Gas separation: apparatus – Electric field separation apparatus – Including gas flow distribution means
Reexamination Certificate
1998-03-12
2001-01-23
Chiesa, Richard L. (Department: 1724)
Gas separation: apparatus
Electric field separation apparatus
Including gas flow distribution means
C096S088000, C096S097000, C096S098000, C110S216000
Reexamination Certificate
active
06176902
ABSTRACT:
RELATED APPLICATION
This application is a national stage application of PCT/JP98/00846 filed on Feb. 27, 1998, which claims priorty of Japanese Patent Application 9-62281 filed on Feb. 27, 1997.
TECHNICAL FIELD
The present invention relates to an electric dust collector and an incinerator, the electric dust collector having both an exhaust pipe with a metallic pipe whose interior surface lined with refractory matter and a discharge pipe supported within the exhaust pipe.
BACKGROUND ART
A conventional electric dust collector is shown in Japanese Utility Model Publication No. 3021572 by way of example. That is, a metallic beam crosses above the exit of an exhaust pipe, the exhaust pipe having a metallic pipe whose interior surface lined with refractory matter. On approximately the center line of the exhaust pipe, a discharge electrode is hung from the crossbeam into the exhaust pipe so that it is electrically insulated from the exhaust pipe. A high DC voltage is applied between the discharge electrode and the metallic pipe through the crossbeam, whereby dust is collected at a high temperature from exhaust gases passing through the exhaust gases.
Practically the conventional high-temperature type electric dust collector, however, has restrictions on the operating voltage of a high-tension power supply. For this reason, when the diameter of the exhaust pipe is large, the electric field between the exhaust pipe and the discharge electrode cannot be increased to infinity. As a result, there is a possibility that the smoke dust flowing along the central portion of the exhaust pipe will pass through the exit of the exhaust pipe without being guided to the pipe exterior surface of a dust-collecting electrode. For this reason, the conventional high-temperature type electric dust collector lengthens the axial length of the dust collecting section of the exhaust pipe to eliminate the aforementioned disadvantage. However, since the exhaust pipe lengthens, there is a problem that the production cost will increase.
The present invention has been made in view of the aforementioned problems. Accordingly, it is an object of the present invention to provide an electric dust collector and an incinerator that are capable of enhancing collection efficiency without lengthening the dust collecting section of an exhaust pipe.
DISCLOSURE OF THE INVENTION
To achieve the aforementioned object, an electric dust collector according to the present invention comprises: (1) an exhaust pipe with a metallic pipe whose exterior surface is lined with refractory material; (2) an electrode provided to spread within the exhaust pipe, the electrode having a plurality of air holes for disturbing passage of smoke dust charged_with electricity to the polarity of the same kind; (3) a supporting member supported outside the exhaust pipe, the electrode being electrically insulated from the exhaust pipe by the supporting member; and (4) a high-tension power supply for applying high DC voltage between the electrode and the metallic pipe, the power supply being provided outside the exhaust pipe and also being electrically connected to the electrode.
The exhaust pipe is circular in cross section, polygonal, or in other shapes. It is preferable that the metallic pipe constituting the exhaust pipe consist of steel. The refractory material covering the interior surface of the metallic pipe may be an insulator at normal temperature. The interior surface of the exhaust pipe does not necessarily have a perfect conducting property like metal at all times. This is because the interior surface will be sufficient if it has a conducting property necessary for neutralizing the electric charge of the smoke dust collected only at a high temperature. It is particularly preferable that the refractory material covering the interior surface of the metallic pipe consist of castable refractory material (refractory concrete with SiO
2
and Al
2
O
3
as main components) and the like. The electrode spreads interiorly of the exhaust pipe and has a three-dimensional shape other than a bar-shaped electrode. The electrode may be either in frame form or in surface form. The electrode may consist of a metal wire, a chain, line material concentrically wound at intervals of a predetermined pitch, line material spirally wound at intervals of a predetermined pitch, a punched metal, an expanded metal or the like, if they have a plurality of air holes for disturbing passage of the smoke dust charged with electricity to the polarity of the same kind. The supporting member may be an insulator, if it is wired interiorly so that it can supply electricity to the electrode.
The first electric dust collector disposes burned exhaust gases with the exhaust pipe. The exhaust pipe is exposed to the high temperature of the exhaust gases; however, since the interior surface has been covered with refractory material, the exhaust pipe can prevent degradation due to a high temperature. Between the electrode and the metallic pipe, a high DC voltage is supplied by a high-tension power supply. For polarities, it is preferable that as in electric dust collectors for general industry, the exhaust pipe be positive and the electrode negative.
The interior surface of the exhaust pipe consists of refractory material, so it has an insulating property at normal temperature and rarely conducts electricity. However, if the internal surface reaches a high temperature of 400° C. or more, it will lose the insulating property and conduct electricity. When the exhaust pipe passes burned exhaust gases therethrough, the interior surface reaches 400° C. or higher and usually reaches a high temperature of 800° C. or so, so that the exhaust pipe becomes a dust-collecting electrode. Since a great number of thermions are present, active corona discharge takes place between the electrode and the exhaust pipe. Due to corona discharge, the smoke dust in the exhaust gases passing through the exhaust pipe is negatively charged with electricity and adheres and condenses on the interior surface of the exhaust pipe. In this manner, smoke dust is removed from exhaust gases, which are in turn discharged from the exit of the exhaust gas.
Incidentally, in the case where the electric field in the interior of the exhaust pipe is weak, even if a bar-shaped electrode were coaxially provided within the exhaust pipe, there will be a possibility that the smoke dust flowing through the exhaust pipe will not be driven to the interior surface of the exhaust pipe. However, an electrode is provided to spread within the exhaust pipe and the distance between the interior surface of the exhaust pipe and the electrode is shortened, whereby the strength of the electric field therebetween is increased. The electrode has air holes. The exhaust gases passing through the air holes are allowed to pass, while passage of the smoke dust charged with electricity to the polarity of the same kind is inhibited. Because of corona discharge, the smoke dust charged with electricity to the polarity of the same kind is guided to the direction of the exhaust pipe along the electrode and adheres and condenses to the interior surface of the exhaust pipe. Thus, even when the electric field in the interior of the exhaust pipe is weak, collection efficiency is enhanced, whereby the smoke dust in exhaust gases can be removed.
A second electric dust collector is characterized in that in the first electric dust collector, the electrode comprises a discharge electrode and a surface electrode. The discharge electrode is arranged substantially coaxially with the exhaust pipe, and the surface electrode has the air holes, is also connected to the discharge electrode protruding downward, and furthermore spreads toward a wall surface of the exhaust pipe.
It is preferable that the discharge electrode be supported to be electrically isolated from the exhaust pipe by a supporting member. It is also preferable that the discharge electrode be provided with a great number of discharge needles radially. Provision of the discharge needles renders it possible for corona
Chiesa Richard L.
Galaxy Yugen Kaisha
Snider Ronald R.
Snider & Associates
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