ARR - Annual Report
Executive Summary
driven model for granulation.
for granulation, and the application of inverse methods to create a product performance
incorporates the development, validation and integration of process and product models
A research plan for the remaining three years of the project is presented. This plan
characterisation of feed materials and granular products.
models, however this initial experimentation has emphasised the need for careful
will take place after critical decisions are made on choices of product and process
development for granulation and granule dissolution. Full methodology development
Also presented within this report is preliminary experimental methodology
absence of disintegration.
dispersion model, and the second a model for drug dissolution from granules in the
two potential product models presented here for use in this project. The first is a granule
available to describe these mechanisms. This review has informed the development of
disintegration and dissolution, and also includes a review of the mathematical models
review incorporates the current state of knowledge on the mechanisms of compact
behaviour, culminating in the literature review presented in this report. This literature
survey of the literature on granule, tablet and compact disintegration and dissolution
of Granular Products. Focus has been placed in this first year of the project on a critical
This report provides a summary of the progress of the project Model Assisted Design
address this need.
product models to enable performance driven process design. The aim of this project to
develop improved performance models for granular products, and to link these with
models have received less attention than process models, and there is a clear need to
not describe the performance of the products being produced. Product performance
outputs of these models are typically limited to one or two particle attributes, and do
processes. This is an exciting and welcome development for the field, however the
process design. Process models are increasingly being developed and used for these
and laborious experimentation, due to a lack of knowledge and predictive tools for
Traditionally, the design and scale-up of granulation processes has involved expensive
tool that predicts relative growth rates and crystal morphology of solution-grown faceted crystals [5].
into ADDICT (Advanced Design and Development of Industrial Crystallization Technology), an engineering
in the literature for validation. Once we have established effective models, we will look to incorporate them
considered in the context of KMC simulations for model development, and compared to experimental values
the growth-inhibiting effect of impurities, such as step pinning and spiral pinning. These mechanisms are
for desolvation and attachment/detachment works. Various mechanisms have been proposed to explain
centrosymmetric organic crystal growth. Rare event rates are determined as functions of energetic barriers
for growth inhibition. We employ Kinetic Monte Carlo (KMC) methods to simulate the time evolution of
ne to examine experimentally in real time. Thus, we use simulations to study the proposed mechanisms
Impurities affect growth kinetics at the scale of kink attachment and detachment events, which are too
and hence affect crystal morphology and size.
process and to develop theoretical models for the mechanisms by which impurities influence crystal growth
The goal of this project is to investigate the effect of impurities or `imposter molecules' on the crystal growth
are more representative of realistic conditions. One such non-ideality involves the presence of impurities.
equal surfaces). There is interest in studying crystal systems in which non-idealities are introduced, as these
systems i.e., Kossel crystals with a single centrosymmetric growth unit (simple cubic single molecules with
mechanistic modelling of crystallization. Crystallization of organic molecules is well understood for ideal
Given the ubiquity of crystal growth in industrial processes, there is substantial demand for predictive and
such as OLEDs [3] and for altering the impact sensitivity of energetic materials such as RDX and HMX [4].
crystallization is desirable for varying electrical and optical properties in the field of electronic materials
importance for developing catalysts with tailored surfaces to maximize active sites [2]. Furthermore, tuning
to selectively formulate specific crystal habits for optimal bioperformance [1]. Crystal engineering is also of
a structured solid state. Pharmaceutical companies often crystallize APIs in the form of organic molecules
Crystallization is commonly used in industrial processes to convert solute molecules dissolved in solvent to
Abstract
compare with the formulation guidelines obtained from (1).
3. Apply these methods to simpli ed industrial dispersion by industrial partners and
- Local scale tribological measurements using AFM.
during ow (4D imaging)
- High resolution confocal microscopy to probe structural development in situ
which aspect of the particles or formulation controls the rheology
the nature of the stress during ow (elastic or viscous), which helps to identify
high frequency rheometry and superposition rheometry, which help identify
- Advanced rheological methods which allow for stress deconvolution such as
the rheological response of the such dispersions, focusing on
2. To further develop a limited number of rheological and structural tools to interrogate
control of shear thickening and the control of the thixotropic response.
within. The properties aimed for, after discussing with IFPRI members, are the
formulation guidelines to do "more with less" or simplifying formulations from
simple formulations a wide range of behaviors can be `built in", i.e. obtaining
changing the properties of the building blocks of the suspensions, so that even in
with near hard interactions, we can widen the range of rheological responses by
- To explore how, moving away from model systems containing spherical colloids
project and more globally within our groups are threefold
(all started in 2020) being the graduate students involved. Our goals within the IFPRI
Jan Vermant, with C. Hsu (graduated in 2020), V. Niggel, F. Muller, and P. Lehercy
The work at ETH Zurich represents a combined e ort of the labs of Profs. Lucio Isa and
Executive Summary
Type and dosage of grinding aid.
Mill geometry and design;
Process parameters;
Product transport behavior;
Product breakage characteristics;
consumption in relation to:
dynamical population balance model predicting product size distribution and energy
Moreover, the continuous grinding process modelling approach is being structured as a
stressing and transport independently.
grinding. The results also confirm the necessity of describing the phenomena of powder
behavior, although beneficial for continuous processing, does not guarantee an effective
but with good results for milling efficiency for both materials. It is clear that improved flow
flowability for both materials. The glycol presented negligible effect on powder flowability,
In terms of flowability measurements, the carboxylic acid promoted notable increase in
additive.
similar effects compared to each other, but improving efficiency in comparison to no
similar to grinding without additive. For the calcium carbonate the additives presented
Alcohol and glycol were quite effective, while the use of carboxylic acid resulted in results
alumina, the grinding aids show different efficiency in reducing energy consumption:
and powder flowability measurements of the product were conducted. In the case of
After defining materials and establishing experimental methods, first batch grinding tests
or continuously operated ball mill as well as an reflector-wheel air classifier are selected.
acid and a Glycol. For the experiments, a 4 liter batch ball mill and a 47 liter, batch-wise
studied. Three substance classes were adopted as grinding aids: An Alcohol, a Carboxylic
In this project, dry grinding of the materials alpha alumina and calcium carbonate is
Amount of material coated on equipment surfaces.
Total mass of product inside the mill and residence time
Powder flowability;
Tendency of fine particle agglomeration;
Product fineness after grinding;
aids impact powder material mainly in:
consumption and/or to reach a certain product fineness. During milling operations, grinding
to the process in order to increase the product throughput, decrease the specific energy
by grinding aids. Grinding aids are defined here as liquid or dry substances that are added
manipulation of the material properties and, thus, the grinding and classification efficiency
optimizing and scaling industrial dry grinding processes, with a special focus on the
This project aims in developing a system engineering approach for understanding,
Executive Summary
groups, including carboxylates and amines, and other solvents.
crystals on the SAM surface, as well as exploration of other SAM surface functional
steps will include changing sample angle in order to increase the low number of observed
of yellow needles (YN), while methyl SAMs preferred red prisms (R). Next experimental
for selection of additional polymorphs. Besides Y, hydroxyl SAMs preferred the nucleation
surfaces. However, hydroxyl and methyl terminated SAMs showed a different tendency
that yellow crystal (Y) was the dominating polymorph on both -OH and -CH3 terminated
polymorph characterization of nucleated crystals. First experimental results demonstrated
jump at three different levels of supersaturation. Raman microscopy was applied for
solution and the nucleation was induced on the SAM surface by generating a temperature
project, control over the degree of supersaturation. SAMs were placed vertically in the
Crystallization by cooling experiments were conducted to allow, for the first time in this
[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) in toluene as solvent.
groups (-OH and -CH3) as nucleating surfaces for the organic model system 5-methyl-2-
based self-assembled monolayers (SAMs) with different terminal (omega) functional
number of industries. This project has moved to the formation of alkane-thiols on gold
as well as inorganic compounds are scientifically and technologically important to a
Understanding and control of crystallographic polymorphism and crystal habit of organic
EXECUTIVE SUMMARY
2 conditions for the first time, and address the main Aims.
Rheology (I). This will allow us to separately determine constitutive parameters and boundary data of the type collected here, we will soon be fully able to calculate the fluidity g(r) and the elucidate the nontrivial connection between these observations, which so far is confounding. Using techniques, are similarly affected by the roughness and compliance of the wall. Future work will of the flow, allowing us to observe that the pressure P and shear stress, measured by photoelastic of the flow most sensitive to nonlocal effects. Photoelastic techniques provide us full stress profile v(r) and shear rate profile _ (r), particularly as measured at the outer wall. This is also the region boundaries. We have observed that boundary roughness strongly controls both the flow profile both particle-dynamics and stress fields under controlled conditions for six different-roughness.
As Year 5 comes to a close, we have used fully-developed experimental protocols to measure properties.
On separating which flow properties are set by the particle properties, versus those set by the wall and (2) use these parameters to predict flows in other geometries. Thus, our current work focuses can we (1) make flow measurements in one geometry which determine the constitutive parameters and apply NLR to real granular systems. We aim to establish that, for a given set of particles, in Years 4-6 of this project, we aim to address current shortcomings in how to calibrate (A; b; s), but that we must know the amount of slip at the wall from geometry-dependent measurements.
Packing densities, particle sizes and shapes, and shear rates, using just 3 constitutive properties. In Years 1-3, we established that NLR successfully models granular flows across different both the particle properties, and the boundary conditions at the walls. The same particles). Doing this requires a quantitative understanding of which properties are set by and then determine the constitutive parameters for use in predicting flows in other geometries (for to be useful, the aim is to make a set of flow measurements for a set of particles in one geometry, large range of intermittent, creeping, quasi-static, and intermediate flows. In order for these models for a particular set of particles, which then can be used to predict flow fields and stresses over a models hold the promise of permitting the determination of a small number of empirical parameters been the development of various nonlocal rheologies [2, 4, 5, 11, 13, 15, 25]. These constitutive.
In the field of granular rheology, one of the most promising advances of the past decade has.
also presented into this report particularly in Annex 2.
scheduled as telecommuting was possible for these deliverables. Therefore, the first results of year 3 are
During the lockdown, the third year of the PhD work about modeling was started earlier than
reconstitution conditions in agitated vessels.
(3) Definition of a reconstitutability index reflecting powder reconstitution behavior independently from
(2) Empirical models able to predict reconstitution times from powder physicochemical characteristics;
(1) Fitting of reconstitution kinetics followed by granulometric;
Deliverables of year 3 ((January 2021 – January 2022)
message in Figure 1).
wetting) and sugar nature, location, quantity, coating depth were thoroughly investigated (see take-home
transition temperature, hydrophilicity…Links between powder reconstitutability (more particularly
chosen to cover a whole range of physicochemical properties: solubility, chain length, structure, glass
agreement with IFPRI partners, five sugars (i.e. sucrose, lactose, glucose, fructose, and galactose) were
presenting a low wetting ability (i.e. whey protein powder) and coating was achieved with sugars. In
progress due to the lockdown caused by the CoViD-19 health crisis. The work was focused on a powder
The second year of the PhD work should meet these two stated deliverables which are still in
surface, minimal quantity necessary to improve wetting. etc.).
(2) Determine the effect of surface modifiers (quantities to cover the surface, distribution at the particle
reconstitutability.
(1) Surface chemical mapping and nanoindentation to establish correlations with powder
Deliverables of year 2 (January 2020 – January 2021)
related to year 1 deliverables (Annex 1).
Papers I and II, respectively submitted to Powder Technology and Journal of Food Engineering, are
ranking.
(3) First statistical correlations between the various powder characteristics and their reconstituability
(2) For selected powders: reconstitution kinetics in different conditions of temperature, stirring, etc.,
(1) Powder classification according to their reconstitution behavior,
2020 with the following deliverables:
and their classification according to their reconstitution ability. It was achieved at the end of January
The first year of the PhD work dealt with the systemic physicochemical analysis of powders
(PhD duration: 1st February 2019 –31th January 2022)
Executive summary until October 2020 – year 2
Executive Summary
detailed flow, and motivate further refinement in our modelling efforts.
experimental screw feeder assembly to test our model predictions, provide insight into the
constitutive model for the stress that accounts for dilatancy. We have recently built an
request of several IFPRI members at the GBM. For this, we are implementing a non-local
fluctuations in the inlet flow or spontaneous fluctuations within the screw – this was the
Our ongoing work is to model dynamical changes in the feed rate, due to
of gravity and friction at the screw surface.
volumetric discharge rate on the geometry of the feeder is not altered by the introduction
value of p/d at which the feed rate is maximum. Thus, the qualitative dependence of the
find that the discharge rate exhibits the same qualitative trend, in that there is an optimum
conditions of no friction at the screw surface and no gravity, employed in the model. We
frictionless screw in the absence of gravity. We then assess the effect of relaxing the
model to be in excellent agreement with the results of the DEM simulations for a
motion, in agreement with the assumption of the model. We find the prediction of the
simulations show that a significant fraction of the material does indeed exhibit solid body
by particle dynamics simulations using the discrete element method (DEM). Our
We then studied the detailed flow within the screw feeder for non-cohesive particles
yields a non-trivial result that could be useful in the design of screw feeders.
to a specific value. Thus, despite the assumptions that simplify the analysis, the model
discharge can be maximized by setting the ratio of the screw pitch p to barrel diameter d
the discharge rate for a given angular velocity and screw geometry. We show that the
and barrel, and neglecting the effects of gravity and friction on the screw surface, we obtain
that the granular medium moves as a rigid body that slips along the surfaces of the screw
and angular momentum on a suitably chosen continuum element. With the assumptions
We first constructed a mechanics-based model by enforcing the balances of linear
flow in a twin-screw feeder.
we have studied powder flow in a single-screw feeder, as the first step towards modelling
model. Such a model would assist in optimal design of screw feeders. In this investigation,
particulate materials, there has been no attempt to derive a detailed, mechanics-based
Despite the widespread use of screw feeders in industry for the transport of
In 2019, we started to investigate the microstructure and shear properties of capillary suspensions using confocal microscopy and rheology. The chosen model system was an index-matched mixture of Hexamoll DINCH/dodecane (oily bulk phase), aqueous glycerol (watery secondary liquid) and silica particles (Kromasil 100-7-SIL, average radius 3.21 m). Confocal measurements were performed on a Leica TCS SP8 inverted confocal microscope equipped with a linear shear cell (RheOptiCAD). Rheological measurements were performed on a stress-controlled MCR702 rheometer using an 8 mm parallel plate geometry. For the analysis of the confocal image stacks, a particle detection program based on Canny edge detection and Hough transform was written in IDL, which has an improved detection accuracy for concentrated and polydisperse suspensions compared to the classical Crocker and Grier algorithm [13].
The rst experiments were designed to examine the in uence of compression and shear on the microstructure of capillary suspensions with varying solid volume fraction, while keeping the relative ratio of secondary liquid and particles constant. The confocal microscopy study revealed an increase in coordination number with increasing particle volume fraction, compression, and shear. The clustering coe - cient only exhibited only slight variation. The increase in coordination number was also re ected in a higher storage modulus for higher solid volume fraction samples. By compressing capillary suspensions in the shear cell and the rheometer, it appeared that a transition in the relative cluster compaction could be observed around an e ective solid volume of 30 % to 35 %. The increase in coordination number was signi cantly higher after compression for samples above this boundary and a normal force was measured on the rheometer when going to the gap.
Figure 1: Close-up micrographs of porous Kromasil particles wetted by a) lms and b) patches of secondary liquid might suggest a critical volume fraction determining the change from a oppy to a rigid network. In the work of Domenech and Velankar [18], a change towards a more heterogeneous microstructure was reported around a similar solid volume fraction. However, the change in structure did not a ect the scaling of the elastic modulus or yield stress in their study.
While the transition between a oppy and rigid network appears to be compelling, the porosity of the Kromasil particles induced large variations in the wetting behaviour. Porous particles were chosen due to the need for fully-dyed spheres in the Crocker-Grier-based particle detection program. After dyeing the particles, their porosity was reduced using a modi ed St ober synthesis to prevent secondary liquid imbibition in the pores. The poor reproducibility of this procedure was the reason for a multitude of observed bridge shapes, as shown in Figure 1. The desired toroidal bridge shape was not observed for the prepared capillary suspensions, which predominantly showed the liquid lm behaviour of Figure 1a. Hence, these experiments were repeated in 2020 using non-porous particles showing toroidal bridges, shown on Figure 2, which was now possible due to the new particle detection program.
Key updates
I was not able to recruit a dedicated PhD student, hence we are now on gap year. This issue was addressed in January 2020 and a PhD student Vishal Shinde was recruited. He graduated from Leicester in 2018 with an MSC with Distinction. He is expected to start in 2-3 months time after getting his visa.
Complementary to the project, I will be hosting a visiting PhD student from China (Ruochen Sun) from September 2020 for a period of 1 year, subject to approval of his China Scholarship Council application for funding. He will perform molecular dynamics simulations to analyse the interaction of mannitol and ibuprofen with iron. This is not related to the IFPRI project, but it could provide relevant insight.
A detailed planning for the following year will be prepared 1 month after the start of the PhD project. Also, I am planning an open workshop with participation of all academics and industrialists who are actively researching the problem of sticking at the present time of who have recently completed projects. This workshop will be planned 2-3 months after the start of the PhD project.