Application of In Situ Calcium Carbonate Process for Producing Papermaking Fillers from Lime Mud

Area of Science:

• Chemical Engineering
• Materials Science
• Environmental Science

Background:

• Lime mud is a waste byproduct of kraft pulping's causticizing process.
• Disposing of lime mud incurs waste management costs and environmental concerns.
• Pulping chemical quality is maintained by purging lime mud from the calcium cycle.

Purpose of the Study:

• To transform industrial waste lime mud into a valuable papermaking filler.
• To develop and evaluate hybrid calcium carbonate (HCC) and post-HCC (pHCC) technologies for lime mud valorization.
• To assess the impact of these technologies on paper properties and production costs.

Main Methods:

• Lime mud was heat-treated and size-reduced.
• Two methods were developed: LHCC (lime mud + calcium oxide + CO2) and pLHCC (lime mud + calcium oxide + CO2).
• Preflocculation with ionic polymers and CO2 injection were key steps in both processes.

Main Results:

• LHCC and pLHCC achieved brightness comparable to ground calcium carbonate (GCC).
• pLHCC exhibited slightly higher brightness than LHCC.
• The resulting fillers improved paper bulk, stiffness, and tensile strength.

Conclusions:

• The HCC and pLHCC technologies effectively convert waste lime mud into high-performance papermaking fillers.
• This valorization strategy offers a dual benefit of reducing waste disposal expenses and enhancing paper quality.
• The developed methods present a sustainable approach for the pulp and paper industry.