A novel intensified microreactor for syngas production by coupling reduction-oxidation reactions in chemical looping reforming process

Syngas production in micro-scale reactors could enhance heat and mass transfer with suitable dynamic behavior. Seeking environmentally friendly and energy efficient, chemical looping reforming could be employed for not only syngas production, but also lower CO2 emission. In this process, while the reduction part has a role of indirect clean combustion of fossil fuels such as methane with an oxygen carrier such as NiO without NOx emission, oxygen is transferred to the depleted NiO in the oxidation part. In the present work, a microreactor assembly is proposed to thermally couple the reduction and oxidation reactors. The proposed geometry is mathematically modeled and analyzed. The configuration not only uses the heat of oxidation, but also mitigates temperature fluctuations inside the channels which is harmful for all oxygen carriers. After the performance study of two separate reduction and oxidation reactors in adiabatic mode, coupling of two reactors is analyzed for syngas production in the reduction reactor. The results show that in contrast to the separate adiabatic reactors, lower temperature changes with a maximum of 125 K is attained in the thermally coupled mode. Effective parameters such as thermal conductivity, reaction rates, H2 and CO production rates and solid conversions are investigated. The produced syngas has a H2:CO ratio of about 6 which is reduced by adding CO2 gas into the feed. The results also show that a 38% decrease in H2:CO ratio is resulted from a 100% increase of CO2:CH4 ratio. Analysis of the channel dimension shows that the syngas production is dropped with increasing channel width due to decrease in effective surface to volume of the reactor. The results demonstrate feasibility of an intensified micro system for small scale syngas production using chemical looping reforming technology.