PTQ Q3 2025 Issue

Figure 4 Fouled tray in LK-HK fractionation section

Figure 5 Fouled tray in HK section

sections, all trays were in good mechanical condition without any fouling deposits. • The HGO wash bed was also found to be in good condition and clean. The analysis of the tray deposits revealed varied appear- ances, with colours ranging from reddish-brown to black, and a high phosphorus content of approximately 21% by weight. Based on the extent of fouling and the analysis of deposits on the LKPA and HKPA zone trays, it was concluded that fouling was primarily due to phosphate salts, mainly contributed by the type of crude processed and, to some extent, by the high TAN corrosion inhibitor dosage. To prevent such occurrences in the future, it was recommended to replace the trays in these sections with fouling-resistant trays. After cleaning the trays and resuming operation, the pres- sure drop across the column started increasing again after a few months. To maintain unit throughput, some parts of the LKPA section continued to slip to the HKPA section. Severe fouling solutions To address fouling concerns on the trays in the LH-HK sec- tion of the column, NEL and Koch-Glitsch collaborated and studied the column with the following objectives: • Improve the fouling resistance for trays in the naphtha and kerosene sections. • Minimise required modifications to the existing trays and internals. • Maximise the vapour-liquid handling capacity with minimal modifications. Proper design of internals for severe services requires identifying potential severe conditions and understanding the nature or cause of the problem. Modifying operating con- ditions or the process scheme may help minimise potential

hazards. For severe conditions that cannot be eliminated, appropriate equipment designs can provide longer run times. To extend run times in severe fouling service, fouling- resistant trays with anti-fouling valve options promote self-cleaning of the active areas. These trays have foul- ing-resistant fixed valves that use vapour energy to create a forward lateral push to the froth, maintaining proper tray activity and reducing the residence time of solids on the tray deck (see Figure 6 ). Special attention is given to the periph- eral areas of the deck where stagnation may lead to solids deposition. Directional valves in these areas increase bub- bling activity and promote a uniform flow profile. These com - ponents work together to reduce residence time distribution and enhance the fouling resistance of the trays. The final design combines features suitable for specific applications to produce a tray capable of longer run times between cleaning shutdowns. This solution has been demonstrated in similar applications (see Table 3 ). Superflux trays were accepted by NEL and installed during the 2020 shutdown. Shutdown 2020 observations and action In 2020, after approximately two years of operation, the crude column was opened for inspection and modifications. During the inspection, pitting and fouling of trays were observed, varying between the sections described below: • HN-LK fractionation section : In the upper section, pitting and deposits were observed, while in the lower section, heavy deposits were found in the valve openings. • LKPA section: Severe fouling was observed, with approx- imately 70-80% of valve openings choked with hard depos- its. Fouling was mainly in valve openings, with less on the tray deck and valve top surface. Downcomers were slightly dislocated from support brackets. Improved stability and column performance following installation of Superflux trays

Fouling-resistant solutions for crude columns

Year

Country

Diameter

Quantity (trays)

Section

Pressure drop post Pressure drop after installation of two-year operation, Superflux kg/cm² trays, kg/cm²

2024 2021 2020 2020 2019 2018 2016 2015 2015 2014

India India India India India India India India India India

9,600 mm 9,600 mm 8,500 mm 7,500 mm 9,600 mm 9,600 mm 9,600 mm 9,600 mm 9,600 mm 9,600 mm

Column top to HN draw-off

0.06 0.05 0.01 0.03

5 5

HN to LKPA return

LKPA return to LK draw LK draw to HKPA return Pressure drop column

22 22 17 17

0.4

top to flash zone

Table 4

Table 3

PTQ Q3 2025