Bausch + Lomb, a global eye health company located in Waterford city, has recently installed and commissioned a nitrogen generation plant, which is rated to produce 1,313Nm3/hr and has a backup facility of 1,500Nm3/hr, writes Derek O'Connor.

The new plant supplies 100 per cent of the site’s high purity nitrogen, and is one of the biggest nitrogen generation plants in Ireland.

Project background and overview

The new nitrogen generation plant (ECOGAN 1) replaces the existing nitrogen generation plant that was installed on site in 1999.

The existing plant had come to its end-of-life operation and couldn’t match the demand of the site due to the recent expansions.

Because of the high demand of the site’s nitrogen requirements, tankers of liquid nitrogen had to be delivered to supplement the generation plant to match the demand.

This method of using liquid nitrogen as well as a generation plant was expensive and a business risk if the road freight and well as other external factors went wrong.

Following an in-house assessment, market research and detailed technical analysis process it was decided to replace the existing plant with the larger nitrogen generation plant.

BOC Gases Ireland Ltd. was chosen due to their proven track record, technical capabilities in providing similar projects and their aftersales service team in Ireland.

Concrete plinth, electrical substation and pipe bridge

The commercial value of the project is being shared by both Bausch +Lomb and BOC. To facilitate the equipment that BOC provided and to connect the new plant into the campus, a substantial concrete plinth, an electrical substation and a pipe bridge had to be built.

The project required planning permission for the generation tower that stands an impressive 20m in height and weighs 28 tonnes.

The compressor that compresses the air uses a Siemens induction motor and has an in-rush current of 1.2MW when starting.

The backup nitrogen tanks are also physically imposing structures and stand at 16m in height and can hold more than 120,000 litres of back-up liquid nitrogen.

The project commenced in January 2018 where a comprehensive in-house study was under taken to map the nitrogen profile of the site for one full year, thus ensuring that all the operational and climate conditions were recorded.

Once a detailed load profile was conducted in April 2018 Bausch + Lomb engaged with BOC on both commercial and technical design issues to identify a suitable nitrogen generation plant and a backup system for the site.

ECOGAN 1 plant selected

Based on these discussions, a commercial contract, design criteria and the load profile for the site, an ECOGAN 1 plant was selected.

The ECOGAN 1 plant is a containerised cryogenic plant for production of high purity nitrogen gas and is suitable for outdoor installation on suitable foundations.

The construction period lasted six months where a concrete plinth had to be constructed to install all the necessary equipment from BOC.

There was more than 300m3 of concrete with reinforcing rebar used to construct this plinth. A bespoke electrical substation was also built as the new plant is energy intensive and this included installing a 2MW transformer to power the plant.

Finally, a pipe bridge was constructed to bring the necessary services to the nitrogen plinth as well as the nitrogen pipes feeding the building; more than 200 tonnes of galvanised steel was used on the pipe bridge construction.

Commissioning of the new nitrogen plant was successfully completed in September 2019 and included the electrical, nitrogen and water tie-ins. The new plant became operational in October 2019.

Nitrogen generation technology

The nitrogen generation system is a containerised standard cryogenic plant for production of high purity nitrogen gas. The plant equipment is based on liquid injection technology.

The ECOGAN 1 model produces a maximum of 1,313Nm3 of gaseous nitrogen per hour. The ECOGAN 1 plant consists of two main parts, warm end/TSA containers and a cold box.

The warm end/TSA containers house the equipment required to pre-heat the atmospheric air before entering the cold box. Within the cold box the air is separated at cryogenic temperatures (≈100K / -1750C), to produce nitrogen gas purity less than 10ppm of oxygen.

For the plant to operate at these low temperatures an external source of liquid nitrogen (LIN) is required to aid refrigeration.

The LIN that is injected into the plant counteracts the heat in-leak from the surroundings and heat exchanger efficiencies and LIN pump losses within the cold box.

Other than the atmospheric air and LIN the plant only requires a source of three-phase electricity to function. The only discharges, other than the nitrogen product, are condensate water and oxygen rich waste air.

The nitrogen backup system consisting of two storage vessels and two vaporiser vessels giving a backup capacity of a maximum of 1,500Nm3 of gaseous nitrogen per hour.

The backup system is comprised of two cryogenic liquid tanks and ambient temperature heat exchange vaporisers to convert the liquid product to a gas.

The backup system also supplies the cold box with liquid nitrogen to achieve the cryogenic temperature of -1750C and to aid in the overall refrigeration process of the production plant. This equipment and ancillary components are further expanded in figures 1 and 2.

The main benefits

1.) The new plant is sized to match the load profile of the site.
2.) Better business continuity for the site by being able to produce all the nitrogen on site without the need for liquid nitrogen top-up.
3.) Environment benefit of removing 54 monthly liquid nitrogen deliveries to the site, an annual CO2 saving of 191 tonnes.

The nitrogen plant service and maintenance is covered by a bespoke 15-year 'Product Supply Agreement' contract between Bausch + Lomb and the BOC.

Under this agreement, it will perform routine maintenance and breakdown responses for the 15-year period. The nitrogen plant will be remotely monitored by BOC Gases Ireland Ltd via its SCADA control systems that will automatically detect and alert the service desk of any issues on site.

As part of this agreement contract the availability runtime of the plant is 97 per cent or 8,497 hours per annum.

Independent verification of all the nitrogen plant output data in terms of nitrogen gas usage, electrical inputs, and flow rates is via the site’s comprehensive EMS and BMS where 15-minute interval data is uploaded automatically to tract the plant performance.

The nitrogen plant has been in operation since October 2019 and based on the first month of data has exceeded expectations in terms on availability (currently running at 99.2 per cent), and nitrogen output of 1,342Nm3/hr.

During the six-month construction period a total of 25,228 man hours involving 20 construction workers were completed without incident during the implementation of the project.

The project concept, detailed design and project management was conducted in-house by Bausch + Lomb and BOC and was completed within schedule and budget.

Creativity and innovation and was also a key aspect of this project between both parties in terms of the bespoke plinth, electrical substation, metering, sound attenuation, pipe bridge and controls systems applied.

Author and project lead: Derek O’Connor BSc(HONS) Eng, MSc Eng, MIEI, MIET. Derek O’Connor holds a master’s degree in building services engineering and an honours degree in engineering. He is the facilities engineering and structural manager for Bausch + Lomb Ireland having joined the company in November 2003. He was also the project manager for the CHP project, and is the site’s energy champion, having achieved runner-up at the SEAI National Energy Awards in 2008 and 2017 in the 'large user' category and was the team lead in obtaining ISO50001 accreditation for the site in April 2013, the first B+L site worldwide to achieve this.