Title
SLRP^TM - An innovative lignin-recovery technology
Authors
MICHAEL A. LAKE and JOHN C. BLACKBURN

Published Volume 48 Issue 9-10 November-December
Keywords lignin, liquid-lignin, lignin recovery, SLRP, black liquor

Abstract
The Sequential Liquid-Lignin Recovery and Purification (SLRP) process precipitates lignin from black liquor as a true liquid phase that separates by gravity. This is different from traditional processes that precipitate lignin as small solid particles that have to be filtered. The capital and operating costs are much lower than competitive processes, mainly due to small equipment resulting from SLRP’s continuous operation. SLRP has high energy efficiency; residual lignin depleted black liquor is returned to the host mill at a higher temperature than the black liquor feed. The acidification reactor vent gases, which contain zero air but significant levels of CO2 and H2S, are recycled and reacted with the incoming black liquor. This recycle reduces the carbon dioxide consumption by 30%. An efficient vent-gas system captures almost all the sulfur gases. The development of SLRP was funded by the US Department of Energy. A pilot plant is operating in Clemson SC.