Numerical study on coal/ammonia co-firing in a 600 MW utility boiler

Co-firing NH3 in coal-fired power plants is an attractive method to accelerate the pace of global decarbonization. However, the contradiction between achieving elevated temperature within the furnace and maintaining low NOx emission constrains the utilization of NH3 as fuel. In this study, 3-dimensional numerical simulations on coal/NH3 co-firing cases were conducted in a full-scale boiler for the first time. The influences of NH3 blending ratio, O2 enrichment combustion and deep air-staging technology were investigated. The results show that the burnout properties of NH3 are excellent in co-firing boiler. Higher NH3 blending ratio leads to lower temperature in the furnace. Enriching O2 concentration to 30% in the secondary air can compensate the temperature decline caused by 50% NH3 co-firing, while it brings an undesired surge in NOx concentrations. The high temperature and strong reducing atmosphere (HT&SRA) could be created by combining the O2 enrichment and deep air-staging combustion. The NO emission drops by 49.6% due to HT&SRA. Then, high flue gas temperature and low NOx emission can be achieved simultaneously. HT&SRA improves the overall exergy efficiency for 50% NH3 co-firing case from 51.65% to 51.78%. The findings open up a promising strategy for utilizing NH3 as a stationary fuel.