“Heaven’s light is our guide”
Rajshahi University of Engineering & Technology
DEPARTMENT OF CHEMICAL AND FOOD PROCESS
ENGINEERING
Course Code
: CFPE 3122
Course Name
: Unit Operations in Chemical and Food Process
Engineering Sessional
Topic name
: Rotary drum filter
Submitted by
Name & Roll :
Mst.Nusrat Jahan(1911004)
MD.Nasibur Rahman(1911005)
Shauvik Das Shuvo(1911006)
Submitted to
Sajib Dey
Lecturer
Department of Chemical and Food
Process Engineering
Rajshahi University of Engineering &
Technology
Date of submission : 27 November 2023
Table of contents:
Serial number
Contents
Page
01
Introduction
Page no 3
02
Underlying Theories
Page no 3
Working Principles
03
Page no 4
(schematic diagram)
04
Advantages & Disadvantages
Page no 5
05
Conclusion
Page no 5
06
References
Page no 6
Introduction
Filtering is the process of passing a liquid through a filter in order to remove solid particles,
where the solids are collected. Separating the liquid and solid phases of a suspension is
known as solid-liquid separation. The reason this process is called “Mechanical Separation”
is that it uses physical techniques to separate the materials. The initial separation is
accomplished by physical techniques, though it can be enhanced by chemical or heat
treatments. [1]
The most common type of continuous vacuum filter is the Rotary drum filter. This is a type
of filter that can accommodate a large thickness of cake and can take a precoat of filter aid
which is up to 150 mm in depth. [2]
Many other filters are made specifically to extract particles from liquid solutions. In addition
to being utilized for this purpose, the rotary drum filter is also employed in solids recovery
and compression, drying .There are two types of rotary drum filters: pressurized (pressure
drum filters) and vacuum (rotary drum vacuum filters). [3] These filters have minimal power
needs, effective cake washing, and continuous operation. They can handle a variety of
discharge techniques for filter cakes with varying consistencies and work with a variety of
filter cloths. [3]
The rotary filter is most suitable for continuous operation on large quantities of slurry. If the
slurry contains considerable amount of solids, that is, in the range of 15-30% [4] . The
vacuum-driven ones are available in a variety of sizes and types to meet the needs of a wide
range of industries, including food processing, wastewater treatment, mineral engineering,
and even laboratory settings. [3] Examples of pharmaceutical applications include the
collection of calcium carbonate, magnesium carbonate and starch. The separation of the
mycelia from the fermentation liquor in the manufacture of antibiotics. Also, Block and
instant yeast production. [4]
Underlying Theories :
A rotary drum filter works on the principle of slurry filtration through a sieve-like mechanism
on the surface of a rotating drum, under vacuum conditions . [5]
Sieving is a physical mechanism of particle removal, where a particle is denied access
through a pore or passageway that is smaller than the particle itself. The liquid passes through
the sieve while retaining larger particle itself. [6]
The drum is made up of a perforated plate that supports a filter cloth, and the slurry is
introduced into the trough of the drum filter. [5] As the drum rotates, a vacuum is applied to
the segment it is submerged in, causing the liquid to be sucked through the filter cloth and
leaving solids to cake on the membrane surface in sieving-like mechanism. [5] The sieve-like
mechanism of the rotary drum filter is suitable for filtering slurries containing a high
proportion of solids up to 15 to 30 percent. [5]
3D Model:
Working principle :
A rotary vacuum drum filter consists of a horizontal drum with a slotted face turns at 0.1 to 2
rpm in an agitated slurry trough. A filter medium, such as canvas, covers the face of the
drum. [7]
The filter operates by slowly rotating the drum in a trough of slurry with the drum from 10 to
35% submerged. (189/1063). The drum rotates at creating a vacuum of about 400 to 160 torr.
[3]
Rotary drum filler is divided into several sections, including a pickup zone, a drain zone, a
watering zone, a drying zone, and a cake removal zone. Pick-up zone and draining zone are
also called filtration zone. In the first four zones under vacuum and in the last zone, vacuum
is released, and compressed air is worked.
In pick-up zone, the rotary drum filter is partially submerged in the slurry to be filtered. As
the drum begins to rotate, it picks up the incoming liquid along with suspended solids. In
draining zone, the drum, with the slurry on its surface, moves into a drainage or vacuum
zone. Excess liquid is drawn through the filter medium, leaving behind a layer of filtered
solids (cake) on the drum surface.
In washing zone, the drum may be subjected to additional liquid, either by spraying water
onto the cake or by submerging the drum in a washing liquid which helps improve the purity
of the filtrate by removing any remaining impurities on the cake surface. Following the
washing zone, the drum rotates further, exposing the cake to air. This allows for partial
drying of the cake, reducing its moisture content before the cake removal stage. The cake
removal zone involves methods to remove the solid cake from the drum’s surface. This can
include scraping the cake off using a blade, vacuum removal, or other techniques. The
removed cake may be collected for disposal or further processing.
Advantages
•
•
•
•
•
The rotary vacuum drum filter is a continuous and automatic operation, so the
operating cost is low. [4]
The variation of the drum speed rotating can be used to control the cake thickness.
The process can be easily modified (pre-coating filter process). [4]
Can produce relatively clean product by adding a showering device. [4]
The cake is removed simultaneously during operation. Therefore, suitable for use
with concentrated slurries. [5]
Disadvantages
•
•
•
•
•
•
Due to the structure, the pressure difference is theoretically limited to atmospheric
pressure (1 bar), and in practice somewhat lower. [4]
The discharge cake contains residual moisture. [4]
The cake tends to crack due to their air drawn through by the vacuum system, so that
washing and drying are not efficient. [4]
High energy consumption by the vacuum pump [4]
A rotary drum filter is expensive equipment with complex functioning. It contains
moving parts and also requires a number of accessories such as agitators and vacuum
pump, vacuum receivers, slurry pumps, traps etc. [5]
The rotary filter is suitable only for straightforward slurries. It is less satisfactory if
the solids form an impermeable cake or if it is difficult to remove the cake adequately.
[5]
Conclusion :
In conclusion, the rotary drum filter is a reliable method of separating solids from liquids that
is well-suited to a variety of industrial settings (drying, compression). Its sturdy construction
and modifiable operating parameters, like flow rate and drum speed, provide flexibility in
meeting various filtration needs. Sustaining performance and longevity requires proper
maintenance, which includes routine cleaning and observation. The ongoing progress in
filtering technology offers prospects for additional improvements in efficacy and efficiency.
The rotary drum filter is still a viable option for solid-liquid separation as a crucial part of
industrial processes, which enhances product quality and operational dependability.
References
[1 G. V. A. V. K. T. Sivakumar, "ENHANCING THE PERFORMANCE OF ROTARY VACUUM DRUM
] FILTER," International Journal of Advanced Engineering Technology, p. 2.
[2 A. R. H. A.Rushton, Solid-Liquid Filtration and SeparationTechnology, VCH .
]
[3 K. Sutherland, "Rotary drum filter," in Filters and Filtration Handbook, Elsevier Science, 2007, p.
] 117.
[4 "Wikipedia, the free encyclopedia," [Online]. Available:
] https://en.wikipedia.org/wiki/Rotary_vacuum-drum_filter.
[5 S. Ray, "Pharmacy Scope," 18 May 2022. [Online]. Available: https://pharmacyscope.com/rotary] drum-filter/. [Accessed 26 November 2023].
[6 "Science Direct," [Online]. Available: https://www.sciencedirect.com/topics/agricultural-and] biologicalsciences/sieving#:~:text=Sieving%20is%20a%20physical%20mechanism,smaller%20than%20the%
20particle%20itself.
[7 J. S. P. H. Warren McCabe, "Unit Operations Of Chemical Enigneering," in Mechanical Separations,
] McGraw Hill, 2004, p. 1007.
Table of work distribution :
Tasks
Roll number
1911004
Lab report
1911005
1911006
1911004
Presentation Slide
1911005
1911006
Design
1911005