Beloit Technologies, Inc.

William J Miller

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.

Oxygen delignification of medium consistency pulp slurry using two

A method of oxygen delignification of medium consistency pulp slurry, which includes the steps of providing a pulp slurry of from approximately ten percent to sixteen percent consistency, at a temperature of from approximately 170-240.degree. F., preferably from 190 to 220.degree. F., thoroughly impregnating the slurry with oxygen gas, and with alkali to bring the slurry to a pH of at least 11, more preferably 12, introducing the slurry to oxygen gas in a high shear mixer, for agitating mixing therein, reacting the slurry in a first pressurized reactor for between 5 to 10 minutes, returning the pH of the slurry to at least 11, more preferably 12, with a residual alkali concentration of at least 1.25 gpl, thoroughly impregnating the slurry with H.sub.2 O.sub.2 and oxygen gas, and reacting the slurry in a second reactor for between 30 to 180 minutes. By only employing the hydrogen peroxide during the slower bleaching reaction, a lower Kappa number with higher % ISO is obtained in the product, these beneficial characteristics being retained in subsequent processing steps.

Oxygen delignification of medium consistency pulp slurry

The invention described a method of oxygen delignification of medium consistency pulp slurry, which includes the steps of providing a pulp slurry of from approximately ten percent to sixteen percent consistency, at a temperature of from approximately 170-240.degree. F., preferably from 190 to 220.degree. F., thoroughly impregnating the slurry with oxygen gas, and with alkali to bring the slurry to a pH of at least 11, more preferably 12, introducing the slurry to oxygen gas in a high shear mixer, for agitating mixing therein, reacting the slurry in a first pressurized reactor for between 5 to 10 minutes, returning the pH of the slurry to at least 11, more preferably 12, with a residual alkali concentration of at least 1.25 gpl, thoroughly impregnating the slurry with H.sub.2 O.sub.2 and oxygen gas, and reacting the slurry in a second reactor for between 30 to 180 minutes. By only employing the hydrogen peroxide during the slower bleaching reaction, a lower Kappa number with higher %ISO is obtained in the product, these beneficial characteristics being retained in subsequent processing steps.

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Manchester, NH, United States of America

William J Miller