A device for improving the thermal desorption efficiency of soil in a base pipe based on Hartmann whistle structure

Abstract

The present invention discloses a device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure, and belongs to the field of enhanced heat exchange. The present invention includes a base pipe, and a plurality of enhanced heat exchange units are arranged inside the base pipe; the enhanced heat exchange unit is composed of a flue gas diversion unit and a flue gas turbulence unit; the flue gas diversion unit includes a diversion plane and a diversion platform; the flue gas diversion unit is fixed inside the base pipe through a plurality of support frames; the flue gas inlet of the enhanced heat exchange unit is formed between adjacent support frames; the flue gas turbulence unit is a Hartmann whistle resonance chamber. The Hartmann whistle resonance chamber in each enhanced heat exchange unit of the present invention can generate sound waves with a high sound pressure level, which strongly disturbs the airflow and promotes the heat exchange between the hot flue gas in the pipe and the wall surface; at the same time, the vibration brought by the sound waves in the pipe makes it difficult for solid impurities in the hot flue gas to adhere to the pipe wall, and a high heat exchange efficiency can be maintained for a long time, which is beneficial to the thermal desorption of soil.

Description

Technical Field

[0001] The invention relates to the technical field of enhanced heat exchange, and in particular to a device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure. Background Art

[0002] In recent years, the soil pollution problem left behind by the relocation of heavily polluting enterprises and the treatment of pollutants has attracted attention from all walks of life. Among soil pollutants, volatile and semi-volatile pollutants have received widespread attention due to their high migration ability and high toxicity. At present, soil thermal desorption technology is the main means of treating organic contaminated soil. This technology heats the soil directly or indirectly to a certain temperature, and the organic pollutants contained in the organic contaminated soil will be gasified or decomposed, and the pollutants will eventually enter the gas phase and enter the next process for removal.

[0003] A Chinese invention patent with application publication number "CN104438313A" discloses a contaminated soil thermal desorption system and method for efficient waste heat recovery. The patent uses the high-temperature flue gas generated by the tail gas incineration system as a heat source to desorb pollutants in the soil.

[0004] The base tube heat exchange technology uses the high temperature gas inside the tube to exchange heat with the organic contaminated soil outside the tube, and the heat exchange efficiency between the gas and the soil affects the effect of soil thermal desorption. The actual use of the base tube heat exchange technology is best to use high temperature flue gas as a heat source to utilize waste heat. However, high temperature flue gas generally carries impurities, and the organic contaminated soil outside the tube is easy to adhere to the base tube wall. These factors affect the wall heat exchange.

[0005] Most of the existing technologies deform the heat exchange tubes and add fins of various shapes to enhance heat transfer. However, such measures may significantly reduce the heat transfer efficiency of the heat exchange tube wall due to insufficient turbulence intensity, low energy utilization efficiency and impurities adhering to the wall during the actual soil thermal desorption process, thereby affecting the thermal desorption efficiency of organic contaminated soil. Summary of the invention

[0006] In order to make up for the deficiencies of the prior art, the present invention provides a device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure.

[0007] The technical solution of the present invention is:

[0008] A device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure comprises a base pipe, wherein a plurality of enhanced heat exchange units are arranged inside the base pipe; the enhanced heat exchange unit is composed of a smoke diversion unit and a smoke turbulence unit; the smoke diversion unit comprises a diversion plane and a diversion platform extending from the diversion plane toward the inner wall of the base pipe; the smoke diversion unit is fixed inside the base pipe by a plurality of support frames; a smoke inlet of the enhanced heat exchange unit is formed between adjacent support frames; the smoke turbulence unit comprises an annular panel fixed to the inner wall of the base pipe, a smoke channel with an outer diameter smaller than the inner diameter of the base pipe is fixed on the annular panel, and an annular groove between the outer wall of the smoke channel, the annular panel and the inner wall of the base pipe is a Hartmann whistle resonance chamber; the position where the end of the smoke channel connects with the annular panel constitutes the smoke outlet of the enhanced heat exchange unit.

[0009] The diversion plane and the diversion platform guide the hot flue gas entering the base pipe to between the diversion platform and the inner wall of the base pipe. As the airflow flow area is reduced, the flue gas flow rate is accelerated; after passing through the diversion platform, the flue gas directly enters the annular Hartmann's whistle resonance chamber, and the hot flue gas with a faster flow rate is squeezed in the Hartmann's whistle resonance chamber, generating sound waves with a high sound pressure level, which forms a strong disturbance to the airflow and promotes the heat exchange between the hot flue gas in the pipe and the wall; at the same time, the vibration caused by the sound waves in the pipe makes it difficult for solid impurities in the hot flue gas to adhere to the pipe wall, and a high heat exchange efficiency can be maintained for a long time, which is beneficial to soil thermal desorption; when the flue gas pressure in the Hartmann's whistle resonance chamber reaches a certain value, part of the flue gas flows out of the Hartmann's whistle resonance chamber and enters the next enhanced heat exchange unit through the flue gas channel.

[0010] As a preferred solution, the area of ​​the diversion plane is 10% to 40% of the cross-sectional area of ​​the base tube; the maximum cross-sectional area of ​​the diversion platform is 60% to 90% of the cross-sectional area of ​​the base tube. The diversion plane can divert the incoming flue gas along the diversion platform to the pipe wall, so that the gas flows along the wall, increasing the flow rate while ensuring that the incoming flue gas enters the Hartmann whistle resonance chamber.

[0011] As a preferred solution, the diversion plane is circular or regular polygonal; the diversion platform is prism-shaped or truncated cone-shaped.

[0012] As a preferred solution, each of the enhanced heat exchange units is evenly distributed inside the base pipe. This arrangement can increase the uniformity of soil desorption treatment.

[0013] As a preferred solution, the spacing between adjacent enhanced heat exchange units is 1-20 cm.

[0014] As a preferred solution, the support frame is a support rod fixed between the diverter table and the inner wall of the base tube. The diverter table and the diverter plane are stably fixed inside the base tube through the support rod, which has a simple structure and is stable and reliable, and can ensure that the flue gas enters the enhanced heat exchange unit.

[0015] As a preferred solution, the central axis of each of the enhanced heat exchange units coincides with the central axis of the base tube.

[0016] The method for improving the thermal desorption efficiency of soil in a base pipe by using the device is as follows: hot flue gas is introduced into the base pipe, and after the airflow touches the diversion plane, it enters the Hartmann whistle resonance chamber of the first enhanced heat exchange unit along the diversion platform from the flue gas inlet, and the hot flue gas accumulates in the Hartmann whistle resonance chamber to generate sound waves, which strongly disturb the flue gas; after the pressure of the hot flue gas in the Hartmann whistle resonance chamber of the first enhanced heat exchange unit increases to a certain level, part of the hot flue gas flows out of the Hartmann whistle resonance chamber and enters the next enhanced heat exchange unit through the flue gas channel and the flue gas outlet; accordingly, the pressure of the flue gas in the Hartmann whistle resonance chamber of each enhanced heat exchange unit changes periodically and generates sound waves, so that the flue gas is strongly disturbed and the heat exchange efficiency is enhanced.

[0017] As a preferred solution, the temperature of the hot flue gas is 300~1200℃.

[0018] As a preferred solution, the pressure of the hot flue gas entering the substrate tube is 0.12~0.5MPa.

[0019] The beneficial effects of the present invention are:

[0020] In the present invention, hot flue gas flows in the base tube, and organic contaminated soil is outside the base tube, and the heat of the hot flue gas is used to thermally desorb the organic contaminated soil. The hot flue gas flows from the flow channel through the hot flue gas diversion plane and accelerates to the diversion platform. After being accelerated by the diversion platform, the high-speed flowing flue gas makes it difficult for the flue gas in the Hartmann whistle resonance chamber to flow out and accumulates pressure. After reaching a certain critical point, the pressure in the chamber is high enough to flow out part of the flue gas. The pressure range is generally 5-100kPa. The flue gas pressure in the Hartmann whistle resonance chamber changes periodically and produces stable sound waves. According to experiments, the Hartmann whistle resonance chamber in the device of the present invention can produce a frequency range of 2-5kHz, and the sound pressure level can reach 90-120dB. The sound wave strongly disturbs the flue gas in the tube, significantly enhancing the heat exchange efficiency. At the same time, the vibration brought by the sound wave in the tube makes it difficult for solid impurities to adhere to and accumulate inside and outside the tube wall, ensuring that the wall heat exchange efficiency remains at a high level, which is conducive to soil thermal desorption.

[0021] The flue gas flowing out of the upper-stage Hartmann whistle sounding structure enters the next-stage Hartmann whistle sounding structure through the hot flue gas channel, and the energy of the flue gas is effectively utilized in a multi-stage utilization manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 It is a schematic diagram of the radial cross-sectional structure of the device of the present invention;

[0024] Figure 2 It is a schematic cross-sectional structure diagram of the device of the present invention in the vertical direction;

[0025] Figure 3 It is a schematic diagram of the radial cross-sectional structure of the device of the present invention from another angle;

[0026] Figure 4 It is a schematic cross-sectional structure diagram of the device of the present invention in the vertical direction from another angle;

[0027] Figure 5 It is a schematic diagram of the cross-sectional structure of the annular panel in the vertical direction and the radial direction;

[0028] Figure 6 This is a comparison chart of the thermal desorption efficiency of pollutant PAHs between the device of the present invention and the control group;

[0029] Figure 7 It is a comparison chart of the thermal desorption efficiency of pollutant PCBs by the device of the present invention and the control group. DETAILED DESCRIPTION

[0030] In the description of the present invention, the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "vertical", "horizontal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the purpose of describing the present invention rather than requiring the present invention to be constructed or operated in a specific position, and therefore should not be construed as limiting the present invention. The terms "connected" and "connected" in the present invention should be understood in a broad sense, for example, it can be a connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate component. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0031] Example 1

[0032] like Figure 1-Figure 5 As shown, a device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure includes a base pipe 10; the base pipe 10 is made of a heat-resistant and corrosion-resistant metal material.

[0033] like Figure 2 , Figure 4 As shown, a plurality of enhanced heat exchange units are arranged inside the base tube 10. Each enhanced heat exchange unit has the same structure and is evenly distributed, and the spacing between adjacent enhanced heat exchange units is 1-20 cm. Each enhanced heat exchange unit is composed of a flue gas diversion unit and a flue gas turbulence unit.

[0034] Among them, the flue gas diversion unit includes a diversion plane 2 and a diversion platform 6 extending from the diversion plane 2 toward the inner wall of the base tube 10. In this embodiment, the diversion plane 2 is circular and the diversion platform 6 is truncated. The diameter of the diversion plane 2 is 1 / 3 of the inner diameter of the base tube 10. The diversion platform 6 is integrally formed with the diversion plane 2 and is made of heat-resistant and corrosion-resistant materials. The diversion platform 6 is fixedly connected to the inner wall of the base tube 10 through a plurality of support frames 1. The flue gas inlet 8 of the enhanced heat exchange unit is formed between adjacent support frames 1.

[0035] The flue gas turbulence unit includes an annular panel 9 fixed to the inner wall of the base tube 10, a flue gas channel 4 having an outer diameter smaller than the inner diameter of the base tube is fixed on the annular panel 9, and the outer wall 5 of the flue gas channel fits the inner wall of the annular panel 9. The annular groove between the outer wall 5 of the flue gas channel, the annular panel 9 and the inner wall of the base tube 10 is the Hartmann whistle resonance chamber 3; the position where the end of the flue gas channel 4 is connected to the annular panel 9 constitutes the flue gas outlet 7 of the enhanced heat exchange unit.

[0036] In this embodiment, the central axis of each enhanced heat exchange unit coincides with the central axis of the base tube.

[0037] In order to ensure that the hot flue gas enters the Hartmann whistle resonance chamber 3 as directly as possible, the maximum diameter of the diverter 6 is slightly larger than the outer diameter of the flue gas channel 4 .

[0038] The diversion plane 2 and the diversion platform 6 guide the hot flue gas entering the base pipe 10 to between the diversion platform and the inner wall of the base pipe. As the airflow flow area is reduced, the flue gas flow rate is accelerated; after passing through the diversion platform 6, the flue gas directly enters the annular Hartmann whistle resonance chamber 3, and the hot flue gas with a faster flow rate is squeezed in the Hartmann whistle resonance chamber, generating sound waves with a high sound pressure level, which forms a strong disturbance to the airflow and promotes the heat exchange between the hot flue gas in the pipe and the wall; at the same time, the vibration caused by the sound waves in the pipe makes it difficult for solid impurities in the hot flue gas to adhere to the pipe wall, and a high heat exchange efficiency can be maintained for a long time, which is beneficial to soil thermal desorption; when the flue gas pressure in the Hartmann whistle resonance chamber 3 reaches a certain value, part of the flue gas flows out of the Hartmann whistle resonance chamber 3 and enters the next enhanced heat exchange unit through the flue gas channel 4.

[0039] Example 2 Application Example

[0040] In order to verify that the device of the present invention can improve the thermal desorption efficiency of soil, the following experiments are designed, as follows:

[0041] The test soil was collected from a site of an organochlorine pesticide production enterprise and an abandoned coking plant in Hangzhou, Zhejiang. The soil was air-dried to remove stone impurities, passed through an 18-mesh (1 mm) sieve, and stored at low temperature as a soil sample. A control group was set up for the experiment. The inside of the heat exchange base tube of the control group was a smooth light tube without any structure to improve the heat exchange efficiency. The heat exchange tube material was the same as the base tube material of the present invention. The experimental group used the device of Example 1.

[0042] Control group (traditional method):

[0043] The lower part of the base tube without any internal heat exchange efficiency is fixed on the bracket; the bracket and the base tube are placed in the laboratory model XTL1100-100 vacuum tube rotary furnace (the base tube is placed in the middle of the rotary furnace as much as possible through the bracket), and the gas supply pipe of the rotary furnace is connected to one end of the base tube, and the other end of the base tube is connected to the tail gas absorption device; 5 kg of test soil is filled in the rotary furnace. High-temperature nitrogen at 800 ° C is introduced, and the supply pressure of hot nitrogen is 0.15 MPa, and ventilation is carried out for 60 minutes under static conditions.

[0044] Experimental group (enhanced heat transfer):

[0045] The lower part of the substrate tube in the device of Example 1 is fixed on the bracket; the bracket and the substrate tube are placed in the laboratory model XTL1100-100 vacuum tube rotary furnace (the substrate tube is placed in the middle of the rotary furnace as much as possible through the bracket), and the gas supply pipe of the rotary furnace is connected to one end of the substrate tube, and the other end of the substrate tube is connected to the tail gas absorption device; 5 kg of test soil is filled in the rotary furnace. High-temperature nitrogen gas at 800°C is introduced, and the supply pressure of the hot nitrogen gas is 0.15 MPa, and the gas is ventilated for 60 minutes in a static state.

[0046] The non-desorbed soil, the soil after thermal desorption in the control group, and the soil after thermal desorption in the experimental group were subjected to Soxhlet extraction, rotary evaporation, silica gel column, and low-temperature nitrogen blowing before being tested on the machine.

[0047] Gas chromatography-mass spectrometry (GC / MS) was used to perform qualitative and quantitative analysis of PAHs. The results showed that Figure 6 As shown, the thermal desorption efficiency of PAHs in the control group was 79.6%, and that in the experimental group was 86.3%.

[0048] The JMS800D high-resolution chromatograph-mass spectrometer (HRGC / HRMS) was used to detect the PCBs content in the samples. The analysis results showed that Figure 7 As shown, the thermal desorption efficiency of PCBs in the control group was 64.2%, and that in the experimental group was 72.5%.

[0049] In summary, it can be seen that the device of the present invention can improve the thermal desorption efficiency of soil with remarkable effect.

[0050] Due to the limitations of laboratory conditions, the thermal desorption efficiency is average. If industrial high-temperature flue gas is used as a thermal fluid to desorb the soil, the desorption efficiency will be higher.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure, comprising a base pipe, characterized in that: A plurality of enhanced heat exchange units are arranged inside the base tube; the enhanced heat exchange unit is composed of a smoke diversion unit and a smoke turbulence unit; the smoke diversion unit includes a diversion plane and a diversion platform extending from the diversion plane to the inner wall of the base tube; the smoke diversion unit is fixed inside the base tube through a plurality of support frames; a smoke inlet of the enhanced heat exchange unit is formed between adjacent support frames; the smoke turbulence unit includes an annular panel fixed to the inner wall of the base tube, a smoke channel with an outer diameter smaller than the inner diameter of the base tube is fixed on the annular panel, and an annular groove between the outer wall of the smoke channel, the annular panel and the inner wall of the base tube is a Hartmann whistle resonance chamber; the position where the end of the smoke channel connects with the annular panel constitutes the smoke outlet of the enhanced heat exchange unit; The area of ​​the diversion plane is 10% to 40% of the cross-sectional area of ​​the base tube; the maximum cross-sectional area of ​​the diversion platform is 60% to 90% of the cross-sectional area of ​​the base tube; The diversion plane is circular or regular polygonal; the diversion platform is truncated cone or prism-shaped; The enhanced heat exchange units are uniformly distributed inside the base tube.

2. The device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure as claimed in claim 1, characterized in that: The distance between adjacent enhanced heat exchange units is 1-20 cm.

3. The device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure according to claim 1, characterized in that: The support frame is a support rod fixed between the diversion platform and the inner wall of the base pipe.

4. The device for improving the thermal desorption efficiency of soil in a base pipe based on a Hartmann whistle structure according to claim 1, characterized in that: The central axis of each of the enhanced heat exchange units coincides with the central axis of the base tube.

5. A method for improving the thermal desorption efficiency of soil in a base pipe by using the device of claim 1, characterized in that: The hot flue gas is introduced into the base pipe, and after the airflow touches the diversion plane, it enters the Hartmann whistle resonance chamber of the first enhanced heat exchange unit along the diversion platform from the flue gas inlet. After the hot flue gas accumulates in the Hartmann whistle resonance chamber, it generates sound waves, which strongly disturb the flue gas. After the pressure of the hot flue gas in the Hartmann whistle resonance chamber of the first enhanced heat exchange unit increases to a certain level, part of the hot flue gas flows out of the Hartmann whistle resonance chamber and enters the next enhanced heat exchange unit through the flue gas channel and the flue gas outlet. Accordingly, the pressure of the flue gas in the Hartmann whistle resonance chamber of each enhanced heat exchange unit changes periodically and generates sound waves, which causes the flue gas to be strongly disturbed and the heat exchange efficiency is enhanced.

6. The method for improving thermal desorption efficiency of soil in a base pipe according to claim 5, characterized in that: The temperature of hot flue gas is 300~1200℃.

7. The method for improving the thermal desorption efficiency of soil in a base pipe according to claim 5 or 6, characterized in that: The pressure of the hot flue gas entering the base pipe is 0.12~0.5MPa.

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