The steam methane reformer (SMR) is the most complex operation and equipment design in an ammonia, hydrogen, or methanol plant. It is also the most expensive single item of capital expenditure and the dominant energy and variable cost consumer in the plant. Most reformer operations have a ‘set & forget’ culture when it comes to operating their reformer furnace, i.e. Take it back to the operating settings we’ve always used. Conversely some plants have a greater emphasis on plant efficiency and continually focus on ‘balancing’ their reformer. A reformer is in essence a heat exchanger and as such there is significant potential for energy cost savings and increased production output through optimizing firing efficiencies and reforming.
In addition to the obvious loss of gas efficiency, a poorly balanced reformer can also be a major contributor to a reduction in catalyst tube, pigtail and even manifold life.
Most SMR operators take spot temperature measurements of their radiant catalyst tubes and carry out strain measurements during maintenance turnarounds to establish remnant life of their tubes so that they can be replaced before they fail. However very few operators use this very valuable data to optimize the performance of their SMR’s as well as increase the reliability and serviceable life of catalyst tubes, pigtails and manifolds. Becht engineers have worked with plant owners to achieve significant improvements in both performance and reliability.
Case 1 – During a condition assessment of an SMR, Becht analyzed the catalyst tube strain data which showed:
- The catalyst tubes had typically only consumed on average less than 50% of their safe serviceable life after 18 years’ service, and
- A significant imbalance in the furnace heat distribution with a tube temperature delta of >60°C / 105°
Recommendations were made and guidance provided on improving the furnace balance. This process brought the tube temperature delta down to around 35°C / 60°F. The outcome of this was that the temperature of the hottest tubes dropped significantly. Bearing in mind a 15°C / 25°F reduction in temperature will roughly double the life of the tube. The next stage was to increase overall furnace firing to the point where the hottest tubes were back to the previous temperature. In other words, the mean tube temperature had been increased without impacting tube life or reliability. This improved furnace balance delivered a 5% increase in plant rates and contributed over $1MM in additional revenue to the plant each future year.
Case 2 – During a whole of reformer condition assessment / remnant life study, Becht found that an SMR had suffered tube failures after only 8 years’ service whilst other tubes in the furnace were predicted to have a service life more than 30 years. In addition, there was a clear linkage between the hot catalyst tubes and the life and integrity of the adjoining pigtails and of local higher temperatures in the outlet manifold. This was another example of an imbalanced furnace. Becht made recommendations with respect to how to improve furnace balance as well as how to improve component life thereby delivering an improvement in reformer performance as well as improved component reliability.
Becht’s SMR assessment work process includes a review of heater fabrication and inspection records, heater process data (historical and current), and includes interviews with plant operations, maintenance, and engineering personnel. The review of heater data combined with the interviews gives the consultant a starting point for performance and equipment gap analysis, the comparison of client plant data and conditions against industry norms and experience.
To conclude, the application of ammonia industry experience and review of plant equipment (SMR) data, coupled with interviews of plant personnel revealed an opportunity to optimize the serviceable life of the catalyst tubes as well as other critical components such as pigtails and manifolds. In many cases there may also be an opportunity to increase plant production rates delivering increased revenue to the business.
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