Energy efficiency can save Parmalat from being milked

South African industry can increase its profits by simple improvements in energy efficiency, implemented at low cost and with short payback periods, says UCT's Richard Drummond of the Energy Research Institute (ERI) in Mechanical Engineering.

A good example of this is the Parmalat processor in Parow where a two-day study co-ordinated by the ERI and an American energy management team from Philadelphia's University City Science Centre revealed that their processing plant could save R144 297 a year with energy efficiency improvements costing only R72 605.

The American team, called Industrial Technology and Energy Management (ITEM), specialises in energy audits at industrial and commercial plants using standardised techniques that deliver quick, accurate results and recommendations.

The exercise aims to educate industrialists, officials from the Department of Minerals and Energy and engineering students about energy efficiency, using Parmalat as the case study.

The Parow plant processes ultra high temperature milk and juices from fruit concentrate. After a day in the plant, the team returned to UCT to discuss and analyse what they had seen and to draw up lists of actions to improve energy use. A number of areas provided room for improvements. Light savings, for one, were recommended by reducing operating hours from 24 to 18 and by decreasing the number of lamps and replacing fluorescent lighting with 250W mercury vapour lighting.

There was a simple proposal for air compression. Extracting air from outside (180 C) rather than indoors (320 C) yielded a sizeable increase in energy efficiency as outside air, being cooler, is denser. For Parmalat's 85kW compressor, a decrease of 140 C would yield an energy savings of 29 328kW a year.

In the case of the refrigeration system, the team proposed that the cooling tower be shut down when not in use as it only needed to run for a maximum of 20 hours a day, four days a week. For the coal boiler, the recommendation was to optimise the air/fuel ratio to reduce excess air and improve boiler efficiency. Another proposal for the boiler was to warm the intake air using the heat of the exhaust stack. This would be done by constructing a cylindrical sleeve around the housed section of the stack.

The last recommendation was to replace the standard V-belts driving the milk homogeniser with high-efficiency belts (cog-type V-belts). These can increase energy efficiency by 2% to 4% because of reduced slippage.

According to Drummond, Parmalat welcomed their proposals and are actively working to implement these. "It will be interesting to see how successful they are and how closely the actual savings in energy and money match the estimated ones."

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