mechanical process engineering – particle · pdf filefig_mpe_2017 i.doc mechanical...

Fig_MPE_2017 I.doc Mechanical Process Engineering – Particle Technology Prof. Dr. J. Tomas 05.04.2017

Process Engineering Department summer semester 2017 Chair for Mechanical Process Engineering Lecture: "Mechanical Process Engineering (Introduction into Particle Technology)" We. 09:00 - 11:00 G05- H4 Tutorial: We. 11:00 - 13:00 G10-110 Handouts: http://www.mvt.ovgu.de/mvt/en/Lectures/Lecture+MPE.html, lecture manuscript with

chapters 0 – 8: *.pdf, tutorials, solutions, lab instructions. date L/T content responsible

5.4. 5.4.

2L 2T

introduction/disperse systems particle size distribution

Hintz Hintz

12.4. 12.4.

2L 2T

fundamentals of comminution comminution

Trüe Trüe

19.4. 19.4.

2L 2L

comminution particle characterisation techniques

Trüe Hintz

26.4. 26.4.

2L 2T

particle size distribution particle characterisation

Hintz Hintz

3.5. 3.5.

2L 2T

particle separation separation function/grade efficiency

Trüe Trüe

10.5. 10.5.

2L 2T

sieving sieving

Trüe Trüe

17.5. 17.5.

2L 2T

particle flow in a fluid particle flow in a fluid

Lukas Lukas

24.5. 24.5.

2L 2T

flow separation flow separation

Lukas Lukas

31.5. 31.5.

2L 2T

flow separators flow separators

Lukas Lukas

7.6. 7.6.

2L 2T

particle interactions/adhesion forces particle interactions/adhesion forces

Müller Müller

14.6. 14.6.

2L 2T

powder flow properties powder flow properties

Müller Müller

21.6. 21.6.

2L 2T

silo design silo design

Müller Müller

28.6. 28.6.

2L 2T

particle agglomeration particle agglomeration

Müller Müller

5.7. 5.7.

2L 2T

particle mixing particle mixing

Müller Müller

written examination (120 min) lab exercises: particle size measurement (Hintz), comminution (Jebelisinaki), fine particle flow separation (Schlinkert)

http://www.mvt.ovgu.de/mvt/en/Lectures/Lecture+MPE.html


Recommended literature to Mechanical Process Engineering: Editor Title Publishers Year Perry, R.H., Green, D.W., Maloney, J.O.

Perry’s Chemical Engineers’ Hand-book (CD version)*

McGraw-Hill, New York 1999

Rumpf, H. Particle Technology Chapman & Hall, London 1991 Coulson, J.M., Rich-ardson, J.F.

Chemical Engineering, Vol 2 Parti-cle Technology

Pergamon Press, Oxford 1991

Fayed, M.E., Otten, L. Handbook of Powder Science & Technology

Chapman & Hall, New York 1997

- Ullmann's Encyclopedia of Industri-al Chemistry

VCH-Verlagsgesellschaft, Wein-heim

1988

Gotoh, K. Powder Technology Handbook Marcel Dekker Inc., New York 1997 Schulze, D. Powders and Bulk Solids: Behav-

iour, Characterization and Flow Springer Berlin 2008

Schubert, H. Handbuch der Mechanischen Ver-fahrenstechnik

Wiley-VCH, Weinheim 2003

Schubert, H. Mechanische Verfahrenstechnik Deutscher Verlag für Grundstoff-industrie, Leipzig

1990

Löffler, F., Raasch, J. Grundlagen der Mechanischen Ver-fahrenstechnik

F. Vieweg Verlag, Braunschweig 1992

Schubert, H. Aufbereitung fester mineralischer Rohstoffe, Bnd I

Deutscher Verlag für Grundstoff-industrie, Leipzig

1989

Schubert, H. Aufbereitung fester Stoffe, Bnd II: Sortierprozesse

Deutscher Verlag für Grundstoff-industrie, Stuttgart

1996

Schubert, H. Aufbereitung fester mineralischer Rohstoffe, Bnd III

Deutscher Verlag für Grundstoff-industrie, Leipzig

1984

Stiess, M. Mechanische Verfahrenstechnik - Partikeltechnologie 1

Springer Verlag, Berlin 2009

Stiess, M. Mechanische Verfahrenstechnik 2 Springer Verlag, Berlin 1994 Molerus, O. Principles of Flow in Disperse Sys-

tems Chapman & Hall, London 1993

Buhrke, H., Kecke, H.J., Richter, H.

Strömungsförderer F. Vieweg Verlag, Braunschweig 1989

Löffler, F., Raasch, J. Staubabscheiden Georg Thieme Verlag, Stuttgart 1988 * recommended Aufbereitungs-Technik Bulk Solids Handling Chemical Engineering Science Chemie-Ingenieur-Technik Chemical Engineering & Technology Particle Characterization Particulate Science & Technology Powder Technology Powder Handling and Processing TIZ International Powder Magazine


Content: 1. Introduction, characterisation of disperse material systems, particle charac-

terisation, particle size distributions, quantities, statistical moments, distribution characteristics, surface, physical particle test methods, particle shape, packing states

2.1 Particle processing by comminution, process objectives, solid bindings, material behaviour and fracture mechanics, cracking, stressing modes, micro-processes of comminution,

2.2 Evaluation and characteristics of macroscopic process performance, work principles and applications of crushers and mills, machine design

3.1 Separation of particles, mechanical separation processes, evaluation of sep-aration efficiency by separation function, evaluation of separation sharpness

3.2 Sieving (screening), particle dynamics, work principles and applications of screens, machine design

4.1 Flow separation, particle flow in a fluid, fluid and field forces, stationary parti-cle settling velocity,

4.2 Introduction into characterisation of turbulent flow, turbulent particle diffusion, turbulent counter-current and cross-flow classification of particles in water and air,

4.3 Separation models, work principles and applications of turbulent counter-current and cross-flow separators, hydro cyclone design, air separators

5. Combination of comminution and separation processes 6.1 Transport and storage of particle systems, interactions, molecular bindings

and micromechanical particle adhesion forces, 6.2 Macroscopic stress states, flow properties, test methods, evaluation of flow

behaviour of cohesive powders, 6.3 Problems at practical powder handling, problem solutions by appropriate de-

sign of mass and funnel flow hoppers 7. Particle formulation by agglomeration, objectives of agglomeration and physi-

cal product design, agglomerate strength, work principles and applications of pelletizing, briquetting and tabletting machines, roller press

8. Mixing of particles, stochastic homogeneity, mixing kinetics, work principles

and applications of solid mixers, rotating drum mixers and agitators, permeation

of fine particle packings and homogenisation in a fluidized bed.


Mechanical Process Engineering 4 SWS 6.0 Credit Points

Scope: The students are introduced into the fundamentals of particle technology. They should learn how to produce particles or powders by size reduction, separation, mixing and agglomeration as a sequence of typical operations. As the consequence, the lectures are designed to focus on the essential microprocesses, particle characterisation and tailoring of the physical product properties of particulate solids. Prerequisite: Mechanics, Fluid dynamics

Content:

0 Introduction, 0.1 Definitions, 0.2 Hierarchic order of processing plants, 0.3 General tasks

1 Dispersity of particulate systems, 1.1 About rocks, gravel, lumps, nuggets, corn, particles, nanoparticles and colloids 1.2 Particle characterisation - Granulometry, 1.3 Particle size distributions, 1.4 Physical particle properties

2 Particle production by comminution,

2.1 Fundamentals of material bonds 2.2 Strong and weak bonds in solids 2.3 Mechanical properties of solids 2.4 Solid cracking and breakage 2.5 Microprocesses of particle stressing and breakage 2.6 Crushing and milling processes and machines

3 Particle separation

3.1 Process principles of particle separation in particle technology 3.2 Evaluation of separation efficiency by separation probability (function) 3.3 Particle separation by sieving, 3.4 Fundamentals and microprocesses of sieving 3.5 Model of screening dynamics 3.6 Sieving machines and screens

4 Particle separation in a fluid flow

4.1 Single particle flow in a fluid and flow-around pattern 4.2 Micro- and macroturbulence 4.3 Particle diffusion in a dispersion medium 4.4 Dynamics of particle transport in turbulent fluids (turbulent particle diffusion) 4.5 Models of particle separation in a turbulent flow field

4.5.1 Separation efficiency by cross-flow separation model 4.5.2 Separation efficiency by counter-current separation model 4.5.3 Multistage cross-flow separation model

4.5.2.1 Separation function, cut point and separation efficiency 4.5.2.2 Utilization of separation stages 4.5.2.3 Examples of zigzag air separator

4.6 Machines and apparatuses of particle classification and dust collection


5 Combination of comminution and separation units 5.1 Basic elements of processing systems 5.2 Basic structures and element combinations of processing systems 5.3 Combination of comminution and classification units

6 Particle interactions, powder storage and flow

6.1 Dynamics of a flowing particle packing 6.2 Fundamentals of particle adhesion and adhesion forces 6.3 Mechanics of particle adhesion 6.4 Testing methods of particle adhesion 6.5 Flow properties of cohesive powders 6.6 Testing devices and techniques of powder flow properties 6.7 Applications in silo hopper design

7 Particle formulation by agglomeration, 7.1 Fundamental agglomeration principles 7.2 Agglomerate strength 7.3 Pelletizing of moist powder 7.4 Press agglomeration

7.4.2 Powder compression behaviour 7.4.3 Briquetting and tabletting 7.4.4 Roller press

8 Product tailoring by particle mixing,

8.1 Microprocesses and mixing efficiency of particles 8.1.2 Model of stochastic homogeneity 8.1.3 Mixing kinetics

8.2 Rotating vessels, kneaders and agitators 8.3 Pneumatic mixing

8.3.2 Permeation of particle beds 8.3.3 Fluidized bed mixer


Definitions

Subject of Process Engineering: • Engineering discipline with integrating character, including

- Energy process engineering (energy conversion) - Information technology (system engineering, data processing)

• Subject is the sustainable, energetically efficient, ecologically tolerable industrial material conversion for economic utilisation and consumption

• Minor importance of exact product shape (⇒ subject of produc-tion engineering)

Material conversion (processing): • Change of physical, physico-chemical and/or • Chemical, bio-chemical material properties

Mechanical Process Engineering: • Focus on physical or physico-chemical material properties of sol-

id particles and droplets, bubbles (≈ 10 nm to 1 m) • Material conversion by mainly mechanical energy input Comminution (size reduction), dispersion and agglomeration Separation and mixing

• statistically distributed material parameters (mainly particle size dependent)

• stochastic process dynamics, efficiency and performance • Particle Technology


Balance boundary of material, energy, information and costs flowsRaw materials

Store (R)

Store (H)

Raw materialprocessing

Materialconversion

Materialseparation

Auxiliarymaterialsupply

Auxiliarymaterialprocessing

Store (W)Recycling process(Reuse)

Raw materials(R)

Auxiliarymaterials (H)

Infor-mation (I)

Energy (E)

Costs (K)

Pro-duct B

Mainproduct

By-product

Waste

Infor-mation

Energy

Store (A)

Store (B)Store (W)

Productformu-lation

Proceeds

Waste

Pro-duct A

Block Flow Chart of Material Processing System


Survey about Unit Operations in Particle Processing Draft of operation principle Process Related processes Physical operation principle

Size reduc-tion

Comminution of solids (irreversible) Disintegration of weakly bonded agglomerates

(reversible)

Classifying Separation according to particle size Sieving or screen-ing

according to geometrical dimen-sions

Fluid flow separa-tion

according to settling velocity

Sorting and grading

Separation according to physical material properties Density sorting According to density Hand sorting Optical properties Mech. sorting Mechanical properties (elasticity) Magnetic grading magnetic properties Electrical grading according to conductivity Flotation according to wettability

Leaching Dissolution Soluble phase Extraction Liquid-liquid phase transition

Crystalli-zation

Crystallization Evaporation of liquid Precipitation Generation of new insoluble solid

phase

Mixing and blending

Homogenisation of various particle phases Solid mixing Solid-solid mixing Homogenization Temporary constant properties Suspension Solid in liquid Aeration Gas in liquid

Agglome-ration

Adhesion of many primary particles to a few coarser agglomerates (clumps) Pelletizing Moist agglomeration Press agglomeration under pressure (tabletting) Sintering Contact fusion Coagulation Liquid-liquid

Solid-liquid separation

Thickening of all particles, clarifying of liquid Sedimentation Particle settling Filtration Retention of particles by semi-

permeable membrane Drying Evaporation of liquid

Dust collec-tion

Precipitation of all particles from gas Absorption from emission sources Gas cleaning Separation of all particles from

gas

Thermal Roasting Degassing of volatile phases


treatment Calcination Chemical reactions within solids (e.g. lime)

Combustion Gasification of organic phases


Multiscale Hierarchic Order of Processing Industries Process Explanation Scale,

equipment Examples

fundamen-tal princi-ples, effects, laws

Physical fundamentals of mate-rial conversion, transport laws (ba-sics of molar number, mass, momen-tum and energy conservation), mo-lecular interactions, molecular to par-ticle dispersion

nm- to µm-range

diffusive, convec-tive transport of molecules and par-ticles; creation, de-struction of inter-actions

Micropro-cess

Material conversion in a typi-cally microscopic-smallest ma-terial element, particle dispers

Contact zone of ma-chine tools, mm-range

Particle stressing, particle flow, parti-cle agglomeration

Subprocess Typical material conversion and transport in macroscopic zone or sub-chamber,

Apparatus zones, cm-range

Feed zone, separa-tion unit, discharge zone

(Macro-) Process, unit operation

Material conversion in a macro-scopic process chamber of op-eration unit

Appa-ratus, machine

Mill, mixer, classi-fyer, cyclon, filter, centrifuge

Process group Primitive combination of processes (chain, parallel or circuit arrange-ments, to 10 processes)

Group of apparatuses

Cascade of classi-fyers or mixers, mill-ing circuit

Processing unit

Partially independent system for ma-terial conversion (to 50 processes)

Subplant Waste recycling plant

Processing System

Independently operating, integrated System to make main- and by-products, waste; with raw material and product store, energy and auxiliaries supply (to 300 processes)

Plant Central heating sta-tion, cereals mill, brewery, pharmaceu-tical plant

Chain of pro-cessing sys-tems

primitive combination of processing systems (vertical production line: raw material to final product, regional dis-tributed)

Plant com-plex

Crude oil ⇒ raffi-nation ⇒ ethylen ⇒ polyethylen ⇒ PE-products

Integrated pro-cessing system

horizontal and vertical network of processing systems, single site

Integrated plant system

Chemical enterprise, Power station

Integrated ma-terial pro-cessing net-work

Integrated site and material conversion system of different international pro-ducers; integrated distribution, con-sumption and recycling

Integrated site system

Crude oil ⇒ raffi-nation ⇒ basic chemicals


General Process Model of Mechanical Process Engineering 1. General formulation of quantity balance of a material component:

Accumulation = Σinput streams - Σoutput streams + sources – sinks (1)

Following fundamental principles are to consider: • Directional particle transport (convection) • Non-directional particle transport (thermal or turbulent particle diffusion) • Sources and sinks: Creation and destruction of interactions between particles, macromol-

ecules, ions or atoms ⇒ Chemical reactions: Creation and failure of strong interactions (= major valence -

bonding: covalent, ionic, metallic bonds), e.g.: chemical syntheses and decomposition reactions, rock crushing or particle size reduction, crystallisation and dissolution;

⇒ Creation and failure of weak interactions (= minor valence bonding: hydrogen bridg-es, van der Waals, electrostatic bonds), e.g.: Solidification and melting, condensation and vaporising, adsorption and desorption, coagulation and dispersion, agglomeration and disintegration.

2. Discrete mathematical formulation of quantity balance of type mass or number of parti-

cle size or particle property fraction i:

[ ] [ ] ( )[ ] iibiiibib GgradDdivvdiv

t±µ⋅r⋅−⋅µ⋅r=

∂µ⋅r∂

(2)

rb Mass fraction of all particles in a volume element dV (= powder bulk density), ≡ total solid mass concentration in a suspension cs = ms/dV µi mass fraction (= dQ3(di)) of fraction i in the observed volume element dV [ ]∂ r µ∂b i

t⋅

Accumulation (storage) of fraction or class i in the observed volume or continuum

element dV=dx.dy.dz vi Particle flow rate of fraction i by external field force or potential difference r µb i iv Convective (directional) mass flow of fraction i through the observed volume

element dV Di Diffusion coefficient of fraction i D gradi b i( )r µ Diffusive (non-directional) mass flow of fraction i through the observed vol-

ume element dV Gi ∼ µi

.µj Particle interaction term = conversion rate ≡ change of mass content of fractions i and j in the observed volume element dV by • creation of particle interactions (agglomeration → 2nd order kinetics) or • destruction of particle interactions (disintegration → 1st order kinetics Gi ∼ µi)


Symbols a mm distance, separation a m/s2 acceleration A m2 area, apparatus area Ar - ARCHIMEDES number b mm characteristic width or breadth of volume element, zone width or breadth b mm subprocess chamber width, apparatus discharge opening width B - statistical fit B m process chamber width B Vs/m2 magnetic induction Bo - BODENSTEIN number c - constant, coefficient c g/l mass concentration c mol/l molar concentration C As/V electric charge capacity d µm particle size, diameter d mm characteristic diameter of volume element, zone diameter d mm subprocess chamber diameter, apparatus discharge opening diameter dp nm pore size D m process chamber diameter D m2/s diffusion coefficient e As electronic charge E N/mm2 modulus of elasticity E V/m electric charge strength E Nm energy Eu - EULER number f - function f s-1 frequency ff - flow factor ffc - flow function F N force Fr - FROUDE number g m/s2 gravity acceleration G N/mm2 shear modulus h mm characteristic height of volume element h mm subprocess chamber height, zone height H m process chamber height H A/m magnetic field strength I A electric current k - constant, co-ordination number k s-1 reaction-rate constant k kg/(m2*s) mass transfer coefficient l mm characteristic length of volume element l mm subprocess chamber length, zone length L m process chamber length Lj - LJA SC ENKO number m kg mass m kg/h mass flow rate

M Nm moment M g/mol molar mass n - exponent, n - compressibility index


n - particle number, molar number n min-1 number of revolutions N - total particle number p kPa pressure P kW power q µm-1 frequency distribution Q - cumulative distribution (quantil) Q As electric charge Q J/s heat flow rate

rxy - correlation coefficient r mm characteristic radius of volume element r mm subprocess chamber radius, zone radius R m process chamber radius R kJ/(kmol*K) general gas constant R V/A electric resistance Re - REYNOLDS number Rm kg/kg mass recovery s - standard deviation s mm distance, film thickness, wall thickness s2 - variance S m³/m³ pore (volume) saturation S kg/(m2*h) particle mass flow rate related to cross-sectional area Sc - SCHMIDT number t h time t mm thickness T kg/kg separation function, grade efficiency curve T K temperature T s time constant Tu - degree of turbulence u m/s flow rate, fluid velocity U m process chamber circumference U V electrostatic potential v m/s flow rate, particle velocity V m3 process chamber volume V m3/h volumetric flow rate

w mm mesh W - probability W kWh work We - WEBER number x - independent variable x, y, z - co-ordinates dx, dy, dz mm incremental dimensions of volume element X kg/kg mass fraction y - dependent variable α - failure probability α deg failure angle, wetting angle, angle α m-2 filter medium resistance β deg angle β m-1 specific filter cake resistance β kg/(s*m2) mass transfer coefficient δ deg angle ∆ - difference


ε m³/m³ porosity ε m/m normal strain ε W/kg energy dissipation ε0 As/(V*m) permittivity of vacuum εr - permittivity ϕ m³/m³ particle volume fraction φ - partial pressure ratio ϕ deg friction angle, angle ϕ s-1 angle rate Φ - probability distribution function γ deg angle γ m/m shear strain γ s-1 shear rate gradient η Pa*s dynamic (fluid) viscosity κ - separation efficiency κ - elastic-plastic particle contact consolidation coefficient κ - exponent κV - (volume related) magnetic susceptibility κm m3/kg mass related magnetic susceptibility λ - parameter λ kPa/kPa lateral pressure ratio λ µm micro-dimension of turbulence Λ m macro-dimension of turbulence µ kg/kg mass fraction µ - friction coefficient µ0 N/A2 magnetic field constant µr - magnetic permittivity ν - safety factor ν - stoichiometric factor ν m2/s kinematic (fluid) viscosity θ °C temperature θ deg contact angle Θ deg process chamber inclination angle, cone angle r kg/m3 density σ - standard deviation σ kPa normal stress σ J/m2 surface energy (tension) σ2 - variance σc kPa uniaxial compressive strength (unconfined yield strength of powder) σF kPa tensile strength (yield strength of material) σ1 kPa major principal stress σZ kPa isostatic tensile strength σ2 kPa minor principal stress τ kPa shear stress τc kPa cohesion τ0 kPa yield strength ω s-1 circular frequency Ω - Ω-number ζ mV Zeta-potential ξ - particle characteristic, variable


ψ - particle shape factor ψ mV electric double-layer potential Indices a external, apex A feed, output, area related b bulk B bottom, bubble c compressive, critical C COULOMB d discharge D pressure, diffusion, vapour, nozzle e effective, electric el elastic E feed, input f fluid F fill, fines, filter, filtrat g gaseous, limit G coarse, gravity ges total h horizontal, homogeneous, hydraulic H adhesion, major design, homogenisation i running index of size fractions, internal j running index of density fractions k running index of constituents or material components, continous phase krit critical K particle contact, capillary, spherical, core flow l liquid ln logarithmic L light material, storage, air, pneumatic m mass related, medium M mixture, mass flow, centre, model, magnetic max maximum min minimum n number, normal state N normal 0 non-loaded, initial state o overflow, upper p particle pl plastic P pore, packing, probe, power r quantity, roughness R ring, radius, margin s solid, stationary st stationary, steady-state S surface, suspension, heavy material, shear ST SAUTER t time dependent, turbulent T separation, tangential, inertia, surfactant Tr suspension, mud u underflow, below


v vertical, viscous V volume related w wall, resistance W water x x-axis y y-axis z centrifugal, circulation, z-axis zul permissible Z tensile, zone, cell, comminution ε pore volume related ϕ influenced by particle volume concentration 0 number as quantity (from l0) 1 length as quantity (from l1) 2 area as quantity (from l2) 3 volume or mass as quantity (from l3)

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