Venturi Scrubber Pressure Drop Calculator

Model industrial air pollution control venturi scrubbers, calculate throat velocities, evaluate Hesketh pressure drops, and determine PM2.5 capture efficiencies.

Gas Flow Rate Q_g (ACFM)

Gas Temp T_in (°F)

Throat Area A_t (sq ft)

Liquid-to-Gas Ratio (L/G) Gal / 1,000 ACFM

Particulate & Scrubber Specs

Mean Particle Dia d_p (μm):

Particle Density (g/cm³):

Fan Total Efficiency η_fan (%):

Throat Geometry:

Scrubber Scrubbing Water Flow:

Hydraulic & Collection Performance

Venturi Pressure Drop (ΔP) -

Collection Efficiency (η) -

Gas Throat Velocity (v_t): -

Differential Pressure (kPa): -

Cut Diameter (d_p50): -

Induced Draft Fan Power (BHP): -

Motor Power Draw (kW): -

PM2.5 & Sub-Micron Removal Status

Hesketh Formulation: ΔP ≈ 1.03×10⁻⁴ · v_t² · (L/G)

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Principles of Industrial Venturi Scrubbers

A venturi scrubber is a high-energy wet collection device widely used in steel mills, cement plants, and hazardous waste incinerators to capture sub-micron particulate matter and toxic aerosols. The gas stream accelerates through a converging cone into a narrow throat, reaching extreme velocities of $60\ \text{m/s}$ to $120\ \text{m/s}$ ($12,000$ to $24,000$ FPM). Liquid injected into the throat is atomized by the shearing force of the gas into millions of microscopic droplets.

Hesketh Semi-Empirical Pressure Drop Formulation

The static pressure drop across the venturi throat is directly related to gas kinetic energy and liquid atomization:

\[ \Delta P = 1.03 \times 10^{-4} \cdot v_t^2 \cdot (L/G) \quad (\text{inches of water gauge, in. w.g.}) \]

Where:

$v_t = \frac{Q_g}{A_t}$: Gas velocity in the throat in feet per second (fps).
$L/G$: Liquid-to-gas ratio in gallons of water per $1,000\ \text{ACFM}$ of gas (typically 6 to 12).

Inertial Impaction & Cut Diameter ($d_{p50}$)

Sub-micron particles are captured via inertial impaction. High pressure drop creates smaller water droplets and greater relative velocity between gas and liquid, driving the aerodynamic cut diameter $d_{p50}$ down into the sub-micron range:

\[ d_{p50} \propto \frac{1}{\sqrt{\Delta P}} \]

At $\Delta P = 30 - 50\ \text{in. w.g.}$, PM2.5 collection efficiency routinely exceeds $98\% - 99.5\%$.

Frequently Asked Questions

Why does capturing sub-micron PM2.5 require extreme fan power?

Sub-micron particles possess negligible mass and tend to follow gas streamlines around water droplets without touching them. To force inertial collision, droplets must be atomized to ultra-fine sizes and accelerated violently, requiring pressure drops of 35 to 60+ inches w.g. A 50,000 CFM scrubber at 40 in. w.g. demands over 450 BHP in fan power.

What is an adjustable throat venturi scrubber?

Industrial boilers experience variable steam demand, causing flue gas CFM to fluctuate. An adjustable throat uses movable damper blades or an axial plug to vary throat area A_t in real time, maintaining constant throat velocity and constant collection efficiency regardless of load.

How are water droplets separated after the venturi throat?

The venturi throat exits into a diverging diffuser that recovers static pressure, followed by a cyclonic mist eliminator. Tangential gas entry creates centrifugal force that flings the slurry droplets against the outer wall, draining clean gas out the top stack.