Hydrogen production via chemical looping dry reforming of methane: Process modeling and systems analysis

Abstract

AbstractThe present study presents and analyses a family of “chemical looping dry reforming” (CLDR) processes that produce inherently separated syngas (H2 and CO) streams via a combination of methane cracking in a “cracker reactor” and the Boudouard reaction (i.e., conversion of the formed carbon with CO2 to CO) in a “CO2 reactor,” and then further maximize the H2 yield via conversion of the produced CO via water‐gas‐shift. Remaining CO2 emissions are minimized via CO2 capture and sequestration. Four different configurations are evaluated which differ in how the heat required for the highly endothermic dry reforming reaction is supplied: (i) combustion of additional CH4 feed (CLDR‐CH4); (ii) combustion of some of the CO produced in the CO2 reactor (CLDR‐CO); and combustion of some of the carbon produced in the cracker reactor with (iii) pure oxygen (CLDR‐C‐oxy); or (iv) with air (CLDR‐C‐air). Process models are developed to comparatively analyze the mass and energy balances of these configurations, and benchmark them against H2‐production via conventional dry reforming and steam reforming of methane. Our results show that CLDR‐C‐oxy is the most promising H2‐production pathway among the chemical looping and conventional technologies both in terms of chemical energy efficiency and in terms CO2 emissions. Thus, the unique flexibility offered by the production of inherently separated syngas streams in CLDR enables overcoming the disadvantage of the strongly endothermic dry reforming reaction by combusting carbon internally in the reactor and thus achieving highly effective heat integration. Overall, the results support the technical viability and demonstrate the promise for strong process intensification of CLDR compared to conventional dry reforming and even steam reforming, the most widely used H2‐production pathway to‐date.