Fibrous Web Calendering with Cooling and Steam Conditioning
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Solution Overview
Problem
Existing methods for producing fibrous webs face a trade-off between achieving smoothness and maintaining thickness, as increased smoothing through calendering compresses the web and reduces strength, while cooling methods either complicate smoothing or require high costs and space.
Innovation Solution
A method involving convection cooling followed by steam application creates a temperature and moisture gradient in the fibrous web, allowing for smoothing in a calendering nip without significant thickness loss, using a combination of passive and active convection cooling and steam treatment to condition the web before calendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the fibrous web is cooled before calendering, then the web thickness is preserved, but the smoothing effect is reduced
Solution Approach 1:
The patent applies steam to the cooled web surface, changing the temperature parameter locally to create a temperature gradient. The web core remains cool (preserving thickness) while the surface is heated (improving smoothness). This parameter change in the surface region resolves the contradiction between thickness preservation and smoothness achievement.
Solution Approach 2:
The patent creates different thermal conditions in different regions of the web: the core remains cool while the surface is heated by steam. This local quality differentiation allows the cool core to maintain thickness while the warm surface accepts calendering pressure for smoothing, thus resolving the contradiction.
2Strength
If more fiber material is used to increase web thickness, then the mechanical strength is improved, but the production cost increases
Solution Approach 1:
The patent changes the temperature parameter of the web through steam application and controlled cooling, which modifies the physical properties of the existing fiber structure. This allows the same quantity of fiber to achieve both thickness preservation and improved mechanical strength through thermal conditioning, avoiding the need to add more expensive fiber material.
3Manufacturing precision
If high calender load is applied to achieve smoothness, then the surface quality is improved, but the web compression and strength reduction increase
Solution Approach 1:
The patent applies steam to the web before calendering, preliminarily heating the surface to improve its plasticity and receptivity to calendering. This preliminary thermal action allows the subsequent calendering to achieve smoothness with lower mechanical load, thus preserving web strength while achieving the desired surface quality.
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 method achieves effective smoothing while preserving web thickness and strength by utilizing temperature and moisture gradients, reducing the need for high-calender loads and toxic heating fluids, and enabling efficient production at various speeds.
Implementation Method 1
subsequent cooling of at least one first side of the fibrous web by ways of convection cooling
Implementation Method 2
In active cooling, air is blown from suitable nozzle devices onto one or both sides of the web
Implementation Method 3
application of steam onto at least the first side of the fibrous web, wherein the temperature, in particular on the first side following steam application is at least 70°C
Implementation Method 4
treatment of the fibrous web in at least one calendering nip
Data Source
AI summary
A process for the production or treatment of a fibrous web, in particular a paper or cardboard web, includes the following steps: a. drying of the fibrous web in a dryer section; b. subsequent cooling of at least one first side of the fibrous web by way of convection cooling, whereby the fibrous web has a temperature of 65° C. or less on at least the first side after cooling, in particular 50° C. and less; c. apply steam to at least the first side of the fibrous web, in particular the temperature on the first side after steam application is at least 70° C., optionally more than 80° C. or 90° C.; and d. treatment of the fibrous web in at least one calendering nip.