Design Development of Integrated Methane Pyrolysis and Reforming Processes for Low-Carbon Urea Production

Abstract

As the world’s population continues to grow, the demand for fertilizers is expected to be large. Natural gas through steam methane reforming (SMR) is a major source of greenhouse gas (GHG) emissions during traditional ammonia-urea synthesis. Especially in case of ammonia and urea production rates unbalance, CO₂ emissions will increase. By contrast, methane pyrolysis (MP) offers a more sustainable alternative. Besides making solid carbon as a saleable byproduct, this method also enables the continuous synthesis of ammonia and urea with zero CO₂ emissions. This research explores the technical and financial viability of incorporating MP into a traditional SMR-ammonia-urea facility by dividing the NG feed between the SMR and MP sections. A simulation model was developed using Aspen Plus to analyze the integrated system. Results indicate that the proposed model achieves an optimal methane conversion rate of 73.2%, while targeting carbon black (CB) as a coproduct in the noncatalytic MP process. In contrast to the traditional plant, the proposed model demonstrates a reduction in power consumption of approximately 5.8 MW and reduced total direct CO₂ emission intensity (t-CO₂/t-urea) up to 47.72%. Under conditions mirroring projected trends in the Middle East, where NG prices stand at 2 USD/MMBTU, with a CO₂ tax policy of 8 USD/ton-CO₂ and a CB price of 1500 USD/ton, the proposed model exhibits approximately 8 million USD/yr more profit than the base model. Sensitivity analysis further highlights that the proposed model consistently achieves a higher net present value (NPV) than the base model under varying product prices, confirming its superior economic performance across different scenarios.