NSSC Fluting Containerboard Pressing for Lower Drying Energy
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Solution Overview
Problem
Existing methods for producing containerboard from Neutral Sulfite Semi-Chemical (NSSC) pulp face inefficiencies in energy consumption and productivity, particularly due to high residual lignin content and the need for additional refining to enhance strength, which often requires external fossil fuels and limits drying capacity.
Innovation Solution
A method involving low refining of NSSC pulp to a Schopper-Riegler value of 15-19, forming a web with a shoe press having a line load of 1400-2000 kN/m and using a shoe press belt with discontinuous grooves, followed by drying, to produce containerboard with a geometric SCT index of 37.0-42.0 Nm/g, reducing energy consumption and increasing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If NSSC pulp is subjected to more refining to increase SCT strength, then the SCT strength of containerboard is improved, but energy consumption increases
Solution Approach 1:
The patent changes the Schopper-Riegler (SR) value parameter to a specific range of 15-19, representing a low degree of refining. This parameter optimization achieves the desired SCT strength (37.0-42.0 Nm/g) while minimizing energy consumption, resolving the contradiction between strength improvement and energy usage.
2Productivity
If the line load in the shoe press is increased to improve dewatering, then the dewatering efficiency is improved, but energy consumption in the drying section increases
Solution Approach 1:
The patent optimizes the line load parameter to a specific range of 1400-2000 kN/m. This parameter change achieves effective dewatering in the shoe press while controlling energy consumption in the subsequent drying section, resolving the contradiction between dewatering efficiency and drying energy usage.
3Productivity
If the production speed is increased to improve productivity, then the productivity is improved, but the SCT strength decreases
Solution Approach 1:
The patent applies preliminary action by optimizing the pressing conditions in the shoe press (line load 1400-2000 kN/m) and controlling the SR value (15-19) before drying. This preliminary consolidation of the web structure ensures that high production speeds do not compromise the final SCT strength, as the fiber network is already properly formed before the high-speed drying phase.
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 reduced energy consumption in the drying process, allowing higher production speeds and productivity while maintaining SCT strength, thus overcoming the limitations of traditional NSSC pulping processes.
Implementation Method 1
pressing the web in a press section comprising a shoe press, wherein the shoe press comprises a shoe press belt having discontinuous grooves and the line load in the shoe press is in the range of 1400-2000 kN/m
Implementation Method 2
drying the web from the press section in a drying section to obtain said containerboard
Implementation Method 3
drying the web from the press section in a drying section
Data Source
Figure 1
AI summary
There is provided a method of producing a containerboard having a geometric SCT index of 37.0-42.0 Nm/g when measured according to ISO 9895:2008, comprising the steps of: - providing a pulp having a Schopper-Riegler (SR) value of 15-19 when measured according to ISO 5267-1:1999, wherein at least 70% by dry weight of the pulp is NSSC pulp; - forming a web from the pulp; - pressing the web in a press section comprising a shoe press, wherein the shoe press comprises a shoe press belt having discontinuous grooves and the line load in the shoe press is in the range of 1400-2000 kN/m; - drying the web from the press section in a drying section to obtain said containerboard.