Design and optimization of the flexible poly-generation process for methanol and formic acid from CO2 hydrogenation under uncertain product prices

• Published in: International journal of hydrogen energy 2024-02, Vol.54, p.635-651
• Main Authors: Li, Qiao, Machida, Hiroshi, Ren, Xusheng, Feng, Zemin, Norinaga, Koyo
• Format: Article
• Language: English
• Subjects: CO2 hydrogenation; Flexible poly-generation process; Mixed integer nonlinear programming; Two-stage optimization; Unscented transform
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.01.205

During the design of the carbon capture and hydrogen storage process, a static CO2 hydrogenation poly-generation process for methanol and formic acid synthesis was developed, thereby reducing recycling flow and feedstock losses in the single methanol synthesis process and increasing product diversity. Additionally, a novel flexible poly-generation process was proposed as the product prices fluctuated with the market environment throughout the plant's life cycle. For the static poly-generation process, a mixed integer nonlinear programming model was established, followed by the Mesh Adaptive Direct Search algorithm to determine the optimal parameter design. For flexible processes, with the unscented transform tool, a two-stage optimization strategy is proposed for obtaining optimal design and operating parameters that are computationally tractable. With an input CO2 flow rate of 200 kmol/h, the results show (1) the static process with an optimal Return On Investment of 13.05%, a fixed investment cost of $ 34.14 × 106, and an annual net profit of 4.46 × 106 $/year; and (2) the flexible process, in which the flexibility indices of the methanol and formic acid production units are 1.088 and 1.194, respectively, resulting the fixed investment cost increase to $ 39.19 × 106, an increase of 14.79%. Accordingly, the annual net profit increased by 8.97% to 4.86 × 106 $/year, while the Return On Investment decreased by 4.67%–12.44%. For investment decision-makers, the flexible poly-generation process can achieve higher profits and reduce potential market risks when they have adequate financing. •A static CO2 hydrogenation process for MeOH and FA poly-generation process is established.•A MINLP model is developed to obtain the optimal parameter design for the static process.•Conversion continuous variables into scenario variables by unscented transform tool.•The optimal flexible poly-generation process design is obtained by the two-stage optimization strategy.