首页|Investigating The NOx Emission From CAL Radiant Tube Burners
Investigating The NOx Emission From CAL Radiant Tube Burners
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NSTL
The continuous annealing line (CAL) has been widely adopted to anneal the coldrolling steel strip. China Steel Corporation (CSC) introduced CAL to its cold rolling mill in the 1980' s. In CAL, steel strip is heated by a radiant tube (RT) burner, which fires COG fuel gas. After 2-3 years' operation, it showed that the top left hand side of RT is vulnerable to be ruptured owing to the left-eccentric burner design. To solve this problem, a series of tests have been conducted to investigate the influence of burner design and operation parameters on the RT life and NOx emission. The investigated operation parameters include burner load, off-stoichiometric combustion, total stoichiometric ratio (PHI_T), primary stoichiometric ratio (PHI_1) , secondary air swirl number (Sg), etc. From the experiments, it has become apparent that NOx concentration increases with burner load, that the initial left-eccentric combustion exhibits lower NOx emission than the bottom-eccentric flame, that NOx formation is quite low in the fuel-rich combustion region until the CD T reaches nearly 0.8, and that PHI_1 and Sg has little and more effect on the NOx concentration for the left-eccentric combustion respectively. Finally the suggested low NOx operation parameters for the left- and bottom-eccentric combustion are PHI_1 =0.55 & Sg = 0.0 and PHI_1 =0.35 & Sg = 0.56 respectively. From the temperature measurements, it is found that the bottom-eccentric flame has a better temperature uniformity for the RT outer surface. This worse temperature distribution for the left-eccentric flame is attributed to the fact that combustion occurs too close to the RT top surface, which results in a higher localized temperature occurring at the top RT outer surface.
NSTL
