1. Sulphate process
   1. Conversion of wood into wood pulp consisted of pure cellulose
   2. WHITE LIQUOR - treatment of wood chips into a mixture of sodium hydroxide and sodium sulphide (known as WHITE LIQUOR
      1. Breaks down the lignin to the cellulose
   3. BLACK LIQUOR - mixture of digested pulp wood consisting of lignins/hemicellulose/15% solids/ 10% inorganics and 5% organics
2. Process
   1. 1. Wood chips enter pre steaming
   2. 2. Impregnate chips with black or wihite liquor
   3. 3. Digester at below 100 C (40-60% of all alkali consumption in the impregnation stage)
      1. Continuous digester
      2. Batch digester
   4. 4. Digesters process
      1. Delignification requires several hours @ 130 to 180C
      2. Lignins and hemicellulose degrade into fragments
      3. BROWN STOCK: Solid pulp is collected and washed 50% based on wood chips, known as BROWN STOCK
   5. 5. Evaporators
      1. 1. Black liquor - 15% solids, rosin soaps rises to the surface and skimmed off
         1. lignins/sodium carbonate/sodium sulphate
      2. 2. Collected soap is further process into Tall Oil
      3. 3. Removal of the soap improves evaporation operation
      4. 4. Weak black liquor is further evaporated to 65% or even 80% solids (HEAVY BLACK LIQUOR)
         1. HEAVY BLACK LIQUOR -burnt off in the recovery boiler
         2. Recovery boiler - recover inorganics chemicals for reuse in the pulping process
         3. Plugging of equipment occurs because of the viscosity
   6. 6. Recovery Boilers
      1. Heavy black liquor
         1. Sodium sulphate is reduced to sodium sulphite by the organic carbon in the mixture
      2. Smelt (molten salts) dissolved in a process water known as "weak wash"
      3. Generates high pressure steam
         1. Steam is fed to turbo generators to generate electricity for site , excess
         2. Self sufficient in terms of electricity
   7. 7. Process Water
      1. Weak white liquor
         1. Composed of all liquors used to wash the lime mud and "green liquors" precipitates
            1. GREEN LIQUORS - mixture of sodium carbonate/sodium sulphide
            2. This mixture is mixed with calcium oxide which becomes calcium hydroxide, to regenerate the WHITE LIQUOR used in the pulping process
            3. Calcium carbonate pptes from the white liquor and is recovered and heated in a lime kiln converted to calcium oxide (lime)
            4. Sodium carbonate is reacted to generate Sodium Hydroxide
   8. 8. Washing
      1. Pulp washing
   9. 9. Bleaching
   10. 10. Chemicals used
       1. Surfactants - improve impregnation of the wood chips with the cooking liquors
       2. Anthraquinone - digester additive, redox catalyst- oxidising cellulose and reducing lignins. Protects cellulose from degradation/makes lignin more water soluble
       3. Emulsion breaker - soap separation to speed up from used cooking liquors by flocculation
       4. Defoamers - remove foam and speed up production process. Drainage of washing equip to give cleaner pulp
       5. Dispersing, detackifiers and complexing agents
       6. Fixation agents , reduced potential deposits- transporting it out of the process