Abstract

Catalyst activity loss reduces both the performance and operating flexibility of industrial sulfur dioxide converters, yet its consequences are rarely assessed beyond conversion declines. This work develops an activity-loss vulnerability framework for a four-bed double-contact SO2 converter model evaluated against an industrial fresh-catalyst benchmark and applies it to four prescribed activity scenarios (a=1.0, 0.8, 0.6, 0.4). At the reference inlet-temperature policy, reducing activity from a=1.0 to a=0.4 lowered conversion from 99.758% to 96.812%, increased outlet SO2 slip from 230 to 2960 ppmv, and raised the hotspot from 613.7 to 660.3 °C, exceeding the adopted illustrative limit of 650 °C. Sensitivity, vulnerability, hotspot risk, and feasible-region maps show that the prescribed activity loss progressively shrinks the permissible operating envelope and creates a coupled productivity–emissions–thermal-safety tradeoff. A non-uniform activity profile at the same mean activity as uniform a=0.6 produced a hotspot that was 9.3 °C higher, demonstrating that average activity alone is insufficient for thermal-risk assessment. Finally, a scenario-relative Operating Efficiency Reduction Index (OERI) integrates conversion loss, SO2-slip increase, and thermal-margin loss into an illustrative scenario-screening score. The results show that catalyst activity loss should be assessed as a coupled performance, emissions, and operational-vulnerability problem rather than conversion decline alone.

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