NON-PORTLAND CEMENT ACTIVATION OF BLAST FURNACE SLAG

The purpose of this project was to produce a “greener” cement from granulated ground blast furnace slag (GGBS) using non-Portland cement activation. By eventually developing “greener” cement, the ultimate goal of this research project would be to reduce the amount of Portland cement used in concrete, therefore reducing the amount of carbon dioxide emitted into the atmosphere during cement production. This research studies the behavior of mineral binders that do not contain Portland cement but instead comprise GGBS activated by calcium compounds or fluidized bed combustion (FBC) bottom ash. The information described in this paper was collected from experiments including calorimetry, which is a measure of the release of heat from a particular reaction, the determination of activation energy of cement hydration, mechanical strength determination, and pH measurement and identification of crystalline phases using X-ray diffraction (XRD). The results indicated that it is possible to produce alkali-activated binders with incorporated slag, and bottom ash, which have mechanical properties similar to ordinary Portland cement (OPC). It was determined that the binder systems can incorporate up to 40% bottom ash without any major influence on binder quality. These are positive results in the search for “greener cement”

Changes in the Nature of Midwestern Fly Ash Over the Past Two Decades- I. Chemistry, Mineralogy and Beneficiation Potential

Changes in the Nature of Midwestern Fly Ash Over the Past Two Decades: I. Chemistry, Mineralogy, and Beneficial Potential Authors Dr. Bob Jewell - United States - University of Kentucky Center for Applied Energy Research Ms. Anne Oberlink - United States - University of Kentucky Center for Applied Energy Research Dr. Thomas Robl - United States - University of Kentucky Center for Applied Energy Research Abstract Environmental regulations regarding coal combustion have become more stringent over time. The percentage of plants equipped with scrubbers in Kentucky increased from ~4% in 1978 to ~48% in 1997 to the point where flu gas scrubbers are essential to all plants regardless of coal type. Although still of importance in the production of coke, the ability to produce a “compliant” low-sulfur coal is no longer an advantage for central Appalachian coal mines in the electrical generation market. The past two decades have seen a substantial shift to higher sulfur and lower-cost Illinois basin coal in much of the Midwest. This has resulted in shifts in the overall composition of fly ash. The collection and examination of fly ash from six Kentucky power plants found a substantial increase in Fe2O3 (~14% to 30%) compared to previous collections where fly ash as low as 5% Fe2O3 was collected from plants that used low sulfur coal. This increase in Fe2O3 was concomitant with a decrease in Al2O3 (~16-19% compared to ~27-30%) and SiO2 (~36-45% compared to ~54-58% for low sulfur coals). Much of the higher sulfur content of the Illinois basin coal is in the form of pyrite, which, upon combustion, produces a fly ash predominantly composed of magnetite, Fe3O4. This has resulted in denser fly ash that is darker in color, ranging from olive brown to dark brown to almost black, compared to the grays and buff colors of the low-sulfur coal ash. More significantly, the increase in magnetite is at the cost of reduced glass content, which is essential to the pozzolanic reactivity of the fly ash

Proppant for Use in Hydraulic Fracturing to Stimulate a Well

A proppant for use in hydraulic fracturing to stimulate a well is provided. The proppant is fly ash particles having a mean particle size (d50) of between 45 μm and 150 μm and a size distribution defined by (d10) ≤ 5 μm and (d98) ≤ 250 μm

New Applications for Beneficial Reuse of Coal Combustion Ash

New Applications for Beneficial Reuse of Coal Combustion Ash Authors Ms. Anne Oberlink - United States - University of Kentucky Center for Applied Energy Research Dr. Bob Jewell - United States - University of Kentucky Center for Applied Energy Research Dr. Thomas Robl - United States - University of Kentucky Center for Applied Energy Research Mr. Curtis Wilie - United States - Commonwealth Energy Technologies Mr. Jim Crenshaw - United States - Commonwealth Energy Technologies Mr. Scott Hoskins - United States - Commonwealth Energy Technologies Ms. Hailey Mattingly - United States - Office of Energy Policy, Commonwealth of Kentucky Abstract The University of Kentucky Center for Applied Energy Research, along with its industrial partner, Commonwealth Energy Technologies, Inc., with the support of the Office of Energy Policy, has initiated a project to explore and develop new uses for both current production and ponded coal combustion fly ash. This research will characterize and modify the fly ash for enhanced oil & gas recovery and provide materials for improved efficiency and safety of plugging and abandonment of wells in Kentucky. This effort is partly based on new fly ash technology for recovering and enhancing production from pre-existing oil and/or gaswells. In some cases, the rejuvenated wells have surpassed their original production levels. This technology has been successfully pilot-tested in heritage oil and gas fields in Eastern Texas and the Texas panhandle and is currently well into implementation. Ash fracking is a patented technology that uses a micro-proppantproduced from coal combustion fly ash to open and maintain micro-fractures in shale and sandstone. This approach reduces the energy needed for the operation by as much as 95%, improving efficiency and reducing greenhouse gas emissions. This green technology is conducted with simple pumping equipment, creating a small operational footprint, a crucial factor in Eastern Kentucky’s topography. Because using fly ash eliminates the need for viscosity modifiers, it results in a simpler post-fracking cleanup. It also uses less water and can reuse well water, eliminating environmental contamination. This approach also provides theultimate disposal solution for fly ash, storing it thousands of feet below the earth’s surface

Changes in Midwestern Fly Ash II. Air Classification, Magnetic Separation and the Pozzolanic Characteristics of the Ash

Changes in Midwestern Fly Ash II. Air Classification, Magnetic Separation and the Pozzolanic Characteristics of the Ash Authors Ms. Anne Oberlink - United States - University of Kentucky Center for Applied Energy Research Ms. Sydney Dendekker - United States - University of Kentucky Center for Applied Energy Research Ms. Haley Johnson - United States - University of Kentucky Center for Applied Energy Research Dr. Thomas Robl - United States - University of Kentucky Center for Applied Energy Research Dr. Bob Jewell - United States - University of Kentucky Center for Applied Energy Research Abstract Six current production fly ashes from Kentucky power plants were processed into coarse and fine-size fractions with an air classifier. This process separates material by size and density. The strong contrast with the silicate fraction of the fly ash in density to that of the magnetite (~5.2 to ~2.4 g/cm3) makes this separation less challenging than that of carbon. The classification of these fly ashes resulted in finer-sized ash yields ranging from +90% to ~50%. As expected, the coarse ash had high concentrations of magnetite (up to ~55% by weight). The fine fraction had increased SiO2 and Al2O3 content and reduced Fe2O3. This is reflective of greater fused glass content. The fine fraction was also substantially improved in fineness as defined by retention on a 325-mesh screen. It did have an increased LOI over the parent material. However, with one exception, this increase was within the requirement of ASTM C-618 of 5%. Preliminary results found that the fine fraction of the fly ash had improved the pozzolanic activity, as measured by the EN-196 strength index test and resistivity measurements over the parent ash. The coarse fraction of the ash did not pass the strength index test and showed little improvement in resistivity. The beneficiation potential for these fly ashes and new uses for coarse and fine materials will be discussed

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

Alite calcium sulfoaluminate cement: chemistry and thermodynamics

Calcium sulfoaluminate (C$A) cement is a binder of increasing interest to the cement industry and is undergoing rapid development. Current formulations do not contain alite; however, alite calcium sulfoaluminate (a-C$A) cements can combine the favourable characteristics of Portland cement (PC) with those of C$A cement while also having a lower carbon dioxide footprint than the current generation of PC clinkers. This paper presents two results on the formation of a-C$A clinkers. The first is a thermodynamic study demonstrating that the production of a-C$A clinker is possible without the use of mineralisers, doping with foreign elements, or using multiple stages of heating. It is established that a-C$A clinker can be readily produced in a standard process by controlling the oxygen and sulfur dioxide fugacity in the atmosphere. This allows for the stabilisation of ye’elimite to the higher temperatures required for alite stability. The second result establishes that when using fluorine to mineralise a-C$A clinker production, the iron content in the clinker is also an important variable. Although the exact mechanism of alite stabilisation is not known, it is shown that alite formation increases with the combination of calcium fluoride and iron (III) oxide in the mix

World of Coal Ash 2022

Proceedings of the 2022 World of Coal Ash Conferenc