EP0045531A1 - Process for the continuous direct smelting of metallic lead from sulfidic lead concentrates - Google Patents

Abstract

A melt consisting of a slag phase (3) and a lead phase (5) is maintained in an elongated, horizontal reactor, and the charge (1) is charged on one side of the reactor into a melting zone (2) while maintaining such an oxidation potential that the melt Metallic lead and slag are formed; on the other side of the reactor, reducing substances are introduced into the slag phase in a reduction zone (8). To collect the bismuth lead in the smallest possible amount of lead, the oxidation potential in the melt is set in the melting zone so that the sulfur content of the lead phase is 0.05 to 2% by weight, the bi-rich primary lead occurring in this zone deducted separately and the bi-poor secondary lead (10) accumulating in the reduction zone also deducted separately.

Description

The invention relates to a process for the continuous direct melting of metallic lead from sulfur-containing lead materials in an elongated, lying reactor, wherein a melt from a slag phase and a lead phase is maintained in the reactor, the loading on one side of the reactor into a melting zone while maintaining a such oxidation potential is charged to the melt that metallic lead and slag are formed, on the other side of the reactor reducing substances are introduced into the slag phase in a reduction zone, and low-lead slag and metallic lead are drawn off from their phases.

DE-OS 28 07 964 discloses such a process for the continuous conversion of lead sulfide concentrates into a liquid lead phase and a slag phase in an elongated, lying reactor, under a gas atmosphere containing zones of SO2, with sulfidic lead concentrates and additives being charged onto the melt , the lead phase and a non-ferrous metal-poor slag phase are discharged at the opposite end of the reactor and the phases in countercurrent to one another in essentially continuously layered streams flow to the outlet ends, at least a portion of the oxygen is blown into the melt from below through a plurality of independently controlled nozzles distributed over the length of the oxidation zone of the reactor, the solid feed through a plurality of independently controlled and over a considerable length of the reactor-fed feeders is gradually charged into the reactor, the gradient of melt oxygen activity is adjusted by choosing the local addition and control of the amounts of oxygen and solid material introduced so that it is at a maximum for the production of lead at its outlet end progressively decreases in the reduction zone to a minimum for the generation of low-ferrous metal slag phase at the outlet end, with the oxygen gaseous and / or liquid protective media in controlled amounts to protect the nozzles and the surrounding lining and to help the control of the process temperature is blown into the melt, the quantities of gas blown into the melt are regulated in such a way that sufficient turbulence is created in the bath for a good mass exchange without substantially disturbing the layered flow of the phases and the gradient of the oxygen activity, and the gas atmosphere in the reactor is countercurrent to the flow direction of the slag phase and the exhaust gas is withdrawn from the reactor at the outlet end of the non-ferrous metal-rich phase.

Such a method is known from DE-AS 24 17 978 in which the gas atmosphere is conducted in cocurrent to the slag phase.

A direct lead melting process is known from US Pat. No. 3,6E3,207, in which the slag phase and lead phase in the Direct current is passed through the reactor, the slag at one end of the reactor and the lead in a central zone is withdrawn from the reactor.

A direct lead smelting process is known from "Engineering Mining Journal" April 1978, pages 88 to 91, 118, in which the fine-grained concentrate is ignited in a vertical shaft in the presence of oxygen and is roasted, melted and partially reduced to metallic lead in the suspended state. A hearth furnace is arranged under the shaft, from which the melt enters under a partition into an electric resistance-heated hearth space. There is a reduction of non-ferrous metal oxides to liquid lead and the removal of slag and lead.

In these known direct lead smelting processes, the stripped lead contains the entire bismuth. Bismuth is on the one hand a contamination that has to be removed from the end product (fine lead) at high costs, and on the other hand it is a by-product that has a commercial value. A large part of the production of refined lead can be sold with bi contents of 100 ppm and more. With certain varieties, however, 70 ppm Bi and less must not be exceeded. In the case of bi-rich lead concentrates, the refining costs required for separating the bismuth are more than offset by the commercial value of this metal, but the costs exceed the proceeds for bi-poor raw materials. Many lead smelters therefore separate their bi-rich and bi-poor raw materials and process them separately for each campaign. This leads to many difficulties in the smelting and refining operations, including loss of interest, especially when concentrates rich in precious metals have to be stacked over a long period of time.

It is also known to process sulfidic lead ores in two stages to metallic lead by the _R oste reaction process. In the first stage, part of the lead content is generated in the form of metallic primary lead in addition to a Pb-rich slag. The Pb-rich slag is tapped and used in the second stage, where, under reducing conditions, the metallic secondary lead is produced next to a low-Pb slag. The primary lead of the first stage contains the predominant part of the bismuth in the lead. The secondary lead is bi-poor (DE-PS 589 738, DE-PS 590 505, DE-OS 27 39 963). However, these processes are not suitable for the continuous, one-step, direct lead melting processes described at the beginning.

The object of the invention is to collect the lead bismuth content in the feed in the smallest possible amount of lead in a continuous, one-step direct lead melting process.

This object is achieved according to the invention in that the oxidation potential in the melt is set in the melting zone so that the sulfur content of the lead phase is 0.05 to 2% by weight, and the bi-rich primary lead obtained in this zone is drawn off separately, and the _B i-poor secondary lead occurring in the reduction zone is also drawn off separately. Sulfidic, sulfatic and oxidic lead materials with sulfides or sulfates are suitable as lead materials containing sulfur. If the material is charged onto the melt in the solid state, the melting zone lies in the melt itself. Then the oxidation potential in the melt is adjusted by introducing oxygen so that it forms metallic lead and slag is sufficient, and that the required sulfur content is achieved in the lead phase. If the material already reacts in a melting zone in the floating state above the melt at the bottom of the reactor and is melted down, then the oxidation potential is already set in the floating zone so that the required sulfur content of the lead phase is achieved after settling in the melt. If there is a combined melting in the suspended state and in the melt, the oxidation potentials are coordinated accordingly. The oxidation potential results from the stoichiometric ratio of oxidizing agents - such as oxygen, metal sulfates, metal oxides - to oxidizable components - such as sulfide sulfur, possibly added fuels - the sum of which is such that the partial oxidation required to achieve the required sulfur content in the lead phase he follows. The amount of primary lead drawn off is kept as small as possible, but so large that the major part of the lead bismuth is contained in the primary lead. The primary lead contains only small amounts of tin, arsenic and antimony, while the secondary lead contains the main part of the leading Sn, As and Sb.

A preferred embodiment consists in that when using lead materials with a lead content above 55% by weight, the sulfur content of the lead phase in the melting zone is set to 0.1 to 0.4% by weight. As a result, a good collection of bismuth in a relatively small amount of primary lead is achieved with richer lead materials.

A preferred embodiment consists in the fact that when using lead materials with a lead content between 55 and 40% by weight, the sulfur content of the lead phase in the melting zone is between 0.3 and 1.0% by weight. is set. This results in a good collection of bismuth in a relatively small amount of primary lead in poorer lead materials.

A preferred embodiment is that when using lead materials with a lead content below 40% by weight, the sulfur content of the lead phase in the melting zone is set to 0.8 to 2.0% by weight. As a result, a good collection of bismuth in a relatively small amount of primary lead can be achieved even with very poor lead materials.

A preferred embodiment consists in that the slag phase and lead phase are passed in countercurrent through the reactor, the primary lead is drawn off at the end of the reactor delimiting the melting zone, and the secondary lead is attached behind one at the other end of the melting zone on the bottom of the reactor and into the Slag phase protruding weir is withdrawn. A method according to DE-OS 28 07 964 and DE-AS 24 17 978 described at the outset is particularly suitable for carrying out the method according to the invention if a separate removal of primary and secondary lead is made possible by a weir. The bottom of the reactor can be inclined so that both primary lead and secondary lead flow in the direction of the melting zone. Then the secondary lead on the weir is drawn off. The bottom of the reactor can also be inclined so that only the primary lead flows to the end of the melting zone and the secondary lead flows to the other end and is drawn off there.

One embodiment is that where the tapping of the primary lead is arranged a narrow zone into which no feed is charged and in which sulfur is removed from the lead by oxidation. In this Zone a particularly precise adjustment of the sulfur content of the lead phase can be achieved, so that it is possible to collect a large part of the bismuth in a particularly relatively small amount of primary lead drawn off.

• Fig. 1 ist ein schematischer Längsschnitt durch einen Reaktor mit Gegenstromführung von Schlacken- und Bleiphase, bei dem das Sekundärblei vor einem Wehr abgezogen wird;
• Fig. 2 ist ein schematischer Längsschnitt, bei dem das Sekundärblei an der Stirnwand der Reduktionszone abgezogen wird.

The invention is illustrated by the figures.

• Fig. 1 is a schematic longitudinal section through a reactor with countercurrent flow of slag and lead phase, in which the secondary lead is drawn off in front of a weir;
• Fig. 2 is a schematic longitudinal section in which the secondary lead is drawn off on the end wall of the reduction zone.

The feed 1 is charged to the slag phase 3 in the melting zone 2. Oxygen 4 is passed from below into the lead phase 5 and from there flows further through the slag phase 3. The primary lead is drawn off from the melting zone on the end wall. The slag flows over the weir 7 into the reduction zone 8. There coal dust is blown in as a reducing agent 9 from below. The low-lead slag is withdrawn from the slag stitch 11. The exhaust gas 12 is discharged through the end wall of the melting zone 2. In FIG. 1 the secondary lead 10 is drawn off in front of the weir 7 and in FIG. 2 on the front side of the reduction zone 8.

Examples

In a fireproof bricked, rotatably mounted reactor in the form of a horizontal cylinder with a 4.5 m inside length and 1.20 m inside diameter, with a burner and tap holes on the front face, an exhaust port on the back face, in the top Part of the jacket with charging openings and in the lower part of the jacket with vertically upward directed nozzles, pelletized lead concentrates were melted with flying dust and additives.

The pellets had the following composition:

The pellets were melted in such a way that the reactor was heated to a temperature of 950 ° C. with the aid of the burner, passed technically pure oxygen at a rate of 150 m ³ / h (NPT) through the nozzles and pellets through the charging openings were charged into the reactor in a time quantity which varied between 1.9 and 2.1 t / h.

1. In a first experiment, with the burner switched off, a pellet quantity of exactly 2.1 t / h was charged into the reactor, in which a temperature of 950 C was set. By partial oxidation of the _B leisulfids developed under these conditions metallic lead with a S content of 0.42% and in an amount which is 44% of the leading pellets in the lead content corresponded. The metals Sn, Bi, Sb and As were distributed as follows:

Obviously, the lead formed contained 96% of the preceding Bi, while only minor amounts of the three other metals were taken up by the lead.

The slag contained 40% of the lead in the pellets and had the following concentrations of the metals in question:

In a second experiment, with the burner switched off and an oxygen supply of 15 ₀ m ³ / h (NPT), the amount of pellet in time was reduced to 2, 0 t / h. As a result of the increased oxidation of the lead sulfide to lead oxide, the temperature of the melt rose to 965 ° C. The S content of the lead formed, the amount of which now corresponded to only 30% of the lead in the pellets, fell to 0.27%. The metals Sn, Bi, Sb and As were distributed as follows:

Obviously, the increase in the oxidation potential of the melt to values that corresponded to an S content of lead of 0.27% did not significantly change the distribution of the metals with the exception of Bi.

Compared to Example 1, however, a 1.5-fold enrichment of the Bi in the lead phase was achieved.

3. In a third test, the conditions of the pellet quantity were reduced again by 0.1 t / h to 1.9 t / h under conditions that were otherwise unchanged from the second test.

The temperature of the melt rose to 985 ° _C , while the lead phase contained only 0.18% S.

The amount of metal formed corresponded to 10% of the lead leading in the pellets.

The metals Sn, Bi, Sb and As were distributed as follows:

Obviously, the increase in the oxidation potential of the melt to values that corresponded to an S content of lead of 0.18% did not significantly change the distribution of the metals with the exception of the Bi. Although the output of Bi in the lead phase is 11% lower than in Example 1, more than 4-fold enrichment is achieved.

4. In a fourth experiment, the slag from the first experiment, which contained only 2.3% of the _B i present in the pellets, but the majority of the As, Sb and Sn, was subjected to a reducing treatment.

For this purpose, the lead located under the slag as the bottom phase was selectively drawn off through a tap hole at the level of the reactor base, while the slag was left in the reactor. The nozzles were then replaced by coal dust injectors. The slag temperature was then slowly raised to a final value of 1150 C with the help of the burner, while at the same time a mixture of coal dust and carrier gas was blown into the slag bath in a metered amount.

This measure simulated the spatially separate, but simultaneous course of oxidation and reduction, which was only possible in an elongated reactor, by means of a temporally separate course in the same space.

• Metallisches Blei, in dem sich die in Betracht kommenden Metalle wie folgt verteilten:
  

The following molten products were obtained:

• Metallic lead, in which the metals in question were distributed as follows:
  

Slag with the following metal contents (in%)

It can be seen that only a small part of the Bi contained in the pellets, but the majority of the Sn, _S b and As was collected in the secondary lead phase.

5. In a fifth experiment, a low-lead concentrate with fly dust and aggregates was pelletized so that pellets of the following composition were formed:

When this material was partially oxidized, metallic lead was only formed if the oxidation potential was maintained, which corresponded to an S content of 1.6% in the lead phase.

Again 91% of the Bi leading in the pellets was collected in the lead phase, which reached a Bi content of 0.26%.

The slag obtained in equilibrium with this lead phase had a Pb content of 23.9% and a Bi content of 0.002%.

The advantages of the invention are that in the case of single-stage, direct lead melting processes, the lead bismuth can be accumulated in a simple manner to a large extent in a relatively small amount of primary lead.

Claims (6)

1. A process for the continuous direct melting of metallic lead from sulfur-containing lead materials in an elongated, lying reactor, wherein a melt consisting of a slag phase and a lead phase is maintained in the reactor, the loading on one side of the reactor into a melting zone while maintaining such an oxidation potential is charged to the melt that metallic lead and slag are formed, on the other side of the reactor, reducing substances are introduced into the slag phase in a reduction zone, and low-lead slag and metallic lead are withdrawn from their phases, characterized in that in the melting zone Oxidation potential in the melt is set so that the sulfur content of the lead phase is 0.05 to 2% by weight, the bi-rich primary lead accumulating in this zone is drawn off separately, and the bi-poor secondary lead accumulating in the reduction zone is likewise drawn off separately becomes. 2. The method according to claim 1, characterized in that when using lead materials with a lead content above 55 wt .-%, the sulfur content of the lead phase in the melting zone is set to 0.1 to 0.4 wt .-%. 3. The method according to claim 1, characterized in that when using lead materials with a lead content between 55 and 40 wt .-%, the sulfur content of the lead phase in the melting zone is set to 0.3 to 1.0 wt .-%. 4. The method according to claim 1, characterized in that when using lead materials with a lead content below 40 wt .-%, the sulfur content of the lead phase in the melting zone is set to 0.8 to 2.0 wt .-%. 5. The method according to any one of claims 1 to 4, characterized in that the slag phase and lead phase are passed in countercurrent through the reactor, the primary lead is drawn off at the end of the reactor delimiting the melting zone, and the secondary lead behind one at the other end of the melting zone attached to the bottom of the reactor and withdrawn weir protruding into the slag phase. 6. The method according to any one of claims 1 to 5, characterized in that a narrow zone is arranged before tapping the primary lead, in which no charge is charged and in which sulfur is removed from the lead by oxidation.

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