The objective is maximum evaporation rate per unit of pumping energy — which means maximizing the total surface area of airborne droplets. This favors smaller droplets (higher surface area per unit volume) and longer airborne time before the droplets re-enter the pond. Hydraulic atomizing nozzles on risers 2–4 meters above the pond surface, positioned to spray upward or outward into the prevailing wind, are the standard configuration.

Wind is an asset in pond evaporation, not a problem — the evaporation rate from a droplet moving through air is significantly higher than from a still droplet. Nozzle positioning should maximize the downwind travel distance before droplets fall back to the pond surface. Arrays are typically spaced 15–25 meters apart in a grid or perimeter pattern depending on pond geometry.

For brine ponds with TDS above 50,000 mg/L, nozzle material selection is critical. PVDF body with PTFE seals is the standard choice for highly concentrated brines and acid mine drainage. 316 SS is acceptable for lower-concentration municipal and agricultural effluent. Hastelloy C-276 is required for high-chloride, low-pH acid brines such as those from acid in-situ leach (ISL) mining operations.

The critical design constraint for turbine inlet fogging is complete evaporation before the compressor inlet. Any unevaporated water droplets entering the compressor cause blade erosion — even small droplets at high velocity carry significant erosive energy. This requires very fine atomization: Dv50 values of 10–50 µm are typical for inlet fogging systems, produced by high-pressure hydraulic atomizing nozzles at 500–1,500 PSI or twin-fluid (air-assisted) nozzles.

For industrial compressor inlet cooling at lower pressure requirements, hollow cone hydraulic atomizing nozzles at 100–300 PSI producing Dv50 50–150 µm are used in the inlet duct or inlet filter house. The fog evaporates within the inlet duct, cooling the air by 5–15°F depending on ambient wet-bulb depression — recovering 0.5–1.5% power output per degree Fahrenheit of cooling in most gas turbine configurations.

In quench towers, hot combustion gas (typically 600–1,800°F inlet) is cooled to 250–400°F by water evaporation before entering downstream equipment. The tower must be sized to give complete evaporation — unevaporated water at the tower outlet causes downstream corrosion, caking, and equipment damage. Full cone nozzles in the 90°–120° range at 40–80 PSI with Dv50 200–500 µm are the standard for quench tower applications, typically fired downward into the rising gas stream (countercurrent) or horizontally (cross-flow) to maximize residence time.

In spray dryer absorbers, lime slurry is atomized into the hot flue gas stream. The water evaporates and the lime reacts with SO₂ to form calcium sulfite/sulfate, which is collected as a dry powder. Rotary atomizers are the classic SDA atomization method, but hydraulic twin-fluid nozzles are increasingly used in smaller SDA installations. Nozzle material must withstand continuous exposure to SO₂, SO₃, and HCl — Hastelloy C-276 or ceramic-lined nozzle bodies are required for slurry SDA service.

For ESP conditioning, a small amount of water (far below the adiabatic saturation limit) is injected into the gas stream upstream of the electrostatic precipitator to increase gas humidity, which reduces resistivity of the collected fly ash and improves collection efficiency. Hollow cone nozzles at moderate pressure (30–60 PSI) producing Dv50 150–300 µm are used — residence times are shorter than in a quench tower, so finer droplets are needed.