【作者】 蒋受宝；

【导师】 蒋绍坚；

【作者基本信息】 中南大学 ， 热能工程， 2006， 硕士

【摘要】 本文以空气预热温度、含氧浓度和空气过剩系数三因素联合作用下钢坯加热炉热效率和氧化烧损率的变化规律为研究对象，目的是为进一步提高钢坯加热炉操控优化水平和降低钢铁生产成本提供理论依据。首先以步进式钢坯加热炉为对象，运用STEEL-TEMP软件，耦合钢坯热流密度模型、热平衡模型和氧化皮线性及抛物线性增长组合模型，编制了钢坯热过程模拟计算程序。利用该程序可以直接得到钢坯升温曲线、炉内各区温度、炉墙内表面温度曲线、金属氧化烧损等数据。从这些数据中，可以计算出热效率和氧化烧损率。然后利用这一程序，采用不同的空气预热温度、含氧浓度和空气过剩系数组合，研究了钢坯加热热效率和氧化烧损随空气温度、含氧浓度和空气过剩系数的变化规律。研究中空气温度变化范围为200-900℃，含氧浓度变化范围为21-54％，空气过剩系数变化范围为1.0-1.3。研究结果表明，在加热终了温度相同的情况下：(1)空气温度越高，加热时间越短，加热速率越大，热效率和生产率越高，总的氧化皮生成量越少。(2)烟气含氧浓度对氧化皮生成量有重要影响。低的烟气含氧浓度可抑制Fe的氧化反应，增加烟气发射率，缩短加热时间，从而可减小氧化皮生成量，降低吨钢能耗。(3)空气过剩系数越低，加热速率越大，热效率和生产率越高，加热时间越短，氧化皮生成量越小。氧化皮生成速率最慢的燃烧条件是空气过剩系数1.0-1.1且空气温度400-500℃。空气过剩系数越低，最小氧化皮生成速率所对应的空气温度范围越宽。(4)空气含氧浓度越高，加热速率越大，热效率和生产率越高，加热时间越短，氧化皮生成量就越小。氧化皮生成速率最慢的燃烧条件是空气温度400-600℃且空气含氧浓度低于45％。在以上研究的基础上，本文最后提出了“逐级配风”的热工操作制度。即：控制总空气过剩系数为1.0，执行“从加热一区、加热二区到均热区空气过剩系数按5-10％逐级递减，使高温均热区处于弱氧化气氛。采用“逐级配风”热工操作制度，可提高热效率，并降低氧化皮生成量。更多还原

【Abstract】 The change of both the thermal efficiency of reheating furnace and the formationof scale during the heating process with time under different combination of airpreheat temperature, oxygen concentration and excess air coefficient have beenstudied in this paper. The objective is to obtain theoretical basis for improving theoptimization level of design, operation and control to the heating process of billet anddecreasing the billet production cost.Firstly taking the walking beam furnace as an example, using STEEL-TEMPsoftware and coupling with billet heat-flow-density model, thermal-balance modeland linear-parabola increase model of oxidation scale, simulation calculation programhas been constructed. The temperature curve of billet, the flue gas temperature in eachzone and the temperature curve of inner surface of furnace wall, scale formation canbe obtained. The thermal efficiency and the rate of scale formation can be calculatedfurther.Secondly the change of thermal efficiency and scale formation with the changeof air temperature, oxygen concentration and air excess coefficiency has beenresearched under the different combination of air preheat temperature, the oxygenconcentration and the air excess coefficiency. The temperature of preheated air rangesfrom 200℃to 900℃, the air excess coefficient from 1.0 to 1.3 and oxygenconcentration from 21% to 54%.To compare the effects of the significant factors above on heating efficiency andscale formation, the fmal temperature of billet is set at 1235℃+2℃. The followingresults have been obtained:(1) The higher the air temperature is, the shorter the heating time is, the larger theheating velocity is, the higher the thermal efficiency is, the higher the productivity isand the less the scale formation is.(2) The oxygen concentration of flue gas has an important effect on the scaleformation. The low oxygen concentration of flue gas can restrain the ferrous oxidationreaction, increase the flue gas emissivity and shorten the heating time. Further more,the low oxygen concentration of flue gas lead to the low scale formation and the lowenergy consumption per ton steel. (3) The lower the air excess coefficient is, the larger the heating rate is, thehigher the thermal efficiency is, the higher the productivity is, the shorter the heatingtime is and the less scale formation is. The combustion conditions for the minimumrate of scale formation should be the air excess coefficient 1.0-1.1 and the airtemperature 400-500℃. The lower air excess coefficient is, the wider range of airtemperature corresponding to the minimum rate of scale formation is.(4) The higher the air oxygen concentration is, the larger the heating rate is, thehigher the thermal efficiency is, the higher the productivity is, the shorter the heatingtime is and the less the scale formation is. The combustion conditions for theminimum rate of scale formation should be the air temperature 400-600℃and the airoxygen concentration below 45%.Finally, based on the above studies, a thermo-technical operation system called"stepwise distribution" has been brought forward. According to this system, the airexcess coefficient decreases from 5% to 10% in turn Zone One, Zone Two and thesoaking zone while the total air excess coefficient remains at the value of 1.0. Thesemeasures make the soaking zone be at the weak oxidative atmosphere. The newoperation system can lead to high thermal efficiency and low scale formation.更多还原