Pulp making
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The document discusses different methods of pulp making including mechanical, chemical, and semi-chemical processes. It describes the chemical pulping process which involves debarking logs, chipping the wood, cooking the chips in a digester tower under high temperature and pressure to dissolve lignin, and separating the brown pulp from residual black liquor through filtering and screening. The brown pulp can then be sent to further processing or bleaching.
Pulp making
- 1. PULP MAKING Prepared by- Mr. Vishal B. Thakare (M.Tech, Chemical SVNIT Surat) Assistant Professor PARUL UNIVERSITY Vadodara vishalbt88@gmail.com
- 2. Pulp Manufacturing Pulp is a commercial fibrous material obtained from bamboo, wood, bagasse(waste material) etc. by mechanical and chemical means. Pulping means disintegration of bulky fibrous material to small fibers. There are mainly three modes of production of pulp: (a) Mechanical (b) Chemical (c) Semi chemical
- 5. Logs with bark are debarked by tumbling and rubbing action, then conveyed to chippers where large rotary disks with many heavy knives reduce the wood to 2-5 cm flat chips. The chips are metered via star valve to a deaerator-preheater. After several minutes, the chips are discharged through a rotating tapered plug into the lift line where recirculating digestion liquor at 12 atms get contacted. Transfers chips to the upper soaking zone of the 25-30 m tall digester tower where lignin and other non-cellulosic content digestion is done at 170oC and about 1.5 hr.
- 6. Cooking liquor is withdrawn as side streams and circulated through external heat exchangers to reheat and control the digestion temperature within the tower. The digested chips are cooled to 65oC at the base of the tower by injection of cold black liquor. This is to avoid mechanical weakening of fibers from steam explosion of the hot liquor when passed through the blow-down valve. The pulp liquor slurry is passed through the valve to a blow tank where residual heat is recovered in the form of steam which passes overhead with turpentine vapor to the chip preheater.
- 7. The pulp is filtered to separate black liquor and screened to remove wood knots and other undigested residue. The brown pulp goes either to product finishing operations or to the bleaching plant.