Thermodynamic Study of Transformation of Methane to Synthesis Gas Over Metal Oxides

Abstract

A metal oxide reduction-water splitting cycle is a new developing method to produce synthesis gas without using a catalyst. In the reduction stage, metal oxide reduction and methane activation are combined in an efficient and energy-saving process using methane as a reducing agent. In this study, the effect of temperature and reductant (oxidant) amount on the equilibrium composition of products, graphitic carbon formation, yield of synthesis gas (water splitting stage), and produced H 2 /CO ratio are thermodynamically investigated. This investigation includes metal oxides of zinc, tin, cobalt, and nickel. The results show that the synthesis gas is produced simultaneously with gaseous zinc, molten tin, solid cobalt, and solid nickel for those metal oxides in the reduction process. In the case of tin oxide, the feasibility of the graphitic carbon formation is less than the other oxides. The maximum yield of synthesis gas occurs in the stoichiometric molar ratio of methanothermal reduction reactions. From the methane consumption point of view, zinc oxide has a much higher synthesis gas yield. Finally, it is proposed that cobalt and nickel oxides can be used only in the reduction stage to produce synthesis gas and reduced metals due to low equilibrium conversion in the water splitting stage. The metal oxide reduction-water splitting cycle can be developed as an environmentally friendly technology for synthesis gas production over metal oxides.

Analysis of Biphasic Cracking of Methane for Hydrogen Production Using Solar Energy

“…Geometry of the calculation domain reason, the methane is almost completely converted to hydrogen. Table 2 summarizes the hydrogen mass fractions obtained by simulation while applying a maximum radiation of 16 MW/m 2 to the side wall of the reactor, as shown in Figure 4, bearing in mind that we used [11][12][13][14] to choose values between 16 and 1 MW/m 2 Figure 5 shows the mass fraction of carbon through the reactor at time t = 27s, knowing that ANSYS FLUENT calculates each phase separately. It is clear that at the reactor inlet, the fraction of the carbon is equal to zero and as at t=27s, the reactor becomes entirely hot, which allows the cracking of methane before reaching the wall subjected to concentrated solar radiation.…”

“…Figure 7. Profiles of the static temperature of the gas phase obtained by simulation between 1 and 27 second along the reactor with maximum solar radiation of 16MW/m 2 Figure 8 summarizes the percentage of hydrogen obtained by simulation while applying a maximum radiation of 5MW/m 2 on the side wall of the reactor as shown in Figure 4, based on work of [11][12][13][14][15][16] to select values between 5 and 1 MW/m 2 (q1=5MW/m 2 , q2=2MW/m 2 and q3=1MW/m 2 ). As the previous case and initially (t = 0s) the reactor is empty, the first quantities of methane will be cracked (between 0 and 5seconds) and with time these quantities become important (between 10 and 40seconds) and the conversion of these methanequantities, require more energy and therefore the cracking rate decreases but this cracking rate resumes and increases again from the 40 th second under the effect of the transport of energy by the flow.At time about 90 seconds the permanent regime is reached.…”

“… Thermo-chemical cycles [2,[5][6][7][8][9][10][11][12][13] with two steps taking place under moderate temperatures, require the preparation of the metal oxides or others used in chemical reactions. These cycles also require special equipment and major problems of contamination are posed.…”

Comparison of the exergy efficiency of four power generation systems from methane using fuel cells

“…11,14,15 Later, proposals on the application of CLC for H 2 production have been expanded signicantly over the last 10 years, e.g. SMR integrated with CLC (SMR-CLC), 5,[16][17][18] auto-thermal chemical-looping reforming (CLR) 19,20 and MC integrated with CLC (MC-CLC). 9 Chen et al 21 recently incorporated a coal gasication process with SOFC and CLC.…”

“…The predicted plant net power efficiency is about 49.8% with complete CO 2 separation. The thermodynamics of CLC-GT, 11,14,15 SMR-CLC 16,17 and CLR 19,20 have been intensively studied. Nevertheless, investigations on process simulation and thermodynamics of the processes of the SOFC integrated with CLC and the MC integrated with fuel cells are limited.…”