On-site nitrogen generator system

16 February, 2023

Nitrogen is being supplied to the furnace 24/7 in varied quantities dependant on requirements, e.g. production or standby. At the end of a production cycle, the furnaces are purged with nitrogen to remove the combustible gases. After this procedure, it can take up to eight hours before a production run can start again due to recreation of atmosphere, an interval that differs slightly from furnace to furnace.

This need for precise control of the nitrogen volume and purity level is one of the major benefits of the Atlas Copco NGP+ nitrogen generator system, which has been designed from the outset to protect the process application and the users’ equipment investment.

By default, NGP+ generators feature an automatic off-spec check purity control so that nitrogen with a purity level less than the pre-set threshold can never reach a sensitive application. At the same time, feed air conditions such as temperature, pressure and pressure dewpoint are continuously monitored by fail-safe sensors. When not matching the generator requirements, the feed air is blown off automatically before entering the machine to eliminate the risk of contamination and damage to components.

The source of clean dry compressed air feeding the on-site nitrogen generation process at the Deeside plant is an Atlas Copco GA 15-37 VSD+ FF (full feature) rotary screw compressor with integrated refrigerant dryer and quality air ancillaries downstream. These include coalescing filters, to remove liquid water and oil aerosols plus an active carbon filter tower to deal with oil vapours and hydrocarbon odours. Output from the rotary screw compressor is at the rate of 7.3 - 43 l/s of 7 bar air.

With its innovative vertical design, the GA 15-37 VSD+ is a game changer in the compressor industry. It offers Variable Speed Drive as standard, a compact, direct drive, oil cooled iPM (permanent magnet) technology motor, and a small footprint thanks to its in-house design. All features have been developed to reduce energy consumption by an average 50% and to assure uptime even in the harshest conditions.

The whole on-site nitrogen generation system has been designed with duty standby so that from a safety and servicing perspective it can easily be switched over from running both units to a single machine when needed. There are two receiver tanks for air and nitrogen respectively as a secondary back up in case the system should stop working for any reason, and, for additional safety, there is a restart system.

As Sementa observes: “We are pleased to report that currently it is all running very nicely 24/7 and, although production cycles vary in frequency and duration, as a precaution we have to keep the furnaces’ atmosphere fully on at all times because of the extensive stabilisation time cycle. The really good news is that I am not at the mercy of suppliers and relying on vendor deliveries of nitrogen anymore.”

Atlas Copco Industrial Assembly Solutions production costs have already been reduced as a consequence of the energy efficiency of the installation and by the freedom from dependence on costly deliveries of over-spec nitrogen supplies. Additionally, the return on capital investment will see a payback completed within one and a half years from the system’s installation.

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