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Projects aimed at improving distillation column operation may encounter a variety of hurdles. This article looks at ten common problems and provides guidance on how to avoid them.
project for improving the operation of a distillation unit typically begins as an idea, which turns into a proposal. There are many reasons for undertaking a distillation column revamp project, including: achieving higher capacity or better separation; debottlenecking; changing the feed rate or composition; improving water handling or heat integration; updating the control system; and repairing or fixing corrosion and metallurgy issues. Some major changes may have a project life of several years, while simple projects may take only months. Emergency changes during plant turnarounds may be measured in weeks or days.
The road from idea conception to improved operation is filled with bumps and potholes. This article discusses ten of the many issues that a project leader might face:
* incorrect estimation of project economics
* failure to account for long-term capacity needs
* changes in engineering personnel
* use of incorrect data in the process simulation model
* incorrect interpretation of the simulation model output
* failure to consider heat transfer in addition to hydraulic capacity
* limitations of existing equipment
* overdependence on vendors' and contractors' design capabilities
* lack of design reviews by subject matter experts
* incorrect installation of the new design.
1. Perform an objective economic reality check
All revamp projects must be justified based on the economics of demand for the product and/or the value of improved or more-efficient recovery.
When setting out to justify improving the recovery of a product, it is important to establish the correct basis for product values, including whether the product's value goes through cycles, for instance, based on seasonal demand fluctuations or economic swings. The justification must accurately reflect the yearly average values and reasonable projections of future values. For example, gasoline and heating oil values cycle between summer and winter. Many projects have been designed to optimize recovery of the most valuable products on a seasonal basis.
Incremental supply and demand cycles can be introduced by the startup of a new plant. For example, construction of a toluene dealkylation plant was shelved several times due to fluctuations in the demand for benzene....