Which cathode blocks for a 500kA line?
If you were running an aluminium smelter with 500,000 amps running through each cell, what sort of cathode block would you plump for?
The modern market for such blocks can be divided into two – those which are made from anthracite, but with varying percentages of graphite added (commonly called graphitic block), or blocks which are made from petroleum coke. These blocks have an extra step, where they go into an electric in-line furnace, for a process which is called graphitisation. These blocks therefore, are called graphitised blocks.
The typical modern smelter these days, with currents of at least 300,000 to 400,000 amps (more usually referred to as 300kA – 400kA), usually opts to go to graphitised block. These blocks are better able to handle the incredible current densities, and resist voltage drop.
So if you were running Chalco’s new 500kA plant, wouldn’t you use graphitised blocks? Well, you would be wrong.
The new 500kA smelter in Liancheng, which is now going through start-up (it won’t be finished the start-up until June), has opted for graphitic blocks with 50% graphite. What’s more, we understand that the blocks came from one single producer. This was because the block size was beyond the capability of other manufacturers. With dimensions of 700*530*3990mm, these are quite bulky, weighing in at more than 1.5 tonnes each.
You might also be wondering if Chalco opted for the “chocolate block” shape, which has been the buzz of the cathode market these last 2 years. The answer is no, but not because they have used the traditional flat surface block, but because the shape is neither flat nor like a chocolate block.
But if you want to know more, you need to be a subscriber to our Black China Reports. I will provide more information in the April report, which is due out next week.