(200b) Innovative Processes Design for Value-Added Products from Natural Gas Liquids in Shale Gas

Recent advances in hydraulic fracturing and horizontal drilling have led to a surge in shale resource production and transformed the US energy landscape. Compared to natural gas, shale resources contain a substantial amount of condensate and natural gas liquids (NGLs). Many shale basin regions located in remote areas are lacking the infrastructure to distribute the extracted NGLs to other regions—particularly the Gulf Coast, a major gas processing region. Therefore, upgrading NGLs to value-added products that are easier to distribute is necessary for the remote shale basins.

In current research, shale gas processing and NGLs upgrading processes all strictly follows a three-section hierarchy including gas treatment, separation and reaction^{[1, 2]}. Under this hierarchy, shale gas from reservoirs or wellheads first goes through shale gas treatment such as acid gas removal and dehydration. Then in the separation section, methane and NGLs are separated and usually methane is sent to pipeline. In the reaction section, NGLs are often dehydrogenated to produce corresponding olefins and then goes through further processing.

However, if we look at the synergistic interaction within the shale gas upgrading process, the “treatment – separation – reaction” hierarchy could be broken. For instance, since alkane dehydrogenation favors low partial pressure of alkanes by equilibrium thermodynamics, methane can be present in the dehydrogenation reactor as an inert to lower the partial pressure of NGLs, leading to higher conversion during dehydrogenation. By this method, separation section can be delayed to a point after the dehydrogenation reaction.

In this work, we propose innovative processes by employing a design strategy where possible synergistic interaction within sections is investigated and the “treatment – separation – reaction” hierarchy is abandoned. By process simulation, we have proved that these processes are subjected to simpler flowsheets, fewer unit operations and versatile possibilities of process integration and intensification. In addition, higher yields of value-added products compared with current research can be achieved by these new process designs.

Reference:

[1] Taufik Ridha, Yiru Li, Emre Gençer, Jeffrey Siirola, Jeffrey Miller, Fabio Ribeiro, and Rakesh Agrawal. Valorization of Shale Gas Condensate to Liquid Hydrocarbons through Catalytic Dehydrogenation and Oligomerization. Processes 6, no. 9 (2018): 139.

[2] He, Chang, and Fengqi You. "Shale gas processing integrated with ethylene production: novel process designs, exergy analysis, and techno-economic analysis." Industrial & Engineering Chemistry Research 53, no. 28 (2014): 11442-11459.