Transforming an oil tank into a clean water tank - case study


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It would be an almost impossible task, many would claim, to turn an 86 diameter large Orimulsion 400 tank, that has been out of service for years, into a clean watertank. But this was whatEcologica was contracted to do for their client ENELS.p.A.
ENEL S.p.A. chose Italian-based Ecologica S.p.A. as service provider for this tank clean atthe ENEL Central e Federico power plant in Brindisi as they offered a competitive solution both technically and economically compared to the other service providers ENEL evaluated. And atthe same time ENEL wanted to be certain that the job was conducted with environment-friendly processes.

Environmental concern and cost-efficiency

As Mr. Grigoris Stubos, site responsible and commercial director at Ecologica explains: 'Protection of the environment is an integral part of Ecologi-ca's activity and mindset. With the purchase of the BLABO unit we were able to offer complete tank cleaning solutions with an excellent value for money with quality, safety, health, and environmental protection.' The mere size of the tank, the nature and viscosity of the fuel, the requirement of using the tank as water tank which necessitated an absolutely oil-freed tank, and the fact that it was the first job Ecologica performed with the newly acquired BLABO system would be too big a mouthful for many, but not for Ecologica.

The challenges

The tank at the Federico power plant was a very large floating double roof tank, reaching 86 meters in diameter and with a volume of 100,000 m3. It contained Orimulsion 400, which is an emulsion of 70% bitumen and 30% water. It was earlier commonly used as an alternative to coal or fuel oil for use as boiler fuel in power plants. The challenge with this type of fuel is that when the temperature drops below 30°C it becomes practically impossible to pump. Orimulsion 400 has a viscosity that is much higher than the oil types normally operated by the BLA.BO system. Due to the age of the Orimulsion 400, the viscosity had raised to 19,000 cSt at 50°C. In comparison, the viscosity of the cutterstock used in the process was 44 cSt at the same temperature.

The process

After installing the BLAEO modules and equipment, the main challenge was now to start circulating the oil as part of the desludging process. The low temperature and high viscosity made the oil difficult to operate. But Ecologica came up with a simple solution to the problem; they doubled the capacity of suction pumps and soon after the oil started circulating and the temperature could be raised to 50°C to obtain a steady flow. Several batches of cutterstock were delivered to the tank to liquefy the sludge to guarantee a constant circulating mixture. When the tank was emptied of oil except a thin layer on the tank walls, Ecologica performed a final hot water wash to make the tank ready for its new life as a water tank.

The result

After a total of 30 days of cleaning, the man-holes were opened and Ecologica entered the tank together with the tank owner to inspect the result. The tank owner was satisfied with what he saw. The target was to clean the tank completely, and Ecologica was pleased to conclude that they fulfilled their client's expectations on all accounts. Both Ecologica and the BLABO technology demonstrated that even the most challenging tank cleaning task can be turned into a success with the right equipment and competences.

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