Chemical plant electrification for optimization

Abstract

Chemical manufacturing and refining produce crucial materials for everyday life but also release over 325 million tons of greenhouse gases (GHGs) annually in the United States. Most of these emissions are from the production of process heat. Ethylene is one of the most common chemical precursors for plastics and packaging and its market is expected to grow by 60% over the next decade. Ethylene is produced from endothermic reactions, commonly in steam cracking processes, which require massive quantities of heat and demand 8% of the global chemical industry’s energy use. However, process heat can be produced and managed using alternative methods. Heat integration can reduce but not eliminate external energy demand. Electrification enables heat generation without direct emissions but may create indirect emissions depending on the electricity’s source. Current power grids produce some electricity from renewable sources but still rely heavily on fossil fuels. Renewable sources can generate electricity at the plant, but differences between electricity production and plant demand timing require the plant to store energy. Fossil-fuel-based generators at the plant may reliably produce electricity quickly but also produce emissions. A combination of these sources could balance reductions in costs and GHG emissions. This presentation examines various methods of process electrification and their potential effects on operation within an ethylene production plant on the U.S. Gulf Coast. The primary operations within the ethylene plant include reactions, separations, and energy storage, which have been modeled using a differential-algebraic equation (DAE) optimization model and an Aspen HYSYS process simulation. Electrified reactors, electrolytic hydrogen production, and heat pump-assisted distillation (HPAD) were explored as plant electrification methods. HPAD was found to require approximately 17% less total energy than conventional ethane-ethylene distillation. Electrifying the ethylene plant by 20% was found to optimize sustainability with respect to total expected cost, reducing GHG emissions by 19%. The cost of renewable energy generation and storage was found to limit the viability of complete electrification and decarbonization. Expected future developments include operation optimization using a multi-objective model that considers plant data security and heat integration.Chemical Engineerin