IntroductionThe aim of this study is the production of an environmentally friendly fuel (Dimethyl ether-DME) that uses the biogas produced in the anaerobic digestion (AD) from grass silage liquor as a feedstock. Reforming of biogas to synthesis gas (syngas) is a highly endothermic process. Alternative methods of heating (traditional electrical furnace and a 2kW induction heating unit for low and high pressure) are being investigated for less carbon deposition and energy savings. ExperimentalBiogas Production.   Batch and continuous mesophilic anaerobic digestion of grass silage liquor was studied. The continuous process was carried out in Armfield digesters.Biogas Reforming.   A sol-gel method was applied to prepare perovskite Na0.5La0.5Ni0.3Al0.7O2.5 catalyst. Herein two different reactor configurations have been used for the reforming of biogas in a temperature range 600-900 �C.DME Synthesis.   CuO/ZnO/Al2O3 (CZA)/HZSM-5(80) was used as admixed catalyst for DME production from Syngas.DME synthesis was carried out in an isothermal fixed bed reactor. The pressure of the reactor was controlled by means of back pressure regulator. The activity tests were carried out in a temperature range of 200�260 �C, at 20 bar.Catalyst Charactarizations.   XRD, BET, elemental analysis, XPS, DRIFTS and Raman S. were used. Results and Discussion Grass silage liquor can produce a high quality methane stream between 70% and 80% and achieve methane yields of 0.385 m3 kg-1 COD. The catalytic activity of the Na0.5La0.5Ni0.3Al0.7O2.5 perovskites remained stable for 6 h on stream and the catalyst is active enough to give the equilibrium conversion at high reaction temperatures with H2/CO ratio close to 1 as shown in Figure (1).  Figure 1.   Effect of reaction temperatures on CH4 conversion for Na0.5La0.5Ni0.3Al0.7O2.5 perovskite catalyst. For the one step DME synthesis, CZA/HZSM-5 bifunctional catalyst with a 0.25 acid fraction showed high stability over a continuous period of 212 h.  ConclusionsThis work has demonstrated that grass silage liquor can be used to produce a high quality methane stream between 70% and 80% in both batch and continuous reactors. Herein experiments using radiofrequency heating have been performed in order to demonstrate the potential of using rapid heating techniques to convert biogas to a higher heating value syngas. For DME from Syngas, the stability of the CZA/ HZSM-5 with a ratio of 3:1 was studied over a continuous period of 212 h (~9 days) the results showed that the selectivity of DME keep constant over all the period.

Dimethyl ether synthesis for biogas conversion using different heating techniques

247th National Meeting (2014)

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