چكيده به لاتين
Abstract:
In recent years, several attempts have been done to reduce the consumption of oil. Nowadays, using natural gas especially methane, and its conversion to liquid fuels is important dueto ease of transportation. Dry reforming of methane consumes two well known harmful greenhouse gases. Fluidized bed reactors have more efficiency than fixed bed ones due to having pros including uniform temporal distribution, prevention of hot spot in reactor, good mixing and high mass transfer, capcability of regeneration of catalyst within the reactor.
In this study, performance of Dry reforming of methane reaction to gas synthesis using Co-Ni/TiO2 as catalyst in bothfixed and fluidized bed reactors is investigated. Increasing the temperature, reducing the space velocity and increasing the amount of carbon dioxide in inlet feed of reactor leads to increase of the conversion of methane as well as H2/CO ratio. Comparisons between fixed and fluidized bed results show that at any temperature, conversions and selectivity relative to H2 is much higher in fluidized beds rather than fixed ones. For instance, at 810°C with feed ratio of CO2/CH4 =1 and space velocity of 7600 ml/grcat.hr, conversions for methane and carbon dioxide is 24.71%, 46.97% in fixed bed and 39.64%, 62.35% in fluidized bed, respectively. This implies the advantage of fluidized bed reactors in methane’s dry reforming rather than fixed bed reactor. In addition, there is more selectivity relative to produced H2/CO in fluidized bed in contrast to fixed bedreactor. For example at 860°C and similar operational conditions in both reactors, the ratio of resulting gas synthesis was 0.92 and 0.96 in fixed and fluidized bed, respectively. Higer ratio of H2/CO in reforming in fluidized bed may be related to the lower relative selectivity with respect to reverse water gas shift reaction in these reactor operations. In fluidized bed, due to the circulation of particles in bed and placement of them in different areas of oxidation and reduction, inactivation of catalyst takes place with lower rate than in fixed beds where there is concentration difference in different regions. After all, SEM and TGA analysis is done on output samples. In order to model the fluidized bed reactor, STP and DTP models are used. Results indicate that STP model represents lower presicion than DTP due to the simplified assumptions. Moreover, DTP model has good match with experimental results except in conditions where the reaction kinetic plays the role of limitor.
Key words: Dry reforming of methane, Ni-Co/TiO2 catalyst, fluidized bed, fluidized bed modeling.
