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  • Our Vacuum gas oil hydrotreater feed blend has got three feeds,  Light Vacuum Gas Oil/Heavy Vacuum gas oil from VDU & Heavy Coker gas oil from Delayed coker unit (Blend distillation IBP to FBP in the range of 260 to 600 degC and specifically Temperature to distill 5% volume is approx at 350degC). After hydrotreating, in the fractionation column we draw Diesel and Naphtha. As the feed doesn't contain Naphtha and Diesel cuts specifically & being hydrotreater but not hydrocracker, how does generation of Naphtha and Diesel in the fractionation column is happening (Both product streams combined Approx 14%)? Is it purely by thermal cracking at the hydrotreater conditions of Vacuum Gas Oil? How should I understand this?

    Jan-2023

Answers


  • Madi ASIRI, SATORP, Madi911@hotmail.com

    The yield lose in the VGO HDT unit is something not up normal. The products below (370) yield is function of the reactors section operating conditions (WABT, LHSV and H2 PP)

    The bi-function catalyst (mainly NiMo) in VGO HDT will have the ability to hydro-crack the VGO/HCGO feed.

    10-15% yield lose is normal. In the HDT where the operating Temp is below 420 degC, the thermal cracking is very remote. Some, you can adjust your reactors to lower the yield of DSL and Naph.

    Jan-2023

  • Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

    Despite being a Residue Hydrotreater, it's possible to carry out some cracking reaction in hydrotreating units under some operating conditions. It's important to remember that thermal cracking reactions are favoured by high temperature which is normally the case of residue hydrotreaters specially in the end of operational campaign.

    Furthermore, some references quotes that can be observed conversion rates varying from 10 to 20 % of the feedstream for hydrotreaters while is expected conversion rates between 20 to 50 % for mild hydrocrackers and above 50 % to severe hydrocrackers, considering these parameters and the information from the question the condition can be considered "normal" at at a preliminary analysis.

    Despite this, please consider to check the severity conditions of the processing unit (especially the temperature and interbed quench strategy) aiming to identify operating conditions which can favours the thermal cracking reactions.

     

    Jan-2023