Date of Award

4-2007

Degree Name

Master of Science

Department

Chemical and Paper Engineering

Department

Paper Engineering, Chemical Engineering and Imaging

First Advisor

Dr. John Cameron

Second Advisor

Dr. Peter Parker

Third Advisor

Dr. Andrew Kline

Access Setting

Masters Thesis-Open Access

Abstract

Borate autocausticizing is a promising approach to the operational and environmental improvement of Kraft pulping and its chemical recovery. Its advantages include partial or total elimination of the lime cycle, pulp strength improvement, and energy savings. Borate autocausticizing involves the use of an amphoteric salt, sodium metaborate, to de-carbonize sodium carbonate and produces trisodium borate, the reaction occurs at high temperatures. Tran and Cameron (1999) suggest that the reaction follows the path below.

NaBO2 + Na2CO3 → Na3BO3 + CO2

This thesis systematically analyzes the reaction kinetics of borate autocausticizing. The uniqueness of this research is the usage of a thermo-gravimetric analysis to study the kinetics of the borate/carbonate reaction. The weight loss data generated by the TGA are used to monitor the concentration of the reactants; the data are analyzed using the differential method/excess method for batch reactor o obtain a kinetic expression for the reaction. The equimolar reaction produces bisodium borate and has an overall order of 2.5 at 700 °c. The reaction produces trisodium borate when the metaborate to carbonate molar ratio is 0.1-0.2, the order of sodium metaborate is 1.5 at 700 °c. In addition, the reaction conversion reduces in the presence of CO2 at 850 °c.

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