(207e) Optimal Selection and Design of a Methanol Process with Enhanced CO2 Utilization

The recent discoveries of significant reserves of shale gas have spurred various monetization pathways including the production of methanol. There are several routes to convert shale/natural gas to methanol. The decisions for technology selection and process design were typically based on techno-economic criterial. Because of the growing interest in reducing the greenhouse gas emissions of gas processing, carbon footprint is emerging as a primary criterion in the selection and design of the process. The purpose of this work is to carry out process synthesis, selection, and design of a shale-gas to methanol process with multiple objectives including profitability and carbon footprint. Several reforming pathways along with the associated downstream processing are considered. In addition to the screening of individual types of reforming, the study also considers combined reforming of methane which incorporates three types of reforming, namely steam reforming, partial oxidation, and dry reforming. It is desired to consider existing technologies and to also modify the design of an existing methanol technology to include combined reforming. Utilization of CO₂ is addressed while maintaining the suitable syngas ratio for methanol synthesis, and minimizing CO₂ emissions, waste water generation, and energy requirements of the overall process. A methanol from natural gas production plant with a capacity of 5000 metric tonnes per day is considered as the base case scenario. The plant employs conventional steam reforming to generate syngas for methanol synthesis. Aspen HYSYS along with optimization software (LINGO) are used to simulate the process scenarios and to determine the optimum reforming configuration, respectively. Mass and energy integration are performed to improve the sustainability and profitability of the process, through identifying water and heat sinks in the design. A techno-economic analysis of the proposed design is conducted, including the cost of retrofitting, carbon taxes, and utility requirements.