CUI Baochong,WANG Xiaoxiao,SHU Yixiang,et al. An experimental study on the characteristics of ammonia/coal mild gasification-combustion and the Fuel-N transformation[J]. Journal of China Coal Society,2024,49(10):4071−4079. DOI: 10.13225/j.cnki.jccs.LC24.0135
Citation: CUI Baochong,WANG Xiaoxiao,SHU Yixiang,et al. An experimental study on the characteristics of ammonia/coal mild gasification-combustion and the Fuel-N transformation[J]. Journal of China Coal Society,2024,49(10):4071−4079. DOI: 10.13225/j.cnki.jccs.LC24.0135

An experimental study on the characteristics of ammonia/coal mild gasification-combustion and the Fuel-N transformation

  • Ammonia (NH3) is a carbon-free and hydrogen-rich fuel. NH3 co-firing in coal-fired boiler is an effective approach to reduce carbon emissions from the combustion source. However, it can lead to problems such as high NOx emissions and poor coal burnout. To address the issues above, this paper investigated the Fuel-N conversion and NOx emissions during co-firing 20%NH3 in gasifier (G-20% NH3) and in combustor (C-20%NH3) using a self-built mild gasification-combustion experimental rig. The research found that the co-firing NH3 in the gasifier can decrease the gasifier temperature. However, it has little effect on the coal gasification reactions in gasifier. Compared with a pure coal condition, the conversion ratio of coal-nitrogen was only reduced by 3.64%, and the conversion ratio of volatile matter and fixed carbon decreased by only 0.70% and 2.54%, respectively. Besides, the conversion of NH3 in the gasifier can reach 69.55% during the condition of G-20%NH3. The 68.88% of total fuel-N was conversed to N2 in the gasifier, with NH3-N converting to N2 was 67.73% in G-20%NH3. In addition, the NH3 co-firing in the gasifier promoted the transformation of coal-N and NH3-N to HCN, with the value of 0.36%. Moreover, the coal pyrolysis in the gasifier promoted the NH3 pyrolysis. Compared with pure coal, the NH3 co-firing in the gasifier increased the H2 concentration at the outlet of the gasifier by 69.23% than that of pure coal. The NH3 co-firing also decreased the temperature during the preliminary stage of combustion. Compared with pure coal, the NH3 co-firing in the gasifier and combustor decreased the temperature peak by 46 ℃ and 62 ℃, respectively. Simultaneously, the NH3 co-firing delayed the occurrence of temperature peaks. Additionally, the NH3 co-firing delayed the gasified char combustion in the combustor. The average temperature in the burnout zone increased by 135.8 ℃ and 72.8 ℃ during G-20%NH3 and C-20%NH3, respectively, compared to PC. It was more conducive to the burnout of pulverized coal. The NH3-cofiring in combustor had more significant promoting effects on the burnout of pulverized coal, in which the unburned carbon in fly ash decreased by 1.8% compared PC. However, the NH3 co-firing in gasifier was more effective in reducing NOx emissions. During the G-20%NH3, NO emissions were decreased by 23.51% compared to C-20%NH3. The study offers some innovative ideas and data reference for the development of low NOx emission technology for NH3 co-firing in coal-fired boiler.
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