Design Calculation Excel Hot | Scrubber

This write-up covers the thermodynamic principles, the step-by-step calculation logic required for the Excel model, and the critical design parameters.

Step 2: The Psychrometric Macro (VBA)

Standard Excel cannot loop adiabatic saturation easily. Write a simple VBA function:

Function AdiabaticSaturation(T_gas, RH_in, P_atm)
    ' Iterative loop to find T_out where heat lost = evaporation heat
    Do While Abs(HeatBalance) > 0.01
        T_out = T_out - 0.1 * (HeatBalance / Slope)
    Loop
End Function

Why this is "Hot": This macro transforms a static calculator into a dynamic tool for variable flue gas temperatures.

Why Excel is Still the King for Scrubber Sizing

While heavy simulation software (Aspen, HYSYS) is powerful, nothing beats an Excel sheet for rapid iteration, especially for hot gas scrubbing (e.g., exhaust from 150°C to 300°C). Temperature changes density, viscosity, and vapor pressure—if your sheet ignores these, your scrubber will flood or dry out. scrubber design calculation excel hot

This post walks you through building a packed bed wet scrubber calculator for hot gas streams (SO₂, HCl, or particulate removal with cooling).

2. Scrubber Type Selector & Geometry Engine

Excel drop-down drives different calculation pathways:

| Scrubber Type | Key Design Outputs | |---------------|--------------------| | Venturi | Throat velocity (60–120 m/s), pressure drop (based on Johnstone eq.), liquid-to-gas ratio (L/G) | | Spray Tower | Sauter mean diameter (SMD) of droplets, tower height, gas residence time | | Packed Bed | Packing factor (Fp), flooding % (≤75%), pressure drop via Leva or Eckert correlation | | Tray (Impinement) | Number of trays, slot velocity, weir loading | Step 2: The Psychrometric Macro (VBA) Standard Excel

• Dynamic L/G ratio optimizer – finds minimum liquid flow for target outlet temperature or particulate removal efficiency.

Why "Hot" Changes Everything

Standard scrubber design assumes isothermal conditions. But when your inlet gas is at 400°C (752°F) or higher, three critical physics problems emerge:

1. Adiabatic Saturation: The gas cools by evaporating water. This is not a linear process; it requires solving heat and mass transfer simultaneously.
2. Volume Expansion: A hot gas occupies vastly more volume. A 500°C gas has roughly 2.6x the volumetric flow rate of gas at 20°C. If your Excel sheet uses standard flow, your vessel will be catastrophically undersized.
3. Material Limits: High temperatures warp PVC and melt polypropylene. Your Excel calculator must flag when outlet temperatures exceed material ratings.

A standard scrubber calculator fails here. You need a thermal scrubber design calculation Excel hot version that includes psychrometrics.

1. Input Data (Hot Conditions)

| Parameter | Example Value | Unit | | :--- | :--- | :--- | | Gas flow rate (actual) | 10,000 | m³/h | | Gas inlet temperature | 220 | °C | | Gas outlet temp (cooled) | 65 | °C | | Operating pressure | 1.013 | bar(a) | | Packing type | 2" Plastic Pall Ring | - | | L/G ratio (target) | 1.5 - 2.5 | L/m³ | Why this is "Hot": This macro transforms a

The "Hot" factor: Always convert gas flow from Normal/Standard to Actual at operating temp.

$$Q_actual = Q_std \times \fracT_op + 273273 \times \frac1.013P_op$$

In Excel: =B2*((B3+273)/273)*(1.013/B4)