NOx scrubber refers to an air pollution control device used to reduce or eliminate nitrogen oxide (NOx) emissions from industrial processes, power plants, and other sources. Nitrogen oxides are a class of harmful pollutants that adversely affect human health and the environment. NOx scrubbers are designed to reduce these emissions by employing various chemical and physical processes.

The basic principle of a NOx scrubber is to pass the exhaust gas through a scrubbing system where the exhaust gas comes into contact with a liquid solution or slurry containing chemical reagents. Reagents react with nitrogen oxides, converting them into less harmful compounds, or capturing them for subsequent disposal.

There are different types of NOx scrubber systems, and they may use different chemicals such as ammonia (NH₃), urea (CO(NH2)2), or other compounds. The choice of reagent usually depends on the specific application, emission characteristics and environmental regulations.

How NOx scrubber systems typically work:

Exhaust gas collection:

Flue gases or exhaust gases enter the scrubber system from industrial processes, power plants, or other exhaust emission sources.

Detergent injection:

A liquid solution containing chemical reagents is injected into the scrubber system. Common chemical agents include ammonia (NH₃) or urea (CO(NH2)2). Generally, an automatic dosing system is used to maintain the effective concentration of the washing liquid.

Gas-liquid contact:

The exhaust gas comes into contact with the liquid solution in the scrubber. This can be accomplished through the use of wet scrubbers or other equipment.

Nitrogen oxide absorption:

Cleaners contain chemicals that react with nitrogen oxides in exhaust gases. These reactions typically convert nitrogen oxides into water-soluble compounds.

Hazardous products formed:

Nitrogen oxides react with reagents in detergents to form relatively harmless products that can be dissolved in the wash liquor.

Separation:

After treatment, gas and liquid are separated. The treated gases, called emissions, contain lower concentrations of nitrogen oxides and can be released into the atmosphere. The wash liquor contains trapped nitrogen oxides.

Liquid handling:

The captured nitrogen oxides can be disposed of or recycled through further processing steps. This may include neutralization, precipitation or other chemical treatments. The captured solid emissions cannot be discharged directly and need to undergo special harmless treatment or recycling.

Monitor and control:

A continuous monitoring system ensures scrubber system performance and makes adjustments as needed. Develop a daily schedule for equipment maintenance.

These steps may vary depending on the cleaning technology used, the type of reagents used, and the specific application and environmental regulations. The goal of a NOx scrubber system is to reduce NOx emissions to levels that comply with environmental regulations to ensure minimal impact on air quality.