Membrane Contactor Degasser Simulator
Liqui-Cel Hollow Fiber Dynamics • Liquid-Film Mass Transfer (k_L) • Henry Law Equilibrium • Sub-ppb DO & CO₂ Sizing
1. Feed Water Stream & Target Gas
2. Contactor Cartridge Hardware
3. Stripping Mode & Lumen Vacuum
Hydrophobic Microporous Membrane Contactor Degasser Cutaway
Mass Transfer & Hydrodynamic Operating Diagnostics
Governing Membrane Contactor Mass Transfer Equations
NTU = \ln \left[ \frac{C_{in} - C^*}{C_{out} - C^*} \right] | C^* = H(T) × P_{gas,partial}
In vacuum + N₂ sweep mode, P_{gas,partial} → 0, yielding maximum log-mean concentration gradient.
Sh = \frac{k_L × d_h}{D_{AB}} = 0.38 × Re^{0.55} × Sc^{0.33} | A_{mem,req} = \frac{Q_{water} × NTU}{k_L} × (1 + f_{safety})
\alpha_{CO2,free} = \frac{1}{1 + 10^{pH - pK_1} + 10^{2pH - pK_1 - pK_2}} | pK_1 \approx 6.35, pK_2 \approx 10.33
5 Fatal Traps & Engineering Pitfalls
1. Trace Surfactant Pore Wetting & Irreversible Water Ingress
Hollow-fiber degassers rely on the high surface tension of pure water (72 mN/m) to prevent liquid from penetrating 0.04 μm hydrophobic pores. If feed water contains trace surfactants, IPA (isopropyl alcohol), or membrane cleaning detergents that lower surface tension below 30 mN/m, capillary pressure turns negative. Liquid water rushes into the micropores, drowning the gas phase. Mass transfer coefficient collapses by 99.9%, requiring expensive chemical drying or total cartridge replacement.
2. Alkaline pH Carbonate Ion Trapping in CO₂ Stripping Systems
At neutral to alkaline pH (7.5 to 8.5), inorganic carbon dissociates into charged bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻) anions. Because charged ions cannot diffuse across hydrophobic gas-permeable pores, attempting to degas CO₂ without acid dosing only strips the tiny 2% to 5% free gaseous fraction. Total inorganic carbon enters downstream EDI or mixed-bed polishers, exhausting ion exchange resins within days.
3. Excessive Shell-to-Lumen Differential Pressure (TMP) & Fiber Crushing
Hollow fibers have thin polymer walls (30 to 50 μm). If the shell-side water pressure exceeds lumen pressure by more than 3.5 to 4.0 bar—or if a fast-acting isolation valve creates hydraulic water hammer—the external overpressure crushes thousands of hollow fibers flat like squashed straws. Crushed fibers choke off lumen vacuum and nitrogen sweep flow, permanently destroying degassing capacity across the module.
4. Upstream Particulate Bridging & Severe Shell-Side Maldistribution
Hollow-fiber cartridges contain dense fiber bundles with inter-fiber spacings of only 50 to 100 μm. Operating without high-efficiency 1.0 μm absolute cartridge pre-filters allows suspended silt, resin fragments, and bio-slime to lodge in the bundle entrance. Particle bridging creates severe liquid channelling: high-velocity water bypasses peripheral fibers while stagnant zones breed bacterial biofilm, elevating shell-side pressure drop beyond 2.0 bar.
5. Insufficient Sweep Gas Ratio & Equilibrium Choking in High-CO₂ Feeds
When treating water with high dissolved CO₂ (>25 ppm), rapid mass transfer releases large volumes of CO₂ gas into the fiber lumens. If operating in vacuum-only mode without N₂ sweep gas, desorbed CO₂ gas accumulates inside the narrow fiber bores faster than the vacuum pump can evacuate it. Lumen pressure surges from 30 mbar to 200 mbar, raising equilibrium concentration C* and stalling mass transfer, leaving effluent CO₂ stuck above 5 ppm.