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

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.

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

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-033 ◽

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.

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Attrition Behavior of Coal Ash Under Circulating Fluidized Bed Combustion Conditions

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-129 ◽

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.

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Combustion Characteristics of Natural Gas in a Circulating Fluidized Bed

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-053 ◽

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.

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Characterization of Solid Wastes From Circulating Fluidized Bed Combustion

Journal of Energy Resources Technology ◽

10.1115/1.2835314 ◽

1995 ◽

Vol 117 (1) ◽

pp. 18-23 ◽

Cited By ~ 10

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.

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The Phase Transformations during Fluidized-Bed Combustion of Biomass

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.419.366 ◽

2013 ◽

Vol 419 ◽

pp. 366-369 ◽

Cited By ~ 2

Author(s):

Hai Peng Teng ◽

Bin Yang ◽

Bin Liang

Keyword(s):

Gas Phase ◽

Fluidized Bed ◽

Solid Phase ◽

Fluidized Bed Reactor ◽

Biomass Combustion ◽

Material Surface ◽

Fluidized Bed Combustion ◽

Biomass Ash ◽

Equilibrium Modeling ◽

Bed Material

FactSage6.1 was used to study the phase transformation at high temperature when biomass combustion in a fluidized bed reactor. The results show that eutectic was formed during the reaction process, the eutectics are formed mainly by the reaction between the silica in bed particles and the alkali species in biomass ash. The solid phase transformed to melt layer on the surface of sands particle mainly contains potassium, some calcium and magnesium, and also a few phosphorus and chlorine are found in the melt layer. The result utilizing FactSage equilibrium modeling shown that the distribution ratio of potassium in the gas phase increased with the increase of temperature, moreover, the melt of bed material surface increased when defluidized occurred.

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Fluidized Bed Combustion: Technology for Efficient Utilization of Biomass Residues

Asian Journal of Engineering and Applied Technology ◽

10.51983/ajeat-2018.7.2.951 ◽

2018 ◽

Vol 7 (2) ◽

pp. 73-79

Author(s):

Vishal Sharma ◽

Rajeev Kamal Sharma

Keyword(s):

Fluidized Bed ◽

Fossil Fuels ◽

Renewable Energy Sources ◽

Biomass Combustion ◽

Fluidized Bed Combustion ◽

Technical Approach ◽

Fast Pace ◽

Combustion Technology ◽

Alternate Source ◽

Fluidized Bed Combustor

Fossil fuels are the most common and reliable energy source, which presently fulfill 80% energy requirements all across the world. In the last few decades, over-consumption, fast pace modernization and population growth are some prominent factors which are exploiting the fossil fuels. The degradation of natural resources has gone up at an alarming rate which provoked to look for an alternate source of energy. From all available alternative renewable energy sources, biomass is the only carbon-based sustainable option. But, its diversity makes it a complex and difficult fuel. Among all technologies used for energy generation from the biomass, fluidized bed combustion is emerging as a suitable best option to handle fuel diversity. This article deals with biomass fluidization and its combustion in a fluidized bed. The difficulties encountered during biomass combustion and different solutions for the same have been highlighted. Problems like deposition, corrosion, agglomeration and trace metal emission have been discussed and their remedies to avoid the discontinuity in the operation of biomass-fired fluidized bed combustor. This technical approach will help to reduce environmental problems, improve the economic structure of the nation, and remove obstacles for sustainable energy development.

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Bed Agglomeration During the Fluidized Bed Combustion of Olive Husk

18th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2005-78098 ◽

2005 ◽

Author(s):

Antonio Cammarota ◽

Riccardo Chirone ◽

Fabrizio Scala

Keyword(s):

Fluidized Bed ◽

Dynamic Pressure ◽

Mediterranean Area ◽

Operating Conditions ◽

Pressure Gradients ◽

Fluidized Bed Combustion ◽

High Propensity ◽

Olive Husk ◽

Bed Agglomeration ◽

High Alkali

The fluidized bed combustion of a biomass residue (olive husk) common in the Mediterranean area has been investigated in a bench scale reactor. The focus of the study was the high propensity of this fuel to give rise to bed agglomeration problems during combustion, as a consequence of the high alkali content of the ash. Bed agglomeration characteristic times as well as temperature and pressure gradients were measured at different operating conditions. In addition, a diagnostic tool based on the measurement of the dynamic pressure signal inside the bed was tested for its capability to predict the bed agglomeration onset.

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Combustion of Waste Fuels in Sound-Assisted Fluidized Beds

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-052 ◽

2003 ◽

Author(s):

A. Cammarota ◽

R. Chirone ◽

M. Urciuolo

Keyword(s):

Fluidized Bed ◽

Sound Intensity ◽

Carbon Conversion ◽

Fluidized Bed Combustion ◽

Combustion Time ◽

Fixed Carbon ◽

Optimum Frequency ◽

Combustion Of Solid Fuels ◽

Minimum Intensity ◽

Carbon Loading

In the present work, sound-assisted fluidized bed combustion has been investigated by means of a 41mm laboratory scale apparatus fed with combustible powders of different fuels: a tyre derived fuel, a lignite and a petroleum coke. The experiments aim at studying the effect of sound intensity and frequency on carbon conversion of elutriable fines generally produced during fluidized bed combustion of solid fuels. The effectiveness of sound application is evaluated in terms of effects on bed carbon loading, carbon elutriation rate, combustion time and degree of conversion of fixed carbon. Experimental data prove that application of acoustic fields of appropriate intensity and frequency may: increase bed carbon loading and combustion time, reduce elutriation of carbon fines and increase efficiency of fixed carbon conversion. The effects are different for each fuel depending on its characteristics. A simplified model of sound-assisted fluidized bed has been developed. The model has been validated by comparing the experimental optimum intensity and frequency with calculated values of minimum intensity and optimum frequency. The present formulation of the model is useful for the design of the acoustic field to be used in sound-assisted fluidized bed combustors.

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A Study of Operation Performance of Circulating Fluidized Bed Combustion Boiler

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-001 ◽

2003 ◽

Author(s):

Zhengshun Wu ◽

Hanping Chen ◽

Dechang Liu ◽

Jie Wang ◽

Chuangzhi Wu ◽

...

Keyword(s):

Regression Analysis ◽

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Fluidized Bed Combustion ◽

Operation Performance ◽

Cfb Boiler ◽

Bed Temperature ◽

Suitable Temperature ◽

Bed Material ◽

Circulating Fluidized Bed Combustion

The operation performance of circulating fluidized bed combustion (CFBC) boiler was studied in this paper. The experimental results indicate that the load of CFB boiler has linear relation with bed temperature and bed material height of operation. By multiple regression analysis, the relation of the load of CFB boiler with bed temperature and bed material height of operation can be expressed as a formula. The suitable temperature and the bed material height corresponding to the load of CFB boiler can be found using the formula; the problem of the boiler to be blindly operated can be reduced in practice.

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