Numerical Analysis of Coal Combustion in Circulating Fluidized Bed
combustion of coal is used in circulating fluidized bed combustion system. This work is concerned about gas–solid two-phase mixtures flowing upwards through the fast beds. The type of information resulting from various ways of analyzing the pressure variations and the effect of superficial velocity on pressure in fluidized beds are discussed. This paper presents the standard k–є and two-phase turbulence model used to describe the gas–solids flow in a CFB.The analysis of temperature and density in coal combustion is done by discrete phase model (DPM) and non pre mixed combustion in species model through the PDF file creation in DPM model. The flow temperature and density in the system were modeled by solving the continuity and momentum equations of the gas flow by using the CFD analysis. The fluidizing velocity has been taken as 4 m/s and the effects of operating parameters on mole fraction, mean density and mean temperature are discussed in this paper. It is observed that the mean density of minimum and maximum mean mixture fraction along the scaled variance is significant.
Numerical Investigation on Hydrodynamic Combustion and NOx Emission Behavior in 8 MW Circulating Fluidized Bed
Multi-phase flow is one of the types of flow which is frequently observed in natural phenomena and engineering applications. Circulating fluidized beds constitute an important application of multi-phase flow. The combustion and emission behaviours in circulating fluidized beds are determined by hydrodynamic of bearing. The most appropriate combustion can be provided with the hydrodynamic structure of bearing, taking into account fuel and operating parameters. Therefore, the hydrodynamic structure of circulating fluidized beds should be displayed with mathematical/physical modelling and simulation approach for its analysis and synthesis. Mathematical analysis in today’s conditions is very difficult or impossible because of excessive turbulence, unstable and two-phase flow characteristics of the bed. Therefore, the most effective way to do this is the use the physical modelling and simulation approach. In this study, 8 MW circulating fluidized bed hydrodynamic analysis are made by ANSYSFLUENT R14 commercial CFD code and then combustion and emissions analysis are made with hydrodynamic analysis results. These analysis results show that combustion chamber exit mean NOx emission was 38.5 ppm and combustion chamber exit mean temperature was 1123 K.
Scaffolds Containing Spirulina sp. LEB 18 Biomass: Development, Characterization and Evaluation of In Vitro Biodegradation.
Polymer nanofibers are nanomaterials that can be used as scaffolds in tissue engineering. The objective of this study was to develop, characterize and evaluate the in vitro degradation of a biomaterial consisting of nanofibers produced from biodegradable and biocompatible polymers with potential applications as a scaffold for tissue regeneration and containing Spirulina sp. LEB 18 biomass as the bioactive compound. The polymers used were poly(hydroxybutyrate-co-hydroxyvalerate) and polycaprolactone. The polymeric solutions exhibited sufficiently high viscosity to produce uniform nanofibers with diameters between 335 and 617 nm. The applied conditions were as follows: a voltage of 25 kV, a distance from the capillary to the collector of 120 mm, a capillary diameter of 0.80 mm, and 12% polycaprolactone and a blend of 5% polycaprolactone and 10% poly(hydroxybutyrate-co-hydroxyvalerate). The biomass was incorporated into the nanofibers at a concentration of 3%, and the incorporation was confirmed using confocal microscopy. The nanofibers were characterized using differential scanning calorimetry and thermogravimetric analysis, which showed that the addition of biomass did not alter the thermal properties of the biomaterial. The addition of biomass improved the tensile strength and elongation of the scaffolds compared with those produced with polymers alone. A biodegradation assay showed enzymatic action toward the biomaterial, simulating the behavior of natural tissue. Based on the analysis, it was concluded that the scaffolds that were produced have the potential to be applied in the field of tissue regeneration as biomaterials with pharmacological properties.