2 replies to this topic

[jigs1980]

What is the key properties for the torch oil?
Can we use any light diesel/Light Cycle oil type hydrocarbon as a torch oil? if not...what is the reason?
If our DFAH is not able to rise the temperature up to 350 Deg C. Can we line up torch oil (Like LCO/LDO etc...)

[suhas]

In principle you can use LCO/ HCO as torch oil, the only difference is in the economics, as light end fractions are generally costlier compared to heavier ends. LCO is costlier than HCO.

you can line up torch oil to raise the temperature, just ensure that bed temperature is sufficient so that oil can burn.

[Himanshu Sharma]

Sir

Kindly confirm that whether you are trying to run FCC under CRO mode !

Catalyst recirculation (CRO) mode is used to allow quick start-ups of FCC after short shutdowns. CRO consists in keeping the catalyst circulation by maintaining vapor lift injections upholding high enough catalyst temperature substituting FCC feed by torch oil (LCO or Straight run gas-oil).

CRO impacts on feed injection rate, regenerator temperature and reactor temperature. During CRO, the unit fractionation part is only used to condense and separate the vapor lift coming from the reactor. Vapor lift comes through the main fractionator and then condenses in the fin fan air coolers; the water formed is collected in the reflux drum.

• If this is not the case

Getting back to basics ,any gasoil can be used as Torch oil provided it ignites at the injection points (Injection Nozzles).Torch oil that does not ignite at the injection points in the dense Catalyst bed will pass into the upper zones of the regenerator, i.e. cyclones, and overhead system, where it may ignite, possibly even explode, with obvious undesirable consequences.

This is what shall be taken care in your case,Generally, the lighter the oil, the higher is its ignition temperature !

There are certain 'Do's' for torch oil injection in the system

• Adequate Depth of Dense Phase of catalyst over Torch Oil Nozzles for heat dispersion,typically 6ft plus works alright.
• Temperature of Dense Phase shall be above ignition temperature of Gasoil.
• Properly Designed Injection Nozzles with atomization steam.

Hope this Helps !