We've made previous report of the rather extensive technology that Pittsburgh's Dravo Lime Company, once a much larger manufacturing corporation with broader interests, has developed for the profitable employment of Coal utilization byproducts, primarily in the manufacture of Cement, as a substitute for natural raw materials; some of which conventional raw materials, such as limestone, generate copious amounts of Carbon Dioxide during cement plant processing.
Our reports have included:
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; 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. Sulfur dioxide released from the calcium sulfite hemihydrate and calcium sulfate hemihydrate during calcination may be used to produce sulfuric acid, while heat recovered in the process is used to dry the agglomerating feedstock. (And) wherein said source of aluminum and iron comprises fly ash"; and:
West Virginia Coal Association | Pittsburgh Makes Coal Flue Gas Gypsum for Fly Ash Cement | Research & Development; concerning: "United States Patent 5,312,609 - Sulfur Dioxide Removal from Gaseous Streams with Gypsum Product Formation; 1994; 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".
The above "gypsum" product, by the way, made in this case from flue gas desulfurization sludge, is a commonly-utilized mineral additive in, a component of, what we call "Portland" cement.
In the above-cited :"United States Patent 5,766,339 - Producing Cement from a Flue Gas Desulfurization Waste", note that "sulfuric acid" is a byproduct of the process; and, as we noted in the full text of our dispatch concerning US Patent 5,766,339, sulfuric acid is a commercial product with broad utility in various manufacturing industries, though it is, in fact, at industrial grades, a commodity that typically sells for a relatively low price.
Of perhaps more value is elemental Sulfur, which has utility in the manufacture of various plastics, in the vulcanization of rubber, as a component of gunpowder, and, in the compounding of various fertilizers, pesticides, dyes and pharmaceuticals.
Herein, we learn that Dravo Lime also developed a process, related to that of US Patent 5,766,339, where, in the making of cement from Coal utilization byproducts, elemental Sulfur, rather than sulfuric acid,
could be the outlet byproduct for any excess Sulfur contained within the initial raw materials of Flue Gas Desulfurization (FGD) Sludge and Coal Fly Ash.
And, interestingly, the process is made possible by utilizing a portion of the products that can be made from Coal, by one of the process that can generate Coal Ash and FGD sludge.
As seen, with comment inserted and appended, in excerpts from:
"United States Patent 5,769,940 - Producing Cement and Elemental Sulfur from a Flue Gas
Date: June, 1998
Inventor: John College, Pittsburgh
Assignee: Dravo Lime Company, Pittsburgh
Abstract: Cement and elemental sulfur are produced by forming a moist mixture of a flue gas desulfurization process waste product containing 80-95 percent by weight calcium sulfate 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. Sulfur dioxide produced during the calcination is cooled and contacted with hydrogen and carbon monoxide to reduce the same to elemental sulfur.
(Note: Yes, we must interrupt here. Where, do you suppose, we might get a little "hydrogen and carbon monoxide" to use in extracting the "elemental sulfur" from a "flue gas"? How's about another process that just might have generated the "flue gas" in the first place? A few are disclosed and described by another one-time major Pittsburgh-based corporation, in our reports of:
West Virginia Coal Association | Pittsburgh 1976 CO2-Free and Waste-Recycling Coal Gasification | Research & Development; concerning: "United States Patent 3,971,635 - Coal Gasifier Having An Elutriated Feed Stream; 1976; Assignee: Gulf Oil Corporation, Pittsburgh; Abstract: A process for gasifying coal to produce carbon monoxide and hydrogen in which a first stream of coal is burned without bed formation in a combustion zone in the presence of water under oxidation conditions to produce gases containing carbon dioxide and steam. A second stream of coal is maintained as a fluid bed in a separate gasifier zone by upflowing carbon dioxide and steam from the combustion zone while being gasified under reducing conditions to produce carbon monoxide and hydrogen"; and:
West Virginia Coal Association | Pittsburgh 1954 Hydrocarbon Syngas from Coal and Steam | Research & Development; concerning: "United States Patent 2,694,047 - Production of Gas Comprising Hydrogen and Carbon Monoxide; 1954; Gulf Research and Development Company, Pittsburgh; Abstract: This invention relates to the production of a gas comprising hydrogen and carbon monoxide at a superatmospheric pressure. More particularly, it relates to the production of a mixture of hydrogen and carbon monoxide at superatmospheric pressure from a fluidized mixture of steam and coal".
With such "a mixture of hydrogen and carbon monoxide" intended for use in a process like that described in our report of:
Pittsburgh 1941 Coal Syngas to Motor Fuel | Research & Development; concerning: "United States Patent 2,244,710 - The Manufacture of Hydrocarbons from Carbon Monoxide and Hydrogen; 1941; Assignee: Koppers Company, Pittsburgh; The present invention relates to the manufacture of hydrocarbon mixtures suitable for use as motor fuel or as lubricating means, by the reaction of a gas containing hydrogen and carbon monoxide".)
Claims: A process for producing cement and elemental sulfur 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;
- 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;
- agglomerating said moist mixture while removing water therefrom, by contact with hot air, to provide a dry agglomerated kiln feedstock containing about 6 percent or less water (and) calcining said dry agglomerated kiln feedstock in a rotary kiln to produce a cement clinker and a sulfur dioxide-containing gas;
- discharging said sulfur dioxide-containing gas from said rotary kiln into an indirect heat exchanger to cool said gas;
- contacting the resultant cooled sulfur dioxide-containing gas with hydrogen and carbon monoxide in the presence of a reducing catalyst sufficient to form elemental sulfur;
- (and) separating said elemental sulfur therefrom.
The process for producing cement from a flue gas desulfurization process waste product ... wherein said source of aluminum and iron comprises fly ash.
The process for producing cement from a flue gas desulfurization process waste product ... wherein said waste product results from a flue gas desulfurization process using a magnesium-enhanced lime slurry for reaction with sulfur dioxide in a gas stream.
The process for producing cement from a flue gas desulfurization process waste product ... wherein said waste product results from a flue gas desulfurization process using lime for reaction with sulfur dioxide in a gas stream.
The process for producing cement from a flue gas desulfurization process waste product ... wherein said waste product results from a flue gas desulfurization process using limestone for reaction with sulfur dioxide in a gas stream.
(Regarding the above three claims, they are not, necessarily, describing three different reactant materials. The "magnesium-enhanced lime" can be easily and directly obtained from what is known as "dolomitic" limestone, which is quite common. Nearly all limestone consists of a basic blend, in greater or lesser relative quantities, of Calcium Carbonate, CaCO3, and Magnesium Carbonate, MgCO3. Those limestones high in MgCO3, but still predominantly CaCO3, are referred to as "dolomitic" limestones; while those where MgCO3 predominates are called "dolomite". And, the differentiation is, for most practical purposes, of little consequence. Magnesium and Calcium are so closely similar in chemical reactivity and behavior that the only difference in, especially, products made from the compounds of either of them will be a slight variation in density, i.e., weight.)
The process for producing cement from a flue gas desulfurization process waste product ... wherein said dry agglomerated kiln feedstock has a solid content comprising, by weight, 82.77 percent flue gas desulfurization process waste product, 5.80 percent fly ash, 6.43 percent sand, and 5.0 percent coke.
(Not a lot of "fly ash" is needed for this process for making cement out of FGD wastes. But, keep in mind the potentials for, as seen in:
West Virginia Coal Association | Fly Ash Facts for Engineers | Research & Development; concerning: "Fly Ash Facts for Highway Engineers; Report Number: FHWA-IF-03-019; 2003; Coal fly ash is a coal combustion product that has numerous applications in highway construction. This document is sponsored by the U.S. Department of Transportation, through the Federal Highway Administration, in cooperation with the American Coal Ash Association and the United States Environmental Protection Agency. FLY ASH IN PORTLAND CEMENT CONCRETE: Fly ash is used in concrete admixtures to enhance the
performance of concrete. Portland cement contains about 65 percent lime. Some of this lime becomes free and available during the hydration process. When fly ash is present with free lime, it reacts chemically to form additional cementitious materials, improving many of the properties of the concrete. Some of the benefits of fly ash in concrete (include): Higher ultimate strength; Improved workability; Reduced bleeding; Reduced heat of hydration; Reduced permeability; Increased resistance to sulfate attack; Increased resistance to alkali-silica reactivity (ASR); Lowered costs; Reduced shrinkage; Increased durability";
adding even more Fly Ash to that cement, as a reactive aggregate, which serves to make lower-cost, but higher-performance, concrete.)
The process for producing cement from a flue gas desulfurization process waste product ... wherein said sulfur dioxide-containing gas is discharged from said rotary kiln at a temperature in excess of about 1100C and cooled in said indirect heat exchanger to a temperature of between about 340 -580C.
(Not well-reflected in our excerpts herein, or in other of our reports concerning the Dravo Fly Ash utilization technologies, is the fact, that, when, as above, high-temperature products are specified to be "cooled in (a)heat exchanger", the "heat" is, indeed, to be exchanged, that is, recycled, to other steps in the total process where heat is needed, thus contributing to the efficiency of the total process. But, make note, especially, of the following claim.)
The process for producing cement from a flue gas desulfurization process waste product ... wherein said hydrogen and carbon monoxide are components of a synthesis gas produced by gasification of coal.
(They are, in other words, making this technology directly applicable to a process for converting Coal into a "synthesis gas" composed of "hydrogen and "carbon monoxide", the bulk of which "synthesis gas", presumably, would be generated by processes and used in applications defined by another well-known company, in our report of:
West Virginia Coal Association | Standard Oil 1952 Coal to Gasoline Emits No CO2 | Research & Development; concerning: "United States Patent 2,620,348 - Hydrocarbon Synthesis with Two-Stage Coke Gasification; 1952; Assignee: Standard Oil Development Company; Abstract: The present invention relates to the catalytic reaction between carbon monoxide and hydrogen to form valuable liquid products, and more specifically to a novel process for the preparation of synthesis gas. More particularly, the present invention is concerned with improvements in the reaction based upon an improved two-stage process for preparing synthesis gas from coke or coal, and a two-stage process for reacting synthesis gas thus produced to give high yields of valuable high octane gasoline".)
A process for producing cement and elemental sulfur 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; adding fly ash containing aluminum and iron, carbon, and sand to said flue gas desulfurization process waste product to form a moist mixture thereof; agglomerating said moist mixture while removing water therefrom, by contact with hot air, to provide a dry agglomerated kiln feedstock containing about 6 percent or less water; calcining said dry agglomerated kiln feedstock in a rotary kiln to produce a cement clinker and a sulfur dioxide-containing gas; discharging said sulfur dioxide-containing gas from said rotary kiln into an indirect heat exchanger to cool said gas and heat air; passing said heated air to said agglomerating step to remove water from further said moist mixture during agglomeration; contacting the resultant cooled sulfur dioxide-containing gas with hydrogen and carbon monoxide in the presence of a reducing catalyst sufficient to form elemental sulfur; (and) separating said elemental sulfur therefrom.
Object: It is an object of the present invention to produce cement from a flue gas desulfurization process waste product and also to produce elemental sulfur from the off-gases of the calcination step of the cement-making process.
Summary: A process for producing cement from a flue gas desulfurization waste product is carried out by providing a moist flue gas desulfurization waste product containing 80-95 percent by weight solids of calcium sulfite hemihydrate and 5-20 percent by weight solids of calcium sulfate hemihydrate and adding thereto a source of aluminum and iron, such as fly ash, carbon, such as coke, and a siliceous material, such as sand, to form a moist mixture. The moist mixture is agglomerated, such as by pelletizing, while removing water therefrom to provide a dry agglomerated feedstock. The dry agglomerated feedstock is charged to a rotary kiln and calcined to produce a cement clinker which is cooled and pulverized to produce a cement. Sulfur dioxide that is released by calcination of the feedstock is discharged from the rotary kiln and cooled in an indirect heat exchanger while heating air fed to the feedstock agglomerator. The cooled sulfur dioxide is contacted with hydrogen and carbon monoxide in the presence of a reducing catalyst so as to form elemental sulfur which is separated and collected. The hydrogen and carbon monoxide source is preferably a reducing gas produced by gasification of coal."
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In other words, in a process such as that disclosed in our report of:
Shell Oil Coal + CO2 + H2O = Hydrocarbon Syngas | Research & Development; concerning: "United States Patent 7,829,601 - Partial Oxidation Process of a Solid Carbonaceous Feed; 2010; Assignee: Shell Oil Company, Texas; The invention is directed to a process for preparing a mixture comprising CO and H2 by operating a partial oxidation process of a solid carbonaceous feed, which process comprises the steps of: (Supplying) the solid carbonaceous feed and an oxygen-containing stream to a burner, wherein a CO2 containing transport gas is used to transport the solid carbonaceous feed to the burner; (and) partially oxidizing the carbonaceous feed in the burner wherein a gaseous stream comprising CO and H2 is being discharged from said burner into a reaction zone (and) wherein the solid carbonaceous feed is coal (and wherein the process is designed to effect) the optimal production of CO and H2 (which can be) subjected to a methanol synthesis reaction to obtain methanol; to a dimethyl ether synthesis reaction to obtain dimethyl ether; or to a Fischer-Tropsch reaction to obtain various hydrocabons";
a portion, and no doubt a relatively minor portion, of the "gaseous stream comprising CO and H2" produced from "a solid carbonaceous feed", that is, "coal", and a "CO2 containing transport gas", can be diverted from the primary "Fischer-Tropsch reaction", and, instead of being catalytically reacted "to obtain various hydrocarbons", be used to help convert any Flue Gas Desufurization wastes extracted from the Coal gasification product gases, and a portion of the Ash, into both "cement" and commercially-valuable "elemental sulfur".
All in all, the process of our subject herein, "United States Patent 5,769,940 - Producing Cement and Elemental Sulfur from a Flue Gas", can be viewed and treated as one component of a complete system that could, if all the components were put together, at a much reduced net cost, generate a non-polluting and low-Sulfur synthesis gas, consisting of Carbon Monoxide and Hydrogen and suitable for the synthesis of "various hydrocarbons", from Coal.