Filtration Services Ltd

Rotary Drum Vacuum Filters for

the Filtration of Tallow

Definition: Filtration is the mechanical

separation of solid particulates from a fluid.

Purpose of the filter is to:-

• remove the solids (filter cake)

• recover the liquid (filtrate)

Filtration and Separation

Filter System Requirements • Continuous operation

• System can be automated for incorporation

within the entire plant

• Minimum labour requirement for maintenance

• High equipment reliability

• Robust construction

We can supply • Rotary drum vacuum filter

– Continuous operation?

– Automation?

– Easy maintenance?

– Reliable?

– Robust?

YES

YES

YES

YES

YES

How a rotary drum vacuum filter works ...

As the panel is immersed,

the liquid is drawn through

the panel and the solids are

retained on the panel

surface.

As the panel continues to

rotate, air is drawn through

the panel to dewater the

solids.

The filtered solids are

removed from the

panel surface.

Vacuum is applied to the

panel through the rotary

valve assembly.

Solids

Discharge Filtration

Drying

Initial Dewatering

For a multi-panel system ...

Scraper discharge mechanism

RDVF – sectional view

Scraper Discharge

Rotary Drum Vacuum Filter (RDVF)

Filtration area from <1m2 to >60m2

Standard Scraper Filtration Circuit

What if the solids are very fine, gelatinous

and difficult to filter, and have a tendency

to blind the filter medium?

Can a rotary drum vacuum filter still be

used? Yes

The most suitable filter for

difficult filtration applications

For difficult filtration applications we supply

precoated rotary drum vacuum filters.

Used in many applications where the solids

have a tendency to blind a standard filter

medium.

The precoat is a sacrificial filter medium which

is easily replaced.

A precoat layer of a

sacrificial filter

medium is pre-filtered

onto the drum surface

This can be:-

• wood flour

• perlite

• diatomaceous earth

A thick layer of precoat

is formed around the

drum surface – up to a

depth of 100mm

The process stream is

then filtered through the

precoat layer.

The solids are retained

on the precoat surface

and the cleaned filtrate

passes through.

To prevent the filter

medium from blinding,

the surface

contaminants are

peeled away using a

slow advancing knife

discharge system.

A thin layer of precoat

is also removed with

the knife to ‘refresh’

the filtering surface.

The drum continues to

rotate and the knife

advances slowly, cutting

away the precoat layer.

Eventually, the precoat

layer is spent and will

need to be reformed.

The life of the precoat

bed is a function of the

drum speed and knife

advance rate, and can

range from several hours

to a few days.

Types of Precoat

Wood Flour

Perlite

DE

Precoat discharge mechanism

Precoat Discharge RDVF

Standard Precoat Filtration Circuit

Tallow Filtration - Requirements

• Requirements:

– Reduction in total solids content to less than

0.15% by weight

– Effective removal of polyethylene

– Robust, reliable filtration system

– Cost effective operation

Tallow - viscosity profile

0

5

10

15

20

25

30

50 60 70 80 90 100 110

Temperature (deg C)

Vis

co

sit

y (

cP

)

Tallow Filtration - Considerations

• Operation of the filter at elevated

temperature (typ. 78 to 80°C)

– Reduction in viscosity

– Improved fluid flow characteristics

• Melting point of average, commercial, low-

density Polyethylene is ~105 to 115°C.

– Maximum ‘stable’ temperature 80°C

Recommended Filtration

Technology

• Precoated rotary drum vacuum filter

– Digital knife advance system

• Synchronous operation

• 5µm incremental steps

– Variable drum speed via a frequency inverter

– Steady-state operation

– Simple control and monitoring

Filtration Services’ AKAS Automatic Knife Advance System

• Touchscreen interface for easy operation

• Graphical and numerical representation of the

precoat bed depth

• Fully synchronous operation with drum rotation

• Adjustable in 5µm steps (~0.0002”)

• Use of PIN numbers to prevent unauthorised

modifications to parameters

Ancillary Equipment

All of the ancillary equipment is sized to suit the RDVF installation

• Filtrate receiver

• Filtrate pump

• Vacuum pump

• Precoat tank and mixer

• Feed / dump tank and mixer

Filter Optimisation

• Operate under steady-state conditions

– Constant temperature profile

– Constant trough level

• Minimise knife advance rate

– Minimise precoat usage

• Minimise drum speed

– Maximise the precoat bed life

• Maximise applied vacuum

Filter Condition Monitoring

• Drum speed

– Inverter output or via a limit switch on the drum shaft

• Knife advance rate and precoat bed depth

– Link into the AKAS control panel PLC

• Applied vacuum

– Vacuum transmitter on the filtrate receiver

• Operating temperature

– Temperature transmitter on the filter trough

• Filter throughput

– Cyclic discharge from the filtrate receiver (level switch ON/OFF)

Filtration Services Ltd Unit 5, Sutton Mill, Byrons Lane

Macclesfield, Cheshire SK11 7JL

United Kingdom

Tel: +44 (0)1625 616109

Fax: +44 (0)1625 434678

Email: info@filtrationservices.co.uk

Website: http://www.filtrationservices.co.uk