The Experts below are selected from a list of 61860 Experts worldwide ranked by ideXlab platform
Mikko Hupa - One of the best experts on this subject based on the ideXlab platform.
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cfd modeling to study Fluidized Bed Combustion and gasification
Applied Thermal Engineering, 2013Co-Authors: Ravi Inde Singh, Anders Ink, Mikko HupaAbstract:Abstract The increase in application of Fluidized Bed Combustion and gasification devices throughout world means that more consideration will be given to improve design and reduce emissions of these. Due to excellent thermal and mixing properties Fluidized Beds are generally preferred over the fixed Bed combustors and gasifiers. Computational Fluid Dynamic (CFD) is a technique which helps to optimize the design and operation of Fluidized Bed combustor and gasifiers. Recent progression in numerical techniques and computing efficacy has advanced CFD as a widely used practice to provide efficient design solutions in Fluidized Bed industry. In this paper an extensive review of CFD modeling to study Combustion and gasification in Fluidized Beds has been done. This paper introduces the fundamentals involved in developing a CFD solution for Fluidized Bed Combustion and gasification. Mathematical equations governing the fluid flow, heat and mass transfer and chemical reactions in Fluidized Bed Combustion and gasifiers systems are descriBed and main CFD models are presented. The aim is to illustrate what can be done and also to identify trends and those areas where further work is needed.
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characterization of ash forming matter in various solid fuels by selective leaching and its implications for Fluidized Bed Combustion
Energy & Fuels, 2012Co-Authors: Maria Zevenhove, Patrik Yrjas, Engtjoha Skrifvars, Mikko HupaAbstract:This paper presents the results of standard fuel analyses of 112 different fuels, along with the results from chemical fractionation through selective leaching. The samples, obtained from boilers during the period 1995–2010, represent the following fuel classes: coal, peat, wood-derived fuels, agricultural wastes, and sewage sludge. The leaching results show that coal consists mainly of insoluble ash forming matter, dominated by different silicates. The ash-forming matter in wood-derived fuels is mainly soluble and is dominated by potassium, calcium, and phosphorus; the insoluble ash-forming matter originates from soil contamination. The ash-forming matter in peat has the characteristics of both wood-derived fuels and coal. In agricultural waste, the ash-forming matter is mainly soluble, even though it may contain some silicon, and is dominated by potassium, chlorine, and phosphorus. The ash-forming matter in sludge is mainly acid-soluble or insoluble. It is also important to note that the aluminum silica...
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ash related issues in Fluidized Bed Combustion of biomasses recent research highlights
Energy & Fuels, 2012Co-Authors: Mikko HupaAbstract:Finland and Sweden are leaders in the use of biomass fuels in large-scale boilers. In these countries, the dominating large-scale Combustion technology for biomass fuels is Fluidized-Bed Combustion (FBC). Biomass fuels differ in many ways from the standard fossil fuels used in FBC, such as coal. They often have high moisture contents, lower heating values, and a variety of impurities, such as chlorine, sulfur, phosphorus, nitrogen, and a variety of ash-forming metals. FBC of biomass fuels is often connected with operational challenges, which are related to the fuel chemistry and fuel properties. Bed sintering, superheater fouling, and high-temperature corrosion are crucial factors to take into account when fuels are selected for FBC. It is of vital interest to find ways of predicting the degree of these kinds of ash-related problems for various fuels or fuel mixtures. This paper reviews some of the recent progress in our understanding of the fate and behavior of ash-forming matter in FBC. The following to...
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the fouling behavior of rice husk ash in Fluidized Bed Combustion 1 fuel characteristics
Energy & Fuels, 2005Co-Authors: Bengt-johan Skrifvars, Jouni Kinni, Peter Siefen, Patrik Yrjas, Mikko HupaAbstract:Rice husk can be considered as an “opportunity fuel” for energy production. However, although rice husk has long been identified as a source for energy production, only limited experience exists from rice husk firing in larger-scale combustors. Only a few units worldwide are reported to be using rice husk as their main fuel. One concern in rice husk firing is the behavior of the ash, i.e., its slagging and fouling tendency, as well as its abrasiveness. This paper presents the very characteristic properties of the rice husk ash, as measured by a variety of laboratory tests and analyses, and compares these characteristics with eucalyptus bark and rice straw, as well as with some other biomass fuels. The paper is the first in a series of two, where we report from a recently finished study on the slagging and fouling behavior of rice husk when fired alone or in combination with other fuels in a Fluidized-Bed boiler. In the second part of the series, we will report the results of fireside fouling measurements ...
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the fouling behavior of rice husk ash in Fluidized Bed Combustion 2 pilot scale and full scale measurements
Energy & Fuels, 2005Co-Authors: Bengt-johan Skrifvars, Jouni Kinni, Patrik Yrjas, Tor Laurén, Honghi Tran, Mikko HupaAbstract:This paper is the second in a series of two on the slagging and fouling behavior of rice husk when fired alone or in combination with other fuels in a Fluidized-Bed boiler. The first paper involved the fuel properties of rice husk, as investigated by a variety of laboratory methods. In this second paper, we report the results of fireside fouling measurements when burning rice husk alone and together with eucalyptus bark in various ratios. This study is based on short-term (3−10 h) deposit samples taken with air-cooled deposit probes in the superheater region of a large-scale (157 MWth) bubbling Fluidized-Bed (BFB) boiler burning rice husk and eucalyptus bark. Using an entrained-flow type of pilot furnace, we further made more, systematic measurements of the influence of the fuel mixture ratio on the fouling tendency of the fly ash formed. Burning of rice husk alone did not result in any detectable fouling, neither in the pilot furnace nor on the deposit probes in the superheater area of the Fluidized-Bed ...
Fabrizio Scala - One of the best experts on this subject based on the ideXlab platform.
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Fluidized Bed technologies for near zero emission Combustion and gasification
2013Co-Authors: Fabrizio ScalaAbstract:Part 1 Introduction to fluidization science and technology: Overview of fluidization science and Fluidized Bed technologies Particle characterization and behaviour relevant to Fluidized Bed Combustion and gasification systems Properties of stationary (bubbling) fluidised Beds relevant to Combustion and gasification systems Properties of circulating Fluidized Beds relevant to Combustion and gasification systems Heat and mass transfer in Fluidized Bed Combustion and gasification systems Attrition phenomena relevant to Fluidized Bed Combustion and gasification systems. Part 2 Fundamentals of Fluidized Bed Combustion and gasification: Conversion of solid fuels and sorbents in Fluidized Bed Combustion and gasification Conversion of liquid and gaseous fuels in Fluidized Bed Combustion and gasification Pollutant emissions and their control in fluidised Bed Combustion and gasification Fluidized Bed reactor design and scale up Modelling of Fluidized Bed Combustion processes Modelling of Fluidized Bed gasification processes Economic evaluation of circulating Fluidized Bed Combustion (CFBC) power generation plants. Part 3 Fluidized Bed Combustion and gasification technologies: Atmospheric (non-circulating) Fluidized Bed Combustion Pressurized Fluidized Bed Combustion (PFBC) Circulating Fluidized Bed Combustion (CFBC) Fluidized Bed gasification Measurement, monitoring and control of Fluidized Bed Combustion and gasification. Part 4 Emerging CO2 capture technologies: Oxy-fired Fluidized Bed Combustion: Technology, prospects and new developments Chemical looping Combustion (CLC) Calcium looping for CO2 capture in Combustion systems Sorption-enhanced gasification. Part 5 Other applications of Fluidized Bed technology: Applications of Fluidized Bed technology in processes other than Combustion and gasification.
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the influence of temperature on limestone sulfation and attrition under Fluidized Bed Combustion conditions
Experimental Thermal and Fluid Science, 2010Co-Authors: Fabio Montagnaro, Piero Salatino, Fabrizio ScalaAbstract:Abstract The influence of temperature on attrition of two limestones during desulfurization in a Fluidized Bed reactor was investigated. Differences in the microstructure of the two limestones were reflected by a different thickness of the sulfate shell formed upon sulfation and by a different value of the ultimate calcium conversion degree. Particle attrition and fragmentation were fairly small under moderately bubbling fluidization conditions for both limestones. An increase of temperature from 850 °C to 900 °C led to an increase of the attrition rate, most likely because of a particle weakening effect caused by a faster CO 2 evolution during calcination. This weakening effect, however, was not sufficiently strong to enhance particle fragmentation in the Bed. The progress of sulfation, associated to the build-up of a hard sulfate shell around the particles, led in any case to a decrease of the extent of attrition. Sulfation at 900 °C was less effective than at 850 °C, and this was shown to be related to the porosimetric features of the different samples.
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Fluidized Bed Combustion of pelletized biomass and waste derived fuels
Combustion and Flame, 2008Co-Authors: Riccardo Chirone, Piero Salatino, Fabrizio Scala, Roberto Solimene, Massimo UrciuoloAbstract:The Fluidized Bed Combustion of three pelletized biogenic fuels (sewage sludge, wood, and straw) has been investigated with a combination of experimental techniques. The fuels have been characterized from the standpoints of patterns and rates of fuel devolatilization and char burnout, extent of attrition and fragmentation, and their relevance to the fuel particle size distribution and the amount and size distribution of primary ash particles. Results highlight differences and similarities among the three fuels tested. The fuels were all characterized by limited primary fragmentation and relatively long devolatilization times, as compared with the time scale of particle dispersion away from the fuel feeding ports in practical FBC. Both features are favorable to effective lateral distribution of volatile matter across the combustor cross section. The three fuels exhibited distinctively different char conversion patterns. The high-ash pelletized sludge burned according to the shrinking core conversion pattern with negligible occurrence of secondary fragmentation. The low-ash pelletized wood burned according to the shrinking particle conversion pattern with extensive occurrence of secondary fragmentation. The medium-ash pelletized straw yielded char particles with a hollow structure, resembling big cenospheres, characterized by a coherent inorganic outer layer strong enough to prevent particle fragmentation. Inert Bed particles were permanently attached to the hollow pellets as they were incorporated into ash melts. Carbon elutriation rates were very small for all the fuels tested. For pelletized sludge and straw, this was mostly due to the shielding effect of the coherent ash skeleton. For the wood pellet, carbon attrition was extensive, but was largely counterbalanced by effective afterburning due to the large intrinsic reactivity of attrited char fines. The impact of carbon attrition on Combustion efficiency was negligible for all the fuels tested. The size distribution of primary ash particles liberated upon complete carbon burnoff largely reflected the Combustion pattern of each fuel. Primary ash particles of size nearly equal to that of the parent fuel were generated upon complete burnoff of the pelletized sludge. Nonetheless, secondary attrition of primary ash from pelletized sludge is large, to the point where generation of fine ash would be extensive over the typical residence time of Bed ash in Fluidized Bed combustors. Very few and relatively fine primary ash particles were released after complete burnoff of wood pellets. Primary ash particles remaining after complete burnoff of pelletized straw had sizes and shapes that were largely controlled by the occurrence of ash agglomeration phenomena.
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an sem edx study of Bed agglomerates formed during Fluidized Bed Combustion of three biomass fuels
Biomass & Bioenergy, 2008Co-Authors: Fabrizio Scala, Riccardo ChironeAbstract:Abstract The agglomeration behaviour of three biomass fuels (exhausted and virgin olive husk and pine seed shells) during Fluidized Bed Combustion in a lab-scale reactor was studied by means of SEM/EDX analysis of Bed agglomerate samples. The effect of the fuel ash composition, Bed temperature and sand particle size on agglomeration was investigated. The study was focused on the main fuel ash components and on their interaction with the Bed sand particles. Agglomeration was favoured by high temperature, small sand size, a high fraction of K and Na and a low fraction of Ca and Mg in the fuel ash. An initial fuel ash composition close to the low-melting point eutectic composition appears to enhance agglomeration. The agglomerates examined by SEM showed a hollow structure, with an internal region enriched in K and Na where extensive melting is evident and an external one where sand particles are only attached by a limited number of fused necks. Non-molten or partially molten ash structures deposited on the sand surface and enriched in Ca and Mg were also observed. These results support an ash deposition–melting mechanism: the ash released by burning char particles inside the agglomerates is quantitatively deposited on the sand surface and then gradually emBedded in the melt. The low-melting point compounds in the ash migrate towards the sand surface enriching the outermost layer, while the ash structure is progressively depleted of these compounds.
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a single particle model of the Fluidized Bed Combustion of a char particle with a coherent ash skeleton application to granulated sewage sludge
Fuel Processing Technology, 2007Co-Authors: Gabriele Cano, Piero Salatino, Fabrizio ScalaAbstract:Abstract A single particle model of the Fluidized Bed Combustion and of the parallel course of attrition of a fuel particle characterized by a coherent ash skeleton is presented. The model combines a shrinking core feature to represent carbon Combustion with a shrinking particle feature to represent attrition of the carbon-depleted ash layer. Moreover, the establishment of non-uniform temperature profiles within the particle as a consequence of the resistance exerted to thermal conduction from the unreacted core across the ash layer is taken into account. The inherent stiffness of the model has been dealt with by developing a solution procedure that proved to be efficient and not time-consuming. The model has been applied to the description of the Fluidized Bed Combustion of pelletized sewage sludge. Experiments consisting of the Fluidized Bed Combustion of single pellets in a bench scale reactor have been purposely carried out with the aim of determining the values of selected model parameters and of enabling model validation. The experiments confirmed the relevance of the formation of a coherent ash skeleton to Combustion and attrition. In particular, it appeared that attrition departs significantly from the Combustion-assisted attrition pattern typical of fuels characterized by incoherent ash. Model results highlight the role of the coherent ash skeleton to the establishment of oxygen concentration and temperature fields within the particle. The interplay of the different processes that contribute to the apparent kinetics of char Combustion, namely boundary layer and intraparticle diffusion of oxygen and heterogeneous reaction between oxygen and carbon at the core surface, is analyzed and discussed. The relevance of model variables to the time–temperature history of the particle is assessed.
Riccardo Chirone - One of the best experts on this subject based on the ideXlab platform.
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Fluidized Bed Combustion of pelletized biomass and waste derived fuels
Combustion and Flame, 2008Co-Authors: Riccardo Chirone, Piero Salatino, Fabrizio Scala, Roberto Solimene, Massimo UrciuoloAbstract:The Fluidized Bed Combustion of three pelletized biogenic fuels (sewage sludge, wood, and straw) has been investigated with a combination of experimental techniques. The fuels have been characterized from the standpoints of patterns and rates of fuel devolatilization and char burnout, extent of attrition and fragmentation, and their relevance to the fuel particle size distribution and the amount and size distribution of primary ash particles. Results highlight differences and similarities among the three fuels tested. The fuels were all characterized by limited primary fragmentation and relatively long devolatilization times, as compared with the time scale of particle dispersion away from the fuel feeding ports in practical FBC. Both features are favorable to effective lateral distribution of volatile matter across the combustor cross section. The three fuels exhibited distinctively different char conversion patterns. The high-ash pelletized sludge burned according to the shrinking core conversion pattern with negligible occurrence of secondary fragmentation. The low-ash pelletized wood burned according to the shrinking particle conversion pattern with extensive occurrence of secondary fragmentation. The medium-ash pelletized straw yielded char particles with a hollow structure, resembling big cenospheres, characterized by a coherent inorganic outer layer strong enough to prevent particle fragmentation. Inert Bed particles were permanently attached to the hollow pellets as they were incorporated into ash melts. Carbon elutriation rates were very small for all the fuels tested. For pelletized sludge and straw, this was mostly due to the shielding effect of the coherent ash skeleton. For the wood pellet, carbon attrition was extensive, but was largely counterbalanced by effective afterburning due to the large intrinsic reactivity of attrited char fines. The impact of carbon attrition on Combustion efficiency was negligible for all the fuels tested. The size distribution of primary ash particles liberated upon complete carbon burnoff largely reflected the Combustion pattern of each fuel. Primary ash particles of size nearly equal to that of the parent fuel were generated upon complete burnoff of the pelletized sludge. Nonetheless, secondary attrition of primary ash from pelletized sludge is large, to the point where generation of fine ash would be extensive over the typical residence time of Bed ash in Fluidized Bed combustors. Very few and relatively fine primary ash particles were released after complete burnoff of wood pellets. Primary ash particles remaining after complete burnoff of pelletized straw had sizes and shapes that were largely controlled by the occurrence of ash agglomeration phenomena.
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an sem edx study of Bed agglomerates formed during Fluidized Bed Combustion of three biomass fuels
Biomass & Bioenergy, 2008Co-Authors: Fabrizio Scala, Riccardo ChironeAbstract:Abstract The agglomeration behaviour of three biomass fuels (exhausted and virgin olive husk and pine seed shells) during Fluidized Bed Combustion in a lab-scale reactor was studied by means of SEM/EDX analysis of Bed agglomerate samples. The effect of the fuel ash composition, Bed temperature and sand particle size on agglomeration was investigated. The study was focused on the main fuel ash components and on their interaction with the Bed sand particles. Agglomeration was favoured by high temperature, small sand size, a high fraction of K and Na and a low fraction of Ca and Mg in the fuel ash. An initial fuel ash composition close to the low-melting point eutectic composition appears to enhance agglomeration. The agglomerates examined by SEM showed a hollow structure, with an internal region enriched in K and Na where extensive melting is evident and an external one where sand particles are only attached by a limited number of fused necks. Non-molten or partially molten ash structures deposited on the sand surface and enriched in Ca and Mg were also observed. These results support an ash deposition–melting mechanism: the ash released by burning char particles inside the agglomerates is quantitatively deposited on the sand surface and then gradually emBedded in the melt. The low-melting point compounds in the ash migrate towards the sand surface enriching the outermost layer, while the ash structure is progressively depleted of these compounds.
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mechanism and prediction of Bed agglomeration during Fluidized Bed Combustion of a biomass fuel effect of the reactor scale
Chemical Engineering Journal, 2006Co-Authors: Riccardo Chirone, Francesco Miccio, Fabrizio ScalaAbstract:The Fluidized Bed Combustion of a biomass residue (pine seed shells) was investigated both in a bench-scale and in a pilot-scale reactor. Extensive Bed agglomeration problems were experienced during Combustion of this fuel, as a consequence of the high content of alkali species in the ash. The focus of the study was the effect of the combustor scale and of the operating conditions on the characteristic time and the extent of Bed agglomeration during Combustion. Bed defluidization times as well as the extent of ash accumulation in the Bed were measured at different operating conditions in the two reactors. Results indicated that sand size, combustor size, and presence of internals had a significant influence on the agglomeration phenomenon. SEM/EDX analysis on agglomerate samples discharged from the Bed after defluidization confirmed that Bed agglomeration is a consequence of potassium and sodium enrichment on the sand particle surface, in conjunction with high temperature spots near burning char particles. The competition between formation of stable bonds between Bed particles and the breaking of the agglomerates by inertial forces is the key mechanism leading to Bed agglomeration. In addition, a previously developed diagnostic tool based on the measurement of the dynamic pressure signal inside the Bed was successfully tested with the present biomass fuel and at both combustor scales for its capability to predict the Bed defluidization onset.
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characterization and early detection of Bed agglomeration during the Fluidized Bed Combustion of olive husk
Energy & Fuels, 2006Co-Authors: Fabrizio Scala, Riccardo ChironeAbstract:The Fluidized Bed Combustion of a biomass residue (olive husk) common in the Mediterranean area was investigated in a bench-scale reactor. The focus of the study was the high propensity of this fuel to have Bed agglomeration problems during Combustion as a consequence of the high potassium content of the ash. Temperature and pressure profiles in the Bed were followed as a function of time during steady Combustion tests at different operating conditions. Bed defluidization characteristic times were measured and correlated to the fuel ash buildup on the Bed sand particles. In addition, a diagnostic tool based on the measurement of the dynamic pressure signal inside the Bed was tested for its ability to predict Bed agglomeration. On the basis of SEM/EDX analysis of agglomerate samples discharged from the Bed after defluidization had occurred, the mechanisms of fuel ash−Bed particle interaction and agglomerate formation are discussed.
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Combustion and attrition of biomass chars in a Fluidized Bed
Energy & Fuels, 2006Co-Authors: Fabrizio Scala, Riccardo Chirone, Piero SalatinoAbstract:The Fluidized Bed Combustion of char from three different biomass fuels, pine seed shells, olive husk, and wood chips, was investigated in a bench scale combustor. A combination of experimental techniques was used to characterize the relevance of attrition phenomena during the Combustion of the chars and their impact on the fuel particle size distribution and overall carbon conversion. Results showed that, depending upon the biomass, extensive primary and secondary fragmentation could be experienced by the char particles, significantly influencing the particle size distribution of the fuel in the Bed. This is the result of the mechanical properties of the raw fuel particles and the large porosity of the char after devolatilization. Char conversion closely followed the shrinking-particle constant-density model and occurred to a large extent via the generation of carbon fines by percolative fragmentation followed by postCombustion during their residence time in the Bed. Approximately 25−45% of the initial f...
Edward J Anthony - One of the best experts on this subject based on the ideXlab platform.
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effects of steam on the sulfation of limestone and nox formation in an air and oxy fired pilot scale circulating Fluidized Bed combustor
Fuel, 2012Co-Authors: Michael C Stewart, Robert T Symonds, Arturo Macchi, Vasilije Manovic, Edward J AnthonyAbstract:Abstract The existing Fluidized Bed Combustion literature on sulfation shows that above 30% conversion, direct sulfation via reaction with CaCO 3 is faster than indirect sulfation with CaO. However, while this is true for dry flue gases, it is not the case if steam (H 2 O (g) ) is present at realistic levels for coal Combustion, and it has been confirmed by experiments employing thermogravimetric analysis (TGA) and tube furnace (TF) testing that direct sulfation is in fact slower than indirect sulfation for nearly all levels of conversion if steam (H 2 O (g) ) is present. In this work we have also examined the effects of H 2 O (g) on SO 2 capture and NH 3 oxidation to NO x over calcium-containing compounds under air- and oxy-fired conditions in a pilot-scale circulating Fluidized Bed combustor (CFBC) utilizing limestone addition. The results of the pilot-scale tests confirm suggestions from our previous work that sulfur capture from the air firing of low-moisture fuels benefits from steam-sulfation. For petroleum coke, the addition of 8%vol H 2 O (g) resulted in increased SO 2 retention and Ca utilization, as well as decreased NO x emissions by up to 44%. The simultaneous reduction of SO 2 and NO x was attributed to enhanced solid-state diffusion (sintering) by H 2 O (g) . Under oxy-fuel-firing conditions, H 2 O (g) addition also resulted in decreased NO x emissions, but the pilot-scale tests showed poorer sulfur capture performance and calcium utilization as compared to air firing when H 2 O (g) was present, thereby reconfirming the TGA/TF results. It appears that most bench-scale work on sulfation to date has underestimated the true rate of reaction for sulfation in the presence of H 2 O (g) . This conclusion explains at least in part why indirect sulfation is often faster than direct sulfation in pilot plant studies on oxy-fuel circulating Fluidized Bed Combustion. Moreover, this work stresses the importance of including H 2 O (g) in bench-scale experiments that attempt to simulate real Combustion environments.
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emissions of so2 and nox during oxy fuel cfb Combustion tests in a mini circulating Fluidized Bed Combustion reactor
Energy & Fuels, 2010Co-Authors: L Jia, Edward J AnthonyAbstract:Anthropogenic CO2 production is primarily driven by fossil fuel Combustion, and the current energy demand situation gives no indication that this will change in the near future. In consequence, it is increasingly necessary to find ways to reduce these emissions when fossil fuel is used. CO2 capture and storage (CCS) appears to be among the most promising approaches. All of the CCS technologies involve producing a nearly pure stream of CO2, either by concentrating it in some manner from the flue gases or by using pure oxygen as the Combustion gas. The latter option, oxy−fuel Combustion, has now been well studied for pulverized coal Combustion, but to date has received relatively little attention in the case of oxy−fuel circulating Fluidized Bed Combustion (CFBC). Recently, oxy−fuel FBC has been examined in a 100 kW pilot plant operating with flue gas recycle at CanmetEnergy. The results strongly support the view that this technology offers all of the advantages of air-fired FBC, with one possible exception...
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design process simulation and construction of an atmospheric dual Fluidized Bed Combustion system for in situ co2 capture using high temperature sorbents
Fuel Processing Technology, 2005Co-Authors: Robin W Hughes, Edward J Anthony, Dennis Y Lu, Arturo MacchiAbstract:Abstract An atmospheric dual Fluidized Bed Combustion system using high-temperature sorbents for in situ CO 2 capture has been designed and simulated and is now under construction. The pilot plant is expected to burn petroleum coke and coal or biomass in a clean and efficient manner, generating a carbonator flue gas containing 2–5 mol% CO 2 , while producing a relatively pure carbon dioxide stream ready for compression. The concentration of sulphur dioxide in the resulting flue gas is expected to be on the order of a few parts per million by volume. Initial investigations are to be carried out using limestone-derived sorbents enhanced using a simple single step process for pore modification developed at CETC-Ottawa. Carbonation occurs in a two-stage Fluidized Bed carbonator–combustor allowing for optimal temperature control for both Combustion (850–950 °C) and carbonation (650–750 °C). Calcination occurs in a single-stage Fluidized Bed combustor burning petroleum coke. Pilot plant operational data will be used for on-going scale-up activities using the ASPEN Plus process simulator.
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Fluidized Bed Combustion systems integrating co2 capture with cao
Environmental Science & Technology, 2005Co-Authors: Carlos J Abanades, Edward J Anthony, Jinsheng Wang, J E OakeyAbstract:Capturing CO2 from large-scale power generation Combustion systems such as Fluidized Bed combustors (FBCs) may become important in a CO2-constrained world. Using previous experience in capturing pollutants such as SO2 in these systems, we discuss a range of options that incorporate capture of CO2 with CaO in FBC systems. Natural limestones emerge from this study as suitable high-temperature sorbents for these systems because of their low price and availability. This is despite their limited performance as regenerable sorbents. We have found a range of process options that allow the sorbent utilization to maintain a given level of CO2 separation efficiency, appropriate operating conditions, and sufficiently high power generation efficiencies. A set of reference case examples has been chosen to discuss the critical scientific and technical issues of sorbent performance and reactor design for these novel CO2 capture concepts.
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advanced ash management technologies for cfbc ash
Waste Management, 2003Co-Authors: Edward J Anthony, E E Berry, J Blondin, E M Bulewicz, S BurwellAbstract:The Combustion of high-sulphur coal demands the reduction of sulphur emissions. The sorbent most often used in sulphur capture technology is calcium-based. Ashes from technologies such as circulating Fluidized Bed Combustion (CFBC), therefore, contain high calcium levels. The use and disposal of these ashes poses challenges, because of highly exothermic reactions with water, high-pH leachates, and excessive expansion of solidified materials. This paper looks at the potential of two post-Combustion ash treatment processes, CERCHAR hydration and AWDS disposal, in solving these challenges. A high-sulphur coal-derived CFBC ash is examined, after CERCHAR hydration treatment, in conjunction with a conventionally hydrated ash, in a range of chemical, geotechnical and utilization scenarios. The ashes are used to make no-cement and roller-compacted concrete as well as Ash Water Dense Suspensions (AWDS). The solidified mortar paste from no-cement concrete is subjected to an extensive geochemical examination to determine how solidification progresses and strength develops, from a chemical point of view.
Piero Salatino - One of the best experts on this subject based on the ideXlab platform.
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the influence of temperature on limestone sulfation and attrition under Fluidized Bed Combustion conditions
Experimental Thermal and Fluid Science, 2010Co-Authors: Fabio Montagnaro, Piero Salatino, Fabrizio ScalaAbstract:Abstract The influence of temperature on attrition of two limestones during desulfurization in a Fluidized Bed reactor was investigated. Differences in the microstructure of the two limestones were reflected by a different thickness of the sulfate shell formed upon sulfation and by a different value of the ultimate calcium conversion degree. Particle attrition and fragmentation were fairly small under moderately bubbling fluidization conditions for both limestones. An increase of temperature from 850 °C to 900 °C led to an increase of the attrition rate, most likely because of a particle weakening effect caused by a faster CO 2 evolution during calcination. This weakening effect, however, was not sufficiently strong to enhance particle fragmentation in the Bed. The progress of sulfation, associated to the build-up of a hard sulfate shell around the particles, led in any case to a decrease of the extent of attrition. Sulfation at 900 °C was less effective than at 850 °C, and this was shown to be related to the porosimetric features of the different samples.
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Fluidized Bed Combustion of pelletized biomass and waste derived fuels
Combustion and Flame, 2008Co-Authors: Riccardo Chirone, Piero Salatino, Fabrizio Scala, Roberto Solimene, Massimo UrciuoloAbstract:The Fluidized Bed Combustion of three pelletized biogenic fuels (sewage sludge, wood, and straw) has been investigated with a combination of experimental techniques. The fuels have been characterized from the standpoints of patterns and rates of fuel devolatilization and char burnout, extent of attrition and fragmentation, and their relevance to the fuel particle size distribution and the amount and size distribution of primary ash particles. Results highlight differences and similarities among the three fuels tested. The fuels were all characterized by limited primary fragmentation and relatively long devolatilization times, as compared with the time scale of particle dispersion away from the fuel feeding ports in practical FBC. Both features are favorable to effective lateral distribution of volatile matter across the combustor cross section. The three fuels exhibited distinctively different char conversion patterns. The high-ash pelletized sludge burned according to the shrinking core conversion pattern with negligible occurrence of secondary fragmentation. The low-ash pelletized wood burned according to the shrinking particle conversion pattern with extensive occurrence of secondary fragmentation. The medium-ash pelletized straw yielded char particles with a hollow structure, resembling big cenospheres, characterized by a coherent inorganic outer layer strong enough to prevent particle fragmentation. Inert Bed particles were permanently attached to the hollow pellets as they were incorporated into ash melts. Carbon elutriation rates were very small for all the fuels tested. For pelletized sludge and straw, this was mostly due to the shielding effect of the coherent ash skeleton. For the wood pellet, carbon attrition was extensive, but was largely counterbalanced by effective afterburning due to the large intrinsic reactivity of attrited char fines. The impact of carbon attrition on Combustion efficiency was negligible for all the fuels tested. The size distribution of primary ash particles liberated upon complete carbon burnoff largely reflected the Combustion pattern of each fuel. Primary ash particles of size nearly equal to that of the parent fuel were generated upon complete burnoff of the pelletized sludge. Nonetheless, secondary attrition of primary ash from pelletized sludge is large, to the point where generation of fine ash would be extensive over the typical residence time of Bed ash in Fluidized Bed combustors. Very few and relatively fine primary ash particles were released after complete burnoff of wood pellets. Primary ash particles remaining after complete burnoff of pelletized straw had sizes and shapes that were largely controlled by the occurrence of ash agglomeration phenomena.
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a single particle model of the Fluidized Bed Combustion of a char particle with a coherent ash skeleton application to granulated sewage sludge
Fuel Processing Technology, 2007Co-Authors: Gabriele Cano, Piero Salatino, Fabrizio ScalaAbstract:Abstract A single particle model of the Fluidized Bed Combustion and of the parallel course of attrition of a fuel particle characterized by a coherent ash skeleton is presented. The model combines a shrinking core feature to represent carbon Combustion with a shrinking particle feature to represent attrition of the carbon-depleted ash layer. Moreover, the establishment of non-uniform temperature profiles within the particle as a consequence of the resistance exerted to thermal conduction from the unreacted core across the ash layer is taken into account. The inherent stiffness of the model has been dealt with by developing a solution procedure that proved to be efficient and not time-consuming. The model has been applied to the description of the Fluidized Bed Combustion of pelletized sewage sludge. Experiments consisting of the Fluidized Bed Combustion of single pellets in a bench scale reactor have been purposely carried out with the aim of determining the values of selected model parameters and of enabling model validation. The experiments confirmed the relevance of the formation of a coherent ash skeleton to Combustion and attrition. In particular, it appeared that attrition departs significantly from the Combustion-assisted attrition pattern typical of fuels characterized by incoherent ash. Model results highlight the role of the coherent ash skeleton to the establishment of oxygen concentration and temperature fields within the particle. The interplay of the different processes that contribute to the apparent kinetics of char Combustion, namely boundary layer and intraparticle diffusion of oxygen and heterogeneous reaction between oxygen and carbon at the core surface, is analyzed and discussed. The relevance of model variables to the time–temperature history of the particle is assessed.
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Combustion and attrition of biomass chars in a Fluidized Bed
Energy & Fuels, 2006Co-Authors: Fabrizio Scala, Riccardo Chirone, Piero SalatinoAbstract:The Fluidized Bed Combustion of char from three different biomass fuels, pine seed shells, olive husk, and wood chips, was investigated in a bench scale combustor. A combination of experimental techniques was used to characterize the relevance of attrition phenomena during the Combustion of the chars and their impact on the fuel particle size distribution and overall carbon conversion. Results showed that, depending upon the biomass, extensive primary and secondary fragmentation could be experienced by the char particles, significantly influencing the particle size distribution of the fuel in the Bed. This is the result of the mechanical properties of the raw fuel particles and the large porosity of the char after devolatilization. Char conversion closely followed the shrinking-particle constant-density model and occurred to a large extent via the generation of carbon fines by percolative fragmentation followed by postCombustion during their residence time in the Bed. Approximately 25−45% of the initial f...
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modelling Fluidized Bed Combustion of high volatile solid fuels
Chemical Engineering Science, 2002Co-Authors: Fabrizio Scala, Piero SalatinoAbstract:Abstract A model of an atmospheric bubbling Fluidized Bed combustor operated with high-volatile solid fuel feedings is presented. It aims at the assessment of axial burning profiles along the reactor and of the associated temperature profiles, relevant to combustor performance and operability. The combustor is divided into three sections: the dense Bed, the splashing region and the freeboard. Three combustible phases are considered: volatile matter, relatively large non-elutriable char particles and fine char particles of elutriable size. The model takes into account phenomena that assume particular importance with high-volatile solid fuels, namely fuel particle fragmentation and attrition in the Bed and volatile matter segregation and postCombustion above the Bed. An energy balance on the splashing zone is set up, taking into account volatile matter and elutriated fines postCombustion and radiative and convective heat fluxes to the Bed and the freeboard. Results from calculations with a high-volatile biomass fuel indicate that Combustion occurs to comparable extents in the Bed and in the splashing region of the combustor. Due to volatile matter segregation with respect to the Bed, a significant fraction of the heat is released into the splashing region of the combustor and this results in an increase of the temperature in this region. Extensive Bed solids recirculation associated to solids ejection/falling back due to bubbles bursting at Bed surface promotes thermal feedback from this region to the Bed of as much as 80–90% of the heat released by afterburning of volatile matter and elutriated fines. Depending on the operating conditions a significant fraction of the volatile matter may burn in the freeboard or in the cyclone.