Mitigating fouling in crude distillation columns
Case study on increasing crude column throughput by using fouling-resistant trays in the kerosene section
Abhijit Gogoi Nayara Energy Limited Neil Sandford and Sandeep Yadav Koch-Glitsch
T his case study delves into the troubleshooting and resolution of fouling issues in the crude distillation column of a petroleum refinery. The column, equipped with distillation trays, experienced fouling concerns in the light and heavy kerosene sections, accompanied by a signif - icant pressure drop limiting crude throughput. The fouling, attributed to phosphorus deposits from chemicals used to process high total acid number (TAN) crudes, was confirmed in a detailed study. Subsequent intervention involved the implementation of special fouling-resistant trays, leading to improved reliability and column performance. The Nayara Energy Ltd. (NEL) Vadinar refinery atmos - pheric (crude) distillation column (CDU) is equipped with trays in the fractionation, pumparound, and steam stripping sections and a packed gasoil wash section above the flash zone. Overhead light naphtha is routed to the saturated gas unit, and reduced crude oil (RCO) bottoms are routed to the vacuum tower as a feed. Five side draw products – heavy naphtha (HN), light kerosene (LK), heavy kerosene (HK), light gasoil (LGO), and heavy gasoil (HGO) from the crude tower – are further processed in secondary units of the refinery. The tower has four pumparounds (PAs): light kerosene, heavy kerosene, light gasoil, and heavy gasoil. Figure 1 illustrates the overall crude column arrangement. After about 1.5 years of operation, the crude distillation col - umn started experiencing a higher pressure drop across the upper section. The pressure drop increased by 40-60%, with fluctuations during a month of operation. In the upper part of the column, section-wise pressure drops were monitored to understand the pressure drop across individual sections. Table 1 indicates the average pressure drop across individ- ual sections during normal operation and after one month of
O gas
Light naphtha
Heavy naphtha
Light kerosene PA
Light kerosene
Heavy kerosene PA
Heavy kerosene
Light gasoil PA
Light gasoil
Heavy gasoil PA
Heavy gasoil
Feed
Average pressure drop across individual sections
Section
Pressure drop at Pressure drop after normal column 1 month column operation, kg/cm 2 operation, kg/cm²
Steam
HN draw to LKPA return LKPA return to LK draw LK draw to HKPA return Column top to flash zone
0.07 0.04 0.05 0.48
0.14 0.13 0.08 0.70
Reduced crude oil
Table 1
Figure 1 Arrangement of crude distillation column
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