Numerical simulation of industrial scale autothermal Chemical Looping Methane Reforming for syngas production in a dual fluidised bed reactor

Methane reforming is one of the important technologies that produce syngas or hydrogen for the production of significant products, e.g. ammonia, methanol, and for petrochemical processes [1]. Steam methane reforming (SMR), the dominating methane reforming technology, produces almost 7 kg of CO2 while producing 1 kg of H2, which accounts for 3% of CO2 emission from industrial sector [2]. Converting methane to syngas and hydrogen efficiently and environmental friendly is of vital importance under the background that climate change and global warming is largely caused by greenhouse gas emission. Autothermal Chemical Looping Reforming (aCLR) is a process that intrinsically avoids CO2 emission and minimizes energy loss [3]. It is generally realised in a dual-fluidised bed reactor that act as fuel reactor (FR) and air reactor (AR), respectively. The oxygen carrier (OC) particles is oxidised by air in AR, while in FR, the OC is reduced by the syngas and acts as catalyst for methane reforming. In this work, an industrial scale a-CLR plant (equals to 50 SMR pipes) that consists of a bubbling fluidised bed FR and a riser AR was designed via the numerical simulation of aCLR system by 1-D model couples fluidised bed hydrodynamics with reaction kinetics. The system is schematically shown in Figure 1.Nickel based OC/catalyst was selected due to its high hydrogen selectivity and catalytic activity. The mass and heat balance were done to guarantee the designed operating temperature and CH4 conversion. The system is considered that syngas is the only desired product and as a self-sustained that only blow energy is imputed from the outside. The effects of desired operating parameters on the design and performances of both reactors were discussed from the system point of view. Results show that the catalyst particle size affects the dimensions of FR when the production capacity is specified. Unlike in Chemical Looping Combustion (CLC), slightly oxidation of OC in the AR is sufficient to maintain autothermal condition in the aCLR and OC is basically existed as Ni in FR. The diffusion of methane limits its conversion in FR, while operating temperature hardly affects the conversion of methane. However, the operating temperature of FR does affect the conversion of OC in AR due to the faster oxidisation rate of Ni at higher temperature. Although higher temperature difference between AR and FR, at the expense of increasing the solids’ resistance time in the AR, leads to lower solids circulating rate, the oxygen/fuel ratio remains unchanged. As expected, the steam/CH4 ratio in the FR inlet affects the outlet CO/CO2 ratio. With energy recover from the outlet of both reactor, the hydrogen production ratio is slightly higher than POM