Oxygen delignification of medium consistency pulp slurry using two alkali additions
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United States of America Patent
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Dec 19, 2000
Issued Date -
N/A
app pub date -
Oct 14, 1997
filing date -
Dec 7, 1995
priority date (Note) -
Expired
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Abstract
An improved process is described for oxygen delignification of medium consistency pulp slurry which teaches control parameters and their resultant effect on final product characteristics. Specifically, a process is described wherein pulp slurries of from approximately eight percent to sixteen percent consistency, are heated to a temperature of at least 170.degree. F. and impregnated oxygen gas and alkali to bring the slurry to a pH of from approximately 11-12.5. The slurry is mixed in a high shear mixer, for agitating mixing therein, under pressure of from approximately 20-180 psig for a first reaction time of typically 5 minutes. Additional alkali is added to the slurry to return the pH to at least 11, preferably at least 12, and the residual alkali concentration to at least 4.0 gpl at the end of the first reaction time. The temperature of the slurry is raised to at least 170.degree. F. followed by mixing for a second reaction time of typically 55 additional minutes.
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