Thermodynamic Investigation of Process Enhancement in Chemical Looping Reforming of Methane through Modified Ca–Fe Oxygen Carrier Utilization

Abstract

Production of various value-added chemicals through natural gas conversion with syngas as an intermediate is becoming increasingly popular because of the abundance of natural gas and maturation of syngas-producing technologies. Chemical looping reforming is one such technology that is envisioned as a substitute to the existing syngas production processes such as steam methane reforming, autothermal reforming, and partial oxidation of natural gas (POX) because of its superior thermodynamic capabilities and less parasitic energy requirements. The proposed work makes use of CuO-modified Ca 2 Fe 2 O 5 -based oxygen carriers for syngas production through chemical looping, where the system performance is subjected to thermodynamic scrutiny. The main objective of the proposed work is to assess the change in syngas production capability and other process parameters because of reduced endothermicity of the process through CuO incorporation. Thermodynamic simulations are carried out to assess the system performance at various operating temperatures, pressures, and lattice oxygen availability. Parameters such as the effective thermal efficiency, cold gas efficiency, and exergy efficiency are calculated to evaluate the performance of oxygen carriers with varying compositions of CuO. These parameters are measured for two process configurations: isothermal and thermoneutral. An overall process simulation is further carried out to gain a deeper perspective of the changes occurring in the chemical-looping system because of CuO modification of the oxygen carrier.

Acetic Acid Production Using Calcium Ferrite-Assisted Chemical Looping Gasification of Petroleum Coke With In Situ Sulfur Capture

“…The selection of oxygen carriers can be carried out through the thermodynamic screening as reported by Fan et al, where a modified Ellingham diagram is used to identify metal oxides that are capable of selectively oxidizing carbonaceous fuel to syngas. ,, The authors here have used a similar methodology to select an oxygen carrier that could produce syngas with high purity and identified Ca 2 Fe 2 O 5 as the ideal candidate. As reported by Shah et al, the use of Ca 2 Fe 2 O 5 allows selective oxidation of CH 4 to produce CO over a wide range of [O]:CH 4 , where [O] is the lattice oxygen available in the carrier . Another study performed using the Ca 2 Fe 2 O 5 -based oxygen carriers shows an increase in the syngas yield by ∼6% when methane reforming is carried out using chemical looping as compared to autothermal reforming .…”

“…The selection of oxygen carriers can be carried out through the thermodynamic screening as reported by Fan et al, where a modified Ellingham diagram is used to identify metal oxides that are capable of selectively oxidizing carbonaceous fuel to syngas. 10,22,23 The authors here have used a similar methodology to select an oxygen carrier that could produce syngas with high purity and identified Ca 2 Fe 2 O 5 as the ideal 24 Another study performed using the Ca 2 Fe 2 O 5based oxygen carriers shows an increase in the syngas yield by ∼6% when methane reforming is carried out using chemical looping as compared to autothermal reforming. 25 Ca 2 Fe 2 O 5 produces high-quality syngas because of being a weaker oxidant and possesses the capability to be fully regenerated using steam (or CO 2 ) instead of air as opposed to Fe 2 O 3 .…”

The thermodynamic evaluation and process simulation of the chemical looping steam methane reforming of mixed iron oxides

“…Moreover, in the chemical looping field, it is common practice to employ thermodynamic and process simulations to assess the viability and potential of proposed oxygen carriers and processes. 47–49 Previous studies employed the Aspen Plus thermodynamic module to perform simulations and the results were compared to experimental data, which showed very close agreement. Accordingly, Li et al 50 performed syngas chemical looping gasification process simulation and reactor studies using the Aspen Plus simulator in the temperature range of 750–900 °C, where methane and an iron-based oxygen carrier were used to produce syngas in the reducer reactor.…”

Coal-Direct Chemical Looping Process with In Situ Sulfur Capture for Energy Generation Using Ca–Cu Oxygen Carriers

“…Exergy is defined as the total amount of extractable work when the system equilibrates with the reference state. 30 It contains three terms, namely, the physical exergy (eq R9), chemical exergy and mixing exergy (eq R10), and heat exergy (eq R11). For the devices associated with heat exchange, the exergy is defined as the heat exergy.…”

“…Exergy analysis has been identified as a means of comparing the systems on the same basis. Exergy is defined as the total amount of extractable work when the system equilibrates with the reference state . It contains three terms, namely, the physical exergy (eq ), chemical exergy and mixing exergy (eq ), and heat exergy (eq ).…”