IL26121A - Blast-furnaces - Google Patents

Description

Π1ΠΙ1 1Π3 1*11Π1"Ί "ΙΊ PATENT ATTORNEYS □ 1 D ] 13 D ' Ί 111 DR. REINHOLD COHN |Π3 TJini"T · n DR. MICHAEL COHN 1 Π 3 "7 N 3 ' D 'Π ISRAEL SHACHTER B.Sc. .0.3 3 H 3 HI ΐΜ ΐ αΐ ' 24903 PATENTS AND DESIGNS ORDINANCE SPECIFICATION IMPROVEMENTS IN OR RELATING TO BLAST—FURNACES I ( e) METALLURGICAL PROCESSES LIMITED, A COMPANY INCORPORATED IN THE BAHAMAS, OF TRUST BUILDING, FREDERICK STREET,NASSAU, BAHAMAS, AND IMPERIAL SMELTING CORPORATION (N.S.Q.) LIMITED, A BRITISH COMPANY, OF 9, BASINGHALL STREET, E.G.2, IN THE CITY OF LONDON, ENGLAND, CARRYING ON BUSINESS TOGETHER IN THE BAHAMAS UNDER THE NAME AND STYLE OF METALLURGICAL DEVELOPMENT COMPANY, OF TRUST BUILDING, FREDERICK STREET, NASSAU, BAHAMAS. do hereby declare the nature of this invention and in what manner the same is to "be performed, to be particularly described and ascertained in and by the following statement: - This invention relates to improvements in blast-furnaces.

The technique of smelting oxidic zinc-bearing materials in a blast-furnace with recovoy of metallic zinc vapour from the top of the furnace is now well established. In this process, sintered zinc-lead oxidic material and carbonaceous reducing material are charged to the top of the furnace, slag, lead bullion and sometimes copper matte are removed from the bottom of the furnace and zinc vapours and carbon monoxide/carbon dioxide are withdrawn from the top of the furnace into condensers. Here the zinc is condensed by shock-chilling the vapours with a spray or shower of molten lead.

Any dust present in the gases leaving the top of the furnace interferes with the efficiency of condensation of the zinc because this dust prevents coalescence of the metal droplets and hence good condensation is impaired.

For this reason, it is particularly important that the charge entering the top of the furnace should be as free as possible from small-particle-size solids. The removal of small particle solids from the charge is one object of this invention. The ways in which this removal is achieved may be various. Hence the fines may be screened out of the charge before it is elevated to the top of the furnace or may be removed from the charge by blowing or sucking air through it.

One aspect of the invention consists in a method of oper-ating a zinc/lead blast-furnace in which oxidic zinc/lead material and carbonaceous reducing agent are introduced into the top of the furnace and metallic zinc vapour is withdrawn from the top of the furnace, characterized in that at least 50% of the fine material, (less than 20 microns) is removed from the charge before the charge enters the furnace, thus reducing » » In one embodiment of the invention the fines are removed from the charge in the charging-gear at the top of the furnace, mmediately before the charge enters the furnace.

In this way, the dust is removed from the charge immediately before the latter enters the furnace and thus further mechanical breakdovm of the charge is not likely to produce many more fines before the charge enters the smelting zone.

An advantage of carrying out the invention by means of the method described above is that this method results in the minimum loss of heat from the pre-heated charge material.

Alternative ways of achieving the object of the invention will be appreciated by those skilled in the art. Thus, the fines may be sieved or screened out of the charge either at the sinter plant from which the oxidic material originates or immediately before being elevated to the top of the furnace.

One type of sinter is the zinc oxide sinter prepared by the sintering of zinc blende ores e.g. on a travelling sinter bed.

Air is blown into the product sinter or charge and suction is applied to remove the dust blown off.

Preferably the blowing and sucking is applied simultaneously and continuously although these operations could be carried out alternately and intermittently.

The air velocities induced and the corresponding fan sizes will depend on the size of sinter fines to be removed. Thus, to remove fines less than 36 B.S.S. (420 microns) a control velocity of 16 feet per second is required.

The invention will be further described with reference to the accompanying drawings.

Figure 1 is a side elevation, and - n l n I-II f Figure 3 is a diagrammatic vertical section of a feed device for a weighing hopper for sinter, and Figure is a view in the direction of the arrow A of Figure 3· In Figures 1 and 2 is shown a conventional hopper 1 forming part of a bell and hopper charging gear for a blast-furnace.

Inserted within the conventional hopper is a section 2 which comprises a cylindrical shell part 2a some 10 inches wide and six feet in diameter and which over half its diameter is embraced by a claw-shaped feed duct 2b having a nine inch stream-lined aperture 2ba adapted to be supplied with air under pressure from a fan of, say, 2, 000 cubic feet per minute capacity.

The air under pressure enters the cylindrical shell 2a through circumferentially spaced holes 2aa, of two inch diameter at six inch spacing.

Diametrically opposite to the air inlet aperture 2ba is a streamlined outlet aperture 2ab of ten inch diameter to which is applied an exhaust fan of 2, 000 c.f.m. capacity.

In operation Jets of air will enter the sinter inside the hopper, prior to it being dropped into the furnace, in the form a jet flow through the apertures 2aa inwardly directed in a fan shape towards the outlet aperture 2ab as shown by the arrows. Dust blown out of the sinter will be picked up and removed through the oppositely disposed exhaust outlet 2ab .

In Figures 3 and 4- sinter is shown as fed from a screen-feeder 3 in a weigh-hopper 4-, above which is an exhaust hood 5« Attached to this hood is the exhaust duct 6.

Immediately above and to one side of the hopper 4-, under the outlet of the feeder 3* is provided a nozzle 7 which is supplied with air from a 2, 000 c.f.m. fan 8 mounted at ground exhaust duct and blows out the fines which are removed by the exhaust suction.

Alternatively the fines may be removed by blowing air in at the top of the screen-feeder 3 and sucking out the air together with the entrained dust particles from the duct 10 below the screen.

Various modifications may be made in accordance with the invention.

Claims (15)

1. HAVING NOW PARTICULARLY DESCRIBED AND ASCERTAINED THE NAT'JRE OC OUR 8AI0 INVENTION AND IN WHAT MANNER THE SAME IS TO BE PERFORMED, W6 DECLARE THAT WHAT WE CLAIM ISt What we claim is : - 1» A method of operating a zinc blast-furnace in which oxidic zinc/lead material and carbonaceous reducing agent are introduced into the top of the furnace and metallic zinc vapour is withdrawn from the top of the furnace, characterized in that at least 50% of the fine material, (less than 420 microns) is removed from the charge before the charge enters the furnace, thus reducing the dust carry over into the lead-splash condensers and improving the efficiency of zinc condensation.

2. A method as claimed in claim 1 in which the fines are removed from the charge in the charging-gear at the top of the furnace, immediately before the charge enters the furnace.

3. A method as claimed in claim 1 in which the fines are sieved or screened out of the charge at the sinter plant.

4. A method as claimed in claim 1 in which the fines are sieved or screened out of the charge immediately before being elevated to the top of the furnace.

5. A method as claimed in any of the preceding claims in which air is blown into the product sinter or charge and suction is applied to remove the dust blown off.

6. A method as claimed in claim 5 in which blowing and sucking is applied simultaneously.

7. A method as claimed in claim 6 in x^hich the blowing and sucking is carried out continuously.

8. A method as claimed in claim 7 in which blowing and sucking is carried out intermittently.

9. A method as claimed in claim 5 i which the blowing and sucking operations are carried out alternately.

10. A method as claimed in claim 2 in which the fines are removed from the hopper forming part of the charging-gear.

11. A method as claimed in claim 10 in which air under pressure is supplied over one half of the diameter of the hopper and removed from an exhaust outlet opposite thereto.

12. A method as claimed in claim 1 in which the sinter is fed to a weigh-hopper which is blown by means of an air nozzle blowing out the fines into an exhaust duct. ,

13. A method as claimed in claim 1 in which fines are removed by blowing air in at the top of a screen-feeder and sucking out the air together with the exhaust dust particles from a duct below the screen.

14. -. A method of operating a blast-furnace as claimed in claim 1 using apparatus substantially as described and shown in Figures 1 and 2.

15. A method of operating a blast-furnace as claimed in claim 1 using apparatus substantially as described and shown in Figures 3 and 4. PMG/LG.