Automatic Process Synthesis for Olefin Production from Shale Gas

Arsh Bhatia, Zewei Chen, Rakesh Agrawal

Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47906

As the world transitions toward sustainable energy sources, shale gas provides a strong option as a carbon source for this period. Shale gas is rich in natural gas and is a good source for olefin production which is used in manufacturing plastic, rubber etc. The current shale gas manufacturing processes use a sequence of front-end separation, natural gas activation and back-end separation. This has led to repeated separations which drive up costs and energy consumption. As a result, large amount of shale gas at remote areas are directly flared, leading to increased wastage of shale resources and carbon emission. Recently, developments by Chen et al. [2] have shown that eliminating some of the front end separation and postponing them for after NGL activation reduces costs and energy consumption, leading to a more intensified process design.

Chen et al.’s work, although provided a systematic procedure to rearrange the process sequence, still highly rely on researchers and practitioners’ engineering intuition. In this study we investigate the automation of the synthesis procedure using mathematical programming and relying on the optimization framework to decide the optimal process arrangement. By creating an algorithm that can construct the proper search space and sort through configurations based on deciding factors such as cost and energy demand, we are able to identify unique alternatives which are more efficient.

We consider a small-scale liquid production plant from natural gas liquid in shale gas consisting of a dehydrogenation reactor and an oligomerization reactor. The algorithm considers a reaction-separation network wherein all reactions and separations are nodes and all submixture streams are edges. The algorithm can synthesize the conventional configuration, the configurations in Chen et al’s work as well as several other attractive process options.

References

[1] Z. Chen and R. Agrawal, “Alternative Processing Sequence for Process Simplification, Cost Reduction, and Enhanced Light Olefin Recovery from Shale Gas,” ACS Sustain. Chem. Eng., 2021, doi: 10.1021/acssuschemeng.1c05091.

[2] Z. Chen, Y. Li, W. P. Oladipupo, E. A. Rodriguez Gil, G. Sawyer, and R. Agrawal, “Alternative ordering of process hierarchy for more efficient and cost-effective valorization of shale resources,” Cell Reports Phys. Sci., p. 100581, 2021, doi: 10.1016/j.xcrp.2021.100581.