ARR - Annual Report
Executive Summary
Segregation model development holds promise for translation of academic research into industrial practice. Two significant issues that hamper the applicability of models in industry, however, are (1) the inherent difficulty in measuring segregation rates (especially in an experimental setting) for validation purposes and (2) the significant dearth of validated scale-up studies for these models. In this project, we seek to alleviate these two shortcomings of segregation research through a combined theoretical, computational, and experimental program. One unique aspect of our work is that we use flow perturbations to establish an “equilibrium” between segregation and mixing in free surface granular flows in order to alter the steady-state distribution of particles. By achieving this balance between the rate of segregation and the perturbation rate, we can combine the model expressions that we are interested in testing with dramatically simplified experiments to ultimately deduce the segregation rate (and validate the expressions). Moreover, by exploring a novel view of the interplay between granular rheology and segregation, we aim to continue to develop a new way of structuring segregation rate models that make them inherently more scalable than any models previously reported. Thus far we have demonstrated which models from the literature may be considered state-of-the-art, but, more importantly, we developed several novel inherently scalable, theoretical models based on rheologically-relevant dimensionless groups that are applicable to density, size, shape, and cohesive segregation. We have experimentally validated some of these segregation models and plan to expand others, while incorporating the validated models into device-level transport equations in order to supply quantitative prediction of segregation at process scale.
Executive Summary
scale.
device-level transport equations in order to supply quantitative prediction of segregation at process
our ultimate aim is (experimentally) validated segregation models that can be incorporated into
applicable to density, size, shape, and cohesive segregation. As this project continues to mature
novel inherently-scalable models based on rheologically-relevant dimensionless groups that are
be considered state-of-the-art, but, more importantly, we have begun theoretical development of
previously reported. Thus far we have demonstrated which models from the literature may
way of structuring segregation rate models that make them inherently more scalable than any models
of the interplay between granular rheology and segregation, we aim to continue to develop a new
deduce the segregation rate (and validate the expressions). Moreover, by exploring a novel view
expressions that we are interested in testing with dramatically simplified experiments to ultimately
this balance between the rate of segregation and the perturbation rate, we can combine the model
free surface granular flows in order to alter the steady-state distribution of particles. By achieving
is that we use flow perturbations to establish an “equilibrium” between segregation and mixing in
combined theoretical, computational, and experimental program. One unique aspect of our work
In this project, we seek to alleviate these two shortcomings of segregation research through a
- for validation purposes
- the significant dearth of validated scale-up studies for these models.
are (1) the inherent difficulty in measuring segregation rates (especially in an experimental setting)
practice. Two significant issues that hamper the applicability of models in industry, however,
Segregation model development holds promise for translation of academic research into industrial
Executive Summary
2 and 3.
publication in Q1 2019. This report summarises the progress to date and the remaining work for years
of this work is included in this report, and the first “proof of principle” paper will be ready for
out for the first time which showed the layer by layer detail of the 3D printing process. A description
something which had not been previously observed. X-ray tomography of the agglomerate was carried
agglomerate bonds to determine the optimum bond material to prevent individual particle breakage,
more detail. Soft, rigid and a hybrid mixture of both soft and rigid materials were used for the
orientation, individual particles and observe the breakage behaviour with much more accuracy and in
agglomerates in colour. By dividing the agglomerate into coloured sections, it will be possible to track
of strength behaviour at different strain rates. A Stratasys Object 500 Connex 3 was used to print the
identical spherical agglomerates 3D printed in colour were carried out to investigate the distribution
ideas and implement them broadly. In year one of this project, quasi-static compression tests of
work from this project would enable the particle technology worldwide community to take up the
disintegration and powder flow and segregation using the newly developed approach. The published
The new IFPRI project contains three sub projects which focus on agglomerate breakage, agglomerate
successfully conducted and the results were highly reproducible.
structure. For the first time, experimental tests on “perfect” particles with tuneable properties were
and the breakage behaviour was compared with a DEM simulation of an agglomerate with an identical
techniques. In the previous IFPRI project, identical copies of agglomerates were designed and printed
orientations. To date, this has not been possible via experimental agglomeration production
under the same condition/orientation and then repeated for various other conditions and
3D printing technology allows mass fabrication of identical agglomerates that can be tested repeatedly
from a ‘single’ individual agglomerate can never be replicated.
possibility of reproducing the data under the same conditions. Therefore, experimental data produced
destructive nature of the experimental tests i.e. breakage, dissolution etc., which would eliminate the
inability to capture the true complexity of the agglomerate structures in simulations and 2) the
actual experimental measurements. The two key drawbacks of the current approach are 1) the
entered into a computer for imprecise estimates of the model simulations, then compared against the
measure the relevant properties of existing non-identical particles. These parameters are then
due to lack of suitable test particles. To date, the cumbersome approach has been to individually
Accurate and systematic validation of particle systems with a simulated model has not been possible
Executive Summary
size distribution, capillary pressure distribution.
- Generation (proof of concept) of characteristic data of the pore system, e.g. pore
- Image analysis of 3D-tomography data using VG Studio (expert software).
- Generation (proof. of concept) of tomography images of filter cakes
- Selection of compact and needle-shaped particle system
- Formation of filter cakes with different prose structure due to wetting effects.
proven:
The actual state of the project is that the methods have been developed and the concept is investigations.
method, it delivers precise and reproducible surface properties for the scientific (wet) coating with highly hydrophobic silanes. Even though this is a quite time consuming solution. The second one is the modification of the particle surface. For this case, we do a in which we change the wetting properties by changing the ethanol concentration in the shape two scenarios). The first approach is to change the composition of the mother liquid, in particle-particle interaction, we defined two main filtration scenarios (for each particle analyse the overall effect of wettability change in our system, which plays an essential role Particle-particle interaction during the filtration process was another scope of focus. To certain size range to fit to the voxel size of the measurements.
measurements, thus the solids need to have a certain X-ray adsorption as well as a sample. The material selection also was influenced by the specifications of the Xray filler and plastics. In the case of compact particles, we selected Al2O3 T60/46 alphaalumina we selected Wollastonite, which is widely used in ceramics, friction products, painting a fibrous behaviour when creation the filter cake structure. For the needle-like particles, progress, we applied compact and needle-like particles. The needle-like particles showed In order to analyse the effect of particle shape on the filter cake structure and filtration characteristics.
This study was done on two main particle shapes, which generated different filter cake comprehensive research by producing and interpreting laboratorial and micro-CT data.
Due to the complexity of the parameters affecting the cake filtration process, we do a
Executive Summary
2019.
Compacting GmbH. It is expected that the system will be ready for some preliminary test in Q2 of
Furthermore, a forced filling system is currently under construction in collaboration with Fette
obtained but further data analysis is required. These results will be reported at IFPRI 2019 AGM.
constructed and a systematical experimental work was perfomed. Some interesting results were
In addition, significant progress was also made in exploring suction filling, an experimental rig was
air sensitivity index increase, while it decreases with the increase of specific energy and cohesion.
filling velocity increases proportionally as the mean particle size, flow function, air permeability and
as cohesion, flowability, average particle size and air sensitivity index. In particular, the critical
filling velocity. It was found that the critical filling velocity is strongly dependent on such properties
properties were examined. The efficiency of die filling is evaluated using the concept of critical
material characteristics (e.g. particle size distribution, sphericity and morphology) and flow
this system, die filling behaviours of 7 commonly used pharmaceutical excipients with various
filling occurs when the die passes through a stationary shoe positioned above the die table. Using
rectangular die. The die table can rotate at an equivalent translational velocity of up to 1.5 m/s. The
tablet press. The system consists of a round die table of 500 mm diameter, equipped with a
A model rotary die filling system was developed to mimic the die filling process in a typical rotary
Ms. Zakhvatayeva. It primarily covers a comprehensive study of rotary die filling.
This report summarizes the work performed during the last 12 month primarily by the project student,
Executive Summary
constraint factor increases with an increase in rolling friction coefficient or interface energy.
suggest that the constraint factor remains constant across all stress levels, and that
the addition of coarse material and decrease with the addition of fines. DEM simulations
The constraint factor of bi-disperse, cohesive glass beads has been shown to decrease with
long as they cover a sufficiently wide range.
applied in a shear test are shown to have limited influence on the generated yield locus, so
insufficient to overcome the influence of prior handling. The precise normal stresses
driven by variability in the pre-shear shear stress, thus implying the conditioning is
at lower stresses the variability in measured yield data increases; this appears to be largely
normal stress data being unavailable. Repeated testing in the Schulze shear cell shows that
titania powders. A direct comparison could not be made with the Schulze shear cell due to
been shown to apply normal stresses noticeably greater than the target stresses for these
shear cell and the Schulze RST.XS.s shear cell. At lower pre-shear stresses the FT4 has
The flow behaviour of various titania grades is found to be largely similar between the FT4
universal for all powders.
measurements to be made at lower stresses, though the optimal lid design is unlikely to be
in the shear plane. Reducing the vane height of the shear cell lid allows indentation
to critically consolidated beds since an insufficient fraction of the exposed bed is located
consolidated beds. It is shown that at lower stresses it is challenging to apply indentation
condition, with critically consolidated beds providing a greater hardness than vertically
Indentation hardness measurements have been shown to be dependent on the loading
investigated using the Discrete Element Method (DEM).
experimentally, and the influence of a broader range of particle properties has been
size distribution and interface energy on constraint factor have been assessed
for several grades of titania with two different shear cells. Furthermore, the influence of
has been assessed in ball indentation, and shear cell measurements have been carried out
used to measure flowability of titania under a range of stresses. The bed preparation method
inconsistent. The ball indentation, uniaxial compression and shear cell methods have been
Measurement of powder flowability under low stress conditions is often unreliable or
Executive Summary This report summarizes the main achievements of the second year’s effort of development of new crystallization technologies for improved crystal size and shape control during the crystallization process. The successful crystallization process and system design requires an interdisciplinary effort, which ranges from population balance model (PBM) development of the system concept, through efficient implementation of model equations to soft-sensor development, which is required for the model predictive control (MPC) design as well. This report gives a deeper insight into these interdisciplinary development efforts, which also highlights the achievable improvements enabled by the combination of process modeling, high performance process simulation and optimization. In the first report we showed that the application of wet-milling during crystallization can significantly improve the process flexibility and attainable crystal size domain. The GPU acceleration halved the simulation time, which enabled faster optimization. In this year, we applied the same principles, but we investigate the effect of milling in addition to crystal size also on the crystal shape. Since the computational cost associated to numerically solve the model equations is a power-law function of number of dimensions, the application of 2D PBMs for this purpose is not feasible without GPU acceleration, which in this case brought ~1.5 order of magnitude speedup. The first, full PBM based nonlinear model predictive control (NMPC) was implemented for the batch crystallization of L-ascorbic acid. The NMPC showed good control behavior, produced significantly better crystals than the direct nucleation control under considerably shorter batch time. The novel aspect of this NMPC was that it applied the fast, approximate CSDCLD transformation, that was presented in the previous report. The development work of the analogue control system for simultaneous size and shape control has been started. A major challenge, associated to the calculation time was solved.
Realized deliverables
- Model development, simulation and preliminary optimization of an integrated batch crystallizer-wet mill system for bivariate crystal size distribution control
- Implementation of a full PBM based NMPC for crystal size distribution control
- Preliminary development work of a real-time feasible full 2D PBM based adaptive predictive simultaneous crystal size and shape control algorithm
structures collected from a lab scaled spray dryer.
Structures obtained from the single droplet drying experiments showed high similarities to
The differences in these drying metrics have been related to key material properties.
final particle size, moisture content at locking were collated at different drying conditions.
encountered above boiling. Several drying metrics including relative size at locking, relative
further understand the differences in drying behaviour and morphology evolution route
conditions collected from the single droplet drying rig have been extensively investigated to
deflation, inflation and puffing. Drying kinetics and morphology time-series at different drying
different drying mechanisms, boiling without any inflation/deflation cycles, inflation and
concentrations using a filament single droplet drying rig. The three materials showed three
and drying kinetics have been investigated across a range of air temperatures and initial solid
sucrose, sodium silicate and Hydroxypropyl Methylcellulose (HPMC). The drying behaviour
and morphology evolution. Three skin forming materials were chosen for this study namely,
The aim of this study is to investigate the effects driven by boiling on the drying behaviour
Wael Ebrahim
above boiling point
An experimental investigation of the drying mechanisms of single droplets
The solution of this model is currently underway.
expression for the expansion of a single centralized bubble within a liquid droplet was derived.
transfer on the expansion of a single bubble in an infinite liquid media was conducted and an
to the asymmetric pressure and velocity field. An initial assessment of the influence of mass
An off-centre bubble was also investigated and a self-centering behaviour was observed due
oscillations which decayed with time. The rate of decay increasing with increasing viscosity.
dynamics of a initially over pressured bubble, behaved as anticipated showing bubble
constructed and solved to allow for asymmetry to be investigated. The 2-D model, of the
spherically symmetric 1-D equations were derived and solved and a 2-D model was also
derived from the mass and the momentum balances and the Navier-Stokes equation. Both
The governing equations for the oscillations dynamics of the bubble and the droplet are
within a droplet, which is termed as ‘bubble-droplet system’ in this report, are investigated.
The effects of mass transfer on the oscillation dynamics of a single bubble centrally located
Tien Nguyen
BUBBLE DYNAMICS INSIDE A DROPLET
Executive Summary
hydrates/solvates, and cocrystals crystallized from solution.
we plan to continue with the remaining modifications required to implement models for organic salts,
ADDICT v3.0 against molecular crystals with multiple molecules in the asymmetric unit. Following this,
Upon completion of this new architecture, we will demonstrate improved functionality by testing
co habit predictions of organic salts, cocrystals and solvates grown from solution.
quires a complete rewrite of the existing codes, these modifications lay the groundwork for rapid in sili-
lographic complexity. We are currently implementing this redesign within the software. Although it re-
of the solid-state interactions that is independent of the asymmetric unit and applicable to any crystal-
solvates and cocrystals). With our redesigned input preparation architecture, we can build a description
sponds to the growth unit itself, many systems do not satisfy this criterion (including all organic salts,
from the asymmetric unit. While this approach is feasible for systems where the asymmetric unit corre-
architecture for acquiring this information is to apply crystallographic operations to generate a unit cell
growth models is to calculate and organize solid-state interactions between growth units. The typical
salts, cocrystals and solvates. A necessary, but not sufficient, condition to enact mechanistic crystal
shape-prediction design aid that is applicable to all crystalline solids, from organic molecules to organic
vanced Design and Development of Industrial Crystallization Technology). Our goal is to produce a
important solid forms, and especially drug substances. We call our software design aid Addict (Ad-
morphology software tool in order to generalize the methodology to a much broader class of industrially
In the first year of this project we have used IFPRI funds to redesign and rewrite our crystal growth and
Executive Summary
relations based directly upon PEPT-derived stress computations.
in greater detail in the next phase of the project wherein we formulate mixing scaling
timescale to the macroscopic shearing timescale more naturally. This idea will be explored
like the Inertial number, also appears to describe the ratio of the microscopic rearrangement
extend beyond simply quantifying the relative importance of advection and di.usion, and
number that is computed directly from the PEPT data. Interestingly, it’s validity seems to
an alternate definition. In this regard we propose a granular temperature-dependent Péclet
The limitations in the standard definition of the Péclet number precipitated the need for
mills) that operate in the high Froude regimes.
the data. These findings have significant implications for industrial systems (like tumbling
cascading and cataracting) the Reverse Brazil Nut E.ect (RBNE) is clearly evident from
the Brazil Nut E.ect (BNE) at low Froude numbers; however, at higher Froude numbers
The initial analyses of PEPT data clearly show radial segregation by size consistent with
developed flow conditions.
assumption, we extract the bed shape, solids fraction and kinematics for steady, fully
of representative radio-labelled beads (the tracer) into Eulerian fields under the ergodic
and cataracting Froude regime. After converting the measured Lagrangian trajectories
matrix spanned four fill fractions and seven drum rotation rates across the cascading
plastic beads) within a laboratory rotating drum fitted with lifter bars. The experimental
was used to measure the 3D trajectory of a binary mixture (3mm and 5mm diameter
In our first phase of the project (year one) Positron Emission Particle Tracking (PEPT)
many investigators that ultimately lead to a restricted mechanistic interpretation.
is not well understood. A further limitation relates to the low Froude regimes explored by
known to exhibit axial and radial mixing; however, their interplay for optimal performance
system encountered in the mineral processing, food and pharmaceutical industry is well
the high shear zones where most of the energy is dissipated. The canonical rotating drum
processes is the inability to control the relative mix of grinding balls and small rocks in
ingredient and excipient. Central to the low efficiency (< 5%) reported in mineral grinding
industry, the e.ectiveness of the drug is directly related to the mixture of active
Mixing (and segregation) play a vital role in several industrial processes. In the pharmaceutical