LU84186A1 - COPPER FIRE REFINING PROCESS - Google Patents

Description

The present invention relates to improvements in the so-called copper refining process.

It is known that refining for the production of commercial copper is carried out in static reverberatory ovens and, more recently, rotary, in which air (possibly enriched in oxygen) is blown in to gradually oxidize the less noble elements than copper (Zn, Fe etc.) and pass them through the slag. This is then eliminated and the partially oxidized copper undergoes a deoxidation (perching) operation which ultimately makes it possible to obtain relatively pure metallic copper.

The copper thus treated represents what is known as fire-refined commercial copper which can be cast in desired commercial forms or in anodes; in the latter case, thermal refining is generally less extensive since its complement is entrusted to the subsequent electrolytic process.

The residual content of fire refined and perched copper is generally on the order of 0.05% or less.

In the past, the reduction was carried out by various techniques (use of plant materials such as trunks and branches of tree etc.) but according to modern techniques, this reduction is generally carried out by a gas treatment using a nozzle or lance, the reducing agent being in particular cracked ammonia gas (75% H ^ and 25% ^) or hydrocarbons (JJ Oudiz, Journal of Metals, Dec.1973, p.35-38).

In industrial practice, these operations are generally carried out in a relatively empirical manner, for lack of a technique making it possible to control the operating parameters and to regulate the course of operations.

The operator is generally satisfied with taking a sample, the examination of which reveals whether the reduction has been completed.

The present invention is based on the unexpected observation that it is possible to follow the progress of copper refining operations with the fact that the change in temperature within the molten bath constitutes an indication of the change in the reduction. In fact, if we allow the temperature to evolve freely during the reduction according to conventional industrial processes, possibly after having stopped the burner, the temperature goes through a maximum which makes it possible to identify the final stage of reduction. There is therefore a simple way to determine precisely when the reduction can be stopped.

The unexpected nature of the principle described results from the fact that the simple means of measuring the maximum temperature and incidentally of its evolution, is sufficiently significant and reliable for an industrial application, without the need to resort to conventional tools for measuring the oxygen content of baths of the "OXYCELL" type which are difficult to use under industrial conditions.

The present invention therefore relates more precisely to a process for refining copper in fire in static or preferably rotary ovens successively comprising an oxidation operation with a view to oxidizing the elements which are less noble than copper, an elimination of the slag formed and a reduction, characterized in that said reduction is adjusted as a function of the maximum temperature observed during the reduction and incidentally of the temperature evolution.

According to the invention, the temperature measurements transmitted by a probe are preferably recorded continuously during the reduction and are processed electronically in order to act on the parameters of the reduction. This electronic processing is advantageously carried out by a microprocessor or by conventional techniques of data processing by computer.

Use is preferably made in the art of nozzles made of refractory steel with a double jacket, the internal part serving to inject oxidizing gas (generally air or air enriched in oxygen) in the phase of oxidation! and reducing gas (generally cracked ammonia) during the reduction phase, this internal part itself being sheathed in a second envelope into which nitrogen is admitted, used both for cooling the nozzle, to the possible release of the latter in the event of obstruction and to regulate the kinetics of the reaction by turbulence effects.

In this type of installation, it is possible to continuously measure the pressure and the gas flow rate in the two zones of the nozzle and act automatically or not on the intake settings, in particular in the event of blockage. It has been observed in particular that a "rocking" effect, that is to say alternation of high pressure with the central nozzle and with the peripheral envelope, can in particular alleviate a possible blockage.

Having a reliable and easily measurable measurement parameter of the reduction evolution offers the possibility of making the refining process continuous or semi-continuous.

By adapting the equipment using an ASARCO type furnace in particular, it is possible to introduce solid charges upstream, to operate the oxidation and reduction by zone and to continuously sample the treated molten copper, l 'admission' of the reducing gas by a nozzle of the type described being controlled continuously as a function of the temperature data recorded by a thermal probe placed in the reduction zone.

Advantageously, three ovens are arranged in cascade, the first serving for melting, the oxidation being carried out in a second oven and finally, the perching or reduction taking place in a third oven.

Again, in the aforementioned case, the temperature data and possibly the flow and pressure data in the central part and in the peripheral part of the nozzle are integrated y i electronically and serve to regulate the reduction process.

Programming is carried out in practice on the basis of calibration curves of the ideal evolution of the bath temperature for a determined maximum value.

It should be noted that the use of complementary analytical techniques such as emission spectrometry further refines the precision of the adjustment of the operating process.

The additional data of such techniques can be integrated with the temperature measurement data for automatic or semi-automatic adjustment of the oven operation.

The technique used has the inconstable advantage of allowing, better than in the past, to precisely regulate the reduction and therefore to obtain not only excellent quality products but also to greatly reduce the total consumption of the fuel • used to heat the ovens. Continuous transposition naturally offers the specific advantages of this technique (reduction in production cost, reduction in labor) combined with the advantages mentioned above.

Although particularly preferred embodiments of the invention have been described, it should be understood that these have been given by way of illustration without limitation, and that numerous variants and modifications remain possible in the context of the invention as defined in the claims which follow.

Claims (11)

1. A method of refining copper with fire in static or preferably rotary ovens successively comprising an oxidation operation with a view to oxidizing the elements nobler than copper, an elimination of the slag formed and a reduction, characterized in that said reduction is adjusted as a function of the maximum temperature observed during the reduction and incidentally as the temperature changes. 2. Method according to claim 1 characterized in that the temperature measurements transmitted by a probe are continuously recorded during the reduction and are processed electronically in order to act on the parameters of the reduction. 3. Method according to claim 1 characterized in that said electronic processing is exercised by a microprocessor or by conventional techniques of data processing by computer. 4. Method according to any one of claims 1 to 3 characterized in that nozzles made of refractory steel with double jacket are used, the inner part serving to inject oxidizing gas in the oxidation phase and reducing gas during the reduction phase, this inner part itself being sheathed in a second envelope into which nitrogen is admitted serving both for cooling the nozzle, for possibly unblocking the latter in the event of obstruction and for adjustment of the reaction kinetics by turbulence effects. * · 5. Method according to any one of claims 1 to 4 characterized in that the pressure and gas flow are continuously measured in the two zones of the nozzle and acts automatically or not on the intake settings, in particular in case of blockage. 6. Method according to any one of claims 1 to 5 characterized in that solid charges are introduced upstream of an installation with a view to melting and operates the oxidation and reduction by zone and continuously samples the copper treated melt, the admission of the reducing gas through a nozzle being controlled continuously as a function of the temperature data recorded by a thermal probe placed in the reduction zone. 7. Method according to claim 6 characterized in that one operates in three ovens which are arranged in cascade, the first serving for melting, the oxidation being carried out in a second oven and finally, the. perching or reduction done in a third oven. 8. Method according to any one of claims 1 to 6 characterized in that the temperature data and the flow and pressure data in the central part and in the peripheral part of a nozzle are integrated electronically and are used to adjust | the reduction process. 9. Method according to any one of claims 1 to 8 characterized in that the programming of! oven operation is carried out in practice on the basis of calibration curves of the ideal evolution of the bath temperature for a determined maximum value. ”- 9 - 10. Method according to any one of claims 1 to 9 characterized in that complementary analytical techniques, in particular emission spectrometry, are used to refine the precision of the adjustment of the operating process. * 11. Method according to claim 10 characterized ί in that the complementary data of the analytical techniques cited are integrated with the temperature measurement data for automatic or semi-automatic adjustment of the operation of the oven. Have