Research And Development Of Direct Flame Impingement Heating Technology

Direct flame impingement heating technology is a new and efficient heating technology,which replace radiation heat transfer with convection heat in traditional reheating furnace.It has a high flame temperature and a fast flow rate of airflow,which is one of the core technologies for the rapid heat treatment of strip steel.And the key part of the technology is the heating burner.Taking the new three layer concentric tube burner burner as the research object,this paper analyzes the characteristics of C3H8-air-oxygen diffusion flame and heating performance by combining flame impact and oxygen enriched combustion.Direct flame impingement heating combined with oxygen enriched combustion technology can significantly improve the flame temperature and C3H8 utilization rate,reduce the C3H8 ignition point,increase the ignition concentration limit of C3H8,the combustion speed and the combustion process are improved,the combustion of C3H8 is more sufficient and the emission of nitrogen oxides is reduced.A new type of three layer concentric tube burner was designed in this paper.A set of single burner flame heating experimental system was built based on burner structure,which included the combustion supporting system,the combustion test bench and the temperature collection system.The main contents of the experimental research included two parts:flame characteristics and heating characteristics.In the experiment of flame characteristics,the main research contents were the measurement of flame length,flame stability and flame temperature distribution on the central axis under different gas flow rate,oxygen content,air excess coefficient and the ratio of the outer layer of the burner to the central layer combustion suporting agent.In the experiment of the heating characteristics,the main research contents were the influence on the heating rate at different height,and find out the height range of the fastest heating rate.On the basis of the experimental results,the effects of oxygen content,C3H8 consumption and excess air coefficient on the heating rate were studied and the rules were summarized.At the same time,the heating uniformity was explored.The experimental results showed that:When the C3H8 consumption was 0.5m3/h and oxygen content was 35%,flameout occured.In order to stabilize the flame,the oxygen content should be above 40%.Under the condition of a certain C3H8 consumption,with the increased of oxygen enrichment concentration,the flame temperature rised,the distance between the highest temperature position and the exit of the burner decreasd.With the increased of the excess air coefficient the flame temperature increased and the jet velocity increased.When the distribution ratio of combustion promoter in the outer layer and central layer was 1:20,the flame was ejected rapidly,the turbulence effect was strong,and the temperature was obviously higher than that of other flame.It was suitable for direct flame impingement heating.When the C3H8 consumption was 0.5m3/h oxygen content was 70%,the excess air coefficient was 1.0 and the distribution ratio of combustion promoter in the outer layer and central layer was 1:20,the flame jet velocity reached 70m/s,the maximum flame temperature reached 2300?.Heating rate was calculated when heat the steel plates were heated to 300?,600?,and 800?,it was found that the fastest heating rate was located at the highest flame temperature point and the heating rate was up to 120?/s.It was also found that the oxidizer in the outer layer of the burner can improve the stability of the flame and prevent the occurrence of blo w-of and flameout.