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PAPTAC Bleaching Committee
PAPTAC Bleach Sequence Letter Designations

Letter Designations

  1. Acid Wash
  2. Unassigned
  3. Chlorine
  4. Chlorine Dioxide
  5. Alkaline Extraction (caustic, white liquor, Papricycle)
  6. Formamidine Sulfinic Acid (FAS)
  7. Unassigned
  8. Hypochlorite, Sodium and Calcium
  9. Unassigned
  10. Unassigned
  11. Unassigned
  12. Unassigned
  13. Hypochlorous Acid, including Monox-L
  14. Nitrogen Compounds
  15. Oxygen
  16. Hydrogen Peroxide
  17. Chelation
  18. Unassigned
  19. Unassigned
  20. Unassigned
  21. Unassigned
  22. Unassigned
  23. Wash
  24. Hemicellulase
  25. Hydrosulphite
  26. Ozone

 

Examples

  1. DEop(DE)D

    2. A fully substituted chlorination stage, a wash, an oxygen and peroxide reinforced extraction stage, a wash, a chlorine dioxide stage, a short extraction stage, a wash, and a final chlorine dioxide stage.

  2. OQZEop(ZQ)P

    3. An oxygen delignification stage, a wash, a chelation stage using EDTA, a wash, an ozone stage, a wash, an oxygen and peroxide reinforced extraction stage, a wash, an ozone stage, pH adjustment and then a chelation stage, a wash, and a final peroxide stage where DTPA and magnesium sulphate are also added with the peroxide.

 

Definitions

  1. A bleaching stage is defined as the addition of chemical(s) to pulp to perform a specific function with an identifiable retention time.

  2. The primary treatment chemical will be designated by a single capital letter and secondary or subordinate chemicals each with a single lower case letter. The secondary chemicals will be listed in alphabetical order: e.g., Eop.

  3. A �chlorination� stage is considered to be 100% substituted if less than 5% of the total available chlorine is present as Cl2.

  4. An alkaline oxygen stage will be designated as O before the first chlorination stage and Eo after the first chlorination stage.

Principles

  1. The purpose of the bleach sequence designation is to convey the order of the bleaching stages and the primary reactants of each stage.

  2. The following information will not be conveyed in a bleaching sequence: use of chemicals for pH control, stabilization of other chemicals, or chelation (other than as a separate stage); order of addition of chemicals within a stage; consistency; extent of delignification or brightening.

  3. No numbers, slashes, commas, plus signs, arrows, or other symbols shall be used. The only permissible symbols are upper and lower case Roman letters and brackets.

  4. For discussion of test conditions in a single beach stage, a subscript number may be used in describing that stage. For example, the use of 100% substitution in the first chlorination stage would be indicated by the symbol D0. The symbol D100 will not be used for this purpose. Another example, the second extraction stage could be represented by the symbol E2.

  5. Brackets will be used to indicate sequential stages without intermediate washing. E.g., DEop(DED) to indicate a 100% substituted first chlorination (D0) followed by a wash, an Eop, a wash, chlorine dioxide stage, no wash, extraction, no wash, and a final chlorine dioxide.

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