An Overview of Non-Catalytic NOx Control

After the U.S. Environmental Protection Agency added another pollutant for WTE plants to control-NOx, several options became available to reduce NOx emissions.

NOx is an air pollutant and a major part of smog formation. In sunlight, it reacts with various chemicals to form ozone and oxidation products of hydro­carbons. At high concentrations, NOx can harm human health, vegetation, and other materials.

Non-catalytic NOx emmision control is a simple way to remove NOx from combustion gases is to inject a reducing agent, which converts NOx to molecular nitrogen. Gases that can produce free nitro­gen atoms, such as ammonia (NH3), can reduce NOx by reacting with it to form nitrogen and water. Ammonia is a selective reductant for NOx-if proper conditions are used, it efficiently reduces NOx. Other reducing com­pounds include hydrazine hydrate [(H2N4) solution] and urea [CO(NH2)z solution].

In the Spring 1982, the Los Angeles Department of Water and Power installed the first major non­catalytic ammonia application for NOx reduction at a 230 MW boiler. Later that year, design began on the SERRF project in Long Beach, California. That design, created by Exxon and ESA Engineering, became the state-­of-the-art ammonia injection system for NOx reduction at WTE plants. Now 59 ammonia reduction processes are operating, and another 24 units are under design or construction.

For more information see the detailed overview.