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Topic: Theory and factors affecting filtration, discuss

diferent types of filters used in pharmaceutical

Md. Tanvir IslamId:123-29-417

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Content• Introduction• Filtration • Factors affecting filtration• Rate of filtration• Factors affecting rate of filtration• Theory of filtration• Mechanism of filteration• Filtering media• Factors affect the selection of filtering media• Different types of filters

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• Introduction: Although filters don’t play as glamorous a role as the actual machines or operational concepts, industrial filters are an important part of any manufacturing process.

• Industrial filters are used in several different industries, including pharmaceutical, food and beverage, cosmetic and chemical. Without efficient filters, the end products would be of poor quality and the safety element wouldn’t be there.

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Filtration

• Is a process of separating liquids form solids by means of a porous medium.

• Is a unit operation .• The porous medium used for the purpose of

the filtration is called the filter • The fluid which has passes through the filter

is called the filtrate. • The particles larger than the pores of the

filter are retained on the surface of the filter medium

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• The ability of the filter- medium to eliminate solid particles from a fluid is called retention.

• Fluids are of two types o Liquids - Gases • Suspension of solids in liquid is often referred to

as slurry.• During filtration, the suspended solid materials

build up a filter bed on the filter medium and may resist filtration, this is referred to as filter cake.

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Factors affecting filtration

• Properties of the liquid• Density, viscosity, corrosiveness etc. • Properties of the solid Particle shape, particle size, particle

size distribution, compressibility of solid• Proportion of solids in the slurry.• Objective of filtration Whether to collect solid or liquid

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• Rate of filtration• Filter slurry as quickly as possible • Rate of flow through the capillaries of the

filter medium and filter cake • Factors affecting rate of filtration • Area of filter surface. • Resistance of the filter medium and filter

cake. • Viscosity of the filtrate• The pressure difference across the filter

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Theory of filtration• The flow of liquid through a filter follows the basic rules that govern

flow of any liquid offering resistance. The rate of flow may be expressed as Rate = driving force / resistance

.The rate may be expressed as volume per unit time and the driving force has a pressure differential. Resistance is not constant since it increases as solids are deposited on the filter medium.

The rate concept could be stated as: where; V= volume of filtrate, T = time, A= filter area, P= total pressure drop through cake and filter medium. m = filtrate viscosity, a = average specific cake resistance W= weight of dry cake solid R= resistance of filter medium and filter.

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Any convenient units may be used in this equation, since inconsistencies are absorbed in the cake and filter resistances. The practical limitation of this equation is that the constants must be determined on the actual slurry being handled.

It is convenient to summarize the theoretic relationship as (area of filter) x (pressure difference)Rate of Filtration = (viscosity) x (resistance of cake and filter)

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Mechanisms of filtration

• Straining: – Simplest filtration process. – Particles are bigger than the pores. – Particles retain on the filter

• Impingement: – Occurs when the particles moving along the liquid strike on object and where

some will follow the stream lines and some will be collected / re-entrained • Entanglement:

– The filter medium having a porous felt / a cloth with a nap – The particles get entangled in the mass of fibers.

• Attractive forces: – The particles are attracted on to the filtrate medium.

_ Effected by straining mechanism

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• Filtering media:• Selection of suitable filtering media is depend on the purpose of

filtration and quantity to be filtered• Ideal filter medium should be• inert • able to confirm the maximum passage of liquid while retaining

the solid • able to withstand against the filtration pressure • Factors affect the selection of filtering media • Acceptable resistance to mechanical wear • Good removal competence / ability to discharge cake easily and

effectively • Resistance to chemical attack • Minimum cost

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Different types of filters:

Bag filter:Filter Bags are made of felt material, which has the advantage of providing three dimensional filter media and offers both, a surface and depth filtration effect.

• Filter Bags are available in different types of filter media in different ratings. Polypropylene filter bag offers a broad range of chemical compatibility and is suitable for many applications

• Bag filter is mainly used for the preparation of adhesives, fruit juices, petroleum products and high viscosity fluids

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Fig..1. Bag filter

Fig..1. Bag filter

Cartidge filters:

Bag filters:

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Cartidge filters:

• Cartridge filters are the machines which is used in filtration purpose by uses the filtration technology of removing solid matter and suspended impurities from a fluid stream by passing it through a variety micro porous filters, ultrafiltration units, green sand cartridge filters, activated carbon cartridge filters, diatomaceous earth and multimedia cartridge filtersCartidge filters:

• Cartridge filters are the machines which is used in filtration purpose by uses the filtration technology of removing solid matter and suspended impurities from a fluid stream by passing it through a variety micro porous filters, ultrafiltration units, green sand cartridge filters, activated carbon cartridge filters, diatomaceous earth and multimedia cartridge filters

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Cartidge filters

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Air filters

• Air filters are an important part of most industrial processes, as they remove dust, dirt and other particles from the air. Most air filters consist of a mesh that catches the particles when air is forced through.

• If the air must be protected from gases and odors as well as particles, a high efficiency particulate air filter is used.

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HEPA filter

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Gas filters

Gas filters are a type of industrial filters that helps to remove contaminants or particulates from a dry or liquid gas stream. Depending on the situation, the contaminants may be solid or liquid.

Some of the different elements and accessories for gas filters include:

• Gas filter separators• Coalescers • Gas scrubbers

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gas filter

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Strainers

• Strainers often become part of the manufacturing process when the process contains solids that are too large to be caught up in other types of filter media. Strainers consist of baskets that can be removed and cleaned out regularly to prevent them from being bogged down.

• Some strainers can be cleaned without interrupting the system, while others will cause some disruption each time they are cleaned.

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strainer