CLARIFICATION Flashcards
Used to describe processes that involve
the removal or separation of a solid from a
fluid, or a fluid from another fluid
Clarification
encompasses both liquids
and gases
fluid
Clarification can be achieved using either ___________ or ________ techniques
filtration or
centrifugation
2 main reasons for clarification
- To remove unwanted solid particles from
either a liquid product or from air - To collect the solid as the product itself (eg
following crystallization)
Types of Clarification
- Filtration
- Centrifugation
Types of Filtration
- Solid/fluid filtration (solid/liquid filtration,
solid/gas filtration) - Fluid/fluid filtration
Separation of an insoluble solid from a fluid by
means of a porous medium that retains the solid
but allows the fluid to pass
Solid/Fluid Filtration
Most common type of filtration encountered
during the manufacture of pharmaceutical
products
Solid/Fluid Filtration
Solid/Fluid Filtration is Subdivided into 2 types:
solid/liquid filtration and
solid/gas filtration
Removal of immiscible oils or liquid by
passing them through an appropriate filter
Fluid/Fluid Filtration
Mechanisms of Filtration
- Straining/Sieving
- Impingement
- Attractive forces
- Autofiltration
f the pores in the filter medium through which
the fluid is flowing are smaller than the material
that is required to be removed, the material will
be retained
Straining/Sieving
Filtration occurs on the surface of the filter in this
case, and therefore the filter can be very thin.
Straining/Sieving
Filter media of this type is referred to
MEMBRANE FILTER
Straining/Sieving
Use of membrane filters include the removal of
bacteria and fibers from parenteral preparations
Straining/Sieving
As flowing fluid approaches and passes
an object, doe example a filter fiber, the
fluid flow pattern is disturbed.
Impingement
Suspended
solids, may, however, have sufficient
momentum that they do not follow the fluid
path but impinge on the filter fiber and are
retained, owing to attractive forces
between particles and the fiber
Impingement
Electrostatic and other surface forces may
exert sufficient force on the particles to
attract and retain them on the filter
medium
Attractive Forces
Air can be freed from dust particles is an
electrostatic precipitator by passing the air
between highly charged surfaces, which
attract the dust particles
Attractive Forces
Describe the situation when filtered
material ( termed as filter cake) acts as its
own filter medium.
Autofiltration
Mechanism is used by metafilter
Autofiltration
Factors affecting the rate of
filtration
- Area available for filtration-
Pressure difference across the filter bed - Viscosity of the fluid passing through the
filter - Thickness of the filter medium and any
deposited cake
Methods used to increase
filtration rate
- Increase the area available for filtration
- Increase the pressure difference across
the filter cake - Decrease the filtrate viscosity
- Decrease the thickness of the filter cake
- Increase the permeability of the cake
Filtration Equipment
n Used for filtering liquids
n Filtering gases (mainly air) are also
available
n Equipment selection
Ideally the equipment chosen should allow
a ____________ to minimize production
costs, be cheap to buy and run, be easily
cleaned and resistant to corrosion, and be
capable of filtering large volumes of
products before the filter needs stripping
down for cleaning or replacing
fast filtration rate
Product-related factors that should
be considered when selecting a filter
for a particular process
Chemical nature of the products
n Volume to be filtered and the filtration rate
required
n Operating pressure needed
n Amount of material to be removed
n Degree of filtration required
n Product viscosity and filtration temperature
Filters for liquid products may be classified
by the method used to drive the filtrate
through the filter medium
Industrial Filtration Equipment
Filters can be organized into 3 classes:
Gravity, vacuum and pressure filters
Filters that rely solely on gravity only
generate _________ operating pressures, and
therefore, use on a large scale is limited
low
use on a large scale is limited
Gravity Filters
Simple and cheap, and are frequently
used in laboratory, where volumes are
small and a low filtration rate is relatively
unimportant
Gravity Filters
Rotary vacuum filters
Vacuum Filters
Continuous in operation and has a system
for removing the cake so that it can be
rum for long periods handling
concentrated slurries
Vacuum Filters
Automatic and continuous in operation, so that
labor costs are very low
Rotary Vacuum
Filters
Filter has a large capacity
Rotary Vacuum
Filters
Variation of the speed of rotation enables the
cake thickness to be controlled, and for solids
that form an impenetrable cake the thickness
may be limited to less than 5mm
Rotary Vacuum
Filters
(Rotary Vacuum
Filters) On the other
hand, if the solids are coarse, forming a ___________, the thickness may be 100 mm or more
porous
Complex piece of equipment with many moving parts
and is very expensive
Rotary filters
ancillary equipment such as vacuum pumps, slurry
receivers and traps, slurry pumps and agitators are
required
Rotary filters
Cake tends to crack because of the air drawn through by
the vacuum system, so that washing and drying are not
efficient
Rotary filters
Being a vacuum filter, pressure difference is limited to 1
bar and hot filtrates may boi
Rotary filters
suitable only for straightforward slurries,
being less satisfactory if the solids form an impermeable
cake or will not separate cleanly from the cloth
Rotary filters
Most suitable for continuous operation on a
large quantities of slurry, especially of the slurry
contains considerable amounts of solids, that is,
in the range of 15-30%
Pressure Filters
Collection of calcium carbonate, magnesium
carbonate and starch, and the separation of the
mycelia from the fermentation liquor in the
manufacture of antibiotics
Pressure Filters
Feed the products to the filter at a
pressure greater than that which would
arise from gravity alone
Pressure Filters
Most common type of filter used on the
processing of pharmaceutical products
Pressure Filters
Metafilters, cartridge filters, cross-flow
microfiltration
Pressure Filters
Consists of a grooved drainage rod on which is
packed a series of metal rings. These rings,
usually of stainless steel, are about 15 mm
inside diameter, 22 mm outside diameter and
0.8 mm in thickness, with a number of
semicircular projections on one surface
Metafilters
Strainer for coarse particles, but for finer
particles abed of a suitable material is first build
up over the rings
Metafilters
The pack of rings, serves
essentially as a base on which the true filter
medium is supported
Metafilters
Possesses considerable strength and high
pressures can be used with no danger of
bursting
Metafilters
As there is no filter medium as such, the running
costs are low and it is very economica
Metafilters
Can be made from materials (such as stainless
steel) that can provide excellent resistance to
corrosion and avoid contamination of the
product
Metafilters
By selecting of a suitable grade of material to
form the filter bed it is possible to remove very
fine particles; in fact, it is possible to sterilize a
liquid using this filter
Metafilters
Used almost exclusively for clarifying
liquids where contaminant level is low
Metafilters
The strength of the metafilter permits the
use of high pressures (up to 15 bar),
making the method suitable for __________
viscous
liquid
Clarifying syrups, injection solutions,
insulin liquors
Metafilters
Commonly used in the preparation of pharmaceutical
products, as they possess a very large filtration area in a
small unit and are easy and relatively cheap to operate
Cartridge Filters
Consist of cylindrical cartridge containing highly pleated
material (PTFE or nylon) or string wound material
(wound like a ball of string)
Cartridge Filters
Cartridge then fits in a metal supporting cylinder and the
product is pumped under pressure into one end of the
cylinder surrounding the filter cartridge.
Cartridge Filters
The filtrate (in Cartridge Filters) is
forced through the filter cartridge from the __________________, from where it exits through the
other end of the support cylinder
periphery to
the inner hollow core
Disposable and good for applications where there is low
contamination levels
Cartridge Filters
Cross flow microfiltration’s membrane consists of _________, is laid down within
fiber which forms a rigid porous outer support
polysulphone,
acrylonitrile or polyamide
Lumen of each fiber is small, typically 1-2
micrometer – but a large number of them can be
contained in a surrounding shell to form a
cartridge which have an effective filtration area
of over 2 m2
Cross-Flow Microfiltration
Used for fractionation of biological products by
first using a filter of pore size sufficient to let all
the wanted molecules through, and then passing
the permeate through a filter which will retain the
required molecules while passing smaller
unwanted molecules
Cross-Flow Microfiltration
Blood plasma can be processed to remove
alcohol and water and prepare concentrated
purified water.
Cross-Flow Microfiltration
The process has been suggested
for the recovery of antibiotics from fermentation
media
Cross-Flow Microfiltration
_________ can be used either to provide
the driving force for the filtration process or to
replace the gravitational force in sedimentation
processes
Centrifugal force
used in the laboratory to
separate solid material from liquid, the solid
typically forming a plug at the bottom of the test
tube at the end of the process
Centrifuges
Perforated basket centrifuges and tubular bowl
centrifuges
Centrifugation
