The process design and simulation for the methanol production on the FPSO (floating production, storage and off-loading) system

•We propose a novel Methanol-FPSO process to utilize off-shore stranded gas and CO2.•The optimal recycle conditions were obtained using the constrained optimization.•To maximize CO2 utilization, SCR and RWGS were adopted in the process.•RWGS increases total CO2 consumption and methanol production, decreases process size.

A process for methanol production from 100 MM scfd of stranded gas and CO2 is proposed and simulated using a commercial process simulator, PRO/II v.9.1, for a FPSO (floating production, storage, off-loading) system. The process consists of Steam-CO2 Reforming (SCR), methanol synthesis, a Reverse Water-Gas Shift (RWGS) reaction and ancillaries with recycle streams to SCR and RWGS. All reactors were simulated using the Gibbs reactor model. Also, the Plug Flow Reactor (PFR) model with reaction rate equations was used for the methanol reactor and the result was compared to the Gibbs reactor model. To maximize the use of the carbon source in stranded gas and CO2 while avoiding an undesirable increase in process size, the optimum recycle ratios were calculated with a satisfying constraint, a steam-to-carbon ratio ≥ 1 in the SCR. In the proposed Methanol-FPSO process the RWGS reactor can maximize CO2 utilization and case studies were performed to analyze the influence of RWGS.