Multi-Layer Air Dryer for Wood Chip Moisture Control
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Solution Overview
Problem
Existing block manufacturing processes face inefficiencies in achieving low residual moisture content in chip material, leading to suboptimal extrusion processing and block quality.
Innovation Solution
A multi-layer continuous air dryer system is employed, where chip layers with varying moisture content are arranged vertically, allowing dry air to progressively adjust its moisture content, and the air flow direction is opposite to the chip movement, optimizing thermal energy utilization and moisture absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-layer dryer with parallel drying lines is used, then the drying process can be performed with simple structure, but the residual moisture content cannot be reduced sufficiently (only down to 6% dry matter)
Solution Approach 1:
The drying system is divided into multiple drying lines (at least two) with different drying air temperatures. Each drying line operates independently with its own conveyor belt and drying chambers, allowing simultaneous drying of different chip layers at different temperature levels to achieve both low residual moisture and manageable structural complexity
Solution Approach 2:
The invention transitions from a single-layer drying approach to a multi-layer vertical stacking configuration. Chip material is distributed across multiple conveyor belts stacked vertically, with drying air flowing through each layer separately. This three-dimensional arrangement enables progressive moisture removal while maintaining a compact footprint
2Productivity
If high temperature drying air is used throughout, then drying speed increases, but thermal energy is wasted and chip material may be overheated
Solution Approach 1:
Different regions of the drying system (different drying lines and drying chambers) are assigned different air temperatures based on local needs. Fresh hot air enters at higher temperatures for initial rapid drying, while subsequent layers receive progressively cooler air. This localized temperature control optimizes both drying speed and energy efficiency
Solution Approach 2:
The drying air temperature parameter is dynamically adjusted across different drying stages and lines. The system utilizes a temperature gradient where earlier drying chambers receive higher temperature air and later chambers receive lower temperature air, optimizing the drying rate at each stage while minimizing energy waste
3Manufacturing precision
If multiple drying lines with different temperatures are used, then optimal drying effect is achieved, but the system complexity and air flow control difficulty increase
Solution Approach 1:
The air supply system is segmented into independent control units for each drying line and drying chamber. Each segment has its own air inlet, flow control mechanism, and temperature regulation, allowing individual optimization without affecting other parts of the system. This modular approach manages complexity while maintaining precise drying control
Solution Approach 2:
The air flow system is designed to be dynamically adjustable, with controllable air inlets and flow regulators that can adapt to different operating conditions. The system can modify air flow rates and temperatures in real-time based on moisture content requirements, enabling flexible response to varying drying needs across different chip layers
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 low residual moisture content of 2-4% in the dried chip material, enhancing extrusion processing and resulting in blocks with high compressive, impact, and fracture strength.
Implementation Method 1
a multi-layer continuous air dryer (22) is employed, where chip layers with varying moisture content are arranged vertically, allowing dry air to progressively adjust its moisture content
Implementation Method 2
the air flow direction is opposite to the chip movement, optimizing thermal energy utilization and moisture absorption
Implementation Method 3
a heated dry air stream through several, e.g. two, chip layers (23, 24) formed from the chip material (2) one after the other
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a system (1) and a method for producing blocks (3) from a binder-containing chip material (2) made from small plant parts, in particular small wood parts. The system (1) comprises an extrusion unit (10) and an upstream drying unit (4) with an air dryer (21) for the chip material (2). The air dryer (21) directs a heated dry air stream (32) through the chip material (2). It is designed as a multi-layer continuous dryer (22) in which the dry air stream (32) flows through several layers of chip material (23, 24) with different moisture contents successively, in particular directly one after the other.