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Too much grading – not enough benefit from your bulk catalyst
Conversely, with the kinds of feedstocks that many refineries now have to deal with, e.g. renewable feedstocks or opportunity crudes, featuring large amounts of contaminants difficult to deal with, we see a growing tendency to use more and more grading as a protective measure.
But if you use too much grading, you’ll end up missing out on the full potential of the unit, as the excess grading material takes up the space from the bulk catalyst.
Your grading load should help you:
- Provide a stepwise increase in activity to control the hydrogenation of more reactive components present in the feed
- Make sure all feedstock contaminants are removed
- Make sure any corrosion products from upstream equipment are removed
- Control exotherm
- Prevent catalyst milling
- Prevent crust formation
- Prevent pressure drop problems
Finding the right balance for your exact needs
If you are processing an easy straight run and there are no obvious corrosion issues, there is no reason for grading material to take up space that you can put to better use for the workhorse in your reactor – the bulk catalyst.
In order to get the maximum cycle length out of your catalyst loading, the right balance between bulk catalyst and grading is crucial. If too little grading is loaded, the cycle will be shortened by premature catalyst poisoning or too high pressure drop (top). If too much grading is loaded, the unit will be limited by activity of the bulk catalyst before the grading capacity has been fully utilized (middle). With the right balance, you obtain the optimal (bottom).
It’s all a question of balancing the specifics of your operation’s particular feedstocks, budgets, practical challenges, and operating profiles. Our aim is to enable you to maximize catalyst cycle length and make sure the pressure drop across your reactor doesn’t limit throughput until the activity of the bulk catalysts has reached the scheduled End-Of-Run (EOR).