System and method for reclaiming rejects in sulfite pulping
AssigneeUniversity of New Brunswick
InventorsYonghao Ni, Guojun Kang
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Abstract
Systems and methods are provided for refining and reclaiming rejects in a sulfite pulping process. Wood chips and sulfite cooking liquor are provided to a digester for delignification. The slurry obtained from the digester is screened to obtain a reject portion containing sulfite rejects. The sulfite rejects are disintegrated in a refiner, such that the rejects are refined to a freeness suitable for digestion in a subsequent re-cooking step. Refined rejects are then returned to the digester for re-cooking with wood chips.
Claims13
A method of refining sulfite rejects obtained during acid sulfite pulping or bisulfite pulping, the method comprising:
- providing wood chips and a sulfite cooking liquor to a digester and digesting the wood chips at a suitable temperature for obtaining delignification;
- screening a slurry obtained from the digester to separate a reject portion from an accept portion, the reject portion including sulfite rejects comprising condensed lignin, wherein the condensed lignin was formed by acid-induced condensation;
- providing the sulfite rejects to a refiner, wherein the refiner is adapted to disintegrate the sulfite rejects;
- refining the sulfite rejects to obtain refined sulfite rejects having a Canadian standard freeness between approximately 600 ml and 900 ml;
- and
- returning at least a portion of the refined sulfite rejects to the digester for re-cooking in the sulfite cooking liquor with additional wood chips.
Dependencies are inferred from the claim text.