Calculation Excel Hot ((install)): Scrubber Design

Mastering Scrubber Design: A Guide to Calculation Spreadsheets

11. Advanced Features (for “Pro” version of the sheet)

  • pH & solubility modeling – for acid gas removal (HCl, SO2) using mass transfer coefficients.
  • Multi-stage scrubbing – cascaded water loops (dirty vs clean water).
  • Real-time sensitivity slider – scroll bar to vary L/G and see ΔP & efficiency update instantly (Excel form control).
  • Chart generator – plots:
    • Efficiency vs particle size
    • Pressure drop vs L/G ratio
    • Gas cooling curve (T vs water flow)

Technical Write-Up: Venturi Scrubber Design & Sizing Calculations

Introduction

Packed bed scrubbers are the workhorses of industrial air pollution control, tasked with removing corrosive gases, particulates, and volatile organic compounds (VOCs) from exhaust streams. While sophisticated simulation software exists, Microsoft Excel remains the industry standard for preliminary sizing, vendor verification, and rapid troubleshooting.

Designing a "hot" (active) scrubber calculation sheet requires a blend of thermodynamics, mass transfer theory, and hydraulic correlations. This guide breaks down the essential components of a robust scrubber design Excel spreadsheet.

Tab 3: Mechanical Sizing

  • Vessel diameter based on Souders-Brown equation (using gas density at average temperature).
  • Height based on Number of Transfer Units (NTU) for mass transfer.
  • Critical: Check for flooding velocity using the corrected hot gas density.

Module 3: Required Liquid-to-Gas Ratio (L/G)

For hot acidic gases (HCl, SO2), the L/G ratio is driven by two factors: cooling duty and absorption. scrubber design calculation excel hot

Cooling L/G (gal/1000 ACFM): L/G_cool = (Q_sensible) / (Cp_water * Delta_T_water * 8.34)

Because the gas is hot, the water temperature will rise significantly. A common mistake is assuming the water temperature is constant. In your Excel sheet, add a heat balance on the water loop to compute the outlet water temperature. If the water exceeds 140°F, you risk scaling and reduced gas absorption. pH & solubility modeling – for acid gas

Step 1: Input Parameters & Gas Conversion

User inputs are marked in Bold.

  • Inputs:
    • Gas Flow Rate, $Q_actual$ (m³/s or ACFM)
    • Gas Temperature, $T_gas$ (°C or °F)
    • Gas Molecular Weight / Density, $\rho_g$
    • Particle Density, $\rho_p$
    • Target Particle Size (MMD), $d_p50$
  • Calculation (Hot Gas Conversion): Convert actual flow to standard flow if input is volumetric, or calculate actual density using the Ideal Gas Law: $$ \rho_g = \fracP \times MWR \times T_abs $$

5. Water Balance & Evaporative Cooling (The Really Hot Part)

When a hot gas enters, water evaporates. If you don't account for this, you'll run dry. Efficiency vs particle size Pressure drop vs L/G

Heat to remove: $$Q_sensible = m_g \times C_p,g \times (T_in - T_out)$$

Water evaporated: $$m_evap (kg/h) = \fracQ_sensible2257 , kJ/kg$$

Excel check: Add a cell that calculates Evaporation % of recirc flow. If > 3-5%, you need blowdown or a bigger pump.