Development of novel oil recovery methods for petroleum refinery oily sludge treatment

Abstract

Oily sludge is one of the most significant wastes generated in the petroleum industry.It is a complex emulsion of various petroleum hydrocarbons (PHCs), water, metals, and fine solids. Due to its hazardous nature and increased generation quantities around the world, the effective treatment of oily sludge has attracted widespread attention. The complexity of its composition and diversity of its origin sources make oily sludge management a difficult and costly undertaking. Many methods have been developed for the treatment of oily sludge through oil recovery or sludge disposal approaches, but no single specific process can be considered as a panacea since each method is associated with different advantages and limitations. Efforts should focus on the improvement of current technologies and the combination of oil recovery with sludge disposal in order to comply with both resource reuse recommendations and environmental regulations. The object of this study was to develop novel combined methods for oil recovery treatment on different refinery oily sludges. The investigation focused on the oil recovery performance of combined methods based on four individual treatment processes including ultrasonic irradiation, solvent extraction, freeze/thaw, and pyrolysis in oily sludge treatment.Firstly, the oil recovery and salt removal effects of ultrasonic irradiation on oil refinery tank bottom sludge were investigated, together with those of direct heating.Ultrasonic power, treatment duration, sludge-to-water ratio, and initial sludge-water slurry temperature were examined for their impacts on sludge treatment. It was found that the increased initial slurry temperature could enhance the ultrasonic irradiation performance, especially at lower ultrasonic power level (i.e., 21 W), but the application of higher-power ultrasonic irradiation could rapidly increase the bulk temperature of slurry. Ultrasonic 2 irradiation had a better oil recovery and salt removal performance than direct heating treatment. More than 60% of PH Cs in the sludge was recovered at an ultrasonic power of 75 W, a treatment duration of 6 min, an initial slurry temperature of 25 °C, and a sludgeto-water ratio of 1 :4, while salt content in the recovered oil was reduced to <5 mg/L, thereby satisfying the salt requirement in refinery feedstock oil. In general, ultrasonic irradiation could be an effective method in terms of oil recovery and salt removal from refinery oily sludge, but the separated wastewater still contains relatively high concentrations of PH Cs and salt which requires proper treatment.Two types of ultrasonic assisted extraction (UAE) treatment including UAE probe (UAEP) system and UAE bath (UAEB) system were investigated for oil recovery from refinery oily sludge. Their oil recovery efficiencies were compared to that of mechanical shaking extraction (MSE). Three solvents including cyclohexane (CHX), ethyl acetate (EA), and methyl ethyl ketone (MEK) were examined as the extraction solvents. The influence of experimental factors on oil an...

An Overview of the Current State and Prospects for Oil Recovery from Oily Sludge

“…However, their capital or operating costs may be prohibitively costly, or their adoption in a large-scale treatment may be difficult. A wide range of applications and cheap operating costs may be provided by other processing techniques, such as farming and composting, although their microbial breakdown processes may take some time [17].…”

“…Because technology selection incorporates several factors, assessing the overall performance of available technologies is challenging. Some multi-criteria assessment analysis methodologies can aid in developing a standard technology evaluation system and selecting the most appropriate disposal methods by researchers [17].…”

“…Oil sludge is a substance that collects at the bottom of storage tanks and combines oil, sediments, and water. These are taken out through tank cleaning procedures and shipped for additional processing or disposal [16][17].…”

“…Alkanes, cycloalkanes, benzene, toluene, xylenes, naphthalene, phenols, and other polycyclic aromatic hydrocarbons, for instance, methylation derivatives of fluorine, phenanthrene, anthracene, chrysene, and pyrene account for up to 75% of PHCs in oily sludge [17]. Polar molecules such as naphthenic acids, mercaptans, thiophenes, and pyridines are noticed in the NSO fraction.…”

“…Polar molecules such as naphthenic acids, mercaptans, thiophenes, and pyridines are noticed in the NSO fraction. The quantity of nitrogen (N) in oily sludge is less than 3%, with the bulk found in the distillate residue as a component of the asphalt and resin fraction [17].…”