Calcium Bicarbonate Pulp Refining for Paper Dewatering
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Solution Overview
Problem
Current press dewatering technologies face limitations in efficiently removing water from paper sheets due to issues like rewetting and the need for significant capital investment, while traditional filler addition methods fail to optimize sheet properties and water removal.
Innovation Solution
A method involving the use of a cellulosic fibrous material with a calcium bicarbonate solution to form a pulp mixture, refining it to associate calcium ions with fiber walls, and then wet pressing to enhance water removal and sheet properties by preventing rewetting and improving filler retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional filler addition methods are used, then sheet properties can be modified, but water removal efficiency is not optimized and rewetting occurs
Solution Approach 1:
The invention changes the chemical form of calcium carbonate from traditional filler particles to calcium bicarbonate solution, which reacts with fiber wall sites during refining. This parameter change in chemical state and delivery method prevents rewetting while optimizing water removal efficiency during press dewatering.
Solution Approach 2:
Calcium bicarbonate acts as an intermediary substance that reacts with reactive sites in fiber walls during refining. This intermediary reaction modifies the fiber surface properties to prevent rewetting, while the byproducts enhance water removal during pressing without the harmful effects of traditional fillers.
2Productivity
If extended nip pressing or other advanced dewatering technologies are implemented, then press dewatering performance is improved, but significant capital investment is required
Solution Approach 1:
The invention achieves improved press dewatering performance by changing the chemical parameters of the pulp slurry through calcium bicarbonate addition and refining reactions. This chemical modification approach delivers enhanced dewatering without requiring capital investment in new equipment or facility modifications.
Solution Approach 2:
The calcium bicarbonate solution performs multiple functions: it reacts with fiber walls to prevent rewetting, provides calcium ions for strength, and modifies slurry properties to enhance water removal. This self-service approach consolidates multiple functions into a single additive system, avoiding the need for additional dewatering equipment.
3Productivity
If calcium bicarbonate solution is added to form pulp mixture, then water removal efficiency and sheet solids content increase, but refining process is required to associate calcium ions with fiber walls
Solution Approach 1:
The calcium bicarbonate solution is added to the pulp slurry before refining, allowing the calcium ions to become associated with reactive sites in fiber walls during the subsequent refining process. This preliminary addition ensures proper distribution and reaction, achieving the desired water removal efficiency without requiring complex multi-step processing.
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 method significantly enhances water removal efficiency, increases sheet solids content, and improves paper strength and brightness, while reducing rewetting and energy consumption in the drying process.
Implementation Method 1
refining the pulp mixture such that at least some of the calcium ions become associated with the reactive sites in the fiber walls
Implementation Method 2
wet pressing the web
Data Source
AI summary
A method of making paper is described. The method includes providing a cellulosic fibrous material, the cellulosic fibrous material comprising a plurality of elongated fibers having a fiber wall surrounding a hollow interior, the fibrous material having moisture content. The method also includes adding calcium bicarbonate solution to the cellulosic fibrous material to form a pulp mixture, the calcium bicarbonate solution containing up to the saturation level of about 16% solids of calcium bicarbonate, the resulting pulp mixture having between 0.1% to 65% total solids by weight. Further, the method includes refining the pulp mixture such that at least some of the calcium ions become associated with the reactive sites in the fiber walls. Further still, the method includes forming a web from the pulp mixture and wet pressing the web.