{"title":"Numerical modeling of a coal/ammonia Co-fired fluidized bed: Control and kinetics analysis of nitrogen oxides emissions","authors":"","doi":"10.1016/j.joei.2024.101777","DOIUrl":null,"url":null,"abstract":"<div><p>The potential increase in nitrogen oxide emissions in the coal/ammonia co-firing can hinder the large-scale utilization of ammonia to reduce carbon emissions. In this work, a fluidized bed simulation model was established to investigate the NO<sub><em>x</em></sub> and N<sub>2</sub>O behaviors in the process of coal/ammonia co-firing. The effects of several variables on nitrogen oxides emission characteristics were studied, including the ammonia ratio, temperature, excess air ratio, and air/ammonia distribution strategies. The findings indicate that NO<sub><em>x</em></sub> and N<sub>2</sub>O concentrations rise and then decline with the NH<sub>3</sub> co-firing ratio (CR-NH<sub>3</sub>) increased, peaking at 10 % and 5 % CR-NH<sub>3</sub>. The formation of N<sub>2</sub>O is insensitive to the addition of ammonia, while NO<sub><em>x</em></sub> emissions vary dramatically with different ammonia ratios. Higher temperatures enhance the formation of NO<sub><em>x</em></sub> but inhibit the generation of N<sub>2</sub>O within 750 °C–950 °C. As the temperature rises, the primary decomposition path of N<sub>2</sub>O shifts from N<sub>2</sub>O→N<sub>2</sub>H<sub>2</sub>→NNH→N<sub>2</sub> to N<sub>2</sub>O→NO<sub>2</sub>→NO→N<sub>2</sub>. The generations of NO<sub><em>x</em></sub> and N<sub>2</sub>O are both enhanced due to the weakness of the reduced atmosphere with the excess air ratio increased. When the primary air ratio is raised, N<sub>2</sub>O gradually takes over as the main source of nitrogen oxides instead of NO<sub><em>x</em></sub>. The specific primary air ratio in the fluidized bed should be considered in the priority treatment of NO<sub><em>x</em></sub> or N<sub>2</sub>O in the process of lowering nitrogen oxides emissions. Ammonia distribution strategies have opposite effects on NO<sub><em>x</em></sub> and N<sub>2</sub>O emissions. With more NH<sub>3</sub> introduced as a secondary fuel, the dilute phase area can change from the main source of NO to the consumption area of NO. The present findings can help control the emissions of nitrogen oxides during coal/ammonia co-combustion in coal-fired circulating fluidized bed power plants.</p></div>","PeriodicalId":17287,"journal":{"name":"Journal of The Energy Institute","volume":null,"pages":null},"PeriodicalIF":5.6000,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of The Energy Institute","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1743967124002551","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
The potential increase in nitrogen oxide emissions in the coal/ammonia co-firing can hinder the large-scale utilization of ammonia to reduce carbon emissions. In this work, a fluidized bed simulation model was established to investigate the NOx and N2O behaviors in the process of coal/ammonia co-firing. The effects of several variables on nitrogen oxides emission characteristics were studied, including the ammonia ratio, temperature, excess air ratio, and air/ammonia distribution strategies. The findings indicate that NOx and N2O concentrations rise and then decline with the NH3 co-firing ratio (CR-NH3) increased, peaking at 10 % and 5 % CR-NH3. The formation of N2O is insensitive to the addition of ammonia, while NOx emissions vary dramatically with different ammonia ratios. Higher temperatures enhance the formation of NOx but inhibit the generation of N2O within 750 °C–950 °C. As the temperature rises, the primary decomposition path of N2O shifts from N2O→N2H2→NNH→N2 to N2O→NO2→NO→N2. The generations of NOx and N2O are both enhanced due to the weakness of the reduced atmosphere with the excess air ratio increased. When the primary air ratio is raised, N2O gradually takes over as the main source of nitrogen oxides instead of NOx. The specific primary air ratio in the fluidized bed should be considered in the priority treatment of NOx or N2O in the process of lowering nitrogen oxides emissions. Ammonia distribution strategies have opposite effects on NOx and N2O emissions. With more NH3 introduced as a secondary fuel, the dilute phase area can change from the main source of NO to the consumption area of NO. The present findings can help control the emissions of nitrogen oxides during coal/ammonia co-combustion in coal-fired circulating fluidized bed power plants.
期刊介绍:
The Journal of the Energy Institute provides peer reviewed coverage of original high quality research on energy, engineering and technology.The coverage is broad and the main areas of interest include:
Combustion engineering and associated technologies; process heating; power generation; engines and propulsion; emissions and environmental pollution control; clean coal technologies; carbon abatement technologies
Emissions and environmental pollution control; safety and hazards;
Clean coal technologies; carbon abatement technologies, including carbon capture and storage, CCS;
Petroleum engineering and fuel quality, including storage and transport
Alternative energy sources; biomass utilisation and biomass conversion technologies; energy from waste, incineration and recycling
Energy conversion, energy recovery and energy efficiency; space heating, fuel cells, heat pumps and cooling systems
Energy storage
The journal''s coverage reflects changes in energy technology that result from the transition to more efficient energy production and end use together with reduced carbon emission.