Selecting the Most Time-Saving Chemical Decontamination Approach
Welcome to Part Three of Becht’s four-part series on chemical decontamination in refinery turnarounds. Our teams have seen firsthand how effective planning and the right chemistry make a measurable impact on turnaround performance. This series shares practical insights from real projects and highlight approaches to help refineries achieve safer, more efficient shutdowns. Read Part One here and Part Two here.
Which decontamination approach will save refineries the most turnaround time?
This question can only be answered by looking at the scope of work in great detail and identifying the best chemical approach for each circuit – whether a combination of vessels, exchangers, or columns. There is no “silver bullet” chemical that will do everything, despite what many chemical decontamination companies claim. Plus, every refinery is different!
The “best” chemical approach will be determined by the expected contamination – sometimes based on the experience of refinery personnel, sometimes on the chemical decontamination contractor’s experience at other sites with similar fouling or contamination. In some cases, there may even be analysis of fouling or contamination from the previous turnaround to provide guidance.
As described in the first article of this series, there are certain critical contaminants that will dictate a preferred chemical approach, and the contractor will propose whether to vapor phase a piece of equipment or wash it, in broad terms. In many cases, a combination of vapor-phase decontamination and washing can be applied simultaneously for optimum results.
Vapor-phase decontamination
In recent times, people have reported entire process units being decontaminated by a single vapor-phase procedure, which apparently generates significant time – and probably cost – savings for the refinery. The vapor phase itself can be steam, though a recent innovation uses hydrogen. However, I rarely read about how much cleaning was required to remove solids once certain vessels were opened. Was this factored into the time savings quoted? I am definitely not against vapor phase as an approach, and have used it myself, very successfully, on many occasions. I just cannot see how it removes solids, especially from locations such as chimney trays in a distillation column.
If the objective is simply to “gas-free” a column or vessel, particularly on light hydrocarbon sections of a process unit, then vapor phase delivers great results in as little as eight hours. It requires less equipment than washing and is easier and faster to set up before the turnaround starts. Thus, it makes sense to apply vapor-phase decontamination in as many areas of the process units during a turnaround as possible to save time.
Washing procedures
On columns and in vessels where past turnaround experience clearly shows that there will be sludge or solids, I believe a washing procedure is advisable. Correctly applied, it will avoid the need for confined space entry to remove solids when the vessel or column is opened. This, along with the achievement of gas-free, H2S-free conditions, can provide rapid, safe access for mechanical contractors to start work, all of which delivers time savings for the turnaround.
It is also necessary to use demineralized water for certain process systems, where chloride stress corrosion may be a concern for the client. The washing formulations I am familiar with all work just as well with demineralized water as with industrial water.
Yes, washing generates more effluent and more temporary storage requirements. However, correctly managed and with temporary equipment suitably located, the effluent will not create any delays for the turnaround. Indeed, it has been demonstrated on some refinery turnarounds that it is possible to a) reuse some “spent” solutions on a second system or circuit, saving the cost of fresh chemical, and b) treat the decontamination effluent to remove hydrocarbons down to <0.01% in the water, allowing the water to be reused on another, new circuits during the same turnaround. In some parts of the world, this significant savings in water consumption can be a major factor. This latter aspect illustrates that it is possible to treat spent solutions and safely allow disposal via the refinery effluent treatment plant.
Finally, a word on coke. Thus far I have not found a reliable way to chemically remove coke from refinery units, whether in an FCCU, the bottom of a vacuum column, or a visbreaker. I am aware that there are contractors who say they can do it – I just have not seen it for myself or spoken to a refinery contact who says, “Yes, I have seen the results!” What I do know is that certain chemistries are very good at penetrating the microporous structure of some coke types and removing the resins that have not yet fully carbonized, which renders the coke quite friable in many cases. This means that they are susceptible to fracturing and being washed out of the system, which in turn can reduce water jetting time. This is the default approach for most sites.
I will not get into which decontamination chemistries are best. There are now so many chemical decontamination contractors out there, globally, that I probably do not know them all anyway! As a colleague recently suggested: where there is the opportunity to obtain samples of foulant, either get the potential contractors to test their formulations against those samples, or run tests within the refinery yourself.
In the final part of this series, I will move from theory to practice by sharing real examples of how well-planned chemical decontamination has delivered measurable time savings and safety improvements across different refinery units.
If you would like to discuss how Becht can help you plan or optimize chemical decontamination during your next turnaround, contact us anytime to start the conversation.
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