Numerical study of further NO _x emission reduction for coal MILD combustion by combining fuel‐rich/lean technology

Abstract

Summary This paper numerically examines the feasibility of further reducing NOx emission from a semi‐industrial scale coal MILD (moderate and intense low‐oxygen dilution) combustion furnace by adopting fuel‐rich/lean technology. The implementation is achieved by separating the original fuel jet into two parallel jets which will be used as rich and lean streams. An effort has been made to develop a 13‐step reaction mechanism and NOx evolution UDFs (user defined functions) for better understanding the interactions between MILD combustion and fuel‐rich/lean technology. The experiment of the reference case (Combustion and Flame 156.9 (2009): 1771‐1784) is well reproduced by the present numerical simulation, indicating high reliability of developed models. The validity of the further reduction of NOx emission is assessed by the comparison among inner‐fuel‐rich (IFR), outer‐fuel‐rich (OFR), and reference cases resulting from the adjustment of the fuel supply through the two fuel‐rich/lean jets. The results show that both IFR and OFR configurations succeed in achieving further reduction of NOx emission as compared with the reference case, which stems from both thermal and fuel paths. Specifically, the decrease of thermal‐NO emission originates from the contraction of high‐temperature regions (>1800 K), where nearly 94% reduction occurs within the temperature range of 1800 K and 1950 K while only 6% within 1950 K and 2030 K despite their high temperature sensitivity. The reduction of the fuel‐NO emission is mainly attributed to the promoted NO reduction on char surface and neutralization with HCN and NH3. Generally, the NOx emission can be minimized by enlarging the equivalence ratio difference between rich and lean jets, and the OFR configuration exhibits a higher potential than the IFR counterparts. However, since a relatively high temperature (1623 K) secondary air was used in the experiment, the maximum NOx reduction potential was limited to only 2.5%.

Renewable Energy Green Innovation, Fossil Energy Consumption, and Air Pollution—Spatial Empirical Analysis Based on China

“…This may be related to the advancement of clean coal combustion technology and the increase in the exhaust emission requirements for coal combustion. Xu et al (2019) [45] verified that adopting fuel-rich/lean technology can further reduce NOx emissions through experiments. Does the above-mentioned correlation still exist in geographic space?…”

Assessing the thermal efficiency and emission reduction potential of alcohol-based fuel curing equipment in tobacco-curing

“…Due to the extremely low sulfur content of ABF, it is difficult to detect the quantity of SO 2 and H 2 S, which further confirming that ABF is a potential clean fuel. The reasons why the barn ABF did not produce NO X may include that the ABF does not contain nitrogen oxides, the ABF and air are less mixed in the early stage, and the peak temperature of ABF combustion is lower 32 , 33 . In this study, the BBF burning is also produced a lot of pollutant gas.…”

Renewable Energy Green Innovation, Fossil Energy Consumption and Air Pollution--- Spatial Empirical Analysis Based on China

“…However, fossil energy consumption has a negative correlation with comprehensive pollutant emissions and NOx emissions, which may be related to the progress of clean coal combustion technology and the increase of coal combustion exhaust emission standards. Mingchen Xu et al (2019) verifiedthrough experiments that adopting fuel-rich/lean technology can further reduce NOx emissions[44].But do they still exist spatially? We need to further verify through the spatial Dubin model.…”