US3737554A

US3737554A - Electric smelting furnace of closed-type having dust removing means fixed to exhaust gas vent pipes thereof

Info

Publication number: US3737554A
Application number: US00242976A
Authority: US
Inventors: K Horibe; T Yosida; T Machida; S Kaneko; T Sato
Original assignee: Tanabe Kakoki Co Ltd
Current assignee: Tanabe Kakoki Co Ltd
Priority date: 1971-04-14
Filing date: 1972-04-11
Publication date: 1973-06-05
Anticipated expiration: 1990-06-05
Also published as: SU520056A3; BR7202231D0; JPS4848305A; ZA722229B

Abstract

A closed-type electric furnace to be used for extremely high temperature smelting of a ferroalloy such as metallic silicon or 70 percent ferrosilicon. The furnace has at least two dual service pipes, each of which functions as a raw material charging chute and concurrently as an exhaust gas vent pipe with the aid of its branch pipe, and a plural number of single raw material charging chutes through the furnace lid, whereby each dual service pipe has an automatic dust removing machine at the forked position thereof.

Description

United States Patent 1 Horibe et al.

[541 ELECTRIC SMELTING FURNACE OF CLOSED-TYPE HAVING DUST REMOVING MEANS FIXED T0 EXHAUST GAS VENT PIPES THEREOF [75] Inventors: Koichi Horibe; Tsunenobu Yosida;

Tokuji Machida; Shoji Kaneko; Tomoyuki Sato, all of Arai-shi, Niigata-ken, Japan [73] Assignee: Tanabe Kakoki Co., Ltd., Niigataken, Japan [22] Filed: Apr. 11, 1972 21 Appl. No.: 242,976

[30] Foreign Application Priority Data Apr. 14, 1971 Japan ..46/23566 52 US. Cl. ..13/33 51 rm. Cl.

[58] Fieldof Search .L ..13/9,33,

[ 51 June 5,1973

[56] References Cited UNITED STATES PATENTS 3,598,888 8/1971 Tada et al ..13/33 3,441,651 4/1969 Viens et al ....l3/9 3,372,223 3/1968 Menegoz et al. 1 3/9 Primary Examiner-Roy N. Envall, Jr. Att0rney-So|o'n B. Kemon, Carroll Palmer and William T. Estabrook 57 ABSTRACT A closed-type electric furnace to be used for extremely high temperature smelting of a ferroalloy such as metallic silicon or 70 percent ferrosilicon. The furnace has at least two dual service pipes, each of which functions as a raw material charging chute and concurrently as an exhaust gas vent pipe with the aid of its branch pipe, and a plural number of single raw material charging chutes through the furnace lid, whereby each dual service pipe has an automatic dust removing machine at the forked position thereof.

4 Claims, 6 Drawing Figures PATENTEDJUN Sim SHEET 2 OF 3 I FIG 3 l l I.

FIG-4 ELECTRIC SMELTING FURNACE OF CLOSED-TYPE HAVING DUST REMOVING MEANS FIXED TO EXHAUST GAS VENT PIPES THEREOF This invention relates to an electric smelting furnace of closed-type, and more particularly to the one having dust removing means fixed to exhaust gas vent pipes thereof.

Heretofore, electric smelting furnaces of closed-type have been used for the industrial production of calcium carbide, ferromanganese, ferrochromium, 50% ferrosilicon or other similar substances, the smelting temperature of these substances being comparatively low. In smelting of extremely high temperature such as those of metallic silicon or a ferrosilicon containing more than 70 per cent of silicon, there is evolution a large amount of dust evolution mixed with the exhaust gas. Therefore, it has been considered practically impossible to produce such substances using a closed-type smelting furnace, because that the passage of exhaust gas vent pipe communicated to the furnace lid is liable to be blocked by said largeamount of dust. Unfortunately, the dust of such case has an exceedingly cohesive and solidifying nature, and it is very difficult to remove such coherent dust block from the vent pipe wall.

In a conventional electric smelting furnace of closedtype, the dust accumulated in the exhaust vent pipe is occasionally cleaned out by a band poking means when the furnace operation is temporarily stopped. However, in the case of aforementioned high temperature smelting, frequent stoppage of its operation would not be permitted because that a smooth and economical production could not be continued.

An object of the present invention is to manufacture a ferroalloy necessitating an extremely high temperature smelting by the use of closed-type electric furnace. Another object of the present invention is to provide a closed-type electric furnace suitable for the continuous production of 70% ferro'silicon or metallic silicon. These objects may be attained in accordance with the present invention by setting up a plural number of single raw material charging pipes and at least two dual service pipes having a branched part respectively which function as exhaust gas vent pipes and simultaneously as raw material charging chutes, whereby each dual pipe has an automatic dust removing machine installed at the branched position thereof.

Further objects and advantages of this invention will become apparent with reference to the following description and the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-sectional view, taken along the line AA in FIG. 2, of the upper portion of a preferred embodiment of closed-type electric furnace according to the present invention;

FIG. 2 is a cross-sectional plan view of the same taken along the line B-B in FIG. 1;

FIG. 3 is an enlarged plan view of dust removing machine 10 attached to a dual service pipe 1 in FIG. 1;

FIG. 4 is a longitudinal sectional view of the same taken along the line D-D in FIG. 3;

FIG. 5 is an enlarged plan view of another dust removing machine attached to a dual service pipe; and FIG. 6 is a longitudinal sectional view of the same taken along the line E-E in FIG. 5.

In FIGS. 1 and 2, the reference numeral 1 designates a plurality of raw material charging chutes, each of which being designed to serve concurrently as an exhaust gas vent pipe. This kind of chute pipe will be referred to in this specification as a dual service pipe hereinafter. The dual pipe 1 has a branch pipe 7 for gas exhaustion at a forked position 7a, and is equipped with an automatically acting dust removing machine 10 at this position.

- As shown in FIG. 2, the number of dual pipe is three in this case. The furnace lid 20 is dotted with a plural number of single raw material charging chutes therethrough (in FIG. 2, the number thereof being seven,) near the three electrodes 9 in a usual way. Imaginary lines designated by the reference numeral 2 or 3 show examples of the mounting position and configuration of conventional sole exhaust gas vent. In the present invention, however, such conventional mounting positions can not be adopted by the following reason (1).

As illustrated in FIG. 1, the manners in which the dust may invite clogging in the electric furnace are roughly classified into the following three types: (1 the dust is accumulated in a peripheral space of the furnace lid 20; (2) the dust is deposited on the interior surface of each dual service pipe 1 at the lower part thereof, and the deposition increases in thickness gradually until it invites such clogging as denoted by the reference numeral 5; and (3) the dust is deposited at the forked position 7a of each dual service pipe 1 as shown by the reference numeral 6.

In order to avoid the dust clogging indicated by the reference numeral 5 in FIG. 1, there may be employed a known method which has been actually practiced in some closed-type electric smelting furnace. That is, the longitudinal interior surface of dual service pipe 1 may be cleaned out with the charging raw materials la while they fall down through the dual service pipe 1 intermittently or continuously. The dust particles deposited are mostly those of raw materials which have been scattered or evaporated. Therefore, even if they are again thrown into the furnace accompanied with new raw materials, there is no harmful effect derived therefrom and the'utilization rate of the raw materials is rather improved.

Next, an explanation about the prevention of dust ac cumulation 4 at a peripheral space in the'furnace lid 20 of FIG. 1 will be described hereinafter. In a large scale furnace of closed-type for extremely high temperature smelting, such as those of metallic silicon or ferrosilicon, a large amount of gas and dust are generated from the surrounding area of every electrode. Therefore, only one exhaust gas pipe 2 or 3, as shown in FIG. 1, is not suitable for the above-mentioned furnace because that the dust accumulation 4 at a part of peripheral space in the furnace lid 20, which is remote from the sole exhaust gas dust outlet 2 or 3, (the relative po sitions of 4 and 2 or 3 is not shown in FIG. 1,) is liable to occur. In the present invention, at least two, preferably three or more, dual service pipes 1 should be set up through the furnace lid 20 at as near positions as possible to the electrodes 9 as shown in FIGS. 1 and 2. By this means, the dust accumulation at a peripheral space of furnace lid can be readily ceased to exist.

On the other hand, in case where all of the raw material charging chutes are constructed likewise as the dual service pipe to serve simultaneously as exhaust gas vent pipes, the velocity of gas flowing through said pipes would be too low, resulting in that the formation rate of dust clogging at the lower part of each dual service pipe would become higher than the velocity at which the accumulated dust particles are all buried into the raw material layer in the furnace. This tends to cause the accumulated dust to block the inlets of the dual service pipes. Therefore, other than a suitable number, at least two, of dual service pipes which give a proper velocity to the passing gas therethrough, there must be a plural number, appropriate to that of dual service pipes, of single raw material charging chutes set up through the furnace lid.

For removing the dust clog 6 at the forked position 7a of each dual service pipe 1 in FIG. 1, there must be equipped with an automatically acting dust removing machine 10 at said position, and it is operated continuously or intermittently, whereby the dust clog 6 is separated from the branch and is dropped into the inclined,

branch pipe 7 which is a part of vent pipe. Concurrent use of water flushing into the inclined branch pipe 7, as shown in the later figures, will further increase the dust removing effect like as hitherto. The dust removing machine 10 according to the present invention permits a long-type operation with unchanged performance and safety upon the production of metallic silicon or 70% ferrosilicon which accompanies a large quantity of coagulative dust in the exhaust gas generated by the reductive reaction in the furnace.

Detailed views of the dust removing machine 10 in FIG. 1 are shown in FIGS. 3 and 4. As will be seen, a cleaning piston disc 13 is arranged in a horizontal portion at the juncture of ascending portion 11 of the chute having a water cooling jacket 17 and descending branch pipe 12 of the dual service pipe. Said cleaning piston disc 13 is connected to a piston rod 14 of the dust removing machine 16 to make said cleaning disc 13 drive reciprocally, and the driving may be performed either continuously or intermittently and automatically by a suitable mechanism (not shown in the figure). The accumulated and coagulated dust on the juncture part is pushed down into the descending branch pipe 12 by the moving disc 13, and the dust thus swept off is flashed away with water which is injected into the branch pipe 12 from water spray nozzles affixed to said branch pipe 12.

FIGS. 5 and 6 show another embodiment of the dust removing machine according to the present invention. In this embodiment, a cylindrical rotary disc 24 is disposed on a horizontal juncture end of ascending chute portion 21 in the top part of descending branch pipe 22 of the dual service pipe, and has a vertical cleaning blade 23 fixed thereto. The cylindrical rotary disc 24 is connected to a motor 27 by means of gears 26 and a shaft 25 so as to rotate the cleaning blade 23 around the vertical axis of the cylindrical rotary disk 24, whereby the rotation is performed continuously or intermittently and automatically to sweep off the deposited dust at the juncture portion. The dust thus swept off is flashed away with water which is injected into the branch pipe 22 from water spray nozzles 28 affixed to saidbranch pipe 22.

After several test operations conducted by the usage of 15,000 KVA closed-type furnace just as shown in FIGS. 1 and 2 for the production of to ferrosilicon, it was ascertained that continuous and smooth operations could be carried out successfully for a long time without occurring any accumulation of dust and any clogging or blockage in gas passages of the furnace.

What we claim is:

1. An improved electric smeltingfurnace of the closed-type which comprises a furnace lid, a plurality of single raw material charging chutes having their discharge end extending through said lid, a plurality of dual service pipes extending at their discharge end through said lid, each of said dual service pipes comprising a raw material charging chute and an exhaust gas vent pipe, said chute and vent pipe being joined at a forked position above said lid and automatically operated means to remove dust from the junction of said chute and vent pipe at said forked position.

2. An improved electric furnace used for extremely high temperature smelting of a ferroalloy according to claim 1, wherein said dual service pipes are set up through the furnace lid as near electrodes as possible.

3. An improved electric furnace used forextremely high temperature smelting of a ferroalloy according to claim 1, wherein said automatically operated means comprises a reciprocating cleaning piston'disc connected with a horizontal piston rod and an automatic driving apparatus therefor.

4. An improved'electric smelting furnace according to claim 1 wherein each dual service pipe comprises'a lower chute portion having an upper-end that terminates within said forked position and said automatically operated means to remove dust comprises'a cylindrical rotary disc horizontally disposed on said upper end of said lower chute portion, a vertical cleaning blade fixed to said rotary disc and drive means to rotate said rotary disc.

Claims

1. An improved electric smelting furnace of the closed-type which comprises a furnace lid, a plurality of single raw material charging chutes having their discharge end extending through said lid, a plurality of dual service pipes extending at their discharge end through said lid, each of said dual service pipes comprising a Raw material charging chute and an exhaust gas vent pipe, said chute and vent pipe being joined at a forked position above said lid and automatically operated means to remove dust from the junction of said chute and vent pipe at said forked position.

3. An improved electric furnace used for extremely high temperature smelting of a ferroalloy according to claim 1, wherein said automatically operated means comprises a reciprocating cleaning piston disc connected with a horizontal piston rod and an automatic driving apparatus therefor.

4. An improved electric smelting furnace according to claim 1 wherein each dual service pipe comprises a lower chute portion having an upper end that terminates within said forked position and said automatically operated means to remove dust comprises a cylindrical rotary disc horizontally disposed on said upper end of said lower chute portion, a vertical cleaning blade fixed to said rotary disc and drive means to rotate said rotary disc.