Urea Injection Design Analysis for NOx Control using CFD

There are many industrial pollutants produced from coal fired power generation plants. Recent legislation is pushing to reduce these emissions. Greenhouse gasses as well as nitrous oxides (NOX) and sulfur dioxide (SO2) are the targeted pollutants. Governmental legislation outlined by Environmental Protection Agency (EPA) through its Maximum Achievable Control Technology (MACT) guideline is a major thrust. One method of NOx reduction is selective non-catalytic reduction (SNCR) which is implemented prior to gases venting to the atmosphere. In SNCR systems a reagent is injected into the flue gas, in an effort to reduce NOx levels by up to 50%. The operation of this equipment is highly dependent on the temperature and distribution of the gases requiring careful control of the system. Spray nozzles are an important factor in this process; spray nozzles add value by providing controlled volumes of liquid with predictable drop size and consistent spray coverage. Knowing these values remains vital for the optimization of gas conditioning processes. In addition, the all-important placement of nozzles is often times misunderstood and therefore inaccurate. While immense care is taken to optimize placement, this often leads to failure due to the inability to predict spray performance in the application environment. This process can be facilitated by using computational fluid dynamics (CFD). In this case study, CFD is used to simulate NOx levels produced in the coal combustion process and estimate the NOx reduction that can be achieved with the urea injection. In the end, adjustments were made to original nozzle placement suggestions in order to optimize gas conditioning process while minimizing the slip through the system. As presented at: 10th International Conference on Combustion and Energy Utilization, Mugla, Turkey, May 2010 *Corresponding author