This is more of a schematic flow diagram, as it doesn’t show any quantities. The blue boxes are processing steps. Two nice recycling loops in there from the crystalization step back to the electrolysis and from the other crystalization step back to the refining. ‘Szlam’ seems to be sludge. The individual Sankey arrows don’t show an arrow head, but little gray arrows indicate the flow direction from top to bottom.
The whole Sankey just looks kind of odd, because the main product flow is not aligned vertically. But then again, that’s up to the designer. After all, it is a fine sample of a process flow Sankey diagram.