Bed Agglomeration Characteristics in Fluidized-Bed Combustion of Biomass Fuels Using Olivine as Bed Material

2012 ◽  
Vol 26 (7) ◽  
pp. 4550-4559 ◽  
Author(s):  
Alejandro Grimm ◽  
Marcus Öhman ◽  
Therése Lindberg ◽  
Andreas Fredriksson ◽  
Dan Boström
Keyword(s):  
Fluidized Bed ◽  
Fluidized Bed Combustion ◽  
Biomass Fuels ◽  
Bed Agglomeration ◽  
Bed Material

Bed Agglomeration Characteristics during Fluidized Bed Combustion of Biomass Fuels

2000 ◽  
Vol 14 (1) ◽  
pp. 169-178 ◽  
Author(s):  
Marcus Öhman ◽  
Anders Nordin ◽  
Bengt-Johan Skrifvars ◽  
Rainer Backman ◽  
Mikko Hupa
Keyword(s):  
Fluidized Bed ◽  
Fluidized Bed Combustion ◽  
Biomass Fuels ◽  
Bed Agglomeration

A New Method to Inhibit Bed Agglomeration Problems in Fluidized Bed Boilers

2003 ◽  
Author(s):  
Jaani Silvennoinen
Keyword(s):  
Fluidized Bed ◽  
Industrial Scale ◽  
Fluidized Bed Combustion ◽  
Natural Sand ◽  
Worst Case ◽  
Free Quartz ◽  
Bed Materials ◽  
Bed Agglomeration ◽  
High Alkali ◽  
Bed Material

Fluidized bed combustion (FBC) technology was commercialized in the 70s. Both bubbling fluidized bed (BFB) and circulating fluidized bed (CFB) technology are capable of handling a wide variety of solid fuels. Natural sand is typically used as the fluidizing material. However, the properties and behavior of some solid fuel ash may limit the use of these fuels due to bed agglomeration problems. Natural sand contains several minerals, typically mainly consisting of 20–50 wt.-% of plagioclase (NaAlSi3O8 + CaAlSi3O8), 10–30 wt.-% of potash feldspar (KAlSi3O8), and 25–100 wt.-% of quartz (SiO2). Biomass based fuels contain high amounts of alkali. Ash high in alkali may react with the free quartz of the natural sand, producing an alkali silicate mixture with low melting point. This mixture may act as an adhesive between fluidized bed particles and may, in the worst-case, result in serious fluidization problems. This problem can be avoided by using AGGLOSTOP™ quartz-free bed material. Four different bed materials were tested in a 15 kW laboratory-scale FBC test rig with plywood residue, which is known to cause severe fluidization problems in FB boilers. Two of the tested bed materials were quartz-free. When quartz-free bed materials were used, no signs of bed agglomeration were observed. The other two bed materials containing free quartz caused total defluidization at a temperature of around 750°C after about half an hour of operation. The concept of using AGGLOSTOP™ quartz-free bed material with high alkali fuels has been successfully applied in two industrial scale BFB boilers (15 and 74 MWth). The use of AGGLOSTOP™ fluidized bed material enables energy production in FB boilers based on high alkali fuels, which were earlier impossible to utilize due severe bed agglomeration problems. This paper focuses on the bed agglomeration phenomenon by discussing the results from laboratory and industrial-scale boilers and presents a new solution to extend the use of high alkali fuels in FB boilers.

Mechanisms of Bed Agglomeration during Fluidized-Bed Combustion of Biomass Fuels

2005 ◽  
Vol 19 (3) ◽  
pp. 825-832 ◽  
Author(s):  
Elisabet Brus ◽  
Marcus Öhman ◽  
Anders Nordin
Keyword(s):  
Fluidized Bed ◽  
Fluidized Bed Combustion ◽  
Biomass Fuels ◽  
Bed Agglomeration

Biomass Ash – Bed Material Interactions Leading to Agglomeration in FBC

2003 ◽  
Author(s):  
H. J. M. Visser ◽  
S. C. van Lith ◽  
J. H. A. Kiel
Keyword(s):  
Coating Thickness ◽  
Problem Area ◽  
Critical Conditions ◽  
Fluidized Bed Combustion ◽  
Biomass Ash ◽  
Fundamental Study ◽  
Fluidization Velocity ◽  
Bubbling Fluidized Bed ◽  
Bed Agglomeration ◽  
Bed Material

In (bubbling) fluidized-bed combustion and gasification of biomass, several potential problems are associated with the inorganic components of the fuel. A major problem area is de-fluidization due to bed agglomeration. The most common found process leading to de-fluidization in commercial-scale installations is “coating-induced” agglomeration. During reactor operation, a coating is formed on the surface of bed material grains and at certain critical conditions (e.g., coating thickness or temperature) sintering of the coatings initiates the agglomeration. In an experimental approach, this work describes a fundamental study on the mechanisms of de-fluidization. For the studied process of bed de-fluidization due to sintering of grain-coating layers, it was found that the onset of the process depends on: a) a critical coating thickness, b) on the fluidization velocity when it is below approx. four times the minimum fluidization velocity and c) on the viscosity (stickiness) of the outside of the grains (coating).

scholarly journals Atmospheric fluidized bed gasification of promising biomass fuels in southern European regions

2007 ◽  
Vol 11 (1) ◽  
pp. 5-15 ◽  
Author(s):  
Kyriakos Panopoulos ◽  
Lydia Fryda ◽  
Emmanuel Kakaras
Keyword(s):  
Fluidized Bed ◽  
Lignin Content ◽  
Giant Reed ◽  
Co2 Production ◽  
European Regions ◽  
Biomass Fuels ◽  
Product Gas ◽  
Sorghum Bagasse ◽  
Bed Material ◽  
The Impact

Three promising biomass fuels from southern European regions were gasified atmospherically with air in a lab-scale fluidized bed reactor with quartz or olivine as bed material. The fuels used were an agro-industrial residue (olive bagasse) and the energy crops giant reed and sweet sorghum bagasse. Varying air ratios and temperatures were tested to study the impact on the product gas composition and tar load. Tars were higher in the case of olive bagasse, attributed to its higher lignin content compared to the other two biomasses with higher cellulose. Giant reed gasification causes agglomeration and defluidisation problems at 790?C while olive bagasse shows the least agglomeration tendency. The particular olivine material promoted the destruction of tars, but to a lesser level than other reported works; this was attributed to its limited iron content. It also promoted the H2 and CO2 production while CO content decreased. Methane yield was slightly affected (decreased) with olivine, higher temperatures, and air ratios. Air ratio increase decreased the tar load but at the same time the gas quality deteriorated. .

Catalytic Decomposition of N2O over the Bed Material from Circulating Fluidized-Bed (CFB) Boilers Burning Biomass Fuels and Wastes

2004 ◽  
Vol 18 (6) ◽  
pp. 1909-1920 ◽  
Author(s):  
Vesna Barišić ◽  
Ahmad Kalantar Neyestanaki ◽  
Fredrik Klingstedt ◽  
Pia Kilpinen ◽  
Kari Eränen ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Catalytic Decomposition ◽  
Biomass Fuels ◽  
Bed Material

The Phase Transformations during Fluidized-Bed Combustion of Biomass

2013 ◽  
Vol 419 ◽  
pp. 366-369 ◽  
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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