papr6 - Wood Yard Operations Lecture 6 PAPR 1000...

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Unformatted text preview: Wood Yard Operations Lecture 6 PAPR 1000 Introduction to Pulp and Paper Manufacturer 1 Bonus Questions Name three products other than paper that are derived from the pulping process. What are the four chemical components of wood? Name two species of hardwood and softwood used to make paper. 2 HW Hints One kilogram-force = exactly 9.80665 newtons. One gram-force = exactly 9.80665 millinewtons 101.3 kPa = 1 atm =14.7psi 3 Wood Preparation Covert wood into a form suitable for pulping In most cases the ultimate product is chips For groundwood pulping- short blocks are used 4 Wood Yard Operations The woodyard is the first step in the papermaking process. It includes wood receiving, storage, debarking, chipping & screening. Logging Debarking Chipping Screening 5 Wood Logging Logging: operations involved in getting standing trees from the forest to the point of utilization Logging methods: based on the tools, equipment, machines and personnel used (Fig. 3-2 to 3-14): The shortwood system consists of felling, delimbing, cutting into prescribed length, piling, and transporting the wood to roadside The full tree system, where the entire tree biomass above the felling cut is extracted to roadside intact for further processing In the tree length system, sophisticated machines delimb, top, sever the tree from its stump, and piles the logs and take them to roadside 6 Wood Debarking Ensure pulp is free of bark and dirt Several types of mechanical debarkers are used as well as hydraulic debarkers Drum barker (Fig 3-22) Ring barker (Fig 3-24) Rosser head barker (Fig 3-25) Hydraulic Jet barkers (Fig 3-26) Bark burnt in waste boiler 7 Wood Chipping After debarking, the wood logs are reduced to chips suitable for the subsequent pulping operations Optimum chip size: 20 mm long, 4 mm thick Acceptable chip size: 10-30 mm long, 2 to 8 mm thick Minimize overthick, fines and overlongs Flywheel with series of blades used Chip size and distribution very important to operation 8 Wood Screening Acceptable chips isolated from fines and oversized pieces Chips screened on a vibratory screens with holes or specialized chip thickness screens Oversized chips are rejected and reprocessed Undersized chips or fines are usually burned along with bark 9 Chip Handling and Storage Transportation Different type of conveyers Storage bins or silos (keep moist to prevent fire-mulch pile) Quality no contamination i.e. sand, grit, oversized, fines etc. degrade with time, temperature Safety temperature control (fire problem) water spray 10 Pulping Methods Pulping processes are of three principal types: Chemical Sulfate or Kraft Sulfite (high energy and environmental) Mechanical SGW RMP TMP Semichemical Many combinations of both 11 Pulping Methods Pulping processes are of three principal types: Chemical Sulfate or Kraft Sulfite Mechanical SGW RMP TMP Semichemical Many combinations of both 12 ...
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