Bilingual Tech Mapping for Pulp Paper Guideline - Asosiasi Pulp ...

Kraft pulping process using alkaline cooking
solution consisting of sodium hydroxide (NaOH) and
sodium sulfide (Na2S) to dissolve the lignin of wood, while
the soda process uses only NaOH. Cooking condensation
(white liquor) is mixed with wood chips in a reactor
(digester). After the flakes of wood to cook, the digester
contents removed by pressure into the tank. Wood is
softened, broken down into pulp fibers. Pulp and waste
cooking condensation (black liquor) and then separated in
a series of brown pulp washing. Dissolving pulp can be
made via the sulfite or Kraft process, in order to obtain
wood pulp with high purity which is used for conversion into
products such as rayon, viscose, acetate and cellophane.
c. Pulp Bleaching
This process removes color from the pulp (due to the
residual lignin) by adding chemicals to the pulp with varying
combinations, depending on end use product. The same
bleaching process can be used for each category of
pulping process.
The most common bleaching chemicals are
chlorine, chlorine dioxide, hydrogen peroxide, oxygen,
sodium hydroxide and sodium hypochlorite. Concerns the
formation of chlorinated compounds such as dioxins,
furans, and chloroform, has resulted in a shift from the use
of chlorinated compounds in the bleaching process.
Chemicals are added to bleach pulp in the reactor
bleaching gradually. Spent bleaching liquor remove at
every washing stage. Washing effluent is collected in a
particular tank and reused as washing water at another
stage or sent to the waste processing.
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