Study On Biommass Char Catalytic Reforming Technology Of Pyrolysis Tar

The use of biomass energy is an important way in solving the energy problem and gasification technology is the most effective technology at present. The high tar concentration in pyrolysis gas is the bottleneck of biomass gasification technology for large-scale extension. Biomass char is a product of the pyrolysis process of biomass and can be used as catalyst in tar cracking. Steam at high temperature has the function of tar reforming. The combination of biomass char catalytic cracking technology with steam reforming technology is an effective technical means in eliminating tar.Firstly, the progress of catalytic cracking and steam reforming of tar nowadays were reviewed, including the performances of various catalysts, the effects of operating conditions on catalytic performance, catalyst coking and regeneration, the effect of steam reforming and mechanism of catalytic reforming. On the basis, the technical route was proposed, combining biomass char catalyst technology with steam reforming technology in tar degradation.Secondly, by laboratory-scale experiment, the catalytic reforming performances of tar were studied. And from the studies of tar conversion rate, pyrolysis products and pyrolysis gas composition, it was known that the reforming technology would promote production of condensed phase reduced and gas production increased, with maximum tar conversion rate up to 96.1%. The combustible components increased in pyrolysis gas, in which change of hydrogen content was the most significant, up to 50.2% of pyrolysis gas volume. From the results of experiments, it was known that catalytic cracking temperature and S/C had greater impact on the catalytic properties while that of nitrogen flow was relatively small. The length of catalytic cracking zone and steam addition method also had a certain effect. And under different experimental conditions, the microstructure of biomass char also changed.Thirdly, the gasification performances of two kinds of biomass char by experiment method were studied, including conversion rate and gasification gas component with temperature. And experimental results showed that gasification temperature had important effect on the conversion rate. With the increasing of gasification temperature, carbon conversion rate increased, but the trend slowed down. In the range of experimental temperature, char conversion rate was no more than 30.0%. The gas yields of biomass char gasification increased with the increasing of temperature and gas component were also changed significantly. In addition, experimental results also indicated that gas output of char gasification was about 20.0% of general gas output.Fourthly, on the basis of experiment, the kinetics of tar catalytic reforming and biomass char gasification were studied and the first order kinetic model was obtained by regression method. Through the comparison of simulation data and experimental data, the model was proved to be correct. So, the general kinetic model of tar catalytic reforming was proposed to simulate the tar catalytic reforming process under different conditions.Finally, on the basis of experimental and theoretical analysis, the new biomass gasification system of combination biomass carbon catalyst and tar steam reforming was put forward. And the mass and energy balance of system were analyzed, especially the carbon balance and waste heat utilization of the system was studied.