Attrition Behavior of Coal Ash Under Circulating Fluidized Bed Combustion Conditions

2003 ◽  
Author(s):  
Franz Winter ◽  
Xin Liu
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Silica Sand ◽  
Electrical Heating ◽  
Fluidized Bed Combustion ◽  
Bed Temperature ◽  
Wide Range

The attrition behavior of ash produced from two bituminous and one anthracite coal was studied under laboratory-scale circulating fluidized bed combustor (CFBC) conditions. After the ash was produced in the oven, the ash sample with a size range from 0.1 to 1 mm was fed into the hot CFBC, which was heated by electrical heating shells and fluidized by air. The laboratory-scale CFBC was operated with using fine silica sand (40 to 80 μm) as bed material. After a certain time the operation was stopped, all particles were collected and sieving analysis was performed to obtain the actual particle size distribution (PSD) of the coal ash. The operating conditions were changed in a wide range, i.e. the bed temperature from 600 to 850°C, the fluidizing velocity from 1.2 to 2 m/s, the residence time from 60 to 120 min and the design of the cyclone. The effects of operating conditions and coal type were studied and their relative importance is discussed. Elemental analysis of the coal ashes showed that Si and Ca may play an important role during attrition.

scholarly journals Research in the fluidized bed combustion in the Laboratory for thermal engineering and energy - Part A: Achievements in targeted fundamental research

2019 ◽  
Vol 23 (Suppl. 5) ◽  
pp. 1637-1653
Author(s):  
Borislav Grubor ◽  
Dragoljub Dakic ◽  
Stevan Nemoda ◽  
Milica Mladenovic ◽  
Milijana Paprika ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Thermal Engineering ◽  
Fluidized Bed Combustion ◽  
Particle Combustion ◽  
Research Activities ◽  
Energy Part ◽  
Char Particle ◽  
Fundamental Research

The paper gives a review of the most important results of extensive targeted fundamental research program on fluidized bed combustion in the Laboratory for Thermal Engineering and Energy of the VINCA Institute of Nuclear Sciences. The paper presents a detailed overview of research activities from the beginning in the second half of the 1970'' up to present days. Starting with the motives for initiating the investigations in this field, the paper highlights various phases of research and points out the main results of all research activities, not only the ones that are focused in this paper. Targeted fundamental research topics that are overviewed in this paper are heat and mass transfer, coal particle fragmentation, char particle combustion, sulfur self-retention by coal ash itself, as well as circulating fluidized bed modeling.

A Study of Operation Performance of Circulating Fluidized Bed Combustion Boiler

2003 ◽  
Author(s):  
Zhengshun Wu ◽  
Hanping Chen ◽  
Dechang Liu ◽  
Jie Wang ◽  
Chuangzhi Wu ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Fluidized Bed Combustion ◽  
Operation Performance ◽  
Cfb Boiler ◽  
Bed Temperature ◽  
Suitable Temperature ◽  
Bed Material ◽  
Circulating Fluidized Bed Combustion

The operation performance of circulating fluidized bed combustion (CFBC) boiler was studied in this paper. The experimental results indicate that the load of CFB boiler has linear relation with bed temperature and bed material height of operation. By multiple regression analysis, the relation of the load of CFB boiler with bed temperature and bed material height of operation can be expressed as a formula. The suitable temperature and the bed material height corresponding to the load of CFB boiler can be found using the formula; the problem of the boiler to be blindly operated can be reduced in practice.

Combustion Characteristics of Natural Gas in a Circulating Fluidized Bed

2003 ◽  
Author(s):  
Dennis Y. Lu ◽  
Edward J. Anthony
Keyword(s):  
Natural Gas ◽  
Gas Phase ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Pilot Scale ◽  
Combustion Characteristics ◽  
Air Pollutant ◽  
Operating Conditions ◽  
Fluidized Bed Combustion ◽  
Gas Combustion

Recently there has been interest in extending the application of fluidized bed combustors (FBCs) to fuels with difficult handling properties or ones that are associated with non-conventional air pollutant problems. These fuels, such as biomass, plastic wastes, black liquors and heavy liquid fuels, have very high volatiles contents and, because they are often treated as easily-burned materials, they have received much less attention than has been given say to the combustion processes for char in FBCs. Understanding their gas-phase chemistry is helpful in optimizing their combustion. This paper describes the study of natural gas combustion in a fluidized bed as a simple model for studying gas-phase reactions involving C/H/N/O chemistry in the absence of char. The experimental work was conducted using a pilot-scale CFBC unit. Combustion characteristics and emissions were investigated by varying the operating conditions and in particular the combustion temperature, fluidizing velocity and bed material. The results indicated that fluidized bed combustion chemistry is associated with superequilibrium free radical processes, similar to high-temperature flame systems. In this system, prompt-NO mechanisms are the only routes for NO formation and this work shows that they can lead to significant NOx production.

The Relative Importance of Radicals on the N2O and NO Formation and Destruction Paths in a Quartz CFBC

1999 ◽  
Vol 121 (2) ◽  
pp. 131-136 ◽  
Author(s):  
F. Winter ◽  
C. Wartha ◽  
H. Hofbouer
Keyword(s):  
Circulating Fluidized Bed ◽  
Combustion Process ◽  
Operating Conditions ◽  
Fuel Particle ◽  
Relative Importance ◽  
No Formation ◽  
Bed Temperature ◽  
Wide Range ◽  
Ft Ir ◽  
Concentration Changes

In a laboratory-scale circulating fluidized bed combustor (CFBC), which mainly consists of quartz-glass, the relative importance of the radicals, generated by the combustion process, on the N2O and NO formation and destruction paths are studied. The CFBC unit is electrically heated and operating conditions can be nearly independently changed over a wide range; e.g., the bed temperature was varied between 700 and 900°C. The radicals’ importance on the destruction reactions of N2O has been investigated under CFBC conditions by a recently developed iodine-addition technique to suppress the radical concentrations. Additionally, CO, CH4 and H2O have been added to study their influence and to change the pool of radicals. Time-resolved concentration changes at the top of the riser have been measured by using a high-performance FT-IR spectrometer in combination with a low-volume, long-path gas cell. The FT-IR analysis is focused on the carbon-containing species, viz., CO2 CO, CH4 NO2 and other hydrocarbons, as well as on the nitrogen-containing species, viz., NO, NO2, N2O, and HCN. In the continuous combustion tests, petroleum coke has been burned in the CFBC. Concentration profiles and concentration changes at the top of the riser have been measured. Iodine has been added and the bed temperature and the initial fuel particle size are varied. With the knowledge of the N2O destruction reactions, the relative importance of the radicals on N2O and NO formation reactions has been identified and is discussed.

scholarly journals Utilization of CFBC Fly Ash as a Binder to Produce In-Furnace Desulfurization Sorbent

2018 ◽  
Vol 10 (12) ◽  
pp. 4854 ◽  
Author(s):  
Chulseoung Baek ◽  
Junhyung Seo ◽  
Moonkwan Choi ◽  
Jinsang Cho ◽  
Jiwhan Ahn ◽  
...  
Keyword(s):  
Fly Ash ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Limestone Powder ◽  
Fluidized Bed Combustion ◽  
High Concentration ◽  
Cfbc Fly Ash ◽  
Desulfurization Efficiency ◽  
Free Cao

Circulating fluidized bed combustion (CFBC) power generation technology is known to efficiently reduce the emission of air pollutants, such as SO2 and NO2, from coal combustion. however, CFBC coal ash contains high contents of free CaO, making it difficult to recycle. This research has been conducted to find ways to use the self-hardening property of CFBC coal ash, one of its inherent characteristics. As part of these efforts, the present study intended to investigate the properties and desulfurization efficiency of Ca-based desulfurization sorbents using CFBC fly-ash as a binder. Limestone powder was mixed with CFBC fly-ash and Ca(OH)2 to fabricate desulfurization sorbents, and it generated hydrate of cement, including portlandite, ettringite, and calcium silicate, etc. The compressive strength of the desulfurization absorbent prepared by CFBC fly ash and Ca(OH)2 was 72–92% that of the desulfurized absorbent prepared by using general cement as a binder. These absorbents were then compared in terms of desulfurization efficiency using a high-temperature fluidized bed reactor. It was confirmed that the desulfurization absorbents fabricated using CFBC fly-ash as a binder achieved the best performance in terms of absorption time, which reflects the time taken for them to remove over 90% of high-concentration SO2 gas, and the conversion ratio, which refers to the ratio of CaO turning into CaSO4.

Study on Expansion of Circulating Fluidized Bed Combustion Coal Ash

2012 ◽  
Vol 518-523 ◽  
pp. 3501-3506
Author(s):  
Shun’ai He ◽  
Xiao Yan Zhu ◽  
Wen Zhong Bao ◽  
Wen Xin Zhao ◽  
Dong Min Jin
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Coal Ash ◽  
Expansion Rate ◽  
Hydration Products ◽  
Fluidized Bed Combustion ◽  
Free Expansion ◽  
Free Lime ◽  
Circulating Fluidized Bed Combustion

Expansive hydration products of circulating fluidized bed combustion (CFBC) ash with different finesses are investigated in this paper. The results show that expansion occurred in hardened paste of CFBC ashes is mainly due to formation of dihydrate gypsum and ettringite. Besides, the free lime does indirectly cause expansion due to its effects on crystallization of ettringite. It also has been observed that linear free expansion rate of paste with ground CFBC ash is higher than that of paste using original ash at 1 day of hydration, but lower than paste with original ash 3 days and longer period of hydration later.

Characterization of Solid Wastes From Circulating Fluidized Bed Combustion

1995 ◽  
Vol 117 (1) ◽  
pp. 18-23 ◽  
Author(s):  
E. J. Anthony ◽  
G. G. Ross ◽  
E. E. Berry ◽  
R. T. Hemings ◽  
R. K. Kissel
Keyword(s):  
New Brunswick ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Pilot Scale ◽  
Full Scale ◽  
Operating Conditions ◽  
Solid Wastes ◽  
Fluidized Bed Combustion ◽  
Scale Unit

The characterization of solid wastes from full-scale circulating fluidized bed combustors (CFBC) is necessary to ensure that disposal procedures or utilization strategies for the waste solids are successful. Pilot plants are extremely useful in providing hydrodynamic heat and mass transfer data that can be used to design and predict the performance of larger units. Combustion studies indicate that data from pilot-scale units can be used to approximate the behavior of a full-scale plant for different fuels and operating conditions, even when the pilot plant is not designed to properly scale the commercial unit. However, the same does not seem to be true for the determination of reduced sulphur, the other is species and geotechnical or physical properties of the solid wastes generated from pilot plants. The results of analyses of samples generated from two units are discussed. One is a 150 by 150 mm square, 7.3 m high pilot-scale CFBC located at the University of British Columbia and 22 MWe CFBC located at Chatham, New Brunswick. This unit is operated by the New Brunswick Electric Power Commission (NBEPC). Both used the same New Brunswick coal containing 7 percent sulphur. The data presented indicate that the pilot-scale unit can significantly overpredict the formation of sulphides, and compared with the full-scale unit, produces residues with much less promise for either disposal or utilization in low-strength concretes. The results strongly suggest that further work is necessary to understand better the phenomena that produce sulphides and affect the geotechnical properties of wastes.

Experimental and Theoretical Information on Solid Flow in a Circulating Fluidized Bed

1995 ◽  
Vol 117 (2) ◽  
pp. 133-141
Author(s):  
F. R. Steward ◽  
M. F. Couturier ◽  
S. Poolpol ◽  
S. Wang
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Equations Of Motion ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Laboratory Scale ◽  
Experimental Results ◽  
Solid Flow ◽  
Model Based ◽  
Fundamental Equations

Data are presented on a laboratory-scale circulating fluidized bed for various column geometries, solid fluxes, and gas velocities. Particular attention is paid to the solid flux profiles under various operating conditions. A model based on the fundamental equations of motion has been developed to describe the flow patterns of the solids particles and gas within a circulating fluidized bed. The predictions of the model are compared with experimental results. The model predicts that instabilities at the base of the bed propagate up the column for significant distances before uniform flows of solids and gas are established.

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