Conceptual Design and Analysis of a Natural Gas Assisted Coal-to-Olefins Process for CO2 Reuse

Olefins have been regarded as one of the most important platform chemicals. The production of olefins and their derivatives are highly subject to oil. Developing coal-to-olefins processes is therefore of great interest to many countries, especially China. However, people have to face and pay for the severe environmental problems resulting from coal-to-olefins development. Of these problems, high CO2 emission of a coal-to-olefins process, always attracts the most attention since it is about five to six times of that of an oil-to-olefins process. For this problem, this paper proposes a new natural gas assisted coal-to-olefins process integrating CO2 recovery gasification and CH4/CO2 reforming techniques. The former technique increases the amount of syngas from the gasifier, while the latter one uses additional natural gas reacting with CO, to produce H-2-rich syngas. Key parameters are studied during the simulation of the new process. The advantages of the process are manifested by comparison with a conventional, coal-to-olefins process from the techno-economic point of view. Results show that the new process is promising since it reduces the CO2 emission by 29.9% and increases the carbon efficiency and the energy efficiency by 20.7% and 7.8%. With the high market price of natural gas, the product cost of the new process is slightly higher than the coal-to-olefins process. But the new process will be more competitive if considering that the carbon tax is larger than $18.2/t CO2 or that shale gas is available in China.