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QRA Study and Building Risk study for Nayara VGO (Vacuum Gas Oil) Revamp

Thyssenkrupp Industrial Solutions has awarded iFluids Engineering to carry out Quantitative Risk Assessment (QRA) study for the VGOMHC Unit- Revamp project, Nayara Energy Limited at Vadinar in the state of Gujarat.

Vadinar is an all-weather deep draft port capable of handling very large crude carriers (3,00,000 DWT). Crude oil imported from Middle East, is discharged through a Single Buoy Mooring (SBM) stationed off the coaster site at a distance of about 5 km. An underwater pipeline transfers the crude to onshore storage tanks.

In revamp project the processing objective of VGO MHC Unit shall be to produce diesel product with sulfur< 8 ppmw, sweet VGO product with sulfur < 500 ppmw and meet minimum gross conversion of 45 % @ Diesel D-86 T95% - 360°C by processing a wide varying feedstock comprising of Heavy Gas Oils (SR HGO), Heavy Vacuum Gas Oils (SR HVGO) & Light Vacuum Gas Oils (SR LVGO) from crude units and Heavy Coker Gas Oils (HCGO) & Heavy Heavy Coker Gas Oils (HHCGO) from Delayed Coker Unit.

  1. High Pressure Section: VGO Mild Hydrocracking (MHC) Reactor section: Existing MHC contains 2 parallel reactors, each with 5 catalyst beds. As part of the revamp solution, a new third reactor will be added.
  2. Low Pressure Fractionation: Hot Flash liquid and Cold Flash drum liquid goes to existing stripper for removing H2S and other lighter Hydrocarbons. Stripper bottoms is sent to existing Fractionator after heating in existing fired heater. Naphtha, Kerosene and diesel are separated from Fractionator and bottoms is sent to existing FCC unit.
  3. Diesel Polishing section: Diesel produced from existing VGOMHC doesn’t meet BS-VI diesel specifications and will be upgraded in the new diesel polishing section.
  4. Other Equipment: Since H2 consumption after revamp increases, a new Heat Exchange Reformer (HTER) will be added in existing HMU-2 to produce more hydrogen from existing facilities. Shell arrangement is already installed in existing HMU-2 and only need to add a new HTER bundle in the HMU – 2.

This additional hydrogen needs to be compressed to required VGOMHC separator pressures using 2 stage new makeup gas compressor in parallel to existing compressors having 3 trains installed in DHDT unit.

The assessment will be based on the hazards that may occur during the operations of the project according to information available. The scope of work is limited to the different components associated with the proposed facility and revamp facility. The scope includes revamp of VGO MHC, new Diesel Polishing Section.

VGOMHC Revamp consists of 4 sections:

  • High Pressure Section: VGO Mild Hydrocracking (MHC) Reactor section.
  • Low Pressure Fractionation
  • Diesel Polishing Section
  • Other Equipment.

The main objective of QRA Study is to evaluate the potential risk levels for personnel due to accidental release of hazardous materials from loss of containment scenarios from the facilities and to demonstrate that individual risks are within the broadly acceptable regions.

QRA Study is followed by Building Risk Study.

The main objective of Building Risk Study is to evaluate the potential risk levels for buildings from loss of containment scenarios from the facilities and to assess the feasible working place. The Objectives of Building Risk Assessment Study are as follows:

  • Identification of Hazards and Major Loss of Containment (LOC) events
  • Calculation of physical effects of failure case scenarios which include Estimation of Jet Fire, Pool Fire heat radiation distances, Flammable gas dispersion distances, and overpressure explosion distances.
  • Building Hazards are evaluated based on exceedance results, LFL contour and toxic contour.

Recommend suitable fire proofing and blast proofing for buildings impaired by fire and explosion.

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