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Air Separation

We appreciate the extremely compact design of the xEnergy switchboard system.

Peter Lochmann, plant manager of the Gablingen air separation plant of Linde AG

Background

When Lithuanian intelligent engineering solutions company Fima won the contract to modernize the signaling and power systems along a key 112 km Trans-European rail freight corridor, the company chose Eaton medium voltage (MV) equipment as the basis of the power system upgrade.

With well over 60,000 employees worldwide, the Linde Group is one of the leading gas and engineering companies. At its Bavarian plant in Gablingen, Germany, the company separates and liquefies oxygen, nitrogen and the noble gas argon from the air. These are used for applications in industry, medicine, and the food and beverage sector. The lowvoltage main distribution system consists of Eaton xEnergy switchboard systems and remotely monitored NRX circuit-breakers.

In order to separate gases from the air, a thermal separation process such as rectification is used. This method is based on the inventions of Carl von Linde, the founder of the present day Linde AG. As far back as 1902 he introduced it in the world's first industrial application. Rectification is synonymous with the principle of countercurrent distillation. This special separation process enables the individual components of a compound substance to be extracted with a high degree of purity and a good yield, even with relatively similar boiling points.

A so-called double column unit is used for this at the Gablingen plant of Linde AG: Evaporator and condenser, the process intersection of the countercurrent distillation are combined in a heat exchanger unit. It divides an approximately 20 meter high cylinder into two rectification columns that operate at different pressures. These produce gaseous and liquid oxygen (GOX and LOX) and nitrogen (GAN and LIN). At the so-called "Argon belly", a point in the low pressure column at which the argon concentration reaches a maximum of around 4 percent, a gas flow is diverted for further rectification in the raw argon column: Here the remaining oxygen and remaining nitrogen are removed and liquid argon (LAR) extracted at a high level of purity.

Challenges

In order to separate air into its component parts through rectification, part of the air volume used has to be liquefied. This is a very energyintensive process since the air has to be cooled to at least -172 degrees Celsius at a pressure of 5 bar. Multi-stage compressors and large expansion turbines with several megawatts of refrigeration power make this possible. "Around 13 megawatts of electrical power at full load, as much as a small town of 35,000 inhabitants, are required for this by the Linde AG plant in Gablingen," explains Peter Lochmann, plant manager of the Gablingen air separation plant of Linde AG.

Solution

The low-voltage power distribution at the Gablingen plant was modernized in 2010. The 400 V system supplies all plant equipment and utilities with electricity, such as the cooling water and auxiliary oil pumps, the large cooling tower fans, and the office buildings. "It is planned for the Gablingen plant to be connected in future to the Remote Operation center at the largest gas production facility of Linde AG in Leuna, Germany," Peter Lochmann describes the initial situation. He continues: "This meant that our existing switchboard system had to be renewed as it could not be remotely controlled." As a result, Linde AG assessed the products of various manufacturers and finally chose Eaton's type-tested xEnergy modular system. "We have been using the products of this manufacturer for several decades, value their high availability and have had a good experience with them," Peter Lochmann explains the decision.

The low-voltage power supply is implemented redundantly with two 1.6 MVA block transformers connected via coupling switches. Normally both transformers are run at partial load on the grid, however, each one can supply the plant's total power requirement. It is thus also possible to carry out overhauls during operation. Nine outgoers are connected to the individual subdistribution systems, three more are installed to meet any reserve requirements for further expansions. "Operating space is always short, and therefore we appreciate the extremely compact design of the switching cabinets that the Eaton components allow," Peter Lochmann says.

The IZMX16 circuit-breakers used from Eaton's NRX series are the smallest air circuitbreakers in the world. With a volume of only 24 dm3 and a front face that is only a little larger than an A4 sheet, they do not involve any losses in rating capacity. Even the motor for tensioning the springoperated stored energy mechanism and the magnet coils for the on and off switch commands from the central control room are integrated in this volume.

Fifteen xEnergy panels are installed at the plant, and these include 12 IZMX16 circuitbreakers with a Profibus DP network connection. The relevant interface modules are simply plugged onto the circuitbreaker between the control circuit terminals. "The modules, that are also available for Modbus and Ethernet, increase plant transparency and thus shorten response times," Jürgen Nauwartat, Eaton sales engineer for Power Distribution South explains. "The fast intervention into a process enables plant outages to be prevented or preventative maintenance to be planned. This considerably increases system availability."

The long-standing Eaton partner KLÖMÖ Energie- und Automatisierungstechnik GmbH from Regensburg in Bavaria was responsible for assembling the system. "The conversion was completed without a hitch during our annual maintenance window," Peter Lochmann confirms. A maximum downtime of 14 days was permitted for the system, in order to ensure the supply to the customer. The preassembled switchboards were already installed at the plant within three days. "We would also like to emphasize the close support that Eaton provided during commissioning. Any unforeseen issues were solved very flexibly during assembly and our time schedule could be kept," Peter Lochmann further explains.

Results

"The Eaton IZMX16 circuitbreakers provided us with the right solution for Linde and also ensured an extremely space saving design for the new power distribution system," Jürgen Nauwartat explains with delight. The small number of xEnergy panels needed for the assembly reduced the amount of copper required and therefore also the costs. Peter Lochmann also confirmed: "Eaton is always there for us whenever there is a challenge to solve. This is something we appreciate very much."