Review on ammonia/coal co-combustion fundamental and technology in thermal power generation

Abstract

Abstract Ammonia, as a carbon-free fuel, promises a significant cut of CO 2 emissions from power sectors, especially in coal-fired power plants. Direct combustion of ammonia in existing boiler systems is hindered owing to low flame temperature, decreased flame velocity, low reactivity, and elevated NO x emissions. To efficiently utilize ammonia during combustion in boilers, the ammonia/coal co-combustion is an auspicious application. The state-of-the-art research of ammonia/coal co-combustion technology is systematically reviewed in the present investigation, including both simulation and experimental studies of lab-scale tests and industrial-scale applications. The present work provides a detailed insight of ammonia/coal co-combustion performance and its dependence on various optimization strategies. Co-firing 20%–30% of ammonia is viable in existing coal-fired boilers and the NO x emissions would be possibly equal to or even lower as compared to individual combustion of coal. Further rise in the co-firing ratio could result in higher NO x emissions and lower boiler efficiency. Studies emphasized mitigating elevated NO x emissions from NH 3 co-firing by manipulating design and operational parameters, such as ammonia injection location, air staging, moderate-to-intense low-oxygen dilution (MILD) burning. The present study assists in identifying the most suitable conditions for co-combustion by examining the attributes of NH 3 co-firing. The devoted fuel-injection technologies for NH 3 , chemical kinetics models, and industrially efficient numerical analytical approaches need to be further established for efficient and low NO x co-combustion. The study also comprehensively covers the economic aspects of ammonia/coal co-combustion technology. The current study offers a summary knowledge of NH 3 /coal co-firing characteristics at present and also proposes potential future research.