Siemens drives power compressors for Qatargas LNG |

Siemens drives power compressors for Qatargas LNG

July 9, 2009 – Siemens Energy and Automation recently participated in the successful completion of a liquefied natural gas (LNG) compressor train for the Qatargas 2 project, the world’s largest onshore natural gas liquefaction train. The LNG train uses Siemens Perfect Harmony Variable Frequency Drives (VFD), which are crucial to the safe liquefaction and efficient transportation of LNG.

Qatar is home to one of the world’s largest reserves of natural gas, the cleanest burning fossil fuel. Qatargas 2 will facilitate the transport of Qatar’s natural gas to customers all over the world. In order to ship the natural gas to customers in Europe, North America and Asia, the gas must be compressed and liquefied then transported on trains to the waiting tankers.

Siemens Perfect Harmony 45-megawatt Variable Frequency Drives are used on the main refrigerant compressors in the train. Siemens director of project systems Huw Carey explained how Siemens variable frequency drives play a key role in the gas liquefaction process.

“The variable frequency drives start a motor generator that powers the gas turbines and gas compressors used to process the gas for transport.”

In addition to starting the gas turbines, Siemens variable frequency drives also help the gas turbines run more efficiently while the train is operating. The quantity of power generated by the gas turbines is dependent on the air temperature. During the winter when the air is cool, the gas turbine can at times generate more power than the compressors need. The Siemens variable frequency drives are able to direct this excess energy via the motor (acting as a generator) back to the electrical grid to improve overall energy use. In the summer, hot temperatures make the turbines operate less efficiently. To counterbalance this effect, the Siemens variable frequency drive can provide up to 45 megawatts of additional power to the compressor train to keep operations running smoothly.

Siemens variable frequency drives were also selected for the project because of their high reliability. The Siemens Perfect Harmony Variable Frequency Drive’s cell bypass feature enables continued operation even during the unlikely event of a component failure. The Siemens Perfect Harmony Variable Frequency Drive also has the best electrical waveforms on the market, providing superior smooth rotational performance of the compressor and the highest waveform quality into the Qatar electrical grid system. This greatly reduces the harmonic distortion that can negatively affect electrical grid performance.

“The Siemens global team who worked on this project has helped create history in the LNG world by designing, developing and commissioning critical equipment for this application,” said Anne Cooney, vice president of the Power Conversion Division, Siemens Energy & Automation. “This five-year project is a historic milestone for Qatargas, our project team and Siemens employees in the United States and around the world.”

About Siemens
Siemens Energy & Automation, Inc. is one of Siemens' operating companies in the U.S. Headquartered in the Atlanta suburb of Alpharetta, Ga., Siemens Energy & Automation, Inc. manufactures and markets one of the world's broadest ranges of electrical and electronic products, systems and services to industrial and construction market customers. Its technologies range from circuit protection and energy management systems to process control, industrial software and totally integrated automation solutions. The company also has expertise in systems integration, technical services and turnkey industrial systems.