Low-temperature distillation method for capturing carbon dioxide

A distillation method for capturing carbon dioxide, comprising:

• (a) collecting a tail gas containing carbon dioxide and nitrogen from a methanol steam reforming (MSR) section, and pretreating the tail gas to obtain a feed gas;
• wherein the feed gas contains 84-98% by volume of carbon dioxide, 2-16% by volume of nitrogen, less than 1,000 ppm of hydrogen, less than 10 ppm of carbon monoxide and less than 1 ppm of methanol;
• (b) subjecting the feed gas sequentially to a first-stage compression, a first-stage cooling, a second-stage compression, a second-stage cooling, a third-stage compression and a third-stage cooling to obtain a processed gas with a moisture content less than 5 ppm, wherein the third-stage compression is performed to reach a pressure of 1.4-1.8 MPa, and the third-stage cooling is performed to reach a temperature of −100° C. to −70° C.;
• (c) feeding the processed gas into a distillation column packed with structured packing for distillation and separation, and collecting a liquid stream predominated by carbon dioxide from a bottom of the distillation column;
• wherein the distillation column are operated according to optimized process parameters, and the optimized process parameters are determined through simulation and optimization using an Aspen process simulation software;
• wherein the simulation and optimization is performed through steps of:
• establishing a distillation column model by using a RadFrac module and a Peng-Robinson model;
• setting, in the distillation column model, a carbon dioxide purity in the liquid stream to be equal to or larger than 99%;
• and setting, in the distillation column model, a theoretical-stage flooding percentage to be 60%-80%;
• and
• determining the optimized process parameters utilizing a sensitivity analysis tool of the Aspen process simulation software with minimization of a total system energy consumption as an optimization objective;
• and
• (d) pressurizing the liquid steam obtained from step (c) to 2.1-2.5 MPa to obtain an industrial-grade carbon dioxide product with a carbon dioxide purity of ≥99%, and transferring the industrial-grade carbon dioxide product to a vacuum-insulated buffer tank for storage.