AIR-DRIVEN CONTACT FILTER

Abstract: An air-driven contact filter for biological cleaning of waste water has spiral wound channels with an axis placed below the surface of the water. Air is blown into the center and water is displaced so that the channels will rotate.

Description: The present invention relates to an air-driven contact-filter designed for use in a system for biological cleaning of waste water and of the kind referred to in the opening part of claim 1. To avoid use of gear and/or other mechanical transmissions it has been proposed to provide the rotor with vanes on the periphery and to injet air under the rotor slightly off-centre so that the-air is caught by the vanes at one side, thus causing the rotor to rotate( US-A-4,351,721). Air injected in this way apparently yields work/torque during half a rotor revolution, but in practice the torque is only present over a rather short angle of rotation, viz. in the part of the angle of rotation where the upward force is offset most relatively to a vertical line through the centre. In order to utilize the torque resulting from this rather short distance, the rotor has to be submerged almost completely. Therefore the typical counter-pressure against injected air is at least two thirds of the rotor diameter, i.e. fans are required which have an energy waste relative to this counter-pressure. According to the present invention the contact filter is designed as indicated in claim 1. The air-driven filter according to the invention differs from the prior art apparatus in that rotation is effected by weight transfer by displacing the water content in the submerged part of spiral channels composing the rotor by injection of air so that their weight is mainly at one side of the rotor and the injected air creates a lift at the other side of the rotor. Further, the invention differs from the prior art apparatus in that the counter-pressure is considerably lower. Effective utilization of the injected air is obtained at a counter-pressure of only 25 cm H₂O even if the rotor diameter is upwards of 3 metres. In the following the invention will be explained in more detail in connection with the drawing which schematically shows a section perpendicular to the axis of rotation 7 through a rotor 1 of a contact filter according to the invention. On a horizontally rotatably placed centre pipe 4 at least two circular gable plates are placed. Near the centre pipe these circular gable plates are provided with openings to a mixing chamber 2 surrounding the centre pipe 4. Between two adjoining circular gable plates a number of spiral guiding plates 5 extend in radial direction from the mixing chamber 2 to the periphery of the circular gable plates thus forming a rotor with spiral channels 6 which are rotatable around the axis of the centre pipe. The centre pipe 4 is closed at one end, whereas the other end has an inlet stub for connection with a compressed air source. In the mantle surface of the centre pipe 4 there are piercings (not shown) which are placed and dimensioned such that air let in at the inlet stub leaves the pipe evenly in radial direction. The described contact filter is placed with the axis of rotation 7 somewhat below the water surface 8 as shown in the drawing, and air is ted into the centre pipe. Through the openings in the circular gable plates water pours into the mixing chamber 2 and the by then submerged parts 9 of the spiral channels 6. The fed air will displace the water content in the submerged part of the channels, so that the weight mainly is at one side of the rotor (right side on the drawing) and the air gives a lift at in the other side. The rotor 1 will therefore revolve clockwise with respect to the drawing caused by the weight transfer effected by the induced air. When the inner diameter of the centre pipe is e.g. 10 cm and its axis is submerged 30 cm the counter-pressure against the induced air is 25 cm H₂O. A contactfilter for 1000 person equivalents (PE) only requires 7,5 m³ air per minute. With a standard fan with a max. pressure of 30 cm H₂O the operation costs 0,75kW per hour. With presupposed perpetual operation the consumption of electricity is less than 7kW/PE/year. In a contact-filter with several circular gable plates mounted on a centre pipe,.e.g. at intervals of 10 cm, which circular gable plates two by two delimit spiral channels 6 mounted next to each other, the possibility of supply of water sets limits to the axial extension of the filter. For that reason it is suggested that e.g. every 5 of the spiral wound channels are wounded opposite to the others so that this instead of leading water from the mixing chamber 2 to the periphery of the rotor leads water (and air) from the periphery into the mixing chamber. With such counter directed channels the rotor can have any axial extension.

Claims: 1. Air-driven contact filter designed for use in a system for biological cleaning of waste water comprising a rotor (1) which is rotatable around a horizontal axis (7) characterized in that a mixing chamber (2) surrounds a centre pipe (4) including said axis (7) which centre pipe is closed at one end and is provided with piercings in its surface such that air let in at the other end leaves the pipe in substantially radial direction into said mixing chamber (2), and that said rotor comprises at least one spiral channel (6) formed by means of spiral guiding plates extending from said mixing chamber (2) to the periphery of two circular gable plates, said spiral channel also extending between said two circular gable plates which are disposed on said axis (7) and are provided with openings so that waste water flows into said mixing chamber (2). 2. Contact filter according to claim 1 characterizied in that a plurality of said rotors are mounted on the same centre pipe between two respective circular gable plates, the spiral channels of at least one rotor, e.g. every 5, having a direction reversed with respect to the spiral channels of the other rotors so that the rotor comprising channels with reversed direction leads water from the periphery into the mixing chamber.

Inventors: FRANDSEN, AKSEL SONDERGARD
Applicants: FRANDSEN, AKSEL SONDERGARD
Application year: 1987
Main classification: C02F3
IPC codes: C02F3