Superior Tools for Adjustable Screening Process Metso Paper Valkeakoski Oy, Finland Minna Puro 8th Research Forum on Recycling
Content of the presentation • Introduction • Numerical study • Results - simulation results - pilot trial results • Conclusions 2 10/17/2007 Minna Puro
Introduction • Operational demands set for DIP screening have intensified - raw material contains more and more impurities - accept pulp quality has to remain at high level - economical and environmental aspects become more significant • Intensifying demands force us to use narrower slots ⇒ capacity problems ⇒ strong reject thickening ⇒ remarkable operation problems and fiber losses with conventional technology ⇒ new foil and screen basket technology was needed 3 10/17/2007 Minna Puro
Numerical study The basic data of simulated foils and baskets 4 10/17/2007 Minna Puro
Foil simulations • Flow geometry static pressure [Pa] - 2D periodically accept frame basket symmetric slice - screen basket modelled as a porous media rotor frame - no inlet or outlet - different viscosity values tested periodic boundaries 5 10/17/2007 Minna Puro
Screen basket simulations • Comparison of different wire designs - slot speeds 1–10 m/s } corresponds foil-induced - tangential velocity 0,5 m/s pulsation on the feed side feed static pressure [Pa] - 2D periodically symmetric section wires - constant slot width #0.12 mm - constant 0.5 m/s tangential velocity on the accept side - water material accept properties periodic boundaries 6 10/17/2007 Minna Puro
Simulation results of foil study • New foil shape - ProFoil - very effective suction pulse - less co-rotation radial velocity tangential velocity ProFoil ProFoil Conventional foil 7 10/17/2007 Minna Puro
Simulated foil pressure pulses results • New foil shape - adjustability in respect to foil speed 8 10/17/2007 Minna Puro
Simulation results of screen basket wire study • New wire shape - Nimax - smooth and streamlined accept channel - optimised basket surface shape Conventional wire Nimax wire 9 10/17/2007 Minna Puro
Simulation and measured pressures Screen basket wire study • Good correlation between simulation and measurements 10 10/17/2007 Minna Puro
Foil pilot-scale trial results Capacity study • Comparison of reference and new foil - with #0.12 mm narrow slot and reference foil, plugging occurred at 0.8 m/s slot speed ⇒ too low capacity - with #0.12 mm narrow slot and new foil, operation was excellent 11 10/17/2007 Minna Puro
Foil pilot-scale trial results Energy consumption study • Comparison of reference and new foil - with #0.12 mm narrow slot, new foil used 10 % less energy than reference foil - energy saving can be even 30 % less as reported in one customer project 12 10/17/2007 Minna Puro
Foil pilot-scale trial results Reject thickening • Comparison of reference and new foil - reference foil is not in operation window with narrow #0.12 mm slot due to very strong thickening - new foil fulfilled the target of controlled thickening regardless of slot size and reject rate 13 10/17/2007 Minna Puro
Foil pilot-scale trial results Stickies • Comparison of reference and new foil - quality is at the same level with new foil and reference foil when running with #0.15 mm basket - with narrow #0.12 mm slot high quality was reached with reasonable low reject rates 14 10/17/2007 Minna Puro
Screen basket pilot-scale trial results Capacity study • Comparison of conventional wires (A, B) and new wire - new wire gives 20 % more capacity 15 10/17/2007 Minna Puro
Screen basket pilot-scale trial results Energy consumption study • Comparison of conventional wires (A, B) and new wire - new wire energy consumption is 10 % less than conventional wires 16 10/17/2007 Minna Puro
Screen basket pilot-scale trial results Reject thickening • Comparison of conventional wires (A, B) and new wire - new wire gives low level of thickening 17 10/17/2007 Minna Puro
Screen basket pilot-scale trial results Stickies • Comparison of conventional wires (A, B) and new wire - quality is at the same level with new foil and conventional foils 18 10/17/2007 Minna Puro
Conclusions Major benefits • By combining the new screen basket wire with the new foil design, optimal screening result can be summed up: - 20 - 30 % more capacity - 10 - 30 % energy saving - 10 - 20 % less thickening - excellent pulp quality - excellent runnability 19 10/17/2007 Minna Puro
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