Wet Electrostatic Precipitator (WESP) Sizing & Acid Mist Removal Calculator
Perform industrial sizing of Wet Electrostatic Precipitators (WESP) for sub-micron particulate, condensed organic aerosol, and sulfuric acid mist capture using Deutsch-Anderson and modified Matts-Ohnfeldt models. Size hexagonal tubular bundles, calculate migration velocity, high-voltage T-R set electrical power, and wash water demand.
1. Flue Gas & Particle Specifications
2. Precipitator Geometry & Electrical Results
Governing Principles & Mathematical Derivations for WESPs
Wet Electrostatic Precipitators utilize strong DC electrostatic fields to impart negative charge to suspended sub-micron droplets and solid particles, driving them to grounded, water-washed collection surfaces.
1. Sizing Models: Deutsch-Anderson vs Modified Matts-Ohnfeldt
In the classical Deutsch-Anderson model, collection efficiency is governed by the exponent of the product of specific collecting area and migration velocity:
For fine acid mists, the modified Matts-Ohnfeldt model incorporates an empirical exponent (m = 0.5) to accurately capture polydisperse sub-micron drift kinetics:
2. Hexagonal Tubular Bundle Geometry
Hexagonal tubes arranged in a honeycomb bundle maximize surface area while maintaining uniform gas velocity across the vessel cross-section:
Design gas velocity is held between (1.2 ext{--}1.8, ext{m/s}) to prevent aerodynamic shearing and re-entrainment of the liquid film cascading down the tube walls.
3. High-Voltage Corona Power & Transformer-Rectifier (T-R) Sizing
The electrical power delivered to the ionizing corona discharge must be sufficient to maintain avalanche ionization without triggering continuous spark arcs:
Modern switched-mode power supplies (SMPS) operate at 50–70 kV DC with current densities of (0.5 ext{--}1.2, ext{mA/m}^2), yielding typical power consumption of (30 ext{--}60, ext{W/m}^2) of collecting surface.
5 Fatal Traps & Engineering Pitfalls in WESP Design & Operation
1. The Gas Distribution Maldistribution Catastrophe
Because WESP collection efficiency is logarithmic, non-uniform gas flow destroys performance. If 30% of the gas channels through a high-velocity core at 3.0 m/s, that portion experiences severe penetration, dropping overall collection efficiency from 99.8% to 94%. Dual perforated perforated gas distributor plates and CFD flow modeling are mandatory to achieve a coefficient of variation (C_v < 0.15).
2. Insulator Purge Air Failure & High-Voltage Flashover
The support insulators that suspend the rigid high-voltage discharge mast must be isolated from wet, corrosive process gas. If the heated purge air blower trips, acidic moisture condenses on the cold alumina insulator surfaces, creating a conductive liquid bridge that triggers catastrophic dielectric tracking, electrical flashover, and shattered insulator ceramics.
3. Dry-Spot Acid Corrosion & Pitting Breakdown
In wet precipitators constructed from high-alloy austenitic stainless steels (e.g. Alloy 20, Hastelloy C-276), complete and continuous wetting of the tube walls is vital. If water distribution weirs foul and dry spots form, concentrated sulfuric acid (50–70% H2SO4) concentrates under high heat, triggering rapid stress corrosion cracking and pinhole pitting that destroys the tube bundle in under 12 months.
4. Spark Quenching from Inadequate Water Washing Drainage
During intermittent wash cycles, if water drain sumps are undersized or header nozzles discharge uneven torrents, liquid bridges form between the central discharge electrode and the tube wall. The T-R controller interprets these liquid bridges as continuous dead shorts, collapsing voltage to zero and discharging unscrubbed acid mist directly out the stack.
5. Corona Wire Vibration & Misalignment Fatigue
Weighted wire or rigid mast discharge electrodes must remain precisely centered within ±3 mm of the tube axis. If gas vortex shedding or asymmetric electrostatic pull induces lateral wire oscillation, the gap to one wall narrows, triggering continuous local spark-overs while the opposite wall remains un-ionized, slashing collection efficiency by 50%.