Petroleo Brasileiro (Petrobras) has carried out a major project to increase its production of ultra-low sulphur diesel in order to reduce Brazil's dependence on foreign markets. This is in response to growth in internal demand for fuels and environmental restrictions limiting the market's tolerance to heavier diesel grades with higher sulphur content. As part of this effort the fractionation of several crude distillation towers, both atmospheric and vacuum, has been improved to increase the diesel yield while still meeting the quality requirements of the hydrotreating units. The project is presented as a case study of the successful revamp of a distillation unit where old multi-pass valve trays have been replaced by up-to-date structured packing and the associated internals, highlighting the importance of the chimney trays and their design to ensure proper liquid and vapour distribution throughout the packing bed.
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