Sulfuric acid plants manufacture acid by burning sulfur with air in a smelter to form sulfur dioxide (SO2), oxidizing sulfur dioxide catalytically into sulfur trioxide (SO3), and absorbing sulfur trioxide into water to form sulfuric acid. An unwanted coproduct of sulfur combustion is nitrogen oxide (NO). In the catalyst beds, nitrogen oxide partially converts to nitrogen dioxide (NO2) and the two react with sulfuric acid to form nitrosylsulfuric acid (NOHSO4). Candle filters located downstream of the catalyst beds collect most of the nitrosylsulfuric acid.
Candle filters require periodic maintenance. To maintain the equipment, operators wash the candle filters with water to remove the sulfuric acid contained within them before entering the candle filters for maintenance activities. Unfortunately, water reacts with built-up nitrosylsulfuric acid to reform NOx. Since there is no diluting gases, NOx concentrations leaving the candle filter during the wash may be very high, both dangerous to operators and potentially forming an opaque brown cloud.
Recently, Envitech developed an economical solution to this problem by designing a mobile NOx scrubber. A mobile NOx scrubber, rather than a fixed system, has several advantages in this application. First, a mobile system does not consume valuable footprint during normal operation. The area around the candle filters is often congested. A fixed system requires "shoe-horning" the equipment in a hazardous location, adding cost. A mobile solution provides flexibility to position the scrubber in optimal locations near the candle filter without permanently consuming valuable space. Temporary utility connections suffice for a mobile solution, further reducing installation costs. Second, a mobile scrubber can service multiple candle filters or other process vessels, even at different facilities. Finally, Envitech's mobile scrubber is multi-functional, designed to abate a number of hazardous chemicals in addition to nitrosylsulfuric acid, such as hydrochloric acid, sulfur dioxide, and other soluble gaseous emissions.
Envitech's mobile NOx scrubber offers the ability to abate over 99% of the NOx emissions during maintenance activities for flow rates of up to 1,000 acfm for a single reagent system and 15,000 acfm for a multi-reagent NOx reduction system. Envitech's mobile NOx scrubbers are fully automated, stand-alone scrubbers requiring only utility and gas connections, and configurable to handle a variety of pollutants. If you are interested in more information about Envitech's mobile scrubber, click on the link below to download a cut sheet for the scrubber.