Structure Formation within Spray-Dried Droplets; Mathematical Modelling of Spray Polymerisation

Chemie Ingenieur Technik

2022

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Dedicated to Prof. Dr. Thomas Hirth on the occasion of his 60th birthday Spray drying is a widely used process to obtain solid porous products from a liquid feed. Whereas the product's morphology is important for its further processing, established one-dimensional single droplet models are limited in predicting the final structure depending on drying conditions and functional additives as binders. A novel approach based on a meshfree method is employed to calculate the final morphology from first principles by accounting for physical effects like surface tension and wetting. Generation of dense porous products and buildup of hollow particles with a porous crust can be modelled, depending on the model parameters.

Section: The Sph Methods and Its Application To Structure Formation D...mentioning

confidence: 99%

“…Solid particles interact with each other by attractive forces

{\vec{F}}_{a}^{S}

. For a more detailed description and the mathematical model please refer to 7, 8.…”

Section: Physical Processes In Suspension Dryingmentioning

confidence: 99%

Simulation of Morphology Evolution in Spray Drying of Suspensions by a Meshfree Approach

Säckel

Chemie Ingenieur Technik

2022

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“…To archive this, two simplifications of the Stefan‐Maxwell diffusion were derived, which convert the transport equation of polymeric species to a closed set of transport equations for the polymer moments. The first approach corresponds to an infinitely diluted polymer system, whereas the second one describes a highly concentrated polymer system 12–14. Both formulations were compared with the full Stefan‐Maxwell model of a ternary mixture of a solvent and two polymer species of different chain length.…”

Section: Introductionmentioning

confidence: 99%

Wall Layer Formation in Continuously Operated Tubular Reactors for Free‐Radical Polymerizations

Welzel

Zander

Chemie Ingenieur Technik

2023

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Polymer fouling is a major problem for the operation of continuous reactors. Therefore, it is important to understand and quantitatively describe the mechanisms leading to formation of fouling deposits. In this work, a CFD model for the radical polymerization of N‐vinylpyrrolidone is presented, where the reaction kinetics, a viscosity model, and a transport model for polymer moments are determined from independent experiments. The model is compared to experimental obtained residence time distributions in capillary reactors over a wide range of concentrations. Model predictions are in good agreement with experimental findings.

“…This might be irrelevant if diffusion is subordinate to convection. In special cases like spray polymerization, [3][4][5] regions of low convective transport (i.e., behind mixing elements) or polymer fouling close to walls of micro reactors, the assumption of "No Polymer Friction" introduces large errors. This is especially true at high polymer content.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Diffusive Transport of Polymers Moments Using Limiting Cases of the Maxwell–Stefan Model

Welzel

Säckel

Macro Reaction Engineering

2022

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A polymer distribution is usually represented by its moments. Thus, to calculate transport in a polymer system, a formulation for the transport of moments of the polymer is needed. This is only possible if the moments close or if there is a suitable closing condition. To archive this, two simplifications of the Stefan–Maxwell diffusion are derived, which convert the transport equation of polymeric species to a closed set of transport equations for the polymer moments. The first approach corresponds to an infinitely diluted polymer system, whereas the second one describes a highly concentrated polymer system. Both formulations are compared with the full Stefan‐Maxwell model of a ternary mixture of a solvent and two polymer species of different chain length.