During the COVID-19 pandemic, an increasing amount of evidence has suggested that the virus can be transmitted through the air inside buildings. The ventilation system used to create the indoor environment would facilitate the transmission of the airborne infectious diseases. However, the existing ventilation systems in most buildings cannot supply sufficient clean outdoor air for diluting the virus concentration. To reduce the airborne infection risk and minimize energy consumption, especially in existing buildings with well-mixed ventilation systems, this investigation used an ultraviolet-C (UV-C) air disinfection device (Rheem's third generation products, RM3) with 99.9% disinfection efficiency to clean air carrying the COVID-19 virus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) which could help promote environmental sustainability and create healthy cities. This investigation assessed the impact of the RM3 UV-C units on the infection risk, the number of RM3 UV-C units required, and the strategy for decreasing the infection risk, with the use of computational-fluid-dynamics (CFD) numerical simulations. An actual office building with a combination of individual offices and workstations was selected as an example for the research. According to the numerical results, the best strategy would be to use a combination of 100% outside air and UV-C in heating, ventilation and air-conditioning (HVAC) ducts with air disinfected by the RM3 UV-C units. The infection risk in the office building could thus be reduced to a negligible level. These findings could provide theoretical basis and engineering application basis for COVID-19 epidemic prevention and control.

Selective catalytic reduction (SCR) technology is being increasingly applied for controlling emissions of nitrogen oxides (NOx) from coal-fired boilers. For many power plants, temperature control becomes an essential challenge to ensure optimal SCR performance and to keep the material integrity of the SCR structure. Progress Energy MAYO Plant has a tandem boiler design with a Gross Power Generation Capacity of 2 × 400 MW. The plant decided to change their coal source to a lower HHV type PRB coal and integrated Clyde Bergemann’s SmartClean technology to deal with the changes in the coal quality and ensure a stable flue gas temperature going into the SCR. The new SmartClean technology optimized the cleaning to control the Economizer Exit Gas Temperature (EEGT) at a desired set temperature. The results of the performance tests showed that the EEGT control was successful and the temperature profile stabilized after implementing the new SmartClean technology. The new technology derives decisions and changes the cleaning strategy based on the effect of the sootblowers on the heat transfer performance rather than the traditional approach of targeting a static cleanliness level in the boiler. The performance data of the closed loop tests are presented as well as the economical justification of the project.