STUDENTSPEN NO. SHELADIYA HARDIK L SOJITRA HARSHIT L SOJITRA JALPA B GUIDED BY: Prof. Jigna S. Patel FACULTY OF ENGINEERING TECHNOLOGY & RESEARCH Rotary Drum Vacuum Filter

2 Removal of solid particles from a fluid by passing it through a septum on which the solids are deposited. 9/29/ Filtration

3 In the form of cake on the septum Or Trapped inside the pores of the septum 9/29/ Solid Deposition

4  Vacuum filter with continuous operation.  Drum turns at 0.1 – 2 rpm in slurry trough.  Filter covers the face of the drum.  Rotary drum filter has four zones : 1. Filtering zone 2.Washing and drying zone 3.Cake removal zone 4.Dead zone  Vacuum is applied in first two zones.  Permeate and washing liquid discharge into separate compartments.  Doctor blade is used in third zone. 9/29/ Rotary Drum Filter

 In large –scale operation, continuous operation is sometimes desirable and it may be necessary to filter slurries containing a high proportion of solids.  The rotary filter is continuous in operation and has a system for removing the cake that is formed, so, it is suitable for use with concentrated slurries.  It is a metal cylinder mounted horizontally, the curved surface being a perforated plate, supporting a filter cloth. Internally, it is divided into several sectors and a separate connection is made between each sector and a special rotary valve.

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 The drum is immersed to the required depth in the slurry, which is agitated to prevent settling of the solids, and vacuum is applied to those sectors of the drum which is submerged.  A cake of the desired thickness is produced by adjusting the speed of rotation of the drum. Each sector is immersed in turn in the slurry and the cake is then washed and partially dried by means of a current of air. Finally, pressure is applied under the cloth to aid the removal of the cake. Removal of the washed and partially dried cake is affected by means of a doctor knife.

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 The drum is dipped into the slurry and vacuum applied to the outlet, which is connected to the filtrate receiver. When the cake has formed, the cake drained or partially dried by vacuum.  The drum is sprayed with water to wash the cake. Retaining the vacuum connection drains the cake and produces partial dryness then, removed by a doctor knife.  When the solids of the slurry are too much that the filter cloth becomes blocked with the particles, a pre-coat filter may be used. A pre-coat of filter aid is deposited on the drum prior to the filtration process.

 The rotary filter for continuous operation on large quantities of slurry.  Suitable for slurry contains considerable amounts of solids in the range 15-30%.  Examples of pharmaceutical application include the collection of calcium carbonate, magnesium carbonate, and starch, and the separation of the mycelium from the fermentation liquor in the manufacture of antibiotics.

ADVANTAGES  The rotary filter is automatic and is continuous in operation, so that the labor costs are very low.  The filter has a large capacity, so it is suitable for the filtration of highly concentrated solution.  Variation of the speed of rotation enables the cake thickness to be controlled.  Pre-coat of filter aid could used to accelerate the filtration rate.

9/29/  The rotary filter is a complex piece of equipment, with many moving parts and is very expensive,.  In addition to the filter itself, some accessories are connected. e.g., a vacuum pump, vacuum receivers, slurry pumps and agitators are required.  The cake tends to crack due to the air drawn through by the vacuum system, so that washing and drying are not efficient.  Being a vacuum filter, the pressure difference is limited to 1 bar and hot filtrates may boil.

9/29/ REFERENCES 1.Auistin, E. P., `The rotary drum filter application and design', Filtration &Separation, July/August, (1978). 2.Baluais, G., Rebouillat, S., Laclerc, D. and Dodds, J. A., `Modification of Compression dewatering and the application to filter design, I', Chem. Eng.Symp. On Solid/Liquids Separation Practice and the Influence of New Techniques (Leeds, 5 April 1984), Paper 3, pp , Institute of Chemical Engineers, Yorkshire Branch (1984). 3.Bott, R., Anlauf, H. and Stahl, W., `Continuous pressure filtration of very fine Coal concentrates', Aufbereitungstechnik, 5, (1984). 4.Carleton, A. J., `Choosing a compression filter', Chem. Eng., April, (1985). 5.Carleton, A. J. and Moir, D. N., `Optimization of compression filters, I', Chem. Eng. Symp. On Solid/Liquids Separation Practice and the Influence of New Techniques (Leeds, 3-5 April 1984), Paper 2, pp , Institute of Chemical Engineers, Yorkshire Branch (1984). 6.Johnsen, F., Madsen, R. F. and Nielsen, W. K., DDS-vacuum pressure filter, 2nd World Filtration Congress 1979, pp , Filtration Society, London (1979).

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