NL9400591A - Aluminium reduction process involving the injection of carbon monoxide - Google Patents

Abstract

The invention relates to the injection of carbon monoxide and carbon condensate into the electrolyte of the known "Hall-Heroult" process. This process achieves the electrolytic reduction of aluminium oxide to aluminium. Surprisingly it proved possible, in the production of carbon monoxide, as known under the name Boudouard equilibrium, for the equilibrium at which the maximum amount of carbon monoxide vis-à-vis carbon dioxide is formed to be likewise at the temperature of about 950 degree Celsius, which is about the same as the electrolyte temperature in the "Hall-Heroult" process. The carbon monoxide and carbon condensate is bubbled through the electrolyte where it then dissolves and electrolytically combines with the oxygen of the aluminium oxide in order then to form carbon dioxide and therefore aluminium.

Description

The invention relates to the injection of carbon monoxide and carbon condensate into the electrolyte of the known "Hall-Heroult" process. ALUMINUM REDUCTION PROCESS WITH INJECTION OF CARBON MONOXIDE. In this process, the electrolytic reduction of aluminum oxide to aluminum is achieved. Surprisingly, it has been found that in the production of carbon monoxide as known under the name "Boudouard-Gleichweight", the equilibrium at which the maximum carbon monoxide versus carbon dioxide is / is at the temperature of about 950 degrees Celsius, which is about the same as the electrolyte temperature in the Hall-Heroult process. The carbon monoxide and carbon condensate is bubbled through the electrolyte where it then dissolves and electrolyses with the oxygen of the alumina to then carbon dioxide and so to form aluminum.

BACKGROUND AND PERSPECTIVE OF THE INVENTION It is estimated that currently 18 million tons of aluminum are produced worldwide each year, nearly 99 percent of which through the "Hall-Heroult" process.

In the prior art, two more basic differences apply, that of the consumable anode in this process n.1.1 / the so-called "Prebaked" pre-baked anode, and 2 / the so-called "Soderberg" continuous anode.

The invention is independent of the type of anode or electrode and applicable to all, and thus also has specific advantages for ceramic and metal electrodes which are a new mindset.

The invention is explained in more detail below with reference to the drawing, in which:

Five gas-permeable elements 16 through 20 are shown. The drawing shows in general a non-limiting exemplary embodiment, typically of an aluminum reduction unit "pot" or "cell" with the addition of a majority of gas-permeable elements, at least one of which is required for this invention.

The carbon "prebaked" anode 10 made from petro-coke is shown and the positive electrical pole is shown in electrical connection through the electrolyte 13 and shown through the aluminum 14 with the carbon cathode 15 showing the negative pole, production of aluminum by this electrolytic process is well known where aluminum oxide 11 dissolves in molten salts electrolyte 13 such as cryolite A1F3.3NaF and is then subjected to the flow of a very high current in this process 80 000 amperes and low volt voltage. The current energy consumption is as an example about 13kWh / kg aluminum.

The composition of the bath 13 and 14 with the addition of typically 3 percent alumina Al 2 O 3 is very important because the solution of the alumina, carbon monoxide and carbon condensate depends both on the flow efficiency and the separation of the aluminum 14. Also, the bath would be AlF3.3NaF. CaF2. May contain LiF and MgF2. Shown is the cathode and negative contact element which is low porosity in the prior art and made from anthracite coke in a semi-graphite form. This cathode could also be made porous and used as a gas-permeable element. The porous gas permeable elements and devices 16, 17, 19 and 20 are well known in the steel industry. 27 shows the anode coupler and 12 shows the refractory lining surrounded by insulation (not shown) and steel outer boundary.

At 21 a schematic representation of a gas production unit is shown with the input of 22 shown low or high degree petro-coke as well as anode residues. 23 shows the oxygen influx. Thus, the output gas 24 shown is high temperature carbon monoxide as an example between 800 ° C and 1000 ° C, with limitation from 700 to 1200 ° C. This carbon monoxide is passed through to the various gas permeable elements, shown.

26 shows the finely divided carbon monoxide bubbles that flow through one or more gas-permeable elements with sufficient pressure. This carbon monoxide largely dissolves in the molten electrolyte and then reacts electo / endothermally with the aluminum oxide to form aluminum and carbon dioxide, this temperature loss is replaced by the electric current flow.

Claims (7)

1. Aluminum reduction processes with specific in this invention injecting CARBON MONOXIDE AND CARBON CONDENSATE which flow through one or more of the gas permeable elements into the molten bath of metal and electrolyte, flow through and largely dissolve and then react electrochemistry with aluminum oxide to form aluminum metal. The process of claim 1 reduces the consumption of the carbon anodes because the oxygen of the aluminum oxide primarily combines with the already dissolved carbon monoxide and possibly dissolved carbon. The process of claims 1 and 2 reduces energy consumption by allowing conversion of alumina to aluminum and carbon dioxide closer to the theoretical minimum. The process of claims 1 and 2 may function faster than the prior art process. The process according to claim 1, 2, 3, 4 reduces the overall energy consumption as well as the consumption of the anodes in that the addition of thermal energy from the gas production unit is more economical. The process according to claims 1,3,4 and 5 extends to the new technology namely. deflated refractory hard metal cathodes and inert anodes as well as metal catalysts. 7. The process according to claim 1, 4, and 6 prevents the formation of sludge on the cathode and is therefore energy saving. Hereby 1 sheet drawing