WO2004108621A2 - Procede pour enrichir des cendres volantes - Google Patents

Procede pour enrichir des cendres volantes Download PDF

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Publication number
WO2004108621A2
WO2004108621A2 PCT/US2004/016266 US2004016266W WO2004108621A2 WO 2004108621 A2 WO2004108621 A2 WO 2004108621A2 US 2004016266 W US2004016266 W US 2004016266W WO 2004108621 A2 WO2004108621 A2 WO 2004108621A2
Authority
WO
WIPO (PCT)
Prior art keywords
fly ash
process according
phase
amorphous phase
heating step
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2004/016266
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English (en)
Other versions
WO2004108621A3 (fr
Inventor
Hugh H. Wang
Stephen M. Bryan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cemex Inc
Original Assignee
Cemex Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US10/249,935 external-priority patent/US20040231566A1/en
Application filed by Cemex Inc filed Critical Cemex Inc
Publication of WO2004108621A2 publication Critical patent/WO2004108621A2/fr
Publication of WO2004108621A3 publication Critical patent/WO2004108621A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • C04B7/00—Hydraulic cements
    • C04B7/24—Cements from oil shales, residues or waste other than slag
    • C04B7/243—Mixtures thereof with activators or composition-correcting additives, e.g. mixtures of fly ash and alkali activators
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding
    • 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

  • Coals are used in power plants throughout the world to produce electricity.
  • One byproduct of coal combustion is an inorganic residue known in the building materials industry as "fly ash.”
  • Fly ashes accumulate rapidly and can cause enormous waste disposal problems unless an effective use is found for these by-products.
  • the building materials industry is a leader in utilizing the fly ash in cement and concrete.
  • Using coal fly ash has great benefit to society for resource conservation and environmental protection. For example, using fly ash in place of cement conserves energy by reducing the demand for cement, which takes energy to produce.
  • Each ton of fly ash that replaces a ton of cement not only saves the equivalent of about one barrel of oil, this substitution also reduces the production of greenhouse gases that would otherwise contribute to global warming.
  • Fly ash is termed a "pozzolan" in the cement and concrete industry.
  • a pozzolan is defined as a finely divided material that reacts with calcium hydroxide and alkalis to form compounds possessing cementitious properties. Only the glassy (amorphous) phase of the fly ash is the active pozzolanic portion. Typical fly ash contains about 50-80% glassy phase. The remainder of the fly ash is composed of mineral phases, including the aluminum silicates mullite (3Al 2 O 3 -2SiO 2 ) and sillimanite (Al 2 O 3 -SiO 2 ); quartz (SiO 2 ); and iron oxides such as magnetite (Fe 3 O 4 ), and hematite (Fe 2 O 3 ).
  • ⁇ fly ash Other constituents that may be present in high-calcium fly ash include periclase (MgO), anhydrite (CaSO 4 ), lime (CaO/Ca(OH) 2 ), alkali metal sulfates (for example sodium sulfate and potassium sulfate), melilite, merwinite, dicalcium silicate (2CaO-SiO 2 or "C 2 S"), and tricalcium aluminate (3CaO-Al 2 O 3 or "C 3 A”).
  • periclase MgO
  • CaSO 4 anhydrite
  • lime CaO/Ca(OH) 2
  • alkali metal sulfates for example sodium sulfate and potassium sulfate
  • melilite merwinite
  • tricalcium aluminate 3CaO-Al 2 O 3 or "C 3 A”
  • the successful cement performance of the fly ash depends significantly on the percentage of the glassy portion of the phases in the fly ash. A larger fraction of glassy phase results in better and more consistent performance.
  • a process for converting crystal phases in the fly ash to the glassy or amorphous phase by heating the fly ash to its melting point, then rapidly cooling the heated fly ash to preserve the high temperature glassy phase, thereby producing a highly reactive pozzolanic material.
  • the fly ash is heated to at least about 1150°C.
  • the heating step is carried out in a kiln, furnace, or fluidized bed, but other heating apparatus are also suitable.
  • Figure 1 is a composition diagram depicting the relative amounts of calcium oxide, silica and alumina in a number of cementitious and pozzolanic materials.
  • Figure 2 is a graphical representation of the relationship between phase structure (crystalline or glassy) and reactivity with alkaline, which is a qualitative measurement of a pozzolanic material's performance.
  • Figure 3 depicts the difference in X-ray diffraction (XRD) patterns observed for crystalline and glassy materials. It will be noted that crystalline materials are characterized by sharp, narrow peaks in the XRD pattern.
  • Figure 4 depicts XRD spectra for a number of materials including vitrified and untreated fly ash and ground granulated blast furnace slag.
  • Figures 5 and 6 are a comparison of cement hydration performance for cements including a variety of pozzolanic additives including treated and untreated fly ash and granulated blast furnace slag. While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is intended to cover all modifications, equivalents and alternatives falling within the scope of the invention as defined by the appended claims.
  • FIG. 1 the compositions of a number of cementitious and pozzolanic materials are shown. It has long been known that granulated blast furnace slag is a useful pozzolan for cement and concrete applications, both used alone and as a component in concrete mixtures. For example, blast furnace slag has been used for decades as an inexpensive additive to portland cement concrete. As Figure 1 indicates, the chemical composition of Class C fly ash is quite similar to that of granulated blast furnace slag. However, untreated commercial fly ash contains a significant fraction of crystalline material that is not reactive. By way of contrast, blast furnace slag is composed nearly entirely of amorphous material.
  • Figure 2 is a representation of the increased reactivity with alkaline that results as the fraction of amorphous phase in the material increases.
  • the crystalline and amorphous materials are represented by idealized depictions of their respective structures, which show the difference between the materials in terms of their degree of disorder.
  • Figure 3 depicts the same relationship between reactivity and degree of disorder as shown in Figure 2, but in Figure 3 the crystalline and amorphous materials are represented by X-ray diffraction (XRD) patterns, which differ significantly depending on the degree of crystallinity in a material.
  • XRD X-ray diffraction
  • the present inventors have devised a process for converting most (or all) of the mineral phases in fly ash into the glassy phase.
  • the process involves heating the fly ash to (or nearly to) the melting point to convert the mineral phases to a single glassy phase, and then quenching the melted fly ash to preserve this glassy phase.
  • This process is defined as fly ash phase conversion or vitrification.
  • the term "vitrify" means to convert a material from one or more crystalline phases to a single glassy phase.
  • fuse ash should be understood to refer not only to coal fly ash but to include any ash generated as a power generation by-product, including but not limited to bottom ash, and other waste ash or waste material that is composed mostly of silica, alumina and calcium oxide. It should also be understood that “fly ash” includes such waste materials whether freshly generated or after any period of nondestructive storage such as landfiling.
  • the fly ash may be subjected to heat treatment in any apparatus that can heat the fly ash to a temperature at or near its melting point and provide a mechanism to rapidly quench the melted fly ash, preserving the high temperature glassy phase.
  • the apparatus is not limited to traditional rotary or shaft kilns but can be a fluidized bed, tunnel furnace, a microwave oven, or the like, though kilns and fluidized beds are preferred.
  • the applicants have found that a minimum temperature of about 1150°C is required to vitrify a typical fly ash. At or above this temperature, all of the mineral phases in the fly ash can be converted to the amorphous phase. It appears that temperatures above about 1350°C do not provide any significant additional benefit.
  • the quench temperature can be any temperature sufficiently low to prevent any reversal of the phase transition. Ambient temperatures, for example about 20°C, are preferred.
  • the quenching step may be carried out, for example, by contacting the vitrified fly ash with a stream of air or water.
  • FIG 4 depicts the effects of the present process.
  • the upper XRD spectrum 1 in the figure is that of a sample of ground granulated blast furnace slag, which is substantially all amorphous as stated above, and is provided for comparison.
  • the middle XRD spectrum 2 in Figure 4 is that of an untreated fly ash sample. It will be apparent from the numerous sharp peaks in the XRD pattern and the discussion hereinabove that this sample contains a significant quantity of crystalline material.
  • the lower spectrum 3 in Figure 4 represents the same material after treatment by the present process. In comparison to the untreated sample, it will be clear that the process has eliminated the crystalline material, leaving only the amorphous phase.
  • Figures 5 and 6 depict the hydration performance over time of a number of cement samples prepared by adding 25% pozzolanic material to portland cement.
  • a number of pozzolans were used, including granulated ground blast furnace slag; a commercial fly ash from the Tampa, Florida area; and vitrified fly ash according to the present invention (87.5% passing 44 microns).
  • the heat evolution rate (mW/g) over time is shown in Figure 5; the total heat of hydration (J/g) over time is shown in Figure 6.
  • the onset of heat evolution rate (Figure 5) is an indication of the cement setting characteristics after mixing with water.
  • Figure 6 shows that although the total heat release at 24 hours for all three pozzolans is about the same, the vitrified fly ash releases more heat before 24 hours. This is an indication of higher strength development in the time frame of several hours.
  • the process described herein provides a number of benefits.
  • the conversion of the crystalline mineral phases to a single glassy phase increases the active pozzolanic portion of fly ash and improves the predictability of fly ash performance. Additional benefits of the process include (1) reducing the potential of the fly ash-cement-chemical admixture incompatibility in the concrete application; (2) reducing the possibility of fly ash-induced slow setting or slow early age strength development, and (3) eliminating or reducing the negative effect by the organic matter and highly volatile components present in the fly ash.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Civil Engineering (AREA)
  • Processing Of Solid Wastes (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

L'invention concerne un procédé pour convertir des cendres volantes faiblement réactives en matière pouzzolanique très réactive, comprenant la combustion des cendres volantes, jusqu'à ce qu'au moins une partie des cendres volantes fonde ; puis le refroidissement rapide des cendres volantes. Lesdites cendres volantes vitrifiées ainsi obtenues présentent des propriétés de cimentation améliorées par rapport aux cendres volantes non traitées.
PCT/US2004/016266 2003-05-20 2004-05-20 Procede pour enrichir des cendres volantes Ceased WO2004108621A2 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US24993003A 2003-05-20 2003-05-20
US10/249,935 US20040231566A1 (en) 2003-05-20 2003-05-20 Process for Fly Ash Beneficiation
US10/249,935 2003-05-30
US10/249,930 2003-05-30

Publications (2)

Publication Number Publication Date
WO2004108621A2 true WO2004108621A2 (fr) 2004-12-16
WO2004108621A3 WO2004108621A3 (fr) 2005-06-16

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2004/016266 Ceased WO2004108621A2 (fr) 2003-05-20 2004-05-20 Procede pour enrichir des cendres volantes

Country Status (1)

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WO (1) WO2004108621A2 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2168930A4 (fr) * 2007-05-10 2011-11-30 Cementos Portland Vaderrivas S A Matériau vitreux possédant des propriétés de cimentation et son procédé de fabrication
EP3514219A1 (fr) * 2012-03-14 2019-07-24 Mercury Capture Intellectual Property, LLC Système et procédé de traitement de cendres de charbon
EP3405446A4 (fr) * 2016-01-19 2019-12-04 Solidia Technologies, Inc. Nouvelles chimies du ciment

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4977837A (en) * 1990-02-27 1990-12-18 National Recovery Technologies, Inc. Process and apparatus for reducing heavy metal toxicity in fly ash from solid waste incineration
US5616160A (en) * 1993-05-24 1997-04-01 Corning Incorporated Process for vitrifying incinerator ash
US5521132A (en) * 1994-09-01 1996-05-28 The United States Of America As Represented By The Secretary Of The Navy Ash-based ceramic materials
US5584255A (en) * 1995-06-07 1996-12-17 Proler Environmental Services, Inc. Method and apparatus for gasifying organic materials and vitrifying residual ash
JPH0938620A (ja) * 1995-07-25 1997-02-10 Ebara Corp 灰の溶融方法
EP0892765A4 (fr) * 1996-04-09 2000-03-15 Vortec Corp Fabrication de tuiles en ceramique a partir de cendres volantes

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2168930A4 (fr) * 2007-05-10 2011-11-30 Cementos Portland Vaderrivas S A Matériau vitreux possédant des propriétés de cimentation et son procédé de fabrication
EP3514219A1 (fr) * 2012-03-14 2019-07-24 Mercury Capture Intellectual Property, LLC Système et procédé de traitement de cendres de charbon
EP3514121A3 (fr) * 2012-03-14 2019-09-04 Mercury Capture Intellectual Property, LLC Système et procédé de traitement de cendres de charbon
US11364481B2 (en) 2012-03-14 2022-06-21 Mercury Capture Intellectual Property, Llc Coal ash treatment system and method
AU2019200331B2 (en) * 2012-03-14 2024-11-21 Mercury Capture Intellectual Property, Llc Coal Ash Treatment System and Method
EP3405446A4 (fr) * 2016-01-19 2019-12-04 Solidia Technologies, Inc. Nouvelles chimies du ciment
EP4230584A3 (fr) * 2016-01-19 2023-12-13 Solidia Technologies, Inc. Nouvelles chimies du ciment

Also Published As

Publication number Publication date
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