制浆造纸黑液结垢组成及静态蒸发规律研究

Study on Scaling Composition and Static Evaporation Regularity of Pulping and Papermaking Black Liquor

摘要: 制浆造纸黑液蒸发过程中的结垢问题严重制约着其蒸发系统的稳定运行和能效的提升。为研究其静态蒸发规律及结垢组成，本文采用X射线衍射与滴定法相结合的方法，在明确制浆造纸黑液结垢组成的基础上，通过静态蒸发实验系统开展了蒸发规律分析。研究结果表明，制浆造纸黑液结垢产物主要为碳酸钠和硫酸钠构成的无机盐，其质量分数分别为1.69%和0.54%，测定结果的相对标准偏差分别为1.54%、3.55%；在80℃、100℃和120℃工况下黑液静态蒸发过程呈现出明显的三段式变化，蒸发初期速率较快，分别接近于11 g/h、15 g/h、25 g/h，随着水分大量蒸发，蒸发速率降至5 g/h，最后由于黑液中大量结垢析出，其蒸发速率以小于0.1 g/h的速率变化。基于此，构建了考虑残余质量的黑液静态蒸发预测数学模型，利用90℃、110℃工况下的蒸发数据进行模型检验，其平均相对误差分别为1.6%、2.0%，满足工程精度要求。研究结果可为制浆造纸黑液流动过程中结垢的预测及有效预防提供一定的参考依据。

Abstract: Scaling during the evaporation of pulping black liquor severely restricts the stable operation and energy efficiency of evaporation systems. To investigate the static evaporation regularity and scaling composition of pulping black liquor, this study combines X-ray diffraction characterization with titration analysis. On the basis of identifying the scaling composition, systematic static evaporation experiments were conducted to analyze the evaporation regularities. The results indicate that the primary inorganic components of black liquor scale are sodium carbonate and sodium sulfate, with mass fractions of 1.69% and 0.54%, respectively. The relative standard deviations of the measurements are 1.54% and 3.55%, confirming good analytical reliability. Under operating temperatures of 80˚C, 100˚C, and 120˚C, the static evaporation process of black liquor exhibits a distinct three-stage variation. The initial evaporation rates are relatively high, reaching approximately 11 g/h, 15 g/h, and 25 g/h, respectively. As a large amount of water evaporates, the evaporation rate decreases to approximately 5 g/h. Finally, due to the extensive scaling precipitation in the black liquor, the evaporation rate changes at a rate of less than 0.1 g/h. Based on these observations, a predictive mathematical model for the static evaporation of black liquor incorporating residual mass was established. The model was validated using evaporation data obtained at 90˚C and 110˚C, yielding average relative errors of 1.6% and 2.0%, respectively, satisfying engineering accuracy requirements. The research results can provide a certain reference basis for predicting and effectively preventing scaling during the flow process of pulping and papermaking black liquor.