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In order to simulate the performance of chemical looping combustion (CLC) of pure methane in a continuous bubbling fluidized bed process using a NiO-based oxygen carrier under various operating conditions, this study has developed a mathematical model based on the reaction kinetics and population balance of oxygen carrier (OC) particles in each reactor. Proper operating conditions have been discussed for complete combustion of methane. The minimum OC circulation rate for complete combustion was determined with the variation of temperature and fuel bed mass. The methane combustion efficiency was strongly affected by the distribution of OC between the air reactor (AR) and fuel reactor (FR) at a constant temperature, circulation rate of OC, and total bed mass. The range of OC distribution possible to achieve complete combustion became wider with increasing either the temperature or the circulation rate of OC at a constant total bed mass. In tested conditions of a labscale process, the range on the OC mass ratio of the fuel reactor to the total bed mass extended from 0.527−0.607 to 0.430− 0.705 with an increasing temperature of AR and FR from 850 to 900 °C (circulation rate of OC = 3 g/s, total bed mass = 22.89 kg). It also extended from 0.527−0.607 to 0.491−0.643 with increasing the circulation rate of OC from 3 g/s to 10 g/s (temperature of AR and FR = 850 °C, total bed mass = 22.89 kg). In this range, the amount of elutriated OC particles decreased a little as the FR mass increased because of the higher rates of particle elutriation and attrition in AR than in FR.

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Steam-methane reforming (SMR) reaction was studied using a tubular reactor packed with NiO/γ-Al 2 O 3 catalyst to obtain synthesis gases with H 2 /CO ratios optimal for the production of synthetic diesel fuel from steamhydrogasification of carbonaceous materials. Pure CH 4 and CH 4 -CO 2 mixtures were used as reactants in the presence of steam. SMR runs were conducted at various operation parameters. Increasing temperature from 873 to 1,023 K decreased H 2 /CO ratio from 20 to 12. H 2 /CO ratio decreased from 16 to 12 with pressure decreasing from 12.8 to 1.7 bars. H 2 /CO ratio also decreased from about 11 to 7 with steam/CH 4 ratio of feed decreasing from 5 to 2, the lowest limit to avoid severe coking. With pure CH 4 as the feed, H 2 /CO ratio of synthesis gas could not be lowered to the optimal range of 4-5 by adjusting the operation parameters; however, the limitation in optimizing the H 2 /CO ratio for synthetic diesel fuel production could be removed by introducing CO 2 to CH 4 feed to make CH 4 -CO 2 mixtures. This effect can be primarily attributed to the contributions by CO 2 reforming of CH 4 as well as reverse water-gas shift reaction, which led to lower H 2 /CO ratio for the synthesis gas. A simulation technique, ASPEN Plus, was applied to verify the consistency between experimental data and simulation results. The model satisfactorily simulated changes of H 2 /CO ratio versus the operation parameters as well as the effect of CO 2 addition to CH 4 feed.