准东煤分步和直接化学链燃烧特性

Combustion characteristics of Zhundong coal by staged and direct chemical looping

化学链燃烧作为高效的低碳排放燃烧技术,在提高燃料利用率和减少CO_(2)排放方面显示出其独特优势。采用Fe_(2)O_(3)/Al_(2)O_(3)载氧体,利用两段式固定床反应器开展了准东煤直接和分步化学链燃烧试验,探究了载氧体反应前后理化特性。发现准东煤热解挥发分化学链燃烧碳转化率和CO_(2)选择性随温度和载氧体与煤质量比(OC/C)增加而升高。OC/C和温度升高提高半焦化学链燃烧碳转化率,但降低CO_(2)选择性。相比煤直接化学链燃烧,在相同条件,分步化学链燃烧CO_(2)选择性大幅提高、碳转化率有所降低。反应温度800℃,分步化学链燃烧CO_(2)选择性达89.51%,相比直接化学链燃烧提升了29.18%。反应温度950℃,分步化学链燃烧碳转化率在60.40%,比直接化学链燃烧降低6.78%。与半焦反应后载氧体还原程度高于与煤热解挥发分反应后载氧体,半焦与载氧体的反应是煤化学链燃烧的限制因素之一。本研究为实现准东煤低碳清洁燃烧提供重要理论依据和技术支撑。

Chemical looping combustion is recognized as an efficient technology for low-carbon emissions,offering distinct advantages in enhancing fuel utilization and decreasing CO_(2)emissions.In this study,Fe_(2)O_(3)/Al_(2)O_(3)oxygen carrier was employed in a two-stage fixedbed reactor to conduct direct and staged chemical looping combustion experiments of Zhundong coal.The physicochemical properties of the fresh and spent oxygen carrier has been investigated.Results indicate that the carbon conversion and CO_(2)selectivity of the chemical loo⁃ping combustion of Zhundong coal pyrolysis volatiles increase with increasing temperature and OC/C ratio.The enhanced OC/C ratio and temperature contribute to an improves carbon conversion during the chemical looping combustion of Zhundong coal char,but with a de⁃crease in CO_(2)selectivity.Compared to direct chemical looping combustion of coal,staged chemical looping combustion significantly im⁃proves the CO_(2)selectivity and slightly reduced the carbon conversion under the same condition.At a reaction temperature of 800℃,the CO_(2)selectivity of staged chemical looping combustion reaches to 89.51%,representing a 29.18%increase compared to direct chemical looping combustion.At a reaction temperature of 950℃,the carbon conversion of staged chemical looping combustion is 60.40%,which is 6.78%lower than that of direct chemical looping combustion.The reduction of degree the oxygen carrier with char is higher than with coal pyrolysis volatiles,suggesting that the reaction between char and the oxygen carrier is one of the limiting factors in the chemical looping combustion of coal.This study provides a crucial theoretical foundation and technical support for achieving low-carbon clean com⁃bustion of Zhundong coal.