Selective Catalytic Reduction System Design
Alden simulated the planned Kansas City Power and Light Iatan Unit 2 (POWER Magazine’s 2011 plant of the year) Selective Catalytic Reduction Systems (SCR) to maximize the NOx removal efficiency. An SCR operates by injecting a reagent, typically ammonia (NH3), into the flue gas stream, and then catalyzing a reaction to convert the NO2 and NO3 into nitrogen and water. For optimum system operation, the distribution of the NOx, reactant, gas velocity, and temperature must be very uniform entering the catalyst to maximize the reaction and prolong catalyst life. Upstream collection of large particle ash (LPA), and the distribution of fine ash at the inlet face of the first catalyst are also important components of SCR operation that must be considered to inhibit premature outages caused by pluggage.
Work Performed
Physical and computational flow modeling techniques were used to develop and optimize duct and SCR flow controls, ammonia injection grid, mixing devices, and ash handling devices to achieve best performance targets for NOx removal. The new connecting ductwork from the retrofit SCR to the existing air preheaters was also included in the study to provide flow controls designs to optimize air preheater performance. The models simulated the field gas velocities, temperatures, pressure losses, NOx concentrations, NH3 injections, and ash particulate transport and removal.
Capability
Civil InfrastructureServices
Gas Flow Modeling and DesignRelated Projects
An existing roof vent arrangement was allowing rainwater to enter the Pot Room. Alden supported efforts to develop a roof vent geometry to eliminate the intrusion of rain water. The purpose of the CFD study was to ensure that the roof vent modification did not increase pot room temperature levels beyond specified limits for workers in the plant.
To evaluate the existing and proposed Pot Room arrangements, thermal and fluid flow profiles in the immediate vicinity of the pots were determined based on air flows through the plant floor and wall mounted vents. The detailed CFD model was developed from plant drawings to include all major basement, pot room and roof venting geometries. The surrounding ambient environment was included with quiescent atmospheric conditions and average ambient temperature. Thermal losses form the pots to the pot room air and from the pot room to the environment were included in the analysis. The results of the CFD modeling showed that the proposed modification to the roof venting arrangement was acceptable and would not increase the temperature in the worker-occupied spaces by more than 2 degrees F.
}', 13='{type=image, value=Image{width=2250,height=847,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Smelter-Pot-Room/Smelter-Pot-Room-Diagram.jpg',altText=''}}', 14='{type=string, value=Thermal and fluid flow profiles were evaluated for both existing and proposed venting arrangements}', 15='{type=image, value=Image{width=2250,height=847,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Smelter-Pot-Room/Smelter-Pot-Room-Temperature-CFD.jpg',altText=''}}', 16='{type=string, value=Heat transfer from the pots to the air passing through the pot room were evaluated}', 17='{type=image, value=Image{width=2400,height=869,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Smelter-Pot-Room/Smelter-Pot-Room-Ventilation-CFD.jpg',altText=''}}', 18='{type=string, value=CFD confirmed the efficacy of the modified roof vent system to maintain safe temperatures.}', 25='{type=number, value=0}', 27='{type=number, value=1}', 28='{type=number, value=0}', 29='{type=number, value=50}'}
Civil Infrastructure
Smelter Pot Room Roof Ventilation System
Read how a CFD study ensured that a roof vent modification did not increase pot room temperature levels beyond safe levels
Plant McDonough, owned and operated by Southern Company, has experienced excessive siltation at the makeup water intake. The intake uses cylindrical wedgewire screening within an intake originally designed for much larger, once-through cooling water flows. Flow modeling was performed to provide a viable passive solution to reducing the sediment accumulation at the intake. To model the geometric details of the system accurately, a field survey was performed prior to the flow modeling efforts. The flow study included both CFD modeling and scale physical modeling.
For this investigation, Alden developed a 1:20 scale live bed physical model. This model was extremely well tuned to reproduce the behavior of bed load sediment. Even with the very fine crushed walnut shell particles, however, it was challenging to reproduce the behavior of suspended load. The use of a high fidelity CFD model, therefore, proved extremely useful for this project, in that suspended load is generally very accurately tracked with CFD models, which are not well validated for bed load simulation. By using the two together, the two extremes of sediment transport are captured, and developing a solution that covers this range has a high likelihood of success.
}', 13='{type=image, value=Image{width=3872,height=2592,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Plant-McDonough/Physical-Model-Plant-McDonough.jpg',altText=''}}', 14='{type=string, value=A 1:20 live bed physical model was constructed to reproduce the behavior of suspended sediment load}', 15='{type=image, value=Image{width=2977,height=2386,url='https://20952198.fs1.hubspotusercontent-na1.net/hubfs/20952198/PROJECTS/ALDEN/Plant-McDonough/Original-Construction-Plant-McDonough.jpg',altText=''}}', 16='{type=string, value=Image of the plant under original construction, provided courtesy of Southern Company}', 25='{type=number, value=0}', 27='{type=number, value=1}', 28='{type=number, value=1633353195000}', 29='{type=number, value=60}'}
Civil Infrastructure | Hydrology Hydraulics and Fluids
Plant McDonough Intake Modification
CFD and physical model study to assist in the evaluation of a solution to reduce the sediment accumulation.