Investigation of combustion characteristics of biomass and coal mixtures in a circulating fluidized bed combustor

Varol, Murat
In this study, combustion and co-combustion tests of Bursa/Orhaneli lignite with two biomass fuels (olive cake and woodchips) were carried out in a laboratory scale Circulating Fluidized Bed (CFB) combustor, 6 m high and 108 mm inside diameter, in order to investigate the effect of excess air ratio (l), secondary air ratio (SAR) and location of secondary air injection along the combustor wall on the emissions. Optimum l and SAR was determined for each test. The flue gas emissions were compared with limits in the EU and Turkish Regulation. A series of co-combustion tests of olive cake (50% by wt.) with Bursa/Orhaneli lignite (Stotal < 2.7%) and with Denizli/Kale lignite (Stotal > 3.6%) were also done to investigate the effect of sulfur content of fuel and coal+biomass interaction on the ash composition. Olive cake was chosen to represent high alkali content biomass (50% K2O in ash). Samples taken from the bottom ash, fly ashes from cyclones and bag filter were subjected to XRF and XRD analyses. A Deposit Sampling Probe was used to simulate a heat exchanger surfaces in a boiler. The deposit accumulated on the probe and bottom ash samples were subjected to XRD and SEM-EDS analysis. The results showed that increasing share of biomass in the fuel mixture shifted combustion characteristics from char combustion to volatile combustion. Addition of biomass increased CO emission, reduced char formation and NO emission. It was proved that sulfur in coal helped to prevent agglomeration, slagging and fouling in the combustor. Optimum excess air ratio increased with addition of biomass to fuel mixture.


Investigation of co-combustion of coal and olive cake in a bubbling fluidized bed with secondary air injection
Atımtay, Aysel (2009-06-01)
In this study, a bubbling fluidized bed of 102 mm inside diameter and 900 mm height was used to burn olive cake and coal mixtures. Tuncbilek lignite coal was used together with olive cake for the co-combustion tests. Combustion performances and emission characteristics of olive cake and coal mixtures were investigated. Various co-combustion tests of coal with olive cake were conducted with mixing ratios of 25%, 50%, and 75% of olive cake by weight in the mixture. Operational parameters (excess air ratio, se...
Mathematical Modeling of a Bubbling Fluidized Bed Combustor Cofired with Lignite and Biomass
Külah, Görkem; Selçuk, Nevin (2010-01-01)
A comprehensive system model of fluidized bed combustor, previously developed and tested for the prediction of combustion behavior of fluidized bed combustors fired with lignite was extended for the modeling of cofiring of lignite with biomass by incorporating volatile release, char combustion, and population balance for biomass. The model predictions were validated against measurements taken on a Middle East Technical University 0.3 MWt Atmospheric Bubbling Fluidized Bed Combustor fired with lignite only, ...
Investigation of ash deposition in a pilot-scale fluidized bed combustor co-firing biomass with lignite
Gogebakan, Zuhal; Gogebakan, Yusuf; Selçuk, Nevin; Seliuk, Ekrem (2009-01-01)
This study presents the results from investigation of ash deposition characteristics of a high ash and sulfur content lignite co-fired with three types of biomass (olive residue, 49 wt%; hazelnut shell, 42 wt%; and cotton residue, 41 wt%) in 0.3 MWt Middle East Technical University (METU) Atmospheric Bubbling Fluidized Bed Combustion (ABFBC) Test Rig. Deposit samples were collected on all air-cooled probe at a temperature of 500 degrees C. Samples were analyzed by SEM/EDX and XRD methods. The results reveal...
Investigation of co-combustion characteristics of low quality lignite coals and biomass with thermogravimetric analysis
Varol, Murat; Atımtay, Aysel; Bay, B.; Olgun, H. (2010-10-20)
In this study, combustion and co-combustion characteristics of three biomass fuels and three Turkish lignite coals were investigated by using a thermo gravimetric analyzer. There are just a few studies investigating the co-combustion characteristics of coal and biomass, and the synergistic effect of their various combinations on the peak temperatures and burnout times.
Characterization of gas-solid flow in conical spouted beds operating with heavy particles
Sari, Salih; Külah, Görkem; KÖKSAL, MURAT (2012-07-01)
This study presents the results of an experimental investigation of the hydrodynamics of conical spouted beds operating with high density particles. This type of spouted beds is frequently encountered in chemical vapor deposition coating of nuclear fuel elements. Measurements were performed in three 15 cm ID full circular (gamma = 30 degrees, 45 degrees, 60 degrees) and one half circular conical spouted (gamma = 30 degrees) bed with yttria-stabilized zirconia particles (d(p) = 0.5, 1 mm; rho(p) = 6050 kg/m(...
Citation Formats
M. Varol, “Investigation of combustion characteristics of biomass and coal mixtures in a circulating fluidized bed combustor,” Ph.D. - Doctoral Program, Middle East Technical University, 2013.