The rolling mill, which is situated in the Differdange, Luxembourg plant of ArcelorMittal, a worldwide leader in the coal and steel industry, has a greatly fluctuating consumption of compressed-air. Production is ensured only if the pressure drops caused by short-term large withdrawals are duly compensated for.
Aerzen’s objective was to complement an existing turbo compressor with two additional fast reacting oil-free compressors, in order to compensate for these pressure drops both quickly and efficiently. Both Delta Twin DTS 35 WG compressors (3,142 m3/h, 6.5 bar, 355 kW) fulfill these requirements exactly due to their large control range and short start-up period, with simultaneously high volume flow. In order to ensure a suitably energy-efficient compressed-air production, a superordinated control option was selected through which the Turbo compressor and both Aerzen compressors could be combined into an intelligent compressed-air production unit. An absorption drier protects the process against the effects of humidity and the risk of external pipes freezing in winter. Moreover, challenging installation conditions had to be considered in order to ensure a safe operation, including the high dust load in the rolling mill.
After the planning phase had been completed by Aerzen Systems, the unit was taken into operation at the end of 2011, in close co-operation with the maintenance department of the rolling mill.Due to its slow control and long preparation time the Turbo compressor handles the base load. One of the Delta Twin compressors balances out the peaks, while the second one provides redundancy. However, to ensure constant utilisation and extended maintenance intervals, the screw compressors alternate every 24 hours.
Initial minor difficulties during commissioning were resolved thanks to Aerzen Systems. Since then, the unit has fulfilled the projected requirements and is easily able to balance the high volume flow differences. On the advice of Aerzen Systems, in the future any partly large withdrawal quantities will be additionally intercepted by a sufficiently dimensioned buffer. The unit is also supplemented by a refrigeration drier during the summer months in order to save additional energy.
