CA1337579C - Method for the refining of lead - Google Patents
Method for the refining of leadInfo
- Publication number
- CA1337579C CA1337579C CA 609401 CA609401A CA1337579C CA 1337579 C CA1337579 C CA 1337579C CA 609401 CA609401 CA 609401 CA 609401 A CA609401 A CA 609401A CA 1337579 C CA1337579 C CA 1337579C
- Authority
- CA
- Canada
- Prior art keywords
- lead
- bath
- dross
- amount
- calcium
- 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.)
- Expired - Fee Related
Links
- 238000007670 refining Methods 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims description 30
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000011575 calcium Substances 0.000 claims abstract description 25
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 25
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 25
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 20
- 239000006023 eutectic alloy Substances 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 16
- 239000002184 metal Substances 0.000 claims abstract description 16
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 claims abstract description 13
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000002844 melting Methods 0.000 claims abstract description 10
- 230000008018 melting Effects 0.000 claims abstract description 10
- 239000004317 sodium nitrate Substances 0.000 claims abstract description 6
- 235000010344 sodium nitrate Nutrition 0.000 claims abstract description 6
- 230000015572 biosynthetic process Effects 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 2
- 238000011282 treatment Methods 0.000 abstract description 4
- 229910045601 alloy Inorganic materials 0.000 description 10
- 239000000956 alloy Substances 0.000 description 10
- 150000002739 metals Chemical class 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 239000012535 impurity Substances 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 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 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 3
- 229910052787 antimony Inorganic materials 0.000 description 3
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 3
- 229910052785 arsenic Inorganic materials 0.000 description 3
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 3
- 239000011777 magnesium Substances 0.000 description 3
- 229910052749 magnesium Inorganic materials 0.000 description 3
- 229910052725 zinc Inorganic materials 0.000 description 3
- 239000011701 zinc Substances 0.000 description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 238000007792 addition Methods 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 229910052797 bismuth Inorganic materials 0.000 description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 150000003388 sodium compounds Chemical class 0.000 description 2
- 229910052714 tellurium Inorganic materials 0.000 description 2
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical class [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910000882 Ca alloy Inorganic materials 0.000 description 1
- 229910000978 Pb alloy Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 229910001128 Sn alloy Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 229910001297 Zn alloy Inorganic materials 0.000 description 1
- YVIMHTIMVIIXBQ-UHFFFAOYSA-N [SnH3][Al] Chemical compound [SnH3][Al] YVIMHTIMVIIXBQ-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- FJMNNXLGOUYVHO-UHFFFAOYSA-N aluminum zinc Chemical compound [Al].[Zn] FJMNNXLGOUYVHO-UHFFFAOYSA-N 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000002142 lead-calcium alloy Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011135 tin Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B13/00—Obtaining lead
- C22B13/06—Refining
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
Lead that forms dross upon melting is refined by treatment with refining agents consisting essentially of calcium metal and aluminum-silicon eutectic alloy. The refining agents are mixed into a bath of molten lead preferably at 600°C, the bath is cooled to preferably 450°C, and sodium hydroxide and sodium nitrate are added to remove the refining agents. The formed dross is skimmed and refined lead is recovered. The refined lead forms less dross upon remelting.
Description
METHOD FOR THE REFINING OF LEAD
This invention relates to the refining of lead and, particularly, to a method for the refining of lead for reducing the amount of dross formed on remelting.
BACKGROUND OF THE INVENTION
Numerous methods are known for the refining of lead bullion that is made by the various smelting processes for the recovery of lead from ores and concentrates. The refining is necessary for the removal of impurities which include antimony, arsenic, bismuth, copper, iron, selenium, silver, tellurium, tin, zinc, gold and other metals, and which impurities may be present in varying amounts. A great number of refining processes are known. These processes include electrorefining processes, and processes wherein metals and alloys are used. In the electrorefining process, the lead bullion electrodes contain certain amounts of arsenic and antimony that are necessary for preventing slime from falling off the electrodes. Although electrorefining removes most of the impurities from the lead, and the electrorefined lead meets the specifications for purity, the small amount of impurities remaining, usually less than 0.1% total, causes undesirable formation of dross when the electrorefined lead is remelted.
S~
~ 2 1 337579 BRIEF DESCRIPTION OF PRIOR ART
The refining of lead by treating molten lead with metals or alloys is well documented. According to most of these refining treatments, molten lead is contacted with suitable metals or alloys for the formation of dross of alloys or compounds of the added metals or alloys with the impurities in the lead. The dross is separated, and refined lead is recovered. According to the numerous patents on lead refining, the metals and alloys used in refining include calcium, barium, magnesium, zinc, sodium, lithium, potassium, aluminum, aluminum-tin alloy, aluminum-zinc alloy, calcium-lead alloy, and calcium and magnesium.
Residuals of the added metals and alloys are often removed by adding a suitable drossing agent such as ammonium chloride, sodium or potassium hydroxide, phosphorus, sulfur, coal, a halide, or air.
The oxidation of molten lead affects its refining and the degree of drossing. It has been determined that certain impurities in or additives to stationary or moving melts of lead accelerate or reduce the rate of oxidation, while some have little effect. Lithium, sodium, calcium, magnesium, arsenic, antimony, copper, silver and tellurium increase the rate, aluminum and tin reduce the rate, and bismuth, cadmium and zinc have little effect on the rate tLead Handbook, ed. Heubner etal., Metallgesellschaft AG, _ 3 1 337579 Frankfurt, 1983). The reduction of the oxidation of lead with aluminum has been investigated by Krysko (Krysko W.W., Oxidation of molten lead, Third International Conference of Lead, Venice, September 1968). According to Canadian Patent 1 204 596, deoxidation of molten metal (steel) is accomplished with a refining agent essentially consisting of calcium and at least one of aluminum and silicon, and a flux composed mainly of calcium and aluminum oxides, the alloy and the flux being integrally bonded to one another.
It is disclosed that an aluminum-silicon alloy may be used in the calcium alloy. The use of the aluminum-silicon eutectic alloy and its oxidation inhibiting effect in the manufacture of lead alloys for storage batteries are known from German Patent DE 27 46 713 Al.
SUMMARY OF THE INVENTION
It has now been found that molten lead may be refined by a treatment with refining agents consisting essentially of calcium metal and aluminum-silicon eutectic alloy. More specifically, we have found that when molten lead is treated with calcium metal and aluminum-silicon eutectic alloy and the resulting melt is treated with sodium compounds, a dross is formed, and a refined lead is recovered that contains less than 0.0001% of combined calcium, aluminum and silicon (<lppm), and that reduces the amount of dross formed upon remelting.
_ 4 It is an object of the present invention to provide a method for the refining of lead. It is another object to provide a method for reducing the amount of dross formed upon remelting of lead. These and other objects of the invention will become clear from the following detailed description.
Accordingly, there is provided a method for the refining of lead that forms dross upon melting which comprises the steps of forming a bath of molten lead; heating said bath to a temperature in the range of about 585 to 620C; adding to the heated bath effective amounts of refining agents consisting essentially of calcium metal and aluminum-silicon eutectic alloy, said effective amounts being sufficient to effectively reduce the amount of dross formed upon remelting of the solidified lead recovered from said method; when said refining agents are substantially completely dissolved, allowing said bath to cool to a temperature in the range of about 375 to 475C; adding suitable amounts of sodium hydroxide and sodium nitrate to said bath for the substantial removal of said refining agents in a dross with the formation of refined lead and a layer of dross on the bath; skimming said dross from the bath; and recovering solidified refined lead that forms a reduced amount of dross upon remelting.
DETAILED DESCRIPTION
Lead that forms dross upon melting is added in molten form to a suitable vessel to form a bath of molten lead therein.
The lead that forms dross upon melting may be, for example, lead that has been refined by the Betts process or other refining processes. Other lead that is subject to excess dross formation upon melting may also be treated by the method according to the invention. Any dross on the bath of molten lead in the vessel is removed, and the bath is heated to a temperature that is somewhat above the melting temperature of the to-be-added aluminum-silicon eutectic alloy. A convenient temperature is in the range of about 585 to 620C. The preferred temperature is about 600C, allowing rapid dissoluton of refining agents. Effective amounts of refining agents, consisting essentially of calcium metal and aluminum-silicon eutectic alloy, are added to the heated bath, and are submerged therein until molten. The bath is agitated to ensure rapid and complete dissolution of the refining agents. The refining agents are preferably loaded into a perforated basket that is subsequently submerged in the bath. Pieces, chunks, bars or other suitable forms of calcium metal and aluminum-silicon eutectic alloy are loaded in the basket such that the alloy is substantially surrounded by calcium. When the ?5 loaded basket is submerged in the bath of molten lead, the strongly exothermic reaction of calcium with lead causes rapid melting of the calcium and the eutectic alloy. The 1 33757q eutectic alloy contains about 12.0 to 12.5% silicon, and melts at about 575 to 580C. The required amounts of refining agents are small, but should be effective in reducing the amounts of dross formed upon remelting of the solidified lead recovered according to the method of the invention. Effective amounts are, for example, an amount of calcium in the range of about 0.03 to 0.09% and an amount of aluminum-silicon eutectic alloy in the range of about 0.01 to 0.04% by weight of the amount of lead being treated in the bath of molten lead. The preferred amounts are about 0.06% calcium and about 0.03% aluminum-silicon eutectic alloy. When the refining agents are substantially completely dissolved the basket is removed from the vessel, and the bath is allowed to cool to a temperature in the range of about 375 to 475C. Cooling to a temperature of about 450C is preferred, as at this temperature refined lead may be cast conveniently. The bath is then treated for the substantial removal of the refining agents from the refined lead in a dross. Suitable amounts of sodium hydroxide and sodium nitrate are added to the bath while the bath is being agitated with the formation of refined lead and the formation of a layer of dross on the surface of the bath. Additions of sodium hydroxide and sodium nitrate are continued until a skilled operator judges by visual observations that the refined lead has the right appearance. Agitation is then stopped, the agitator is removed from the bath, and the dross is skimmed from the surface of the bath. The refined lead is subsequently poured into moulds and solidified. The solidified refined lead is recovered. Upon remelting, the recovered solidified lead forms an amount of dross that is reduced, and is considerably less than the amount formed on remelted lead not treated according to the method of the present invent lon .
The invention will now be illustrated by means of the following non-limitative example.
Example 177 metric tonnes of lead from the Betts electrorefining process were melted and added to a kettle. Dross was skimmed, and the lead was heated to 600C. 113 kg of calcium metal and 45 kg of aluminum-silicon eutectic alloy were loaded as refining agents in a wire mesh basket, alloy being substantially surrounded by calcium, and the loaded basket was submerged in the bath. The bath was agitated, drawing a slight vortex. Dissolution was completed in ten minutes. The basket was withdrawn from the bath, and the bath was allowed to cool to 450C. Portions of sodium hydroxide and sodium nitrate were then added to the bath, while the bath was being agitated. Additions and agitation were continued until the operator judged visually that the refined lead had the right appearance, the refining agents at that time having been substantially removed from the refined lead into a dross. The dross was skimmed, and refined lead was cast into moulds and solidifed. The solidified lead was sampled and found to contain less than one part per million of combined calcium, aluminum and silicon. 32 metric tonnes of the solidified lead were remelted and the dross formed on the surface of the remelted lead was removed and weighed. The amount of dross was 0.2% of the weight of the refined lead. In a parallel test, it was determined that lead recovered from the Betts electrorefining process and remelted produced 0.4% of its weight in dross. The results show that the method according to the invention produces a refined lead that upon melting forms half the amount of dross of lead not so refined, and that the treatment with sodium compounds effectively removes the refining agents from the refined lead.
It is understood that variations may be made in the method according to the invention without departing from the scope and purview of the appended claims.
This invention relates to the refining of lead and, particularly, to a method for the refining of lead for reducing the amount of dross formed on remelting.
BACKGROUND OF THE INVENTION
Numerous methods are known for the refining of lead bullion that is made by the various smelting processes for the recovery of lead from ores and concentrates. The refining is necessary for the removal of impurities which include antimony, arsenic, bismuth, copper, iron, selenium, silver, tellurium, tin, zinc, gold and other metals, and which impurities may be present in varying amounts. A great number of refining processes are known. These processes include electrorefining processes, and processes wherein metals and alloys are used. In the electrorefining process, the lead bullion electrodes contain certain amounts of arsenic and antimony that are necessary for preventing slime from falling off the electrodes. Although electrorefining removes most of the impurities from the lead, and the electrorefined lead meets the specifications for purity, the small amount of impurities remaining, usually less than 0.1% total, causes undesirable formation of dross when the electrorefined lead is remelted.
S~
~ 2 1 337579 BRIEF DESCRIPTION OF PRIOR ART
The refining of lead by treating molten lead with metals or alloys is well documented. According to most of these refining treatments, molten lead is contacted with suitable metals or alloys for the formation of dross of alloys or compounds of the added metals or alloys with the impurities in the lead. The dross is separated, and refined lead is recovered. According to the numerous patents on lead refining, the metals and alloys used in refining include calcium, barium, magnesium, zinc, sodium, lithium, potassium, aluminum, aluminum-tin alloy, aluminum-zinc alloy, calcium-lead alloy, and calcium and magnesium.
Residuals of the added metals and alloys are often removed by adding a suitable drossing agent such as ammonium chloride, sodium or potassium hydroxide, phosphorus, sulfur, coal, a halide, or air.
The oxidation of molten lead affects its refining and the degree of drossing. It has been determined that certain impurities in or additives to stationary or moving melts of lead accelerate or reduce the rate of oxidation, while some have little effect. Lithium, sodium, calcium, magnesium, arsenic, antimony, copper, silver and tellurium increase the rate, aluminum and tin reduce the rate, and bismuth, cadmium and zinc have little effect on the rate tLead Handbook, ed. Heubner etal., Metallgesellschaft AG, _ 3 1 337579 Frankfurt, 1983). The reduction of the oxidation of lead with aluminum has been investigated by Krysko (Krysko W.W., Oxidation of molten lead, Third International Conference of Lead, Venice, September 1968). According to Canadian Patent 1 204 596, deoxidation of molten metal (steel) is accomplished with a refining agent essentially consisting of calcium and at least one of aluminum and silicon, and a flux composed mainly of calcium and aluminum oxides, the alloy and the flux being integrally bonded to one another.
It is disclosed that an aluminum-silicon alloy may be used in the calcium alloy. The use of the aluminum-silicon eutectic alloy and its oxidation inhibiting effect in the manufacture of lead alloys for storage batteries are known from German Patent DE 27 46 713 Al.
SUMMARY OF THE INVENTION
It has now been found that molten lead may be refined by a treatment with refining agents consisting essentially of calcium metal and aluminum-silicon eutectic alloy. More specifically, we have found that when molten lead is treated with calcium metal and aluminum-silicon eutectic alloy and the resulting melt is treated with sodium compounds, a dross is formed, and a refined lead is recovered that contains less than 0.0001% of combined calcium, aluminum and silicon (<lppm), and that reduces the amount of dross formed upon remelting.
_ 4 It is an object of the present invention to provide a method for the refining of lead. It is another object to provide a method for reducing the amount of dross formed upon remelting of lead. These and other objects of the invention will become clear from the following detailed description.
Accordingly, there is provided a method for the refining of lead that forms dross upon melting which comprises the steps of forming a bath of molten lead; heating said bath to a temperature in the range of about 585 to 620C; adding to the heated bath effective amounts of refining agents consisting essentially of calcium metal and aluminum-silicon eutectic alloy, said effective amounts being sufficient to effectively reduce the amount of dross formed upon remelting of the solidified lead recovered from said method; when said refining agents are substantially completely dissolved, allowing said bath to cool to a temperature in the range of about 375 to 475C; adding suitable amounts of sodium hydroxide and sodium nitrate to said bath for the substantial removal of said refining agents in a dross with the formation of refined lead and a layer of dross on the bath; skimming said dross from the bath; and recovering solidified refined lead that forms a reduced amount of dross upon remelting.
DETAILED DESCRIPTION
Lead that forms dross upon melting is added in molten form to a suitable vessel to form a bath of molten lead therein.
The lead that forms dross upon melting may be, for example, lead that has been refined by the Betts process or other refining processes. Other lead that is subject to excess dross formation upon melting may also be treated by the method according to the invention. Any dross on the bath of molten lead in the vessel is removed, and the bath is heated to a temperature that is somewhat above the melting temperature of the to-be-added aluminum-silicon eutectic alloy. A convenient temperature is in the range of about 585 to 620C. The preferred temperature is about 600C, allowing rapid dissoluton of refining agents. Effective amounts of refining agents, consisting essentially of calcium metal and aluminum-silicon eutectic alloy, are added to the heated bath, and are submerged therein until molten. The bath is agitated to ensure rapid and complete dissolution of the refining agents. The refining agents are preferably loaded into a perforated basket that is subsequently submerged in the bath. Pieces, chunks, bars or other suitable forms of calcium metal and aluminum-silicon eutectic alloy are loaded in the basket such that the alloy is substantially surrounded by calcium. When the ?5 loaded basket is submerged in the bath of molten lead, the strongly exothermic reaction of calcium with lead causes rapid melting of the calcium and the eutectic alloy. The 1 33757q eutectic alloy contains about 12.0 to 12.5% silicon, and melts at about 575 to 580C. The required amounts of refining agents are small, but should be effective in reducing the amounts of dross formed upon remelting of the solidified lead recovered according to the method of the invention. Effective amounts are, for example, an amount of calcium in the range of about 0.03 to 0.09% and an amount of aluminum-silicon eutectic alloy in the range of about 0.01 to 0.04% by weight of the amount of lead being treated in the bath of molten lead. The preferred amounts are about 0.06% calcium and about 0.03% aluminum-silicon eutectic alloy. When the refining agents are substantially completely dissolved the basket is removed from the vessel, and the bath is allowed to cool to a temperature in the range of about 375 to 475C. Cooling to a temperature of about 450C is preferred, as at this temperature refined lead may be cast conveniently. The bath is then treated for the substantial removal of the refining agents from the refined lead in a dross. Suitable amounts of sodium hydroxide and sodium nitrate are added to the bath while the bath is being agitated with the formation of refined lead and the formation of a layer of dross on the surface of the bath. Additions of sodium hydroxide and sodium nitrate are continued until a skilled operator judges by visual observations that the refined lead has the right appearance. Agitation is then stopped, the agitator is removed from the bath, and the dross is skimmed from the surface of the bath. The refined lead is subsequently poured into moulds and solidified. The solidified refined lead is recovered. Upon remelting, the recovered solidified lead forms an amount of dross that is reduced, and is considerably less than the amount formed on remelted lead not treated according to the method of the present invent lon .
The invention will now be illustrated by means of the following non-limitative example.
Example 177 metric tonnes of lead from the Betts electrorefining process were melted and added to a kettle. Dross was skimmed, and the lead was heated to 600C. 113 kg of calcium metal and 45 kg of aluminum-silicon eutectic alloy were loaded as refining agents in a wire mesh basket, alloy being substantially surrounded by calcium, and the loaded basket was submerged in the bath. The bath was agitated, drawing a slight vortex. Dissolution was completed in ten minutes. The basket was withdrawn from the bath, and the bath was allowed to cool to 450C. Portions of sodium hydroxide and sodium nitrate were then added to the bath, while the bath was being agitated. Additions and agitation were continued until the operator judged visually that the refined lead had the right appearance, the refining agents at that time having been substantially removed from the refined lead into a dross. The dross was skimmed, and refined lead was cast into moulds and solidifed. The solidified lead was sampled and found to contain less than one part per million of combined calcium, aluminum and silicon. 32 metric tonnes of the solidified lead were remelted and the dross formed on the surface of the remelted lead was removed and weighed. The amount of dross was 0.2% of the weight of the refined lead. In a parallel test, it was determined that lead recovered from the Betts electrorefining process and remelted produced 0.4% of its weight in dross. The results show that the method according to the invention produces a refined lead that upon melting forms half the amount of dross of lead not so refined, and that the treatment with sodium compounds effectively removes the refining agents from the refined lead.
It is understood that variations may be made in the method according to the invention without departing from the scope and purview of the appended claims.
Claims (6)
1. A method for the refining of lead that forms dross upon melting which comprises the steps of forming a bath of molten lead; heating said bath to a temperature in the range of about 585 to 620°C; adding to the heated bath effective amounts of refining agents consisting essentially of calcium metal and aluminum-silicon eutectic alloy, said effective amounts being sufficient to effectively reduce the amount of dross formed upon remelting of the solidified lead recovered from said method; when said refining agents are substantially completely dissolved, allowing said bath to cool to a temperature in the range of about 375 to 475°C; adding suitable amounts of sodium hydroxide and sodium nitrate to said bath for the substantial removal of said refining agents in a dross with the formation of refined lead and a layer of dross on the bath; skimming said dross from the bath; and recovering solidified refined lead that forms a reduced amount of dross upon remelting.
2. A method as claimed in claim 1, wherein said effective amounts are an amount of calcium in the range of about 0.03% to 0.09% by weight of the lead in said bath of molten lead and an amount of said eutectic alloy in the range of about 0.01% to 0.04% by weight of the lead in said bath of molten lead.
3. A method as claimed in claim 1, wherein said lead that forms dross upon melting is electrorefined lead.
4. A method as claimed in claim 1, wherein said effective amounts of refining agents are loaded in a basket such that said eutectic alloy is substantially surrounded by calcium; the loaded basket is submerged in said bath; and said bath is agitated until said refining agents are dissolved in said bath.
5. A method as claimed in claim 1, 3 or 4, wherein said effective amounts are an amount of calcium of about 0.06%
by weight of the lead in said bath of molten lead and an amount of said eutectic alloy of about 0.03% by weight of the lead in said bath of molten lead.
by weight of the lead in said bath of molten lead and an amount of said eutectic alloy of about 0.03% by weight of the lead in said bath of molten lead.
6. A method as claimed in claim 1, 3 or 4, wherein said bath is heated to a temperature of about 600°C, said bath is cooled to a temperature of about 450°C, and said effective amounts are an amount of calcium of about 0.06%
by weight of the lead in said bath of molten lead and an amount of said eutectic alloy of about 0.03% by weight of the-lead in said bath of molten lead.
by weight of the lead in said bath of molten lead and an amount of said eutectic alloy of about 0.03% by weight of the-lead in said bath of molten lead.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 609401 CA1337579C (en) | 1989-08-25 | 1989-08-25 | Method for the refining of lead |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 609401 CA1337579C (en) | 1989-08-25 | 1989-08-25 | Method for the refining of lead |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1337579C true CA1337579C (en) | 1995-11-21 |
Family
ID=4140501
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 609401 Expired - Fee Related CA1337579C (en) | 1989-08-25 | 1989-08-25 | Method for the refining of lead |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1337579C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112981132A (en) * | 2019-12-15 | 2021-06-18 | 湖南省桂阳银星有色冶炼有限公司 | Lead bullion electrolytic refining method beneficial to cadmium removal |
| EP4417719A1 (en) * | 2023-02-16 | 2024-08-21 | Baterpol Spolka Akcyjna | Method of refining a lead-tin alloy |
-
1989
- 1989-08-25 CA CA 609401 patent/CA1337579C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112981132A (en) * | 2019-12-15 | 2021-06-18 | 湖南省桂阳银星有色冶炼有限公司 | Lead bullion electrolytic refining method beneficial to cadmium removal |
| EP4417719A1 (en) * | 2023-02-16 | 2024-08-21 | Baterpol Spolka Akcyjna | Method of refining a lead-tin alloy |
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