Method for obtaining pure copper

A method for obtaining pure copper is provided wherein oxygen is blown onto a copper melt, in a melting furnace lined with refractory material, having a waste heat boiler set onto it, in order to oxidize contaminants contained in the melt and thereby remove them from the melt, and wherein a splash protection device through which water flows is provided above the copper melt, on the inside wall of the melting furnace, which prevents copper that splashes out of the copper melt from penetrating into the waste heat boiler. Boiling water is used for cooling the splash protection device, which water is under a pressure of more than 5 bar and is evaporated, at least in part, as it flows through the splash protection device.

CROSS REFERENCE TO RELATED APPLICATIONS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for obtaining pure copper. More specifically, in the method, oxygen is blown onto a copper melt, in a melting furnace lined with refractory material, having a waste heat boiler set onto it, in order to oxidize contaminants contained in the melt and thereby remove them from the melt. In addition, a splash protection device through which water flows is provided above the copper melt, on the inside wall of the melting furnace. The splash protection device prevents copper that splashes out of the copper melt from penetrating into the waste heat boiler.

2. The Prior Art

Methods having the characteristics described above are known in practice. The splash protection device, which is frequently also referred to as a so-called splash block, generally is made of copper. The splash protection device is necessary because moisture that is introduced into the melt together with the oxygen, for example, through a lance, evaporates explosively and entrains liquid copper a long way upward with it, as it explodes. The splash block, which is attached to the inside wall of the melting furnace, below the waste heat boiler, prevents the entry of drops of melt into the waste heat boiler, and protects the boiler from an inside coating of solidified copper.

Within the scope of the known measures, the splash block has pipes that are made of copper, for guiding a non-pre-heated cooling water, which pipes are cast into a copper block. However, although melting of the copper is effectively prevented by means of the cold cooling water, erosion corrosion takes place at the copper block, because of sulfur contained in the copper melt. As a result, it becomes necessary to replace the splash block after only a few months. Another problem is that if a crack caused by corrosion phenomena occurs in the splash block, cold cooling water penetrates into the copper melt. The water evaporates explosively there and thereby results in a massive impact of solidifying copper splashed out of the melt against the waste heat boiler.

DE 100 47 555 A1 describes a cover for a metallurgical melting furnace, which cover has cooling channels through which cold water flows. Furthermore, it is known from the German Offenlegungsschrift D 13484 VI/18b to use boiling water for cooling chimney walls, and to use the evaporation enthalpy for cooling. The water is passed along the chimney wall in long, vertical riser lines. Because of the great height of the chimney, a vigorous water circulation occurs in the riser lines, in this connection, allowing effective cooling of the chimney wall. The measures described in the Offenlegungsschrift do not make any contribution toward solving the set of problems described above.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method having the characteristics described above, which guarantees an increased useful lifetime of the splash protection device.

These and other objects are accomplished, according to the invention, by using boiling water for cooling the splash protection device. The water is under a pressure of more than 5 bar and reaches boiling temperature as it flows through the splash protection device.

The invention is based on the recognition that the erosion corrosion speed decreases with an increasing temperature of the splash protection device and, in particular, that erosion corrosion that is relevant for practice can no longer be found at temperatures above 200° C.

According to a preferred embodiment of the invention, the boiling water pressure is more than 20 bar, corresponding to a boiling temperature of about 212° C. Under some circumstances, however, boiling water pressures of more than 5 bar or more than 10 bar, respectively, are already sufficient to guarantee a sufficiently long useful lifetime. It is practical if the water is already close to the boiling point as it enters into the splash protection device. Having the water close to boiling has the additional advantage that a crack occurs in the splash protection device, or if another kind of leak occurs, no cold water gets into the copper melt, because the boiling water evaporates immediately upon entering the melting furnace atmosphere.

In another embodiment, the boiling water is connected to a cooling water circuit of the waste heat boiler in the inflow and outflow. In this way, circulation pumps of a boiler system that includes the waste heat boiler, which are present, can be advantageously used to transport the water that flows through the waste heat boiler. Furthermore, the steam that is generated as the water flows through the splash protection device can be passed to a heat recovery device of the boiler system.

It is practical if the splash protection device has pipes through which the boiling water flows, and which are cast into a copper block that serves as the splash protection. The pipes can be made of steel, preferably alloy steel, and thereby also withstand higher pressures. The splash protection device may also have steel pipes that are mantled with a monolithic lining material. For example chamotte or a similar material may be used as the lining material.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1shows a detail of a system for obtaining pure copper. The system has a melting furnace2lined with refractory material. Melting furnace2has a waste heat boiler3set onto it at a lateral offset. Oxygen, or even air, is blown onto a copper melt5that is located in the melting furnace, using a lance4, in order to oxidize contaminants contained in melt5and thereby remove them from melt5. While the solid oxidation products generally accumulate at the surface of the copper melt5as slag, the gaseous oxidation products are transported away from the melt furnace2by way of waste heat boiler3. The temperature of copper melt5is approximately 1,300° C., whereas the waste gases that are formed in waste heat boiler3are cooled off to approximately 700° C.

Waste heat boiler3is followed by another cooling device in the form of a quench, not shown, which cools the waste gases down to approximately 350° C. Above copper melt5, on the inside wall of melting furnace2, a splash protection device6is attached. Splash protection device6prevents copper that splashes out of copper melt5from penetrating into waste heat boiler3. Boiling water under pressure, which flows through the splash protection device, is used to cool splash protection device6. Boiling water means water at a pressure of more than 5 bar, which reaches boiling temperature as it flows through the splash protection device and is partially evaporated. In the exemplary embodiment, the boiling water pressure is 40 bar, which corresponds to a boiling temperature of approximately 250° C. The water enters into splash protection device6at a temperature below the boiling point, and reaches boiling temperature as it flows through the splash protection device.

Splash protection device6is connected with a cooling water circuit7of waste heat boiler3. The boiling water/steam mixture that leaves splash protection device6is returned to a heat recovery device8assigned to the waste heat boiler.

As shown inFIG. 2, splash protection device6has pipes9through which the boiling water flows. The pipes are cast into a copper block10that serves as splash protection. The pipes are made of an alloy steel. Copper block10furthermore has a bore11for accommodating a temperature sensor12for detecting the temperature of copper block10.