Archive for November, 2008
A Simple Gasifier Model That Runs in Aspen Dynamics
Gasification has been used in industry on a relatively limited scale for many years, but it is immerging as the premier unit operation in the energy and chemical industries. The switch from expensive and insecure petroleum to solid hydrocarbon sources (coal and biomass) is occurring due to the vast amount of domestic solid resources, national security and global warming issues. Gasification (or partial oxidation) is a vital component of “clean coal” technology. Sulfur and nitrogen emissions can be reduced, overall energy efficiency is increased and carbon dioxide recovery and sequestration are facilitated. Gasification units in an electric power generation plant produce a fuel gas for driving combustion turbines. Gasification units in a chemical plant generate synthesis gas, which can be used to produce a wide spectrum of chemical products. Future plants are predicted to be hybrid power/chemical plants with gasification as the key unit operation. › Continue reading
An Introduction to Galois Groups of CM Fields
A CM field is an imaginary quadratic extension of a totally real number field. In this talk we will explore the properties of the Galois groups of CM fields and consider some research problems related to the classification of all Galois groups of CM fields of a given degree.
Materials for Reversible High Temperature Chemisorption of CO2
Results of experimental tests into the equilibrium and column dynamic data for the chemisorption of CO2 on two materials has identified the materials as potential candidates for the capture of CO2. The first of the materials is a K2CO3 – promoted hydrotalcite that displays good sorption capacity in 400-500 C range. The second is a Na2O -promoted alumina that has shown good sorption capacity in 250-400 C temperature range. The two materials both exhibited Langmuirian behavior in the low pressure region, but deviated substantially in higher pressure regions. A new analytical model that simultaneously accounts for Langmuirian chemisorption and an additional surface complexation reaction between gaseous and sorbed CO2 has been proposed to describe the measured equilibrium data for both materials. Experimental breakthrough tests showed fast kinetics and narrow mass transfer zones for CO2 adsorption. The isosteric heats of chemisorption and heats of additional complexation reaction on both materials were estimated to be low, indicating that desorption of CO2 from both materials could be achieved with relative ease. Tests have confirmed that both materials show stable sorption capacity after several sorption-desorption cycles. These characteristics make them attractive candidates for use in cyclic processes for the capture of CO2. The Na2O promoted alumina shows promise as a candidate for capture of CO2 from flue gas of a coal fired power plant, while the K2CO3 promoted hydrotalcite will be a better candidate for the Sorption Enhanced Reaction process to simultaneously produce fuel cell grade H2 and high purity CO2 at feed gas pressure.