CE283e
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Experiment Instructions CE 283
Drum Cell Filter
Prj_7 10/2010
DRUM CELL FILTER
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
CE 283
Experiment Instructions Please read and follow the safety regulations before the first installation!
Publication-no.: 918.000 02 D 285 12 (A)
Prj_7
i
10/2010
CE 283
DRUM CELL FILTER
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
Table of Contents 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2
Unit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1 Components of drum cell filter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.3 Components of the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.4 Startup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.5 Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.6 Maintenance/Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3
Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Health hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 Hazards for unit and function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4
Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1 Principles of filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5
4.1.1
Surface filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1.2
Deep bed filtration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1.3
Cake filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1 Preliminary remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.2 Experimental method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.3 Evaluation of the experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6.1 Worksheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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10/2010
DRUM CELL FILTER
CE 283 1
Introduction The CE 283 - Drum Cell Filter enables a suspension to be mechanically separated into liquid and solid particles using a filter material. Drum cell filters consist of a slowly rotating perforated drum covered with a filter cloth.
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
The drum cell filter is a continuously operating filter unit, which performs a complete work cycle during a 360° revolution. This means that during a drum revolution, a suspension is picked up using a vacuum, dehydrated and the remaining filter cake is peeled off from the drum.
1 Introduction
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10/2010
DRUM CELL FILTER
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
CE 283 2
Unit description
2.1
Components of drum cell filter
Fig. 2.1
2.2
3
4
2
5
1
6
Drum cell filter
1
Suspension
4
Filter cake discharge
2
Filter cake
5
Adjustable scraper
3
Vacuum
6
Agitator
Function In the drum cell filter, a continuously slowly rotating filter drum divided into cells is around one third immersed in a suspension (1). The perforated filter drum is covered with a filter cloth. The cells in the drum are individually connected to an intake line (3) by a hollow shaft on the drum. On the filter surface, which is immersed in the suspension, this sucks filtrate through the filter cloth into the inside of the drum. Fresh filter surface is continuously being immersed in the suspension. During immer-
2 Unit description
2
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CE 283
DRUM CELL FILTER sion, an increasingly large filter cake (2) grows on the filter cloth in the direction of rotation. When this emerges from the suspension, it is dehydrated by the vacuum created. Before the drum is immersed in the suspension again, the filter cake is peeled off (4) and the filter cloth is clear again.
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
To ensure that no solid particles can settle on the base of the suspension tank, an agitator (6) is continuously running inside it. Drum cell filters are suitable for filtering mediumfine suspensions and are used for large mass flow rates.
2 Unit description
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DRUM CELL FILTER
CE 283 2.3
Components of the system
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
1
9
Fig. 2.2
7
8
2
6
3
4
5
Example of a drum cell filter 1
Filter drum divided into 12 sections
6
Overflow
2
Distribution plate
7
Scraper
3
Valve
8
Rinsing connection
4
Vacuum tank
9
Filter drum drive
5
Drain valve (vacuum tank)
2 Unit description
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DRUM CELL FILTER
CE 283 2.4
Startup Make the connections to the supply lines.
–
Connect vacuum
–
Completely drain vacuum tank
–
During operation, check the filling level of the vacuum tank and drain if necessary. This ensures that no water can get into the vacuum system.
–
Close vent cock and drain valve on vacuum tank
–
Close overflow and rinsing connection
–
Set scraper to 3 mm distance from filter drum.
4 Up / Down
–
Make electrical connection
5 Units
–
Switch on agitator
–
Check direction of rotation of filter drum and adjust if necessary with shaft direction of rotation button (3).
–
Select speed of filter drum using frequency. Select SET mode (1) using the ENTER button (8) and then select the frequency with the UP / DOWN (4) buttons.
–
Create vacuum
–
Open suspension valve and feed in suspension at a low volumetric flow rate.
–
Observe the system
–
An even filter cake should form on the drum.
–
The scraper removes filter cake from the filter drum and this falls into a container.
–
To blow off the filter cake with the fine reduction station, adjust the compressed air to max. 0.3 bar. This blows off the filter cake from inside with compressed air.
5 6
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
1 2
7
3
8 4
Fig. 2.2
Control panel
1 Display modes 2 Start / Stop 3 Change direction of rotation
6 Direction of rotation display 7 Menu 8 Enter
2 Unit description
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DRUM CELL FILTER
CE 283
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
2.5
2.6
Shutdown
–
Disconnect suspension supply
–
Turn off vacuum
–
Disconnect compressed air supply
–
Vent and drain vacuum tank
–
Rinse the drum cell filter with water
–
(Caution! Protect the electrical components from splash water!)
–
Drain water and remaining suspension
–
Turn off agitator and filter drum drive
–
Disconnect system from mains
Maintenance/Care See instructions in manufacturer’s operating manual supplied.
2 Unit description
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DRUM CELL FILTER
CE 283 3
Safety
3.1
Health hazards
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
See operation of the system in the manufacturer’s manual supplied.
3.2
Hazards for unit and function
See operation of the system in the manufacturer’s manual supplied.
3 Safety
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DRUM CELL FILTER
4
Theory
4.1
Principles of filtration
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
Suspension
Filtration separates suspensions into a solid (residue) and liquid (filtrate) - see Fig. 3.1). This is achieved by a pressure change using a porous material, the filter material. The liquid passes through the pores or openings in the filter material, while the solids are retained by the filter material.
Residue Filter material
Filtrate
Fig. 4.1
Principle of filtration process
The driving force is a pressure difference between the suspension on one side of the filter material and the filtrate on the other. The difference is created by a vacuum on the filtrate side or excess pressure on the suspension side (hydrostatic or pressure generated using pumps). Three types of filtration are differentiated:
•
Surface filtration
•
Deep bed filtration
•
Cake filtration
In addition, it is possible to distinguish by the objective of the filtration:
4 Theory
•
Clarification filtration: Only the filtrate is to be recovered.
•
Separating filtration: Both the filtrate and the residue are to be recovered for processing.
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DRUM CELL FILTER
CE 283
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
Filtration type
Size of retained particles in µm
Filtration
>5
Microfiltration
0.1 to 5
Ultrafiltration
0.05 to 0.1
Nanofiltration
0.001 to 0.01
Reverse osmosis
0.0005 to 0.005
4.1.1
Surface filtration
Filter cake
Filter material
In the simplest case, a filter process is based on a sieve effect. Particles with a diameter greater than the size of the pores and openings in the filter material are retained. This process is known as surface filtration. Surface filtration is primarily used to recover solids from dispersions.
Filtrate Small particles
Fig. 4.2
Surface filtration
4 Theory
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CE 283 4.1.2
Deep bed filtration As well as surface filtration, deep bed filtration can normally also be used. In this case, relatively thick filter material layers are used. Particles that are smaller than the filter material pores enter these pores. As the pore channels are not straight lines but are branched, the solid particles are deposited slowly by adsorption. This adsorption reduces the pore diameter, so that small particles can be retained later in the filtering process.
Filtrate side Solid particles
Channels
Fig. 4.3
Deep bed filtration is frequently used to clarify suspensions with a low solid content.
Deep bed filtration
4.1.3
Cake filtration Cake filtration is a mixture of surface and deep bed filtration. Suspension
Filter cake
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
Suspension side
Filtrate Fig. 4.4
Filtermaterial
Cake filtration
4 Theory
The progress of filtration develops dynamically. Metallic cloth or needle felting is used as the filter material, in some cases covered with a fine textile cloth. To support this, perforated plates or sieves are placed underneath. The suspension fed onto the initially clean filter material first of all flows almost completely through the filter material with only the largest solid particles being retained. More and more solid particles are gradually deposited on the filter material, creating a filter cake that becomes increasingly thick. The actual filtration only occurs when a sufficiently thick filter cake has formed. For the suspension to pass through this filter cake, there must be a pressure difference between the feed side and the filtrate outlet side. This can be generated by:
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CE 283
DRUM CELL FILTER –
Hydrostatic pressure
–
Creation of excess pressure on the suspension side (pressure filtration)
–
Creation of a vacuum on the filtrate side (vacuum filtration)
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
Above a certain filter cake thickness, it must be removed. However, a residual layer is left behind so that there is no unclarified initial filtrate. There does not need to be a density difference between the solid particles and the suspension liquid for separation to take place.
4 Theory
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DRUM CELL FILTER
CE 283 5
Experiments
5.1
Preliminary remarks There are two ways to separate the filter cake from the rotary filter:
•
Mechanical scraping
•
Blowing off with compressed air
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
With scraping, the filter cake is mechanically separated from the filter cloth. This leaves residual cake on the drum. This acts as an additional filter on the filter cloth when the drum is immersed in the suspension again. The gap between the scraper and the drum can be adjusted with practically no limits. However, it is important to ensure that the scraper does not damage the filter cloth. With blowing off, the mechanical construction of the filter breaks the vacuum before the scraper and the filter cloth is blown off from inside with compressed air at 0.3 bar. This separates the entire layer of filter cake and it falls into the collecting container.
Fig. 5.1
Filter cake, blown off
The filling level of the suspension in the drum cell filter or the overflow can be adjusted using plug-in plates. The supply of suspension such be selected in such a way that as little suspension as possible is drained at the overflow. The vacuum must be turned off if the level tube on the vacuum tank shows a maximum filling level. The suspension supply should also be turned off.
5 Experiments
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DRUM CELL FILTER
CE 283 5.2
Experimental method
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
The rotary cylinder is supplied with a suspension from the CE 285 system.
–
Connect vacuum tank (filtrate tank) to the vacuum connection
–
Use the operator controls to select the speed and direction of rotation of the drum. (The filter drum must rotate in the opposite direction to the scraper)
–
Using the eccentric screw pump on the CE 285, pump suspension into the rotary filter at a constant volumetric flow rate.
–
Turn on the agitator in the rotary filter so that the particles in the suspension remain suspended
The filter cake can be collected and weighed during the experiment. To reduce the time taken for the experiments, 3 sections corresponding to ¼ of the filter drum are collected and the results are then multiplied by 4 Recommended settings: Volumetric flow rate of suspension ~4,8 ltr/min Vacuum
-0.48 …-0.52 bar
Compressed air for blowing off filter cake
max. 0.3 bar
–
5 Experiments
Weigh sample quantity removed and note measuring result.
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CE 283
Frequency in Hz
Speed in rpm
¼ filter cake in g
Filter cake Total in g
Mass flow rate in g/min
Cake thickness in mm
1
10
0,11
332
1328
144,35
18
2
20
0,39
139
556
219,47
9
3
30
0,60
106
424
254,40
7
4
40
0,79
94
376
296,84
6
5
50
1,00
79
316
316,00
5
Filter cake mass flow rate:
g/min
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
No.
Filter cake mass flow rate:
M = mFK × n M
5 Experiments
mFK Filter cake mass
g
n
rpm
Filter drum speed
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CE 283
Filter cake mass in g
Evaluation of the experiment
Frequency in Hz Filter cake
Frequency in Hz Fig. 5.1
The speed of the filter drum is the variable in the experiment and is plotted on the x axis. Fig. 5.2 shows the total filter cake quantity depending on the drum speed. The faster the filter drum rotates, the less filter cake accumulates per revolution. As the dwell time of the drum segments in the suspension is increasingly short, less suspension can accumulate. However, it is notable that in absolute terms the mass of filter cake deposited per unit of time increases. The cake mass flow rate is the product of the speed and the filter cake mass. It increases at an increased speed (see Fig. 5.3)
Mass flow rate in g/min
Fig. 5.2
The faster the filter drum rotates, the lower the thickness of the layer of filter cake (see Fig. 5.4).
Cake mass flow rate
From the figures, it can be seen that the dependency on the speed can be assumed to be linear. The optimum operating point of this filter system is where the recovery of filter cake is at a maximum while the filtrate is simultaneously pure.
Thickness in mm
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
5.3
Frequency in Hz Fig. 5.4
Thickness of filter cake
5 Experiments
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DRUM CELL FILTER
CE 283 6
Appendix
6.1
Worksheets
Frequency in Hz
Speed in rpm
¼ filter cake in g
Filter cake total in g
Mass flow rate in g/min
Cake thickness in mm
Filter cake mass in g
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
No.
Frequency in Hz Fig. 6.1
Filter cake
6 Appendix
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DRUM CELL FILTER
Filter cake mass flow rate in g/min
Frequency in Hz
Fig. 6.2
Filter cake mass flow rate
Thickness of cake in mm
All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 05/2005
CE 283
Frequency in Hz
Fig. 6.3
Thickness of filter cake
6 Appendix
17
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