(156a) Troubleshooting a Methanol Recovery Unit

New plants are usually designed for a stable operation meeting all the requirements of the plant operators. However, sometimes it happens that the plant does not operate properly anymore, for example, due to a change in upstream or downstream components and compositions or a change in load range. In this case, a troubleshooting is required to get the column operated again and to ensure product quality at the outlet.

In this context, one of our clients approached us, reporting unstable column operation and unsatisfactory separation of his methanol recovery tower. The tower is divided in two packed beds equipped with high-capacity structured packing made of stainless steel and has so far been operating without any issues. After a regular turnaround of the column, the column does not come back to a satisfactorily operating point. Therefore, a troubleshooting was carried out in close collaboration with the operational team and engineers of the client.

In this study, the different steps of our troubleshooting will be presented. Firstly, a comprehensive simulation study and sensitivity analysis has been carried out to be able to get a first understanding of the issue. Based on the simulation model, former and current column operation modes and set-ups are compared to detect the possible reason for male function. The simulation results show that the HETP of the bottom bed was much higher than initially expected during column design. In addition, when the column was opened up, the findings confirmed the results of our simulation study.

After identifying the root cause, a revamp is developed to get the column working properly again. A two-step revamp procedure is used to overcome bottlenecking of the column and even increase column capacity due to implementing elements of our high-capacity product line.

The study gives a comprehensive insight in the way forward of trouble shooting of distillation columns. The presentation will show the advantage of combination of process simulation calibrated with plant data, operational experience and customized engineering of high-capacity column internals leading to solutions to overcome process issues and increase column capacity.