MAN B&W ME-C series for LNG Carriers. Demonstration plants
One test plant for the Moss Reliquefaction System (Moss RS) is located at the Ukrainian company Sumy Frunze located in Sumy, Ukraine. The Moss RS patent holder, Moss Maritime of Norway, is responsible for this plant. It comprises a pre-treatment plant and a liquefaction plant. Gas is supplied from the local gas grid, and a large pre-treatment plant is used for delivering gas over a wide specification range.
The purpose of the test plant is to verify all technical aspects of the reliquefaction concept, in particular:
- Demonstrate the nitrogen Brayton cooling cycle
- Test the operating procedures
- Control system development
For another demo plant, Hamworthy KSE was awarded the contract by the Norwegian gas distribution company Gansor in October 2001. The LNG production capacity is 60 ton/day (2500 kg/hr), which corresponds to boil-off rate on traditional size LNG carriers. This plant uses the same type of cooling cycle (Brayton) and control principles as the reliquefaction system for LNG carriers. The same 3-stage N2 compressor with expander and the same type of cold box that will be used on LNG C are also installed.
However, as the plant is onshore and the feed gas comes from the gas pipelines from the offshore fields in the North Sea, this plant needs additional equipment and systems.
The plant consists of the following basic parts:
- Natural gas dehydration unit
- Natural gas CO2 removal unit
- Nitrogen cooling circuit (same as proposed for LNG carriers)
- Main liquefier (cold box) with LNG receiver (similar type as proposed for LNG carriers)
- LNG storage tank and truck loading station.
Natural gas from the high-pressure feed line is reduced in pressure down to 120 bar and dehydrated down to a H2O content of 1 ppm. The dry feed gas is further reduced in pressure down to 52 bar prior to removal of CO2 down to a level of 50 ppm.
Liquefaction is accomplished at about 50 bar against cold nitrogen gas, which is cooled in a single-expansion cycle with three compressor stages and one expander stage.
The heaviest gas fractions are separated out and the gas liquefies in the lower-mid section of the cold box. The liquid is sub-cooled in the bottom section and led to the LNG flash drum via a valve, where the pressure is reduced to 0,5 bar, and the LNG is sent to a storage tank. The system is equipped to give a variable production rate by adjusting the mass flow of nitrogen.
The first LNG was produced o this plant on March 15, 2003.