Dr Vivek Garg BE, ME, PhD

Research and Consultancy

Young Researcher Award in 2020 by Green Thinkerz, India
Young Engineer Award in 2015 by Bhushan Power and Steel Limited, India
ISTE Best Student Award for the two-consecutive years 2014 and 2015
Best All-Rounder Student in SCIENZA 2014 at CT Group of Institutions, India
Adesh Foundation Best Student Award for the year 2014 in SCINTILLA 2K14, India

President of Student Chapter of Indian Society for Technical Education (ISTE)
Associate Member of Indian Society of Mechanical Engineers (ISME)
Associate Member of Indian Innovators Association (IIA)

From my PhD in modelling flow properties of the bulk solids, I have gained major experimental skills in performing various characterisation measurements, modelling powder flow, including calibration, testing, data acquisition and analysis. The combination of topics that I have learnt during my PhD is unique and emergent needs of industries, whereas most topics (experimental work, modelling, characterisation of powders, testing, validating) are aligned to my current area of research and would benefit the latest fundamental breakthroughs and applied practices. The current interest will be learning interdisciplinary knowledge, and applying skills learnt during the PhD. Interaction with peers in a truly international forum will instigate me to explore other cutting-edge areas of contemporary research. My main interest is to work in the areas that will significantly contribute towards providing sustainable solutions to the concerning energy, environmental and health science issues of the world. My goal is to pursue a research career in developing improved, sustainable technologies for Bulk Solids and Handling.

Key funded projects

Project Title: Development of a software tool for predicting and optimising manufacturability and stability of advanced solids-based formulations funded by Roche Pharmaceuticals, Switzerland.

Objectives and Scope of Work

The purpose of the work described is to undertake a study to investigate and validate:

(i) The use of the new small-scale Mechanical Surface Energy Measurement technique that has been developed in The Wolfson Centre, on a number of materials (both ingredients and blends) that are specific to the needs of Roche Pharma.

(ii) The use of the Wolfson Virtual Powder Blending Laboratory to predict the flow properties of blends from those of individual ingredients, will also be validated for a selected combination of those ingredients and blends.

As a validation of the flowability measurement and prediction techniques developed by the Wolfson Centre, this will give confidence that the objectives and intentions of the main project can be achieved, namely the goal of giving Roche Pharma a sound technique and protocol by which manufacturing problems related to flow with new formulations can be identified at the earliest possible opportunity (from milligram samples of new or existing chemical entities).

Project title: Feasibility Study on Particle Adhesion Measurements funded by EPSRC Future Manufacturing CMAC Research Hub

This project summarises a programme of study to evaluate a novel means for measurement and characterisation of inter-particle forces (“Mechanical Surface Energy Tester”) in relation to its application to enhanced design of formulations by prediction and control of flow behaviour to assist efficient pharmaceutical manufacturing. The objective of the feasibility study was to test extensively a novel technique and model developed at The Wolfson Centre, University of Greenwich, for (a) characterising by mechanical means the apparent surface energy of particles, by detection of particle adhesion forces, and (b) using the model to predict the flow properties of the powder at bulk scale. The intention was to test its utility for powder cohesiveness characterisation and powder flow properties prediction for manufacturing-scale application. The key features of the novel tester are:

* It requires only milligrams of powders, unlike traditional techniques for flow properties measurement, which require at least grammes and often tens to hundreds of grammes. Commonly, it is difficult, if not impossible, to obtain these larger quantities of samples at an early formulation stage, especially with new chemical entities; however, a knowledge of potential flow properties is an essential aid to formulating a blend that can be processed efficiently.

* Unlike previous methods of measuring inter-particle forces, which use a single particle (Atomic Force Microscopy), it uses a population of particles dispersed across a range of orientations, enabling the stochastics of particle shapes, sizes and orientations in a powder to be captured in one test.

The novel mechanical surface energy tester under evaluation determines the Bond number for the powders (defined as a ratio of particle adhesion to weight forces at the median particle size). This is detected using a few milligrams of sample and used as a measure of powder cohesiveness. The Bond number and particle physical properties (size and density) are used in a model to predict powder flowability, also developed previously by The Wolfson Centre through a wide-ranging empirical study on some 50-plus materials. This project involved 16 different ingredient materials which are widely used in the pharmaceutical industry. For the study, the particle physical properties have also been characterised, including particle size distribution, shape, and solid density. The 16 materials have a wide range of substances, particle sizes and solid particle density. Based on the Bond number

measurements from the novel tester, powder flow functions were predicted using the model previously developed. Comparison of flow functions measured conventionally on two different shear testers reveals the feasibility of the mechanical surface energy tester technique for applications of powder flowability tests in manufacturing by using a small quantity of sample materials (50-100mg). Finally, this work has been extended into evaluating the utility of the adhesion force measurements from the novel tester to inform constitutive modelling of particle adhesion force for applications in simulation modelling using discrete element method (DEM).

Outline of the outcomes

A review of prior relevant work reveals that conventional adhesion measuring methods have limitations in describing powder bulk behaviours, particularly powder flow. The novel mechanical surface energy tester for adhesion force measurement shows suitability, relative benefits and practical applicability for powder cohesiveness and prediction of powder flow functions from the Bond number measured. The test requires a substrate from which to detach the particles, but the particle detachments from different substrates show only a very slight influence on the measurement, which allows a substrate of a commonly available material to be used in the test so that only milligrams of sample need to be used.

With the correlations created in previous work between the Bond number and the flow functions, the predicted flow functions compared favourably against the measurements

from both the Powder Flow Tester (Brookfield) and the FT4 Powder Shear Cell Rheometer (Freeman Technology). The comparison of adhesion measurements to theoretical values using three adhesion models (JKR, DMT, and Rumpf) revealed a more significant agreement for JKR and DMT but not for Rumpf. Based on different components of surface energy measured by FD-IGC, i.e., dispersive, acid-base and total surface energy, the total surface energy gives a better correlation of contact area to particle size (D50). One journal article has been published using the data collected, and two more are in preparation. Overall, the study results have been very encouraging. It has opened up the substantial potential for future research using the new test method and supporting models, particularly in fundamental questions of the interplay of particle surface texture at nanoscale, substance surface

energy at the atomic scale, and how these link to bulk scale powder behaviour. In this sense, it can be said to be a breakthrough in facilitating the linking of these diverse scales in a way that has not hitherto been possible. In addition, it shows substantial promise in practical applications for formulators, such as extended uses in manufacturing. Based on the above, further research funding proposals are being developed.

Project title: Assuring powder-machine compatibility of direct compression formulations for continuous manufacturing processes funded by Roche Pharmaceuticals, Switzerland

OBJECTIVES AND SCOPE OF WORK

* Suitable validated means for measuring the segregation tendency of a formulation (“blend susceptibility factor”) from a small bulk sample (likely tens of grammes) in terms of different mechanisms of segregation in standard tests.

* We will also attempt to link the blend susceptibility factor to the blend design, i.e. the material properties (particle shape and size differences, and Flow Function of components) by building on extensive work that has already been done by INSTITUTE in its Virtual Formulation Laboratory project8.  This will assist formulators in guiding their blend design at an early stage, to avoid high susceptibility to segregation.

* Suitable means for evaluating the “process harshness factor” of a production line, by either engineering analysis or empirical testing or a mix thereof;

* A quantitative definition of the function in the above equation, to allow the likely CU or risk to CU to be predicted by combining the material and process factors, so risks of segregation can be identified;

* An objective assessment that the methods and the relationship apply across the practical operational window of platform formulations and processing lines of specific relevance to ROCHE operations, or identification of limits of applicability.

* Depending on the risk levels established in the product lines studied, and the progress on the above aspects, it may be possible to link the powder flow aspects of the segregation study to a “material sparing” method of predicting flow properties from a few milligrammes of sample at the early stage of formulation design, which has recently been

introduced at The INSTITUTE (the further development of which is the subject of another project application with ROCHE).

Project title: On Developing Improved Storage and Pneumatic Transport Systems for Fly Ash in Thermal Power Plant funded by NTPC Limited
Need of the project
1. Reduced ash flow rate due to inaccurate estimation of total pipeline pressure drop – deviation from the optimum operating point on the conveying characteristics --Inaccurate estimation of minimum air flow rate requirement – leading to pipeline blockage
2. Too heavy (for coarse ash) or too low (for fine ash) flow of fly ash from the ESP hoppers – causing line chocking due to product surge or inadequate product flow rate 3. Lack of comprehensive knowledge on the effectiveness of heaters and fluidizing aeration system on ash flowability in ESP and buffer hoppers
4. Lack of understanding of the root cause of fly ash agglomeration in boiler that results in unexpectedly high average particle size
Project objectives
1. To amend and/or develop test facilities for vacuum and pressure conveying systems, hopper flowability testing in trapezoidal and conical hoppers
2. To predict minimum air flow rate requirement in vacuum and pressure conveying pipeline for different samples of fly ash and pipe diameters
3. To predict pressure drop and optimum operating point on conveying characteristics in vacuum and pressure conveying systems for different samples of fly ash, pipe lengths, pipe diameters and layout
4.To evaluate the effectiveness of heaters and fluidizing air on flowability of fly ash from ESP and buffer hoppers – effect of heating/fluidizing air temperature, nozzle/pad type, air injection points etc.
5. To validate the model/process optimized parameter to be developed in laboratory scale under actual power plant condition
6. Preparation of a technical specification for 500/800/1000 MW plants including specific design for a certain plant and delivery of formulae/tables/figures to select compressor sizing, pipe sizing etc. for different solids/ash flow rates and ash properties (such as for different ash particle size distribution, bulk densities etc).
Project outcomes and benefits to NTPC
1. Achieving higher solids (fly ash) transport rates using pneumatic conveying systems (vacuum and pressure systems) without pipeline blockage and significant reduction in transport gas and operating power consumption, especially under stepped-up pipelines.
2. Optimal pipe sizing for given product, capacity and pipe layout
3. Achieving higher fly ash flow rate coming out of storage vessels for fine, cohesive ash and controlled feed for excessive free flowing coarser ash
4. Identification of possible root cause of unusually high level of agglomeration fly ash particles
5. Improved ability to troubleshoot existing systems
6. Getting a technical specification for 500/800/1000 MW plants including specific design for a certain plant and delivery of formulae/tables/figures to select compressor sizing, pipe sizing etc. for different solids/ash flow rates and ash properties (such as for different ash particle size distribution, bulk densities etc.)

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