United States Patent: 4780144
We remind you of a fairly recent dispatch, now accessible via:
West Virginia Coal Association | US EPA Examines Use of Coal Ash - in the Netherlands | Research & Development; concerning the US EPA report:
"'Aardelite Technology: Turning a residue into a building material'; United States Environmental Agency; Case Study 20; April, 2008; Aardelite pellets were used as natural gravel replacement for the construction of a housing compound consisting of 120 units for retired people at Dronten in the Netherlands. ... The Aardelite pellets used for this project were made from pulverized coal fly ash made available at a power station in Nijmegen, the Netherlands. The composition of the Aardelite pellets was as follows: Fly Ash 79.7%; Calcium Oxide 3.3%; Water 17.0%. The pellets used in the concrete are made using the Aardelite process. The Aardelite technology is based on the activation and control of pozzolanic reactions in the fly ash/lime/water mixture by using the pozzolanic properties of fly ash".
As indicated, the "Aardelite pellets" employed in the Netherlands housing project as a concrete aggregate, a substitute for quarried gravel or crushed stone, were composed in large part of Coal power plant Fly Ash.
And, as we've documented in a number of previous reports, including, for example:
West Virginia Coal Association | Wyoming Converts Coal Ash to Construction Aggregates | Research & Development; concerning: "United States Patent 6,334,895 - Producing Manufactured Materials from Coal Combustion Ash; 2002; Assignee: The University of Wyoming Research Corporation; Abstract: This invention ... relates to processing techniques which enhances both density and strength of ... consolidated combustion ash materials. ... Embodiments for both normal weight and light weight combustion ash aggregates are disclosed which meet various ASTM and AASHTO specifications"; and:
West Virginia Coal Association | Consol Converts Coal Ash to Concrete Aggregate | Research & Development; concerning: "United States Patent 5,364,572 - Process for Making High-Strength Synthetic Aggregates; 1994; Assignee: Consolidation Coal Company; Abstract: A process for making high-strength aggregates ... containing coal combustion ash";
it's been pretty well established around the country that Coal Ash can, indeed, be processed and made into a completely satisfactory, even superior, aggregate material for use in Concrete.
Make no mistake: The potential market for such aggregate is almost staggering. As can be calculated from graphic data presented by the United States Geologic Survey, in:
http://pubs.usgs.gov/circ/1998/c1176/c1176.pdf; "Aggregates from Natural and Recycled Sources; Economic Assessments for Construction Applications; U.S. Geological Survey Circular 1176';
the US market for such coarse concrete aggregates likely exceeds 600 million tons per year. Other sources we have cited in other reports put it at one billion tons - as incredible as that might seem.
And, herein, via excerpts from the initial link in this dispatch, with an additional link or two, with excerpts, appended, is exposition of how and where the Coal Ash aggregate which the US EPA reviewed with seeming favor in their report of "Aardelite Technology: Turning a residue into a building material", is made:
"United States Patent 4,780,144 - Method for Producing a Building Element from a Fly Ash Comprising Material and Building Element Formed
Method for producing a building element from a fly ash comprising material and building element formed - Aardelite Holding B.V
Date: October, 1988
Inventor: Hendreet Loggers, The Netherlands
Assignee: Aardelite Holding B.V., The Netherlands
Abstract: A method is described for producing a building element in which a hardenable binder-material is mixed with a coarse particles comprising material after which the mixture is used for forming unhardened building elements. The building elements are subsequently hardened at a temperature up to 100 C and at atmospheric pressure in a water-vapor containing atmosphere. The hardenable binder material is constituted by a separately prepared mixture of fly ash; Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water. Optionally the hardenable mixture may be partially granulated before use.
(Note: A "substance which may be converted into Ca(OH)2" or Calcium Hydroxide, would be, simply, lime, CaO, the primary product of a cement kiln - Portland-type cement, in other words - after the lime had been hydrated with water, H2O, which would make the Calcium Hydroxide according to the equation:
CaO + H2O = Ca(OH)2. Pretty simple and straightforward stuff, really.)
Claims: Method for producing a building element by forming a mixture of fly ash, slaked lime, water and a coarse particles comprising material into an unhardened building element and by hardening said unhardened building element at elevated temperature and in a water vapor containing atmosphere comprising the steps of forming a hardenable mixture at least comprising fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water, granulating at least partially the hardenable mixture, subsequently mixing said hardenable mixture with a suitable coarse particles comprising material, and hardening the resulting mixture of the hardenable material and coarse particles comprising material at a temperature of maximum 100 C and at atmospheric pressure to produce the building element.
(Note, again, the "substance which may be converted into Ca(OH)2" is, simply, CaO, i.e., Cement.)
Method ... in which the coarse particles comprising material (are) materials which are conventional in the building elements producing industry (or) said hardenable mixture comprising fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water in granulated condition (or) mixtures of conventional material and the mixture comprising fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water in granulated condition.
Method ...in which a fly ash is used which contains free CaO per se and that said fly ash is optionally mixed with fly ash having a different CaO content in order to obtain a desired average CaO content.
(Class C Fly Ash, as derived from the combustion of Lignite Coal is likely to contain some appreciable amount of "CaO", while Class F Fly Ash, as derived from the combustion of our eastern US bituminous Coal, is not. The above claim confirms other of our reports documenting that Lignite Fly Ash and Bituminous Fly Ash can be "mixed ... to obtain" the needed "CaO content".)
Method ... in which a fly ash is used which also contains CaSO4.
(Note, that, as seen for one instance in:
West Virginia Coal Association | Pennsylvania Improves Use of Coal Flue Gas Gypsum | Research & Development; concerning: "United States Patent 5,362,471 - Producing Gypsum Flake from Flue Gas Desulfurization; 1994; Air Products and Chemicals, Incorporated (PA), This invention relates to an improved process for producing gypsum calcium sulfate dihydrate flakes from powdered gypsum calcium sulfate dihydrate obtained from the desulfurization of flue gas by the wet limestone process";
we can obtain any needed "CaSO4", i,e., "calcium sulfate", as a Coal combustion byproduct, as well.)
Method ... in which the hardenable mixture which at least comprises fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water is partially replaced by raw materials which are conventional in the sand-lime brick industry such as slaked-lime and sand, the latter optionally being mixed with quartz flour, and the coarse particles comprising material is constituted by a mixture of fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water in granulated form ... .
(In other words, once the mixture of "fly ash, Ca(OH)2 ... , and water" is made up, we can add to it already hardened "particles" made "of fly ash, Ca(OH)2 ... and water"; as will be better illustrated further on.)
Method ... in which the granulated fly ash comprising mixture is hardened prior to its use ... (and) in which the building element is formed into a format which is substantially equal to the format of use after hardening and that the forming is carried out with use of devices which are conventional in the concrete-and/or sand-lime brick-industry.
The invention relates to a method for producing a building element by forming a mixture of fly ash, slaked lime, water and a coarse particles comprising material into an unhardened building element and by hardening said unhardened building element at elevated temperature and in a water vapor containing atmosphere.
Background and Field: The invention relates to a method for producing a building element by forming a mixture of fly ash, slaked lime, water and a coarse particles comprising material into an unhardened building element.
Summary: The present invention has as a goal to provide a method of the indicated type which allows a hardening procedure at milder conditions and in which there is a broader choice of usable coarse particles comprising materials.
Said goals are attained with the method according to the invention which is characterised in that firstly a hardenable mixture at least comprising fly ash, Ca(OH)2 .. and water is formed which mixture optionally is granulated partially and that subsequently said hardenable mixture is mixed with the coarse particles comprising material while hardening of the element is carried out at a temperature of maximum 100 C and at atmospheric pressure.
Upon carrying out the method according to the invention a broad choice may be made out of possible coarse particles comprising materials.
The choice in particular may be made from
(a) materials which are
conventional in the building elements producing industry
(b) said hardenable mixture comprising fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water in granulated condition or
(c) mixtures of one or more conventional materials and the mixture comprising fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water in granulated condition."
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Believe us, we know it's confusing, but, concerning "the mixture comprising fly ash, Ca(OH)2 or a substance which may be converted into Ca(OH)2, and water in granulated condition", see:
United States Patent: 4490178 - Granulated Material
Granulated material - Aarding Weerstandlas B.V.
Date: December 25, 1984
Inventors: Hendrik Loggers, et. al., The Netherlands
Assignee: Aarding Weerstandlas B.V., The Netherlands
Abstract: Granulated material, at least comprising a filler, being bound by an inorganic binder, which filler consists at least partially of a substance possessing latent hydraulic properties, in the form of a substance possessing pozzolanic properties, preferably fly ash, and process for obtaining said material by starting from a calcium oxide product, silica granulate and water in which a portion of the heat development is absorbed by said granulate and is recuperated.
Claims: A process for forming granules by simultaneously mixing water, calcium oxide, and fly ash obtained from combustion of coal at elevated temperatures, forming granules of said mixture and curing said granules at a temperature between about 30 C and about 100 C.
Summary: It is therefore a primary object of the present invention to provide a granulated material, the particles of which possess great strength properties, whilst a considerable economy on energy is obtained.
This object is attained in accordance with the present invention in that the filler consists at least partially, of a substance having latent hydraulic properties, said latent hydraulic properties having been activated by a heat treatment of over 30 C.
In a very favorable embodiment of the invention the filler consists of a substance possessing pozzolanic properties, more particularly fly ash.
Said fly ash is, as is known per se, emitted on a large scale during the combustion of fossilic solid fuels, such as e.g. coal".
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The two Aardelite/Aarding US Patents we include in this dispatch are only a selection taken from their body of Coal Ash utilization technology; and, are ones we take to relate directly to the use of Coal Ash as a concrete aggregate in the US EPA's report of "Aardelite Technology: Turning a residue into a building material", as we earlier documented.
We might treat some of their other Coal Ash utilization technologies in future dispatches; but, our discourse herein is already over-long, and, before closing, we wanted to note that this suite of Coal Ash technologies isn't just an obscure art practiced in an isolated European enclave.
First, as can be learned via:
Aarding Lightweight Granulates BV; "Aarding Lightweight Aggregates BV; The Aardelite technology concerns a process of agglomerating inorganic fines like fly-ash from pulverized coal fired power stations.
This technology was developed many years ago when fly-ash was a major problem in The Netherlands.
During the last 15 years the Aardelite pellets have proven to be a perfect substitute for natural gravel.The aggregate produced with this technology can be used in building materials like masonry blocks and concrete products. Aardelite aggregates are processed in a continuous production installation. An Aardelite plant consist of standard equipment like a mixer, pelletizer, silos and conveyors. Measures are taken to prevent the nuisance of dust in the environment. The Aardelite process itself does not generate any waste streams. Because Aardelite is a cold bonded process there is no fume or water-treatment equipment required. During the years 4 Aardelite plants have been built. The Aardelite plant in Crystal River has been in operation since 1988 and has produced millions of tons of Aardelite pellets up to today. The building blocks produced with these pellets and the houses made with these building blocks have well proven the Aardelite technology during the years";
the technology and it's products have been around for awhile. And, lest you miss the reference, as can be learned further via:
PMI Ash Technologies, LLC | Aardelite® Aggregate for the Concrete and Aggregate Industry; "PMI owns a facility in Crystal River, Florida, for the production of Aardelite(R) medium weight aggregate from nonsaleable fly ash. Since startup in 1988, this plant has produced in excess of 1,700,000 tons of high-quality aggregate, thereby providing the ash producer, Progress Energy Florida, with an ash utilization rate exceeding 85 percent, compared with a 25 percent average rate for U.S. coal-fired power plants",
the process is being operated in at least one location in the United States, where a company about whom we've previously reported, as seen in:
Virginia Converts Coal Ash to Cash | Research & Development; concerning: "South Carolina Electric and Gas Successful Application of Carbon Burn-Out (CBO) at the Wateree Station; 1999 International Ash Utilization Symposium; Center for Applied Energy Research, University of Kentucky; South Carolina Electric and Gas Company; Progress Materials, Inc.; and, Southeastern Ash Co., Inc.; CBO combusts residual carbon in fly-ash, producing a very consistent, low-carbon, high-quality pozzolan";
and which report contained separate documentation of:
"United States Patent 7,462,235 - System and Method for Decomposing Ammonia from Fly Ash; 2008; Assignee: Progress Materials, Inc., FL; A system and method for decomposing ammonia from fly ash contaminated with ammonia is provided"; and:
"United States Patent 7,703,403 - System and Method for Recomposing Ammonia from Fly Ash; 2010; Inventors: Vincent Giampa and Joseph Cochran, FL; Assignee: PMI Ash Technologies; Abstract: A system and method for decomposing ammonia from fly ash contaminated with ammonia is provided";
with Progress Materials Incorporated, having changed their name to PMI Ash Technologies, is seen to be reducing the Aardelite Coal Ash utilization technology to commercial practice, in conjunction with their own technologies and processes for the beneficiation of Coal Ash.
The gist of it all is, that, Coal-fired power plant Fly Ash can be seen and treated as a valuable raw material resource; a raw material from which we can manufacture, as seen for one example in:
Pittsburgh Converts Coal Ash and Flue Gas into Cement | Research & Development; concerning: "United States Patent 5,766,339 - Producing Cement from a Flue Gas Desulfurization Waste; 1998; Assignee: Dravo Lime Company, Pittsburgh; Abstract: Cement is produced by forming a moist mixture of a flue gas desulfurization process waste product (and) aluminum, iron, silica and carbon, (and) wherein said source of aluminum and iron comprises fly ash";
not only a substitute for Portland-type Cement, but, as seen in the subjects of our report herein, "United States Patent 4,490,178 - Granulated Material" and "United States Patent 4,780,144 - Method for Producing a Building Element from a Fly Ash", the structural aggregates, replacements for sand, gravel and crushed stone, to be added to that Cement.
