辊底炉炉辊改进前后的热损分析和控制优化

Heat loss analysis and control optimization of furnace roller for roller hearth furnace

采用数学模型分析辊底炉炉辊改进前后的水冷合金辊、纤维辊的热损规律.分析辊底炉存在的问题,指出炉辊改进的原因和关键点;建立两种炉辊的传热模型,提出基于牛顿搜索的迭代规划求解算法;研究冷却水流速和进水温度与两种炉辊截面上不同材质界面处的温度、出水温度、温升、吸热量及换热系数的关系.结果表明：炉辊分界面温度、出水温度、冷却水温升随流速增加而减小,两种辊临界流速为0.07和0.09 m/s,大于临界流速发生湍流,冷却效果倍增;考虑到减少结垢和水系统造价,还应控制出水温度在45℃之下和温升小于10℃,合适流速为0.4~0.8 m/s和0.2~0.6 m/s,此时完全湍流,冷却效率高,温升小;再增大流速,冷却水吸热量变化不大,能耗增大;强制湍流换热时,纤维辊热损约为合金辊的78%.应用效果表明：炉辊改进及优化控制后,由于纤维炉辊热损小,并且不用磨辊,产量大大提高,吨钢燃料消耗量大幅降低.

To design and control furnace roller better,heat loss law of water-cooled furnace roller which surface coat is composed of heat-resistant alloy or asbestos fibers before and after improvement was studied by mathematical models.After analyzing the problems of traditional roller hearth furnace,the improvement reason and key point were pointed out.Heat transfer models for cooling process of two kinds of rollers were established and solved with iteration planning algorithm based on Newton search.Then,the relation between water flow velocity（ uw）,inlet water temperature（ tw-in） and roller cross section temperatures,outlet water temperature（ tw-out）,water temperature rise（ Δtw）,cooling water heat absorption（ Qw） was studied.The conclusions and recommendations are mainly as follows： 1） Roller cross section temperatures,tw-out,Δtw decrease with the increase of uw.The water critical velocity（ uwcv） of two kinds of furnace rolls is 0.07 m/s and 0.09 m /s respectively,and when uwis larger than uwcv,turbulent flow occurs.Considering less water scale and water treatment system cost,tw-outshould be under 45 ℃ and Δtwshould be less than 10 ℃.So suitable uw should be 0.4 ~ 0.8 m /s and 0.2 ~ 0.6 m /s,when cooling water is entire turbulent flow,cooling efficiency is high,and Δtwis small,above which energy consumption increase greatly and uselessly,but Qwalmost remains unchanged.2） Qwof asbestos fibers roller is small and 78% of heat-resistant alloy roller when cooling water is entire turbulent flow.Application result indicates that consumption of per ton steel is greatly reduced after the improvement and optimization control of furnace rollers,of which the reason is that production is greatly increased due to not grinding rollers,except for optimal control,fiber furnace roller heat loss is small.