Recovery of Lignin Using Separation by Heat “RUSH” Process

Technical Summary:

The RUSH (Recovery Using Separation with Heat) process recovers lignin from acidified black liquor by using heat to induce phase separation, resulting in a solid lignin phase and a liquid spent black liquor phase, simplifying recovery without the need for filtration or centrifugation. The process works effectively with wood and non-wood sources, such as agricultural residues including wheat straw and corn stover, and avoids the foul odors typically associated with wood-based sources. RUSH utilizes standard alkaline agents (e.g., sodium or ammonium hydroxide) and acids (e.g., acetic, sulfuric). Increasing temperature enhances the solids content of the lignin phase, improving its purity and robustness. Lab scale tests have yielded up to 75% of the lignin present in black liquor, and its elimination of energy-intensive steps like evaporation making it a cost-effective lignin precipitation method.