Effect of Ash Addiction on the Rheological and Thermal Behavior of the Black Liquor Resulting from CENIBRA's Kraft Process

The aim of this work was the evaluation of the ash addition effect in composition, thermal, and rheological behavior of the black liquor (LN) from CENIBRA/Belo Oriente-MG. Elementary analysis by ICP showed high percentage of sodium to both samples of black liquor containing ashes (LNCC) and black liquor without ashes (LNSC), and also the presence of low amounts of the non-process elements (Mg, Ca, Al, Fe). The superior calorific power (PCS) of LNSC was 7% greater than for LNCC, as consequence of greater percentage of organic compounds. The DTA and TGA curves showed a lower boiling point for LNCC, which was attributed to the greater degradation rate of lignin molecules. In rheological experiments (at 80 degrees C), flow and viscosity curves for LNSC showed a pseudoplastic behavior, while the LNCC exhibited an intricate flow profile, with lower values of viscosity and greater thixotropy.