煤粉的增压富氧燃烧特性及煤灰矿物演变

为了更好地了解煤粉在增压富氧条件下的燃烧过程,利用加压热天平(PTGA)结合X射线衍射仪(XRD),研究了增压富氧燃烧条件下压力对煤粉燃烧特性及煤中矿物演变的影响。研究表明,随着压力的升高,煤粉常压时的非均相着火逐渐转变为均相着火,当压力升高到3 MPa开始向非均相着火过渡,并在5 MPa时完全转变成非均相着火。由于煤粉着火机理的转变,综合燃烧特性指数S随着压力的增加先升高后降低。不同的着火机理下,煤粉的燃烧温度也会有所差别。常压时非均相着火较高的燃烧温度使得反应生成了莫来石等矿物,而1 MPa时均相着火较低的燃烧温度则使得煤灰中出现了伊利石等矿物。压力继续升高,均相着火开始向非均相着火过渡,燃烧温度逐步升高,伊利石逐渐转变为莫来石。

Combustion characteristics of pulverized coal and mineral conversion under pressurized oxy-fuel condition

To better understand the combustion process of pulverized coal under pressurized oxy-fuel atmosphere, the influence of pressure on the combustion characteristics and mineral conversion during the pressurized oxy-fuel combustion was investigated by using the combination of pressurized thermogravimetric analyzer (PTGA) and X-ray diffractometer (XRD). The results indicate that the heterogeneous ignition at atmospheric pressure changes to the homogeneous ignition with the increase of pressure, but starts to change to the heterogeneous ignition gradually at 3 MPa, and becomes the heterogeneous ignition at 5 MPa. As a result of the transformation of ignition mechanism of pulverized coal, the combustibility index S increases firstly and then reduces with pressure. And the combustion temperatures may be different for different ignition mechanisms. Because of higher combustion temperature of the heterogeneous ignition at atmospheric pressure, some minerals, such as mullite, are generated in the ash, while some other minerals, such as illite, are found in the ash owing to lower combustion temperature of the homogeneous ignition at 1 MPa. As the pressure continues rising, the illite converts to mullite due to the homogeneous ignition transforming to the heterogeneous ignition.