A Non-linear PI Averaging Level Controller for Plantwide Systems

This work develops a novel non-linear Proportional-Integral (PI) Averaging Level Control (ALC) algorithm designed to optimally utilize the available surge capacity in surge tanks, ensuring that the high and low alarm limits are not breached for the worst-case disturbance scenario. Building upon insights from previous studies, the proposed algorithm incorporates a tunable parameter for an acceptable flow overshoot. The algorithm’s performance is compared with existing popular ALC algorithms for a single tank and a realistic methanol dehydration process. The proposed algorithm significantly outperforms these alternatives in mitigating manipulated flow variability for small to moderate disturbances while delivering comparable performance for large disturbances. The significant flow variability mitigation results in up to 8.25% reduction in energy consumption compared to conventional P-only ALC for the methanol dehydration process due to lower back-offs from the active constraint limits. The quantitative results highlight the significant potential of the proposed ALC algorithm towards efficient and sustainable process operation.