Natural gas is the cleanest burning fossil fuel. It produces less emissions and pollutants than both coal or oil. The North American supply basins are maturing and as demand for natural gas increases in California and throughout the United States, alternative sources of natural gas are being investigated. Natural gas is available outside of North America, but this gas is not accessible by pipelines. Natural gas can be imported to the United States from distant sources in the form of LNG. Since LNG occupies only a fraction (1/600) of the volume of natural gas, it is more economical to transport across large distances and can be stored in larger quantities. LNG is a price-competitive source of energy that could help meet future economic needs in the United States.(1)
Southern LNG, a business unit of El Paso Corporation, operates the Elba Island facility near Savannah GA. The Elba Island facility is one of seven LNG terminals in the USA. The plant, built in 1973, receives imported LNG, which is gasified at the plant and placed into the US natural gas transmission and pipeline system. LNG is stored at minus 261 degrees F at atmospheric pressure in double walled storage tanks. The LNG naturally boils-off, some of which is used for fuel gas and some is captured and re-liquefied, and injected back into the storage tanks. LNG is safe in its liquid state but temperatures and pressures must be maintained within close tolerances. If utility power is lost, the plant must vent the boil-off LNG vapor.
To prevent this scenario, the plant has 2x Cooper-Bessemer LSVB PG units and 2x Solar Turbines PG units for emergency/stand-by power at the plant. Each of the units produce 2.8 MW of power. The Cooper- Bessemer LSVB-12 PG units drive 2.8 MW Ideal generators at 4160 VAC connected to the plant’s medium voltage switchgear and distribution system.
As the existing control systems had became obsolete, the United Controls Group retrofitted both LSVB engines/ generator control systems with current state of the art Allen-Bradley PLC systems. Engine control is performed by the A-B CompactLogix processor, providing start/stop sequencing, performance monitoring, and engine protection. Generator control and monitoring is by an Allen-Bradley CGCM. Engine speed is by a Woodward governor and Woodward actuator with a mechanical linkage to the gas fuel valve. An Allen-Bradley PanelView Plus is used for visualization of the system, and annunciation of the system events, alarms and shutdowns. All system events are time/date stamped and system variable are available for data logging and trending. The existing Altronic CPU-2000 ignition system was re-used.
UCG engineers developed the control system software in full compliance with OEM standards. Load acceptance and load rejection tests were accomplished at site, with all results showing extremely stable operation during all transient load conditions. The unit starts/stops reliably now and the customer is extremely satisfied with UCG’s performance.