University of Pécs

Institute of Pharmaceutical Technology and Biopharmacy

2019.10.09. 15:191

Fluidization

Theory of

Fluidization

Different solid systems in the pharmaceuticaltechnology

3

powders

agglomerates

granules

pellets

In pharmaceutical practice can be:

Granules may be created by

1. Aggregation from smaller particles - building up granulation(wet, melt granulation), or

2. Desaggregation from larger particles e.g. briquette(compaction, dry granulation)

Fluidization is the operation by which fine solids are transformed into a fluidlike state through contact with a gas or liquid.

A material is converted from a static solid-like state to a dynamic fluid-like state.

This process occurs when a fluid (liquid or gas) is passed up through a solid material (ie. powders, granules, tabletts).

Definition

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Dust colector

Air distributor

plate

Air inlet

Column

Equipment Exhaust

Fae

Fg

Equipment

Air inlet

Dust colector

Air distributor

plate

Air inlet

Column

Exhaust

Before fluidization Fluidization

(like boiling water)

Buoyancy, surface tension, viscosity…

"Water Level„ pourable

The formation of fluid state

The particles in the bed can

be expanded by increasing

air (fluidum) speed till the

point, of starting of

fluidization.

In the fluid state surface of the bed begins to wave (fluctuate).

The system seems like a boiling liquid.

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fluid statestationary state

The effect of the fluidum speed to the behaviour of the system

Pneumatic

transport

Lf

Fluidized

bed

Lmf

Particles starts

to fluidize

Ll

Expanded

bed

Lo

Stationary

bed

Stationary-bed

height of the

fixed-bed (Lo)

Xspeed of the fluidum v = 0

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Loosen-bed

speed of the fluidum (vl )

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height of the

loosen-bed (Lo)

Fluid bed

heihgt of

(tumbling) fluid bed (Lf)

speed of the fluidum (vf)

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Pneumatic transport

speed of the fluidum (vp)

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Investigationof

the fluid bed

Disorders

Snapshots of fluidization: particle positions at different points in time.

Disorders

bubbling slugging chanel geyser deposition

Disorders

Bubble formation

Disorders

Slugging

Disorders

Channel, geyser formation

v

Disorders

sorting

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Smaller

particles

Larger

particles

Particle positions at different points in time.

The mean operation parameters of the process

Independent variables

• mass of content (m),

• geometry and volume of the fluid-bed reactor,

• the properties of the base plate (sieve),

• speed of air,

• pressure of air,

• speed and pressure of the spraying (injector) air.

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compressor

rota-meter

fluidizator manometerheater unit

dust

bag

constantpressure tank

distributor,

mano-meter

pressure dropcontrol

air speedcontrol

air speedcontrol

air temperaturecontrol

Examination of the operation parameters

Δp

The mean operation parameters of the process

Dependent variables

• pressure drop (Δp),

• height of the bed (L),

• viscosity of the bed (η),

• minimum of the fluidization velocity (vfmin),

• material loss, delivery of fine powders(mk).

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The pressure drop of the fluidum against the fluid air

velocity

Δp

vvfmin vfmax

Δp↑ Δp↓Δp=k

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Partiallyfluidized

bed

Fullyfluidized

bed

pneumatictransport

stationarybed

Pressure drop during the initial phase

v

Δp

minimal fluidization

velocity (Vfm)

0

fluid bed

the start point of the fluidization,

rising of the whole bed,

independent movement of the particles

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Changing of the bed-height (L) in the fluid bed

L

vVfm34

Ratio of beds(R)

minf

f

L

LR

Lf height of the fluid bed

Lfmin the height of the minimal fluidized bed ( V= Vfmin )

LfLfmin

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g))(1(Lp fsz

p1

p2

Δp=p1-p2L height of the fluid bed

ε porosity (or void fraction)

ρsz density of fixed bed

ρf density of the fluid bed

36g gravity force

The pressure drop (Δp)

Void volume (ε)

)(AL

m1

fszf

sz

msz mass of content

Lf height of the fluid bed

A cross-section area of the fluidizer

psz

ε

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Void volume (ε)

f

szf

V

VV

Vf volume of the fluid bed

Vsz mass of the content

Vf

Vf - Vsz volume of the void (space) between the particles

Pressure drop (Δp=p1-p2)

sz

fszsz

A

)(mp

msz mass of the content

ρsz density of the fixed bed

ρf density of the fluid bed

A cross-section area of the fluidizer

p1

p2

A

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sieve (base plate)

colonna

dust collector

ventillator

calorifer

Mean parts of a fluidizer

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Base plate (sieve)

sieve porous plate

A cross-section area42

Rotameter

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The pressure control valve

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Spraying nozzle

air

liquid for granulation

multi-headed

spraying nozzle

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Dust-collector

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collecting return

Practice of

Fluidization

Equipment in the laboratory

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Equipment in the laboratory

• 30 kg

120 kg

250 kg

60 kg

Equipments in the industry

scale-up process

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Glatt granulator

Intermittent operation

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Industrial fluidization instrument

control center

Aim of the fluidization:

• drying,

• agglomeration (granulation),

• coating (granules, pellets, tablets).

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Drying

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fluid bed

- large contact surface

- excelent heat transfer

- the heat sensitive substancies can be dried byfluidization because of the excelent heat transfere needsa lower temperature

- good material transport (wetting-drying) – moisturesensitive ingredients

Drying with fluidization

advantages

disadvantages

- powder formation

- powder flow out

- costs56

Drying with fluidization

granulation liquid

air inlet (filtered, heated)

Fluid bed

atomizing air

Granulation

(higher atomizing) exhaust

distributor plate

Industrial fluidization instrument for granulation

measuring materials

in instrument

product

(dried granules)

granulation

with solution of

granulation

material

starting of

fluidization

end of

fluidization

- all steps in one equipment(mixing, wetting, agglomeration, drying)

- huge contact surface(heat and material transport is very good)(continuous particle formation with paralell drying)

Granulation with a fluidizer

advantages

disadvantage

- inhomogenity may be occured (see the fluidization disorders)

- dust (fine powder) formation (and so flow out phenomenon)

- energy costs61

Fluid granulation with inner mixer

fliud bed

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inner mixer

coating liquid

exhaust

atomizing air

Fluid bed

air inlet (filtered, heated)

Fluid coating

(higher atomizing)

distributor plate

Fluidization in

Wurster system

(lower atomizing)

foutain region

spray region

exhaust

Fluid bed

air inlet (filtered, heated)

coating solution

atomizing air

spray nozzle

expanded region

distributor plate

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bottom spray

(Wurster)

Fluid coating

Precision-Coater™ module

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bottom spray

(Wurster)

Fluid coating

Industrial fluidization instrument for coating

measuring materials

in instrumentstarting of

fluidization

end of

fluidization

product

(dried coated

material)

coating with

solution of

coating material

- all steps in one equipment(mixing, wetting, multi layer coating, drying)

- huge contact surface(heat and material transport is very good)(continuous particle formation with paralell drying)

Fluid coatingadvantages

disadvantages

- inhomogenity may be occured (see the fluidization disorders)

- dust (fine powder) formation (and so flow out phenomenon)

- energy costs

- damages of the film coat

- the particles adhere to each other and also to the wall 69

Intermittent operation

Continuous operation

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Security technology

RISK OFDUST EXPLOSION

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The end