Method For Thermal Desorption Treatment Of Organic-Contaminated Soil

Abstract

The present disclosure relates to a method for thermal desorption treatment of organic-contaminated soil. The method includes: subjecting thermal desorption flue gas with a temperature of 120-700 C. and the organic-contaminated soil to a countercurrent contact reaction for 5-30 min to obtain desorption waste gas comprising an organic pollutant and thermally desorbed soil; drying biomass to a water content of 12%, and crushing to a length of 20 cm to obtain a biomass segment; uniformly mixing the thermally desorbed soil with the biomass segment to obtain a mixture A, carrying out low-temperature pyrolytic carbonization of the biomass in the mixture A at a temperature of 250-450 C., heating the soil to obtain remedied soil including organic carbon and pyrolysis gas from the low-temperature pyrolytic carbonization. The disclosure mixes the thermally desorbed soil with the biomass for pyrolytic carbonization, greatly improving the content of an organic matter, recovering a soil function.

Claims

1. A method for thermal desorption treatment of organic-contaminated soil, comprising the following specific steps: (1) subjecting thermal desorption flue gas with a temperature of 120-700 C. and the organic-contaminated soil to a countercurrent contact reaction for 5-60 min to obtain desorption waste gas comprising an organic pollutant and thermally desorbed soil; (2) drying biomass to a water content of 12%, and crushing to a length of 20 cm to obtain a biomass segment, wherein the biomass is one or more of crop straw, a weed, a rice husk, a chaff, a shrub branch, a dead tree leaf and sawdust; and (3) uniformly mixing the thermally desorbed soil of the step (1) with the biomass segment of the step (2) to obtain a mixture A, carrying out low-temperature pyrolytic carbonization of the biomass in the mixture A at a temperature of 250-450 C., and heating the soil to obtain remedied soil comprising organic carbon and pyrolysis gas from the low-temperature pyrolytic carbonization.

2. The method for thermal desorption treatment of organic-contaminated soil according to claim 1, wherein in the step (1), the thermal desorption waste gas is high-temperature gas of a burner and/or the pyrolysis gas from the low-temperature pyrolytic carbonization in the step (3).

3. The method for thermal desorption treatment of organic-contaminated soil according to claim 1, wherein in the step (3), a mass ratio of the thermally desorbed soil in the mixture A to the biomass segment is 1:(2-9).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a flowchart of a process according to the present disclosure.

DETAILED DESCRIPTION

[0021] The present disclosure will be further described below with reference to specific implementations.

Example 1: Organic-Contaminated Soil from a Chemical Engineering Site

[0022] As shown in FIG. 1, a method for thermal desorption treatment of organic-contaminated soil includes the following specific steps:

[0023] (1) subject thermal desorption flue gas (high-temperature gas of a burner) with a temperature 500 C. and the organic-contaminated soil to a countercurrent contact reaction for 15 min to obtain desorption waste gas including an organic pollutant and thermally desorbed soil;

[0024] (2) dry biomass (crop straw) to a water content of 12%, and crush to a length of 20 cm to obtain a biomass segment; and

[0025] (3) uniformly mix the thermally desorbed soil of the step (1) with the biomass segment of the step (2) to obtain a mixture A, carry out low-temperature pyrolytic carbonization of the biomass in the mixture A at a temperature of 250 C., and heat the soil to obtain remedied soil including organic carbon and pyrolysis gas from the low-temperature pyrolytic carbonization, where a mass ratio of the thermally desorbed soil in the mixture A to the biomass segment is 1:2.

[0026] After the treatment of the present embodiment, the organic matter removal rate of the soil reaches 98.33%. The results of a planting experiment indicates that under the condition of consistent cultivation and fertilization, the yield of rapeseed planted in the soil before treatment was 200 kg/mu, and the yield of rapeseed planted in the soil after treatment was 580 kg/mu.

Example 2: Organic-Contaminated Soil from a Chemical Engineering Site

[0027] As shown in FIG. 1, a method for thermal desorption treatment of organic-contaminated soil includes the following specific steps:

[0028] (1) subject thermal desorption flue gas (the pyrolysis gas from the low-temperature pyrolytic carbonization in the step (3)) with a temperature 400 C. and the organic-contaminated soil to a countercurrent contact reaction for 20 min to obtain desorption waste gas including an organic pollutant and thermally desorbed soil;

[0029] (2) dry biomass (a mixture of crop straw, a weed, a rice husk, a chaff, a shrub branch, a dead tree leaf and sawdust) to a water content of 10%, and crush to a length of 18 cm to obtain a biomass segment; and

[0030] (3) uniformly mix the thermally desorbed soil of the step (1) with the biomass segment of the step (2) to obtain a mixture A, carry out low-temperature pyrolytic carbonization of the biomass in the mixture A at a temperature of 300 C., heat the soil to obtain remedied soil including organic carbon and pyrolysis gas from the low-temperature pyrolytic carbonization, and return the pyrolysis gas from the low-temperature pyrolytic carbonization to the step (1) for a countercurrent contact reaction with the organic-contaminated soil, where a mass ratio of the thermally desorbed soil in the mixture A to the biomass segment is 1:4.

[0031] After the treatment of the present embodiment, the organic matter removal rate of the soil reaches 97.58%. The results of a planting experiment indicates that under the condition of consistent cultivation and fertilization, the yield of dry rice planted in the soil before treatment was 178 kg/mu, and the yield of dry rice planted in the soil after treatment was 310 kg/mu.

Example 3: Organic-Contaminated Soil from a Chemical Engineering Site

[0032] As shown in FIG. 1, a method for thermal desorption treatment of organic-contaminated soil includes the following specific steps:

[0033] (1) subject thermal desorption flue gas (high-temperature gas of a burner) with a temperature 700 C. and the organic-contaminated soil to a countercurrent contact reaction for 5 min to obtain desorption waste gas including an organic pollutant and thermally desorbed soil;

[0034] (2) dry biomass (a mixture of crop straw, a weed and a rice husk) to a water content of 9%, and crush to a length of 15 cm to obtain a biomass segment; and

[0035] (3) uniformly mix the thermally desorbed soil of the step (1) with the biomass segment of the step (2) to obtain a mixture A, carry out low-temperature pyrolytic carbonization of the biomass in the mixture A at a temperature of 400 C., heat the soil to obtain remedied soil including organic carbon and pyrolysis gas from the low-temperature pyrolytic carbonization, and return the pyrolysis gas from the low-temperature pyrolytic carbonization to the step (1) for a countercurrent contact reaction with the organic-contaminated soil, where a mass ratio of the thermally desorbed soil in the mixture A to the biomass segment is 1:7.

[0036] After the treatment of the present embodiment, the organic matter removal rate of the soil reaches 98.62%. The results of a planting experiment indicates that under the condition of consistent cultivation and fertilization, the yield of rapeseed planted in the soil before treatment was 220 kg/mu, and the yield of rapeseed planted in the soil after treatment was 545 kg/mu.

Example 4: Organic-Contaminated Soil from a Chemical Engineering Site

[0037] As shown in FIG. 1, a method for thermal desorption treatment of organic-contaminated soil includes the following specific steps:

[0038] (1) subject thermal desorption flue gas (mixed gas of high-temperature gas of a burner and the pyrolysis gas from the low-temperature pyrolytic carbonization the step (3)) with a temperature 500 C. and the organic-contaminated soil to a countercurrent contact reaction for 25 min to obtain desorption waste gas including an organic pollutant and thermally desorbed soil;

[0039] (2) dry biomass (a mixture of a weed, a rice husk, a chaff, a shrub branch, a dead tree leaf and sawdust) to a water content of 11%, and crush to a length of 12 cm to obtain a biomass segment; and

[0040] (3) uniformly mix the thermally desorbed soil of the step (1) with the biomass segment of the step (2) to obtain a mixture A, carry out low-temperature pyrolytic carbonization of the biomass in the mixture A at a temperature of 450 C., heat the soil to obtain remedied soil including organic carbon and pyrolysis gas from the low-temperature pyrolytic carbonization, and return the pyrolysis gas from the low-temperature pyrolytic carbonization to the step (1) for a countercurrent contact reaction with the organic-contaminated soil, where a mass ratio of the thermally desorbed soil in the mixture A to the biomass segment is 1:9.

[0041] After the treatment of the present embodiment, the organic matter removal rate of the soil reaches 97.69%. The results of a planting experiment indicates that under the condition of consistent cultivation and fertilization, the yield of dry rice planted in the soil before treatment was 202 kg/mu, and the yield of dry rice planted in the soil after treatment was 345 kg/mu.

Example 5: Organic-Contaminated Soil from a Chemical Engineering Site

[0042] As shown in FIG. 1, a method for thermal desorption treatment of organic-contaminated soil includes the following specific steps:

[0043] (1) subject thermal desorption flue gas (mixed gas of the pyrolysis gas from the low-temperature pyrolytic carbonization the step (3)) with a temperature 120 C. and the organic-contaminated soil to a countercurrent contact reaction for 30 min to obtain desorption waste gas including an organic pollutant and thermally desorbed soil;

[0044] (2) dry biomass (a mixture of a rice husk, a shrub branch, a dead tree leaf and sawdust) to a water content of 10%, and crush to a length of 16 cm to obtain a biomass segment; and

[0045] (3) uniformly mix the thermally desorbed soil of the step (1) with the biomass segment of the step (2) to obtain a mixture A, carry out low-temperature pyrolytic carbonization of the biomass in the mixture A at a temperature of 350 C., heat the soil to obtain remedied soil including organic carbon and pyrolysis gas from the low-temperature pyrolytic carbonization, and return the pyrolysis gas from the low-temperature pyrolytic carbonization to the step (1) for a countercurrent contact reaction with the organic-contaminated soil, where a mass ratio of the thermally desorbed soil in the mixture A to the biomass segment is 1:5.

[0046] After the treatment of the present embodiment, the organic matter removal rate of the soil reaches 98.62%. The results of a planting experiment indicates that under the condition of consistent cultivation and fertilization, the yield of rapeseed planted in the soil before treatment was 230 kg/mu, and the yield of rapeseed planted in the soil after treatment was 562 kg/mu.

[0047] The specific implementations of the present disclosure are described in detail above, but the present disclosure is not limited to the above implementations. Within the knowledge of a person of ordinary skill in the art, various variations can also be made without departing from the spirit of the present disclosure.