Agitated Nutsche Filter

Agitated Nutsche filter (ANF) is a filtration technique used in appliactions such as dye, paint, and pharmaceutical production [cite book |title=Pharmaceutical Production: An Engineering Guide |last=Bennett |first=Bill |coauthors=Cole, Graham |year=2002 |publisher=Institution of Chemical Engineers (IChemE) |isbn=0852954409 |pages=p. 89 |url=http://books.google.co.uk/books?id=pp_53D5GejYC&pg=PA89&dq=Agitated+%22Nutsche+Filter%22&num=100&client=firefox-a&sig=m527oHRMqJWYhrb_tJ3Nc16Dnvg |accessdate=2008-06-24] and waste water treatment. [cite book |title=Handbook of Water and Wastewater Treatment Technologies |last=Cheremisinoff |first=Nicholas P. |year=2001 |publisher=Butterworth-Heinemann |isbn=0750674989 |pages=p. 199 |url=http://books.google.co.uk/books?id=sP5Bj3pByTsC&pg=PA199&dq=Agitated+%22Nutsche+Filter%22&num=100&client=firefox-a&sig=T91TNrFOVQoyERjQKldo7D9C1Cs |accessdate=2008-06-24] Safety requirement and environmental concerns due to solvents evaporation lead to development of this type of filter wherein filtration under vacuum or pressure can be carried out in closed vessel even solids can be discharged straightaway into drier.

Filter features

It consists of a dished vessel with a perforated plate. The entire vessel can be kept at desired temperature by having a limpet jacket,bottom dish jacketed & stirrer(blade & shaft) through which heat transfer medium can be passed. The vessel can be made completely leak proof for vacuum or pressure service.

A multipurpose agitator is the unique feature of this system. The agitator performs the following operation by vertical movements and even in direction of rotation.
* Slurry contents can be kept fluidized till most of the M.L. is filtered through.
* When filtration is complete, the cake develops cracks causing upsets in the vacuum operation. This hinders removal of M.L... The agitator can be used to maintain a uniform cake.
* Washing of the cake can be done after filtration by reslurrying the cake.
* After washing, the M.L. can be refiltered. The cake can then be discharged by lowering the agitator and rotating it in such a manner that it brings all the cake towards discharge port.

Power pack

A power pack is a unit attached to the ANF’s agitator system. It consists of an oil tank on which a pump is provided for circulating high pressure oil through control valve system and to hydraulic cylinders. These cylinders are provided for vertical movement of the agitator. Operating pressure of oil various from 2 kg/cm² to 80 kg/cm² (200 kPa to 8 MPa).

M.O.C.

ANF’s can be fabricated in materials like Hastelloy C-276, C-22,Stainless Steel., Mild Steel., and Mild Steel with rubber lining as per service requirements. Recently ANF’s have been fabricated out of PPFRP (PolyPropylene Fibre Reinforced Plastic).

Advantages

1. Vacuum or pressure filtration possible.2. Inert gas atmosphere can be maintained.3. Very high solvent recovery.4. Considerable saving in manpower5. Solvents are in closed systems, so no toxic vapors are let off in the atmosphere.6. Personal safety is maintained and heat transfer surfaces can be provided to maintain filtration temperature.

References