| PATENT ASSIGNEE'S COUNTRY | USA |
| UPDATE | 08.99 |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT CLAIMS |
Process for bleaching Kraft wood pulp comprising subjecting wood pulp after a brown stock washing stage to steps - O delignification in presence of O & base - Post O washing stage - Acid treat. to remove non-process metals - Bleaching with first Cl dioxide stage - Neutralization - Extraction stage in presence of base - Water washing - Final Cl dioxide bleaching stage - Washing - Discharging filtrate from wash. stage, recycling counter cu rrently all filtrate from washing after final Cl dioxide bleach. stage to extraction stage as wash water - Recycling counter currently all filtrate from post extraction wash stage to neutralize first bleached pulp from first Cl dio xide bleach. stage in neutralization stage prior to subjec ting said first bleached pulp to extraction stage such that all filtrate from extraction stage & all filtrate from first Cl dioxide bleach. stage are combined with first bleached pulp to form a mixt. comprising first bleached pulp & a combined filtrate comprising all filtrate from extraction stage & all filtrate from first Cl dioxide bleach stage - Separating all combined filtrate from first bleached pulp & recycling at least a portion to said post O washing stage as wash water - Recovering filtrate from post O wash. stage in the cooking liquor recovery process by recycling said filtrate counter cu rrently through the brownstock washing stage constituting a weak black liquor which is evaporated to produce strong black liquor - Combusting strong black liquor in recovery boiler to produ ce a smelt & flue gas such that chloride from counter curren tly recycled filtrates from Cl dioxide bleach. stages is enri ched in flue gas from combustion - Collecting particles contg K, chloride & sulfate salts in flue gas as ash - Removing chloride & K salts from ash to produce solid stream contg sulfate salts & stream contg chloride & K salts - Discharging the stream contg chloride & K salts - Mixing said stream contg sulfate salts with strong black li quor prior to combustion of liquor in boiler - Dissolving said boiler smelt in water to form green liquor & - Converting green liquor to pulping liquor in causticizing process |
| PATENT PHOTOCOPY | Available on request |
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