Applied Cleaning Methods of Oil Residues from Industrial Tanks

Abstract

The oil industry is facing a major problem with the large amount of oil residue generated in the tanks that store and process crude oil or its products. Research has shown that the residues of petroleum sludge, which according to a sample from the Azzawiya oil refinery in Libya mainly consist of oil, water and solid residues in 42.8%, 2.9% and 55.2% respectively, result in the alteration of the product quality and reduced capacity of the tanks. The solution for this problem as well as the need for inspection and maintenance requires the removal of this oil sludge and the internal cleaning of the tanks. This report aims to review the applied clean-up methods available in the world market and to identify the most efficient, safest, most economical and most environmentally friendly cleaning process. It must be noted that until now, there is not any published work which presents the applied techniques. To accomplish this goal, a total of five manual, automatic and robotic cleaning systems were analyzed and evaluated according to their advantages and disadvantages. The results show that the MEGAMACS with sludge extractor automatic cleaning system with an output of 14.8 m3/h is the fastest cleaning system, while the MARTin where the presence of people inside the tank is not necessary at any stage is the safest. In terms of cleaning costs and environmental impact, the automated BLABO, COW and MEGAMACS systems as well as the MARTin robotic system are the most economical and environmentally friendly due to the closed cleaning circuit and the ability to recover up to 95% of the oil from the sludge, which is returned to the customer and the earnings cover the costs of cleaning. The conclusion drawn is that the current need in the oil industry, in the field of tank cleaning, is the use of high-efficiency automatic or robotic cleaning methods, which aim to reduce the tank downtime, without the need for staff entrance into a permit-required confined space and with the ability to recover up to 100% of the hydrocarbons present in the composition of the sludge.