Mist recovery apparatus

Abstract: A mist recovery apparatus is provided, which comprises a casing (10), a set of an upper pipe plate (9) and a lower pipe plate (9), a number of exhaust passing pipes (6) each having a twisted plate therein, apertures formed at the side part of the casing to permit a cooling air flow to pass through the casing along the direction perpendicular to the exhaust passing pipes (6), a fume supply duct (1) connected to the upper portion of the casing, and an exhaust duct (11) disposed upwardly from the lower portion of the casing (10) to the side of the casing (10) so as to flow the exhaust from the exhaust passing pipes (6) along the side of the casing (10) and discharge the exhaust out of the casing. In such a structure, the mist contained in the exhaust produced from, for example, a rolling mill can be effectively separated and recovered and evolution of white smoke or fumes is greatly reduced. In order to achieve a more sufficient mixing of the exhaust and the air, a vertical chamber may be provided onto the discharge duct.

Description: 1. Field of the Invention The present invention relates to an apparatus for recovering mist from the exhaust fumes containing mist of water, oil (e.g., kerosine) and the like, and, in particular, to a separation and recovery apparatus of mist part contained in the exhaust fumes exhausted from, for example, a metal plate rolling mill. 2. Description of the Prior Art The fumy mist (emulsion of water and oil) produced from the rolling mill whitens and is diffused when it is discharged into the atmosphere. Because the fumy mist has a bad-smelling or offensive odor and pollutes the air, the fumy mist has been treated to remove the mist. Filtration installations provided with a filter removing the mist have been employed as mist removal devices. However, the filter is apt to be choked up or clog with the mist for a short period, resulting in a high maintenance cost. In consequence, the conventional filtration installations are hardly used in the industrial field. The US-A-4 382 807 discloses an apparatus for separating foreign matter from a gas with a heat exchanger. This device uses either an air or a liquid-cooled jacket surrounding a tubular passage for the exhaust. Since the exhaust is discharged into the atmosphere after removing mist without further cooling, for example by mixing it with cooling air, evolution of white smoke occurs due to the large temperature difference between the exhaust and the atmosphere. Accordingly, it is the object of the present invention to provide an apparatus for effectively separating the mist part contained in exhaust gases and recovering the seperated stream through liquefying and cooling at low maintenance cost, in which evolution of white fumes is effectively prevented. This object is achieved by a apparatus including the features of claim 1. A further prefered embodiment of the apparatus according to the present invention includes the features of claim 2. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partly broken perspective view of the mist recovery apparatus according to an embodiment of the present invention; FIG. 2 is an enlarged sectional view of the part circled in the exhaust passing pipes of the apparatus shown in FIG. 1; FIG. 3 is an exhaust flow chart of a system including the mist recovery apparatus shown in FIG. 1; FIG. 4 is a view similar to that of FIG. 1, however according to another embodiment of the mist recovery apparatus; FIG. 5 is an exhaust flow chart of a system including the mist recovering apparatus shown in FIG. 4; and FIGS. 6 (a) to 6 (c) show various modifications of the chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the mist recovery apparatus according to the present invention will be described with reference to the accompanying drawings. As apparently shown in FIG. 1 depicting a perspective view of the fist embodiment of the mist recovery apparatus according to the present invention, a casing 10 of the apparatus has a pair of an upper and a lower pipe plates 9 and a number of exhaust passing pipes 6, made of copper or copper alloy, are arranged between the upper and the lower pipe plates 9. Within the interior of each exhaust passing pipe 6, a twisted plate 7 made of metal, such as stainless steel or aluminum alloy, and having an outer diameter smaller a little than the inner diameter of the exhaust passing pipe 6 is provided, as shown in FIG. 2. Upper and lower ends of the exhaust passing pipes 6 extend through the upper and lower pipe plates 9 and open. Through the exhaust passing pipes 6, exhaust containing mist passes. These exhaust passing pipes 6 are arranged in row and cooling air flows around the outer walls of the respective exhaust passing pipes 6 along the direction substantially perpendicular to the direction of the exhaust passing pipes 6 in order to cool the interior of the exhaust passing pipes 6 through their outer walls. A discharge duct 11 provided with a discharge outlet 4 is disposed from the bottom portion to one side of the casing 10. Flowing streams of the exhaust containing mist and the cooling air will be made apparent with reference to FIG. 1. The exhaust containing mist of water and oil from the a rolling mill and the like installation is supplied to the mist recovery apparatus through a duct connected to the top portion of the casing 10. In detail, the exhaust is fed to the casing 10 of the apparatus through the fumy exhaust inlet 1. Then, the exhaust flows into the exhaust passing pipes 6 open on the upper pipe plate 9, contacts with the inner wall of the pipe 6 and the twisted plate 7 placed in the exhaust passing pipe 6 and thereby is cooled. In consequence, the mist contained in the exhaust is separated on the interior of respective exhaust passing pipes 6 and the surface of the twisted plate 7. The exhaust is flown out of the exhaust passing pipes 6 open on the lower pipe plate 9, passes through the fume discharge outlet 8 formed at the lowest portion of the discharge duct 11, and rises along the side wall of the casing 10. There is a guide vane 5 in the interior of the discharge duct 11, so that the flow speed of the rising exhaust increases and the exhaust acts as an ejector at the end portion of the guide vane 5. In the interior space at the top end of the guide vane 5, the rising exhaust sucks the cooling air flow passing through the casing 10, is mixed with the cooling air and discharged into the air through the discharge outlet 4 formed at the upper portion of the duct 11. Due to the exhaust flow rising along the side of the casing 10, suction effect or siphon phenomenon is generated, so that the cooling air is sucked from a cooling air inlet side 3 into the casing 10 and passes between the exhaust passing pipes 6, thereby cooling the exhaust passing pipes 6 through their outside walls. The cooling air is discharged from a cooling air outlet side 2 opposite to the cooing air inlet side 3 and is mixed with the exhaust discharged from the fume discharge outlet 8, at the end portion of the guide vane 5. The mixture is flown out of the discharge outlet 4 to the atmosphere. FIG. 3 is a flow chart including the mist recovery apparatus of the present invention. When fumy mist generated from a rolling installation (mill) and floats upward, it is sucked by a blower B through a hood and supplied to the mist recovery apparatus according to the present invention. After the mist contained in the exhaust fume is separated in the mist recovery apparatus, the remaining exhaust is mixed with cooling air by its ejection function (i.e, suction mixing function), and discharged to the atmosphere. The separated mist is drained through a pump P to the oil cellar positioned under the hood, as shown in FIG. 3, and reused. Since the exhaust is mixed with flowing-out air, which is warmed-up by heat exchange between it and the hot exhaust, the mixture is unsaturated with water steam, resulting in a considerable reduction of white smoke to be discharged from the discharge outlet 4. According to another preferred embodiment of the mist recovery apparatus, a chamber 12 is provided on the discharge duct 11 which is disposed upwardly from the lower portion to the side portion of the casing 10, as shown in FIG. 4. As described above, the discharge duct 11 has the guide vane 5 extending upwardly from the fume discharge outlet 8 to the discharge duct 11. A cooling air flow is sucked by the exhaust flowing along the guide vane 5 and mixed with the exhaust. The chamber 12 has a lower bell mouth 12a and an upper bell mouth 12b. Due to the provision of the chamber 12, the exhaust and cooling air are further mixed and then discharged to the atmosphere. It is possible to change the shape of the chamber 12, as shown by FIG. 6(a), FIG. 6(b) and FIG. 6(c). The chamber 12 having the shape as shown in FIG. 4 and appropriate dimensions is most effective, because, at the inlet part (lower bell mouth 12a) of the chamber 12, the blended exhaust fume is converged to the center of the chamber 12 so as to permit a more intimate mixing and, at the outlet of the chamber 12 (the upper bell mouth 12b), the discharging fume is diffused. As described above, the mist recovery apparatus of the present invention provides the following effects. (1) Scattering of offensive and ill-smelling white smoke and mist is reduced or prevented. (2) Mist with a particle size of 10 µm or more is sufficiently recovered. (3) Recovery efficiency of at least 95% is attained, when the particles size distribution of the mist is less than 150 µm. (4) Rolling oil used in a rolling mill is reused after being recovered.

Claims: A mist recovery apparatus comprising a casing (10) with an upper pipe plate (9) and a lower pipe plate (9'); a plurality of exhaust passing pipes (6) arranged perpendicularly to and between the lower and upper pipe plates (9, 9') and each having a twisted plate (7) therein; apertures formed at the sides of said casing (10) to permit a cooling air flow to pass through said casing (10) along the direction perpendicular to that of the exhaust passing pipes (6); an exhaust supply duct connected to an upper chamber (13) extending above said upper pipe plate (9) of said casing (10), said upper chamber (13) receiving an exhaust (1) containing mists; a mist reservoir (13', 14) disposed below the lower pipe plate (9'); a discharge outlet (8) extending upwardly from the lower chamber (13') to the side of said casing (10) so as to flow an exhaust flow from said exhaust passing pipes (6) to a discharge duct (11) disposed along the side of and in communication with said casing (10) to discharge said exhaust out of said casing (10); and a guide vane (5) provided into the discharge duct (11) so that the rising exhaust, from which the mists have been removed, sucks at the top end of the guide vane (5) the cooling air flow passing through the apertures and is mixed therewith. A mist recovery apparatus as claimed in Claim 1, in which a vertical chamber (12) is connected to the top end of said exhaust duct.

Inventors: KISARAGI TAKAYASU, SATOMI KINZO, KISARAGI, TAKAYASU, SATOMI, KINZO
Applicants: SUMITOMO LIGHT METAL IND, SUMITOMO LIGHT METAL INDUSTRIES LIMITED
Application year: 1990
Main classification: B01D45
IPC codes: B01D50, B01D45, B08B15