Hydraulic Properties of Fluidized Bed Combustion Ashes

1989 ◽  
Vol 178 ◽  
Author(s):  
I. Odler ◽  
K. -H. Zysk
Keyword(s):  
Flexural Strength ◽  
Fluidized Bed ◽  
Hydraulic Properties ◽  
Strength Development ◽  
Fluidized Bed Combustion ◽  
Free Lime ◽  
Blended Cements ◽  
Positive Effect

AbstractSeven fluidized bed combustion ashes of different composition were studied as to their hydraulicity and pozzolanicity. Four of them exhibited hydraulic reactivity and hardened when mixed with water. All of them exhibited a positive effect on strength development if used as constituents of blended cements. However, the presence of significant amounts of Fe2+ and free lime in the ash, as well as excessive amounts of SO3 in the produced cement caused unsoundness associated with the decline of flexural strength after longer hydration times.

Performance Characteristics of Concrete Produced with Fluidized Bed Combustion Ash Residue

1988 ◽  
Vol 136 ◽  
Author(s):  
A. E. Bland ◽  
C. E. Jones ◽  
J. G. Rose ◽  
J. L. Harness
Keyword(s):  
Fluidized Bed ◽  
Performance Characteristics ◽  
Strength Development ◽  
Fluidized Bed Combustion ◽  
Portland Cement Concrete ◽  
Conventional Concrete ◽  
Setting Times ◽  
Pulverized Fuel ◽  
Tennessee Valley ◽  
Pulverized Fuel Ash

ABSTRACTOver the last five years, the Kentucky Energy Cabinet (KEC) and the Tennessee Valley Authority (TVA) have developed and demonstrated the production of concrete from atmospheric fluidized bed combustion (AFBC) spent bed (SB) ash, and pulverized fuel ash (PFA). This AFBC concrete contains no cement and relies on the reaction of residual lime in the SB ash to react with the pozzolan PFA to form cementitious products. The SB ash is prehydrated in order to reduce exothermic lime hydration reactions and minimize molar volume expansion. Laboratory tests were conducted to establish the performance characteristics of AFBC concretes relative to conventional concrete. AFBC concretes exhibit slower strength gain characteristics, but long term (60 day), unconfined compressive strengths of 5,000 psi have been documented. This slow strength development is typical of pozzolanic concretes. AFBC concrete is more flexible and less brittle than conventional Portland cement concrete, as evidenced by its much lower modulus of elasticity. Setting times for AFBC concretes are extended, requiring the use of accelerators under certain applications. Field demonstrations of the AFBC concretes in ready mix concrete, masonry units, and road base applications have indicated excellent workability and finishing characteristics and confirm the laboratory performance characteristics.The paper describes the results of the testing program with emphasis on the ash chemistry/conditioning, the performance characteristics and field demonstrations.

Influencing Factors of Hydraulic Property of CFBC Ashes

2012 ◽  
Vol 532-533 ◽  
pp. 282-286
Author(s):  
Yuan Ming Song ◽  
Jing Xiang Liu ◽  
Chao Wang ◽  
Hong He Zhong ◽  
Tian Ding
Keyword(s):  
High Activity ◽  
Fluidized Bed ◽  
Influencing Factors ◽  
Circulating Fluidized Bed ◽  
Great Influence ◽  
Fluidized Bed Combustion ◽  
Hydraulic Property ◽  
Free Lime ◽  
Circulating Fluidized Bed Combustion

The hydraulic property of Circulating Fluidized Bed Combustion (CFBC) ashes has a significant impact on their treatment and re-utilization. The studies on several CFBC ashes show that the hydraulic property of them is obvious, and even the hydraulic rate is so fast that CFBC pastes can harden within several hours after molding. The influencing factors of hydraulic property of CFBC ashes are investigated. The results confirm that the content of the free lime and the high-activity components has great influence on the hydraulic property of CFBC ashes.

Use of Fluidized Bed Combustion Fly Ash as Addition Reducing Shrinkage of Concrete

2016 ◽  
Vol 865 ◽  
pp. 141-144 ◽  
Author(s):  
Lucia Osuská ◽  
Rudolf Hela
Keyword(s):  
Composite Material ◽  
High Temperature ◽  
Fly Ash ◽  
Fluidized Bed ◽  
Fresh Concrete ◽  
Fluidized Bed Combustion ◽  
Free Lime ◽  
Natural Properties ◽  
Temperature Combustion ◽  
High Temperature Combustion

Volumetric changes during ageing belong to natural properties of concrete. These changes, either growing or shrinking, can present a problem, which has to be taken into account during design and realization phases. This phenomenon is influenced by various factors and volumetric changes can be eliminated in many ways. One of the possibilities is setting appropriate combination of input materials and use of special additions and admixtures. This paper focused on verification of the method reducing shrinkage of concrete by means of using high temperature combustion fly ash combined with fluidized bed combustion fly ash as addition. The precondition is growth of new forms, in particular primary ettringite and monosulphate, which form because of the content free lime and sulphates in fluidized fly ash. If these minerals are formed in fresh concrete, they can positive prevent shrinkage without destruction of the composite material.

scholarly journals Circulation Fluidized Bed Combustion Fly Ash as Partial Replacement of Fine Aggregates in Roller Compacted Concrete

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4204 ◽  
Author(s):  
Wei-Ting Lin ◽  
Kae-Long Lin ◽  
Kailun Chen ◽  
Kinga Korniejenko ◽  
Marek Hebda ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Fluidized Bed ◽  
Setting Time ◽  
Unit Weight ◽  
Fluidized Bed Combustion ◽  
Sulfate Resistance ◽  
Roller Compacted Concrete ◽  
Fine Aggregates

Recently, many people around the world have been concerned with environmental protection and sustainability. The goal of various countries’ research has been focused on how to regenerate existing resources. Circulation fluidized bed combustion (CFBC) technology is one of the emerging combustion technologies for electricity generation and produces more than 800,000 tons of CFBC fly ash (CFA) per year for combustion. CFA has been widely applied in cement additive, new building materials and cement-based materials. The goal of this study was to discuss the engineering properties of roller-compacted concrete containing CFA. Test subjects included compressive strength, flexural strength, absorption, setting time, unit weight, sulfate resistance, SEM microscopic observations and XRD ingredient analysis. Test results indicate the following: (1) using CFA as a substitute of fine aggregates up to 10 wt.% would improve the development of later flexural strength; (2) the increases in pre-pressure would increase the compressive strength and unit weight and decrease absorption; (3) using CFA would reduce the initial setting time by 30%–60% and reduce the final setting time by 16%–20%; (4) using CFA would reduce the absorption; (5) using CFA would reduce the unit weight by 0.5%–2.8%, and the increases in pre-pressure would increase the unit weight by about 0.9%–2.1%; (6) CaO in CFA helps to improve sulfate resistance; (7) scanning electron microscopy (SEM) observation shows that the increases in pre-pressure would reduce the pores; and (8) X-ray diffraction (XRD) analysis shows that the inclusion of CFA would increase the content of Ca(OH)2 in concrete.

Understanding the Behavior of Calcium Compounds in Petroleum Coke Fluidized Bed Combustion (FBC) Ash

2006 ◽  
Vol 128 (4) ◽  
pp. 290-299 ◽  
Author(s):  
E. J. Anthony ◽  
L. Jia ◽  
S. M. Burwell ◽  
J. Najman ◽  
E. M. Bulewicz
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Petroleum Coke ◽  
Bound Water ◽  
Mineral Matter ◽  
Fluidized Bed Combustion ◽  
Free Lime ◽  
Size Fractions ◽  
Lime Content ◽  
Calcium Compounds

With growing understanding of the differences between solid residues from the fluidized bed combustion of petroleum coke and of coal, the significance of fuel-derived and sorbent-derived components of the ash has become clearer. It is well documented that hydration of the ashes is necessary prior to disposal or utilization or as a reactivation method. Initially, hydration of the lime was thought to involve water reacting only with CaO to form Ca(OH)2 but when the free lime content of the ashes is looked at before and after hydration, it is apparent that the process is more complex. Detailed analyses have shown that the free lime can decrease and vary within the same ash in different particle size ranges. The complexity of the reactions is reflected in problems with the assessment of the free lime content of the materials and the effect of hydration on different particle size fractions of the ash. The free lime content of the ash is significantly lower than expected based on the elemental analysis. Bed ash from the circulating fluidized bed combustion boilers owned and operated by the Nelson Industrial Steam Company Ltd. (NISCO) was examined in detail to elucidate the fate of calcium in the ash during hydration, using a range of techniques. The objective of the study is to determine the amount of CaO available for hydration/reactivation and to better understand interactions of Ca and other mineral components of the ash. Analysis results indicate that in NISCO ashes up to about 6% of the analytical CaO may be combined as acid soluble and insoluble OCCs (other calcium compounds). This implies up to about 10% less free lime than would be inferred from standard chemical analyses. About 1% of the missing CaO can be present as acid insoluble Ca and Mg vanadates, with up to 2% bound in soluble OCCs. The remaining 3-4% is still not accounted for. It is clear that even very minor quantities of mineral matter, other than CaO or CaSO4, associated mainly with the coarser size fractions, are important. The amount of bound water in the hydrated ash, other than that combined in portlandite or brucite, can be as large as 3-5%. This cannot be ignored when sample mass change on hydration or heating is used as a measure of the extent of CaO to Ca(OH)2 conversion.

Influence of Use Fluidized Fly Ash Combined with High Temperature Fly Ash on Microstructure of Cement Composite

2016 ◽  
Vol 722 ◽  
pp. 146-150
Author(s):  
Lucia Osuská ◽  
Rudolf Hela ◽  
Martin Ťažký
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Fly Ash ◽  
Fluidized Bed ◽  
Cement Hydration ◽  
Cement Composite ◽  
Hardened Concrete ◽  
Hydration Products ◽  
Fluidized Bed Combustion ◽  
Free Lime

The constraint of using fluidized bed combustion fly ash as addition for concrete is mainly its chemical composition. Increased contents of sulphates and free lime in fluidized bed combustion fly ash causes development of undesirable ettringite during hydration. Expansive character of this mineral can have degrading effect on hardened concrete. Fluidized bed combustion fly ash as well as high temperature fly ash are considered pozzolanic addition, which is capable of reacting with Ca(OH)2 and form similar hydration products as cement hydration. Use of small amount of fluidized bed combustion fly ash can cause production of ettringite, however, when combined with high temperature fly ash, possible micro-failures could be healed with new hydration products - CSH gels. The paper deals with possibilities of confirming this theory mainly through examination of microstructure of cement composite with an electron microscope and clarifying observed hydration products.

Hydration of Partially Sulphated CFBC Ash With Saturated Steam

2003 ◽  
Author(s):  
Yinghai Wu ◽  
Edward J. Anthony ◽  
Lufei Jia
Keyword(s):  
Fly Ash ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Bottom Ash ◽  
Size Fraction ◽  
Hydration Process ◽  
Saturated Steam ◽  
Fluidized Bed Combustion ◽  
Free Lime ◽  
X Ray

The hydration of partially sulphated fluidized bed combustion (FBC) ash with saturated steam was carried out in the laboratory. The ash samples were obtained from a commercial-scale 165 MWe circulating fluidized bed combustor (CFBC) firing a petroleum coke and coal blend. Both bottom ash and fly ash were tested, and in addition the bottom ash was also separated into five size fractions and tested. These solid streams and the “as-received” fly ashes were hydrated by steam produced in a pressure bomb for different lengths of time at different saturated temperatures. Samples of the ashes were analyzed for free lime and calcium hydroxide content before and after the hydration process. Scanning electron microscopy (SEM) with an energy dispersive X-ray system (EDX) was employed to determine physical characteristics of the samples. X-ray diffractograms (XRD) were also used to determine the phase composition. These results show that after hydration treatment with saturated steam at elevated pressures, the unreacted CaO in the partially sulphated material can be quantitatively converted to Ca(OH)2. However, the free lime content is also observed to change throughout the hydration process, which indicates that the hydration of CaO is not the only reaction occurring in this system. It is also clear that for fines, i.e., fly ash and <75 μm size fraction bottom ash, the effectiveness of the hydration depends much more strongly on hydration time and temperature than for coarser ashes and it is also clear that the behaviour of each particle size fraction is different.

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.

Fluidized bed combustion of char pellets made from blends of shrubs and cork residues

2017 ◽  
Author(s):  
Tânia Ferreira ◽  
Carlos Alberto Catorze Pereira ◽  
Carlos Pinho ◽  
JOÃO LUÍS MONNEY DE SÁ PAIVA ◽  
Edmundo Manuel Tavares Marques
Keyword(s):  
Fluidized Bed ◽  
Fluidized Bed Combustion

Analysis of the pore structure of Longkou oil shale semicoke during fluidized bed combustion

Oil Shale ◽  
2020 ◽  
Vol 37 (2) ◽  
pp. 89 ◽  
Author(s):  
H Liu ◽  
S Feng ◽  
S Zhang ◽  
C Jia ◽  
H Xuan ◽  
...  
Keyword(s):  
Pore Structure ◽  
Fluidized Bed ◽  
Oil Shale ◽  
Fluidized Bed Combustion
Sign in / Sign up

Export Citation Format

Share Document