Industrial Filters

7/21/2019 Industrial Filters

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Assignment

Submitted by:

Hifza Inam

Mirza Muhammad Jamal

Qasim Ali

Zarrar Salahuddin

Che-05

Particulate Technology



Industrial Filters

Gravity FiltersGravity filters are commonly constructed of painted carbon steel; however, systems can be

designed from corrosion-resistant materials such as stainless steel or aluminum. Gravity

filters allow for design flexibility to help fit into tight footprint requirements when needed.

Gravity filters internals can be customized based on applications and customer’s

preferences. Various options are available for underdrain and over drain design.

Rapid Sand FilterThe rapid sand filter differs from the slow sand filter in

a variety of ways, the most important of which are the

much greater filtration rate and the ability to clean

automatically using backwashing. The mechanism of

particle removal also differs in the two types of filters

- rapid sand filters do not use biological filtration and

depend primarily on adsorption and some straining.

The filter is contained within a filter box, usually made

of concrete. Inside the filter box are layers of filter

media (sand, anthracite, etc.) and gravel. Below the

gravel, a network of pipes makes up the under-drain which collects the filtered water and

evenly distributes the backwash water. Backwash troughs help distribute the influent water

and are also used in backwashing.

Most rapid sand filters contain a controller, or filter control system, which regulates flow

rates of water through the filter. Other parts, such as valves, a loss of head gauge, surface

washers, and a backwash pump, are used while cleaning the filter.

Operation

Operation of a rapid sand filter during filtration is similar to operation of a slow sand filter.

The influent flows down through the sand and support gravel and is captured by the under-

drain. However, the influent water in a rapid sand filter is already relatively clear due to

coagulation/flocculation and sedimentation, so rapid sand filters operate much more

quickly than slow sand filters.

Applications

Most commonly used type of filter for surface water treatment.





Automatic Gravity FiltersThe automatic gravity filter automatically

treats drinking, process and cooling water.

The effluent is pumped into the feed-tank.

The water then flows, solely by gravity,

through the filter bed into the clear-water-

chamber, and eventually up a riser pipe to

the outlet.

Dirt particles are held back in the filter

bed. The more dirt is held back in the filter

bed, the higher the flow resistance, and

therefore, the counter pressure rises. This

causes the water level in the discharge

pipe to rise. The water starts to flow as soon as the highest point of the pipe is reached. The

whole backflow-water-chamber is sucked empty due to the siphon effect. The turbulence in

the sand bed, needed to wash out the dirt particles, is created by the high backwash

velocity. At the end of the backwash process, the flow rate slows down and the sand settles

back to a smooth bed.

ApplicationsThe automatic gravity filter is used for the filtration of drinking and process water. The filter

allows a separation of very fine particles. Additionally, chemicals (e.g. precipitation,

flocculation, or sanitization agents) can be dosed prior to the filtration process.

Vacuum Filters Vacuum filtration is a technique for separating a solid product from a solvent or liquid

reaction mixture. In vacuum filters, the driving force for filtration results from the

application of suction on the filtrate side of the medium. Although the theoretical pressuredrop available for vacuum filtration is 100 kPa, =1 Kg/cm2 in practice it is often limited to 70

or 80 kPa or even less.

In applications where the fraction of fine particles in the solids of the feed slurry is low, a

simple and relatively cheap vacuum filter can yield cakes with moisture contents

comparable to those discharged by pressure filters. Vacuum filters are available in a variety

of types, and are usually classified as either batch-operated or continuous.



Rotary vacuum filter drum

The Rotary Vacuum Drum Filter belongs to the bottom feed group and is one of the oldest

filters applied to the chemical process industry.

The filter consists of the following subassemblies:

Drum: The drum is supported by a large diameter trunion on the valve end and a

bearing on the drive end. The drum face is divided into circumferential sectors eachforming a separate vacuum cell.

Valve: A valve with a bridge setting controls the sequence of the cycle so that each

sector is subjected to vacuum, blow and a dead zone. When a sector enters

submergence vacuum commences and continues through washing, if required, to a

point that it is cut-off and blow takes place to assist in discharging the cake.

Internal Piping: The trail pipes are always connected to the outer row and have a bigger

diameter than the lead pipes that are connected to the inner row. The reason for this

arrangement is that the trail pipes handle more liquid than the lead pipes so require a

bigger cross section to avoid vacuum losses.

Filter Cloth: The filter cloth retains the cake and is fastened to the drum face by inserting

special caulking ropes into the grooved division strips.

The Cake Discharge Mechanism: The cake discharge mechanism that can be either a

scraper, belt, roll and in very rare cases a string discharge.

The Drum Speed Variation: The drum filter has a drive with a variable speed that rotates

the drum at cycle times that normally range from 1 to 10 MPR.

Agitator: An agitator keeps gently the slurry in suspension and reciprocates between the

drum face and tank bottom at 16 or so CPM.



Tank: The tank that houses the drum and agitator has baffled slurry feed connections, an

adjustable overflow box to set a desired drum submergence and a drain connection.

Disc Filter The disc filter consists of several discs, up to 15 in the larger machines, each made up from

sectors which are clamped together to form the disc. The sectors are ribbed towards the

neck and designed for a high capacity drainage rate. One of the main features is that the

required floor space taken up by disc filters is minimal and the cost per m2 of filtration area

is the lowest when compared to other vacuum filters.

The filter consists of the following subassemblies:

Discs and sectors which may be made in injection

moulded polypropylene, metal or special redwood.

A centre barrel supported by the main bearings

and consisting of piped or trapezoidal filtrate

passages. The sectors are attached to the barrel

through "o" ring sealed connections in a number

equal to the number of disc sectors.

An agitator with paddles that are positioned

between the discs and far enough not to interfere

with the forming cake.

A tank which, on its discharge side, has separated slurry compartments for the discs

and discharge chutes for the blown-off cake

Two cake discharge blades on both sides of each disc are suspended from a frame

mounted on the tank and serve to deflect and guide the cake to the discharge

chutes.

An overflow trough that spans across the entire tank length and ensures full

submergence of the sectors in the cake formation zone since an exposed sector in

the 6 o'clock position will cause immediate loss of vacuum.

Applications

Disc Filters are generally used in heavy duty applications such as the dewatering of iron ore taconite,

hematite, coal, aluminum hydrate, copper concentrate, pyrite flotation concentrates and other

beneficiation processes.

Belt Filters

The belt filter (sometimes called a belt press filter, or

belt filter press) is an industrial machine, used for

solid/liquid separation processes. The process

of filtration is primarily obtained by passing a pair



of filtering cloths and belts through a system of rollers. The system takes

a sludge or slurry as a feed, and separates it into a filtrate and a solid cake.

Applications

Mainly used for dewatering of sludge and slurry and juice extraction from apples,

pears and other fruits, as well as grapes for winemaking, etc.

used both municipally and industrially in a range of areas including

urban sewage and wastewater treatment, metallurgy and mining, steel plants, coal

plants, breweries, dyeing, tanneries, as well as chemical and paper factories.

The applications of a belt filter are only limited to the sludge, slurry or mashed fruit

that it can process. The sludge from municipal use include raw, anaerobically

digested and aerobically digested sludge, alum sludge, lime softening sludge, and

river water silt.

Pressure filters Pressure filters are those filters in which the liquid feed is fed into the filter medium at a

pressure higher than the pressure at the discharge end. This is also one way of improving

the filtration rate as we see by the following equation:

Here, ΔP is the pressure drop, so whereas dV/dt is the rate at which filtrate passes through

the filter medium. Thus, we see that rate of filtration is directly proportional to pressure

drop, and pressure drop can be increased by increasing pressure of feed side.

Plate and Frame Filter Press

This type of filter consists of plates and frames arranged

alternately and supported on a pair of rails. The plates

have a ribbed surface and the edges stand slightly proud

and are carefully machined. The hollow frame is

separated from the plate by the filter cloth. A chamber is

therefore formed between each pair of successive plates.

The slurry may be fed to the press through the

continuous channel formed by the holes in the corners ofthe plates and frames; in which case it is necessary to cut



corresponding holes in the cloths which themselves act as gaskets.

Pressure leaf filtersA pressure leaf filter features a pressure vessel in which are located

one or more filter elements or leaves of circular or rectangular

construction. The filter media may be in the form of a synthetic

fibre or other fabrics, or metallic mesh. The material to be filtered is

fed into the vessel under pressure, and separation takes place with

the solids being deposited on the leaf surface, and the liquid passing

through the drainage system and out of the filter. Where

particularly fine solids must be removed, a layer of pre-coat

material may be deposited on the leaves prior to filtration, using

diatomaceous earth, Perlite, or other suitable pre-coat materials.

Cartridge Filter

One particular design of pressure filter is

the cartridge filter, which employs a filter

bed deposited on a base of rings mounted

on a fluted rod, and is extensively used

for clarifying liquids containing small

quantities of very fine suspended solids.

The rings are accurately pressed fromsheet metal of very uniform thickness.

The bed is formed by feeding a dilute

suspension of material, to the filter

usually a form of kieselguhr, which is

strained by the packs to form a bed about

3 mm thick. During filtration, the solids

build up mainly on the surface and do not generally penetrate more than 0.5 mm into the

bed. The filtrate passes between the discs and leaves through the fluted drainage rod, and

operation is continued until the resistance becomes too high.

Centrifugal Filters

Basket Centrifuge Basket centrifuges are often called centrifugal filters or

clarifiers. They have a perforated wall and cylindrical tubular

rotor. In many cases the outer wall of a basket centrifugeconsists of a fine mesh screen or a series of screens with the



finer mesh screens supported by the heavier coarse screen, which in turn is supported by

the bowl. The liquid passes through the screen, and the particles too large to pass through

the screen are deposited.

Applications

The basket centrifuge is employed in the manufacture of cane sugar, in the home and in

laundries for the rapid drying of clothes, and in the washing and drying of many kinds of

crystals and fibrous materials, etc.

Peeler Centrifuge

The peeler centrifuge is a device

that performs by rotating filtration

basket in an axis. A centrifuge

follows on the principle of

centrifugal force to separate solids

from liquids by density difference.

High rotation speed provides high

centrifugal force that allows the

suspended solid in feed to settle on

the inner surface of basket, also washing and washing processes at the same rotational

speed and in same centrifuge vessel. There are three kinds of centrifuge, horizontal, vertical

peeler centrifuge and siphon peeler centrifuge.

Applications

Fertilisers

Pharmaceutical

Plastics

Food including artificial sweetener and modified starch

Pusher Centrifuge

A pusher centrifuge is a type of filtration

technique that offers continuous operation to

de-water and wash materials such as relatively

in-compressible feed solids, free-draining

crystalline, polymers and fibrous substances. It

consists of a constant speed rotor and is fixed

to one of several baskets. This assembly is

applied with centrifugal force that is generated

http://en.wikipedia.org/wiki/Polymers

http://en.wikipedia.org/wiki/Rotor_%28electric%29

http://en.wikipedia.org/wiki/Centrifugal_force

http://en.wikipedia.org/wiki/Centrifugal_force

http://en.wikipedia.org/wiki/Rotor_%28electric%29

http://en.wikipedia.org/wiki/Polymers



mechanically for smaller units and hydraulically for larger units to enable separation.

A suspension feed enters the process to undergo pre-acceleration and distribution. The

subsequent processes involve main filtration and intermediate de-watering, after which the

main filtrate is collected. Wash liquid enters the washing step and final de-watering follows.

Wash filtrate is extracted from these two stages. The final step involves discharge of solidswhich are then collected as the finished product. These process steps take place

simultaneously in different parts of the centrifuge.

Applications

Pusher centrifuges can be used for a variety of applications. They were typically used in

inorganic industries and later, extensively in chemical industries such as organic

intermediates, plastics, food processing, and rocket fuels.

http://en.wikipedia.org/wiki/Centrifuge

http://en.wikipedia.org/wiki/Inorganic

http://en.wikipedia.org/wiki/Rocket_fuels

http://en.wikipedia.org/wiki/Rocket_fuels

http://en.wikipedia.org/wiki/Inorganic

http://en.wikipedia.org/wiki/Centrifuge

Documents

Industrial Filters