Biomass Torrefaction Reactor Oxygen Injection Control
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Solution Overview
Problem
Current torrefaction methods face challenges in achieving precise temperature control, leading to inefficient heating, inhomogeneous biomass treatment, and the risk of over-torrefaction, which results in energy loss and safety issues due to the exothermic nature of the process, especially in continuous industrial settings.
Innovation Solution
A method involving the injection of oxygen underneath or inside a biomass bed in a reactor, where the oxygen supply is controlled to maintain a target temperature between 220 °C and 330 °C, using both external heat transfer and reaction with oxygen to ensure homogeneous heating and prevent excessive torrefaction, with oxygen injection locations and flow rates adjusted to manage temperature and exothermic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If oxygen is added to the reaction gas volume above the biomass bed to combust combustible gasses and obtain additional heat, then heating efficiency is improved, but heat transfer to biomass becomes inefficient and temperature control precision deteriorates
Solution Approach 1:
The patent extracts the combustion process from the gas phase above the biomass bed and relocates it to the solid-liquid interface by injecting oxygen directly into the biomass bed. This separates the heat generation function (combustion) from the heat transfer medium (gas phase), allowing combustion to occur where heat can be directly transferred to biomass particles through conduction and convection, thereby improving both heating efficiency and temperature control precision.
Solution Approach 2:
The patent introduces oxygen injection as an intermediary mechanism that mediates between the external heat source and the biomass. By controlling oxygen flow rate and injection position, the system creates a controlled exothermic reaction zone within the biomass bed that acts as an intermediate heat transfer stage, improving overall heat transfer efficiency while enabling precise temperature control through oxygen flow regulation.
2Stability of the object's composition
If thermal treatment temperature is increased to achieve desired brittleness and hydrophobicity, then biomass properties are improved, but energy content is lost due to over-torrefaction
Solution Approach 1:
The patent implements feedback control by continuously monitoring biomass temperature and adjusting oxygen injection rate accordingly. The control system uses temperature sensors to detect the actual torrefaction temperature and modulates oxygen flow to maintain the temperature within the optimal range (200-300°C), preventing both under-torrefiction (insufficient brittleness) and over-torrefiction (excessive energy loss), thereby optimizing the balance between biomass property improvement and energy content preservation.
Solution Approach 2:
The patent changes the key parameter of oxygen concentration from zero (traditional torrefiction) to a controlled positive value, transforming the process from purely endothermic to a combination of endothermic and exothermic reactions. This parameter change enables precise temperature control and allows operation at optimal torrefiction temperatures without excessive energy input, improving both biomass properties and energy efficiency.
3Temperature
If oxygen injection rate is increased to control temperature upward, then target temperature is reached, but risk of thermal runaway and over-torrefiction increases
Solution Approach 1:
The patent applies dynamic control by making the oxygen injection rate a variable parameter that continuously adjusts in response to real-time temperature measurements. Rather than using a fixed oxygen flow rate, the system dynamically modulates oxygen supply based on the difference between actual and target temperature, enabling stable temperature control while preventing thermal runaway through automatic reduction of oxygen input when temperature approaches the upper limit.
Solution Approach 2:
The patent implements beforehand cushioning by setting the oxygen injection rate to approach but not exceed the threshold that would cause thermal runaway. The control system maintains oxygen flow at levels that provide sufficient heating power to reach target temperature while leaving a safety margin below the critical oxygen concentration that would trigger uncontrolled exothermic reactions, thereby preventing thermal runaway before it can occur.
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 allows for more efficient and precise control of the torrefaction process, producing homogeneously treated biomass with enhanced energy density, reduced risk of over-torrefaction, and self-sustaining thermal energy, minimizing external energy requirements and ensuring safer operation.
Implementation Method 1
the decomposition reactions during torrefiction, even in an oxygen free atmosphere, can be strongly exothermic, at least for most types of biomass, leading to an uncontrolled temperature increase of 30 to 40 °C of the biomass undergoing torrefiction
Implementation Method 2
oxygen is added to this volume above the biomass to combust the combustible gasses therein and thereby obtain additional heat to enhance heating of the biomass
Implementation Method 3
in the reactor the biomass is heated by means of heat transfer from an external heat source, meaning external to the reactor but not necessarily external to the method, through a reactor wall
Implementation Method 4
in the case that this combustion occurs above the bed, only a fraction of this heat is transferred to the biomass
Data Source
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AI summary
Method for torrefying biomass (28) whereby the method comprises a torrefaction step in which said biomass (28) is thermally treated at a temperature between 220 ºC and 330 ºC in a reactor (3), whereby the biomass (28) is present as a bed (29) of particles of biomass (28), whereby in the torrefaction step oxygen (30), is injected into said reactor (3), whereby said oxygen (30) is injected into said reactor (3) underneath said bed (28) or inside said bed (28), whereby in the reactor (3) the biomass (28) is heated by means of heat transfer through a reactor wall (7), whereby in the reactor (3) the biomass (28) is also heated by reaction with said oxygen (30), whereby a temperature of the biomass (28) in said reactor (3) is controlled, whereby the amount of oxygen (30) that is injected is used for controlling said temperature.