Particle Engineering using Spray Drying and Fluid Beds

Summary

In this informative webinar, David Calvert and Jim Bullock introduce the fundamentals of particle engineering with spray drying and fluid bed techniques. Bringing over 60 years of experience, the presenters offer insights into the applications, processes, and benefits of these methods. I Formulate Ltd, in collaboration with the University of Leeds, highlights its division into consulting, strategy, and skills for formulation science and technology. The session delves into the science behind spray drying and fluid beds, including droplet atomization, drying conditions, and the limitations and capabilities of each process. The collaborative event aims to enhance understanding among industries involved in formulation technology, offering further learning opportunities through detailed courses.

Highlights

• Jim Bullock and David Calvert, with over 60 years of experience, dive into particle engineering using spray drying and fluid beds. 🌟
• Spray drying begins with a fluid feed atomized into droplets, which are dried into solid particles, offering rapid and efficient drying. 💧
• Fluid bed technology complements spray drying, allowing intricate modifications and enhancements to particle properties post-drying. 🔄
• The webinar explains the nuances and technicalities of atomization, droplet sizes, and drying chambers in spray drying setups. 🌀
• Lab demonstrations and real-world case studies are available through I Formulate's training programs at the University of Leeds. 🏫

Key Takeaways

• Spray drying and fluid beds are pivotal in particle engineering, offering unique opportunities to influence particle size, shape, and structure. 🤓
• I Formulate Ltd collaborates with the University of Leeds, offering comprehensive consulting, strategic projects, and training in formulation science. 🧠
• Understanding the material properties and process conditions are crucial for optimal spray drying results, influencing final product properties. 🧐
• Fluid beds allow for extensive particle manipulation post-spray drying, offering enhanced control over drying time and temperature. 🌡️
• The integration of spray drying and fluid beds can yield innovative particle engineering solutions, improving product characteristics like flowability and stability. 🚀

Overview

Particle engineering is a fascinating field that blends chemistry, engineering, and practical science to create specialized particles with desired properties. Through spray drying and fluid beds, experts can tweak particle attributes like size, shape, and density to meet specific needs. Think of it as crafting the perfect snowflake—except in this case, it's about designing particles with precision.

Spray drying kicks things off with a fluid feed that's atomized into tiny droplets. As these droplets are introduced into a drying chamber, the magic happens. Heated air transforms them into solid particles quickly and efficiently, thanks to the high surface area interaction. Pretty cool, right? Watch out, though, because understanding that good ol' material property science is key to ensuring those particles come out just right.

Fluid beds take the baton from spray drying, providing even more finesse in crafting particle features. This involves a kind of balletic manipulation, allowing for delicate operations like agglomeration or coating—perfect for when you need particles just so. The ability to play with drying times and temperatures further exemplifies fluid beds' role in innovation within pharmaceutical and industrial formulations. Truly a dance of the particles!

Chapters

• 00:00 - 01:30: Introduction to the Webinar and Company Overview The 'Introduction to the Webinar and Company Overview' chapter begins with a welcome message to the webinar focused on particle engineering using spray drying and fluid beds, conducted in association with the University of Leeds. The speakers, David Calvert and Jim Bullock, introduce their company, I Formulate, sharing that they each have over 60 years of experience in the formulating industries and have been in business for over seven years.
• 01:30 - 03:00: Business Areas and Experience The chapter outlines the diverse experience and knowledge accrued across various industries and functional roles by the team. They collaborate with associate partners to merge expertise and optimize client assistance. The team's activities are segmented into three main business areas. The 'Formulate Consult' area focuses on innovation and technology consulting, particularly in formulation technology for client companies.
• 03:00 - 04:00: Introduction to Spray Drying and Fluid Bed Processes The chapter provides an introduction to spray drying and fluid bed processes, focusing on their applications in private sector industries. It highlights the strategic importance of formulation in these processes and mentions collaborative projects with organizations like the UK's Knowledge Transfer Network, National Formulation Centre, and the Royal Society of Chemistry. The chapter also discusses the role of training programs in formulation science and technology, offered independently or in partnership with other entities.
• 04:00 - 14:00: Details on Spray Drying Process The chapter titled 'Details on Spray Drying Process' begins with introductions. Jim Bullock from 'I' Formulate and Professor David York from the University of Leeds are the speakers. Since 2012, David York has been serving as the Chair of Structured Particulate Products in the Department of Chemical Engineering at the University of Leeds. Before this, he held senior roles in both process and product development at Procter & Gamble (P&G). The webinar is described as an introductory session focusing on the basics.
• 14:00 - 39:00: Introduction to Fluid Bed Processes The chapter introduces the topics of spray drying and fluid bed processes in the context of particle engineering. It outlines the focus on both design and operation implications of these processes. The overview includes a discussion on particle engineering first with spray drying, followed by fluid bed processes. The chapter also mentions an upcoming webinar session lasting around 40 minutes, including a question and answer segment and indicates it will be recorded.
• 39:00 - 47:00: Fluid Bed Applications and Capabilities The chapter titled 'Fluid Bed Applications and Capabilities' likely serves as an introduction or overview. The transcript mentions the availability of a recording and slides for participants, indicating a formal or educational webinar setting where participants can engage with the content later. There is an indication of an interactive element through a question box on a platform called GoToWebinar, where participants' questions are encouraged, though responses are reserved for the end to maintain order and minimize noise, as all participants are muted. The speaker seems to begin explaining terms related to particles and engineering, particularly 'particle engineering,' suggesting the chapter will explore technical aspects of this subject. The chapter might serve as an introduction to more detailed discussions or specific applications of particle engineering in fluid bed technologies.
• 47:00 - 50:00: Comparison of Spray Drying and Fluid Bed Processes The chapter discusses the engineering of particles focusing on the spray drying and fluid bed processes. It highlights the importance of particle shape, size, structure, and surface for desired product properties. The basic principles of spray drying are introduced, starting with a fluid feed.
• 50:00 - 59:00: Training Opportunities and Closing Remarks The chapter discusses the process of using an atomizer nozzle to form droplets from a solution, emulsion, or suspension in water or other solvents for spray drying. It highlights the flexibility in terms of viscosity, as long as the fluid can be pumped through the nozzle. The discussion points out that sometimes high pressure is necessary, but a wide range of viscosities can still be accommodated.

Particle Engineering using Spray Drying and Fluid Beds Transcription

• 00:00 - 00:30 hello everybody and welcome to this I formulate webinar on particle engineering using spray drying and fluid beds which we're running in association with the University of Leeds in this webinar we wanted to give you a brief overview of I formulate to start with the company was founded by David Calvert and myself Jim Bullock and between us we have well over 60 years experience working in the formulating industries we've been in business for over seven
• 00:30 - 01:00 years now together and to have experience and knowledge gained across many industries and in varied functional roles and we also work together with associate partners who we use expertise we can combine with our own and assist our clients as effectively as possible we divide our activities into three business areas in I formulate consult we carry out innovation and technology consulting mainly in formulation technology for client companies in
• 01:00 - 01:30 private sector industry and that's the majority of our business in I formulate strategic we've carried out an assisted strategic crop projects in the area of formulation for industry organizations such as the UK's knowledge transfer network the UK's national formulation center and the Royal Society of Chemistry and under I formulate skills we design deliver and promote training courses and programs in formulation science and technology under our own banner or in partnership with third
• 01:30 - 02:00 parties so my name is Jim Bullock from I formulate and I'm joined today by Professor David York from the University of Leeds since 2012 David has been chair of structured particulate products in the Department of Chemical Engineering at the University of Leeds and he previously held senior roles in process development and product development at P&G and this webinar is designed as an introduction into the basics
• 02:00 - 02:30 underpinning the processes of spray drying and fluid bed in terms of particle engineering as well as the implications for the options you got for design and operation now the overview I'll start by covering particle engineering using spray drying David will move on to discuss particle engineering using fluid bed and we'll wrap up with some ways to learn more and and a brief question and answer session webinar will last around 40 minutes and it's being recorded so we will be made
• 02:30 - 03:00 available to participants afterwards both the recording and the slides if you last like to ask questions then there's you'll see on your GoToWebinar panel a question box which you're welcome to use and we'll try to answer those at the end you're all muted to prevent any background noise and we look forward to hearing questions at the end so first of all what is particle engineer in case some of you aren't familiar with the term here's my definition at least particle engineering
• 03:00 - 03:30 is really about making particles with the right shape size structure and surfaces to give you the product properties that you want and today we're going to be talking about two alternative ways to engineer particles spray drying and fluid bed processing so let's go through the basic principles of spray drying first in spray drying you start with a fluid feed which can be a
• 03:30 - 04:00 solution and an emulsion or suspension in water or alternatively other solvents and this is pumped through an atomizer nozzle to form droplets you can actually get away with quite a wide range of viscosities as long as it can be pumped through and through the atomizer to form those droplets that's all you need to be able to do sometimes the pressure needs to be quite high but a wide range of viscosity for that fluid is possible those droplets enter the spray drying
• 04:00 - 04:30 chamber or tower together with a separate stream of heated gas which is usually air but not always has the droplets fall to the base of the drying chamber they're dried by that hot air and as they dry they form solid particles so the idea is that by the time they reach the base those droplets are dry solid particles those particles are then removed and set rated using things like a bag filter or cyclone system spray joins a rapid an
• 04:30 - 05:00 efficient process due to the very high specific area of those refined droplets and that high specific area allows a rapid heat transfer and mass transfer and that last point is important because drying actually happens at the interface between the droplet and the hot air so that surface area is critical to the speed of drying when you atomized to form small droplets you're creating surface area but more surface area means a higher surface area energy because of
• 05:00 - 05:30 surface tension therefore you do need to put in energy to do that atomization that's why you use a norm you need to apply pressure to your fluid through the atomizer let's have a look at one configuration for spray drying this is the co-current spray drying system there are many variants but this is this is a very common one in the current system liquid is atomized here you can see the liquid feed passing through the atomizer
• 05:30 - 06:00 here at the top of the vertical tower these droplets fall by gravity through the tower the hot air in a co-current system comes in close by so the hot gas feed is also fed in at the top of the tower and at the bottom of the tower your particles exit and also the hot humid air which has been formed from from the drying and also exits bigtrack big dry particles are quite easily
• 06:00 - 06:30 separated from the altair finer particles can be separated by cyclone and dust is removed in filters so what sorts of particle engineering options might you have using spray drawing first of all size and controlling size the primary effect on size is the droplet size and the droplet size is controlled by the atomizer and atomization conditions but you've got to consider here will any big particles be
• 06:30 - 07:00 dry by the time they reach the bottom if not and you want big particles and big droplets that might might mean that you need a taller dryer so size is important shape then the droplet is usually spherical so we'd expect the particle to be spherical too this is often the case but not always and that depends on the drying conditions as we will see later and then structure we can build internal
• 07:00 - 07:30 structure for instance called shell structure using spray drying or an external structure by agglomerating particles together to form granules and as a result of engineering that the particle we can influence and enhance the product properties so for instance we can make a granules strong such that it doesn't break down to form a dust or we can encapsulate an active component to control its release properties or we
• 07:30 - 08:00 can make a a solid flow better by altering particle size shape and smoothness or we can get reduce purrs better in water for instance by altering its size its shape or its density let's have a look at in more detail about what happens to droplets in a spray dryer and we'll start the journey on the left hand side here's the droplet and at the start of its journey through
• 08:00 - 08:30 the spray dryer the droplet has a uniform want of water content and the surface is saturated with with water or salt now here the drying takes place from the surface of the droplet assuming the water can get there fast enough the air here outside the droplet is hotter than the droplet and initially all of the the heat goes into evaporation of the water and not by heating the droplet as long as the relative humidity around
• 08:30 - 09:00 the droplet is low there's a driving force for that drying process to happen over time let's move on to what happens after a little bit of time here once water transfer from the center stops the surface water level decreases so the surface is no longer saturated and the crust can begin to form around the outside of the particle and this can
• 09:00 - 09:30 happen for water moving from the inside is not coping with the demand from evaporation so it's actually too slow to move from the outside and the outside is no longer saturated transfer of water and this is where sizing problem is important here because transfer of water takes a finite time so bigger droplets will have a bigger difference in water content between the core and the surface this is also where material properties of the formulation becomes important so
• 09:30 - 10:00 if your solute bonds to water for instance things like surfactants or starch as your solvent this can limit the weight of the rate of water moving through the droplet so the temperature rises and in some cases water water transfer becomes so low that it turns to steam inside the droplet causing rapid expansion blowing a hole in a particle and making porous material so what happens in these latter stages is really very much dependent
• 10:00 - 10:30 on the material properties of the droplet and the details of the drying conditions so another word on the importance of the droplet size and as we've seen smaller droplets will drive faster due to a higher surface area the water also has less distance to get to the surface so these diffusion and particle heating effects that we've talked about are less likely to happen for small spherical particles and you're more likely to end up with uniform
• 10:30 - 11:00 smooth spheres with bigger drop droplets as we've seen there's the chance of larger water gradients form forming so bigger droplets will take longer to dry but they do fall faster in the tower and that's the reason you might need a very tall tower to get your droplets dry below you might want big particles for low dust or for good flow properties there's going to be a limit then to that maximum droplet size and you might have to settle for spraying smaller droplets
• 11:00 - 11:30 and making smaller particles and then agglomerating them either in the tower or afterwards in in something like a fluid bed and there'll be a little bit more on that in a moment now so far we haven't said too much about the atomizer or the atomizers that can be used to make the droplets now there is a lot of choice and a lot of different atomizer designs and atomizer design is a big
• 11:30 - 12:00 topic in its own right so we're going to be just very very brief here but very briefly you can atomize by use of a spinning disk and that sprays tangentially in the tower and the tower for that reason is relatively short and wide in a spray atomizer a nozzle atomizer you might choose a tall and thin thinner tower for longer residence time so let's go back
• 12:00 - 12:30 that co-current design with the the heat and the atomization at the top this is a much more common design both the fluid and the drying gas all four follow the same direction through the tower very often you're dealing with the lower this got the fluid here and creating spherical particles that we said you're creating a relatively fine powder 100 to 200 microns in diameter now an advantage
• 12:30 - 13:00 of this kind of design is that you've got fine particles that dry relatively quickly you've got rapid dry drying a load time in the dryer and relatively hot and wet conditions you're getting all of that energy going into drying the droplet and not heating the particle up and so it can be used for temperature sensitive products and you can use it also for
• 13:00 - 13:30 high water content products with little resistance to internal diffusion let's move on to engineering the particles shape and there are many possible morphologies here we've mentioned small droplets becoming small spheres and as we've said larger droplets may blow open so if the material is rigid the droplet of the particle may more or less returning there it retain its spherical shape when blown just with a hole in it
• 13:30 - 14:00 but if the material is flexible the sphere may collapse once it's blown open and you might get that kind of squashed raisin shape or squash football shape that is quite often seen if the material is more brittle then when it's blown open the sphere can actually fracture forming a dust will come on to hollow spheres encapsulates and the government's in a moment but just to stress the importance here of understanding the material properties the process conditions and the equipment
• 14:00 - 14:30 factors and ideally what you want to do is work out the advanced what kind of shape you want and then work back to optimize the formulation or the process conditions promised a short word here on shale formation and in spray drying a useful concept is the peclet number and the peclet number is defined as the ratio of the rate of evaporation of solvent to the rate of diffusion of the solute so
• 14:30 - 15:00 for low peclet number solutes these diffuse faster than the droplet can shrink and therefore they Sol you can move to form a small solid sphere like this as the water is lost or the solvent is lost for high peclet number solutes these solids diffuse slower than the droplet can evaporate so the evaporation is happening quick more quickly than the
• 15:00 - 15:30 diffusion rate the sweet cometh gets left behind as the water is lost and the hollow shell particle can be formed now these are the extremes of morphology and and there are a lot of other possible morphologies that are possible and I've included here a couple of references if you're interested in going to more detail about peclet numbers and about drying conditions and material properties and morphology if you want to
• 15:30 - 16:00 follow those up let's talk here about micro encapsulation and more complex structures that can be formed within the spray dried particle so maybe you want to encapsulate a volatile oil a fragrance or a flavor for instance within a solid particle here your fluid feedstock will be an emulsion of that
• 16:00 - 16:30 oil in water for instance and included in that feed will be other materials such as starch or a protein as well as a filler polymer on top of our as well so that's on the left-hand side here you can see our droplet our water droplet that is atomized containing within in an emulsion of a oil droplet and dissolve starch and filler let's just you mean on one of those droplets and have a look at the oil droplet itself
• 16:30 - 17:00 starch migrates to the oil water interface to some extent it's as if it's active and as the drying particle gets hotter starch can Center to form a coating around the droplet to encapsulate that oil droplet and on the right hand side you can see what the final particle will look like essentially it will consist of oil droplets surrounded by that solid start
• 17:00 - 17:30 coating all embedded in the Phillip Fulmer and that's actually quite a potentially cost effective approach to encapsulation compared with other methods such as interfacial polymerization so earlier I promised to mention agglomeration of particles and one way of doing that is in the spray drying tower itself and here you would need probably a counter-current design or spray dryer and then a counter-current spray dryer the product fluid enters at
• 17:30 - 18:00 the top but the hot air the drying gas flows up from below and that means that the drain the greatest driving force for drying is where that hot air is hottest and that's at the bottom of the tower and by creating circulation forces for the droplets in the tower you can get those droplets to collide with each other and to agglomerate as they dry in the tower and the tower design needs to be such to extend the residence time and to maximize the probability of
• 18:00 - 18:30 collisions of particles you also need to be careful about your material properties so that the particles adhere to each other and don't bounce off each other when they collide and using counter current granulation and gamma raishin you can get to to high particle sizes up to over half a millimeter in size very often use for detergents and slower drying flurries and you can make here from these sorts of materials quite low density porous products that
• 18:30 - 19:00 will read as burst very nicely in water for instance after on use and here's a schematic of a counter-current dryer just wanted to point out the differences here here again is your liquid Inlet and atomization into the tower at the top the difference here being that you've actually got hot air coming in the bottom and here in the middle of the tower is where you get the drying and
• 19:00 - 19:30 the agglomeration and then you get feed of the larger particles out of the bottom of the tower as before another method of agglomeration is by following the spray drying step with a fluid bed at the basis of spray drying tower and dave is going to talk in a moment about fluid bed in much more detail the design in this case is usually a co-current spray dryer and that will produced as we've seen primary particles which are typically pretty fine and spherical and these can then be
• 19:30 - 20:00 agglomerate 'add in the second step using a fluid bed after the spray throwing step so let's just run briefly through the pros and cons of spray drying before moving on to flowing bed fluid bed the advantages it's a very rapid drying process due to that large surface area and very good contact between the droplet and the hot air got
• 20:00 - 20:30 a high mass and heat transfer as a consequence it's a semi continuous process in a single stage is pretty flexible therefore and reduces the amount of handling a product that you need to do if you get your conditions right the heat can be used to vaporize a solvent and not heat the solid very much so it's got potential for use for sensitive materials there's a very good method simply of drying there's a very efficient way of moving removing water at the end of a formulation or a
• 20:30 - 21:00 synthesis process which might might have given you a formulation with too much water in it you want to get a dry product out of it so it's simply as a method of drying it's useful it's got a high potential for particle engineering as we've seen and we can change things like size morphology in collaboration and capsulation disadvantages well the equipment can be large and complex and expensive it must be able you must be
• 21:00 - 21:30 able to pump and atomized that starting suspension solution or a molten so there's gotta there's got to be a pumpable feed to start with and as we've seen you need to understand the properties of your formulation new material as well as your process conditions to control that properly for optimum results and for that reason also the scale-up may require some care so now before we move on to fluid bed I'm just going to unmute David and home hand over to David York to talk about
• 21:30 - 22:00 particle engineering with fluid beds David thanks Jim food ice beds and spray dryers have things that are in common in the sense that you are dealing with surface cities that are particles or droplets which are very small and consequently you can get a very high surface area to volume ratio which allows you to do lots of things more
• 22:00 - 22:30 efficiently because you can increase the high you can have high heat and mass transfer coefficients one of the two differences is that spray dryers are limited in time as Jim mentioned because you basically have a droplet which falls under gravity from the top of the bed tower down to the bottom so there's a time limitation and you can see when I
• 22:30 - 23:00 describe fluid beds that that time limitation disappears with fluid bed so that's a difference between the two the other difference that's important is that spray dryers start off with a liquid drop and form the particle as it flies fluid beds require a particle already to exist either as a solid or a semi solid on to which you can do lots of different transformations so that often you will
• 23:00 - 23:30 have a fluid bed at the end of a spray drying tower in order to the way the Spade wire produces the solid particles which then go into the fluid bed and we'll talk a bit more about that but basically as I said clear beds have to start with a bed of particles and that bed of particles is basically a static bed and what you do is you pass a gas
• 23:30 - 24:00 typically air up through the particles through the pause in the particles and as the gas flows across those particles a pressure drop occurs which is due to the resistance in flow of the gas caused by the the size of the particles as you increase that flow rate of the gas the pressure drop starts to increase and you get to a stage where that pressure drop is equal to the the pull
• 24:00 - 24:30 of gravity on the particles and they basically escape gravity and become fluid like increasing the fluid rate of a gas a gas rate anymore just increases the amount of turbulence in the system but will not increase the pressure drop and as long as that gas flow rate is maintained the fluid bed is maintained let's have a look at a quick diagram as to what that looks like on
• 24:30 - 25:00 the left hand side you can see a static bed the surface is fairly rough and uneven and there's no movement of the particles but you can see that there's a porosity of the of the bed there's gaps between the particles that the air can flow through and as you start to flow the air through upwards nothing much happens for a while except the pressure drop increases and then all of a sudden
• 25:00 - 25:30 you will fluidize you'll come to the minimum state of fluidization and the the surface of the bed will go level horizontal and you just start to behave like a fluid like a liquid and you can look at view these things as basically huge molecule like liquids where the particles start to move around and as you increase the flow rate those particles move around from side to side
• 25:30 - 26:00 up up and down and you get very good mixing of the particles and very good interaction between the air and the fluid so that's a very simplified view of what's going on in the bed the next slide talks about the properties of fluid beds so there is a defined pressure drop across the height of the bed and that's dependent upon how how
• 26:00 - 26:30 high the bed is the nature of the particles that you've got in the bed how heavy the particles are and what sort of shape and porosity I won't say too much more about that but we cover that in the the course Jim's going to mention later one of the advantages though if you have lots of movement in random directions and you have like a bubbling surface so you like a pan of water and so you get lots of
• 26:30 - 27:00 mixing and lots of interaction between the gas and the particles so you have lots of particle particle interactions and lots of gas particle interactions and so you can you can do lots of interesting chemistry onto the surface and physical transformations because of that excellent heat and mass transfer so the point here though around time is that you can have very long residence
• 27:00 - 27:30 times in your bed because it's maintained by the gas flow rate rather than the height of the of the tower with with respect to gravity so it gives you opportunities of drawing at much lower temperatures over longer periods of time so that on the next slide we can see how those properties drive the use of fluidized beds and there are many different uses of fluid ice beds and a
• 27:30 - 28:00 lot of those that we cover in the course first two the first one is because of that good mass transfer you've got lots of gas hitting the surfaces of the particles and so they're very good for heterogeneous reactions so coal power stations typically will use a very fine pulverized fuel of coal it's ground very
• 28:00 - 28:30 fine and then fluidized and so you have a huge surface area and you pump in oxygen in the form of air and you can get very high reaction rates lots of energy created in a very small space so power stations tent use fluidized beds because they're much more efficient because of that very high surface area the surface area is also used for weather particles instead of being burnt those particles are
• 28:30 - 29:00 heterogeneous catalysts where you have typically a porous particles where the surface is coated with catalysts and these move around and you pump your gas through them so instead of burning them with air you pour hydrocarbon gases through and they they crack under the conditions of the catalytic reaction so you can get very good and efficient with
• 29:00 - 29:30 their formations of hydrocarbons in these systems fluidized beds are also very good at drawing you get very good heat transfer like you do in a spray drying tower but you also then have the benefit of a large time window so you can dry particles over a long period of time and at a lower temperature particularly useful for temperature sensitive materials also sometimes used
• 29:30 - 30:00 at the back of spray drying processes to increase the capacity of the system whereby you only partially dry your particles in the spray dryer to form a particle which is can be moved about enough to read baby and then you can increase the amount of drying you do by putting it through a fluidized bed often what comes out of a fluidized bed is hot material that can have flow problems
• 30:00 - 30:30 themselves if they're allowed to settle and so often you'll have a fluidized bed dryer followed by a fluidized bed cooler and I've used these many times with agglomeration particularly for detergent particles so we would have a fluidized bed dryer and then we'll follow that with a caller where instead of pumping hot air in with cold air in in order to
• 30:30 - 31:00 cool the particles and again they're very efficient and is used then to give a nice crisp free-flowing product this ability to move the particles around also gives us the opportunity to coat so as well as fluidizing and moving the particles around or what you can do is to spray a solution onto the particles and with good control of the spray conditions you can get the liquid to coat the surface
• 31:00 - 31:30 of the particles and typically you would use a film forming polymer solution that spreads around the surface and as it spreads you provide hot air into the fluid bed and that dries the the liquid and forms the solid polymer film around the surface so it's used a lot for protecting particles and also for for coating them for controlled release you
• 31:30 - 32:00 can use the same process or the same idea but instead of having a fairly dilute polymer solution if the liquid you're spraying on is quite viscous and doesn't have the chance to spread around the particles then the before it dries then as the particles come together with the sticky surface of the liquid on top
• 32:00 - 32:30 of them they'll stick together and they'll start to a go away and you can control the degree of agglomeration by the posttest conditions how how fast you move the particles and how fast you move and the amount of Spion that you put on the density of these argon which tends to be very low because they're hitting each other but under quite low shear conditions and you end up with particles that look more like a raspberry than a compressed vomit and it's this process
• 32:30 - 33:00 is used to grow particle sizes dimension from fluidized beds and is used to instantize food products such as coffee and no powders by growing the particles and making them slower to to wet and dissolve so you allows the particles to be dispersed in the liquid before they dissolve moving on here's a description that you've seen
• 33:00 - 33:30 before from Jim it just gives you an idea as to why fluidized beds are often used as additional dryers you can see that often it's difficult to get the very last part of a solvent out of the core of a particle by the time it reached the bottom of the spray dryer this can be not this is not a problem in lots of instances with sprayed wine but it can be in certain circumstances
• 33:30 - 34:00 particularly since you when you realize that after the particle comes out of the dryer and start to age that liquid in the center starts to reduce reduce burst and under some conditions that liquid can diffuse out and back to the surface and make the surface quite sticky which is not to be desired or if you're looking to dry formulations very dry for stability reasons you want to have a
• 34:00 - 34:30 there's lower moisture active water content as as possible so you put it through a fluidized bed trying it slowly low temperature to give the time for that water or that solvent in the center to diffuse out and to be dried off and so that's one of the reasons why you'll often see fluidized beds at the back end of a spray drying tower the next slide
• 34:30 - 35:00 is a just a quick picture of what happens when you hit the particles with a liquid you can see in example a the liquid hits the droplet and starts to spread and as it spreads it dries and particularly if you've got a particular particular polymer that is not sticky Rhys then your former nice film over
• 35:00 - 35:30 time has that liquid spreads interestingly it also shows that with fluidized beds these particles as they move around need to be hit in different places by the liquid in order to get a consistent coat around the surface and that's why this movement within a fluidized bed is very useful by contrast on the right hand side you've got a particle where the liquid is very
• 35:30 - 36:00 viscous tends to be sticky and it doesn't spread very well and consequently by the time that particle with that blob on its another particle then there's a chance for those two particles to be glued together and start to form the grommet so lots of interesting things you can do there important to say that you're actually starting off with the core particle having a particular structure on its own
• 36:00 - 36:30 so fluidized beds is a way of adding structure to an aged already existing particle structure here's a typical example of a kotor flue those beds can come in various different shapes and sizes they can be batch or continuous the batch processes tend to be circular in cross section as shown here continuous tend to be rectangular and
• 36:30 - 37:00 some of them can be quite long and thin so it gives you a lot more control over the the particle flows through the bed so here is the gold standard for coating in industry the verse decoder it's a batch process and you can see the the outside wall shown at the top and it also has another cylinder in the middle
• 37:00 - 37:30 what happens then is the the unit is charged with powder and the hot air enters the Senate of that bed with a fairly large hole and a large velocity it pushes the particles up through the center of that bed and as it pushes it up you spray your coating
• 37:30 - 38:00 solution into that highly fluidized bed the particles then will get hit by liquid droplets on part of their surface they will move to the top as they come out of that center core they area cross sectional area is bigger and therefore the air velocity is lower and therefore the particles drop down down the side and then they'll get as they come down to the bottom they'll get picked up again by the high velocity in the in the
• 38:00 - 38:30 center and get blown up again through the center so these particles will go around many times during the process and each time they go through they'll get hit with a liquid drop which will coat part of the surface and over time you get a very nice recently even distribution on the left-hand side you can see two particles one is a particle which we've actually made and sliced and if you look closely you can see a very
• 38:30 - 39:00 thin layer of polymer around the outside where it's dried you can also see bearing in mind Jim's comments about shape except the fluid beds tend to maintain the shape of the particles that they put in there compared to fluid with very drawing where you can actually control the the shape by formulation and closest conditions but you're starting off with a solid it's difficult to change the shape at the bottom just for
• 39:00 - 39:30 a bit of fun we've taken a core and we've sprayed it with different inorganic salt solutions and dried them and we've put in a particular different dye to show you that you can get many different layers of coating on these particles to give you different properties so you could have a core particle and this is sometimes used by the farmer people you have a core inner particle you will spray your particular active ingredient
• 39:30 - 40:00 to form a coating on that and then you all can spray another coating on top of that which would probably be an enteric or controlled-release coating to allow you to to deliver the the active ingredient at the right place in the right time so on the next slide you can see that we've got lots of possibilities for engineering particles using fluid beds you can create additional structure
• 40:00 - 40:30 onto an existing structure you could even if you wanted the user solution as an emotion to spray onto the surface of which which would include micro encapsulates and therefore you could have a core particle structure and then you could put another different structure on top of that and then you could put a coating on top of that that ability to keep the particles inside of the bed for long periods of time give
• 40:30 - 41:00 you lots of possibilities for playing lots of tubes on the process so you can enhance the structure I'll spray dry particles as well as just drawing and and cooling and consequently it's often used to make particles more free-flowing so you can make a put-on crisp coating on top of a sticky particle and make it crisp and free-flowing you can also control the stability of ingredients by
• 41:00 - 41:30 coating them with materials which are such as fats and other polymers to protect them for water Inglis during storage and within that you can also by taking the changing the material properties of the solution that you spray on you can increase the ability but you also control the release rate of these things however there are some
• 41:30 - 42:00 limitations as with everything particles need to be free-flowing so harder to have fluidized beds with lots of sticky particles that's not too least to say that you can't manage these situations it just becomes more challenging and you'll sometimes see fluidized beds with vibrating plates on the outside to give the particles that expert kick to to break any bonds that they form in the fluidized bed so one
• 42:00 - 42:30 way of handling Stickney particles the particle properties are very important in a fluidized bed and that can determine how easy that they can fluid iZombie process if they're too fine then it's difficult to keep them in the bed and it's difficult to get that control on the porosity of the bed so that they behave a bit like dust they'll ways around it just like with anything but you are getting to the
• 42:30 - 43:00 limits of fluidized beds if the particles are too heavy which is particularly so as they grow in if they become big uns in size it's difficult to get the air to flow fast enough to lift the particles so you often get very high flow rates with heavy particles and it it makes things harder but not impossible and then finally if the particles are too fragile the movement within the fit in
• 43:00 - 43:30 the bed ask them you carefully can fold so because what you don't want is to fracture the particles all autumn erode the surfaces and create fine dusts because those particles are going to collide you need to be careful about breaking the particles off so you can see there are lots of tunes you can play with fluidized beds and the what those tunes are and the formulations you can
• 43:30 - 44:00 put through them depend on what you want to produce and how you want to go to produce it so as I said before both processes benefit from having very high heat and mass transfer rates because you're making are the liquid small droplets or small particles inside the fluid ice sprayed lying is very fast because it for basically the blockage fall down into gravity and this has many
• 44:00 - 44:30 opportunities for quick drying particularly with the materials that have very low high water content through ice beds you can have a much longer process residence time and this can provide the opportunity to give you other structures so there's as benefits for each of them what you choose depends on what you want to make and the materials that you start off with you can both of those processes you can have
• 44:30 - 45:00 a big in fact impact by the design of your equipment and how you run your process thank you David for that overview of fluid processing and particle engineering we just wanted to let you know as we've concluded the main part of the webinar before the question and answer session about two more opportunities to learn a little bit more
• 45:00 - 45:30 about these processes and the first of those is at the end of March dawn of April three-day course run by the University of Leeds covering spray drying and atomization of formulations you can see the details there there's a web link I'll just briefly mention the fact we start with the basics of the science and lab demonstrations we move on to industrial formulation case studies and some demonstrations on on day three talking more about finishing
• 45:30 - 46:00 of paradis modeling and future developments so highly interactive caused plenty of opportunities to interact with the lecturers and and is always highly rated by the attendees we've been running that for a number of years now and the second opportunity is on fluid bed processing and formulation in in May again you'll see the web link there we concentrate in a similar format the first of a one day one on basic science and understanding including lab
• 46:00 - 46:30 demonstrations moving on to up the Asians and real industrial case studies we've got a good mix in both courses actually of industrialists and academics so there's a really good grounding in both in the science and the practical practical applications on day three moving on to some further case studies and new developments in fluid bed processing so two opportunities there details on those web links and from ourselves with the email address if
• 46:30 - 47:00 that's of interest to you so now we're going to give you the opportunity and thank you very much for your attention today and thank you very much once again David for your contribution we're going give you the opportunity that for any any questions I see we do have one here so it is a question I think it's a fluid bed question for you David I'm just going to unmute you and the question here move
• 47:00 - 47:30 back to the question from Sharla as can we make a uniform particle shape particles of uniform shape using fluidized bed drying David no you can't take a an oval particle and make it into a sphere because of that
• 47:30 - 48:00 you can actually sew a lot of depends on the shape of the starting material you can if you are willing to agglomerate then build up glommer particles of a similar shape and size yes you can do that but you it's difficult if you've got a a non spherical particle and a range of different particles in the fluid I've been to make them all the
• 48:00 - 48:30 same you the only way of making them saying is to build them up to a nagawa which is as similar shapes and sizes okay thank you very much again I think that's all we have time for today so thank you very much for your attention today and as usual we will send you within a day or so details I've had to access the recording of this webinar as well as to download the slides any other information you can get from us via the
• 48:30 - 49:00 email info art I formulate dot biz and information is also on our webinar on our website about training and webinars so thanks very much for your attention today and goodbye and we hope to see you again thank you