Oil Shale Fly Ash Research Articles

Concentration of lanthanides in the Estonian environment: a screening study

Lanthanides (Ln) are crucial for several future green technologies, such as wind turbines, solar panels and electric cars. However, the current use of Ln is already remarkable and they are considered emerging contaminants. To evaluate the hazard of Ln to ecosystems the data on their environmental concentrations are needed. This study aimed to provide new information on concentration of Ln for Estonian environment where oil-shale industry may be considered a potential pollution source of Ln. In the sampled riverine sediments the Ln concentrations varied in the range of 39-117 mg/kg dry wt and in the riverine macrophytes from 1.7 to 14 mg/kg dwt being higher near the potential pollution sources. In the leaves of silver birch Betula pendula the Ln concentrations ranged from 0.1 to 0.7 mg/kg dwt. In particular, we showed that the use of the oil-shale fly ash for soil amelioration may lead to the Ln accumulation in the plants and the long-term application of mineral fertilizers may increase Ln concentrations in the plants growing near the arable land.

Cement-based materials with oil shale fly ash additives

Experimental studies on the influence of oil shale fly ash additives on thermal expansion, strength, shrinkage, and heat release of concrete were carried out. The addition of 30% fly ash over cement content increases the thermal expansion by 6 times. The addition of 40% fly ash increases the thermal expansion by 16 times. The expansion is due to the high free calcium oxide content (10%) in the fly ash and the high sulfuric acid anhydrite SO3 content (10.3%). The anhydrite forms a highly expanding calcium hydrosulfoaluminate upon reaction with tricalcium aluminate cement in an unlimited amount of water. The oil shale fly ash addition above cement content significantly reduces shrinkage. If the ash content is higher, then the shrinkage decreases more. Shrinkage is on average 1.3 times less at a 30% fly ash content, and shrinkage is 1.8 times less at a 40% fly ash content. The fly ash has a higher sorption capacity than cement. Samples with the oil shale fly ash addition absorb more moisture than mixes without fly ash. Oil shale fly ash increases the compressive strength. If the fly ash content is 30% by weight of cement, then the compressive strength is higher than if the fly ash content is 40% by weight of cement for all concrete hardening periods. The flexural strength of mixes containing the fly ash turned out to be lower than the flexural strength of the mix without fly ash in the initial period of up to 15-22 days. Mixes with fly ash content in the amount of 30% and 40% by weight of cement exceeded the flexural strength of the mix without fly ash, respectively, by 24 and 17%. The fly ash addition provides a calmer, extended in time heat release with low self-heating of concrete in the initial period from 1 to 3 days. That is especially valuable for the thermal crack resistance of concrete.

Study on Cold Resistance Performance of Composite Subgrade Structure in Seasonal Frozen Regions

In order to achieve the purpose of subgrade frost damage control and waste utilization, this paper proposes a specific kind of composite subgrade structure which is suitable for subgrade in seasonal frozen regions, especially wet subgrade. The composite subgrade structure is composed of extruded polystyrene (XPS) plates as a cold resistance layer and modified subgrade soil with excellent frost resistance which can consume a lot of oil shale residue and fly ash. To provide valuable reference for engineering applications, an outdoor model test is designed and carried out based on indoor test results and actual engineering data. The cold resistance performance of this new type subgrade structure is evaluated by comparing the temperature distribution, energy transfer, and freezing index of the composite subgrade and the common subgrade during the freezing process. The results show that, firstly, the cold resistance layer can effectively preserve temperature inside the subgrade and form a positive temperature zone beneath XPS plates, which can ensure that the subgrade soil in a certain range will not freeze during the freezing period. Secondly, the position with the best cold resistance effect of the cold resistance layer is directly under the XPS plate. In actual application, the key position should be covered as completely as possible by XPS plates to ensure the cold resistance effect. Thirdly, the cold resistance layer can not only protect subgrade soil under XPS plates from frost damage, but also raise and keep the service temperature of the structure above XPS plates in a certain range, which is beneficial to the cold resistance durability of the entire road. This means that the composite subgrade can greatly reduce the occurrence of subgrade frost damage, thereby even improving the service capability of roads in seasonal frozen regions.

The use of oil shale fly ash to improve the properties of Irbid soil

PurposeThe purpose of this paper is to evaluate the possible use of oil shale as a soil stabilizing agent for expansive soils.Design/methodology/approachAn experimental work has been fulfilled to investigate the influence of oil shale ash (OSA) on the geotechnical behavior of the expansive soil of Irbid, Jordan. Three swelling-shrinkage soils were considered in this study along with various percentages of OSA varying at 2, 4, 6, 8, 10 and 12 per cent by dry weight of the soil. A series of laboratory tests were conducted on the soil samples before and after mixing it with OSA. These tests were soil classification, Atterberg limits, compaction test, falling head permeability test, unconfined compression test, free swelling, swelling pressure and California bearing ratio (CBR) test.FindingsLaboratory tests results indicated that OSA is effective in improving the texture and strength of the treated soil by reducing plasticity index, swelling potential and swelling pressure and moderately enhancing soil strength properties including the unconfined compressive strength (qu), maximum dry unit weight (γd-max.) and CBR test.Originality/valueOSA showed potential as a low-cost soil stabilizing agent for swell-shrink soils.

Laboratory investigation on high- and low-temperature performances of asphalt mastics modified by waste oil shale ash

The objective of this study was to use two kinds of waste oil shale ash (OSA) as partial replacements of conventional mineral filler for evaluating high- and low-temperature performances of asphalt mastics. First, asphalt mastics with conventional mineral filler replacement by OSA (OSA/MF) of 0, 10, 15, 30% by volume based on filler–asphalt (F/A) ratios of 0.8, 1.1, 1.4 were prepared. Then, based on the measured penetration, softening point and ductility of modified asphalt mastics, the overall desirability analysis was adopted to determine the optimal OSA/MF. Subsequently, the high-temperature and low-temperature properties of asphalt mastics with the optimal OSA/MF were studied through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. Results indicated that OSA could improve the high-temperature stability but reduces the temperature susceptibility of asphalt mastics, whereas the asphalt consistency is influenced insignificantly. Besides, the high- and low-temperature properties of asphalt mastics could be improved by the addition of OSA and the oil shale semi-coke (OSSC) modified asphalt mastic is slightly better than oil shale fly ash (OSFA) modified asphalt mastic in some aspects. Based on these results, the optimum F/A ratios could be obtained to enhance the high-temperature and low-temperature properties of asphalt mastics.

Effect of air and oxyfuel staged combustion on oil shale fly ash formation with direct in-furnace limestone addition for sulphur retention

El-Lajjun oil shale fly ash formation and S retention during in-furnace limestone injection were investigated in this work. Staged air-firing and 27% O2/CO2 combustion was performed at 1200 °C in a vertical once through reactor. Ash samples were collected at 2.5 m far from the burner and from the conductive section of the reactor. Limestone was added with oil shale before burning in both combustion modes. Ultimate, proximate, and XRF analyses were done for all collected samples, while XRD and SEM analyses were performed for some of them. Sulphur retention in the convective section increased by 13% compared to the radiative section of the reactor. Sulphur retention in the collected ashes ranged from 22 to 32% and 35 to 45% at 2.5 m from the burner and at the candle filter, respectively. The combustion mode had a slight effect on the collected ashes chemical composition. In both combustion modes, the ash samples were enriched with lime and depleted in sulphur, which proved sulphur capture. Fly ash particles were spherical in shape with some aggregates. XRD analysis showed that the main crystalline phases formed in the produced fly ashes were the same regardless the combustion mode and environment, some differences in the relative intensities of anhydrite and lime peaks were present.

Afforestation of cutaway peatlands: effect of wood ash on biomass formation and carbon balance

Abstract Alternatives to the restoration of cutaway peatlands include afforestation, energy forests, agricultural production, wetland restoration (restoration of peataccumulating function), reed canary grass (energy mower) or wild berries (blueberry, cranberry) cultivation, protected area for birds, and artificial lakes. Investigations made in several countries suggest that one of the most promising ways of regenerating cutaway peatlands is afforestation. The re-vegetation of Estonian cutaway peat production fields is mainly the result of natural processes, which are generally very slow: vegetation covers only 10–20% of a peat field. Carbon dioxide is not bound anymore in cutaway peatlands where vegetation layer has been destroyed and therefore photosynthetical processes no more occur. Using biofuel ashes (wood ash, etc.) for the afforestation of cutaway peatlands helps to balance the content of nutrients in peat substrate, which improves the survival of planted seedlings and significantly increases bioproduction. Drained and mined peatlands have become a significant source of CO2 but stimulated woody biomass production can be helpful to balance CO2 emission from cutaway peatlands. Because of the limited resources of fossil fuels and negative impacts on the environment in recent decades alternative sources of energy have been actively looked for. In Scandinavia a lot of attention has been paid to finding possibilities for using biofuels. The situation in Estonia is that only very few types of ashes (for example certified oil shale fly ash with product name Enefix) have been founded to be suitable for utilization and have been used for recycling in agriculture.

Remedial processing of oil shale fly ash (OSFA) and its value-added conversion into glass–ceramics

Recently, various solid wastes such as sewage sludge, coal fly ash and slag have been recycled into various products such as sintered bricks, ceramics and cement concrete. Application of these recycling approaches is much better and greener than conventional landfills since it can solve the problems of storage of industrial wastes and reduce exploration of natural resources for construction materials to protect the environment. Therefore, in this study, an attempt was made to recycle oil shale fly ash (OSFA), a by-product obtained from the extracting of shale oil in the oil shale industry, into a value-added glass–ceramic material via melting and sintering method. The influence of basicity (CaO/SiO2 ratio) by adding calcium oxide on the performance of glass–ceramics was studied in terms of phase transformation, mechanical properties, chemical resistances and heavy metals leaching tests. Crystallization kinetics results showed that the increase of basicity reduced the activation energies of crystallization but did not change the crystallization mechanism. When increasing the basicity from 0.2 to 0.5, the densification of sintering body was enhanced due to the promotion of viscous flow of glass powders, and therefore the compression strength and bending strength of glass–ceramics were increased. Heavy metals leaching results indicated that the produced OSFA-based glass–ceramics could be taken as non-hazardous materials. The maximum mechanical properties of compression strength of 186±3MPa, bending strength of 78±6MPa, good chemical resistances and low heavy metals leaching concentrations showed that it could be used as a substitute material for construction applications. The proposed approach will be one of the potential sustainable solutions in reducing the storage of oil shale fly ash as well as converting it into a value-added product.

Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite

Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000°C and sintering time of 2h) showed the properties of density of 1.92±0.05g/cm3, weight loss on ignition of 6.14±0.18%, sintering shrinkage of 22.06±0.6% and compressive strength of 67±14MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced compared to conventional vitrification and sintering method. Chemical resistance and heavy metals leaching results of glass ceramic composites further confirmed the possibility of its engineering applications.

DIRECT CO2SEQUESTRATION ONTO ALKALINE MODIFIED OIL SHALE FLY ASH

The present study focuses on the direct chemical adsorption of CO2 onto alkaline hydrothermally activated oil shale fly ash (OSFA). The CO2 chemisorption experiments were conducted in a high-pressu ...

Atmospheric chamber study of oil shale fly ash particles from circulating fluidized bed and pulverized firing processes

Atmospheric chamber study of oil shale fly ash particles from circulating fluidized bed and pulverized firing processes

Atmospheric chamber study of oil shale fly ash particles from circulating fluidized bed and pulverized firing processes

Oil shale combustion fly ash collected to electric precipitators from pulverized firing (PF) and circulating fluidized bed combustion (CFB) processes was investigated in atmospheric chamber experiments. The aim of the work was to detect differences in the atmospheric behaviour of the fine particles from CFB and PF boilers of the Estonian Power Plant (PP), located close to Narva, Estonia. One series of experiments was performed in a dual outdoor Teflon film smog chamber (270 m 3 ) at the University of North Carolina at Chapel Hill (USA) under normal weather conditions (temperature, humidity, sunlight). Parallel tests were carried out in an outdoor smog chamber (108 m 3 ) at Tuulna, Harju County, Estonia, where the experiment was made under meteorological conditions similar to those at the location of the PP. The size distribution and number concentration of particles in the chamber were monitored during the experiment. The fractional distribution results demonstrate that the CFB aerosol in the chamber air had more fine particles than the PF aerosol. Approximately 2 h after injection the fly ash particles larger than 4 µm had settled out from both samples. The initial fly ash aerosol had a trimodal fractional distribution. Both PF and CFB fly ash formed stable aerosols 1-3 µm in diameter during the 6 h experiment and are therefore prone to long-range transport.

Alkaline modified oil shale fly ash: Optimal synthesis conditions and preliminary tests on CO 2 adsorption

Environmentally friendly product, calcium–silica–aluminum hydrate, was synthesized from oil shale fly ash, which is rendered so far partly as an industrial waste. Reaction conditions were: temperature 130 and 160 °C, NaOH concentrations 1, 3, 5 and 8 M and synthesis time 24 h. Optimal conditions were found to be 5 M at 130 °C at given parameter range. Original and activated ash samples were characterized by XRD, XRF, SEM, EFTEM, 29Si MAS-NMR, BET and TGA. Semi-quantitative XRD and MAS-NMR showed that mainly tobermorites and katoite are formed during alkaline hydrothermal treatment. Physical adsorption of CO 2 on the surface of the original and activated ash samples was measured with thermo-gravimetric analysis. TGA showed that the physical adsorption of CO 2 on the oil shale fly ash sample increases from 0.06 to 3–4 mass% after alkaline hydrothermal activation with NaOH. The activated product has a potential to be used in industrial processes for physical adsorption of CO 2 emissions.

SYNTHESIS OF CALCIUM-ALUMINO-SILICATE HYDRATES FROM OIL SHALE ASH IN DIFFERENT ALKALINE MEDIA

Synthesis of Ca-Al-Si-hydrates from oil shale ash using NaOH, KOH and OH-substituted alkaline ionic liquid was carried out. The material from ionothermal activation was used in carbon dioxide fixation experiments. The influence of the alkaline medium on the activation of oil shale fly ash was studied using physisorption (BETN2), SEM/EDX, FESEM, XRD, and Si-29 high-resolution MAS-NMR measurement techniques. In the presence of strong alkali (8 M NaOH) the silicon in the original fly ash was completely converted into Ca-Al-Si-hydrates, mainly into tobermorite and katoite structure during 24-hour treatment at 160 degrees C. In similar reaction conditions, the hydrothermal activation with KOH converted fly ash into tobermorites only partially. The silicon was not converted into Ca-Al-Si-hydrates by ionothermal activation with OH-substituted alkaline ionic liquid, tricaprylylmethylammonium hydroxide, either with conventional or microwave heating. It was found that both the original material and ionothermally activated oil shale ash displayed similar CO2-adsorption capacity.

Synthesis of nucleated glass-ceramics using oil shale fly ash

Nucleated glass-ceramics materials were produced from oil shale fly ash obtained from Huadian thermal power plant in China with the addition of analytic reagent CaO. On basis of differential thermal analysis (DTA) results, the nucleation and crystallization temperature of two parent glass samples with different alkalinity (Ak=m(CaO)/m(SiO(2)) were identified as Tn(1)=810 degrees C, Tc(1)=956 degrees C and Tn(2)=824 degrees C, Tc(2)=966 degrees C, respectively. X-ray diffraction (XRD) analysis of the produced nucleated glass-ceramics materials revealed that there was a coexistence phenomenon of multi-crystalline phase and the main crystalline phase was anorthite ([Ca,Na][AI,Si](2)Si(2)O(8)). The microstructure of the glass-ceramics materials was examined by scanning electron microscope (SEM). SEM observation indicated that there was an increase in the quantity of sphere-shaped crystals when crystallization time increased. Furthermore, the increase of alkalinity caused more amorphous phase occurring in glass-ceramics materials. Through the tests of physical and mechanical properties, the glass-ceramics materials with more crystalline phase and fine microstructure had high density, fine performance of resisting compression (328.92 MPa) and negligible water absorption. Through chemical resistance tests, the glass-ceramics samples showed strong corrosion resistance. Overall results indicated that it was a feasible attempt to produce nucleated glass-ceramics materials for building and decorative materials from oil shale fly ash.

Synthesis and characterization of calcium–alumino-silicate hydrates from oil shale ash – Towards industrial applications

The influence of the alkaline medium on the hydrothermal activation of the oil shale fly ash with NaOH and KOH was studied using SEM/EDX, XRD, 29Si and 27Al high-resolution MAS-NMR spectra. In the presence of NaOH the silicon in the original fly ash was completely converted into calcium–aluminum–silicate–hydrates, mainly into 1.1nm tobermorite structure during 24-h treatment at 160°C. At similar reaction conditions, the activation with KOH resulted only to the formation of amorphous calcium–silica-hydrate gel on the surface of ash particles at temperature. The results obtained in this study indicate that the oil shale fly ash can be used for production of Al-substituted tobermorites when strongly alkaline media (NaOH) is applied. The synthesized product was used in a catalytic d-lactose isomerization reaction.

Hydrothermal alkaline treatment of oil shale ash for synthesis of tobermorites

The hydrothermal alkaline activation of the oil shale fly ash was studied using SEM/EDX, XRD and 29Si and 27Al high-resolution MAS-NMR spectra. The silicon in the original fly ashes was completely converted into calcium-alumino-silicate hydrates, mainly into 1.1 nm tobermorite structure during 24 h treatment under hydrothermal conditions at 160 °C in the presence of NaOH. The local structure of synthesized tobermorite samples implies long silicate chains with small number of bridging sites. The results obtained in the study prove that the oil shale fly ash can be used for production of Al-substituted tobermorites.

Effect of Jordanian Oil Shale Fly Ash on Asphalt Mixes

It is estimated that about 40 billion tons of oil shale is available in the southern part of Jordan. Several studies are being carried out to utilize this source of energy efficiently. Upon direct combustion of this oil shale, more than 50% of its quantity will be left as fly ash. Resulting fly ash is considered undesirable and environmentally hazardous. This investigation was conducted to make use of the fly ash in the modification of local asphalt mixes. The modification efficiency was evaluated by the improvement in the performance of prepared asphalt concrete mixes. To carry out this study, enough quantity of oil shale was collected from Al-Lajjoun quarries (about 100 km south of Amman, Jordan). This material was then crushed, sieved, and burned to obtain the fly ash. Chemical and physical analyses of the fly ash were then performed. Asphalt concrete mixes having different percentages of fly ash (0, 10, 50, and 100%) as a replacement of the mineral filler, material passing the 0.075 mm sieve, were prepared. These samples were characterized using the Marshall Stability, indirect tensile strength, stripping resistance, resilient modulus, dynamic creep, fatigue, and rutting tests. Test results were statistically analyzed and indicated that, in general, the addition of fly ash improved both strength, and water sensitivity of the asphalt concrete mixes. Replacing 10% of the mineral filler by fly ash proved to be the most effective percentage in improving the mechanical properties of all the prepared samples.

Impact of Contaminants From Oil Shale Processing on Forest Ecosystems

Oil shale mining and processing in northeast Estonia have brought about several ecological problems. The mined oil shale is used as fuel in power stations and in processing plants producing crude oil and about 40 manufactured articles. Pollutants emitted from oil shale processing and chemical plants include SO2, CO, NO x , oil shale fly ash, and organic compounds in which aromatic and aliphatic hydrocarbons, phenols, formaldehyde, etc., are represented. Pollution has caused changes in the condition of the forest ecosystem and the chemical character of soil and ground water. The condition of coniferous forest sites was investigated in 1995–1998. Because of the high concentration of alkaline fly ash in the air, the pH of rain water is somewhat elevated (pH = 7.0–7.1) and exceeds the level regarded as normal for rain water. The analysis of the soil samples showed that the concentrations of Ca, Mg and K, which dominate in the solid fraction of the pollutant mixture, are high, being respectively 18, 14, and 4 times as high as the control. The increases in the concentrations of K, Mg, Cu, Pb, and Ni in stemwood reflect increases in the regional oil shale fly ash deposition. Conifers influenced by high levels of air pollution emitted from the oil shale industry are characterized by retarded growth of needles and shoots and radial growth as a result of disturbances in their mineral nutrition and imbalance in their mineral composition.

Oil-Shale Fly Ash Utilization as Independent Binder of Natural Clayey Soils for Road and Airfield Base Construction

ABSTRACT This article describes physicochemical interactions of different natural clayey soils with oil-shale fly ash (OSFA) from thermal power plants, dealing with the strengthening processes of new materials. Toward this end, a range of traditional and modern research methods were used, i.e., definition of the ultimate strength under uniaxial compression and rupture by the Brazilian method, temporary changes in moisture content and linear deformation, water and frost resistance, free CaO and SO3, CaCO3, XRD, and SEM. It was established that the surfaces of the initial component (OSFA and soils) particles were dissolved in porous alkaline solutions. The dissolution products gave rise to new amorphous and crystal formations. After 28 days, the strength of the samples reached 2–12 MPa but, after 90 days, it rose to 4–31 MPa. It was found that the strength at every stage of hardening can be increased significantly by changing the proportion of the initial mixture's composition. The materials displayed very high water and frost resistance, with coefficients equaling or exceeding the 1.0 level, except the OFSA and loess combination. The materials developed are applicable for the construction of roads, airfields, and dam bases and for various types of foundations without traditional binders, such as cement, and without heating.