We include in this dispatch two United States Patents, issued to unrelated companies, that demonstrate related technologies which could, we would think, be integrated to enable a better, fuller use of two byproducts arising from our economically essential use of Coal in the generation of truly abundant and truly affordable electric power.
Our guess is that the majority of our readers will find our presentation herein at least a little tedious. The bulk of the subject matter, and our excerpts, dwell on the treatment of "wastes" arising from Coal-based power generation in some considerable detail; and, without doubt, the technical minutiae don't exactly fire the imagination.
Our point in reporting them to you is to demonstrate and document the fact, that, commercially-viable and practical technologies do exist which, if implemented and reduced to industrial practice, would help to provide for the complete consumption and productive utilization of the solid and semi-solid residues arising from our, again essential, use of Coal in the generation of, again genuinely affordable, electricity.
Such options are crucial to our being able to avoid additional mandated costs, for "waste disposal", imposed on Coal-fired power generation - - mandated costs the true, underlying motivations for which we must now, given the undue, unwarranted popular press attention being paid to highly-suspect alternatives to Coal, such as the hugely-exaggerated Shale Gas reserves supposedly extant in deep formations all across the country, hold suspect.
It is, in fact, conceivable to us now, given what we have begun to learn, that ways are being found to unjustly increase the cost of Coal-based electricity, so that the alternatives, like Shale Gas, or even wind and solar, become artificially more competitive.
As alien and repugnant as such ways of thinking might seem to those of you common, honest citizens of Coal Country who just get up and go to work everyday, take care of your kids and keep your check book balanced, we can, from sad personal experience, assure you: There are people in positions of power and business influence who spend their lives thinking that way. We owe it to ourselves and to our children to be alert to evidence of it, to react to it, and to continue moving openly forward in productive ways so that the less than scrupulous among us don't drag us, to their profit, all the way under.
That said, concerning our first subject United States Patent, we have cited the Pittsburgh, PA, inventor named in it previously, from when he was employed by the well-known Dravo Lime Company, as in, for one example, our report of:
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; 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".
And, we remind you that Dravo, commendably, developed additional technologies for the use of such Coal flue gas Gypsum, along with Coal Fly Ash, as seen, again for one example, in our report of:
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; Inventor: Manyam Babu, et. al., PA; 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. Claims: A process for producing cement from a flue gas desulfurization process waste product. The process for producing cement from a flue gas desulfurization process waste product ... wherein said source of aluminum and iron comprises fly ash".
Subsequent to his career at Dravo, the named inventor of "United States Patent 5,312,609 - Sulfur Dioxide Removal from Gaseous Streams with Gypsum Product Formation", John College, seems to have moved on, to another Pittsburgh-area company, Eastroc LLC, whose specialty, as indicated by web-based industrial directories, they don't have their own web site, seems to be the manufacture of Gypsum-based building products, such as "dry wall" boards.
At Eastroc, John College continued his development work in the manufacture, and use, of Gypsum derived from the effluent of Coal-fired power plant desulfurization scrubbers, as seen in excerpts from the initial link in this dispatch to:
"United States Patent 6,197,200 - Purifying Flue Gas Waste Slurries for use in Gypsum Production
Method of purifying flue gas waste slurries for use in gypsum production - Eastroc LLC
Date: March, 2001
Inventor: John College, Pittsburgh, et. al., PA and OH
Assignee: Eastroc LLC, Shippingport, PA
Abstract: A method of purifying a flue gas desulfurization aqueous waste slurry containing calcium-sulfur salts and residual solid grits, fly ash, carbon and oils by supplying the aqueous waste slurry to a screening station to remove the grits, passing the grit-free aqueous waste slurry to a magnetic separator to remove fly ash components, and transferring the aqueous slurry to a floatation cell to remove carbon and oils therefrom. A purified aqueous slurry of calcium-sulfur salts is removed from the floatation cell which can be used in producing quality plaster, wallboard, or feedstock in producing .alpha.-hemihydrate gypsum.
Claims: A method of purifying a flue gas desulfurization aqueous waste slurry, removed from a wet scrubbing unit for removing sulfur dioxide from a flue gas in a wet scrubbing unit using calcium scrubbing components for said removal, with substantially all fly ash being removed prior to passage to the wet scrubbing unit, said aqueous waste slurry containing solid calcium-sulfur salts, residual solid grits, residual fly ash containing magnetic components, carbon and oils, in an aqueous medium ... .
Background and Field: The present invention is a method for purifying aqueous waste slurries formed in sulfur dioxide removal systems that use calcium scrubbing components and form solid calcium-sulfur salts.
Numerous processes exist for the removal of sulfur dioxide from flue gases, such as flue gases produced in electric power plants where a carbonaceous material, such as coal ... is combusted to produce heat and power. Such flue gases containing sulfur dioxide also contain fly ash from coal combustion, carbon and oils which sometimes pass through particulate collecting devices and are passed to the flue gas desulfurization unit and subsequently to aqueous waste slurries discharged from the flue gas desulfurization unit. When calcium scrubbing components such as limestone or lime are used to capture the sulfur dioxide, calcium-sulfur salts, such as solid calcium sulfite or calcium sulfate are formed and discharged in an aqueous waste slurry.
It is, of course, desirable to sell or use the calcium sulfite or calcium sulfate in such aqueous waste slurries so as to reduce costs, with such use being the production of gypsum or .alpha.-hemihydrate gypsum as a salable product. A problem exists, however, in that even minor amounts of grits, fly ash, carbon or oils that contaminate the gypsum product from flue gas desulfurization waste slurries seriously affect the quality of the gypsum product, since carbon and oil contaminants can cause release of paper from a core of a gypsum wallboard material, and carbon, oil or fly ash contaminants will discolor plaster formed from such a gypsum product. An additional problem exists in that when lime or limestone are used as the sulfur dioxide-capturing calcium components in a scrubber, poorly ground limestone grits or lime grits, coarse particles, may also be found in the aqueous waste slurry which are also not wanted in a wallboard or plaster byproduct. Coarse particles, if not removed, can cause lumps in the final gypsum material and are also detrimental to the color of the by-products.
It is an object of the present invention to provide a method for purifying an aqueous waste slurry from a flue gas desulfurization system, containing calcium sulfite or calcium sulfate solids, grit material, fly ash and carbon and oil, so as to allow use of the calcium sulfite or calcium sulfate in production of .alpha.-hemihydrate gypsum, plaster or plaster related products.
It is another object of the present invention to provide a method for purifying an aqueous waste slurry from a flue gas desulfurization system, containing calcium sulfite, grit material, fly ash, and carbon and oils, so as to provide an enhanced starting material for use in the production of .alpha.-hemihydrate gypsum or dihydrate gypsum.
Summary: A flue gas desulfurization aqueous waste slurry, resulting from a system for removing sulfur dioxide from a flue gas using calcium scrubbing components, containing solid calcium-sulfur salts, residual solid grits, fly ash containing magnetic components, carbon and oils, is purified by the present method. The present method includes a step of supplying the aqueous waste slurry to a screening station so as to remove solid grits and other large solid particles therefrom, passing the screened aqueous waste slurry to a magnetic separator to remove magnetic components of the fly ash, and then transferring the aqueous waste slurry to a flotation cell so as to remove carbon and oils therefrom and produce a purified aqueous slurry containing solid calcium-sulfur salts, which aqueous slurry is removed from the flotation cell for subsequent treatment or use."
------------------------
Given that an accomplished Coal Ash utilization scientist in Pittsburgh, PA, demonstrated how Coal combustion residuals could be better prepared for use in the manufacture of commodity building products, we wanted also to document the fact that such knowledge isn't confined to just one commendably-focused individual toiling away in one of the hearts of US Coal Country. Following is a United States Patent which John College, in Pittsburgh, cites specifically as a key record of technology upon which he based his further invention.
And, it ain't from around here.
Comment follows excerpts from:
"United States Patent: 5500197 - Process of Purifying Gypsum
Process of purifying gypsum - Metallgesellschaft Aktiengesellschaft
Date: March, 1996
Inventor: Dieter Grone, Germany
Assignee: Metallgesellschaft Aktiengessellschaft (AG), Germany
(Metallgesellschaft - Wikipedia, the free encyclopedia; "Metallgesellschaft AG was formerly one of Germany's largest industrial conglomerates ... . It had over 20,000 employees and revenues in excess of 10 billion US dollars. It had over 250 subsidiaries specializing in mining, specialty chemicals, commodity trading, financial services, and engineering."
We have cited Metallgesellschaft AG for you previously, as, for one example, in our report of:
West Virginia Coal Association | Germany Coal to Substitute Natural Gas | Research & Development; concerning: "United States Patent 4,061,475 - Process for Producing a Gas which can be Substituted for Natural Gas; 1977; Assignee: Metallgesellschaft AG; Abstract: A high methane gas which can be substituted for natural gas is produced from a primary gas made by the gasification of coal".)
Abstract: The process for purifying gypsum suspensions, particularly those formed in a flue gas desulfurizing plant, includes feeding the gypsum suspension to a first hydrocyclone, which is operated to produce an underflow with a comparatively high underflow concentration and an overflow fed to a collecting tank. The underflow of the first hydrocyclone stage is further diluted to a form another underflow with a lower solids content in a suspension tank and then is fed to a second hydrocyclone stage, the overflow of which is also fed to the collecting tank. Depending on purity of the gypsum required or attained, the gypsum contained in an underflow of the second hydrocyclone stage is either immediately dewatered and removed or is first fed to one or more hydrocyclone stages, which operate analogously. The combined overflows of the first and second or further hydrocyclone stages are fed from the collecting tank to a third hydrocyclone stage. In a thickener solid particles are removed from the overflow of the third hydrocyclone and the clear effluent, which is an overflow from the thickener, is used for diluting in the suspension tank.
Claims: A process for purifying gypsum using hydrocyclones ... further comprising obtaining the gypsum suspension ... from a flue gas desulfurizing plant and supplying said limestone suspension to said flue gas desulfurizing plant to bind sulfur oxides generated by said flue gas desulfurizing plant.
Background: The present invention relates to a process of purifying gypsum using hydrocyclones. Gypsum suspensions which are purified using hydrocyclones are generated mainly in flue gas desulfurizing plants which are supplied with an aqueous suspension of a low-grade limestone.
Summary: It is an object of the present invention to produce a high-purity gypsum, preferably in flue gas desulfurizing plants supplied with low-grade limestone ... ."
------------------------
We've abbreviated our excerpts in the extreme, of course. The full patent document file, by the way, contains diagrams and illustrations which the Disclosure makes heavy reference to, and which do help to clarify the process. Our point was to demonstrate that complete processes and designs have evolved, and are in place and available, to enable, first, the recovery of Sulfur from Coal flue gas in the form of a product, Gypsum, for which processes have been developed around the world to further refine that Coal flue gas Gypsum, so that it can be more profitably and successfully employed in the manufacture of commodity, though value-added, building products.
And all of that, of course, is in addition to the utility of Flue Gas Desulfurization Gypsum in the manufacture of Portland-type cement from Coal Fly Ash.
In sum, all of the solid residua resulting from our economically essential use of Coal in the generation of abundant and truly affordable electric power could, and should, be seen and treated as valuable mineral resources.
We can, as herein, employ Coal Flue Gas Gypsum and Coal Fly Ash in the manufacture of commodity building and construction materials that would otherwise, at considerable expense and environmental disruption, have to be mined and transported from their sites of natural deposit.
Further, the manufacture of Flue Gas Gypsum, and subsequently the products made from that Gypsum, would represent an economic, and consequent employment, opportunity for US Coal Country.
Can we ever have enough of those?