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Chemical pulp manufacturing is a process where the cellulosic material (primarily from wood chips or bagasses, agricultural waste, etc.) is cooked in a high pressure steam cooker in association with caustic soda (NaOH) in order to produce pulp. The steam pressure is in the range of 7 to 10 ata.

The process helps in dissolving the lignin content in the wood by the caustic soda. The resultant product is a cooked pulp, which is the outcome of defragmentation of the wood chips into finer fibres. The resultant material in the cooker contains black liquor (watery content which has lignin dissolved in caustic soda) and pulp.

The process normally takes anywhere between 3 to 12 hours per batch for complete cooking, depending upon the design of the equipment. The whole cooked mass is sent for pulp washing, where the black liquor is separated from the mixture and sent for recovery in a soda recovery system. The remaining material is pulp, which goes on for production of paper.

[edit] See also

• Pulping