Revamps 2022 Issue

ATB bypass circuit in the flashed crude preheat train. The first model was with the SS and TS design fouling factors from the exchanger data sheets, which yielded U Design, and the other model was with the SS and TS fouling factors derived from the rigorous modelling of the test run to rep - resent fouled exchangers which yielded U Actual. The per cent fouling for the design and the actual of each exchanger was calculated using the formula. Several options for series or parallel configuration for the addition of one or two exchangers were investigated to determine incremental heat recovery, reduction in E-30 inlet temperature/duty, and increased pressure drop in the ATB bypass and the flashed crude circuit. All options reduced the atmospheric heater duty by 4 to 8%. The selected option is a single shell E-37 placed in series after E-20 A/B. This option was selected as it maintains min - imum ATB temperature for export during clean and fouled conditions, provides heat recovery for the flashed crude to minimise atmospheric heater firing, minimises change in temperature and duty for the downstream exchangers, and finally minimises incremental pressure drop in the flashed crude circuit. Also, the partial bypass around E-30 can be used to reduce pressure drop in the ATB bypass circuit. The selected option is illustrated in Figure 6 , and the performance of all exchangers, including the new exchanger shell E-37, is shown in Figure 7 . There is some variation in per cent foul - ing due to the difference in U Actual for some exchangers at higher throughput compared to the test run. This is due to variation in the flow bypass of hot streams around these exchangers to meet product rundown and PA return tem - perature/duty for the two columns and the inclusion of E-37 in the flashed crude preheat train. Conclusion This article examined a crude preheat exchanger train in an existing refinery and measured the actual overall foul - ing of the exchangers through a rigorous exchanger sizing program within the atmospheric and vacuum unit simula - tion model, which was calibrated against the actual perfor - mance. This type of examination can be used to monitor the performance of exchangers in the crude preheat train and identify them in terms of cleaning priority and the effect in terms of crude throughput, furnace inlet temperature and duty, system hydraulics, product rundown, and the column PA heat removal to meet product yield and fractionation requirements. Modification of the crude preheat train by installing an additional exchanger shell at an appropriate location was also investigated to provide increased heat recovery and throughput within the furnace duty limitation and reduce excessive rundown cooling duty.

Random Packings, Catalyst Support Material and Column Equipment

Largest Capacity and Biggest Stock in Europe

Cost-Saving due to Modern High Performance Random Packings

Catalyst Support Material

High Performance Random Packings

Ceramic Random Packings

Plastic Random Packings

Demister and Column Internals

S D Radia is Process Engineering Director at Fluor Canada Ltd., specialising in the design of gas processing, refining, and upgrading facilities. He has extensive front-end engineering and detailed design process experience.

Please visit: www.vff.com

Vereinigte Füllkörper-Farbriken GmbH & Co.KG P. O. Box 552, 56225 Ransbach-Baumbach, Germany, +49 26 23 / 895 - 0, info@vff.com