DE19844667A1 - Process for polishing copper - Google Patents

Abstract

Copper poling process employs a deoxidizing gas mixture of hydrogen and inert gas. Copper poling is carried out using a deoxidizing gas mixture of inert gas (preferably nitrogen) and 35-90 (especially 60-72) volume % hydrogen.

Description

The invention relates to a process for polishing (deoxidizing) copper in melt liquid state in which a gaseous deoxidizer in and / or on the Melt is passed.

The use of hydrogen gas and natural gas to deoxidize copper is not an option ben of wood or materials derived from it - known (see. DE-PS 3427 435).  

1. Introductory considerations for the reduction of liquid copper

The refining process for producing anode copper is the last one Process stage before casting a reduction in the molten copper bath. The technical term for this process stage is Poland. The Re used reducing agents (various feedstocks) primarily have the gave the oxygen content to a certain final dimension and itself expel sulfur dioxide in the copper bath. The currently requested applied technology provides for the use of hardwood trunks with be pressed into the liquid copper bath using a crane. The taking place very intense reactions of the wood with the melt lower the oxygen - and if present the sulfur di oxide component. It is always of the utmost importance that before starting the most important harmful additions to the reduction process have been slagged and the bathroom surface has been wiped clean. Otherwise, those in the slag are on the copper Bad floating metal oxides reduced to metals, occur as metal Contamination in the anode copper again and sometimes very disturbing significant in further processing by wet metallurgy.

For the entire reduction process 3-4 hours, approx. 7-8 sc Logs needed with bound indoor crane and crane operator.

The process runs discontinuously, because after burning the on led wood new logs must be provided.

Part of the wood that is not immersed in the copper bath burns away outside the melt or the flame furnace and lowers the overall we degree of efficiency additionally to approx. 35%. Due to the length dimension of the pole rods cannot be completely avoided that exhaust gases are emitted into the furnace hall be animals. The high heat development at the work gate puts a strain on them there work very hard (crane operators, first and second refiners).

2. Use of hydrogen for poling

In the area of the former copper smelter, the pole process already took place various reducing agents.

In addition to the original method with logs, the 80s Years of crude oil of the HT-B grade below 2% sulfur content to the anode generation used.

Attempts were made almost simultaneously to design the reduction phase with CH ₄ . Oil poling posed major environmental problems because the technical equipment was very poor, ie the resulting carbon in the exhaust gas was not subjected to any aftertreatment and there was no filtering either.

In addition, the deduction ratios (without suction fan) and Overpressure conditions in the furnace chamber responsible for the soot clouds moved outside through the hall atmosphere.

The poling with CH ₄ had to be stopped in anode operation after several failed attempts because a very important requirement, the high starting temperature of the oxidized anode copper, which could only be achieved with great economic effort, was missing.

However, in the remelting work for the production of wire bars that natural gas Poland will be partially introduced.

The fact that the lead material was of cathode quality, the temperatures of about 1250 ° C he reached, even without large energy losses, which then allow a natural gas poling with two lances economically. The technological conditions provided, with an oxygen content of about 800-1000 ppm, to continue the pole process with logs to the end, because the O ₂ removal is quick at these contents and the sampling and O ₂ determinations do not work together accumulated.

Since in the examples mentioned the reducing agent can act directly with the oxygen in the copper, a breakdown into reactive components (CO / H ₂ ) must first take place, which, however, can only be achieved by supplying energy.

So the considerations went there, a gas to be used as a reducing agent, which is already a reducing agent, and adds energy to the process through its "combustion".

There was the use of hydrogen for experimental purposes on the flame furnace 6 used.

2.1. Furnace data

The polymer searches with hydrogen were carried out on a flame furnace Anode operation of a former copper smelter. The flame furnace is stationary; the delivery consists of CM material inside as well as Fireclay outside and in the range from the 2nd layer down. The Oven racking is located on the front opposite the two fixed ones Natural gas / oxygen burner. The exhaust gas leaves the furnace through an un terrestrial channel system to the furnace filter and through the work gate via the system of the auxiliary hood filter. The furnace is Cold-filled openings and has a capacity of approx. 155 t total use with an anode output of about 135-140 t per Batch.

Special furnace data

Batch time = 28-30 hours
Natural gas consumption = 105 m ³

/ t on.
O ₂

-Consumption = 185 m ³

/ t on.
Slag accumulation = 10% of Vorlf.
Anode copper = 99.2% Cu
Copper bath surface = approx. 24-26 m ²

Gas pipe ¾ "was used as the outer jacket in which an approx. ⅜" pipe was inserted. Because the gas flow should flow through the inner tube Both gas pipes were welded to the threaded head piece. The pipe length of the pollanze was 3 m. The lower part experienced one Thermal protection made of plastic fabric combined with firebrick mortar and soda water glass. Both components became a mushy Ge mixed and generated via a spindle with roller seat for the Aubahnie des Tissue drawn evenly, spirally over the outer tube. In a The lance was covered at the lower end with a length of approx. 1.5 m.

The overall design thus met the following factors:

• - Long service life due to mechanical stability (double pipe) and fire Fixed protection by applying the insulation in-house.
• - Tight connection by screwing at the end of the lance with a fle xiblen metal hose with ball valve.
• - Good outflow velocities at the lance to liquid copper transition at a constant set pressure.
• - Simple manufacture, uncomplicated handling when changing Due to the pole process, low manufacturing costs (<50 DM / lance complete).

3. Poles with pure hydrogen 3.1. Test execution Initiation of the pole process

Before the pole process, the piping system is flushed with nitrogen.

Operating steps

• - immersing the injection lances in the Cu melt,
• - closing the main shut-off for hydrogen (valve 30),
• - opening the string shut-offs for hydrogen (valves 31 and 32),
• - opening the connected nitrogen bundle (handwheel on the bundle),
• - opening the main shut-off for nitrogen (valve 33),
• - rinsing time 2 min.

Pole process Operating steps

• - Closing the connected nitrogen bundle (handwheel on the bundle),
• - closing the main shut-off for nitrogen (valve 33),
• - opening the main shut-off for hydrogen (valve 30),
• - Poland under hydrogen entry.

The use of hydrogen gas for deoxidation has the following disadvantages:

• - The pollanzes are subject to relatively high wear;
• - In particular towards the end of the deoxidation process it takes a long time Deoxidation target achieved;
• - Oven atmosphere has an impact.

The present invention is therefore based on the task, a simple feasible, functional and also effective deoxidation process on the Specify the basis of gaseous treatment agents.

According to the invention, this is achieved in that a hydrogen is used as the deoxidation gas and a gas mixture containing 35 to 90% by volume, preferably nitrogen, Hydrogen is applied.

According to the invention, a hydrogen-nitrogen gas is preferably used as the deoxidation gas. Mixture with 60 to 72 vol% hydrogen applied.

Further design variants can be found in the appended subclaims. An exemplary embodiment of the invention is described below:
Before the pole process, the piping system is flushed with nitrogen.

Operating steps

• - immersing the injection lances in the Cu melt,
• - Close the main shut-off for hydrogen (valve 30) and the Ab locks (valves 34, 35) and the skin barrier (valve 36) for Nitrogen from the tank,
• - opening string shut-offs for hydrogen (valves 31 and 32),
• - opening the connected nitrogen bundle (handwheel on the bundle),
• - opening the main shut-off for nitrogen (valve 33),
• - rinsing time 2 min.

Pole process Operating steps

• - Closing the connected nitrogen bundle (handwheel on the bundle),
• - closing the main shut-off for nitrogen (valve 33),
• - Open the main shut-off for hydrogen (valve 30) and one Shut-off (valve 34 or 35) and the main shut-off (valve 36) for nitrogen from the tank,
• - Poland under hydrogen nitrogen entry.

End of the pole process

Before the pole process ends, the line system is connected again Nitrogen purged.

Operating steps

• - The injection lances remain in the Cu melt,
• - closing the main shut-off for hydrogen (valve 30),
• - opening the connected nitrogen bundle (handwheel on the bundle),
• - opening the main shut-off for nitrogen (valve 33),
• - rinsing time 2 min.,
• - Closing the connected nitrogen bundle (handwheel on the bundle),
• - closing the main shut-off for nitrogen (valve 33),
• - Closing the string shut-offs for hydrogen (valves 31 and 32) and the shut-off (valve 34 or 35) and the main shut-off (Valve 36) for nitrogen from the tank,
• - pulling the injection lances out of the Cu melt,
• - Relief of pressure in the line system by briefly opening one Line shut-off for hydrogen (valve 31 or 32).

Test results and evaluation

The wear of the pollanzas compared to the first attempts with rei hydrogen has been significantly reduced. The pollanzas could for 2 to max. 3 batches can be reused.

The volume fraction of H ₂ in the H ₂ / N ₂ mixture is in the range between ≧ 61- ≦ 72 vol .-%.

Average H ₂ / N ₂ consumption based on the test period:

• - H ₂ = 8.474 m ³ N / t anodes
• - H ₂ = 4.45 m ³ N / t anodes

In order to find the optimal delivery of the pollanzers, it was possible to determine, based on the existing conditions, that with the increase in the supply pressure and the associated lower outlet cross sections d _i = 10 mm and increasing outlet velocity beyond 12 bar, no intensification of the reduction could be achieved.

The disadvantage of these experiments with injection pressures of up to 15 bar higher wear of the pollanzes. The operating time per lance was max. just in one batch.

The flow rates per lance (H ₂ / N ₂ mixture) range from 200-350 m ³ N / h and lance.

With injection pressures of 10 bar in front of the lance and lances, outlet cross-sections of 1.2265.10 ^-4 m ² (d _i = 12.5 mm) were achieved.

With the selected lance construction, exit speeds are in The speed of sound has been reached. The pressures on Outlet cross-section is estimated to be around 2-3 bar.

When using nozzles, the result is based on the form of 10 bar, higher dynamic pressures at the outlet of the lances about 5-6 bar. There This also results in higher exit speeds otherwise lead to a further intensification of the reduction.

Energetic efficiency

Of the previously known methods for reducing copper melts with the use of

• - wood (so-called pole poles),
• - heating oil, L u. M (hard coal heating oil) and
• - natural gas, H

the trend in the manufacture of copper anodes goes to gas poling the use of Group II natural gas.

Although for a comparison of the degree of use the respective furnace type, the Batch weight and the copper-containing feed materials from Influence can - based on an oxygen content in the bath of ≦ 1% - a comparison to those in the corresponding specialist literature for specific consumption in the manufacture of copper anodes Evaluation of the degree of utilization can be accepted.

The production process for the production of the copper anodes is in the batch regime and the breakdown of the process stages

• - Deploy,
• - melting,
• - oxidize,
• - Poland,
• - shedding and
• - To prepare.

Based on the batch regime, the average for the pole process 10% of the time required.

To evaluate the degree of utilization, the first approximation can be Average oxygen quantity to be reduced with 9 kg / t anodes be placed.

This corresponds to a degree of utilization = 1.  

It applies

Compilation of the actual Polgas consumption as well as the theoretically required hydrogen consumption quantities

The ratio of the amounts of hydrogen in m ³ N / batch of theoretical consumption / actual consumption results in utilization rates of ≧ 0.77 to ≧ 1. Due to this fact, it is likely that the swirling up of the copper bath in the immersion area of the pollen by the flame gases of the natural gas / Oxygen firing is a noteworthy reduction.

An air ratio was used to heat the furnace during this polymer search number of λ ≧ 0.6 observed.

Compared to Poland with natural gas, the use of H ₂ / N ₂ mixture <60/40 vol .-% increases the degree of energy efficiency by a factor of two.

Claims (6)

1. A process for polishing (deoxidizing) copper in the molten state, in which a gaseous deoxidizing agent is passed into and / or onto the melt, characterized in that a gas mixture containing hydrogen and inert gas, preferably nitrogen, containing 35 to 90 vol. Is used as the deoxidizing gas -% hydrogen is used. 2. The method according to claim 1, characterized in that a deoxidation gas Hydrogen-nitrogen mixture with 50 to 75 vol .-%, preferably 60 to 72 vol .-%, Hydrogen is applied. 3. The method according to claim 1 or 2, characterized in that over the Melt creates a deoxidizing atmosphere. 4. The method according to any one of claims 1 to 3, characterized in that the deoxidizing atmosphere above the melt by adjusting the Heating burner is generated. 5. The method according to any one of claims 1 to 3, characterized in that the gaseous deoxidizer is passed into and onto the melt and thus at least part of the reducing atmosphere is generated above the melt. 6. The method according to any one of claims 1 to 5, characterized in that in In the case of pipe lances, the deoxidation gas with admission pressures of 5 to 15 bar, preferably 8 to 12 bar, is introduced into the melt.