Improvement of ethylene plant operations through the application of advanced control and closed-loop, real-time optimization

An advanced control and closed-loop real-time optimization system has been applied to an ethylene plant consisting of six furnaces, quench tower, cracked gas compressor, front-end deethanizer, demethanizer, C2 splitter, depropanizer, debutanizer, C3 splitter, ethylene refrigeration system and propylene refrigeration system. The refrigeration systems are significantly integrated throughout the plant. The process water from the quench tower provides heat for the C3 splitter and deethanizer towers. There are a total of ten multivariable controllers ranging from 3 to 17 manipulated variables each. The optimization system includes rigorous first-principles models representing the ethylene plant. The optimization system determines a number of optimization targets for implementation via the multivariable controllers. The scope includes the entire ethylene plant. The achieved benefits include 55% from the controllers and 45% from the optimization system. Benefits include reduced variability, increased feed flow rate and increased product flow rates of more valuable products.