PCC Production Using Processed Lime Mud to Lower Specific Surface Area
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Solution Overview
Problem
The use of certain types of lime mud in paper production leads to high specific surface area (SSA) in precipitated calcium carbonate (PCC), which consumes sizing chemicals and reduces paper sizing performance, particularly due to high silicon content in non-wood based lime muds.
Innovation Solution
A process involving the addition of processed lime mud with controlled weight median diameter to a calcium hydroxide suspension before carbonation, followed by carbonation to form PCC, which encapsulates or coats the lime mud particles, reducing SSA and improving morphology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lime mud with high silicon content is used in PCC production, then production cost is reduced and waste is recycled, but specific surface area increases and paper sizing performance deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the weight median diameter of lime mud particles within a specific range (0.3-10 μm) and optimizing the carbonation process parameters (CO2 flow rate, temperature, pH) to produce PCC with desired SSA and morphology, thereby resolving the contradiction between using low-cost high-silicon lime mud and controlling final PCC quality
Solution Approach 2:
The patent applies local quality by selecting specific morphological forms of PCC (such as spherulitic or compact crystalline structures) that have lower SSA characteristics, thereby locally optimizing the filler properties to reduce sizing chemical consumption while still using economical lime mud feedstock
2Quantity of substance
If PCC with high specific surface area is produced, then filler quantity in paper is increased, but sizing chemical consumption increases and printability deteriorates
Solution Approach 1:
The patent changes the SSA parameter of PCC by controlling particle size distribution and morphology during carbonation, producing PCC with optimized SSA that maintains adequate filler quantity while minimizing sizing chemical consumption and improving printability
3Manufacturing precision
If lime mud is processed to reduce particle size, then SSA is reduced and sizing performance improves, but processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-processing lime mud through classification and size control before carbonation, ensuring particles are within the optimal size range (0.3-10 μm weight median diameter) to produce PCC with desired SSA and morphology, thereby simplifying overall processing while achieving sizing performance goals
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 process results in PCC with reduced SSA and improved paper sizing performance by minimizing the consumption of sizing chemicals, enhancing printability and reducing ink smudging.
Implementation Method 1
PCC is prepared by introducing CO2 into an aqueous suspension of calcium hydroxide (Ca(OH)2), which is commonly referred to as 'milk of lime': Ca(OH)2+CO2→CaCO3+H2O
Implementation Method 2
The carbonating step (b) can grow the PCC crystals on processed lime mud crystal clusters
Implementation Method 3
PCC exists in three primary crystalline forms: calcite, aragonite, and vaterite. PCC can harbor many different polymorphs. The crystal habits can include scalenohedral, rhombohedral, hexagonal prismatic, cubic, and prismatic
Data Source
AI summary
A method for making precipitated calcium carbonate is provided. The process includes providing a suspension having calcium hydroxide and adding a processed lime mud to the suspension prior to the completion of carbonation to precipitate calcium carbonate.