Small Pilot System for the Manufacture of in Situ Precipitated Calcium Carbonate in the Presence of Pulp Fibers

Paper fillers materials are less expensive than fiber, allowing reduced production costs and improvement of paper properties.

A small pilot scale in-situ laboratory calcium carbonate filler precipitation unit was developed and designed with the objective to provide enough pulp fiber containing in-situ precipitated calcium carbonate for a small 12-inch (304 mm) wide laboratory paper machine. The in-situ precipitation system requires the reactants calcium hydroxide and carbon dioxide and was tested with a eucalyptus pulp fiber pulp suspension.

The final precipitated in-situ filler content achieved was 38.2%, 55.5% and 66.6% based on initial eucalyptus pulp fiber content. The precipitation time from an initial pH of 12.77, 12.76 and 11.98 to an final pH of 7.29, 7.55, and 7.28 for the 3 kg, 6kg, and 9 kg of calcium hydroxide reactant addition was 45 minutes for the 3 kg and 9 kg calcium hydroxide addition and 40 min. for the 6 kg calcium hydroxide addition.