Dynamic simulation and optimization targeting emission source reduction during an ethylene plant start-up operations

Chemical plant flare minimization has been practiced not only during regular operating conditions but also abnormal operations such as start-ups, shutdowns, and process upsets. This paper focuses on introducing a generic approach by using dynamic simulation for emission and greenhouse gas reductions, which is demonstrated by a case study of a front-end de-ethanizer ethylene plant start-up. The new merits presented in this work include investigating different approaches of using intermediate storage units to accumulate and recycle off-specification streams from the recovery section, ultimately targeting flareless start-up for the entire ethylene plant. Large-scale dynamic simulations, emission characterizations, operation scheduling, and solution evaluation are carried out systematically to achieve the goal of flare minimization. It shows that the proposed optimization procedure contributes a great deal in evaluating new strategies and predicting process dynamic behaviors. It also helps achieve precise timing to control the recycle loop; hence, flaring can be minimized while the start-up time is shortened.