The Sulfur Recovery unit does not always get the attention of being a primary process in a refinery, except when it is not working properly. The sulfur plant is one key unit that can slowdown or shutdown the entire refinery, thus reliability and safe operations are essential.
Challenge: Maintaining the proper ratio control of H2S to combustion air is an important balance to avoid too much H2S or too much SO2. In addition, the unit must operate reliably and safely at low operating (optimum) cost.
Solution: With the use of MPC, the combustion air ratio can be controlled to avoid too little air (decrease sulfur recovery and increase H2S concentration in the tail gas) and avoid too much air (decrease sulfur recovery and increase SO2 in the tail gas).