Recycling of carbon dioxide
Résumé
Direct or indirect CO2 emissions are generated in the phosphate industry; they come from phosphate treatment, electricity and steam / heat used. In addition to reducing emissions by developing innovative processes, the use of captured CO2 can become a profitable business. For the CO2 chemical transformation pathways, the carbon dioxide reacts with other highly reactive components in order to complete the synthesis of basic chemicals or products with high energetic value. Among these pathways: The hydrogenation of CO2 can lead to methane, methanol, or synthetic fuels production. There are already pilot plants for the hydrogenation of CO2, and is expected to become industrialized in few years. The recycling of CO2 has the advantage of recycling large volumes of CO2 with a medium-term CO2 sequestration. Many technological challenges, and very few of feedback are the main challenges of this pathway. It should be noted that these pathways differ with respect to their degree of maturity, their potential for emergence, duration of CO2 sequestration, energy consumption, volume of CO2 recovery and energy efficiency. Several case studies are presented; special attention is focused on an innovative process for producing fuel grade methanol from captured CO2. This process is designed and simulated with Aspen Plus. The CO2 is captured by chemical absorption. The hydrogen is produced by water electrolysis using carbon-free electricity. The methanol plant provides 36% of the thermal energy required for CO2 capture, reducing considerably the costs of the capture. The CO2 balance of the process showed that it is possible to abate 1.6 ton of CO2 per ton of methanol produced if oxygen by-product is sold.