Community Research and Development Information Service - CORDIS

Final Report Summary - STEELWATER (Effective use of water in coal and steel industry)

The ultimate aim of the STEELWATER project was to introduce new technologies in Egypt for a more effective treatment of the water resources. The cleaner technologies that could be used in the coal and steel industry were the recovery of acids, recovery of alkaline cleaning baths, rinse water treatment and the closed loop system for rolling oil emulsions. Based on the Swedish Central Metallurgical Research and Development Institute (CMRDI) the possibilities to implement such solutions in Egyptian steel industry were examined.

Recovery of acids

There are a number of different existing treatment methods for recovery of spent acids, such as spray roasting, acid retardation and crystallisation. Under certain condition metals and fluorides crystallises forming a sludge that may be separated. The crystals can be burned in a fluidised bed or a rotary kiln in order to recover both hydrofluoric acid and metals.

Spray roasting is a common process for treatment of hydrochloric pickling bath. It can also be used for recycling of mixed acid. With the spray roasting process, about 40 to 70 % of the nitric acid can be recycled and about 95 % of the hydrofluoric acid can be recycled. The metal oxides formed by the process may be re-melted, if the density is high enough. A disadvantage of the method is that scrubbers are needed for separation from nitrous oxides from the exhaust air. A possible solution may be to apply an electro dialysis for nitric acid separation before spray roasting. With the acid retardation system, the lifetime of a pickling bath can be extended significantly as the metals are separated continuously. When electro dialysis is used for treatment of the by-product from the acid retardation, the most of the nitric acid is re-used for pickling. The metals end up as metal hydroxides. This sludge is difficult to treat for recycling of metals, but there were ongoing investigations in order to find an efficient method.

Treatment of pickling bathes with crystallisation is not applied nowadays. There was a full-scale installation in Italy, but as the works were shut down the technique was not used any longer. A problem of the technique is that the crystallisation process for the metal fluorides takes long time. As it is a promising method, new investigations were made in order to improve the method.

Recovery of alkaline cleaning baths

Treatment of spent degreasing baths with evaporation and ultrafiltration in combination with reverse osmosis can reduce the waste volume up to 20 times. The permeation from the ultrafiltration plant or the evaporation condensate is polished by treatment with reverse osmosis. Systems for treatment of spent degreasing baths, as well as systems for semi-continuous separation of oil and fat existed in a great number more than ten years in full-scale installations. The recycling of chemicals and water by reverse osmosis treatment of rinse water is not common in full scale. IVL was involved in a European project with the aim to solve this problem.

Closed loop system for rolling oil emulsions-sustainable rolling

There are few procedures for the effective treatment of emulsions or for making them suitable for recycling. The emulsions are generally treated in flotation/sedimentation systems combined with magnetic separation. It was shown that a conditional emulsion was successfully tested in pilot scale the aluminium industry. The formulations' main ingredients are ethylene glycol-based. Some trials were done to introduce also this formulation in steel industry but the result was poor. The advantages are that no mineral oil is used, the composition is well-defined and the possibility to prolong the lifetime is enlarged. Therefore, from an environmental point of view it was a good alternative. There is also a possibility that introduction of this solution can improve the rolling process in such a way that the energy consumption can be lowered.

The project progress did not follow the plan and failed to meet the milestones and achieve the deliverables. As it delayed half a year the project prolonged its execution time.

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