Sweet As
Chris Howell and Associates – Consulting Engineers for the refinery project.
No Waste
That bottom ash is also recovered and turned into a useful product. It drops into a waste water tank, and is mixed with mud-cake waste from the first-stage filter and sold to people who make garden mulch. Nothing is wasted. All that remains is a minimal amount of fly ash, which is emitted into the air in an after-burner process that is strictly controlled through resource consents.
The decolourisation process, which removes about 88 percent of the colour from the raw sugar liquor, takes place in a plant that was cobbled together using Kiwi ingenuity, the latest automation techniques and vessels rescued from a disused Australian factory. A refinery in Brisbane had closed after operating for 17 years, and Chelsea made a successful bid for their tanks.
The 62kl tanks were disassembled, and rebuilt in New Zealand to suit Chelsea ’s specific needs. More than 160 tonnes of steel was used to construct the plant, which at its highest point rises to 28 metres. The foundation piles go 19 metres deep and are anchored by 300 metres of concrete. The whole process was redesigned to work with state-of-the-art equipment. There are 340 valves in the plant and 950 computer interface outputs.
“We managed to design and build the decolourisation plant here and it’s running like a top. In fact we’re doing things here that have never been done before,” says Mr Van Niekerk. For example, the way Chelsea automatically transfers the carbon into the tops of the vessels is unique – in all the other plants in the world this has to be done manually using a rubber hose. Mr Van Nie
kerk remarks on the complexities of designing the pipe work – “The bends need to be one metre in radius and specifically sloped. You cannot have any cavities where you might get bacterial growth.”
