Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
  • C04B18/04—Waste materials; Refuse
  • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
  • C04B18/08—Flue dust, i.e. fly ash
  • C04B18/081—Flue dust, i.e. fly ash from brown coal or lignite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L9/00—Treating solid fuels to improve their combustion
  • C10L9/10—Treating solid fuels to improve their combustion by using additives
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/10—Compositions or ingredients thereof characterised by the absence or the very low content of a specific material
  • C04B2111/1087—Carbon free or very low carbon content fly ashes; Fly ashes treated to reduce their carbon content or the effect thereof
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Definitions

• the present invention relates to coal combustion products, and more particularly relates to the production of coal combustion products having improved properties for use in cementitious materials.
• fly ashes can contain high levels of free carbon, measured as loss on ignition (LOI) or by other analytical methods, such as thermogravimetric analysis.
• LOI loss on ignition
• thermogravimetric analysis measures the presence of free carbon levels.
• Air entrainment in concrete is essential to ensure the durability of concrete under repeated freeze-thaw cycles.
• the use of combustion products in concrete is limited by the presence of free carbon.
• Some methods involve the use of external grinding facilities to reduce the particle size of combustion product particles.
• Other existing methods include carbon burn-out methods, utilizing the application of heat to the combustion product to reduce the levels of free carbon.
• Yet other methods utilize electrolytic methods to sequester carbon atoms. All of the aforementioned methods require high capital and ongoing costs in building and operating separate facilities.
• the present invention provides a method and system for producing modified coal combustion products for addition to concrete, mortar and other hydraulic mixtures comprising Portland cement clinker and coal combustion products for use in construction and other industries.
• the invention provides a method for decreasing the particle size and increasing the total surface area of the resulting combustion product, thus increasing the rate of development of mechanical properties in hydraulic mixtures containing such combustion products.
• the invention further relates to the improvement of combustion efficiency resulting from the smaller particle size and resulting increased surface area of coal particles, and the dilution effect of the original combustion product after addition of the aforementioned materials, both leading to lower levels of total free carbon in the resulting combustion product.
• An embodiment of the invention provides for the selection and addition of raw materials to be added in a coal combustion process to increase the reactivity of the resulting coal combustion products without any retarding effects on the alite hydration in Portland cement clinker used together with said coal combustion products in a hydraulic mixture.
• limestone is added to the combustion chamber of coal burning boilers to reduce sulfur emissions from flue gases to achieve sulfur removal rates range from 75 to 95 percent, however with very limited, if any, improvement of the development of mechanical properties when used with Portland cement clinker in a hydraulic mixture.
• An aspect of the present invention is to provide a method of producing a modified coal combustion product comprising combusting coal and a particle size-reducing additive, wherein the modified coal combustion product has an average particle size less than an average particle size of a coal combustion product combusted from the coal without the additive.
• Another aspect of the present invention is to provide a system for producing a modified coal combustion product comprising a combustion chamber for co-combusting coal and a particle size-reducing addititive, a source of the coal, a source of the particle size- reducing additive, and at least one injector configured to deliver the coal and the particle size- reducing additive to the combustion chamber.
• Fig. 1 is a partially schematic diagram of certain elements of a coal-fired power plant in which coal combustion products are produced in accordance with an embodiment of the present invention.
• Figs. 2 and 3 are graphs of particle size distributions of additives and the particle size distributions of the combustion products obtained by the addition of such additives in various combinations and dosages in accordance with the embodiments of the present invention.
• additives containing calcium oxide, alumina, silica, magnesium oxide, titanium oxide, ferrous oxides and the like are co-combusted with coal to produce modified coal combustion products.
• the average particle size of the modified coal combustion product is smaller than an un-modified coal combustion product.
• the "average particle size" may be determined by the standard procedure of ASTM B822 - 10 Standard Test Method for Particle Size Distribution of Metal Powders and Related Compounds by Light Scattering.
• the raw material particles are typically much larger than the resulting coal combustion product particles, indicating that the intense high-temperature mixing causes particle reduction/attrition both through intense collisions as well as through chemical combustion.
• the average particle size of the modified combustion product may be less than 50 microns, typically less than 20 or 10 microns, while the average particle size of at least some of the starting additive materials may be greater than 20 or 50 or 100 microns.
• the average particle size of the modified coal combustion product is at least 5 percent less than an average particle size of a coal combustion product combusted from similar coal without the additive, for example, at least 15 percent less.
• a coal fired boiler can be used as a co-generator to produce both heat for electrical power generation as well as excess heat, combustion synthesis, and thermal blending to produce a highly reactive pozzolanic powder in the form of the modified coal combustion product having reduced particle sizes.
• a comparison of the starting material particle size and the resulting product particle size demonstrates that a combination of combustion and comminution within the boiler takes place, rapidly reducing large oxide materials into fine powders.
• the combustible additives may blend with the fume from the coal combustion to permit the formation of a chemically enhanced coal ash.
• the raw materials for use as the additives may be derived either from industrial waste streams or not, and may include concrete dust, ground blast steel slag, fine ground soda lime glass, fine ground E glass, fine ground geopolymer cements, blends and mixes of fly ash and high alkali chemicals in the presence of heat, or any other materials which increase levels of silica or alumina in the resulting fly ash.
• the raw materials may also be used to decrease the levels of total free carbon in the resulting combustion ash.
• Such carbon-reducing materials can be derived either from industrial waste streams or not, and may include recycled concrete dust, ground blast steel slag, fine ground soda lime glass, fine ground E glass, fine ground geopolymer cements, blends and mixes of fly ash and high alkali chemicals in the presence of heat, or any other materials which increase levels of silica or alumina in the resulting fly ash.
• the modified coal combustion product has a carbon content less than a carbon content of a coal combustion product combusted from similar coal without the additive.
• the carbon content of the modified coal combustion product may be at least 10 weight percent less than the untreated coal, typically, at least 50 weight percent less.
• the carbon content of the modified coal combustion product may be less than 5 weight percent, for example, from 0.5 to 2 weight percent.
• metal oxide strength enhancing additives are used as raw materials that undergo co-combustion with coal to produce a useful cement additive material having controlled amounts of calcium oxide, silicon dioxide and aluminum oxide.
• Table 1 lists the relative amounts of strength enhancing metal oxides, expressed in terms of CaO, Si0 2 and A1 2 0 3 , that are present in combustion products in accordance with embodiments of the present invention.
• the terms "CaO”, “Si0 2 " and “Al 2 03" appearing in Table 1 and used herein mean the relative weight percentages of calcium oxide, silica and alumina contained in the cement additive material in accordance with the ASTM CI 14 standard.
• the coal may comprise bituminous coal and/or sub-bituminous coal.
• the relative amounts of CaO, Si0 2 and A1 2 0 3 present in the modified combustion product typically range from about 20 to about 60 weight percent CaO, from about 25 to about 60 weight percent Si0 2 , and from about 5 to about 30 weight percent A1 2 0 3 .
• the relative amounts of CaO, Si0 2 and A1 2 0 3 in the bituminous coal combustion product may range from about 25 to about 50 weight percent CaO, from about 30 to about 55 weight percent Si0 2 and from about 10 to about 25 weight percent A1 2 0 3 .
• the relative amounts of CaO, Si0 2 and A1 2 0 3 present in the modified combustion product typically comprise from about 47.5 to about 70 weight percent CaO, from about 10 to about 40 weight percent Si0 2 , and from about 5 to about 30 weight percent A1 2 0 3 .
• the relative amounts of CaO, Si0 2 and A1 2 0 3 in the sub-bituminous coal combustion product may range from about 50 to about 65 weight percent CaO, from about 15 to about 35 weight percent Si0 2 , and from about 10 to about 25 weight percent A1 2 0 3 .
• the additives producing the CaO, Si0 2 and A1 2 0 3 levels above may be low cost minerals, including waste products containing calcium oxide, silicon dioxide and/or aluminum oxide that can be beneficiated by virtue of the temperatures in a combustion chamber such as a coal fired boiler when injected in the system at selected particle sizes, dosage and temperature levels.
• combinations of additives are selected from limestone, concrete including waste concrete such as recycled Portland cement concrete, kaolin, recycled ground granulated blast furnace slag, recycled crushed glass, recycled crushed aggregate fines, silica fume, cement kiln dust, lime kiln dust, weathered clinker, clinker, aluminum slag, copper slag, granite kiln dust, rice hulls, rice hull ash, zeolites, limestone quarry dust, red mud, fine ground mine tailings, oil shale fines, bottom ash, dry stored fly ash, landfilled fly ash, ponded fly ash, sopodumene lithium aluminum silicate materials, lithium-containing ores and other waste or low-cost materials containing calcium oxide, silicon dioxide and/or aluminum oxide.
• waste concrete such as recycled Portland cement concrete, kaolin, recycled ground granulated blast furnace slag, recycled crushed glass, recycled crushed aggregate fines, silica fume, cement kiln dust, lime kiln dust, weathered
• the additives may comprise one or more of the following materials: 7-20 weight percent limestone; 1-5 weight percent ground granulated blast furnace slag; 1-5 weight percent crushed concrete; 0.1-2 weight percent crushed glass; 0.1-5 weight percent kaolin; and 0.01-1 weight percent silica fume.
• the additives typically comprise at least 8 weight percent of the combined total weight of the coal and the additives, for example, greater than 10 weight percent.
• the additives may be provided in desired particle size ranges and introduced into the combustion chamber in the same region as the coal, or in other regions.
• One embodiment of the present invention uses the coal fired boiler of an electric power plant as a chemical processing vessel to produce the coal combustion products, in addition to its normal function of generating steam for electrical energy. This approach may be taken without reducing the efficiency of the boiler's output while, at the same time, producing a commodity with a controlled specification and a higher commercial value to the construction market.
• the resulting ash product may be designed to have beneficial properties for use in
• Fig. 1 schematically illustrates certain elements of a coal-fired power plant 10.
• the power plant includes a combustion chamber 12 such as a conventional tangential firing burner configuration. Pulverized coal is introduced into the combustion chamber 12 via at least one coal inlet line 14. A coal hopper 15 feeds into a coal pulverizer 16 which comminutes the coal to the desired particle size for introduction into the combustion chamber 12. The pulverized coal may be mixed with hot air and blown through the inlet(s) 14 into the combustion chamber 12 where the coal is burned.
• the additives may be introduced into the combustion chamber 12 from a source of additives such as a delivery system 19 via a feed line 11 that feeds into the pulverizer 16 or coal feed line 14 and/or via another feed line 13 that feeds into the bottom region of the combustion chamber 12.
• a source of additives such as a delivery system 19
• the additives may be fed separately through one or more additional inlet lines 17 and 18.
• the additive delivery system 19 may comprise conventional particulate material storage hoppers, metering systems and delivery systems for delivering the additives to the feed lines 11 and/or 13, and/or to the additional inlet lines 17 and 18.
• Coal fly ash is essentially formed from the combustion gases as they rise from the combustion zone and coalesce above that zone. Typically, when temperatures are in the range of 1,800 - 2,200°F, these gases form predominantly amorphous hollow spheres.
• additives like those listed can be added directly to the boiler in such a way that an ash from coal can be enhanced for optimum ash performance.
• additives such as clays, including kaolin, can be added to the boiler.
• Such materials may not decompose and recombine with the ash, but rather may be thermally activated and intimately mixed through the highly convective flow patterns inherent in the boiler. The result is a uniform ash/additive blend achieved completely through the boiler combustion process, and requiring no secondary processing. Essentially, as the vapor from the combusted products coalesce when they rise from the high temperature zone, glassy calcia-alumina-silicates will form.
• Vaporized additives dispersed in the plume will become part of the glassy phase, while those that have not vaporized will act as nuclei for the coalescing vapors.
• Other additives that do not take part with the glassy phase formation may be intimately mixed with the ash, producing a highly reactive pozzolanic mixture.
• kaolin introduced in the boiler may not take part in the ash formation, but may transform to metakaolin, an otherwise costly additive.
• the intimate blending of the additives directly into a boiler permits the combustion synthesis of the additives together with the coal and relies upon the intimate mixing generated by the convective flow in or near the boiler to produce chemically modified fly ash.
• This blending may take place in the main combustion zone of the boiler, directly above the main combustion zone in the boiler, or downstream from the boiler.
• additives such as kaolin, metakaolin, titanium dioxide, silica fume, zeolites, diatomaceous earth, and the like may be added at such downstream locations at other points where the coal combustion products coalesce into amorphous fly-ash particles.
• relatively low cost kaolin may be added and converted into metakaolin during the process, thereby resulting in the economical production of metakaolin having desirable strength enhancing properties when added to cement.
• the resulting ash byproduct can be designed to have a chemical structure that will enable it to act as a cementitious binder together with Portland cement for strength enhancing properties of a cement or a concrete.
• geopolymer cements may be added in the combustion process to reduce pollutants in flue gas.
• Such geopolymer cements may serve as binding agents for mercury, heavy metals, nitrogen oxides and sulfur oxides, and additional silica.
• the resultant fly ash formed in the coal combustion process may be modified by the inclusion of the chemical compounds within these additives directly into the coalescing fly ash.
• some chemical species added in this manner that do not become chemically bound to the coalescing fly ash are intimately blended with the fly ash through the natural convection in the boiler resulting in a very uniform blending process achieved without the need for secondary, cost intensive, powder blending of the resultant ash product.
• a method is provided for testing the resulting coal combustion ash after addition of other materials and adjusting the combustion parameters and materials to reach target levels of calcium oxide, silicon dioxide and aluminum oxide in the resulting coal combustion ash.
• Such testing and adjusting may include measuring contents of calcium oxide, silicon dioxide and aluminum oxide and other reactive and non-reactive elements directly.
• the method also may include measuring properties of concrete made from the resulting coal combustion ash so as to determine early strength, late strength, slump and setting time of the concrete made of the resulting coal combustion ash.
• the measurements may be coupled to algorithms to rapidly assess the data and make changes to the feed rates in real time.
• the testing methods may measure components such as calcium oxide, silicon dioxide and aluminum oxide and other reactive and non-reactive elements using x-ray diffraction (XRD) methods, including Rietvield analysis, x-ray fluorescence (XRF) or any other methods to identify said components. Such methods can be used in-line or end-of-line. Methods to measure strength (early and late), set time and slump can be derived from methods provided in ASTM standards relative to the measurement of such properties, or measures of heat of hydration through calorimeters, or measures of conductivity, or ultrasonic methods, or any other method that can measure or infer any of the aforementioned properties.
• XRD x-ray diffraction
• XRF x-ray fluorescence
• the incorporation of sensors in a boiler that can monitor the in-situ quality/chemistry of an ash product as it is being generated.
• the sensors can include conventional residual gas analyzers, x-ray fluorescence spectrometers, mass spectrometers, atomic absorption spectrometers, inductively-coupled plasma optical emission spectrometers, Fourier transform infrared spectrometers, and lasers for performing laser induced breakdown spectroscopy, as well as mercury analyzers, NO x detectors and SO x detectors.
• the levels of gases, etc. measured by such techniques can be linked to the optimum chemistry of an ash product.
• the sensors can provide real-time monitoring feedback to a human controller or an automated analysis system.
• the sensor(s) may transmit the value of a measured property to a controller which compares the measured value to a reference value and adjusts the flow rate of the strength enhancing material based thereon.
• the controller may transmit a signal to one or more additive injectors in order to increase or decrease the flow rate of the additive into the combustion zone.
• This feedback system is to link directly to the individual sources of chemical additives and adjust their feed rates to maintain the ash chemistry quality required for optimum concrete performance.
• the modified combustion products of the present invention may be added to various types of cement, including Portland cement.
• the combustion products may comprise greater than 10 weight percent of the cementitious material, typically greater than 25 weight percent.
• the additive comprises 30 to 95 weight percent of the cementitious material.
• Limestone, granulated blast furnace slag and kaolin were injected in the combustion chamber of a coal combustion boiler with the following dosages: Limestone: 7.8 percent by weight of coal; Granulated blast furnace slag: 4.9 percent by weight of coal; and Kaolin: 1.4 percent by weight of coal.
• the total quantity of additives amounts to 14.1 percent by weight of coal.
• the invention provides a method and system to reduce disposal of coal combustion ashes in landfills by converting them into higher value hydraulic binders, usable as a substitute of cement in quantities in excess of 40 percent of substitution. Another advantage of the invention is that it provides a cost-effective alternative to other methods to beneficiate coals combustion ashes, such as external grinding facilities or existing

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Organic Chemistry (AREA)
• Structural Engineering (AREA)
• Materials Engineering (AREA)
• Combustion & Propulsion (AREA)
• Environmental & Geological Engineering (AREA)
• Inorganic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Civil Engineering (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

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• 2013
  • 2013-01-14 EP EP13704640.5A patent/EP2802547A1/de not_active Withdrawn

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