Modernization of the extraction tower in the selective treatment section on the KM-2 unit

Abstract

In 2003, the problem of increasing takeoff of residual raffinate while preserving its quality and reducing power consumption in the selective treatment section of the combined KM-2 unit for production of lube oils and waxes was set before Slavneft'-Yaroslavnefteorgsintez Co. The bid of IMPA Engineering Ltd. -a specialized enterprise for development of modern extraction equipment whose efficiency was confirmed by experience in industrial operation -was selected to solve this problem [1].After examining operation of the extraction unit in this section, IMPA Engineering developed a plan for modernizing the extraction tower and fabrication and installation of internals and master assembly. Extraction treatment of deasphalted product with N-methylpyrrolidone is conducted in the tower (23.7 m high, 2.4 m in diameter). Inspection of operation of the tower before and after modernization included generalizing the process parameters in a wide feedstock charge range -from 12.5 to 17.5 m 3 /h -and laboratory studies of selected industrial samples.Several operating regimes that differed by the feedstock charge and quality of the treated feedstock were distinguished (Table 1). With an increase in the charge, the overall unit load of contacting phases increases so that the efficiency of their reaction increases and the ratio of solvent to feedstock decreases. The quality of the feedstock additionally affects the tower operating indexes: to obtain raffinate of standardized quality -carbon residue of 0.40-0.45 wt. % from deasphalted product with high carbon residue -from 1.14 to 1.42%, the ratio of solvent to feedstock must be increased from 1.14 to 1.42 %.Laboratory modernization of selective treatment of the feedstock was conducted with the psendoreflux method in [2,3]. The essence of the method consists of varying the number of theoretical treatment plates to determine its effect on the quality indexes and product takeoff. The efficiency of operation of the tower in