Lyocell Fiber Dissolution via Segmented Thin-Film Evaporation
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Solution Overview
Problem
Current methods for producing lyocell fibers are limited by suboptimal dissolvers that restrict production capacity to less than 100 metric tons per day, as they fail to ensure adequate swelling and homogenization of natural fibers, leading to inefficient spinning solution formation.
Innovation Solution
The process is optimized by subdividing the dissolution of pulp in NMMO into three sections, combining a thin-film evaporator for high-rate water evaporation with a thick-layer dissolver for homogenization, and incorporating a multi-stage pilot plant with direct communication between devices, along with back-dilution and concentration control using optical index monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a vertical thin-film dissolver is used, then heat-transfer performance is improved, but residence time is insufficient leading to inadequate fiber swelling and homogenization
Solution Approach 1:
The dissolution process is divided into two distinct stages: a vertical thin-film dissolver for rapid water evaporation and a horizontal thick-layer dissolver for extended residence time and homogenization. This segmentation allows each device to be optimized for its specific function, resolving the contradiction between heat-transfer performance and residence time.
2Duration of action of moving object
If a horizontal thick-layer dissolver is used, then residence time is improved leading to good homogenization, but device size becomes excessively large limiting production capacity
Solution Approach 1:
The process is segmented into two stages with different device configurations. The vertical thin-film dissolver handles the water evaporation stage with high productivity, while the horizontal thick-layer dissolver handles the homogenization stage. This segmentation allows the system to achieve both long residence time and high production capacity.
Solution Approach 2:
The solution transitions from a single horizontal thick-layer dissolver to a two-dimensional arrangement combining vertical and horizontal dissolvers. This dimensional change allows the system to achieve the same homogenization effect with reduced overall device size and increased production capacity.
3Device complexity
If single-stage dissolvers are used, then device complexity is reduced, but production capacity is limited to less than 100 metric tons per day
Solution Approach 1:
The dissolution process is segmented into two distinct stages with different device configurations. The vertical thin-film dissolver handles rapid water evaporation, while the horizontal thick-layer dissolver handles homogenization. This segmentation enables the system to achieve high production capacity of more than 100 metric tons per day while maintaining manageable device complexity through functional specialization.
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 enables a balanced equilibrium, increasing production capacity beyond 100 metric tons per day by ensuring effective swelling, homogenization, and viscosity management, making the process more efficient and competitive with viscose or modal production.
Implementation Method 1
In the thin-film evaporator (2), heat is added to effect intensive evaporation of water from the suspension
Implementation Method 2
the main dissolution with a pronounced increase in viscosity and the lower rate of water evaporation needed for this, down to the approximately 1.5 hydrate of NMMO, take place
Data Source
AI summary
A method for producing molded articles from a base substance which is mixed with a solvent to produce a molding solution, and subsequently this solvent is at least partially removed from the molding solution and the molding solution is supplied to a device (8) for molding, the molding solution is supplied to a vertical cylindrical thin-film evaporator (2) and a horizontal cylindrical thick-film dissolver (4).