Multiple Hearth Torrefaction Heating Using Steam Drum Hot Water
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Solution Overview
Problem
Existing torrefaction processes using thermal oil as a heat transfer medium require large inventories, pose environmental hazards, and involve complex control systems due to the coupling of torrefaction furnaces with oxidizing units, necessitating auxiliary fuels and cooling systems.
Innovation Solution
A torrefaction unit utilizing a multiple hearth furnace heated by a water or steam heat transfer fluid, decoupling the control of the torrefaction furnace from the partial oxidation reactor, and integrating a steam drum for indirect thermal energy use, allowing retrofitting into existing facilities without thermal oil cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal oil is used as heat transfer medium, then heating capability is achieved, but large inventory is required and environmental hazards arise
Solution Approach 1:
The patent replaces thermal oil with water as the heat transfer medium. Water is inherently safer, environmentally friendly, and does not require large inventories or special safety measures. The system uses water/steam cycles that are readily available and can be integrated with existing facilities, eliminating the hazards associated with thermal oil while maintaining effective heating capability for torrefaction processes.
2Loss of energy
If torrefaction furnace is coupled with oxidizing unit, then heat recovery is achieved, but control complexity increases
Solution Approach 1:
The patent separates the torrefiction furnace from the oxidizing unit, allowing them to operate independently. The torrefaction furnace uses water/steam for heating while the oxidizing unit processes torrefaction gas separately. This segmentation simplifies control by eliminating the need for complex coordination between coupled systems, while heat recovery is still achieved through the water/steam cycle that can be integrated with existing steam systems.
3Temperature
If thermal oil cycle is implemented, then heating system is established, but apparatus expense increases
Solution Approach 1:
The patent utilizes existing water/steam cycles and infrastructure in industrial facilities for heating purposes. Instead of implementing a dedicated thermal oil cycle with all its associated equipment (reservoirs, pumps, heat exchangers, safety systems), the system leverages the universally available water/steam infrastructure. This multi-functional approach reduces apparatus expense by repurposing existing facilities while maintaining effective heating capability for torrefaction.
4Reliability
If auxiliary fuel and cooler are provided, then all circumstances are covered, but device complexity increases
Solution Approach 1:
The patent employs a water/steam heat transfer system that inherently provides process stability without requiring auxiliary fuel or complex cooling systems. Water/steam cycles are self-regulating and can naturally handle heat load variations. The system integrates with existing steam infrastructure that already has built-in control mechanisms, eliminating the need for additional auxiliary equipment while maintaining reliability and process stability.
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 reduces apparatus costs, simplifies control efforts, minimizes environmental risks, and enables efficient production of syngas for further chemical synthesis, while maintaining process stability and flexibility.
Implementation Method 1
a heating system which can be flown through by a heat transfer fluid, wherein the heating system is connected to a water circuit by which water is heatable and conveyable through the heating system
Implementation Method 2
Torrefaction is understood as a process in which material such as waste is heated to temperatures of up to 300° C. in the absence of oxygen. The products of this torrefaction are a torrefaction gas comprising water, carbon monoxide, carbon dioxide, smaller oxygenated hydrocarbons and tars, and the charred solids remaining from the waste.
Implementation Method 3
a partial oxidation reactor including a burning chamber being connected to the at least one multiple hearth furnace for the partial oxidation of torrefaction gas with oxygen creating a syngas
Data Source
AI summary
The torrefaction unit 1 comprises at least one multiple hearth furnace 2 which is heated by a heat transfer fluid 16 comprising hot water taken from a water space 21 of a steam drum 11. The heat transfer fluid 16 is guided through a water circuit 20 to a heating system 19 of the at least one multiple hearth furnace 2. This means the multiple hearth furnace 2 is heated to a torrefaction temperature indirectly by the use of hot water as heat transfer fluid 16. This is environmentally advantageous. The torrefaction gas 3 created by the torrefaction of material comprising biomass such as municipal solid waste is preferably partially oxidized in a partial oxidation reactor 23 for creating syngas. Preferably, a part of the thermal energy of the syngas is used in an evaporator 9 and/or a superheater 13 to heat water and/or steam and/or to evaporate water. The evaporated water is preferably guided to a steam space 22 of the steam drum 11 and can, thus, be used to heat the heat transfer fluid 16. The partial oxidation reactor 23 and the temperature of the heat transfer fluid 16 can be controlled independently allowing to one single partial oxidation reactor 23 for at least two multiple hearth furnaces 2.