AU602586B2

AU602586B2 - Device and process for closing off the partitions of a chamber ring furnace for firing carbonaceous blocks

Info

Publication number: AU602586B2
Application number: AU17492/88A
Authority: AU
Inventors: Bernard Boffa; Christian Dreyer
Original assignee: Aluminium Pechiney SA
Current assignee: Rio Tinto France SAS
Priority date: 1987-06-09
Filing date: 1988-06-08
Publication date: 1990-10-18
Anticipated expiration: 2008-06-08
Also published as: NO170744B; MY103300A; CN1016539B; AU1749288A; CN88103424A; BR8802793A; NO882522L; NO882522D0; DE3864592D1; IN169512B; EP0295192B1; IS1509B; SU1641199A3; NO170744C; FR2616525A1; CA1333329C; FR2616525B1; EP0295192A1; IS3355A7

Description

S F Ref: 58715 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

60 2586 FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: P, riority: aRelated Art: IF a -rr Name and Address S of Applicant: 4 e Aluminium Pechiney 23, rue Balzac 75008 Paris

FRANCE

4 Address for Service: Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Device and Process for Closing off the Partitions of a Chamber Ring Furnace for Firing Carbonaceous Blocks The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3

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ABSTRACT

The invention relates to a deployable, detachable closure device for an open chamber ring furnace, for interrupting air circulation between each of the heating partitions of a chamber and the corresponding partitions of the adjacent chamber, this circulation normally taking place through a passage formed in the upper part of the transverse separation wall between the partitions of adjacent chambers, each partition having a plurality of draft holes in its upper part. This device consists of a flexible, rectangular, substantially air-impermeable closure means 22, supported on each of its two opposite long sides by a rigid section 21,21', these two sections being connccted at their terminal parts by two link rods 19,19' o 26,26' articulated on the one har' on each section 19,19' and on the other ,4 at their junction point 18,24, the first articulated junction 18 being 1arranged on a main section 12 forming a support, and the second articulated oil junction being arranged on a traction arm 14 which is mobile along the main section 16.

CMG/1117P TECHNICAL FIELD OF THE INVENTION The invention relates to a device and a process for closing off the partitions of a so-calied "ring furnace" or "progressive fire" open chamber furnace for firing carbonaceous bl cks such as anodes for the electrolytic production of aluminium by the Hall-Heroult process.

STATE OF THE ART The carbonaceous anodes for cells for the production of aluminium by electrolysis of alumina dissolved in molten cryolite are obtained by shaping a carbonaceous paste resulting from malaxing a mixture of pitch and pulverised coke at approximately 120 to 200'C. After shaping, the anodes are fired for about one hundred hours at a temperature of the order of 1100 to 12000C. Other types of carbonaceous blocks are obtained by the same process.

Although some processes exist for continuous firing in a tunnel i furnace, a large proportion of the firing plant in service in the world today are of the "chamber furnace" type known as "ring furnaces" or "advancing fire furnaces". These furnaces are themselves divided into two categories, closed furnaces and "open chamber" furnaces which are the most >1 used, described notably in US Patent No. 2 699 931, or French Patent No. 2 535 834 GB 2 129 918) in the name of Aluminium Pechiney. The present invention applies more particularly to open chamber furnaces. This type of furnace includes two parallel spans, the total length of which may i be more than one hundred meters. Each span 2 has a succession of chambers 1 which are separated by transverse walls and open at the top for charging green blocks and discharging cooled fired blocks. Parallel with W the long axis XX' of the furnace, each chamber includes an assembly of hollow partitions 3 with thin walls, in which the hot firing gases will circulate, these partitions alternating with cavities 5 in which the blocks 6 to be fired are staked, buried in a carbonaceous dust (coke, anthracite, pulverized carbonaceous residues or any other pulverulent filling material). There are, for example, 6 cavities and 7 alternating partitions per chamber.

The hollow partitions have at the top closeable openings known as "draft holes" or "partition draft holes"; they also have baffles 4 to extend and distribute more uniformly the path of the combustion gases.

Moreover, each partition of a chamber communicates with the corresponding partition of the upstream chamber and the downstream chamber through openings (known as wall draft holes) 8 formed in the upper part of the transverse wall and which are closable by introduction of shutters known as CMG/I1117P -ir- i- "registers" into a slot formed in the upper part of the wall.

In figure 1, the different lines of partition draft holes are designated from the pipe 9 by the references 7A, 7B and 7C, the reference 7 designating a partition draft hole generally.

The furnace is heated b. rows of burners having a length equal to the width of the chambers and the injectors of which are positioned in the draft holes of the relevant chambers. Upstream of the burners (relative to the advance direction of the fire) is arranged a combustion air blow pipe and, downstream, a pipe for aspiration of the burned gases. Heating is effected both by combustion of the injected fuel (gas or fuel oil) and that of the pitch vapours emitted by the blocks during firing. Each pipe, such S as 9, has the same number of outlet tubes 10 as there are partition draft S holes 7 in a line (here 7) into which they penetrate.

o 00 Progressively as firing takes place, e.g. every 24 hours, the assembly of blow pipes burners aspiration pipes is advanced, each o chamber thus successively undergoing the functions of charging the green carbonaceous blocks, natural preheating (by the combustion gases), forced preheating and firing at 1100-1200' (known as the high fire zone), cooling of the carbonaceous blocks (and preheating of the combustion air), ;Po 0 0 discharging of the fired carbonaceous blocks, possible repairs and so on.

0 "o TECHNICAL PROBLEM TO BE SOLVED Optimal management of an open chamber ring furnace involves o monitoring numerous parameters and more particularly the circulation of air and combustion gases effected by at least one blow pipe upstream of the so-called "fire" zone and an aspiration pipe situated downstream of the zone and having burners in which the anodes to be fired are preheated by the combustion gases. It is essential that the aspiration pipe only draws in combustion gases and the smallest possible amount of outside air. For this purpose, it is necessary to block passage of the gases between the last preheating chamber and the next chamber downstream, known as the "dead chamber", which is usually done by means of sliding registers introduced into the wall draft holes.

Experience shows that this blocking is often far from perfect and that there are often substantial intakes of ambient air by infiltration.

The aim of the present invention is to resolve this disadvantage and ensure a tight closure between the last natural preheat chamber and the dead chamber.

CMG/ 11 17P OBJECT OF THE INVENTION A first object of the invention is a deployable, detachable closure device for closing the communication opening between each partition of a chamber and the corresponding partition of the adjacent chamber, and more particularly of the last natural preheat chamber and the dead chamber which follows it in the downstream direction (relative to the circulation direction of the gases).

A second object of the same invention is a process for closing off the partitions of a chamber furnace, permitting interruption of the air circulation between two successive partitions, using the deployable closure device, which process is characterised in that the device, in the occluded position, is introduced into the draft hole of the partition in question and then deployed.

The circulation can then be re-established by occluding the device in the partition and withdrawing it, in the occluded position, through the o same draft hole.

The deployable closure which is the object of the invention consists 0 of a closure means which is flexible, rectangular, substantially impermeable to air and is supported on each of its two opposite long sides by a rigid section, these two sections being connected at their end o sections by two link rods articulated on the one hand on each section and on the other at their junction point, the first articulated junction being rranged on a main section forming a support, the second hinged junction being arranged on a traction arm mobile along the main section. This tra tion arm has, at its upper end opposite to the articulation, a means for moving it relative to the main section and a means for locking it relative to this main section.

DESCRIPTION OF THE DRANINGS Figure 1 relates to the prior art and has been described above.

Figure 2 shows a diagrammatic plan of a part of a span of an open chamber furnace to which the invention relates.

Figures 3 to 8 relate to the invention.

Figure 3 shows a section through the deployable closure in position in one of the partitions of a chamber furnace.

Figure 4 shows a front view of the deployed closure in the deployed position.

Figure 5 shows a front view of the occluded closure.

Figures 6 and 7 show sections through two levels of the deployed closure.

CMG/ I 17P Figure 8 shows a section of the deployed closure in position in a partition.

The deployable closure includes an upper portion, with a support handle and an open/close control, this portion extending beyond the draft hole into which the closure is introduced, and a lower portion including a closing means, which is generally a flexible fabric, the open/close mechanism, and the means for resting on the lower edge of the opening which is to be closed off.

The upper portion consists of a main rigid profile 12, forming a support, e.g. U-shaped, provided at its upper part with a support handle 13. Along this section slides a traction arm 14, the upper part of S which, situated above the support handle 13, is linked to a sliding means, e.g. a threaded rod 15 cooperating with a threaded sleeve 16 fixed to the upper part of the section 12, and rotation of which is controlled by the operating handle 17. Rotation of the handle 16 relative to the axis of the threaded rod 15 (which is connected to the arm 14 by a swivel joint) therefore causes, depending on the direction of rotation, upward and downward sliding of the traction arm 14 relative to the rigid section 12.

The lower portion is composed in the following manner: the lower part of the section 12 is provided with an articulation 18 on which bear two upper link rods 19, 19' of equal length, arranged on either side of the traction arm 14 and the lower ends of which are connected by an articulation 20/20' to a section (support 21, 21') which acts as a support for the flexible fabric 22 forming the closure means for the opening 23 which normally provides communication with the heating partition 3 of the upstream adjacent chamber.

The lower part of the arm 14 is provided with an articulation 24 on which bear at one end two lower link rods 25, 25' of equal length, the other ends of which are connected by an articulation 26, 26' to the lower parts of the sections 21 and 21' respectively. The fabric 22 is fixed along each section 21 and 21' by a, for example, bolted or riveted counter-section 27 and 27'. It exceeds a certain length so that the tightness of the closure is ensured even if the nartition in question is slightly deformed. The width of the fabric can be greater by 5 to 50% than the maximum separation of the sections 21-21' in the deployed position, the excess being substantially symmetrical on each side relative to the axis of the traction arm 14.

Taking account of the moderated temperature (less than 100°C) in the partitions of the dead chamber, the choice of fabric is not critical and CMG/l 1 17P .strength and tightness will be more important considerations. Successful use has been made of fabrics woven from mineral fibres (glass, various silicoaluminates), covered with a heat fixed sheet of aluminium-Mylar composite or coated with silicone.

The operation of the closure is as follows: the traction arm 14 is lowered to the maximum by operation of the handle 17. This operation moves articulation 24 away from articulation 18, which has the effect of bringing together the sections 21, 21' which are finally practically in contact, as shown in figure 6, and the fabric can be folded around the adjacent sections by hand. In this occluded position the closure is introduced through the partition draft hole 7 and lowered on the slant, bearing on the S lateral edges of the draft hole until the lugs 28 and 28' arranged at the o0 bases of the sections 21-21' come into contact with the lower edge 11 of the passage 8.

0 The closure can then be deployed by turning the handle 17 in the S0o opposite direction, which results in the rising of arm 14 and therefore the moving together of the articulation 24 and the articulation 18, link rods 19-19' and 25-25' opening out, thus causing the moving apart of the sections 21-21' parallel to the arm 14 to the maximum permitted by contact o%2O between each section 21-21' and the lateral walls 29, 29' of the "o partition. In this position the fabric prevents any entry of air into the corresponding partition of the last natural preheating chamber (which is in o,:oo depression), from the partitions of the dead chamber which is in communication with the open air.

It is important to stress that the seal with the sides of the partition is formed even if the partition is deformed, due to the excess of the fabric relative to the axes 21, 21' and the depression in the upstream chamber.

By use of the invention, air circulation between two successive partitions is interrupted not at the level of the draft hole in the transverse wall, but by closure of the gas passage at the outlet of the partition. In fact this closure means is introduced into the partition draft hole and is deployed inside the latter. This closure is no longer introduced at the level of the wall draft holes as in the past with the old registers.

The location and withdrawal of the n closures (seven in the illustrated case) in the seven partition draft holes is quick and without risk to personnel or equipment. Moreover it requires no modification of the existing partition draft holes.

CMG/l 117P

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The invention can be used with certain modifications, particularly with regard to the mechanism for controlling the traction arm 4: instead of rotation of a threaded rod 15 controlled by a handle (which takes a long time to operate if the thread is fine), a cam and lever movement can be used, with swinging of the operating handle.

When the opening control is effected by rotation of a threaded rod, the control is an irreversible principle and therefore self locking, especially if the thread is fine. In the case of a cam and lever control, control must be effected so that locking is effected in the extreme S 10 position of the handle corresponding to the deployed position of the closure.

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Claims

1. Closure device for an open chamber ring furnace comprising: a flexible, rectangular, substantially air impermeable fabric, the fabric fastened along opposite sides to two generally parallel rigid sections the sections having upper and lower ends, the lower ends each connected by first pivotable linking rods to a lower junction on a main elongated rigid section, the upper ends each connected by second pivotable linking rods to an articulation on a displaceable traction arm which slides with respect to the main elongated rigid section.

2. Closure device in accordance with claim 1, characterised In that, the traction arm is provided with a means for moving it relative to the main rigid section.

3. Closure device in accordance with claim 1 or 2, further comprising: I means for immobilizing the traction arm relative to the main rigid section.

4. Closure device in accordance with claim 2, charactersed in that 0 the means for moving the traction arm Is a threaded rod fixed to the upper end of the traction arm, and cooperating In its extension by means of a 0 swivel joint with a threaded sleeve rigidly attached to the upper part of the main rigid section.

Closure device in accordance with any oine of claims 1 to 4, o characterlsed in that the fabric is selected from fabrics and felts made of 0100 mineral fibres or synthetic fibres. 00

6. Closure device In accordance with any one of claims 1 to characterised in that the width of the fabric is greater by 5 to 50% than the maximum spacing between the sections in a deployed position, the excess being substantially symmetrical on each side.

7. Process for interrupting the air circulation between two consecutive partitions of a chamber ring furnace by means of a deployable closure in accordance with any one of claims 1 to 6, characterised in that the deployed closure device is introduced in an occluded position through the draft hole of the partition and is then deployed by action at a distance on the traction arm. -9- -J

8. Process In accordance with claim 7 characterised in that the lower part of the closure is placed in contact with the lower edge of the passage between the two partitions in question.

9. Process in accordance with claim 7, characterised in that, to re-establish the air circulation between the two partitions in question, the closure is occluded in the partition, by action on the traction arm, and it is withdrawn in the occluded state through the draft hole. A closure device substantially as hereinbefore described with reference to Figs. 3-8. DATED this TWENTY-FIFTH day of JULY 1990 Aluminium Pechlney Patent Attorneys for the Applicant SPRUSON FERGUSON .t i:2 _1 i i i I .A S j :-a 1 ii ;-r i i 10 rhk/0174E _L ii~..