FB Combustion of a Biomass Fuel: Comparison Between Pilot Scale Experiments and Model Simulations

2003 ◽  
Author(s):  
Francesco Miccio ◽  
Fabrizio Scala ◽  
Riccardo Chirone
Keyword(s):  
Heat Release ◽  
Pilot Scale ◽  
Combustion Efficiency ◽  
Volatile Matter ◽  
High Reactivity ◽  
Operating Conditions ◽  
Biomass Combustion ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Carbon Loading

In the present work the efficiency of the fluidized bed combustion of high-volatile fuels and the extent of volatile matter post-combustion in the splashing zone and freeboard are investigated. A typical Mediterranean biomass (pine-seed shells) has been burned in a pilot-scale bubbling FB combustor (200kWt) at different operating conditions. Both over- and under-bed fuel feeding options have been considered. A FBC model specifically developed for high-volatiles fuels has been also applied to provide a comparison with bed carbon loading, in-bed heat release and splashing region temperature experimental data. Experimental results showed that the biomass combustion efficiency is always very high as a consequence of the high reactivity of the fuel. Extensive volatiles post-combustion above the bed is observed, whose extent appears to be sensitive to the over/under bed feeding option and to the excess air. Approximately 80% of the total heat is released/recirculated in the bed, the remainder leading to appreciable overheating of the freeboard with respect to the nominal bed temperature. Very low bed carbon loadings have been found. Model results compare well with the experimental temperature, heat release and carbon loading trends. However, detailed prediction of the freeboard temperature profiles requires further improvements of the model.

Fluidized Bed Combustion of a Biomass Fuel: Comparison Between Pilot Scale Experiments and Model Simulations

2005 ◽  
Vol 127 (2) ◽  
pp. 117-122 ◽  
Author(s):  
Francesco Miccio ◽  
Fabrizio Scala ◽  
Riccardo Chirone
Keyword(s):  
Heat Release ◽  
Fluidized Bed ◽  
Pilot Scale ◽  
Volatile Matter ◽  
High Reactivity ◽  
Operating Conditions ◽  
Biomass Combustion ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Carbon Loading

In the present work the efficiency of the fluidized bed combustion (FBC) of high-volatile fuels and the extent of volatile matter post-combustion in the splashing zone and freeboard are investigated. A typical Mediterranean biomass (pine-seed shells) has been burned in a pilot-scale bubbling FB combustor (200 kWt) at different operating conditions. Both over-and under-bed fuel feeding options have been considered. A FBC model specifically developed for high-volatile fuels has been also applied to provide a comparison with bed carbon loading, in-bed heat release and splashing region temperature experimental data. Experimental results showed that the biomass combustion efficiency is always very high as a consequence of the high reactivity of the fuel. Extensive volatile post-combustion above the bed is observed, whose extent appears to be sensitive to the over/under bed feeding option and to the excess air. Approximately 80% of the total heat is released/recirculated in the bed, the remainder leading to appreciable overheating of the freeboard with respect to the nominal bed temperature. Very low bed carbon loadings have been found. Model results compare well with the experimental temperature, heat release and carbon loading trends. However, a detailed prediction of the freeboard temperature profiles requires further improvements of the model.

GTL Kerosene and N-Butanol in RCCI Mode: Combustion and Emissions Investigation

2018 ◽  
Author(s):  
Valentin Soloiu ◽  
Jose Moncada ◽  
Remi Gaubert ◽  
Spencer Harp ◽  
Marcel Ilie ◽  
...  
Keyword(s):  
Heat Release ◽  
Fuel Injection ◽  
Negative Temperature ◽  
Combustion Efficiency ◽  
High Reactivity ◽  
Ultra Low Sulfur Diesel ◽  
Low Viscosity ◽  
Constant Volume Combustion Chamber ◽  
High Volatility ◽  
Lower Load

High reactivity gas-to-liquid kerosene (GTL) was investigated with port fuel injection (PFI) of low reactivity n-butanol to conduct reactivity controlled compression ignition (RCCI). In the preliminary stage, the GTL was investigated in a constant volume combustion chamber, and the results indicated a narrower negative temperature coefficient (NTC) region than ultra-low sulfur diesel (ULSD#2). The engine research was conducted at 1500 RPM and various loads with early n-butanol PFI and dual DI pulses of GTL at 60 crank angle degrees (CAD) before top dead center (TDC) and at a timing close to TDC. Boost and PFI fractions (60% by mass n-butanol) were kept constant in order to analyze the fuel reactivity effect on combustion. Conventional diesel combustion (CDC) mode with a single injection and the same combustion phasing (CA50) was used as an emissions baseline for RCCI. RCCI increased ignition delay and combustion duration decreased compared to CDC. Results showed that in order to maintain CA50 for RCCI within 1 CAD, GTL mass required for the first DI pulse to be 15% lower than that of ULSD#2 at higher loads. Peak heat release rate decreased for GTL by 25% given the high volatility and low viscosity of GTL. In general, using GTL, NOx and soot levels were reduced across load points by up to 15% to 30%, respectively, compared to ULSD RCCI, while maintaining RCCI combustion efficiency at 93–97%. Meanwhile, reductions of 85% in soot and 90% in NOx were determined when using RCCI compared to CDC. The more favorable heat release placement of GTL led to increased thermal efficiency by 3% at higher load compared to ULSD#2. The higher volatility and increased reactivity for GTL achieved lower UHC and CO than ULSD#2 at lower load. The study concluded that GTL offered advantages when used with n-butanol for this RCCI fueling configuration.

Attrition Behavior of Coal Ash Under Circulating Fluidized Bed Combustion Conditions

2003 ◽  
Author(s):  
Franz Winter ◽  
Xin Liu
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Silica Sand ◽  
Electrical Heating ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Wide Range

The attrition behavior of ash produced from two bituminous and one anthracite coal was studied under laboratory-scale circulating fluidized bed combustor (CFBC) conditions. After the ash was produced in the oven, the ash sample with a size range from 0.1 to 1 mm was fed into the hot CFBC, which was heated by electrical heating shells and fluidized by air. The laboratory-scale CFBC was operated with using fine silica sand (40 to 80 μm) as bed material. After a certain time the operation was stopped, all particles were collected and sieving analysis was performed to obtain the actual particle size distribution (PSD) of the coal ash. The operating conditions were changed in a wide range, i.e. the bed temperature from 600 to 850°C, the fluidizing velocity from 1.2 to 2 m/s, the residence time from 60 to 120 min and the design of the cyclone. The effects of operating conditions and coal type were studied and their relative importance is discussed. Elemental analysis of the coal ashes showed that Si and Ca may play an important role during attrition.

Fluidized Bed Technologies for Biomass Combustion

2009 ◽  
Author(s):  
Aku Rainio ◽  
Vinod Sharma ◽  
Markus Bolha`r-Nordenkampf ◽  
Christian Brunner ◽  
Johannes Lind ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Distribution System ◽  
Circulating Fluidized Bed ◽  
Close Contact ◽  
Combustion Efficiency ◽  
Biomass Combustion ◽  
Fluidized Bed Combustion ◽  
Biomass Fuels ◽  
So2 Emissions ◽  
Gas Treatment

Biomass, a renewable fuel source for generating energy, is available in large quantities in the USA. Typical biomass consists of wood chips, construction and demolition wood, bark, residual logging debris, saw dust, paper rejects, and paper and sewage sludge. Composition and moisture content of biomass vary greatly and affect its heating value. There are several combustion technologies available to generate power from biomass. Fluidized bed boilers are preferred, because of their ability to burn a wide variety of biomass fuels while achieving high combustion efficiency and low emissions. This paper discusses basic design and operation features of bubbling (BFB) and circulating fluidized bed (CFB) boilers, both offering high fuel flexibility. In fluidized bed combustion, reactive biomass fuels are almost completely burned out because of close contact between the hot bed material and the fuel. In advanced BFB and CFB boilers, an open bottom design is used for ash and coarse material removal through the fluidizing air distribution system. This allows combustion of fuels containing large inert particles, such as rocks and metal pieces. If limestone is added to the bed, SO2 emissions are reduced. By using ammonia or urea in high temperature areas, NOx emissions are reduced. In order to achieve very low emissions, back-end flue gas treatment for SO2, NOx, HCl, HF, and Hg is required. To treat flue gases, several technologies can be used — such as activated carbon and sodium bicarbonate or Trona injection, Turbosorp® circulating dry scrubber, and SCR. Normally the preferred particulate matter cleaning device is a baghouse since the filter cake allows further reactions between pollutants and sorbents. Different fluidized bed designs are shown and recommended for various biomass fuels. This paper describes design, fuels, and emissions for an advanced BFB boiler producing steam at a rate of 230,000 lb/hr/930 psig/860°F (29.0 kg/s/64 barg/460°C).

Combustion Characteristics of Natural Gas in a Circulating Fluidized Bed

2003 ◽  
Author(s):  
Dennis Y. Lu ◽  
Edward J. Anthony
Keyword(s):  
Natural Gas ◽  
Gas Phase ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Pilot Scale ◽  
Combustion Characteristics ◽  
Air Pollutant ◽  
Operating Conditions ◽  
Fluidized Bed Combustion ◽  
Gas Combustion

Recently there has been interest in extending the application of fluidized bed combustors (FBCs) to fuels with difficult handling properties or ones that are associated with non-conventional air pollutant problems. These fuels, such as biomass, plastic wastes, black liquors and heavy liquid fuels, have very high volatiles contents and, because they are often treated as easily-burned materials, they have received much less attention than has been given say to the combustion processes for char in FBCs. Understanding their gas-phase chemistry is helpful in optimizing their combustion. This paper describes the study of natural gas combustion in a fluidized bed as a simple model for studying gas-phase reactions involving C/H/N/O chemistry in the absence of char. The experimental work was conducted using a pilot-scale CFBC unit. Combustion characteristics and emissions were investigated by varying the operating conditions and in particular the combustion temperature, fluidizing velocity and bed material. The results indicated that fluidized bed combustion chemistry is associated with superequilibrium free radical processes, similar to high-temperature flame systems. In this system, prompt-NO mechanisms are the only routes for NO formation and this work shows that they can lead to significant NOx production.

Investigation of Ammonia Formation During Gasification in an Air Blown Spouted Bed

2002 ◽  
Author(s):  
N. Paterson ◽  
Y. Zhuo ◽  
D. R. Dugwell ◽  
R. Kandiyoti
Keyword(s):  
Temperature Control ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Spouted Bed ◽  
Fuel Gas ◽  
Bed Temperature ◽  
Control Options ◽  
High Concentrations ◽  
Ammonia Formation

High NH3 concentrations were measured in the fuel gas produced by a pilot scale, air blown gasifier that was operated by British Coal. A laboratory scale gasifier has subsequently been developed to investigate the reactions that produce these potentially high concentrations. It has been found that in addition to the NH3 formed through pyrolytic processes, the introduction of steam (or H2 produced by its decomposition) increases the amount formed. The latter reaction produced the higher proportion of the total NH3. The effect of the gasifier operating conditions on the amount of NH3 formed has been studied. The main control options to minimise the NH3 formed are using an alternative method of bed temperature control (i.e. avoid the use of steam), operating with higher bed temperatures and operation at lower pressures.

An Investigation on Low-Temperature Fluidized Combustion of Liquid Fuels

2005 ◽  
Author(s):  
Lorenzo Ferrante ◽  
Michele Miccio ◽  
Roberto Solimene ◽  
Francesco Miccio
Keyword(s):  
Low Temperature ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Liquid Fuels ◽  
Experimental Program ◽  
Data Series ◽  
Low Temperature Combustion ◽  
Splash Zone ◽  
Fuel Injector ◽  
Bed Temperature

Presently, the combustion at low temperature is receiving a great deal of interest because emissions of micro- and nano-pollutants are expected to be greatly reduced. Following previous studies on the low temperature combustion behavior, the authors report results and discussion of steady-state experiments on an atmospheric, pre-pilot scale, 140 mm ID, FB reactor, equipped with an under-bed, air-assisted, liquid-fuel injector. The experimental program was focused on the operation at temperatures lower than the classical value for FBC of solid fuels (i.e., 850°C). The data series taken into consideration are the concentrations of the main unburned species in the splash zone, those of oxygen measured in the bed and in the splash zone as well as the freeboard pressure. The interpretation of the results is mainly based on the statistical analysis in the time domain. The combustion pattern of bio-diesel is compared to that of the diesel fuel under varying operating conditions (e.g., bed temperature, dispersion air velocity at the fuel nozzle, injector height in the bed). Conclusions that were previously published on the base of lab-scale results are checked against new data obtained on the pilot scale. An innovative technique for the analysis of the micro-explosive regime is presented. It consists in the comparison of oxygen concentration measured by the zirconia-based probes at different heights in the bed and in the splash region, pressure signals measured in the freeboard and purposely filtered, and video-recordings of the bed surface phenomena.

Characterization of Solid Wastes From Circulating Fluidized Bed Combustion

1995 ◽  
Vol 117 (1) ◽  
pp. 18-23 ◽  
Author(s):  
E. J. Anthony ◽  
G. G. Ross ◽  
E. E. Berry ◽  
R. T. Hemings ◽  
R. K. Kissel
Keyword(s):  
New Brunswick ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Pilot Scale ◽  
Full Scale ◽  
Operating Conditions ◽  
Solid Wastes ◽  
Fluidized Bed Combustion ◽  
Scale Unit

The characterization of solid wastes from full-scale circulating fluidized bed combustors (CFBC) is necessary to ensure that disposal procedures or utilization strategies for the waste solids are successful. Pilot plants are extremely useful in providing hydrodynamic heat and mass transfer data that can be used to design and predict the performance of larger units. Combustion studies indicate that data from pilot-scale units can be used to approximate the behavior of a full-scale plant for different fuels and operating conditions, even when the pilot plant is not designed to properly scale the commercial unit. However, the same does not seem to be true for the determination of reduced sulphur, the other is species and geotechnical or physical properties of the solid wastes generated from pilot plants. The results of analyses of samples generated from two units are discussed. One is a 150 by 150 mm square, 7.3 m high pilot-scale CFBC located at the University of British Columbia and 22 MWe CFBC located at Chatham, New Brunswick. This unit is operated by the New Brunswick Electric Power Commission (NBEPC). Both used the same New Brunswick coal containing 7 percent sulphur. The data presented indicate that the pilot-scale unit can significantly overpredict the formation of sulphides, and compared with the full-scale unit, produces residues with much less promise for either disposal or utilization in low-strength concretes. The results strongly suggest that further work is necessary to understand better the phenomena that produce sulphides and affect the geotechnical properties of wastes.

Biomass Combustion With Emphasis on Interactions Between Metals and Inorganic Particulate

2005 ◽  
Author(s):  
Fadi Eldabbagh ◽  
Appadurai Ramesh ◽  
Karl K. Rink ◽  
Janusz A. Kozinski
Keyword(s):  
Heavy Metals ◽  
Co2 Emissions ◽  
Inductively Coupled Plasma ◽  
Fossil Fuels ◽  
Analytical Techniques ◽  
Pilot Scale ◽  
Solid Particles ◽  
Biomass Combustion ◽  
Fluidized Bed Combustion ◽  
Inorganic Particles

Biomass is clean, stored solar energy. Not only is it a plentiful fuel, but its use also reestablishes the natural carbon cycle helping mitigate greenhouse gas emissions. This renewable energy source is nearly CO2 neutral. Overall, it is possible to achieve a 93% reduction in net CO2 emissions per unit heating value by switching from coal to biomass and a 84% reduction by switching from natural gas-fired cogeneration to biomass. Due to inherent advantages of the biomass in substituting fossil fuels, and increasing legislative pressures against CO2 emissions (Kyoto Protocol), biomass-based power is genuinely considered. It seems practically impossible to meet Kyoto requirements by replacing fossil fuels combustion with nuclear energy, hydropower or fuel cells. Simply, there is not enough time. In this context, there exists a niche for the biomass-based power generation. This paper compares interactions between metals and solid particles evolving from biomass during the classical Fluidized Bed Combustion (FBC) and a new Low-High-Low temperature (LHL) combustion. Experiments, conducted at a pilot-scale, reveal a clear pattern of surface predominance of light metals (Ca, K) and core predominance of heavy metals (Cd, Cr) within the LHL-generated particles. No such behavior was induced by the classical FBC approach. Metals migration is linked to the evolution of inorganic particles. A composite picture of the metals rearrangements in the particles was obtained by the combination of independent analytical techniques including electron probe microanalysis, field emission scanning electron microscopy, inductively-coupled plasma spectrometry and X-ray diffractometry. It is suggested that the combination of (i) the high-temperature region in the LHL and (ii) changes in the surface free energy of the particles is the driving force for the metal-particle behavior. Important practical implications of the observed phenomena are proposed including removal of hazardous submicron particulate and reduction in fouling/slagging during biomass combustion. These findings may contribute to redesigning currently operating FBC units in order to generate non-hazardous, non-leachable, re-usable particles where heavy metals are immobilized while environmental and technological problems reduced.

Experimental Study on Removal of Alkali-Metal and Incineration of High Concentration Organic Liquid Wastes

2006 ◽  
Vol 1 (3) ◽  
Author(s):  
J.Y. Ma ◽  
Z.Y. Ma ◽  
H.L. Jia ◽  
J.H. Yan ◽  
M.J. Ni ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Alkaline Earth ◽  
Organic Liquid ◽  
Combustion Efficiency ◽  
Alkaline Earth Metals ◽  
Fluidized Bed Combustion ◽  
High Concentration ◽  
Bed Temperature ◽  
Heat Value ◽  
Lower Temperature

To resolve the operational problems such as agglomeration, fouling, sintering and corrosion due to low-melting eutectics formed by alkali and alkaline-earth metals in the wastewater, evaporation-crystallization method was used to remove alkali and alkaline-earth metals and decrease demand of assistant fuel before incineration. Salty concentrated liquid was recycled to be re-evaporated. The removal efficiency of Na+ in NaCl is 99.88%. The ratio of organic compounds volatilization is higher than 99.00%. Organic waste steam was incinerated in fluidized bed combustion (FBC). Combustion efficiency is influenced by bed temperature and air flux. As the temperature is increased from 650?C to 900?C at the air flux of 20m3/h, combustion efficiency is increased from 88.74% to 99.90%. When the air flux is increased from 20m3/h to 30m3/h, combustion efficiency is decreased, especially at the lower temperature. Reduction of the concentration of organic compounds can decrease the heat value of the steam, and then, reduce combustion efficiency.

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