Abstract
Detailed chemical equilibrium analysis based on minimisation of Gibbs Energy is conducted to illustrate the benefits of integrating sorption enhancement (SE) and chemical looping (CL) together with the conventional catalytic steam reforming (C-SR) process for hydrogen production from a typical shale gas feedstock. CaO(S) was chosen as the CO2 sorbent and Ni/NiO is the oxygen transfer material (OTM) doubling as steam reforming catalyst. Up to 49% and 52% rise in H2 yield and purity respectively were achieved with SE-CLSR with a lower enthalpy change compared to C-SR at S:C 3 and 800K. A minimum energy of 159kJ was required to produce 1mol of H2 at S:C 3 and 800K in C-SR process, this significantly dropped to 34kJ/mol of produced H2 in the CaO(S)/NiO system at same operating condition without regeneration of the sorbent, when the energy of regenerating the sorbent at 1170K was included, the enthalpy rose to 92kJ/mol H2, i.e., significantly lower than the Ca-free system. The presence of inert bed materials in the reactor bed such as catalyst support or degraded CO2 sorbent introduced a very substantial heating burden to bring these materials from reforming temperature to sorbent regeneration temperature or to Ni oxidation temperature. The choice of S:C ratio in conditions of excess steam represents a compromise between the higher H2 yield and purity and lower risk of coking, balanced by the increased enthalpy cost of raising excess steam.
Highlights
Hydrogen is at present of enormous value in the production of synthetic fertilizers via ammonia manufacture, as well as an essential reagent in petroleum refinery operations [1,2]
Two scenarios were considered in the processes that featured solids: ‘A’ is used for a total energy balance which does not account for the energy of regeneration of the CO2 sorbent while ‘B’ includes the sorbent regeneration energy
Using ideal materials properties, represented by an oxygen transfer material little diluted by inert support, and by fully active CO2 sorbent, sorption enhanced chemical looping steam reforming can have considerable advantages compared to conventional steam reforming for H2 production because of the substantial increase in H2 yield and purity, as well as significant drop in temperature of the maximum H2 yield with effective capture of CO2 under well-chosen operational conditions
Summary
Hydrogen is at present of enormous value in the production of synthetic fertilizers via ammonia manufacture, as well as an essential reagent in petroleum refinery operations [1,2]. In 2013, the Annual Energy Outlook projected that the U.S (world largest producer of shale gas) natural gas production will increase an estimate of 44% over the 30 years. Enormous amount of this projected increase is expected from shale gas extraction. Despite having reached technological maturity, steam reforming is one of the most energy consuming processes in hydrocarbon processing and ammonia production via its heating requirement, with additional disadvantages such as greenhouse gas and other air pollutants emission, high operational and maintenance cost [17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
