Membranes for Kraft black liquor concentration and chemical recovery: Current progress, challenges, and opportunities

ABSTRACT

Membranes can significantly reduce energy consumption during concentration of black liquor (BL) in the Kraft papermaking process, but the harsh conditions (pH ~12, 80°C–95°C, ~15 wt% solids) make this challenging. We elucidate challenges and opportunities for membranes in BL applications. We critically review membrane materials, processes, and operational modes investigated in the literature. Future advances will involve fabrication of higher-rejecting (≥95% lignin and inorganics), BL-resistant, NF, and RO membranes. Opportunities exist for molecular sieving and electrically driven membranes to recover other valuable chemicals such as carboxylic acids. We also discuss the economics of BL concentration with a single-stage membrane process.

KEYWORDS:

• Black liquor
• Kraft process
• lignin removal
• membrane
• nanofiltration

Acknowledgements

The authors also thank Steven Lien and Scott Sinquefield (Renewable Bioproducts Institute) and Zhongzhen Wang (Georgia Tech) for valuable discussions and assistance.

Funding

The authors acknowledge financial support by the Renewable Bioproducts Institute and the Paper Science & Engineering Fellowship, both at the Georgia Institute of Technology.

Supplemental data

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Additional information

Funding

The authors acknowledge financial support by the Renewable Bioproducts Institute and the Paper Science & Engineering Fellowship, both at the Georgia Institute of Technology.