Abstract
Abstract The periodic cleaning of the bottom of crude oil storage tanks in vessels, terminals and refineries has become a big problem for industrial maintenance, principally due to the temporary inoperability of the equipment and the high environmental impact caused by the conventional treatments used. The storage of crude oil in large tanks invariably creates a gradual deposition process of organic sediments of high molecular weight. PETROBRAS has developed a thermochemical method aimed at removing wax deposits in submersed oil pipelines, wax damage in production reservoirs and petroleum sludge removal from storage tanks. This work presents the chemical treatment performed inside an oil storage tank located onboard an oil tanker as well as the laboratory methodology for the organic deposit physical-chemical characterization, kinetics of reaction, physical simulation, treatment dimensioning and operational treatment, aimed at the removal of 800 M3 of organic deposit. The thermochemical method consists of a chemical reaction between two nitrogen salts that produce a strong exothermic chemical reaction. The heat produced by the reaction, together with the turbulence due to the generation of a large volume of nitrogen and the solvency, dispersed the initially solid compacted sludge at the bottom of the tank. The heat of the solution, estimated at 90°C, in contact with the sludge, irreversibly melted the organic fractions according to the previously studied phases diagram. The method demonstrated itself to be efficient, safe and of low cost, when compared to existing classic methods. The process financial balance showed that the cost of the oil recovered from the organic deposit paid for the investment in chemical reagents and operational facilities.
Published Version
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