Method for Hydraulically Separating Carbon and Classifying Coal Combustion Ash

A method for selective separation of particles from a particle-containing material includes preparing a slurry of the particle-containing material and a dispersant, passing the slurry through a hydraulic classifier in a first direction, establishing a particle flow in a direction that is different from the first direction, and recovering particles having a mean particle size of about 2-7 μm. The flow of particles defines a cross-current flow relative to the slurry feed direction. The method further includes providing the classifier with an interior divider assembly defining at least one inclined channel. The divider assembly typically includes a plurality of substantially parallel dividers separating the classifier into multiple channels having a substantially equal internal volume. A hydraulic classifier for separating particles having a mean particle size of from about 2-7 μm in accordance with the present method is provided also

Technology and Methodology for the Production of High Quality Polymer Filler and Super-Pozzolan from Fly Ash

A novel method for producing fly ash material with a range of particle sizes from about 2.0 to about 4.0 μm is provided utilizing superplasticizers. The method produces fly ash material suitable for use as filler material in the plastics industry and super pozzolan for the concrete industry

Method for Improving the Pozzolanic Character of Fly Ash

A method for improving the pozzolanic character of fly ash includes the steps of first hydraulically classifying and then flotation separating the fly ash in order to reduce particle size distribution and remove carbon. The method also includes the steps of spiral concentrating separated coarse particles to recover iron, pyrite and marcasite and screening the fly ash to remove ultra-light carbon and plant debris

Synthesis and Characterization of High-Iron Alite-Calcium Sulfoaluminate-Ferrite Cements Produced from Industrial By-Products

Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC) are well-known and commonly used construction materials. The clinker phases mainly responsible for their strength development are C3S (alite) in OPC, which hydrates to form a calcium silicate gel phase; and C4A3S ´ (calcium sulfoaluminate) in CSAC, which hydrates to rapidly form ettringite. The purpose of this work was to produce high-iron alite-calcium sulfoaluminate-ferrite cements, by combining C4AF (ferrite), from 5% to 50% by weight, to the C3S and C4A3S ´ clinker phases. Producing this alite-calcium sulfoaluminate-ferrite cement would decrease the requirement of bauxite in the raw materials, which would consequently reduce its cost. The use of industrial by-products would also reduce the CO2 emissions and the firing temperature by 200–250uC compared with OPC. This article presents the synthesis and characterization of five compositions produced from industrial by-products (hydrated lime related to carbide lime, fly ash, slag, and red mud) and bauxite, formulated as follows: C3S from 20% to 50%, C2S from 10% to 20%, C4A3S ´ from 10% to 20%, C4AF from 5% to 50%, and CS ´ from 4% to 6% by weight. The clinker with the lowest ferrite content required a higher firing temperature (1275uC) than the compositions with high ferrite contents (1250uC). Impurities, such as MgO and TiO2, introduced by the industrial by-products affected the mineralogical compositions. Consequently, some adjustments of the raw mix were necessary to obtain the desired clinker compositions

Cementitious Compositions

The invention provides a cementitious composition comprising a cement component comprising (i) an accelerant, (ii) a calcium sulphate source and (iii) an ettringite forming cement; an aggregate; and optionally water; wherein the cement has a minimum unconfined compressive strength of 1500 psi when tested in accordance with ASTM C1140 and/or C1604 at 15 minutes after placement; methods for its use and concrete formed from it

Chemistry of coal and coal combustion products from Kentucky power plants: Results from the 2007 sampling, with emphasis on selenium

Kentucky produced over 8 Mt of coal combustion products (CCPs) in 2006, with 30% of the CCPs being utilized, a significant increase from our 1996 and 2001 surveys. As much of the increase is related to increased utilization of flue-gas desulfurization (FGD) gypsum, the increased production of FGD gypsum coincident with the commissioning of new FGD units and the saturation of the (currently) weak market for new construction, the percentage of utilization may decrease by the time of the next planned survey (2011). The concentration of volatile trace elements in the feed coal and in the pulverizer reject, while associated with pyritic sulfur, are somewhat independent of the pyritic sulfur content owing to provincial variations in the trace element content of coal minerals. Consequently, high-pyrite/high-S coals do not necessarily produce the highest-As,-Se, and–Hg (among other elements) fly ashes. Among the power plants in Kentucky, plants with intermediate sulfur contents have some of the highest concentrations of volatile trace elements in their fly ashes. In general, volatile trace elements in fly ash increase in concentration from the first through to the last row of the pollution control system owing to the decrease in flue gas temperature and decrease in particle size (and increase in surface area) in that direction. Mercury is dependent upon the carbon content in addition to the flue gas temperature. Selenium is more problematical, showing no consistent trend within the ash collection systems

Interfacial Bond between Reinforcing Fibers and Calcium Sulfoaluminate Cements: Fiber Pullout Characteristics

The results of an experimental investigation on the influence of the interfacial bond of reinforcing fibers embedded in a calcium sulfoaluminate matrix on the fiber-pullout peak load and energy consumption are presented. Bonding at the fiber-matrix interface plays an important role in controlling the mechanical performance of cementitious composites—in particular, composites formed from sulfate-based systems (calcium sulfoaluminate [CSA] cements), as opposed to the silicate systems found in portland cement. Various types of fibers were selected, including polyvinyl alcohol (PVA), polypropylene, and copper-coated steel. The fibers were embedded in three different matrixes: two sulfate-based cements including one commercially available CSA cement and a CSA fabricated from coal-combustion by-products. The third matrix was a silicatebased ordinary portland cement (OPC). In this study, the results of the single-fiber pullout test were coupled with scanning electron microscopy (SEM) to examine the interfacial bond between the fiber and CSA matrix for evidence of debonding and possible hydration reaction products

Low-Silica and High-Calcium Stone in the Newman Limestone (Mississippian) on Pine Mountain, Harlan County, Southeastern Kentucky

The coal industry of Kentucky is an important market for limestone. Coal producers use limestone as rock dust for explosion abatement in underground coal mines and as a neutralizing agent in surface-mine reclamation and acid-drainage control. Crushed stone is also used for constructing and maintaining haulage roads. In the Eastern Kentucky Coal Field, the coal-bearing rocks of Pennsylvanian age generally do not contain limestones that are thick enough to quarry or mine economically. But movement on the Pine Mountain overthrust fault has brought the Newman Limestone (Mississippian) to the surface along Pine Mountain in the southeastern part of the coal field. The Newman on Pine Mountain in Harlan County was sampled at 1-foot intervals to determine its chemical quality and potential for industrial use, particular as low-silica rock dust. The sampled section contains two zones of low-silica stone, 64 and 25 feet thick, averaging 0.82 and 1.01 percent silica (SiO2), respectively. Intervals of high-calcium limestone are present in the low-silica zones. These deposits are potentially suitable for use as rock dust in underground coal mines and as neutralizing agents in surface-mine reclamation and acid-drainage control. The intervals of chemically pure stone in Harlan County may be sufficiently thick to produce by selective quarrying or underground mining. Exploitation of the Newman deposits, however, will be complicated by the steep southeastward to southward dip (13 to 42°) of the beds, displacement along small faults within the limestone, and fracturing

Coal Ash By-Product from Shanxi Province, China, for the Production of Portland–Calcium Sulfoaluminate

Twenty bulk samples were collected from ponded coal combustion ash in Shanxi Province, China, as part of an investigation of their beneficiation potential. The samples were shipped to the University of Kentucky, where they were chemically analyzed. The samples were highly consistent in chemistry, falling within the ASTM C-618 class F compositional range. The particle size of the ponded ash was relatively coarse, with only ,7% by weight on average, falling below 200 mesh (75 mm) particle size. The bulk of the material (.80%) was within 50 by 200 mesh (equivalent to 300 by 75 mm). X-ray diffraction investigation combined with microscopy indicated that the agglomeration was probably due to the presence of small amounts (i.e., ,3.5%) of gypsum. The utilization potential of the ash was assessed in light of its characteristics and location. The presence of sulfate and relatively high alumina concentration, which averaged ,37%, suggested that it may serve as an important ingredient in the fabrication of a Portland–calcium sulfoaluminate (CSA) hybrid cement. Portland-CSA hybrid clinkers were successfully produced from this ponded ash when mixed with hydrated lime, gypsum, fluorite, and bauxite. The raw mixture was fired at 1250uC for 60 minutes twice (sample D) and consisted of approximately 40% alite (C3S), 21% belite (C2S), 3% ferrite (brownmillerite or C4AF), 32% CSA (ye’elimite, Klein’s compound, or C4A3SO3), and no free lime by weight

Use of Ponded and Fresh Ashes from China for the Production of Portland/Calcium Sulfoaluminate Clinkers

This article summarizes the use of two fly ashes in the synthesis of Portland/calcium sulfoaluminate (OPC/CSA or A/CSA) clinkers. They are from the Shentou second power plant located in the Shanxi Province and from the Zhungeer power plant located in Inner Mongolia, China. The Zhungeer ash was collected dry, and the Shentou ash is from a pond. Their chemical compositions differ highly, especially the SiO2 and Al2O3 contents. The high contents of silica and alumina make both ashes candidates as a partial or total substitute for bauxite, an expensive source of alumina, in the production of OPC/CSA clinkers. These particular hybrid clinkers are composed mainly of alite (C3S) and calcium sulfoaluminate (C4A3 ´ S), both phases responsible for the high early strength development in OPC and CSA cements, respectively. The production of high-quality OPC/CSA clinkers was produced with both ashes with the additions of hydrated lime, flue gas desulfurization (FGD) gypsum, fluorite, and bauxite at 1250°C for 60 minutes with final composition ranges of 29–41 wt% C3S, 20–22 wt% C2S, 30–45 wt% C4A3 ´ S, and 1–4 wt% C4AF