High accuracy online measurement of multidimensional particle size distributions during crystallization

Schorsch, Stefan; Ochsenbein, David R.; Vetter, Thomas; Morari, Manfred; Mazzotti, Marco

doi:10.1016/j.ces.2013.11.003

Cited by 80 publications

(96 citation statements)

References 26 publications

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“…However, for on-line monitoring, optimisation and control of shape and size distributions in a crystalliser, it is essential to accurately and efficiently obtain 3D crystal information of the whole crystal population and the associated properties. Of the many techniques [1,[41][42][43][44][45][46][47][48][49][50][51] for the imaging and reconstruction of 3D objects, optical imaging and image analysis techniques proved to be the most promising ones for 2D shape measurements [1,17,19,23,24,26,29,30,32,34,37,39,[52][53][54], and the techniques that are likely the most suitable ones for obtaining 3D crystal shape, hence growth rate of each crystal face, have made some advances in recent years [1, 45-50, 55, 56]. This is a very active research area with huge challenges and opportunities to innovatively develop process instrument and/or process probes and the associated image processing and shape reconstruction software for the real-time monitoring, optimisation and control of particulate processes.…”

Section: Discussionmentioning

confidence: 99%

Measurement, modelling, and closed-loop control of crystal shape distribution: Literature review and future perspectives

2016

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Crystal morphology is known to be of great importance to the end-use properties of the crystal product and affect the down-stream processing such as in filtration and drying, but was previously regarded as too challenging to achieve automatic closed-loop control. As a consequence, previous work has focused on control the crystal size distribution (CSD) where the size of a crystal is often defined as the diameter of a sphere that has the same volume of the crystal. This paper reviews very promising new advances made in recent years in morphological population balance models for modelling and simulation of crystal shape distribution (CShD), measurement and estimation of crystal facet growth kinetics, as well as in 2D and 3D imaging for on-line characterisation of crystal morphology and CShD. A framework is presented integrating various components in order to achieve the ultimate objective of model-based closed-loop control of CShD. The knowledge gaps and challenges that require further research are also identified.

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Section: Discussionmentioning

confidence: 99%

Measurement, modelling, and closed-loop control of crystal shape distribution: Literature review and future perspectives

2016

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“…By observing 2279 particles among the crystal seeds using the above imaging system, it was verified that the shape density distribution of these seeds is approximately the bivariate normal distribution, with the mean values of 83.0 m and 48.1 m and the corresponding variances of 33.8 and 17.0 for the length and width, respectively. Note that the image analysis method developed in our recent paper [13] was adopted to measure the crystal -4-lengths and widths, which was based on the best-fit rectangle method [26] for each crystal shape.…”

Section: Seed Preparationmentioning

confidence: 99%

“…Huo et al developed a synthetic image analysis strategy for in-situ crystal shape identification [12]. Based on using a noninvasive stereoscopic image acquisition system, multidimensional population crystal morphology analysis was explored in terms of image processing methods [13,14]. The influence of amino acid additives on the LGA crystal morphologies was investigated in the references [15,16].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the operating conditions to morphology evolution of β-l-glutamic acid during seeded cooling crystallization

Zhang

Liu

Huo

et al. 2017

Journal of Crystal Growth

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Abstract:In this paper the effects of operating conditions including cooling rate, initial supersaturation, and seeding temperature were investigated on the morphology evolution of -L-glutamic acid ( -LGA) during seeded cooling crystallization. Based on the results of in-situ image acquisition of the crystal morphology evolution during the crystallization process, it was found that the crystal products tend to be plate-like or short rod-like under a slow cooling rate, low initial supersaturation, and low seeding temperature. In the opposite, the operating conditions of a faster cooling rate, higher initial supersaturation, and higher seeding temperature tend to produce long rod-like or needle-like crystals, and meanwhile, the length and width of crystal products will be increased together with a wider crystal size distribution (CSD). The aspect ratio of crystals, defined by the crystal length over width measured from in-situ or sample images, was taken as a shape index to analyze the crystal morphologies. Based on comparative analysis of the experimental results, guidelines on these operating conditions were given for obtaining the desired crystal shapes, along with the strategies for obtaining a narrower CSD for better product quality. Experimental verifications were performed to illustrate the proposed guidelines on the operating conditions for seeded cooling crystallization of LGA solution.

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“…Mazzotti and co-workers (Kempkes et al, 2010;Schorsch et al, 2012) developed a clever method for measuring the 3D shape of crystals in slurry that passes a flow-through cell (though not directly in a stirred crystalliser): it uses a single camera but two mirrors to obtain two projections of the same particle. However, later, they improved the design by replacing the two mirrors with a second camera (Schorsch et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Stereo imaging camera model for 3D shape reconstruction of complex crystals and estimation of facet growth kinetics

Zhang

Cai

Liu

et al. 2017

Chemical Engineering Science

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The principle that the 3D shape of crystals that grow from a solution can be characterised in real-time using stereo imaging has been demonstrated previously. It uses the 2D images of a crystal that are obtained from two or more cameras arranged in defined angles as well as a mathematical reconstruction algorithm. Here attention is given to the development of a new and more robust 3D shape reconstruction method for complicated crystal structures. The proposed stereo imaging camera model for 3D crystal shape reconstruction firstly rotates a digitised crystal in the three-dimensional space and varies the size dimensions in all face directions. At each size and orientation, 2D projections of the crystal, according to the angles between the 2D cameras, are recorded. The contour information of the 2D images is processed to calculate Fourier descriptors and radius-based signature that are stored in a database. When the stereo imaging instrument mounted on a crystalliser captures 2D images, the images are segmented to obtain the contour information and processed to obtain Fourier descriptors and radius-based information. The calculated Fourier descriptors and radius-based signature are used to find the best matching in the database. The corresponding 3D crystal shape is thus found. Potash alum crystals that each has 26 habit faces were used as a case study. The result shows that the new approach for 3D shape reconstruction is more accurate and significantly robust than previous methods. In addition, the growth rates of {111}, {110} and {100} faces were correlated with relative supersaturation to derive models of facet growth kinetics.

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High accuracy online measurement of multidimensional particle size distributions during crystallization

Cited by 80 publications

References 26 publications

Measurement, modelling, and closed-loop control of crystal shape distribution: Literature review and future perspectives

Measurement, modelling, and closed-loop control of crystal shape distribution: Literature review and future perspectives

Investigation of the operating conditions to morphology evolution of β-l-glutamic acid during seeded cooling crystallization

Stereo imaging camera model for 3D shape reconstruction of complex crystals and estimation of facet growth kinetics

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