Fiber Web Drying Using Dry Gas Blows
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fiber web production lines face inefficiencies in drying and calendering processes, particularly in achieving desired surface properties and bulkiness while minimizing raw material usage and energy consumption.
Innovation Solution
The method involves using dry gas to create a partial steam pressure difference for evaporation, followed by traditional drying methods, and incorporating a long run with cool, dry gas before calendering to enhance drying efficiency and reduce energy consumption, thereby improving bulkiness and surface properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional drying methods (drying cylinders, convection, steam boxes, infrared) are used to dry fiber webs, then the fiber web is dried by thermal energy transfer, but towards the end of the drying process efficiency decreases due to small temperature difference and small heat flow
Solution Approach 1:
The patent changes the drying parameters by introducing a controlled atmosphere with specific temperature and humidity levels. The drying chamber maintains a temperature gradient and controls moisture content in the air to optimize the drying rate throughout the process, preventing the efficiency drop that occurs in traditional methods when temperature differences become small.
Solution Approach 2:
The patent introduces an intermediary drying chamber that acts as a transition zone between the fiber web formation and final drying stages. This chamber uses controlled air flow and humidity to facilitate moisture removal without the direct contact or extreme temperature gradients of traditional drying methods, maintaining high efficiency throughout the drying process.
2Manufacturing precision
If fiber webs are dried to high dryness before calendering, then surface properties improve, but energy consumption increases and bulkiness decreases
Solution Approach 1:
The patent performs preliminary drying to a controlled moisture level before calendering, rather than drying to complete dryness. This preliminary action prepares the fiber web for calendering with optimal surface properties while avoiding the excessive energy consumption and bulk loss that would result from over-drying. The calendering process then completes the surface finishing.
3Manufacturing precision
If fiber webs are cooled before calendering, then bulkiness is improved, but additional cooling equipment and process complexity are required
Solution Approach 1:
The patent designs the drying chamber to serve multiple functions: it dries the fiber web to the appropriate moisture level and simultaneously cools it to the optimal temperature for calendering. This multi-functionality eliminates the need for separate cooling equipment while achieving the desired bulkiness improvement through controlled temperature and humidity management.
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 results in energy-efficient drying, improved calendering performance, and reduced raw material usage, achieving enhanced bulkiness and surface properties while maintaining high production capacity.
Implementation Method 1
thermal energy of the fiber web is utilised such that difference of partial steam pressures of the fiber web and the ambient air is created by providing dry gas blows on at least one surface of the fiber web. The thermal energy of the fiber web will thus be utilised for evaporation as dry gas is blown onto at least surface of the fiber web, whereby moisture of the fiber web evaporates, where by latent thermal energy is combined with the evaporation and thus the fiber web cools
Implementation Method 2
where by latent thermal energy is combined with the evaporation and thus the fiber web cools
Implementation Method 3
The run cools the free surfaces of the fiber web, whereby the partial pressure of steam on the surfaces decreases and in middle of the fiber web the partial pressure of steam remains high. Thereby the difference in partial steam pressures conveys the moisture by diffusion from middle of the fiber web to the surfaces of the fiber web and drying is enhanced
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a method for producing a fiber web (W), in which method furnish is fed from at least one head box to at least one forming section for forming the furnish to the fiber web, the fiber web is pressed in a press section, the fiber web is dried in at least one drying section, the fiber web is calendered in at least one calender (15) and reeled in a reel-up. In drying of a fiber web (W) thermal energy of the fiber web (W) is utilized such that difference of partial steam pressures of the fiber web (W) and the ambient air is created by providing dry gas blows on at least one surface of the fiber web whereby thermal energy of the fiber web is utilized for evaporation of moisture from the fiber web. The invention also relates to a production line for producing fiber webs comprising at least one head box, which can be a two or three layer head box, forming means for each layer or layer combination of the fiber web (W), a press section with at least one press nip, at least one drying section, at least one calender, a reel-up. Length of the fiber web run between the at least one calender (15) and the previous drying or cooling cylinder, before it is 7 - 20 m, advantageously 10 - 15 m.