Papers by Keyword: Coal Ash

Abstract: This paper presents the development of a binder from coal ash and rice husk ash for manufacturing hollow blocks. Experiments were conducted to determine the compressive strength of the coal ash and rice husk ash as binders using cylindrical specimens at different curing periods. The mixture proportion with the highest compressive strength in the experiment was adopted in making the 4” hollow blocks. The compressive strength of the hollow blocks with the coal ash and rice husk ash binder was also determined at different curing periods.Cylindrical specimens with four different alkali activators were made and subjected to compression testing on the 3rd, 5th, and 7th day of curing. The mean compressive strength of the cylindrical specimen with all sodium hydroxide activator (RS0CS0) after 7 days curing is 2.54 MPa as compared to 3.05 MPa with the 2.5 sodium silicate to sodium hydroxide ratio (RS1CS0). As the amount of sodium silicate from rice husk was doubled (RS2CS0), the average compressive strength of the 7 days old cylindrical samples increased from 3.05 MPa to 3.49 MPa. Meanwhile, the 7th-day compressive strength of the cylindrical specimen with commercial silica (RS0CS1) was 5.5 Mpa.Hollow blocks were also manufactured based on the material proportion that utilizes RHA with the highest compressive strength or the design mixture RS2CS0. These blocks have a mean compressive strength of 1.22 MPa on the 3rd day, 1.88 MPa on the 7th day, and 2.7 MPa on the 14th day of the curing period.

Abstract: In various countries, a variety of waste by-products are disposed-off to the local environment, mostly due to lack of innovative initiatives for their utilisation. With human population growing strongly in most developing countries such as in Africa etc., lack of housing has become an endemic concern exacerbated by poverty and unaffordability of conventional construction products. Geopolymer technology provides new insights and possibilities into potential utilisation of a variety of mining and industrial waste by-products, currently being dumped in landfills leading to environmental pollution. This paper focusses on mining and industrial waste products that are currently not being utilised. In South Africa, mine tailings and bottom ash, also colloquially referred to “ash dumps”, exist in enormous quantities. Moreover, some of these waste products are presently an environmental menace responsible for discharge of acid mine drainage found in different geographical locations. The present study reviewed the potential utilization of mine tailings for brick making based on geopolymer technology. Also discussed are risks, hinderances and challenges to waste utilization including lack of public confidence attributed to radioactivity of some tailings-based brick products. While drawing from literatures worldwide, emphasis is placed on environmental and economic benefits of utilising these otherwise disregarded waste materials, to meet local societal needs of poor communities.

Abstract: Currently, application of industrial waste or by-product in road construction industrials is a major interest by researchers, government officers and engineers. Coal ashes by-product from industrial parks negatively impact environment, costly in treatment, and require large ground for disposing areas. Therefore, this paper proposes on using the coal ash from furnace products of an industrial park in South of Vietnam to be incorporated into dense graded asphalt concrete using Nominal Maximum Aggregate Size 12.5mm. Laboratory performance tests including Marshall stability, indirect tensile strength, Cantabro loss, and dynamic fatigue test were conducted. The effects of coal ash contents in replacement of fine aggregate which is passing 4.75mm sieve from asphalt mixture into laboratory performance of mixture is also discussed in detail.

Abstract: Alloy 617 OCC, a variant of INCONEL 617 with optimised chemical composition, has been produced in India for manufacture of superheater and reheater tubing in boilers operating in advanced ultrasupercritical (A-USC) power plants. The tubing encounters intense hot corrosion conditions during service. The present study deals with hot corrosion behaviour of 617 OCC in A-USC environment. The environment occurring in A-USC plants was simulated in the laboratory by exposing the material coated with a mixture of salts at 700°C in a flowing gas mixture. For use in A-USC boiler technology, the metal loss due to fireside corrosion of the material should be less than 2 mm in 200,000 hours. The loss obtained in the present study was nearly 5 times this value. The corrosion processes were studied using SEM/EDAX, XRD and thermogravimetry. The degradation mechanisms coming into play, disqualifying the material for use in A-USC plants, would be discussed.

Abstract: Craiova Energy Complex, which is the most important facility is the thermoelectric power plant from Isalnita, produces altogether approximately six million tones of ash every year. If these were to be spread across the whole surface of the district Dolj, a five-centimeter-layer of ash would form. In present, the impoverishment of the agricultural ecosystems is due not only to the industrial objectives or to the cole mining, but also to the deposit of waste and ash from the coal-fired power plant. In this work are presented the results of research on ecological rehabilitation of the coal ash dump site in Isalnita-Dolj, in order to establish the fertility and the opportunity to cultivate them completely.

Abstract: Coal ash as flame retardant was used to PVC, the mechanical properties and flame retardance of the samples were studied. The resultant data show that coal ash better effect on the mechanical properties of the sample, especially tensile strength, impact strength, and 4% of coal ash obtained good flame retardance. PVC treated with flame-retardants showed a high limiting oxygen index, high decomposition temperature, which indicated that the flame retardance of the treated PVC was improved.

Abstract: This paper presents the adsorption behaviors of humic acid (HA) on coal ashes and powdered activated carbons (PACs). A bituminous coal, with or without calcium-loading, was used as a feedstock for coal ash preparation. The working solution of HA with a concentration of 20 mg/L was used in all adsorption tests. The results showed that calcium-enriched coal ash (CECA) gave rise to the removal rate of HA as high as 84.05%, much higher than those of raw coal ash (RCA) and PACs. The impacts of solution pH and adsorbent dosage on HA adsorption capacity were also investigated. It was found that lower pH facilitated to the removal of HA from aqueous solution by means of CECA, and the optimal CECA dosage was about 1.0g/L at pH 7.00. The data obtained in this study suggested that calcium-enriched coal ash could be useful and cost-effective in the treatment of wastewaters containing HA-like organic macro-molecules.

Abstract: The modified digested sludge (MDS) can be used as landfill biocover that serve to minimize CH₄ emissions by optimizing CH₄ oxidation. MDS composited by coal ash and digested sludge was studied in this paper. The permeability coefficient and the compressive strength of MDS were tested in full factorial L₉(3⁴) experiment using simulation column. Results show that when the mix ratio of coal ash and digested sludge is about 1:1-1.5:1, the permeability coefficient < 10^-4 cm/s and compressive strength 50 kPa, MDS can meet the engineering requirements for landfill operation. The optimal conditions of MDS were as follow: mix ratio of coal ash/digested sludge = 1:1, nutrient solution = 0.05 ml/g, thickness of biocover = 400mm, and moisture content of MDS = 40%. The maximum CH₄ oxidation efficiency was 88.6% and the volume flow rate of CH₄ was 0.75 mmol/(kgd) under the optimal conditions.

Abstract: The coal of Zichang was selected as the sample coal, the physical properties of the ash is analyzed with ICP-AES. The ash fusion temperature was researched by adding different basic oxide contents. The results show that the general trend is decrease firstly, and then increase when adding basic oxides. Blended ash fusion temperatures do not change linearly with blending ratios and ash fusion will decrease when adding the contents of CaO, Na₂O and MgO, but the effect is different. Na₂O is best and CaO is second. Mineral composition and type at addition oxides were determined by XRD analysis. Some combinations of component coals mineral produce eutectic minerals at high temperature;It can explain the reason of oxides decrease the ash fusion. Vitreous minerals are formed to explain increase the fusion temperature.

Abstract: A series of tests were conducted with laboratory normal devices to investigate the engineering property of coal ash mixed with various clay contents. By analyzing experimental data, some conclusions were made: It is helpful to improve the compaction effect and significantly reduce the consumption of the water needed in engineering by mixing the clay into coal ash. The shear strength of coal ash decreased slightly with increase of clay content. The shear strength of coal ash mixed with the 30% clay content is nearly equal to that of pure coal ash. With the increase of clay content, the coefficients of compressibility a_1-2 have a little irregularly growth. It always belongs to medium compressibility soils.