A dynamic process model for the simulation of the separation process in countercurrent decanter centrifuges is presented. The numerical approach uses an interconnection of compartments to characterize the residence time distribution of the particles within the centrifuge. First, the theoretical basis of the numerical approach is described. Compared to the state-of-the-art modeling of decanter centrifuges, the proposed approach allows the simulation of the temporal filling process. The short computing time results in further advantages of the dynamic process model. The so-called real-time simulation is an opportunity for a modelbased control of the separation process. An exemplary simulation with the product limestone demonstrates the main features of the numerical approach.
Mathematical modeling of the separation process in counter‐current decanter centrifuges was performed, taking into account the influence of the sediment build‐up and the flow pattern. Thus far, separation processes in centrifuges have been calculated by means of simplified empirical models based on the so‐called sigma theory. To reduce experimental efforts, a new model was developed that describes the separation process by considering material functions for sedimentation and the gel point. In addition, an arising sediment build‐up and changes in the flow conditions were taken into account. The conducted numerical simulations were validated by experiments. Simplified models such as the sigma theory usually depend on experimental data of industrial machines. The approach presented here shows an enhanced accuracy while not depending on such information. The proposed simulation procedure is adaptable to other types of decanter centrifuges such as co‐current machines.
Summary
An electrochemical model that is capable to simulate charge and species transport within the three‐dimensional particulate cathode structure of lithium‐ion battery half‐cells is applied to blended electrodes. The electrodes are assumed to consist of physical mixtures of LiMn2O4 (LMO) and Li[Ni1/3Co1/3Mn1/3]O2 (NMC) as cathode active materials. The results of the numerical simulations reveal that there is a significant temporal variation in the distribution of the intercalation current between the active materials on the particulate level. In this context, the LMO component was found to be electrochemically inactive at the beginning and at the end of a simulated discharge process that leads to the identification of a suitable operating window of the half‐cells between 0.2 < DOD < 0.8. It is shown that within this range, a relaxation of the maximum lithium concentration gradients within the NMC component is achievable. As this provides indications of reduced mechanical stresses within the active material particles, an increased cycling stability of this kind of blended electrodes is expectable. Because of the NMC component's higher volumetric capacity compared with LMO, the separator‐near arrangement of NMC allows the magnitude of ionic current density to be reduced by up to 11% compared with a random particle arrangement. As this indicates a reduction of potential temperature‐induced side reactions of the electrolyte, an increased cycle life of the half‐cells, especially for high‐performance applications, is anticipated. Consequently, multiple‐layer coating processes appear particularly attractive for the production of optimized blended positive electrodes for lithium‐ion batteries.
Increasing global competition, volatile markets and the demand for individual products challenge companies in almost all business sectors and require innovative solutions. In the chemical and pharmaceutical industries, these include modular design, the integration of several unit operations in one apparatus and the development of small-scale, versatile multipurpose plants. An example for such a modular, integrated and small-scale system is the belt crystallizer. This device combines the process steps cooling crystallization, solid-liquid separation and contact drying in a single plant. The basis of the apparatus is a belt filter in which the vacuum trays below the filter medium are replaced by temperature control and filtration units. Due to identical dimensions, it is possible to arrange the individual functional units in any order, which in turn allows a high degree of flexibility and rapid adaptation to customer requirements. Within the scope of the publication, the commissioning of the belt crystallizer takes place. First of all, the general functionality of the plant concept is demonstrated using sucrose as model system. Further experiments show that the particle size and the distribution width of the manufactured crystals can be specifically influenced by the selected process parameters, e.g., temperature profile during cooling and residence time.
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