Nitric Acid Catalyst Basket (Doubling the Lifespan)

When it comes to manufacturing practices, many of us operate under the status quo. We accept things as they are without realizing there might be a better, faster or more effective way to do things. Several years ago, we started a conversation with a customer who accepted that the lifespan of their nitric acid catalyst basket was two years. After discussing the specifics of their situation, industry norms and ultimately testing an upgraded design, we’ve extended the service life of their nitric acid catalyst basket significantly.

A typical high pressure catalyst basket should last four to eight years, and in some cases longer depending on the conditions. The most common reasons why catalyst baskets fail is due to (1) distortion on the top flange and (2) cracking in various high stress areas.

The Situation

Our customer, a 43-year-old chemical company runs a high-pressure nitric acid production plant. Their unit has very high catalyst gauze velocities where the basket was pushed to an extreme. During our conversations, we discovered that their catalyst baskets were only providing a two-year service life. Based on the company’s documentation, this has been the lifespan for the last 15 years – but it certainly could have been the case since the plant started operation.

The Opportunity

The customer’s basket was failing in two different areas. First, distortion on the top flange meant that it was going out of round. The gauze flange was also failing to a side radial tear. And finally, the jack bolts and heat shield bolts had galling issues.

The plant investigated several options but decided to partner with Alloy Engineering and implement a design upgrade.

Action Taken

Our strategy involved an “in kind” basket replacement exactly like their current basket. This gave us two years to design and approve upgrades for the new basket. Like clockwork, the “in-kind” basket failed after two years, at which point we had the upgraded basket completed and ready for install.

Our design incorporated several key upgrades. We modified the material construction and the side wall design. This helped increase the strength, minimize top flange distortion and minimize side wall stress.

In addition, we improved the strength of the catalyst support grid to resist deflection. This wasn’t an issue for the customer because the basket wasn’t lasting long enough for the grid to fail, but we wanted to plan for this potential scenario. Our final design modification eliminated the bolts to avoid bolt galling.

Results

The upgraded basket was installed in January of 2014 and has been in service 24/7/365 – that’s more than five years of service and an extended life of 2.5 times beyond the original design. Currently there are no signs of distortion or cracking.

While the new basket was a larger up-front investment, the results show that it was an effective choice for long-term ROI.

Have you explored how you might be able to extend the life of your nitric acid catalyst basket? Through innovative design and alternative materials, you might be able to extend its life and minimize life cycle costs.

To learn more about catalyst baskets from Alloy Engineering, contact us here or call us at 440.243.6800.