EP1236816A1 - Procédé de dézingage de l'acier galvanisé - Google Patents
Procédé de dézingage de l'acier galvanisé Download PDFInfo
- Publication number
- EP1236816A1 EP1236816A1 EP02075407A EP02075407A EP1236816A1 EP 1236816 A1 EP1236816 A1 EP 1236816A1 EP 02075407 A EP02075407 A EP 02075407A EP 02075407 A EP02075407 A EP 02075407A EP 1236816 A1 EP1236816 A1 EP 1236816A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- galvanized steel
- zinc
- steel
- process according
- scrap
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000000034 method Methods 0.000 title claims abstract description 46
- 229910001335 Galvanized steel Inorganic materials 0.000 title claims abstract description 43
- 239000008397 galvanized steel Substances 0.000 title claims abstract description 43
- 230000008569 process Effects 0.000 title claims abstract description 40
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 96
- 239000011701 zinc Substances 0.000 claims abstract description 96
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 93
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Inorganic materials [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 71
- 239000003792 electrolyte Substances 0.000 claims abstract description 35
- 239000000463 material Substances 0.000 claims abstract description 26
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims abstract description 21
- 238000005260 corrosion Methods 0.000 claims abstract description 19
- 230000007797 corrosion Effects 0.000 claims abstract description 19
- 229910052793 cadmium Inorganic materials 0.000 claims abstract description 6
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 claims abstract description 6
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 4
- 229910000831 Steel Inorganic materials 0.000 claims description 81
- 239000010959 steel Substances 0.000 claims description 81
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- 238000000576 coating method Methods 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 8
- 229910052742 iron Inorganic materials 0.000 claims description 8
- 229910045601 alloy Inorganic materials 0.000 claims description 7
- 239000000956 alloy Substances 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 239000000243 solution Substances 0.000 description 24
- 235000011121 sodium hydroxide Nutrition 0.000 description 20
- 239000010406 cathode material Substances 0.000 description 12
- 238000012360 testing method Methods 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 9
- 239000003518 caustics Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 230000003068 static effect Effects 0.000 description 7
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 5
- 229910017052 cobalt Inorganic materials 0.000 description 5
- 239000010941 cobalt Substances 0.000 description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 5
- 238000004090 dissolution Methods 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 4
- 235000011118 potassium hydroxide Nutrition 0.000 description 4
- 238000013459 approach Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000007654 immersion Methods 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- QXZUUHYBWMWJHK-UHFFFAOYSA-N [Co].[Ni] Chemical compound [Co].[Ni] QXZUUHYBWMWJHK-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- WWNBZGLDODTKEM-UHFFFAOYSA-N sulfanylidenenickel Chemical class [Ni]=S WWNBZGLDODTKEM-UHFFFAOYSA-N 0.000 description 2
- 150000004763 sulfides Chemical class 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 239000007868 Raney catalyst Substances 0.000 description 1
- 229910000564 Raney nickel Inorganic materials 0.000 description 1
- 229910007570 Zn-Al Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 238000003621 hammer milling Methods 0.000 description 1
- 239000002920 hazardous waste Substances 0.000 description 1
- KFZAUHNPPZCSCR-UHFFFAOYSA-N iron zinc Chemical compound [Fe].[Zn] KFZAUHNPPZCSCR-UHFFFAOYSA-N 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- QELJHCBNGDEXLD-UHFFFAOYSA-N nickel zinc Chemical compound [Ni].[Zn] QELJHCBNGDEXLD-UHFFFAOYSA-N 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 229910000648 terne Inorganic materials 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F5/00—Electrolytic stripping of metallic layers or coatings
Definitions
- the present invention relates, in general, to a process for dezincing steel scrap and, in particular, to a galvanic dezincing process in which the cathode is steel or another metal or alloy which does not have a low hydrogen overvoltage.
- Zinc coated (galvanized) steel is widely used in automotive, construction, and agricultural equipment and other industries. These industries and the mills producing galvanized sheet generate a considerable quantity of fresh steel scrap, at least some of which is galvanized, which can be recycled and reused as a starting material in steel and iron-making processes.
- the presence of zinc in the steel scrap used in steel and iron-making processes increases the cost of compliance with environmental regulations due to costs associated with dust disposal and possible pretreatment of dust as a hazardous waste, treatment of waste water for removal of zinc and collection of fumes to maintain the shop floor environment and to restrict roof-vent emissions. As a result, there is great interest in development of an economical method of removing zinc from steel scrap.
- the steel scrap is immersed in an acid such as hydrochloric acid or sulfuric acid.
- an acid such as hydrochloric acid or sulfuric acid.
- Iron however, is co-dissolved with the zinc in the acid solution and the separation of the iron from the zinc has not been found to be economically feasible.
- caustic soda solution to dissolve zinc from galvanized steel scrap has also been proposed.
- An inherent advantage of this method is that iron is stable in caustic and thus, separation of iron from zinc in solution is not a significant problem.
- a disadvantage of this method is the relatively slow rate at which zinc is removed from the galvanized surface which leads to low productivity or inadequate zinc removal.
- LeRoy et al. disclose other methods for accelerating the dissolution of zinc from galvanized steel in caustic electrolyte in U.S. Patent Nos. 5,302,260 and 5,302,261.
- LeRoy et al. suggest that the galvanized steel be immersed in a caustic electrolyte and electrically connected to a cathodic material which is stable in the electrolyte and which has a low hydrogen overvoltage.
- such cathodes include high-surface-area nickel-based and cobalt-based materials such as Raney nickel type and Raney Cobalt type, nickel molybdates, nickel sulfides, nickel-cobalt thiospinels and mixed sulphides, nickel aluminum alloys, and electroplated active cobalt compositions. If the scrap is clean, unpainted, or shredded, no external source of voltage is applied to the cathode material.
- LeRoy et al. U.S. Patent No. 5,302,261 at col. 2, lines 37-47. If bundles of scrap are to be dezinced, however, they suggest applying an external source of voltage to the cathode to increase the rate of zinc stripping.
- the provision of a process for dezincing steel scrap in a caustic electrolyte is the provision of a process for dezincing steel scrap in a caustic electrolyte; the provision of such a process in which the cathode is steel or another metal having a relatively high hydrogen overvoltage; the provision of such a process in which an external source of voltage need not be applied to the cathode material to increase the dissolution rate; and the provision of such a process in which the zinc removal rate is accelerated relative to the rate at which zinc would be removed from scrap which is simply immersed in caustic electrolyte.
- the process of the present invention is carried out in a system in which the steel scrap is immersed in a caustic electrolyte such as caustic soda (sodium hydroxide) or caustic potash (potassium hydroxide).
- a caustic electrolyte such as caustic soda (sodium hydroxide) or caustic potash (potassium hydroxide).
- caustic soda is preferred over potassium hydroxide, however, due to its relative cost advantage.
- the zinc-coated steel is galvanically corroded with the zinc-coated surface of the scrap serving as the anodic material and an exposed steel surface or another metal having a relatively high hydrogen overvoltage serving as the cathodic material.
- the scrap is treated in a manner to increase the surface area of the cathodic material relative to the surface area of the anodic material.
- the rate of dissolution of the zinc increases with increasing concentration of the caustic soda in and the temperature of the electrolyte.
- the electrolyte is an aqueous solution comprising caustic soda in a concentration of at least about 15% by weight. More preferably; the concentration of caustic soda in the electrolyte is between about 25% and about 50% by weight and most preferably it is maintained within the range of about 30% to 40% by weight. At these concentrations, the electrolyte can be relatively viscous depending upon the temperature.
- the temperature of the electrolyte is preferably at least 75° C but less than the temperature at which the electrolyte boils, more preferably between about 85° C and about 95° C, and most preferably between about 90 °C and about 95 °C.
- the cathodic material may be any metal or alloy which is more noble than zinc in the galvanic series of metals and alloys.
- High-surface-area nickel-based or cobalt-based materials, nickel molybdates, nickel sulfides, nickel-cobalt thiospinels and mixed sulphides, nickel aluminum alloys, and electroplated active cobalt compositions and any other such low-hydrogen overvoltage materials are too expensive and thus are preferably not used as the cathodic material.
- the cathodic material is principally iron, an alloy of steel, or another alloy or metal having a standard electrode potential (reduction potential) intermediate that of the standard electrode potential of zinc (-0.76 V) and cadmium (about -0.4 V) in the electrochemical series which is relatively inexpensive.
- the cathodic material pieces of galvanized scrap or regions thereof from which the zinc coating has been removed serve as the cathodic material.
- the size of the cathodic area relative to the size of the anodic area of the steel scrap may be increased by a variety of methods.
- the steel scrap may be heated or mechanically abraded or deformed to increase the number density and total surface area of cathodic areas in the scrap, or (ii) it may be intimately mixed with a cathodic material.
- these methods may be carried out before the scrap is immersed in the electrolyte or while it is immersed in the electrolyte.
- the galvanized scrap is heated to a temperature in excess of the melting point of zinc in order for this transformation to occur in a commercially acceptable time period. More preferably, the galvanized scrap is heated to a temperature of at least about 470° C, still more preferably at least about 500 °C, and most preferably at least about 600° C.
- the period of time at which the galvanized scrap is held at these temperatures to achieve the desired effect will be a function of temperature. In general, however, it is preferred that the holding period be between about 5 and about 20 minutes, with time periods of about 10 to 15 minutes being particularly preferred.
- the steel scrap may be mechanically abraded or deformed to increase the galvanic corrosion rate. Abrading the steel scrap will remove the zinc from local areas. Deforming the steel scrap may crack or otherwise stress the zinc coating. Because these exposed and deformed areas are generally surrounded by zinc-coated regions, the number density and total surface area of cathodic areas in the scrap is increased at the surface of the steel scrap thus increasing the galvanic corrosion rate of the scrap when it is immersed in the electrolyte.
- the steel scrap may be mechanically abraded or deformed, for example, by shredding the scrap, by relative movement of the scrap against itself or another abrasive surface, or by hammer-milling it. Steel scrap is typically available in pieces ranging in size from about 2.5 to about 120 cm.
- the shredded pieces preferably have a size distribution of about 10 to about 20 cm., with the majority of shredded pieces having a size distribution of about 10 to about 15 cm. wherein size is determined by reference to the dimensions of square openings in a grate through which the pieces are passed. If the pieces of steel scrap are mechanically deformed, e.g., bent or scraped, it is preferred that the de formation sites be uniformly distributed over the galvanized surface and that, on average, the deformed surface area exceed about 10%, more preferably about 15%, and most preferably at least about 20% of the surface area of steel scrap.
- the size of the cathodic area may be increased relative to the size of the anodic area of the galvanized steel scrap by forming a mixture of galvanized steel scrap and uncoated material, i.e., a metal or alloy which is more noble than zinc in the galvanic-series and which lacks a zinc coating.
- the mixture of uncoated material and galvanized steel scrap comprises at least- about 5% by weight uncoated material, preferably at least about 10% uncoated material, more preferably at least about 20% uncoated material, and optimally at least about 30% uncoated material.
- Such mixtures may be available directly from some scrap producers or may be formed by mixing the galvanized steel scrap with uncoated material.
- the uncoated material is steel scrap from which the zinc coating has at least been partially removed.
- the steel scrap is immersed in and/or carried through the electrolyte by a conveyor consisting essentially of a cathodic material which is more noble than zinc, such as a steel alloy.
- the conveyor may be, for example, an endless moving steel belt or a track with a carriage for holding the steel scrap suspended from the track.
- the carriage is a rotating drum having openings in the wall thereof through which electrolyte can pass when it is immersed in the electrolyte.
- Rotation of the drum in the electrolyte causes movement of the steel scrap relative to itself and to drum which causes mechanical abrasion of the galvanized steel and acceleration of the galvanic corrosion rate.
- rotation of the drum causes the steel scrap to move relative to the electrolyte, thereby decreasing the thickness of the boundary layer and further accelerating the galvanic corrosion rate.
- reference numeral 10 generally illustrates a preferred embodiment of an apparatus for carrying out the process of the present invention.
- Dezincing apparatus 10 comprises dezincing tank 12, rinse tanks 14, 16 and a series of endless moving belts 18, 22, 24 and 26.
- Steel scrap such as shredded loose clippings is fed to conveyor 18 which delivers the steel scrap to dezincing tank 12 which contains an aqueous sodium hydroxide solution containing from 150 grams/liter to 500 grams/liter NaOH at temperatures ranging from 50° C to 100° C.
- moving belt 20 is supported by pads 21 which, in addition, electrically isolate moving belt 20 from dezincing tank 12 and from ground.
- Moving belt 20 delivers the black scrap to moving belt 22 which carries the black scrap up and out of dezincing tank 12 and delivers it onto moving belt 24.
- Moving belt 24 carries the scrap through rinse tank 14 and delivers the rinsed scrap onto moving belt 26 which carries the scrap through rinse tank 16 for a second rinsing. The rinsed, black scrap is then transferred to a storage bin or directly to a customer.
- Electrolyte containing dissolved zinc is continuously withdrawn from dezincing tank 12 via line 28, purified to remove aluminum, lead, copper, bismuth and iron in a tank 30, pumped by slurry pump 32, filtered in a vacuum drum or other suitable filter 34 and delivered to electrolytic zinc recovery cell 36 connected to a transformer rectifier 38.
- electrolytic zinc recovery cell 36 the zinc metal is deposited on the cathode (e.g., a magnesium cathode) as a powder and/or in dendritic form and is continuously caused to be removed from the cathode to settle to the bottom of the electrolysis cell.
- zinc metal powder slurry is withdrawn and pumped via line 40 and slurry pump 42 to filter 44 (or centrifuge).
- Damp zinc cake discharged from horizontal tank filter 44 is transferred by line 46 to a briquetting unit 48 which produces zinc powder briquettes 50 which are ready for storage or sale to a customer.
- the electrolytic process regenerates caustic soda which is returned to the dezincing tank; the spent electrolyte with a reduced zinc content (i.e., less than about 20 gm./l of zinc) is returned to the dezincing tank for further use.
- Preferred operating temperatures for the electrolysis solutions are about 30 to about 45 °C and an input range of about 25 to about 40 grams/liter of zinc with a free caustic level of about 150 to about 300 grams/liter of NaOH.
- the removal rate of zinc can be increased by deforming the surface of the scrap prior to immersion in the tank of sodium hydroxide solution with dezincing times being reduced from 80 minutes to less than 20 minutes.
- the dezincing effect starts at the deformed site on the steel, e.g. a bend or scratch and proceeds across the surface of the steel. It has been demonstrated that the greater the number of these deformed sites the greater the improvement in rate of effectiveness of the process, e.g., if the steel is shredded into smaller pieces in a hammer mill. This creates sites of high energy (deformation) and areas where zinc has been mechanically removed in close proximity to coated areas. In all of the above cases the galvanic dezincing effect is enhanced. No external current or oxidant need to be used.
- a further improvement in the process can be achieved by heating the coated steel prior to feeding it into the dezincing tank. This can be achieved by passing the steel through a heated furnace on a moving grate at 400° C to 800° C and feeding the hot material into the solution. These post-heated materials assist in effectively heating the dezincing solution, achieve the temperature of the electrolyte much earlier than colder materials, and the hot surfaces cause rapid convection movement of the solution across the surface of the steel thus reducing diffusion gradients of the zinc into the solution boundary layer.
- the process can be performed by charging the materials to be dezinced to a shredder such as a hammer mill which is operated to deform the steel, mechanically remove zinc from part of the surface and concurrently heat the steel.
- a shredder such as a hammer mill which is operated to deform the steel, mechanically remove zinc from part of the surface and concurrently heat the steel.
- Example 3 The tests of Example 3 were repeated, except that the temperature of NaOH solution was 95 °C. The results are presented in Table 4. Time (Minutes) in Solution Residual Zinc Percent Linear Rotary 5 2.32 2.01 10 1.81 1.24 20 0.34 0.04 30 0.061 0.003 40 0.008 0.001 60 0.008 0.001
- Example 3 The tests of Example 3 were repeated, except that galvalume (Zn-Al) coated steel with a coating of 1.4% zinc was used for all tests. The results are presented in Table 5. Time (Minutes) in Solution Residual Zinc Percent Linear Rotary 5 1.31 1.24 10 0.74 0.43 20 0.13 0.08 30 0.011 0.003 40 0.009 0.003 60 0.009 0.001 80 0.008 0.001 Removal rates in this test are greater than those in Example 3 in both linear and rotary units because the zinc is alloyed with aluminum in the galvalume coatings. The rotary unit dezincs faster than the linear unit.
- Example 1 The test of Example 1 was repeated, except that the temperature of the NaOH solution was increased to 95 °C. The results are presented in Table 6. Time (Minutes) in Solution Residual Zinc Percent Linear Rotary 5 2.10 1.81 10 1.41 0.60 20 0.13 0.006 30 0.04 0.001 40 0.006 0.001 60 0.004 0.001
- Example 2 The test of Example 2 was repeated except that some of the samples were heated to a temperature of 750 °C prior to being immersed in the NaOH solution. The results are presented in Table 8. TIME IN DEZINCING BATH MINUTES TEMPERATURE °F (°C) PREHEAT TEMPERATURE °C RESIDUAL ZINC% 5 180(82) No 1.8 5 180(82) 600 0.6 10 180(82) No 0.9 10 180(82) 600 0.15 15 180(82) No 0.4 15 180(82) 600 0.10 20 180(82) No 0.24 20 180(82) 600 0.004 30 180(82) No 0.11 30 180(82) 600 0.002 40 180(82) No 0.006 40 180(82) 600 0.002 10 180(82) No 0.9 10 180(82) No 0.04 20 180(82) No 0.24 20 180(82) 750 0.002 30 180(82) No 0.11 30 180(82) 750 0.001 Both shredding and pre-heat have the same
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP98918703A EP0996775B1 (fr) | 1996-07-17 | 1998-04-24 | Procede de dezingage de l'acier galvanise |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP98918703A Division EP0996775B1 (fr) | 1996-07-17 | 1998-04-24 | Procede de dezingage de l'acier galvanise |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP1236816A1 true EP1236816A1 (fr) | 2002-09-04 |
Family
ID=8237248
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP02075407A Withdrawn EP1236816A1 (fr) | 1998-04-24 | 1998-04-24 | Procédé de dézingage de l'acier galvanisé |
Country Status (1)
| Country | Link |
|---|---|
| EP (1) | EP1236816A1 (fr) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996002689A1 (fr) * | 1994-07-19 | 1996-02-01 | Hoogovens Staal B.V. | Procede pour la dissolution electrochimique d'un metal tel que le zinc ou l'etain |
| US5779878A (en) * | 1996-07-17 | 1998-07-14 | Metal Recovery Industries (Us) Inc. | Process for dezincing galvanized steel |
-
1998
- 1998-04-24 EP EP02075407A patent/EP1236816A1/fr not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996002689A1 (fr) * | 1994-07-19 | 1996-02-01 | Hoogovens Staal B.V. | Procede pour la dissolution electrochimique d'un metal tel que le zinc ou l'etain |
| US5779878A (en) * | 1996-07-17 | 1998-07-14 | Metal Recovery Industries (Us) Inc. | Process for dezincing galvanized steel |
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