(87g) Journey to Increase Light End Unit Run-Length

In recent times, motivated by market competition and the drive for more sustainable processes, ethylene-cracking units have made significant progress in reducing costs and enhancing efficiency by lengthening the intervals between plant maintenance shutdowns. Within the Olefins unit, the depropanizer and debutanizer systems are particularly crucial due to the tendency for fouling formation, needing careful process monitoring measures and treatment during this industry shift.

A Braskem plant located in the south of Brazil increased the operational time of reboilers during a six-year campaign. Additionally, it achieved a reduction in fouling in the distillation columns and extended the intervals between plant turnarounds from six to eight years, setting a record for the unit. The more stable operation and improved control of the columns also resulted in reduced product losses and risk prevention in the storage area.

Through process optimization studies - based on multivariable analysis - it was possible to modify the temperatures control of the depropanizer, which stabilized the composition of the product at the bottom of the columns, a critical point of the system. In addition, the rigorous maintenance of the reboilers and the precise dosing of specific chemical agents in the process, kept the indicators within the appropriate parameters to prevent fouling, avoiding premature system shutdowns and allowing the campaign to be extended to eight years.