Effect of oxygen-enriched combustion conditions on heat transfer characteristics of reheating furnace
Oxygen-enriched combustion has the advantages of increasing theoretical combustion temperature,reducing excess air coefficient and enhancing flue gas radiation capacity,so it has become a hot research topic in the field of in-dustrial furnace.However,the influence of oxygen-enriched combustion position and the volume percent of oxygen on the flow and heat transfer process in steel rolling furnace is still unclear.In this paper,the flow models,oxygen-enriched combustion model and heat transfer model in the heating furnace are established and applied in the case re-heating furnace.After the accuracy of the model is verified by the test data,the variation rules of temperature field,velocity field and billet heat transfer process in the furnace are analyzed when the oxygen-enriched combustion is lo-cated in the preheating stage,the first heating stage and the second heating stage respectively.Then the best position of oxygen-enriched combustion is obtained.Secondly,the variation law of flue gas heat loss,furnace thermal efficien-cy and energy saving rate is analyzed when the volume percent of oxygen changes from 21％to 49％in the fixed oxy-gen-enriched combustion position.Then the optimal range of the volume percent of oxygen is obtained.The results show that when the volume percent of oxygen is fixed,oxygen-enriched combustion is carried out in the preheating stage,the first heating stage and the second heating stage,the most obvious heat flux changes occur in the furnace positions of 17-25,17-34 and 29-44 m,respectively.The average heat flux increases at these locations were 4.95,7.42,and 7.95 kW/m2,respectively.When the oxygen rich combustion positions are fixed in the pre heating sec-tion,heating section 1,or heating section 2,and the volume percent of oxygen varies between 21％and 37％,for each 1％increase in the volume percent of oxygen,the flue gas loss decreases by 0.25％,0.55％,and 0.72％,the furnace thermal efficiency increases by 0.13％,0.3％and 0.39％,and the energy saving rate increases by 0.2％,0.99％and 1.09％,respectively.However,when the volume percent of oxygen is in the range of 37％-49％,the changes of flue gas loss,furnace thermal efficiency and energy saving rate are not obvious even if the oxygen-enriched combustion is implemented in the second heating stage.It can be seen that in the steel rolling reheating furnace,the high heat load stage implements oxygen rich combustion and the volume percent of oxygen is in the range of 21％-37％is the ener-gy-saving effect most obvious.
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