02544 Effects of fly ash particle size on strength of Portland cement fly ash mortars

02544 Effects of fly ash particle size on strength of Portland cement fly ash mortars

04 By-products related to fuels Synthesis gas enerator with combustion and quench chambers for process Png fossil and refuse-derived fuels 9910253...

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related to fuels

Synthesis gas enerator with combustion and quench chambers for process Png fossil and refuse-derived fuels


Kohnen, K. er al. PCT Int. Appl. WO 98 45,388, (Cl. ClOJ), 15 Ott 1998, DE Appl. 19,714,376, 8 Apr 1997, 20 pp. Apparatus for the generation, cooling and cleaning of gases is described. The synthesis gas generator has a combustion chamber, where the gases are generated by partial oxidation, and a quench chamber. These two separate chambers are connected by a flow channel. In the gas inlet area of the quench chamber, nozzle assemblies with nozzle heads, which spray in a quenching medium, are arranged. The quench zone within the quench chamber is joined by a useful gas-quenching medium-mixing zone. At the outlet of the quench chamber is a cone, followed by a water bath. The useful gas leaves the synthesis gas generator via gas outlet openings in the rearside area of the cone. 99102536 Synthesis gas purification system of hydrocarbon fuels containing volatfle elements Koyama, S. et al. Jpn. Kokai Tokkyo Koho JP 10 259,385 [98 259,385], (Cl. ClOJ3/46), 29 Sep 1998, Appl. 97/66,052, 19 Mar 1997,6 pp. (In Japanese) In this paper, a system is described for the purification of synthesis gas from hydrocarbon fuels by coal gasification, comprising gasification, heat recovery and dedusting stages. Inorganic compound particles and carboncontaining particles are added to the synthesis gas formed at the gasification stage. The inorganic compound particles and the dust generated from gasification are classified. The dust and carbon-containing particles are then recycled back to the gasification stage.




Application of coal fly ash from power plants to treat dyeing intermediate wastewater


Xiao, Y. and Xu, J. Huanjing Gongcheng, 1998, 16, (2) 30-33. (In Chinese) The study describes a process involving coal fly ash adsorption, pH adjustment, and sand filter for treating dyeing intermediate wastewater containing refractory dinitrochlorobenzene. It also discusses the effects of pH, addition of coal fly ash and flow rate of wastewater on COD removal efficiency. Static experiments showed that the COD removal efficiency was 79.8-82.7%, decolourization rate was 87-89% at pH 2.0, coal fly ash 8.0% and treatment time 10 min. In dynamic experiments it was found that the lower the flow rate of wastewater, the higher the COD removal efficiency (may reach 90%), and the adsorption capacity of 30 g coal fly ash was ~0.5954.672 g COD. The treatment costs of this process are lower than those for activated carbon. 99102536

Chemical and leaching characteristics of ash from combustion of coal, peat and wood in a 12 MW CFB - a comparative study

Steenari, B.-M. et al. Fuel, 78, (2), 249-258. The chemical characteristics of fly ash samples from combustion of three fuels: coal, peat and wood chips, have been studied. The ash materials were collected in the 12 MW CFB at Chalmers University of Technology during full load combustion with similar standard combustion parameters. The samples were characterized in terms of chemical composition, mineralogy and leaching behaviour. The special characteristics of the mineral matter in each fuel were reflected in the leaching results. Upon reaction with moderate amounts of water secondary mineral phases such as ettringite and calcite, were formed. These compounds were shown to affect the leaching rates for calcium and sulfate as well as the pH of the leachates.

traffic and construction considerations associated with the transport and placement of the fly ash are considered. The new landfill cell resulted in considerable cost savings to the Delaware Solid Waste Authority. 99102541

Jakob, A. et al. EnfsorgzmgsPraxis, 1998, 16, (7-8), 29-32. (In German) Hea, y metals were removed from fly ashes by mixing inert gas, such as nitrogen, carbon dioxide or air, moistened by passing through a temperature controlled water bath, with HCl(g) from a supply of compresses HCl(g), then passing the gas mixture through a fluidized-bed reactor containing the fly ash at 900°C. The heavy metals were converted into chlorides that evaporated (together with other volatile components) and condensed. The paper discusses the effect of HCI concentration and temperature on the evaporation of zinc, lead, copper and cadmium when using this method. The detoxified fly ash can be used in cement or as aggregate in concrete. The heavy metal chlorides were recovered and the off gas passed through a scrubber. 99102542

Wakimura, Y. Jpn. Kokai Tokkyo Koho JP 10 272,305 (98 272,305], (Cl. BOlD21/01), 13 Ott 1998, Appl. 97/80,260,31 Mar 1997,4 pp. (In Japanese) The title coagulant comprises water-solution, aluminium salts and/or iron salts, alkali metal carbonates, coal-fly ashes or calcium compound powder and an anionic or nonionic organic polymer such as hydrolysed polyacrylamides.

Coal combustion fly ash as construction material in a sanitary landfill prolect


Bachor, J. R. et al. Proc., Annu. Meef. - Air Was?e Manage. Assoc., [computer optical disk], 1997, 90, WA7805/1-11. At a sanitary landfill in Southern Delaware, a project has been implemented in which nearly one million tons of Class F fly ash were used as a substitute fill material in place of natural soil during the construction of a new cell. Additionally, the fly ash, from different sources, was used for berm construction. The basic design of the landfill cell, the engineering properties of the fly ash that led to its acceptance as a select borrow material and the relative economics of substituting fly ash for natural soil in this application are discussed in this paper. Additionally, the logistical,


Fuel and Energy Abstracts

July 1999

Development of chloride-resisting concrete using

fly ash

Dhir, R. K. and Jones, M. R. Fuel, 78, (2) 137-142. This paper describes how low-lime fly ash can be used to develop chlorideresistant concrete by improving both its physical resistance to the ingress of chlorides and binding capacity of these ions in the cover zone. This includes optimizing the fly ash content, reducing the water/binder ratio of the concrete, processing fly ash to improve its particulate characteristics and, finally, using ternary blends with silica fume or metakaolin. This last method is shown to provide the highest degree of chloride resistance. A tentative classification of chloride bearing environments together with recommendations for the specification of concrete for structures exposed to these environments, is proposed.

Direct speciation of chromium in coal combustion by-products by X-ray absorption fine-structure spectroscopy


Huggins, F. E. et al. Fuel, 78, (2), 233-242. Chromium X-ray absorption fine structure (XAFS) spectroscopy has been used to determine the relative amounts of Cr(V1) and Cr(II1) in coal combustion by-products, principally fly ash and bottom ash. The method, which is based on the relative heights of the pre-edge peaks for the different chromium oxidation states in X-ray absorption near-edge structure (XANES) spectra, can be used to speciate as little as 50 ppm of chromium in ash. The results indicate that the fraction of Cr(V1) oxidation state present in combustion ash samples from most commercial combustion plants is typically below or close to the detection limit (approximately 3-5% of the total chromium). There are exceptions, however, that have been found to reach as high as 20%. Such findings provide justification for a reappraisal of whether or not chromium should be considered a significant hazardous air pollutant in coal combustion.

Effects of fly ash particle size on strength of Portland cement fly ash mortars


Erdogdu, K. and Turker, P. Cent. Concr. Res., 1998, 28, (9) 1217-1222. The properties of fly ashes vary according to the different size fractions. The effect of a fly ash on mortar strength is a result of the combined effect of its size fractions. It has been concluded that the combined bulk effect of a fly ash on strength is better analysed by replacing cement with separated size fractions. Here, different size fractions of fly ash were used to partially replace cement in standard compressive strength mortars. The strength of Portland cement-fly ash mortars was interpreted in terms of the chemical, mineralogical, morphological and physical properties of the different fly ash size fractions used. The strength of the mortars was compared at 2, 7, 28 and 90 days. The strength of mortars containing all-in ash (original ash containing all the fractions) was estimated by using strength of mortars with size fractions. The applicability of this type of estimate is examined. 99102545

Coagulant or municipal sewage or industrial wastewater treatment


Detoxification and recycling of fly ash from waste


Evaluation of permeability characteristics of FGD


Butalia, T. S. and Wolfe, W. E. Fuel, 78, (2) 149-152. The suitability of clean coal technology by-products as impervious liners in place of commonly used clay or geomembranes is investigated. A laboratory program to characterize the permeability of stabilized flue gas desulfurization (FGD) material is presented. Several mixes were prepared and tested. The laboratory samples exhibit low permeabilitics and high strengths necessary for liner applications. The permeability values measured in the laboratory for some samples are much lower than the 1 x lo-’ cm s-’ value required by EPA for constructing liners for waste containment facilities.

Influence of freeze-thaw cycling on the resilient modulus of PFBC materials


Wolfe, W. E. et al. Fuel, 78, (2), 143-148. The dynamic stress strain characteristics of a pressurized fluidized bed combustion (PFBC) material, before and after freeze and thaw cycling, were studied to evaluate its suitability as a substitute for conventional road construction materials in the design of flexible pavement systems. Samples compacted in the laboratory at two different moisture contents (optimum and 8% above optimum) were cyclically load tested after being allowed to cure for various durations. The results of the cyclic tests are presented in terms of the resilient modulus, which is a measure of the elastic property of