Clay Boswell Energy Center Unit 4 is a coal fired station owned by Minnesota Power. The plant had a need to reduce flue gas temperatures upstream of their NID emissions control system for removing SO2 from the flue gas stream—while the plant remained online. This created a design limitation for the injection system since the nozzles would have to fit through the duct ports, and the lances would only be supported by the duct penetration, not internally.

Our engineers calculated the quench water requirements to achieve the desired gas temperature cooling and then selected candidate spray nozzles for the system. The sulfuric acid dewpoint temperature was also calculated for design considerations. Remaining above the acid dewpoint is important to avoid corrosion of the ductwork. Then a computational fluid dynamic (CFD) model of the scope of ductwork was created, and prepared using inlet boundary conditions representative of the plant flue gas profiles. Based on the desired gas flow pattern for optimal spray injection, required residence time for evaporation, and access in the field to the ductwork for lance installation and quench system piping, a location for the quench system was selected. The candidate spray nozzle injection characteristics, such as droplet size distribution, spray pattern, and droplet velocity, were input into the model and used to evaluate various nozzle arrangements. The final arrangement provided the target gas temperature reduction, within the desired uniformity, and minimized wetting of surfaces.

ALDEN worked closely with plant personnel to design a quench system that could be installed while the plant remained online · ALDEN used CFD modeling to simulate numerous quench spray nozzles types and arrangements to determine the best option · ALDEN designed a cost-effective functional design for the quench system