Dusko Posarac

Assessment of four biodiesel production processes using HYSYS.Plant

Four continuous biodiesel processes were designed and simulated in HYSYS. The first two employed traditional homogeneous alkali and acid catalysts. The third and fourth processes used a heterogeneous acid catalyst and a supercritical method to convert a waste vegetable oil feedstock into biodiesel. While all four processes were capable of producing biodiesel at high purity, the heterogeneous and supercritical processes were the least complex and had the smallest number of unit operations. Material and energy flows, as well as sized unit operation blocks, were used to conduct an economic assessment of each process. Total capital investment, total manufacturing cost and after tax rate-of-return were calculated for each process. The heterogeneous acid catalyst process had the lowest total capital investment and manufacturing costs, and had the only positive after tax rate-of-return.

Simulation, Case Studies and Optimization of a Biodiesel Process with a Solid Acid Catalyst

A commercial process simulator was used to develop a detailed simulation of a biodiesel production process, and carry out case studies and optimization. The simulated process produced biodiesel from a feedstock containing 5 wt.% free fatty acids in a fixed-bed reactor with sulfated-zirconia as an acidic catalyst. Sized unit operation blocks, material and energy flows were used to conduct an economic assessment of the process. Total capital investment, total manufacturing cost, after tax rate-of-return and production cost (

Modeling of Autothermal Steam Methane Reforming in a Fluidized Bed Membrane Reactor

/kg) were all determined for the process. The process was then optimized by maximizing the after tax rate-of-return (ATROR). Based on our previous work, the most economical process for transesterification of waste vegetable oil at the scale of 8000 metric tones/yr of biodiesel production among the four processes examined was based on a solid acid catalyst reaction. Our results showed that the process is economically feasible, even without government subsidy, while at the same time, the produced biodiesel met the required ASTM standard for purity.

Heterologous expression of LamA gene encoded endo-β-1,3-glucanase and CO2 fixation by bioengineered Synechococcus sp. PCC 7002

Fluidized bed reactors for steam methane reforming, with and without immersed membrane surfaces for withdrawal of hydrogen, are modeled with oxygen added in order to provide the endothermic heat required by the reforming reactions. Porous alumina, palladium and palladium-coated high-flux tubes are investigated as separation materials, the latter two being permselective. Hydrogen yield and permeate hydrogen molar flow are predicted to decrease with increasing oxygen flow, and to increase with temperature. When the steam-to-carbon ratio increases, permeate hydrogen yield decreases slightly, while the total hydrogen yield increases for all configurations. The flow of oxygen required to achieve autothermal conditions depends on such factors as the reactor temperature, steam-to-carbon ratio and preheating of the feed.

Modeling, Simulation and Experimental Study of Methanol Synthesis for 11C Radiopharmaceuticals

The gene for the catalytic domain of thermostable endo-β-1,3-glucanase (laminarinase) LamA was cloned from Thermotoga maritima MSB8 and heterologously expressed in a bioengineered Synechococcus sp. PCC 7002. The mutant strain was cultured in a photobioreactor to assess biomass yield, recombinant laminarinase activity, and CO2 uptake. The maximum enzyme activity was observed at a pH of 8.0 and a temperature of 70°C. At a CO2 concentration of 5%, we obtained a maximum specific growth rate of 0.083 h–1, a biomass productivity of 0.42 g∙L–1∙d–1, a biomass concentration of 3.697 g∙L–1, and a specific enzyme activity of the mutant strain of 4.325 U∙mg–1 dry mass. All parameters decreased as CO2 concentration increased from 5% to 10% and further to 15% CO2, except enzyme activity, which increased from 5% to 10% CO2. However, the mutant culture still grew at 15% CO2 concentration, as reflected by the biomass productivity (0.26 g∙L–1∙d–1), biomass concentration (2.416 g∙L–1), and specific enzyme activity (3.247 U∙mg–1 dry mass).

Process simulation and economic analysis of biodiesel production processes using fresh and waste vegetable oil and supercritical methanol

Carbon-11 radiopharmaceuticals are gaining an increasing importance in positron emission tomography due to their importance in diagnostic medicine. The most wide spread method of production of these radiopharmaceuticals is by methylation of an appropriate precursor with the highly reactive [11C]methyl iodide. Conventional synthesis of this intermediate involves liquid phase synthesis of [11C]methanol, which is the step that limits the specific activity of the final product. To avoid the loss of specific activity, a catalytic gas phase methanol synthesis process was evaluated. In this procedure, [11C]carbon monoxide would be reduced to [11C]methanol using a copper zinc oxide catalyst in the presence of hydrogen.In this study, a reactor to catalytically convert 50 ppm carbon monoxide to methanol was developed. A copper zinc oxide catalyst was prepared by a co-precipitation method. The catalyst was activated by reduction with hydrogen and passivated with oxygen prior to methanol synthesis. The effects of temperature, pressure and flowrate on the conversion of carbon monoxide to methanol were studied. The experimental results were used in conjunction with a commercially available process simulator to fit a kinetic model for methanol synthesis from carbon monoxide. This model was used to determine optimal operating conditions for this reactor and predicts a 60% conversion of [11C]carbon monoxide to [11C]methanol. These findings suggest that gas phase [11C]methanol synthesis is a viable alternative to the conventional liquid phase method, meriting further studies with carbon-11.