Study on combustion characteristics of two sizes pulverized coal in O2/CO2 atmosphere

• The co-combustion of superfine and conventional sized pulverized coal can enhance ignition.
• Mixed superfine and conventional sized pulverized coal combustion decreases NOx emission.
• Increases the ratio of superfine coal accelerates pulverized coal combustion.
• The ratio of superfine coal from 30% to 50% reduces the NOx significantly.

Pulverized coal combustion technology in O2/CO2 atmosphere is widely accepted as a new combustion technology. This method does not only recycle CO2, but also lowers NOx emission. However, pulverized coal combustion technology has several problems such as pulverized coal ignition delay, low flame temperature, and incomplete burning. Such issues have attracted the attention of the local and international academic communities. This study adopts a numerical simulation to analyze the combustion characteristics of conventional sized pulverized coal (70 μm) mixed with superfine pulverized coal (20 μm) in O2/CO2 atmosphere. The influences of co-combustion of two sizes pulverized coal on ignition, combustion flame structure, and NOx generation were analyzed. Results showed that the co-combustion of superfine and conventional-sized pulverized coal can enhance the ignition and combustion performance of pulverized coal in O2/CO2 atmosphere. The improved ratio of superfine pulverized coal promotes ignition process of pulverized coal and combustion intensity. Moreover, co-combustion can decrease NOx generation. As the ratio of superfine to conventional sized pulverized coal increases, NOx emission decreases. The reduction effect of NOx is most significant when the ratio of superfine to conventional sized pulverized coal increases from 30% to 50% and the co-combustion of superfine and conventional sized pulverized coal in O2/CO2 atmosphere can simultaneously improve combustion performance and reduce NOx discharge.

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