Torrefaction Unit for C&D Waste Volume Reduction
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Solution Overview
Problem
Existing methods for processing construction and demolition (C&D) waste are inefficient and costly, particularly in handling large volumes of waste from natural disasters, which overburden landfills and pose environmental and health risks.
Innovation Solution
The implementation of a multistep process involving size reduction and torrefaction to reduce the volume of C&D waste, where a torrefaction unit uses low-temperature heat and an oxygen lean environment to evaporate moisture, reduce debris hardness, and separate volatile compounds, thereby facilitating more efficient packing and disposal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If C&D waste is directly disposed of in landfills, then disposal costs are reduced, but landfill space is quickly depleted and disposal costs increase
Solution Approach 1:
The patent applies preliminary action by processing C&D waste through size reduction and torrefaction before landfill disposal. The waste is pre-treated to reduce its volume and improve its properties, thereby extending landfill life and reducing long-term disposal costs. The torrefaction process is performed in advance to convert the waste into a more compact form suitable for efficient landfill packing.
2Quantity of substance
If C&D waste volume is reduced through size reduction and torrefaction, then landfill space efficiency increases, but processing time and energy consumption increase
Solution Approach 1:
The patent applies parameter changes by conducting torrefaction at low temperatures (100-400°C) for extended periods (0.5-10 hours). This parameter optimization achieves significant volume reduction (20-90%) while managing energy consumption and processing time. The low-temperature approach reduces energy input compared to high-temperature pyrolysis, and the extended time allows for thorough moisture evaporation and hardness reduction.
Solution Approach 2:
The patent applies partial action by selectively targeting specific properties of C&D waste for modification. The size reduction unit reduces particle size to a specific range (0.1-10 mm), and torrefaction selectively removes moisture and reduces hardness without completely carbonizing the material. This partial treatment achieves sufficient volume reduction for landfill efficiency without the excessive energy input required for complete transformation.
3Productivity
If torrefaction is performed at higher temperatures for faster processing, then processing speed increases, but energy consumption and volatile compound emissions increase
Solution Approach 1:
The patent applies parameter changes by operating the torrefaction unit at low temperatures (100-400°C) with extended residence times (0.5-10 hours). This parameter combination achieves effective volume reduction while minimizing energy consumption and volatile emissions. The low-temperature approach contrasts with high-temperature pyrolysis processes that consume more energy and generate greater emissions.
Solution Approach 2:
The patent converts the potentially harmful effect of extended processing time into a benefit by using the extended low-temperature torrefaction to thoroughly evaporate moisture and reduce hardness without generating excessive volatiles. The extended time at low temperature allows for complete moisture removal and property modification while avoiding the energy-intensive and emission-heavy high-temperature approach.
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
This approach achieves a significant reduction in waste volume, typically by 20 to 90%, leading to increased landfill space efficiency, reduced disposal costs, and improved handling and processing of C&D waste, especially in emergency situations.
Implementation Method 1
heating it for at least 0.5 hours in a torrefaction unit operating at a temperature of 100-400° C., wherein the heating evaporates moisture
Implementation Method 2
heating it for at least 0.5 hours in a torrefaction unit operating at a temperature of 100-400° C.
Implementation Method 3
An oxygen lean sweep gas removes the moisture, volatile compounds, and generated ultrafines from the torrefaction vessel
Implementation Method 4
The heated C&D debris feedstock is then transferred to a heat exchanger to produce a cooled torrefied C&D debris feedstock
Data Source
AI summary
Systems and methods for reducing the volume of construction and demolition (C&D) debris waste are described. The systems include a torrefaction unit that reduces the hardness of the waste while degrading it into volatiles and particles having a range of sizes. The variation in particle size allows for a more efficient compaction due to minimal void space and the imparted softness allows for increased compressibility. This results in the processed debris having a much smaller volume than had it not undergone the presently described methods, which reduces landfill tipping fees and extends the life of the landfill.