Showing papers on "Fly ash published in 1972"

Engineering Properties of Compacted Fly Ash

Abstract: The lower compacted density of fly ash relative to conventional earthfill recommends its use when a fill or embankment must be constructed over soft, compressible ground. Field evidence to date indicates that compressibility or settlement of compacted fly ash fills is not significant. Long-term field settlements cannot be predicted satisfactorily on the basis of short-term laboratory tests because fly ash exhibits age-hardening or pozzolanic properties. Low-level additions of lime to the fly ash before compaction accentuate this behavior. Frost susceptibility likewise is not as serious a problem in compacted fly ash as might be presumed from its grain size distribution. Gradation alone does not suffice as a criterion of frost susceptibility; pozollanic properties also play an important role. Undesirable frost heave in compacted fly ash can be reduced to tolerable levels by addition of lime or cement.

Fly Ash as Structural Fill

Abstract: Field and laboratory tests on fly ash from power plant disposal areas are presented with parameters for design and construction of fly ash embankments. Controlled compaction permits 20% more storage in disposal area and, with proper drainage and slope design, structures can be safely supported on spread footing type foundations. Eight direct shear tests and sixteen triaxial shear tests show φ angle related to dry unit weight. The φ angle varied from 30° to 40° in the range of 60 pcf to 80 pcf. Unconfined compression on moist fly ash showed a maximum cohesion of 500 psf under ideal conditions, but no cohesion when dry or saturated. Nine consolidation tests showed an average compression index of 0.2 in the range of 2 tsf to 20 tsf. Five series of vibratory field compaction tests relate dry unit weight to number of equipment passes and show that higher frequencies (up to 2,000 vpm) are more effective and compacted density is independent of initial water content.

Lime-fly ash-sulfite mixtures

Abstract: A hardenable cementitious mixture comprised of lime, fly ash, and sulfite salts in predetermined portions may be produced from a combination of the fly ash product from combustion equipment and the slurry produced in scrubbing stack gases from such equipment to remove sulfur oxides therefrom. Generally, the cementitious mixture comprises a water solids mixture with about 30 - 90 weight percent solids. Further, the solids comprise 0.25 - 70 percent by weight alkaline earth metal hydroxide, 10 - 99.5 weight percent fly ash, and 0.25 - 70 percent by weight of alkaline earth metal sulfite of which some portion thereof may be replaced by alkaline earth metal sulfates. This cementitious mixture may be used either by itself or with a filler or aggregate material.

Lime-fly ash cementitious mixture with improved hardening and expansion characteristics

Abstract: Cementitious mixture comprised of fly ash and lime-sulfate material, as contrasted with lime as used in conventional mixtures, hardens more rapidly and has improved characteristics with respect to dimensional stability. Preferably, the limesulfate material is made by the addition of sulfuric acid solution to quicklime in a modified lime hydration process. Alternatively, the lime-sulfate material may comprise lime and a separate sulfate compound such as gypsum. The cementitious mixture of this invention may be used, alone or in conjunction with filler material, as a subsurface base material or as a soil stabilization agent. It may also find use as a land fill or in making pre-stressed structural members.

Cementitious composition containing activated lime-fly ash mixture

Abstract: Improved cementitious composition results from a process comprised of mechanical size reduction and activation of a mixture of lime and fly ash and the addition thereto of fly ash and aggregate, as needed, to make a mix of the desired proportions. A quicker and more complete reaction between the lime and fly ash results from deagglomeration of lime particles caused by interaction with the fly ash and/or by the increased availability of reactant materials due to particle size reduction of both the lime and the fly ash. The mechanical size reduction and activation process may be carried out, for example, in a ball mill or centrifugal impact mill.

Coal mine spoil and refuse bank reclamation with powerplant fly ash

Abstract: Numerous coal mine refuse piles and strip spoil banks mar the countryside, contributing to stream and air pollution and land degradation. Experimental reclamation of several such sites with fly ash from bituminous coal-fired powerplants was conducted in West Virginia and Pennsylvania. Conventional farm equipment was used at some of the sites; large earthmovers were required at others. The fly ash served as a neutralizing agent, diluent, and soil amendment, providing some nutrients that encouraged vegetation of the barren areas while disposing of significant quantities of the powerplant waste. Estimated cost of reclamation by this method is $300 per acre of previously leveled area. This figure can vary considerably depending upon the topography of the site, distance from the source of fly ash, and quality of the fly ash.

Air pollution control

Abstract: COMBUSTION GASSES FROM FUEL-BURNING FURNACES ARE TREATED TO SEPARATE SOLID PARTICLES SUCH AS FLY ASH AND TO OXIDIZE THE SULFUR DIOXIDE GAS (SO2) CONTAINED THEREIN TO SULFUR TRIOXIDE (SO3). THE SO3 IS REACTED WITH EXCESS LIME (CAO) TO FORM CALCIUM SULFATE (CASO4). THE CASO4, UNSPENT LIME PARTICLES, SOME OF WHICH HAVE CRACKED OUTER SHELLS OF CASO4, AND COLLECTED FLY ASH ARE PACKAGED DRY AND USED IN APPROPRIATELY BLENDED FORM TOGETHER WITH CEMENT AND SAND, GRAVEL, OR ROCK TO FROM CONSTRUCTION MATERIALS, THE AVERAGE PERCENTAGE OF CASO4 THEREIN BEING REGULATED TO CONTROL THE SETTING TIME OF THE CEMENT. THE PROPORTION OF THE EXCESS LIME IS AUTOMATICALLY REGULATED BY PROCESS-CONTROL DEVICES WHICH CONTINUOUSLY MONITOR AND CONTROL THE REACTION APPLYING THE PARAMETERS OF FUEL COMPOSITIONS, AND SULFUR OXIDE LEVEL IN THE COMBUSTION GASSES.

Process for the treatment of fly ash

Abstract: Fly ash is subjected to a plurality of operations to recover therefrom a multiplicity of valuable products, including an iron concentrate, an improved pozzolanic material, a high carbon content product and an agglomerable material, suitable for formation into a controlled sintered aggregate product.

Bloated fly ash aggregates

Abstract: Bloated fly ash aggregates suitable for use in concrete, asphalt and the like are produced by: homogeneously admixing with fly ash, first an aqueous solution of a alkali compound such as ammonium hydroxide, and then an aqueous dispersion of a watersoluble carbohydrate; forming the resulting admixture into aggregates, drying the aggregates; and finally firing the aggregates at a temperature causing fusion and bloating of the aggregates.

Mineral matter and trace elements in U. S. coals. Interim report, Sep 1966--Feb 1972

Abstract: The report summarizes the study of the mineral matter content of 57 coal samples ranging in rank from lignite through anthracite. Analyses for 8 major metallic elements and 22 trace metallic elements are provided. Results show that the average trace element concentration in coal ash is greater than the abundance in the earth's crust, with the exception of silver, chromium, and manganese. The data presented should be useful in optimizing the utilization of coal by conventional methods, in conversion processes, and in future MHD power systems. (Modified author abstract) (GRA)

Heat-insulating shaped compositions

Abstract: Heat insulating compositions useful as slabs, riser sleeves, and the like are disclosed which consist essentially of a refractory fibrous material such as synthetic mineral wool, a binder, and a crushed coke or fly ash filler. The compositions can be used in the casting of copper based alloys or iron where the fibers themselves are not suitable.

Air pollution control system

Abstract: An air pollution control system for treating the flue gases from a fossil fuel fired furnace scrubs the gases with a solution of NaOH whereby Na and HSO3 are formed in solution. The HSO3 is then oxidized to form H and SO4 ions. The solution is then causticized with CaO to form NaOH and precipitate CaSO4. The precipitated CaSO4 and the fly ash collected in the scrubber are then separated from the NaOH solution. The solution is then diluted with make-up water to form the NaOH scrubbing solution for recycle to the scrubber.

Studies of sulfur compounds adsorbed on smoke particles and other solids by photoelectron spectroscopy

Abstract: Photoelectron spectroscopy as a means of air pollution monitoring and as a tool for smoke pollution research has been studied. Field samples of fly ash from a power plant and smoke particles from a home furnace have been analyzed. It is shown that the oxidation states of sulfur in compounds adsorbed on these solids can be determined. The use of photoelectron spectroscopy for studying the effects of combustion variables and downwind conditions on the oxidation state of sulfur on fly ash and smoke particles is discussed. The composition of the solid on whtch SO2 is adsorbed was found to be an important variable in the rate at which oxidation to sulfate occurs.

Disposal of plastics

Abstract: To eliminate plastics waste and recover the metals and metal compounds contained in the waste, the plastics waste, whether in a solid, pasty or liquid form, is converted into a combustible fluid-like form and is directed through a burner into a combustion chamber. The combustion of the waste results in combustion gas and fly ash which is cooled and directed through a separator to obtain the metals and metal compounds from the fly ash in the form of oxides.

Mercury in Coal: A New Standard Reference Material

Abstract: Sources of environmental mercury contamination are generally related to industrial and mining activity. However, close examination of the sources reveal how complex the task of dealing with mercury pollution is. For example, virtually none of the mercury in fossil fuel is trapped in the fly ash, instead it is released in gaseous form as a product of combustion. Evidence now exists that this gaseous mercury is washed from the air by rain, being cycled to rivers, lakes and oceans where further evidence indicates that it may be methylated to its most toxic form, methylmercury. Mercury releases to the environment from burning of fossil fuels have been calculated to contribute a significant portion of the total mercury released. Unfortunately, mercury concentrations in coals used to calculate mercury release differ by a wide range. This paper presents the results of a concerted analytical program by the National Bureau of Standards to develop a coal standard of proven homogeneity with an accurate valu...

Sulphur dioxide removal from waste flue gases - - using magnesium oxide and sulphite aq slurry

Abstract: The dust-laden gas stream is scrubbed with an aq soln so that the SO2 and Mg cpds in the dust are removed as Mg(HSO3)2 The inert solids are separated, MgO is added to the soln to give solid MgSO3 which is separated off and the MgSO3 is calcined with the solid portion of the slurry to give regenerated MgO and a dust stream of high SO2 concn Used to remove and recover SO2 and entrained solid fly ash from gas discharged by coated burning steam power plant or wood pulp processing plant

Permeability of High Ash Papermill Sludge

Abstract: Most deposits of high ash papermill clarifier sludges contain very high water contents, show little drainage over the years, are unstable, and are subject to large settlements under surface loads. Poor drainability is a major part of the problem. Permeability data presented show the influence of gas bubbles trapped in the sludge mass, solids content, organic content of the solids, and admixtures of lime or flyash on the sludge drainage characteristics. Hydraulic pressures required to eliminate the influence of bubbles on drainage were approximated by an expression which considered Boyle's law and Henry's law of solubility. A threshold gradient, required to initiate flow at low pressures, approached zero when the gas bubbles were eliminated. For a constant solids content, data show that permeability increases with an increase in organic content. Lime or flyash admixtures, used as an aid in sludge dewatering methods, increase the sludge permeability.

Fly ash building material

Abstract: Fly ash has a content of 3-15% by weight SO3 and 40-90% active ingredients which are SO3 free & 100% active. The latter comprises by weight %, 8-25 SiO2, 18-45 Al2O3 + Fe2O3, and 35-75 CaO + MgO. The mixture is bound with water at 50-90 C, pref. 60-80 C, & the building material is obtained in less than 24 hrs. Specifically, the fly ash is lignite or oil shale filter ash.