Advanced process for precipitation of lignin from ethanol organosolv spent liquors

•Softening temperature ranges of lignin in presence of ethanol were measured.•A new (semi-) continuous precipitation process for organosolv lignin was developed.•By targeted precipitation of solid lignin particles incrustations are specifically avoided.•Lignin particles can be enlarged by specific coalescence of softened lignin.•The process was successfully evaluated in a pilot scale plant. An advanced process for lignin precipitation from organosolv spent liquors based on ethanol evaporation was developed. The process avoids lignin incrustations in the reactor, enhances filterability of the precipitated lignin particles and significantly reduces the liquor mass in downstream processes. Initially, lignin solubility and softening properties were understood, quantified and exploited to design an improved precipitation process. Lignin incrustations were avoided by targeted precipitation of solid lignin at specific conditions (e.g. 100mbar evaporation pressure, 43°C and 10%wt. of ethanol in lignin dispersion) in fed-batch operation at lab and pilot scale. As result of evaporation the mass of spent liquor was reduced by about 50%wt., thus avoiding large process streams. By controlled droplet coalescence the mean lignin particle size increased from below 10μm to sizes larger than 10μm improving the significantly filterability.