Marine Vapor Recovery System

Loading Displaces Vapors

During loading of bulk liquid tankers or barges, the liquid introduced displaces vapors from previous cargoes that still exist in the tank and those vapors generated by the current cargo loading. The vapors of certain cargoes contain volatile organic compounds (VOCs) that include hydrocarbons, oxygenated hydrocarbons, and organic compounds containing nitrogen or sulfur.

Chevron MVR System meets federal requirements

The Clean Air Act of 1990 requires the control of VOC emissions, and the Marine Vapor Recovery units at the refinery’s marine facility meet Coast Guard (Title 33, Code of Federal Regulations, Part 154) and Clean Air Act (Title 40, Code of Federal Regulations, Part 61 and 63) requirements.

The Pascagoula Refinery’s Marine Vapor Recovery (MVR) system includes two units that serve Berths 2-5 and a separate unit at Berth 6, which is located a good distance away from Berths 2-5.

MVR at Main Product Dock (Berths 2 - 5)

• Units "A" and "B"; each with 35,000 barrels liquid loading per hour vapor recovery capacity; combined vapor recovery capacity 70,000 barrels per hour of liquid loading.
• Recovers vapors from VOC emissions containing vapor pressure of 1.5 psi or greater.
• The process uses Lean Oil Absorption. While a regulated product is being loaded, vapors are recovered from the marine vessels by a header system. This header carries the vapors, either by pressure from loading or pulled by vapor boosters that provide a slight vacuum on the header. The vapors are routed through a chilled absorber, entrained in the Lean Oil, then passed through a series of exchangers, and then into a stripper column where the VOCs are stripped out by heat and held in a holding drum. The recovered VOCs are then pumped in to a crude transfer line for reprocessing.

MVR at Berth 6

MVR at Berth 6 provides vapor recovery for Berth 6 only and has vapor recovery capacity of 8,000 barrels per hour of liquid loading. Like its sister unit at the Main Product Dock, this unit uses the Lean Oil Absorption system, but does not feature the vapor boosters. This unit recovers vapors from special products and chemicals including Penhep, Hydrobate, Heptane, Hexane, Penhex and Straight-run (or unblended) gasoline.