The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform

Pongjet Promvonge - One of the best experts on this subject based on the ideXlab platform.

  • Combustion behavior in a dual-staging vortex rice husk combustor with snail entry☆
    International Communications in Heat and Mass Transfer, 2008
    Co-Authors: Smith Eiamsa-ard, Chinaruk Thianpong, Y. Kaewkohkiat, Pongjet Promvonge
    Abstract:

    Abstract 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, CO2, O2, NOx), 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 CO2 = 8.1%, O2 = 9.3%, CO = 352 ppm, NOx = 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.

  • Combustion behavior in a dual-staging vortex rice husk combustor with snail entry
    International Communications in Heat and Mass Transfer, 2008
    Co-Authors: S. Eiamsa-ard, Chinaruk Thianpong, Y. Kaewkohkiat, Pongjet Promvonge
    Abstract:

    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, CO2, O2, NOx), 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 CO2= 8.1%, O2= 9.3%, CO = 352 ppm, NOx= 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.

Shaohua Wu - One of the best experts on this subject based on the ideXlab platform.

  • numerical simulation of the gas solid flow in a square circulating fluidized bed with Secondary Air Injection
    International Symposium on Coal Combustion, 2013
    Co-Authors: Zhengyang Wang, Ningbo Zhao, Shaohua Wu
    Abstract:

    The dynamic behavior of gas-solid flow in an experimental square circulating fluidized bed setup (0.25 m × 0.25 m × 6.07 m) is predicted with numerical simulation based on the theory of Euler-Euler gas-solid two-phase flow and the kinetic theory of granular flows. The simulation includes the operation cases with Secondary Injection and without Air-staging. The pressure drop profile, local solids concentration and particle velocity was compared with experimental results. Both simulation and experimental results show that solids concentration increases significantly below the Secondary Air Injection ports when Air-staging is adopted. Furthermore, the flow asymmetry in the solid entrance region of the bed was investigated based on the particle concentration/velocity profile. The simulation results are in agreement with the experimental results qualitatively.

  • Experimental Study on the Penetration Model of Secondary Air Injection in CFB
    2011 Asia-Pacific Power and Energy Engineering Conference, 2011
    Co-Authors: Zhengyang Wang, Ningbo Zhao, Shaohua Wu
    Abstract:

    This work presents some experimental research on the penetration of Secondary Air Injection in a cold circulating fluidized bed (CFB) which has a square cross-section of 0.25m × 0.25m and a height of 6.07m. Using CO2 as Secondary Air Injection tracer, a simple model was developed to predict the penetration depth of Secondary Air in the CFB. Based on the fundamental momentum ratios of cross flows, this model mainly takes into account the primary Air velocity, Secondary Air nozzle diameter, solids circulation rate. Finally, experimental results and model predictions show good agreements.

  • Experimental Research on the Corner Secondary Air Injection of Square Circulating Fluidized Bed
    2010 Asia-Pacific Power and Energy Engineering Conference, 2010
    Co-Authors: Zhengyang Wang, Hao Chen, Shaohua Wu
    Abstract:

    Abstract-Corner Secondary Air Injection which four nozzles respectively located on four corners of square circulating fluidized bed (CFB) was investigated in this study. The cold CFB model has a square cross-section of 0.25 m × 0.25 m and a height of 6.07 m. The axial pressure drop profile along the riser has been got by differential pressure measurement to evaluate the axial solids concentration distribution in different operating conditions. Solids concentration increases significantly below the Secondary Air Injection ports especially when high Secondary Air rate is adopted. Using CO2 as tracer, the dispersion of corner Secondary Air jet was investigated. It is found that if the solids concentration near nozzles' outlet is lean, the Secondary Air Injection with high velocity will make a swirling flow in the riser. However, higher solids concentration distribution especially in the corner region will limit the penetration of Secondary Air Injection and no apparent swirling flow was found in these conditions.

  • Gas-Solids Flow Properties of a Square Circulating Fluidized Bed with Secondary Air Injection
    International Journal of Chemical Reactor Engineering, 2010
    Co-Authors: Zhengyang Wang, Hao Chen, Dong Li, Qigang Deng, Shaohua Wu
    Abstract:

    Effects of Secondary Air (SA) Injection or Air-staging on the gas-solids flow properties in the riser of a circulating fluidized bed (CFB) were investigated. The experiments were carried out in a CFB cold model with a square cross-section of 0.25m×0.25m and a height of 6.07m. The axial pressure drop profile along the riser was reported. And the local solids holdup profile at the centerline and the diagonal line of some cross sections which influenced by the SA Injection was measured with an optical fiber probe. Two SA arrangement modes, i.e. four SA nozzles located on four walls (Wall SA) and four corners (Corner SA) were conducted. Air-staging results in a denser bottom bed for both two SA modes. The Wall SA case has a higher solids holdup than the Corner SA case in most regions of lower bed except the corner region but was leaner in the vicinity of SA Injection level. W-shaped solids concentration profile was found in the region immediately above the SA Injection level for Wall SA case but not obvious for Corner SA case. Fractal dimension was analyzed for pressure drop fluctuations and local solids concentration signal. Air-staging led to smaller fractal dimension value than the case without SA Injection. The SA jets affected the local gas-solids distribution and fluctuation in the region close to the SA Injection. Radial and axial solids transfer should be considered for the fractal analysis.

S. Eiamsa-ard - One of the best experts on this subject based on the ideXlab platform.

  • Combustion behavior in a dual-staging vortex rice husk combustor with snail entry
    International Communications in Heat and Mass Transfer, 2008
    Co-Authors: S. Eiamsa-ard, Chinaruk Thianpong, Y. Kaewkohkiat, Pongjet Promvonge
    Abstract:

    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, CO2, O2, NOx), 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 CO2= 8.1%, O2= 9.3%, CO = 352 ppm, NOx= 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.

F Hamdullahpur - One of the best experts on this subject based on the ideXlab platform.

  • heat transfer in circulating fluidized beds with Secondary Air Injection
    Annals of the Assembly for International Heat Transfer Conference 13, 2006
    Co-Authors: Murat Koksal, Mohammad R Golriz, F Hamdullahpur
    Abstract:

    In this study, we present an empirical model for bed-to-surface heat transfer in Circulating Fluidized Beds (CFB) with Secondary Air (SA) Injection. The model is based on a correlation that relates ...

  • cfd simulation of the gas solid flow in the riser of a circulating fluidized bed with Secondary Air Injection
    Chemical Engineering Communications, 2005
    Co-Authors: Murat Koksal, F Hamdullahpur
    Abstract:

    ABSTRACT A comprehensive investigation was carried out to study hydrodynamics aspects of Secondary Air Injection in circulating fluidized beds. This article presents modeling and results of computational fluid dynamics simulations of gas-solid flow in the riser section of a laboratory-scale (ID = 0.23 m, height = 7.6 m) circulating fluidized bed with a radial Secondary Air injector. The gas-solid flow model is based on the two-fluid (Eulerian-Eulerian) approach, where both gas and solids phases are treated as interpenetrating continua. A granular kinetic theory model is used to describe the solids phase stresses. The simulation results are compared with measured pressure drop and axial particle velocity profiles; reasonable agreement is obtained. Qualitatively, excellent agreement is obtained in predicting the increase in solids volume fraction below Secondary Air ports, the accumulation of solids around the center of the riser due to momentum of Secondary Air jets, and the absence of the solids down-flow...

  • gas mixing in circulating fluidized beds with Secondary Air Injection
    Chemical Engineering Research & Design, 2004
    Co-Authors: Murat Koksal, F Hamdullahpur
    Abstract:

    This paper presents the results of a gas mixing study carried out in a laboratory scale (I.D. = 0.23 m, height = 7.6 m) circulating fluidized bed with Secondary Air (SA) Injection. Steady-state tracer gas experiments were performed to investigate the effects of SA injector design on radial gas dispersion under varying operating conditions ( U o = 3, 5ms −1 ; 0 s −2 s −1 ) with silica sand particles ( p s = 2650 kgm −3 , d p = 250 μm). Three different types of SA injectors that could feed the SA to the riser at different orientations were tested in the experiments; tangential, radial and mixed. Axial pressure measurements show that the tangential SA injector considerably increases the solids hold-up in the riser compared with non-SA operation at the same superficial gas velocity and solids circulation rate. Tracer gas measurements and calculated dispersion coefficients indicate that SA Injection significantly increases the radial gas dispersion regardless of the design of the injector. The most effective injector in improving gas mixing was found to be the radial injector. This is attributed to the large-scale fluctuations caused by impinging radial SA jets. Furthermore, the mixing pattern of SA with rising gas–solid flow shows considerable differences with different injector types.

  • Circulating fluidized bed hydrodynamics with Air staging: an experimental study
    Powder Technology, 2004
    Co-Authors: L E Ersoy, Murat Koksal, Mohammad R Golriz, F Hamdullahpur
    Abstract:

    The influence of Secondary Air Injection (SA) on the hydrodynamics of circulating fluidized beds was studied in a 0.23-m ID riser. The Secondary to primary Air ratio, the vertical position, and the mode of Injection (radial, tangential, and 45° entrance) are considered to be the key parameters of SA Injection. It was found that the amount and location of SA have direct influence on the solids holdup and the segregation patterns in the riser. The SA divided the riser into two different flow zones: a dense turbulent zone below and a relatively dilute bed above the Injection port. The mean solids velocity is found to be upwards with a greater magnitude in the center region. It is downwards with a smaller magnitude along the walls, suggesting core-annular flow structures for both above and below the SA Injection region.

  • effects of Secondary Air Injection on the hydrodynamics of circulating fluidized beds
    1997
    Co-Authors: L E Ersoy, J Militzer, F Hamdullahpur
    Abstract:

    Circulating fluidized bed combustion of fossil fuels has many advantages over the conventional combustion systems, such as effective NO$\sb{\rm x}$ control, high sulfur capture efficiency, and high combustion efficiency. These advantages are much more pronounced with the application of staged combustion by Secondary Air Injection. The concept of Secondary Air arises from splitting the fluidization Air into a primary Air stream, which is injected axially from the bottom of the riser, and a Secondary Air stream injected laterally to the riser.

Hideaki Kobayashi - One of the best experts on this subject based on the ideXlab platform.

  • numerical study of a low emission gas turbine like combustor for turbulent ammonia Air premixed swirl flames with a Secondary Air Injection at high pressure
    International Journal of Hydrogen Energy, 2017
    Co-Authors: Kapuruge Don Kunkuma Amila Somarathne, Sotaro Hatakeyama, Akihiro Hayakawa, Hideaki Kobayashi
    Abstract:

    Abstract The present study is dedicated to understand the emission characteristics of turbulent premixed ammonia/Air swirl flames in a gas turbine like combustor at high pressure with and without Secondary Air Injection. Ammonia has recently created an attention as a sustainable energy source not only because of its carbon free nature but also owing to its high hydrogen capacity of 17.8% in weight. Thus, in the present study, the effect of pressure on NO, unburnt NH3, and H2 emissions in ammonia/Air premixed combustion was discussed by having space and time average emissions (STAE) at the exit of cylindrical combustor for various equivalence ratios and high pressures up to 0.5 MPa. The study found that NO emission decreases with an increase in pressure whereas unburnt NH3 emission in rich flame conditions also decreases with increase in pressure, and the study realizes that, at the equivalence ratio of 1.2, NO and unburnt NH3 emissions are minimal and in the same order of 200 ppm of mole fraction, even though still there is an unburnt H2 emission of 6% volumetric exhaust flow at the operating pressure of 0.5 MPa. Subsequently, Secondary Air Injection system was introduced to the combustor, and eventually, the study realizes a low emission combustor with the STAE of NO in the order of 100 ppm of mole fraction at 16% of O2 concentration and zero NH3 and H2 emissions, at the primary zone equivalence ratio of 1.2.

  • Numerical study of a low emission gas turbine like combustor for turbulent ammonia/Air premixed swirl flames with a Secondary Air Injection at high pressure
    International Journal of Hydrogen Energy, 2017
    Co-Authors: Kapuruge Don Kunkuma Amila Somarathne, Sotaro Hatakeyama, Akihiro Hayakawa, Hideaki Kobayashi
    Abstract:

    Abstract The present study is dedicated to understand the emission characteristics of turbulent premixed ammonia/Air swirl flames in a gas turbine like combustor at high pressure with and without Secondary Air Injection. Ammonia has recently created an attention as a sustainable energy source not only because of its carbon free nature but also owing to its high hydrogen capacity of 17.8% in weight. Thus, in the present study, the effect of pressure on NO, unburnt NH3, and H2 emissions in ammonia/Air premixed combustion was discussed by having space and time average emissions (STAE) at the exit of cylindrical combustor for various equivalence ratios and high pressures up to 0.5 MPa. The study found that NO emission decreases with an increase in pressure whereas unburnt NH3 emission in rich flame conditions also decreases with increase in pressure, and the study realizes that, at the equivalence ratio of 1.2, NO and unburnt NH3 emissions are minimal and in the same order of 200 ppm of mole fraction, even though still there is an unburnt H2 emission of 6% volumetric exhaust flow at the operating pressure of 0.5 MPa. Subsequently, Secondary Air Injection system was introduced to the combustor, and eventually, the study realizes a low emission combustor with the STAE of NO in the order of 100 ppm of mole fraction at 16% of O2 concentration and zero NH3 and H2 emissions, at the primary zone equivalence ratio of 1.2.