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Defoamers Defoamers and and Deaerators Deaerators Chemistry, Mechanisms and Analytical Techniques
Dr. Christoph Hamers
BASF Aktiengesellschaft 67056 Ludwigshafen/Germany Phone + 49 621 60 21845e-mail: [email protected]
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Outline
Definition
Air introduction into a PM
Stabilization mechanisms
Mechanisms of defoamers and deaerators
Physical and chemical properties of deaerators
Analytical techniques
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What is foam?
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Cork
Sponge
Coral
Tree leaf
Balsa wood
Plant stalk
Natural foam structures
NaturalNaturalcellularcellularmaterialsmaterials
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Aqueous foam
H2OH2O
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White water
Pumps
Cascades
Broke
Dissolved air from fresh water
Air introduction Stabilization Consequences
Ligninsulfonate
Emulsifiers (e.g. deinking process)
Pitch
Oligo/Polysaccharides
Higher volume
Decreased efficiency of pumps/deculators
Surface foam
Flotation
Pinholes
Drainage problems
Sources of entrained air
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Stabilization of air bubbles
Air
In pure waterNo foam
In paper stockStable foam
Water
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Air bubble
Amphiphilic character
Water
Structure of a stabilized foam lamella
Air
Water
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Surface energy increases
Stabilization of bubbles – Gibbs’ effect
Expansion of lamella
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Expansion of lamella
Increase of surface tension
Decrease of surfacetension over time
Stabilization of foam – Marangoni effect
DiffusionDiffusion
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Methods of deaeration
Physico-mechanicalDeculator (vacuum)
Centrifugal cleaners (vacuum)
High-power ultrasound – rare
ChemicalHydrophobic particles
Surfactants
Spreading agents
Oil
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Structure of defoamers and surfactants
Non-emulsifiable emulsifiable water soluble
Deaerator/defoamer Deaerator/defoamer
SurfactantSurfactant
Hydrophilic group = – OH, – COOH, – EO, – NR2, – SO3H
Hydrophobic hydrocarbon chain = – CH2 – CH2 –
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Surfactant molecules
Amphiphilic, micelle-forming
Decrease surface tension
Defoamer molecules
Hydrophobic
Insoluble in water
Difference betweendefoamer and surfactant molecules
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Mechanisms of defoamers – Part 1
Defoamer
Ruptured surfactant filmSurfactant
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Mechanisms part 2 – Aggregation model
Deaeration
Dispersed air
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Active substance Formulation Classification
Liquid 100% Oil defoamer
Emulsified Defoamer emulsion
Solid Dispersed Deaerator dispersion
Definitions
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Non-emulsifiableoil
Emulsifiableoil
Dispersion
Defoamer/deaerator formulations
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Deaeration performance
Emulsion-forming tendency
Deaeration vs. chemical properties
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20 30 40 50 60 70°C
Deaerator A
Deaerator B
high
poor
Performance
Impact of temperature on deaeration
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Impact of furnish on deaerator consumption
0 10 20 30 40 50 60 70 80 90ml 1% Afranil dilution
Afranil SLO consumption in different model stocksSONICA air content 0.3%
100% TMP
70/30 Langfaser - Kurzfaser; *
2kg 70/30 Langfaser - Kurzfaser; *
Holzschliff Rückseite + Einlage;Decke 60/40 - Kiefer/BucheWellpappe
50% Steinschliff / 50% gebl. Sulfit
Typ - 100 % Steinschliff
* gebleichter Zellstoff + Stärke (Oberfläche)
40°C50°C
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Impact of wet-end chemicals on deaerator consumption
Impact of paper chemicals on performance of deaerator dispersions at 50°C (Sonica)
Additional consumption of deaerator dispersion
2 % Fastusolgelb PR 81760,75% Basazolrot 40L0,75% Basazolviolett 46L0,75% Basazolgelb 46L8% Luresin KTU0,8% Luresin KTU2% Solvitose0,5% Solvitose1% Ligninsulfonat2% Harzl.+Alaun pH 5 0,1% Harzl.+Alaun pH 5 2% Harzleim0,1% Harzleim5% Basoplast 265 D1% Basoplast 265 D0,5 % Basoplast 2030 LC10 % CaCO³+ 0,2% Poly.SK10 % CaCO³ PCC0,2% Polymin KE 20201 % Polymin SK0,1% Polymin SKohne Zusatz
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Analytical methods of air measurement in suspensions
Compression and expansion (1953)
Density changes (1951)
Optical methods, bubble count (1970)
Light scattering (1982)
Ultrasound
Indirect air measurement on PMs viaspeed of mixing pumpvacuum levels in process equipment (deculator)foam volume
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Pump
45°C
Aircontentanalyzer
Temperaturecontrol
Air content measurement in the laboratory
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Air content measurement by ultrasound –SONICA instrument
Pressure indicatorPiston
Valve
Receiver
From head box
Trans-mitter
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Mütek – GAS 60gas determination by compression
Lab test for gas determination similar to SONICA
Measurement of dissolved gas by expansion
Measurement of dispersed gas by compression
Sampling rate 2 min, slower than sonica
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Bleed valveLid
1 atmosphere markBubble chamber
Sample cylinder
O-ringPistonCap with graduation
Knob
Entrained gas tester –Gas measurement by compression
9 18 0
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BASF foam tray
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SITA foam tester
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0
20
40
60
80
100
120
140
0 1 2 3
SITA foam tester
Schaumvolumen [ml]
Messwert
Afranil® PR 8177
33/04-b
33/04-c33/04-dAfranil® SLO
33/04-e
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BASF Defoamers and Deaerators:Afranil®
Stock deaeration using quality BASF productsInhibits foam
Improves retention
Enhances stock dewatering on the wires and in the wet presses
Reduces pinholes and surface roughness of the paper
Results in considerable energy savings when pumping the furnish and pumps
Has a positive effect on paper machine runnability and productivity
Enhances the efficiency of other process chemicals such as retention aids
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BASF Defoamers and Deaerators:Afranil®
Customer benefitsStock deaeration
low high0 51 2 3 4
Energy savings when pumping the furnish
Performance enhancement of other process chemicals
Paper qualaity
Foam inhibition
Fibrer and filler retention
Dewatering on the wire
Dewatering in the wet press
Runnability/productivity
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Oil based products
destroying surface foam
Defoamers
20 30 40 50 60 70
Afranil®MG
Afranil®SLO
Afranil®PR 8177
Temperature [°C]
Afranil® RSAfranil® F fluid, Afranil® T fluid, Afranil® AW
Deaerators
Emulsion type products
preventing foam formation
BASF Defoamers and Deaerators:Afranil®
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Afranil® RS
Afranil® PR 8177
Afranil® SLO
Afranil® MG
Temperature [°C]20 7030 40 50 60
BASF Defoamers and Deaerators:Afranil®
Application range for deaeratorsSpecial
applications
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Afranil® T Liquid BGVV/FDA Also acts as stock deaerator Can be metered direct via pumps or by drip feed Dangerous to the environment
Afranil® AW Mainly used against surface foam Can be metered directly
BASF Defoamers and Deaerators:Afranil®
BASF Product Portfolio Defoamer OilAfranil® F Liquid
Can be used in groundwood and sulphite pulping Also acts as stock deaerator Can be metered direct via pumps or by drip feed
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BASF Defoamers and Deaerators:Afranil®
Afranil® dosing system of BASFPrepares the productRegulates the flow rateMixes the deaerator with fresh waterSupplies the mixture
Undilutedproduct
Afranil®
To the dosing point
Afranil®mixer
Transferpump
Meteringpump with
MI flow meter
Fresh water200-400l/hStirrer
Flow meterset at 3.5l/h
