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Rotary Drum Vacuum Filter Unit operation report Group (1( 3/30/2011

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Faculty of Engineering

Chemical Engineering Department

Cairo University

Rotary Drum Vacuum Filter

Unit operation report

Submitted to: Dr/ Ahmed Sherief

By: Group Hussein Taha

Bn Sec name

1 1 Ebthal Hamed

2 1 Ebthal Mohamed

3 1 Ibrahim Nasser

4 1 Ahmed Ibrahim

5 1 Ahmed Ashraf iu

6 1 Ahmed Gaber

7 1 Ahmed Khalid

9 1 Ahmed zakria

10 1 Ahmed Safi

Date: 30/3/2011

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Table of content

Title Page

Abstract III

1. Introduction 1

2. Principal and theory of

operation

2.1 General theory

2.2 Drum operation

2.3 Handling of cake

1

1

1

1

2

3. Mechanical parts

3.1Drum

3.1.1Drum deck

3.1.2 Drum speed variation

3.2 Agitator

3.3 Filter valve

3.3.1Duty of the bridges

3.4 Discharge system

3.4.1 knife discharge

3.4.2string discharge

3.4.3 cloth belt discharge

3.4.4 roll discharge

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3

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3

3

4

5

6

6

6

7

7

4. Design equations

4.1required area of drum

4.2power required

4.3 design of air suction rate

by vacuum pump

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8

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5. Cost 9

6. Manufacturers 10

7. Summary 11

References 12

III

Abstract

This report is concerned about the rotary drum vacuum filter, we will talk about its theory of

work, principle, mechanical parts, design equations, cost and how to calculate it and its

famous manufacturers

Rotary drum vacuum filter is a solid liquid filtration equipment depending on using vacuum

to suck liquid a cross a filter medium and filtrate it from solids then removing the solids

(cake)

The importance of this equipment that it has various applications in the industrial field

The advantage of this equipment that it is relatively small space, low cost and easy to be

maintained

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1. Introduction

Rotary drum vacuum filter is a very important tool for solid-liquid separation; it has various

applications in the industrial field. The main advantage of this equipment is its relatively

small space, low cost and easy to be maintained

2. Principal and theory of operation

2.1 General theory

All Rotary Vacuum Filters operate on a similar principle. A pressure differential between the

surface and inside of the drum (or disc) is applied by means of vacuum. This pressure

differential cause's transport of liquid through the filtration surface while the filter medium

arrests solid particles and a cake is formed. As the drum rotates, the cake rises above the

slurry level in the filter tank and air is drawn through the cake, forcing out liquid. The liquid

(filtrate) exits the filter through the internal piping and the vacuum head

2.2 drum operation

The drum is commonly divided into three zones:

*Cake building zone is operated under vacuum pressure.

*De-watering zone is operated under vacuum pressure.

*Cake removal zone is operated under high pressure.

Fig2.1

Drum

operation

2

The control head divides the filter drum into the different sections for filtration, washing,

suction drying and cake discharge, so that in the course of one revolution each point of the

drum area passes through these zones in succession.

The filtrate (clarified liquid) runs off through the separator receiver and is discharged by

pumping.

2.3 Handling of cake

The filtered solid layer emerges from the suspension as the drum rotates, and following its

emergence is washed (to remove impurities or to extract more product), suction-dried and

discharged from the filter cloth. The wash liquid is fed onto the cake either directly by means

of wash devices such as weirs or spray nozzles, or of a wash belt lying on top of the cake.

The filtrate from the wash zone can be drained off separately from the mother filtrate. The

filter cake is discharged by means of a discharge device of some kind, which covers the entire

drum and which is specially suited to the cake thickness, consistency and structure.

3. Mechanical parts

Fig 3.1

RDVF detailed

figure

3

Rotary drum vacuum filter consist of:

3.1 Drum

A multi-compartment drum type vacuum filter consists of a drum rotating about a horizontal

axis, arranged so that the drum is partially submerged in the trough into which the material to

be filtered is fed (slurry), Most drum filters are fed by operating the drum with about 35

percent of its circumference submerged in a slurry trough, although submergence can be set

for any desired amount between zero and almost total.

3.1.1 Drum deck:

The perphorated surface of the drum is divided into a number of longitudinal sections of

about 20 mm in thickness. Each section is an individual vacuum chamber, connected through

piping to the drum centre and out through a central outlet valve at one end of the drum. The

and the filtration filter medium which retains the cake cloth drum surface is covered with a

takes place as each section is submerged in the feed slurry.

3.1.2 Drum speed variation

Most drum filters operate at a rotation speed in the range of 0.1 to 10 rpm. Variable-speed

drives are usually provided to allow adjustment for changing cake-formation and drainage

rates

3.2 Agitator

Some units contain an oscillating rake agitator (slowly moving agitator) in the trough to aid

solids suspension in the slurry reservoir, without disturbing the cake formation. Others use

propellers, paddles, or no agitator.

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3.3 filter valve

All drum filters (except the single-compartment filter) utilize a rotary-valve arrangement in

the drum-axis support trunnion to facilitate removal of filtrate and wash liquid and to allow

introduction of air or gas for cake blowback if needed. The valve controls the relative

duration of each cycle as well as providing “dead” portions of the cycle through the use of

bridge blocks. A typical valve design is shown below. Internal piping manifolds connect the

valve with various sections of the drum.

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. The valve has on certain filters adjustable blocks

and on others a fixed bridge ring. Adjustable bridge blocks enable the optimization of form to

dry ratio within the filtration cycle as well as the "effective submergence" of the drum when

the slurry level in the tank is at the maximum.

Fig3.2

Component

arrangement of a

continuous filter

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3.3.1 Duty of the bridges

off the vacuum so it is : This Bridge cuts Vacuum and blow zones separating bridge -1

slightly wider than the internal pipe port.

: This Bridge opens to vacuum once a compartment submerges.Dead Zone Bridge -2

up the upper vacuum zone is open to atmosphere and a -. : At startbridge assistup -Start -3

cake may be formed only when closing the valve that controls this zone. Once the cake starts

to emerge from the tank the valve is gradually opened and fully opened when the entire drum

face is wrapped with the cake. Since in continuous operation both lower and upper zones are

under vacuum this bridge is slightly narrower than the internal pipe port so that the vacuum is

continuous and the cake is held onto the drum.

It is to be noted that in some applications, compression rolls or belts are used to close

possibly cracks in the cake before washing or to further dewater the cake by mechanical

compression.

Fig3.3

Duty of valve

bridge

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3.4 Discharge system

3.4.1 Knife discharge

Consists of a blade that removes the cake from the drum by direct contact with the filter cake,

It is normally used for granular materials with cake thickness greater than about 6mm. n order

not to damage the filter cloth, a safety distance of 1 to 3 mm between the blade and the cloth

must be observed. If the residual layer is made not of filter aid but of the product, then there

might be danger of its blocking by fine particles and by successive consolidation by the

scrapper blade.

3.4.2 String discharge

Fig3.4

Knife discharge

Fig3.5

String discharge

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Uses a number of parallel strings (wire, chains or coil springs have also been used) tied

completely around the filter at a pitch of 1 to 2 cm, passing over the discharge and return rolls

.As the strings leave the drum before the discharge point, they lift the filter cake from the

medium and discharge it at the discharge roll. This type of discharge is recommended for

gelatinous or cohesive cakes.

3.4.3 Cloth belt discharge

Is based on taking the cloth endless belt off the drum in the same way as with the string

discharge, the advantage here is the ease of washing both sides of the cloth before the cloth

returns to the drum. The disadvantage is in the need for an additional control device for the

guidance of the cloth.

3.4.4 Roll discharge

Fig3.6

Belt discharge

Fig3.7

Roll discharge

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Use a roll, which rotates at a slightly greater peripheral speed than the cake and is in contact

with the cake. The cake is transferred from the drum to the discharge roll by adhesion which,

by giving the roll a rough surface or because of the presence of residual cake on the roll, is

designed to be greater to the roll than to the drum. The cake is usually removed from the roll

by a knife. This type of discharge is designed to discharge tacky cakes, which cannot be

handled effectively by either of the previously described designs. The cake thickness is small

here from 0.5 to 3mm.

4. Design equations

For continuous flow, Incompressible cake with (constant pressure drop), neglect resistance of

filter medium

4.1 Required Area of drum:

Time of filtration:

=

,

, and F= (0.3-0.4)

: Time of filtration, sec - , sec- V: volume of filtrate, - :

viscosity of slurry, pa.sec- : concentration of solids in slurry, / - : specific

cake resistance - , pa- F: time factor- Q: volumetric flow rate,

4.2 Power required:

(

– 1)

K: ratio of specific heat of gas at constant pressure to specific heat of gas at constant volume,-

-

- : theoretical horse power,

hp- : cubic feet of gas per minute at intake conditions , -Actual horse power

=

9

4.3 Design of air suction rate by vacuum pump:

: Viscosity of air at temperature and pressure surroundings, lb/hr ft - : fraction of total

surface available for air suction, lb/hr ft - : the fraction of this area immersed in the slurry

lb dry-cake solids/ filtrate - : the specific air-suction cake resistance.

5. Cost

Drum Filter is a vacuum type, multi compartment cylinder shell with internal filtrate piping

with polypropylene filter cloth, feed box with inlet and drain nozzles, suction valve, and

discharge trough, driver consisting of rotor, drive motor base plate, worm, gear reducer and ,

two pillow block bearing with supports

Defaults for Drum Filter

Medium filtration rate, 0.5 tons per day/ square feet solids handling rate, 20% consistency

(percent of solids in feed stream)

Design Basis:

1st Quarter 1998 Dollars-Material: A285C (Low and intermediate strength carbon steel plates

for pressure vessels.)

Cost 2009= cost from figures*

= cost of figures*

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6. Manufacturers

Web-site City-country Company name

www.scmp.net.cn Shanghai-china Shanghai chemical machinery plant

www.aaronequipment.com

Chicago-Chicago Aaron

www.komline.com New jersey- USA Komline-Sanderson

Engineering Corporation www.abhishekfilter.com

Mumbai- India Abhishek filtertechnik

www.petersonfilters.com Salt Lake City- USA Peterson filters

Fig5.1

Cost vs.

area

chart

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Summary

Finally this report discussed one of most important filters in industry, rotary drum vacuum

filter is fundamental support in any industrial scale ,as previously shown its simple principals,

components, work theory, design equations and famous manufacturers.

Report discussed RDVF briefly to more details ,check references below.

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References

1-http://www.solidliquid-separation.com/VacuumFilters/Drum/drum.htm

2-Ladislav Svarosky, solid liquid separation, fourth edition, 2000

3- Don w. green, Robert h. Perry, Perry's chemical Engineers' Handbook, Eighth Edition,

2009.

4- http://www.komline.com/docs/rotary_drum_vacuum_filter.html

5- J M. COULSON & J. F. RICHARDSON, Coulson & Richardson's Chemical Engineering,

fifth edition, 2002.

6-Max S.Peters and Klaus D.Timmerhaus plant Design and Economics for Chemical Engineers, 5th

edition, McGraw-Hill,2003.

7-Dr. Ahmed Sherif, unit operation course, lecture 4, 3rd year chemical engineering department