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CO2 Addition (co2 + addition)
Selected AbstractsChemical effects of CO2 addition to oxidizer and fuel streams on flame structure in H2,O2 counterflow diffusion flamesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2003Jeong Park Abstract Numerical simulation of CO2 addition effects to fuel and oxidizer streams on flame structure has been conducted with detailed chemistry in H2,O2 diffusion flames of a counterflow configuration. An artificial species, which displaces added CO2 in the fuel- and oxidizer-sides and has the same thermochemical, transport, and radiation properties to that of added CO2, is introduced to extract pure chemical effects in flame structure. Chemical effects due to thermal dissociation of added CO2 causes the reduction flame temperature in addition to some thermal effects. The reason why flame temperature due to chemical effects is larger in cases of CO2 addition to oxidizer stream is well explained though a defined characteristic strain rate. The produced CO is responsible for the reaction, CO2+H=CO+OH and takes its origin from chemical effects due to thermal dissociation. It is also found that the behavior of produced CO mole fraction is closely related to added CO2 mole fraction, maximum H mole fraction and its position, and maximum flame temperature and its position. Copyright © 2003 John Wiley & Sons, Ltd. [source] Thermal and chemical contributions of added H2O and CO2 to major flame structures and NO emission characteristics in H2/N2 laminar diffusion flameINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2002Seung-Gon Kim Abstract Numerical simulation with detailed chemistry has been carried out to clearly discriminate the thermal and chemical contributions of added diluents (H2O and CO2) to major flame structures and NO emission characteristics in H2/N2 counterflow diffusion flame. The pertinence of GRI, Miller,Bowman, and their recent modified mechanisms are estimated for the combined fuel of H2, CO2, and N2. A virtual species X, which displaces the individual CO2 and H2O in the fuel sides, is introduced to separate chemical effects from thermal effects. In the case of H2O addition the chain branching reaction, H + O2 , O + OH is considerably augmented in comparison with that in the case of CO2 addition. It is also seen that there exists a chemically super-adiabatic effect in flame temperature due to the breakdown of H2O. The reaction path of CH2O,CH2OH,CH3 and the C1-branch reactions become predominant due to the breakdown of CO2. In NO emission behaviour super-equilibrium effects caused by the surplus chain carrier radicals due to the breakdown of added H2O are more superior to the enhanced effects of prompt NO with the breakdown of added CO2. Especially, it is noted that thermal NO emission is directly influenced by the chemical super-equilibrium effects of chain carrier radicals in the case of H2O addition. As a result the overall NO emission in the case of the addition of H2O is higher than that in the case of CO2 addition. Copyright © 2002 John Wiley & Sons, Ltd. [source] NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/ArINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2002Jeong Park Abstract Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. [source] Combined Carbon Dioxide and High Pressure Inactivation of Pectin Methylesterase, Polyphenol Oxidase, Lactobacillus plantarum and Escherichia coliJOURNAL OF FOOD SCIENCE, Issue 2 2002H. Corwin ABSTRACT: High pressure processing (HPP) and CO2have both been shown to increase food product shelf-life. CO2 was added at approximately 0.2 molar % to solutions processed at 500 to 800 MPa in order to further inactivate pectin methylesterase (PME), polyphenol oxidase (PPO), L. plantarum ATCC 8014, and E. coli K12. An interaction was found between CO2 and pressure at 25 °C and 50 °C for PME and PPO, respectively. Activity of PPO was decreased by CO2 at all pressure treatments. The interaction between CO2 and pressure was significant for L. plantarum with a significant decrease in survivors due to the addition of CO2 at all pressures studied. No significant effect on E. coli survivors was seen with CO2 addition. [source] Nonstationary model of the semicontinuous depolymerization of polycarbonateAICHE JOURNAL, Issue 12 2006Raúl Piñero-Hernanz Abstract The experimental work for the depolymerization process of Bisphenol A polycarbonate pellets and CD/DVD wastes in a semicontinuous reactor and a novel nonstationary model to describe the process is presented. The different steps of the process to develop the model are analyzed thoroughly. The kinetics of the alkali-catalyzed methanolysis of polycarbonate was determined. The reactor and kinetic models were validated by a series of 21 experiments performed in a laboratory semicontinuous tubular reactor at isothermal conditions from 90 to 180°C and pressures from 1.0 to 20.0 MPa in liquid phase, with and without NaOH concentrations of 1 × 10,3 to 5 × 10,3 kg/L, flow rates from 2.3 × 10,3 to 10.2 × 10,3 L/min, and CO2 molar fractions from zero to 0.374. The effects of temperature, pressure, catalyst amount, mass transfer (solvent flow rate), and CO2 addition in kinetics were investigated. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Addition of Carbon Dioxide to Dairy Products to Improve Quality: A Comprehensive ReviewCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 4 2006Joseph H. Hotchkiss ABSTRACT:,Changes in distribution patterns and demand for increased food quality have resulted in a desire to improve the shelf life of nonsterile dairy products. Refrigerated shelf life extension typically requires, at a minimum, reductions in the growth rate of spoilage microorganisms and subsequent product deterioration. Reducing initial bacterial loads, increasing pasteurization regimes, and reducing postprocessing contamination have all been employed with measured success. The use of antimicrobial additives has been discouraged primarily due to labeling requirements and perceived toxicity risks. Carbon dioxide (CO2) is a naturally occurring milk component and inhibitory toward select dairy spoilage microorganisms; however, the precise mechanism is not fully understood. CO2 addition through modified atmosphere packaging or direct injection as a cost-effective shelf life extension strategy is used commercially worldwide for some dairy products and is being considered for others as well. New CO2 technologies are being developed for improvements in the shelf life, quality, and yield of a diversity of dairy products, including raw and pasteurized milk, cheeses, cottage cheese, yogurt, and fermented dairy beverages. Here we present a comprehensive review of past and present research related to quality improvement of such dairy products using CO2. [source] | ||||||||||