Mantaining Optimum Process Trains Operation Mode to Achieve Specified LNG Product Quality during Feed Gas Entrance

Badak LNG Plant, designed to process rich feed gas, is currently facing operational challenge due to leaner feed entrance. This condition is causing a decrease of the LNG heating value (HHV) below the LNG sales contract specification. As a countermeasure, some amount of LPG were reinjected to the feed gas stream to maintain the LNG product quality as specified.

In order to optimize LPG consumption for this purpose, some improvements have been implemented. One the effort is separating process trains operating mode to produce two LNG qualities, known as dual HHV mode. Rich LNG (HHV ≥ 1,107 btu/scf) is produced by Rich Trains, while lean LNG (HHV < 1,107 btu/scf) is produced by Lean Trains.

Implementation of dual HHV mode has been optimized by increasing feed gas temperature inlet Scrub Column of Rich Train to enhance C2+ content at top product, setting the LNG product temperature warmer in order to increase LNG's HHV, and transferring propane product from Lean Train into Rich Train through existing propane interconnecting line.

Meanwhile, Lean Trains have been optimized to enhance C₃ and C₄ extraction by decreasing feed gas temperature inlet Scrub Column in order to extract more C2+ from bottom product of Scrub Column and increasing temperature of Debutanizer to increase C₄ production. Thus, more C₃ and C₄ product can be transferred to increase LNG's HHV of Rich Train.

By conducting several optimizations in Lean Train and Rich Train, LNG product quality can meet the specified quality and LPG consumption can be reduced significantly with a saving of approximately 80k USD/day.