Flare minimization for an olefin plant shutdown via plant-wide dynamic simulation

Abstract

During shutdown operations of chemical plants, significant amounts of raw materials, intermediates, and products may be flared leading to economic losses and emissions such as carbon dioxide, nitrogen oxides, and volatile organic compounds. Thus, flare minimization during plant shutdown is a desirable goal towards economic benefit and environmental sustainability. In this paper, a systematic flare minimization methodology for an olefin plant shutdown operation has been developed. It includes three iterative stages: (i) steady-state modeling and validation to build the foundation of the dynamic modeling; (ii) dynamic modeling and validation to enable plant-wide simulations under designated plant control strategies; and (iii) plant shutdown simulation and optimization to iteratively examine, validate, quantify various flare minimization opportunities so as to identify the improved shutdown strategy. Particularly, dynamic performances of the critical equipment (e.g., the cracked gas compressor) has been thoroughly investigated to ensure the operating safety associated with the developed new shutdown strategy. Compared with the conventional plant shutdown strategy, the case study has shown that the new development can significantly reduce flared raw materials and emissions by 90.23%, which result in estimated economic savings by 91.03% and the social cost of carbon saving by 90.37%. 2020 Elsevier Ltd