Improving Flow Characteristics of High Black Liquor with a Practical Processing Aid, 1998 International Chemical Recovery Conference Proceedings

A proprietary processing additive enables high solids firing in order to make the kraft recovery process more energy efficient and increase the recovery capacity. When used, in a kraft mill’s recovery cycle, the processing additive enabled the mill to increase the solids content from 63 wt.% to almost 80 wt.%. To give an insight to how the additive works on black liquor, flow properties such as viscosity, yield stress and slippage at the surface are investigated on various black liquors. Comparison of flow characteristics of black liquor with and without the additive is made. Results show that the additive reduces the viscosity as well as the yield stress of the black liquor dramatically and also makes the black liquor slip on the surfaces easily. Therefore, it eliminates the problems associated with high solids firing such as dramatic increase in the viscosity and handling and pumping difficulties in transfer lines and blockage in nozzles and non-ideal droplet size formation problems in furnaces. Reduced yield stress of the high solids black liquor also results in clean concentrator operations.