Decarbonization of Steam Cracking for Clean Olefins Production: Optimal Microgrid Scheduling

TL;DR

The paper tackles decarbonizing steam cracking for olefins by embedding electrified and conventional crackers in a flexible microgrid framework. It couples a detailed dynamic reactor model with a scenario-based MILP to optimize microgrid scheduling under renewable and price uncertainties. Key findings show that, with current technology, higher electrification does not always reduce emissions or costs; benefits depend on grid decarbonization, electricity prices, and storage costs. The work emphasizes the need for integrated planning across chemical and power systems to achieve meaningful decarbonization in practice.

Abstract

Ethylene is one of the most ubiquitous chemicals and is predominantly produced through steam cracking. However, steam cracking is highly energy- and carbon-intensive, making its decarbonization a priority. Electrifying the steam cracking process is a promising pathway to reduce carbon emissions. However, this is challenged by the intrinsic conflict between the continuous operational nature of ethylene plants and the intermittent nature of renewable energy sources in modern power systems. A viable solution is to pursue a gradual electrification pathway and operate an ethylene plant as a microgrid that adopts diverse energy sources. To optimize the operational strategy of such a microgrid considering uncertainties in renewable energy generation and market prices, in this work, we propose a novel superstructure for electrified steam cracking systems and introduce a stochastic optimization framework for minimizing the operating costs. Results from a case study show that, given the current status of the power grid and renewable energy generation technologies, the process economics and sustainability of electrified steam cracking do not always favor higher decarbonization levels. To overcome this barrier, electricity from the main grid must be cleaner and cheaper, and energy storage costs per unit stored must decrease. Furthermore, it is important for both chemical and power systems stakeholders must seamlessly coordinate with each other to pursue joint optimization in operation.

Figures (8)

• Figure 1: Our envisioned framework for using electricity to supply process heat for steam cracking. Diverse energy sources supply heat for both electrified and conventional crackers that are present in the superstructure. Depending on the nature of the energy carriers, the connections shown in the superstructure can represent either energy or mass flows.
• Figure 2: The output electricity market prices of five scenarios considered.
• Figure 3: The output power of wind turbines of five scenarios considered.
• Figure 4: The output power of photovoltaic panels of five scenarios considered.
• Figure 5: Average natural gas (NG) consumption for conventional crackers, natural gas consumption for dispatchable generators, power usage from the main grid, and ESS charging/discharging status for grid-connected mode under different degrees of electrification.