scholarly journals Hydrodynamic experiments on a small-scale circulating fluidized bed reactor at elevated operating pressure, and under an O2/CO2 environment

2017 ◽  
Vol 21 (2) ◽  
pp. 1093-1104 ◽  
Author(s):  
Yerbol Sarbassov ◽  
Azd Zayoud ◽  
Pinakeswar Mahanta ◽  
Sai Gu ◽  
Panneerselvam Ranganathan ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Atmospheric Pressure ◽  
Circulating Fluidized Bed ◽  
Elevated Pressure ◽  
Small Scale ◽  
Operating Pressure ◽  
Hydrodynamic Parameters ◽  
Hydrodynamic Experiments ◽  
Promising Development

Pressurized circulating fluidized bed technology is a potentially promising development for clean coal technologies. The current work explores the hydrodynamics of a small-scale circulating fluidized bed at elevated operating pressures ranging from 0.10 to 0.25 MPa. The initial experiments were performed at atmospheric pressure with air and O2/CO2 environments as the fluidization gas to simulate the hydrodynamics in a circulating fluidized bed. A comparison between the effects of air and O2/CO2 mixtures on the hydrodynamics was outlined in this paper for particles of 160 ?m diameter. A small but distinct effect on axial void-age was observed due to the change in gas density in the dense zone of the bed at lower gas velocity, while only minimal differences were noticed at higher gas velocities. The hydrodynamic parameters such as pressure drop and axial voidage profile along the height were reported at two different bed inventories (0.5 and 0.75 kg) for three mean particle sizes of 160, 302, and 427 ?m and three superficial gas velocities. It was observed that the operating pressure had a significant effect on the hydrodynamic parameters of bed pressure drop and axial bed void-age profiles. The effect of solids loading resulted in an exponential change in pressure drop profile at atmospheric pressure as well as at elevated pressure. The experimental results on hydrodynamic parameters are in reasonable agreement with published observations in the literature.

Gas-solid Flow Behaviors in a Pressurized Multi-stage Circulating Fluidized Bed with Geldart Group B Particles

2019 ◽  
Vol 17 (12) ◽  
Author(s):  
Wei Nie ◽  
Rongtao Feng ◽  
Junguo Li ◽  
Zhenhua Hao ◽  
Haijuan Zhan ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Elevated Pressure ◽  
Operating Pressure ◽  
Gas Velocity ◽  
Cold Model ◽  
Pressure Transducers ◽  
Multi Stage ◽  
Solids Holdup ◽  
Group B

Abstract A comprehensive study of gas-solids flow behaviors was conducted in a novel multi-stage circulating fluidized bed (MCFB). Experiments were carried out in a cold model apparatus (a jetting fluidized bed, JFB, of 0.3 m diameter and 1.95 m tall, a riser of 0.15 m diameter and 12 m tall) at different elevated pressure, solids circulation rates and gas velocities. Geldart group B polystyrene particles of 400 μm in diameter and 1020 kg/m3 in density were used as bed materials. The characteristic of L-valve, axial and radial distributions of solids holdup were systematically tested at elevated pressures by pressure transducers with the frequency of 100 Hz and model PC6M of the optical fiber probes. Operating the L-valve at elevated pressure needs less cross-section average gas velocity compared to that at atmospheric pressure. Experimental results showed that under elevated pressure and high solids flow rate, the MCFB could more easily couple JFB with a riser, where the solids that entered could form three-level step-by-step supplement entrainment and multi-flow regimes formed. Besides, increasing operating pressure led to a higher the apparent solids holdup and local solids holdup. The local solids profiles behaved less uniform distribution at elevated pressure due to decreasing the gas velocity.

Effect of elevated pressure on gas-solid flow characteristics in a circulating fluidized bed

2020 ◽  
Vol 366 ◽  
pp. 470-476 ◽  
Author(s):  
Daoyin Liu ◽  
Jinding Hu ◽  
Jialong Song ◽  
Cai Liang ◽  
Chuanlong Xu ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Flow Characteristics ◽  
Elevated Pressure ◽  
Solid Flow

Solids Holdup of High Flux Circulating Fluidized Bed at Elevated Pressure

2012 ◽  
Vol 35 (5) ◽  
pp. 904-910 ◽  
Author(s):  
S. Yin ◽  
B. Jin ◽  
W. Zhong ◽  
Y. Lu ◽  
Y. Zhang ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Elevated Pressure ◽  
High Flux ◽  
Solids Holdup

Scaling of flow phenomena in circulating fluidized bed boilers

2011 ◽  
Vol 32 (2) ◽  
pp. 91-100 ◽  
Author(s):  
Paweł Mirek
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Circulating Fluidized Bed ◽  
Scaling Law ◽  
Governing Equations ◽  
Dimensionless Numbers ◽  
Hydrodynamic Parameters ◽  
Scaling Models ◽  
Flow Phenomena ◽  
Fluidized Bed Boilers

Scaling of flow phenomena in circulating fluidized bed boilers The paper presents an overview of scaling models used for determining hydrodynamic parameters of Circulating Fluidized Bed boilers. The governing equations and the corresponding dimensionless numbers are derived and presented for three different approaches to the scaling law of fluidized beds: classical dimensional analysis, differential equations and integrated solutions and experimental correlations. Some results obtained with these equations are presented. Finally, the capabilities and limitations of scaling experiments are discussed.

scholarly journals Experimental and numerical study of wall layer development in a tribocharged fluidized bed

2018 ◽  
Vol 849 ◽  
pp. 860-884 ◽  
Author(s):  
Petteri Sippola ◽  
Jari Kolehmainen ◽  
Ali Ozel ◽  
Xiaoyu Liu ◽  
Pentti Saarenrinne ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Fluidized Bed ◽  
Numerical Study ◽  
Single Layer ◽  
Wall Layer ◽  
Small Scale ◽  
Average Charge ◽  
Particle Layer ◽  
Column Wall ◽  
Triboelectric Charging

The effects of triboelectricity in a small-scale fluidized bed of polyethylene particles were investigated by imaging the particle layer in the vicinity of the column wall and by measuring the pressure drop across the bed. The average charge on the particles was altered by changing the relative humidity of the gas. A triboelectric charging model coupled with a computational fluid dynamics–discrete element method (CFD-DEM) model was utilized to simulate gas–particle flow in the bed. The electrostatic forces were evaluated based on a particle–particle particle–mesh method, accounting for the surface charge on the insulating walls. It was found that simulations with fixed and uniform charge distribution among the particles capture remarkably well both the agglomeration of the particles on the wall and the associated decrease in the pressure drop across the bed. With a dynamic tribocharging model, the charging rate had to be accelerated to render the computations affordable. Such simulations with an artificial acceleration significantly over-predict charge segregation and the wall becomes rapidly sheeted with a single layer of strongly charged particles.

scholarly journals Effects of Riser Diameter on Solids Holdup and Particle Velocity Profiles in Circulating Fluidized Bed Riser Systems

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Ronald W. Breault ◽  
Steven L. Rowan ◽  
Justin M. Weber ◽  
Jingsi Yang
Keyword(s):  
Fluidized Bed ◽  
Particle Velocity ◽  
Circulating Fluidized Bed ◽  
Velocity Profiles ◽  
Small Scale ◽  
Sauter Mean Diameter ◽  
Particle Size Range ◽  
Cold Flow ◽  
Solids Holdup ◽  
Radial Profiles

Abstract Tests were performed in a 0.1-m diameter small circulating fluidized bed (SCFB) and 0.3 m diameter cold flow circulating fluidized bed (CFCFB) riser systems located at the National Energy Technology Laboratory (NETL) to study the effects of riser diameter on the riser hydrodynamics. These tests were performed at solids circulation rates of Gs = 20 and 75 kg/m2 s and superficial gas velocities of Ug = 5.8 and 6.5 m/s using high-density polyethylene (HDPE) pellets with a density of 0.863 g/cm3, particle size range of 600–1400 µm (with a Sauter mean diameter of 871 µm, placing them in the Geldart B classification). Comparisons of riser axial pressure and solids fraction profiles, radial particle velocity profiles, and radial profiles of higher statistical moments and select chaos analysis parameters were considered. The results showed that for a given Ug and Gs, the smaller diameter riser exhibited characteristics associated with more dilute solids flow than that observed in the larger diameter riser. Additionally, the larger diameter riser exhibited a downward flow of solids near the wall under all test conditions, whereas the smaller diameter riser data exhibited little or no indications of solids downflow near the wall. These findings suggest that, from an industrial standpoint, a direct scaleup of small-scale tests cannot readily be accomplished as the solids holdup and the solids velocity profiles in small units (those normally tested in the laboratory) are not similar to those of large units and the performance of large units can therefore not be predicted from small-scale tests.

scholarly journals Combustion adjustment and operation optimiztion of a 240 t/h circulating fluidized bed boiler

2020 ◽  
Vol 24 (5 Part A) ◽  
pp. 2689-2698
Author(s):  
Xuemin Liu ◽  
Songsong Zhang ◽  
Yongqiang Chang ◽  
Zhongwei Wang ◽  
Guoli Qi
Keyword(s):  
Fly Ash ◽  
Pressure Drop ◽  
Fluidized Bed ◽  
Flue Gas ◽  
Circulating Fluidized Bed ◽  
Air Flow ◽  
Nox Emission ◽  
Unburned Carbon ◽  
Boiler Efficiency ◽  
Co Concentration

The influence of main operating parameters on boiler performance was studied, such as bed pressure drop, primary air-flow and secondary air-flow. Combustion adjustment tests were carried out on a circulating fluidized bed boiler with rated capacity of 240 t/h. From the test results, it can be seen that the loss due to exit flue gas is the largest heat loss of the boiler, accounting for more than 70% of the total heat losses. For coal fired boilers, compared with the loss due to unburned solids, the loss due to unburned gases is quite small. The unburned carbon con-tent in bottom ash is far lower than the value in fly ash. The trend of CO concentration in the exit flue gas is similar to that of the unburned carbon content in fly ash. To achieve higher boiler efficiency, the bed pressure drop is suggested to be maintained in about 8.5-9.0 kPa and the oxygen content in exit flue gas around 4%. The NOx emission concentration usually presents a negative correlation with CO concentration in exit flue gas. Through combustion adjustment and operation optimization, the NOx emission can be decreased by about 30% without affecting the boiler efficiency.

Sign in / Sign up

Export Citation Format

Share Document