PTQ Q3 2023 Issue

Focused revamp increases diesel and HVGO recovery

Refiners have the best opportunity to maximise return through identification of creative solutions during a focused capital revamp

Scott Golden, Tony Barletta and Steve White Process Consulting Services Ben C Miller CITGO

C ITGO Petroleum Corporation’s Lake Charles Refinery started up its Crude Vacuum 1 (CV1) unit revamp in 2020. The revamp recovered more than 11 kBPD of incremental diesel from FCC feed and reduced vacuum residue (VR) yield by 5 kBPD while concurrently increas - ing the capability to process refinery gasoil (RGO) and excess atmospheric residue (AR) from other crude units in the refinery. Vacuum column HVGO product TBP cutpoint increased from 960 to 1,060°F by lowering vacuum column operating pressure, increasing heater outlet temperature, and improving stripping section efficiency. No additional fuel gas was needed for atmospheric or vacuum heaters, and steam consumption decreased by more than 37,000 lb/hr. No new equipment services were added; exchanger services were repurposed to allow column heat balances to be adjusted to yield higher value product and increase heat recovery to oil feed streams. CV1 is an integrated crude vacuum unit. It was originally designed to process heavy bitumen crudes with deepcut vacuum unit operation. The vacuum unit was sized to pro - cess excess refinery AR, which was being processed in the coker, as well as other crude unit RGO to improve over - all refinery diesel yield (see Figure 1 ). When the unit was

built, the vacuum system, column, and associated equip - ment were some of the largest in the world. World-class equipment sizes often introduce another layer of design complexity. For example, designing a fractionation section liquid distributor in a 38 ft-diameter column section is very different mechanically compared with a typical distributor used for more frequently encountered diameters. Uniformly distributing an inherently low liquid rate (less than 1.0 gpm/ ft 2) to fractionation beds is essential to maximise vacuum diesel yield, but realising it is difficult at world scale. Prior to the revamp, the vacuum column operating pres- sure would increase to more than 50 mmHg absolute during the summer. Even though the pressure was lower during cooler months, it was still above original design pressure, and HVGO recovery suffered. A thorough vacuum system troubleshooting effort was done to identify the root cause. Poor first-stage inter-condenser performance was the root cause of high operating pressure. As part of a baseline unit evaluation, profitability improvement opportunities were framed for CITGO’s refinery leadership team to consider. Once this work was completed and opportunities prioritised, a feasibility study was completed to better develop scope options and firm up the cost/benefit analysis. Ultimately, a

Slop oil

LVGO

Diesel

RGO

MVGO

Atmospheric column

Hydrocracker or FCC

HVGO

FCC

LGO

Atmospheric heater

HGO

Preheat

Hydrocracker

Crude

Vacuum column

Renery AR

Coker feed

Vacuum heater

Preheat

Figure 1 CV1 block flow diagram

PTQ Q3 2023