Indirect Thermal Desorption with Two-Section Screw Conveyors
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Solution Overview
Problem
Existing thermal desorption techniques for contaminated soil face issues such as high energy consumption, long remediation cycles, high disposal costs, complexity, and risks of secondary contamination, particularly in the treatment of organic and mercury contaminated soils.
Innovation Solution
An indirect thermal desorption device with two-section screw conveyors, featuring an upper and lower skid with specific components like thermal desorption chambers, screw conveyors, fume jackets, quench spray towers, activated carbon filters, and a combustion chamber, utilizing high-temperature fumes for efficient contaminant separation and recycling waste heat, facilitating continuous and efficient contaminant removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If direct heating is used in thermal desorption, then heating efficiency is improved, but risk of secondary contamination increases and device complexity increases
Solution Approach 1:
The patent introduces an indirect heating system where a heating medium (thermal oil or molten salt) circulates through pipes within the rotary kiln, serving as an intermediary to transfer heat to the contaminated soil without direct contact between the heat source and soil. This eliminates secondary contamination risks while maintaining high heating efficiency through controlled thermal transfer.
2Object-affected harmful factors
If indirect heating is used in thermal desorption, then risk of secondary contamination is reduced, but heating efficiency decreases
Solution Approach 1:
The patent implements a continuous circulation system for the heating medium, where thermal oil or molten salt continuously flows through heating pipes in the rotary kiln, ensuring sustained and efficient heat transfer. The system maintains optimal heating efficiency through continuous thermal energy delivery while preserving the benefits of indirect heating.
3Device complexity
If single-stage screw conveyor is used, then device complexity is reduced, but productivity decreases
Solution Approach 1:
The patent divides the screw conveyor system into two separate sections: a feeding screw conveyor that controls material input rate, and a discharging screw conveyor that removes treated soil. This segmentation enables independent optimization of each conveyor's speed and capacity, significantly increasing overall treatment capability while maintaining manageable system complexity through modular design.
4Productivity
If two-section screw conveyors are used, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent combines two screw conveyors into a single integrated rotary kiln system, where both conveyors operate within the same thermal processing environment. This merging approach achieves high productivity through coordinated dual-conveyor operation while managing complexity through unified system design and shared control mechanisms.
5Productivity
If high treatment capability is achieved, then productivity is improved, but operation cost increases
Solution Approach 1:
The patent implements a waste heat recovery system where exhaust gases from the thermal desorption process are captured and used to preheat the heating medium (thermal oil or molten salt) before it enters the rotary kiln. This recovery of waste heat maintains high treatment capability while significantly reducing operation costs by minimizing energy consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device achieves a contaminant removal rate of over 99.9% with low operation costs, compact design for easy transportation and installation, and efficient heat utilization, addressing the limitations of previous methods.
Implementation Method 1
The thermal desorption technique utilized direct or indirect heat-exchange heating to make the contaminated components in the soil reach a high enough temperature to evaporate and be separated from the soil media
Implementation Method 2
indirect heat-exchange heating to make the contaminated components in the soil reach a high enough temperature
Implementation Method 3
The separated contaminated components are further treated by incineration, adsorption or chemical reaction
Implementation Method 4
The separated contaminated components are further treated by incineration, adsorption or chemical reaction
Data Source
AI summary
An indirect thermal desorption device with two-section screw conveyors, includes: an upper skid and a lower skid below the upper skid. An upper layer thermal desorption chamber, a feeding hopper, an feed airlock, an air pre-heater, a blower; a first quench spray tower, a second quench spray tower, a demister and an induced draft fan are provided in the upper skid. A lower layer thermal desorption chamber, an activated carbon filter tank, a combustion chamber, a discharge hopper and an discharge airlock are provided inside the lower skid. A first screw conveyor is provided in the upper layer thermal desorption chamber, and an upper layer fume jacket is covered on the upper layer thermal desorption chamber. A second screw conveyor is provided in the lower layer thermal desorption chamber, and a lower layer fume jacket is covered on the lower layer thermal desorption chamber.