CA1067001A - Converter treatment - Google Patents
Converter treatmentInfo
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- CA1067001A CA1067001A CA254,283A CA254283A CA1067001A CA 1067001 A CA1067001 A CA 1067001A CA 254283 A CA254283 A CA 254283A CA 1067001 A CA1067001 A CA 1067001A
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Abstract
Abstract of the Disclosure A process for substantially removing the magnetite layer from the linings of converters used for smelting nickel and copper furnace mattes. A mixture of molten furnace matte and a silicon-containing substance, preferably ferrosilicon, are reacted with the magnetite-containing layer at substantially lower temperatures for shorter time periods than used in prior practice. Intermittent agitation of the molten, silicon-containing charge by the passage of a gas or by the use of a rocking motion improves the effectiveness of this magnetite removal process.
Description
PC~ CAN 1067001 The present invention i8 directed to a process for removing the magnetlte layer which forms on the refractory lining of a converter as a result of processing reverberatory furnace matte.
A converter is used in the smelting operation to oxidize the ferrous sulphide contained within the reverberatory furnace matte to ferrous oxide, so that it can be slagged, and to convert cuprous sulphide to copper. Generally, the heat required for this operation is supplied by these simul-taneous reactions.
During conversion of a furnace matte, a layer ofmagnetite (Fe3O4) forms upon the refractory lining of the converter. The formation of magnetite can occur in the presence of up to about 60~ nickel in the matte, and its formation is related to the blowing practice used. The magnetite-containing layer increases in thickness until it becomes so thick that it reduces the effective volume of the converter and operation becomes less economical.
Frequently the refractory brick in the vicinity of the tuyere line on a converter is attacked at a faster rate than refractories in other locations within the converter.
AB a result, it is desirable to replace the refractories in the vicinity of the tuyere line only. Complete removal of magnetite from the brick work prior to repairing the converter can assist the selective removal and replacement of the refractory brick at the tuyere line. When a converter is completely relined with refractories, removal of the magnetite layer from the converter walls greatly assists in the ease with which the old re~fractories can be removed.
. ' 1, ~k ~06700~
With the copper furnace matte and current converting practice, the magnetite layer may require removal after about 30 batches of matte have been processed. Removal, until the time of the present invention, has been routinely accomplished by charging solid ferrosilicon into the converter by shoveling, in part, through the flux gun opening and, in part, through a hole cut in the oppo~ite end of the converter. The ferro-silicon charge is subsequently melted and allowed to react with and dissolve away the magnetite layers. Temperatures in the vicinity of 1500C for time periods of about 20 hours are used for this ferrosilicon treatment. With this prior art process, the ferrosilicon reduces magnetite (Fe3O4) to ferrous oxide (FeO) which is removed from the converter as a slag. Although the process substantially removes the built up magnetite-containing layer, it has the disadvantage of requiring high temperature which can, and does, lead to deterioration of the refractory lining and buckling of steel work supporting refractories at the mouth of the converter.
The high temperature required for the reaction is dependent, to a large degree, upon the addition of heat energy which is generally supplied by the combustion of natural gas or fuel oil above the surface of the charge.
It has now been discovered that the magnetite-containing layer, formed within a converter used to process reverberatory furnace matte, can be more effectively removed in a shorter period of time while consuming smaller quantities of raw materials and fuel by reacting the magnetite-containing layer with a charge composed of furnace matte and ferrosilicon.
Generally speaking, the present invention is directed to a process for substantially removing a built-up magnetite-containing layer from the surface of a lining of a converter comprising the steps of placing a molten charge of furnace matte and a silicon-containing alloy within said converter having said built-up magnetite-containing layer, reacting said charge with said built-up magnetite-containing layer thereby forming a slag and a silicon depleted charge, and removing said slag and said silicon depleted charge from said converter.
The silicon depleted charge is processed, to advantage, for iron removal in a conventional manner, e.g., in a reverberatory furnace.
Al*hough the mixture of molten furnace matte and ferrosilicon will substantially remove the magnetite-containing layer after prolonged contact, the rate at which the magnetite layer is removed can be ~ignificantly increased by agitation of the bath. Effective agitation can be accom-plished by passage of a gas stream through the melt at frequent intervals. 810wing for periods of about 10 to about 40 seconds at intervals of about 5 minutes, or even 15 minutes, has been found to be ef~ective for agitating the bath and substantially removing the magnetite layer. Increasing the total agitation time and/or the number of gas blasts has been found to increase the amount of magnetite removed within a given time period. The gas used to agitate the bath is preferably introduced throuyh the converter's tuyeres;
however, it i9 also contemplated that the gas can be intro-duced through a lance immersed below the surface of the molten mixture of the silicon-containing furnace matte.
Air and air-oxygen mixtures containing up to about 40 volume percent oxygen can be used for agitation. Such oxygen-containing gases also serve to react with the ferrosilicon during passage through the charge thereby maintaining the temperature of the converter within the desirable 1230 to 1300C temperature range. It is contemplated that other gases could be used for agitation such as nitrogen, inert gases, carbon-dioxide, reducing gases (natural gas), etc.
Agitation with a reducing gas can aid in the reduction of the magnetite layers.
Agitation of the bath can also be accomplished by imparting a rocking motion to the converter. The use of a rocking motion or a rocking motion in combination with agita-tion by blown gas is considered within the scope of the invention.
Sufficient silicon should be added to the furnace matte to provide a silicon content of from about 1~ to about 5%, by weight of the charge. This amount of silicon corre-sponds to an addition of a low-silicon grade of ferrosilicon in an amount of from about 10% to about 30%, where the ferro-silicon alloy it~elf contains from about 10~ to about 20%
silicon. A low-silicon grade of ferrosilicon is the preferred addition to the furnace matte; however, the form of ~ilicon addition used is considered to be dictated solely by price and availability, and it is contemplated that other forms of silicon, e.g., higher silicon grades of ferrosilicon (50% Si), silicon metal, silicon alloys, etc., can be used in the process of this invention. The silicon-containing substance is added in solid form to an already molten charge of furnace matte.
By way of contrast, in prior practice substantial quantities of fuel were required to heat and melt the ferrosilicon charge.
~067001 The process of this invention is predominantly useful for the removal of magnetite build-up from converters used for processing nickel sulphide furnace mattes rather than those containing copper sulphide as the non-ferrous constituent.
The furnace matte used in conjunction with ferro-silicon to prepare the charge for cleaning the converter is preferably a nickel matte from a reverberatory furnace such as a matte containing about 50% nickel, 27% copper, 1% cobalt, 1~ iron, 0.5% silica, balance esRentially sulphur. A copper matte from a flash furnace can also be used such as one containing about 46% copper, 205~ nickel, 0.1% cobalt, 24% iron, balance essentially sulphur. In addition, pyrrhotite concentrate (about 58~ iron) has been found to be useful.
It is most effective to maintain the temperature of the charge containing the furnace matte and ferrosilicon in the range of about 1230C to about 1300C. This temperature range is considerably lower than the 1500C operating temperature used in the conventional magnetite removal opera-tion. The magnetite layer is essentially removed from the converter as a slag after an operating period of from about 3 to about 15 hours using the aforedescribed removal condi-tions. This time period is considerably shorter than the 20-hour treatment period required with the previously used ferrosilicon process. The shorter time period and lower operating temperature requires less fuel for heating the converter, provides substantial labor savings, limits down-time, increases refractory life, and results in less deterio-ration of the refractories and steelwork supporting therefractories at the mouth of the converter.
~ 1067001 The operation of the process for magnetite removal resembles the process used in the normal operation of the converter and requires no abnormal facilities or work crews.
The molten charge of furnace matte is poured into the converter conventionally. Since the process consumes roughly only 1/2 to 1/3 as much silicon as the previously used process, silicon in the form of ferrosilicon can be charged directly through the mouth of the converter into the molten matte. The entire silicon addition can be added at once or in intervals until the required addition level is achieved.
It has been found expedient to add a portion of the total silicon, or ferrosilicon, requirement to the converter, agitate with air, skim the iron oxide-containing slag, add another portion of this ingredient or the balance of this ingredient, agitate and again skim the qlag that has formed.
By adding silicon to the molten matte in intervals, a more controllable rate of magnetite removal is attained than when a single charging procedure is used.
For the purpose of giving those skilled in the art~
a better understanding of the invention, the following examples are given:
EXAMPLE I
This example shows a preferred method for operation of the process of this invention in which five air agitation periods were e~ployed.
Four ladles ~about 96 tons) of molten reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1% Co, 1% Fe, 0.5% SiO2, bal. S were charged into a converter having a magnetite-containing built-up layer coating the refractory ; 106700~
lining. About 7 tons of converter flux containing about 65~
silica was next introduced to the converter and the tempera-ture of this charge raised to about 1290C by blowing oxygen-enriched air containing about 30% oxygen through the matte for 40 minutes.
The blow was stopped, about 20 tons of slag skimmed, and about 8 tons of ferrosilicon charged through the mouth of the converter. The charge was agitated by blowing air through the tuyeres for two periods separated by about 5 minutes, each period having a duration of 20 seconds. The bath was held at about 1290C for 75 minutes and again air agitated in two periods of about 30 seconds each in duration separated by a time interval of S minutes. At this point, one ladle of slag (about 20 tons) was skimmed and removed from the converter.
The temperature at the time of skimming was about 1230C.
Following this first skimming operation, a second charge of 8 tons of ferrosilicon was added through the con-verter mouth. The ferrosilicon was mixed with the matte by blowing alr through the tuyeres for two periods separated by about 5 minutes, the periods being 25 seconds in duration.
The matte and ferrosilicon addition were held at a temperature ~ of about 1290C for 40 minutes. At the end of this time - period, air was blown through the tuyeres two times for periods lasting 30 seconds and separated by 5 minutes. The slag was skimmed and one ladle (about 20 tons) of slag removed. The charge was held at about 1290C for 50 minutes and then subjected to four 30-second blasts of air separated by 5-minute intervals. The total agitation period for this example was 330 seconds. Two ladles of slag and four ladles of matte were removed from the converter and the cleaned converter returned to service.
~06700~
The operation required 96 tons of matte, 7 tons of flux, and 16 tons of ferrosilicon for a total charge weight of ll9 tons. The cleaning operation produced 5 ladles of slag (lO0 tons) and four ladles (88 tons) of matte for a total of 188 tons of product. As a result of this treatment, 69 tons of magnetite-containing build-up were removed from the lining of the converter. The entire treatment required 6 hours to perform. By way of comparison, the standard cleaning method used prior to the time of this invention required about 41 tons of ferrosilicon, a treatment time of about 20 hours, and operating temperatures in the vicinity of 1500C.
EXAMPLE II
The treatment used in this example was similar to that shown in Example I except that only two mixing periods were used.
Four ladles (about 96 tons) of a molten reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1% Co, 1% Fe, 0.5~ SiO2, bal. S, and 5 tons of converter flux were charged into a converter having a built-up magnetite layer.
The converter was blown for 13 minutes using air followed by 23 minutes with oxygen-enriched air containing about 30 oxygen to achieve a temperature of 1290C.
A five-ton charge of ferrosilicon was introduced through the converter mouth and mixed with the furnace matte using two air blasts through the tuyeres of 20-second dura-tion separated by a 15-minute interval. The molten charge was maintained at a temperature of 1250C for 75 minutes at which point one ladle of slag was skimmed and removed from the converter.
A second ferrosilicon addition of 7 tons was intro-duced through the converter mouth. This was mixed with the charge by blowing air through the tuyeres. Eight blasts of 20-second duration separated by 5-minute intervals were used.
The total agitation time, including the first and second series of air blasts, was 200 seconds. Following the second agitation procedure, the charge was held at temperature for 120 minutes and three ladles of slag, about 60 tons, and 3 1/2 ladles of matte, about 84 tons, were removed and the converter returned to service.
The converter cleaning operation involved the use of 96 tons of furnace matte, S tons of converter flux, and 12 tons of ferrosilicon. This resulted in the removal of 51 tons of the built-up magnetite layer and required 5 1/2 hours for completion.
EXAMPLE III
This example represents a variation on the charging, slag skimming, and agitation procedures illustrated in the preceding exal~tples.
Three ladles (about 72 tons) of a reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1% Co, 1~ Fe, 0.5% SiO2, bal. S, and 12 tons of converter flux were blown for 62 minutes with air with a resultant bath tempera-ture of 1280C. Two ladles of slag weighing about 40 tons were removed from the converter following this treatment.
Five tons of ferrosilicon were introduced through the mouth of the converter and the charge was held at tempera-ture by heat supplied through gas burners above the melt for a time period of 50 minutes. An additional five tons of ferrosilicon were then introduced through the mouth of the converter and mixed with the charge by air agitation through the tuyeres consisting of one blast of 20-second duration.
The charge was held at temperature for 90 minutes at which point one ladle~ about 20 tons, of slag was skimmed and removed from the converter.
A third addition of five tons of ferrosilicon was introduced to the charge and mixed therewith by two air blast of 20-second duration separated by a five-minute interval. The total agitation period for this example was 60 seconds. The charge was held for 120 mimltes when one ladle of slag was skimmed, 2 1/2 ladles of matte were removed and the converter returned to service.
Throughout the aforedescribed operation, the posi-tion of the converter was changed from time to time. This action also contributed to the agitation of the charge.
Cleaning of the converter required 72 tons of furnace matte, 12 tons of converter flux, and 15 tons of ferrosilicon and resulted in 80 tonc of slag and 60 tons of matte. The built-up magnetite-containing layer removed weighed 41 tons and required 8 hours to remove.
EXAMPLE IV
This example highlights the dependence of the magnetite removal process upon agitation of the green matte plus ferrosilicon charge in that agitation was not applied to the molten charge.
Two ladles (about 48 tons) of a molten reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1~ Co, 1~ Fe, 0.5% SiO2, bal. S, and 10 tons of converter flux were charged into the converter. The converter was blown for 12 minutes with air followed by 20 minutes with oxygen-enriched air containing about 3Q% oxygen to achieve a tempera-ture of 1290C.
Following the blow, 8 tons of ferrosilicon were charged through the converter mouth and the converter main-tained at temperature for a time period of 145 minutes.
Two ladles of slag were skimmed from the surface of the charge and removed from the converter. Seven tons of ferro-silicon were charged through the converter mouth followed by one ladle (24 tons) of nickel matte. This charge was held at about I290C for 180 minutes. Two ladles of slag were skimmed, 2 1/2 ladles of matte removed and the converter returned to service.
Thé operation required 3 1/2 ladles (84 tons) of furnace matte, 10 tons of flux, and 15 tons of ferrosilicon for a total of 109 tons. Four ladles (80 tons) of slag and
A converter is used in the smelting operation to oxidize the ferrous sulphide contained within the reverberatory furnace matte to ferrous oxide, so that it can be slagged, and to convert cuprous sulphide to copper. Generally, the heat required for this operation is supplied by these simul-taneous reactions.
During conversion of a furnace matte, a layer ofmagnetite (Fe3O4) forms upon the refractory lining of the converter. The formation of magnetite can occur in the presence of up to about 60~ nickel in the matte, and its formation is related to the blowing practice used. The magnetite-containing layer increases in thickness until it becomes so thick that it reduces the effective volume of the converter and operation becomes less economical.
Frequently the refractory brick in the vicinity of the tuyere line on a converter is attacked at a faster rate than refractories in other locations within the converter.
AB a result, it is desirable to replace the refractories in the vicinity of the tuyere line only. Complete removal of magnetite from the brick work prior to repairing the converter can assist the selective removal and replacement of the refractory brick at the tuyere line. When a converter is completely relined with refractories, removal of the magnetite layer from the converter walls greatly assists in the ease with which the old re~fractories can be removed.
. ' 1, ~k ~06700~
With the copper furnace matte and current converting practice, the magnetite layer may require removal after about 30 batches of matte have been processed. Removal, until the time of the present invention, has been routinely accomplished by charging solid ferrosilicon into the converter by shoveling, in part, through the flux gun opening and, in part, through a hole cut in the oppo~ite end of the converter. The ferro-silicon charge is subsequently melted and allowed to react with and dissolve away the magnetite layers. Temperatures in the vicinity of 1500C for time periods of about 20 hours are used for this ferrosilicon treatment. With this prior art process, the ferrosilicon reduces magnetite (Fe3O4) to ferrous oxide (FeO) which is removed from the converter as a slag. Although the process substantially removes the built up magnetite-containing layer, it has the disadvantage of requiring high temperature which can, and does, lead to deterioration of the refractory lining and buckling of steel work supporting refractories at the mouth of the converter.
The high temperature required for the reaction is dependent, to a large degree, upon the addition of heat energy which is generally supplied by the combustion of natural gas or fuel oil above the surface of the charge.
It has now been discovered that the magnetite-containing layer, formed within a converter used to process reverberatory furnace matte, can be more effectively removed in a shorter period of time while consuming smaller quantities of raw materials and fuel by reacting the magnetite-containing layer with a charge composed of furnace matte and ferrosilicon.
Generally speaking, the present invention is directed to a process for substantially removing a built-up magnetite-containing layer from the surface of a lining of a converter comprising the steps of placing a molten charge of furnace matte and a silicon-containing alloy within said converter having said built-up magnetite-containing layer, reacting said charge with said built-up magnetite-containing layer thereby forming a slag and a silicon depleted charge, and removing said slag and said silicon depleted charge from said converter.
The silicon depleted charge is processed, to advantage, for iron removal in a conventional manner, e.g., in a reverberatory furnace.
Al*hough the mixture of molten furnace matte and ferrosilicon will substantially remove the magnetite-containing layer after prolonged contact, the rate at which the magnetite layer is removed can be ~ignificantly increased by agitation of the bath. Effective agitation can be accom-plished by passage of a gas stream through the melt at frequent intervals. 810wing for periods of about 10 to about 40 seconds at intervals of about 5 minutes, or even 15 minutes, has been found to be ef~ective for agitating the bath and substantially removing the magnetite layer. Increasing the total agitation time and/or the number of gas blasts has been found to increase the amount of magnetite removed within a given time period. The gas used to agitate the bath is preferably introduced throuyh the converter's tuyeres;
however, it i9 also contemplated that the gas can be intro-duced through a lance immersed below the surface of the molten mixture of the silicon-containing furnace matte.
Air and air-oxygen mixtures containing up to about 40 volume percent oxygen can be used for agitation. Such oxygen-containing gases also serve to react with the ferrosilicon during passage through the charge thereby maintaining the temperature of the converter within the desirable 1230 to 1300C temperature range. It is contemplated that other gases could be used for agitation such as nitrogen, inert gases, carbon-dioxide, reducing gases (natural gas), etc.
Agitation with a reducing gas can aid in the reduction of the magnetite layers.
Agitation of the bath can also be accomplished by imparting a rocking motion to the converter. The use of a rocking motion or a rocking motion in combination with agita-tion by blown gas is considered within the scope of the invention.
Sufficient silicon should be added to the furnace matte to provide a silicon content of from about 1~ to about 5%, by weight of the charge. This amount of silicon corre-sponds to an addition of a low-silicon grade of ferrosilicon in an amount of from about 10% to about 30%, where the ferro-silicon alloy it~elf contains from about 10~ to about 20%
silicon. A low-silicon grade of ferrosilicon is the preferred addition to the furnace matte; however, the form of ~ilicon addition used is considered to be dictated solely by price and availability, and it is contemplated that other forms of silicon, e.g., higher silicon grades of ferrosilicon (50% Si), silicon metal, silicon alloys, etc., can be used in the process of this invention. The silicon-containing substance is added in solid form to an already molten charge of furnace matte.
By way of contrast, in prior practice substantial quantities of fuel were required to heat and melt the ferrosilicon charge.
~067001 The process of this invention is predominantly useful for the removal of magnetite build-up from converters used for processing nickel sulphide furnace mattes rather than those containing copper sulphide as the non-ferrous constituent.
The furnace matte used in conjunction with ferro-silicon to prepare the charge for cleaning the converter is preferably a nickel matte from a reverberatory furnace such as a matte containing about 50% nickel, 27% copper, 1% cobalt, 1~ iron, 0.5% silica, balance esRentially sulphur. A copper matte from a flash furnace can also be used such as one containing about 46% copper, 205~ nickel, 0.1% cobalt, 24% iron, balance essentially sulphur. In addition, pyrrhotite concentrate (about 58~ iron) has been found to be useful.
It is most effective to maintain the temperature of the charge containing the furnace matte and ferrosilicon in the range of about 1230C to about 1300C. This temperature range is considerably lower than the 1500C operating temperature used in the conventional magnetite removal opera-tion. The magnetite layer is essentially removed from the converter as a slag after an operating period of from about 3 to about 15 hours using the aforedescribed removal condi-tions. This time period is considerably shorter than the 20-hour treatment period required with the previously used ferrosilicon process. The shorter time period and lower operating temperature requires less fuel for heating the converter, provides substantial labor savings, limits down-time, increases refractory life, and results in less deterio-ration of the refractories and steelwork supporting therefractories at the mouth of the converter.
~ 1067001 The operation of the process for magnetite removal resembles the process used in the normal operation of the converter and requires no abnormal facilities or work crews.
The molten charge of furnace matte is poured into the converter conventionally. Since the process consumes roughly only 1/2 to 1/3 as much silicon as the previously used process, silicon in the form of ferrosilicon can be charged directly through the mouth of the converter into the molten matte. The entire silicon addition can be added at once or in intervals until the required addition level is achieved.
It has been found expedient to add a portion of the total silicon, or ferrosilicon, requirement to the converter, agitate with air, skim the iron oxide-containing slag, add another portion of this ingredient or the balance of this ingredient, agitate and again skim the qlag that has formed.
By adding silicon to the molten matte in intervals, a more controllable rate of magnetite removal is attained than when a single charging procedure is used.
For the purpose of giving those skilled in the art~
a better understanding of the invention, the following examples are given:
EXAMPLE I
This example shows a preferred method for operation of the process of this invention in which five air agitation periods were e~ployed.
Four ladles ~about 96 tons) of molten reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1% Co, 1% Fe, 0.5% SiO2, bal. S were charged into a converter having a magnetite-containing built-up layer coating the refractory ; 106700~
lining. About 7 tons of converter flux containing about 65~
silica was next introduced to the converter and the tempera-ture of this charge raised to about 1290C by blowing oxygen-enriched air containing about 30% oxygen through the matte for 40 minutes.
The blow was stopped, about 20 tons of slag skimmed, and about 8 tons of ferrosilicon charged through the mouth of the converter. The charge was agitated by blowing air through the tuyeres for two periods separated by about 5 minutes, each period having a duration of 20 seconds. The bath was held at about 1290C for 75 minutes and again air agitated in two periods of about 30 seconds each in duration separated by a time interval of S minutes. At this point, one ladle of slag (about 20 tons) was skimmed and removed from the converter.
The temperature at the time of skimming was about 1230C.
Following this first skimming operation, a second charge of 8 tons of ferrosilicon was added through the con-verter mouth. The ferrosilicon was mixed with the matte by blowing alr through the tuyeres for two periods separated by about 5 minutes, the periods being 25 seconds in duration.
The matte and ferrosilicon addition were held at a temperature ~ of about 1290C for 40 minutes. At the end of this time - period, air was blown through the tuyeres two times for periods lasting 30 seconds and separated by 5 minutes. The slag was skimmed and one ladle (about 20 tons) of slag removed. The charge was held at about 1290C for 50 minutes and then subjected to four 30-second blasts of air separated by 5-minute intervals. The total agitation period for this example was 330 seconds. Two ladles of slag and four ladles of matte were removed from the converter and the cleaned converter returned to service.
~06700~
The operation required 96 tons of matte, 7 tons of flux, and 16 tons of ferrosilicon for a total charge weight of ll9 tons. The cleaning operation produced 5 ladles of slag (lO0 tons) and four ladles (88 tons) of matte for a total of 188 tons of product. As a result of this treatment, 69 tons of magnetite-containing build-up were removed from the lining of the converter. The entire treatment required 6 hours to perform. By way of comparison, the standard cleaning method used prior to the time of this invention required about 41 tons of ferrosilicon, a treatment time of about 20 hours, and operating temperatures in the vicinity of 1500C.
EXAMPLE II
The treatment used in this example was similar to that shown in Example I except that only two mixing periods were used.
Four ladles (about 96 tons) of a molten reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1% Co, 1% Fe, 0.5~ SiO2, bal. S, and 5 tons of converter flux were charged into a converter having a built-up magnetite layer.
The converter was blown for 13 minutes using air followed by 23 minutes with oxygen-enriched air containing about 30 oxygen to achieve a temperature of 1290C.
A five-ton charge of ferrosilicon was introduced through the converter mouth and mixed with the furnace matte using two air blasts through the tuyeres of 20-second dura-tion separated by a 15-minute interval. The molten charge was maintained at a temperature of 1250C for 75 minutes at which point one ladle of slag was skimmed and removed from the converter.
A second ferrosilicon addition of 7 tons was intro-duced through the converter mouth. This was mixed with the charge by blowing air through the tuyeres. Eight blasts of 20-second duration separated by 5-minute intervals were used.
The total agitation time, including the first and second series of air blasts, was 200 seconds. Following the second agitation procedure, the charge was held at temperature for 120 minutes and three ladles of slag, about 60 tons, and 3 1/2 ladles of matte, about 84 tons, were removed and the converter returned to service.
The converter cleaning operation involved the use of 96 tons of furnace matte, S tons of converter flux, and 12 tons of ferrosilicon. This resulted in the removal of 51 tons of the built-up magnetite layer and required 5 1/2 hours for completion.
EXAMPLE III
This example represents a variation on the charging, slag skimming, and agitation procedures illustrated in the preceding exal~tples.
Three ladles (about 72 tons) of a reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1% Co, 1~ Fe, 0.5% SiO2, bal. S, and 12 tons of converter flux were blown for 62 minutes with air with a resultant bath tempera-ture of 1280C. Two ladles of slag weighing about 40 tons were removed from the converter following this treatment.
Five tons of ferrosilicon were introduced through the mouth of the converter and the charge was held at tempera-ture by heat supplied through gas burners above the melt for a time period of 50 minutes. An additional five tons of ferrosilicon were then introduced through the mouth of the converter and mixed with the charge by air agitation through the tuyeres consisting of one blast of 20-second duration.
The charge was held at temperature for 90 minutes at which point one ladle~ about 20 tons, of slag was skimmed and removed from the converter.
A third addition of five tons of ferrosilicon was introduced to the charge and mixed therewith by two air blast of 20-second duration separated by a five-minute interval. The total agitation period for this example was 60 seconds. The charge was held for 120 mimltes when one ladle of slag was skimmed, 2 1/2 ladles of matte were removed and the converter returned to service.
Throughout the aforedescribed operation, the posi-tion of the converter was changed from time to time. This action also contributed to the agitation of the charge.
Cleaning of the converter required 72 tons of furnace matte, 12 tons of converter flux, and 15 tons of ferrosilicon and resulted in 80 tonc of slag and 60 tons of matte. The built-up magnetite-containing layer removed weighed 41 tons and required 8 hours to remove.
EXAMPLE IV
This example highlights the dependence of the magnetite removal process upon agitation of the green matte plus ferrosilicon charge in that agitation was not applied to the molten charge.
Two ladles (about 48 tons) of a molten reverberatory furnace nickel matte containing about 50% Ni, 27% Cu, 1~ Co, 1~ Fe, 0.5% SiO2, bal. S, and 10 tons of converter flux were charged into the converter. The converter was blown for 12 minutes with air followed by 20 minutes with oxygen-enriched air containing about 3Q% oxygen to achieve a tempera-ture of 1290C.
Following the blow, 8 tons of ferrosilicon were charged through the converter mouth and the converter main-tained at temperature for a time period of 145 minutes.
Two ladles of slag were skimmed from the surface of the charge and removed from the converter. Seven tons of ferro-silicon were charged through the converter mouth followed by one ladle (24 tons) of nickel matte. This charge was held at about I290C for 180 minutes. Two ladles of slag were skimmed, 2 1/2 ladles of matte removed and the converter returned to service.
Thé operation required 3 1/2 ladles (84 tons) of furnace matte, 10 tons of flux, and 15 tons of ferrosilicon for a total of 109 tons. Four ladles (80 tons) of slag and
2 1/2 ladles (60 tons) of matte were removed for a total output of 140 ton~. The built-up magnetite layer removed by this 8-hour,treatment without the u~e of agitation was 31 tons.
Although results of this treatment were still superior to tho~e attained with the previously used or conventional ferrosiliaon treatment process, the results were not equiva-lent to those obtained with the preferred treatment in which agitation is used,.
~ -Although the present invention has been described in - conjunction with pr~ferred embodiments, it is to be understood that modifications and variations may be resorted to without departing~from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifi-cations and variations are con~idered to be within the purview and scope of the invention and appended claims.
Although results of this treatment were still superior to tho~e attained with the previously used or conventional ferrosiliaon treatment process, the results were not equiva-lent to those obtained with the preferred treatment in which agitation is used,.
~ -Although the present invention has been described in - conjunction with pr~ferred embodiments, it is to be understood that modifications and variations may be resorted to without departing~from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifi-cations and variations are con~idered to be within the purview and scope of the invention and appended claims.
Claims (13)
1. A process for substantially removing a built-up magnetite-containing layer from the surface of a lining of a converter comprising: placing within said converter and in contact with said built-up magnetite-containing layer a molten charge which contains from about 1% to about 5% silicon and is comprised of furnace matte and a silicon-containing alloy;
reacting said charge with said built-up magnetite- containing layer thereby forming a slag and a silicon depleted charge, and removing said slag and said silicon depleted charge from said converter.
reacting said charge with said built-up magnetite- containing layer thereby forming a slag and a silicon depleted charge, and removing said slag and said silicon depleted charge from said converter.
2. A process as defined in claim 1, wherein said charge is intermittently agitated.
3. A process as defined in claim 2, wherein said charge is intermittently agitated by passage of an air stream.
4. A process as defined in claim 2, wherein said charge is intermittently agitated by passage of an oxygen-enriched air stream containing up to about 40 volume percent oxygen.
5. A process as defined in claim 2, wherein said charge is intermittently agitated by passage of an inert gas stream.
6. A process as defined in claim 2, wherein said charge is intermittently agitated by passage of a reducing gas stream.
7. A process as defined in claim 2, wherein said silicon-containing alloy is a ferro-silicon alloy, said ferrosilicon alloy containing, in weight percent, from about 10% to about 50% silicon.
8. A process as defined in claim 7, wherein said ferro-silicon alloy contains from 10% to about 20% silicon.
9. A process as defined in claim 1, where said furnace matte contains up to about 60% of at least one element selected from the group consisting of copper and nickel, up to about 5%
of iron, and the balance essentially sulfur.
of iron, and the balance essentially sulfur.
10. A process as defined in claim 1, wherein said charge is contacted with said built-up magnetite layer in said converter for from about 3 to about 15 hours.
11. A process as defined in claim 1, wherein said charge is heated to about 1230°C to about 1300°C.
12. A process for substantially removing a built-up magnetite-containing layer from the surface of a lining of a converter comprising: placing a molten furnace matte within said built-up magnetite-containing layer; heating said furnace matte to about 1230°C to about 1300°C by oxidation; adding a silicon-containing alloy to said molten furnace matte to form a charge which contains from about 1% to about 5% silicon; reacting said charge with said built-up magnetite-containing layer thereby forming a slag and a silicon depleted charge; and removing said slag and said silicon depleted charge from said converter.
13. A process as defined in claim 12, wherein said molten charge is intermittently agitated by passage of an oxygen-enriched air stream containing up to about 40 volume percent oxygen.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA254,283A CA1067001A (en) | 1976-06-08 | 1976-06-08 | Converter treatment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA254,283A CA1067001A (en) | 1976-06-08 | 1976-06-08 | Converter treatment |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067001A true CA1067001A (en) | 1979-11-27 |
Family
ID=4106159
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA254,283A Expired CA1067001A (en) | 1976-06-08 | 1976-06-08 | Converter treatment |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1067001A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4814004A (en) * | 1987-05-29 | 1989-03-21 | Falconbridge Limited | Non-ferrous metal recovery |
-
1976
- 1976-06-08 CA CA254,283A patent/CA1067001A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4814004A (en) * | 1987-05-29 | 1989-03-21 | Falconbridge Limited | Non-ferrous metal recovery |
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