Methanation Of Gas Product From Solid Waste Pyrolysis On Ni-Fe Catalysts Under Atmospheric Pressure

Solid waste pyrolysis gasification is a high value utilization of solid waste conversion method. The methanation of solid waste pyrolysis gas can not only reduce the demand for natural gas, but also improve the utilization rate of pyrolysis gas. And if the non-condensable gas product from solid waste pyrolysis continue to proceed methanation reaction under normal pressure, that will save operating costs and energy. Hence, we need a further research on the methanation process conditions and methanation catalysts under atmospheric pressure, in order to find a economic and efficient methanation catalyst which can be directly coupled with them.At first, a series of Ni-Fe/Al2O3 catalysts were prepared with the γ-Al2O3 as the support. The catalysts were synthesized by impregnation method. The results show that the reaction conditions of GHSV of 30000 mL/(g·h)-450000 mL/(g·h), reaction temperature 230℃-33O℃ and atmosphere pressure are the best for conditions for methanation. The Ni-Fe/y-Al2O3 catalysts show high activity. In case of Ni and Fe load in 15%, the catalytic effect is best. BET, XRD and H2-TPR analysis show that, a significant Ni-Fe interaction is observed in the bimetallic Ni-Fe/y-Al2O3 catalyst which can reduce the catalyst reduction temperature. Then we test the lifetime of 15Ni-15Fe/y-Al2O3 catalyst, found the catalyst lifetime is about 12 to 15 h.Then in order to study the influence of TiO2 and preparation methods on catalysts activity and lifetime, a series of 15Ni-15Fe/TiO2-Al2O3 catalysts were prepared by precipitation, co-precipitation and sol-gel method. The results show that 15Ni-15Fe/TiO2-Al2O3 catalysts has a wider methanation suitable temperature range.15Ni-15Fe/TiO2-Al2O3 catalyst prepared by sol-gel method shows best activity. BET, XRD, TEM and H2-TPR analysis show that, TiO2 can weaken the interaction between Al2O3 and NiO. The highly dispersed titanium oxide on the surface of γ-Al2O3 inhibit the formation of nickel aluminate-like phase, which is responsible for the better dispersion of Ni species and easier reduction of NiO species. The stability test on catalysts revealed that the new catalyst had much longer lifetime than Ni-Fe/Al2O3.At last, methanation catalysts macro dynamics model were established by the Powell (PO) optimization method. The methanation process simulation was proceeded by using Aspen Plus software. The results show that the 15Ni-15Fe/TiO2-Al2O3 catalyst shows higher CH4 selectivity, and the methanation on 15Ni-15Fe/TiO2-Al2O3 catalyst reacts more quickly.