Evaporation technology efficient for purifying rinse water

"The main reason for utilising this technology is to wholly prevent the leakage of environmentally harmful chrome from rinse water. However, there are other advantages with a closed-loop water purification system," says Ari Mastokangas, director at Mäkelä Alu. "For example, fresh water consumption is virtually eliminated and the high-quality distillate produced by the evaporator has improved the quality of treated products."
The new plant is the first application of the company's special evaporation technology in an aluminium profile treatment process. The co-operation with Mäkelä Alu began early this year with the plant being tested since March.
Mäkelä Alu operates in a location where there is no municipal sewage network. This means that the company must assume full responsibility for its own waste water.
"Costs are reduced as less fresh water is needed and therefore the amount of waste water reduced. Hence, closed-loop evaporation is an economically viable solution," says Peter Koistinen of Hadwaco.
The evaporator concept is based on Mechanical Vapour Recompression (MVR) and the Falling Film (FF) principle. The heart of the evaporator is a special heat transfer surface design that employs high quality polymeric materials. By using such materials, large heat transfer surface areas can be constructed at a significantly lower cost compared with metallic surfaces of the same size. A large heat transfer surface results in low energy consumption. The polymeric material is, of course, highly resistant to corrosion.
Because of their modular design, Hadwaco evaporator-based solutions are flexible and can be dimensioned for various volumes of rinse water. In addition to purifying rinse water at aluminium and other metal surface treatment plants, the technology can be used in a wide range of applications. Treatment of effluents in the pulp and paper, steel, industrial laundry, food and beverage industries, production of process water from saline and brackish water, and treatment of landfill leachate are the most obvious.

Caption:
1. The first plant using Hadwaco evaporation technology has commenced operations at an aluminium surface treatment plant in Finland. The closed water loop system applying the new evaporation technology is cost effective.
2. Flow chart for a closed water loop process at an aluminium profile surface treatment plant.

For further information, please contact:
Hadwaco Ltd
Mr. Peter Koistinen or Mr. Erkki Kasanen
Hämeentie 135, FIN-00560 HELSINKI
Tel. +358 204 3911, fax. +358 204 39 5655