In this process, precooled natural gas is introduced at the bottom of the MCHE. As it rises through a long series of coil-wound tube bundles, a counter flow of subcooled multi-component refrigerant captures the heat from the natural gas, cooling it to minus 256 degree Fahrenheit. Liquefied natural gas then exits from the top of the unit.
The refrigerant exits the bottom of the MCHE in vapor form and is recompressed through a series of compressors and used to continue the cycle of heat exchange. "It works a whole lot like your air conditioner at the house," says Pate, "with a compressor, condensers and fin fans that are set up to displace the heat that is being extracted."
Two weeks after the arrival of the first MCHE, the first of three compressors for train one were also delivered. Weighing 530,000 pounds, the propane refrigerant compressor was equally challenging to rig and install (overall weight of compressor, electrical motor and associated items is 1,340,000 pounds).
These units will be paired with unique electric motors for operation. Developed by GE, these 100,000-horsepower, 75-megawatt motors are among the largest designed for liquefaction compression and will see their first operation at the FLNG terminal on Quintana Island. Gas turbines fueled by natural gas typically drive most main refrigerant compressors for liquefaction worldwide.
"It's a major milestone in our overall construction process," observes Pate. "A lot of safe work went into this, and I am very proud to be part of this organization. I am looking into the future... because this is the future."
Construction has advanced to the point at which many of the large, critical process components have begun to arrive on site. One of the most imposing is the MCR® MCHE (Multi-Component Refrigerant Main Cryogenic Heat Exchanger). Not only is it a towering piece of process machinery— measuring 164 feet in height and 15 feet in diameter, with a total estimated empty weight of 713,630 pounds—but its role in the liquefaction facility is crucial.
Delivering a component of this size and complexity is a fascinating story itself. The facility's MCHE units are designed and manufactured by Air Products and Chemicals, Inc. (APCI) in Wilkes-Barre, Pennsylvania, and in Port Manatee, Florida. Once completed at the APCI facility, the MCHE is put on a transport trailer and trucked to a barge that will bring it down the Intracoastal Waterway to the Port of Freeport. Its final stop is the custom-built construction dock at the FLNG terminal on Quintana Island.
"We offload it onto an SPMT (self-propelled modular transporter) and remove it from the barge," explains FLNG’s
Operations and Maintenance Readiness Manager Robert Pate. "They'll do a wash of the exchanger itself with fresh water to get the salt spray off that collects during transit."
Then, slowly and carefully, the MCHE is transported by the SPMT from the dock to a position as close as possible to the foundation where it will be permanently set. Crews prepare for the lift and positioning by starting their rig-out work for the dual cranes that will be used. This means ensuring that the cabling produces a safe balance for a nearly million-pound load.
From its horizontal position, the cranes—one connected mid-height and the other to the bottom base plate—lift the MCHE from the trailer, which is driven from underneath it. The cranes work in concert to orient the MCHE into a vertical alignment. The bottom cables are removed, and the remaining crane swings over and sets it onto the baseplate connections on the foundation. This process takes several hours during which crews carefully monitor weather conditions, including wind speeds and storm conditions, throughout the lift.
After bolting the MCHE to the foundation, it is connected to the process plant piping. The unit is completely self-contained. Much of its immense weight is due to the nearly 1,500 miles of small-bore tubing enclosed within its shell. When it is operational, it becomes the heart of the liquefaction process.