Design & Manufacturingof Press Fabrics for

Improved Dewatering

Chad A. Hume & Dr. David W. Rosen

George W. Woodruff School of Mechanical EngineeringRenewable Bioproducts InstituteGeorgia Institute of Technology

RBI Dewatering Project

• Press Fabric DesignGoal: Design features, such as holes and grooves, for inner layer of multi-layer fabric to:

– Facilitate dewatering

– Prevent/reduce rewetting

• Inner Layer ManufacturingGoal: Develop 2D and 3D ink-jet printing testbeds to fabricate designed inner layers using high viscosity fluids such as thermoplastic polyurethane (TPU)

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Agenda 2020 Drier Web Roadmap

• High Priority R&D Area– Next-generation nip/press design for single-direction

flow – eliminate rewet

• High Priority Projects– Develop adaptive felt materials or structures that have

high permeability at high nip-loads and low permeability at low loads

– Identify or develop a membrane that will support unidirectional or preferential flow of water away from the fiber web

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Outline

• Press Fabric Introduction

• Press Fabric Flow Modeling

– Passive

– Active

• Inkjet Printing

– Prototyping

– High viscosity droplet generator

– Process modeling

• Conclusions

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Paper Machine Overview

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Increasing Dry Solids

1% 20% 50% 95%

𝑑. 𝑠.

=𝑚𝑓𝑖𝑏𝑒𝑟

𝑚𝑓𝑖𝑏𝑒𝑟 +𝑚𝑤𝑎𝑡𝑒𝑟

Recent trends and directions

• Non-woven bases– Research observed better pressure uniformity,

higher solids, less marking, and less rewet

• Inclusion of polymer membranes and layers

• New manufacturing techniques– Additive manufacturing can build optimized geometry

for polymer layer7

Outline

• Press Fabric Designs

• Press Fabric Flow Modeling

– Passive

– Active

• Inkjet Printing

– Prototyping

– High viscosity droplet generator

– Process modeling

• Conclusions

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Press Fabric Design

• Focus on barrier layer

• FEA & CFD to simulate

deformation and flow

• Various designs are studied including woven, nonwoven, conical, etc., as well as “active” geometries

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Data Available

• Stream Lines

• Velocity/Pressure

• Pressure Drop

– This is related to flow resistance

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3D Results

• Can we design a hole that opens for forward flow and closes to prevent rewet

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• 145% increase in resistance to back flow

Outline

• Press Fabric Designs

• Press Fabric Flow Modeling

– Passive

– Active

• Inkjet Printing

– Prototyping

– High viscosity droplet generator

– Process modeling

• Conclusions

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Inkjet Printing – 3D Printing

• High Resolution

• Fast

• Scalable – just add more nozzles

• Multiple materials

• $15-20B industry and growing

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Fabric Prototyping

• Prototype fabric designs were fabricated using the Stratasys Connex to explore both passive and active designs

•

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Georgia Tech Inkjet System

• Print high viscosity (>100cP) and complex fluids (non-Newtonian, suspensions/colloids)

• Ultrasonic droplet generation technology– New approach to printing. Excite at resonant frequency +

acoustic focusing in nozzle causes ejection of droplet.

– Easily scaled for printing repeated patterns.

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4 mm droplets

Droplet Modeling

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• Efficiently model how different machine parameters and material affect print quality

Closure

• 1st order approximation for how hole design affects flow.

• Promising new design to facilitate unidirectional flow. Investigating variants.

• Inkjet printing proposed as manufacturing process with high viscosity materials

• Developing process simulation to predict as-fabricated geometries

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Design & Manufacturingof Press Fabrics for

Improved Dewatering

Chad A. Hume & Dr. David W. Rosen

George W. Woodruff School of Mechanical EngineeringRenewable Bioproducts InstituteGeorgia Institute of Technology

Pressing Overview: Basic Physics

• Water movement occurs only with pressure differential• Pressure must be higher in the sheet than felt• If hydraulic pressure exists, saturation must exist at least

locally– There must be a continuum of fluid

• To move fluid:– Voids must exist in the felt, or– Voids must exist beyond the felt, or– Water must flow in MD or CD, or– Sheet explodes (Crushing)

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Flow Modeling: 2D and 3D

• 2D Simulations

• 3D Simulations

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3D Results

• Investigation of passive geometries

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Summary

• 1st order approximation for how hole design affects flow

• Various designs tested and one proposed which improves through flow and resists backflow

• Phase 2:

– How can we manufacture these membranes?

– Inkjet Printing!

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