Published on February 14, 2008
Slide1: EDECAD Efficient DEsign and Control of Agglomeration in Spray Drying Processes Project team Full time: Dr. Geraldo Nhumaio (the presenter) Contributors: Dominic Kirkman, Anna Carruthers, Dr. Yusuf Al-Suleimani & Dr. Hassan Abduljalil Supervisors: Dr. A. P. Watkins & Prof. A. J. Yule Atomisation and Sprays Research Group Slide2: Introduction Definition of spray drying Definition of agglomerates Advantages of agglomeration by spray drying EDECAD project participants UMIST role in the project Test cases on collisions and agglomerations UMIST cold laboratory case Bremen cold industrial case Anhydro (APV) hot industrial case Summary of achievements Contents considerable time to be spent here Slide3: Definition of spray drying Definition of agglomerates: Definition of agglomerates Why the need for agglomerates: Why the need for agglomerates Porous agglomerates (e.g. instant coffee/milk, laundry detergents, agrochemicals) Have improved solubility in water Disperse better Have low propensity to formation of lumps Have dust-free flow (e.g., in vending machines) Advantages of agglomeration by spray drying over other drying technologies: Advantages of agglomeration by spray drying over other drying technologies Quick drying -vs- minimum heat shock to processed material (friendly for heat sensitive products) Processed sticky material does not contact solid surfaces until dry => equipment experiences minimum corrosion problems Slide7: EDECAD project participants Slide8: UMIST role in the project Provision of experimental spray data (initial conditions and validation data) for two interacting sprays in a wide range of boundary and nozzle operating conditions To coordinate the development and implementation of the “collision sub-model”, i.e., the consortium Work Package 2 (WP2) To implement and test novel sub-models on collision, agglomeration and drying using the (in-house) Spray3D code Slide9: The UMIST twin-fluid atomizers cold case Slide10: The UMIST twin-fluid atomizers cold case (Nozzles used in the study) Liquid velocity at orifice = 0 ~ 20 m/s Air velocity at orifice = 0 ~ 340 m/s Sonic flow External mix AutoJet Air Atomizing Nozzles SUV113A from Spraying Systems Co. Slide11: The UMIST twin-fluid atomizers cold case (Measurement levels for initial spray data) Slide12: The UMIST twin-fluid atomizers cold case (Measurement levels for numerical validation) =45° Slide13: The UMIST twin-fluid atomizers cold case (Different test cases and conditions) Slide14: The UMIST twin-fluid atomizers cold case (CFD simulations) Slide15: The UBremen (industrial, cold & HP) case Slide16: The UBremen (industrial, cold & HP) case Slide17: The APV/Anhydro/Invensys (industrial, hot & HP) case Slide18: The APV/Anhydro/Invensys (industrial, hot & HP) case Slide19: The APV/Anhydro/Invensys (industrial, hot & HP) case Slide20: The APV/Anhydro/Invensys (industrial, hot & HP) case Slide21: Summary of achievements (mainly for reporting at EU HQ in Brussels) Novel validation data to aid the prediction of impacting water sprays were produced and made available to all the EDECAD consortium partners A 3rd yr project (rated excellent) was achieved in the spray drying topic A M.Sc. and a Ph.D. graduates were trained in the field of spray drying technology A research associate gained experience in developing FTN routines for collision & agglomeration modelling as well as for post-processing of PDA data Higher collision and agglomeration rates occur where larger particles negotiate their paths with massive clouds of smaller momentum droplets Appendix: Appendix Would you like to see more information? If so, please see next slides after the meeting. The UMIST Spray3D code(General Features): The UMIST Spray3D code (General Features) Staggered grid (at each location 3 different cells are used to store different vectors and scalar quantities) Transient solution for both continuum and discrete phases Non-iterative (pressure) predictor corrector method is used All parcels are tracked regardless of being collectors or collected Basic features of this code were used as reference for the improved (i.e., stochastic) collision model Slide24: Original UMIST Spray3D collision sub-model (Simultaneous Particle Tracking) The colliding droplets are assumed to be in the same cell Droplets within the cell are assumed uniformly distributed The probability that the collector parcels undergo n collisions with the smaller ones within a time step is obtained from the linearized form of Poisson distribution (Sommerfeld, 2000) A collision occurs if a random number X, generated between 0 and 1, is less than Pcoll Slide25: Original UMIST Spray3D coalescence s/model (Simultaneous Particle Tracking) The parcels of larger diameter collect their smaller counterparts if a random number Y, generated in the range [0,1], does not exceed the minimum surface energy required to reform the individual colliding drops, i.e. The droplet parcels reduce by one if a small size parcel is collected by its larger counterpart Slide26: Particles classification for the “(novel) agglomeration sub-model” Slide27: 15 categories of possible interactions for the collision & agglomeration models Yes = Implemented collision & agglomeration models Slide28: Evaporation -vs- drying sub-models (Diff. eqns.: droplets external heat transfer) Slide29: Evaporation -vs- drying sub-models (Diff. eqns.: droplets internal mass transfer) D - diffusivity Dd –droplet diameter Pt – total pressure Pv, - partial pressure of vapour far from the droplet Pv,s - partial pressure of vapour at droplet surface Rf – vapour gas constant Tm – man film temperature Spray3D approach for evaporation of droplets of pure liquids Slide30: Spray3D evaporation sub-model (Discretized equations: pure liquid droplets) Slide31: Drying sub-model from WP 4 (Discretized equations: droplets w/ solids contents) Slide33: In Out Ceramic Kiln Wet clay slab Brick Strength & durability Brick industry Example drying technology 2
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