Berre Petrochemical Cluster is one of the largest petrochemical complexes in the south of France, with 470 kton of ethylene a year and over 1000 employees. Their Thomassen cracked gas compressor K-201 had been in operation for 35 years. Unfortunately, and despite regular services having been conducted, the compressor had some polymerisation from charge gas, which left a deposit on the gas path that narrowed it, hence reducing its mass flow and efficiency. This meant that the plant’s efficiency was decreasing between turnarounds. For this reason, Berre Petrochemical Cluster contacted Howden to request an anti-fouling coating on the compressor internals.
At Howden, we not only solve our customers’ problems but we help them improve their day to day operations. For that reason, after undertaking an initial engineering study, we informed the client that by rerating the compressor not only they would solve their fouling problem but also reduce the compressor’s power consumption. After considering all available options, we finally offered the customer either a total rerate or a partial rerate with a 10% or 3% power reduction target respectively. Berre Petrochemical Cluster chose the latter, which involved the anti-fouling coating of newly designed diaphragms and existing rotors while the current impellers, labyrinths and casing grooves remained in place. The newly redefined diffusers and return channels were designed by Howden in such a way as to minimize losses and to maintain the required operating range.
We achieved this by comparing the performance of the existing stages with the newly designed stages by baseline comparison method. Then, through Computational Fluid Dynamics (CFD) we compared the existing design against the optimised one as designed by Howden. Basing our options on this method, we were able to guarantee a minimum power saving of 3% – or more if possible – by reducing the losses, thus increasing the pressure recovery and relative efficiency of the compressor.
Despite having a tight schedule to deliver the service, Howden was able to deliver the newly designed diaphragms and existing rotors after coating to the plant two months before turnaround. This ensured the timely installation of the equipment during the outage. After start up, the customer did a performance test and concluded that the power saving was greater than guaranteed. That is, a 7% reduction in power costs. By believing in Howden’s unique solution, Berre Petrochemical Cluster was able to achieve a higher return on investment in comparison to the anti-fouling coating of the existing diaphragm that was initially requested.
Redesigning and upgrading the internals of the centrifugal compressors and their drivers will improve the efficiency and/or capacity while limiting the impact on the machinery’s surroundings.
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