Thermal desorption rotary kiln cylinder for organic matter contaminated soil and preparation method of thermal desorption rotary kiln cylinder

Abstract

The invention discloses a thermal desorption rotary kiln cylinder for organic matter contaminated soil, a base material of the cylinder is prepared by processing FeCrAl alloy, the surface of the base material is provided with a catalyst coating and an active precursor layer, the catalyst coating is coated on the inner wall of the base material of the cylinder, the active precursor layer is sprayed on the catalyst coating, and the active precursor layer is coated on the inner wall of the base material of the cylinder. The catalyst coating is prepared by adding a carrier and an inorganic binder into an organic binder solution and stirring. The invention further discloses a preparation method of the rotary kiln barrel, which comprises the following steps: S1, processing FeCrAl alloy into a cylindrical shape, and calcining to obtain a barrel base material; s2, adding a carrier and an inorganic binder into an organic binder solution, coating the solution on the inner wall of the barrel base material, drying and calcining; and S3, preparing an aqueous solution of an active component precursor, an auxiliary agent A precursor and an auxiliary agent B precursor, spraying the solution on the inner wall of the barrel base material, drying and calcining to prepare the thermal desorption rotary kiln barrel for the organic matter contaminated soil.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and specifically relates to a rotary kiln cylinder for thermally desorbing organic contaminated soil and a preparation method thereof. Background Art

[0002] Organic substances are a typical type of soil pollutants, mainly including persistent organic pollutants (POPs), organic pesticides, petroleum hydrocarbons, etc. These pollutants have stable chemical properties, are difficult to degrade in soil, and are easily enriched in organisms, thus having a serious impact on the natural environment and human health.

[0003] The ex-situ thermal desorption technology is a typical process for remediating organic contaminated soil at present. The main principle is to heat the soil to a high enough temperature through direct heating or indirect heating, so that the organic substances in the soil evaporate and are separated from the soil medium. A typical ex-situ soil thermal desorption device uses a rotary kiln system. For example, in Chinese invention patent CN113941593A, the overall system includes soil transportation, a rotary kiln, and a tail gas treatment device, which can realize continuous thermal desorption treatment of organic contaminated soil with high efficiency.

[0004] For some volatile organic compounds (VOCs) with low boiling points, such as dichloromethane, chloroform, carbon tetrachloride, etc., ex-situ soil thermal desorption can effectively remove them. For some organic substances with higher boiling points, such as polychlorinated biphenyls, naphthalene, benzo[a]pyrene, benzo[a]anthracene, etc., higher heating temperatures and longer residence times are required, resulting in an increase in energy consumption. In recent years, in order to reduce the system energy consumption, researchers in this field have proposed that granular catalysts can be added to the organic contaminated soil. During the heating process of the soil, the high-boiling organic substances can be decomposed into small molecules to promote desorption, so as to achieve the purpose of reducing energy consumption. Chinese invention patent CN115254131A discloses a solid heat carrier organic contaminated soil thermal desorption catalyst and a preparation method thereof. The catalyst uses hollow alumina spheres prepared by 3D printing as the solid heat carrier, copper-nickel-vanadium composite oxide as the catalytic active component, and vinyltriethoxysilane as the masking agent. After the catalyst is added to the soil, the thermal desorption temperature of benzo[a]anthracene can be reduced. However, in the existing technology, the catalysts used are mixed with the soil, resulting in the need for further treatment after the soil is thermally desorbed to separate the catalyst from the thermally desorbed soil. In addition, the catalysts used also contain heavy metal components such as Cu, which has the risk of secondary pollution. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: aiming at the technical problems existing in the prior art, the present invention provides a rotary kiln cylinder for thermally desorbing organic contaminated soil and a preparation method thereof, which can realize the desorption of high-boiling organic substances in the soil and save energy consumption.

[0006] To solve the above technical problems, the technical solution proposed by the present invention is as follows:

[0007] A rotary kiln cylinder for thermally desorbing organic-polluted soil, the cylinder base material is processed and prepared from FeCrAl alloy, and the surface of the base material is provided with a catalyst coating and an active precursor layer. The catalyst coating is coated on the inner wall of the cylinder base material, and the active precursor layer is sprayed on the catalyst coating. The catalyst coating is prepared by stirring a carrier and an inorganic binder into an organic binder solution. The carrier is one of SiO2, ZSM-5, SAPO-34, and TiO2.

[0008] As a further improvement of the above technical solution:

[0009] In the above technical solution, the active precursor layer is an aqueous solution of an active component precursor, a promoter A precursor, and a promoter B precursor. The active component precursor is one of manganese nitrate, manganese acetate, and manganese chloride. The promoter A precursor is one of neodymium nitrate, holmium nitrate, and lanthanum nitrate. The promoter B precursor is one of iron nitrate, nickel nitrate, copper nitrate, and yttrium nitrate.

[0010] In the above technical solution, the inorganic binder is one of Al2O3, pseudo-boehmite, attapulgite, and sepiolite.

[0011] In the above technical solution, the organic binder is one of methyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose.

[0012] In the above technical solution, the molar ratio of Mn, Ce / Nd / Ho / La, and Fe / Ni / Cu / Y in the active precursor layer is 1:0.2:0.2 to 1:1:1. In the above technical solution, the total mass of MnO2, CeO2 / Nd2O3 / Ho2O3 / La2O3, and Fe2O3 / NiO / CuO / Y2O3 in the active precursor layer accounts for 0.5 to 5% of the sum of the masses of the carrier and the inorganic binder.

[0013] A preparation method of a rotary kiln cylinder for thermally desorbing organic-polluted soil, used to prepare the above cylinder, includes the following steps:

[0014] Step S1, process the FeCrAl alloy into a cylindrical shape and calcine it at 950 - 1150 °C for 5 - 15 h to obtain the cylinder base material;

[0015] Step S2, weigh the carrier and the inorganic binder according to a mass ratio of 90:10 to 95:5, add them to the organic binder solution, stir until a uniform solution is formed, uniformly coat the solution on the inner wall of the cylinder base material, after drying, calcine the cylinder base material at 450 - 550 °C for 3 - 5 h;

[0016] Step S3, prepare an aqueous solution of the active component precursor, promoter A precursor, and promoter B precursor, uniformly spray the solution on the inner wall of the cylindrical substrate, and after drying, calcine the cylindrical substrate at 350-500 °C for 2-4 h to obtain a thermal desorption rotary kiln cylinder for organically contaminated soil.

[0017] In the above technical solution, in step S1, calcination is carried out in an atmosphere of 0.5-5 vol% O2 / N2.

[0018] In the above technical solution, in step S2, the solid-liquid ratio of the carrier and inorganic binder mixture to the organic binder solution is 1:5-1:10.

[0019] In the above technical solution, in step S2, the concentration of the organic binder solution is 1-5 wt%.

[0020] The thermal desorption rotary kiln cylinder for organically contaminated soil and its preparation method provided by the present invention have the following advantages compared with the prior art:

[0021] (1) For the thermal desorption rotary kiln cylinder for organically contaminated soil and its preparation method of the present invention, an FeCrAl alloy is used as the cylindrical substrate. Through high-temperature calcination, an alumina film appears on the surface of the substrate, so that the catalyst coating can be firmly loaded and there will be no coating peeling. Moreover, the catalyst coating is uniformly distributed on the inner wall of the cylindrical substrate, with a large contact area with the soil, and can fully contact and react with high-boiling organic pollutants.

[0022] (2) For the thermal desorption rotary kiln cylinder for organically contaminated soil and its preparation method of the present invention, SiO2, ZSM-5, etc. are used as catalyst carriers, MnO2 is used as the active component, and oxides such as CeO2 and Fe2O3 are used as promoters. The catalyst participates in the thermal desorption process and can catalytically oxidize macromolecular organic matter into small molecules and low-boiling organic matter, thereby reducing the thermal desorption temperature and reducing the energy consumption of the thermal desorption process;

[0023] (3) The catalyst of the present invention is loaded on the inner wall of the cylinder in the form of a coating. The soil after thermal desorption does not contain the catalyst, so there is no problem of secondary pollution. Moreover, there is no need to separate the soil and the catalyst after thermal desorption.

[0024] (4) For the thermal desorption rotary kiln cylinder for organically contaminated soil and its preparation method of the present invention, the preparation process is simple, the energy consumption of soil thermal desorption can be effectively reduced, and the disposal cost of organically contaminated soil can be reduced. Specific embodiments

[0025] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0026] Example 1

[0027] The FeCrAl alloy is processed into a cylindrical shape to match the inner cavity of the rotary kiln. Subsequently, it is calcined at 1150 °C for 5 h in an atmosphere of 0.5 vol% O2 / N2 to obtain the cylindrical substrate. SiO2 and sepiolite are weighed according to a mass ratio of 90:10, and then added to a hydroxypropyl cellulose solution with a concentration of 2.5 wt% according to a solid-liquid ratio of 1:5. After vigorous stirring to form a homogeneous solution, the solution is uniformly coated on the inner wall of the cylindrical substrate. After drying, the cylindrical substrate is calcined at 450 °C for 5 h. An aqueous solution of manganese acetate, cerium nitrate, and iron nitrate is prepared, and the molar ratio of Mn, Ce, and Fe is 1:0.2:0.2. The solution is uniformly sprayed on the inner wall of the cylindrical substrate. After drying, the cylindrical substrate is calcined at 350 °C for 4 h to obtain a rotary kiln cylinder for thermal desorption of organic contaminated soil. The total mass of MnO2, CeO2, and Fe2O3 accounts for 0.5% of the sum of the masses of the carrier and the inorganic binder.

[0028] Example 2

[0029] The FeCrAl alloy is processed into a cylindrical shape to match the inner cavity of the rotary kiln. Subsequently, it is calcined at 950 °C for 15 h in an atmosphere of 5 vol% O2 / N2 to obtain the cylindrical substrate. ZSM-5 and attapulgite are weighed according to a mass ratio of 95:5, and then added to a methyl cellulose solution with a concentration of 3 wt% according to a solid-liquid ratio of 1:10. After vigorous stirring to form a homogeneous solution, the solution is uniformly coated on the inner wall of the cylindrical substrate. After drying, the cylindrical substrate is calcined at 550 °C for 3 h. An aqueous solution of manganese nitrate, neodymium nitrate, and copper nitrate is prepared, and the molar ratio of Mn, Nd, and Cu is 1:1:1. The solution is uniformly sprayed on the inner wall of the cylindrical substrate. After drying, the cylindrical substrate is calcined at 500 °C for 2 h to obtain a rotary kiln cylinder for thermal desorption of organic contaminated soil. The total mass of MnO2, Nd2O3, and CuO accounts for 5% of the sum of the masses of the carrier and the inorganic binder.

[0030] Example 3

[0031] The FeCrAl alloy is processed into a cylindrical shape to match the inner cavity of the rotary kiln. Subsequently, it is calcined at 1000 °C for 10 h in an atmosphere of 1 vol% O2 / N2 to obtain the cylinder substrate. Weigh SAPO-34 and Al2O3 according to a mass ratio of 91:9, and then add them to a 1 wt% hydroxypropyl methylcellulose solution according to a solid-liquid ratio of 1:8. Stir vigorously until a homogeneous solution is formed. Coat this solution evenly on the inner wall of the cylinder substrate. After drying, the cylinder substrate is calcined at 500 °C for 3 h. Prepare an aqueous solution of manganese chloride, holmium nitrate, and nickel nitrate, with the molar ratio of Mn, Ho, and Ni being 1:0.5:0.5. Spray the solution evenly on the inner wall of the cylinder substrate. After drying, the cylinder substrate is calcined at 400 °C for 3 h to obtain the rotary kiln cylinder for thermal desorption of organically contaminated soil. The total mass of MnO2, Ho2O3, and NiO accounts for 1% of the sum of the masses of the carrier and the inorganic binder.

[0032] Example 4

[0033] The FeCrAl alloy is processed into a cylindrical shape to match the inner cavity of the rotary kiln. Subsequently, it is calcined at 1150 °C for 8 h in an atmosphere of 2 vol% O2 / N2 to obtain the cylinder substrate. Weigh TiO2 and pseudoboehmite according to a mass ratio of 92:8, and then add them to a 5 wt% methylcellulose solution according to a solid-liquid ratio of 1:5. Stir vigorously until a homogeneous solution is formed. Coat this solution evenly on the inner wall of the cylinder substrate. After drying, the cylinder substrate is calcined at 500 °C for 4 h. Prepare an aqueous solution of manganese acetate, lanthanum nitrate, and yttrium nitrate, with the molar ratio of Mn, La, and Y being 1:0.3:0.6. Spray the solution evenly on the inner wall of the cylinder substrate. After drying, the cylinder substrate is calcined at 450 °C for 2.5 h to obtain the rotary kiln cylinder for thermal desorption of organically contaminated soil. The total mass of MnO2, La2O3, and Y2O3 accounts for 2% of the sum of the masses of the carrier and the inorganic binder.

[0034] Example 5

[0035] The FeCrAl alloy is processed into a cylindrical shape to match the inner cavity of the rotary kiln. Subsequently, it is calcined at 950 °C for 12 h in an atmosphere of 4 vol% O₂ / N₂ to obtain the cylinder substrate. SiO₂ and Al₂O₃ are weighed according to a mass ratio of 95:5, and then added to a 2 wt% hydroxypropyl cellulose solution according to a solid-liquid ratio of 1:10. After vigorous stirring to form a homogeneous solution, the solution is uniformly coated on the inner wall of the cylinder substrate. After drying, the cylinder substrate is calcined at 480 °C for 4 h. An aqueous solution of manganese nitrate, cerium nitrate, and iron nitrate is prepared, and the molar ratio of Mn, Ce, and Fe is 1:0.8:0.4. The solution is uniformly sprayed on the inner wall of the cylinder substrate. After drying, the cylinder substrate is calcined at 500 °C for 3 h to obtain the rotary kiln cylinder for thermal desorption of organic contaminated soil. The total mass of MnO₂, CeO₂, and Fe₂O₃ accounts for 3% of the sum of the mass of the carrier and the inorganic binder.

[0036] Comparative Example 1

[0037] The FeCrAl alloy is processed into a cylindrical shape to match the inner cavity of the rotary kiln. Subsequently, it is calcined at 1150 °C for 5 h in an atmosphere of 0.5 vol% O₂ / N₂ to obtain the rotary kiln cylinder for thermal desorption of organic contaminated soil.

[0038] Comparative Example 2

[0039] The FeCrAl alloy is processed into a cylindrical shape to match the inner cavity of the rotary kiln. Subsequently, it is calcined at 950 °C for 15 h in an atmosphere of 5 vol% O₂ / N₂ to obtain the cylinder substrate. ZSM-5 and attapulgite are weighed according to a mass ratio of 95:5, and then added to a 3 wt% methyl cellulose solution according to a solid-liquid ratio of 1:10. After vigorous stirring to form a homogeneous solution, the solution is uniformly coated on the inner wall of the cylinder substrate. After drying, the cylinder substrate is calcined at 550 °C for 3 h to obtain the rotary kiln cylinder for thermal desorption of organic contaminated soil.

[0040] Detection Example 1

[0041] Contaminated soil containing 200 mg / kg of 3,3',4,4',5-pentachlorobiphenyl is prepared with clean soil.

[0042] The thermal desorption experiment is carried out on a small-scale rotary kiln in the laboratory. The feed rate of the organic contaminated soil is 500 g, the residence time of the organic contaminated soil in the rotary kiln is 30 min, and the air inlet flow rate in the rotary kiln is 2 L / min.

[0043] Before and after thermal desorption, the content of 3,3',4,4',5-pentachlorobiphenyl in the soil is detected according to GB36600-2018 "Soil Environmental Quality - Risk Control Standards for Soil Pollution of Construction Land".

[0044] Table 1 Desorption effect of 3,3',4,4',5-pentachlorobiphenyl in soil

[0045]

[0046]

[0047] Detection Example 2

[0048] Use clean soil to prepare contaminated soil containing 400 mg / kg of benzo[a]anthracene.

[0049] The thermal desorption experiment was carried out on a small rotary kiln in the laboratory. The feeding amount of organic contaminated soil was 500 g, the residence time of the organic contaminated soil in the rotary kiln was 30 min, and the air inlet flow rate in the rotary kiln was 2 L / min.

[0050] Before and after thermal desorption, the content of benzo[a]anthracene in the soil was detected in accordance with GB36600-2018 "Soil Environmental Quality Risk Control Standards for Soil Pollution of Construction Land".

[0051] Table 2 Desorption effect of benzo[a]anthracene in soil

[0052]

[0053] The above-mentioned embodiments are only preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A rotary kiln cylinder for thermal desorption of organic polluted soil, characterized in that: The cylinder substrate is made of FeCrAl alloy, and the surface of the substrate is provided with a catalyst coating and an active precursor layer. The catalyst coating is coated on the inner wall of the cylinder substrate, and the active precursor layer is sprayed on the catalyst coating. The catalyst coating is prepared by adding a carrier and an inorganic binder to an organic binder solution and stirring. The carrier is one of SiO2, ZSM-5, SAPO-34, and TiO2.

2. The rotary kiln cylinder for thermal desorption of organic polluted soil according to claim 1, characterized in that: The active precursor layer is an aqueous solution of an active component precursor, an auxiliary agent A precursor, and an auxiliary agent B precursor. The active component precursor is one of manganese nitrate, manganese acetate, and manganese chloride. The auxiliary agent A precursor is one of cerium nitrate, neodymium nitrate, holmium nitrate, and lanthanum nitrate. The auxiliary agent B precursor is one of iron nitrate, nickel nitrate, copper nitrate, and yttrium nitrate.

3. The rotary kiln cylinder for thermal desorption of organic polluted soil according to claim 1, characterized in that: The inorganic binder is one of Al2O3, pseudo-boehmite, attapulgite and sepiolite.

4. The method for preparing a rotary kiln cylinder for thermal desorption of organic polluted soil according to claim 1, characterized in that: The organic binder is one of methyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose.

5. The method for preparing a rotary kiln cylinder for thermal desorption of organic polluted soil according to claim 1, characterized in that: The molar ratio of Mn, Ce / Nd / Ho / La and Fe / Ni / Cu / Y in the active precursor layer is 1:0.2:0.2 to 1:1:

1.

6. The method for preparing a rotary kiln cylinder for thermal desorption of organic polluted soil according to claim 5, characterized in that: The total mass of MnO2, CeO2 / Nd2O3 / Ho2O3 / La2O3 and Fe2O3 / NiO / CuO / Y2O3 in the active precursor layer accounts for 0.5-5% of the total mass of the carrier and the inorganic binder.

7. A method for preparing a rotary kiln cylinder for thermal desorption of organic polluted soil, characterized in that: The method for preparing the cylinder according to any one of claims 2 to 6 comprises the following steps: Step S1, processing the FeCrAl alloy into a cylindrical shape, calcining at 950-1150° C. for 5-15 hours to obtain a cylindrical substrate; Step S2, weighing a carrier and an inorganic binder in a mass ratio of 90:10 to 95:5, adding the mixture to an organic binder solution, stirring until a uniform solution is formed, uniformly coating the solution on the inner wall of the cylinder substrate, drying, and calcining the cylinder substrate at 450 to 550° C. for 3 to 5 hours; Step S3, preparing an aqueous solution of an active component precursor, an auxiliary agent A precursor, and an auxiliary agent B precursor, spraying the solution evenly on the inner wall of the cylinder substrate, and after drying, calcining the cylinder substrate at 350-500° C. for 2-4 hours to obtain a thermal desorption rotary kiln cylinder for organic contaminated soil.

8. The method for preparing a rotary kiln cylinder for thermal desorption of organic polluted soil according to claim 7, characterized in that: In the step S1, calcination is performed in an atmosphere of 0.5 to 5 vol% O2 / N2.

9. The method for preparing a rotary kiln cylinder for thermal desorption of organic polluted soil according to claim 7, characterized in that: In the step S2, the solid-to-liquid ratio of the carrier and inorganic binder mixture to the organic binder solution is 1:5 to 1:10.

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