Deployment of a Novel Soft Sensor in the Real Time Optimizer Architecture to Enhance the Integrity and Energy Efficiency of Sulfur Recovery Units

Commercial analyzers for measuring the aromatics in the Claus furnace exit gas are currently not available and this leads to sub-optimal energy efficiency and poses asset integrity concerns. To address this problem a high-fidelity model is developed to function as a real time analyzer. Objective of this work is to incorporate the soft sensor in the architecture of Real Time Optimizer (RTO) to monitor the presence of aromatics in the Claus furnace exit stream. The soft sensor is incorporated in the RTO server which provides the access to the plant operating data and the DCS (Distributed Control System). Soft sensor function in the RTO involves the following steps: Soft sensor accesses the plant data and collects the needful input data for simulation Simulation software available in the RTO executes the softs sensor model simulation and generates the aromatics composition data Aromatics composition data is written to the DCS interface as a soft measurement Operators monitor the aromatic composition and accordingly adjust the fuel gas firing Aromatic soft sensor is developed as a kinetic model, which is function of rate parameters of several key reactions of the Claus furnace. The kinetic model of the Claus furnace is incorporated in a process simulation model and catalytic convertors are simulated too. Model is validated with large plant data to show that model predicts furnace temperature within +/- 5% error and aromatics composition within +/- 5 ppm. Simulation analysis shows that the furnace temperature can be decreased by at least 5 °C while ensuring no BTEX slip. Such change in furnace temperature leads to a reduction in fuel gas flow by ~200 Nm3/h, which translates to a monetary benefit of 0.5 million $/yr. Deployment of the soft sensor is currently in progress through engagement with RTO licensor. To the best knowledge of authors, currently, there is no simulator in the market which can adequately model aromatics oxidation phenomena and predict the aromatic content in the furnace exit. This soft sensor being deployed is novel and first of its kind and expected to achieve a sustainable energy efficiency.