Study on tall oil solubility for improved resource recovery in chemical pulping of wood

• Tall oil is one of the most valuable by products in chemical pulpingof wood and is considered an important renewable alternative to petroleum.Its fractions have a large spectrum of applications including chemicalprecursors, detergents and energy. High recovery of tall oil is important forthe economic, sustainability, and environmental profile of industrial chemicalpulping. The purpose of this study was to develop ways to increase the yieldof tall oil based on its solubility in black liquors.To investigate this in a controlled way, a model system with a “synthetic”black liquor and a complete methodology for soap skimming anddetermination of recovered tall oil was developed based on solvent extractionand colorimetric analysis with good reproducibility. This model system allowsinvestigations of different parameters in small scale with high control overdifferent conditions.The developed system was used to study the effect of fatty acid addition andthe effect of lignin content on improving tall oil recovery. The presence ofrosin acids in the black liquor significantly reduced soap separation, whileincreasing the fatty acid content up to 60-70% greatly improved soaprecovery. Addition of lignin reduced tall oil recovery in the case of liquors withmore than 50% fatty acids, but slightly increased recovery in liquors withmore than 50% rosin acids. Furthermore, the presence of some ligninseemed to promote separation of the tall oil (reduced its solubility), while highamounts led to inhibition of its recovery.The experimental results clearly indicated that manipulating the content offatty acids and/or lignin before the soap skimming step significantly affect thetall oil solubility, opening up for chemical ways to improve its recovery.However, experiments in real industrial liquors and pulp mill conditions shouldbe considered to assess the actual tall oil yield improvement and processeconomics.

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Publikations- och innehållstyp

vet (ämneskategori)

art (ämneskategori)