Infrared and Its Application For Drying Coatings On Webs

AIMCAL FALL TECHNICAL CONFERENCE2005

By: Bob NarangRadiant Energy Systems, Inc.

www.radiantenergy.com

Water or solvent based wet coatings applied on webs,are generally dried using three technologies:

1. Convection – such as a hot airimpingement or flotation dryer

2. Conduction –oil or steam heated drums

Heated Drum

Web Path

3. Infrared or Radiant Heating

IR Emitter

Web Path

Electric/Gas Infrared Heating System

Typical Conduction Heating System

Exhaust Air Plenum

Web Path

Recirc/ Exhaust

Heated Supply Air

Direct Impingement Convection Dryer

•• Theory of InfraredTheory of Infrared•• Different types of infrared heatersDifferent types of infrared heaters•• ApplicationsApplications•• Advantages and LimitationsAdvantages and Limitations•• AcknowledgementsAcknowledgements

Infrared Drying

Theory of InfraredTheory of Infrared

Electromagnetic Spectrum showing varioustypes of energy based on wavelength

Infrared SpectrumInfrared Spectrum

The Infrared spectrum can beThe Infrared spectrum can bedivided into three divided into three

categories:categories: 1. Short Wave Length2. Medium Wave Length3. Long Wave Length

3 Basic Laws of Radiation3 Basic Laws of RadiationWienWien’’s Laws Law

The peak wave length of The peak wave length of emission of an infrared heater emission of an infrared heater can be calculated by Wiencan be calculated by Wien’’s Laws Law

λ = C/T

λ – wavelength in microns

C - Constant 2898

T - Source temperature (ºK)

Stefan Boltzman LawStefan Boltzman Law

W = kTW = kT44

W – Emitted Power

k - Constant

T – Source temperature (°K)

PlanckPlanck’’s Laws Law

Spectral Characteristics of InfraredSpectral Characteristics of Infrared

-- Absorbed by the object (A)Absorbed by the object (A)-- Reflected by the object (R) Reflected by the object (R) -- Transmitted through the Transmitted through the

object (T) object (T)

A + R + T = 100% of A + R + T = 100% of energy received.energy received.

Absorption Curves for Different ProductsAbsorption Curves for Different Products

Types of HeatersTypes of Heaters

Short Wavelength Quartz Tube Short Wavelength Quartz Tube Emitter (TEmitter (T--3 lamp)3 lamp)

Medium Wavelength Quartz Tube Emitters

Medium Wavelength Stamped Foil Type Heaters

Types of HeatersTypes of Heaters

Long Wavelength Infrared Long Wavelength Infrared HeatersHeaters

Gas Fired Infrared Heaters

ApplicationsApplications

Infrared Air & Hot Air Dryeron a Coating Line

Infrared Air Pre-dryer

ApplicationsApplicationsThere are numerous applications where Infrared and Infrared Air There are numerous applications where Infrared and Infrared Air Dryers have been successfully used to enhance drying and curing Dryers have been successfully used to enhance drying and curing capabilities of coating lines. Listed below are some of the morecapabilities of coating lines. Listed below are some of the morecommon and more successful applications:common and more successful applications:Dry and PreDry and Pre--Dry Water and Solvent based Pressure Sensitive Dry Water and Solvent based Pressure Sensitive AdhesivesAdhesivesLaminate foam to fabric using web adhesives for automotive and Laminate foam to fabric using web adhesives for automotive and furniture industries furniture industries Dry and PreDry and Pre--Dry Water based latex and clay coatings on paperDry Water based latex and clay coatings on paperMoisture profiling across the machine direction in paper industrMoisture profiling across the machine direction in paper industryyPreheat films for laminating and embossingPreheat films for laminating and embossingDry Dry flexoflexo and gravure printed inksand gravure printed inksDry and cure PTFE coatings on fiberglass fabricsDry and cure PTFE coatings on fiberglass fabricsCure Silicone coatings on various substratesCure Silicone coatings on various substratesCure PVC coatings on scrim, Cure PVC coatings on scrim, nonwovensnonwovens and woven fabricsand woven fabricsDry and cure solvent base resin coatings for electronics industrDry and cure solvent base resin coatings for electronics industryyCure 100% solids resin coatings on fiberglass for Printed CircuiCure 100% solids resin coatings on fiberglass for Printed Circuit t BoardsBoardsPrePre--Dry, dry and cure coatings on industrial fabricsDry, dry and cure coatings on industrial fabricsDry food, Dry food, nutraceuticalnutraceutical and pharmaceutical coatings on filmand pharmaceutical coatings on film

Advantages of Infrared DryersAdvantages of Infrared Dryers

High efficiency conversion of electrical energy into heat for High efficiency conversion of electrical energy into heat for electrical IRelectrical IRHigher rate of heat transferHigher rate of heat transferFloor space savings due to smaller sizeFloor space savings due to smaller sizeHeats only the object without heating the surroundingsHeats only the object without heating the surroundingsEasy to zone for uniform heating of the productEasy to zone for uniform heating of the productFaster response to changing process conditionsFaster response to changing process conditionsQuick start up and shut downQuick start up and shut downEasy to have cut off zones for narrow widthsEasy to have cut off zones for narrow widthsEase of controlEase of controlLower capital and installation cost Lower capital and installation cost Can be easily be added to existing conventional dryers to Can be easily be added to existing conventional dryers to increase line speedincrease line speedInfrared Air dryers suitable for solvent based coatingsInfrared Air dryers suitable for solvent based coatings

Limitations of Infrared DryersLimitations of Infrared Dryers

Some coatings may not be able to take advantage of higher Some coatings may not be able to take advantage of higher rates of heat transfer and may skin and blisterrates of heat transfer and may skin and blisterDifficult to work with temperature sensitive substrates Difficult to work with temperature sensitive substrates Scaling up of the heaters is not always straightforwardScaling up of the heaters is not always straightforwardSince IR is basically a surface phenomenon, harder to Since IR is basically a surface phenomenon, harder to dry heavier coatingsdry heavier coatingsAlmost essential to run trials in lab or on the pilot line toAlmost essential to run trials in lab or on the pilot line toconfirm designconfirm design

AcknowledgementsAcknowledgements

Infrared Process Heating Handbook by Industrial Infrared Process Heating Handbook by Industrial Heating Equipment AssociationHeating Equipment AssociationHandbook of Industrial Drying by Arun MujumdarHandbook of Industrial Drying by Arun MujumdarWatlow IR HandbookWatlow IR HandbookPhillips Lighting HandbookPhillips Lighting HandbookLitex Infrared Lamps Litex Infrared Lamps Electric Process Heating by Maurice OrfeuilElectric Process Heating by Maurice OrfeuilHydro QuebecHydro Quebec