제강공정 래들 버너의 COG 대체를 위한 천연가스의 적정 연소 조건및 NOx 배출 영향에 대한 전산해석 연구
Numerical study on ideal combustion condition and NOx emission for natural gas replacing COG in a ladle burner of steel making process
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Because of increasing demand to utilize the coke oven gas (COG) for hydrogen production, there is a need to replace COG with natural gas (NG) in the steel making industry. In this study, ideal combustion condition and impact on NOx emission were evaluated in a burner to preheat a ladle used for transport of molten iron. Computational fluid dynamics (CFD) were employed to analyze the distribution of temperature and heat flux in the refractories of an existing ladle. Then, different combustion conditions were assessed for the burner introducing NG. It was found that the same thermal condition of the refractories with the reference case can be achieved for NG combustion by reducing the excess air ratio to match the adiabatic flame temperature. A major NOx reduction was expected by the fuel switching because of lower peak temperatures and reduced contribution of NNH mechanism, which agreed with the field data. Increasing the thermal input of the burner led to a linear increase in the wall temperature and decrease in the thermal efficiency while NOx emission remained steady. Further investigations are required to improve the thermal efficiency by utilizing the enthalpy of the hot flue gas.
Abstract
Because of increasing demand to utilize the coke oven gas (COG) for hydrogen production, there is a need to replace COG with natural gas (NG) in the steel making industry. In this study, ideal combustion condition and impact on NOx emission were evaluated in a burner to preheat a ladle used for transport of molten iron. Computational fluid dynamics (CFD) were employed to analyze the distribution of temperature and heat flux in the refractories of an existing ladle. Then, different combustion conditions were assessed for the burner introducing NG. It was found that the same thermal condition of the refractories with the reference case can be achieved for NG combustion by reducing the excess air ratio to match the adiabatic flame temperature. A major NOx reduction was expected by the fuel switching because of lower peak temperatures and reduced contribution of NNH mechanism, which agreed with the field data. Increasing the thermal input of the burner led to a linear increase in the wall temperature and decrease in the thermal efficiency while NOx emission remained steady. Further investigations are required to improve the thermal efficiency by utilizing the enthalpy of the hot flue gas.
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