United States Patent Application: 0120167804
We've previously documented that Coal Ash can be advantageously used in the manufacture of Gypsum Board, i.e., Wall Board, a commodity element of construction for the interiors of buildings, as in our report:
West Virginia Coal Association | Coal Fly Ash Makes Wallboard Stronger | Research & Development; concerning, in part: "United States Patent 4,403,006 - Sag-resistant Gypsum Board Containing Fly Ash; 1983; Assignee: United States Gypsum Company; Abstract: A gypsum board consisting essentially of a monolithic cellular core of set gypsum and a fiberous cover sheet encasement provided with improved properties by the gypsum core having incorporated therein coal fly ash in an amount of about 1-20% by weight of stucco in the gypsum slurry used in forming the board".
That, of course, in addition to the fact, that, as seen for example in:
Synthetic Gypsum from Coal Power Plant Flue Gas | Research & Development; concerning: "United States Patent 7,776,150 - Process and Apparatus for Handling Synthetic Gypsum; 2010; Assignees: Koppern Equipment Company, NC, and Giant Cement Company, SC; Abstract: Method and apparatus for converting wet synthetic gypsum from a flue desulphurization process (FGD)"; and, separately, in:
http://library.acaa-usa.org/2-FGD_Gypsum_in_Wallboard_and_Other_Products.pdf; "FGD Gypsum in Wallboard and Other Products; United States Gypsum Company; 2007; Gypsum Key Commercial Properties: Safe and non-toxic mineral; Common by-product from sulfur processing (i.e.,) FGD Gypsum. FGD Gypsum in Wallboard: 63% of all FGD Gypsum produced is recovered into wallboard (and over) 27% of wallboard (is) produced from FGD Gypsum";
the Gypsum used in wallboard can itself be made from the effluent of a "flue desulphurization process", installed on a Coal-fired power plant exhaust system.
Herein, the United States Gypsum Company, USG, corporate assignee of the above-referenced "United States Patent 4,403,006 - Sag-resistant Gypsum Board Containing Fly Ash", explains that Coal Ash can be used, as well, in the manufacture of other, related, building elements similar to wall board; but, of a more structural, more durable nature.
As seen in excerpts from the initial, and additional, links in this dispatch to:
"US Patent Application 20120167804 - In-Situ Manufacture of a Lightweight Fly Ash Based Aggregate
Method for In-Situ Manufacture of a Lightweight Fly Ash Based Aggregate - United States Gypsum Company
Date: July, 2012
Inventor: Marianela Perez-Pena, IL
Assignee: United States Gypsum Company, Chicago
(We interrupt here to provide a little information about United States Gypsum, aka "USG Corporation"; and, to affirm that the use of Coal Ash herein is in addition to the use of Flue Gas Desulphurization material as described in the above-referenced USG publication: "FGD Gypsum in Wallboard and Other Products".
Via USG's corporate web site:
USG Corporation - Leading the building materials industry.; and: Sustainable Solutions by USG Corporation;
information can be found, relating that: "SECUROCK(R) brand gypsum fiber roof board is made from 95 percent recycled materials including synthetic gypsum, an environmentally-friendly byproduct of coal-fired utility plants"; and: "FIBEROCK(R) brand panels are made from 95-percent recycled materials including synthetic gypsum"; "We use more synthetic gypsum, an environmentally-friendly byproduct of coal-fired utility plants, than any other manufacturer in North America, a practice encouraged by the EPA";
and, confirming that USG are sincere about their use of recyclable materials, especially some byproducts "of coal-fired utility plants", specified to mean, primarily, "synthetic gypsum". And, what is being disclosed herein by inventor Perez-Pena is the use of Fly Ash in addition to FGD Gypsum, to make products that are more durable than interior "dry wall"; and, which we take to be similar in intended applications to the above "SECUROCK(R)" and "FIBEROCK(R)" products.)
Abstract: A method of making a rapid setting lightweight homogeneous foamed fly ash based cementitious aggregate composition with improved compressive strength for products such as panels is disclosed. The method mixes fly ash, alkali metal salt of citric acid, foaming agent for entraining air, optional foam stabilizing agent, a calcium sulfate such as stucco or gypsum, and water. Compositions are also disclosed which include mixtures of fly ash, particularly Class C fly ash alone or in mixtures with Class F fly ash, alkali metal salts of citric acid, foaming agents, a calcium sulfate such as calcium sulfate dihydrate or hemihydrate and an optional portland cement.
(Again, as in other of our reports: "Class C fly ash", typically derived from the burning of lower-Btu lignite found mostly in western states, is most often considered to be "high-calcium" and is sometimes referred to as "self-cementing". The "Class F fly ash" has reactive, "pozzolanic" properties of it's own, and results from burning high-Btu eastern bituminous Coal.
And, as we've documented a number of times, as in:
West Virginia Coal Association | 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; Dravo Lime Company, Pittsburgh; Abstract: Cement is produced (from) flue gas desulfurization process waste product (and) aluminum, iron, silica and carbon ... wherein said source of aluminum and iron comprises fly ash";
we can make a perfectly acceptable Portland-type Cement, if an "optional portland cement", as per the Abstract of "US Patent Application 20120167804", is desired, out of more FGD material and even more of our Coal-fired power plant Fly Ash.)
Claims: A method of providing a lightweight cementitious mixture for making aggregate particles comprising: form a mixture by mixing water, cementitious reactive powder comprising fly ash and a calcium sulfate selected from the group consisting of calcium sulfate hemihydrate, calcium sulfate dihydrate, and mixtures thereof, an alkali metal salt of citric acid selected from the group consisting of sodium citrate, potassium citrate and mixtures thereof, a foaming agent, and in situ forming aggregate particles comprising the fly ash and calcium sulfate in the mixture and a crystalline form of hydration products of fly ash and calcium sulfate which are also formed in situ and are interspersed within and between the aggregate particle to bind the aggregate particles.
(Again, the "calcium sulfate hemihydrate, calcium sulfate dihydrate, and mixtures thereof" could all be derived from the products of a Flue Gas Desulphurization process.)
The method ... wherein the fly ash in the reactive powder comprises 88.5 to 100% class C fly ash, and wherein the mixture has a set time of about 4 to 6 minutes (and) wherein the calcium sulfate is calcium sulfate dihydrate.
The method ... wherein the cementitious reactive powder is selected from the group consisting of class C fly ash and calcium sulfate hemihydrate or stucco, mixtures of class C and class F fly ash, calcium sulfate hemihydrate or stucco and/or Portland cement and mixtures of class F fly ash with class C fly ash and/or Portland cement and calcium sulfate hemihydrate or stucco.
The method ... wherein the alkali metal salt of citric acid is in an amount of about 1.5 to 6 wt. % based on the weight of the cementitious reactive powder (and) wherein the cementitious reactive powder comprises 60 to 95 wt. % fly ash and 5 to 40 wt. % calcium sulfate selected from the group consisting of calcium sulfate hemihydrate, calcium sulfate dihydrate, and mixtures thereof.
The composition ... wherein the cementitious reactive powder is selected from the group consisting of class C fly ash and calcium sulfate hemihydrate or stucco, mixtures of class C and class F fly ash and calcium sulfate hemihydrate or stucco; and mixtures of class F fly ash with class C fly ash and/or Portland cement and calcium sulfate hemihydrate stucco.
(As in the above: "mixtures of class F fly ash with class C fly ash and/or Portland cement", the "Class C fly ash" isn't really required, if we have some Portland-type Cement - - perhaps itself as made, via the process of the above-cited "United States Patent 5,766,339 - Producing Cement from a Flue Gas Desulfurization Waste", in large part from Coal Ash.)
The composition ... wherein the cementitious reactive powder mixture comprises 30-46 wt % class F fly ash and 54-70 wt % class C fly ash and no portland cement.
(We remind you that "class C fly ash" has cementitious properties of it's own and can, in some cases and in some applications, serve as a substitute for Portland-type Cement.)
A composition comprising a lightweight cementitious aggregate, said composition comprising an essentially homogeneous mixture of spherical shaped particles of fly ash based cementitious material and a calcium sulfate having a diameter of less than about 1 mm and a crystalline form of hydration products, of said fl ash and calcium sulfate which are also formed and interspersed in and between the particles and binding said particles together in the aggregate (and) further comprising a binder of cementitious material, said aggregate distributed within the cementitious material.
Background and Field: This invention relates generally to fast setting cementitious compositions that can be used for a variety of applications in which rapid hardening and attainment of early strength is desirable. In particular, the invention relates to a method of making a homogenous lightweight fly ash based cementitious aggregate composition which has properties similar to expanded clay aggregates and lightweight fillers that can be used to make boards with excellent moisture durability for use in wet and dry locations in buildings. These aggregates plus a pre-formed foam are added to a fast setting cementitious mixture so that precast board products can be handled soon after the cementitious mixture is poured into a stationary or moving form or over a continuously moving belt. Ideally, this setting of the cement mixture may be achieved as soon as about 20 minutes, preferably as soon as 10 to 13 minutes, more preferably as soon as 4 to 6 minutes, after mixing the cement mixture with a suitable amount of water.
U.S. Pat. No. 6,869,474 to Perez-Pena et al, incorporated herein by reference, discusses extremely fast setting of cementitious compositions for producing cement-based products such as cement boards ... .
(United States Patent: 6869474 - Very Fast Setting Cementitious Composition; 2005; United States Gypsum; Abstract: Extremely fast setting of cementitious compositions for producing cement-based products such as cement boards ... reactive materials may be included such as ... fly ash. The extremely fast rapid set permits rapid production of cementitious products.)
There is a need to find a method to reduce the weight of fly ash based binder mixes so these formulations can be used to manufacture of lightweight cementitious concrete products for applications such as backer board and other wall or ceiling applications with improved strength. The present method has developed formulations with enhanced compressive strength at reduced weight and with reduced cost.
The very fast setting cementitious compositions of this invention can be used for a variety of applications in which rapid hardening and attainment of early strength is desirable. Using the alkali metal salt of citric acid, such as potassium citrate and/or sodium citrate, to accelerate setting of the cementitious composition, when the slurry is formed at elevated temperatures, makes possible increased rate of production of cementitious products such as cement boards.
The method generally further includes setting the mixture to form a solid product containing the in situ formed aggregate particles. The solid product can be used as is or can be broken up, for example by crushing, to form loose aggregate particles of the present invention.
This cementitious reactive powder includes at least fly ash and stucco or gypsum and plaster (stucco is calcium sulfate hemihydrate, gypsum is calcium sulfate dihydrate) and may also contain ordinary portland cement (OPC), calcium aluminate cement (CAC) (also commonly referred to as aluminous cement or high alumina cement), and a non-fly ash mineral additive. However, typically there is no added ordinary portland cement (OPC) or calcium aluminate cement (CAC).
(Not much else but the Fly Ash is really needed, in other words.)
The lightweight cementitious compositions can be used in any concrete product application including concrete panels, flooring, overlays, finishes, capping, as well as patching mixes for concrete roads. The concrete products made with the lightweight compositions of this invention have particular advantages for use which require water durability compared to compositions which contain gypsum and applications which require higher compressive strength than cement containing compositions which have a higher carbon foot print.
Fly ash material is mostly aluminosilicates. Thus, it is theorized the lightweight aggregate of the invention may be similar to that of the most expensive perlite or expanded clay aggregate."
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There is a bit more to it; but, Perez-Pena had earlier developed even additional and related Fly Ash-cement compositions, that we think should be noted herein, as well, as seen via the links to and excerpts from:
"United States Patent Application: 0100071597 - Fly Ash Based Lightweight Cementitious Composition
FLY ASH BASED LIGHTWEIGHT CEMENTITIOUS COMPOSITION WITH HIGH COMPRESSIVE STRENGTH AND FAST SET - United States Gypsum Company
Date: March, 2010
Inventor: Marianela Perez-Pena, IL
Assignee: United States Gypsum Company, Chicago
Abstract: A method of making a rapid setting lightweight cementitious composition with improved compressive strength for products such as boards is disclosed. The method mixes fly ash, alkali metal salt of citric acid and lightweight aggregate with water. Compositions which include fly ash, alkali metal salts of citric acid and lightweight aggregate are also disclosed.
Claims: A method of providing a lightweight cementitious mixture having improved compressive strength and water durability comprising: mixing water, reactive powder, an alkali metal salt of citric acid, and lightweight aggregate wherein the ... reactive powder (comprises) 75 to 100 wt. % fly ash, and 0 to 25 wt. % hydraulic cement and gypsum (or) wherein the reactive powder comprises 88.5 to 100% fly ash, no hydraulic cement and no gypsum, based upon weight of the reactive powder.
(Note: What is being described is a "cementitious composition", by far the largest component of which is Coal power plant "fly ash", for use in "Compositions which include ... lightweight aggregate"; and, which "lightweight aggregate" could itself be made via the process of our earlier subject: "United States Patent Application 20120167804 - In-Situ Manufacture of a Lightweight Fly Ash Based Aggregate", out of Coal power plant "Fly Ash".
Virtually the entire end product, which can be used in "any concrete product application including concrete panels, flooring, overlays, finishes, capping, as well as patching mixes for concrete roads", can, in other words, be made out of Coal-fired power plant Fly Ash.)
The cementitious reactive powder contains fly ash and optionally non-fly ash mineral additives, hydraulic cement and optionally gypsum. The cementitious reactive powder typically contains 75 to 100% fly ash and 0 to 25 wt. % of a member selected from the group consisting of hydraulic cement, gypsum and non-fly ash Mineral Additives. The cementitious reactive powder preferably contains 88.5-100 wt % fly ash. The cementitious reactive powder more preferably contains 88.5-100 wt % fly ash and no hydraulic cement and no gypsum.
Preferably the cementitious reactive powder contains 10 to 40 wt. % lime.
However, this lime is generally not added lime. Rather it is included in another ingredient of the cementitious reactive powder, for example, the fly ash.
The principal ingredient of the cementitious reactive powder of the cementitious composition of the invention is a fly ash mineral additive, preferably Type C fly ash."
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We'll close our excerpts there to explain, that, in the full disclosure of "United States Patent Application 20100071597 - Fly Ash Based Lightweight Cementitious Composition", Perez-Pena does state a preference for use of Class C Fly Ash; but, notes that Class F Fly Ash, as we obtain by combustion of our high-grade eastern bituminous Coal, can be used, as well, but requires the addition of supplemental lime, CaO, which is a primary component of Portland Cement; as made by the calcination of limestone via the basic equation:
CaCO3 (limestone) + Heat = CaO (lime) + CO2.
That would, of course, seem undesirable. But, as we've been documenting, as, for just one example, in:
West Virginia Coal Association | US Navy Announces $3/Gallon Jet Fuel from CO2 | Research & Development; concerning the US Naval Research Laboratory's publication: "Fueling the Fleet, Navy Looks to the Seas; The U.S. Naval Research Laboratory (NRL) is developing the chemistry for producing jet fuel from renewable resources in theater. The process envisioned would catalytically convert CO2 and H2 directly to liquid hydrocarbon fuel ... . NRL has successfully developed and demonstrated technologies for the recovery of CO2 and the production of H2 from seawater using an electrochemical acidification cell, and the conversion of CO2 and H2 to hydrocarbons ... that can be used to produce jet fuel. (And) initial studies predict that jet fuel from (CO2 and H2) would cost in the range of $3 to $6 per gallon to produce";
the potential exists to make $3/gallon liquid hydrocarbon fuels out of Carbon Dioxide.
So, why wouldn't we be interested in making some more of it, in a concentrated form, at an industrial facility already partly equipped with necessary infrastructure, as the byproduct of a process that's making an ingredient necessary for the profitable and productive recycling of Coal power plant Fly Ash?
In point of fact, although nearly all of our reports so far concerning the productive recycling of Carbon Dioxide relate to CO2 as recovered either from Coal-fired power plant, or Coal-to-Liquid-Fuel conversion plant, exhaust streams, or, from the atmosphere itself, a significant amount of work has been focused on the recovery and recycling of CO2 as it is emitted from plants that calcine limestone to make Portland-type cement. And, we will supplement our future reportage with exposition of some of those Cement plant CO2 utilization processes.
Finally, in sum, via the disclosures of both our subjects herein, "US Patent Application 20100071597 - Fly Ash Based Lightweight Cementitious Composition" and "US Patent Application 20120167804 - In-Situ Manufacture of a Lightweight Fly Ash Based Aggregate"; which are expositions of processes which, when combined, according to a very major manufacturing participant in the building and construction products industries, produce "panels, flooring, overlays, finishes, capping, as well as patching mixes for concrete roads" out of a "reactive powder" which, conceivably, can consist of "88.5 to 100% fly ash", we are presented with yet another body of evidence confirming the point we've made many times:
Our economically essential use of Coal in the generation of abundant and truly affordable electric power doesn't produce what some would have us believe to be valueless, or even harmful, pollutants.
Our vital Coal-based generation of electricity, instead, co-generates a wealth of useful byproducts, the true, immense value and utility of which we are now in the process of discovering and implementing.
