| 摘要 |
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 DEG F., preferably from 190 to 220 DEG 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 H2O2 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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