Elemental sulfur reduction in gypsum

Abstract

This invention generally relates to a method for the reduction of elemental sulfur content in gypsum, and by extension, products that are derived from it such as gypsum wallboard. More specifically, and in one embodiment, this invention relates to using the effectiveness of potassium permanganate or sodium permanganate in reducing elemental sulfur content in a gypsum wallboard or its precursor materials.

Description

ELEMENTAL SULFUR REDUCTION IN GYPSUMCROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application hereby claims the benefit of provisional patent applications of the same title, Serial No. 63 / 725,752, filed on November 27, 2024, and Serial No.63 / 733,590, filed on December 13, 2024, the disclosures of which are herein incorporated by reference in their entirety.FIELD OF INVENTION

[0002] This invention generally relates to a method for the reduction of elemental sulfur content in gypsum, and by extension, products that are derived from it such as gypsum wallboard. More specifically, and in one embodiment, this invention relates to using the effectiveness of potassium permanganate or sodium permanganate in reducing elemental sulfur content in a gypsum wallboard or its precursor materials.BACKGROUND

[0003] Calcined gypsum is rendered into a stucco slurry, by addition of water. At this stage, additives such as accelerators, retarders, or starch material can be included into the stucco slurry.

[0004] The slurried gypsum or stucco can be rolled into various forms. More specifically, in manufacturing gypsum board, the slurry is poured over a bottom sheet of paper and then enclosed with a top sheet. The excess bottom sheet can be turned upward to form the edges of the gypsum board. Formation is further engendered using rollers, guides, or hinge plates that are spaced out over a series of forming tables.

[0005] As the board passes over the forming tables, the water reacts with the stucco to reverse the calcium sulfate hemihydrate (CaSO4.½H2O) back to calcium sulfate dihydrate (CaSO42H2O):CaSO4. ' / HEO+l AJEO— > CaSO4.2H2O+ AH

[0006] After the gypsum completely sets, the boards are delivered to a gypsum board dryer where excess water is driven out of the board. Finally, the boards are cut into desired lengths.

[0007] High sulfur content in the gypsum wallboard is a problem. It is believed to lead to corrosion of pipes, household items, and other potential problems for example, release of sulfurous gases such as carbon disulfide, carbonyl sulfide, and hydrogen sulfide, which could pose potential health hazards. These problems culminated in the adoption of a consumer product safety rule under section 4.7 of ASTM C1396-14a requiring that gypsum wallboard manufactured or sold within the United States contain no more than 10 ppm of elemental sulfur (orthorhombic cyclooctasulfur S8) when tested in accordance with Test Methods ASTM C471M. U. S. Patent No. 9,656,876 discloses a method for reducing elemental sulfur content in gypsum wallboard via the addition of copper powder.BRIEF SUMMARY

[0008] To address the issues above, the present invention generally relates to the discovery of the effectiveness of permanganates, specifically potassium and sodium permanganate in the reduction of elemental sulfur content in gypsum wallboard, for example, when high sulfur-containing gypsum rock is used as the starting raw material.

[0009] The predominant content of gypsum wallboard is gypsum which in turn is a naturally occurring rock. Gypsum rock is often found with various impurities, including elemental sulfur, at various levels. The gypsum rock is mined, ground, and calcined into stucco before being used in the reaction process that results in gypsum wallboard. To meet the 10-ppm maximum limit for elemental sulfur, mined gypsum containing high levels of elemental sulfur would need to be segregated and cannot be used in the wallboard production process. Indeed, gypsum deposit locations where elemental sulfur is also widespread could result in whole gypsum deposits being unusable for gypsum wallboard production, resulting in cost prohibitive situations.

[0010] The present invention discloses the reduction of elemental sulfur in gypsum used for wallboard via a reaction between the elemental sulfur and potassium permanganate. The potassium permanganate could be added as a powder or as a solution at various stages in thegypsum production process. For example, it could be added as a solution or a powder to the gypsum rock prior to milling. It could be added as a powder or a solution to the milled gypsum prior to calcination. It could be added as a powder during or after calcination. Finally, it could be added as a solution or in the form of a powder into the pin mixer along with the stucco, soap, and the other minor constituents of the wallboard formulation.

[0011] In one embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material, the method comprising the following steps:(i) providing gypsum material comprising a level of elemental sulfur, wherein the gypsum material is in its untreated crushed or uncrushed raw form, synthetic form, mixture of raw and synthetic form, in a calcined form, in a partially calcined form, in an un-calcined form, is in form of a slurry comprising gypsum, in form of a stucco, in a wallboard formulation, and / or a wallboard form;(ii) contacting the gypsum material with at least one oxidizing agent, wherein the oxidizing agent is selected from the group consisting of potassium permanganate, sodium permanganate, potassium dichromate, perchloric, acid, chlorine, hydrogen peroxide, potassium persulfate, potassium peroxymonosulfate, sodium perborate, sodium percarbonate, mixtures thereof, and combinations thereof; and(iii) utilizing the gypsum material in the production of the gypsum product.

[0012] In another embodiment, the oxidizing agent reacts with the elemental sulfur, thereby reducing the level of elemental sulfur within the gypsum material.

[0013] In yet another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, wherein said oxidizing agent is KMnO4.

[0014] In one embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, wherein said oxidizing agent is NaMnO4.

[0015] In another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, wherein said oxidizing agent is a mixture of KMnCh and NaMnO4.

[0016] In one embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, the method comprising the following steps:forming a gypsum slurry comprising calcium sulfate hemihydrate (CaSCh % H2O) and water, the gypsum slurry also including an amount of elemental sulfur;mixing an amount of KMnCh into the gypsum slurry;allowing the KMnCh to react with the elemental sulfur within the gypsum slurry; reducing the amount of elemental sulfur present in the gypsum slurry;utilizing the gypsum slurry in the production of the gypsum product.

[0017] In another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material, the method comprising the following steps:forming a gypsum slurry comprising calcium sulfate hemihydrate (CaSCh % H2O) and water, the gypsum slurry also including an amount of elemental sulfur;mixing an amount of NaMnCh into the gypsum slurry;allowing the NaMnCh to react with the elemental sulfur within the gypsum slurry; reducing the amount of elemental sulfur present in the gypsum slurry;utilizing the gypsum slurry in the production of the gypsum product.

[0018] In yet another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material, the method comprising the following steps:forming a gypsum slurry comprising calcium sulfate hemihydrate (CaSCh % H2O) and water, the gypsum slurry also including an amount of elemental sulfur;mixing an amount of KMnCh and NaMnCh into the gypsum slurry;allowing the KMnCh and NaMnCh to react with the elemental sulfur within the gypsum slurry;reducing the amount of elemental sulfur present in the gypsum slurry;utilizing the gypsum slurry in the production of the gypsum product.

[0019] In another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, wherein the slurry includes at least one of starch, sugar, accelerator, soap, dispersant, and a retarder.

[0020] In yet another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, wherein the slurry further comprises one or more of the following: foam, wax, glass fibers, and sugars.

[0021] In one embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, wherein the level of elemental sulfur within the gypsum following the reaction is below that prescribed in ASTM C1396M-14a.

[0022] In another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum material as recited above, wherein the gypsum product is a wall board.

[0023] In yet another embodiment, this invention relates to a method for reducing elemental sulfur in gypsum wallboard, the method comprising the following steps:providing a volume of calcium sulfate dihydrate (CaSO4.2H2O) containing an amount of elemental sulfur;crushing the calcium sulfate dihydrate (CaSO4.2H2O) in a mill;heating and calcining the crushed calcium sulfate dihydrate (CaSCh 2H2O) to produce calcium sulfate hemihydrate (CaSCh % H2O), the calcium sulfate hemihydrate (CaSCh % H2O) containing an amount of elemental sulfur;mixing an amount of KMnCh with the calcium sulfate hemihydrate (CaSCh % H2O), with the KMnO4 dosage range of 0.1 Ibs / MSF to 30 Ibs / MSF; whereinthe KMnO4 reacts with the elemental sulfur within the heated calcium sulfate hemihydrate (CaSCh % H2O);the amount of elemental sulfur (S8) present in the calcium sulfate hemihydrate (CaSO4 % H2O) is decreased; andthe calcium sulfate hemihydrate (CaSCh % H2O) remains present the production of gypsum wallboard.

[0024] In one embodiment, this invention relates to a method for reducing the level of elemental sulfur in gypsum wallboard, the method comprising the following steps:providing a volume of calcium sulfate dihydrate (CaSCh 2H2O) containing an amount of elemental sulfur;crushing the calcium sulfate dihydrate (CaSC 2H2O) in a mill;qheating and calcining the crushed calcium sulfate dihydrate (CaSO42H2O) to produce calcium sulfate hemihydrate (CaSCh % H2O), the calcium sulfate hemihydrate (CaSCh % H2O) containing an amount of elemental sulfur;mixing an amount of NaMnCh with the calcium sulfate hemihydrate (CaSCh % H2O),with the NaMnCh dosage range of 0.1 Ibs / MSF to 30 Ibs / MSF; whereinthe NaMnCh reacts with the elemental sulfur within the heated calcium sulfate hemihydrate (CaSCh i H2O);the amount of elemental sulfur (S8) present in the calcium sulfate hemihydrate (CaSCh i H2O) is decreased; andthe calcium sulfate hemihydrate (CaSCh i H2O) remains present in the production of gypsum wallboard.

[0025] In another embodiment, this invention relates to a method for reducing the level of elemental sulfur in gypsum wallboard, the method comprising the following steps:providing a volume of calcium sulfate dihydrate (CaSCh 2H2O) containing an amount of elemental sulfur;crushing the calcium sulfate dihydrate (CaSC 2H2O) in a mill;heating and calcining the crushed calcium sulfate dihydrate (CaSCh 2H2O) to produce calcium sulfate hemihydrate (CaSCh i H2O), the calcium sulfate hemihydrate (CaSCh i H2O) containing an amount of elemental sulfur;mixing an amount of KMnCh and NaMnCh with the calcium sulfate hemihydrate (CaSCh ’ / z H2O), with the NaMnCh dosage range of 0.1 Ibs / MSF to 30 Ibs / MSF; whereinthe KMnO4 and NaMnCh reacts with the elemental sulfur within the heated calcium sulfate hemihydrate (CaSCh i H2O);the amount of elemental sulfur (S8) present in the calcium sulfate hemihydrate (CaSCh i H2O) is decreased; andthe calcium sulfate hemihydrate (CaSCh i H2O) remains present in the production of gypsum wallboard.

[0026] In yet another embodiment, this invention relates to the method for reducing elemental sulfur in gypsum material as recited above, wherein the KMnO4, the NaMnO4, or the combination of KMnCh and NaMnCh is added to the natural gypsum, to synthetic gypsum, to a blend of natural and synthetic gypsum, to gypsum feed stream; is added immediately after the formation of a stucco slurry; is directly added after calcination; and / or is added via a stucco feed stream.

[0027] In one embodiment, this invention relates to a method for producing a gypsum product with enhanced physical properties, the method comprising:providing a volume of gypsum, the gypsum containing an amount of elemental sulfur; mixing an amount of KMnCh with the gypsum;allowing the KMnCh to react with the elemental sulfur in the gypsum;utilizing the gypsum in the production of the gypsum product.

[0028] In another embodiment, this invention relates to a method for producing a gypsum product with enhanced physical properties, the method comprising:providing a volume of gypsum, the gypsum containing an amount of elemental sulfur; mixing an amount of NaMnCh with the gypsum;allowing the NaMnCh to react with the elemental sulfur in the gypsum;utilizing the gypsum in the production of the gypsum product.

[0029] In yet another embodiment, this invention relates to a method for producing a gypsum product with enhanced physical properties, the method comprising:providing a volume of gypsum, the gypsum containing an amount of elemental sulfur; mixing an amount of KMnCh and NaMnCh with the gypsum;allowing the KMnCh and NaMnCh to react with the elemental sulfur in the gypsum; utilizing the gypsum in the production of the gypsum product.

[0030] In one other embodiment, this invention relates to a method for producing a gypsum product with enhanced physical properties, comprising the further step of calcining the gypsum and wherein the step of mixing the KMnO4is carried out before the calcining step.

[0031] In another embodiment, this invention relates to the method as recited above, comprising the further step of calcining the gypsum and wherein the step of mixing the NaMnO4is carried out before the calcining step.

[0032] In yet another embodiment, this invention relates to the method as recited above, comprising the further step of calcining the gypsum and wherein the step of mixing the combination of KMnO4and NaMnO4is carried out before the calcining step.

[0033] In one embodiment, this invention relates to a method for producing a gypsum product with enhanced physical properties, comprising the further step of calcining the gypsum and wherein the step of mixing the KMnO4is carried out after the calcining step.

[0034] In another embodiment, this invention relates to a method for producing a gypsum product with enhanced physical properties, comprising the further step of calcining the gypsum and wherein the step of mixing the NaMnO4is carried out after the calcining step.

[0035] In yet another embodiment, this invention relates to a method for producing a gypsum product with enhanced physical properties, comprising the further step of calcining the gypsum and wherein the step of mixing the KMnO4and NaMnO4is carried out after the calcining step.DETAILED DESCRIPTION

[0036] Before the present compositions, articles, devices, and / or methods are disclosed and described, it is to be understood that the aspects described below are not limited to specific methods and as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0037] Disclosed are materials, compositions, and components that can be used for, can be used in conjunction with, can be used in preparation for, or are products of the disclosed method and compositions. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, and the like of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds cannot be explicitly disclosed, each is specifically contemplated and described herein. Thus, if a class of adhesives A, B, and C are disclosed as well as a class of additives D, E, and F and an example of a combination A-D is disclosed, then even if each is not individually recited, each is individually and collectively contemplated. Thus, in this example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D. Likewise, any subset or combination of these is also specifically contemplated and disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E are specifically contemplated and should be considered disclosed from disclosure of A, B,and C; D, E, and F; and the example combination A-D. This concept applies to all aspects of this disclosure including, but not limited to, compositions, and steps in methods of making and using the disclosed compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed.

[0038] Unless expressly stated otherwise, it is not intended that any method outlined herein be construed as requiring that its steps be performed in a particular order. Accordingly, where a method claim does not expressly recite an order to be followed by its steps, or where neither the claims nor the descriptions specifically state that the steps are to be limited to a precise sequence, it should not be inferred that a specific order is intended or required. This holds for any possible non-express basis for interpretation, including, but not limited to logical flow or arrangement of steps; interpretations derived from the grammatical organization, syntax, or punctuation; and the quantity or variety of embodiments detailed in the specification. The description of the invention should not be read as mandating a fixed sequence of steps, unless such a requirement is articulated explicitly.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In case of conflict, the present specification, including definitions, will control.

[0040] Except where expressly noted, trademarks are shown in upper case.

[0041] Unless stated otherwise, all percentages, parts, ratios, and the like are by weight. Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is alsoherein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0042] Unless stated otherwise, pressures if expressed, are in psi units would be gauge, and pressures expressed in kPa units would be absolute. Pressure differences, however, are expressed as absolute (for example, pressure 1 is 25 psi higher than pressure 2).

[0043] When an amount, concentration, or other value or parameter is given as a range, or a list of upper and lower values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper and lower range limits, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the present disclosure be limited to the specific values recited when defining a range.

[0044] When the term “about” is used, it is used to mean a certain effect or result can be obtained within a certain tolerance, and the skilled person knows how to obtain the tolerance. When the term "about" is used in describing a value or an endpoint of a range, the disclosure should be understood to include the specific value or endpoint referred to.

[0045] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0046] The transitional phrase "consisting of' excludes any element, step, or ingredient not specified in the claim, closing the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase "consists of' appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[0047] The transitional phrase "consisting essentially of' limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the claimed invention. A “consisting essentially of’ claim occupies a middle ground between closed claims that are written in a “consisting of’ format and fully open claims that are drafted in a “comprising” format. Optional additives as defined herein, at a level that is appropriate for such additives, and minor impurities are not excluded from a composition by the term “consisting essentially of.”

[0048] As used in the specification and in the claims, the term “comprising” may include the embodiments “consisting of’ and “consisting essentially of.”

[0049] Further, unless expressly stated to the contrary, "or" and “and / or” refers to an inclusive and not to an exclusive. For example, a condition A or B, or A and / or B, is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0050] The use of "a" or "an" to describe the various elements and components herein is merely for convenience and to give a general sense of the disclosure. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise. As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0051] The term “predominant portion” or “predominantly,” as used herein, unless otherwise defined herein, means greater than 50% of the referenced material. If not specified, the percent is on a molar basis when reference is made to a molecule (such as hydrogen and ethylene), and otherwise is on a weight basis (such as for additive content).

[0052] The term “substantial portion” or “substantially,” as used herein, unless otherwise defined, means all or almost all or the vast majority, as would be understood by the person of ordinary skill in the context used. It is intended to take into account some reasonable variance from 100% that would ordinarily occur in industrial-scale or commercial-scale situations.

[0053] All parts, percentages and ratios used herein are expressed by weight unless otherwise specified.

[0054] In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined herein.

[0055] “Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0056] While aspects of the present invention can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of skill in the art will understand that each aspect of the present invention can be described and claimed in any statutory class. Unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification. Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which they pertain. The references disclosed are also individually and specifically incorporated by reference herein for the material contained in them that is discussed in the sentence in which the reference is relied upon. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided herein may be different from the actual publication dates, which can require independent confirmation. In the context of the present description, all publications, patent applications, patents and other references mentioned herein, if not otherwise indicated, are explicitly incorporated by reference herein in their entirety for all purposes as if fully set forth.

[0057] The following describes exemplary embodiments of the present invention in the building construction context, which pertains to gypsum-based boards that are suitable for use in the construction of residential and commercial buildings.Definitions

[0058] By “gypsum material” is meant a material that comprises gypsum, including natural or raw gypsum, artificially-prepared gypsum, ground gypsum, uncalcined gypsum, or calcium sulfate dihydrate (CaSO4.2H2O), partially calcined gypsum, calcined gypsum or (CaSCh.’ / zEbO), gypsum slurry, gypsum product, combinations thereof, gypsum board, or gypsum wallboard.

[0059] By “gypsum product” is meant any gypsum material that has been treated by one or more process steps of the present invention. For example, the gypsum product can include uncalcined gypsum, calcined gypsum, gypsum slurry, gypsum board, and gypsum wallboard.

[0060] The process of preparing a gypsum wallboard is described in U. S. Patent No. 9,656,876. That reference has been incorporated into this paper by reference as if it were set forth fully herein.

[0061] The present disclosure relates to methods for reducing levels of elemental sulfur within gypsum products such as board or a wallboard. Natural gypsum often includes increased levels of elemental sulfur. Such elemental sulfur can lead to corrosive compounds like H2S and SO2 and otherwise harmful at elevated levels. In one aspect, this invention contemplates reacting the elemental sulfur with oxidizing agents to decrease the concentration of the elemental sulfur in the final gypsum product such as a wallboard.

[0062] This reaction has the benefit of reducing the levels of elemental or orthorhombic cyclooctasulfur (S8) present within the final gypsum product. The oxidizing agent can be added at any of the manufacturing steps. For example, the oxidizing agent may be added to the gypsum material, which is to the raw material that is still uncalcined (calcium sulfate dihydrate), that is prior to any calcining of the gypsum. It can be added to the output of the calciner, that is to calcium sulfate hemihydrate. The oxidizing agent can also be added prior to the mixer step, or within the mixer.

[0063] The oxidizing agent as disclosed herein includes, potassium permanganate, sodium permanganate, potassium dichromate, perchloric, acid, chlorine, hydrogen peroxide, potassium persulfate, potassium peroxymonosulfate, sodium perborate, sodium percarbonate, or a combination thereof. In a preferred embodiment, the oxidizing agent is potassiumpermanganate. In another preferred embodiment, the oxidizing agent is sodium permanganate. In yet another preferred embodiment, the oxidizing agent is a combination or a mixture of potassium permanganate and sodium permanganate. A permanganate include permanganate oxidizing agents, which include potassium permanganate and sodium permanganate.

[0064] It should be noted that in the gypsum industry, ratios of additives are presented in terms of pounds per MSF (thousand square feet). In one embodiment, the dosage range of KMnO4 or NaMnO4 would be between 0.1 lbs / MSF to about 30 Ibs / MSF. Stated differently, the KMnO4 or NaMnO4 dosage is selected from any one of the numbers below, or a number selected from within a range defined by any two numbers below including the endpoint of such range, in terms of lbs / MSF: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, .0.7, 0.8, 0.9, 1.0,.. 2.0,.., 3.0,.. 4.0,.. 5.0,.. 6.0,.. 7.0,.. 8.0,,, 9.0,.. 10.0,.. 11.0,.. 12.0,.. 3.0,.. 14.0,.. 15.0,..16.0,.. 17.0,..18.0,..19.0,.. 20.0,.., 25,..., and 30 lbs / MSF.

[0065] In one embodiment, the gypsum material prior to exposure to the oxidizing agent comprises from about 5 ppm to about 2000 ppm of elemental sulfur. Stated differently, the gypsum material that is to be treated with an oxidizing agent has an S8 concentration as measured in ppm selected from any one of the numbers below: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100,..., 200,..., 300,..., 400,..., 500,..., 600,..., 700,..., 800,..., 900,..., 1000,..., and 2000.

[0066] In another embodiment, the gypsum materials that is to be treated with the oxidizing agent has an Ss concentration in a range as defined by any two numbers above, including the endpoints of such range, in ppm units.

[0067] In one embodiment, the removal of elemental sulfur from about 5% to about 99.9% from the gypsum material. Stated differently, the reduction in elemental sulfur in a gypsum material that has been treated with an oxidizing agent is any one of the following numbers, or a number within a range defined by any two numbers including the endpoints of such range, as defined by percent weight (ppm) of the original gypsum material: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, and 99.9.Process of Treating Gypsum

[0068] The apparatus for calcining includes a gypsum conveyor for transporting a volume of gypsum from a source of stored or untreated or raw gypsum. The stored gypsum can be natural or synthetic gypsum or combinations thereof. The gypsum is in the form of calcium sulfate dihydrate (CaSO4.2H2O). As discussed supra, calcium sulfate dihydrate can contain elevated levels of elemental sulfur (S) that can remain even in the finished gypsum product. For example, in mineral form calcium sulfate dihydrate may contain up to 800 mg / kg (or 800 ppm) of elemental sulfur. On the other hand, processed or recycled calcium sulfate dihydrate may contain up to 50 mg / kg (or 50 ppm) of elemental sulfur.

[0069] In the traditional process, the stored gypsum is ground in a mill then transported to a kettle through the conveyor, where the gypsum is heated and calcined. The calcining kettle may be replaced by an impact mill for grinding and subsequent or simultaneous calcining. The kettle includes a discharge conveyor for subsequent transport of the calcined gypsum to a hot silo or to a stucco cooler and to a storage silo. An admix screw can be provided for the purpose of transporting the calcined gypsum to a mixer.

[0070] An alternative calcining apparatus likewise includes a gypsum conveyor for transporting a volume of gypsum. This gypsum is then crushed and calcined in an impact mill or CP mill. A downstream cyclone and bag house are also included as is known in the art. The resulting stucco is then transported via screw to a storage silo. An additional conveyor is included for transporting the stored stucco to the admix screw as needed.

[0071] As is known, heating the ground gypsum causes calcination which results in calcium sulfate hemihydrate (CaSO4 ½H2O) (or stucco). Calcination temperatures are generally about 300 to 320°F. Calcination produces calcium sulfate hemihydrate (CaSCh ’A H2O) and water vapor in accordance with the following equation:CaSO4·2H2O + ΔH → CaSO4·½H2O + 1½H2O

[0072] The calcium sulfate hemihydrate (CaSO4 ½H2O) likewise may contain elevated amounts of elemental sulfur. In one embodiment, the elemental sulfur level is reduced by mixing an amount of KMnO4 or potassium permanganate with the calcium sulfate hemihydrate following the calcination. In one embodiment, the potassium permanganate is added to kettlefollowing calcining. In another embodiment, the potassium permanganate is added along the discharge conveyor of the calcining kettle. This allows for optimal contact between the potassium permanganate and elemental sulfur while the stucco is at an elevated temperature. In a similar fashion, the potassium permanganate can be added to the mill or along the conveyor. The amount of potassium permanganate added can range from approximately 20 ppm to approximately 1000 ppm. Once mixed, the potassium permanganate chemically reacts with the elemental sulfur within the calcium sulfate hemihydrate to produce manganese sulfide in accordance with the following equation. In one embodiment, the pH is neutral for this reaction. In another embodiment, the pH is basic for this reaction. In one embodiment, the pH is acidic for this reaction. Here is an exemplary reaction with basic pH:2KMnO4+ S + 4OH’ 2MnO2+ K2SO4 + 2H2O

[0073] The calcium sulfate hemihydrate (CaSO4% H2O) likewise may contain elevated amounts of elemental sulfur. In one embodiment, the elemental sulfur level is reduced by mixing an amount of NaMnO4or sodium permanganate with the calcium sulfate hemihydrate following the calcination. In one embodiment, the sodium permanganate is added to kettle following calcining. In another embodiment, the sodium permanganate is added along the discharge conveyor of the calcining kettle. This allows for optimal contact between the sodium permanganate and elemental sulfur while the stucco is at an elevated temperature. In a similar fashion, the sodium permanganate can be added to the mill or along the conveyor. The amount of sodium permanganate added can range from approximately 20 ppm to approximately 1000 ppm. Once mixed, the sodium permanganate chemically reacts with the elemental sulfur within the calcium sulfate hemihydrate to produce manganese sulfide in accordance with the following equation. In one embodiment, the pH is neutral for this reaction. In another embodiment, the pH is basic for this reaction. In one embodiment, the pH is acidic for this reaction. Here is an exemplary reaction with basic pH:2NaMnO4+ S + 4OH’ 2MnO2+ Na2SO4+ 2H2O

[0074] The production of manganese-based compounds is advantageous because it reduces the levels of elemental sulfur present in the calcium sulfate hemihydrate. The treated calcium sulfate hemihydrate can then be converted into a slurry and formed into a gypsum product. For example, the slurry can be used in a production line to produce gypsum wall board.It has been discovered that utilizing the disclosed method reduces the amount of elemental sulfur within the final gypsum product to levels that comply with industry standards, such as ASTM C1396M-14a.

[0075] A production line for forming gypsum wallboards includes a supply of calcined gypsum or stucco. Stucco is then delivered by an add-screw to a mixer. The add-screw can be used to mix water, accelerators, retarders, starches, soaps, and other constituents. This results in the formation of a gypsum slurry. In accordance with an alternative method of the present disclosure, the KMnO4 or NaMnO4 is added using the add mix screw to the gypsum slurry. This again results in a reaction between the elemental sulfur and KMnO4 or NaMnO4 to form manganese compounds.

[0076] The formation of manganese compounds, in turn, reduces the levels of elemental sulfur both within the slurry and in the final gypsum product. As is known in the art, formed gypsum panels are cut and are then delivered to one or more dryers to completely dry the cut gypsum panel. It has been discovered that heating the panels results in a further reaction between the potassium permanganate and sulfur or the sodium permanganate and sulfur and further reductions in the amount of elemental sulfur present within the board. This also improves the efficiency of the added potassium permanganate or sodium permanganate resulting in less KMnO4 of NaMnO4, respectively, being needed to achieve the goal of less than 10 ppm.

[0077] In one embodiment, the potassium permanganate is added to the crushed or uncrushed natural gypsum, synthetic gypsum, or a mixture of natural and synthetic gypsum that is used as the raw material to prepare a gypsum product, for example, the gypsum board. In another embodiment, the potassium permanganate is added to the uncalcined gypsum, partially-calcined gypsum, or calcined gypsum. In another embodiment, the potassium permanganate oxidizing agent is added to stucco. In yet another embodiment, the potassium permanganate is added to a slurry comprising stucco.

[0078] In one embodiment, the sodium permanganate is added to the crushed or uncrushed natural gypsum, synthetic gypsum, or a mixture of natural and synthetic gypsum that is used as the raw material to prepare a gypsum product, for example, the gypsum board. In another embodiment, the sodium permanganate is added to the uncalcined gypsum, partially-calcined gypsum, or calcined gypsum. In another embodiment, the sodium permanganate oxidizing agent is added to stucco. In yet another embodiment, the sodium permanganate is added to a slurry comprising stucco.

[0079] While the above embodiments describe potassium permanganate or sodium permanganate as the oxidizing agent to be added to various forms of gypsum material and at various stages of the gypsum board manufacturing process, potassium permanganate or sodium permanganate is only used in an exemplary fashion as an oxidizing agent herein. Other oxidizing agents listed supra, or a blend of one or more of the oxidizing agents can also be added in a manner similar to potassium permanganate or sodium permanganate. In some embodiments, the oxidizing agent or permanganate reacts with the elemental sulfur while the gypsum is formed into the gypsum product.EXAMPLES

[0080] During lab trials, the following results were obtained for the change in elemental sulfur content in Panel Rey brand wallboard formulas with the addition of potassium permanganate. Generally, the gypsum wallboard contains a few raw materials: stucco, water, soap, dispersant, sugar, starch, accelerator, and a retarder. There may be one or two more additives depending on the type of wallboard, but these are the primary ones. In the lab, the powders — stucco, starch, sugar, accelerator, and retarder — were premixed. Similarly, the liquids — soap, water, KMnO4 solution — were premixed. The pre-mixed powders and the liquids were then mixed together for a predetermined amount of time, about 15 seconds, after which the resulting slurry was poured into a forming paper envelope where the gypsum was allowed to set and create a roughly 14” x 14” wallboard. In one embodiment, the KMnO4 was also mixed with the powders as a solid powder. It is preferred, however, to make an aqueous solution out of it and mix it with the liquids. Tables 1 and 2 show gypsum with different starting Ss content, as measured in ppm, treatment with KMnO4, and the final Ss content after the treatment, and the percent reduction in the Ss content. It should be noted that the gypsum mined from different places can have a highly varying S8 levels of sulfur impurities. For example, the gypsum in Table 1 experiments have an S8 content of 16 ppm and an outlier content at 79 ppm. In other words, different lots may naturally contain different S8 content that could significantly vary fromlot to lot. Thus, a gypsum sample had a sulfur content of 16.3 ppm, while another sample had the content at 79 ppm, and yet another had 17 ppm.Table 1: Sulfur S8 Reduction Through KMnO4 Addition to Wallboard Formulation WallboardWallboard Starting S8 KMnO4 dosage Final S8Type content (ppm) (lbs / MSF) content (ppm) % S8 reduction PRX 16.3 0 16.0 -1.8%PRX 16.3 0.5 10.7 -34.4% PRX 16.3 2.0 8.0 -50.9% PRX 16.3 5 5.3 -67.5% PRX 79 5 12 -84.8%LW 17 1 7 -58.8%

[0081] Based on the lab results, plant production trials were conducted whereby a 6.6% solution of KMnO4 in water was prepared and this solution was metered into the pin mixer at predetermined dosage levels of the potassium permanganate. The level of elemental sulfur in the stucco was measured each time a change in KMnO4 dosage was being made. Results are shown in Table 2.

[0082] Without wishing to be bound by any theory, we believe that the reaction between S and KMnO4 occurs when KMnO4 is in solution and KMnO4 dissolves in water very readily. So, no matter where one introduces KMnO4, even as a powder in the gypsum rock, because that gypsum would need to be calcined and then mixed with water along with other ingredients in the mixer, it is entirely feasible that during calcination— where gypsum (calcium sulfate dihydrate) is converted to stucco (calcium sulfate hemihydrate)— the water released may be sufficient to hydrate KMnO4 and cause it to react with any elemental sulfur impurity.Example 1 - Preparation of Gypsum Wallboard

[0083] It should be noted that in the gypsum industry, ratios of additives are presented in terms of pounds per MSF (thousand square feet). In one embodiment, the dosage range of KMnO4 would be between 0.1 Ibs / MSF to about 30 Ibs / MSF.

[0084] Gypsum wallboard production is a continuous process. In the first step, the elemental sulfur content in the stucco is measured. A control sample was used without any addition of KMnO4, which was run for about an hour. Elemental S8 content was measured forthe stucco sample, and immediately, KMnO4 was added at a feed rate of 3.5 lbs / MSF of KMnO4 or as a 6.6% solution, and the sample was run for 30 minutes. In the next step, a stucco sample was taken, and elemental sulfur content was measured again. Again, as next step, a control sample without any addition of KMnO4 was run for 1 hour. As the next step, the stucco sample was again measured for elemental sulfur content, returning to an addition of 3.5 lbs / MSF of KMnO4. This sample too was run for 30 minutes. In a further repetitive step, the elemental sulfur content in the stucco is measured. A control sample was used without any addition of KMnO4, which was run for about an hour. Elemental S8 content was measured for the stucco sample, and immediately, KMnCh was added at a feed rate of 4.2 Ibs / MSF and the sample was run for 30 minutes.Table 2. Plant Production for S8 Reduction via KMnO4 Addition in Wallboard Formulation Starting Wallboardstucco Line KMnO4 S8 contentWallboard Ss speed dosage in final % Ss Test no. Type content (ft / min) (Ibs. / MSF) wallboard reduction1 PRX 116 440 0 80.0 -31% 2 PRX 126 440 3.5 23 -82% 3 PRX 117 440 0 105 -10% 4 PRX 135 440 3.5 25 -81% 5 PRX 130 440 0 87 -33% 6 PRX 138 440 4.2 17 -88%

[0085] While there was negligible reduction in elemental sulfur content for wallboards containing no KMnO4 in the formula, there was a surprising and significant reduction in S8 levels when KMnO4 was present in the formulation with the S8 reduction being proportional to the dosage level of KMnO4

[0086] Additional plant production was carried out for Panel Rey’s ’A” Light and 5 / 8” PRX wallboards. The effect of adding potassium permanganate on the elemental sulfur content of the resulting wallboards is shown in Tables 3 and 4Table 3. Effect of potassium permanganate on elemental sulfur content in gypsum in plant produced 1 / 2-inch gypsum wallboardStarting S8Content Wallboard KMnO4dosage Final S8content Wallboard type (ppm) (lbs / MSF) (ppm) / 2" light weight 23 4.2 3.0 / 2" light weight 25 4.2 3.1 / 2" light weight 20 4.2 2.5 / 2" light weight 24 4.2 2.5 / 2" light weight 23 0.0 18.0 / 2" light weight 25 0.0 21.5Table 4. Effect of potassium permanganate on elemental sulfur content in gypsum in plant produced 5 / 8-inch gypsum wallboardWallboard Starting S8Content Wallboard KMnO4dosage Final S8content type (ppm) (lbs / MSF) (ppm) 5 / 8" PRX 9.1 7.2 0.5 5 / 8" PRX 7.4 7.2 0.1 5 / 8" PRX 8 7.2 0.4 5 / 8" PRX 9.1 0.0 12.1 5 / 8" PRX 7.4 0.0 7.7

[0087] Additional plant production was carried out for Panel Rey’s ’A” Light wallboards. The effect of adding sodium permanganate on the elemental sulfur content of the resulting wallboards are shown in Tables 5Table 5. Effect of sodium permanganate on elemental sulfur content in gypsum in plant produced _ 1 / 2-inch gypsum wallboard _Starting S8Content Wallboard KMnO4dosage Final S8content Wallboard type _ (ppm) _ (lbs / MSF) _ (ppm) _ 1 / 2" light weight 13 4.2 0 1 / 2" light weight 12.2 4.2 0.5 1 / 2" light weight 15.6 4.2 0 1 / 2" light weight 13 0.0 7.7 1 / 2" light weight 12.2 0.0 9.4

Claims

CLAIMS1. A method for reducing elemental sulfur in gypsum material, the method comprising the following steps:(i) providing gypsum material comprising a level of elemental sulfur, wherein the gypsum material is in its untreated crushed or uncrushed raw form, synthetic form, mixture of raw and synthetic form, in a calcined form, in a partially calcined form, in an un-calcined form, is in form of a slurry comprising gypsum, in form of a stucco, in a wallboard formulation, and / or a wallboard form;(ii) contacting the gypsum material with at least one oxidizing agent, wherein the oxidizing agent is selected from the group consisting of potassium permanganate, sodium permanganate, potassium dichromate, potassium peroxymonosulfate, perchloric, acid, chlorine, hydrogen peroxide, potassium persulfate, sodium perborate, sodium percarbonate, mixtures thereof, and combinations thereof.

2. The method as recited in claim 1, wherein the oxidizing agent reacts with the elemental sulfur, thereby reducing the level of elemental sulfur within the gypsum material.

3. The method as recited in claims 1 or 2, wherein said oxidizing agent is KMnO4.

4. The method as recited in claims 1 or 2, wherein said oxidizing agent is NaMnO4.

5. The method as recited in claims 1 or 2, wherein said oxidizing agent is a mixture of KMnO4 and NaMnO4.

6. A method for reducing elemental sulfur in gypsum material, the method comprising the following steps:forming a gypsum slurry comprising calcium sulfate hemihydrate (CaSO4 ’A H2O) and water, the gypsum slurry also including an amount of elemental sulfur;mixing an amount of KMnCh into the gypsum slurry;allowing the KMnCh to react with the elemental sulfur within the gypsum slurry; reducing the amount of elemental sulfur present in the gypsum slurry.

7. A method for reducing elemental sulfur in gypsum material, the method comprising the following steps:forming a gypsum slurry comprising calcium sulfate hemihydrate (CaSCh % H2O) and water, the gypsum slurry also including an amount of elemental sulfur;mixing an amount of NaMnCh into the gypsum slurry;allowing the NaMnCh to react with the elemental sulfur within the gypsum slurry; reducing the amount of elemental sulfur present in the gypsum slurry.

8. A method for reducing elemental sulfur in gypsum material, the method comprising the following steps:forming a gypsum slurry comprising calcium sulfate hemihydrate (CaSCh % H2O) and water, the gypsum slurry also including an amount of elemental sulfur;mixing an amount of KMnCh and NaMnCh into the gypsum slurry; allowing the KMnCh and NaMnCh to react with the elemental sulfur within the gypsum slurry;reducing the amount of elemental sulfur present in the gypsum slurry.

9. The method as described in claims 6-8, wherein the slurry includes at least one of starch, sugar, accelerator, soap, dispersant, and a retarder.

10. The method as described in claims 6-8, wherein the slurry further comprises one or more of the following: foam, wax, glass fibers, and sugars.

11. The method as recited in claims 1-10, wherein the level of elemental sulfur within the gypsum following the reaction is below that prescribed in ASTM C1396M-14a.

12. The method as described in claim 11, wherein the gypsum is formed into a wallboard.

3. A method for reducing the level of elemental sulfur in gypsum wallboard, the method comprising the following steps:providing a volume of calcium sulfate dihydrate (CaSCh 2H2O) containing an amount of elemental sulfur;crushing the calcium sulfate dihydrate (CaSC 2H2O) in a mill;heating and calcining the crushed calcium sulfate dihydrate (CaSCh 2H2O) to produce calcium sulfate hemihydrate (CaSCh ’A H2O), the calcium sulfate hemihydrate (CaSO4’ / z H2O) containing an amount of elemental sulfur;mixing an amount of KMnCh with the calcium sulfate hemihydrate (CaSCh ’A H2O), with the KMnO4 dosage range of 0.1 Ibs / MSF to 30 Ibs / MSF; whereinthe KMnO4 reacts with the elemental sulfur within the calcium sulfate hemihydrate (CaSC % H2O);the amount of elemental sulfur (S8) present in the calcium sulfate hemihydrate (CaSO4’ / z H2O) is decreased; andthe calcium sulfate hemihydrate (CaSCh % H2O) remains present in the production of gypsum wallboard.

4. A method for reducing the level of elemental sulfur in gypsum wallboard, the method comprising the following steps:providing a volume of calcium sulfate dihydrate (CaSCh 2H2O) containing an amount of elemental sulfur;crushing the calcium sulfate dihydrate (CaSC 2H2O) in a mill;heating and calcining the crushed calcium sulfate dihydrate (CaSCh 2H2O) to produce calcium sulfate hemihydrate (CaSCh ’A H2O), the calcium sulfate hemihydrate (CaSO4’ / z H2O) containing an amount of elemental sulfur;mixing an amount of NaMnCh with the calcium sulfate hemihydrate (CaSCh ’A H2O), with the NaMnCh dosage range of 0.1 Ibs / MSF to 30 Ibs / MSF; wherein the NaMnCh reacts with the elemental sulfur within the calcium sulfate hemihydrate (CaSC % H2O);the amount of elemental sulfur (S8) present in the calcium sulfate hemihydrate (CaSO4’ / z H2O) is decreased; andthe calcium sulfate hemihydrate (CaSCh % H2O) remains present in the production of gypsum wallboard.

15. A method for reducing the level of elemental sulfur in gypsum wallboard, the method comprising the following steps:providing a volume of calcium sulfate dihydrate (CaSCh 2H2O) containing an amount of elemental sulfur;crushing the calcium sulfate dihydrate (CaSC 2H2O) in a mill;heating and calcining the crushed calcium sulfate dihydrate (CaSCh 2H2O) to produce calcium sulfate hemihydrate (CaSCh ’A H2O), the calcium sulfate hemihydrate (CaSO4’ / z H2O) containing an amount of elemental sulfur;mixing an amount of KMnCh and NaMnCh with the calcium sulfate hemihydrate (CaSO4 % H2O), with the NaMnCh dosage range of 0.1 Ibs / MSF to 30 Ibs / MSF; wherein the KMnO4 and NaMnCh reacts with the elemental sulfur within the calcium sulfate hemihydrate (CaSO4 % H2O);the amount of elemental sulfur (S8) present in the calcium sulfate hemihydrate (CaSO4’ / z H2O) is decreased; andthe calcium sulfate hemihydrate (CaSCh % H2O) remains present in the production of gypsum wallboard.

16. The method as recited in claims 1-15, wherein the KMnO4, the NaMnO4, or the combination of KMnO4and NaMnO4is added to the natural gypsum, to synthetic gypsum, to a blend of natural and synthetic gypsum, to gypsum feed stream; is added immediately after the formation of a stucco slurry; is directly added after calcination; and / or is added via a stucco feed stream.

17. A method for producing a gypsum product with enhanced physical properties, the method comprising:providing a volume of gypsum, the gypsum containing an amount of elemental sulfur;mixing an amount of KMnCh with the gypsum;allowing the KMnCh to react with the elemental sulfur in the gypsum; utilizing the gypsum in the production of the gypsum product.

18. A method for producing a gypsum product with enhanced physical properties, the method comprising:providing a volume of gypsum, the gypsum containing an amount of elemental sulfur;mixing an amount of NaMnCh with the gypsum;allowing the NaMnCh to react with the elemental sulfur in the gypsum; utilizing the gypsum in the production of the gypsum product.

19. A method for producing a gypsum product with enhanced physical properties, the method comprising:providing a volume of gypsum, the gypsum containing an amount of elemental sulfur;mixing an amount of KMnCh and NaMnCh with the gypsum;allowing the KMnCh and NaMnCh to react with the elemental sulfur in the gypsum;utilizing the gypsum in the production of the gypsum product.

20. The method as recited in claim 17, comprising the further step of calcining the gypsum and wherein the step of mixing the KMnO4is carried out before the calcining step.

21. The method as recited in claim 18, comprising the further step of calcining the gypsum and wherein the step of mixing the NaMnO4is carried out before the calcining step.

22. The method as recited in claim 19 comprising the further step of calcining the gypsum and wherein the step of mixing the combination of KMnO4and NaMnO4is carried out before the calcining step.

23. The method as recited in claim 17, comprising the further step of calcining the gypsum and wherein the step of mixing the KMnO4is carried out after the calcining step.

24. The method as recited in claim 18, comprising the further step of calcining the gypsum and wherein the step of mixing the NaMnO4is carried out after the calcining step.

5. The method as recited in claim 19, comprising the further step of calcining the gypsum and wherein the step of mixing the KMnO4and NaMnO4is carried out after the calcining step.