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H2S Release Rate Calculator (Evaporating Pool)
This tool provides a screening estimate of the Hydrogen Sulfide (H2S) gas release rate from a liquid pool evaporating into the atmosphere. This is a simplified model and should not replace professional hazard modeling software.
Estimated Release Rate Output
Based on the inputs provided, the estimated H2S evaporation rate is:
*Note: This estimate assumes a passive evaporation mechanism constrained by mass transfer and vapor pressure proxies. Real-world scenarios involving boiling, reactive chemicals, or pressurized leaks require advanced modeling.
Understanding H2S Evaporation from Liquid Pools
Hydrogen Sulfide (H2S) is a highly toxic, colorless gas with a characteristic "rotten egg" odor at low concentrations. In industrial settings, such as oil and gas production or wastewater treatment, H2S can exist dissolved in liquids like water or crude oil. When a spill occurs, forming a pool, the H2S will partition from the liquid phase into the gas phase, releasing toxic vapors into the surrounding atmosphere.
Estimating the rate of this release is crucial for emergency response planning, determining hazardous area zoning, and assessing occupational safety risks.
⚠️ Safety Warning: H2S is immediately dangerous to life and health at relatively low concentrations. This calculator provides a theoretical estimation only and must not be relied upon for active safety critical decisions during an actual incident. Always use appropriate Personal Protective Equipment (PPE) and detection devices when dealing with potential H2S sources.
Key Factors Influencing Release Rate
The rate at which H2S evaporates from a liquid pool is driven by several physical and environmental parameters. This calculator uses a simplified mass transfer approach that considers the following key drivers:
- Surface Area (m²): The primary determinant of total release. A larger pool surface area directly results in a higher quantity of gas being released per unit of time, as there is more interface for mass transfer to occur.
- Wind Speed (m/s): Wind blowing across the surface of the pool strips away the saturated boundary layer of gas just above the liquid. Higher wind speeds increase the mass transfer coefficient, thereby increasing the evaporation rate. This tool assumes wind speed measured at a standard height of 10 meters.
- Ambient Temperature (°C): Temperature significantly affects the vapor pressure of dissolved H2S. As temperature rises, the volatility of H2S increases, leading to a higher driving force for evaporation. The model uses an Arrhenius-type approximation to scale release with temperature changes.
- H2S Concentration (Mass %): The amount of H2S actually available in the liquid is fundamental. A higher concentration of dissolved H2S results in a higher partial pressure of H2S at the liquid surface, driving a faster release rate.
Interpreting the Results
The output provides the release rate in both grams per second (g/s) and kilograms per hour (kg/hr). These values represent the "source term" that would then be used in atmospheric dispersion modeling to calculate downwind concentrations (ppm).
For example, a release rate of just a few grams per second can result in dangerous concentrations downwind depending on atmospheric stability. It is vital to understand that this calculator assumes a stable liquid pool. It does not account for splashing, boiling pools, or pressurized jet releases, which result in significantly higher release rates.
function calculateH2SRelease() {
// 1. Retrieve Inputs
var areaInput = document.getElementById("h2sArea").value;
var windInput = document.getElementById("h2sWind").value;
var tempInput = document.getElementById("h2sTemp").value;
var concInput = document.getElementById("h2sConc").value;
// 2. Validate Inputs
if (areaInput === "" || windInput === "" || tempInput === "" || concInput === "") {
alert("Please fill in all fields to calculate the release rate.");
return;
}
var area = parseFloat(areaInput);
var wind = parseFloat(windInput);
var temp = parseFloat(tempInput);
var conc = parseFloat(concInput);
if (isNaN(area) || isNaN(wind) || isNaN(temp) || isNaN(conc) || area <= 0 || wind < 0 || conc < 0) {
alert("Please enter valid numeric values. Area must be positive, wind and concentration cannot be negative.");
return;
}
// 3. Calculation Logic
// This is a simplified empirical model for educational screening purposes.
// It combines a mass transfer coefficient proxy (wind) with a vapor pressure proxy (temp) and concentration scaling.
// Proxy for mass transfer dependence on wind (often ~U^0.78 in literature)
// We use a small base value for zero wind conditions.
var windFactor = Math.pow(Math.max(0.1, wind), 0.78);
// Proxy for vapor pressure dependence on temperature relative to a baseline of 20°C.
// Using an exponential relationship to approximate the Clausius-Clapeyron effect.
// A factor of 0.05 approximates a near-doubling of rate every ~14 degrees C, typical for volatile solutes.
var tempFactor = Math.exp(0.05 * (temp – 20));
// Concentration scaling (normalized fraction)
var concFraction = conc / 100;
// Base emission factor constant to align the simplified model with typical magnitudes for H2S volatility.
// This constant is empirically adjusted for this simplified screening tool.
var baseEmissionConstant = 1.5; // arbitrary unit scaler for this specific model mixture
// Calculate Release Rate in g/s
// Formula: Rate = Constant * Area * WindFunction * TempFunction * ConcentrationFraction
var releaseRateGS = baseEmissionConstant * area * windFactor * tempFactor * concFraction;
// Convert to kg/hr
var releaseRateKGHR = (releaseRateGS * 3600) / 1000;
// 4. Display Results
document.getElementById("h2sResult").style.display = "block";
document.getElementById("h2sOutputGS").innerHTML = releaseRateGS.toFixed(3) + " g/s";
document.getElementById("h2sOutputKGHR").innerHTML = releaseRateKGHR.toFixed(2) + " kg/hr";
}