Modelling of integrated processes for the pyrolysis and steam reforming of rice husk (Oryza sativa)

Thermochemical processes can be used to harness the energetic content of agricultural residues. This study utilises ASPEN Plus v8.8 to develop thermodynamic models for pyrolysis and in-line steam reforming of rice husk (Oryza sativa). The pyrolysis simulation at 500 degrees C and 1 atm gave a product yield of 36.3% oil, 49.6% char and 14.1% gas. Whilst the gas was composed of lighter hydrocarbons, the char was primarily elemental carbon and SiO2. The pyrolysis oil was composed of higher hydrocarbons, an assortment aromatic compounds and pyrolytic water. Optimum parameters for the steam reforming process were 700 degrees C, 1 atm and a steam-to-gas molar ratio of 7. The product composition at optimal conditions was 67% hydrogen gas, 19% carbon dioxide, 12% carbon monoxide and 2% methane. For a theoretical biomass feed of 200 kg/h and steam feed of 1400 kg/h, the synthesis gas flowrate obtained from the process was 204 kg/h and the rest were char and condensate water. This has gone a long way to reinforce our idea that the energy content of locally sourced rice (O. sativa) husk can be harnessed via different thermochemical techniques to give good yields of very useful products.