Oil refinery plant
Crude distillation unit
The column trays that were in use could not meet customer's requirements to the operation flexibility. High pressure drop resulted in high steam flow and low yield of the light fractions.
Column's Performance History
Crude distillation unit in which packing was used after the revamping has high operation flexibility and better rectification effect. Standard trays were applied in the crude distillation column with capacity of 3,500,000 tons per year and with diameter of 4800 mm. Tray pressure drop increased dramatically at full capacity operation of the column, light fractions yield increased and water vapour flow rate significantly increased because of an insufficient opening coefficient. Before installation of the unit at the plant Zehua revamped another crude distillation unit (3200 mm diameter) with regular structured packing. Due to efficient operation of this column and better performance during several years the plant decided to revamp 4800 mm diameter crude distillation unit with regular structured packing.
High-performance EDV™ valve trays were applied instead of standard packing for two pumparound sections and stripping section. Regular structured packing was used for five rectifying sections to increase separation coefficient and to reduce pressure drop. This regular structured packing has a large specific surface area and a specific surface property (it is very important for skin formation on the packed layers) has more theoretical trays. Trough liquid distributors were used for all the packed beds to allow uniform passage of the liquid flows over the packed beds. Liquid collectors were designed with the application of chimney trays in order to use running implements. Large construction investments were saved for the plant as a result of these measures.
Crude distillation unit where its part was revamped with the packing, has high operation flexibility and better rectification effect. Max. operating range increased by 15%. Light fractions yield increased by at least 0,5% on the basis of crude petroleum. Mixing of side-cut distillates decreased significantly. Initial boiling pint of the third side-cut distillate increased by 33 °С after revamping.