NOx Control System - Injecting Life in NOx Control
The aqueous ammonia (NH3) injection system for nitrogen oxide (NOx) emission reductions at a cement plant in Florida, provided limited ability for flow downturn and material usage efficiency. A new injection system, provided by Lechler, considerably lowered the use of NH3 in its NOx reduction system.
The objective of NOx Control Systems
The goal of all nitrogen oxide (NOx) control systems at cement plants is to produce the highest NOx removal with minimal reagent use and cost while preventing ammonia slip. Lechler, Inc uses selective non-catalytic reduction (SNCR) systems injecting aqueous ammonia. The SNCR systems are installed in high temperature kilns and calciner ducts to scrub NOx from the flue gas of coal-fired kilns which is formed as a combustion by-product. This SNCR-NOx process works by injecting a finely-atomised aqueous ammonia (NH3) solution into the flue gas that contains the acid gas precursors. The goal is to enable the complete reduction (ie, chemical reaction) needed within a short residence time to allow production to establish a reliable output.
Multiple upgrade benefits
The upgrade in nozzles on the SNCR-NOx system has enabled the cement producer to:
- Increase the reliability of the system,
- Reduce costs and improve environmental compliance.
The existing hydraulic nozzle used for fluid atomization was retrofitted by upgrading to Lechler VarioClean twin fluid spray nozzles, which provided:
- Higher SNCR reliability and efficiency
- Lower maintenance cost
- Ease of operation at both start-up and full load.
The nozzles can operate reliably inside a kiln or duct which has been designed for a spray atomizer at widely fluctuating loads. Smaller ammonia droplet sizes support the more efficient use of aqueous ammonia and air consumption. The retrofit required little downtime and only minor changes to the vessel structure.
The overall process to upgrade the existing SNCR-NOx system was simple. A compatible process support system, including installed equipment (including pumps, compressors, gauges and hoses) was provided as part of the final solution. All of the existing consumption data was thoroughly confirmed along with efficiency capabilities to provide the best design for improvement before agreeing on the actions to be taken. This type of collaboration and review minimized overall costs for the project implementation and provided the baseline for ROI and the tremendous material savings on an ongoing basis. While the initial economic justification for this upgrade was very attractive in a cost-conscious industry, the final result indicated less than a three-month payback and annual six-figure aqueous NH3 savings.