scholarly journals Research on the Expansion Characteristics and Compressive Strength of Mortars Containing Circulating Fluidized Bed Combustion Desulfurization Slag

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Zhi Cheng ◽  
Zhijun Cheng ◽  
Hua Hou ◽  
Tao Han ◽  
Lan Liu
Keyword(s):  
Compressive Strength ◽  
Fluidized Bed ◽  
Power Plants ◽  
Circulating Fluidized Bed ◽  
Linear Expansion ◽  
Chemical Activation ◽  
Expansion Rate ◽  
Fluidized Bed Combustion ◽  
Mechanical Grinding ◽  
Circulating Fluidized Bed Combustion

Circulating fluidized bed combustion (CFBC) desulfurization slag is a waste residue discharged from coal power plants. In this article, expansion characteristics and compressive strength of mortars containing CFBC desulfurization slag were evaluated, subjected to mechanical grinding time, the amount of additive, and chemical activation. Correlations between the linear expansion rate and compressive strength were investigated. The hydration products of cement-slag cementitious system were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that mechanical grinding can increase both the expansion and compressive strength of mortars containing CFBC desulfurization slag, and the compressive strength and linear expansion can develop in coordination. While increasing the amount of the fine desulfurization slag, the linear expansion rate increases, and the compressive strength reaches to the maximum when the amount is 30%. Moderate sodium sulfate as an activator can both promote the compressive strength and increase the expansion of mortars.

scholarly journals Mechanical Activation of the Ca-Rich Circulating Fluidized Bed Combustion Fly Ash: Development of an Alternative Binder System

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 3
Author(s):  
Peeter Paaver ◽  
Päärn Paiste ◽  
Martin Liira ◽  
Kalle Kirsimäe
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Mechanical Activation ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Chemical Activation ◽  
Fluidized Bed Combustion ◽  
Strength Performance ◽  
Mineral Characteristics ◽  
Circulating Fluidized Bed Combustion

Mechanical activation of the calcium-rich fly ash formed in circulating fluidized bed combustion (CFBC) boilers was investigated to enhance the compressive strength performance of the pastes. We studied the effect of the activation on the physical, chemical, and mineral characteristics of fly ash and its pastes. Our study shows that already a short mechanical activation yields a 10-fold improvement in the compressive strength of the pastes, reaching 60 MPa after 90 days of curing without any chemical activation or blending. Mechanical activation caused fragmentation of large porous aggregates in the raw ash enhancing the physical properties and reactivity of fly ash particles. Similarly to calcium sulfoaluminate cements, the mechanical strength was provided by the formation of abundant ettringite and possibly C-(A)-S-H gel-like phase that created a highly compact microstructure. Our findings suggest that mechanically activated Ca-rich CFBC fly ash can be successfully used as an alternative binder.

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.

scholarly journals Utilization of low sulfur fly ash from circulating fluidized bed combustion burner as geopolymer binder

2020 ◽  
Vol 22 (2) ◽  
pp. 94-100
Author(s):  
Antoni Antoni ◽  
Stacia Dwi Shenjaya ◽  
Maria Lupita ◽  
Samuel Santosa ◽  
David Wiyono ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Fluidized Bed ◽  
Water Demand ◽  
Circulating Fluidized Bed ◽  
Fluidized Bed Combustion ◽  
Naoh Solution ◽  
Cfbc Fly Ash ◽  
Low Sulfur ◽  
Circulating Fluidized Bed Combustion

Circulating fluidized bed combustion (CFBC) is a newer type of burner that employ a circulating process to burn fuel effectively. CFBC burning process is gaining more popularity due to its compact size, high efficiency and lower burning temperature compared to the pulverized coal combustion (PCC) burner. The CFBC burner produces fly ash with different physical properties compared to the PCC burner, i.e. the fly ash is not rounded, and required higher water content for comparable workability. The CFBC fly ash also has a high sulfur content that is detrimental for hardened concrete. Due to its drawbacks, the CFBC hardly used as cementitious material and geopolymer precursor. This study focuses on comparing variations in the concentration of NaOH solution and variations in the ratio of alkaline activators to the setting time and compressive strength of geopolymer mortars on a new class of CFBC fly ash, which have low sulfur content. The concentrations of NaOH solution were 6M, 8M, 10M, and 12M, while the alkaline activator ratios used were 3.0, 2.5, 2.0, 1.0, and 0.5. It was concluded that the low sulfur CFBC fly ash has a potential to be utilized as geopolymer precursor, however, with a shortcoming in its high water demand. The CFBC fly ash used in this study resulted in a geopolymer matrix with good compressive strength and stability. The water demand varies with the fly ash sampling time shows the challenges in the utilization of the fly ash. The highest mortar’s compressive strength, 33.4 MPa at 90 days was achieved at NaOH concentration of 8M and ratio of sodium silicate solution to sodium hydroxide solution of 2.5 with excellent stability.

scholarly journals Development of a cementless eco-binder as an alternative to traditional Portland cement in construction activities

2020 ◽  
Vol 14 (3) ◽  
pp. 40-52
Author(s):  
Huynh Trong Phuoc ◽  
Vu Viet Hung ◽  
Bui Le Anh Tuan ◽  
Pham Huu Ha Giang
Keyword(s):  
Compressive Strength ◽  
Fluidized Bed ◽  
Rice Husk Ash ◽  
Circulating Fluidized Bed ◽  
Drying Shrinkage ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Fluidized Bed Combustion ◽  
Circulating Fluidized Bed Combustion

In this research, the performance of a cementless eco-binder, a mixture of waste materials including slag, circulating fluidized bed combustion ash (CFA), and rice husk ash (RHA) was investigated, in which CFA acted as an activator. One hundred and twenty paste samples were prepared by using the RHA/(slag + RHA) ratios of 0, 15, 30, 45% while keeping a constant ratio of CFA/(slag + RHA) at 25%. The setting period, compressive strength, the ultrasonic pulse velocity (UPV), and drying shrinkage of paste samples were determined at the samples’ age of up to 91 days. In addition, the microstructures of all paste samples were also characterized by scanning electron microscopy (SEM). It was found that the use of cementless eco-binder significantly increased the setting times, lower compressive strength, drying shrinkage, and UPV values compared to the control OPC sample. The maximum 91-day-old compressive strength gained by the binary binder of slag and CFA (R00C25) was 90% of that of the control specimen. Incorporation of RHA with higher replacement levels up to 45% resulted in a significant decrease in compressive strength up to 50%. Moreover, the SEM analysis revealed that there was a large difference in the microstructures of the control and the cementless eco-binder samples, in which the main hydration products were C-S-H/C-A-S-H gels and ettringite (AFt) due to relatively high amount of SO3 and SiO2 in the CFA and RHA, respectively. Thus, it can be realized that the potential for the use of slag, CFA, and RHA as a sustainable cement-free binder is promising in the construction industry, especially for lower strength or no required early high strength structures. Keywords: cementless eco-binder; circulating fluidized bed combustion; rice husk ash; slag; microstructure; compressive strength; drying shrinkage; setting time; ultrasonic pulse velocity.

scholarly journals Highly Effective Adsorption Process of Ni(II) Ions with the Use of Sewage Sludge Fly Ash Generated by Circulating Fluidized Bed Combustion (CFBC) Technology

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3106
Author(s):  
Tomasz Kalak ◽  
Kinga Marciszewicz ◽  
Joanna Piepiórka-Stepuk
Keyword(s):  
Fly Ash ◽  
Sewage Sludge ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Municipal Sewage ◽  
Municipal Sewage Sludge ◽  
Fluidized Bed Combustion ◽  
Nickel Ions ◽  
Suitable Material ◽  
Circulating Fluidized Bed Combustion

Recently, more and more attention has been paid to the removal of nickel ions due to their negative effects on the environment and human health. In this research, fly ash obtained as a result of incineration of municipal sewage sludge with the use of circulating fluidized bed combustion (CFBC) technology was used to analyze the possibility of removing Ni(II) ions in adsorption processes. The properties of the material were determined using analytical methods, such as SEM-EDS, XRD, BET, BJH, thermogravimetry, zeta potential, SEM, and FT-IR. Several factors were analyzed, such as adsorbent dose, initial pH, initial concentration, and contact time. As a result of the conducted research, the maximum sorption efficiency was obtained at the level of 99.9%. The kinetics analysis and isotherms showed that the pseudo-second order equation model and the Freundlich isotherm model best suited this process. In conclusion, sewage sludge fly ash may be a suitable material for the effective removal of nickel from wastewater and the improvement of water quality. This research is in line with current trends in the concepts of circular economy and sustainable development.

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