(391a) Dynamic Simulation and Control of a Dry Reforming Plant for Methanol Production: Dual Effects of Feedstock Variability and Operational Turndown

Methanol is a critical platform chemical and clean fuel, playing a pivotal role in reducing greenhouse gas emissions through applications in transportation, energy storage, and synthetic hydrocarbon production. Dry reforming of methane (DRM) offers a sustainable pathway to methanol synthesis by utilizing CO₂ and methane, two potent greenhouse gases, to produce syngas (H₂/CO), a precursor for methanol. While DRM is thermodynamically challenging, its potential for carbon-neutral methanol production has driven significant research interest. However, existing studies predominantly focus on steady-state optimization, neglecting dynamic operational challenges such as feedstock variability and flowrate fluctuations, which are critical for industrial scalability.

The objectives of this study are to (1) develop a dynamic simulation framework for a DRM-methanol plant integrating a novel microwave reactor and (2) propose advanced control strategies to mitigate disturbances caused by feedstock composition and flowrate variability. The process begins with natural gas feedstock (primarily methane), which undergoes desulfurization to remove contaminants like H₂S and organic sulfur compounds, protecting downstream catalysts. The purified methane is mixed with recycled CO₂ and fed into a microwave reactor operating at 800°C and 1 bar, where DRM converts CH₄ and CO₂ into syngas. Supplemental hydrogen is introduced to optimize the H₂/CO ratio, and the syngas is compressed to 76 bar for methanol synthesis. Two adiabatic reactors operate at 255°C and 220°C, respectively, to maximize conversion efficiency. The product stream is distilled to separate methanol (target: 14,200 lbmol/h, matching industrial benchmarks from unreacted gases, with CO₂ recycled to the microwave reactor.

Dynamic simulations in Aspen Dynamics evaluate the system’s response to feedstock disturbances, including ±20% fluctuations in natural gas flowrate and composition. A hierarchical control strategy is proposed: (1) a ratio controller adjusts supplemental H₂ flow to maintain the syngas H₂/CO ratio at 2.1, and (2) a composition controller manipulates the distillation column’s side-draw flowrate to stabilize methanol purity (>99.5 wt%). Model predictive control (MPC) is tested against traditional PID controllers to assess robustness.

This work advances DRM-methanol technology by demonstrating how dynamic simulation and advanced control strategies can stabilize production under real-world variability. By integrating a novel microwave reactor and automated control loops, the study provides a template for scalable, carbon-neutral methanol synthesis.