system 4 includes a floor heating system 41, a turning device 42 and a greenhouse 43. The floor heating system 41 is provided with a circuitously arranged floor heating pipe, and the high-temperature flue gas flows in the floor heating pipe to heat the ground of the ex situ thermal desorption system, and then heat the contaminated soil; the turning device 42 ensures the uniformity of soil heating by turning the soil pile; the greenhouse 43 stores the contaminated soil, maintains the temperature to reduce heat loss, and prevents the escape of polluted gas; the exhaust heat of the gas thermal desorption system is transferred to the ex situ thermal desorption pretreatment process.

[0037] Example description:

[0038] The present invention is described in detail below through examples. A method of arranging heating wells in series is as follows: Figure 4 As shown, the secondary heating well 13 is used as a supplementary heat source and is distributed at the cold spot of the primary heating well 12. The soil heating target is 100°C. After field measurement, the burner power is 20kw, the exhaust temperature of the primary heating well is about 550°C, and the exhaust temperature of the secondary heating well is about 350°C. The effective radius of the primary heating well is 2-3m, and the effective range of the secondary heating well is 1-2m.

[0039] Embodiment 1:

[0040] A chemical plant remediation site in Suzhou was repaired in situ using the series heating well technology. After the exhaust gas was extracted and dehumidified through the gas-liquid separator, the moisture content of the exhaust gas was about 50% and the temperature was 90°C; the temperature of the high-temperature flue gas was 350-400°C, and the high-temperature flue gas and the exhaust gas entered the first heat exchanger for heat exchange at a gas volume ratio of 0.8-1:1. After the heat exchange, the exhaust gas temperature rose to 200°C, and the high-temperature flue gas temperature dropped to 220°C. The exhaust gas entered the secondary combustion chamber for oxidation treatment, and the high-temperature flue gas entered the second heat exchanger for secondary heat exchange; the combustion air temperature was about 20°C, and the high-temperature flue gas temperature was 220°C. The high-temperature flue gas and the combustion air entered the second heat exchanger for heat exchange at a gas volume ratio of 1:1. After the heat exchange, the combustion air temperature rose to 100°C, and the high-temperature flue gas temperature dropped to 120°C. The combustion air entered the secondary combustion chamber, and the high-temperature flue gas was discharged through the chimney; the results show that 15-25% energy savings can be achieved after heat exchange.

[0041] Embodiment 2:

[0042] In a chemical plant remediation site in Jiangsu, VOC pollution in groundwater was treated by an aeration tank with a volume of 150m 3In winter, the water temperature is relatively low, at around 10°C, and the treatment efficiency is low. In order to speed up the treatment efficiency, a heat exchange tube spiraling from bottom to top is set in the aeration tank, and the high-temperature flue gas discharged from the series heating well group enters the heat exchange tube from below. After heat exchange, the temperature of the high-temperature flue gas is reduced from 350°C to about 80°C, and the temperature of the aeration tank sewage rises from 10°C to 40°C, which effectively speeds up the heat exchange efficiency and increases the treatment speed by 30-40%.

[0043] The above description is only illustrative rather than restrictive of the present invention. Those skilled in the art will understand that many modifications, changes or equivalents may be made without departing from the spirit and scope defined by the claims, but all will fall within the scope of protection of the present invention.

Claims

1. A fuel gas thermal desorption energy-saving structure, characterized in that: It includes a gas thermal desorption system, an exhaust gas treatment system and a groundwater extraction and treatment system, as well as a room temperature analysis or thermal desorption pretreatment system; The gas thermal desorption system can selectively connect to the tail gas treatment system and heat the extracted tail gas of the tail gas treatment system and the combustion air of the secondary combustion chamber through the heat exchange system; The gas thermal desorption system can selectively connect to the groundwater extraction and treatment system, and recycle the heat energy of the groundwater extraction and treatment system through the heating pipe; The gas thermal desorption system can be selectively connected to a normal temperature analysis system or a thermal desorption pretreatment system, and the thermal energy of the normal temperature analysis system or the thermal desorption pretreatment system can be recycled through a heating pipe; When the exhaust gas temperature of the fuel gas thermal desorption system is 300-500°C, the exhaust gas is connected to the tail gas treatment system; When the exhaust gas temperature of the gas thermal desorption system is less than 300°C, the exhaust gas is connected to the groundwater extraction and treatment system, and is also connected to the normal temperature analysis or thermal desorption pretreatment system; When the exhaust gas temperature of the gas thermal desorption system is greater than 500°C, the exhaust gas is first reinjected through the secondary heating well. The reinjected and cooled exhaust gas is then connected to the tail gas treatment system, or to the groundwater extraction and treatment system and the normal temperature analysis or thermal desorption pretreatment system according to its temperature.

2. The fuel gas thermal desorption energy-saving structure according to claim 1 is characterized in that: The gas thermal desorption system includes a burner, a primary heating well and an extraction well. The primary heating well consists of an inner tube and an outer tube. The inner tube allows high-temperature flue gas to flow downward to the bottom and then flow out from the outer tube. The wall of the outer tube can exchange heat with the surrounding soil. The burner can spray the high-temperature flame generated by the combustion of liquefied petroleum gas or natural gas into the inner tube of the primary heating well. The wall of the extraction well is provided with a slit as a channel for soil gas to enter the extraction tube.

3. The fuel gas thermal desorption energy-saving structure according to claim 2 is characterized in that: The gas thermal desorption system also includes a burner secondary heating well, which is connected in series downstream of the primary heating well and is also composed of an inner tube and an outer tube.

4. The fuel gas thermal desorption energy-saving structure according to claim 1, characterized in that: The exhaust gas treatment system includes a first heat exchanger, a second heat exchanger, a blower, a secondary combustion chamber and a chimney. The first heat exchanger is used to transfer the heat of the high-temperature flue gas to the extracted exhaust gas; the second heat exchanger is used to transfer the heat of the high-temperature flue gas to the combustion-supporting air; the secondary combustion chamber is used to purify and burn the extracted exhaust gas before discharging it into the atmosphere; the chimney is used to discharge the low-temperature flue gas after two-stage heat exchange.

5. The fuel gas thermal desorption energy-saving structure according to claim 1 is characterized in that: The groundwater extraction and treatment system includes an aeration tank, a heat exchange pipe and an aeration pipe. The aeration tank stores the extracted contaminated groundwater. The heat exchange pipe is composed of a plurality of branch pipes arranged side by side and spirally arranged inside the aeration tank from bottom to top. The branch pipes are provided with flow regulating valves for regulating the flue gas flow in each branch pipe. The aeration pipe can aerate the inside of the aeration tank.

6. The fuel gas thermal desorption energy-saving structure according to claim 1 is characterized in that: The room temperature analysis system or thermal desorption pretreatment system includes a floor heating system, a turning device and a greenhouse.

7. The fuel gas thermal desorption energy-saving structure according to claim 1, characterized in that: A temperature sensor is arranged at the smoke exhaust position of the gas thermal desorption system, and the temperature sensor signal is connected to the controller, and the controller can select the connection direction of the smoke exhaust according to the temperature signal.

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