Gain Deeper Insights Into Your Distillation Column Operations
Distillation columns are critical pieces of equipment for many process industries, especially oil refineries. When refinery operators observe issues with their column operations such as column weeping and flooding, they typically resort to what they have learned from their past experiences to relieve the situation. These ad-hoc methods are available only to those operators who have had years of experience with that unit. Furthermore, these operational tweaks may only provide temporary relief and could lead to non-optimal functioning of the broader process unit. In addition, the lack of insight into the internal operations of the column forces refineries to operate columns very conservatively to meet product specifications. This situation causes additional energy to be consumed in reboilers and reflux condensers, increasing costs.
The ideal solution to this problem sheds light on the root cause of operational issues without requiring a unit shutdown or expensive physical inspections.
There are even more benefits if that solution offers visualization into the operating point of the unit. Visual presentations can be very effective when process engineers want to communicate their analysis to operators and plant engineers. In addition to visualization capabilities, engineers can use the same solution to predict the impact of alternative courses of actions and select the most optimal. In other words, this approach brings intelligent insights to operators, helping them maintain optimal operation while considering thermodynamic and hydraulic limitations.
This solution calls for an integrated process simulator that can accurately simulate the hydraulics of the column unit. The challenge with many types of process simulation software is that they do not have the necessary rigor to provide enough information on column operations. This rigor is needed to give the process engineers the confidence to suggest effective operating decisions. Without it, engineers have-to conduct their analysis through the tedious workflow of switching back and forth between separate software tools for process simulation and column analysis.
Process simulation software, like Aspen HYSYS enables users to accurately simulate thermo-hydraulic functioning of columns based on their construction and operating conditions. As a result
, users can better understand the behavior of their columns and avoid operational mishaps. Simulating the operation of the column unit in the broader setting of the overall process lets users identify root causes and figure out the optimal point of operation for the whole process unit. Moreover, the visualization tools can provide insight into the operating point of the column and impending breach of operational limits causing issues such as jet flooding, weeping, down-comer backup and others. This capability provides refiners with the confidence needed to optimize column capacity and operate columns closer to the limits.
This capability allows refineries to build up a work culture of continual process optimization and preventive maintenance by taking advantage of advanced process simulation technology.
Tüpraş, Turkey’s only oil refiner, was experiencing problems with a naphtha splitter column that did not consistently provide on-spec products to downstream units. With a turnaround coming up, engineers wanted to explore changes to the column and surrounding equipment to improve its efficiency. Engineers set out to monitor the performance of the column, confirm insufficient separation, verify cause, and identify changes to increase capacity. With Aspen HYSYS V9, they were able to confirm that the overall efficiency is 50%, instead of the expected 70-75%, and that flooding was to blame. The engineers created a plan to switch out the trays in the column to reduce the weir loading and the head loss under the downcomers. They also verified that the heat exchangers serving the column could accommodate the changes without problems. As a result of the revamp to the column trays, Tüpraş expects to see the available capacity to increase by 40% or 15% reduction in utility consumption at current capacity with on-spec naphtha production at both cases.
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