高浓竹浆黑液高温动态黏弹性研究

Dynamic Viscoelasticity of Thick Bamboo Kraft Pulping Black Liquor at High Temperature

关键词:  竹浆黑液  动态黏弹性  储能模量  动态黏度

Key Words:bamboo kraft black liquor  dynamic viscoelasticity  storage modulus  dynamic viscosity

摘要:实现造纸黑液的高浓燃烧已成为碱回收单元的发展趋势，了解并掌握高浓黑液的流变学性质对优化改进黑液燃烧技术具有重要意义。本研究利用动态流变仪对高浓竹浆黑液的动态黏弹性进行了研究，阐明了储能模量（G′）、损耗模量（G″）、损耗因子（tanδ）与动态黏度（η′）的变化规律。结果表明，高浓竹浆黑液在高温下表现出较强的弹性固体性质，动态黏度呈现出显著的剪切稀化特性。提高温度有助于黑液软化，缩短链段松弛时间，降低动态黏度，减小流动阻力。Cross模型可以很好地描述高温条件下高浓竹浆黑液η′与角频率（ω）的关系，但Carreau-Yasuada模型不适用于描述耗散角（δ）与ω的关系。

Abstract:It has become a development trend that the black liquor was burned at a high solid content in alkali recovery unit. Hence, it is significant to learn and master the rheological properties of thick black liquor in order to optimize the combustion technology. The change rules of storage modulus G′, loss modulus G″, loss factor tanδ and dynamic viscosity η′, which were important indicators of the dynamic viscoelasticity of thick bamboo kraft pulping black liquor, were investigated by using a rotational rheometer in this article. The results proved that thick black liquor still exhibited obvious elastic solid properties at high temperature. In addition, dynamic viscosity showed distinct shear-thinning behavior. Black liquor could be softened by increasing the temperature. meanwhile the relaxation time of chain segments and dynamic viscosity were decreased, therefor, the flow resistance of black liquor was reduced. Cross model could very well describe the relation between η′ of thick black liquor and angular frequency ω under high temperature conditions. However, the Carreau-Yasuada model could not be used to describe the relation between loss angle δ and ω．