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Dynamic modelling optimisation and control of lactose crystallisations: Comparison of process alternatives

机译：乳糖结晶的动态建模优​​化和控制：工艺选择的比较

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A general technique is derived to formulate and solve the dynamic optimisation problems for crystallisation,in order to re-evaluate the growth rate correlations and search for the optimal cooling and heating strategies (evaporative mode only).The dynamic model of a process making alpha-lactose monohydrate is first revised for these operations using seed crystals: batch cooling,semi-batch cooling and heating,and continuous cooling.Experiments are conducted in 2 and 20 L crystallisers under various seeding,cooling and heating strategies to evaluate the constants in the power law function,which correlates the growth rate of the particles with supersaturation.Using a nonlinear least square method,the best curve fitting of experimental data to the model yields G = 0.007T(100(x_(alpha)/x_w) - sol_(alpha))~(2.7).The value of n = 2.7,which is applicable to all operations investigated in the study.The value of k however,must be estimated for selected seeding and cooling strategies,and most importantly for the type of syrup fed to the crystalliser.Using k = 0.007 in simulations and experiments of jet-milled seeds at 1.5% seeding ratio,the experimental results agreed well with predictions before the growth became slow.A semi-batch is slightly faster than a batch process and evaporative semi-batch is much faster than cooling operation but is more difficult to control.The performance of a cooling and seeding run in continuous mode is simulated.The system reached steady state after seven residence times but the predicted particle size could only be stabilised after 100 h.The developed methodology can be applied to the crystallisation of many other substances but is not limited to the food or dairy industries.
机译：推导了一种通用技术来制定和解决结晶的动态优化问题，以便重新评估生长速率的相关性并寻找最佳的冷却和加热策略（仅限蒸发模式）。乳糖一水合物首先通过晶种进行以下操作：分批冷却，半分批冷却和加热以及连续冷却。在2升和20升结晶器中进行各种晶种，冷却和加热策略的实验，以评估功率常数定律函数，该函数将颗粒的生长速率与过饱和相关。使用非线性最小二乘法，将实验数据与模型进行最佳曲线拟合，得出G = 0.007T（100（x_α/ x_w）-sol_（alpha ））〜（2.7）.n = 2.7的值适用于研究中的所有操作。但是，k的值必须根据所选的播种和降温策略进行估算，并且大多数情况下对于送入结晶器的糖浆类型非常重要。在以1.5％的播种比例进行喷射研磨的种子的模拟和实验中，使用k = 0.007，在生长变慢之前，实验结果与预测基本吻合。比分批处理和蒸发式半分批处理要快于冷却操作，但更难控制。模拟了连续模式下冷却和播种的性能。系统在七个停留时间后达到稳态，但预测的粒径只能在100 h后稳定下来。所开发的方法可以应用于许多其他物质的结晶，但不仅限于食品或乳制品工业。

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