Research Of The Characteristics Of Burner With Direct Flame Impingement For Continuous Annealing Of Strip

Energy problem is the basic element of sustainable development in the world today.It is a consensus that we need to save energy and reduce emission in modern socirty.Meanwhile,cleaner energy needs to be more developed and utilized than ever before.The continuous annealing direct flame impact heating technology emerges in this social background.The high temperature flame of high speed combustion is directly impacted on the surface of the workpiece by the combination of direct flame impact and oxygen-enriched combustion technology.It is an efficient and rapid heat treatment technology with convection heat transfer.At present,the burner heating temperature in industrial application is 200～500℃,which is mostly used in preheating stage.In addition,the distance between the burner arrangement is more than 50mm,and the temperature of the workpiece is uneven.In the continuous production of strip,the quality and adaptability of the workpiece are becoming more and more demanding.Through the design of reasonable burner structure and optimization of operating conditions,a rapid heating technology with heating rate of 120℃/S and heating temperature of 600～700℃ is developed.The main work and results are as follows:(1)The experiment is based on the reverse diffusion jet flame formed by the mixture ofpropane-air-oxygen,the flame stability was studied in terms of burner structure and operation conditions.It is found that the flame stability of structure one is better than other three kinds of burner,and it is obviously better than the two-layer concentric tube burner.The key operating conditions of the flame stability are determined by the flow rate of oxygen in the outer layer,so that the flame can still burn stably when the gas low rate is at 140m/s.(2)The flame center temperature was measured by infrared indirect temperaturemeasurement method.It was found that the influence of background plate color on flame center temperature was very weak.The results were checked with thermocouple,and they have a high degree of linearity.The results of flame center temperature measurement are accurate and reliable.The fitting curve of temperature is obtained:y=0.997*x+216.324.(3)The experiment is based on the indirect infrared temperature measurement,it is foundthat the center temperature of the flame increases firstly to the peak value and then decreases with the increase of its heigh.The maximum center temperature reaches 1800℃ when the gas flow rate is 0.5Nm3/h,and it increases with the increase of oxygen enrichment concentration and excess air coefficient.However,the maximum center temperature decrease with the increase of the outer oxygen flow.(4)The experiment is based on the traditional flame height measurement method.It is found that the flame height increase with the oxygen enrichment concentration and the oxygen flow in the outer layer.However,the flame height decrease with the increase of the excess air coefficient.The change trend of the orange part of flame is similar to flame height,the flame burns violently and reacts well.(5)The experiment is based on the record of the heating rate of the steel plate with the temperature recorder and the temperature distribution of the plate recorded by the infrared thermal imager,it is found that the heating rate is the fastest at 20mm near the highest temperature of the flame center.With the increase of oxygen enrichment concentration and the decrease of steel plate thickness,the heating rate continues to accelerate.The uniformity of the plate heating becomes worse with the increase of the heating temperature of the steel plate,and the change of the height will have a weak effect on the uniformity of the plate in the height with the fastest heating rate.