Air Dispersion Laboratory Agricultural and Biosystems Engineering Department Progress on Pit Foaming (what we know, what we don’t know, what we’re doing) 2013 Iowa Pork Congress Steven Hoff, Ph.D., P.E. Professor of Ag & Biosystems Engineering Iowa State University January 24, 2013
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Progress on Pit Foaming - Iowa Pork · Air Dispersion Laboratory Agricultural and Biosystems Engineering Department Progress on Pit Foaming (what we know, what we don’t know, what
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Air Dispersion Laboratory Agricultural and Biosystems Engineering Department
Progress on Pit Foaming (what we know, what we don’t know, what we’re doing)
2013 Iowa Pork Congress
Steven Hoff, Ph.D., P.E. Professor of Ag & Biosystems Engineering
Iowa State University
January 24, 2013
Air Dispersion Laboratory Agricultural and Biosystems Engineering Department
Objectives for Today
General Background on Foaming
Theories Regarding Pit Foaming
Discuss Current IPPA Funded Project
Precautionary Measures
Air Dispersion Laboratory Agricultural and Biosystems Engineering Department
Overall Foaming Requirements
Three-phase Process: 1. Gas generation (i.e. methane, hydrogen sulfide), 2. Surface tension reduction (surfactants; bio- or otherwise), 3. Bubble support structure (clustering bacteria or small fibers).
H2S
CH4
CH4
CH4
H2S
H2S
A surfactant causes surface to “elasticize”
Gases otherwise naturally escaping at very low concentrations are trapped
Foam supported by bacteria or fine fibers or ??
Air Dispersion Laboratory Agricultural and Biosystems Engineering Department
More on Surfactants
Surfactants allow stretching of the liquid interface. Surfactants can be: via detergents, oils, grease, or, via Biosurfactants produced by growing microbes Surfactants reduce the surface tension of the liquid allowing gas
bubbles to form.
Air Dispersion Laboratory Agricultural and Biosystems Engineering Department
More on Foam Support
For foam to persist, it must be supported somehow. This support can come from:
Special “filamentous” bacteria cluster together forming long strands (these bacteria also produce a bio-surfactant)
OR
Fine fibers present provide the required bubble support structure
Air Dispersion Laboratory Agricultural and Biosystems Engineering Department
Air Dispersion Laboratory Agricultural and Biosystems Engineering Department
Foam Forms, now What? Foaming Requires: Gas, Surfactant, Support Structure Reduce one aspect=Foam reduction (this is the good news…we have options) Example….Research has shown that foam will form if the surface tension reduces to 60 mN/m (plain water has a surface tension of 72 mN/m) However, once foam forms, a good remedy to break-up foam slowly is a product with a significantly lower surface tension compared to what caused foam to form in the first place. Comparison of products…. Component SurfaceTension (mN/m) Comment___________________________ Water 72 at 68oF Foam forms 60 on-set of foaming Soybean, corn, canola oils 29-32 at room temperature WD-40/Liquid Wrench 25 very low viscosity resulting in high flowability Diesel fuel 25 Silicon oil 15-20 wide range of viscosities (low viscosity needed) Defoamers 15-20 Silicon-based products (low viscosity)___________
Decrease the effects of foam causing surfactants --- Product with an even lower surface tension compared to 60 mN/m AND low viscosity allowing free-flowing over the foam surface.
Still: Root Cause Needs to be Found!
Air Dispersion Laboratory Agricultural and Biosystems Engineering Department