BOG Compressor Systems 

Cleverly Designed Concept for Zero Emission

 

The second substantial business segment for NEUMAN & ESSER directly following refinery processes is offshore applications. The references for this segment are equally numerous and international. This includes vapor recovery on drilling rigs in the Gulfs of Thailand and Arabia, seal gas pressure for turbo compressors on the deck of the floating natural gas platform (FLNG) Prelude in Australia or flash gas compression for increasing pressure during natural gas production on a platform in Indonesia. The fact that LNG has long since gained momentum at NEUMAN & ESSER is also proven by the NEA send-out compressor on the FSRU system for the reconstructed LNG tanker Explorer, anchored in Dubai.

Depending on the onshore and offshore application, NEUMAN & ESSER has three compressor types for LNG in its portfolio: the BOG compressor, the send-out compressor and the fuel gas compressor.

Currently, the NEUMAN & ESSER cryogenic BOG compressors are enjoying great popularity in Russia. In addition to the delivery of the gastight type 2TZS25-GT, another type 2TEV1-GT machine has already been running to the operator’s utmost satisfaction for one year. A further large BOG compressor system will still be installed this year at an LNG terminal. The three-stage construction size 300 compressor for this system has the task of compressing the liquid natural gas received through the pipelines and heated to boil-off gas via environmental influences. The average inlet temperature is -140°C.

The system design foresees that the powertrain including the compressor is placed on a foundation whilst the containers and oil system are respectively skid mounted. The instrument rack with panels is also placed on its own footing. The local end user has ordered two BOG compressor systems directly, in order to ensure 100% operation. One of them is redundant and will remain in “hot standby” mode. This makes preheating the oil or cooling water unnecessary for starting up.

The technical specifications of these BOG compressors include continuous flow control and a gastight crankcase in NEA design. The scope entails the use of crankshaft mechanical seals as well as a connection from the crankcase to the suction side. This prevents natural gas from escaping into the atmosphere. Temperature controls for the 1st stage optimize flow of process gas through the air cooler. “That not only saves pressure - but primarily also quantity loss - a clever concept!“ as Dirk Walenta, NEA Deutschland Project Manager says. Nonetheless, the cooler is already required after the 1st stage if the compressor is expected to startup again after a planned shutdown with the heated gas. After the 3rd stage cooler, the natural gas is fed to the grid.

“If the maximum gas tightness in the compression chambers is required, we use our contact ring design for LNG”, according to Guido Harsch, Area Sales Manager. Its advantages are fewer leakages and lower power consumption. “Alternatively, we offer contactless sealing piston rings and a packing system with an additional piston rod guided via slide bearings. As always – our customer can choose!“

(Kopie 6)