Abstract Scaling caused by sodium carbonate and sodium sulphate salts is a common problem during black liquor evaporation and mills currently have no proper tools to monitor or follow it up. The method proposed enables automatic evaluation of scaling rates and behaviours, together with washing performance, by using measurements that are already available at most mills, such as the boiling point elevation and the overall heat transfer coefficient. The method identified the scaling correctly in most cases, normally >90 %, although fast and sudden scaling proved to be challenging; its performance was also dependent on the quality of the data used. Historical data from three mills was evaluated and it was found that the scaling rate generally increased at higher concentrations of black liquor: one of the mills had almost no scaling below 70 % dry solids content. Another mill, however, deviated from this trend and had significant problems with fast and sudden scaling in one effect at around 60 % dry solids content. The correlation of process parameters revealed that this scaling was triggered, to a large extent, by the absence of tall oil brine, which is a side stream from the production of tall oil that is normally fed to the evaporators.

中文翻译：

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使用现有工艺数据评估黑液蒸发器中的钠盐结垢

摘要 碳酸钠和硫酸钠盐引起的结垢是黑液蒸发过程中的一个常见问题，目前工厂没有合适的工具来监控或跟进。所提出的方法通过使用大多数工厂已有的测量值（例如沸点升高和总传热系数），能够自动评估结垢率和行为以及洗涤性能。该方法在大多数情况下都能正确识别缩放，通常>90%，尽管事实证明快速和突然缩放具有挑战性；其性能还取决于所用数据的质量。对来自三个工厂的历史数据进行了评估，发现在较高浓度的黑液下结垢率通常会增加：其中一台磨机在干固体含量低于 70% 时几乎没有结垢。然而，另一家工厂偏离了这一趋势，并在一个效果中出现了快速和突然结垢的严重问题，其中干固体含量约为 60%。工艺参数的相关性表明，这种结垢在很大程度上是由于没有妥尔油盐水引发的，妥尔油盐水是通常供给蒸发器的妥尔油生产的侧流。