Filtering device and method

Abstract: A filtering device for separating liquid and solid material from a mixture consists of an endless filter belt. Filtrate is separated off by means of the pressure difference above and below the filter belt. The device is placed in a high pressure space in order to keep liquid substances which at ambient temperature and atmospheric pressure would become gaseous. The applied pressures can rise to roughly 20 bar.

Description: The invention relates to a filtering device and method for separating liquid and solid material from a mixture, provided with an endless filter belt, means for supplying the mixture for separating on the upper side of the filter belt and a suction box on the underside of the filter belt connected to a pump. Such a filtering device is known from EP-A-0 511 710 having a priority date of 29.04.91 and a publication date of 04.11.92. Such a filtering device can only be used for filtering particular mixtures. Mixtures including a substance which at ambient temperature and atmospheric pressure can pass into a gaseous phase cannot be separated with such a filtering device. It is the object of the invention to provide a filtering device which makes this possible. This is achieved according to the invention by the arrangement provided in the claims in that only the filter belt is placed in a pressure chamber, a comparatively high pressure is maintained in the pressure chamber and the difference in the pressure in the chamber and the pressure in the suction box is relatively small. By placing the mixture for separating under a higher pressure than the lowest evaporation pressure applying to any of the components in the mixture at the prevailing temperature, the danger of any of the substances passing into the gas phase is obviated. It is noted that a filtering device is known from EP-A-0 033 371 wherein the whole installation is accommodated in a high pressure chamber accessible to service personnel. Only a limited overpressure can be applied with such an installation. When higher pressures are used the space is no longer accessible to personnel without very special precautionary measures. According to US-A-4,038,193 it is suggested that a device according to the pre-amble of the present specification may be surrounded by a cabinet for operation for example at excess pressure. However there is no indication that the drive means for the filter belt and/or the vacuum and air valves should be arranged outside the pressure chamber. The invention is further elucidated with reference to the drawing. The figure shows a perspective view of an embodiment of the invention. The device 1 has a frame 2 shown fragmentedly and constructed from vertical and horizontal beams, in which an endless belt 3 is movable over rollers 4 and 5 in the direction of the arrow. The belt is a filter belt that is permeable to liquids. A feed device 6 is placed above the belt for feeding the mixture for separating. Placed under the belt in known manner is a suction box 9 which is connected via a transmission 10 to a vacuum connection 11. The latter, which is provided with a closing valve 29, is connected to a pressure or suction device (not drawn). The suction box 9 has on the top side a grid 13. When a pressure is generated in the suction box the filter belt 3 is held fast on the grid 13, whereby the suction box moves along with the filter belt in the direction of arrow P during the so-called filtration stroke. At the end of the filtration stroke, which is determined by the free space between the length of the box and the distance between rollers 4 and 5, the pressure in the box is increased using the closing valves 28 and 29. The suction box is now retracted by the piston 14 to its original position, whereafter the filtration stroke begins again. The suction box 9 can be built up of different sections, each separately connected to the said pressure or suction devices. The active part of the filter belt is placed in a chamber 32. Connected to chamber 32 are feed conduits 31 for bringing the interior of chamber 32 to, and holding it at, a high pressure. Because the drives of the filter belt and the vacuum and air valves are disposed outside the pressure vessel, it is not necessary to take additional steps for these components. The pressure in the chamber can be chosen subject to the substances for treating. In this manner separation of substances which at atmospheric pressure are in the gas phase is made possible.

Claims: A method for separating liquid and solid materials from a mixture, comprising the steps of: providing a pressure chamber containing an endless filter belt and a suction box supplying a mixture of liquid and solid material onto an upper side of that filter belt; arranging a suction box onto an underside of that filter belt and maintaining a higher than atmospheric pressure in said pressure chamber and maintaining a pressure difference between said pressure chamber and said suction box, characterized in that drive means for the filter belt and/or the vacuum and air valves are arranged outside the pressure chamber. A filtering device for separating liquid and solid materials from a mixture, comprising: a pressure chamber containing an endless filter belt and a suction box at the underside of the filter belt means from maintaining a higher than atmospheric pressure in said pressure chamber, means for supplying a mixture of liquid and solid materials into said pressure chamber to an upper side of said filter belt; and means for maintaining a pressure difference between the pressure in said pressure chamber and the pressure in said suction box, characterized in that one or more drives of the filter belt and/or one or more vacuum and/or air valves are disposed outside the pressure chamber. A filtering device according to claim 2, wherein the suction box is moved along with the filter belt for a filtration stroke, and is retracted to its original position to start a new filtration stroke. Method according to claim 1, characterized in that the pressure in the pressure chamber amounts to roughly 20 bar and the pressure difference between the pressure in the pressure chamber and the pressure in the suction box amounts to roughly 1-2 bar. Filtering device as claimed in claim 2 or 3, characterized in that the pressure in the pressure chamber amounts to roughly 20 bar and the pressure difference between the pressure in the pressure chamber and the pressure in the suction box amounts to roughly 1-2 bar.

Inventors: PRINSSEN ALPHONS ARNOLDUS JOHA, PRINSSEN, ALPHONS ARNOLDUS JOHANNES ANTONIUS
Applicants: PANNEVIS BV, PANNEVIS B.V.
Application year: 1993
Main classification: B01D33
IPC codes: B01D33