CA1333664C - Method for softening lead bullion - Google Patents
Method for softening lead bullionInfo
- Publication number
- CA1333664C CA1333664C CA 526971 CA526971A CA1333664C CA 1333664 C CA1333664 C CA 1333664C CA 526971 CA526971 CA 526971 CA 526971 A CA526971 A CA 526971A CA 1333664 C CA1333664 C CA 1333664C
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- furnace
- bullion
- lead
- softening
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- 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
Abstract
Lead bullion is softened with pure oxygen at a temperature in the range of 590 to 650°C without heating the main bullion charge to the required softening temperature. A
portion of the charge is diverted to a small softening furnace, heated and softened to remove at least a portion of the arsenic antimony and tin. Slag and softened bullion are separately removed from the furnace. Softened bullion is either returned to the main charge or fed to a separate vessel. The method is conducted batchwise, semi-continuously or continuously.
portion of the charge is diverted to a small softening furnace, heated and softened to remove at least a portion of the arsenic antimony and tin. Slag and softened bullion are separately removed from the furnace. Softened bullion is either returned to the main charge or fed to a separate vessel. The method is conducted batchwise, semi-continuously or continuously.
Description
_ l 1333664 METHOD FOR THE SOFTENING OF LEAD BULLION
This invention relates to the refining of lead and, more particularly to a method for the softening of lead bullion with pure oxygen.
BACKGROUND OF THE INVENTION
In the production of lead from minerals and concentrates, a lead bullion obtained from a lead smelting process is normally subjected to a number of refining steps. In one of those steps, the bullion is subjected to oxidation or softening to remove impurity metals such as antimony, arsenic and tin in a slag. The softening is usually carried out after the bullion has been decopperized.
In order to soften lead bullion, a relatively high temperature such as a temperature in the range of 590 to 750C is required, but the lead bullion after decopperizing is typically at a temperature in the range of 400 to 450C.
Before the softening of the lead bullion is carried out the temperature of the lead bullion must therefore be raised about 200C to reach the usually required softening temperatures.
BRIEF DESCRIPTION OF PRIOR ART
The softening process is well-documented and generally comprises the blowing of air or oxygen-enriched air into a bath of lead bullion at temperatures of from 590 to 750C, with or without the addition of an alkali metal, usually 2 13336~4 sodium, or an alkaline chemical such as caustic or caustic soda.
Recent descriptions of the softening process can be found in U.S. Patents 4 194 904, 4 308 058 and 4 425 160, German Publications 30 48 860 Al and 33 32 796 Cl, and in a paper by P.J. Dugdale presented in 1977 at the 16th Annual Conference of Metallurgists in Vancouver, B.C.
The prior art processes all use air or oxygen-enriched air.
The use of pure oxygen is considered impractical as it causes considerable damage to the refining vessel or kettle.
The injection of oxygen into molten metal during refining is possible as is disclosed in Canadian Patent 1 141 168, but the oxygen stream must then be surrounded by a protective fluid using specially designed lances.
SUMMARY OF THE INVENTION
We have now found that the softening of lead can be carried out with pure oxygen. We have furthermore found that the softening process can be carried out without heating all of the lead bullion to the high temperature required for the softening process. More particularly, we have found that by diverting a small portion of a charge of lead bullion to a small softening furnace, the softening can be carried out with pure oxygen at about 650C, and the major portion of the lead bullion does not have to be heated to the high temperature required for softening. The small portion of bullion is diverted from the main charge of bullion to the softening furnace, heated and softened in the small , softening furnace, separated from the slag and the softened bullion is either returned to the main charge or fed to a separate vessel. In this manner, the whole bullion charge can be softened. Alternatively, the softening process can be carried out semi-continuously or continuously.
Accordingly, it is an object of the present invention to provide a method for softening lead bullion with pure oxygen. It is another object to provide a method for refining lead bullion whereby the major portion of the lead bullion is kept at a relatively low temperature. These and other objects of the present invention can be achieved by providing, in its broadest aspect, a method for the softening of lead bullion comprising the steps of maintaining a charge of lead bullion comprising antimony, arsenic and tin, removing a minor portion of bullion from said charge, feeding said minor portion to a softening furnace, maintaining a temperature in said furnace in the range of about 590 to 650C, softening said minor portion at said temperature in said furnace with pure oxygen to form softened lead bullion with a predetermined content of antimony and a slag comprising lead and at least a portion of said antimony, arsenic and tin, and separately removing softened lead bullion and slag from said furnace.
DETAILED DESCRIPTION
The method of the invention will now be described in detail.
Lead bullion is one of the intermediates, or the end product, formed in a lead smelting process wherein lead -concentrates or sinter products are treated for the recovery of lead and other contained values. The lead bullion is usually subjected to one or more refining steps for the removal of at least a portion of the impurity metals that include antimony, arsenic, tin, copper, bismuth and silver, and for the recovery of refined lead. One of the refining steps is the softening of lead bullion, usually carried out after the bullion has been decopperized. The softening process is carried out until the antimony, arsenic and tin contents in the lead bullion have been reduced either to very low levels, or to predetermined levels; the latter being necessary when the softened bullion is to be cast into electrodes for electrolytic refining.
The method of the present invention is particularly useful for the partial removal of arsenic, antimony and tin from bullion containing relatively high contents of these metals and for the removal to very low levels when the bullion contains relatively low contents of these metals.
Lead bullion, usually after decopperizing, contains antimony, arsenic and tin as the main impurity metals.
Other impurity metals that may be present comprise bismuth, copper and silver. The lead bullion is maintained as a charge in a suitable vessel, such as a refining pot or kettle. The temperature of the bullion charge in the kettle is usually in the range of about 400 to 450C. The charge of the bullion in the kettle is softened and the softened bullion is removed for a subsequent refining treatment or for casting into electrodes. A portion of the lead bullion - 13336~4 is removed from the charge in the kettle and is fed to a softening furnace wherein the portion is heated and treated with pure oxgyen. Preferably, a minor portion of the charge is intermittently or continuously pumped or flowed from the kettle to the softening furnace. The softening furnace may be a relatively small vessel of suitable shape, preferably brick-lined and equipped with one or more oxygen lances.
The antimony, arsenic and tin are oxidized in part and, together with any oxidized lead, form a slag which separates to the top of the furnace leaving softened lead bullion in the bottom portion of the furnace.
After softening is completed, the minor portion may be returned to the bullion kettle or to a second kettle from which it is discharged for further treatment. The softening of a small portion of the charge is repeated until the whole charge has been softened. In a preferred embodiment, the softening is carried out with consecutive minor portions, softened bullion of each portion is returned to the charge in the bullion kettle and softening is continued until the charge has the desired composition. The softened charge is then transferred to a second kettle from which it is subsequently discharged for casting into anodes for electrorefining. It is also possible to carry out the softening continuously, in which case the volume of the contents of the furnace is maintained substantially constant by continuously displacing softened lead bullion from the furnace with a corresponding volume of lead bullion from the lead bullion charge in the kettle, while allowing for the .. .
volume of slag formed. In a further preferred embodiment, the softening is carried out continuously by continuously feeding oxygen into the furnace to effect softening, intermittently pumping bullion from the kettle to the furnace and returning a substantially equal volume of softened bullion from the furnace to the kettle such that the temperature in the furnace is maintained between about 625C and about 650C. The pumping is started when the furnace charge has a temperature of about 650C and is stopped when the furnace temperature has decreased to about 625C. The furnace charge is then reheated to 650C after which the pumping is started. This cycle of pumping, cooling and heating is continuously repeated. The flow of bullion to the furnace is sufficient to remove the heat generated by the oxidation of metals in the furnace.
The slag accumulated in the top portion of the furnace is periodically or continuously discharged from the softening furnace and recovered for further treatment. The amount of oxygen fed into the furnace contents through the one or more oxygen lances determines the temperature of the furnace contents as well as, together with residence time, the amount of impurity metals removed from the bullion into the slag. The amount of oxygen lanced into the bullion in the furnace should be sufficient, firstly, to raise the temperature to the required softening temperature of about 650C, and, secondly, to reduce the content of the impurity metals to the desired level, i.e. to oxidize the desired amount of impurity metals, as well as lead which is co-oxidized.
-7 133366~
The amount of oxygen is determined from relationships thatexist between the amount of lead bullion to be treated, its arsenic content and the amount of antimony that is to be removed in order to obtain softened bullion with a predetermined antimony content. For example, for partial softening, if 5 t/h of bullion with an As content of 0.6~ is to be softened with removal of 0.7% Sb, 21 Nm3/h (normal cubic metre per hour) of oxygen must be lanced into the bullion in the softening furnace. Similarly, 15 t/h bullion with 0.3% As and 0.3% Sb removal requires 31 Nm3/h oxygen.
Similarly, 20 t/h bullion, containing 0.9% As and requiring 1.0% Sb removal, requires 122 Nm3/h oxygen. In practice, an excess of 5% of the required amounts of oxygen is used.
The temperature in the softening furnace is preferably maintained in the range of about 590 to 650C and most preferably in the range of about 625 to 650C. Below about 590C, slag begins to solidify while above 650C, especially above 670C, the oxygen lance(s) deteriorate(s) rapidly.
The temperature in the softening furnace is controlled by varying the rate at which bullion is added to the furnace.
When softened bullion is to be cast into anodes for subsequent electrolytic refining, the desired antimony content is in the range of about 0.9 to 1.2%. The total amount of antimony and arsenic should be about 1.5%. In other cases, the content of impurity metals, such as antimony arsenic and tin, can be reduced to very low levels in the softened bullion, such as 0.03% or less. It is noted that impurity elements more noble than lead will not oxidize 8 133366~
before lead and are not removed by softening. The more noble impurities will remain in the lead. The residence time of the bullion in the furnace depends on the time required to attain the desired degree of softening.
5 The invention will now be illustrated with the following non-limitative example, wherein the most preferred operation of the method according to the invention is described.
According to this example, lead bullion is partially softened in a continuous operation.
10 In steady-state, continuous operation, decopperized lead bullion containing 1.7% antimony and having an assay as given in Table I was charged at a temperature of 410C and at a rate of 16.4 t/h to a bullion kettle having a capacity of 200 t and containing a charge of partially softened 15 bullion having an antimony content of 1.2%.
Bullion was pumped from the kettle to a softening furnace having a capacity of 40 t and containing bullion at a temperature of 625C. Oxygen was continuously supplied at a rate of 88 Nm3/h to the softening furnace via four lances.
20 The temperature of the bullion in the furnace rose from 625 to 650C due to the heat generated by the softening reactions. Bullion at 410C was then pumped from the kettle to the furnace until the temperature in the furnace decreased to 625C. The fresh bullion displaced partially 25 softened bullion from the furnace which was returned to the kettle and slag which was tapped and collected for further processing.
-133366~
The furnace temperature was then allowed to rise again to650C, and bullion was again pumped into the furnace from the kettle. This cycle of pumping, cooling and heating was continuously repeated. The frequency of this cycle was four per hour.
While the cyclic softening was in progress, partially softened bullion was flowed from the bullion kettle into a second kettle in an intermittent fashion. The second kettle already contained a charge of partially softened lead.
Flowing softened lead from the bullion kettle in the charge of softened lead in the second kettle caused homogenization of the charge of partially softened lead.
Partially softened lead was discharged from the second kettle for casting into anodes for the subsequent electrorefining of lead.
The various flows of bullion were sampled at 3 h intervals and the samples were analyzed. The analysis results and the mass balance for steady state continuous operation are given in Tables I and II, respectively.
Table r Allaly8i8 in 0 Stream N~r~ Pb Sb ~a ~G Ç~ ~i Aa feed to kettle 39397.25 1.70 0.570.04 0.14 0.10 0.159 feed to furnace 36797.98 1.29 0.32O.OZ 0.10 0.10 0.164 partially softened Pb to kettle 35798.80 0.76 0.030.02 0.10 0.10 0.168 slag fro~ furnace 1264.00 17.2 9.300.30 0.05 0 0 feed to 2nd kettle (and to ca~tlng~ 38198.22 1.18 0.290.02 0.09 0.10 0.16 Table II
Mass t/day Stream Name Pb Sb A8 Sn Cu Pi Aa feed to kettle3826.682.24 0.16 0.55 0.39 0.62 feed to furnace 3604.731.17 0.07 0.37 0.37 0.60 partial1y softened Pb to kettle 3532.710.11 0.07 0.36 0.35 0.60 slag from furnace 8 2.061.12 0.03 0.01 0 0 feed to 2nd kettle 0 (and to casting) 3744.501.10 0.08 0.34 0.38 0.62 any discrepancy in data is caused by small unaccounted losses.
It can be seen from this example that lead bullion can be effectively and continuously softened using pure oxygen, and that the main charge of lead bullion does not have to be heated to the softening temperature of 650C.
It is understood that modifications can be made in the embodiments of the method according to the present invention without departing from the spirit and scope of the appended claims.
This invention relates to the refining of lead and, more particularly to a method for the softening of lead bullion with pure oxygen.
BACKGROUND OF THE INVENTION
In the production of lead from minerals and concentrates, a lead bullion obtained from a lead smelting process is normally subjected to a number of refining steps. In one of those steps, the bullion is subjected to oxidation or softening to remove impurity metals such as antimony, arsenic and tin in a slag. The softening is usually carried out after the bullion has been decopperized.
In order to soften lead bullion, a relatively high temperature such as a temperature in the range of 590 to 750C is required, but the lead bullion after decopperizing is typically at a temperature in the range of 400 to 450C.
Before the softening of the lead bullion is carried out the temperature of the lead bullion must therefore be raised about 200C to reach the usually required softening temperatures.
BRIEF DESCRIPTION OF PRIOR ART
The softening process is well-documented and generally comprises the blowing of air or oxygen-enriched air into a bath of lead bullion at temperatures of from 590 to 750C, with or without the addition of an alkali metal, usually 2 13336~4 sodium, or an alkaline chemical such as caustic or caustic soda.
Recent descriptions of the softening process can be found in U.S. Patents 4 194 904, 4 308 058 and 4 425 160, German Publications 30 48 860 Al and 33 32 796 Cl, and in a paper by P.J. Dugdale presented in 1977 at the 16th Annual Conference of Metallurgists in Vancouver, B.C.
The prior art processes all use air or oxygen-enriched air.
The use of pure oxygen is considered impractical as it causes considerable damage to the refining vessel or kettle.
The injection of oxygen into molten metal during refining is possible as is disclosed in Canadian Patent 1 141 168, but the oxygen stream must then be surrounded by a protective fluid using specially designed lances.
SUMMARY OF THE INVENTION
We have now found that the softening of lead can be carried out with pure oxygen. We have furthermore found that the softening process can be carried out without heating all of the lead bullion to the high temperature required for the softening process. More particularly, we have found that by diverting a small portion of a charge of lead bullion to a small softening furnace, the softening can be carried out with pure oxygen at about 650C, and the major portion of the lead bullion does not have to be heated to the high temperature required for softening. The small portion of bullion is diverted from the main charge of bullion to the softening furnace, heated and softened in the small , softening furnace, separated from the slag and the softened bullion is either returned to the main charge or fed to a separate vessel. In this manner, the whole bullion charge can be softened. Alternatively, the softening process can be carried out semi-continuously or continuously.
Accordingly, it is an object of the present invention to provide a method for softening lead bullion with pure oxygen. It is another object to provide a method for refining lead bullion whereby the major portion of the lead bullion is kept at a relatively low temperature. These and other objects of the present invention can be achieved by providing, in its broadest aspect, a method for the softening of lead bullion comprising the steps of maintaining a charge of lead bullion comprising antimony, arsenic and tin, removing a minor portion of bullion from said charge, feeding said minor portion to a softening furnace, maintaining a temperature in said furnace in the range of about 590 to 650C, softening said minor portion at said temperature in said furnace with pure oxygen to form softened lead bullion with a predetermined content of antimony and a slag comprising lead and at least a portion of said antimony, arsenic and tin, and separately removing softened lead bullion and slag from said furnace.
DETAILED DESCRIPTION
The method of the invention will now be described in detail.
Lead bullion is one of the intermediates, or the end product, formed in a lead smelting process wherein lead -concentrates or sinter products are treated for the recovery of lead and other contained values. The lead bullion is usually subjected to one or more refining steps for the removal of at least a portion of the impurity metals that include antimony, arsenic, tin, copper, bismuth and silver, and for the recovery of refined lead. One of the refining steps is the softening of lead bullion, usually carried out after the bullion has been decopperized. The softening process is carried out until the antimony, arsenic and tin contents in the lead bullion have been reduced either to very low levels, or to predetermined levels; the latter being necessary when the softened bullion is to be cast into electrodes for electrolytic refining.
The method of the present invention is particularly useful for the partial removal of arsenic, antimony and tin from bullion containing relatively high contents of these metals and for the removal to very low levels when the bullion contains relatively low contents of these metals.
Lead bullion, usually after decopperizing, contains antimony, arsenic and tin as the main impurity metals.
Other impurity metals that may be present comprise bismuth, copper and silver. The lead bullion is maintained as a charge in a suitable vessel, such as a refining pot or kettle. The temperature of the bullion charge in the kettle is usually in the range of about 400 to 450C. The charge of the bullion in the kettle is softened and the softened bullion is removed for a subsequent refining treatment or for casting into electrodes. A portion of the lead bullion - 13336~4 is removed from the charge in the kettle and is fed to a softening furnace wherein the portion is heated and treated with pure oxgyen. Preferably, a minor portion of the charge is intermittently or continuously pumped or flowed from the kettle to the softening furnace. The softening furnace may be a relatively small vessel of suitable shape, preferably brick-lined and equipped with one or more oxygen lances.
The antimony, arsenic and tin are oxidized in part and, together with any oxidized lead, form a slag which separates to the top of the furnace leaving softened lead bullion in the bottom portion of the furnace.
After softening is completed, the minor portion may be returned to the bullion kettle or to a second kettle from which it is discharged for further treatment. The softening of a small portion of the charge is repeated until the whole charge has been softened. In a preferred embodiment, the softening is carried out with consecutive minor portions, softened bullion of each portion is returned to the charge in the bullion kettle and softening is continued until the charge has the desired composition. The softened charge is then transferred to a second kettle from which it is subsequently discharged for casting into anodes for electrorefining. It is also possible to carry out the softening continuously, in which case the volume of the contents of the furnace is maintained substantially constant by continuously displacing softened lead bullion from the furnace with a corresponding volume of lead bullion from the lead bullion charge in the kettle, while allowing for the .. .
volume of slag formed. In a further preferred embodiment, the softening is carried out continuously by continuously feeding oxygen into the furnace to effect softening, intermittently pumping bullion from the kettle to the furnace and returning a substantially equal volume of softened bullion from the furnace to the kettle such that the temperature in the furnace is maintained between about 625C and about 650C. The pumping is started when the furnace charge has a temperature of about 650C and is stopped when the furnace temperature has decreased to about 625C. The furnace charge is then reheated to 650C after which the pumping is started. This cycle of pumping, cooling and heating is continuously repeated. The flow of bullion to the furnace is sufficient to remove the heat generated by the oxidation of metals in the furnace.
The slag accumulated in the top portion of the furnace is periodically or continuously discharged from the softening furnace and recovered for further treatment. The amount of oxygen fed into the furnace contents through the one or more oxygen lances determines the temperature of the furnace contents as well as, together with residence time, the amount of impurity metals removed from the bullion into the slag. The amount of oxygen lanced into the bullion in the furnace should be sufficient, firstly, to raise the temperature to the required softening temperature of about 650C, and, secondly, to reduce the content of the impurity metals to the desired level, i.e. to oxidize the desired amount of impurity metals, as well as lead which is co-oxidized.
-7 133366~
The amount of oxygen is determined from relationships thatexist between the amount of lead bullion to be treated, its arsenic content and the amount of antimony that is to be removed in order to obtain softened bullion with a predetermined antimony content. For example, for partial softening, if 5 t/h of bullion with an As content of 0.6~ is to be softened with removal of 0.7% Sb, 21 Nm3/h (normal cubic metre per hour) of oxygen must be lanced into the bullion in the softening furnace. Similarly, 15 t/h bullion with 0.3% As and 0.3% Sb removal requires 31 Nm3/h oxygen.
Similarly, 20 t/h bullion, containing 0.9% As and requiring 1.0% Sb removal, requires 122 Nm3/h oxygen. In practice, an excess of 5% of the required amounts of oxygen is used.
The temperature in the softening furnace is preferably maintained in the range of about 590 to 650C and most preferably in the range of about 625 to 650C. Below about 590C, slag begins to solidify while above 650C, especially above 670C, the oxygen lance(s) deteriorate(s) rapidly.
The temperature in the softening furnace is controlled by varying the rate at which bullion is added to the furnace.
When softened bullion is to be cast into anodes for subsequent electrolytic refining, the desired antimony content is in the range of about 0.9 to 1.2%. The total amount of antimony and arsenic should be about 1.5%. In other cases, the content of impurity metals, such as antimony arsenic and tin, can be reduced to very low levels in the softened bullion, such as 0.03% or less. It is noted that impurity elements more noble than lead will not oxidize 8 133366~
before lead and are not removed by softening. The more noble impurities will remain in the lead. The residence time of the bullion in the furnace depends on the time required to attain the desired degree of softening.
5 The invention will now be illustrated with the following non-limitative example, wherein the most preferred operation of the method according to the invention is described.
According to this example, lead bullion is partially softened in a continuous operation.
10 In steady-state, continuous operation, decopperized lead bullion containing 1.7% antimony and having an assay as given in Table I was charged at a temperature of 410C and at a rate of 16.4 t/h to a bullion kettle having a capacity of 200 t and containing a charge of partially softened 15 bullion having an antimony content of 1.2%.
Bullion was pumped from the kettle to a softening furnace having a capacity of 40 t and containing bullion at a temperature of 625C. Oxygen was continuously supplied at a rate of 88 Nm3/h to the softening furnace via four lances.
20 The temperature of the bullion in the furnace rose from 625 to 650C due to the heat generated by the softening reactions. Bullion at 410C was then pumped from the kettle to the furnace until the temperature in the furnace decreased to 625C. The fresh bullion displaced partially 25 softened bullion from the furnace which was returned to the kettle and slag which was tapped and collected for further processing.
-133366~
The furnace temperature was then allowed to rise again to650C, and bullion was again pumped into the furnace from the kettle. This cycle of pumping, cooling and heating was continuously repeated. The frequency of this cycle was four per hour.
While the cyclic softening was in progress, partially softened bullion was flowed from the bullion kettle into a second kettle in an intermittent fashion. The second kettle already contained a charge of partially softened lead.
Flowing softened lead from the bullion kettle in the charge of softened lead in the second kettle caused homogenization of the charge of partially softened lead.
Partially softened lead was discharged from the second kettle for casting into anodes for the subsequent electrorefining of lead.
The various flows of bullion were sampled at 3 h intervals and the samples were analyzed. The analysis results and the mass balance for steady state continuous operation are given in Tables I and II, respectively.
Table r Allaly8i8 in 0 Stream N~r~ Pb Sb ~a ~G Ç~ ~i Aa feed to kettle 39397.25 1.70 0.570.04 0.14 0.10 0.159 feed to furnace 36797.98 1.29 0.32O.OZ 0.10 0.10 0.164 partially softened Pb to kettle 35798.80 0.76 0.030.02 0.10 0.10 0.168 slag fro~ furnace 1264.00 17.2 9.300.30 0.05 0 0 feed to 2nd kettle (and to ca~tlng~ 38198.22 1.18 0.290.02 0.09 0.10 0.16 Table II
Mass t/day Stream Name Pb Sb A8 Sn Cu Pi Aa feed to kettle3826.682.24 0.16 0.55 0.39 0.62 feed to furnace 3604.731.17 0.07 0.37 0.37 0.60 partial1y softened Pb to kettle 3532.710.11 0.07 0.36 0.35 0.60 slag from furnace 8 2.061.12 0.03 0.01 0 0 feed to 2nd kettle 0 (and to casting) 3744.501.10 0.08 0.34 0.38 0.62 any discrepancy in data is caused by small unaccounted losses.
It can be seen from this example that lead bullion can be effectively and continuously softened using pure oxygen, and that the main charge of lead bullion does not have to be heated to the softening temperature of 650C.
It is understood that modifications can be made in the embodiments of the method according to the present invention without departing from the spirit and scope of the appended claims.
Claims (11)
1. A method for the softening of lead bullion comprising the steps of maintaining a charge of lead bullion comprising antimony, arsenic and tin; removing a minor portion of bullion from said charge; feeding said minor portion to a softening furnace; maintaining a temperature in said furnace in the range of about 590 to 650°C; softening said minor portion at said temperature in said furnace with pure oxygen to form softened lead bullion with a predetermined content of antimony and a slag comprising lead and at least a portion of said antimony, arsenic and tin; and separately removing softened lead bullion and slag from said furnace.
2. A method as claimed in claim 1, wherein the temperature of the lead bullion being softened in said furnace is maintained in the range of about 625 to 650°.
3. A method as claimed in claim 1, wherein the amount of oxygen for softening said minor portion is determined from relationships between the amount of lead bullion to be treated, the arsenic content of the lead bullion to be treated and the amount of antimony that is to be removed to form softened lead bullion with said predetermined content of antimony.
4. A method as claimed in claim 1, 2, or 3, wherein said charge of lead bullion is at a temperature in the range of about 400 to 450°C.
5. A method as claimed in claim 1, 2, or 3, wherein lead bullion is fed to said furnace at a predetermined rate and softened lead bullion is returned from said furnace to said charge at substantially said predetermined rate.
6. A method as claimed in claim 1, 2, or 3, wherein softened lead removed from said furnace is returned to said charge of lead bullion.
7. A method as claimed in claim 1, 2, or 3, wherein said charge of lead bullion consists of lead bullion that has been decopperized.
8. A method as claimed in claim 1, 2, or 3, wherein consecutive minor portions of lead bullion from said charge are softened in said furnace, softened lead removed from said furnace is returned to said charge and said softening of consecutive minor portions and said returning of softened lead is continued until the charge of lead bullion has an antimony content in the range of about 0.9 to 1.2%.
9. A method as claimed in claim 1, 2, or 3, wherein said softening is carried out continuously by maintaining the volume of the contents of said furnace substantially constant by continuously displacing a volume of softened lead from said furnace with a substantially equal volume of lead bullion from said charge of lead bullion, while allowing for the volume of slag formed during softening.
10. A method as claimed in claim 1, 2 or 3, wherein said softening is carried out continuously by continuously feeding oxygen into said furnace to effect softening, intermittently pumping bullion from said charge to said furnace and returning a substantially equal volume of softened bullion from said furnace to said charge such that the temperature in said furnace is maintained between about 625°C and about 650°C.
11. A method as claimed in claim 1, 2 or 3, wherein said softening is carried out continuously by continuously feeding oxygen into said furnace to effect softening, intermittently pumping bullion from said charge to said furnace and returning a substantially equal volume of softened bullion from said furnace to said charge such that the temperature in said furnace is maintained between about 625°C and about 650°C, said pumping being started when the temperature in said furnace is about 650°C and said pumping being stopped when the temperature in said furnace is about 625°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 526971 CA1333664C (en) | 1987-01-08 | 1987-01-08 | Method for softening lead bullion |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 526971 CA1333664C (en) | 1987-01-08 | 1987-01-08 | Method for softening lead bullion |
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| CA1333664C true CA1333664C (en) | 1994-12-27 |
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| CA 526971 Expired - Fee Related CA1333664C (en) | 1987-01-08 | 1987-01-08 | Method for softening lead bullion |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114686925A (en) * | 2022-04-07 | 2022-07-01 | 中国恩菲工程技术有限公司 | Crude lead refining device and crude lead refining method |
-
1987
- 1987-01-08 CA CA 526971 patent/CA1333664C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114686925A (en) * | 2022-04-07 | 2022-07-01 | 中国恩菲工程技术有限公司 | Crude lead refining device and crude lead refining method |
| CN114686925B (en) * | 2022-04-07 | 2023-09-29 | 中国恩菲工程技术有限公司 | Lead bullion refining device and lead bullion refining method |
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