Papermaking Press Section Dewatering via MFP and Additives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In papermaking, improving dewatering at the press section often compromises paper sheet properties, and vice versa, due to limitations in mechanical pressure, chemical aids, and press media pore size, which can lead to sheet disruption and reduced solids content.
Innovation Solution
The method involves using a press media with a lower Mean Flow Pore (MFP) size and applying press dewatering additives, such as aldehyde or amine containing polymers, to control hydraulic pressure and enhance dewatering without compromising sheet properties, by optimizing the MFP size and adding chemicals like Nalco 64114 before the last press nip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If mechanical pressure is increased at the press nip to improve dewatering, then solids content exiting the press section increases, but sheet properties deteriorate due to sheet disruption and crushing
Solution Approach 1:
The patent applies parameter changes by modifying the pore size of the press fabric (MFP) to a smaller value and adjusting the chemical composition by adding press dewatering additives. These parameter changes enable enhanced dewatering through chemical mechanisms rather than purely mechanical pressure, thereby increasing solids content while preserving sheet properties without disruption or crushing
Solution Approach 2:
The patent introduces press dewatering additives as intermediary substances that facilitate water removal through chemical interactions. These additives act as mediators between the press section and the paper sheet, enabling dewatering through chemical mechanisms that do not rely on excessive mechanical pressure, thus avoiding sheet disruption while improving solids content
2Manufacturing precision
If press fabric pore size (MFP) is decreased to improve sheet smoothness, then sheet properties improve, but dewatering efficiency decreases due to increased hydraulic back pressure
Solution Approach 1:
The patent simultaneously optimizes two parameters: the press fabric MFP is reduced to improve sheet smoothness, while press dewatering additives are introduced to compensate for the reduced dewatering efficiency. This dual parameter adjustment resolves the contradiction by maintaining dewatering productivity despite the smaller pore size
Solution Approach 2:
Press dewatering additives are introduced as intermediary substances that enable effective dewatering even when the press fabric has small pore size. These additives work through chemical mechanisms that bypass the hydraulic back pressure limitation, allowing the system to achieve both good sheet smoothness and maintained dewatering efficiency
3Productivity
If chemical drainage aids are applied to enhance dewatering, then water removal improves, but sheet strength properties decrease due to interference with hydrogen bonding of cellulose fibers
Solution Approach 1:
The patent applies parameter changes by selecting press dewatering additives with specific chemical characteristics that differ from conventional drainage aids. These additives are chosen to have minimal interference with cellulose fiber hydrogen bonding, thereby maintaining sheet strength while still achieving enhanced water removal through chemical mechanisms
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 allows for improved dewatering and sheet smoothness without reducing solids content, achieving a more uniform paper sheet with increased solids exiting the press section, as demonstrated in pilot trials with specific press configurations and additive dosages.
Implementation Method 1
controlling hydraulic pressure and enhance dewatering
Implementation Method 2
press media with a lower Mean Flow Pore (MFP) size
Implementation Method 3
applying press dewatering additives, such as aldehyde or amine containing polymers, to control hydraulic pressure and enhance dewatering
Implementation Method 4
a paper sheet, which is supported in a press nip by one or more porous media structures, such as press fabrics, is subjected to mechanical pressure at the press nip(s) in the press section
Implementation Method 5
The application of heat raises water temperature and lowers its viscosity, thus making it easier to mechanically remove water from the sheet
Implementation Method 6
The application of heat raises water temperature and lowers its viscosity
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A method of operating a papermaking process containing a press section with at least one press nip is disclosed. The method comprises simultaneously performing the following steps: (a) providing a press media for said papermaking process that has a MFP size that is less than the MFP size of a press media that was originally supplied to said papermaking process; (b) adding an effective amount of one or more press sheet dewatering additives to said papermaking process prior to the last press nip of said papermaking process; (c) providing a sheet moisture ratio of a paper sheet entering a press nip of said press section to between about 2 to about 9; and (d) applying an optimum rate of pressure development at one or more press nips of said papermaking process, wherein said steps a, b, c, and d either: result in the production of a more uniform paper sheet without the reduction in paper solids exiting the press section that would be expected from performing a, c, and d, alone or in combination with one another; or result in the production of a more uniform paper sheet with an increase in solids content of said paper sheet exiting the press section