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

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.