Scrubber Design Calculation Excel Hot Work [ UHD ]
The hum of the plant was usually a comfort to Elias, but today, the caustic scrubber
was screaming. Not literally, of course—though the high-pressure alarm on the control panel was doing a fine job of that.
The inlet gas temperature from the kiln had spiked, and the old design parameters were failing. If the liquid-to-gas ratio stayed this off-balance, the stack would start "yellow-smoking," and the EPA would be at the gates by noon.
Elias ducked into the site office, his boots clacking on the linoleum. He pulled up his master file: Scrubber_Design_Final_v4_HOT.xlsx
"Talk to me," he muttered, fingers flying across the mechanical keyboard. He didn't just need a fix; he needed a recalculation for adiabatic saturation
. As the hot gas hit the recirculating liquor, it would evaporate water instantly, cooling the gas but shrinking its volume and changing the density. The Inputs:
He punched in the new 450°F inlet temp and the soaring flow rate. The Magic:
The spreadsheet’s hidden VLOOKUPs pulled the physical properties of the gas. The NTU (Number of Transfer Units) cells turned a cautionary orange. The Solve:
He adjusted the packing depth from 10 feet to 14. The pressure drop calculation—the heart of the sheet—recalculated.
With a final tweak to the pump frequency on the screen, he watched the "Flood Point %" drop from a dangerous 92% to a stable 70%. He hit 'Save,' exported the setpoints, and ran back to the floor.
Ten minutes later, the alarm fell silent. The plume at the top of the stack turned from a ghost of a haze to invisible, clean air. Elias leaned against the steel railing, the heat of the tower radiating against his back, and smiled.
The math held. The Excel sheet, messy as it was, had saved the day. pressure drop across the packing for your own design?
Designing a scrubber, specifically for "hot" or high-temperature gas streams, requires accounting for gas humidification and volume changes before sizing the vessel. You can find pre-built templates on platforms like Scribd or Cheresources that handle these calculations. Core Calculation Steps for Hot Gas Scrubbers scrubber design calculation excel hot
For high-temperature applications, the "hot" gas must be cooled to its adiabatic saturation temperature before or during the scrubbing process. Gas Inlet Properties: Define your inlet gas temperature ( Tincap T sub i n end-sub
), flow rate, and pressure. Hot gases have lower density, which significantly increases the required tower diameter.
Saturation & Humidity: Calculate the saturated gas flow rate. For example, a gas at 400°F may have a saturation temperature around 127°F, which changes the volumetric flow rate ( Qsatcap Q sub s a t end-sub ) used for sizing.
Liquid-to-Gas (L/G) Ratio: This is the most critical design parameter. For venturi scrubbers, typical ratios are 7–20 gallons per 1,000 cubic feet of gas.
Tower Diameter: Use the gas velocity and pressure drop to find the cross-sectional area. The diameter ( ) is typically calculated as Pressure Drop ( ΔPcap delta cap P
): For venturi types, use the Hesketh or Calvert equations to ensure the fan can handle the resistance. Recommended Excel Templates
Excel calculation sheet for rating of a spray tower scrubber
For designing and calculating wet scrubbers in Excel, there are several specialized templates and resources available that cover hydraulic design, mass transfer, and cost estimation. Excel Calculation Templates Spray Tower Scrubber Rating: Meloni Marco
offers a downloadable spreadsheet for preliminary single-stage spray tower calculations, including removal efficiency and pressure losses.
EPA Scrubber Cost & Design: The U.S. EPA provides comprehensive workbooks like the Wet & Dry FGD Data Inputs
and cost calculation spreadsheets for packed bed and flue gas desulfurization (FGD) systems.
Packed Bed Design: Engineering forums like Cheresources host community-shared files such as scrubber_design.xls and Packed bed+ hetp.xls for tower sizing. Wet Scrubber Design Excel Sheet | PDF - Scribd The hum of the plant was usually a
Designing a scrubber—specifically for hot gas streams—requires accounting for gas cooling (humidification) before sizing the physical vessel. Most Excel-based guides follow a specific sequence to determine the required tower diameter and height based on mass transfer or particulate removal needs. 1. Pre-Design Step: Humidification (Hot Gas Adjustment)
Before sizing the tower, you must calculate the saturated gas flow rate. Hot inlet gas will evaporate scrubbing liquid, increasing the gas volume and cooling it to its adiabatic saturation temperature.
Identify Inlet Conditions: Inlet gas temperature, pressure, and moisture content (lb water/lb dry gas).
Calculate Saturation: Use psychrometric data to find the saturation temperature and the resulting Saturated Gas Flow Rate (ACFM). This saturated volume is the basis for all subsequent diameter calculations. 2. Sizing the Scrubber Diameter
The diameter is typically limited by gas velocity to prevent "flooding" or excessive pressure drop.
Set Design Velocity: For common spray towers, a typical velocity is approximately Calculate Area ( ): Calculate Diameter ( ):
Check Flooding (Packed Towers): If using packing, aim for a "flooding" percentage between . If it exceeds this, increase the diameter. 3. Calculating Scrubber Height
Height depends on the required efficiency for gas absorption (mass transfer) or particulate removal.
Height of a Transfer Unit (HTU): A measure of the mass transfer efficiency of the packing material or spray.
Number of Transfer Units (NTU): Based on the log-mean concentration difference between the inlet and outlet pollutants. Total Height ( ): Safety Factor: For standard designs, adding a
design safety factor to the calculated height is common practice. 4. Pressure Drop and Power
Total system pressure drop dictates the fan size needed to pull or push gas through the scrubber. Calculate ΔPcap delta cap P Step 1: Input Section (The "Hot" Parameters) Create
: Use correlations (like the Hesketh Equation for Venturis) to find the pressure drop based on liquid-to-gas ( ) ratios and gas velocity.
Fan Power: Calculate the required blower capacity based on the total pressure drop and the polluted air flow rate. Recommended Excel Resources
You can find pre-built templates and detailed manuals at these authoritative sites: Scrubber Design and Calculation Report | PDF - Scribd
Step 1: Input Section (The "Hot" Parameters)
Create these mandatory input cells:
T_gas_in (°C)– Inlet gas temperature (>150°C = "Hot")T_water_in (°C)Gas flow rate (ACFM or m³/h)– Absolute, not Normalized.Gas composition(for Cp and MW)Target d50(micron particle size)
1. Energy Balance (Adiabatic Cooling)
The gas will cool to the adiabatic saturation temperature (typically 40°C to 70°C depending on water temperature).
Equation:
m_gas * Cp_gas * (T_in - T_out) = m_water * λ
Where λ is the latent heat of vaporization of water.
- Excel Implementation: Use Solver or Goal Seek to find
T_outwhere the energy out balances the evaporation cooling.
The "Hot" Challenge: Why Temperature Changes Everything
Standard scrubber design assumes isothermal conditions or negligible temperature drop. For hot streams (typically >150°F / 65°C up to 1800°F), the physics shift dramatically:
- Evaporative Cooling: As hot gas contacts liquid water, sensible heat from the gas converts to latent heat of vaporization. This cools the gas but humidifies it.
- Volume Shrinkage: A gas cooling from 500°F to 150°F can reduce its volumetric flow rate by nearly 40%. If you size the scrubber based on the inlet condition, your velocity will be too low at the outlet (causing liquid flooding).
- Differential Saturation: The calculation of the outlet temperature is not linear; it depends on the psychrometric saturation curve.
A "cold" spreadsheet fails here. You need an iterative Excel model.
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.
This post walks you through building a packed bed wet scrubber calculator for hot gas streams (SO₂, HCl, or particulate removal with cooling).
Module B: Packing Height (Mass Transfer)
This is the heart of the scrubber design. It calculates how tall the column must be to achieve the required removal efficiency.
- Equilibrium Line: Use Henry’s Law or vapor-liquid equilibrium data to plot the equilibrium curve.
- Operating Line: Determined by the mass balance ($L_min$ and actual $L/G$ ratio).
- NTU (Number of Transfer Units):
- For dilute systems, approximate using: $NTU = \ln \left( \fracy_iny_out \right)$ (simplified).
- For precise calculation, integrate the area between the Operating and Equilibrium lines.
- HTU (Height of a Transfer Unit):
- Calculate $H_G$ and $H_L$ (Height of gas and liquid transfer units) using empirical correlations (e.g., Norton or Onda correlations).
- Packing Height ($Z$): $Z = HTU \times NTU$.
Five Excel Hot Tips to Avoid Crashes
When dealing with scrubber design calculation excel hot, your spreadsheet will do iterative math. Protect yourself:
- Enable Iterative Calculation: Go to File > Options > Formulas > Enable iterative calculation (Max iterations: 1000, Max change: 0.0001).
- Avoid Circular References (Explicitly): Use a macro or a copy-paste macro for the energy balance. Do not link
T_outandWater_evapin a direct loop without a breaker. - Use Named Ranges: Instead of
$B$12, name cellGas_Temp_C. It makes the Lapple efficiency formula readable:=1-EXP(- (Impaction * L_G_Ratio) / (Viscosity_Hot) ) - Validate Psychrometrics: Compare your Excel's wet-bulb temperature to a known psychrometric chart (e.g., for air-water system at 1 atm). If you are off by >2°C, your whole scrubber sizing is wrong.
- Unit Checking Helper: Add a column that converts units in parallel. Forgetting to convert mm H2O to Pascal is the #1 cause of field failures.