Research On Thermodynamics Of Hydrogen Production And Process Of Hydrofining For Bio-oil Upgrading

Biomass, which can be used for producing large-scale liquid fuel, is considered to be the ideal substitute of petroleum and petro-based chemical products. Bio-oil production by biomass fast pyrolysis is an important way of the transformation of biomass energy. Due to the bio-oil with high oxygen content, bio-oil needs to be upgraded, and hydrofining is an important technique for bio-oil upgrading. In the process development of bio-oil upgrading, the reforming of bio-oil light component for hydrogen production and the hydrofining of heavy compounds are key processes.Concerning the thermodynamics of bio-oil reforming for hydrogen production and the bio-oil hydrofining process for liquid hydrocarbon fuels, these have yet to be further improved. This paper focuses on the two aspects, which provides technical reference for the industrialization of bio-oil fuel.Because of the complexity of the bio-oil component, model compounds were used in many studies. In this paper, using Aspen Plus software, the thermodynamic analysis of hydrogen production from steam reforming was carried out by selecting some bio-oil models, and the integrated process of biomass fast pyrolysis for producing bio-oil and bio-oil reforming for hydrogen production and hydrofining was established. The integrated process is simulated and analyzed.Firstly, acetic acid, acetol, furfural and vanillin were respectively chosen for a single model of bio-oil, and thermodynamic analysis of hydrogen production from steam reforming of these model compounds were presented. The results showed that the effects of temperature, steam to carbon molar ratio and pressure on the product equilibrium yield of the four model compounds were similar. Lower pressure, higher temperature and higher steam to carbon molar ratio are in favor of higher H2 production. Under the condition of pressure 0.1 MPa, temperature 800 ~ 1000 K and the steam to carbon molar ratio 4 ~ 8, H2 yields of four models are greater than 85%.The amount of coke decreases with the increasing of temperature and steam to carbon molar ratio, and little coke forms when steam to carbon ratio is above 4.Secondly, the typical model compounds of bio-oil light component were selectedto form simulated bio-oil. The thermodynamic analysis of hydrogen production from steam reforming of simulated bio-oil was presented. The results show that the thermodynamic law of hydrogen production from simulated bio-oil reforming is similar to that from the single component model. The steam reforming processes of simulated bio-oil, natural gas and ethanol were compared and analyzed. For 1 mol/s H2 yield, the required amount of simulated bio-oil, natural gas and ethanol is 0.190mol/s, 0.245 mol/s and 0.189 mol/s, respectively. Energy analysis results show that energy consumption of hydrogen production from steam reforming of simulated bio-oil is slightly lower than natural gas.Finally, based on related research results, suitable material component models and reactor models were selected, and an integrated process for the preparation and hydrofining of bio-oil was established. The integrated process includs four sections:biomass fast pyrolysis, bio-oil hydrofining, hydrocracking and continuous distillation,light component reforming of bio-oil for hydrogen production. The simulation results show that the yield of gasoline and diesel oil is respectively 8% and 10.3% when using dry corn straw as raw material. The yield of by-product H2 and char is 1.9% and7.1%, respectively. The energy efficiency of the corn stover fast pyrolysis process for producing bio-oil is 74.81%. And, the energy efficiency of the integrated process for producing gasoline and diesel oil by corn straw is 52.5%.