Executive Summary :
|Bio-oil derived from biomass cannot be used as a transportation fuel due to instability by undesirable oxygenated compounds present in it. Thus downstream upgrading process is beneficial in enhancing the properties of bio-oil and hydrodeoxygenation (HDO) process is found to be academically most promising technique. Nevertheless, it has limitations such as expensive catalysts and severe reaction conditions where hydrogen reacting with bio-oil at high temperatures and high pressures. This is the main limitation that the process has not been commercialized in India. Thus, Investigators have proposed the following techniques that address these issues and make the process commercially feasible. The experimental part includes in-situ catalytic pyrolysis of biomass with the introduction of methanol after reaching pyrolysis reactor temperature 200°C. Then pyrolysis would be continued till temperature reaches 600°C and maintain the same for 2 hours. In this first step, partial upgrading takes place because of methanol steam reforming along with biomass thermal degradation; and hydrogen generated by methanol steam reforming cause partial deoxygenation. In the next step, this partially upgraded bio-oil will be mixed with methanol (less than 15 %) and fed into reforming unit where both methanol steam reforming and vaporising of bio-oil takes place; and hydrogen generated due to methanol steam reforming would react with oxygenated vapours of bio-oil in order to further deoxygenate bio-oil. In the final step, output from reforming unit, i.e., vapours consisting of partially upgraded bio-oil and in-situ hydrogen fed into circulating fluidized bed which is filled with bio-char of in-situ catalytic pyrolysis in addition to zeolite or metal-doped carbon catalyst and maintained at 350-450°C. In this final step complete deoxygenation of bio-oil is aimed to be completed by tuning temperature and pressure and by providing external hydrogen and/or nitrogen gas. Unreacted bio-char and catalyst are separated from outgoing vapours in a cyclone and regenerated in a regeneration unit before fed back to riser column. Vapours free from catalyst and bio-char particles would be condensed and separated in a gas-liquid separator and upgraded fuel-grade bio-fuel is collected. The main advantage of this multistage upgrading is that there is no need or negligible need of hydrogen from external source and the entire process is under atmospheric conditions except in the circulating fluidized bed where if required pressure may be increased to a maximum of 10bar. In numerical part, hydrodeoxygenation of bio-oil will be studied using a combined CFD and DFT approach and after establishing its benchmarking this approach would be used for scaling of reactor because scaling by experimentally may be very cumbersome and costly task.
The products expected by end of the project are:
1. Biofuel of HHV 40 – 45 MJ/kg
2. Value added chemicals for Paints and Glue Industries
3. Bio-char as feedstock for fertilizer industries