46 research outputs found
MILD combustion of solid fuels
Get PDFModerate or Intense Low-oxygen Dilution (MILD) combustion has been identified as an innovative technology that offers ultra-low pollutant emissions, high thermal efficiency, enhanced combustion stability, thermal field uniformity, and broad fuel flexibility. MILD combustion of solid fuels has received much less attention than gaseous fuels and its burning characteristics are not well understood. As solid fuels, in particular pulverised coal, form the majority of available fuel sources, there is a need to extend understanding of the application of MILD combustion to pulverised coals. The current research seeks to investigate the MILD combustion characteristics of pulverised coals via experimental and computational approaches. In the first stage of this work, an experimental campaign was conducted to investigate the MILD combustion characteristics of pulverised coal in a laboratory-scale self-recuperative furnace. High volatile Kingston brown coal and low volatile Bowen basin black coal with a particle size in the range of 38-180 μm were injected into the furnace using either CO2 or N2 as a carrier gas. The results point to major differences between the resulting ‘flames’ of the two coals and minor differences associated with the carrier gas in respect to pollutant emissions. Ash content analysis showed that black coal was not burnt effectively, which is thought to be due to the particle residence times being insufficient for complete combustion in the furnace. In the next stage of this research, a comprehensive numerical investigation, using Computational Fluid Dynamics (CFD) modelling, was conducted to understand the influence of three devolatilisation models on the prediction accuracy of pulverised coal MILD combustion. It was found that the advanced chemical percolation devolatilization (CPD) devolatilization model with a three-step global kinetic mechanism gives, as expected, the best agreement with the experimental measurements for the Kingston brown coal case. While all models produced similar results for the Bowen basin black coal case. A new vertical co-flow furnace was also designed and built for this project. The furnace contained an insulated and water-cooled central jet surrounded by a hot and diluted co-flow. The furnace walls, as well as co-flow temperature and local oxygen concentrations, are controlled by a secondary swirling burner using non-premixed natural gas combustion. Loy-Yang brown coal from the Latrobe Valley, Victoria, Australia, with particle sizes in the range of 53-125 μm and 250-355 μm, is injected into the furnace using CO2 as a carrier gas. The bulk jet Reynolds number was varied from Rejet = 5,527 to Rejet = 20,000. In-furnace temperatures and chemical species were measured together with visual observations and CH chemiluminescence (CH*) imaging at the bottom, middle and top parts of the furnace. The CH* signal intensity is found to be significantly lower at the top part of the furnace which is an indication of the slow rate of heterogeneous combustion of char particles. The largest amount of CO concentrations are measured for the highest jet velocity (i.e., Rjet = 20,000) case which implies that with increasing turbulence there is a better mixing and a broad devolatilisation zone is formed which produces more CO. The measured NO emission for any case was less than 125 ppmv (db at 3% O2) which provide evidence to the potential benefits of MILD Combustion application to Victorian brown coal towards reducing NO emission. Complementary CFD modelling study helped in shedding light on the flow field, turbulence intensity, volatiles’ release rate, combustion of volatile matters, and overall carbon consumption inside the furnace for all cases. It was found that increasing the jet Reynolds number increases the volatiles release rates and decrease the rate of overall carbon consumption. It was also found that, for both particles’ size cases, stable MILD combustion is established with a similar large recirculation vortex around the centre of the furnace. Devolatilisation starts earlier for the smaller particles’ case and is completed at the end of the recirculation vortex while for the larger particles’ case the devolatilisation happened post the recirculation vortex. The difference is related to the particle dispersion within the jet and differences in Stokes number. This study provided valuable systematic data for the fundamental understanding of the MILD combustion of solid fuels. The outcomes of this research are a step forward to allow the industry to have better confidence in utilising the MILD combustion technology.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Mechanical Engineering, 2016
Weibull’s analysis of wind power potential at coastal sites in Kuakata, Bangladesh
No full textA statistical analysis of ten minutes interval wind data at 20 m height for different location of Bangladesh has been made. The data has been shorted in sequence of appropriate frequency as hourly, daily and monthly mean wind speed. The data has been presented and analyzed
in velocity friquency bar graph, energy bar graph, velocity duration curve etc. Two important paramets Weibull shape factor “k” and Weibull scale factor “c” have been obtained from the data by three methods. Weibull function F(v), Weibull probability density function f(v) and available energy in the wind (wh/m2) have also been obtained from the wind data.A. K. Azad and Manabendra Sah
Solid fuels flameless combustion
No full textFlameless, also called moderate or intense low-oxygen dilution (MILD) combustion, is an advanced technology to increase combustion stability, enhance thermal efficiency, and reduce pollutant emissions. Flameless combustion of solid fuels has received much less attention than gaseous fuels, and its burning characteristics are not well understood. As solid fuels, particularly pulverized coal, form the majority of available fuel sources, there is a need to extend understanding of flameless combustion to pulverized coals. Furthermore, flameless combustion characteristics of biomass have not been investigated comprehensively. The goal of employing flameless combustion technology to biomass fuels is to eliminate noxious pollutants emissions from renewable and sustainable solid fuels. This chapter presents a technical review of flameless combustion characteristics of solid fuels covering the most recent experimental and computational studies. A complementary experimental case study on the impact of the co-flow oxygen concentration on the flameless combustion characteristics of grape marc as a biomass fuel has been concisely reported. A vitiated co-flow vertical flameless combustion furnace of maximum 60 kW heat capacity is utilized in this experimental campaign. Three different cases with a co-flow oxygen concentration of 6%, 9%, and 12% (v/v) were considered for the investigation. Stable flameless combustion of pulverized grape marc was achieved for all cases. No detectable flame front was observed for any of the experimental cases. A semiuniform thermal field inside the combustion chamber was measured for all cases. The increase of the co-flow oxygen has a positive effect in reducing the NO emission. A fivefold reduction of exhaust NO was measured for the largest co-flow O2 case compared with the lowest O2 case. Future potential research directions on the flameless combustion of solid fuels are described at the end of this chapter.The authors would like to thank Mr. Marc Simpson, Manager, Thebarton Research Laboratory, The University of Adelaide, for his help throughout the experiments
Solvent-free chemoselective protection of aldehydes on the surface of alumina-sulfuric acid
No full textThermo-Mechanical and Morphological Properties of Water Hyacinth Reinforced Polypropylene Composites
Get PDFThis paper focusses on the analysis of thermo-mechanical and morphological properties of water hyacinth (WH) fiber reinforced polypropylene (PP) biocomposites manufactured by using a single screw extruder and an injection molding machine. With a view to increasing the compatibility between the WH fibers and polypropylene matrix, raw WH fibers were chemically treated with Benzenediazonium salt in base media. Composites were manufactured with five different levels of loading (15, 20, 25, 30 and 35 wt%) of both the raw and treated WH fibers. Thermal properties of WH-PP composites were evaluated by thermogravimetric and differential thermal analyses. To analyze mechanical properties of composites, tests of tensile strength and stiffness, flexural strength and stiffness, and Charpy impact strength were carried out following ASTM standards. It was found that thermal stability and all the mechanical properties except tensile strength were improved considerably for chemically treated WH fiber composites in comparison with untreated ones. Fracture surfaces of the tensile and flexural specimens were scanned with scanning electron microscopy (SEM) to understand their surface morphologies. The SEM images clearly revealed that there were fewer fiber agglomerations, microvoids, and fiber pull out traces in treated WH-PP composites than in the untreated ones indicating better distribution of the fibers into the matrix as well as stronger fiber matrix interfacial adhesion due to treatment of WH fibers. Water absorption properties were studied to evaluate the viability of these biocomposites under specified conditions
Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride
No full text4-Aryl-4-oxoesters undergo facile reduction of both the keto and the ester groups with methanolic NaBH4 at room temperature to yield the corresponding 1-aryl-1,4-butanediols whereas 4-alkyl-4-oxoesters furnish the corresponding 1,4-butanolides via selective reduction of the keto moiety. Results of a detailed and systematic investigation of the reaction are described
Moderate or intense low oxygen dilution (mild) combustion characteristics of pulverized coal in a self-recuperative furnace
No full textModerate or Intense Low oxygen Dilution (MILD) combustion is a promising technology that offers high thermal efficiency and low pollutant emissions. This study investigates the MILD combustion characteristics of pulverized coal in a laboratory-scale self-recuperative furnace. High-volatile Kingston brown coal and low-volatile Bowen basin black coal with particle sizes in the range of 38−180 μm were injected into the furnace using either CO₂ or N₂ as a carrier gas. A water-cooled sampling probe was used to conduct in-furnace gas sampling. Measurements of in-furnace gas concentration of O₂, CO, and NO, as well as exhaust gas emissions and in-furnace temperatures, are presented. The results suggest major differences between the two coals and minor differences associated with the carrier gas. It was found that the measured CO level of brown coal cases was 10 times higher than that of black coal cases. However, NO emission for brown coal was only 37% of that measured for black coal at an equivalence ratio of Φ = 0.88. Ash content analysis showed that black coal was not burnt effectively, which is thought to be due to the particle residence times being insufficient for complete combustion in the furnace. To augment the experimental measurements, computational fluid dynamic modeling was used to investigate the effects of coal particle size and inlet air momentum on furnace dynamics and global CO emissions. It is found that coal particle size affects the coal penetration depth within the furnace and the location of the particle’s stagnation point. The effects of air inlet momentum are tested in two ways: first, by raising the inlet temperature at a constant mass flow rate, and, second, by increasing the mass flow rate at a constant temperature. In both cases, increasing the air jet momentum broadens the reaction zone and facilitates MILD combustion, but also lowers reaction rates and increases CO emissions.Manabendra Saha, Bassam B. Dally, Paul R. Medwell, and Emmet M. Clear
Comparative Study of the MILD Combustion Characteristics of Biomass and Brown Coal
No full textThe present paper reports a comparative study on the burning characteristics of pulverized biomass and coal under moderate or intense low-oxygen diluted (MILD) combustion conditions. Two types of biomass fuels—namely, grape marc and almond husk—and a high volatile Victorian brown coal were used as pulverized fuels to burn in a vitiated coflow inside a vertical MILD combustion furnace. The furnace walls, as well as coflow temperature, and local oxygen concentrations were controlled by a secondary swirling burner. Fuels were introduced into the furnace employing CO₂ as a carrier gas with a constant velocity (i.e., bulk jet Reynolds number, Rejet = 20 000) and a fixed range of particle sizes (250–355 μm). Detailed measurements of in-furnace and exhaust temperatures and chemical species (i.e., O₂, CO, CO₂, and NO) are demonstrated and discussed, together with optical images at the top, middle, and bottom sections of the furnace. It was found that MILD combustion was successfully established for all of the fuels investigated without any visible flame inside the furnace. Under similar experimental conditions, biomass volatiles are released earlier leading to a difference of the maximum temperature within the furnace of ∼150 K along the centerline. The largest NO emission was measured to be ∼185 ppmv (db at 3% excess O₂) for grape marc case, because of the higher value of in-fuel N of grape marc and the lowest was ∼125 ppmv (db at 3% excess O₂) for coal case. From the comparison of CO emission, biomass shows more eminent burning characteristics than brown coal under MILD combustion conditions.Manabendra Saha, Giovanni Gitto, Alfonso Chinnici, and Bassam B. Dall
Magnetodielectric effect in composites of nanodimensional glass and CuO nanoparticles
No full textNanocomposites comprising CuO particles of average diameter 21 nm coated with 5 nm silica glass containing iron ions were synthesized by a chemical route. An ion exchange reaction at the nanoglass/CuO interface produced iron-doped CuO with copper ion vacancies within the nanoparticles. Room temperature ferromagnetic-like behavior was observed in the nanocomposites. This was ascribed to uncompensated spins contributed by Fe ions with associated copper ion vacancies. A rather high value of magnetodielectric parameter in the range 16–26% depending on the measuring frequency was exhibited by these nanocomposites at a magnetic field of 10 KOe. This was caused by a magnetoresistance of 33% in the iron doped CuO nanoparticles. The experimental results were fitted to the Maxwell–Wagner Capacitor model developed by Catalan. These materials will be suited for magnetic sensor applications
Intelligent instrumentation: principles and applications
No full textWith the advent of microprocessors and digital-processing technologies as catalyst, classical sensors capable of simple signal conditioning operations have evolved rapidly to take on higher and more specialized functions including validation, compensation, and classification. This new category of sensor expands the scope of incorporating intelligence into instrumentation systems, yet with such rapid changes, there has developed no universal standard for design, definition, or requirement with which to unify intelligent instrumentation. Explaining the underlying design methodologies of intelligent instrumentation, Intelligent Instrumentation: Principles and Applications provides a comprehensive and authoritative resource on the scientific foundations from which to coordinate and advance the field. Employing a textbook-like language, this book translates methodologies to more than 80 numerical examples, and provides applications in 14 case studies for a complete and working understanding of the material. Beginning with a brief introduction to the basic concepts of process, process parameters, sensors and transducers, and classification of transducers, the book describes the performance characteristics of instrumentation and measurement systems and discusses static and dynamic characteristics, various types of sensor signals, and the concepts of signal representations, various transforms, and their operations in both static and dynamic conditions. It describes smart sensors, cogent sensors, soft sensors, self-validating sensors, VLSI sensors, temperature-compensating sensors, microcontrollers and ANN-based sensors, and indirect measurement sensors. The author examines intelligent sensor signal conditioning such as calibration, linearization, and compensation, along with a wide variety of calibration and linearization techniques using circuits, analog-to-digital converters (ADCs), microcontrollers, ANNs, and software. The final chapters highlight ANN techniques for pattern classification, recognition, prognostic diagnosis, fault detection, linearization, and calibration as well as important interfacing protocols in the wireless networking platform
