Wood Fiber Defibration Screw Thread Configuration
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Solution Overview
Problem
Existing installations for preparing wood fibers for cultivation substrates face challenges in achieving effective sterilization and decontamination while preserving the fibers' moisture retention capacity, often requiring complex and energy-intensive processes.
Innovation Solution
An installation with two parallel screws featuring specific thread configurations, including upstream and downstream braking zones with varying notch sizes and an intermediate series, operates at optimized pressures and temperatures to decontaminate wood chips into fibers within a short transit time without external heating or cooling, achieving a porosity of 85-97% and effective decontamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If external heating or cooling is used to control temperature, then temperature control is improved, but device complexity and energy consumption increase
Solution Approach 1:
The system uses the kinetic energy generated during the mechanical defibration process itself to raise the temperature of the wood chips to sterilizing levels (60-120°C). The friction and compression from the rotating screws with different thread configurations naturally heat the material, eliminating the need for external heating or cooling systems.
Solution Approach 2:
The patent replaces thermal processing systems (heaters and coolers) with a mechanically-driven thermal process. The mechanical action of the screws with specific thread configurations generates heat through friction and compression, substituting the need for separate thermal control equipment.
2Temperature
If external heating or cooling is used to control temperature, then temperature control is improved, but energy consumption increases
Solution Approach 1:
The system uses the kinetic energy generated during the mechanical defibration process itself to raise the temperature of the wood chips to sterilizing levels (60-120°C). The friction and compression from the rotating screws with different thread configurations naturally heat the material, eliminating the need for external heating or cooling systems.
Solution Approach 2:
The patent replaces thermal processing systems (heaters and coolers) with a mechanically-driven thermal process. The mechanical action of the screws with specific thread configurations generates heat through friction and compression, substituting the need for separate thermal control equipment.
3Reliability
If treatment time is extended to ensure decontamination, then decontamination effectiveness is improved, but productivity decreases
Solution Approach 1:
The patent changes the parameters of pressure and temperature dynamically during the defibration process. By using screws with different thread configurations (forward threads in drive zones, reverse threads with notches in braking zones), the system creates zones of high pressure and high temperature that effectively sterilize the material quickly, achieving decontamination within the normal processing time.
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 solution enables efficient sterilization and decontamination of wood fibers at temperatures up to 150°C, maintaining their moisture retention capacity and achieving high porosity without energy-intensive processes, while ensuring the fibers are aerated and free from harmful microorganisms.
Implementation Method 1
two parallel screws turning in the same direction and meshing with each other... threads that are successively forward and reverse threads... drive zones and of compression zones
Implementation Method 2
compression zones... pressure upstream from the braking downstream zone of the upstream series is of the order of 90 bars or more
Implementation Method 3
the combination of these parameters makes it possible naturally to obtain a temperature of the order of in the range 120°C to 150°C, without supplying external heat
Implementation Method 4
pressure upstream from the braking downstream zone of the upstream series is of the order of 90 bars or more... temperature of the order of in the range 120°C to 150°C
Implementation Method 5
the above-mentioned ratio RSO of the sum of the sections of the notches of a thread to the fiber output rate makes it possible to obtain fibers that are aerated. Thus, for maritime pine, a porosity of greater than 85%, and in particular lying in the range 85% to 97% is obtained
Data Source
AI summary
The installation comprises a defibration sheath with an inlet for wood chips, an outlet for fibers, and two parallel rotative screws. The screws mesh with each other via their respective threads, which have at least an upstream and a downstream series of segments, with a drive upstream zone having forward threads, and a braking downstream zone having reverse threads with notches that are smaller in the braking downstream zone of the downstream series than in the braking downstream zone of the upstream series. The number of notches per thread in each braking zone is 2 to 6, and the section-to-output ratio RSO of the sum of the sections of the notches of a thread of the braking downstream zone of the downstream series to the fiber output rate is 60 mm2/m3h−1 to 80 mm2/m3h−1.