富氧燃烧条件下加热炉内辐射传热分析

Analysis of radiation heat transfer in reheating furnace under oxy-fuel conditions

为了获取加热炉富氧燃烧的最佳氧气体积分数,对灰气体加权和(WSGG)模型进行改进,使其适用于富氧燃烧条件下的气体辐射传热计算,并利用改进后的模型研究了富氧燃烧条件下加热炉内温度和氧气体积分数对烟气发射率和钢坯表面热流密度的影响.结果表明:随着烟气温度的升高,在增氧燃烧方式和干烟气再循环燃烧方式下,烟气发射率均先增大再减小,在湿烟气再循环方式下,烟气发射率持续减小;在增氧燃烧方式下,烟气温度超过1300 K后,钢坯表面热流密度的降低幅度逐渐增大,而在烟气再循环燃烧方式下,钢坯表面热流密度随烟气温度的升高呈线性下降趋势;随着氧气体积分数的增加,增氧燃烧方式下钢坯表面热流密度增加幅度较大,该燃烧方式下加热炉内预热段、加热段和均热段的最佳氧气体积分数分别为30%~34%,28%~31%,26%~28%;而在干湿烟气再循环燃烧方式下,随着氧气体积分数的增加,炉内钢坯表面热流密度仅略有增大.

In order to obtain the optimal oxygen volume fraction during oxy-fuel combustion in the reheating furnace,the weighted-sum-of-gray-gases model(WSGG)was improved to make it suitable for the calculation of gas radiation heat transfer under oxy-fuel combustion conditions.The improved model was used to study,the effects of temperature and oxygen volume fraction on furnace gas emissivity and heat flux density on the surface of slab under oxy-fuel combustion conditions in a reheating furnace.The results show that with the increase of furnace gas temperature,the emission of furnace gas first increases and then decreases in the oxy-fuel combustion method and dry flue gas circulating combustion method,and the emissivity of furnace gas continues to decrease in the wet flue gas circulation method;Under the oxy-fuel combustion method,the decrease of heat flux density on the surface of slab gradually increases when the furnace gas temperature exceeds 1300 K,while under the flue gas circulating combustion method,the heat flux density on the surface of slab decreases linearly with the furnace gas temperature;With the increase of oxygen concentration,the heat flux density on the surface of slab in the oxy-fuel combustion method increases significantly.In this method,the oxygen concentration in the preheating,heating,and soaking sections of the reheating furnace using oxy-fuel combustion is 30%~34%,28%~31%,and 26%~28%,respectively.For the flue gas recirculation combustion method,as the oxygen concentration increases,the increase in heat flux density on the surface of slab is relatively small.