气流床气化过程产生的煤气化细渣(gasification fine slag,GFS)含碳量较高,已有的资源化利用均包含脱碳处理过程,而循环流化床(circulating fluidized bed,CFB)燃烧技术具有良好的燃料适应性,但业内普遍认为在煤气化细渣(以下简称气化细...气流床气化过程产生的煤气化细渣(gasification fine slag,GFS)含碳量较高,已有的资源化利用均包含脱碳处理过程,而循环流化床(circulating fluidized bed,CFB)燃烧技术具有良好的燃料适应性,但业内普遍认为在煤气化细渣(以下简称气化细渣)形成的过程中,残碳被包裹在熔融玻璃体内,因而在CFB燃烧温度(约900℃)下,很难燃尽。为了探寻CFB锅炉高效燃尽气流床气化细渣的可行性,先后研究了细渣中碳与灰的赋存形态、碳反应活性及其在流化床条件下的燃烧特性。扫描电镜分析结果及细渣破碎前后烧失试验对比结果,揭示了多孔残碳颗粒同灰颗粒分离的微观形貌,且研磨前后细渣失重之差仅为2.86%,进而明确了气化细渣中的残碳主要存在于熔融无机物之外,即“灰炭分离”赋存形态;热重分析(thermogravimetric analysis,TGA)及马弗炉中的燃尽试验证明了在CFB中温燃烧条件下可以实现气化细渣的燃尽。由于气化细渣属于Geldart分类法中的A类粒子,采用传统CFB的常用流化风速无法为其提供足够的系统停留时间,故无法实现细粒度气化细渣在CFB炉中的高效燃烧。根据快速流态化图谱,提出了纯燃气化细渣的低气速细粒子快速流态化(low velocity fine particle fast fluidization,LFFF)‒CFB燃烧技术,选择远低于常规流化风速、稍大于转变速度Utr的流化速度,可显著提高气化细渣在系统内的停留时间;利用一维CFB燃烧模型,对气化细渣在低流化气速下的流动特性及CFB锅炉温度分布进行预测分析。最后,提出了纯燃气化细渣的LFFF燃烧技术,设计了年处理24万t气流床气化细渣的75 t/h CFB锅炉方案。展开更多
The microwave drying of ilmenite was investigated.The effects of power levels and sample mass on drying characteristics of moisture content,drying rate,moisture ratio were studied,with microwave power ranging from 119...The microwave drying of ilmenite was investigated.The effects of power levels and sample mass on drying characteristics of moisture content,drying rate,moisture ratio were studied,with microwave power ranging from 119 W to 700 W and sample mass from 5 g to 25 g.The drying processes were completed within 2-8 min at different conditions.The moisture content and drying rates are found to be dramatically affected by microwave power density.For all drying processes the prior microwave absorption of moisture produces an accelerating peak on the drying rate curves in the initial stage.For the sample mass of 25 g and power of 385 W,the drying kinetics were studied.The experimental results fit better to the Henderson-Pabis index model rather than the Page＇s semi-empirical model;the drying rate constant k is increased with the increase of microwave power and decrease of sample mass.展开更多
文摘气流床气化过程产生的煤气化细渣(gasification fine slag,GFS)含碳量较高,已有的资源化利用均包含脱碳处理过程,而循环流化床(circulating fluidized bed,CFB)燃烧技术具有良好的燃料适应性,但业内普遍认为在煤气化细渣(以下简称气化细渣)形成的过程中,残碳被包裹在熔融玻璃体内,因而在CFB燃烧温度(约900℃)下,很难燃尽。为了探寻CFB锅炉高效燃尽气流床气化细渣的可行性,先后研究了细渣中碳与灰的赋存形态、碳反应活性及其在流化床条件下的燃烧特性。扫描电镜分析结果及细渣破碎前后烧失试验对比结果,揭示了多孔残碳颗粒同灰颗粒分离的微观形貌,且研磨前后细渣失重之差仅为2.86%,进而明确了气化细渣中的残碳主要存在于熔融无机物之外,即“灰炭分离”赋存形态;热重分析(thermogravimetric analysis,TGA)及马弗炉中的燃尽试验证明了在CFB中温燃烧条件下可以实现气化细渣的燃尽。由于气化细渣属于Geldart分类法中的A类粒子,采用传统CFB的常用流化风速无法为其提供足够的系统停留时间,故无法实现细粒度气化细渣在CFB炉中的高效燃烧。根据快速流态化图谱,提出了纯燃气化细渣的低气速细粒子快速流态化(low velocity fine particle fast fluidization,LFFF)‒CFB燃烧技术,选择远低于常规流化风速、稍大于转变速度Utr的流化速度,可显著提高气化细渣在系统内的停留时间;利用一维CFB燃烧模型,对气化细渣在低流化气速下的流动特性及CFB锅炉温度分布进行预测分析。最后,提出了纯燃气化细渣的LFFF燃烧技术,设计了年处理24万t气流床气化细渣的75 t/h CFB锅炉方案。
基金Project(2007CB613606)supported by the National Basic Research Program of ChinaProject(50734007)supported by the National Natural Science Foundation of China
文摘The microwave drying of ilmenite was investigated.The effects of power levels and sample mass on drying characteristics of moisture content,drying rate,moisture ratio were studied,with microwave power ranging from 119 W to 700 W and sample mass from 5 g to 25 g.The drying processes were completed within 2-8 min at different conditions.The moisture content and drying rates are found to be dramatically affected by microwave power density.For all drying processes the prior microwave absorption of moisture produces an accelerating peak on the drying rate curves in the initial stage.For the sample mass of 25 g and power of 385 W,the drying kinetics were studied.The experimental results fit better to the Henderson-Pabis index model rather than the Page＇s semi-empirical model;the drying rate constant k is increased with the increase of microwave power and decrease of sample mass.
