As seen in a recent dispatch, now accessible on the West Virginia Coal Association's web site, via the link:
US Government Coal Ash Cement Stronger than Portland Cement | Research & Development; we made report of: "United States Patent 4,256,504 - Fly Ash-based Cement; 1981; Assignee: The United States of America (as represented by the Secretary of the Interior); Abstract: A cement composition comprising a high calcium-content fly ash and calcium sulfate, and mortar and concrete compositions containing the cement. A cement composition consisting essentially of (1) a major proportion of a fly ash ... and (2) about 5 to 15 percent by weight of calcium sulfate";
our United States Government confirmed that, in the making of Cement, whether we use Limestone as the basic raw material, for traditional "Portland"-type
We indicated in that report that such "Gypsum", a synthetic version of it, can itself be made from the effluent of stack scrubbers designed to remove Sulfur from Coal-fired power plant exhaust gas; a fact confirmed in another of our reports, as accessible via:
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, which report contains separate information, from the United States Gypsum Company, concerning: "FGD Gypsum in Wallboard and Other Products", wherein we can learn that, in addition to the making of Cement, synthetic FGD Gypsum can be, and is, used in the manufacture of dry wall, or "wall board".
In fact, according to the Tennessee Valley Authority, in a report made available by Ohio State University via the link:
the potential market for FGD Gypsum in wallboard applications is larger than that for the making of Cement.
But, again, both Coal Fly Ash and FGD Gypsum can be synergistically utilized in the making of Cement, as confirmed in our report of:
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 containing 80-95 percent by weight calcium sulfite hemihydrate and 5-20 percent by weight calcium sulfate hemihydrate, aluminum, iron, silica and carbon, agglomerating the moist mixture while drying the same to form a feedstock, and calcining the dry agglomerated feedstock in a rotary kiln. A process for producing cement from a flue gas desulfurization process waste product, comprising: providing a moist flue gas desulfurization process waste product containing 80-95 percent by weight of solids of calcium sulfite hemihydrate and 5-20 percent by weight of solids of calcium sulfate hemihydrate (and) adding a source of aluminum, iron, carbon, and a siliceous material to said flue gas desulfurization process waste product to form a moist mixture thereof (and) wherein said source of aluminum and iron comprises fly ash";
and, the combined use of both of them for Cement could represent a truly huge commercial outlet for those Coal combustion by-products.
Herein, again from Pittsburgh's Dravo Lime Company, as in the above US Patent 5,766,339, we have clear direction on how we go about getting that "flue gas desulfurization process waste" for use, with "fly ash", in the making of that Cement.
Comment follows excerpts from the initial link in this dispatch to:
"US Patent 5,312,609 - Sulfur Dioxide Removal from Gaseous Streams with Gypsum Product Formation
Date: May, 1994
Inventor: John College, Pittsburgh
Assignee: Dravo Lime Company, Pittsburgh
Abstract: A method is provided for removing sulfur dioxide from a hot gaseous stream while directly producing .alpha.-hemihydrate gypsum from a scrubber effluent. A portion of an aqueous scrubbing medium containing calcium and magnesium sulfite is removed from a scrubbing unit and passed to a pressurized oxidation vessel where the sulfites are contacted with an oxidizing gas at an elevated temperature to convert calcium sulfite directly to .alpha.-hemihydrate gypsum and magnesium sulfite to magnesium sulfate.
Claims: A method of removing sulfur dioxide from a sulfur dioxide-containing hot gaseous stream and producing .alpha.-hemidydrate gypsum, comprising: contacting said sulfur dioxide-containing hot gaseous stream with an aqueous scrubbing medium containing calcium and magnesium scrubbing components in a scrubbing unit, wherein said sulfur dioxide is converted to calcium and magnesium sulfites in an aqueous medium; continuously removing at least a portion of said aqueous medium containing calcium sulfite and magnesium sulfite from said scrubbing unit; continuously passing at least a portion of said removed aqueous medium containing calcium sulfite and magnesium sulfite, having a solids content of between about 5-35 percent by weight, to a pressurized oxidation vessel; contacting said aqueous medium containing calcium sulfite and magnesium sulfite in said pressurized oxidation vessel with an oxidizing gas at an elevated temperature and super-atmospheric pressure to convert said calcium sulfite to .alpha.-hemihydrate gypsum, which precipitates from said aqueous medium, and said magnesium sulfite to magnesium sulfate, which dissolves in said aqueous medium, with heat of reaction resulting from said conversion used to maintain said elevated temperature and provide a portion of the pressure within said pressurized oxidation vessel, and the presence of magnesium ions from said magnesium sulfite and magnesium sulfate enhancing said conversion of calcium sulfite to .alpha.-hemihydrate gypsum.
(Note: Some of the reactions involved are exothermic and generate heat, which helps to drive other needed reactions and economically reduces the need for energy supplied to the system. Further, as we have explained in previous reports, most Limestone, as it naturally occurs, is actually a blend of Calcium Carbonate and Magnesium Carbonate, in greater or lesser proportions one to another. Thus, when they specify "calcium and magnesium scrubbing components in a scrubbing unit", they are actually specifying, without coming right out and saying so, Limestone as the substance to be converted by the somewhat anonymous "sulfur dioxide-containing hot gaseous stream" into the "sulfite" minerals, which are then oxidized to form "gypsum".)
(Continuously) removing aqueous medium containing precipitated .alpha.-hemihydrate gypsum and dissolved magnesium sulfate from said pressurized oxidation vessel; and separating said .alpha.-hemihydrate gypsum from said aqueous medium.
A method of removing sulfur dioxide (and) and producing .alpha.-hemihydrate gypsum ... wherein said elevated temperature is maintained at between about 100-145C.
(It all doesn't, in other words, have to be kept that hot. The equipment wouldn't be that expensive.)
The method of removing sulfur dioxide from a sulfur dioxide-containing hot gaseous stream ... wherein said superatmospheric pressure is maintained at between about 20-60 pounds per square inch.
(That isn't that high of a pressure, either. Your car's tires are pumped to within that range.)
The method of removing sulfur dioxide from a sulfur dioxide-containing hot gaseous stream and providing gypsum ... wherein said oxidizing gas is oxygen.
The method of removing sulfur dioxide from a sulfur dioxide-containing hot gaseous stream and providing gypsum ... wherein said oxidizing gas is air.
(Note: The Calcium Sulfite produced by the Flue Gas Desulfurization scrubber has to be oxidized into Calcium Sulfate to form the Gypsum; and, as above, plain old inexpensive Air is all that's needed to do that, if pure Oxygen is too hard, too costly, to come by.)
A method of removing sulfur dioxide from a sulfur dioxide-containing hot gaseous stream and producing gypsum, comprising: contacting said sulfur dioxide-containing hot gaseous stream with an aqueous scrubbing medium containing calcium and magnesium scrubbing components in a scrubbing unit, wherein said sulfur dioxide is converted to calcium and magnesium sulfites in an aqueous medium.
(The full Disclosure goes on at considerable length to explain various types of Gypsum products and their uses. The sort of Gypsum produced by our subject herein is, it seems, especially meritorious, with a wide market in addition to that for the making of Cement.)
It is (an) object of the present invention to provide a method for removal of sulfur dioxide from a hot gas stream using an aqueous scrubbing medium containing calcium and magnesium compounds and continuously produce .alpha.-hemihydrate gypsum while using the exothermic energy of calcium sulfite oxidation to produce heat and a portion of the pressure required to form .alpha.-hemihydrate gypsum.
An advantage provided by the present method is that the oxidation of calcium sulfite to .alpha.-hemihydrate gypsum is an exothermic reaction. Thus, once the oxidation reaction has been initiated, the elevated temperature required to produce .alpha.-hemihydrate gypsum is maintained by the exothermic reaction. This is a distinct advantage over processes that produce .alpha.-hemihydrate gypsum from calcium sulfate, since those processes require a continuous supply of heat energy to effect the conversion, which is not exothermic. In addition, the exotherm provided by the present method in a sealed oxidation vessel also provides a portion of the pressure needed to maintain the conversion to .alpha.-hemihydrate gypsum."
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And, thus, again, the energy efficiencies made possible by the exothermic reactions are emphasized.
In sum, it is an economical process for converting one product often labeled as "waste", arising from our essential use of Coal in the generation of electrical power, into a material, synthetic Gypsum, which can then be combined with another by-product of our Coal use, Fly Ash, as explained in our above-cited report concerning "United States Patent 5,766,339 - Producing Cement from a Flue Gas Desulfurization Waste", to make a direct replacement for energy-intensive Portland Cement, a product which, as we have explained and as we will further document in coming reports, entails the generation of large amount of Carbon Dioxide in its manufacture.
In addition, although we do have some domestic US natural Gypsum production, the nearest source to West Virginia and Pennsylvania that we're aware of, whether or not it's still in operation, is in the state of Indiana.
There might be one Gypsum quarry still operating in Michigan. That last one in Ohio closed in 2005.
Otherwise, the natural Gypsum used in our Coal Country cement plants is likely imported from Canada.
More info concerning the current and potential Gypsum supply and demand picture can be had from our United States Geologic Survey, via the link:
http://minerals.usgs.gov/
highways, bridges, buildings, and many other structures that are part of our everyday life. Gypsum is also extensively used as a soil conditioner on large tracts of land in suburban areas and in agricultural regions.
Gypsum has no practical substitute in the manufacturing of portland cement. Synthetic gypsum generated by various industrial processes, including flue gas desulfurization of smokestack emissions, is very important as a substitute for mined gypsum in wallboard manufacturing, cement production, and agricultural applications (in descending tonnage order). In 2009, synthetic gypsum accounted for 57% of the total domestic gypsum supply";
wherein we, surprisingly, learn that "synthetic gypsum", as perhaps made via the process of our subject herein, "US Patent 5,312,609 - Sulfur Dioxide Removal from Gaseous Streams with Gypsum Product Formation", from Coal-fired power plant exhaust gases, already makes up better than half of the Gypsum produced in the United States of America.
Far past time we, all of us who actually, truly do, give a hoot, got off our cans and, publicly, went after the rest of it, before all of those suspect groups seemingly allied against Coal convince the rest of the nation that Coal is nothing but "dirty", and doesn't have anything to offer anyone but pollution and poverty.
Synthetic Gypsum offers us the opportunity not only to clean up our act and quiet some of our critics, but, to make a little money while we do so.