Experimental investigations of the conversion of fuel-N, volatile-N and char-N to NOx and N2O during single coal particle fluidized bed combustion

Abstract

In this work, the attention is focused on the conversion of fuel-N, volatile-N and char-N to NOx and N2O of two types of coal (anthracite with low volatile content and bituminous with relatively high volatile content) in fluidized bed combustion. The experiments are carried out in a single particle combustion test rig, the mass reduction of burning coal particle, NOx and N2O formation in the flue gas are measured. The influence of temperature (1043, 1103, 1163 K) on the conversion of fuel-N, volatile-N and char-N to NOx and N2O is also investigated. The experimental results show that about 70% – 80% of all the NOx produced is formed from char-N for both two types of coal, while 20% – 30% of all the NOx produced is formed from volatile-N. About 45% of all the N2O produced is formed from volatile-N for anthracite, and for bituminous more than 70% of all the N2O produced is formed from volatile-N. With the combustion temperature of 1043 K, the conversion of char-N to NOx is more than 80% for anthracite, while the conversion of volatile-N to NOx is only 36% for anthracite. For bituminous, the conversion of char-N and volatile-N to NOx is both about 45%. About 5% of the volatile-N yields N2O, and 4% of char-N yields N2O for anthracite, while more than 12% of the volatile-N yields N2O and only 2% of char-N yields N2O for bituminous. The temperature produces little influence on the conversion of fuel-N, volatile-N and char-N to NOx for anthracite. For bituminous, the conversion of fuel-N, volatile-N and char-N to NOx increases with the increased temperature. However, the conversion of fuel-N, volatile-N and char-N to N2O decreases when the combustion temperature increases for both two types of coal. These results are favorable for industrial control and the understanding of the formation mechanism of NOx and N2O.