Sweet As
Full Automation
Air and water discharges from char end existing (click to enlarge)
The plant itself is entirely unmanned, and uses an automatic SCADA control system coupled with Siemens S7 400 PLC and Profibus link. The monitoring equipment now sits on the desk of an operator who has responsibility for another part of the plant. “If there are any alarms a warning will pop up on his computer screen. The plant is designed so if there’s a problem it’ll just go to sleep. When the problem is corrected it slowly wakes up.”
The $7 million plant came on line on 21 February this year and was officially opened by Deputy Prime Minister Michael Cullen. It is designed in such a way that another three units can easily be added; and plans are already afoot to speed it up “by replacing a few valves”, which tweaking will increase its capacity, postponing the need for the additional columns.
The combination of creative thinking and modern technology not only saved money and created efficiencies for Chelsea, but also rendered the process of stripping the colour out of raw sugar more environmentally friendly.
The granular activated carbon process is more efficient than bonechar filtering; the plant halved its use of natural gas because it is using its kilns less; the demand for treated water has been reduced; and trade waste and air contaminants have been reduced by 60%, waste heat in water discharged into the Waitemata Harbour by 90%.
Eco award
The new decolourisation plant made it much easier to comply with resource consents, and its achievement was recognised with an environmental merit award. The Auckland Branch of IPENZ presented the New Zealand Sugar Company with a merit award in the Arthur Mead Environmental Awards in July this year.
New Zealand Sugar finalised a voluntary agreement with the Ministry of Energy in 1995 to reduce CO2 emissions by 13% from 1990 levels by 2000. It had already achieved that goal prior to the commissioning of the new decolourisation plant, which has now further decreased greenhouse gas emissions.
Chelsea Sugar produces about 120 packaged and branded offerings ranging from three-gram sachets for retail sale to 24-tonne road tanker-loads of crystal or liquid sugars for large food and beverage manufacturers. About 25% of what is produced locally is exported, the bulk (approximately 35,000 tonnes of sugar and sugar blends each year) heading to Japan, Asia and the Pacific. In the past five years export earnings have doubled, currently representing about 25% or $50 million of Chelsea’s revenue.
