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Author: search.filters.author.Kaewkohkiat, Y.Subject: search.filters.subject.Rice husk

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    Combustion of rice husk in a fluidized bed combustor with wavy-surfaced chambers
    (2009-01-01)
    Kaewkohkiat, Y.
    ;
    Eiamsa-Ard, S.
    ;
    Wongcharee, K.
    ;
    Thungsotanon, D.
    ;
    Promvonge, P.
    The paper deals with an experimental investigation on effects of percent excess airs (EA = 15%, 30%, 45%, 60%, and 75%) on axial/radial temperature distributions, gas emissions and combustion efficiency in a fluidized bed combustor (FBC) with wavy surfaces using rice husk as the fuels. The combustion chamber shape is cylindrical with 200 mm in diameter (D) and 2400 mm in height (H). The top part of the chamber is designed and constructed to be wavy surface walls. In constructing the wavy surface bed at the top chamber, five modules of converging-diverging nozzles are inserted into the bed at which each module has a throat diameter of 100 mm and height of 200 mm. In the experiments, the axial/radial temperature distributions inside the combustor are measured for each percent excess air used while the feeding rate of rice husk is kept constant at 95 kg/hr. From experimental results, the emissions of flue gases are found to be CO = 308 ppm and NO<inf>x</inf> = 298 ppm, at EA = 75%. At all percent excess airs (EA) the axial/radial temperature distributions in the chamber are nearly uniform.
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    Combustion behavior in a dual-staging vortex rice husk combustor with snail entry
    (2008-11-01)
    Eiamsa-ard, S.
    ;
    Kaewkohkiat, Y.
    ;
    Thianpong, C.
    ;
    Promvonge, P.
    The combustion characteristics of rice husk fuel in a dual-staging vortex-combustor (DSVC) are experimentally investigated. In the present work, the vortex flow is created by using a snail entrance mounted at the bottom of the combustor. The temperature distributions at selected locations inside the combustor, the flue gas emissions (CO, CO<inf>2</inf>, O<inf>2</inf>, NO<inf>x</inf>), and the combustion/thermal efficiency are monitored. Measurements are made at a constant rice husk feed rate of 0.25 kg/min with various excess airs (37%, 56%, 74% and 92%) and different secondary air injection fractions (λ = 0.0, 0.15 and 0.2), respectively. The combustion chamber is 1800 mm high and 300 mm in diameter (D) with a centered exhausted pipe while the middle chamber of the combustor is set to 0.5D. The smaller section at the middle chamber is introduced to split the chamber to be dual-staging chamber where a large central toroidal recirculation zone induced by swirl flow through the small section is generated in the top chamber. The experimental results reveal that the highest temperature inside the combustor is about 1000 °C whereas both the thermal and the combustion efficiency are 41.6% and 99.8% for 74% excess air without the secondary air injection (λ = 0.0). In addition, the emissions are CO<inf>2</inf> = 8.1%, O<inf>2</inf> = 9.3%, CO = 352 ppm, NO<inf>x</inf> = 294 ppm and small amount of fly ash. Therefore, the DSVC shows an excellent performance, low emissions, high stabilization and ease of operation in firing the rice husk. © 2008 Elsevier Ltd. All rights reserved.