Systems and methods for thermal treatment of contaminated material

Patent metadata

Field	Value
Publication number	US-10137486-B1
Application number	US-201815906175-A
Country	US
Kind code	B1
Filing date	Feb 27, 2018
Priority date	Feb 27, 2018
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

Contaminant-containing soil can be remediated by subjecting the soil to microwave irradiation to heat the soil to a combustion temperature of from 150° C. to 1200° C. to initiate combustion. A target amount of the contaminant in the soil is destroyed. An oxidizer gas can be flowed through the soil using a gas blower and at least one gas injection line and controlled at a rate such that a self-sustaining smoldering combustion front is formed that moves through the soil. A microwave absorber additive can be added to the soil to accelerate the heating of the soil. At least one waveguide connected to a source of microwave energy directs microwaves into the soil.

First claim

What is claimed is:

1. A method for treating porous media containing an undesired organic substance, comprising:
a. providing a volume containing the porous media and the undesired organic substance;
b. adding a microwave absorber to the volume to thereby form a volume of a mixture to accelerate microwave heating of the volume of the mixture;
c. subjecting a portion of the volume of the mixture to microwave irradiation to heat the portion of the volume of the mixture to a combustion temperature of from 150° C. to 1200° C.;
d. initiating smoldering combustion in the portion of the volume of the mixture;
e. terminating the microwave irradiation once the smoldering combustion in the portion of the volume of the mixture is initiated;
f. initiating a flow of an oxidizer gas through the portion of the volume of the mixture once the smoldering combustion in the portion of the volume of the mixture is initiated and controlling the flow at a rate such that a self-sustaining smoldering combustion front is formed that moves through remaining additional portions of the volume of the mixture; and
g. continuing the flow of the oxidizer gas until a target amount of the undesired organic substance in the volume of the mixture reaches a destructive temperature and is thereby destroyed.

2. The method of claim 1 wherein the portion of the volume of the mixture is subjected to microwave irradiation and the flow of the oxidizer gas by placing at least one dual function waveguide/gas injection line into the volume of the mixture and connecting the at least one dual function waveguide/gas injection line to a source of microwave energy and to a gas blower.

3. The method of claim 1 wherein the destructive temperature is at least 150° C.

4. The method of claim 1 wherein the undesired organic substance comprises a halogen-containing hydrocarbon.

5. The method of claim 1 wherein the undesired organic substance is selected from the group consisting of petroleum hydrocarbons, volatile organic compounds, hexachlorobenzene, tetrachloroethene and combinations thereof.

6. The method of claim 1 wherein the porous media comprises native soil, sludge, drill cuttings, sediment, and/or industrial waste.

7. The method of claim 1 wherein the microwave absorber comprises organic material, inorganic material, and/or soil rich in clay.

8. The method of claim 1 wherein the microwave absorber organic material comprises carbon nanomaterials and/or coker coke.

9. The method of claim 1 wherein the inorganic material comprises magnetite, ferrite and/or iron carbonyl containing compound.

10. The method of claim 1 wherein the microwave absorber is added to the mixture at a rate of from 0.1 to 10% of the mixture by weight.

11. The method of claim 1 wherein the microwave absorber has a dielectric constant of greater than 5 and a loss tangent greater than 0.02.

12. The method of claim 1 wherein the oxidizer gas flow is controlled by a gas blower and the oxidizer gas flows through the mixture at an average velocity of from 0.5 cm/sec to 7 cm/sec.

13. The method of claim 1 wherein the oxidizer gas comprises air.

14. The method of claim 1 wherein the volume of the mixture is subjected to microwave irradiation in step (b) by exposing the volume of the mixture to microwaves having a wave frequency of from 0.1 to 10 GHz.

15. The method of claim 1 wherein the volume of the mixture is subjected to microwave irradiation in step (b) by exposing the volume of the mixture to microwaves emitted from apertures in at least one waveguide connected to a source of microwave energy wherein the at least one waveguide is located below the volume of the mixture.

16. The method of claim 1 wherein the microwave irradiation is terminated 5 minutes to 1 hour after the microwave irradiation of step (c) is begun.

17. The method of claim 1 wherein the microwave absorber comprises carbon nanofiber added to the mixture at a rate of 0.1% of the mixture by weight.

18. The method of claim 1 wherein the portion of the volume of the mixture comprises at least 2 inches in height of the volume of the mixture.

19. A system for treating porous media containing an undesired organic substance, comprising:
a. a source of microwave absorber to add to a volume containing the porous media and the undesired organic substance to thereby form a volume of a mixture to accelerate microwave heating of the volume of the mixture;
b. a source of microwave energy capable of generating microwaves having a wave frequency of from 0.1 to 10 GHz for irradiating a portion of the volume of the mixture to heat the mixture to a combustion temperature of from 150° C. to 1200° C. to initiate smoldering combustion in the mixture;
c. at least one waveguide connected to the source of the microwave energy, wherein each of the waveguides has a plurality of apertures for directing microwaves into the portion of the volume of the mixture;
d. a gas blower for providing a flow of an oxidizer gas through the portion of the volume of the mixture;
e. at least one gas injection line connected to the gas blower;
f. a temperature sensor for monitoring a temperature of the portion of the volume of the mixture; and
g. a control system connected to the temperature sensor and in communication with the gas blower for initiating the flow of the oxidizer gas through the portion of the volume of the mixture once the smoldering combustion in the portion of the volume of the mixture is initiated and for controlling the flow at a rate such that a self-sustaining smoldering combustion front is formed that moves through remaining additional portions of the volume of the mixture.

20. The system of claim 19 wherein the microwave absorber comprises carbon nanofiber.

21. The system of claim 19 wherein the at least one waveguide is located below the mixture and the microwave absorber, the plurality of apertures is located in a top side of the at least one waveguide, and the at least one gas injection line is located below the mixture and the microwave absorber, and further comprising a grate located above the at least one waveguide and the at least one gas injection line for supporting the mixture and the microwave absorber.

22. The system of claim 19 further comprising a solid or liquid oxygen source to be included in the mixture that releases oxygen gas during the heating of the mixture.

23. The system of claim 19 further comprising a flexible tarp flexible tarp and/or a layer of soil for covering the mixture during the smoldering combustion of the mixture.

24. The system of claim 19 wherein the at least one waveguide and the at least one gas injection line are at least one dual function waveguide/gas injection line wherein each dual function waveguide/gas injection line is connected to the source of the microwave energy and the gas blower.

25. The system of claim 24 wherein the at least one dual function waveguide/gas injection line is positioned in the mixture and the microwave absorber in a generally vertical position; and the plurality of apertures are positioned in a lower end of the at least one waveguide.

Assignees

• Chevron Usa Inc

Inventors

• Kamath Roopa
• Smith Schaun Malcolm
• Kong Deyuan
• Dieckmann Gunther H
• Ovalles Cesar

Classifications

• B09C1/065 Primary

  by pyrolysis · CPC title

• B09C1/06 Primary

  thermally · CPC title