In one of our FCCUs we have problems closing heat balance due to the processing of a very hydrotreated feedstock. We have to use torch oil (LCO or fresh feed) to maintain regenerator at its minimum temperature.
We are evaluating the possibility of using other feedstock as torch oil. Has anyone experience in using fuel gas or natural gas as torch oil in the regenerator? What major modifications in hardware are required?
Answers
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12/06/2016
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Chayan Bhalla, Mangalore Refinery and Petrochemicals Ltd, chayan.bhalla@gmail.com
Torch oil firing in regenerator is a known source of potential problems like catalyst sintering, catalyst attrition and high localized temperatures leading to refractory damage and hot spots. If the heat balance is not closing, one viable option could be to reduce the severity of your feed hydrotreater. This will slightly increase nitrogen and poly-ring aromatics (tetra aromatics) in the FCC feed, which are known to be coke precursors. You may also contact your catalyst vendor to supply a higher catalytic coke catalyst. Slurry from fractionator bottom can also be recycled to reactor bed area for increasing the coke make. These actions may significantly reduce or even eliminate torch oil depending on the FCC process conditions and feed quality.
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13/03/2013
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keith bowers, B and B Consulting, kebowers47@gmail.com
The first premise on an FCC is: Get the cracking reaction right, then work the heat balance.
In your case, additional feed pre-heating might be in order if the cat:oil ratio is higher than optimum, resulting in low carbon on cat to the regenerator. However, if the cat:oil ratio and riser temperature are at yield optimum and the conversion reactions are right, adding heat to the regenerator requires 'torch oil'. Usually the lowest value material (slurry, HCO) is used because of economics since this is just fuel. I don't see anything preventing a gaseous fuel instead.
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