Lesson 1Brownstock washing basics: dilution, displacement, and counter-current washingCovers dilution and displacement methods, shower and drum workings, and counter-current setups. Stresses washing efficiency, soda loss, filtrate reuse, and effects on evaporators, recovery boiler, and downstream fibre quality in Botswana mills.
Dilution and displacement washing methodsWashing factor, dilution factor, and soda lossWasher types: drum, DD, pressure, and beltFiltrate segregation and counter-current circuitsEffects on evaporators and recovery boiler loadImpacts on bleaching chemistry and fibre qualityLesson 2Drying section basics: dryer cylinder workings, temperature profiles, runnability factors, and reel windingExplains dryer cylinder workings, steam and condensate systems, and hood ventilation. Covers temperature profiles, pocket ventilation, sheet draws, and runnability, ending with reel winding basics, tension control, and roll structure for Botswanan operations.
Steam groups, condensate removal, and siphonsCylinder surface temperature and heat transferPocket ventilation and humidity managementSheet draws, threading, and runnability limitsDryness profiles and curl or cockle controlReel winding tension, nip, and hardnessLesson 3Bleaching sequences for wood-free papers: typical chemical stages and objectivesDetails common bleaching sequences for wood-free grades, including oxygen, peroxide, and chlorine-free stages. Explains stage objectives, selectivity, brightness targets, chemical interactions, and impacts on strength, dirt, and environmental load in Botswana.
Typical ECF and TCF sequences for wood-free pulpStage objectives: O, D, E, P, and peroxide stagesBrightness development and reversion controlChemical selectivity and fibre strength retentionCarryover limits from washing to bleachingEnvironmental and effluent considerationsLesson 4Overview of kraft pulping and brownstock composition and contaminantsExplains kraft brownstock composition, residual lignin, extractives, and entrained black liquor. Covers contaminants, shives, metals, and carryover that influence washing efficiency, bleaching cost, sheet defects, and recovery load in local mills.
Kraft cooking reactions and delignification profileTypical brownstock kappa, viscosity, and brightnessOrganic and inorganic contaminants in brownstockImpact of shives and knots on downstream operationsCarryover to washing, bleaching, and recoveryLesson 5Stock preparation: screening, cleaning, blend control (hardwood/softwood) and consistency managementDescribes screening, cleaning, refining interface, and hardwood–softwood blending. Focuses on consistency control, contaminant removal, fibre fractionation, and how stock prep settings influence formation, strength, and runnability on the machine in Botswana.
Coarse and fine screening efficiency targetsCentricleaners and removal of heavy contaminantsHardwood and softwood blend strategiesConsistency control loops and instrumentationRefining location relative to screening stagesEffects on formation, strength, and defectsLesson 6Mass and energy balances across the fibre line: yield, solids flow, steam and condensate flowsDevelops mass and energy balances across the fibre line, from brownstock to reel. Includes yield, solids and liquor flows, steam and condensate circuits, and how balances support troubleshooting, optimisation, and cost tracking in Botswanan plants.
Defining system boundaries and process mappingFibre yield, rejects, and loss accountingSolids, liquor, and filtrate flow balancesSteam, condensate, and heat recovery loopsUsing balances for troubleshooting and auditsLinking balances to cost and KPI trackingLesson 7Approach flow systems: save-alls, blending chest, screens, and chemical additionsExplores approach flow layout from machine chest to headbox. Covers mixing and blending chests, screens, cleaners, save-alls, and chemical addition points, emphasising stability, basis weight control, and short-circulation cleanliness in local settings.
Machine chest, mixing chest, and level controlFan pump function and pressure stabilityApproach flow screening and cleaning stagesSave-all systems and white water recoveryChemical addition strategy and timingBasis weight and dilution control systemsLesson 8Interdependencies: how changes in washing, bleaching, refining, or forming affect downstream moisture, strength and steam demandShows how washing, bleaching, refining, forming, pressing, and drying interact. Emphasises how upstream changes shift moisture, strength, porosity, and steam demand, and how to diagnose root causes using cross-section data in Botswana operations.
Washing carryover effects on bleaching and dryingRefining impacts on drainage, strength, and energyForming quality versus pressing and drying limitsPress dryness and downstream steam consumptionBleaching and strength tradeoffs in final sheetSystematic root cause analysis across the lineLesson 9Forming section basics: headbox hydraulics, slice setting, jet-to-wire ratio, and forming fabricsIntroduces headbox hydraulics, slice opening, and jet-to-wire ratio. Explains turbulence generation, fibre orientation, forming fabric design, and drainage elements, linking settings to formation, CD profiles, and two-sidedness in Botswanan mills.
Headbox types: open, hydraulic, and dilutionHeadbox consistency and turbulence intensitySlice opening, lip profile, and CD controlJet-to-wire ratio and fibre orientation effectsForming fabric design and conditioningDrainage elements and vacuum box settingsLesson 10Pressing and consolidation: nip types, press loading, press felts and water removal mechanismsCovers press nip types, loading strategies, and press felt design. Explains water removal mechanisms, nip dwell time, void volume, and rewet, and how pressing influences dryness, bulk, strength, and steam demand in the dryer section locally.
Single, double, and shoe press configurationsPress loading, line pressure, and nip dwell timePress felts, void volume, and conditioningMechanisms of water removal and rewetPress dryness versus bulk and strength tradeoffsImpacts on dryer steam demand and runnability
