Title of Invention

A SLAG FUMING PROCESS FOR PRODUCING CLEANSED SLAG WITH REDUCED CONTENTS OF LEAD AND ARSENIC

Abstract

Abstract A slag fuming process wherein a slag containing arsenic or arsenic and antimony together with zinc and lead is heated and reduced in a slag fuming furnace, and zinc and lead are separated by evaporation, characterized in that it comprises causing a copper melt containing copper in an amount being 5 to 100 wt % relative to that of the slag charged in the above furnace and being 100 wt % or more relative to that of the lead contained in the above slag to be co-present in the above slag melt at a temperature of 1075 to 1500°C, and reacting the copper melt with arsenic or arsenic and antimony contained in the slag, to form a Cu-Fe-Pb-As based uniform melt. The above process of slag fuming and the like can be suitably employed for producing, by the use of a slag generated from a smelting furnace for refining zinc and/or lead, a dust containing zinc and lead and being reduced in the contents of arsenic and antimony, and a slag stably satisfying the environmental standard for soil, at a low treatment cost.

Full Text

SPECIFICATION SLAG FUMING PROCESS BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a slag fuming process, more specifically a slag fuming process in which slag discharged from a smelting furnace in a zinc and/or lead extractive metallurgy is reduced under heating to evaporate zinc and lead, and produce a dust containing zinc and lead with limited contents of arsenic and antimony, and a slag which stably satisfies the criteria of the environmental quality standards for soil, at a low treatment cost. DESCRIPTION OF THE PRIOR ART A blast furnace process by the name of Imperial Smelting Process, which simultaneously smelts zinc and lead, is widely used in the zinc and/or lead extractive metallurgy. This process treats slag discharged from a blast furnace in a furnace fore hearth to preliminarily separate copper-containing crude lead and furnace iron, and then treats them by water granulation to produce a slag product, which is used as a raw material for cement or the like. The slag generally contains zinc at a high content and, at the same time, arsenic, antimony and other metals as speiss components together with lead, and hence is treated by fuming in a fuming furnace before it is treated by water granulation. The slag fuming reduces molten slag under heating to evaporate metals present in the slag, e.g., zinc, lead, arsenic, antimony and so forth. This recovers zinc and lead while removing impurity metals to leave behind cleaned slag. The slag fuming treatment is carried out in a furnace equipped with a lance or tuyere at the bottom through which gases are blown into the furnace. For example, a furnace equipped with a gas-blowing lance reduces and evaporates metals in slag, where a carbonaceous fuel, e.g., heavy fuel oil or fine coal particles, and air are blown from the lance tip immersed in the slag changed into the furnace. The treated slag is withdrawn from the furnace bottom, whereas the evaporated metals are oxidized with air while moving upwards to the furnace top to be recovered in the form of slag fuming dust containing zinc and lead. The conventional slag fuming treatment, however, evaporates low-boiling, high vapor pressure group 15 elements, e.g., arsenic and antimony, together with zinc and lead as the objective metals to be recovered. As a result, the recovered zinc and lead are contaminated with these impurity metals concentrated therein. The dust is recycled back to a sintering step in the blast furnace process, where these group 15 elements are evaporated to cause problems which can disrupt the process operation, e.g., increased load in an exhaust gas treating system. Moreover, they may cause formation of speiss comprising high-melting compounds, when they are recycled back to the blast furnace while being contained in the sintering blocks. Moreover, the treated slag may fail to pass the elution test to determine whether or not it satisfies the criteria of the environmental quality standards for soil, when it is contaminated with the hazardous elements, e.g., lead and arsenic, as a result of fluctuations of the slag fuming operating conditions. Therefore, there are demands for slag fuming processes which can stably produce slag satisfying the criteria of the environmental quality standards for soil. Some slag reforming processes are proposed to solve these problems. One of the representative ones is a two-stage process, where slag discharged from a blast furnace is heated in an electrical furnace to sufficiently separate copper-containing crude lead and furnace iron from the slag by-precipitation, and then treated in a slag fuming furnace, after the slag is treated in a furnace forehearth to preliminarily separate copper-containing crude lead and furnace iron (as disclosed by, e.g., JP-A 11-269567 (Pages 1 and 2)). This process, although giving a product slag which satisfies the criteria of the environmental quality standards for soil with respect to zinc, lead and arsenic contents, inevitably contaminates the slag fuming dust with evaporated arsenic and antimony. It fails to provide a drastic measure against the problems resulting from arsenic and antimony when the dust are recycled back to a sintering step, and hence needs an additional treatment cost. On top of this, the two-stage process itself will need an increased treatment cost. Under these situations, there are demands for slag fuming processes which can treat slag discharged from a smelting furnace in a zinc and/or lead extractive metallurgy to produce a dust containing zinc and lead with limited contents of arsenic and antimony, and a slag which stably satisfies the criteria of the environmental quality standards for soil (Pb and As contents; each 0.01 mg/L or less, determined by the elution test, Environmental Agency notification No. 46). SUMMARY OF THE INVENTION It is an object of the present invention to provide a slag fuming process of low treatment cost which can reduce, under heating, slag discharged from a smelting furnace in a zinc and/or lead extractive metallurgy, and produce a dust containing zinc and lead with limited contents of arsenic and antimony, and a slag which stably satisfies the criteria of the environmental quality standards for soil, in consideration of the problems involved in the conventional techniques. The inventors of the present invention have found, after having extensively studied to accomplish the above object, that a slag fuming process for treating slag containing zinc, lead and arsenic, discharged from a smelting furnace in a zinc and/or lead extractive metallurgy can produce a dust containing zinc and lead with limited contents of arsenic and antimony, and a slag which stably satisfies the criteria of the environmental quality standards for soil, when slag fuming is carried out under specific conditions in the presence of a copper melt, achieving the present invention. The first aspect of the present invention is a slag fuming process which reduces, under heating in a fuming furnace, slag containing arsenic or arsenic and antimony concomitantly with zinc and lead, discharged from a smelting furnace in a zinc and/or lead extractive metallurgy, to separate zinc and lead by evaporation, wherein a melt of the slag is treated in the presence of a copper melt at 1075 to 1500°C, which contains a copper in a quantity of 5 to 100% by mass on the slag and 100% by mass or more on lead originally present in the slag, in order to allow copper to react with arsenic or arsenic and antimony present in the slag to produce a uniform Cu-Fe-Pb-As-based melt. The second aspect of the present invention is the slag fuming process of the first aspect, wherein the melt is kept at 1200 to 1500°C. The third aspect of the present invention is the slag fuming process of the first aspect, wherein the uniform Cu-Fe-Pb-As-based melt contains Fe at 0.01 to 50% by mass on Cu. The fourth aspect of the present invention is the slag fuming process of the first aspect, wherein oxygen partial pressure in a melt of the slag is controlled at a level given by the following formula--8>logPo2>-11.5 (wherein, P02 is oxygen partial pressure (atm) at 1400°C). The fifth aspect of the present invention is the slag fuming process of the first aspect, wherein the uniform Cu-Fe-Pb-As-based melt is recycled repeatedly in the process as a copper melt. The slag fuming process of the present invention for treating slag discharged from a smelting furnace in a zinc and/or lead extractive metallurgy can produce a dust containing zinc and lead with limited contents of arsenic and antimony, to reduce load of arsenic/antimony and treatment cost when the dust is recycled back to the smelting furnace. Moreover, it reduces lead and arsenic contents in the slag to stably satisfy the criteria of the environmental quality standards for soil. As such, it is of very high industrial value. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a phase diagram of two-element system of copper and iron. Fig. 2 is a phase diagram of three-element system of copper, lead and arsenic at 1200°C. Fig. 3 is a conceptual drawing of the slag fuming device used in EXAMPLES. NOTATION 1. Nitrogen-blowing tube for securing a reaction atmosphere 2. Ceramic tube for recovering dust 3. Tube for blowing nitrogen for stirring 4. Temperature sensor (thermocouples) 5. Ceramic outer crucible 6. Thermocouples for controlling temperature 7. Aluminum crucible 8. Crucible-supporting brick 9. Electrical oven DETAILED DESCRIPTION OF THE INVENTION The slag fuming process of the present invention is described below in detail. The slag fuming process of the present invention reduces, under heating in a fuming furnace, slag containing arsenic or arsenic and antimony concomitantly with zinc and lead, discharged from a smelting furnace in a zinc and/or lead extractive metallurgy, to separate zinc and lead by evaporation, wherein a melt of the slag is treated in the presence of a copper melt at 1075 to 1500°C, which contains a copper in a quantity of 5 to 100% by mass on the slag and 100% by mass or more on lead originally present in the slag, in order to allow copper to react with arsenic or arsenic and antimony present in the slag to produce a uniform Cu-Fe-Pb-As-based melt. It is an essential significance for the slag fuming process of the present invention to react arsenic or arsenic and antimony present in the slag with the copper melt at a given temperature while keeping a slag melt/copper melt ratio at a given level to produce a uniform Cu-Fe-Pb"As-based melt (hereinafter sometimes referred to as "uniform copper alloy melt"). This produces dust containing zinc and lead with limited contents of arsenic and antimony, and residual slag which stably satisfies the criteria of the environmental quality standards for soil. In other words, it can produce dust containing zinc and lead, separated by evaporation, and cleaned slag by stably distributing arsenic and antimony in the uniform copper alloy melt while controlling their evaporation, with the result that their distribution in each of the dust and cleaned slag is reduced. Formation of the uniform copper alloy melt is described in more detail by referring to the attached drawing. Fig. 1 is a phase diagram of two-element system of copper and iron. According to the phase diagram given in Fig. 1, iron can melt in copper to around 15% at 1350°C to form a uniform melt. In other words, iron speiss, when is in the presence of metallic copper, melts in copper to form a uniform Cu*Fe-Pb-As-based melt with part of lead, where copper is predominant in the melt. In a high copper content region, quantity of iron melting in copper to form the uniform melt changes with temperature, increasing as temperature increases. Increasing temperature, therefore, brings a merit that treatment can be carried out with a smaller quantity of copper. The slag fuming process of the present invention may be carried out by the reductive blowing described below. For example, the reductive blowing may be carried out using a slag fuming furnace equipped with a gas-blowing lance, in which heavy fuel oil, natural gas, fine coal particles or the like and oxygen-containing gas are blown from the lance tip immersed in a mixture of slag melt and copper melt to keep a reducing atmosphere in the mixture with stirring to reduce zinc, lead, arsenic, antimony and so forth present in the slag to the metallic state. Most of zinc and part of lead reduced to the metallic state are evaporated to be recovered in the form of dust. Arsenic and antimony reduced to the metallic state have a high vapor pressure and strong affinity for iron and copper. Arsenic and antimony react with copper when a copper melt is present. Arsenic, when molten or dissolved in copper, has a very low activity at a low content, and hence a low vapor pressure. Therefore, it forms a copper alloy without being evaporated and hence is contained in a uniform ChrFe-Pb-As-based melt. Antimony shows similar behavior, and is contained in a uniform copper alloy melt. Slag containing arsenic or arsenic and antimony to be treated by the process of the present invention is not limited. It is discharged from a smelting furnace, where it is treated in a reducing atmosphere, in a zinc and/or lead extractive metallurgy to contain arsenic or arsenic and antimony in addition to zinc and lead. The above slag discharged from a smelting furnace is adjusted to have a composition of relatively lowmelting point, e.g., FeO-SiO2-Al2O3-CaO-ZnO"PbO-based one, by mixing a raw material with a flux. The smelting furnace is operated at 1200 to 1350°C in temperature of slag. It contains iron in the form of oxide at a high content, with the result that metallic iron may be produced in a locally high reducing atmosphere in a smelting furnace operating in a reducing atmosphere, e.g., that in the above-described smelting process, to react with arsenic and antimony to produce speiss. The speiss thus produced will be present in a semi-molten or solid state between the slag and metal layers. Therefore, the speiss is suspended in the slag discharged from the smelting furnace. It is known that arsenic and antimony are present in the iron speiss in a very stable state with much reduced activity. As a result, they stably remain in the speiss although slag temperature in a furnace is 1200 to 1350°C, which is higher than their boiling points. Slag fuming temperature adopted in the process of the present invention is 1075 to 1500°C, preferably 1200 to 1500°C, more preferably 1200 to 1400°C. In other words, temperature in the above range is adopted to form a uniform Cu-Fe"Pb-As-based melt by reacting a copper melt with speiss in the slag. Temperature beyond the above range will cause problems. At below 1075°C, the slag may be too viscous or solidified. At above 1500°C, on the other hand, the refractory bricks may be damaged massively and excessive thermal energy may be required for heating. The copper melt for the present invention is not limited. The process uses a copper-containing substance which can form a uniform melt with iron at 1075 to 1500°C in a reducing atmosphere in a slag fuming furnace. Some of the examples are metallic copper, copper scrap and intermediates, e.g., crude copper (copper content- 98 to 99% by mass) from the step of a copper extractive metallurgy, each being molten in a furnace for the present invention. Content of copper in the copper melt for the present invention is controlled to satisfy the following two conditions; (i) 5 to 100% by mass on the slag and (ii) 100% by mass or more on lead originally present in the slag. Regarding the condition (i), when copper is present at below 5% by mass on the slag, arsenic and antimony may not be sufficiently fixed in the uniform copper alloy melt, because of insufficient contact of these elements in the slag with copper. At above 100% by mass on the slag, on the other hand, treatment efficiency may be deteriorated, because of insufficient quantity of slag batch. No copper speiss phase will result in the presence of excess copper, which eliminates concern of copper speiss phase formation in the formation of uniform copper alloy melt. Regarding the condition (ii), when copper is present at below 100% by mass on lead originally present in the slag, a lead-rich phase may be formed. A commercial blast furnace is normally operated to discharge slag together with part of lead from the bottom and directs them to a container or the like by the name of forehearth, where lead is separated from the slag. Nevertheless, however, lead is present in the slag product. Therefore, the uniform copper alloy melt, when a copper melt present in the slag fuming treatment, will be separated into a copper/arsenic-rich phase (copper speiss phase) and lead-rich phase, when a lead content of formed copper alloy at a content beyond a certain level. The conditions under which the lead-rich phase is formed are described in more detail by referring to the attached drawing. Fig. 2 is a phase diagram of three-element system of copper, lead and arsenic at 1200°C (SHIGEN-TO-SOZAI, 1998, No. 4, p.218, Fig. 7). In Fig. 2, the composition has two separated speiss and lead-rich phases within the ellipsoidal area. The lead-rich phase, when present as a separate phase in a furnace, accumulates on the furnace bottom to reduce the furnace volume. Moreover, the refractory bricks in the interface between these separated phases will be worn more as the lead-rich phase grows. Formation of the lead-rich phase, therefore, is undesirable for commercial operation of the process. A uniform melt is formed outside of the ellipsoidal area in the presence of copper in a larger quantity than lead, even in the case of an arsenic-free Cu-lead alloy containing a minimum quantity of lead. It is also shown that no speiss phase is formed in the composition which contains lead at around 10% by mass and arsenic at up to around 20% by mass, and that no speiss phase is formed in the vicinity of metallic lead present at a content below the above level. Content of copper in the copper melt for the present invention is not limited, but preferably 100% or more by mass on arsenic and antimony in the batch. Copper may not be sufficiently fixed when its content is excessively low relative to arsenic and antimony. However, the above condition is generally satisfied when the above-described conditions (i) and (ii) are satisfied. The slag fuming atmosphere for the present invention is not limited, so long as zinc, lead, arsenic and antimony can be reduced to the metallic state. It is particularly preferable to control an oxygen partial pressure in the slag in the range of -8 > logPo2 > "11.5 (wherein, P02 is oxygen partial pressure (atm) in the slag at 1400°C). Reduction of zinc, and hence evaporation of metallic zinc, will be retarded when the oxygen partial pressure exceeds 10"8 atm. Moreover, Fe3O4, which has a high melting point, increases in the slag because of the dependence of the FeO-Fe304 equilibrium on oxygen partial pressure, to disrupt slag fluidity and hence stable slag fuming operation. At an oxygen partial pressure below 10-11. 5 atm, on the other hand, iron is stabilized in the metallic state because of dependence of the Fe-FeO equilibrium on P02, and the furnace iron thus produced will disrupt slag fuming operation. It is more preferable for the slag fuming process of the present invention to keep melt temperature at 1075 to 1500°C and oxygen partial pressure in the slag in the range of "8 > logPo2 > '11.5 (wherein, P02 is oxygen partial pressure (atm) in the slag at 1400°C). The process satisfying the above conditions can form a uniform copper alloy melt containing arsenic and antimony, control formation of iron in the furnace, and moreover recover most of zinc by evaporation. A uniform Cu-Fe-Pb-As-based melt can be produced under the above conditions. It is particularly preferable to control Fe content at 0.01 to 50% by mass on Cu in the uniform melt, more preferably 5 to 50% by mass, at which copper requirement can be reduced. As discussed above, quantity of copper relative to the slag is set at a level at which it reacts with the speiss to form a uniform Cu-Fe-Pb-As-based melt at 1075 to 1500°C. At 1200 to 1500°C, for example, iron is dissolved in the melt at 5 to 50% by mass on copper. The uniform copper alloy melt produced by the present invention may be recovered, after being separated from the slag by differential gravity in a slag fuming furnace, by tilting or tapping the furnace. The recovered copper alloy may be subsequently treated in an oxidative atmosphere, e.g., in a converter in a copper refining plant to recover copper while removing iron as slag and treating lead, arsenic and antimony as dust. Cost increase in treating recovered copper can be kept very low, because it can be treated in an existing process. Use of a large quantity of copper will increase the treatment cost. It is therefore preferable to recycle the uniform copper alloy melt produced for a new batch of slag to be treated thereby minimizing copper requirement. Extent of reaction with speiss in the slag depends on extent of contact between the slag melt and copper melt. It is therefore preferable to use copper as much as possible for a batch of slag. Accordingly, it is preferable to use copper for a batch of the slag at 100% by mass or more on copper in the slag, determined by quantity of iron dissolved in copper, and to recycle a plurality of make-up slag batches until iron is dissolved in copper preferably at 5 to 50% by mass, more preferably 5 to 35% by mass. The copper melt can be recycled repeatedly until arsenic or iron is no longer dissolved in the melt, or a uniform melt is no longer secured. Number of recycling is essentially limited by iron quantity, because arsenic is present in the slag normally at low 0.n% by mass. The copper melt can be repeatedly recycled, even when it is saturated with iron, by replenishing copper, as required. The slag produced by the present invention satisfies the criteria of the environmental quality standards for soil (Pb and As contents: each 0.01 mg/L or less, determined by the elution test, Environmental Agency notification No. 46), and can be used as a raw material for cement or the like. EXAMPLES The present invention is described in more detail by EXAMPLES and COMPARATIVE EXAMPLES. It is however to be understood that the present invention is by no means limited by EXAMPLES. The metals were quantitatively analyzed by ICP emission spectrometry in EXAMPLES and COMPARATIVE EXAMPLES. Slag discharged from a blast furnace was used as the raw material in EXAMPLES and COMPARATIVE EXAMPLES. Table 1 gives its chemical composition. Table 1 The slag fuming procedure used in EXAMPLES and COMPARATIVE EXAMPLES is described below. [Slag fuming procedure] The slag fuming is carried out using the device illustrated in Fig. 3. It was heated by the externally heating type electrical oven 9, where temperature and atmosphere in the oven were controlled by the thermocouples 6 for controlling temperature and nitrogen-blowing tube 1 for securing a reaction atmosphere. The alumina crucible 7, charged with a raw material composition, was put in the ceramic outer crucible 5 set on the crucible supporting bricks 8. Then, the slag fuming was carried out while nitrogen was blown into the heated melt via the tube 3 for blowing nitrogen for stirring and reaction temperature was measured by the temperature sensor (thermocouples 4). The dust generated was withdrawn via the ceramic tube 2 for recovering dust out of the oven to be recovered. EXAMPLE 1 An alumina crucible was charged with a raw material composition, comprising 500 g of the raw material slag, 100 g of metallic copper (copper content; 99.99% by mass) and 28 g of coke (carbon content: 87.5% by mass), where quantity of the coke was set in consideration of oxidation with oxygen mixed into the bath. Quantity of the added metallic copper in the composition corresponded to 20% by mass on the raw material slag, and 1667% by mass on lead originally present in the slag. Then, the raw material composition was heated to 1350°C in a nitrogen gas atmosphere, held for 30 minutes at the same temperature after it was molten, and stirred with nitrogen blown into the bath for 50 minutes in accordance with the slag fuming procedure described above. The treated composition was held for 30 minutes after the stirring was completed, and the slag and copper alloy were sampled. At the same time, the evaporated dust was recovered. On completion of the slag fuming treatment, the alumina crucible was cooled to recover the slag and copper melt after they were separated from each other. Next, the alumina crucible was charged with 500 g of the raw material slag and 28 g of coke, both fresh, together with the copper alloy produced above for the second fuming cycle. A total of 3 fuming cycles were carried out. The slag, copper alloy and dust produced in each cycle were analyzed. Table 2 gives their chemical compositions. The slag produced in each cycle was also elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 3. As shown in Table 2, it is found that arsenic and antimony produced in each cycle are concentrated in the copper melt to decrease their contents in the slag, and that no arsenic or antimony is distributed in the dust, because each cycle was carried out in accordance with the procedure of the present invention. It is also found that recycling of the copper alloy causes no deterioration of the slag and dust compositions. As shown in Table 3, it is found that the slag produced in each cycle has eluted lead and arsenic contents reduced to stably satisfy the criteria of the environmental quality standards for soil (eluted Pb and As contents: each 0.01 mg/L or less), because each cycle was carried out in accordance with the procedure of the present invention. EXAMPLE 2 The slag and dust were produced in the same manner as in EXAMPLE 1, except that the copper alloy layer was not sampled to totally recycle the melt in all of the cycles that followed the first cycle and that the fuming treatment was carried out in 5 cycles. The slag and dust produced in each cycle were analyzed. Table 4 gives their chemical compositions. As shown in Table 4, it is found that the slag has decreased lead and arsenic contents and that no arsenic or antimony is distributed in the dust, because each cycle was carried out in accordance with the procedure of the present invention. It is also found that separation efficiency can be kept even when the copper alloy is recycled repeatedly in the form of melt. EXAMPLE 3 The slag, copper alloy and dust were produced in the same manner as in EXAMPLE 1, except that 42 g of coke was used for the raw material composition, the slag fuming treatment was carried out at 1400°C, and no copper alloy was recycled. The slag, copper alloy and dust produced were analyzed. Table 5 gives their chemical compositions. The slag produced was also elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 6. EXAMPLE 4 The slag, copper alloy and dust were produced in the same manner as in EXAMPLE 1, except that the slag fuming treatment was carried out at 1250°C, and no copper alloy was recycled. The slag, copper alloy and dust produced were analyzed. Table 5 gives their chemical compositions. The slag produced was also elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 6. EXAMPLE 5 The slag, copper alloy and dust were produced in the same manner as in EXAMPLE 1, except that 250 g of metallic copper (copper content: 99.99% by mass) was used for the raw material composition, and no copper alloy was recycled. Quantity of the added metallic copper in the composition corresponded to 50% by mass of the raw material slag. The slag, copper alloy and dust produced were analyzed. Table 5 gives their chemical compositions. The slag produced was also elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 6. As shown in Table 5, it is found that arsenic and antimony produced in each of EXAMPLES 3 to 5 are concentrated in the copper melt to decrease their contents in the slag, and that no arsenic or antimony is distributed in the dust, because each was carried out in accordance with the procedure of the present invention. As shown in Table 6, it is found that the slag produced in each of EXAMPLES 3 to 5 has eluted lead and arsenic contents reduced to stably satisfy the criteria of the environmental quality standards for soil (eluted Pb and As contents- each 0.01 mg/L or less), because each was carried out in accordance with the procedure of the present invention. EXAMPLE 6 An alumina crucible was charged with a raw material composition, comprising 2000 g of the raw material slag, 400 g of metallic copper (copper content: 99.99% by mass) and 40 g of coke (carbon content^ 87.5% by mass), where quantity of the coke was set in consideration of oxidation with oxygen mixed into the oven. Quantity of the added metallic copper content in the composition corresponded to 20% by mass on the raw material slag, and 1667% by mass on lead originally present in the slag. Then, the raw material composition was heated to 1400°C in a nitrogen gas atmosphere, held for 30 minutes at the same temperature after it was molten, and stirred with nitrogen blown into the bath for 120 minutes in accordance with the slag fuming procedure described above. On completion of the stirring, a disposable type oxygen probe was immersed in the slag to measure oxygen partial pressure. It was logPo2 of -9.6 (wherein, P02 is oxygen partial pressure (atm) at 1400°C). Then, the treated composition was held for 60 minutes to settle the slag, and cooled. The slag and copper alloy were sampled. At the same time, the evaporated dust was recovered. Table 7 gives their chemical compositions. The slag produced in each cycle was also elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 8. The slag fuming treatment produced 1,780 g of the slag and 290 g of the copper alloy. EXAMPLE 7 An alumina crucible was charged with a raw material composition, comprising 2000 g of the raw material slag, 270 g of the copper alloy produced in EXAMPLE 6, a given quantity of metallic copper (copper content^ 99.99% by mass) and 40 g of coke, where quantity of the coke was set in consideration of oxidation with oxygen mixed into the oven. Then, the slag fuming treatment was carried out under the same conditions as in EXAMPLE 6 to produce the dust, slag and copper alloy. A total quantity of copper was set at 400 g. The similar procedure was repeated 7 times. Oxygen was present in the slag produced in each of the 8 cycles at a partial pressure of logPo2 of -9.4 to "10.1 (wherein, P02 is oxygen partial pressure (atm) at 1400°C). Then, the slag and copper alloy produced in the 8th cycle were sampled. At the same time, the evaporated dust was recovered. Table 7 gives their chemical compositions. The slag produced in the 8th cycle was also elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 8. The slag fuming treatment produced 1,785 g of the slag and 295 g of the copper alloy in the 8th cycle. EXAMPLE 8 The blowing reduction was carried out under the same conditions as in EXAMPLE 6, except that 60 g of coke was used for the raw material composition. Oxygen was present in the slag at a partial pressure of logPo2 of -11.8 (wherein, P02 is oxygen partial pressure (atm) at 1400°C). Then, the slag, copper alloy and dust were sampled. The slag was viscous. Table 7 gives their chemical compositions. As shown in Table 7, it is found that arsenic and antimony produced in each of EXAMPLES 6 to 8 are concentrated in the copper melt, and that lead, arsenic and antimony are distributed in the slag to a limited extent, and so are arsenic and antimony in the dust, distributed to a limited extent in the slag and dust, because each EXAMPLE was carried out in accordance with the procedure of the present invention. It is also found that the copper alloy produced in EXAMPLE 7 contains iron at a sufficiently low content to be safely recycled, and that copper alloy produced in EXAMPLE 8 contains iron at a content increasing as oxygen partial pressure in the slag decreases to decrease iron content in the slag, which conceivably increases its viscosity. As shown in Table 8, it is found that the slag produced in each of EXAMPLES 6 and 7 has eluted lead and arsenic contents reduced to stably satisfy the criteria of the environmental quality standards for soil, because each was carried out in accordance with the procedure of the present invention. COMPARATIVE EXAMPLE 1 The slag fuming treatment was carried out in the same manner as in EXAMPLE 1, except that the raw material composition was composed only of 500 g of the raw material slag. The slag and dust produced were sampled. Table 9 gives their chemical compositions. The slag was also elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 10. As shown in Tables 9 and 10, it is found that arsenic and lead are largely distributed both in the slag and dust, and that the slag fails to satisfy the criteria of the environmental quality standards for soil (eluted Pb and As contents; each 0.01 mg/L or less) and hence is not satisfactory, because the treatment was carried out under conditions outside of those specified for the present invention. COMPARATIVE EXAMPLE 2 The slag fuming treatment was carried out in the same manner as in EXAMPLE 6, except that 80 g of metallic copper (which corresponded to 4% by mass on the raw material slag) was used for the raw material composition. Formation of the uniform melt of copper alloy was insufficient, as revealed by observation of the cooled sample, and the slag contained dispersed copper alloy on which iron speiss was absorbed. COMPARATIVE EXAMPLE 3 The blowing reduction was carried out under the same conditions as in EXAMPLE 6, except that the metallic copper was replaced by 400 g of a copper-lead alloy (copper content: 40% by mass, and lead content: 60% by mass), molten at 1250°C and then quenched. Quantity of the added copper corresponded to 8% by mass on the raw material slag and to 60% by mass on the lead in the raw material composition (lead quantity: 240 g in the copper-lead alloy and 24 g in the raw material slag). The slag and copper alloy were produced, and a lead layer was deposited on the crucible bottom, as revealed by observation of the cooled sample. The slag produced was elution-tested in accordance with Environmental Agency notification No. 46, to determine eluted lead and arsenic contents. The results are given in Table 11. As shown in Table 11, it is found that the slag fails to satisfy the criteria of the environmental quality standards for soil (eluted Pb and As contents: each 0.01 mg/L or less) and hence is not satisfactory, because the treatment was carried out under conditions outside of those specified for the present invention. As discussed above, the slag fuming process of the present invention, in which a slag discharged from a smelting furnace in a zinc and/or lead extractive metallurgy, e.g., a slag discharged form a blast furnace in a blast furnace process is reduced under heating to evaporate and separate/recover zinc and lead, can produce a dust containing arsenic and antimony at a limited content. Therefore, it is useful as a process which can decrease loads of arsenic and antimony in the dust, even when it is recycled repeatedly into the smelting furnace, to contribute to cost reduction. It is also suitable as a slag reforming process which can decrease lead and arsenic in the product slag. The reformed slag can find wide applicable areas, e.g., cement material. Claims 1.(Amend) A slag fuming process which reduces, under heating in a fuming furnace, slag containing arsenic or arsenic and antimony concomitantly with zinc and lead, discharged from a smelting furnace in a zinc and/or lead extractive metallurgy, to separate zinc and lead by evaporation, wherein a melt of the slag is treated in the presence of a copper melt at 1075 to 1500°C, which contains a copper in a quantity of 5 to 100% by mass on the slag and 100% by mass or more on lead originally present in the slag, in order to allow copper to react with arsenic or arsenic and antimony present in the slag to produce a uniform Cu-Fe-Pb-As-based melt, which contains Fe at 0.01 to 50% by mass on Cu. 2. The slag fuming process according to Claim 1, wherein oxygen partial pressure in a melt of the slag is controlled at a level given by the following formula: -8>logPo2>-11.5 (wherein, P02 is oxygen partial pressure (atm) at 1400°C). 3. The slag fuming process according to Claim 1, wherein the uniform Cu-Fe-Pb-As-based melt is recycled repeatedly as copper melt. Dated this 14 day of July 2006

Documents:

2578-CHENP-2006 CORRESPONDENCE OTHERS 21-09-2011.pdf

2578-CHENP-2006 FORM-3 03-05-2012.pdf

2578-CHENP-2006 AMENDED PAGES OF SPECIFICATION 24-04-2012.pdf

2578-CHENP-2006 AMENDED CLAIMS 24-04-2012.pdf

2578-CHENP-2006 CORRESPONDENCE OTHERS 03-05-2012.pdf

2578-CHENP-2006 EXAMINATION REPORT REPLY RECEIVED 24-04-2012.pdf

2578-CHENP-2006 FORM-1 24-04-2012.pdf

2578-CHENP-2006 FORM-3 24-04-2012.pdf

2578-CHENP-2006 CORRESPONDENCE OTHERS.pdf

2578-CHENP-2006 CORRESPONDENCE PO.pdf

2578-CHENP-2006 FORM 18.pdf

2578-chenp-2006-abstract.pdf

2578-chenp-2006-claims.pdf

2578-chenp-2006-correspondnece-others.pdf

2578-chenp-2006-description(complete).pdf

2578-chenp-2006-drawings.pdf

2578-chenp-2006-form 1.pdf

2578-chenp-2006-form 26.pdf

2578-chenp-2006-form 3.pdf

2578-chenp-2006-form 5.pdf

2578-chenp-2006-pct.pdf