In response to the United Nations Sustainable Development Goal 13─Climate Action, TSMC strives to implement the minimum pollutant emission target through the best feasible control technology. To improve air emission quality, the Company rolled out a nitrogen oxide (NOx) reduction program for the operation of air pollution control equipment. In 2022, TSMC collaborates with the suppliers to modify the combustion furnace structure within the pollution control equipment and optimize combustion temperature for the minimal emission point of targeted pollutants and NOx. While the process does not compromise the performance of exhaust gas treatment, the NOx emission can be reduced by 65% each year. By August 2023, the device has been installed in Fab 18 Phase 7 and Phase 8 and Advanced Backend Fab 6. It will be the standard prevention facility for all new facilities to achieve the goal of green manufacturing.

Moderate or Intense Low Oxygen Dilution (MILD) Thermal Oxidizers and Combustion Flow Field Control Technologies to Reduce NOx Emissions

Air pollution control equipment can remove volatile organic compounds (VOCs) and perfluorinated compounds (PFCs), which are byproducts of wafer manufacturing, by the process of pyrolysis. However, this process also causes dinitrogen (N2) to react with oxygen (O2) and produce nitrogen oxides pollutants. TSMC conducted survey and analysis for comprehensive stacks in the facilities, and the results showed that NOx is mainly produced by pyrolysis in local scrubbers and VOC control equipment. For VOC control equipment, the process exhaust gas directly contact combustion with the flame in conventional burner. The temperature of the main flame is 1,600°C. To reduce the NOx emission, we added an air swirler introduce outside air into oxidizers as assisting combustion air, and setting fuel sprinklers for staged preheating. In the first stage, the oxygen concentration is to be lower in the low-temperature reaction. In the second stage, the air with low oxygen concentration is introduced into the combustion. Under the low-oxygen combustion, flame temperature dip to 1,300°C, resulting in lower thermal NOx production.

In addition to optimize thermal oxidizer structures and treatment process, TSMC continuously evaluates strategy to improve local scrubbers. In 2023, the Company conducted modification and performance testing for the burn-type local scrubber in Fab 18 Phase 8. Upon completion of efficiency assessment and parameter establishment, the implementation will be gradually extended to Fab 20 to reduce NOx emission and achieve the goal of environmental sustainability.