Optimization Approach to the Reduction of CO2 Emissions for Syngas Production Involving Dry Reforming

Dry reforming of methane (DRM) is an important technology that utilizes CO2 to convert methane to a mixture of H-2 and CO (syngas). Commercial applicability of DRM has been challenged by the high energy requirement, susceptibility to coke formation, and low-quality syngas (syngas ratio, H-2/CO similar to 1). On the other hand, DRM provides an attractive pathway to the cost-effective sequestration of CO2 via transformation to value-added chemicals and fuels. DRM may be used in conjunction with other reforming technologies to produce the needed quality of syngas and to exploit synergism in energy release and demand. In this work, an optimization-based approach is used to compare the carbon footprint of conventional reforming technologies with other processes involving DRM to produce syngas of different H-2/CO ratios. Technical, economic, and environmental metrics are used to assess the various options. Additionally, the model accounts for the carbon footprint associated with the reforming process, catalyst regeneration, and other energy requirements. The results of the optimization formulation show that the CO2 fixation using DRM is highly dependent on the desired syngas ratio. Net CO2 fixation occurs only at low syngas ratios of 1 and below. The results also indicate that producing syngas through a parallel reforming network involving existing technologies (steam methane reforming and partial oxidation) with DRM does not result in overall CO2 emissions reduction. Finally, two novel process concepts have been studied CO removal from DRM syngas (DRM + COSORB) and H-2 addition from an external source. Both these cases, while producing high H-2/CO ratio syngas, have potential in terms of CO2 emissions reduction and competitive operating costs but will have certain limitations. The DRM + COSORB (captured CO sold as feedstock) process was found to be the best among all options studied in terms of overall reduction of CO2 emissions and operating costs.