Optimal Process Operation for Biogas Reforming to Methanol: Effects of Dry Reforming and Biogas Composition

Abstract

[EN]We optimized the operation of the process thatreforms biogas with CO 2 and/or steam for the production ofmethanol using a mathematical optimization approach. Theraw biogas is cleaned up before reforming. Part of the biogas isused to provide energy for the process. Next, the unreactedhydrocarbons and CO 2 are removed. Subsequently, syngascomposition may be adjusted, using either water gas shiftreaction or membrane-pressure swift adsorption. Finally,methanol is synthesized. The process is modeled using massand energy balances, chemical and phase equilibria, and rulesof thumb. The problem is formulated as an NLP problem with simultaneous heat integration for the optimal biogas compositionand methanol production. Two objective functions are considered: a simplified production cost and an environmental onedeveloped based on carbon footprint. Biogas is expected to have around 50−52% of CH 4 and 45−47% of CO 2 , depending on theobjective function. The production cost of methanol is $1.75/gal, for a plant size that uses 10% of the potential biogas to beproduced in Madrid, Spain, with an investment of $46 MM.