Ageing coldbox gets a makeover

Revamp or rebuild from scratch? A decision often faced by plant and maintenance managers of ageing industrial plants as asset performance starts to slip. And one that chemicals giant BASF can well relate to. At its biggest chemicals site in Ludwigshafen, Germany, BASF had to decide whether to revamp or rebuild an air separation coldbox. The experts from LINDE PLANTSERV ^® helped BASF find the optimum solution – thanks to their long-standing know-how and wealth of experience. In record time, they managed to return the coldbox to peak operating condition.

Chemicals facilities rely on a host of industrial gases. They may be invisible but they play an essential role in solving process challenges, creating protective and inert atmospheres, and triggering various process reactions. “Oxygen and nitrogen are the two gases most widely used in industry,” explains Jan Segatz, project execution manager at LINDE PLANTSERV^®. “These two industrial gases are produced by air separation units, which are generally located directly on the customer site in the case of larger chemicals complexes.” BASF relies on various air separation units (ASU) from Linde at its site in Ludwigshafen. The oldest of these was built over 50 years ago. It was the first of its scale to be built at the time. With a footprint of almost 100 square meters and standing 50 meters tall, this air separation unit is several thousand cubic meters in size. “It was beginning to show its age, however,” according to Segatz. “BASF noticed a drop in performance levels as well as issues with operational measurements. On top of this, ice deposits were becoming noticeable on the outer surface of the coldbox, which is the main component of every ASU. These deposits are a reliable indicator of weak points, causing the entire plant to consume more energy.”

Rebuild or revamp?

The PLANTSERV ^® experts performed an initial health check on behalf of BASF and then presented the customer with various solution roadmaps. The chemicals group ultimately had to decide between rebuilding from scratch or revamping to increase reliability. The engineers performed a cost calculation for both scenarios, estimated how long the plant would be out of action in both instances, and modeled its availability in future years. “Given the essential role of air separation units in providing gas to industrial sites, we quickly realized that a revamp was the best path forward,” explains Segatz. A new build would have either required a new site or entailed dismantling and scraping the existing plant. The cost of this would have been enormous and the work would also have taken much longer to complete. “Uninterrupted operations and continuity of gas supply at the complex were must-haves for BASF so speed obviously emerged as the decisive factor in the decision-making process,” the PLANTSERV ^® expert relates. “We managed to complete the revamp in a little over four months.” This record speed was also due in part to the highly pragmatic approach taken by BASF. Function over form meant the focus lay firmly on rapid resumption of reliable, efficient operations. Another advantage of a revamp is that it offers a lower energy balance and smaller carbon footprint than a rebuild, thus reflecting Linde’s long-term commitment to energy efficiency and supporting the sustainability objectives of both companies.

Given the essential role of air separation units in providing gas to industrial sites, we quickly realized that a revamp was the best path forward.

Air separation unit with special insulating material

When it came to assessing the health of the ASU in the first place, however, the PLANTSERV ^® experts faced a new challenge. They first had to remove all of the insulating material between the steel exterior of the coldbox and the inner process plant made from aluminum. Because of the size of the coldbox, this added up to a huge volume of material installed around a labyrinth of pipelines and process technology. “Whereas pourable perlite is the insulating material of choice nowadays, rock wool was used when the BASF coldbox was designed. Every bit of this had to be removed by hand before we could even start. If you consider the dimensions of the plant, this project step was extremely time-consuming,” points out Segatz. And since the existing steel cladding of the coldbox would not have been able to withstand perlite insulation – as the inner pressure load would have been too high – the only choice in the end was to stick with rock wool. Linde sourced and refitted the new rock wool to match the original build.

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Repairing the colbox

Once the rock wool had been removed, the LINDE PLANTSERV^® experts could finally get to work. This involved assessing the damage, calculating various scenarios, and preparing cost estimates and modeling analyses. When BASF decided in favor of a revamp, the focus turned to detailed execution planning to ensure a smooth, reliable workflow on site. “We continuously liaised with our internal specialist teams as well as various suppliers,” comments Segatz. “Thanks to the detailed planning, we were able to deliver the project smoothly and on a tight timeline.” The Linde team based in Schalchen played a key role. As the design engineers for Linde coldboxes, they contributed their extensive technical know-how and valuable support on site. “The problem-solving skills of our colleagues was a major success factor for the project,” according to Segatz. The repair to-do list compiled by LINDE PLANTSERV ^® was long. It included support brackets – which were repaired; new supports for columns, vessels and heat exchangers; piping and sheeting – which were replaced; as well as improved measurements and analytics technology.

Thanks to the detailed planning, we were able to deliver the project smoothly and on a tight timeline.

A successful team effort in record time

After just a few months, BASF was able to resume operation of a fully functional air separation unit. The company surprised the PLANTSERV ^® experts at the end of the project with a personal gesture, recalls Segatz. In a letter addressed to the entire Linde team, BASF wrote these words of gratitude: “The successful execution of this unique repair project is attributable to Linde’s high level of commitment, availability and flexibility; ability to build on expert know-how to present solution roadmaps up front; willingness to support us in preparing risk assessments for all required competencies; and readiness to reach beyond rigid lines of responsibility to provide support as needed during execution. Once again, Linde proved its ability to deliver.” An acknowledgement that means a lot to Segatz and his team and that reflects the value of their work and expertise for industry customers. The fact that the solution ultimately implemented was also a more sustainable one is an added bonus – both for the company and for the environment.

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