Troubleshooting and Customized Engineering at the Limit

Abstract

State-of-the-art design know how combined with specific process experience allows to design column performance and capacity more and more to the limit. This is achieved by reduction of safety margins and the use of customized column internals. On the other hand however, there is a trend towards higher inaccuracies of column shells and dimensions of column attachments (“out-of-tolerance”) as well as lower qualified installation workforce. The trade-off between invest and quality is often dominated by short-term economic considerations. The resulting problems then have to be solved during installation and typically in an extremely tight time-schedule.This paper presents different field experiences that RVT-PE encountered in this context and explains the solutions that were developed. In this example, high support ring tolerances - that were only detected after the trays were installed – led to unacceptably high inclination of many trays in a column. The standard way of repairing uneven trays is very time and cost consuming, due to the fact that the trays have to be partially or fully disassembled. RVT-PE has designed a new, time and money saving solution, with which the sagging of trays is rectified and the unevenness of support ring is corrected. In column test runs of a trough type liquid distributor, a client detected extreme splashing at the inlet and in consequence poor distribution quality. The reason was a too small inlet nozzle and therefore very high liquid velocities. As changing the nozzle size wasn’t feasible, the distribution system had to be optimized to eliminate the negative effects of the high inlet velocity. Additionally the optimized distribution system had to fit to the constricted area in the column. RVT developed a novel liquid distributor for a vacuum column for crude oil distillation. This distributor combines the insensitivity against coking of a spray nozzle distributor with the low liquid entrainment generation of a line distributor.