3-Hydroxypropionaldehyde （3-HPA） is a potential valuable chemical and new broad-spectrum antim-icrobial substance. In order to improve the conversion of 3-HPA/glycerol, our work studied the two-step process from gly...3-Hydroxypropionaldehyde （3-HPA） is a potential valuable chemical and new broad-spectrum antim-icrobial substance. In order to improve the conversion of 3-HPA/glycerol, our work studied the two-step process from glycerol to 3-HPA, and investigated the influence of cell harvest time, glycerol concentration, biomass con-centration, pH and temperature on the production of 3-HPA by Lactobacillus reuteri CG001, respectively. The re-sults showed that molar conversion yield of 3-HPA/glycerol reached 97.9% under the condition that 200 mmol·L-1 glycerol was converted by 25.3 g·L-1 resting cell for 1 h at 30 ℃. The cells could not be reused directly because the L. reuteri almost lost its bioconversion activity completely, but the ability of glycerol conversion could gradually recover if the fresh medium was added to the deactivated cell for 4 h.展开更多
A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can ch...A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can change in the radial direction. The carbon dioxide is used as the gasification agent that reacts with the char and form carbon monoxide. The presence of both solid and gaseous phase species makes the reaction heterogeneous. The char particle is considered with varying porosity that also allows the change in the surface area of the particle. A time invariant temperature and pressure profile is used at which the Arrhenius rate constant and diffusion is calculated. The mass conservation of model results in the form of two coupled partial differential and one ordinary differential equation. The equations are solved with a set of initial and boundary conditions using the bulk species concentration at the particle surface. A second order accurate central differencing scheme is used to discretize space while backward differencing is used to discretize time. Finally, the results are presented for the concentration distribution of CO and CO2 in radial direction with respect to time. It shows that, maximum concentration of CO is present at the center of the particle while the concentration gradient becomes higher near the particle surface. The nonlinear concentration trend due to the diffusion is effectively captured. The results show that, completed conversion of char depend upon the time provided for the reaction which can be reduced by decreasing the size of particle or increasing the reaction temperature. The sensitivity study of temperature and initial porosity also performed and showed that temperature has high impact on char conversion as compare to initial porosity.展开更多
Thermodynamically, electric storages can be generally characterized as a type of regenerative machines able to operate in a work and a power machine mode. A consideration of the concentration term of the Nernst equati...Thermodynamically, electric storages can be generally characterized as a type of regenerative machines able to operate in a work and a power machine mode. A consideration of the concentration term of the Nernst equation already shows a first principal difference between batch and flow processes, because the reaction coordinate depends on time for batch processes and on the flow coordinate for flow processes. Ionic substances may be stored within a volume surrounding the electrodes or on the surface of the electrodes itself. The volume concentrations of the reactants are thus a determining parameter of electrochemical storage beside voltage and the ratio of released electrons per reacting reference substance. Surface storage allows only batch processes while volume storage allows batch and flow processes. This characterization identifies the benefits of certain reactions regarding mass and volume related energy density in a simple way at a very early stage of development. It also allows a simple calculation of possible discharging times.展开更多
基金Supported by the National-Natural Science Foundation of China （20906035） and the Fundamental Research Funds for the Central Universities （JB-JX 1002）.
文摘3-Hydroxypropionaldehyde （3-HPA） is a potential valuable chemical and new broad-spectrum antim-icrobial substance. In order to improve the conversion of 3-HPA/glycerol, our work studied the two-step process from glycerol to 3-HPA, and investigated the influence of cell harvest time, glycerol concentration, biomass con-centration, pH and temperature on the production of 3-HPA by Lactobacillus reuteri CG001, respectively. The re-sults showed that molar conversion yield of 3-HPA/glycerol reached 97.9% under the condition that 200 mmol·L-1 glycerol was converted by 25.3 g·L-1 resting cell for 1 h at 30 ℃. The cells could not be reused directly because the L. reuteri almost lost its bioconversion activity completely, but the ability of glycerol conversion could gradually recover if the fresh medium was added to the deactivated cell for 4 h.
文摘A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can change in the radial direction. The carbon dioxide is used as the gasification agent that reacts with the char and form carbon monoxide. The presence of both solid and gaseous phase species makes the reaction heterogeneous. The char particle is considered with varying porosity that also allows the change in the surface area of the particle. A time invariant temperature and pressure profile is used at which the Arrhenius rate constant and diffusion is calculated. The mass conservation of model results in the form of two coupled partial differential and one ordinary differential equation. The equations are solved with a set of initial and boundary conditions using the bulk species concentration at the particle surface. A second order accurate central differencing scheme is used to discretize space while backward differencing is used to discretize time. Finally, the results are presented for the concentration distribution of CO and CO2 in radial direction with respect to time. It shows that, maximum concentration of CO is present at the center of the particle while the concentration gradient becomes higher near the particle surface. The nonlinear concentration trend due to the diffusion is effectively captured. The results show that, completed conversion of char depend upon the time provided for the reaction which can be reduced by decreasing the size of particle or increasing the reaction temperature. The sensitivity study of temperature and initial porosity also performed and showed that temperature has high impact on char conversion as compare to initial porosity.
文摘Thermodynamically, electric storages can be generally characterized as a type of regenerative machines able to operate in a work and a power machine mode. A consideration of the concentration term of the Nernst equation already shows a first principal difference between batch and flow processes, because the reaction coordinate depends on time for batch processes and on the flow coordinate for flow processes. Ionic substances may be stored within a volume surrounding the electrodes or on the surface of the electrodes itself. The volume concentrations of the reactants are thus a determining parameter of electrochemical storage beside voltage and the ratio of released electrons per reacting reference substance. Surface storage allows only batch processes while volume storage allows batch and flow processes. This characterization identifies the benefits of certain reactions regarding mass and volume related energy density in a simple way at a very early stage of development. It also allows a simple calculation of possible discharging times.
