In order to study the effect of minerals on biomass pyrolysis, experiments on pyrolysis of corn straw with different pretreatment methods were performed by using a thermogravimetric analyzer（TGA） coupled with a Four...In order to study the effect of minerals on biomass pyrolysis, experiments on pyrolysis of corn straw with different pretreatment methods were performed by using a thermogravimetric analyzer（TGA） coupled with a Fourier transform infrared （FTIR） spectrometer. The pretreatment methods included water washing and acid washing. The experimental results show that acid washing can remove almost all K^＋ and 78% of Ca^2＋ , while water washing only removes most of K ^＋. The existence of K^＋ and Ca^2＋ obviously favors the formation of compounds containing carbonyl groups and CO2 , but it will decrease the yields of compounds containing C-O-C groups. However, the formation of H2O, CO and CH4 are slightly affected by the removal of inorganic ions. With regard to the structure of the metal ions-adsorbed cellulose characterized by IR analysis, it can be considered that there is an ＂ion force＂ between metal ions and cellulosic biomass. The results of thermal kinetic analysis show that this force can make the reaction activation energy of the biomass pyrolysis decrease. A new mechanism is proposed for explaining the effect of inorganic ions on cellulose pyrolysis.展开更多
Recent studies on hydrogen combustion were reviewed briefly. The laminar flow and combustion of premixed hydrogen/air mixture in a cylindrical channel of a monolith reactor with and without catalytic wall was numerica...Recent studies on hydrogen combustion were reviewed briefly. The laminar flow and combustion of premixed hydrogen/air mixture in a cylindrical channel of a monolith reactor with and without catalytic wall was numerically modeled by solving two-dimensional (2-D) Navier-Stokes (N-S) equations, energy equation, and species equations. Eight gas species and twenty reversible gas reactions were considered. The control volume technique and the SIMPLE algorithm were used to solve the partial differential equations. The streamlines of the flow field, temperature contours, the entrance length, and the concentration fields were computed. It is found that the entrance zone plays an important role on flow and temperature as well as species distribution. Therefore, the flow cannot be assumed either as fully developed or as plug flow. There is a small but strong thermal expansion zone between the wall and the entrance. Both diffusion and convection affect the heat and mass transfer processes in the expansion zone. Thus the equations of momentum, energy and species conservations should be used to describe hydrogen/air combustion in the monolith reactor. The hot-spot location and concentration field of the homogeneous combustion is strongly influenced by the inlet velocity and temperature, and the equivalence ratio. The catalytic combustion of premixed hydrogen/air mixture over platinum catalyst-coated wall in a cylindrical channel was also simulated.展开更多
基金Supported by the National High Technology Research and Development Program of China(No. 2003AA514023) and the Na-tional Basic Research Program of China(No. 2004CB719700)
文摘In order to study the effect of minerals on biomass pyrolysis, experiments on pyrolysis of corn straw with different pretreatment methods were performed by using a thermogravimetric analyzer（TGA） coupled with a Fourier transform infrared （FTIR） spectrometer. The pretreatment methods included water washing and acid washing. The experimental results show that acid washing can remove almost all K^＋ and 78% of Ca^2＋ , while water washing only removes most of K ^＋. The existence of K^＋ and Ca^2＋ obviously favors the formation of compounds containing carbonyl groups and CO2 , but it will decrease the yields of compounds containing C-O-C groups. However, the formation of H2O, CO and CH4 are slightly affected by the removal of inorganic ions. With regard to the structure of the metal ions-adsorbed cellulose characterized by IR analysis, it can be considered that there is an ＂ion force＂ between metal ions and cellulosic biomass. The results of thermal kinetic analysis show that this force can make the reaction activation energy of the biomass pyrolysis decrease. A new mechanism is proposed for explaining the effect of inorganic ions on cellulose pyrolysis.
基金Foundation item: Partially supported by the Key Laboratory of Multiphase Reaction of the Chinese Academy of Sciences State Key of Coal Conversion of the Chinese Academy of Sciences
文摘Recent studies on hydrogen combustion were reviewed briefly. The laminar flow and combustion of premixed hydrogen/air mixture in a cylindrical channel of a monolith reactor with and without catalytic wall was numerically modeled by solving two-dimensional (2-D) Navier-Stokes (N-S) equations, energy equation, and species equations. Eight gas species and twenty reversible gas reactions were considered. The control volume technique and the SIMPLE algorithm were used to solve the partial differential equations. The streamlines of the flow field, temperature contours, the entrance length, and the concentration fields were computed. It is found that the entrance zone plays an important role on flow and temperature as well as species distribution. Therefore, the flow cannot be assumed either as fully developed or as plug flow. There is a small but strong thermal expansion zone between the wall and the entrance. Both diffusion and convection affect the heat and mass transfer processes in the expansion zone. Thus the equations of momentum, energy and species conservations should be used to describe hydrogen/air combustion in the monolith reactor. The hot-spot location and concentration field of the homogeneous combustion is strongly influenced by the inlet velocity and temperature, and the equivalence ratio. The catalytic combustion of premixed hydrogen/air mixture over platinum catalyst-coated wall in a cylindrical channel was also simulated.
