Liquid purification or separation – With repair or assembling means – Sliding or rolling on guide means
Patent
1995-10-04
1997-08-12
Hruskoci, Peter A.
Liquid purification or separation
With repair or assembling means
Sliding or rolling on guide means
210324, 210327, 210332, 210334, 210345, 210396, B01D 3346
Patent
active
056561628
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a rotating filter including a container for a liquid or suspension to be filtered and a rotor structure arranged in the container, said rotor structure being provided at its outer periphery with a filter medium through which the liquid is filtered and on which material is deposited as a filter cake, said filter medium being arranged in the shape of an least one circular ring to having its centre in the rotational axis of the rotor structure and an extension in the radial direction substantially from the outer circumference of the rotor structure.
Ever since rotating filters came into use it has been a desire to construct filters having: filter cake;
Among rotating filters, three main groups can be distinguished, viz., drum filters having a smooth cylindrical filtering surface (smooth drum filters), drum filters having a ridged filtering surface (ridged drum filters), and, disc filters.
Simple, relatively fast rotating smooth drum filters have been used for dewatering of suspensions, such as pulp, up to typically 2% dry content, and such filters completed with filtrate channels connected to a source of vacuum have been used for washing and bleaching of pulp, sometimes further completed with a counter cylinder to obtain a dry content of about 15%. Filter cake removal from a smooth drum filter is a relatively uncomplicated operation utilizing a simple scraper. However, should the filtering medium, generally a filter cloth, be torn or otherwise damaged, the entire cloth must be replaced.
With the demand for increasing filtering capacity, ridged drum filters were developed and have been used for fiber recovery and dewatering up to about 2% dry content. With ridged drum filters, disclosed in, e.g., SE-B-315,490, filtering areas of about 2.5 times that of a smooth drum filter having the same outer diameter and axial length have been achieved. Due to the ridged filtering surface, it has not been practicable to use mechanical devices for filter cake removal, since such use would have involved an evident risk of damaging the filter medium comprising a filter cloth continuously extending over several adjacent ridges and valleys of the drum circumference. In practice, filter cake removal involves the use of liquid spray devices, resulting in unwanted dilution of the removed filter cake material.
Disc filters, used for fiber recovery and dewatering up to about 15% dry content, provide filtering areas of about 5 to 7 times the filtering area of a smooth drum filter. One advantage with disc filters is that each single filter sector of a filter disc has its own filter cloth, meaning that, in case of damage, only that particular filter cloth has to be replaced. However, the increasing filtering areas have resulted in operational drawbacks, such as the necessity to use spray devices for filter cake removal, at the same time as the cost per filtering area unit has become high.
The present invention aims at providing a rotating filter combining the best features of drum filters and disc filters, particularly in regard of filtering capacity, filtering area related to diameter and length, and, reliability of operation, but avoiding the drawbacks of conventional drum filters and disc filters. Particularly, the new filter shall allow mechanical removal of filter cake without primarily requiring water or other liquid spray.
In reaching its aim, the present invention provides a rotating filter including a container for a liquid or suspension to be filtered and a rotor structure arranged in the container, said rotor structure being provided at its outer periphery with a filter medium through which the liquid is filtered and on which material is deposited as a filter cake, said filter medium being arranged in the shape of at least one circular ring having its centre in the rotational axis of the rotor structure and an extension in the radial direction substantially from the outer periphery of the rotor structure, said filter being charcterized in that removal and discharge means being arranged radially
REFERENCES:
patent: 1686092 (1928-10-01), Manning
patent: 2269725 (1942-01-01), Malanowski
patent: 2885083 (1959-05-01), Peterson et al.
patent: 3814260 (1974-06-01), Daubman et al.
patent: 4131548 (1978-12-01), Peterson
patent: 5330645 (1994-07-01), Geldmacher
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