Thermodynamic Analyses of Tri-reforming Reactions To Produce Syngas

Abstract

Thermodynamic analysis of tri-reforming reactions to produce synthesis gas has been conducted by total Gibbs energy minimization to understand the effects of process variables, such as temperature (200−1000 °C), pressure (1−20 atm), and inlet O 2 /CH 4 (0−1.0), H 2 O/CH 4 (0−3.0), and CO 2 /CH 4 (0−3.0) mole ratios on the product distribution. The results reveal that high temperature and low pressure are favorable to achieve high H 2 production and CO 2 conversion. In addition, excessive additions of H 2 O, O 2 , and CO 2 bring about lower H 2 yield and CO 2 conversion, while low concentrations of H 2 O, O 2 , and CO 2 result in more intense carbon formation. To attain the maximum H 2 yield and high CO 2 conversion coupled with a desired synthesis gas (H 2 /CO) ratio for the downstream methanol production and effective elimination of carbon formation, the corresponding optimum feed ratio in tri-reforming process is identified to be CH 4 /CO 2 /H 2 O/O 2 = 1:0.291:0.576:0.088.

Energy efficient methane tri-reforming for synthesis gas production over highly coke resistant nanocrystalline Ni–ZrO2 catalyst

“…7a-c illustrated the effect of variation of O 2 concentration on methane, CO 2 , H 2 O conversions and H 2 /CO ratios. The effect of concentration of O 2 on the reactant conversion was mainly due to the heat generated by the partial oxidation and complete oxidation of methane and the enhanced coke removal process [41,60]. With increase in O 2 concentration, chances of complete oxidation of methane increases.…”

“…The generated heat was utilized by the endothermic reactions taking place in the process minimizing the required temperature to obtain higher CH 4 conversion [57] and the external energy input. Low concentration of O 2 in the reaction feed leads to lower reactant conversion and at high temperature H 2 O and CO 2 reacts with unreacted methane to produce synthesis gas [41]. Up to a certain O 2 concentration, conversion of the reactants increased with increasing O 2 concentration.…”

“…But the main problem with the partial oxidation is, it can lead to hot spot generation, which can be dangerous and increases the possibility of explosions [1]. The heat generated in the process by partial and complete oxidation of methane by O 2 can be used in the process, which increases the energy efficiency and a thermo neutral balance can be achieved [41][42][43]. The partial oxidation of methane also produces CO 2 and H 2 O, which also can be utilized during the reaction without any loss of reaction feed.…”

“…The partial oxidation of methane also produces CO 2 and H 2 O, which also can be utilized during the reaction without any loss of reaction feed. These advantages make this process quite economic and energy saving [41][42][43][44]. The use of tri-reforming process eliminates the most serious problem of coke deposition and high energy consumption by incorporation H 2 O and O 2 in a single reactor system [28].…”

“…The enhanced effect of surface oxygen vacancies on reactant conversions was reported by Pino et al [35] over La doped Ni-CeO 2 catalyst. In a recent article Zhang et al [41] reported about the effect of feed ratios on H 2 -yield and CO 2 conversion by carrying out a thermodynamic analysis. Kang et al [43] carried out methane tri-reforming over Ni-YSZ-CeO 2 catalyst and reported that the process is more favorable than methane dry reforming for synthesis gas production.…”