Scrubber Design Calculation Excel Hot

When a hot gas enters, water evaporates. If you don't account for this, you'll run dry.

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.

For a hot gas stream entering a well-insulated scrubber (adiabatic), the gas will cool to the adiabatic saturation temperature (wet-bulb temperature), assuming sufficient liquid flow and residence time. scrubber design calculation excel hot

The Heat Balance Equation (Imperial Units):

Q_sensible = Q_latent

M_gas * Cp_gas * (T_in - T_out) = M_evap * h_fg

Where:

Excel Challenge: T_out is not known because the humidity ratio changes. You must use Goal Seek or iterative circular logic.

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

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. When a hot gas enters, water evaporates

This is the critical design constraint.

$$ \Delta P = \fracu_t^2 \times L \times \rho_l1000 \times C_d \quad \text(Simplified units) $$

A more robust Excel formula using the Hesketh Equation: $$ \Delta P \approx \fracu_t^2 \rho_g A_t^0.1331270 \times \left( L/G \right) $$ (Note: Ensure consistent units: Pa or in. w.c.)

Scenario: Kiln exhaust – 10,000 m³/h at 500°C, 2% dust (5 micron). For a hot gas stream entering a well-insulated

Result: The "cold" calculator would cause a gas velocity that is too high, massive re-entrainment, and pressure drop spikes. Your "hot" Excel sheet prevents this failure.