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| Last Updated:09/04/2016

Research Articles

National:

 

Mathematical modeling of CO2 uptake by concrete during accelerated carbonation curing

Author: Sormeh Kashef-Haghighi,Yixin ShaoSubhasis Ghoshal

Abstract

Accelerated CO2 curing is a promising carbon capture and storage technology that can provide durable, pre-cast concrete products. A mathematical framework for predicting CO2 uptake and distribution during carbonation curing is presented, incorporating equations describing CO2 gas transport, dissolution in concrete pore water and reaction with cement compounds. The numerical simulations show that carbonation reaction of tricalcium silicate, the most abundant and reactive compound in cement, was the rate-controlling process for CO2 uptake. The specific surface area of compounds available for reaction determines the rate and extent of uptake. The 30-minute carbonation efficiency increased from 16.5% to 23% with a two-fold increase in the total specific surface area. The rate of CO2 uptake by cement doubled with a two-fold increase in CO2 gas partial pressure, but the extent of carbonation did not change significantly due to the formation of solid carbonation products on reactive surfaces and in the pore space.

Source: http://www.sciencedirect.com/science/article/pii/S0008884614001604

 

A Review Article on Uses, Effects & Implications of Fly Ash Due To Its particle Size & Unburned Carbon

 

Author:  Birendra Singh Rajwar, Prof. (Dr.) Inder Kumar Pandey

 

Abstract:

Fly ash is a particulate matter ranging in size from 0.01 to 100 μm released into the flue stream during combustion of coal in power generating stations. The mineralogical, physical and chemical properties of fly ash depend on the type of coal, combustion conditions, emission control devices and handling methods. Chemically it is a mixture of oxides, hydroxides, carbonates, silicates and sulphates of calcium, iron, aluminum and other metals in trace amount. It is grey to black in color, abrasive, alkaline and refractory in nature. Fly ash is regarded as a pollutant due to its negative impact on the ecosystem, although it has alternate, safe and viable utilities.Unburned carbon particles can be assumed to possess a work function equal to that of graphite (4.0 eV) and ash a work function equal to that of silica or alumina (SiO2: 5eV; Al2O3: 4.7 eV) respectively.The fly ash carbons occur in the residual coal ash as a result of the incomplete combustion process. Due to the increasing applications of activated carbons, this study has been focused on the preparation of cost-effective adsorbents as a substitute for activated carbon materials. The main objective of this study is to explore the possibility of using fly ash of different particle size in presence of unburned carbon as an adsorbent. 

 

Source: The International Journal Of Engineering And Science (IJES) || Volume || 3 || Issue || 5 || Pages || 12-18 || 2014 || ISSN (e): 2319 – 1813 ISSN (p): 2319 – 1805

 

A REVIEW: PROMISING APPLICATIONS FOR UTILIZATION OF FLY ASH

 

Author: M. I. M. Loya and A. M. Rawani

 

Abstract:

Fly ash can be utilized as a resources material in numerous innovative applications. The study attempts to identify promising applications that can significantly contribute in maximizing the utilization of fly ash. Based on the synthesis of relevant literature the study identified promising applications and categorized them into two groups: (i) key application groups for sustaining the existing growth in utilization (ii) key application groups for further increasing the utilization of fly ash. The findings of the study are expected to assist in formulation of strategy for sustaining and improving fly ash utilization.

 

Source: http://www.ijates.com/images/short_pdf/1405057989_P143-149.pdf

 

GEOTECHNICAL CHARACTERIZATION OF TWO LOW LIME INDIAN FLY ASHES AND THEIR POTENTIAL FOR ENHANCED UTILIZATION

 

Author:Vaishali Sahu and V. Gayathri

 

In India the present availability of fly ash produced from coal based thermal power plants has exceeded 130 million tons and likely to increase in coming years. The utilization of fly ashes needs to be increased to manage this waste stream, which is possible by understanding the geotechnical and geo-environmental behaviour of fly ash. This paper presents the findings of experimental studies with regard to important physical, chemical and geotechnical properties like grain size, specific gravity, mineralogy, morphology, compaction characteristics, unconfined compressive strength, California bearing ratio and hydraulic conductivity of fly ash. Two low lime fly ashes from Badarpur and Dadri thermal power plants, in and around Delhi have been used in the study. A brief account of various methods adopted in characterization is presented here. The importance of these properties in increasing the bulk utilization of fly ashes has also been brought out.

 

Source: Civil Engineering and Urban Planning: An International Journal (CiVEJ) Vol.1,No.1,June 2014

 

MORPHOLOGICAL AND GEOTECHNICAL PROPERTIES OF DADRI FLY ASH

 

Author: Murtaza Hasan, M A Khan2 and Javed Alam

 

In a developing country like India, population growth demands expansion of metropolitan cities and urban areas. Thus, increasing infrastructural growth has forced the construction industry to look for cheap and suitable materials for construction. In any given area, it is difficult to obtain a pure and perfectly suitable material for construction purposes. It therefore becomes necessary to utilize the available materials either individually or as a mixture to enhance the geotechnical properties. The present study makes an attempt to find a viable solution to save soil and facilitate en masse use of fly ash in conformation with Fly Ash Mission (1994). Physical and chemical properties of Dadri fly ash were investigated in the laboratory. JEOL JSM-6510 Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray Spectroscopy (EDS) were used for the study.
The results show that fly ash particles are mostly spherical. Fly ash was classified as class F and almost cohesion-less material. Maximum dry density, optimum moisture content and shear strength parameters of fly ash exhibit that it can be used as an alternative to soil.

 

Source: http://ijscer.com/ijsceradmin/upload/ijscer_5369f2102acf3.pdf

 

International

 

A review on carbon dioxide capture and storage technology using coal fly ash

 

Author: Jung-Ho Wee

 

Abstract:

This work reviews the availability and the potential of the carbon capture and storage (CCS) technology using coal fly ash (FA). Because the technology can be effectively applied on-site to coal fired power plants and as FA contains sufficient alkali  components, the technology may be another option of CCS technology to a limited extent.

The technology can be divided into wet and dry processes. In the former, the available components for CCS in FA are leached into solution by the solvent where they are subsequently consumed for carbonation to store CO2. Particularly, the CO2 storage capacity of CaO-enriched FA solution mixed with brine under high pressure may be equal to or greater than the true CO2 emission reduction achieved by applying FA as a cement additive.

In the dry process, FA can be used as a direct support or as the raw material of the sorbent supports for CO2 capture. The dry process is effectively applied for CO2 capture rather than storage because the sorbents should be regenerated. Another advantage of the technology is the stabilization of the harmful components present in FA, which are mostly co-precipitated with carbonated FA during the process.

 

Source: http://www.sciencedirect.com/science/article/pii/S0306261913000731

 

Waste Material Adsorbents for Zinc Removal from Wastewater: A Comprehensive Review

 

Author: HaiderM. Zwain, Mohammadtaghi Vakili, and Irvan Dahlan 

 

This review examines a variety of adsorbents and discusses mechanisms, modification methods, recovery and regeneration, and commercial applications. A summary of available researches has been composed by a wide range of potentially low-cost modified adsorbents including activated carbon, natural source adsorbents (clay, bentonite, zeolite, etc.), biosorbents (black gram husk, sugar-beet pectin gels, citrus peels, banana and orange peels, carrot residues, cassava waste, algae, algal, marine green macroalgae, etc.), and byproduct adsorbents (sawdust, lignin, rice husk, rice husk ash, coal fly ash, etc.). From the literature survey, different adsorbents were compared in terms of Zn2+ adsorption capacity; also Zn2+ adsorption capacity was compared with other metals adsorption. Thus, some of the highest adsorption capacities reported for Zn2+ are 168 mg/g powdered waste sludge, 128.8 mg/g driedmarine green macroalgae, 73.2mg/g lignin, 55.82mg/g cassava waste, and 52.91mg/g bentonite. Furthermore, modification of adsorbents can improve adsorption capacity. Regeneration cost is important, but if consumption of virgin adsorbent is reduced, then multiple economic, industrial, and environmental benefits can be gained. Finally, the main drawback of the already published Zn2+ adsorption researches is that their use is still in the laboratory stage mostly without scale-up, pilot studies, or commercialization.

 

 Source: In International Journal of Chemical Engineering, Volume 2014, Article ID 347912, 13 pages, Hindawi Publishing Corporation, http://dx.doi.org/10.1155/2014/347912

 

A review of the alumina recovery from coal fly ash, with a focus in China


Author:  Z.T. Yao, M.S. Xia, P.K. Sarker, T. Chen 


Coal fly ash, an industrial by-product, is derived from coal combustion in thermal power plants. It is one of the most complex and abundant of anthropogenic materials, and its improper disposal has become an environmental concern and resulted in a waste of recoverable resources. Coal fly ash is rich in alumina, making it a potential substitute for bauxite. With the diminishing reserves of bauxite resources as well as the increasing demand for alumina, recovering alumina from fly ash has attracted extensive attentions. The present review first describes the alumina recovery history and technologies, and then focuses on the recovery status in China. Finally, the current status of fly ash recycling and directions for future research are considered.

 

Source: Fuel, Volume 120, 15 March 2014, 74–85

 

Fly Ash Utilization Forecast for its Key Applications

 

Author: M. I. M. Loya and A. M. Rawani

Coal based thermal power plants in India are required to ensure 100% utilization of fly ash. To assist informed decision making and planning, the study aims to forecast quantum of fly ash utilization to be contributed by key applications in coming future.

 

The annual time series data of utilization, published by Central Electricity Authority, categorized in seven application groups, was subjected to regression analysis to identify the pattern of growth. Regression model for each application group were developed.

 

Fitness of the models was accessed based on and t-value and r-square (R2) statistics. Forecast is generated by extrapolating the identified patterns. Further, application groups are ranked based on the quantum of fly ash utilization predicted to be contributed by them. The application group consisting cement and concert is predicted to be the top contributor with utilization quantity about 65 MT (Million Tonne) in the financial year 2020. The group consisting construction of roads, embankments and ash-dykeraising is ranked second, the group consisting reclamation of low lying areas, land filling is ranked third. The group named 'others', which consists various applications of fly ash is ranked forth and predicted to contribute about 13 MT in the financial year 2020. It is suggested that a further investigation of its compositions might reveal some promising applications. The finding
of the study is expected to assist in decision making and planning effective utilization of fly ash.

 

Source: International Journal of Application or Innovation in Engineering & Management (IJAIEM) Web Site: www.ijaiem.org Email: editor@ijaiem.org

 

Opportunities and challenges in the use of coal fly ash for soil improvements – A review

 

Author: Sabry M. Shaheena, Peter S. Hoodab, Christos D. Tsadilasc

 

Coal fly ash (CFA), a by-product of coal combustion has been regarded as a problematic solid waste, mainly due to its potentially toxic trace elements, PTEs (e.g. Cd, Cr, Ni, Pb) and organic compounds (e.g. PCBs, PAHs) content. However, CFA is a useful source of essential plant nutrients (e.g. Ca, Mg, K, P, S, B, Fe, Cu and Zn). Uncontrolled land disposal of CFA is likely to cause undesirable changes in soil conditions, including contamination with PTEs, PAHs and PCBs. Prudent CFA land application offers considerable opportunities, particularly for nutrient supplementation, pH correction and ameliorating soil physical conditions (soil compaction, water retention and drainage). Since CFA contains little or no N and organic carbon, and CFA-borne P is not readily plant available, a mixture of CFA and manure or sewage sludge (SS) is better suited than CFA alone. Additionally, land application of such a mixture can mitigate the mobility of SS-borne PTEs, which is known to increase following cessation of SS application. Research analysis further shows that application of alkaline CFA with or without other amendments can help remediate at least marginally metal contaminated soils by immobilisation of mobile metal forms.
CFA land application with SS or other source of organic carbon, N and P can help effectively reclaim/restore mining-affected lands. Given the variability in the nature and composition of CFA (pH, macro- and micronutrients) and that of soil (pH, texture and fertility), the choice of CFA (acidic or alkaline and its application rate) needs to consider the properties and problems of the soil. CFA can also be used as a low cost sorbent for the removal of organic and inorganic contaminants from wastewater streams; the disposal of spent CFA however can pose further challenges.


Problems in CFA use as a soil amendment occur when it results in undesirable change in soil pH, imbalance in nutrient supply, boron toxicity in plants, excess supply of sulphate and PTEs. These problems, however, are usually associated with excess or inappropriate CFA applications. The levels of PAHs and PCBs in CFA are generally low; their effects on soil biota, uptake by plants and soil persistence, however, need to be assessed. In spite of this, co-application of CFA with manure or SS to land enhances its effectiveness in soil improvements.

 

Source: http://www.ncbi.nlm.nih.gov/pubmed/25079682

 

Recycling of waste fly ash for production of porous mullite ceramic membrane supports with increased porosity

 

Author: Jingjie Caoa, Xinfa Dongc, Lingling Lia, Yingchao Donga, Stuart Hampshired

 

Low-cost porous mullite ceramic membrane supports were fabricated from recycling coal fly ash with addition of natural bauxite. V2O5 and AlF3 were used as additives to cause the growth of mullite crystals with various morphologies via an in situ reaction sintering. Dynamic sintering, microstructure and phase evolution of the membrane supports were characterized in detail and open porosity, pore size, gas permeation and
mechanical properties were determined. It showed the membrane support with 3 wt.% V2O5 and 4 wt.% AlF3 addition exhibits an open porosity of
50%, mechanical strength of 69.8 ± 7.2 MPa, an interlocking microstructure composed of anisotropically grown mullite whiskers with an aspect ratio of 18.2 ± 3.6 at 1300 °C. Addition of more V2O5 lowered the secondary mullitization temperature, resulting in more mullite formation at lower temperatures. The fabricated membrane supports feature high porosity without mechanical strength degradation, possible strengthening mechanism of the mullite whiskers was further discussed.

 

Source: http://www.sciencedirect.com/science/article/pii/S095522191400199X

 

Stabilization of indigenous Saudi Arabian soils using fuel oil flyash

 

Author: Omar S. Baghabra Al-Amoudi a, Alaadin A. Bukhari

 

Fuel oil flyash (FFA) produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR), unconfined compressive strength (USC) and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP), which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

 

Source: http://www.sciencedirect.com/science/article/pii/S1018363914000324

 

Study on Thermal Insulation Zeolite by Coal Fly Ash

 

Author: Huiping Song, Nan Zheng, Fangbin Xue, and Fangqin Cheng

 

This paper takes the coal fly ash as the material and makes zeolite with low thermal conductivity under a two-step synthesis for the purpose of thermal insulation. It studies main factors affecting zeolite such as the different concentration of NaOH, the solidliquid ratio, the silica-alumina ratio, and the crystallization temperature. The optimal conditions were obtained that the NaOH concentration was 3mol/L, the solid-liquid ratio was 10 : 1, the silica-alumina ratio was 2, and the crystallization temperature was 12C. Zeolites have multiple pores and skeletal structures under SEM observation. The mean particle size was 2.78 um of concentrated distribution. The pore volume was 0.148m3/g measured by BET analysis, the specific surface was 118.6m2/g, and the thermal conductivity was 0.153 W/(mK). Zeolite was proved to be a qualified insulation material which can be used in thermal insulation coating as a new material of energy conservation.

 

Source: http://www.hindawi.com/journals/jnm/2014/875940