bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane and Ethane Combustion in an Inert Fluidized Bed
Authors: Z˙ukowski Witold
Published: October 2008

Burning premixed fuel-air mixtures in a bubbling fluidized bed is accompanied by some characteristic phenomena. The most striking one is the production of acoustic effects, indicating that combustion is not really continuous. A second, less obvious effect, is the NOx concentration in the flue gases falling with increasing bed temperature, observed above a certain critical mean bed temperature. To investigate the periodic burning of portions of methane-air mixture, photometric and acoustic signals were recorded simultaneously. Using a laboratory quartz reactor, explosions could be optically recorded in the bed, millimeters above distributor. With ethane fuel, the effective “combustion zone” in the reactor was also located by determining vertical temperature profiles, using eight thermocouples. When the bed temperature rises, maxima in the vertical temperature profiles associated with the “reaction zone” move from above the bubbling bed to the distributor. A mathematical model of unsteady combustion in a single bubble surrounded by bed material was used to simulate the process. Computed temperature maxima were compared with the experimental profiles. This meant finding the region where bubbles of premixed gases exploded, experimentally and from the model. A correlation between the NOx concentration and the location of the explosions (and diameter of the exploding bubbles) has also been found.
FBC: Laboratory Scale Research to Small Scale Practical Operation
Authors: Bulewicz E. M. , Kandefer S. , Pilawska M. , Z˙ukowski W. , Baron J.
Published: October 2008

Working with a small, bubbling laboratory scale fluidised bed combustor for many years, helped to gain some insights into the fundamental physicochemical processes taking place in fluidised bed combustors in general, irrespective of size. For example, it has been demonstrated that during coal combustion as a rule the gases leaving the bed cannot be assumed to be at full thermal equilibrium and that when gases are burned the associated acoustic and visual phenomena can be explained in terms of bubbles of the combustible gases exploding within the bed. Much of the experience gained in running the laboratory system has been used in small scale practice, in designing and controlling small, but successful fluidised bed combustors up to about 3 MW. Several 1MW units have now been in operation for over 10 years. It has also been demonstrated that small bubbling bed combustors can be used for disposing of certain biomass and other wastes.
Observations on the Hydration Behaviour of a Selection of Bed and Fly Ashes From FBC Installations
Authors: Anthony E. J. , Bulewicz E. M. , Go´ra D. , Najman J.
Published: October 2008

The behaviour of FBC ash/water systems is complex and the hydration behaviour of FBC ashes attracts attention both for environmental reasons and because hydration could be used to reactivate the ashes for further use in SO2 capture. In a recent study, hydration of 16 FBC bed and fly ashes from industrial installations firing high-ash coal and mine wastes was studied. Saturated steam at ∼165°C was employed; samples were analyzed chemically and investigated by X-ray diffraction (XRD) and thermal analysis (TGA). One of the more important results was that in some of the ashes there was no unreacted CaO and no Ca(OH)2 after hydration, and they could even consume CaO added to them before hydration. XRD evidence was also obtained to show that a hydrated calcium silico-aluminate (katoite) was formed during the hydration of ashes high in excess, unreacted CaO. The same ashes were used in the present study. The methods used were the same, but the bed ashes were divided into three size fractions and hydration by saturated steam at 100°C was employed. The results generally confirmed the earlier findings. Differences were small but could be significant. First, no katoite could be detected after hydration, so its formation (and possibly that of other compounds of that type) may require more drastic hydration conditions. Second, small quantities of Ca(OH)2 were detected in most hydrated samples. Third, systematic differences between bed ash size fractions were found. In particular, the proportion of anhydrite and the degree of CaO to CaSO4 conversion steadily increased with decreasing particle size fraction, but in the corresponding fly ash was lower and for lime-rich ashes, much lower.
Combustion Tests on a Blend of Liquid Refinery Residues and Coal: CFBC Operation Behaviour and Emissions Characteristics With Special Emphasis on the Intermediate Species CxHy, HCN and NH3
Authors: Kretschmann M. , Barczus Chr. , Scherer V.
Published: October 2008

Investigations on the combustion of a blend of liquid refinery residues and a hard coal are presented in the current paper. The experiments were done in an atmospheric circulating fluidized bed combustor (CFBC) with a thermal capacity of 100 kW. The operation behaviour and pollutant formation characteristics are determined using axial profile measurements at 19 different ports along the combustion chamber. The measurement campaign included the variation of the primary to secondary air ratio, the global air to fuel ratio, the residence time in the primary zone, the overall temperature of the combustion chamber and the Ca/S ratio. The current paper concentrates on results obtained at primary air ratio of 0.65, an overall air ratio of 1.1, a mean combustion temperature of 850°C and a Ca/S-ratio of 0. Measurement of the flue gas components O2, CxHy, CO, CO2, H2, NOx, N2O, NH3 and SO2 are made by standard gas analysing techniques. In order to detect the specific hydrocarbon species produced and oxidized during the combustion process a Fourier Transformation Infrared Spectrometer (FTIR) extends the existing gas analysis system. The gas species measured by FTIR-Spectroscopy are CH4, C2H2, C2H4, C2H6, C3H6 and C3H8. Also the important precursors for the NOx-Formation HCN and NH3 are examined with the FTIR-Spectrometer in the primary and secondary zone. The current experiments are compared with results obtained by burning liquid refinery residues only, with special regard to the consumption of the nitrogenous intermediates HCN and NH3.
An ALSTOM Vision of Future CFB Technology Based Power Plant Concepts
Authors: Jukkola Glen , Liljedahl Greg , Nsakala Nsakala Ya , Morin Jean-Xavier , Andrus Herb
Published: October 2008

ALSTOM is actively working to develop circulating fluidized bed (CFB) based technologies to continue to reduce costs and mitigate CO2. Advanced ALSTOM concepts include “the oxygen-fired CFB,” which uses pure oxygen plus recirculated flue gas (mainly CO2) as a combustion medium, resulting in a flue gas stream with a high CO2 concentration. Consequently, CO2 can be separated from the flue gas stream relatively easily. As such, this technology is geared toward CO2 mitigation. Another advancement, “the circulating moving bed (CMBTM)” system, uses a novel heat exchanger design that heats the energy cycle working fluid to the high temperature levels required for advanced power generation systems. The CMBTM combustion system is also an enabling technology for hydrogen production and CO2 capture from combustion systems utilizing innovative chemical looping gasification and syngas decarbonization. Chemical looping is another development path towards CO2 mitigation. In ALSTOM’s processes, oxygen (from air) is transported by a solid oxygen carrier for combustion or gasification of the fuel. CO2 is captured in a separate chemical loop in the gasification process. The process can be used to produce nearly pure CO2 and steam for a Rankine cycle; or synthesis gas or hydrogen with CO2 capture for IGCC’s, fuel cells, or industrial use. This paper will discuss ALSTOM’s latest work and the technical and economic implications of these advanced CFB-based systems. These advanced power generation units can be built from proven fluid bed design features and systems and the same processes supporting current-state technology enable rational development of future-state power generation and CO2 capture.
Clean Power From Coal: Design and Status of East Kentucky Power Cooperative’s E. A. Gilbert Unit
Authors: Treff Peter , Johnson Craig
Published: October 2008

East Kentucky Power Cooperative’s (EKPC) E. A. Gilbert unit promises to be one of the cleanest coal fired units in the US. Employing Circulating Fluid Bed (CFB) technology and innovative gas cleaning equipment from ALSTOM, this 268 MW unit will fire a variety of coals. The E. A. Gilbert unit is located at EKPC’s Spurlock Station alongside a 300 MW and a 500 MW pulverized coal unit that were built more than 20 years ago. Low SO2 emissions will be achieved by sulfation of limestone sorbent in the CFB and by additional sulfation of unreacted sorbent in the Flash Dryer AbsorberTM (FDA) system located downstream of the CFB. This will permit low SO2 emissions (0.2 lb/MM BTU, >95% removal). Very low NOx emissions (0.1 lb/MM BTU) are enabled by the low combustion temperatures of the CFB and by the use of selective non-catalytic reduction (SNCR). The latter employs the addition of anhydrous ammonia and extended residence times at low temperature to further reduce NOx within the boiler. Having broken ground in June of 2002, the unit is scheduled to begin firing coal in the winter of 2004–5, with commercial operation scheduled for spring, 2005. Its’ design features and status are the focus of this paper.
Appearance of Trace Elements in Co-Firing Fuels
Authors: Zevenhoven Maria , Backman Rainer , Skrifvars Bengt-Johan , Hupa Mikko
Published: October 2008

With the implementation of new EU guidelines the levels of maximum allowable emission levels of Cd, Tl, Hg, Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V will be further restricted. This may have implications for co-combustion of coal with waste derived fuels. In this study chemical fractionation, i.e. a stepwise leaching procedure has been applied on coal, peat, sewage sludge, bark, impregnated wood and forest residue. With this method fuels are leached in three steps, i.e. leached with water, ammonium acetate and hydro chloric acid, respectively. Both solubility in different leaching agents of main ash forming matter and the trace elements Cd, Tl, Hg, Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V and Zn were studied. In this way more information became available about the characteristics of co-firing fuels. Thermodynamic calculations were used to show the consequences of the interaction with main ash forming elements on the partition of Cd, Hg, Pb and Zn in the gas/ash phase.
Steam Reactivation of FB Spent Sorbent for Enhanced SO2 Capture: The Relationship Between Microstructural Properties and Sulphur Uptake
Authors: Montagnaro Fabio , Scala Fabrizio , Pallonetto Fabio , Salatino Piero
Published: October 2008

This paper addresses the regeneration of the sulphur capture ability of FB spent SO2 sorbent particles by steam hydration. The process was characterized in terms of hydration degree, particle sulphation pattern, development of accessible porosity and extent of particle fragmentation. Steam reactivation experiments were carried out in a lab-scale fluidized bed reactor at 250°C for 10 and 30 minutes, and 3h. The sorbent particle size range was 0.4–0.6mm, and the bed was fluidized at 0.2m/s with a steam-N2 mixture. The effectiveness of sorbent reactivation was assessed by reinjecting the reactivated material into the FB reactor (fluidized at 0.8m/s) operated at 850°C under simulated desulphurization conditions (the fluidizing gas consisted of a SO2-O2-N2 mixture), and following the degree of calcium conversion and the attrition rate along with resulphation. The experimental results indicated that steam reactivation is effective in renewing the SO2 uptake ability of the exhausted sorbent particles. Moreover steam reactivation induces, in the samples investigated, a strong sulphur redistribution throughout the particle cross-section, which contributes to the enhancement of the sulphur capture ability of the reactivated sorbent.
Revamping of 2×32 MWe Pulverized Coal-Fired Boilers With Circulating Fluidized Bed Firing
Authors: Dutta Animesh , Sen Amar , Basu Prabir
Published: October 2008

A techno-economic feasibility study has been conducted to investigate revamping two 32 MWe pulverized-coal (PC) boilers with circulating fluidized bed (CFB) firing. The steam generators at Panki Thermal Power Station in Kanpur, Uttar Pradesh, are owned by Uttar Pradesh Rajya Vidyut Utpadon Nigam Limited (UPRVUNL), supplied by Waagner Biro, Austria, and commissioned in 1967–68. The study reveals that: (i) CFB revamping of the boilers is technically feasible and economically viable; (ii) Performance improvement of the plant is significant in terms of such indices as plant load factor, forced outage and a auxiliary oil consumption, among others. The expected performance improvement is due in large part to the elimination of key outage-prone components such as pulverizers (mills) and burners. (iii) Significant improvement in emissions performance due to the reduction in emissions of NOx and fly ash is projected. (iv) The financial analysis indicates that the CFB revamping option gives the highest return on investment compared to alternatives. Finally, to demonstrate the technical soundness and viability of the special design used in this revamping a sub-scale CFB boiler has been design and built at another power plant.
Optimization Process of Biomass Combustion in the Advanced FBC Using Factorial Design and Response Surface Methodology
Authors: Zhu Shijun , Liu Yun , Lee Seong
Published: October 2008

This paper studied the optimization process of the combustion of poultry waste material (i.e. poultry manure) in an advanced fluidized bed combustor (FBC) with the secondary air tangential injection. In order to test the influences of combustion parameters on the carbon combustion efficiency, factorial design (FD) and response surface methodology (RSM) were applied in the experimental process and data analysis. The parameters studied were moisture content, waste/natural gas ratio, excess air ratio, secondary/total air ratio, and the height levels of the secondary air injection. Using the 25−1 fractional factorial design, moisture content, excess air and secondary air injection height were found to be significant for the carbon combustion efficiency at the critical level of type-I error α = 0.1. The RSM was used to approach the optimal combustion condition. The optimal condition regarding the significant factors was found. Then the data from a validation experiment was compared with the computed combustion efficiency under the optimal condition. The result showed the combustion efficiency for poultry manure can reach up to 83%, which indicated that the poultry manure could be effectively burned in the advanced FBC.
A Novel Inertial Separator for CFB Boilers
Authors: Chen Han-Ping , He Qiao , Zhang Shi-Hong , Zheng Chu-Guang , Liu De-Chang , Wu Jun , Ren Lu-Jun , Zhang Hua , Li Chang-Lin , Wang Rong
Published: October 2008

Besides several cyclone separators, some inertial separators had also developed and applied in the circulating fluidized bed (CFB) boilers. The inertial separators have some advantages such as simple structure, small volume, low pressure drop, easy scale-up and so on. But almost every existing inertia separator has great difficulty in solving the main shortage of lower separation efficiency especially for fine particles. Based on the research for the separation mechanism and performances of inertial separators, the State Key Laboratory of Coal Combustion (SKLCC) had developed a novel inertial separator for CFB boilers. The patented separator improves the structure of the U-beam that is the separation element of U-beam separators of Studsvik Energiteknik (Sweden) and Babcok & Wilcox (USA). A ash channel is added to avoid re-entrainment of the separated solid downward along the U-beam. Test result indicates that the novel separator has great higher separation efficiency with the same pressure drop, compared with the U-beams at same conditions. The novel separator is more suitable for a larger CFB boiler or repowering projects as primary separator than the U-beams. The novel inertial separator had been used for designing 25 ∼ 420 tons of steam per hour (t/h) two-stage-recirculation CFB boilers. The two-stage-recirculation CFB boilers in capacity of 25 t/h and 65t/h had been put into operation. This paper presents the work on research, development and application of the novel inertial separator with high separation efficiency and low pressure drop.
Optimizing Ammonia Injection in Bio-Fuelled CFBCs
Authors: Coda Zabetta Edgardo , Yrjas Patrik , Hupa Mikko , Roppo Juha , Nylund Marko
Published: October 2008

The reduction of nitrogen oxides (NOx) via ammonia injection (NH3) was investigated for circulating fluidized bed combustors (CFBCs) fuelled with mixtures of coal, peat, wood, bark, and logging residues. The reference boiler was the Alholmen Kraft, i.e. the largest co-fired unit in the world (550 MWth, 194 kg/s, 165 bar, 545 °C). The boiler featured ammonia injectors at the cyclone. Fuel composition, gas composition, and temperature were measured at suitable locations along the boiler while operating with diverse fuel mixtures. A chemical model was developed for analyzing the NOx reduction and was validated against measurements. The model accounts for the elemental composition of fuels, the composition of gases at the cyclone and in the stack, and the profile of temperature from cyclone to stack. The chemical reactions downstream the ammonia injection are described by gas-phase detailed chemical kinetics and accounting for ideal mixing. Measurements and simulations reveal that NOx reductions of over 50% are achievable for any fuel mixture and with moderate amounts of ammonia. Reductions are mainly affected by the temperature. All simulations show the existence of a maximum reduction vs. temperature, whose extent and location is affected by the concentrations of CO, NO, and the molar ratio [NH3]injected/[NO]cyclone. Simulations also indicate that with fuel mixtures other than the mixtures used in the reference boiler the maximum reduction is also affected by the concentrations of H2O, O2, CxHy, and N2O. Finally, simulations suggest an additional strategy for reducing emissions in co-fired CFBCs, where the N2O formed from coal is used to support the NOx reduction by ammonia, thus reducing NOx while maintaining acceptable N2O emissions. Further investigation is necessary for clarifying the details of this strategy. Under all circumstances, the only N-based pollutants predicted in detectable amounts are NO and N2O.
Development of the Bed Particle Size Distribution in a Circulating Fluidized Bed Combustor
Authors: Klett Cornelis , Hartge Ernst-Ulrich , Werther Joachim
Published: October 2008

In the present work a particle population balance model for a circulating fluidized bed combustor (CFBC) is developed that allows a description of the fate of individual particles in terms of attrition and transport effects. Besides the operating conditions and the particle size distribution the residence time of particles in the system is considered in the modeling of abrasion and shrinking of particles. The model takes account of the fact that fresh particles have a higher attrition rate than particles which have stayed for some time already in the system. The model aims at the description of the dynamic adjustment of the particle size distributions in a given system. The model has been validated with experimental data from a pilot-plant combustor, i.e. a CFBC with an inner diameter of 0.1 m and a height of 15 m. A comparison between experimental and calculated data shows the applicability of the model.
NOx and N2O Emission Formation Tendency From Multifuel CFB-Boilers: A Further Development of the Predictor
Authors: Engblom Markus , Kilpinen Pia , Klingstedt Fredrik , Era¨nen Kari , Katam Kumar Ranjit
Published: October 2008

Present paper is a part of our on-going model development activities with aim to predict formation tendency of gaseous emissions from CFB combustion of different fuels, and especially, fuel-mixtures in real furnaces of various scale. The model is based on detailed description of homogeneous, catalytic, and heterogeneous chemical kinetics, and a sound but simple 1.5D representation of fluid dynamics. Temperature distribution is assumed known. With the tool, different fuels and fuel mixtures can be compared in respect to their tendency to form nitrogen oxides (NOx, N2O). In this paper the model was tested to predict nitrogen oxide emissions from mono- or co-combustion of coal, wood, and sludge. The plants simulated were the 12MWth CFB combustor located at Chalmers Technical University (A = 2.25m2, h = 13.6m) and the pilot scale CFB unit at the Technical University Hamburg-Harburg (d = 0.1m, h = 15m). The results gave reasonable representation of the measured emission data, and reflected correctly to the changes in the fuel characteristics and in the furnace operating conditions in most cases. An extensive laboratory fixed-bed reactor study was also performed in order to obtain input values for the kinetic constants of the catalytic reactions for the reduction and decomposition of nitrogen oxides. In literature, there is a limited data available regarding the catalytic activity of CFB solids during combustion of wood- and waste-derived fuels, especially at co-firing conditions. The kinetics for the NO reduction by CO in the temperature range of 780–910°C was determined to be of the following form (NO = 300ppm, CO = 5000ppm): −rNO=k·[NO]0.48·[CO]0.55mol/g-s with k=8.15·exp(−8869/T)m3/kg-s(emptyreactoreffectincluded)ork=830·exp(−14930/T)(emptyreactoreffectexcluded), when using a bed sample (250–355 μm) taken from the transport zone in the CTH boiler while burning a mixture of wood pellets and a pre-dried municipal sewage sludge. The role of char particle size and shape as well as the incorporation of energy balance on the char reactivity and the formation of nitrogen oxides is further illustrated by single char particle oxidation simulations.
Treatment of Sydney Tar Pond Sludge in CFBC
Authors: Jia L. , Anthony E. J. , Turnbell Richard
Published: October 2008

Test burns of mixtures of Sydney tar pond sludge and coal were carried out using CETC’s mini-circulating fluidized bed combustor (mini-CFBC). The goal was to determine if CFBC technology could be used to treat the tar pond sludge. During the tests, CO2, O2, CO, SO2, and NOx in the flue gas were monitored continuously. Stack gas sampling was carried out for HCl, metals, particulate matter, VOCs, total hydrocarbons, semi-volatile organic compounds, dioxins and furans and PCBs. Results showed that HCl, Hg, particulate matter, PCDD/Fs and metal concentrations were all below both the current limits and the gas release limits to be implemented in 2008 in Canada. Sulphur capture efficiency was about 89–90%. The percentage of fuel nitrogen converted to NOx was of the order of 4.7 to 6.1, which is significantly lower than that of conventional pulverized coal-fired boilers and well within normal range of FBC boilers. PCB and PAH emissions levels were comparable or lower than levels reported in the literature for industrial-scale FBCs. VOC concentrations were low except for benzene, for which the concentration was higher than that reported for utility-scale FBC and pulverized coal-fired boilers. In addition, CO concentration was high at 1200 to 2200 ppm. However, these CO concentrations are typical of CETC’s mini-CFBC firing coal. The trials showed that, for 10% by weight tar pond sludge mixed with 90% by weight coal, the combustion was both stable and efficient. The tests demonstrated that CFBC technology could be an environmentally sound option for eliminating wastes from the Sydney tar pond.
A Innovative Solution to the Problem of Mill Rejects in Thermal Power Plants
Authors: Dutta Animesh , Basu Prabir , Ghosh Amit , Chakraborty Prasun
Published: October 2008

The present paper discusses an innovative means for solving the problem of accumulation of waste coal in some pulverized coal fired plants. A major waste in a pulverized coal fired power plant is the reject produced from pulverizing mills. When coal is ground in a bowl mill heavy mineral matters are separated, but they still contain a small amount of coal mixed. However, the heating value of the rejects is generally too low for combustion in conventional boilers. As a result they find limited commercial use and are dumped in the plant adding to the fugitive dust, leaching problem and most importantly devastating damage to the landscape. The amount of mill reject is significant in older operating plant. In India for example, it is about 0.5–1.0% of coal throughput into the boiler. In this paper, an exercise is undertaken to show how these rejects could be burnt to produce low pressure process steam, which could save the bleeding of main steam of the power plant and thereby augment power generation. A subcompact novel circulating fluidized bed boiler has been designed, built and commissioned for this purpose. The present paper discusses the finding of above exercise.
Chemical Forms of Ash-Forming Matter in Woody Fuels for FBC
Authors: Werkelin Johan , Zevenhoven Maria , Skrifvars Bengt-Johan , Hupa Mikko
Published: October 2008

The prediction of the ash behavior in combustion processes is enhanced by the determination of the ash-forming matter in the fuel. The scope of this work was to characterize Scandinavian wood fuels by studying the wood, bark and leaves from a spruce and an aspen. Chemical Fractionation, a step-wise leaching procedure that treat the fuel in water, ammonium acetate and hydrochloric acid, was used to determine the solubility of the ash elements. The resulting solutions were further analyzed on ionic species, which was coupled to the presence of salt compounds in the original biomass tissues. The leaching procedure dissolved nearly 100% of the ash-forming matter. The phosphorus (P), chlorine (Cl) and some of the sulfur (S) were readily leached with water and found present as HPO42−, SO42− and Cl− in the solutions. The simultaneous dissolving of potassium (K) in this step proved the presence of water soluble potassium salts in the biomasses. The remaining K after the water treatment and all magnesium (Mg) dissolved completely in the ammonium acetate step together with a large part of the tissues’ calcium (Ca) and manganese (Mn). The remaining Ca after the second step was leached in hydrochloric acid together with equivalent amounts of oxalate ions, C2O42−. This proved the presence of acid soluble calcium oxalate in the tissues, a salt with low solubility in neutral pH.
Fluidized Bed Steam Gasification of Solid Biomass: Analysis and Optimization of Plant Operation Using Process Simulation
Authors: Pro¨ll Tobias , Rauch Reinhard , Aichernig Christian , Hofbauer Hermann
Published: October 2008

Fluidized bed steam gasification of solid biomass yields a high quality producer gas, which can be used for efficient combined heat and power production (CHP) and as an intermediate product for chemical syntheses. In order to study the behavior of an 8 MW (fuel power) CHP plant, which has been in successful operation since 2001, a comprehensive model library has been developed for the equation-oriented process simulation software IPSEpro. The models are validated with measured data from the commercial scale plant. Because every model is based on the conservation of mass and energy, the simulation also allows the validation of measured data. By solution of a system describing the entire process, which uses measured data as input, a reference case for actual plant operation can be defined. In a next step, the behavior of the plant is studied during variations of selected parameters. Therefore, a model of the gasification reactor, which is able to describe the behavior during parameter variation, is necessary. It can be shown that fuel water content and gasification temperature significantly influence the global plant performance. The simulation predicts the efficiency of the existing power plant in optimized operation. Finally, part load behavior is investigated and a performance map of the CHP plant is presented. The results show that CHP-concepts based on fluidized bed steam gasification can reach high electric efficiencies and high overall fuel utilization rates even at small plant capacities of 10 MW fuel power.
Influence of Fluidization Velocity on Bed Defluidization in Fluidized Bed Combustors
Authors: Golriz Mohammad R. , Eriksson Morgan , O¨hman Marcus , Nordin Anders , Backman Rainer
Published: October 2008

Effects of superficial gas velocity and bed particle size on bed defluidization during biomass combustion were investigated. Sampled bed particles from four different large-scale circulating- and bubbling fluidized bed combustors, using biomass as fuel, were collected and analyzed. The bed particles from each fluidized bed unit were divided into small and large particle size fractions. The results indicate no significant difference in elemental compositions between small and large coated bed particles but the ratio of coating thickness to the mean particle diameter was higher for the small particles compared to the large ones. Controlled fluidized bed agglomeration tests revealed strong influence from fluidization velocity on initial defluidization temperatures at lower velocities, but little effect at higher velocities. Influence of bed particle size on initial defluidization temperature varied depending on operating conditions. Finally, a model based on viscous flow sintering is proposed for the relation between agglomeration temperature and superficial gas velocity. The model predictions are in good agreement with experimental data.
Determination of Ignition Temperature of Coal by Using Thermogravimetry
Authors: Hu Wenbin , Yang Hairui , Lu Junfu , Zhang Hai , Zhang Jiansheng , Liu Qing , Yue Guangxi
Published: October 2008

In this paper, the ignition temperatures (Ti) of seven kinds of coals were measured by using thermlgravimetric analyzer (TGA). A TG-DTG method was suggested to determine the ignition temperature. This method is simple, convenient, standardized and with high repeatability. The relations between Ti and volatile content and active energy are analyzed. Compared with the ignition temperatures measured in a bench scale fluidized bed and boiler test, Tis derived from TG-DTG method have nearly same tendency with changing volatile content, but have 100°C deviation below those measured in fluidized bed. The results strongly indicate that TG-DTG method can substitute the fluidized bed method and boiler test for measuring ignition temperature of a coal with an off-set adjustment.
Gas Concentration Measurements in the Combustion Chamber of the 235 MWe Circulating Fluidized Bed Boiler Turow No. 3
Authors: Hartge E.-U. , Fehr M. , Werther J. , Ochodek T. , Noskievic P. , Krzin I. , Kallner P. , Gadowski J.
Published: October 2008

Local measurements of concentrations of O2, CO2, CO, NO and SO2 were carried out inside the 235 MWe circulating fluidized bed boiler no. 3 Turow power plant. The combustion chamber had a cross-sectional area of 21.1 × 9.9 m2 and a height of 43 m. Water-cooled probes with a length of 4.7 m were used to take samples from inside the boiler. 20 ports in 5 different heights were used to introduce the probes. The penetration depth inside the boiler was up to 3 m. The sampled gas was led to online analyzers. Even though the number of ports and the penetration length was not sufficient to get a full 3-D mapping of the concentrations the measured horizontal and vertical gas concentration profiles of NO, CO, CO2, O2 and SO2 clearly indicate a core/annulus structure with a wall layer thickness of about 0.5–1 m. Significant differences are observed between gas concentrations near the front wall and those near the rear wall which indicate an uneven distribution of fuel. One consequence is the formation of plumes with high concentrations of CO, NO, CO2 and SO2 near the front wall which extend up to the exit region. The fact that nevertheless the stack emissions are still below the legal limits may be attributed to the excellent performance of the cyclones as gas mixers and post combustion reactors.
Prediction of Ash Behavior and Deposit Formation in Fluidized Bed Combustion of Biofuel Mixtures
Authors: Enestam Sonja
Published: October 2008

When moving towards CO2 neutral biofuels, fluidized bed combustion represents a good and flexible combustion technique. Biofuels typically have a high volatile content and varying moisture content. Fluidized bed combustion can provide even combustion conditions regardless of big variations in the fuel quality and fuel properties. However, compared to conventional fuels, biofuels often contain high amounts of chlorine and alkali metals, which set certain challenges for the boiler design. The problems that might occur due to high alkali and chlorine levels in the fuels are mainly slagging, fouling, corrosion and bed sintering. Since the variations in fuel properties between different fuels are big, it is of outmost importance from the boiler manufacturer’s point of view, to be able to predict the behavior of a specific fuel or fuel mixture in a very early stage of boiler design. For this purpose different kinds of calculation and prediction tools are needed. For prediction of slagging and fouling an ash behavior prediction tool has been developed. The prediction routine is based on advanced multi-phase multi-component equilibrium calculations, using the fuel composition and combustion conditions as input. Based on the calculations, the rate of deposit formation, the composition of the deposits and the corrosivity of the deposits at different locations in the boiler can be estimated. The prediction tool can be used in boiler design for defining the optimum arrangement of the superheaters, maximum flue gas temperature in the superheater area and maximum steam temperature. It can also be used for specification of maximum limits of troublesome high alkali, high chlorine fuels in fuel mixtures. In this study the prediction routine has been performed for three biofuels / biofuel mixtures. The calculated results have been evaluated with full scale and pilot scale probe measurements as well as with full scale long term operational experience.
Opportunities for Implementation of FBC Boilers in Romania
Authors: Dragos¸ Liviu , Giˆrjoaba˘ Mihu , Flueraru Ca˘ta˘lin , Scarlat Nicolae
Published: October 2008

The evolution and current status of fluidized bed technology in Romania are presented. After a period of about 10 years when the FBC technology was rejected as a solution for power generation, due to the new environmental restrictions, the market is open again. Potential users are especially industrial units with high energy consumption, having combustibile wastes resulting from the technological processes. Two case studies are presented. The first is the utility from the city of Motru, producing thermal agent for the town district heating. It is currently equipped with one FB boiler (11.6 MWt hot water) and two pulverized coal boilers (50 t/h steam). The equipment is more than 40 years old, and is no longer acceptable in terms of thermal efficiency and pollutant emmissions. Taking into consideration the important biomass resources from the area, it was decided to build a new CFB boiler firing a mixture of local fuels — lignite and biomass waste. The second case study is ELECTROCARBON S.A. Slatina, the second important polluter from Olt county, producing carbon electrodes for use in metallurgy. Carbon waste resulting from the technological process have been deposited for many years in a nearby landfill, amounting to about 1.2 million tons. In spite of its high calorific value, because of the low volatile content and the grinding difficulties, little use was found for this material. Investigations are carried out to burn it in a fluidized bed boiler located near the site, that would replace two existing heat recovery steam generators producing electricity for the internal consumption.
The A˚bo Akademi Database: Ash Behavior Measurements in Full-Scale Boilers
Authors: Skrifvars Bengt-Johan , Yrjas Patrik , Laure´n Tor , Hupa Mikko , Dittrich Martin
Published: October 2008

This poster paper presents an overview of the A˚bo Akademi full-scale boiler ash behavior measurement database. The database contains data from some 20 full-scale boiler measurement campaigns during which the ash behavior in the boiler has been monitored identically. The measurements have been done in 3 different bubbling fluidized bed boilers and 2 circulating fluidized bed boilers during 11 different campaigns. For comparison data from 2 pulverized fuel fired boilers as well as from 2 grate fired boilers have also been included. The data collection includes conventional analyses of the fuels or fuel mixes used during the measurements, ash deposition measurements performed with the air-cooled probe technique, chemical analyses of the collected deposits (front and back side separately, chemical analyses of the boiler fly ashes, and recordings of chosen relevant boiler operation parameters such as boiler load, air-distribution, and flue gas temperatures. The poster paper presents ash deposition data, so called Rate-of-build-up values (RBU, g/m2h) as a function of fuel mixes, probe surface temperatures and boiler type. The poster also presents compositional data of the collected deposits such as the chlorine content as a function of fuel mix and probe surface temperature.
New 215 MWel CFB Power Units for Estonian Oil Shale
Authors: Loosaar Ju¨ri , Arro Hendrik , Parve Teet , Pihu To˜nu , Prikk Arvi , Tiikma Toomas , Hiltunen Matti
Published: October 2008

Estonian basic power supply is over 90% covered by oil shale fired thermal power plants. Total installed thermal capacity of the boilers is 10.7 GWth and every year about 11 millions tons of oil shale is fired. Two different combustion technologies, the old pulverized oil shale firing and the new CFB technology are used at the moment. The new CFB units totaling 430 MWel delivered by Foster Wheeler Energia started operation in 2003–2004. The very first operational experience of CFB units are very promising and all basic problems of oil shale pulverized firing like high air emissions (SO2 — 820–1360 mg/MJ; NOx — 90–110 mg/MJ), fouling and corrosion of heating surfaces, low efficiency and low operational reliability seemed to be solved. Oil shale CFB firing at much lower temperatures (∼800°C) than pulverized firing (∼1400°C) results only partial decomposition of oil shale contained carbonates, meaning lower specific fuel consumption values and decreased CO2 emissions. Also fly ash composition and properties has been changed, which results in different new prospectives of ash utilization possibilities, but also some additional ash land filling problems. The paper analyses the first data of Estonian oil shale industrial CFB firing in the light of almost 40 year experience of Estonian oil shale use in power production.
Perpendicular-to-Grain Strength of Douglas-Fir
Authors: Barrett J. D. , Foschi R. O. , Fox S. P.
Published: October 2008

Weibull's theory of brittle fracture is applied to the determination of strength of Douglas-fir wood in tension perpendicular to the grain. Results from tests on blocks of glued-laminated material uniformly stressed in tension are used to derive ultimate stresses, at a given survival probability, for pitched-tapered beams, curved beams, and griplam nail connections. The results of the theory are shown to be in agreement with experimental data. Allowable stresses are derived for blocks, pitched-tapered beams, curved beams, and the particular nailed connection studied.
The Fatigue Behavior of Negative Moment Regions of Continuous Composite Beams at Low Temperatures
Authors: Long A. E. , Dalen K. Van , Csagoly P.
Published: October 2008

The fatigue behavior of the negative moment region of continuous steel–concrete composite beams under Canadian temperature conditions was studied. Tests were conducted on three 26 ft 0 in. (7.92 m) long beams, continuous over a central support, and on 11 conventional push-out specimens. These were supplemented by a theoretical study of the internal forces in the beams using an iterative method of analysis.The close agreement between measured and theoretical strains and deflections indicated that good interaction was achieved throughout the length of the beams. The beams sustained 500 000 cycles of loading with no serious deterioration of composite action. The pattern of stud failures was consistent from beam to beam and reflected closely the calculated distribution of horizontal shear force at the steel–concrete interface. Stud shear connectors in the negative moment region where the slab had cracked in tension were found to be slightly less effective than studs in the positive bending moment regions.Neither the detailed study of individual connectors in the beams nor the results of the push-out tests show evidence of a reduction in the fatigue life of studs at −20 °F (−29 °C) relative to room temperature. The beams also exhibited no significant difference in their overall performance at these two temperatures.
Process of failure in ice
Authors: Gold L. W.
Published: October 2008

Information is presented on the failure behavior of columnar-grained ice during compressive creep and constant strain rate tests. The role of crack formation in establishing the failure condition is briefly described. Breakdown of structure is responsible for a marked change in the creep behavior of ice in the stress range of 10 to 12 kg/cm2. A ductile-to-brittle transition is observed at a strain rate of about 5 × 10−3 min−1. The upper yield stress in constant strain rate tests is shown to increase with increase in rate of strain up to the ductile-to-brittle transition.
DESIGNING OF ALL-OPTICAL TRI-STATE LOGIC SYSTEM WITH THE HELP OF OPTICAL NONLINEAR MATERIAL
Authors: CHATTOPADHYAY TANAY , MAITY GOUTAM KUMAR , ROY JITENDRA NATH
Published: October 2008

Nonlinear optics has been of increased interest for all-optical signal, data and image processing in high speed photonic networks. The application of multi-valued (nonbinary) digital signals can provide considerable relief in transmission, storage and processing of a large amount of information in digital signal processing. Here, we propose the design of an all-optical system for some basic tri-state logic operations (trinary OR, trinary AND, trinary XOR, Inverter, Truth detector, False detector) which exploits the polarization properties of light. Nonlinear material based optical switch can play an important role. Tri-state logic can play a significant role towards carry and borrow free arithmetic operations. The principles and possibilities of the design of nonlinear material based tri-state logic circuits are proposed and described.
ELECTROMAGNETIC WAVE PROPAGATION CHARACTERISTICS IN A ONE-DIMENSIONAL METALLIC PHOTONIC CRYSTAL
Authors: ALY ARAFA H. , RYU SANG-WAN , WU CHIEN-JANG
Published: October 2008

We theoretically studied electromagnetic wave propagation in a one-dimensional metal/dielectric photonic crystal (1D MDPC) consisting of alternating metallic and dielectric materials by using the transfer matrix method. We performed numerical analyses to investigate the propagation characteristics of a 1D MDPC. We discuss the details of the calculated results in terms of the electron density, the thickness of the metallic layer, different kinds of metals, and the plasma frequency.
RELATIONSHIP OF MOLECULAR STRUCTURE TO NONLINEAR OPTICAL PROPERTIES OF ORGANIC HETEROCYCLIC COMPOUNDS
Authors: HU YING , DANILOV EVGENY O. , WEX BRIGITTE , NECKERS DOUGLAS C.
Published: October 2008

The nonlinear optical properties of heterocyclic compounds (1-7) were investigated. π-Centers benzo[1,2-b:4,3-b']dithiophene (1) and trithia[5]helicene (5) were studied. Compounds 2-4, 6 and 7 possess either donor-π (D-π) or donor-π-acceptor (D-π-A) structures. The optimized geometry of 7 shows a 3D helical structure. Two-photon absorption cross-sections related to the third-order nonlinear susceptibility were measured using open-aperture Z-scan techniques. Compound 7 has a two-photon absorption cross-section of 103 GM when excited at 720 nm. Important molecular structure-nonlinear optical property relationships are formulated.
IMPEDANCE-MATCHED MULTILAYERED STRUCTURE CONTAINING A ZERO-PERMITTIVITY MATERIAL FOR SPATIAL FILTERING
Authors: JIN YI , HE SAILING
Published: October 2008

Based on the effective medium theory, a multilayered spatial filter is constructed with an ultralow-permittivity material and a typical dielectric. Besides the special property of an ultralow refractive index, the designed periodic structure is impedance-matched to free space, regardless of the total thickness. The present spatial filter works well even when moderate loss exists.
SECOND HARMONIC GENERATION IN Λ-SHAPED ORGANIC MOLECULES
Authors: DAS MALYAJ , TRIVEDI RASHMI , KHATTAK B. Q. , RAMSHANKAR P. , SEN PRATIMA , DOLUI S. K. , SEN PRANAY K.
Published: October 2008

In epoxy based polymeric nonlinear optical (NLO) materials, the nonlinear optically active moiety forms crosslink between polymer chains. Some of the important moieties include 4, 4'diamino diphenyl sulfone (DADS). We have examined second harmonic generation (SHG) in DADS and have compared it with 4, 4'diamino diphenyl methane (DADM). The geometry optimization suggests that both molecules have Λ-shaped structure. The theoretical calculations as well as experimental observations of SHG in both the molecules suggest the suitability of DADS over DADM for making polymeric NLO materials.
DISPERSIVE SWITCHING IN MESOSCOPIC MULTISTABLE SYSTEMS
Authors: SHARABY Y. A. , HASSAN S. S.
Published: October 2008

Dispersive switching effect is examined for a mesoscopic system of coherently injected two-level Rydberg atoms into a driven single-mode superconducting cavity. The effect concerns the switching of the output field by simultaneously varying the atomic and cavity detuning parameters at fixed values of the coherent driving field. For certain atomic coherence parameters, symmetric and asymmetric switching diagrams are exhibited, which include one- and two-way process via multistep transitions between output field states.
NON-DIVERGING DARK-HOLLOW BEAM GENERATION WITH A PIGTAILED LASER DIODE
Authors: BRUNEL M. , MGHARAZ D. , COETMELLEC S. , BOULEZHAR A.
Published: October 2008

A new method to generate non-diverging dark-hollow beams at the output of a single-mode pigtailed laser diode is presented. It consists of positioning a circular aperture at the output of the fiber. The dark-hollow beam generated exhibits an angle of divergence as low as 0.28 degrees. The beam can then be collimated by a lens to observe a non-diverging dark-hollow beam which conserves its structure over more than 20 cm. Experimental results are well-predicted by the theoretical analysis that we have developed.
ANALYTICAL SOLUTIONS FOR THE VARIATIONAL EQUATIONS DERIVED FOR THE NONLINEAR SCHRÖDINGER EQUATION: DISPERSION-MANAGED FIBER SYSTEM
Authors: ABOBAKER ABDOSLLAM M. , MOUBISSI A. B. , EKOGO TH. B. , NAKKEERAN K.
Published: October 2008

We consider the nonlinear Schrödinger equation which governs the pulse propagation in dispersion-managed (DM) optical fiber transmission systems. Using a generalized form of ansatz function for the shape of the pulse, we derive the variational equations. For a particular case of DM fiber systems when the Hamiltonian is zero, we solve the variational equations analytically and obtain the expressions for the pulse energy, amplitude, width and chirp. Finally for Gaussian and hyperbolic secant shaped pulses, we show through numerical simulations that the analytically calculated energy (for the given pulse width and chirp) is good enough to support the periodic evolution of the DM soliton. The simulations are carried out for conventional and dense DM fiber systems for both lossless and lossy cases.