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Manufacturing > B2. Drying and Pellets > Flashcards

B2. Drying and Pellets Flashcards

1
Q

Defination of drying

A

is the removal of fluids, through evaporation, vaporization or subblimation

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2
Q

what is the most used desiccant?

A

air

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3
Q

what is evaporation?

A

when drying occurs below the boling point

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4
Q

what is vaporisation?

A

when drying occures at a temperature close to the boling point and similar vapor pressure

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5
Q

Sublimation

A

conversion from solid ice to water vapour

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6
Q

how can heat be transfer?

A

convection, radiation and conduction

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7
Q

defination of convection

A

density diffrences, moving gas or liquid

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8
Q

radiation

A

wave motion on material

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9
Q

conduction

A

molecular contact solid

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10
Q

types of drying method

A

freeze drying
fluidized bed drying
cabinet or vacuum drying
microwave drying

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11
Q

freeze drying is also know as?

A

lyophilization

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12
Q

When is FD used?

A

for thermolabile and hydrolsis sensitive agents (hormones, vitamines and proteins)

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13
Q

the three steps in freezing drying

A

freezing, primary drying and secondary drying

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14
Q

Learn to draw the FD process

A

do you know how to do it?

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15
Q

Learn to draw the FD process on the water phase diagram and show were the position of the drying chamber and condenser is

A

do you know how to do it

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16
Q

why is the freezing phase of a product crucial?

A

because it determines the morphology and the pore size of the dried product later on

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17
Q

what is the target in FD

A

it is to solidify all the solutes in crystalline or glass form

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18
Q

describe the initial cooling phase

A

it is the initial nucleation, when a small fraction of the water crystallizes out , leading to saturation of the solution

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19
Q

which is reaction is crystallisation?

A

it is an exothermic process

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20
Q

what’s the impact of the exothermic process in crystallization

A

it leads to an increse of tempertaure, which slightly prevent the solidification

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21
Q

when do we have an increase of the freezing point depression

A

during the saturation of the solution

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22
Q

what is the results of the increase of the freezing point depression?

A

Further cooling is required for the solutes and the water to crystallised and completely solidiy

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23
Q

what is the rule of thumb for freezing?

A

10 K less than the eutectic temperature /tg pf the mixture

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24
Q

what other factor has to be consider beside the freezing temperature

A

cooling rate

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25
Q

why is the cooling rate important

A

because it’s influences the nucleation. the faster the cooling rate is the less time there would be for nucleation

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26
Q

What’s the results of less nucleation during the freezing process?

A

less nulceation would lead to

smaller crystal, smaller pores left behine after sublimation

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27
Q

Primary drying

A

where most water content is removed

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28
Q

what is important during freezing drying

A

a constant reduction of the pressure during the all process, to ensure sublimation

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29
Q

How does the reduction of pressure affect the vapor pressure of water?

A

the vapor pressure reduceses as well, leading to a pressure gradient

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30
Q

What’s the importance of the pressure gradient?

A

it eases the sublimation of the water crystal. Leaving behind a porous structure

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31
Q

what is the principle of the freezing drying technique?

A

the vapour pressure of frozen water is significant, which allows the sublimation of water to vapour and it’s removed

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32
Q

how is the pressure gradient maintain?

A

through continuoulsy removal of the vapour that sublimes

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33
Q

what have to be done inoder to maintain the pressure gradient?

A

the temperature and the pressure of the condenser should be lower than the drying chamber

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34
Q

when is th end of primary drying step?

A

when the pressure equalizes on either side of the closed valve marking no further vapour movement

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35
Q

what happend at the secondary drying step

A

the temp. slwoly raosed allowing the loss of the remaining water by diffusion and desorption

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36
Q

the temperature rise is accompanied with?

A

a decrease in pressure to facilitete the diffusion of the after vapor

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37
Q

what is spray drying?

A

is the transformation of fluid feed into dried solid particles by spaying the liquid into gaseouse hot drying medium

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38
Q

three steps of spray drying

A

atomisation, drying and collection of dried products

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39
Q

what is the process of spray drying

A

adiabetic process

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40
Q

what is an adiabetic processs?

A

where th enthalpy of the whole system remains the same at all time

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41
Q

the enthalpy is?

A

the exchanged between the drying air and the vapour released

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42
Q

meaning of atomisation

A

it is the dispersion with the size reduction of the feed to be dried

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43
Q

results of atomisation

A

an increase in the total surface area facilitating prompt evaporation of the liquid

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44
Q

Spray drying: why is the atomisation important?

A

it could affect the pysicochemical properties and morphology of the product

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45
Q

types of nebuliser

A

rotary, pneumatic and hydraulic atomizer

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46
Q

rotary atomizer

A

is in the shape of a disc that revolves, centrigual force atomies the feed

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47
Q

Single fluid nozzle?

A

the liquid is pumped at higher pressure through a small opening causing the liquid to move in a spiral motion in the swirl chamber

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48
Q

what is the results of the motion in the swirl chamber of the rotary nozzle?

A

it results in the breaking of the liquid film into tiny droplets as it leaves the nozzle

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49
Q

what is the pneumatic nozzle?

A

as multi-fluid nozzles that operate by pumping the liquid feed into a stream of compressed gas carrier

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50
Q

what does the resulting friction from the stream of compressed gas carrier caused?

A

it causes the disintegration of the liquid

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51
Q

spray drying: what happend after atomization?

A

the liquid then enters the drying chamber where a stream of hot air/ gas dries out the moisture from the particles

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52
Q

what are the direction of the air/gas flow?

A

co-current, counter current and the combination of both

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53
Q

co-current direction

A

droplet come in contact with the hottest air

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54
Q

what is ad of the co-current direction?

A

it results in faster reaching of the locking point for the droplet

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55
Q

what’s the results of the faster drying?

A

it results to a prompt crust formation

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56
Q

why a crust formation?

A

Because the remaining moisture is release as the particle falls through the chamber

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57
Q

Spray drying, co current air flow what is the results in a spiral movement

A

it increase the residence time of the droplets in the chamber till they are completely dry.

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58
Q

counter current

A

the temp comes in contect with the droplets as it exits the nozzels it lower

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59
Q

what’s the results of the decrease of temp in the counter current air flow?

A

it results in a delay in the locking point and the shrinkage of the droplets before drying

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60
Q

what is one of the draw backs of the counter flow?

A

the hottest air hit the driest particle first which increase the thermal load on the particles in the chamber

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61
Q

how are the particles from the co-current

A

it results in larger particles than thoes from counter current

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62
Q

how does particles in the counter current dried?

A

it dry slowly meeting the hottest air at the end of the flow

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63
Q

spray dryer: step after drying?

A

dried particles now are vacuumed to the cyclone separator

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64
Q

what’s the function of the cyclone separator?

A

it is responsible for the separation of fines

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65
Q

how are the fines separated?

A

through the sprial air flow in the cyclone the fines centrifuge out with the air flow while the larger particle are weighed down to the bottom for collection

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66
Q

what affects the size of the particles to be seperated?

A

through the dimensions of the cyclone and the rate of air flow

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67
Q

what are the parameters in spray drying?

A

outlet temp. , particle size, yield, final humidity product

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68
Q

how does the increase of the inet temp influence the parameter?

A

it increase the outlet temperature, particle size and yield

final humidity of the product decreases

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69
Q

increase in pumpt rate

A

increase of the particle size and product final humidty, decrease of the outlet air temperature

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70
Q

increase of the aspirator rate?

A

increase of the outlet tem, final humity and yield

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71
Q

increase of spray air flow

A

decresse of the outlet temp, the particle size

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72
Q

why do freezing drying results in faster dissolution?

A

due to more pores structure, which are formed from the gaps left behind after the sublimation of water crystals

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73
Q

spray drying products?

A

faster drying due to smaller size, allowing higher surface area for contact with the dissolving

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74
Q

what is the composition of tray dryer?

A

embedded iron or steel with a high insulted chamber where stainless stell trays are positioned on transferable trolleys.

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75
Q

how does the dry air passed through the material

A

through a controlled flow way in a circulation form

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76
Q

tray dryer: on what does the effectivness depends?

A

on circulation and on the supply of regular air

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77
Q

what is important during the tray drying process?

A

to keep a constant temp and proper airflow throughout the whole process

78
Q

what will be the effect of a non- proper flow during tray drying?

A

the deficient flow of air can impacht on uniform drying of the material

79
Q

why is vacuum applied?

A

when drying thermally-sensitive products

80
Q

what does the vacuum does?

A

so that the evaporated water can get into gas process faster through vacuum pump at a lower temp.

81
Q

what can be achieve with the FBD?

A

a homogenous drying of particles

82
Q

what’s the disad von FBD?

A

it time and coste intensive, but the temp. can be maintained

83
Q

why can a better drying process be achieve with FBD

A

due to compulsory airflow velcoity and temp. a thermodynamic equilibrium is guaranteed

84
Q

what’s the first step of FBD

A

the hot air passes through the bed of wet particles with high pressure

85
Q

2 steps in FBD?

A

the steam of air comes through the bottom, wich is the fluidized state

86
Q

how is the vaporized liquid carried out

A

through drying gases

87
Q

what’s the ad von the fluidized state?

A

one has a continuous fluidization , which allows individual solid particles to be freely suspened in the upward flowing air

88
Q

why does the airspeed increases?

A

due to the corrresponding to the underlying gravitational forces

89
Q

what influences most the drying process

A

the choose of the inlet temp.

90
Q

what is the effect of a high inlet air?

A

a crust can be form

91
Q

how does the moisture evaporates?

A

from the surface of the granules

92
Q

how are the evaporated moisture carried out?

A

through capillaries from the innermost granules of the surface

93
Q

what does crust formation means?

A

the innermost part of the particles remain wet

94
Q

what are the four different method to determine the drying kinetics

A

periodic sampling/weighting
continuous weighting
intermitten weighting
indirect methods

95
Q

periodic sampling

A

during the drying process samples are taken at different times intervals

reused of the samples

96
Q

continuous weighing

A

the weight of the sample is continous measured, high noise in the measurement

97
Q

intermittent weighing

A

the airstream is cut off when the sample is measured

98
Q

indirect methods

A

the air humidity coming out of the chamber can be measured

99
Q

how can you plot the drying process (learn how to draw them)

A

the amount of water against time

drying rate against the time

100
Q

was is the drying rate

A

the amount of water removed per kg of dry air per time

101
Q

what is the rate-moisture plot

A

a combination of the drying curve an dthe drying rate curve

102
Q

the last plot is?

A

a temperature-time plot

103
Q

when can the temp-time plot be obtained?

A

when the product temp in the drying chamber is plotted gainst time

104
Q

how is the moisture content measured

A

using a moisture analyzer

105
Q

how does the moisture analyzer works?

A

it uses a thermogravimetric method to determine the mositure content of the sample

106
Q

what is the process of the moisture analyzer

A

the sample of an initial weight is insert inside the instrument and by applying heat, the sample will loss by mass by drying

107
Q

how is the end of the measurement set

A

set by time or by % of variation weight in certain period of time

108
Q

what are pellets?

A

special kind of granules, part of the multiparticulate dosage forms

109
Q

what’s the size of pharmaceutical pellets?

A

between 0.2 and 2 mm

110
Q

use of pellets?

A

compression process, encapsulated and in clinical studies

111
Q

what is the main applications of pellets?

A

for modified or controlled release systems

112
Q

why pellets for modified release?

A

due to their spherical shape, good for coating processess

113
Q

what are the ad von pellets modified relases dosage forms

A

less dose spread, easily disperse at the GI (leass irritation)
less risk of adverse effects
less plasma fluctuation

114
Q

Manufacturing process of pellets?

A

Extrusion-spheronization process

115
Q

what’s are some drawbacks of the Es process

A

several complex unit operations

116
Q

what are the steps in ES?

A

combination, extrusion, spheronization and drying

117
Q

combination?

A

mixing of the powder with liquid in certain L/S

118
Q

what are the equipment used for the combination process

A

HSM. planetary and paddle mixers

119
Q

what’s the aim of the combination steps

A

to obtained a homogeneous wet mass

120
Q

what are properties of the wet mass

A

cohesive plastic mass with self-lubricating peoperties

121
Q

what should be wet mass not be

A

non-adhesive

122
Q

what’s the aim of the Extrusion step?

A

to increase the density and form cylindrical extrudate

123
Q

what influences the density and characteristic of the extrudates?

A

the type of the extrusion

124
Q

what’s the function of the diameter?

A

it determine the size of the pellets

125
Q

which pressure is apply on the extrudates?

A

it depends on the length of the die

126
Q

what does the length/radius ratio gives?

A

the density of the extrudates

127
Q

what is a good extrudate?

A

the one with a high density and as well as some cracks

128
Q

why are cracks beneficial?

A

to break into regular particles for futher rounding

129
Q

why should big fractures be avioded?

A

because they could lead to a big portion of fines

130
Q

what are the characteristic for futher speronization?

A

must have mechanical strength to maintain their structure
also brittle to break into uniform lengths equal to their diamter
low friability
induce plasticity

131
Q

why is plasticity imprtant?

A

to be converted into sperical pellets

non-adhesion between pelltes, to prevent agglomeration or sticking

132
Q

spheronisation

A

broken of the extrudates into small pieces and rounded by two firction forces

133
Q

what are the two forces during speronisation

A

particles-particle and particle equipment

134
Q

what is the aids use in pelletization?

A

MCC

135
Q

why is MCC used as aid?

A

because it is brittle enough for the extrudates that can fragment into small particles an dplastic to deformate into spheres

136
Q

on what does the breaking and deformation depends?

A

on the plate type, spheronization time, velocity and the load of the mass

137
Q

rough plate

A

more friction, more mechanical energy to be transfer into kinetic energy

138
Q

low load

A

i leads into non-spherical pellet, not enough material to particle-particle friction forces acts

139
Q

high load

A

the interaction particle-equipment will also be low to achieve disire pellet shape

140
Q

what is the pelletization process

A

a convension of the cylindrical extrudates into spherical pellets

141
Q

drying

A

the final step of ES process, removal of excesses moisture

142
Q

the drying of the pellets takes place in?

A

tray drier of FBD

143
Q

the characterization parameter of the pettels are?

A

shape and size of the pellets

144
Q

why are the two parameters used?

A

to determined the quality of pellets

145
Q

Aspect ratio
know the equation
know to draw the aspect ratio

A

is based on Feret measuremnet which relates the length or maximum feret diamter and the ortho Feret diameter

146
Q

equivalent diameter

A

the area of each pellet which relates the pellet size

147
Q

when are pellets consider as good?

A

AR below 1.1 and D eq lower than 1400µm

148
Q

overwetted mass over dry mass

A

low liquid mass needs higher forces to extrudates, high possibility to fraction into dust due to its dryness

overwetted mass, faciliate th eextrusion

149
Q

what is the downside of overwetted mass?

A

cause of uncontrollable agglomerations, especially at high radial velocity

150
Q

what is another aid to used?

A

bentonite

151
Q

what is athe use of the aid?

A

they are used to retain solvent that is added to the powder

152
Q

the choice of aid depends on what?

A

if the system is moisture sensitive and prefer the absend of water

153
Q

how are the pellets made with MCC

A

they have low tendency to abrasion and a high yiels strength

154
Q

spheronization process

A 
smaller rods
rounded
dumb-bell structures
ellipsoid structure
sperical particles
155
Q

why can one not generalized the impact of the frictions plates on the quality of the pellets

A

because of different parameters such as speed of rotation, moisture content and spheronization time

156
Q

what’s the essence of the rough plates?

A

for a shorter spheronization time, a rough plate could form rounder partciles

157
Q

smooth friction plate?

A

smooth particle

158
Q

what are the most important parameter when chossing the friction plate?

A

spheronization time and the radial velocity

159
Q

what has to be consider with high feed load?

A

it could cause agglomeration of the particles

160
Q

what is granulac?

A

alphe lactoce monohydrate

161
Q

which parameter are infleunce by the radial velocity?

A

AR and Deq, it decreases with high radial velocity

162
Q

why do the AR and Deq decreases with higher radial velocity?

A

it results into higher kinetic energy causing particles to get in contact more often, fasten the abrasion process

163
Q

what is the affect of higher sp. time

A

longer sp. time would lead to better AR and smaller Deq

164
Q

is there any significant infleunce of the friction plate on the quality of the pelletes

A

no differennce in suing the friction plates regarding the aspect ratio

165
Q

rough plates leads to

A

higher Deq, bigger partciles size

166
Q

are the parameter of spe. process indenpend of each other

A

no

167
Q

what is the downside of using MCC as aid?

A

MCC acts as a matrix in which the pellts stays intact even after the API is dissolved

168
Q

what is the operating principle of the IR moisture analyzer

A

thermo-gravimetery, Loss in drying

169
Q

thermo-gravimetry process

A

to assess the mass loss that occurs when heating up a material

170
Q

learn to draw the LOD cuve of tray dryer and FBD

A

do you know

171
Q

why is the adiabatic process short in tray drying

A

because of the satuartion of the air, close to the saturation line in the mollier diagram

172
Q

partciles in tray dryer and FBD are

A

TD- static, FBD fluidizing

173
Q

what’s the effect of the several layers during drying in the TD

A

limitation of diffusion of the air to the deep layers

inhomogeneous and inefficient

174
Q

what are the process of drying in a FBD?

A

constant rate period

falling drying

175
Q

constant rate period

A

stage where solvent is removed from the saturated surface of the solid particles

176
Q

which kinetics follows the constant rate period

A

zero order kinetics

177
Q

where is the critial moisture content point?

A

no significant change of the LoD

178
Q

falling drying

A

smaller slope, slower drying process

179
Q

why slower drying during falling drying

A

drying depends on diffucion

180
Q

kinetic of the falling drying

A

first order kinetic

181
Q

defination of relative humidity?

A

(partial vapour pressure /saturated vapour pressure )* 100

the amount of moisture the air actually holds and how much it can hold at that temp

182
Q

dew point

A

when the moisture in the air cannot be hold back and it depends on the actual amount of moisture in the air

183
Q

on what does the water qulity depends?

A

on the bounding capacity of water

184
Q

high bounding capacity means?

A

lower is the removal of the water

185
Q

low bounding effect

A

free water

186
Q

example of water with high and low bounding capacity?

A

high: hydration, adsorbed, hydrate water
low: adhesive, capillary and swelling water

187
Q

what can be used to determine the water quality?

A

relative humidity

188
Q

draw the sorption isotherm diagram and define it

A

it is the relation between the moisture content of a sample and the water activity

189
Q

convection
conduction
heat radiation

A

convection: heat transfer by moving molecules of a gas or a liquid
conduction: takes place in a solid
radiation: heat from a warm body through empty or ga filled space

190
Q

absorb body in heat radiation

A

back ( adsorb all hear rays) and white bodyies (reflect)

191
Q

name example of drying method which are convection and conduction

A

convection: FBD, Spray and tray dryer
conduction: freez dryer and vaccum drying oven

192
Q

the mollier H-x diagram is

A

relationship between the raltive humidity, enthalpy, absolute humdity and temperature

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