Soil pyrolysis treatment method and equipment based on direct pyrolysis desorption

Abstract

The present invention belongs to the technical field of regeneration of contaminated soil, and particularly relates to a soil pyrolysis treatment method and equipment based on direct pyrolysis desorption. The soil pyrolysis treatment method based on direct pyrolysis desorption includes soil pretreatment, soil pyrolysis desorption in a direct pyrolysis desorption furnace, and pyrolysis flue gas treatment of the direct pyrolysis desorption furnace. In the pyrolysis flue gas treatment of the direct pyrolysis desorption furnace, the specific steps are: (1) separating the pyrolysis flue gas of the direct pyrolysis desorption furnace to obtain high-temperature smoke and soil pyrolysis gas; (2) mixing the high-temperature smoke with the pretreated soil and introducing it into an indirect pyrolysis desorption furnace for pyrolysis desorption; (3) conducting the pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace, and discharging the treated soil from the indirect pyrolysis desorption furnace. The soil pyrolysis treatment method and equipment based on direct pyrolysis desorption can solve the technical problems of large amount of smoke and high concentration of organic pollutants in the direct pyrolysis desorption process, and at the same time improve the treatment efficiency of the pyrolysis desorption process.

Description

Technical Field

[0001] The present invention belongs to the technical field of regeneration of contaminated soil, and in particular relates to a soil pyrolysis treatment method and equipment based on direct pyrolysis desorption. Background Art

[0002] Thermal desorption technology has been widely used to repair soil contaminated by organic matter. At present, there are two main thermal desorption systems for organic contaminated soil: one is an indirect thermal desorption system, which separates the soil and hot flue gas and indirectly heats the soil through a sleeve or hollow blade. Its advantages are that the amount of tail gas treated and the difficulty of treatment are small, but the heat exchange efficiency of the indirect thermal desorption system is low, and the equipment is relatively complex, the equipment cost is high, and the equipment treatment capacity is not high; the other is a direct thermal desorption system, that is, hot flue gas is directly in contact with the soil to be treated and heated to a specified temperature. The advantage of this method is that the soil is in direct contact with the hot flue gas, the heat exchange efficiency is high, and the equipment treatment capacity is large, but because the hot flue gas is in direct contact with the soil, the gas volume of the hot flue gas is large, and the tiny particles in the soil are carried, resulting in a large amount of desorbed gas dust. In addition, the working temperature of direct thermal desorption is about 500℃, while the flue gas temperature at the flue gas separation device is about 200℃. Organic pollutants will combine with the flue dust at the flue gas separation device, resulting in a high concentration of organic pollutants in the flue dust. The technical solution adopted by our company is: first use a multi-tube dust collector to intercept most of the large particles of smoke, then mix the intercepted large particles of smoke with the raw materials and return them to the direct pyrolysis desorption furnace for secondary pyrolysis desorption treatment. However, in the treatment method of mixing and returning to the direct pyrolysis desorption furnace, the smoke will continue to circulate, resulting in unsatisfactory treatment effects of mixing and returning to the furnace. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a soil pyrolysis treatment method and equipment based on direct pyrolysis desorption, so as to solve the technical problems of large amount of smoke and high concentration of organic pollutants in the direct pyrolysis desorption process, and at the same time improve the treatment efficiency of the pyrolysis desorption process.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows:

[0005] The soil pyrolysis treatment method based on direct pyrolysis desorption includes soil pretreatment, pyrolysis desorption of soil in a direct pyrolysis desorption furnace, and pyrolysis flue gas treatment of the direct pyrolysis desorption furnace; the soil pretreatment includes a step of controlling the moisture content of the soil; the pyrolysis desorption of soil in the direct pyrolysis desorption furnace includes: introducing the pretreated soil into the direct pyrolysis desorption furnace for pyrolysis desorption, the pyrolysis flue gas of the direct pyrolysis desorption furnace is led out from the direct pyrolysis desorption furnace, and the treated soil is discharged from the direct pyrolysis desorption furnace;

[0006] In the treatment of pyrolysis flue gas from the direct pyrolysis desorption furnace, the specific steps are:

[0007] (1) Separating the pyrolysis flue gas from the direct pyrolysis desorption furnace into high-temperature smoke and soil pyrolysis gas;

[0008] (2) mixing the high-temperature smoke with the pretreated soil and introducing the mixture into an indirect pyrolysis desorption furnace for pyrolysis desorption;

[0009] (3) The pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace is discharged, and the treated soil is discharged from the indirect pyrolysis desorption furnace.

[0010] As an improvement, the moisture content of the pretreated soil is controlled within 25% before it is introduced into the direct pyrolysis desorption furnace.

[0011] As an improvement, the high-temperature smoke and pretreated soil are mixed in a screw feeder in the following manner: the pretreated soil is pushed into the indirect pyrolysis desorption furnace in the screw feeder, and the high-temperature smoke falls on the outer surface of the soil to wrap the soil.

[0012] As an improvement, the soil pyrolysis gas obtained by separating the pyrolysis flue gas from the direct pyrolysis desorption furnace is burned and the tail gas is treated before being discharged in compliance with emission standards.

[0013] As a further improvement, in step (2), the moisture content of the pretreated soil is controlled within 40%.

[0014] As an improvement, the pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace is discharged in compliance with emission standards after combustion and tail gas treatment.

[0015] The present invention also provides a soil pyrolysis treatment device based on direct pyrolysis desorption, including a pyrolysis desorption furnace, a flue gas separation device, a feed bin, a pyrolysis gas combustion device, and an exhaust gas treatment device.

[0016] The pyrolysis desorption furnace includes a direct pyrolysis desorption furnace and an indirect pyrolysis desorption furnace. The direct pyrolysis desorption furnace desorbs the soil and then introduces the pyrolysis flue gas to a flue gas separation device.

[0017] The flue gas separation device is used to separate the pyrolysis flue gas into high-temperature smoke and soil pyrolysis gas;

[0018] The feed bin includes a first feed bin and a second feed bin, the first feed bin is used to feed the direct pyrolysis desorption furnace; the second feed bin is connected to the discharge port of the flue gas separation device, and the high-temperature smoke discharged from the discharge port of the flue gas separation device is mixed with the soil entering from the second feed bin and then enters the indirect pyrolysis desorption furnace;

[0019] The pyrolysis gas combustion device is used to burn the soil pyrolysis gas separated from the pyrolysis flue gas of the direct pyrolysis desorption furnace and the pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace;

[0020] The tail gas treatment device is used to purify the tail gas coming out of the pyrolysis gas combustion device.

[0021] As an improvement, the flue gas separation device is a multi-tube dust collector.

[0022] As an improvement, a screw feeder is provided between the second feed bin and the indirect pyrolysis desorption furnace, and the discharge port of the flue gas separation device is connected to the screw feeder.

[0023] As an improvement, the exhaust gas treatment device includes a bag dust removal unit and an activated carbon adsorption unit.

[0024] The beneficial effects of the present invention are:

[0025] (1) High-temperature smoke is easy to float, so its residence time in the direct pyrolysis desorption furnace is short, resulting in insufficient treatment. On the other hand, the working temperature of pyrolysis desorption is about 500°C, while the flue gas temperature at the multi-tube dust collector is about 200°C. Organic pollutants will combine with smoke at the multi-tube dust collector, so the content of organic pollutants in high-temperature smoke is relatively high. The present invention separately sets an indirect pyrolysis desorption furnace for high-temperature smoke. After the high-temperature smoke is collected, the indirect pyrolysis desorption furnace is used for a second pyrolysis desorption, so that the high-temperature smoke is subjected to a more thorough pyrolysis desorption treatment, thereby meeting the requirements for standard emissions.

[0026] (2) Since the high-temperature flue gas will undergo a second thermal desorption in the indirect thermal desorption furnace, the air intake of the direct thermal desorption furnace can be increased to promptly remove the high-temperature flue gas from the direct thermal desorption furnace and reduce the residence time of the high-temperature flue gas in the direct thermal desorption furnace, which is beneficial to the desorption of organic pollutants in the soil, thereby improving the thermal desorption efficiency of the direct thermal desorption furnace.

[0027] (3) To prevent coking, the moisture content of the pretreated soil needs to be controlled within 25% before it is introduced into the direct pyrolysis desorption furnace. The soil introduced into the indirect pyrolysis desorption furnace is not easy to coke because its outer surface is covered with high-temperature smoke, which is equivalent to a layer of dry material wrapped around the wet material. Therefore, its moisture content only needs to be controlled within 40%, saving the cost of soil pretreatment. On the other hand, since the moisture content of the soil in the indirect pyrolysis desorption furnace is relatively high, it will produce more water vapor, which is conducive to taking the organic pollutants out of the soil, thereby improving the soil treatment efficiency.

[0028] (4) Compared with the method of mixing the retained large particles of dust with the raw materials and returning them to the furnace for treatment, the setting of the indirect pyrolysis desorption furnace can remove the high-temperature dust in time, which is beneficial to reduce the coking phenomenon in the direct pyrolysis desorption furnace and the smoke in the transmission pipeline, thereby ensuring the efficient operation of the whole system and improving the soil treatment efficiency.

[0029] (5) Compared with the method of mixing the intercepted large particles of smoke with raw materials and returning them to the furnace for treatment, the high-temperature smoke can immediately enter the indirect pyrolysis furnace for pyrolysis again after passing through the flue gas separation device. Heat will not be lost, which reduces energy loss, avoids mixing with raw materials and returning to the furnace to cause possible air pollution, and saves transportation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the invention.

[0031] In the figure: 1. direct pyrolysis desorption furnace; 11. first feed bin; 2. indirect pyrolysis desorption furnace; 21. second feed bin; 3. flue gas separation device; 4. pyrolysis gas combustion device; 5. tail gas treatment device; 6. combustion chamber; 7. automatic regulating valve; 8. intermediate fan; 9. screw feeder. DETAILED DESCRIPTION

[0032] Example 1

[0033] The soil pyrolysis treatment method based on direct pyrolysis desorption of the present invention includes soil pretreatment, pyrolysis desorption of soil in a direct pyrolysis desorption furnace, and pyrolysis flue gas treatment of the direct pyrolysis desorption furnace; the soil pretreatment includes the step of controlling the soil moisture content; the soil pyrolysis desorption in the direct pyrolysis desorption furnace includes: introducing the pretreated soil into the direct pyrolysis desorption furnace for pyrolysis desorption, the pyrolysis flue gas of the direct pyrolysis desorption furnace is led out from the direct pyrolysis desorption furnace, and the treated soil is discharged from the direct pyrolysis desorption furnace; the soil pyrolysis gas obtained by separation of the pyrolysis flue gas of the direct pyrolysis desorption furnace is discharged after combustion and tail gas treatment. Before the pretreated soil is introduced into the direct pyrolysis desorption furnace, the moisture content of the soil is controlled within 25%.

[0034] In the treatment of pyrolysis flue gas in direct pyrolysis desorption furnace, the specific steps are:

[0035] (1) The pyrolysis flue gas from the direct pyrolysis desorption furnace is separated into high-temperature smoke and soil pyrolysis gas.

[0036] (2) Mix the high-temperature smoke and pretreated soil and introduce them into the indirect pyrolysis desorption furnace for pyrolysis desorption; before introducing them into the indirect pyrolysis desorption furnace, the moisture content of the pretreated soil is controlled within 40%. The high-temperature smoke and pretreated soil are mixed in the screw feeder in the following manner: the pretreated soil is pushed into the indirect pyrolysis desorption furnace in the screw feeder, and the high-temperature smoke falls on the outer surface of the soil to wrap the soil.

[0037] (3) The pyrolysis gas generated by the indirect pyrolysis desorption furnace is discharged, and the treated soil is discharged from the indirect pyrolysis desorption furnace. The pyrolysis gas generated by the indirect pyrolysis desorption furnace is discharged after combustion and tail gas treatment.

[0038] like Figure 1 As shown, the soil pyrolysis treatment equipment based on direct pyrolysis desorption described in the present invention includes a pyrolysis desorption furnace, a flue gas separation device 3, a feed bin, a pyrolysis gas combustion device 4, and an exhaust gas treatment device 5.

[0039] The pyrolysis desorption furnace comprises a direct pyrolysis desorption furnace 1 and an indirect pyrolysis desorption furnace 2. The direct pyrolysis desorption furnace 1 performs pyrolysis desorption on the soil and then introduces the pyrolysis flue gas to a flue gas separation device 3.

[0040] The flue gas separation device 3 is used to separate the pyrolysis flue gas into high-temperature smoke and soil pyrolysis gas, and the flue gas separation device is a multi-tube dust collector.

[0041] The feed bin includes a first feed bin 11 and a second feed bin 21. The first feed bin 11 is used to feed the direct pyrolysis desorption furnace 1; the second feed bin 21 is connected to the discharge port of the flue gas separation device 3, and the high-temperature smoke discharged from the discharge port of the flue gas separation device 3 is mixed with the soil entering from the second feed bin 21 and then enters the indirect pyrolysis desorption furnace 2.

[0042] A screw feeder 9 is provided between the second feed bin 21 and the indirect pyrolysis desorption furnace 2, and the discharge port of the smoke separation device 3 is connected to the screw feeder 9. It is only necessary to open a hole at the top of the existing screw feeder 9 and connect it to the discharge port of the smoke separation device 3 with a pipe. When the soil is spirally advanced in the screw feeder 9, the high-temperature smoke will automatically fall on the outer surface of the soil to wrap the soil.

[0043] The pyrolysis gas combustion device 4 is used to burn the soil pyrolysis gas separated from the pyrolysis flue gas of the direct pyrolysis desorption furnace 1 and the pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace 2 .

[0044] The tail gas treatment device 5 is used to purify the tail gas coming out of the pyrolysis gas combustion device 4. The tail gas treatment device 5 includes a bag dust removal unit and an activated carbon adsorption unit.

[0045] The direct pyrolysis desorption furnace 1 is provided with a heat source by the combustion chamber 6. The furnace temperature of the pyrolysis gas combustion device 4 and the combustion chamber 6 is 900-1100°C. The intermediate fan 8 introduces the soil pyrolysis gas and the pyrolysis desorption gas derived from the indirect pyrolysis desorption furnace 2 into the pyrolysis gas combustion device 4 or the combustion chamber 6, and the toxic and harmful components and combustible components in the soil pyrolysis gas and the pyrolysis desorption gas are decomposed at high temperature in the furnace to achieve harmless treatment.

[0046] The indirect pyrolysis desorption furnace 2 is a screw-propelled indirect pyrolysis desorption furnace, the screw of which is driven by a variable frequency motor, the frequency is continuously adjustable, the furnace body adopts isothermal electric heating, the discharge temperature is controllable at 200-500°C, and the exhaust port of the indirect pyrolysis desorption furnace 2 is connected to the intermediate fan 8 through an automatic regulating valve 7. By adjusting the automatic regulating valve 7, the pressure in the furnace of the indirect pyrolysis desorption furnace 2 is controlled within the range of -150Pa to -50Pa. Compared with the direct pyrolysis desorption furnace 1, the volume and processing capacity of the indirect pyrolysis desorption furnace 2 can be designed to be relatively smaller.

Claims

1. A soil pyrolysis treatment method based on direct pyrolysis desorption, comprising soil pretreatment, pyrolysis desorption of soil in a direct pyrolysis desorption furnace, and pyrolysis flue gas treatment of the direct pyrolysis desorption furnace; the soil pretreatment comprises a step of controlling the moisture content of the soil; the pyrolysis desorption of soil in the direct pyrolysis desorption furnace comprises: The pretreated soil is introduced into a direct pyrolysis desorption furnace for pyrolysis desorption, the pyrolysis flue gas of the direct pyrolysis desorption furnace is led out from the direct pyrolysis desorption furnace, and the treated soil is discharged from the direct pyrolysis desorption furnace; It is characterized in that: in the pyrolysis flue gas treatment of the direct pyrolysis desorption furnace, the specific steps are: (1) Separating the pyrolysis flue gas from the direct pyrolysis desorption furnace into high-temperature smoke and soil pyrolysis gas; (2) mixing the high-temperature smoke with the pretreated soil and introducing the mixture into an indirect pyrolysis desorption furnace for pyrolysis desorption; the high-temperature smoke and the pretreated soil are mixed in a screw feeder in such a way that the pretreated soil is pushed into the indirect pyrolysis desorption furnace in the screw feeder, and the high-temperature smoke falls on the outer surface of the soil to coat the soil; (3) The pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace is discharged, and the treated soil is discharged from the indirect pyrolysis desorption furnace.

2. The soil pyrolysis treatment method based on direct pyrolysis desorption according to claim 1, characterized in that: Before the pretreated soil is introduced into the direct pyrolysis desorption furnace, the moisture content of the soil is controlled within 25%.

3. The soil pyrolysis treatment method based on direct pyrolysis desorption according to claim 1, characterized in that: The soil pyrolysis gas obtained by separation of the pyrolysis flue gas of the direct pyrolysis desorption furnace is burned and the tail gas is treated to meet the emission standards.

4. The soil pyrolysis treatment method based on direct pyrolysis desorption according to claim 1, characterized in that: In the step (2), the moisture content of the pretreated soil is controlled within 40%.

5. The soil pyrolysis treatment method based on direct pyrolysis desorption according to claim 1, characterized in that: The pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace is discharged in compliance with emission standards after being burned and subjected to tail gas treatment.

6. A soil pyrolysis treatment device based on direct pyrolysis desorption, comprising a pyrolysis desorption furnace, a flue gas separation device, a feed bin, a pyrolysis gas combustion device, and an exhaust gas treatment device, characterized in that: The pyrolysis desorption furnace includes a direct pyrolysis desorption furnace and an indirect pyrolysis desorption furnace. The direct pyrolysis desorption furnace desorbs the soil and then introduces the pyrolysis flue gas to a flue gas separation device. The flue gas separation device is a multi-tube dust collector, which is used to separate the pyrolysis flue gas into high-temperature smoke and soil pyrolysis gas; The feed bin includes a first feed bin and a second feed bin, the first feed bin is used to feed the direct pyrolysis desorption furnace; the second feed bin is connected to the discharge port of the flue gas separation device, and the high-temperature smoke discharged from the discharge port of the flue gas separation device is mixed with the soil entering from the second feed bin and then enters the indirect pyrolysis desorption furnace; a screw feeder is provided between the second feed bin and the indirect pyrolysis desorption furnace, and the discharge port of the flue gas separation device is connected to the screw feeder; The pyrolysis gas combustion device is used to burn the soil pyrolysis gas separated from the pyrolysis flue gas of the direct pyrolysis desorption furnace and the pyrolysis desorption gas generated by the indirect pyrolysis desorption furnace; The tail gas treatment device is used to purify the tail gas coming out of the pyrolysis gas combustion device.

7. The soil pyrolysis treatment equipment based on direct pyrolysis desorption according to claim 6, characterized in that: The tail gas treatment device comprises a bag dust removal unit and an activated carbon adsorption unit.

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