COMPRESSOR UPGRADES

Caption: The blade carrier was rebladed at the South Korean facility

HOW TO USE A ROTOR UPGRADE TO INCREASE PRODUCTION AND REDUCE ENERGY CONSUMPTION

BY ROMAIN BAYÈRE

For energy-intensive industries, such as iron and steel, it is crucial to find ways to update aging equipment, boost production and reduce energy consumption to maintain competitiveness. Energy awareness is reflected in ISO-5000, which defines the framework for industrial plants to manage energy. Limited energy resources, though, are an important factor to consider in many regions. South Korea, for example, has a limited supply of conventional thermal power and nuclear facilities; it is heavily dependent on external energy sources.

Environmental concerns are also growing in importance. Since 2000, global steel production has almost doubled, reaching 1.69 billion tons of steel in 2017. The sector is the largest industrial emitter of CO2 in the nation and the second largest industrial user of energy. Although considerable improvements have been made, the iron and steel sector has the potential to further reduce power consumption and emissions. South-Korean steel maker Pohang Iron and Steel Company (POSCO) was the first steelmaker in Asia to acquire the ISO 50001 certification. It must cope with scarce energy sources as well as the strict requirements of the Korean carbon permits trading system. This drove the company to retrofit existing equipment.

Blast furnaces

Blast furnaces play a central role in the steelmaking process. They transform raw materials into molten iron and require a lot of power. Air from the atmosphere is enriched with oxygen, compressed and blown into the blast furnace. In Pohang, three air blowers built between 1978 and 1981 provide air to the third and fourth blast furnaces, which are two of the five large-sized furnaces operated by POSCO. These compressors are driven by electric motors with a power consumption of up to 122 MW. The company decided to upgrade these air compressors. The outer casing was retained, internal parts replaced, and improvements were made to the rotor and stator blades. This approach enabled POSCO to lessen the amount of downtime it would experience compared to the deployment of a new compressor, which would have required a new concrete foundation and modifications outside the machine casing.

The implementation of the latest blade technology meant that the number of stages could be reduced from 17 to 14 while maintaining the same discharge pressure. These design modifications were carried out in such a way that the main structure could be retained without adjustments. The compressor operation envelope could also be increased to higher pressure ratios. New blade roots ensured an easy re-assembly in the circumferential grooves. This permitted the revamp to be completed for all three machines within 12 months.

The project brought energy savings of 6.5%. These types of revamp and modernization projects can be applied to a wide range of air compression trains, many of which remain in operation for more than 40 years. Such revamps applied to a large fleet of machines contribute to more sustainable steel production.

Romain Bayère, Head of Revamp Bids & Execution, MAN Energy Solutions Switzerland Ltd. MAN Energy Solutions supplies system technologies that help industrial customers to increase the efficiency of their plants and reduce emissions . Revamps of machinery, upgrades, and modernization of machine trains belong to the MAN PrimeServ portfolio. For more information, visit www.man-es.co