Gasification of Biomass using Solar Energy by Angelo Maria Sepe Supervisor: Dr. Manosh Paul Introduction Objectives Modeling the gasification process Reactor Concept Chemical Equilibrium Analysis Solar flux sensitivity analysis Main results Principal objectives of this work are: • To perform an analysis of the state of the art of Solar Gasification technology. • To design an efficient solar reactor configuration. • To develop a computational model to asses and evaluate reactor performance. • To asses the solar technology benefits respect to conventional gasifiers. • To compare different type of suitable feedstock to be used in a solar-assisted process Nowadays, one of the most important challenge is the development of sustainable energy processes to satisfy the increasingly demand of energy but also able to slash carbon emissions. The majority of greenhouse gases emission is coming from combustion of fossil fuels, which is still the predominant way to produce energy. The gasification of fossil fuels is a well-studied and established way to generate quality gas products. A promising alternative to the conventional gasification process is represented by Solar-assisted steam-only gasification, which can convert biomass or fossil fuels into a quality syngas, high in H 2 content and CO 2 free. Concentrated solar energy is used to drive the highly endothermic gasification reactions. A 1D multi-phase steady-state model has been created and implemented in MATLAB. The gasification process is modelled by means of heterogeneous and homogenous gasification reactions that were coupled with a radiative transfer method based on the radiative flux density. Pyrolysis was modeled as a one-step mechanism. A system of highly coupled differential equations composed by Mass and Energy balances for both solid and gas phases were solved with a finite volume method and using an implicit solver. Species concentration, temperature profile and gas production rates are examined. Heterogenous (Solid - Gas) reactions: Rs1 C + 1/2O 2 → CO Rs2 C + CO 2 → 2CO Rs3 C + 2H 2 → CH 4 Rs4 C + H 2 O → H 2 + CO Homogeneuous (Gas - Gas ) reactions: Rg1 CO + ½ O 2 → CO 2 Rg2 H 2 + ½ O 2 →H 2 O Rg3 CH 4 + 2 O 2 →CO 2 + 2H 2 O Rg4 C m H n + (m/2 + n/4) O 2 → mCO 2 + n/2 H 2 O Rws CO + H 2 O ←→CO 2 + H 2 Solid energy balance: Irradiance given by Rosseland approx.: A zero-D model has been developed to provide an overview of syngas production in function of key parameters as Temperature, ER, Steam/Carbon ratio. 1. Solar gasification using steam as gasification agent proved to be an extremely efficient way to convert different type of fuels into high quality gas. 2. Fixed bed technology seems to be the most suitable for this scope since it is more efficient than other reactor types. 3. Increasing the solar input increases syngas production rates. 4. An optimal value of the solar input can be found, after what results stall. 5. Biomass is the feedstock with major gains for highly concentrated solar inputs. 6. The most critical zone in a solar reactor is the bed entrance, which is where important reactions and heat&mass transfers take place. 7. Hybrid solar/O 2 systems can be used to prolong the operative time of a solar gasificator. A new solar-assisted gasificator has been proposed in fixed bed, downdraft configuration. This type of reactor was chosen for its documented high efficiency and versatility. Solar - assisted gasification process Source: B.J. Hathaway,Integration of solar gasification with conventional fuel production. Autothermal vs Solar