Wood Drying in CO2 Atmosphere for Rapid Moisture Removal
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Solution Overview
Problem
Current methods for drying wood, such as timber, roundwood, and logs, are inefficient in terms of energy consumption and duration, often requiring extensive processing and struggling to achieve uniform temperature and low residual moisture levels, limiting their industrial applicability.
Innovation Solution
A thermal drying process using a CO2 atmosphere in a drying plant with controlled temperature gradients and CO2 injection, circulation, and recycling, allowing for precise monitoring and adjustment to achieve rapid, energy-efficient drying with a moisture content of less than 5% while maintaining wood integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drying methods are used, then wood can be dried, but energy consumption is high and drying duration is long
Solution Approach 1:
The invention changes the physical-chemical parameters of the drying environment by using CO2 atmosphere instead of conventional air drying. The CO2 environment allows for higher temperature operation (up to 100°C or more) while maintaining controlled humidity levels, enabling rapid drying with lower energy consumption. The specific parameters controlled include CO2 concentration (90-100%), temperature (20-100°C), and humidity (5-95% RH), which together achieve efficient water removal from wood.
Solution Approach 2:
The invention utilizes phase transition of water from liquid to vapor form during the drying process. By controlling temperature and CO2 atmosphere conditions, free water and bound water in the wood are converted to vapor phase and removed efficiently. The process leverages the phase change characteristics to achieve rapid moisture removal while controlling the drying rate to prevent wood damage.
2Productivity
If high temperature is applied to reduce drying time, then drying speed increases, but wood structural integrity is compromised
Solution Approach 1:
The invention changes the drying atmosphere from conventional air to CO2-enriched environment, which allows for higher temperature operation without compromising wood integrity. The CO2 atmosphere modifies the heat and mass transfer characteristics, enabling temperatures of 60-100°C or higher to be applied safely. This parameter change in the drying environment resolves the contradiction between high temperature drying and wood structural preservation.
Solution Approach 2:
CO2 acts as an intermediary substance that mediates between the heat source and the wood material. The CO2 atmosphere serves as a heat transfer medium that distributes thermal energy uniformly throughout the wood load, preventing localized overheating and structural damage. The CO2 environment also controls humidity levels, acting as a buffer that protects wood structure while enabling efficient drying.
3Quantity of substance
If temperature is increased to achieve low residual moisture, then moisture content decreases, but temperature uniformity in wood core is difficult to maintain
Solution Approach 1:
The invention changes multiple parameters simultaneously: CO2 concentration (90-100%), temperature (20-100°C), and relative humidity (5-95%). This multi-parameter control allows the system to achieve low residual moisture content (below 5%) while maintaining temperature uniformity in the wood core. The CO2 atmosphere specifically enhances heat penetration and distribution, resolving the contradiction between moisture removal and temperature uniformity.
Solution Approach 2:
The invention implements continuous circulation and recirculation of the CO2 atmosphere throughout the drying chamber, ensuring continuous and uniform heat distribution to all parts of the wood load. The system maintains continuous monitoring and adjustment of temperature, humidity, and CO2 concentration, providing uninterrupted useful action that achieves uniform drying throughout the wood core while removing residual moisture effectively.
4Productivity
If conventional drying processes are used, then drying can be performed, but the process duration is several days which limits industrial application
Solution Approach 1:
The invention changes the drying atmosphere parameters to CO2-enriched environment with controlled temperature (20-100°C) and humidity (5-95% RH), which dramatically accelerates the drying process. This parameter change enables industrial-scale drying to be completed in hours rather than days, making the process economically viable for industrial application. The CO2 atmosphere specifically enhances mass transfer rates, reducing drying time while maintaining quality.
Solution Approach 2:
The invention replaces the conventional air-based drying mechanism with a CO2-based drying system that utilizes different heat and mass transfer mechanisms. The CO2 atmosphere provides superior thermal conductivity and mass transfer characteristics compared to air, enabling rapid drying suitable for industrial production. This substitution of the drying medium fundamentally changes the drying kinetics, reducing process duration from days to hours.
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 process enables rapid, energy-efficient drying of wood with a moisture content of less than 5%, suitable for industrial scale, while ensuring the structural integrity of the wood through precise temperature and humidity control.
Implementation Method 1
injecting a coolant gas comprising CO2 at a selected pressure and temperature into the drying chamber; forcing the circulation of the coolant gas through the drying chamber; heating the coolant gas circulating in the drying chamber... to extract the free water from the wood... extraction of the bound water specific to the wood to be dried
Data Source
AI summary
The invention relates to a process for the thermal drying of wood using a drying plant comprising:a drying chamber (1);means for supplying CO2 (3) at a selected pressure and temperature;circulation means (307, 203) for forcing the circulation of the gaseous fluid;heating means (2) for heating the gaseous heat transfer fluid;extraction means (4) for extracting the air inside the drying chamber 1; metrology means (5) for measuring variations in the physical measurements of the drying plant during heating; andoperating means (6) for controlling the means used according to programs, adapted to the quality of the dried wood sought, and processing means for readjusting the operating parameters.