Hot air circulation type indirect thermal desorption-based soil remediation system and method

Patent metadata

Field	Value
Publication number	US-11697142-B2
Application number	US-202117545941-A
Country	US
Kind code	B2
Filing date	Dec 8, 2021
Priority date	Dec 8, 2020
Publication date	Jul 11, 2023
Grant date	Jul 11, 2023

Abstract

A hot air circulation type indirect thermal desorption-based soil remediation system and method, belonging to the technical field of soil remediation. The system includes a thermal desorption reactor, a dust remover, a hot air circulating fan, a hot air heater, an air preheater, a combustion fan and a combustion device. By using thermal desorption gas generated by soil being heated and volatilized as a heat transfer medium and by a circular heating manner, hot air efficiently transfers heat to the soil by contact, and the high-temperature fume is kept from direct contact with the soil, so the system has the advantages of high treatment capacity, small equipment scale and the like.

First claim

What is claimed is:

1. A hot air circulation type indirect thermal desorption-based soil remediation method, the method comprising:
generating thermal desorption offgas by heating contaminated soil inside a drum of a thermal desorption reactor, the thermal desorption offgas serving as an initial source of circulating hot air, the hot air flowing to a dust remover through a circulating hot air outlet of the drum, subjecting the hot air to dust removal and driving the hot air by a hot air circulating fan, heating a part of the hot air to 550-650° C. by a hot air heater through indirect heat exchange, returning to the inside of the drum through a circulating hot air inlet of the drum, transferring heat to the contaminated soil by direct countercurrent contact such that the temperature drops to 380-420° C., and carrying the thermal desorption offgas generated by the contaminated soil being heated, wherein a part continues to be recycled in a hot air circulation loop, and a remaining part is discharged after being purified;
combusting fuel in a combustion device to generate fume with a high temperature of 950-1050° C., and subjecting the fume to indirect heat exchange with the circulating hot air through the hot air heater such that the temperature drops to 700-800° C., the fume then entering a fume channel in the reactor through a fume inlet of a heat insulation cover, being subjected to indirect heat exchange with the contaminated soil in the drum such that the temperature drops to about 350-450° C., then flowing to an air preheater through a fume outlet of the heat insulation cover, being subjected to indirect heat exchange with room-temperature air such that the temperature drops to 150-250° C., and being finally discharged to the atmosphere through a chimney, wherein the fume does not contact the soil and the circulating hot air; and
feeding room-temperature raw soil into a feed end of the drum by a feeding device, directly heating the room-temperature raw soil by the hot air inside the drum and indirectly heating the room-temperature raw soil by the fume outside the drum in the process of rotating along with the drum and moving toward a discharge end such that the temperature gradually rises to about 300-500° C., volatizing water and organic contaminants in the soil into a gaseous state and carrying dust to become the thermal desorption offgas that is separated from the solid soil, and discharging the treated soil through a soil outlet of a discharge end fixed hood.

2. The hot air circulation type indirect thermal desorption-based soil remediation method according to claim 1 , wherein the method further comprises passing the remaining part of the circulating hot air from an outlet of the hot air circulating fan through a catalytic oxidation device, the organic contaminants undergo thermal oxidation reaction at 380-420° C. to become carbon dioxide and water vapor, subjecting the mixture to indirect heat exchange with circulating cooling water through a condenser so as to be cooled and condensed to 55-65° C., and driven by an induced draft fan, and is finally discharging the mixture to the atmosphere through an exhaust funnel.

3. The hot air circulation type indirect thermal desorption-based soil remediation method according to claim 1 , further comprising subjecting the room-temperature air passing through the air preheater to indirect heat exchange with the fume at the fume outlet of the heat insulation cover such that the temperature rises to 150-250° C., and driving the room-temperature air by a combustion fan to the combustion device to serve as combustion-supporting air for the combustion of the fuel, thereby realizing reuse of waste heat.

4. The hot air circulation type indirect thermal desorption-based soil remediation method according to claim 1 , further comprising subjecting clean water, serving as circulating water, to indirect heat exchange with the offgas at an outlet of the catalytic oxidation device through the condenser such that the circulating water is heated to 40-60° C., and then cooling the circulating water to about 35° C. by a cooling tower and driving the circulating water by a circulating pump to be recycled.

5. The hot air circulation type indirect thermal desorption-based soil remediation method according to claim 1 , wherein a rotating speed of the drum body is 0.4-10 r/min, and a soil filling factor in the drum body does not exceed 0.25.

6. The hot air circulation type indirect thermal desorption-based soil remediation method according to claim 1 , further comprising continuously generating the thermal desorption offgas with the continuous treatment of the soil, wherein the circulating hot air carries the thermal desorption offgas and is mixed therewith, the amount of gas, 65-90% of the gas in the drum serving as the circulating hot air is recycled in a first fume passage, and the remaining gas enters the catalytic oxidation device and the condenser through a branch of the outlet of the hot air circulating fan and is discharged after being purified.

7. A hot air circulation type indirect thermal desorption-based soil remediation system realized by using the method according to claim 1 , wherein the system comprises:
a thermal desorption reactor;
a drum is-disposed in an inner cavity of the thermal desorption reactor, wherein:
the thermal desorption reactor is provided with two fume passages,
the first fume passage is a heating system inside the drum,
the system is composed of a circulating hot air outlet of the drum, a dust remover, a hot air circulating fan, a hot air heater and a circulating hot air inlet of the drum that are connected sequentially, and
the second fume passage is a heating system used outside the drum, and the system is composed of a fume outlet of the thermal desorption reactor, an air preheater, a combustion fan, a combustion device, the hot air heater and a fume inlet of the thermal desorption reactor that are connected sequentially.

8. The hot air circulation type indirect thermal desorption-based soil remediation system according to claim 7 ,
wherein an outer peripheral side of the drum is provided with a heat insulation cover, one end of the drum is provided with a feed end fixed hood and a feeding device, and the other end is provided with a discharge end fixed hood, and
wherein the feeding device is provided with a raw soil inlet, the feed end fixed hood is provided with a circulating hot air outlet, the heat insulation cover is provided with a fume inlet near a discharge end, and provided with a fume outlet near a feed end, and the discharge end fixed hood is provided with a circulating hot air inlet and a treated soil outlet.

9. The hot air circulation type indirect thermal desorption-based soil remediation system according to claim 7 , wherein the hot air circulating fan is further provided with an output end that is connected to a condenser through a catalytic oxidation device, a cooling tower and a circulating pump are provided above the condenser, and a heat exchange process of the water in the condenser and the cooling tower is realized through the circulating pump.

10. The hot air circulation type indirect thermal desorption-based soil remediation system according to claim 7 , wherein an included angle between an axis of a drum body of the drum and the horizontal plane is generally 0-6°, or there is a guide device leaning to the discharge end inside.

Assignees

• Cssc Nanjing Luzhou Environment Prot Co Ltd
• Nanjing University Of Technology
• Nanjing Institute Of Environmental Seciences Mini Of Ecology And Environment Of The Peoples Republic
• Nanjing Institute Of Environmental Sciences Mini Of Ecology And Environment

Inventors

• Zhou Yongxian
• Chen Jisai
• Xu Haitao
• Zhang Shengtian
• Wang Hongqi
• Wu Qinrui
• Zhang Yongliang
• Ling Xiang

Classifications

• B09C1/065 Primary

  by pyrolysis · CPC title