NOx emission control for Coke Oven Application of Two-Staged combustion to the single-staged combustion

Posted on 09 June 2014
 

NOx emission control for Coke Oven Application of Two-Staged combustion to the single-staged combustion
The operating rate of Coke Oven gives the hightest effect on the emission of NOx in the steel-making process. In case of POSCO, since the coke oven, constructed before 1980's, has single combustion chamber, it has been very difficult for the operators to reduce NOx emission. In general, NOx emission has been controlled by two types techniques - primary measure type and secondary one. The primary measures are waste gas recirculation, staged air combustion, and lowering coking temperatures. Waste gas recirculation is that The lower O2 and higher CO2 concentrations reduce the flame temperature. Staged air combustion is that by adding the combustion air in several stages, combustion conditions become more moderate, and NOX formation is reduced. Lowering coking temperatures make the condition of lower heating chamber, and then results in less NOx formation. The secondary ones is the minimizing the NOx emissions from coke oven firing by process-integration. But end-of-pipe may also be applied. In most cases, those techniques are only applicable to new plant, tend to decrease the coke productivity and to restructure of coke oven. POSCO has tried to introduce two-staged combustion in the ignition chamber by installation of the secondary burners positioned at 1125mm from the bottom of coke-oven. In the test, about 60-70% of combustion air was directed into the primary combustion chamber, while the balance air was introduced into the secondary combustion chamber. It has found that two-staged combustion has resulted in reducing of 35-45% NOx from the Coke oven. Thermal shock to refractory, due to the injection of combustion air, has to be also examined thoroughly. 2012 SEAISI Seminar

 

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